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Molecules, Volume 29, Issue 15 (August-1 2024) – 272 articles

Cover Story (view full-size image): This review explores advancements in the application of nitro(het)aromatic bioreductive agents for hypoxic tumor environments. Their role as gene-directed enzyme prodrugs is examined. These prodrugs are inert until activated by specific tumor enzymes, consequently being transforming into potent cytotoxic agents. The review also covers recent developments regarding prodrug conjugates containing nitro(het)aromatic moieties that are activated under tumor hypoxia, enhancing treatment specificity. Additionally, the use of nitro(het)aromatic compounds as fluorescent probes for imaging hypoxic tumors is discussed, enabling a non-invasive visualization of low-oxygen regions for diagnosis, treatment planning, and monitoring therapeutic responses. We hope this review will inspire researchers to design and synthesize improved compounds for selective cancer treatment and early diagnostics. View this paper
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12 pages, 2733 KiB  
Article
A New BODIPY-Based Receptor for the Fluorescent Sensing of Catecholamines
by Roberta Puglisi, Alessia Cavallaro, Andrea Pappalardo, Manuel Petroselli, Rossella Santonocito and Giuseppe Trusso Sfrazzetto
Molecules 2024, 29(15), 3714; https://doi.org/10.3390/molecules29153714 - 5 Aug 2024
Cited by 1 | Viewed by 1165
Abstract
The human body synthesizes catecholamine neurotransmitters, such as dopamine and noradrenaline. Monitoring the levels of these molecules is crucial for the prevention of important diseases, such as Alzheimer’s, schizophrenia, Parkinson’s, Huntington’s, attention-deficit hyperactivity disorder, and paragangliomas. Here, we have synthesized, characterized, and functionalized [...] Read more.
The human body synthesizes catecholamine neurotransmitters, such as dopamine and noradrenaline. Monitoring the levels of these molecules is crucial for the prevention of important diseases, such as Alzheimer’s, schizophrenia, Parkinson’s, Huntington’s, attention-deficit hyperactivity disorder, and paragangliomas. Here, we have synthesized, characterized, and functionalized the BODIPY core with picolylamine (BDPy-pico) in order to create a sensor capable of detecting these biomarkers. The sensing properties of the BDPy-pico probe in solution were studied using fluorescence titrations and supported by DFT studies. Catecholamine sensing was also performed in the solid state by a simple strip test, using an optical fiber as the detector of emissions. In addition, the selectivity and recovery of the sensor were assessed, suggesting the possibility of using this receptor to detect dopamine and norepinephrine in human saliva. Full article
(This article belongs to the Special Issue Boron Dipyrromethene (BODIPY) Dyes and Their Derivatives)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Comparison of absorption and emission spectra of (<b>2</b>). [<b>2</b>] = 1 μM in CHCl<sub>3</sub>; λ<sub>ex</sub> = 500 nm.</p> Full article ">Figure 2
<p>(<b>a</b>) Fluorescent titration between DA and (<b>2</b>) in CHCl<sub>3</sub> ([<b>2</b>] = 1 × 10<sup>−6</sup> M, [DA] = 0~1.07 × 10<sup>−5</sup> M, λ<sub>ex</sub> 500 nm); (<b>b</b>) fluorescent titration between NE and (<b>2</b>); (<b>c</b>) comparison of the recorded intensities at the maximum emission versus the added equivalents; (<b>d</b>) binding constant values of supramolecular complexes with DA and NE, respectively, calculated using HypSpec version 1.1.33; the detection limit was calculated using the calibration curve method using the formula LOD = 3σ/K, where σ is the standard deviation of the blank and K is the slope of the calibration curve.</p> Full article ">Figure 3
<p>Optimized geometries of the most stable conformations of the <b>DA@2</b> (<b>left</b>) and <b>NE@2</b> complexes (<b>right</b>), calculated at the B3LYP/6-31G(d,p) level of theory in the gas phase. Complexation energy (EComplex) is reported in parentheses below each structure. The hydrogen bonds (A–E) involved in the HG complex formation have been marked as red dashed lines (see <a href="#molecules-29-03714-t002" class="html-table">Table 2</a>).</p> Full article ">Figure 4
<p>Schematic representation of the sensing by the strip test. (<b>a</b>) Real strip test on the left showing the spot of (<b>2</b>) that will serve as a control (Ctrl) and the spot of (<b>2</b>) onto which the analyte will be deposited; (<b>b</b>) analysis using the optical fiber, and (<b>c</b>) the emission spectra recorded.</p> Full article ">Figure 5
<p>Strip test response following exposure to three different solutions of DA and NE (from 10 μM to 1 nM). I<sub>water</sub> represents the control (MilliQ water), I<sub>analyte</sub> represents the emission intensity of (<b>2</b>) following exposure to the analyte, and I<sub>BDPy</sub> represents the emission intensity of probe (<b>2</b>) alone.</p> Full article ">Figure 6
<p>Selectivity tests with interferents commonly found in saliva.</p> Full article ">Figure 7
<p>Recovery tests for (<b>a</b>) DA and (<b>b</b>) NE: zero point represents the emission intensity of probe (<b>2</b>); “DA” or “NE” points represent the emission intensity of (<b>2</b>) after exposure to DA or NE, respectively; and “wash” represents the emission intensity of (<b>2</b>) after exposure to water.</p> Full article ">Scheme 1
<p>Synthetic pathway for the synthesis of BODIPY sensor. Reagents and conditions: (a) Et<sub>3</sub>N, BF<sub>3</sub>(OEt)<sub>2</sub>, CH<sub>2</sub>Cl<sub>2</sub>, r.t., overnight, yield: 30%; (b) K<sub>2</sub>CO<sub>3</sub>, KI, CH<sub>3</sub>CN, r.t., overnight, yield: 40%.</p> Full article ">
22 pages, 28263 KiB  
Article
Investigation of the Sensing Properties of Lanthanoid Metal–Organic Frameworks (Ln-MOFs) with Terephthalic Acid
by Denitsa Elenkova, Yana Dimitrova, Martin Tsvetkov, Bernd Morgenstern, Maria Milanova, Dimitar Todorovsky and Joana Zaharieva
Molecules 2024, 29(15), 3713; https://doi.org/10.3390/molecules29153713 - 5 Aug 2024
Cited by 1 | Viewed by 1270
Abstract
The solvothermal synthesis of LnCl3.nH2O with terephthalic acid (benzene-1,4-dicarboxylic acid, H2BDC) produced metal–organic frameworks (LnBDC), [Ln2(BDC)3(H2O)4]∞, where Ln = Sm, Eu, Tb, and Dy. The materials [...] Read more.
The solvothermal synthesis of LnCl3.nH2O with terephthalic acid (benzene-1,4-dicarboxylic acid, H2BDC) produced metal–organic frameworks (LnBDC), [Ln2(BDC)3(H2O)4]∞, where Ln = Sm, Eu, Tb, and Dy. The materials obtained were characterized by a number of physico-chemical techniques. The influence of the ionic radius of the lanthanides on the microstructural characteristics of the Ln-MOFs was evaluated by performing Rietveld refinement. The MOFs obtained were tested as fluorescent sensors for numerous cations and anions in water. The highly luminescent EuBDC and TbBDC demonstrated multi-responsive luminescence sensing functions to detect Ag(I), Fe(III), Cr(III), and Cr(VI), which are essential for their environmental applications. By applying the non-linear Stern–Volmer equation, the fluorescent quenching mechanism was determined. The stability of the obtained materials in water in a wide pH range (acidity pH = 4 and alkalinity pH = 9 solutions) was confirmed. Full article
(This article belongs to the Special Issue Rare Earth Based Luminescent Materials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Crystals structure images of DyBDC-SC.</p> Full article ">Figure 2
<p>(<b>a</b>) XRD patterns of the as-prepared LnBDC MOFs compared to the simulated XRD pattern of the DyBDC-SC and (<b>b</b>) a close look at the 27—32 2θ part confirming the change in the unit cell parameters.</p> Full article ">Figure 3
<p>SEM images of (<b>a</b>) single crystals of DyBDC-SC and polycrystal samples of (<b>b</b>) SmBDC, (<b>c</b>) EuBDC, (<b>d</b>) TbBDC, and (<b>e</b>) DyBDC.</p> Full article ">Figure 4
<p>Comparison of the emissions registered from different types of LnBDC: (<b>a</b>) pure samples in a solid state; (<b>b</b>) 5 wt% LnBDC in BaSO<sub>4</sub>.</p> Full article ">Figure 5
<p>Luminescence spectra of freshly prepared and 3-week-aged suspensions of (<b>a</b>) EuBDC and (<b>b</b>) TbBDC. Powder XRD just after synthesis and after 3 weeks’ stay in water for (<b>c</b>) EuBDC and (<b>d</b>) TbBDC.</p> Full article ">Figure 6
<p>Luminescence measurements under the same conditions of 0.5 mg/mL of suspension in different solvents: (<b>a</b>) EuBDC and (<b>b</b>) TbBDC.</p> Full article ">Figure 7
<p>Luminescence measurements under the same conditions of 0.5 mg/mL of suspension at different pH values: (<b>a</b>) EuBDC and (<b>b</b>) TbBDC.</p> Full article ">Figure 8
<p>Maximum emission observed at 617 nm for EuBDC (<b>a</b>) and at 547 nm for TbBDC (<b>b</b>) in the presence of different cations (concentration 1 × 10<sup>−3</sup> mol/L, nitrate salts, λ<sub>ex</sub> = 320 nm).</p> Full article ">Figure 9
<p>Maximum emission at 617 nm for EuBDC (<b>a</b>) and at 547 nm for TbBDC (<b>b</b>) in the presence of different anions (concentration 1 × 10<sup>−3</sup> mol/L, sodium and potassium salts, λ<sub>ex</sub> = 320 nm.</p> Full article ">Figure 10
<p>Luminescence of (<b>a</b>) EuBDC (inset: picture of the suspension under a UV lamp with max. 254 nm with and without a quencher) and (<b>b</b>) TbBDC at different concentrations of Ag(I) (inset: picture of the suspension under a UV lamp with max. 254 nm with and without a quencher).</p> Full article ">Figure 11
<p>Stern–Volmer curves for (<b>a</b>) EuBDC and (<b>b</b>) TbBDC (λex = 320 nm). Intensity at 547 nm in the absence of a quencher, divided by the intensity in the presence of a quencher; baseline correction applied.</p> Full article ">Figure 12
<p>(<b>a</b>) EuBDC and (<b>b</b>) TbBDC linear dependency interval.</p> Full article ">Figure 13
<p>Luminescence spectra of TbBDC in the absence of Ag(I) and at concentrations over 1.8 mM.</p> Full article ">Figure 14
<p>(<b>a</b>) Luminescence at different concentrations of Cr(III) and (<b>b</b>) exponential fit of the data.</p> Full article ">Figure 15
<p>Stern–Volmer curve for EuBDC: a linear dependency interval for Cr(III).</p> Full article ">Figure 16
<p>(<b>a</b>) Intensity at 547 nm in the absence of a quencher, divided by the intensity in the presence a of quencher (λex =320 nm); baseline correction applied. (<b>b</b>) Lifetime value in the absence of a quencher, divided by lifetime values in the presence of a quencher.</p> Full article ">Figure 17
<p>Graphical separation of K<sub>S</sub> and K<sub>D</sub> for TbBDC with Fe(III).</p> Full article ">Figure 18
<p>Exponential fit of the data for TbBDC with Fe(III).</p> Full article ">Figure 19
<p>Polynomic (<b>a</b>) and exponential (<b>b</b>) fit of the data for TbBDC with Cr(VI).</p> Full article ">Figure 20
<p>Lifetime value in the absence of a quencher, divided by lifetime values in the presence of a quencher.</p> Full article ">Figure 21
<p>Normalized absorption of solutions with concentration 1×10<sup>−3</sup> mol/L.</p> Full article ">
21 pages, 6341 KiB  
Article
Functionalization of Artwork Packaging Materials Utilizing Ag-Doped TiO2 and ZnO Nanoparticles
by Tilde de Caro, Roberta Grazia Toro, Luminita Cassone, Francesca Irene Barbaccia, Camilla Zaratti, Irene Angela Colasanti, Mauro Francesco La Russa and Andrea Macchia
Molecules 2024, 29(15), 3712; https://doi.org/10.3390/molecules29153712 - 5 Aug 2024
Viewed by 919
Abstract
Most of the artworks stored in museums are often kept in inappropriate climatic and environmental conditions that facilitate the formation and growth of microorganisms, such as fungi, which are responsible for many types of biodegradation phenomena. To mitigate and prevent these deteriorative processes, [...] Read more.
Most of the artworks stored in museums are often kept in inappropriate climatic and environmental conditions that facilitate the formation and growth of microorganisms, such as fungi, which are responsible for many types of biodegradation phenomena. To mitigate and prevent these deteriorative processes, functionalized packaging materials can be used for the storage and handling of artworks. The aim of this study was to develop a potential anti-biodeterioration coating suitable for packaging purposes. TiO2 and ZnO doped with different amounts of Ag (0.5 wt%, 1 wt%, and 3 wt%) were synthesized and dispersed in polyvinyl alcohol (PVA) and acrylic resin (Paraloid B72), then applied on different types of packaging materials (cellulose and the high-density spunbound polyethylene fiber Tyvek®, materials that are frequently used as packaging in museums). Analytical investigations (SEM/EDS, Raman, FTIR, and XRD) were employed to assess dispersion on the packaging material. Furthermore, resistance against biodeteriogens was assessed using Cladosporium sp., a bioluminometer, to define the biocidal efficacy. Full article
(This article belongs to the Special Issue Advances in Analytical Strategies to Study Cultural Heritage Samples, 2nd Edition)
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<p>Stereomicroscope images of TiO<sub>2</sub>, TiO<sub>2</sub>-Ag (0.5%), TiO<sub>2</sub>-Ag (1%), and TiO<sub>2</sub>-Ag (3%).</p> Full article ">Figure 2
<p>X-ray diffraction measurements of TiO<sub>2</sub>, TiO<sub>2</sub>-Ag (0.5%), TiO<sub>2</sub>-Ag (1%), and TiO<sub>2</sub>-Ag (3%). (A: anatase, R: rutile, * Ag).</p> Full article ">Figure 3
<p>Spectra of TiO<sub>2</sub> and TiO<sub>2</sub>-Ag (0.5%, 1%, 3%) acquired from different analyses, respectively. (<b>a</b>) Micro-Raman spectra; (<b>b</b>) UV–Vis spectra; (<b>c</b>) Kubelka–Munch.</p> Full article ">Figure 4
<p>Stereomicroscope images of ZnO (<b>left</b>) and ZnO-Ag NPs (<b>right</b>).</p> Full article ">Figure 5
<p>Spectra of ZnO and doped ZnO with Ag, respectively. (<b>a</b>) Micro-Raman spectra; (<b>b</b>) UV–VIS spectra recorded by diffuse reflectance spectroscopy; (<b>c</b>) Kubelka–Munch spectra; (<b>d</b>) XRD spectra.</p> Full article ">Figure 6
<p>NP UV analysis images of the paper sample (<b>A</b>) and the Tyvek<sup>®</sup> sample (<b>B</b>).</p> Full article ">Figure 7
<p>Paper packaging. Optical microscopy images (50×) acquired using visible light (<b>left</b>) and UV light (<b>right</b>). (<b>A</b>) Paraloid B72 medium (<b>top</b>) and PVA (<b>bottom</b>) + TiO<sub>2</sub> NPs; (<b>B</b>) Paraloid B72 medium (<b>top</b>) and PVA (<b>bottom</b>) + TiO<sub>2</sub>-Ag NPs.</p> Full article ">Figure 8
<p>Paper Packaging. Optical microscopy images (50×) acquired using visible light (<b>left</b>) and UV light (<b>right</b>). (<b>A</b>) Paraloid B72 medium (<b>top</b>) and PVA (<b>bottom</b>) + ZnO NPs; (<b>B</b>) Paraloid B72 medium (<b>top</b>) and PVA (<b>bottom</b>) + ZnO-Ag NPs.</p> Full article ">Figure 9
<p>Tyvek<sup>®</sup> packaging. Optical microscopy images (50×) acquired under visible light (<b>left</b>) and UV light (<b>right</b>). (<b>A</b>) Paraloid B72 medium (<b>top</b>) and PVA (<b>bottom</b>) + TIO<sub>2</sub> NPs; (<b>B</b>) Paraloid B72 medium (<b>top</b>) and PVA (<b>bottom</b>) + TIO<sub>2</sub>-Ag NPs.</p> Full article ">Figure 10
<p>Tyvek<sup>®</sup> packaging. Optical microscopy images (50×) acquired under visible light (<b>left</b>) and UV light (<b>right</b>). (<b>A</b>) Paraloid B72 medium (<b>top</b>) and PVA (<b>bottom</b>) + ZnO NPs; (<b>B</b>) Paraloid B72 medium (<b>top</b>) and PVA (<b>bottom</b>) + ZnO-Ag NPs.</p> Full article ">Figure 11
<p>SEM analysis of NP distribution on packaging paper; (<b>a</b>) spatial distribution of TiO<sub>2</sub>-Ag NPs in Paraloid B72 (TiO<sub>2</sub>-Ag PAR) (<b>top</b>) and PVA (TiO<sub>2</sub>-Ag PVA) (<b>bottom</b>); (<b>b</b>) spatial distribution of ZnO-Ag NPs in Paraloid B72 (ZnO-Ag PAR) (<b>top</b>) and PVA (ZnO-Ag PVA) (<b>bottom</b>).</p> Full article ">Figure 12
<p>SEM analysis of NP distribution on PE; (<b>a</b>) spatial distribution of TiO<sub>2</sub>-Ag NPs in Paraloid B72 (TiO<sub>2</sub>-Ag PAR) (<b>top</b>) and PVA (TiO<sub>2</sub>-Ag PVA) (<b>bottom</b>); (<b>b</b>) spatial distribution of ZnO-Ag NPs in Paraloid B72 (ZnO-PAR) (<b>top</b>) and PVA (ZnO-Ag PVA) (<b>bottom</b>).</p> Full article ">Figure 13
<p>ATP values for several packing materials treated with the different experimental coatings.</p> Full article ">Figure 14
<p>Procedure of TiO<sub>2</sub>/TiO<sub>2</sub>+Ag and ZnO/ZnO+Ag NP application on packaging materials.</p> Full article ">
30 pages, 9980 KiB  
Article
Enhanced Removal of Cd(II) Ions from Aqueous Media via Adsorption on Facilely Synthesized Copper Ferrite Nanoparticles
by Nada S. Al-Kadhi and Maram T. Basha
Molecules 2024, 29(15), 3711; https://doi.org/10.3390/molecules29153711 - 5 Aug 2024
Cited by 1 | Viewed by 1079
Abstract
In this study, magnetic copper ferrite (CuFe2O4) nanoparticles were synthesized via the Pechini sol-gel method and evaluated for the removal of Cd(II) ions from aqueous solutions. PF600 and PF800 refer to the samples that were synthesized at 600 °C [...] Read more.
In this study, magnetic copper ferrite (CuFe2O4) nanoparticles were synthesized via the Pechini sol-gel method and evaluated for the removal of Cd(II) ions from aqueous solutions. PF600 and PF800 refer to the samples that were synthesized at 600 °C and 800 °C, respectively. Comprehensive characterization using FTIR, XRD, FE-SEM, HR-TEM, and EDX confirmed the successful formation of CuFe2O4 spinel structures, with crystallite sizes of 22.64 nm (PF600) and 30.13 nm (PF800). FE-SEM analysis revealed particle diameters of 154.98 nm (PF600) and 230.05 nm (PF800), exhibiting spherical and irregular shapes. HR-TEM analysis further confirmed the presence of aggregated nanoparticles with average diameters of 52.26 nm (PF600) and 98.32 nm (PF800). The PF600 and PF800 nanoparticles exhibited exceptional adsorption capacities of 377.36 mg/g and 322.58 mg/g, respectively, significantly outperforming many materials reported in the literature. Adsorption followed the Langmuir isotherm model and pseudo-second-order kinetics, indicating monolayer adsorption and strong physisorption. The process was spontaneous, exothermic, and predominantly physical. Reusability tests demonstrated high adsorption efficiency across multiple cycles when desorbed with a 0.5 M ethylenediaminetetraacetic acid (EDTA) solution, emphasizing the practical applicability of these nanoparticles. The inherent magnetic properties of CuFe2O4 facilitated easy separation from the aqueous medium using a magnet, enabling efficient and cost-effective recovery of the adsorbent. These findings highlight the potential of CuFe2O4 nanoparticles, particularly PF600, for the effective and sustainable removal of Cd(II) ions from water. Full article
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Figure 1
<p>XRD analysis of the PF600 (<b>A</b>) and PF800 (<b>B</b>) products. Standard JCPDS No. 77-0010 (<b>C</b>).</p> Full article ">Figure 2
<p>EDX analysis of the PF600 (<b>A</b>) and PF800 (<b>B</b>) products.</p> Full article ">Figure 3
<p>FTIR analysis of the PF600 (<b>A</b>) and PF800 (<b>B</b>) products.</p> Full article ">Figure 4
<p>FE-SEM analysis of the PF600 (<b>A</b>) and PF800 (<b>B</b>) samples.</p> Full article ">Figure 5
<p>FE-SEM histograms of the PF600 (<b>A</b>) and PF800 (<b>B</b>) samples.</p> Full article ">Figure 6
<p>HR-TEM analysis of the PF600 (<b>A</b>) and PF800 (<b>B</b>) products.</p> Full article ">Figure 7
<p>The adsorption percentage of cadmium ions on the PF600 and PF800 products throughout a range of pH values (<b>A</b>). The point of zero charge (pH<sub>PZC</sub>) of the PF600 and PF800 products (<b>B</b>).</p> Full article ">Figure 8
<p>FE-SEM image of the PF600 sample after Cd(II) adsorption at magnifications of 15,000× (<b>A</b>) and 3000× (<b>B</b>).</p> Full article ">Figure 9
<p>FTIR spectrum of the PF600 sample after Cd(II) adsorption.</p> Full article ">Figure 10
<p>Impact of contact time on the adsorption percentage of cadmium ions by the PF800 and PF600 products.</p> Full article ">Figure 11
<p>Linear kinetic modeling of Cd(II) ions adsorption onto the PF800 and PF600 products by the pseudo-first-order (<b>A</b>) as well as the pseudo-second-order (<b>B</b>) kinetic plots.</p> Full article ">Figure 12
<p>Non-linear kinetic modeling of Cd(II) ion adsorption onto the PF800 and PF600 products by the pseudo-first-order (<b>A</b>) as well as the pseudo-second-order (<b>B</b>) kinetic plots.</p> Full article ">Figure 13
<p>Impact of temperature on the adsorption percentage of cadmium ions by the PF800 and PF600 products (<b>A</b>). The plot of ln L<sub>d</sub> versus 1/T (<b>B</b>).</p> Full article ">Figure 14
<p>Impact of adsorbent dosage on the adsorption percentage of cadmium ions by the PF800 and PF600 products.</p> Full article ">Figure 15
<p>Impact of initial Cd(II) concentration on the adsorption percentage of Cd(II) ions by the PF800 and PF600 samples.</p> Full article ">Figure 16
<p>Linear equilibrium modeling of Cd(II) ion adsorption onto the PF800 and PF600 products by the Langmuir (<b>A</b>) and the Freundlich (<b>B</b>) equilibrium plots.</p> Full article ">Figure 17
<p>Non-linear equilibrium modeling of Cd(II) ion adsorption onto the PF800 and PF600 products by the Langmuir (<b>A</b>) as well as the Freundlich (B) equilibrium plots.</p> Full article ">Figure 18
<p>Impact of reusability of the PF800 and PF800 products for the sorption of cadmium ions.</p> Full article ">Scheme 1
<p>Production of copper ferrite nanoparticles through the Pechini sol-gel process.</p> Full article ">Scheme 2
<p>Removal mechanism of cadmium ions by the synthesized copper ferrite nanoparticles.</p> Full article ">Scheme 3
<p>Practical steps for producing copper ferrite (CuFe<sub>2</sub>O<sub>4</sub>) nanoparticles using the Pechini sol-gel method.</p> Full article ">Scheme 4
<p>Experimental influences for studying the adsorption of Cd(II) ions by the PF600 and PF800 products.</p> Full article ">Scheme 5
<p>Assessing the regeneration and reusability of adsorbents in the removal of Cd(II) ions under optimal conditions.</p> Full article ">
13 pages, 2091 KiB  
Article
A Formal Synthesis of (+)-Hannokinol Using a Chiral Horner–Wittig Reagent
by Michael Tapera, Federica Borghi, Jan Lukas Mayer-Figge, Fabia Mittendorf, Ibrahim-Ethem Celik, Adrián Gómez-Suárez and Stefan F. Kirsch
Molecules 2024, 29(15), 3710; https://doi.org/10.3390/molecules29153710 - 5 Aug 2024
Viewed by 974
Abstract
Herein, we report a concise and efficient formal synthesis of (+)-hannokinol. Key to this new strategy is the use of a chiral Horner–Wittig reagent, readily available from 2-deoxy-D-ribose, to introduce the chiral 1,3-diol motif. Full article
(This article belongs to the Section Organic Chemistry)
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Scheme 1

Scheme 1
<p>(+)-Hannokinol: properties, synthetic routes, and our approach. (<b>A</b>) (+)-Hannokinol structure and importance. (<b>B</b>) Reported synthesis of (+)-Hannokinol [<a href="#B11-molecules-29-03710" class="html-bibr">11</a>]. (<b>C</b>) Our strategy for the synthyesis of (+)-Hannokinol using a chiral Horner-Wittig reagent.</p> Full article ">Scheme 2
<p>First approach towards the total synthesis of (+)-hannokinol using chiral Horner–Wittig reagent <b>7</b> and Heck coupling as key steps.</p> Full article ">Scheme 3
<p>Synthesis of key intermediate <b>4</b> using a chiral Horner–Wittig reagent and Heck coupling as key steps [<a href="#B11-molecules-29-03710" class="html-bibr">11</a>].</p> Full article ">
15 pages, 2677 KiB  
Article
Adsorption of Bichromate and Arsenate Anions by a Sorbent Based on Bentonite Clay Modified with Polyhydroxocations of Iron and Aluminum by the “Co-Precipitation” Method
by Bakytgul Kussainova, Gaukhar Tazhkenova, Ivan Kazarinov, Marina Burashnikova, Aisha Nurlybayeva, Gulnaziya Seitbekova, Saule Kantarbayeva, Nazgul Murzakasymova, Elvira Baibazarova, Dinara Altynbekova, Assem Shinibekova and Aidana Bazarkhankyzy
Molecules 2024, 29(15), 3709; https://doi.org/10.3390/molecules29153709 - 5 Aug 2024
Cited by 1 | Viewed by 968
Abstract
The physicochemical properties of natural bentonite and its sorbents were studied. It has been established the modification of natural bentonites using polyhydroxoxides of iron (III) (mod.1_Fe_5-c) and aluminum (III) (mod.1_Al_5-c) by the “co-precipitation” method led to changes in their chemical composition, structure, and [...] Read more.
The physicochemical properties of natural bentonite and its sorbents were studied. It has been established the modification of natural bentonites using polyhydroxoxides of iron (III) (mod.1_Fe_5-c) and aluminum (III) (mod.1_Al_5-c) by the “co-precipitation” method led to changes in their chemical composition, structure, and sorption properties. It was shown that modified sorbents based on natural bentonite are finely porous (nanostructured) objects with a predominance of pores of 1.5–8.0 nm in size. The modification of bentonite with iron (III) and aluminum compounds by the “co-precipitation” method also leads to an increase in the sorption capacity of the obtained sorbents with respect to bichromate and arsenate anions. A kinetic analysis showed that, at the initial stage, the sorption process was controlled by an external diffusion factor, that is, the diffusion of the sorbent from the solution to the liquid film on the surface of the sorbent. The sorption process then began to proceed in a mixed diffusion mode when it limited both the external diffusion factor and the intra-diffusion factor (diffusion of the sorbent to the active centers through the system of pores and capillaries). To clarify the contribution of the chemical stage to the rate of adsorption of bichromate and arsenate anions by the sorbents under study, kinetic curves were processed using equations of chemical kinetics (pseudo-first-order, pseudo-second-order, and Elovich models). It was found that the adsorption of the studied anions by the modified sorbents based on natural bentonite was best described by a pseudo-second-order kinetic model. The high value of the correlation coefficient for the Elovich model (R2 > 0.9) allows us to conclude that there are structural disorders in the porous system of the studied sorbents, and their surfaces can be considered heterogeneous. Considering that heterogeneous processes occur on the surface of the sorbent, it is natural that all surface properties (structure, chemical composition of the surface layer, etc.) play an important role in anion adsorption. Full article
(This article belongs to the Special Issue Zeolites and Porous Materials: Synthesis, Properties and Applications)
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Figure 1

Figure 1
<p>X-ray diffraction patterns of the examined sorbents derived from natural bentonite from the Pogodayevo deposit (Kazakhstan): 1—mod.1; 2—mod.1_Al_5-c; 3—mod.1_Fe_5-c, where <span class="html-fig-inline" id="molecules-29-03709-i001"><img alt="Molecules 29 03709 i001" src="/molecules/molecules-29-03709/article_deploy/html/images/molecules-29-03709-i001.png"/></span>—montmorillonite; □—α-cristobalite; ■—plagioclase.</p> Full article ">Figure 2
<p>Kinetic curves of the adsorption process of bichromate (<b>a</b>) and arsenate anions (<b>b</b>) by the studied modified sorbents in a neutral medium.</p> Full article ">Figure 2 Cont.
<p>Kinetic curves of the adsorption process of bichromate (<b>a</b>) and arsenate anions (<b>b</b>) by the studied modified sorbents in a neutral medium.</p> Full article ">Figure 3
<p>Adsorption isotherms in a neutral medium of (<b>a</b>) bichromate and (<b>b</b>) arsenate anions on the obtained sorbents.</p> Full article ">Figure 3 Cont.
<p>Adsorption isotherms in a neutral medium of (<b>a</b>) bichromate and (<b>b</b>) arsenate anions on the obtained sorbents.</p> Full article ">Figure 4
<p>Isotherms of adsorption of (<b>a</b>) bichromate and (<b>b</b>) arsenate anions by the studied sorbents, represented in inverse coordinates in accordance with the Langmuir Equation (3).</p> Full article ">Figure 5
<p>Dependence of –<span class="html-italic">ln</span>(1 − <span class="html-italic">F</span>) on t (spring diffusion model) during adsorption of bichromate and arsenate anions by bentonite and modified iron(III) and aluminum polyhydroxocations by bentonite-based sorbents: (<b>a</b>) bichromate anion; (<b>b</b>) arsenate anion.</p> Full article ">Figure 6
<p>Dependence of qt on <span class="html-italic">t</span><sup>0.5</sup> (internal diffusion model) during adsorption of bichromate and arsenate anions by bentonite and modified iron (III) and aluminum polyhydroxocations by bentonite-based sorbents: (<b>a</b>) bichromate anion; (<b>b</b>) arsenate anion.</p> Full article ">Figure 7
<p>Dependence of <span class="html-italic">ln</span>(<span class="html-italic">q<sub>e</sub></span> − <span class="html-italic">q<sub>t</sub></span>) on <span class="html-italic">t</span> (a pseudo-first-order kinetic model) during adsorption of bichromate and arsenate anions by bentonite and modified iron (III) and aluminum polyhydroxocations by bentonite-based sorbents: (<b>a</b>) bichromate anion; (<b>b</b>) arsenate anion.</p> Full article ">Figure 8
<p>Dependence of <span class="html-italic">t</span>/<span class="html-italic">q<sub>t</sub></span> on <span class="html-italic">t</span> (kinetic model of pseudo-second-order) during adsorption of bichromate and arsenate anions by bentonite and modified iron (III) and aluminum polyhydroxocations by bentonite-based sorbents: (<b>a</b>) bichromate anion; (<b>b</b>) arsenate anion.</p> Full article ">Figure 9
<p>Dependence of <span class="html-italic">t</span>/<span class="html-italic">q<sub>t</sub></span> on <span class="html-italic">t</span> (Elovich model) during adsorption of bichromate and arsenate anions by bentonite and modified iron (III) and aluminum polyhydroxocations by bentonite-based sorbents: (<b>a</b>) bichromate–anion (<b>b</b>) arsenate anion.</p> Full article ">
13 pages, 6204 KiB  
Article
Enhanced Fire Safety of Energy-Saving Foam by Self-Cleavage CO2 Pre-Combustion and Phosphorus Release Post-Combustion
by Fengyun Sun, Lijun Wang, Tiantian Gao, Yuanyuan Zhong and Kefa Ren
Molecules 2024, 29(15), 3708; https://doi.org/10.3390/molecules29153708 - 5 Aug 2024
Viewed by 840
Abstract
Rigid polyurethane foam (RPUF) is widely utilized in construction and rail transportation due to its lightweight properties and low thermal conductivity, contributing to energy conservation and emission reduction. However, the inherent flammability of RPUF presents significant challenges. Delaying the time to ignition and [...] Read more.
Rigid polyurethane foam (RPUF) is widely utilized in construction and rail transportation due to its lightweight properties and low thermal conductivity, contributing to energy conservation and emission reduction. However, the inherent flammability of RPUF presents significant challenges. Delaying the time to ignition and preventing flame spread post-combustion is crucial for ensuring sufficient evacuation time in the event of a fire. Based on this principle, this study explores the efficacy of using potassium salts as a catalyst to promote the self-cleavage of RPUF, generating substantial amounts of CO2, thereby reducing the local oxygen concentration and delaying ignition. Additionally, the inclusion of a reactive flame retardant (DFD) facilitates the release of phosphorus-oxygen free radicals during combustion, disrupting the combustion chain reaction and thus mitigating flame propagation. Moreover, potassium salt-induced catalytic carbonization and phosphorus derivative cross-linking enhance the condensed phase flame retardancy. Consequently, the combined application of potassium salts and DFD increases the limiting oxygen index (LOI) and reduces both peak heat release rate (PHRR) and total heat release (THR). Importantly, the incorporation of these additives does not compromise the compressive strength or thermal insulation performance of RPUF. This integrated approach offers a new and effective strategy for the development of flame retardant RPUF. Full article
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<p>(<b>a</b>) <sup>1</sup>H NMR and (<b>b</b>) <sup>31</sup>P NMR spectra of DFD in DMSO-d6.</p> Full article ">Figure 2
<p>FTIR spectrum of DFD.</p> Full article ">Figure 3
<p>The apparent density and compressive strength of RPUF and flame-retardant RPUF.</p> Full article ">Figure 4
<p>The SEM images of RPUF, RPUF1, RPUF2, RPUF3 and RPUF4, along with their average cell sizes (the pore diameter cannot be measured due to the open pore structure of RPUF1).</p> Full article ">Figure 5
<p>(<b>a</b>) TGA and (<b>b</b>) DTG curves of RPUF and flame-retardant RPUFs in N<sub>2</sub>.</p> Full article ">Figure 6
<p>(<b>a</b>) HRR and (<b>b</b>) THR of RPUFs and flame-retardant RPUFs.</p> Full article ">Figure 7
<p>TG-FTIR spectra of (<b>a</b>) RPUF and (<b>b</b>) RPUF3.</p> Full article ">Figure 8
<p>FTIR spectra of the residues after combustion of RPUF and RPUF3.</p> Full article ">Figure 9
<p>Pseudo-color thermal images of (<b>a</b>) RPUF and (<b>b</b>) RPUF3.</p> Full article ">Scheme 1
<p>Schematic diagram of flame-retardant mechanism.</p> Full article ">Scheme 2
<p>The synthesis route of DFD.</p> Full article ">
11 pages, 3808 KiB  
Article
Gold Nanoparticle Mesoporous Carbon Composite as Catalyst for Hydrogen Evolution Reaction
by Erik Biehler, Qui Quach and Tarek M. Abdel-Fattah
Molecules 2024, 29(15), 3707; https://doi.org/10.3390/molecules29153707 - 5 Aug 2024
Viewed by 908
Abstract
Increased environmental pollution and the shortage of the current fossil fuel energy supply has increased the demand for eco-friendly energy sources. Hydrogen energy has become a potential solution due to its availability and green combustion byproduct. Hydrogen feedstock materials like sodium borohydride (NaBH [...] Read more.
Increased environmental pollution and the shortage of the current fossil fuel energy supply has increased the demand for eco-friendly energy sources. Hydrogen energy has become a potential solution due to its availability and green combustion byproduct. Hydrogen feedstock materials like sodium borohydride (NaBH4) are promising sources of hydrogen; however, the rate at which the hydrogen is released during its reaction with water is slow and requires a stable catalyst. In this study, gold nanoparticles were deposited onto mesoporous carbon to form a nano-composite catalyst (AuNP-MCM), which was then characterized via transmission electron microscopy (TEM), powder X-ray diffraction (P-XRD), and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). The composite’s catalytic ability in a hydrogen evolution reaction was tested under varying conditions, including NaBH4 concentration, pH, and temperature, and it showed an activation of energy of 30.0 kJ mol−1. It was determined that the optimal reaction conditions include high NaBH4 concentrations, lower pH, and higher temperatures. This catalyst, with its stability and competitively low activation energy, makes it a promising material for hydrogen generation. Full article
(This article belongs to the Special Issue Two-Dimensional Materials: From Synthesis to Applications)
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<p>TEM images of the AuNP-MCM catalyst at scales of (<b>a</b>) 200 nm, (<b>b</b>) 100 nm, (<b>c</b>) 20 nm, and (<b>d</b>) 5 nm.</p> Full article ">Figure 2
<p>SEM/EDX analysis with (<b>a</b>) the SEM micrograph of the AuNP-MCM catalyst at scales of 2 µm and (<b>b</b>) the EDS spectrum correlating to the indicated gold nanoparticle.</p> Full article ">Figure 3
<p>P-XRD spectra for the MCM and AuNP-MCM. The asterisks highlight the location of important peaks.</p> Full article ">Figure 4
<p>Volume of hydrogen generated over time in the hydrogen evolution reactions catalyzed by AuNP-MCM at different NaBH<sub>4</sub> concentrations (793 µmol, 952 µmol, and 1057 µmol).</p> Full article ">Figure 5
<p>Volume of hydrogen generated over time in the hydrogen evolution reactions catalyzed by AuNP-MCM at different pHs (pH 6, pH 7, and pH 8).</p> Full article ">Figure 6
<p>Volume of hydrogen generated over time in the hydrogen evolution reactions catalyzed by AuNP-MCM at different temperatures (273 K, 288 K, 295 K, and 303 K).</p> Full article ">Figure 7
<p>Arrhenius plot for calculating the activation energy of a hydrogen generation reaction with the AuNP-MCM catalyst.</p> Full article ">Figure 8
<p>Testing reusability of the AuNP-MCM catalyst after five consecutive hydrogen generation reactions.</p> Full article ">Scheme 1
<p>Proposed mechanism for the hydrolysis of NaBH<sub>4</sub> while catalyzed by AuNP-MCMs.</p> Full article ">
21 pages, 3151 KiB  
Article
Establishing the Thermodynamic Cards of Dipine Models’ Oxidative Metabolism on 21 Potential Elementary Steps
by Guang-Bin Shen, Shun-Hang Gao, Yan-Wei Jia, Xiao-Qing Zhu and Bao-Chen Qian
Molecules 2024, 29(15), 3706; https://doi.org/10.3390/molecules29153706 - 5 Aug 2024
Viewed by 943
Abstract
Dipines are a type of important antihypertensive drug as L-calcium channel blockers, whose core skeleton is the 1,4-dihydropyridine structure. Since the dihydropyridine ring is a key structural factor for biological activity, the thermodynamics of the aromatization dihydropyridine ring is a significant feature parameter [...] Read more.
Dipines are a type of important antihypertensive drug as L-calcium channel blockers, whose core skeleton is the 1,4-dihydropyridine structure. Since the dihydropyridine ring is a key structural factor for biological activity, the thermodynamics of the aromatization dihydropyridine ring is a significant feature parameter for understanding the mechanism and pathways of dipine metabolism in vivo. Herein, 4-substituted-phenyl-2,6-dimethyl-3,5-diethyl-formate-1,4-dihydropyridines are refined as the structurally closest dipine models to investigate the thermodynamic potential of dipine oxidative metabolism. In this work, the thermodynamic cards of dipine models’ aromatization on 21 potential elementary steps in acetonitrile have been established. Based on the thermodynamic cards, the thermodynamic properties of dipine models and related intermediates acting as electrons, hydrides, hydrogen atoms, protons, and two hydrogen ions (atoms) donors are discussed. Moreover, the thermodynamic cards are applied to evaluate the redox properties, and judge or reveal the possible oxidative mechanism of dipine models. Full article
(This article belongs to the Section Organic Chemistry)
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Graphical abstract
Full article ">Figure 1
<p>The chemical structures of dipines and refined dipine models (DH<sub>2</sub>).</p> Full article ">Figure 2
<p>(<b>a</b>) The oxidative metabolism process of Nifedipine in vivo. (<b>b</b>) Some common oxidoreductases in vivo.</p> Full article ">Figure 3
<p>Thermodynamic cards of dipine model (DH<sub>2</sub>) aromatization on 21 potential elementary steps during oxidative metabolism.</p> Full article ">Figure 4
<p>The p<span class="html-italic">K</span><sub>a</sub> of DH<sup>+</sup> and YH<sup>+</sup>, along with the p<span class="html-italic">K</span><sub>a</sub> of common organic acids in acetonitrile.</p> Full article ">Figure 5
<p>Oxidation potentials (<span class="html-italic">E</span><sub>ox</sub>) of DH<sub>2</sub>, DH<sup>−</sup>, DH<sup>•</sup>, and D<sup>•−</sup>, as well as the reduction potentials (<span class="html-italic">E</span><sub>red</sub>) of common coenzyme models and electron acceptors in acetonitrile (V vs. Fc).</p> Full article ">Figure 6
<p>Hydricities of DH<sub>2</sub>, and DH<sup>−</sup>, as well as H<sup>−</sup>-affinities of common coenzyme models and hydride acceptors in acetonitrile (kcal/mol).</p> Full article ">Figure 7
<p>Thermodynamic hydrogen-atom-donating abilities of DH<sub>2</sub>, DH<sup>−</sup>, DH<sub>2</sub><sup>•+</sup>, DH<sup>•</sup>, and DH’<sup>•</sup>, as well as hydrogen atom affinities of common radicals and coenzyme models in acetonitrile (kcal/mol).</p> Full article ">Figure 8
<p>Thermodynamic proton-donating abilities of DH<sub>2</sub>, DH<sup>+</sup>, DH<sub>2</sub><sup>•+</sup>, and DH’<sup>•</sup>, as well as proton-donating abilities of common acids in acetonitrile (kcal/mol).</p> Full article ">Figure 9
<p>Thermodynamic abilities of DH<sub>2</sub> and common hydrogen carriers releasing two hydrogen ions (H<sup>−</sup> + H<sup>+</sup>) in the red brackets, releasing two hydrogen atoms (2H<sup>•</sup>) in the purple brackets, and releasing H<sub>2</sub> in the blue brackets in acetonitrile (kcal/mol).</p> Full article ">Figure 10
<p>Thermodynamic abilities of five possible elementary steps for DH<sub>2</sub> oxidation.</p> Full article ">Figure 11
<p>Thermodynamic analysis of possible oxidative process for intermediate DH<sub>2</sub><sup>•+</sup>.</p> Full article ">Figure 12
<p>Thermodynamic card of iAsc accepting two hydrogen ions (atoms) on nine potential elementary steps.</p> Full article ">Figure 13
<p>Thermodynamic analysis platform of elementary steps for the redox process between 3H<sub>2</sub> and iAsc without any catalyst in acetonitrile.</p> Full article ">
13 pages, 3585 KiB  
Article
Anti-Inflammatory Effect of Xanthones from Hypericum beanii on Macrophage RAW 264.7 Cells through Reduced NO Production and TNF-α, IL-1β, IL-6, and COX-2 Expression
by Wei Ma, Fu-Cai Ren, Xue-Ru Wang and Ning Li
Molecules 2024, 29(15), 3705; https://doi.org/10.3390/molecules29153705 - 5 Aug 2024
Viewed by 1166
Abstract
Hypericum beanii N. Robson, a perennial upright herb, predominantly inhabits temperate regions. This species has been utilized for the treatment of various inflammation-related diseases. One new xanthone 3,7-dihydroxy-1,6-dimethoxyxanthone (1) and twenty-three known xanthones (2–24) were isolated from [...] Read more.
Hypericum beanii N. Robson, a perennial upright herb, predominantly inhabits temperate regions. This species has been utilized for the treatment of various inflammation-related diseases. One new xanthone 3,7-dihydroxy-1,6-dimethoxyxanthone (1) and twenty-three known xanthones (2–24) were isolated from the aerial parts of H. beanii. The structure of the new compound was determined based on high-resolution electrospray ionization mass spectroscopy (HR-ESIMS), nuclear magnetic resonance (NMR), Infrared Spectroscopy (IR), ultraviolet spectrophotometry (UV) spectroscopic data. The anti-inflammatory effects of all the isolates were assessed by measuring the inhibitory effect on nitric oxide (NO) production in LPS-stimulated RAW 264.7 macrophages. Compounds 3,4-dihydroxy-2-methoxyxanthone (15), 1,3,5,6-tetrahydroxyxanthone (19), and 1,3,6,7-tetrahydroxyxanthone (22) exhibited significant anti-inflammatory effects at a concentration of 10 μM with higher potency compared to the positive control quercetin. Furthermore, compounds 15, 19, and 22 reduced inducible NO synthase (iNOS), tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), IL-6, and cyclooxygenase 2 (COX-2) mRNA expression in the LPS-stimulated RAW 264.7 macrophages, suggesting that these compounds may mitigate the synthesis of the aforementioned molecules at the transcriptional level, provisionally confirming their anti-inflammatory efficacy. Full article
(This article belongs to the Special Issue Isolation, Identification and Application of Biologically Active Natural Products—Second Edition)
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<p>Structures of compounds <b>1</b>–<b>24</b>.</p> Full article ">Figure 2
<p>HMBC (<span class="html-fig-inline" id="molecules-29-03705-i001"><img alt="Molecules 29 03705 i001" src="/molecules/molecules-29-03705/article_deploy/html/images/molecules-29-03705-i001.png"/></span>) of compound <b>1</b>.</p> Full article ">Figure 3
<p>The cytotoxic effects of compounds (<b>1</b>–<b>24</b>) on the RAW 264.7 macrophage cells. Values are the mean ± SEM, n = 3. (Compared to the control group **<span class="html-italic">* p</span> &lt; 0.001, ** <span class="html-italic">p</span> &lt; 0.01, or * <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 4
<p>The inhibitory effects of <b>1</b>–<b>24</b> against LPS-induced NO production in RAW264.7 macrophages. Mean ± SEM of three replicates is shown. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001 with the LPS group. <sup>###</sup> <span class="html-italic">p</span> &lt; 0.001 with the CON (control) group.</p> Full article ">Figure 5
<p>Concentrations of NO and mRNA expression of iNOS in RAW 264.7 cells treated with compounds <b>15</b>, <b>19</b>, and <b>22</b>. Values are the mean ± SEM, n = 3. (Compared to the control group <sup>###</sup> <span class="html-italic">p</span> &lt; 0.001. Compared to the LPS group, *** <span class="html-italic">p</span> &lt; 0.001, ** <span class="html-italic">p</span> &lt; 0.01, or * <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 6
<p>Concentrations of TNF-<span class="html-italic">α</span>, IL-1<span class="html-italic">β</span>, and IL-6 in RAW 264.7 cells with compounds <b>15</b>, <b>19</b>, and <b>22</b> treatments. Values are the mean ± SEM, n = 3. (Compared to the control group <sup>###</sup> <span class="html-italic">p</span> &lt; 0.001. Compared to the LPS group, *** <span class="html-italic">p</span> &lt; 0.001, ** <span class="html-italic">p</span> &lt; 0.01).</p> Full article ">Figure 7
<p>mRNA expression of pro-inflammatory cytokines TNF-<span class="html-italic">α</span>, IL-1<span class="html-italic">β</span>, and IL-6 in RAW 264.7 cells treated with compounds <b>15</b>, <b>19</b>, and <b>22</b>. Values are the mean ± SEM, n = 3. (Compared to the control group <sup>###</sup> <span class="html-italic">p</span> &lt; 0.001. Compared to the LPS group, *** <span class="html-italic">p</span> &lt; 0.001, ** <span class="html-italic">p</span> &lt; 0.01, or * <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 8
<p>COX-2 mRNA expression in RAW 264.7 cells treated with compounds <b>15</b>, <b>19</b>, and <b>22</b>. Values are the mean ± SEM, n = 3. (Compared to the control group <sup>###</sup> <span class="html-italic">p</span> &lt; 0.001. Compared to the LPS group, *** <span class="html-italic">p</span> &lt; 0.001 or ** <span class="html-italic">p</span> &lt; 0.01).</p> Full article ">
16 pages, 1534 KiB  
Review
Recent Progress in Photothermal, Photodynamic and Sonodynamic Cancer Therapy: Through the cGAS-STING Pathway to Efficacy-Enhancing Strategies
by Kelan Fang, Huiling Zhang, Qinghong Kong, Yunli Ma, Tianchan Xiong, Tengyao Qin, Sanhua Li and Xinting Zhu
Molecules 2024, 29(15), 3704; https://doi.org/10.3390/molecules29153704 - 5 Aug 2024
Viewed by 1779
Abstract
Photothermal, photodynamic and sonodynamic cancer therapies offer opportunities for precise tumor ablation and reduce side effects. The cyclic guanylate adenylate synthase-stimulator of interferon genes (cGAS-STING) pathway has been considered a potential target to stimulate the immune system in patients and achieve a sustained [...] Read more.
Photothermal, photodynamic and sonodynamic cancer therapies offer opportunities for precise tumor ablation and reduce side effects. The cyclic guanylate adenylate synthase-stimulator of interferon genes (cGAS-STING) pathway has been considered a potential target to stimulate the immune system in patients and achieve a sustained immune response. Combining photothermal, photodynamic and sonodynamic therapies with cGAS-STING agonists represents a newly developed cancer treatment demonstrating noticeable innovation in its impact on the immune system. Recent reviews have concentrated on diverse materials and their function in cancer therapy. In this review, we focus on the molecular mechanism of photothermal, photodynamic and sonodynamic cancer therapies and the connected role of cGAS-STING agonists in treating cancer. Full article
(This article belongs to the Special Issue Nanomaterials in Cancer Therapy: Synthesis, Mechanisms, and Applications)
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Graphical abstract
Full article ">Figure 1
<p>The principles and results of two synergistic therapies of photothermal therapy and STING agonist and their effect on tumor in vivo. (<b>A</b>) Schematic illustration of a synergistic therapy of the photothermal transduction agent Indocyanine green (ICG) with the STING agonist DMXAA [<a href="#B30-molecules-29-03704" class="html-bibr">30</a>]. (<b>B</b>) Temperature development after the injection of ICG of different forms in vivo, the color represents different temperature, and have been shown in the legend [<a href="#B30-molecules-29-03704" class="html-bibr">30</a>]. (<b>C</b>) Tumor growth in vivo after photothermal therapy and a STING agonist alone and synergistic therapy. * <span class="html-italic">p</span> &lt; 0.05 vs. control, *** <span class="html-italic">p</span> &lt; 0.001 vs. control [<a href="#B30-molecules-29-03704" class="html-bibr">30</a>]. Copyright 2023 American Chemical Society. (<b>D</b>) Schematic illustration of a synergistic therapy of the photothermal transduction agent croconaine dye with the STING agonist diABZIs using SAPTNs [<a href="#B60-molecules-29-03704" class="html-bibr">60</a>]. (<b>E</b>) The images of drug distribution in vivo after the injection of SAPTNs with irradiation alone or with irradiation and the myeloperoxidase inhibitor PF1355, the color represents different temperature and the connection can be seen in the legend [<a href="#B60-molecules-29-03704" class="html-bibr">60</a>]. (<b>F</b>) Average volume of tumor reinjected in vivo after no treatment in the untreated group and SAPTNs plus PTT group treated by a synergistic therapy of PTT and a STING agonist using SAPTNs. *** <span class="html-italic">p</span> &lt; 0.001 vs. control [<a href="#B60-molecules-29-03704" class="html-bibr">60</a>]. Copyright 2024 John Wiley and Sons.</p> Full article ">Figure 2
<p>The principle and result of two synergistic therapies of photodynamic therapy and STING agonist on primary tumors and distant tumors in vivo. (<b>A</b>) Schematic illustration of a synergistic therapy of the photosensitizer Meso-tetra(carboxyphenyl) porphyrin (TCPP) and STING agonist SR-717 [<a href="#B96-molecules-29-03704" class="html-bibr">96</a>]. Volume growth of a primary tumor (<b>B</b>) and distant tumor (<b>C</b>) when treated with a photodynamic material polymeric metal−organic framework (PMOF) and SR-717 alone and a synergistic therapy of PDT and a STING agonist by using a nanoparticles called SR@PMOF combining PMOF and a STING agonist (SR-717), without light irradiation (-L) or with light irradiation (+L). ** <span class="html-italic">p</span> &lt; 0.01 vs. control, *** <span class="html-italic">p</span> &lt; 0.001 vs. control [<a href="#B96-molecules-29-03704" class="html-bibr">96</a>]. Copyright 2023 American Chemical Society. (<b>D</b>) Schematic illustration of a synergistic therapy of a nanoparticle named GM@P, consisting of a hydrophobic shell encapsulating the photosensitizer MHI148 and the STING agonist 2′3′-cGAMP [<a href="#B31-molecules-29-03704" class="html-bibr">31</a>]. Tumor growth of primary tumors (<b>E</b>) and distant tumors (<b>F</b>) after photothermal therapy using a nanoparticle with MHI148 (M@P) alone without irradiation (Group B: M@P), with irradiation (Group D: M@P + light irradiation), with a free STING agonist and irradiation (group E: M@P + light irradiation + 2′3′-cGAMP), a STING agonist alone (Group C: 2′3′-cGAMP), and a synergistic therapy of GM@P (Group F: GM@P + light irradiation) and a control group (Group A). * <span class="html-italic">p</span> &lt; 0.05 vs. control, ** <span class="html-italic">p</span> &lt; 0.01 vs. control [<a href="#B31-molecules-29-03704" class="html-bibr">31</a>]. Copyright 2024 American Chemical Society.</p> Full article ">Figure 3
<p>The principle of a synergistic therapy of sonodynamic therapy and a cGAS-STING agonist using a material consisting of triphenyl phosphonium (TPP) and sonodynamic cobalt organic frame-work nanosheets (TPP@CoTCPP) and some experimental results. (<b>A</b>) Graphic illustration of TPP@CoTCPP [<a href="#B111-molecules-29-03704" class="html-bibr">111</a>]. (<b>B</b>) Comparison of the volume of ipsilateral and contralateral tumor in vivo in different groups treated by sonodynamic therapy and a STING agonist alone and a synergistic therapy of sonodynamic therapy and a cGAS-STING agonist. ns indicates not significant, ** <span class="html-italic">p</span> &lt; 0.01 vs. control [<a href="#B111-molecules-29-03704" class="html-bibr">111</a>]. (<b>C</b>) Tumor volume of sonodynamic therapy alone and synergistic therapy [<a href="#B111-molecules-29-03704" class="html-bibr">111</a>]. Copyright 2023 Elsevier.</p> Full article ">
9 pages, 1030 KiB  
Article
Synthesis of N-(3-Acyloxyacyl)glycines, Small Molecules with Potential Role in Gut Microbiome-Endocannabinoidome Communication
by Rosaria Villano and Vincenzo Di Marzo
Molecules 2024, 29(15), 3703; https://doi.org/10.3390/molecules29153703 - 5 Aug 2024
Viewed by 1464
Abstract
The synthesis of some N-(3-acyloxyacyl)glycines, an interesting class of bioactive gut microbiota metabolites, is described. This procedure involves seven reaction steps using the commercially available Meldrum’s acid to obtain highly pure products, in normal or deuterated form. The key point of the [...] Read more.
The synthesis of some N-(3-acyloxyacyl)glycines, an interesting class of bioactive gut microbiota metabolites, is described. This procedure involves seven reaction steps using the commercially available Meldrum’s acid to obtain highly pure products, in normal or deuterated form. The key point of the synthetic strategy was the use of commendamide t-butyl ester as a synthetic intermediate, a choice that allowed the removal of the protecting group at the end of the synthetic procedure without degrading of the other ester bond present in the molecule. The developed synthetic sequence is particularly simple, uses readily available reagents and involves a limited number of purifications by chromatographic column, with a reduction in the volume of solvent and energy used. Full article
(This article belongs to the Section Organic Chemistry)
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<p>Some bioactive <span class="html-italic">N</span>-(3-acyloxyacyl)glycines reported in the literature.</p> Full article ">Scheme 1
<p>Synthesis of normal and deuterated commendamide <b>11</b> [<a href="#B17-molecules-29-03703" class="html-bibr">17</a>].</p> Full article ">Scheme 2
<p>Attempted sequence for the synthesis of <span class="html-italic">N</span>-(3-acyloxyacyl)glycines <b>14</b>, starting from the intermediates <b>10</b>.</p> Full article ">Scheme 3
<p>Modified synthetic sequence for the production of <span class="html-italic">N</span>-(3-acyloxyacyl)glycines <b>14</b>.</p> Full article ">
14 pages, 2152 KiB  
Article
Experimental and Modeling Study on Methane Hydrate Equilibrium Conditions in the Presence of Inorganic Salts
by Qiang Fu, Mingqiang Chen, Weixin Pang, Zhen Xu, Zengqi Liu, Huiyun Wen and Xin Lei
Molecules 2024, 29(15), 3702; https://doi.org/10.3390/molecules29153702 - 5 Aug 2024
Viewed by 843
Abstract
The aim of this study was to determine the influence of four inorganic salts, KCl, NaCl, KBr and NaBr, on the thermodynamic conditions of methane hydrate formation. In order to achieve this, the vapor–liquid water-hydrate (VLWH) equilibrium conditions of methane (CH [...] Read more.
The aim of this study was to determine the influence of four inorganic salts, KCl, NaCl, KBr and NaBr, on the thermodynamic conditions of methane hydrate formation. In order to achieve this, the vapor–liquid water-hydrate (VLWH) equilibrium conditions of methane (CH4) hydrate were measured in the temperature range of 274.15 K–282.15 K by the isothermal pressure search method. The results demonstrated that, in comparison with deionized water, the four inorganic salts exhibited a significant thermodynamic inhibition on CH4 hydrate. Furthermore, the inhibitory effect of Na+ on methane hydrate is more pronounced than that of K+, where there is no discernible difference between Cl− and Br−. The dissociation enthalpy (∆Hdiss) of CH4 hydrate in the four inorganic salt solutions is comparable to that of deionized water, indicating that the inorganic salt does not participate in the formation of hydrate crystals. The Chen–Guo hydrate model and N–NRTL–NRF activity model were employed to forecast the equilibrium conditions of CH4 hydrate in electrolyte solution. The absolute relative deviation (AARD) between the predicted and experimental values were 1.24%, 1.08%, 1.18% and 1.21%, respectively. The model demonstrated satisfactory universality and accuracy. This study presents a novel approach to elucidating the mechanism and model prediction of inorganic salt inhibition of hydrate. Full article
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Graphical abstract

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<p>Thermodynamic consistency of CH<sub>4</sub> hydrate formation conditions in the presence of inorganic salts. (<b>a</b>) VL<sub>W</sub>H of CH<sub>4</sub> hydrate in different inorganic salt solutions. (<b>b</b>) Linear relationship between ln(<span class="html-italic">P</span>) and 1/<span class="html-italic">T</span> in different inorganic salt solutions. (<b>c</b>) The result of linear consistency assessment. (<b>d</b>) The result of <math display="inline"><semantics> <mrow> <mo>∆</mo> <msub> <mrow> <mi>H</mi> </mrow> <mrow> <mi>d</mi> <mi>i</mi> <mi>s</mi> <mi>s</mi> </mrow> </msub> </mrow> </semantics></math> consistency assessment. (<b>e</b>) The values of <math display="inline"><semantics> <mrow> <mstyle scriptlevel="0" displaystyle="true"> <mfrac> <mrow> <mo>∆</mo> <mi>T</mi> </mrow> <mrow> <msub> <mrow> <mi>T</mi> </mrow> <mrow> <mn>0</mn> </mrow> </msub> <mi>T</mi> </mrow> </mfrac> </mstyle> </mrow> </semantics></math> in different inorganic salt solutions. (<b>f</b>) The result of <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>a</mi> </mrow> <mrow> <mi>w</mi> </mrow> </msub> </mrow> </semantics></math> consistency assessment.</p> Full article ">Figure 2
<p>∆P values of CH<sub>4</sub> hydrate in the presence of inorganic salts at different conditions.</p> Full article ">Figure 3
<p>Experimental and predicted results of VL<sub>W</sub>H equilibrium conditions in different solutions. (<b>a</b>) Experimental and predicted results in KCl and NaCl solutions. (<b>b</b>) Experimental and predicted results in KBr and NaBr solutions.</p> Full article ">Figure 4
<p>Schematic diagram of the experimental setup.</p> Full article ">
16 pages, 3164 KiB  
Article
Synthesis and Evaluation of Chloride-Substituted Ramalin Derivatives for Alzheimer’s Disease Treatment
by Tai Kyoung Kim, Yongeun Cho, Jaewon Kim, Jeongmi Lee, Ju-Mi Hong, Heewon Cho, Jun-Sik Kim, Yeongyeong Lee, Kyung Hee Kim, Il-Chan Kim, Se Jong Han, Hyuncheol Oh, Dong-Gyu Jo and Joung Han Yim
Molecules 2024, 29(15), 3701; https://doi.org/10.3390/molecules29153701 - 5 Aug 2024
Cited by 1 | Viewed by 1038
Abstract
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder marked by the accumulation of amyloid-beta plaques and hyperphosphorylated tau proteins, leading to cognitive decline and neuronal death. However, despite extensive research, there are still no effective treatments for this condition. In this study, a [...] Read more.
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder marked by the accumulation of amyloid-beta plaques and hyperphosphorylated tau proteins, leading to cognitive decline and neuronal death. However, despite extensive research, there are still no effective treatments for this condition. In this study, a series of chloride-substituted Ramalin derivatives is synthesized to optimize their antioxidant, anti-inflammatory, and their potential to target key pathological features of Alzheimer’s disease. The effect of the chloride position on these properties is investigated, specifically examining the potential of these derivatives to inhibit tau aggregation and beta-site amyloid precursor protein cleaving enzyme 1 (BACE-1) activity. Our findings demonstrate that several derivatives, particularly RA-3Cl, RA-4Cl, RA-26Cl, RA-34Cl, and RA-35Cl, significantly inhibit tau aggregation with inhibition rates of approximately 50%. For BACE-1 inhibition, Ramalin and RA-4Cl also significantly decrease BACE-1 expression in N2a cells by 40% and 38%, respectively, while RA-23Cl and RA-24Cl showed inhibition rates of 30% and 35% in SH-SY5Y cells. These results suggest that chloride-substituted Ramalin derivatives possess promising multifunctional properties for AD treatment, warranting further investigation and optimization for clinical applications. Full article
(This article belongs to the Section Organic Chemistry)
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<p>Structure of Ramalin chloride derivatives.</p> Full article ">Figure 2
<p>Effects of Ramalin and its chloride derivatives on inflammation. (<b>A</b>) Western blot representative images of NLRP3, COX-2, and β-Actin. (<b>B</b>,<b>C</b>) Quantification data of (<b>B</b>) NLRP3, and (<b>C</b>) COX-2 in (<b>A</b>). The relative protein expression was normalized to β-Actin. Data are shown as mean ± SD.</p> Full article ">Figure 3
<p>Anti-inflammatory activity and cell viability of Ramalin and its chloride derivatives.</p> Full article ">Figure 3 Cont.
<p>Anti-inflammatory activity and cell viability of Ramalin and its chloride derivatives.</p> Full article ">Figure 4
<p>Effects of Ramalin and its chloride derivatives on BACE-1 regulation. (<b>A</b>) Western blot representative images of BACE-1 and β-Actin using N2a. (<b>B</b>) Quantification data of BACE-1 in (<b>A</b>). (<b>C</b>) Western blot representative images of BACE-1 and β-Actin using SH-SY5Y. (<b>D</b>) Quantification data of BACE-1 in (<b>C</b>). The relative expression was normalized to β-Actin. Data are shown as mean ± SD. * <span class="html-italic">p</span> &lt; 0.05.</p> Full article ">Figure 5
<p>Tau inhibition activity assay of Ramalin and its chloride derivatives. Data are shown as mean ± SD. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.005.</p> Full article ">Scheme 1
<p>Scheme showing the synthesis of RA-23Cl using palladium.</p> Full article ">Scheme 2
<p>Scheme showing the synthesis of Ramalin chloride HCl salt derivatives.</p> Full article ">
13 pages, 3706 KiB  
Article
Signal-On Detection of Caspase-3 with Methylene Blue-Loaded Metal-Organic Frameworks as Signal Reporters
by Yaliang Huang, Jiaqiang Wang, Yirui Xu, Jiwen Zhang and Ning Xia
Molecules 2024, 29(15), 3700; https://doi.org/10.3390/molecules29153700 - 5 Aug 2024
Cited by 1 | Viewed by 901
Abstract
In this work, we report on an electrochemical method for the signal-on detection of caspase-3 and the evaluation of apoptosis based on the biotinylation reaction and the signal amplification of methylene blue (MB)-loaded metal–organic frameworks (MOFs). Zr-based UiO-66-NH2 MOFs were used as [...] Read more.
In this work, we report on an electrochemical method for the signal-on detection of caspase-3 and the evaluation of apoptosis based on the biotinylation reaction and the signal amplification of methylene blue (MB)-loaded metal–organic frameworks (MOFs). Zr-based UiO-66-NH2 MOFs were used as the nanocarriers to load electroactive MB molecules. Recombinant hexahistidine (His6)-tagged streptavidin (rSA) was attached to the MOFs through the coordination interaction between the His6 tag in rSA and the metal ions on the surface of the MOFs. The acetylated peptide substrate Ac-GDEVDGGGPPPPC was immobilized on the gold electrode. In the presence of caspase-3, the peptide was specifically cleaved, leading to the release of the Ac-GDEVD sequence. A N-terminal amine group was generated and then biotinylated in the presence of biotin-NHS. Based on the strong interaction between rSA and biotin, rSA@MOF@MB was captured by the biotinylated peptide-modified electrode, producing a significantly amplified electrochemical signal. Caspase-3 was sensitively determined with a linear range from 0.1 to 25 pg/mL and a limit of detection down to 0.04 pg/mL. Further, the active caspase-3 in apoptosis inducer-treated HeLa cells was further quantified by this method. The proposed signal-on biosensor is compatible with the complex biological samples and shows great potential for apoptosis-related diagnosis and the screening of caspase-targeting drugs. Full article
(This article belongs to the Special Issue Metal Organic Frameworks (MOFs) for Sensing Applications)
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<p>SEM images of (<b>A</b>) UiO-66-NH<sub>2</sub> MOF and (<b>B</b>) MOF@MB. (<b>C</b>) XRD patterns of UiO-66-NH<sub>2</sub> MOF (black curve) and MOF@MB (red curve). (<b>D</b>) UV–vis absorption spectra of MB (black curve), UiO-66-NH<sub>2</sub> MOF (red curve), and MOF@MB (blue curve). The inset in panel A shows the size distribution of the UiO-66-NH<sub>2</sub> MOF.</p> Full article ">Figure 2
<p>BET analysis of UiO-66-NH<sub>2</sub> MOF and MOF@MB.</p> Full article ">Figure 3
<p>DPV responses corresponding to the peptide-modified sensing electrode after treatment by biotin-NHS + rSA@MOF@MB (<b>a</b>), caspase-3 + biotin-NHS + rSA@MOF@MB (<b>b</b>), and caspase-3 + rSA@MOF@MB (<b>c</b>).</p> Full article ">Figure 4
<p>The optimized times for peptide modification (<b>A</b>) and proteolysis (<b>B</b>).</p> Full article ">Figure 5
<p>(<b>A</b>) DPV responses of the electrochemical biosensor at different concentrations of caspase-3 (from top to bottom: 0, 0.1, 1, 5, 10, 25, 50, and 100 pg/mL). (<b>B</b>) The relationship between peak current and caspase-3 concentration. The inset shows the linear portion of the fitting curve.</p> Full article ">Figure 6
<p>DPV responses of the electrochemical biosensor for the detection of different samples. The concentrations of caspase-3, inhibitor, BSA, thrombin, and trypsin were 25 pg/mL, 50 pM, 10 ng/mL, 1 ng/mL, and 1 ng/mL, respectively.</p> Full article ">Figure 7
<p>The relationship between peak current and inhibitor concentration for the assay of 25 pg/mL caspase-3.</p> Full article ">Figure 8
<p>The relationship between peak current and cell number for the assays of caspase-3 in HeLa cells with and without treatment by STS.</p> Full article ">Scheme 1
<p>A schematic illustration of the preparation of rSA@MOF@MB and the principle for the electrochemical detection of caspase-3.</p> Full article ">
19 pages, 6568 KiB  
Article
Quantitative Analysis of Pb in Soil Using Laser-Induced Breakdown Spectroscopy Based on Signal Enhancement of Conductive Materials
by Shefeng Li, Qi Zheng, Xiaodan Liu, Peng Liu and Long Yu
Molecules 2024, 29(15), 3699; https://doi.org/10.3390/molecules29153699 - 5 Aug 2024
Viewed by 872
Abstract
Studying efficient and accurate soil heavy-metal detection technology is of great significance to establishing a modern system for monitoring soil pollution, early warning and risk assessment, which contributes to the continuous improvement of soil quality and the assurance of food safety. Laser-induced breakdown [...] Read more.
Studying efficient and accurate soil heavy-metal detection technology is of great significance to establishing a modern system for monitoring soil pollution, early warning and risk assessment, which contributes to the continuous improvement of soil quality and the assurance of food safety. Laser-induced breakdown spectroscopy (LIBS) is considered to be an emerging and effective tool for heavy-metal detection, compared with traditional detection technologies. Limited by the soil matrix effect, the LIBS signal of target elements for soil heavy-metal detection is prone to interference, thereby compromising the accuracy of quantitative detection. Thus, a series of signal-enhancement methods are investigated. This study aims to explore the effect of conductive materials of NaCl and graphite on the quantitative detection of lead (Pb) in soil using LIBS, seeking to find a reliable signal-enhancement method of LIBS for the determination of soil heavy-metal elements. The impact of the addition amount of NaCl and graphite on spectral intensity and parameters, including the signal-to-background ratio (SBR), signal-to-noise ratio (SNR), and relative standard deviation (RSD), were investigated, and the mechanism of signal enhancement by NaCl and graphite based on the analysis of the three-dimensional profile data of ablation craters and plasma parameters (plasmatemperature and electron density) were explored. Univariate and multivariate quantitative analysis models including partial least-squares regression (PLSR), least-squares support vector machine (LS-SVM), and extreme learning machine (ELM) were developed for the quantitative detection of Pb in soil with the optimal amount of NaCl and graphite, and the performance of the models was further compared. The PLSR model with the optimal amount of graphite obtained the best prediction performance, with an Rp that reached 0.994. In addition, among the three spectral lines of Pb, the univariate model of Pb I 405.78 nm showed the best prediction performance, with an Rp of 0.984 and the lowest LOD of 26.142 mg/kg. The overall results indicated that the LIBS signal-enhancement method based on conductive materials combined with appropriate chemometric methods could be a potential tool for the accurate quantitative detection of Pb in soil and could provide a reference for environmental monitoring. Full article
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<p>Spectra of soil with different contents of sodium chloride (NaCl). (<b>a</b>) Full spectra of soil samples; (<b>b</b>) Pb I 283.31 nm spectrum of soil samples; (<b>c</b>) Pb I 368.35 nm spectrum of soil samples; (<b>d</b>) Pb I 405.78 nm spectrum of soil samples.</p> Full article ">Figure 2
<p>Spectra of soil samples with different contents of graphite. (<b>a</b>) Full spectra of soil samples; (<b>b</b>) Pb I 283.31 nm spectrum of soil samples; (<b>c</b>) Pb I 368.35 nm spectrum of soil samples; (<b>d</b>) Pb I 405.78 nm spectrum of soil samples; (<b>e</b>) C I 405.78 nm spectrum of soil samples; (<b>f</b>) CN 386.03 nm, CN387 nm and CN388.22 nm spectra of soil samples. G means graphite.</p> Full article ">Figure 3
<p>Comparison of Pb spectral-line parameters of soils with different contents of NaCl and graphite. (<b>a</b>,<b>d</b>) SBR; (<b>b</b>,<b>e</b>) SNR; (<b>c</b>,<b>f</b>) RSD. G means graphite.</p> Full article ">Figure 4
<p>Comparison of the three-dimensional profile of ablation craters of soil samples with different conductive materials. (<b>a</b>) NaCl; (<b>b</b>) graphite; (<b>c</b>) without additives.</p> Full article ">Figure 5
<p>(<b>a</b>) Instrument-broadening fitting curve; (<b>b</b>) Collision coefficient versus plasma temperature curve; (<b>c</b>) Comparison of plasma temperature; (<b>d</b>) Comparison of electron density. G means graphite.</p> Full article ">Figure 6
<p>Univariate detection models and prediction results of soil Pb content with the optimal addition of NaCl based on the three primary characteristic lines of the Pb element. (<b>a</b>) The univariate model of Pb I 283.31 nm; (<b>b</b>) Prediction results of the univariate model based on Pb I 283.31 nm; (<b>c</b>) The univariate model of Pb I 368.35 nm; (<b>d</b>) Prediction results of the univariate model based on Pb I 368.35 nm; (<b>e</b>) The univariate model of Pb I 405.78 nm; (<b>f</b>) Prediction results of the univariate model based on Pb I 405.78 nm.</p> Full article ">Figure 7
<p>Univariate detection models and prediction results of soil Pb content with the optimal addition of graphite based on the three primary characteristic lines of the Pb element. (<b>a</b>) The univariate model of Pb I 283.31 nm; (<b>b</b>) Prediction results of the univariate model based on Pb I 283.31 nm; (<b>c</b>) The univariate model of Pb I 368.35 nm; (<b>d</b>) Prediction results of the univariate model based on Pb I 368.35 nm; (<b>e</b>) The univariate model of Pb I 405.78 nm; (<b>f</b>) Prediction results of the univariate model based on Pb I 405.78 nm.</p> Full article ">Figure 8
<p>Univariate detection models and prediction results of soil Pb content without additives based on the three primary characteristic lines of the Pb element. (<b>a</b>) The univariate model of Pb I 283.31 nm; (<b>b</b>) Prediction results of the univariate model based on Pb I 283.31 nm; (<b>c</b>) The univariate model of Pb I 368.35 nm; (<b>d</b>) Prediction results of the univariate model based on Pb I 368.35 nm; (<b>e</b>) The univariate model of Pb I 405.78 nm; (<b>f</b>) Prediction results of the univariate model based on Pb I 405.78 nm.</p> Full article ">Figure 9
<p>Schematic diagram of LIBS system.</p> Full article ">
17 pages, 20487 KiB  
Article
The Impact of Cyclodextrins on the Physiology of Candida boidinii: Exploring New Opportunities in the Cyclodextrin Application
by Rita Márton, Márk Margl, Lilla Kinga Tóth, Éva Fenyvesi, Lajos Szente and Mónika Molnár
Molecules 2024, 29(15), 3698; https://doi.org/10.3390/molecules29153698 - 5 Aug 2024
Viewed by 943
Abstract
Cyclodextrins, commonly used as excipients in antifungal formulations to improve the physicochemical properties and availability of the host molecules, have not been systematically studied for their effects and bioactivity without a complex active substance. This paper evaluates the effects of various cyclodextrins on [...] Read more.
Cyclodextrins, commonly used as excipients in antifungal formulations to improve the physicochemical properties and availability of the host molecules, have not been systematically studied for their effects and bioactivity without a complex active substance. This paper evaluates the effects of various cyclodextrins on the physiology of the test organism Candida boidinii. The research examines their impact on yeast growth, viability, biofilm formation and morphological changes. Native ACD, BCD, randomly methylated α- and β-CD and quaternary ammonium α-CD and β-CD were investigated in the 0.5–12.5 mM concentration range in both static and dynamic systems. The study revealed that certain cyclodextrins exhibited notable antifungal effects (up to ~69%) in dynamic systems; however, the biofilm formation was enhanced in static systems. The magnitude of these effects was influenced by several variables, including the size of the internal cavity, the concentration and structure of the cyclodextrins, and the contact time. Furthermore, the study found that CDs exhibited distinct effects in both static and dynamic systems, potentially related to their tendency to form aggregates. The findings suggest that cyclodextrins may have the potential to act as antifungal agents or growth promoters, depending on their structure and surrounding environments. Full article
(This article belongs to the Special Issue Synthesis and Molecular Recognition of Macrocyclic Compounds, 2nd Edition)
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<p>Effect of incremental (<b>a</b>) ACD, (<b>b</b>) RAMEA, (<b>c</b>) QAACD, (<b>d</b>) BCD, (<b>e</b>) RAMEB, and (<b>f</b>) QABCD concentrations on microbial growth in the dynamic system after 6 and 24 h of exposure time. Statistical significance (<span class="html-italic">p</span> &lt; 0.05) is marked by lowercase letters, where a indicates the smallest value. Values signed with the same letter indicate that there was no significant difference between them. Data represent the averages of five replicates.</p> Full article ">Figure 2
<p>Effect of incremental (<b>a</b>) ACD, (<b>b</b>) RAMEA, (<b>c</b>) QAACD, (<b>d</b>) BCD, (<b>e</b>) RAMEB, and (<b>f</b>) QABCD concentrations on cell viability in the dynamic system after 6 and 24 h of exposure time. Statistical significance (<span class="html-italic">p</span> &lt; 0.05) is marked by lowercase letters, where a indicates the smallest value. Values signed with the same letter indicate that there was no significant difference between them. Data represent the averages of five replicates.</p> Full article ">Figure 3
<p>Effect of increasing concentrations of (<b>a</b>) ACD, (<b>b</b>) RAMEA, (<b>c</b>) QAACD, (<b>d</b>) BCD, (<b>e</b>) RAMEB, and (<b>f</b>) QABCD on microbial growth in the static system after 6 and 24 h of exposure time. Statistical significance (<span class="html-italic">p</span> &lt; 0.05) is marked by lowercase letters, where a indicates the smallest value. Values signed with the same letter indicate that there was no significant difference between them. Data represent the averages of five replicates.</p> Full article ">Figure 4
<p>Effect of incremental (<b>a</b>) ACD, (<b>b</b>) RAMEA, (<b>c</b>) QAACD, (<b>d</b>) BCD, (<b>e</b>) RAMEB, and (<b>f</b>) QABCD concentrations on relative viability in the static system after 6 and 24 h of exposure time. Statistical significance (<span class="html-italic">p</span> &lt; 0.05) is marked by lowercase letters, where a indicates the smallest value. Values signed with the same letter indicate that there was no significant difference between them. Data represent the averages of five replicates.</p> Full article ">Figure 5
<p>Effect of increasing (<b>a</b>) ACD, (<b>b</b>) RAMEA, (<b>c</b>) QAACD, (<b>d</b>) BCD, (<b>e</b>) RAMEB, and (<b>f</b>) QABCD concentrations on relative biofilm measured with crystal violet staining in the static system after 6 and 24 h of exposure time. Statistical significance (<span class="html-italic">p</span> &lt; 0.05) is marked by lowercase letters, where a indicates the smallest value. Values signed with the same letter indicate that there was no significant difference between them. Data represent the averages of five replicates.</p> Full article ">Figure 6
<p>Effect of increasing (<b>a</b>) ACD, (<b>b</b>) RAMEA, (<b>c</b>) QAACD, (<b>d</b>) BCD, (<b>e</b>) RAMEB, and (<b>f</b>) QABCD concentrations of on relative biofilm measured with XTT assay in the static system after 6 and 24 h of exposure time. Statistical significance (<span class="html-italic">p</span> &lt; 0.05) is marked by lowercase letters, where a indicates the smallest value. Values signed with the same letter indicate that there was no significant difference between them. Data represent the averages of five replicates.</p> Full article ">Figure 7
<p>Effect of cyclodextrins on the morphology of <span class="html-italic">C. boidinii</span> after 24 h in the static system.</p> Full article ">
12 pages, 2613 KiB  
Article
Sustainable Epoxy Composites with UV Resistance Based on New Kraft Lignin Coatings
by Rubén Seoane-Rivero, Patricia Ares-Elejoste, Koldo Gondra, Sara Amini, Pedro-Luis de Hoyos and Maria Gonzalez-Alriols
Molecules 2024, 29(15), 3697; https://doi.org/10.3390/molecules29153697 - 5 Aug 2024
Viewed by 939
Abstract
Currently, the composite industry is focusing on more environmentally friendly resources in order to generate a new range of biobased materials. In this manuscript, we present a new work using lignocellulosic wastes from the paper industry to incorporate into biobased epoxy systems. The [...] Read more.
Currently, the composite industry is focusing on more environmentally friendly resources in order to generate a new range of biobased materials. In this manuscript, we present a new work using lignocellulosic wastes from the paper industry to incorporate into biobased epoxy systems. The manufactured materials were composed of kraft lignin, glass fiber, and a sustainable epoxy system, obtaining a 40% biobased content. Using a vacuum infusion process, we fabricated the composites and analyzed their mechanical and UV resistance properties. The findings reveal a significant correlation between the lignin content and flexural modulus and strength, showing an increase of 69% in the flexural modulus and 134% in the flexural strength with the presence of 5% of lignin content. Moreover, it is necessary to highlight that the presence of synthesized lignin inhibits the UV degradation of the biobased epoxy coating. We propose that the use of lignocellulosic-based wastes could improve the mechanical properties and generate UV resistance in the composite materials. Full article
(This article belongs to the Special Issue Epoxy Resin Synthesis, Performance and Application Research)
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<p>Infrared spectra obtained by FTIR analysis.</p> Full article ">Figure 2
<p>Thermal properties of polymer systems.</p> Full article ">Figure 3
<p>Mechanical properties of composites.</p> Full article ">Figure 4
<p>Color (<b>left</b>) and brightness (<b>right</b>) variation of fabricated composites.</p> Full article ">Figure 5
<p>(<b>a</b>) Reference; (<b>b</b>) reference after UV treatment; (<b>c</b>) KL (2.5% wt.) sample after UV treatment; and (<b>d</b>) KL (5% wt.) sample after UV treatment.</p> Full article ">Figure 6
<p>(<b>a</b>) Reference; (<b>b</b>) reference after UV treatment; (<b>c</b>) KL (2.5% wt.) sample; (<b>d</b>) KL (2.5% wt.) sample after UV treatment; (<b>e</b>) KL (5% wt.) sample; and (<b>f</b>) KL (5% wt.) sample after UV treatment.</p> Full article ">Figure 7
<p>Scheme of the vacuum infusion technique.</p> Full article ">
11 pages, 18667 KiB  
Article
Corrosion and Interfacial Contact Resistance of NiTi Alloy as a Promising Bipolar Plate for PEMFC
by Yingping Li, Xiaofen Wang, Yuanyuan Li, Zhuo He, Guohong Zhang, Zhen Wang, Shaohua Wang, Fei Hu and Qiongyu Zhou
Molecules 2024, 29(15), 3696; https://doi.org/10.3390/molecules29153696 - 5 Aug 2024
Viewed by 1262
Abstract
Titanium (Ti) is generally considered as an ideal bipolar plate (BPP) material because of its excellent corrosion resistance, good machinability and lightweight nature. However, the easy-passivation property, which leads to increased interfacial contact resistance (ICR) and subsequently decreased cell performance, limits its large-scale [...] Read more.
Titanium (Ti) is generally considered as an ideal bipolar plate (BPP) material because of its excellent corrosion resistance, good machinability and lightweight nature. However, the easy-passivation property, which leads to increased interfacial contact resistance (ICR) and subsequently decreased cell performance, limits its large-scale commercial application in proton exchange membrane fuel cells (PEMFCs). In this paper, we proposed a NiTi alloy prepared by suction casting as a promising bipolar plate for PEMFCs. This NiTi alloy exhibits significantly decreased ICR values (16.8 mΩ cm2 at 1.4 MPa) compared with pure Ti (88.6 mΩ cm2 at 1.4 MPa), along with enhanced corrosion resistance compared with pure nickel (Ni). The superior corrosion resistance of NiTi alloy is accredited to the nobler open circuit potential and corrosion potential, coupled with low corrosion current densities and passive current densities. The improved ICR can be interpreted by the existence of high-proportioned metallic Ni in the passive film, which contributes to the reduced capacitance characteristic of the passive film (compared with Ti) and enhances charge conduction. This work provides a feasible option to ameliorate BPP material that may have desirable corrosion resistance and ICR. Full article
(This article belongs to the Special Issue Electroanalysis of Biochemistry and Material Chemistry)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The (<b>a</b>) scanning electron microscopy (SEM) image and (<b>b</b>,<b>c</b>) corresponding elemental mapping results of the indicated region (white square in subfigure (<b>a</b>)) of the NiTi alloy prepared by suction casting, along with (<b>d</b>) the X-ray diffraction (XRD) pattern.</p> Full article ">Figure 2
<p>The (<b>a</b>) open circuit potential versus time (<span class="html-italic">E</span><sub>OCP</sub>–<span class="html-italic">t</span>) curves and (<b>b</b>) potentiodynamic polarization curves of NiTi alloy, pure Ti and pure Ni.</p> Full article ">Figure 3
<p>The (<b>a</b>) potentiostatic polarization curves, interfacial contact resistance (ICR) values: under (<b>b</b>) different compaction force and (<b>c</b>) the pressure of 1.4 MPa, along with (<b>d</b>) the hardness of NiTi alloy, pure Ti and pure Ni.</p> Full article ">Figure 4
<p>X-ray photoelectron spectroscopy (XPS) analysis results of different materials (NiTi alloy, pure Ti and pure Ni): (<b>a</b>) Ni 2p, (<b>b</b>) Ti 2p and (<b>c</b>) O 1s.</p> Full article ">Figure 5
<p>Electrochemical impedance spectroscopy (EIS) analysis of NiTi alloy, pure Ti and pure Ni before ((<b>a</b>) Nyqusit plots, (<b>c</b>) Bode-phase plots) and after ((<b>b</b>) Nyqusit plots, (<b>d</b>) Bode-phase plots) potentiostatic polarization.</p> Full article ">Figure 6
<p>SEM images of (<b>a</b>) pure Ni, (<b>b</b>) pure Ti and (<b>c</b>) NiTi alloy after potentiostatic polarization measurements, along with (<b>d</b>,<b>e</b>) elemental mapping results and (<b>f</b>) semi-quantitative result of the indicated region (white square in subfigure (<b>c</b>)).</p> Full article ">Figure 7
<p>The schematic diagram for testing the <span class="html-italic">R</span><sub>GDL</sub> and <span class="html-italic">R</span><sub>total</sub> values.</p> Full article ">
13 pages, 5211 KiB  
Article
Thermodynamic Studies of Complexes in Cu(II)/Uridine-5′-Diphosphoglucuronic Acid System
by Klaudia Stachowiak, Michal Zabiszak, Jakub Grajewski, Anna Teubert, Anna Bajek and Renata Jastrzab
Molecules 2024, 29(15), 3695; https://doi.org/10.3390/molecules29153695 - 4 Aug 2024
Viewed by 1159
Abstract
A binary system of uridine-5′-diphosphoglucuronic acid with copper (II) ions was studied. Potentiometric studies in aqueous solutions using computer data analysis were carried out. The pH of dominance, the overall stability constants (logβ), and the equilibrium constants of the formation reaction [...] Read more.
A binary system of uridine-5′-diphosphoglucuronic acid with copper (II) ions was studied. Potentiometric studies in aqueous solutions using computer data analysis were carried out. The pH of dominance, the overall stability constants (logβ), and the equilibrium constants of the formation reaction (logKe) were determined for each complex compound formed in the studied system. Spectroscopic studies were carried out to determine the mode of coordination in the compounds studied. Cytotoxicity and metabolic activity tests of the compounds obtained showed an increase in the biological activity of the complexes tested against the free ligand. The current research may contribute to the knowledge of complex compounds of biomolecules found in the human body and may also contribute to the characterization of a group of complex compounds with potential anticancer properties. Full article
(This article belongs to the Special Issue Synthesis, Structure, Molecular Modeling, and Bioactivity of Metal Complexes)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Formula of the uridine–5′-diphosphoglucuronic acid (highlighted with blue background indicate the potential coordination sites in the ligand molecule).</p> Full article ">Figure 2
<p>Distribution diagram of the protonation of UDP-GluA.</p> Full article ">Figure 3
<p>Lactam–lactim tautomerism in alkaline medium.</p> Full article ">Figure 4
<p>Distribution diagram of the Cu(II)/(UDP-GluA) system (ratio 1:1); <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>C</mi> </mrow> <mrow> <msup> <mrow> <mi>C</mi> <mi>u</mi> </mrow> <mrow> <mn>2</mn> <mo>+</mo> </mrow> </msup> </mrow> </msub> </mrow> </semantics></math> = <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>C</mi> </mrow> <mrow> <mi>L</mi> </mrow> </msub> </mrow> </semantics></math> = 1 × 10<sup>−3</sup> mol/dm<sup>3</sup>.</p> Full article ">Figure 5
<p>UV-Vis spectrum of the Cu(II)/(UDP-GluA) system.</p> Full article ">Figure 6
<p>EPR spectra of (<b>a</b>) Cu(UDP-GluA)H<sub>2</sub>, (<b>b</b>) Cu(UDP-GluA)H.</p> Full article ">Figure 7
<p>Circular dichroism spectra of uridine–5′-diphosphoglucuronic acid in water at pH = 3 (black line) and pH = 10.0 (red line).</p> Full article ">Figure 8
<p>Circular dichroism spectra of the Cu(II) uridine–5′-diphosphoglucuronic acid system in water at pH = 2.5 (black line), pH = 5.0 (red line), pH = 8.0 (green line), and pH = 10.5 (blue line).</p> Full article ">Figure 9
<p>Lactam–lactim tautomerism in the uridine moiety and its derivatives [<a href="#B22-molecules-29-03695" class="html-bibr">22</a>].</p> Full article ">Figure 10
<p>Cell viability after incubation with tested compounds for 24 h and 72 h in different pHs.</p> Full article ">
59 pages, 2461 KiB  
Review
From Classical to Alternative Pathways of 2-Arachidonoylglycerol Synthesis: AlterAGs at the Crossroad of Endocannabinoid and Lysophospholipid Signaling
by Fabienne Briand-Mésange, Isabelle Gennero, Juliette Salles, Stéphanie Trudel, Lionel Dahan, Jérôme Ausseil, Bernard Payrastre, Jean-Pierre Salles and Hugues Chap
Molecules 2024, 29(15), 3694; https://doi.org/10.3390/molecules29153694 - 4 Aug 2024
Viewed by 2386
Abstract
2-arachidonoylglycerol (2-AG) is the most abundant endocannabinoid (EC), acting as a full agonist at both CB1 and CB2 cannabinoid receptors. It is synthesized on demand in postsynaptic membranes through the sequential action of phosphoinositide-specific phospholipase Cβ1 (PLCβ1) and diacylglycerol lipase α (DAGLα), contributing [...] Read more.
2-arachidonoylglycerol (2-AG) is the most abundant endocannabinoid (EC), acting as a full agonist at both CB1 and CB2 cannabinoid receptors. It is synthesized on demand in postsynaptic membranes through the sequential action of phosphoinositide-specific phospholipase Cβ1 (PLCβ1) and diacylglycerol lipase α (DAGLα), contributing to retrograde signaling upon interaction with presynaptic CB1. However, 2-AG production might also involve various combinations of PLC and DAGL isoforms, as well as additional intracellular pathways implying other enzymes and substrates. Three other alternative pathways of 2-AG synthesis rest on the extracellular cleavage of 2-arachidonoyl-lysophospholipids by three different hydrolases: glycerophosphodiesterase 3 (GDE3), lipid phosphate phosphatases (LPPs), and two members of ecto-nucleotide pyrophosphatase/phosphodiesterases (ENPP6–7). We propose the names of AlterAG-1, -2, and -3 for three pathways sharing an ectocellular localization, allowing them to convert extracellular lysophospholipid mediators into 2-AG, thus inducing typical signaling switches between various G-protein-coupled receptors (GPCRs). This implies the critical importance of the regioisomerism of both lysophospholipid (LPLs) and 2-AG, which is the object of deep analysis within this review. The precise functional roles of AlterAGs are still poorly understood and will require gene invalidation approaches, knowing that both 2-AG and its related lysophospholipids are involved in numerous aspects of physiology and pathology, including cancer, inflammation, immune defenses, obesity, bone development, neurodegeneration, or psychiatric disorders. Full article
(This article belongs to the Special Issue Bioactive Lipids in Inflammatory Diseases)
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Figure 1

Figure 1
<p>Main enzymes of the canonical pathway of 2-AG synthesis involved in synaptic retrograde signaling. Glutamate released from excitatory terminal interacts with its ionotropic receptors AMPAR and NMDAR (not represent here), which results in the depolarization of postsynaptic neurons, allowing Ca<sup>2+</sup> influx through NMDAR and voltage-gated Ca<sup>2+</sup> channels. Simultaneous binding of glutamate (blue points) to mGluR1/5 promotes the Gα<sub>q</sub>-dependent activation of PLCβ1. The latter enzyme activity is increased by Ca<sup>2+</sup> but requires Gα<sub>q</sub> interaction to hydrolyze PIP<sub>2</sub>, thus acting as a coincidence detector [<a href="#B15-molecules-29-03694" class="html-bibr">15</a>,<a href="#B25-molecules-29-03694" class="html-bibr">25</a>]. 1-Stearoyl-2-arachidonoyl-<span class="html-italic">sn</span>-glycerol, the major DAG molecular species generated from phosphatidylinositol 4,5-bisphosphate (PIP<sub>2</sub>), can then be converted into 2-AG by diacylglycerol lipase α (DAGLα). The efficiency of this enzymatic cascade rests on the proper positioning of the various actors involving, among other mechanisms, interaction between DAGLα and mGluR1/5 via the scaffold Homer proteins [<a href="#B26-molecules-29-03694" class="html-bibr">26</a>,<a href="#B27-molecules-29-03694" class="html-bibr">27</a>,<a href="#B28-molecules-29-03694" class="html-bibr">28</a>,<a href="#B29-molecules-29-03694" class="html-bibr">29</a>]. 2-AG then diffuses through the synaptic cleft to presynaptic CB1, thus inhibiting the further release of glutamate. Mechanisms of CB1-induced presynaptic changes controlling short- and long-term synaptic plasticity are described in detail elsewhere [<a href="#B19-molecules-29-03694" class="html-bibr">19</a>]. Not shown here, CB1 is also present in GABAergic inhibitory terminals, resulting in the suppression of inhibition [<a href="#B30-molecules-29-03694" class="html-bibr">30</a>]. Abbreviations: 2-AG, 2-arachidonoylglycerol; AMPAR, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor; CB1, cannabinoid receptor 1; DAG, diacylglycerol; DAGLα, DAG lipase α; GABA, γ-amino butyric acid; Gα<sub>q</sub>, α<sub>q</sub> subunit of heterotrimeric G protein; mGluR1/5, metabotropic glutamate receptor 1 or 5; NMDAR, <span class="html-italic">N</span>-methyl-D-aspartate receptor; PIP<sub>2</sub>, phosphatidylinositol 4,5-bisphosphate; PLCβ1, phospholipase Cβ1.</p> Full article ">Figure 2
<p>Canonical and other intracellular pathways of 2-AG synthesis. The acylation of LPA to PA by AGPAT is indicated with dotted lines to describe either the pathological conditions (AGPAT2 inactivating mutations responsible for congenital lipodystrophy [<a href="#B33-molecules-29-03694" class="html-bibr">33</a>]) or, for some yet unknown reasons, physiological situation limiting de novo synthesis to the production of LPA and 2-AG. Abbreviations: 2-AG, 2-arachidonoylglycerol; AGK, acylglycerol kinase; AGPAT, 1-acylglycerol-3-phosphate acyltransferase; DAG, diacylglycerol; DAGK, DAG kinase; DAGL, DAG lipase; DDHD, DDHD containing; G3P, sn-glycerol-3-phosphate; GPAT, sn-glycerol-3-phosphate acyltransferase; HSL, hormone-sensitive lipase; LPA, lysophosphatidic acid; PA, phosphatidic acid; PC, phosphatidylcholine; PHOSPHO1, phosphocholine and phosphoethanolamine phosphatase; PIP<sub>2</sub>, phosphatidylinositol 4,5-bisphosphate; PLC, phospholipase C; PLD, phospholipase D; PNPLA<sub>2</sub>, patatin-like PLA<sub>2</sub>; sHE, soluble epoxide hydrolase; SMS, sphingomyelin synthases (SMS1 and SMS2); SMSr, SMS related protein; TAG, triacylglycerol.</p> Full article ">Figure 3
<p>The three extracellular AlterAG pathways. Abbreviations: 2-AG, 2-arachidonoylglycerol; AlterAG, alternative pathway of 2-AG synthesis; DDHD, DDHD containing; ENPP6–7, ecto-nucleotide pyrophosphatase/phosphodiesterases 6 and 7; GDE3, glycerophosphodiesterase 3; LIPH and LIPI, lipases H and I; LPA, lysophosphatidic acid; LPC, lysophosphatidylcholine; LPI, lysophosphatidylinositol; LPP1–3, lipid phosphate phosphatases 1–3; LYPLA1, lysophospholipase A1; mPA-PLA<sub>1</sub>, membrane-associated PA-selective PLA1 (α or β); PA, phosphatidic acid; PC, phosphatidylcholine; PI, phosphatidylinositol; PLRP2, pancreatic lipase related protein 2.</p> Full article ">Figure 4
<p>Possible relationship between ABHD11 and mitochondrial CB1. Besides the canonical pathway present in the plasma membrane (see also <a href="#molecules-29-03694-f001" class="html-fig">Figure 1</a>), ABHD11 might be another source of 2-AG for mitochondrial CB1 receptors. 2-AG (red triangles) from both origins is postulated to interact with mitochondrial CB1, resulting in the sequential inhibition of sAC and PKA. The scheme is inspired from previous representations found in the literature [<a href="#B97-molecules-29-03694" class="html-bibr">97</a>,<a href="#B98-molecules-29-03694" class="html-bibr">98</a>]. As commented in the text, ABHD11 in mitochondrial matrix is associated with OGDHc. Abbreviations: 2-AG, 2-arachidonoylglycerol; ABHD11, ABHD, α/β-Hydrolase Domain-Containing; CB1, cannabinoid receptor 1; DAG, diacylglycerol; DAGL, DAG lipase; Gα<sub>i</sub>, α<sub>i</sub> subunit of heterotrimeric G protein; OGDHc, oxoglutarate dehydrogenase complex; PIP<sub>2</sub>, phosphatidylinositol 4,5-bisphosphate; PKA, protein kinase A; PLC, phospholipase C; sAC, soluble adenylate cyclase.</p> Full article ">Figure 5
<p>Acyl migration in monoacylglycerols and lysophospholipids. The most stable forms (1-AG and 3-AG, 1-A-LPL) represent roughly 90% of the mixture at the thermodynamic equilibrium. Abbreviations: 1-AG, 2-AG, 3-AG, 1 (or 2 or 3)-arachidonoylglycerol; 1-A-LPL or 2-A-LPL, 1 (or 2)-arachidonoyl-lysophospholipid; LPA, lysophosphatidic acid; LPC, lysophosphatidylcholine; LPE, lysophosphatidylethanolamine; LPG, lysophosphatidylglycerol; LPI, lysophosphatidylinositol; LPS, lysophosphatidylserine.</p> Full article ">Figure 6
<p>Structures of lysophosphatidylcholine (LPC), cyclic phosphatidic acid (cPA), and lysophosphatidic acid (LPA).</p> Full article ">Figure 7
<p>Extracellular reactions of AlterAG pathways. In AlterAG-1, GDE3 exposes to the cell exterior its catalytic site (green line), allowing the conversion of extracellular LPI into 2-AG, thus acting as a switch between GPR55 and CB1 or CB2 receptors. In AlterAG-2, LPPs also display an extracellular catalytic site (green circles), allowing a similar signaling switch between LPA and cannabinoid receptors. Among possible sources of LPA in AlterAG-2, the implication of mPLA<sub>1</sub> (LIPH and LIPI) is considered the most probable compared to lysoPLD, owing to the preference of ATX for 1-acyl regioisomers [<a href="#B220-molecules-29-03694" class="html-bibr">220</a>] and the intracellular localization of GDE4 and GDE7, although GDE7 has also been described as an ectoenzyme [<a href="#B345-molecules-29-03694" class="html-bibr">345</a>]. In AlterAG-3, ENPP6 is anchored to the membrane by a glycosyl-PI anchor and allows the conversion of LPC into 2-AG. As not indicated here, ENPP6 is actually a homodimer with the two 55 kDa subunits being joined by a disulfide bridge [<a href="#B346-molecules-29-03694" class="html-bibr">346</a>]. The same reaction can also be catalyzed by ENPP7, which displays a single-pass transmembrane segment with a short cytosolic C-terminal end. Moreover, both ENPP6 and ENPP7 can generate soluble forms upon C-terminal partial proteolysis [<a href="#B262-molecules-29-03694" class="html-bibr">262</a>,<a href="#B264-molecules-29-03694" class="html-bibr">264</a>,<a href="#B347-molecules-29-03694" class="html-bibr">347</a>]. The signaling switch could occur between LPC receptors GPR82, GPR119, or GPR132 (G2A) and CB1/CB2, but with a number of restrictions discussed in the text. All the lysophospholipids described in this Figure are considered as 2-arachidonoyl species. For the sake of clarity, the various pathways leading to their formation are not indicated, except for LPA. Extracellular (EC) and intracellular (IC) faces of the plasma membrane are indicated. Abbreviations: 2-AG, 2-arachidonoylglycerol; AlterAG, alternative pathway of 2-AG synthesis; ATX, autotaxin; CB, cannabinoid receptor; ENPP, ecto-nucleotide pyrophosphatase/phosphodiesterase; GPR, G-protein-coupled receptor; LPA, lysophosphatidic acid; LPC, lysophosphatidylcholine; LPI, lysophosphatidylinositol; PA, phosphatidic acid; GDE, glycerophosphodiesterase; LIPH and LIPI, lipases H and I; LPP, lipid phosphate phosphatase; mPA-PLA<sub>1</sub> (membrane-associated PA-selective PLA<sub>1</sub> (α or β); PI, phosphatidylinositol.</p> Full article ">Figure 8
<p>Comparative membrane insertion and functions of LPP and PRG-1. The three domains C1 to C3 forming the catalytic site of LPP (green) are colored in red to indicate the loss of phosphatase activity occurring in PRG-1 owing to several point mutations. H in domain C2 corresponds to His252, whose mutation abolishes interactions with LPA. R345T mutation produces a loss of function of PRG-1 by altering cytosolic O-glycosylation of neighboring S346 (as shown in a mouse model involving homologs R346T and S347A [<a href="#B428-molecules-29-03694" class="html-bibr">428</a>,<a href="#B440-molecules-29-03694" class="html-bibr">440</a>]. The lipid phosphatase activity of LPP converts LPA into MAG in the outer half of the plasma membrane. This is followed by the spontaneous translocation of MAG to the inner layer, allowing its possible reconversion into LPA by MAG kinase activity and the diffusion of both lipids to other intracellular membranes. The large cytoplasmic domain of PRG-1 was found to interact with CaM [<a href="#B427-molecules-29-03694" class="html-bibr">427</a>] and PP2A phosphatase, resulting in the last case in β1-integrin activation and allowing to maintain spine density [<a href="#B429-molecules-29-03694" class="html-bibr">429</a>]. Extracellular (EC) and intracellular (IC) faces of the plasma membrane are indicated. Abbreviations: CaM, calmodulin; LPA, lysophosphatidic acid; LPP, lipid phosphate phosphatase; MAG, monoacylglycerol; PP2A, protein phosphatase 2A; PRG1, plasticity-related gene 1.</p> Full article ">Figure 9
<p>Regulation of excitation/inhibition balance at glutamatergic synapses by opposite effects of LPA and 2-AG. Glutamate released from synaptic vesicles activates postsynaptic neurons by interacting mainly with its ionotropic receptors AMPAR and NMDAR, which results in the depolarization of postsynaptic neurons, allowing Ca<sup>2+</sup> influx through NMDAR (as well as voltage-gated Ca<sup>2+</sup> channels, not represented here). In the left part of this Figure, the canonical pathway of 2-AG synthesis (as described in <a href="#molecules-29-03694-f001" class="html-fig">Figure 1</a>) allows 2-AG to reduce glutamate secretion upon interaction with presynaptic CB1. In addition, 2-AG can also increase excitability by suppressing inhibitory GABAergic signals (not represented here). In the right part of this Figure, LPA produced through LPC hydrolysis by ATX secreted from astrocyte induces hyperexcitability upon binding to presynaptic LPA2 receptor. However, this effect is counteracted by the removal of LPA from the synaptic cleft by postsynaptic PRG-1. Thus, both DAGLα (via CB1) and PRG-1 (upon removing pro-excitatory LPA) contribute to reduce hyperexcitability at glutamatergic synapses. The same localization of DAGLα and PRG-1 in postsynaptic membrane generates the question of a possible mixing of 2-AG and of MAG produced as the consequence of LPA internalization by PRG-1 (curved dotted double arrow). Abbreviations: 2-AG, 2-arachidonoylglycerol; AMPAR, α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor; ATX, autotaxin; CB1, cannabinoid receptor 1; DAG, diacylglycerol; DAGLα, DAG lipase α; LPA, lysophosphatidic acid; LPA2, LPA receptor 2; LPC, lysophosphatidylcholine; NMDAR, N-methyl-D-aspartate receptor; PIP<sub>2</sub>, phosphatidylinositol 4,5-bisphosphate; PLCβ1, phospholipase C-β1; PRG1, plasticity-related gene 1.</p> Full article ">
18 pages, 2492 KiB  
Article
Product Selectivity Control in the Brønsted Acid-Mediated Reactions with 2-Alkynylanilines
by Valerio Morlacci, Massimiliano Aschi, Marco Chiarini, Caterina Momoli, Laura Palombi and Antonio Arcadi
Molecules 2024, 29(15), 3693; https://doi.org/10.3390/molecules29153693 - 4 Aug 2024
Viewed by 953
Abstract
Brønsted acid-catalysed/mediated reactions of the 2-alkynylanilines are reported. While metal-catalysed reactions of these valuable building blocks have led to the establishment of robust protocols for the selective, diverse-oriented syntheses of significant heterocyclic derivatives, we here demonstrate the practical advantages of an alternative methodology [...] Read more.
Brønsted acid-catalysed/mediated reactions of the 2-alkynylanilines are reported. While metal-catalysed reactions of these valuable building blocks have led to the establishment of robust protocols for the selective, diverse-oriented syntheses of significant heterocyclic derivatives, we here demonstrate the practical advantages of an alternative methodology under metal-free conditions. Our investigation into the key factors influencing the product selectivity in Brønsted acid-catalysed/mediated reactions of 2-alkynylanilines reveals that different reaction pathways can be directed towards the formation of diverse valuable products by simply choosing appropriate reaction conditions. The origins of chemo- and regioselectivity switching have been explored through Density Functional Theory (DFT) calculations. Full article
(This article belongs to the Special Issue Advances in Heterocyclic Synthesis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Protonation site distribution and relative free-energies of <b>Ia</b>, <b>IIa</b>, and <b>IIIa</b> in DCE and EtOH.</p> Full article ">Figure 2
<p>(<b>A</b>) Reaction scheme for <b>1a</b> dimerization under acid conditions and relative free energies in kJ/mol at 110 °C in DCE (black lines) and EtOH (red lines). (<b>B</b>) Possible reaction pathways for the formation of <b>8a</b> and (<b>C</b>) <b>7a</b>.</p> Full article ">Figure 3
<p>Possible reaction pathways and relative free energies in kJ/mol in EtOH (110 °C) and DCE (40 °C).</p> Full article ">Figure 4
<p>Reaction pathways to <b>5a</b> (Reaction conditions: <a href="#molecules-29-03693-t001" class="html-table">Table 1</a>, entry 7) and <b>VIIIa</b> (Reaction conditions: <a href="#molecules-29-03693-t001" class="html-table">Table 1</a>, entry 14) with relative free energies (kJ/mol) at 40 °C in DCE.</p> Full article ">Scheme 1
<p>Brønsted acid-catalysed/mediated reaction of 2-alkynylanilines <b>1</b>.</p> Full article ">Scheme 2
<p>Product selectivity control in the sequential reaction of 2-alkynylanilines <b>1</b> with ketones.</p> Full article ">Scheme 3
<p>Hydration vs dimerization reaction of <b>1a</b>. Other products are given in <a href="#molecules-29-03693-t001" class="html-table">Table 1</a>.</p> Full article ">Scheme 4
<p>Control experiment ruling out the formation of <b>7a</b> from <b>6a</b> (Reaction conditions: <a href="#molecules-29-03693-t001" class="html-table">Table 1</a>, entry 1).</p> Full article ">Scheme 5
<p>Control experiment to suppress the dimerization of <b>1a</b> (Reaction conditions: <a href="#molecules-29-03693-t001" class="html-table">Table 1</a>, entry 1).</p> Full article ">Scheme 6
<p>Synthesis of 2-(2-aminophenyl)quinoline derivatives <b>7</b>.</p> Full article ">Scheme 7
<p>Hydration vs. dimerization of 2-alkynyl and 2-ethynyltrimethylsilyl anilines in EtOH at 110 °C.</p> Full article ">Scheme 8
<p>Synthesis of 2-(2-aminophenyl)quinoline derivatives <b>8</b> in DCE at 110 °C and influence of the amount of <span class="html-italic">p</span>-TsOH on the regioselectivity.</p> Full article ">
13 pages, 4199 KiB  
Article
Utilization of Lead Nitrate to Enhance the Impact of Hydroxamic Acids on the Hydrophobic Aggregation and Flotation Behavior of Cassiterite
by Saizhen Jin, Xiaobo Liu, Yun Feng, Yanfei Chen, Mengtao Wang and Qingfei Xiao
Molecules 2024, 29(15), 3692; https://doi.org/10.3390/molecules29153692 - 4 Aug 2024
Viewed by 974
Abstract
Lead nitrate (LN) is frequently employed as an activator in the flotation of cassiterite using hydroxamic acids as the collectors. This study investigated the effect of LN on the hydrophobic aggregation of cassiterite when benzohydroxamic acid (BHA), hexyl hydroxamate (HHA), and octyl hydroxamate [...] Read more.
Lead nitrate (LN) is frequently employed as an activator in the flotation of cassiterite using hydroxamic acids as the collectors. This study investigated the effect of LN on the hydrophobic aggregation of cassiterite when benzohydroxamic acid (BHA), hexyl hydroxamate (HHA), and octyl hydroxamate (OHA) were used as the collectors through micro-flotation, focused beam reflectance measurement (FBRM) and a particle video microscope (PVM), zeta potential, and the extended DLVO theory. Micro-flotation tests confirmed that LN activated the flotation of cassiterite using the hydroxamic acids as collectors. Focused beam reflectance measurement (FBRM) and a particle video microscope (PVM) were used to capture in situ data on the changes in size distribution and morphology of cassiterite aggregates during stirring. The FBRM and PVM image results indicated that the addition of LN could promote the formation of hydrophobic aggregates of fine cassiterite, when BHA or HHA was used as the collector, and reduce the dosage of OHA needed to induce the formation of hydrophobic aggregates of cassiterite. The extended DLVO theory interaction energies indicated that the presence of LN could decrease the electrostatic interaction energies (Vedl) and increase the hydrophobic interaction energies (Vhy) between cassiterite particles, resulting in the disappearance of the high energy barriers that existed between the particles in the absence of LN. Thus, cassiterite particles could aggregate in the presence of LN when BHA, HHA, or a low concentration of OHA was used as the collector. Full article
(This article belongs to the Special Issue Molecular Structure of Minerals)
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Figure 1
<p>Recovery of fine cassiterite as a function of pH in the presence and absence of LN using (<b>a</b>) BHA, (<b>b</b>) HHA, and (<b>c</b>) OHA as collectors.</p> Full article ">Figure 2
<p>Aggregation of fine cassiterite in the presence of various BHA concentrations. (<b>a</b>) Counts and square-weighted mean chord length of cassiterite suspension as a function of time after adding (<b>a1</b>) 3 × 10<sup>−4</sup> mol/L, (<b>a2</b>) 5 × 10<sup>−4</sup> mol/L, and (<b>a3</b>) 2 × 10<sup>−3</sup> mol/L of BHA; (<b>b</b>) non-weighted and square-weighted chord-length distributions of the cassiterite suspension before and after adding various concentrations of BHA at 20:00; (<b>c</b>) PVM images of cassiterite before (<b>c1</b>) and after (<b>c2</b>) adding 2 × 10<sup>−3</sup> mol/L BHA at 20:00. (400 rpm; pH = 8.5~9.0).</p> Full article ">Figure 3
<p>Aggregation of fine cassiterite in the presence of various BHA concentrations and Pb<sup>2+</sup>. (<b>a</b>) Counts and square-weighted mean chord length of cassiterite suspension as a function of time; (<b>b</b>) non-weighted and square-weighted chord-length distributions of cassiterite suspension at different times; (<b>c</b>) PVM images of cassiterite after adding BHA at 15:00. (C<sub>(BHA)</sub> = 2 × 10<sup>−4</sup> mol/L (<b>a1</b>,<b>b1</b>,<b>c1</b>), C<sub>(BHA)</sub> = 5 × 10<sup>−4</sup> mol/L (<b>a2</b>,<b>b2</b>,<b>c2</b>), C<sub>(BHA)</sub> = 2 × 10<sup>−3</sup> mol/L (<b>a3</b>,<b>b3</b>,<b>c3</b>); 400 rpm; pH = 8.5~9.0; C<sub>(LN)</sub> = 6 × 10<sup>−5</sup> mol/L).</p> Full article ">Figure 4
<p>Aggregation of cassiterite under different HHA concentrations in the presence of LN. (<b>a</b>) Counts and square-weighted mean chord length of cassiterite suspension as a function of time. (<b>b</b>) Non-weighted and square-weighted CLDs of cassiterite suspension at different times. (C<sub>(LN)</sub> = 6 × 10<sup>−5</sup> mol/L; C<sub>(HHA)</sub> = 5 × 10<sup>−5</sup> mol/L (<b>a1</b>,<b>b1</b>), C<sub>(HHA)</sub> = 1 × 10<sup>−4</sup> mol/L (<b>a2</b>,<b>b2</b>), C<sub>(HHA)</sub> = 4 × 10<sup>−4</sup> mol/L (<b>a3</b>,<b>b3</b>); N = 400 rpm; pH = 8.5~9.0).</p> Full article ">Figure 5
<p>PVM images of cassiterite after adding 6 × 10<sup>−5</sup> mol/L LN and 5 × 10<sup>−5</sup> mol/L HHA at the time points of 4:30, 10:30, and 20:00.</p> Full article ">Figure 6
<p>Aggregation of cassiterite by different OHA concentrations in the presence of LN. (C<sub>(LN)</sub> = 6 × 10<sup>−5</sup> mol/L; C<sub>(OHA)</sub> = 5 × 10<sup>−5</sup> mol/L (<b>a1</b>,<b>b1</b>), C<sub>(OHA)</sub> = 1 × 10<sup>−4</sup> mol/L (<b>a2</b>,<b>b2</b>), C<sub>(OHA)</sub>= 4 × 10<sup>−4</sup> mol/L (<b>a3</b>,<b>b3</b>); N = 400 rpm; pH = 8.5~9.0).</p> Full article ">Figure 7
<p>PVM images of cassiterite after adding OHA and LN. (C<sub>(OHA)</sub> = 5 × 10<sup>−5</sup> mol/L (<b>a</b>), C<sub>(OHA)</sub> = 1 × 10<sup>−4</sup> mol/L (<b>b</b>), C<sub>(OHA)</sub> = 4 × 10<sup>−4</sup> mol/L (<b>c</b>)).</p> Full article ">Figure 8
<p>The EDLVO interaction energy diagram as a function of separation distance between cassiterite particles in the presence of BHA or BHA + Pb<sup>2+</sup>. (<b>a</b>) V<sub>edl</sub> and V<sub>hy</sub> in the absence of LN; (<b>b</b>) presence of <sub>LN</sub>; and (<b>c</b>) V<sub>DT</sub> in the absence and presence of LN.</p> Full article ">Figure 9
<p>The EDLVO interaction energy diagram as a function of separation distance between cassiterite particles in the presence of LN and HHA (<b>a</b>) or OHA (<b>b</b>). HHA + LN (<b>a1</b>,<b>a2</b>) and OHA+LN (<b>b1</b>,<b>b2</b>).</p> Full article ">
28 pages, 9422 KiB  
Review
Comprehensive Review of Synthesis, Optical Properties and Applications of Heteroarylphosphonates and Their Derivatives
by Krzysztof Owsianik, Adrian Romaniuk, Marika Turek and Piotr Bałczewski
Molecules 2024, 29(15), 3691; https://doi.org/10.3390/molecules29153691 - 4 Aug 2024
Viewed by 1395
Abstract
This review focuses on optical properties of compounds in which at least one phosphonate group is directly attached to a heteroaromatic ring. Additionally, the synthesis and other applications of these compounds are addressed in this work. The influence of the phosphonate substituent on [...] Read more.
This review focuses on optical properties of compounds in which at least one phosphonate group is directly attached to a heteroaromatic ring. Additionally, the synthesis and other applications of these compounds are addressed in this work. The influence of the phosphonate substituent on the properties of the described compounds is discussed and compared with other non-phosphorus substituents, with particular attention given to photophysical properties, such as UV-Vis absorption and emission, fluorescence quantum yield and fluorescence lifetime. Considering the presence of heteroatom, the collected material was divided into two parts, and a review of the literature of the last thirty years on heteroaryl phosphonates containing sulfur and nitrogen atoms in the aromatic ring was conducted. Full article
(This article belongs to the Special Issue Organophosphorus Chemistry: A New Perspective, 2nd Edition)
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Figure 1
<p>Absorbance spectra of the four Ru-oligothiophenes (Ru-<b>1</b>, brown; Ru-<b>2</b>, red; Ru-<b>3</b>, green; Ru-<b>4</b>, blue; 0.01 mM in acetonitrile) (Reprinted with permission from [<a href="#B13-molecules-29-03691" class="html-bibr">13</a>], Copyright 2007 American Chemical Society).</p> Full article ">Figure 2
<p>Chemical structures of chalcogenorhodamine dyes <b>18</b>–<b>20</b>.</p> Full article ">Figure 3
<p>Emission spectra of complex Cd<sub>2</sub>[OOCC<sub>5</sub>H<sub>3</sub>NPO<sub>3</sub>H]<sub>2</sub>·H<sub>2</sub>O (<b>28</b>) (<span class="html-italic">λ</span><sub>ex</sub> = 323 nm), Zn[OOCC<sub>5</sub>H<sub>4</sub>NPO<sub>3</sub>]·H<sub>2</sub>O (<b>29</b>) (λ<sub>ex</sub> = 365 nm) and free ligand <b>27</b> (λ<sub>ex</sub> = 521 nm) (reprinted with permission from [<a href="#B28-molecules-29-03691" class="html-bibr">28</a>], Copyright Taylor and Francis Ltd., <a href="http://www.tandfonline.com" target="_blank">http://www.tandfonline.com</a>).</p> Full article ">Figure 4
<p>Chemical structures of iridium complexes <b>39</b>–<b>42</b>.</p> Full article ">Figure 5
<p>Chemical structures of complexes <b>43</b>–<b>45</b>.</p> Full article ">Figure 6
<p>Chemical structures of ligands <b>46</b>–<b>52</b>.</p> Full article ">Figure 7
<p>Chemical structures of <span class="html-italic">N,O</span>-donor <span class="html-italic">N</span>-heterocyclic aromatic diphosphonate ligands <b>53</b>–<b>55</b>.</p> Full article ">Figure 8
<p>Chemical structures of ligands <b>56</b>–<b>58</b>.</p> Full article ">Figure 9
<p>Chemical structures of ruthenium complexes <b>59</b>–<b>61</b>.</p> Full article ">Figure 10
<p>Chemical structures of complexes <b>65</b>–<b>68</b>.</p> Full article ">Figure 11
<p>Chemical structures of iridium(III) complexes <b>84</b> and <b>85</b>.</p> Full article ">Figure 12
<p>Chemical structures of platinum complexes <b>86</b> and <b>87</b>.</p> Full article ">Figure 13
<p>Chemical structures of ligands <b>91</b>–<b>94</b> and equilibrium <b>A</b>–<b>D</b> of <b>92</b> at different pH.</p> Full article ">Figure 14
<p>Chemical structures of complexes <b>95</b>–<b>97</b>.</p> Full article ">Figure 15
<p>Chemical structures of the sensitizer/donor <b>106</b> and the dyad <b>107</b>/<b>108</b>.</p> Full article ">Figure 16
<p>Proposed electron fluxes in the illuminated heterotriad <b>106</b>|TiO<sub>2</sub> on SnO<sub>2</sub> (Reprinted with permission from [<a href="#B53-molecules-29-03691" class="html-bibr">53</a>]).</p> Full article ">Figure 17
<p>Chemical structure of complex <b>112</b>.</p> Full article ">Figure 18
<p>Chemical structure of 2-pyrazinephosphonic acid <b>113</b>.</p> Full article ">Figure 19
<p>Chemical structures of pyrazine-functionalized calix [<a href="#B4-molecules-29-03691" class="html-bibr">4</a>]arene ligands <b>117</b>–<b>119</b>, and a schematic presentation of metal co-ordination.</p> Full article ">Figure 20
<p>Absorption spectra of ligands <b>117</b>–<b>119</b> in BumimTf<sub>2</sub>N (conc.: 0.25 mmol/L at 25 °C) (reprinted with permission from [<a href="#B58-molecules-29-03691" class="html-bibr">58</a>], Copyright The Royal Society of Chemistry 2015).</p> Full article ">Figure 21
<p>Chemical structures of TBCA (<b>123</b>) and TPCA (<b>124</b>).</p> Full article ">Figure 22
<p>Device configuration of multilayer PLEDs and molecular structures of used materials (GPF—green-emitting polyfluorene; PEDOT:PSS—poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate); ETL—electron-transporting layer; EML—emitting layer; ITO—indium tin oxide) (Used with permission of The Royal Society of Chemistry, from [<a href="#B63-molecules-29-03691" class="html-bibr">63</a>], Copyright 2016; permission conveyed through Copyright Clearance Center, Inc.).</p> Full article ">Scheme 1
<p>Synthesis of bithiophenes and tetrathiophenes <b>1</b>–<b>4</b>.</p> Full article ">Scheme 2
<p>Synthesis of chalcogenophosphonato-substituted bithiophenes. Reagents and conditions: (i) 2,2′-biphenol or 2,2-dimethyl-1,3-propanediol, toluene, reflux; (ii) (a) BuLi, −78 °C, THF; (b) Ph<sub>2</sub>PCl, 0 °C—rt, 2 h; (iii) (X = O) H<sub>2</sub>O<sub>2</sub>·urea complex or N(O)Me<sub>3</sub>; (X = S) S<sub>8</sub>; (X = Se) Se powder, DCM, rt.</p> Full article ">Scheme 3
<p>Synthesis of bis(aryl- and heteroaryl)phosphonic acids <b>13</b>–<b>17</b>.</p> Full article ">Scheme 4
<p>The synthesis of compound <b>18</b>.</p> Full article ">Scheme 5
<p>Synthesis of the ligand <b>30</b>.</p> Full article ">Scheme 6
<p>Synthesis of ligands <b>31</b> and <b>32</b>.</p> Full article ">Scheme 7
<p>Synthetic protocol for the preparation of ligands <b>35</b> and <b>36</b>.</p> Full article ">Scheme 8
<p>Synthesis of iridium complex <b>38</b> from complex <b>37</b>.</p> Full article ">Scheme 9
<p>Synthesis of the complex <b>63</b>.</p> Full article ">Scheme 10
<p>Synthesis of complex <b>64</b>.</p> Full article ">Scheme 11
<p>General synthesis of ligands <b>72</b>.</p> Full article ">Scheme 12
<p>Synthesis and spectroscopic data of complexes <b>73</b>–<b>80</b> (absorption maximum measured in 0.1 N sulfuric acid; emission maximum measured for the anionic forms of the complexes at room temperature in deaerated methanol; emission lifetimes for the anionic forms of the complexes).</p> Full article ">Scheme 13
<p>Synthesis of complex <b>82</b>.</p> Full article ">Scheme 14
<p>Synthesis of the dimer <b>83</b> and the regeneration of complex <b>82</b>.</p> Full article ">Scheme 15
<p>Synthesis and chemical structures of phosphonates <b>88</b>–<b>90</b>.</p> Full article ">Scheme 16
<p>The synthesis of terpyridyl ligand <b>99</b> for the identification of ions Fe(II), Fe(III), Ru(III) and Zn(II) in dilute aqueous solutions.</p> Full article ">Scheme 17
<p>Synthetic strategies for the synthesis of Ru complex <b>104</b>.</p> Full article ">Scheme 18
<p>Synthesis of complex sensitizer/donor type <b>105</b>.</p> Full article ">Scheme 19
<p>Synthesis of complex <b>110</b>.</p> Full article ">Scheme 20
<p>Synthesis of the phosphopyrazole <b>120</b> and the pyridyl amino amide <b>121</b>.</p> Full article ">Scheme 21
<p>Synthesis of the aminophenoxazinone <b>122</b>.</p> Full article ">Scheme 22
<p>Synthesis of phosphonate <b>127</b> (TPPO).</p> Full article ">
16 pages, 3519 KiB  
Article
Adsorptive–Photocatalytic Composites of α-Ferrous Oxalate Supported on Activated Carbon for the Removal of Phenol under Visible Irradiation
by Salomé Galeas, Víctor H. Guerrero, Patricia I. Pontón, Carla S. Valdivieso-Ramírez, Paul Vargas-Jentzsch, Paola Zárate and Vincent Goetz
Molecules 2024, 29(15), 3690; https://doi.org/10.3390/molecules29153690 - 4 Aug 2024
Viewed by 1094
Abstract
Adsorptive–photocatalytic composites based on activated carbon (AC) and α-ferrous oxalate dihydrate (α-FOD) were synthesized by an original two-step method and subsequently used for the removal of phenol from aqueous solutions. To obtain the composites, ferrotitaniferous black mineral sands (0.6FeTiO3·0.4Fe2O [...] Read more.
Adsorptive–photocatalytic composites based on activated carbon (AC) and α-ferrous oxalate dihydrate (α-FOD) were synthesized by an original two-step method and subsequently used for the removal of phenol from aqueous solutions. To obtain the composites, ferrotitaniferous black mineral sands (0.6FeTiO3·0.4Fe2O3) were first dissolved in an oxalic acid solution at ambient pressure, and further treated under hydrothermal conditions to precipitate α-FOD on the AC surface. The ratio of oxalic acid to the mineral sand precursor was tuned to obtain composites with 8.3 and 42.7 wt.% of α-FOD on the AC surface. These materials were characterized by X-ray powder diffraction, scanning electron microscopy, and the nitrogen adsorption–desorption method. The phenol removal efficiency of the composites was determined during 24 h of adsorption under dark conditions, followed by 24 h of adsorption–photocatalysis under visible light irradiation. AC/α-FOD composites with 8.3 and 42.7 wt.% of α-FOD adsorbed 60% and 51% of phenol in 24 h and reached a 90% and 96% removal efficiency after 12 h of irradiation, respectively. Given its higher photocatalytic response, the 42.7 wt.% α-FOD composite was also tested during successive cycles of adsorption and adsorption–photocatalysis. This composite exhibited a reasonable level of cyclability (~99% removal after four alternated dark/irradiated cycles of 24 h and ~68% removal after three simultaneous adsorption–photocatalysis cycles of 24 h). The promising performance of the as-prepared composites opens several opportunities for their application in the effective removal of organic micropollutants from water. Full article
(This article belongs to the Special Issue Heterogeneous Catalysis for Sustainability and Carbon-Neutrality)
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Graphical abstract
Full article ">Figure 1
<p>XRPD patterns of the as-synthesized composites (lines of α-FOD correspond to those of JCPDS card 23-0293).</p> Full article ">Figure 2
<p>SEM images of the AC and the AC/α-FOD composites.</p> Full article ">Figure 3
<p>Adsorption isotherms for phenol adsorption by AC (■), composites obtained from the dissolution of 1 g (<span style="color:#4472C4">▲</span>) and 6 g (<span style="color:#BA83E8">⬤</span>) of precursor in oxalic acid. The continuous, dashed, and dotted lines correspond to the best-fitted models.</p> Full article ">Figure 4
<p>Phenol adsorption under dark conditions (first 24 h) and photocatalytic degradation under visible light (last 24 h) by using AC (■), and composites obtained from the dissolution of 1 g (<span style="color:#0070C0">▲</span>) and 6 g (<span style="color:#BA83E8">⬤</span>) of precursor. Adsorbent dosage: 0.5 g/L. Inset: First-order kinetic equations of the photocatalytic degradation of phenol calculated with the first 16 h of visible irradiation.</p> Full article ">Figure 5
<p>Regeneration tests for phenol removal by using composite CS6g. (<b>a</b>) Cycles of phenol removal under alternated cycles of 24 h under dark conditions and 24 h under visible light irradiation; inset: first-order kinetic equations. (<b>b</b>) Three consecutive 24 h cycles of photocatalytic degradation of phenol under visible irradiation; inset: first-order kinetic equations. Adsorbent dosage: 0.5 g/L.</p> Full article ">Figure 6
<p>Schematic representation of the composites’ preparation.</p> Full article ">Figure 7
<p>Set-up for the adsorption and photocatalysis tests.</p> Full article ">
13 pages, 1304 KiB  
Article
Substituent Effects in the Photophysical and Electrochemical Properties of Meso-Tetraphenylporphyrin Derivatives
by Alexandra Cruz Millheim, Enric Ponzano and Albert Moyano
Molecules 2024, 29(15), 3689; https://doi.org/10.3390/molecules29153689 - 4 Aug 2024
Cited by 1 | Viewed by 880
Abstract
Porphyrins were identified some years ago as a promising, easily accessible, and tunable class of organic photoredox catalysts, but a systematic study on the effect of the electronic nature and of the position of the substituents on both the ground-state and the excited-state [...] Read more.
Porphyrins were identified some years ago as a promising, easily accessible, and tunable class of organic photoredox catalysts, but a systematic study on the effect of the electronic nature and of the position of the substituents on both the ground-state and the excited-state redox potentials of these compounds is still lacking. We prepared a set of known functionalized porphyrin derivatives containing different substituents either in one of the meso positions or at a β-pyrrole carbon, and we determined their ground- and (singlet) excited-state redox potentials. We found that while the estimated singlet excited-state energies are essentially unaffected by the introduction of substituents, the redox potentials (both in the ground- and in the singlet excited-state) depend on the electron-withdrawing or electron-donating nature of the substituents. Thus, the presence of groups with electron-withdrawing resonance effects results in an enhancement of the reduction facility of the photocatalyst, both in the ground and in the excited state. We next prepared a second set of four previously unknown meso-substituted porphyrins, having a benzoyl group at different positions. The reduction facility of the porphyrin increases with the proximity of the substituent to the porphine core, reaching a maximum when the benzoyl substituent is introduced at a meso position. Full article
(This article belongs to the Special Issue Porphyrin-Based Compounds: Synthesis and Application, 2nd Edition)
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<p>Porphyrin derivatives studied in this work: (<b>A</b>): previously known compounds. (<b>B</b>): new benzoyl-porphyrin derivatives.</p> Full article ">Scheme 1
<p>Some applications of porphyrins as photoredox catalysts. A: α-alkylation of aldehydes with diazo esters [<a href="#B15-molecules-29-03689" class="html-bibr">15</a>]. B: arylation of heterocycles [<a href="#B16-molecules-29-03689" class="html-bibr">16</a>]. C: desulfonilative alkylation of alkynyl sulfones [<a href="#B17-molecules-29-03689" class="html-bibr">17</a>].</p> Full article ">Scheme 2
<p>Synthesis of 5-(4′-benzoyl)-10,15,20-triphenylporphyrin <b>6</b>.</p> Full article ">Scheme 3
<p>Synthesis of benzoyl-porphyrin derivative <b>7</b>.</p> Full article ">Scheme 4
<p>Synthesis of porphyrin copper complex <b>8</b> and acid-promoted demetallation to <b>7</b>.</p> Full article ">Scheme 5
<p>Synthesis of 5-(benzoyl)-10,15,20-triphenylporphyrin <b>9</b>.</p> Full article ">
14 pages, 5206 KiB  
Article
Carbonized Ganoderma Lucidum/V2O3 Composites as a Superior Cathode for High-Performance Aqueous Zinc-Ion Batteries
by Guilin Zeng, Zhengda Li, Shaohua Jiang and Wei Zhou
Molecules 2024, 29(15), 3688; https://doi.org/10.3390/molecules29153688 - 4 Aug 2024
Viewed by 829
Abstract
In response to the suboptimal electrochemical performance of low-valence vanadium oxides, Ganoderma lucidum biomass-derived carbon@V2O3 (V2O3@CGL) composites were prepared by evaporative self-assembly technology and high-temperature calcination. In the prepared composites, V2O3 effectively encapsulates [...] Read more.
In response to the suboptimal electrochemical performance of low-valence vanadium oxides, Ganoderma lucidum biomass-derived carbon@V2O3 (V2O3@CGL) composites were prepared by evaporative self-assembly technology and high-temperature calcination. In the prepared composites, V2O3 effectively encapsulates CGL, serving as a support for V2O3 and enhancing electrical conductivity and structural stability. This results in improved overall performance for the composites. They revealed satisfactory electrochemical properties when assembled in aqueous zinc-ion batteries (AZIBs). The preliminary discharge specific capacity of the V2O3@CGL-2 (VOCG-2) composite electrode reached 407.87 mAh g−1 at 0.05 A g−1. After 1000 cycles, the capacity retention is 93.69% at 3 A g−1. This research underscores the feasibility of employing V2O3 and abundantly available biomass for high-performance AZIB cathodes. Full article
(This article belongs to the Special Issue Novel Electrode Materials for Rechargeable Batteries, 2nd Edition)
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<p>(<b>a</b>) XRD patterns; (<b>b</b>) FT-IR spectrum; (<b>c</b>) N<sub>2</sub> absorption/desorption isotherms; and (<b>d</b>) pore size distribution of the V<sub>2</sub>O<sub>3</sub>@CGL composites. Inset images show the (012) and (002) diffraction planes of the V<sub>2</sub>O<sub>3</sub>@CGL composites.</p> Full article ">Figure 2
<p>TGA curves of (<b>a</b>) VOCG-1, (<b>b</b>) VOCG-2, and (<b>c</b>) VOCG-3 composites.</p> Full article ">Figure 3
<p>(<b>a</b>) XPS survey spectra; at high-resolution: (<b>b</b>) C 1s, (<b>c</b>) O 1s, and (<b>d</b>) V 2p XPS spectra of the V<sub>2</sub>O<sub>3</sub>@CGL composites.</p> Full article ">Figure 4
<p>SEM pictures of (<b>a</b>–<b>c</b>) VOCG-1, (<b>d</b>–<b>f</b>) VOCG-2, and (<b>g</b>–<b>i</b>) VOCG-3 composites.</p> Full article ">Figure 5
<p>SEM and elemental mapping images of (<b>a</b>) VOCG-1, (<b>b</b>) VOCG-2, and (<b>c</b>) VOCG-3 composites.</p> Full article ">Figure 6
<p>(<b>a</b>) HRTEM map and (<b>b</b>) SAED diagram of the V<sub>2</sub>O<sub>3</sub>@CGL composites.</p> Full article ">Figure 7
<p>GCD profiles of (<b>a</b>) VOCG-1, (<b>b</b>) VOCG-2, and (<b>c</b>) VOCG-3 composites in the original five cycles; (<b>d</b>) rate; (<b>e</b>) cycling properties; and (<b>f</b>) capacity retention after 1000 cycles at 3 A g<sup>−1</sup> (blue), capacity retention after rate cycling to 3 A g<sup>−1</sup> (yellow) and rate cycling back to 0.05 A g<sup>−1</sup> (red) of the three samples.</p> Full article ">Figure 8
<p>(<b>a</b>) CV curves of VOCG-1, VOCG-2, and VOCG-3 composites before and after cycling; (<b>b</b>) EIS spectra of the V<sub>2</sub>O<sub>3</sub>@CGL composite cathodes before and after cycling; and (<b>c</b>) GITT curve and corresponding D<sub>Zn</sub><sup>2+</sup> values for the VOCG-2 composite cathode.</p> Full article ">Figure 9
<p>SEM photographs of the VOCG-2 composite electrodes at various stages: (<b>a</b>) pristine, (<b>b</b>) 200, (<b>c</b>) 400, (<b>d</b>) 600, (<b>e</b>) 800, and (<b>f</b>) 1000 cycles.</p> Full article ">Figure 10
<p>The preparation process of the V<sub>2</sub>O<sub>3</sub>@CGL composites.</p> Full article ">
17 pages, 1623 KiB  
Review
Dynamic and Static Regulation of Nicotinamide Adenine Dinucleotide Phosphate: Strategies, Challenges, and Future Directions in Metabolic Engineering
by Nana Ding, Zenan Yuan, Lei Sun and Lianghong Yin
Molecules 2024, 29(15), 3687; https://doi.org/10.3390/molecules29153687 - 3 Aug 2024
Viewed by 1584
Abstract
Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is a crucial cofactor in metabolic networks. The efficient regeneration of NADPH is one of the limiting factors for productivity in biotransformation processes. To date, many metabolic engineering tools and static regulation strategies have been developed to [...] Read more.
Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is a crucial cofactor in metabolic networks. The efficient regeneration of NADPH is one of the limiting factors for productivity in biotransformation processes. To date, many metabolic engineering tools and static regulation strategies have been developed to regulate NADPH regeneration. However, traditional static regulation methods often lead to the NADPH/NADP+ imbalance, causing disruptions in cell growth and production. These methods also fail to provide real-time monitoring of intracellular NADP(H) or NADPH/NADP+ levels. In recent years, various biosensors have been developed for the detection, monitoring, and dynamic regulate of the intracellular NADP(H) levels or the NADPH/NADP+ balance. These NADPH-related biosensors are mainly used in the cofactor engineering of bacteria, yeast, and mammalian cells. This review analyzes and summarizes the NADPH metabolic regulation strategies from both static and dynamic perspectives, highlighting current challenges and potential solutions, and discusses future directions for the advanced regulation of the NADPH/NADP+ balance. Full article
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<p>The static regulation strategies for increasing the NADPH pool. (<b>A</b>) The promoter engineering to control the NADPH level. (<b>B</b>) The protein engineering to modify the cofactor preference. The endogenous (<b>C</b>) and heterologous (<b>D</b>) cofactor engineering to improve the NADPH level. (<b>E</b>) The photo-chemical method to drive the NADPH regeneration.</p> Full article ">Figure 2
<p>The dynamic regulation strategies for regulating the NADPH/NADP<sup>+</sup> balance. (<b>A</b>) The auto-regulation of NADPH level based on the design of promoter/RBS library. (<b>I</b>) Schematic diagram of the intracellular NADPH dynamic regulation strategy based on promoter libraries. GAP, glyceraldehyde 3-P; 3PG, 3-P Glycerate; PEP, phosphoenolpyruvate; <span class="html-italic">gapN</span>, gene encoding glyceraldehyde-3-phosphate dehydrogenase N; P<span class="html-italic">lys</span>E<sub>lib</sub>, lysE promoter library; (<b>II</b>) Schematic diagram of the intracellular NADPH dynamic regulation strategy based on RBS libraries. <span class="html-italic">edd</span>, gene encoding 6-phosphogluconate dehydratase; <span class="html-italic">eda</span>, gene encoding 2-keto-3-deoxygluconate-6-phosphate (KDPG) aldolase. (<b>B</b>) The construction of mBFP and iNap biosensors to realize the detection and monitoring of NADPH levels in real time. (<b>I</b>) Working mechanisms of mBFP for detecting NADPH; (<b>II</b>) The working mechanism of iNap sensors. CpYFP, circularly permuted YFP. The construction of NADPH/NADP<sup>+</sup> ratio biosensor to control the redox balance in bacteria (<b>C</b>) and plant and animal cells (<b>D</b>).</p> Full article ">
17 pages, 15484 KiB  
Article
Competitive Adsorptive Mechanism of H2/N2 in LTA/FAU Zeolites by Molecular Simulations and Experiments
by Zixu Dong, Zhilu Wang, Lina Zhang, Qiang Fu and Ming Wang
Molecules 2024, 29(15), 3686; https://doi.org/10.3390/molecules29153686 - 3 Aug 2024
Viewed by 1244
Abstract
For industrial tail gas to be converted into high-purity hydrogen, the H2-N2 mixture needs to be separated efficiently. This work examined the adsorption characteristics and competitive mechanisms of H2 and N2 on LTA- and FAU-type zeolites, at 77 [...] Read more.
For industrial tail gas to be converted into high-purity hydrogen, the H2-N2 mixture needs to be separated efficiently. This work examined the adsorption characteristics and competitive mechanisms of H2 and N2 on LTA- and FAU-type zeolites, at 77 K, 298 K, and 0.1–10 bar by thoroughly analyzing results of adsorption capacity experiments and molecular simulations. In the Grand Canonical Monte Carlo (GCMC) simulations, the force field causing a molecular dipole of H2 and the polarization force field of N2 are first applied. The accuracy of the force field was experimentally verified. The findings indicate that N2 and H2 loading on Ca-FAU (Ca-LTA) are higher than Na-FAU (Na-LTA). On NaX at 77 K, the highest adsorption selectivity (N2/H2) is observed; on NaA at 298 K, it is the opposite. The GCMC data findings demonstrate that H2 and N2 have remarkably similar adsorption sites, with framework oxygen atoms and non-framework cations serving as the main adsorption sites for adsorbate molecules. Furthermore, the rate at which H2 diffuses is higher than that of N2. The study of redistribution charge before and after adsorption demonstrated that N2 has a greater affinity for the framework oxygen atoms than H2. This study provides a molecular theoretical foundation for the adsorption behavior of H2-N2 mixture in zeolites. Full article
(This article belongs to the Special Issue Application of Computer Simulation in Materials Science of Molecules, 2nd Edition)
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Full article ">Figure 1
<p>Adsorption isotherms of H<sub>2</sub> (<b>a</b>) and N<sub>2</sub> (<b>b</b>) in NaA, CaA, NaX, and CaX zeolites at 77 K, 0–1 bar, and the reported force fields by K<sup>44</sup>, E<sup>43</sup>, P<sup>46</sup>, G3<sup>42</sup>, V<sup>41</sup>, and H<sup>47</sup>.</p> Full article ">Figure 2
<p>Adsorption isotherms of H<sub>2</sub> (<b>a</b>) and N<sub>2</sub> (<b>b</b>) in NaA, CaA, NaX, and CaX zeolites at 298 K, 0–10 bar, and the reported force fields by K<sup>44</sup>, E<sup>43</sup>, P<sup>46</sup>, G3<sup>42</sup>, V<sup>41</sup>, and H<sup>47</sup>.</p> Full article ">Figure 3
<p>The adsorption selectivity for N<sub>2</sub> over H<sub>2</sub> in NaA, CaA, NaX, and CaX, which corresponds to the binary H<sub>2</sub>-N<sub>2</sub> mixture (H<sub>2</sub>/N<sub>2</sub>, 50/50, <span class="html-italic">v</span>/<span class="html-italic">v</span>): (<b>a</b>) 77 K, (<b>b</b>) 298 K.</p> Full article ">Figure 4
<p>Adsorption energy of H<sub>2</sub> and N<sub>2</sub> in NaA, CaA, NaX, and CaX at 1 bar: (<b>a</b>) 77 K, (<b>b</b>) 298 K.</p> Full article ">Figure 5
<p>Typical binding geometry of H<sub>2</sub> and N<sub>2</sub> adsorbed in the super cage of the zeolite employed according to our computer simulations at 77 K. (<b>a</b>,<b>b</b>) NaA, (<b>c</b>,<b>d</b>) CaA, H<sub>2</sub> molecule (white), N<sub>2</sub> molecule (blue), Si-zeolite (pink), Al-zeolite (yellow), O-zeolite (red), Na<sup>+</sup> cation (purple), and Ca<sup>2+</sup> cation (green).</p> Full article ">Figure 6
<p>Typical binding geometry of H<sub>2</sub> and N<sub>2</sub> adsorbed in the super cage of the zeolite employed according to our computer simulations at 77 K. (<b>a</b>,<b>b</b>) NaX, (<b>c</b>,<b>d</b>) CaX, H<sub>2</sub> molecule (white), N<sub>2</sub> molecule (blue), Si-zeolite (pink), Al-zeolite (yellow), O-zeolite (red), Na<sup>+</sup> cation (purple), and Ca<sup>2+</sup> cation (green).</p> Full article ">Figure 7
<p>Representative interatomic guest–pore radial distribution functions (RDFs) corresponding to H<sub>2</sub> at 77 K in (<b>a</b>) NaA, (<b>b</b>) CaA, (<b>c</b>) NaX, and (<b>d</b>) CaX. H<sub>2</sub> molecules with Al-zeolite (blue), with Si-zeolite (green), with O-zeolite (red), and with Na<sup>+</sup>/Ca<sup>2+</sup> cations (black).</p> Full article ">Figure 8
<p>Representative interatomic guest–pore radial distribution functions (RDFs) corresponding to N<sub>2</sub> at 77 K in (<b>a</b>) NaA, (<b>b</b>) CaA, (<b>c</b>) NaX, and (<b>d</b>) CaX. N<sub>2</sub> molecules with Al-zeolite (blue), with Si-zeolite (green), with O-zeolite (red), and with Na<sup>+</sup>/Ca<sup>2+</sup> cations (black).</p> Full article ">Figure 9
<p>Mean square displacements for H<sub>2</sub>-N<sub>2</sub> mixture (H<sub>2</sub>/N<sub>2</sub>, 50/50, <span class="html-italic">v</span>/<span class="html-italic">v</span>) in (<b>a</b>) NaA, (<b>b</b>) CaA, (<b>c</b>) NaX, and (<b>d</b>) CaX at 77 K. The solid line is a fitted line.</p> Full article ">Figure 10
<p>Mean square displacements for H<sub>2</sub>-N<sub>2</sub> mixture (H<sub>2</sub>/N<sub>2</sub>, 50/50, <span class="html-italic">v</span>/<span class="html-italic">v</span>) in (<b>a</b>) NaA, (<b>b</b>) CaA, (<b>c</b>) NaX, and (<b>d</b>) CaX at 298 K. The solid line is a fitted line.</p> Full article ">Figure 11
<p>A slice of the redistribution of charge density in (<b>a</b>) NaA, (<b>b</b>) NaX, (<b>c</b>) CaA, and (<b>d</b>) CaX after adsorbing H<sub>2</sub> molecules.</p> Full article ">Figure 12
<p>A slice of the redistribution of charge density in (<b>a</b>) NaA, (<b>b</b>) NaX, (<b>c</b>) CaA, and (<b>d</b>) CaX after adsorbing N<sub>2</sub> molecules.</p> Full article ">
39 pages, 18396 KiB  
Review
Asymmetric Synthesis and Applications of Chiral Organoselenium Compounds: A Review
by Yanyu Jian, Thishana Singh, Pher G. Andersson and Taigang Zhou
Molecules 2024, 29(15), 3685; https://doi.org/10.3390/molecules29153685 - 3 Aug 2024
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Abstract
The synthesis and application of organoselenium compounds have developed rapidly, and chiral organoselenium compounds have become an important intermediate in the field of medicine, materials, organic synthesis. The strategy of developing a green economy is still a challenge in the synthesis of chiral [...] Read more.
The synthesis and application of organoselenium compounds have developed rapidly, and chiral organoselenium compounds have become an important intermediate in the field of medicine, materials, organic synthesis. The strategy of developing a green economy is still a challenge in the synthesis of chiral organoselenium compounds with enantioselective properties. This review covers in detail the synthesis of chiral organoselenium compounds from 1979 to 2024 and their application in the fields of asymmetric synthesis and catalysis. Full article
(This article belongs to the Section Organic Chemistry)
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Figure 1

Figure 1
<p>Application of organoselenium compounds.</p> Full article ">Figure 2
<p>Chiral organoselenium compounds.</p> Full article ">Figure 3
<p>Asymmetric synthesis of organoselenium compounds and its application.</p> Full article ">Scheme 1
<p>Asymmetric [2 + 1] cycloaddition reaction of 1-phenylselenium-2-silylethylene.</p> Full article ">Scheme 2
<p>Lewis bases catalyzed asymmetric intramolecular selenium cyclization of unsaturated alcohols.</p> Full article ">Scheme 3
<p>Selenium cyclization catalyzed by chiral square amide catalysts.</p> Full article ">Scheme 4
<p>Asymmetric selenolactonization of olefinic acids.</p> Full article ">Scheme 5
<p>Desymmetrizing enantio- and diastereoselective selenoetherification of olefinic 1,3-diol via supramolecular catalysis.</p> Full article ">Scheme 6
<p>Chiral phosphoric acid catalyzes the synthesis of 3a-(phenylselenyl)-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b]indole derivatives.</p> Full article ">Scheme 7
<p>Asymmetric synthesis of selenium-containing 4H-3,1-benzoxazines.</p> Full article ">Scheme 8
<p>Asymmetric catalytic addition of aryl selenol with 2-cyclohexen-1 one.</p> Full article ">Scheme 9
<p>Asymmetric imidation of aryl selenides.</p> Full article ">Scheme 10
<p>Asymmetric synthesis of α-alkyl α-selenocarbonyl compounds catalyzed by bifunctional organocatalysts.</p> Full article ">Scheme 11
<p>Catalytic asymmetric oxyselenenylation of olefins by chiral Brønsted acid.</p> Full article ">Scheme 12
<p>Enantioselective addition of selenosulfonates to α, β-unsaturated ketones.</p> Full article ">Scheme 13
<p>Organocatalytic enantioselective addition of selenosulfonates to α, β-unsaturated ketones.</p> Full article ">Scheme 14
<p>Rh-catalyzed enantioselective hydroselenation of heterobicyclic alkenes.</p> Full article ">Scheme 15
<p>Stereoselective <span class="html-italic">Se</span>-Michael addition preparation of enantiomerically pure β-selenium-α-amino acids.</p> Full article ">Scheme 16
<p>NHC catalyzed enantioselective <span class="html-italic">Se</span>-Michael addition reactions.</p> Full article ">Scheme 17
<p>Rh-catalyzed enantioselective hydroselenation of styrene.</p> Full article ">Scheme 18
<p>Asymmetric synthesis of selenium-containing 4H-3,1-benzoxazines.</p> Full article ">Scheme 19
<p>Asymmetric selenization reaction of selenol and α, β-unsaturated thioamide.</p> Full article ">Scheme 20
<p>Enantioselective selenization of diselenoacetals.</p> Full article ">Scheme 21
<p>Organocatalytic asymmetric α-selenenylation of aldehydes and its application.</p> Full article ">Scheme 22
<p>Synthesis of highly enantioselective α-alkyl, α-vinyl amino acids.</p> Full article ">Scheme 23
<p>[2,3]-Sigmatropic Rearrangement of Allylic Selenimides.</p> Full article ">Scheme 24
<p>Cr-catalyzed diastereo-and enantioselective synthesis of β-hydroxy selenides.</p> Full article ">Scheme 25
<p>Enantioselective ring-opening reaction of epoxy compounds with aryl selenols.</p> Full article ">Scheme 26
<p>Asymmetric catalytic synthesis of 3,3-disubstituted oxyindole.</p> Full article ">Scheme 27
<p>Lewis acid-catalyzed asymmetric selenocyanation of β-ketoesters with N-selenocyanatosaccharin.</p> Full article ">Scheme 28
<p>Rh(III)-catalyzed atroposelective C−H selenylation of 1-aryl isoquinolines.</p> Full article ">Scheme 29
<p>Synthesis of allyl selenides by palladium-catalyzed decarboxylative coupling.</p> Full article ">Scheme 30
<p>Strategy for asymmetric synthesis of enantiomerically pure 1,2-selenoamines.</p> Full article ">Scheme 31
<p>Se-Michael addition triggered ring-expansion synthesis of chiral organoselenium dihydronaphthoquinone.</p> Full article ">Scheme 32
<p>Visible-light photoredox synthesis of chiral α-selenoamino acid.</p> Full article ">Scheme 33
<p>Stereospecific Al-catalysed tandem C-N/C-Se bond formation of isoselenocyanates with aziridines.</p> Full article ">Scheme 34
<p>Synthesis of di(hetero)aryl diselenides and dibenzylic diselenides from aryl quaternary ammonium salts and selenium compounds.</p> Full article ">Scheme 35
<p>Chiral selenide catalysts.</p> Full article ">Scheme 36
<p>Chiral aminodiselenide compounds catalyze the synthesis of enantioselective secondary alcohols.</p> Full article ">Scheme 37
<p>C<sub>2</sub>-symmetric cyclic selenium-catalyzed enantioselective bromoaminocyclization.</p> Full article ">Scheme 38
<p>Enantioselective trifluoromethylthiolating aminocyclization.</p> Full article ">Scheme 39
<p>Enantioselective oxytrifluoromethylthiolation of aliphatic internal alkenes.</p> Full article ">Scheme 40
<p>Allyl enantioselective reaction and intermolecular difunctionalization of olefins.</p> Full article ">Scheme 41
<p>Enantioselective desymmetrization and trifluoromethylthiolation of <span class="html-italic">gem</span>-diaryl tethered alkenes/alkynes.</p> Full article ">Scheme 42
<p>Chiral selenide-catalyzed enantioselective synthesis of trifluoromethylthiolated 2,5-disubstituted oxazolines.</p> Full article ">Scheme 43
<p>Enantioselective construction of chiral sulfides via chiral selenide-catalytic electrophilic azidothiolation and oxythiolation of <span class="html-italic">N</span>-allyl sulfonamides.</p> Full article ">Scheme 44
<p>Enantioselective construction of P-chirogenic compounds via electrophilic aromatic chlorination.</p> Full article ">Scheme 45
<p>Organoselenium-catalyzed asymmetric cyclopropanations of (<span class="html-italic">E</span>)-Chalcones.</p> Full article ">Scheme 46
<p>Chiral selenide-catalyzed enantioselective electrophilic hydrothiolation of Alkenes.</p> Full article ">Scheme 47
<p>Asymmetric photoaerobic lactonization and Aza-Wacker cyclization of alkenes enabled by ternary selenium-sulfur multicatalysis.</p> Full article ">Scheme 48
<p>Catalytic enantioselective electrophilic difunctionalization of unsaturated sulfones.</p> Full article ">
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