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14 pages, 2097 KiB

Open AccessArticle

Synthesis and Characterization of Novel Co(III)/Ru(II) Heterobimetallic Complexes as Hypoxia-Activated Iron-Sequestering Anticancer Prodrugs

by Tan Ba Tran, Éva Sipos, Attila Csaba Bényei, Sándor Nagy, István Lekli and Péter Buglyó

Molecules 2024, 29(24), 5967; https://doi.org/10.3390/molecules29245967 - 18 Dec 2024

Viewed by 250

Abstract

Heterobimetallic complexes of an ambidentate deferiprone derivative, 3-hydroxy-2-methyl-1-(3-((pyridin-2-ylmethyl)amino)propyl)pyridin-4(1H)-one (PyPropHpH), incorporating an octahedral [Co(4N)]³⁺ (4N = tris(2-aminoethyl)amine (tren) or tris(2-pyridylmethyl)amine (tpa)) and a half-sandwich type [(η⁶-p-cym)Ru]²⁺ (p-cym = p-cymene) entity have been synthesized and characterized [...] Read more.

Heterobimetallic complexes of an ambidentate deferiprone derivative, 3-hydroxy-2-methyl-1-(3-((pyridin-2-ylmethyl)amino)propyl)pyridin-4(1H)-one (PyPropHpH), incorporating an octahedral [Co(4N)]³⁺ (4N = tris(2-aminoethyl)amine (tren) or tris(2-pyridylmethyl)amine (tpa)) and a half-sandwich type [(η⁶-p-cym)Ru]²⁺ (p-cym = p-cymene) entity have been synthesized and characterized by various analytical techniques. The reaction between PyPropHpH and [Co(4N)Cl]Cl₂ resulted in the exclusive (O,O) coordination of the ligand to Co(III) yielding [Co(tren)PyPropHp](PF₆)₂ (1) and [Co(tpa)PyPropHp](PF₆)₂ (2). This binding mode was further supported by the molecular structure of [Co(tpa)PyPropHp]₂(ClO₄)₃(OH)·6H₂O (5) and [Co(tren)PyPropHpH]Cl(PF₆)₂·2H₂O·C₂H₅OH (6), respectively, obtained via the slow evaporation of the appropriate reaction mixtures and analyzed using X-ray crystallography. Subsequent treatment of 1 or 2 with [Ru(η⁶-p-cym)Cl₂]₂ in a one-pot reaction afforded the corresponding heterobimetallic complexes, [Co(tren)PyPropHp(η⁶-p-cym)RuCl](PF₆)₃ (3) and [Co(tpa)PyPropHp(η⁶-p-cym)RuCl](PF₆)₃ (4), in which the piano-stool Ru core is coordinated by the (N,N) chelating set of the ligand. Cyclic voltammetric measurements revealed that the tpa complexes can be reduced at less negative potentials, suggesting their capability to be bioreductively activated under hypoxia (1% O₂). Hypoxia activation of 2 and 4 was demonstrated by cytotoxicity studies on the MCF-7 human breast cancer cell line. PyPropHpH was shown to be a typical iron-chelating anticancer agent, raising the mRNA levels of TfR1, Ndrg1 and p21. Further qRT-PCR studies provided unambiguous evidence for the bioreduction of 2 after 72 h incubation under hypoxia, in which the characteristic gene induction profile caused by the liberated iron-sequestering PyPropHpH was observed. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Figure 1

Figure 1
Structural formulas of the studied and model ligands as well as the metal building blocks. Full article ">Figure 2
Ortep view of the molecular structure of [Co(tren)(PyPropHpH)]3+ (top) and [Co(tpa)(PyPropHp)]2+ (bottom) cations. The anions and solvent molecules are omitted for clarity. Full article ">Figure 3
(A) Cell viability after 72 h treatment of PyPropHpH under normoxia (black) and hypoxia (gray). (B) Cell viability after 72 h treatment with the complexes under normoxia (black) and hypoxia (gray). Data points are presented as mean (SD). Multiple paired t test and Holm–Šidák post hoc test were used to analyze the data. Significance level: ns: p > 0.05, *: p ≤ 0.05, **: p ≤ 0.01, ***: p ≤ 0.001, ****: p ≤ 0.0001. Full article ">Figure 4
Gene expression level changes calculated by 240-ct method after (A) 24 h treatment with PyPropHpH, (B) 24 h treatment with PyPropHpH and 2 at 200 μM and (C) 72 h treatment with PyPropHpH and 2 at 100 μM under normoxia (black) and hypoxia (gray). Data points are presented as mean (SD). Two-way ANOVA for (A,B) and one-way ANOVA for (C) followed by Dunett’s post hoc test for (A) and Tukey’s post hoc test for (B,C) were used to analyze the data. Significance level: ns: p > 0.05, *: p ≤ 0.05, **: p ≤ 0.01, ***: p ≤ 0.001, ****: p ≤ 0.0001. Full article ">Scheme 1
Synthetic procedure of the Co(III) complexes and Co(III)/Ru(II) heterobimetallic complexes. The structures of Co(III)-based geometric isomers are shown. Stereogenic centers are denoted with *. Full article ">

17 pages, 2438 KiB

Open AccessArticle

Synthesis and Characterisation of Phosphino-Aryloxide Rare Earth Complexes

by Elias Alexopoulos, Yu Liu, Alex W. J. Bowles, Benjamin L. L. Réant and Fabrizio Ortu

Molecules 2024, 29(23), 5757; https://doi.org/10.3390/molecules29235757 - 5 Dec 2024

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Abstract

A series of homoleptic rare earth (RE) complexes bearing phosphino-aryloxide ligands (1-RE, 2-La) has been prepared. The complexes have been characterised using multinuclear NMR and IR spectroscopy, X-ray crystallography and elemental analysis. Structural characterisation highlighted the different RE–P interactions as [...] Read more.

A series of homoleptic rare earth (RE) complexes bearing phosphino-aryloxide ligands (1-RE, 2-La) has been prepared. The complexes have been characterised using multinuclear NMR and IR spectroscopy, X-ray crystallography and elemental analysis. Structural characterisation highlighted the different RE–P interactions as a result of differing Lewis acidity and ionic size across the series, hinting at the possibility of FLP-type activity. The potential reactivity of these complexes has been tested by reacting them with small molecules (H₂, CO, CO₂). A series of side-products (3-RE) has also been observed, isolated and characterised, featuring the incorporation of a phosphonium-aryloxide ligand. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
Examples of Zr (I) and RE complexes (I–IV) that display FLP-like reactivity, and selected phosphino-aryloxide complexes (V) [<a href="#B22-molecules-29-05757" class="html-bibr">22</a>,<a href="#B24-molecules-29-05757" class="html-bibr">24</a>,<a href="#B26-molecules-29-05757" class="html-bibr">26</a>,<a href="#B27-molecules-29-05757" class="html-bibr">27</a>,<a href="#B41-molecules-29-05757" class="html-bibr">41</a>]. Full article ">Figure 2
Crystal structures of 1-La and 2-La. Ellipsoids are shown at 30% probability level, hydrogen atoms are omitted, tert-butyl and iso-propyl groups are shown as wireframe for clarity. Symmetry operation used to generate equivalent atoms: i = 1 − x, 1 − y, 1 − z. Full article ">Figure 3
Crystal structure of 1-Sm. Ellipsoids are shown at 30% probability level, hydrogen atoms are omitted and tert-butyl groups are shown as wireframe for clarity. Full article ">Figure 4
Crystal structures of 3-Y and 3-Pr. Ellipsoids are shown at 30% probability level, hydrogen atoms are omitted and tert-butyl groups are shown as wireframe for clarity, with the exception of phosphonium proton. Full article ">Figure 5
Crystal structures of 3-La and 3-Sm. Ellipsoids are shown at 30% probability level, hydrogen atoms are omitted and tert-butyl groups are shown as wireframe for clarity, with the exception of phosphonium proton. Full article ">Scheme 1
Synthesis of 1-RE, 2-La and 3-RE. Crystalline yields are reported in brackets (* denotes spectroscopic yield). Full article ">Scheme 2
Synthesis of 4. Full article ">Scheme 3
Reactivity of 3-RE (RE = Y, La) with B(C6F5)3 and formation of 1-RE and 5. Full article ">

19 pages, 3441 KiB

Open AccessArticle

The Relationship Between Spin Crossover (SCO) Behaviors, Cation and Ligand Motions, and Intermolecular Interactions in a Series of Anionic SCO Fe(III) Complexes with Halogen-Substituted Azobisphenolate Ligands

by Mai Hirota, Suguru Murata, Takahiro Sakurai, Hitoshi Ohta and Kazuyuki Takahashi

Molecules 2024, 29(22), 5473; https://doi.org/10.3390/molecules29225473 - 20 Nov 2024

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Abstract

To investigate the halogen substitution effect on the anionic spin crossover (SCO) complexes, azobisphenolate ligands with 5,5′-dihalogen substituents from fluorine to iodine were synthesized, and their anionic Fe^III complexes 1F, 1Cl, 1Br, and 1I were isolated. The temperature dependence [...] Read more.

To investigate the halogen substitution effect on the anionic spin crossover (SCO) complexes, azobisphenolate ligands with 5,5′-dihalogen substituents from fluorine to iodine were synthesized, and their anionic Fe^III complexes 1F, 1Cl, 1Br, and 1I were isolated. The temperature dependence of magnetic susceptibility and crystal structure revealed that 1F, 1Cl, and 1Br are all isostructural and exhibit SCO with the rotational motion of the cation and ligands, whereas 1I shows incomplete SCO. Note that 1Cl and 1Br showed irreversible and reversible cooperative SCO transitions, respectively. Short intermolecular contacts between the Fe^III complex anions were found despite Coulomb repulsions for all the complexes. The topological analysis of the electron density distributions revealed the existence of X···X halogen bonds, C–H···X, C–H···N, and C–H···O hydrogen bonds, and C–H···π interactions are evident. The dimensionality of intermolecular interactions is suggested to be responsible for the cooperative SCO transitions in 1Cl and 1Br, whereas the disorder due to the freezing of ligand rotations in 1Cl is revealed to inhibit the SCO cooperativity. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
Structural formula of 2,2′-azobisphenol H2LX (a); (TMA)[FeIII(LX)2] 1X [TMA = tetramethylammonium cation] (b). Full article ">Figure 2
The χMT vs. T product for the Fe(III) complexes 1X. Full article ">Figure 3
ORTEP drawings of 50% probability with selected atomic numbering for the asymmetric unit. (a) 1F at 90 K; (b) 1I at 90 K. See text for the occupancy of the TMA cation. Full article ">Figure 4
(a) Two-dimensional molecular network of the [Fe(LBr)2]− anions in 1Br along the a axis at 90 K. (b) Molecular arrangement between two-dimensional networks in 1Br along the b axis at 90 K. Letters P–V with or without a prime are a label of the [Fe(LX)2]− anion molecules with fractional coordinates described in the text and <a href="#molecules-29-05473-t003" class="html-table">Table 3</a>. Dot lines indicate selected intermolecular short contacts between the central reference [Fe(LX)2]− anion molecule and the labeled one. Full article ">Figure 5
(a) Two-dimensional molecular network of [Fe(LI)2]− anions in 1I at 90 K. (b) Molecular arrangement between two-dimensional networks in 1I along the c axis at 90 K. Letters P–V with or without a prime are a label of the [Fe(LI)2]− anion molecules with fractional coordinates described in the text and <a href="#molecules-29-05473-t004" class="html-table">Table 4</a>. Dot lines indicate selected intermolecular short contacts between the central reference [Fe(LI)2]− anion molecule and the labeled one. Full article ">Scheme 1
Synthesis of halogen-substituted azp ligands (H2LX). * The yields of 4Cl and H2LCl in the literature [<a href="#B43-molecules-29-05473" class="html-bibr">43</a>] were 41% and 56%, respectively. Full article ">

14 pages, 2057 KiB

Open AccessArticle

Exploring the Impact of Water Content in Solvent Systems on Photochemical CO₂ Reduction Catalyzed by Ruthenium Complexes

by Yusuke Kuramochi, Masaya Kamiya and Hitoshi Ishida

Molecules 2024, 29(20), 4960; https://doi.org/10.3390/molecules29204960 - 20 Oct 2024

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Abstract

To achieve artificial photosynthesis, it is crucial to develop a catalytic system for CO₂ reduction using water as the electron source. However, photochemical CO₂ reduction by homogeneous molecular catalysts has predominantly been conducted in organic solvents. This study investigates the impact [...] Read more.

To achieve artificial photosynthesis, it is crucial to develop a catalytic system for CO₂ reduction using water as the electron source. However, photochemical CO₂ reduction by homogeneous molecular catalysts has predominantly been conducted in organic solvents. This study investigates the impact of water content on catalytic activity in photochemical CO₂ reduction in N,N-dimethylacetamide (DMA), using [Ru(bpy)₃]²⁺ (bpy: 2,2′-bipyridine) as a photosensitizer, 1-benzyl-1,4-dihydronicotinamide (BNAH) as an electron donor, and two ruthenium diimine carbonyl complexes, [Ru(bpy)₂(CO)₂]²⁺ and trans(Cl)-[Ru(Ac-5Bpy-NHMe)(CO)₂Cl₂] (5Bpy: 5′-amino-2,2′-bipyridine-5-carboxylic acid), as catalysts. Increasing water content significantly decreased CO and formic acid production. The similar rates of decrease for both catalysts suggest that water primarily affects the formation efficiency of free one-electron-reduced [Ru(bpy)₃]²⁺, rather than the intrinsic catalytic activity. The reduction in cage-escape efficiency with higher water content underscores the challenges in replacing organic solvents with water in photochemical CO₂ reduction. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Figure 1
Chemical structures of [Ru(bpy)3]2+, BNAH, and ruthenium diimine carbonyl complexes. Full article ">Figure 2
Effects of water content on the reduction products after 1h of irradiation (λ > 400 nm) using (a) [Ru(bpy)2(CO)2](PF6)2 (1.0 × 10−4 M) [<a href="#B25-molecules-29-04960" class="html-bibr">25</a>] and (b) trans(Cl)-[Ru(Ac-5Bpy-NHMe)(CO)2Cl2] (1.0 × 10−4 M) [<a href="#B34-molecules-29-04960" class="html-bibr">34</a>] in DMA containing [Ru(bpy)3](PF6)2 (5.0 × 10−4 M) and BNAH (0.10 M) under CO2 atmosphere: CO (○), HCOOH (■), H2 (Δ), and CO+HCOOH (+). Full article ">Figure 3
Reaction mechanism for the photocatalytic CO2 reduction, consisting of the electron–relay cycle and the catalytic cycle [<a href="#B8-molecules-29-04960" class="html-bibr">8</a>,<a href="#B51-molecules-29-04960" class="html-bibr">51</a>]. Full article ">Figure 4
Viscosity as a function of water content in the DMA and water-mixed solvent. These plots are reconstructed using the values reported in reference [<a href="#B61-molecules-29-04960" class="html-bibr">61</a>,<a href="#B62-molecules-29-04960" class="html-bibr">62</a>]. Full article ">Figure 5
Plots of (RT ln kq’ + λo/4) vs. ∆GET in DMA/water at 298 K. The line is drawn with slope = 1/2. Full article ">Figure 6
(a) Values of the electrostatic work term (blue diamonds) and viscosity term (red squares) in Equation (10) as a function of water content. (b) Relationship between the relative ratio of the cage-escape rate constants corrected by the quenching constants (black circles) and the relative TONs in the photochemical CO2 reduction catalysed by [Ru(bpy)2(CO)2]2+ (red points) and trans(Cl)-[Ru(Ac-5Bpy-NHMe)(CO)2Cl2] (blue points). Full article ">

11 pages, 2933 KiB

Open AccessArticle

Relaxivity Modulation of Gd-HPDO3A-like Complexes by Introducing Polar and Protic Peripheral Groups

by Sara Camorali, Loredana Leone, Laura Piscopo and Lorenzo Tei

Molecules 2024, 29(19), 4663; https://doi.org/10.3390/molecules29194663 - 30 Sep 2024

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Abstract

In the last three decades, high-relaxivity Magnetic Resonance Imaging (MRI) contrast agents (CAs) have been intensively sought, aiming at a reduction in the clinically injected dose while maintaining the safety of the CA and obtaining the same pathological information. Thus, four new Gd(III) [...] Read more.

In the last three decades, high-relaxivity Magnetic Resonance Imaging (MRI) contrast agents (CAs) have been intensively sought, aiming at a reduction in the clinically injected dose while maintaining the safety of the CA and obtaining the same pathological information. Thus, four new Gd(III) complexes based on modified 10-(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (HP-DO3A) macrocyclic structure were designed and synthesized by introducing further polar and protic functional groups (amides, phosphonates, and diols) adjacent to the metal-coordinated hydroxyl group. A detailed ¹H NMR relaxometric analysis allowed us to investigate the effect of these functional groups on the relaxivity, which showed a 20–60% increase (at 0.5 T, 298 K, and pH 7.4) with respect to that of clinically approved CAs. The contribution of the water molecules H-bonded to these peripheral functional groups on the relaxivity was evaluated in terms of the second sphere effect or prototropic exchange of labile protons. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Figure 1
HPDO3A-like ligands discussed in the text. Full article ">Figure 2
Novel HPDO3A-like ligands synthesized in this work. Full article ">Figure 3
(A): comparison between the r1 values as a function of pH (20 MHz, 298 K) for GdHPPDO3A (black squares) and GdHPPEtDO3A (blue diamonds); (B): r1 values as a function of pH (20 MHz, 298 K) for GdHPADO3A-MP (red diamonds) and GdHPADO3A-Ser (black squares) compared to the variable pH profile reported for the secondary amide analogue GdBzHPADO3A [<a href="#B21-molecules-29-04663" class="html-bibr">21</a>] (blue triangles). Full article ">Figure 4
(A): 1H NMRD profiles at 298 K for GdHPPDO3A (black squares) and GdHPPEtDO3A (blue diamonds); (B): 1H NMRD profiles at 298 K for GdHPADO3A-MP (red diamonds), GdHPADO3A-Ser (black squares), and GdBzHPADO3A (blue triangles). The solid lines correspond to the fits of the data as described in the text. Full article ">Scheme 1
Synthesis of HPPEtDO3A and HPPDO3A. i: tBuOH, reflux, 18 h; ii: TFA, DCM 1:1, 18 h; iii: BrSi(CH3)3, DCM, 0 °C, 15 min, then RT, 18 h. Full article ">Scheme 2
Synthesis of HPADO3A-MP. iv: t-Butyl-2-aminomethylphosphonate, HATU, DIPEA, 0 °C, 3 h; ii: TFA/DCM 1:1, RT, 18 h. Full article ">Scheme 3
Synthesis of HPADO3A-Ser. v: 10 eq. serinol, MeOH, RT, 24 h; ii: TFA/DCM 1:1, 18 h. Full article ">Scheme 4
Synthesis of the Gd(III) complexes of the ligands reported in this work. Full article ">

18 pages, 3424 KiB

Open AccessArticle

Large Number of Direct or Pseudo-Direct Band Gap Semiconductors among A₃TrPn₂ Compounds with A = Li, Na, K, Rb, Cs; Tr = Al, Ga, In; Pn = P, As

by Sabine Zeitz, Yulia Kuznetsova and Thomas F. Fässler

Molecules 2024, 29(17), 4087; https://doi.org/10.3390/molecules29174087 - 28 Aug 2024

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Abstract

Due to the high impact of semiconductors with respect to many applications for electronics and energy transformation, the search for new compounds and a deep understanding of the structure–property relationship in such materials has a high priority. Electron-precise Zintl compounds of the composition [...] Read more.

Due to the high impact of semiconductors with respect to many applications for electronics and energy transformation, the search for new compounds and a deep understanding of the structure–property relationship in such materials has a high priority. Electron-precise Zintl compounds of the composition A₃TrPn₂ (A = Li − Cs, Tr = Al − In, Pn = P, As) have been reported for 22 possible element combinations and show a large variety of different crystal structures comprising zero-, one-, two- and three-dimensional polyanionic substructures. From Li to Cs, the compounds systematically lower the complexity of the anionic structure. For an insight into possible crystal–structure band–structure relations for all compounds (experimentally known or predicted), their band structures, density of states and crystal orbital Hamilton populations were calculated on a basis of DFT/PBE0 and SVP/TZVP basis sets. All but three (Na₃AlP₂, Na₃GaP₂ and Na₃AlAs₂) compounds show direct or pseudo-direct band gaps. Indirect band gaps seem to be linked to one specific structure type, but only for Al and Ga compounds. Arsenides show smaller band gaps than phosphides due to weaker Tr-As bonds. The bonding situation was confirmed by a Mullikan analysis, and most states close to the Fermi level were assigned to non-bonding orbitals. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Figure 1

Figure 1
Overview of all known structure types within the A3TrPn2 system (with A = Li − Cs, Tr = Al, Ga, In, Pn = P, As). The respective structure types (denoted as (A–H) in the picture) are used to reference the structures. For all structures, the alkali metal A is depicted in red, the pnictide Pn in purple and the triel element Tr in grey. Full article ">Figure 2
(a) Band structure and density of states of Li3AlP2 (type F) with a direct band gap of 3.06 eV green arrow); (b) band structure and density of states of Cs3AlP2 (type A) with a pseudo-direct band gap of 2.54 eV (green arrow) and an indirect band gap of 2.56 eV (orange arrow). Full article ">Figure 3
(a) Band structure and density of states of Na3AlP2 (type E) with an indirect band gap of 3.34 eV; (b) band structure and density of states of K3InP2 (type E) with a direct band gap of 2.89 eV. Full article ">Figure 4
(a) COHP for all heteroatomic interactions in Li3AlP2 and Na3AlP2. (b) COHP for Tr-Tr interactions for Na3AlP2 and K3InP2. (c) Al-P bond projected COHP for Li3AlP2 and Cs3AlP2. For all plots, the red line represents the Fermi level at 0 eV and the grey, dashed line the top of the band gap. For Cs3AlP2, the atomic positions in the projected DOS refer to the assigned positions in the scheme. Full article ">Scheme 1
Polyanions in compounds of the composition A5TtP3 and A10Tt2P6 (A = Li − Cs; Tt = Si − Sn). Full article ">Scheme 2
Lewis valence structures of the various building units in A3TrPn2 Zintl phases. Mesomere valence formulae 1a and 1b of the “zero”-dimensional [Tr2Pn4]6− unit of two edge-sharing triangular planar units. The dimeric [Tr2Pn4]6− unit 2 and the one-dimensional <math display="inline"><semantics> <mrow> <mmultiscripts> <mrow> <mo>[</mo> <mi>T</mi> <mi>r</mi> <msub> <mrow> <mi>P</mi> <mi>n</mi> </mrow> <mrow> <mn>4</mn> <mo>/</mo> <mn>2</mn> </mrow> </msub> <mo>]</mo> </mrow> <none/> <mrow> <mn>3</mn> <mo>−</mo> </mrow> <mprescripts/> <mrow> <mo>∞</mo> </mrow> <mrow> <mn>1</mn> </mrow> </mmultiscripts> </mrow> </semantics></math> string 3 of edge-sharing tetrahedra, a TrPn4 tetrahedra 4 and the adamantane type subunit 5. Further connecting atoms are represented in grey colour without formal charges. Full article ">

24 pages, 7874 KiB

Open AccessArticle

A Mechanistic Study on Iron-Based Styrene Aziridination: Understanding Epoxidation via Nitrene Hydrolysis

by Dóra Lakk-Bogáth, Patrik Török, Dénes Pintarics and József Kaizer

Molecules 2024, 29(15), 3470; https://doi.org/10.3390/molecules29153470 - 24 Jul 2024

Viewed by 905

Abstract

Transition-metal-catalyzed nitrene transfer reactions are typically performed in organic solvents under inert and anhydrous conditions due to the involved air and water-sensitive nature of reactive intermediates. Overall, this study provides insights into the iron-based ([Fe^II(PBI)₃](CF₃SO₃) [...] Read more.

Transition-metal-catalyzed nitrene transfer reactions are typically performed in organic solvents under inert and anhydrous conditions due to the involved air and water-sensitive nature of reactive intermediates. Overall, this study provides insights into the iron-based ([Fe^II(PBI)₃](CF₃SO₃)₂ (1), where PBI = 2-(2-pyridyl)benzimidazole), catalytic and stoichiometric aziridination of styrenes using PhINTs ([(N-tosylimino)iodo]benzene), highlighting the importance of reaction conditions including the effects of the solvent, co-ligands (para-substituted pyridines), and substrate substituents on the product yields, selectivity, and reaction kinetics. The aziridination reactions with 1/PhINTs showed higher conversion than epoxidation with 1/PhIO (iodosobenzene). However, the reaction with PhINTs was less selective and yielded more products, including styrene oxide, benzaldehyde, and 2-phenyl-1-tosylaziridine. Therefore, the main aim of this study was to investigate the potential role of water in the formation of oxygen-containing by-products during radical-type nitrene transfer catalysis. During the catalytic tests, a lower yield was obtained in a protic solvent (trifluoroethanol) than in acetonitrile. In the case of the catalytic oxidation of para-substituted styrenes containing electron-donating groups, higher yield, TON, and TOF were achieved than those with electron-withdrawing groups. Pseudo-first-order kinetics were observed for the stoichiometric oxidation, and the second-order rate constants (k₂ = 7.16 × 10⁻³ M⁻¹ s⁻¹ in MeCN, 2.58 × 10⁻³ M⁻¹ s⁻¹ in CF₃CH₂OH) of the reaction were determined. The linear free energy relationships between the relative reaction rates (logk_rel) and the total substituent effect (TE, 4R-PhCHCH₂) parameters with slopes of 1.48 (MeCN) and 1.89 (CF₃CH₂OH) suggest that the stoichiometric aziridination of styrenes can be described through the formation of a radical intermediate in the rate-determining step. Styrene oxide formation during aqueous styrene aziridination most likely results from oxygen atom transfer via in situ iron oxo/oxyl radical complexes, which are formed through the hydrolysis of [Fe^III(N•Ts)] under experimental conditions. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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10 pages, 1739 KiB

Open AccessArticle

Tuning the Coordination Environment of Ru(II) Complexes with a Tailored Acridine Ligand

by Ali Awada, Pierre-Henri Lanoë, Christian Philouze, Frédérique Loiseau and Damien Jouvenot

Molecules 2024, 29(15), 3468; https://doi.org/10.3390/molecules29153468 - 24 Jul 2024

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Abstract

A novel tridentate ligand featuring an acridine core and pyrazole rings, namely 2,7- di-tert-butyl-4,5-di(pyrazol-1-yl)acridine, L, was designed and used to create two ruthenium(II) complexes: [RuL₂](PF₆)₂ and [Ru(tpy)L](PF₆)₂. Surprisingly, [...] Read more.

A novel tridentate ligand featuring an acridine core and pyrazole rings, namely 2,7- di-tert-butyl-4,5-di(pyrazol-1-yl)acridine, L, was designed and used to create two ruthenium(II) complexes: [RuL₂](PF₆)₂ and [Ru(tpy)L](PF₆)₂. Surprisingly, the ligand adopted different coordination modes in the complexes: facial coordination for the homoleptic complex and meridional coordination for the heteroleptic complex. The electronic absorption and electrochemical properties were evaluated. Although both complexes exhibited favorable electronic properties for luminescence, neither emitted light at room temperature nor at 77 K. This study highlights the complex interplay between ligand design, coordination mode, and luminescence in ruthenium(II) complexes. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
The assigned aromatic region of the 1H-NMR spectra of the complex [Ru(L)2]2+ (red top), ligand L (black middle), and complex [Ru(tpy)L]2+ (blue bottom) recorded in acetone-d6 at 500 MHz. Signals with an asterisk indicate peaks attributable to the tpy ligand. Full article ">Figure 2
Different projections of the crystal structure of the complex [Ru(L)2]2+ (40% ellipsoids). Solvent molecules (co-crystallized acetone molecules), hydrogen atoms, and PF6− counterions are omitted for clarity. Full article ">Figure 3
Different projections of the crystal structure of the complex [Ru(tpy)L]2+ (40% ellipsoids). Solvent molecules (co-crystallized acetone molecules), hydrogen atoms, and PF6− counter anions are omitted for clarity. Full article ">Figure 4
The UV–visible absorption spectra of [Ru(L)2]2+ (red) and [Ru(tpy)L]2+ (blue) recorded in an acetonitrile solution. Inset: zoom on the visible region of the spectra. Full article ">Scheme 1
Synthesis of ligand L. Full article ">Scheme 2
Syntheses of complexes [RuL2](PF6)2 and [Ru(tpy)L](PF6)2. Full article ">

12 pages, 1918 KiB

Open AccessArticle

Assembly of Homochiral Magneto-Optical Dy₆ Triangular Clusters by Fixing Carbon Dioxide in the Air

by Cai-Ming Liu, Xiang Hao and Xi-Li Li

Molecules 2024, 29(14), 3402; https://doi.org/10.3390/molecules29143402 - 19 Jul 2024

Cited by 3 | Viewed by 1303

Abstract

A new hydrazone Schiff base bridging ligand (H₂L_Schiff (E)-N′-((1-hydroxynaphthalen-2-yl)methylene)pyrazine-2-carbohydrazide) and L/D-proline were used to construct a pair of homochiral Dy₆ cluster complexes, [Dy₆(CO₃)(L-Pro)₆(L_Schiff [...] Read more.

A new hydrazone Schiff base bridging ligand (H₂L_Schiff (E)-N′-((1-hydroxynaphthalen-2-yl)methylene)pyrazine-2-carbohydrazide) and L/D-proline were used to construct a pair of homochiral Dy₆ cluster complexes, [Dy₆(CO₃)(L-Pro)₆(L_Schiff)₄(HL_Schiff)₂]·5DMA·2H₂O (L-1, L-HPro = L-proline; DMA = N,N-dimethylacetamide) and [Dy₆(CO₃)(D-Pro)₆(L_Schiff)₄(HL_Schiff)₂]·5DMA·2H₂O (D-1, D-HPro = D-proline), which show a novel triangular Dy₆ topology. Notably, the fixation of CO₂ in the air formed a carbonato central bridge, playing a key role in assembling L-1/D-1. Magnetic measurements revealed that L-1/D-1 displays intramolecular ferromagnetic coupling and magnetic relaxation behaviours. Furthermore, L-1/D-1 shows a distinct magneto-optical Faraday effect and has a second harmonic generation (SHG) response (1.0 × KDP) at room temperature. The results show that the immobilization of CO₂ provides a novel pathway for homochiral multifunctional 4f cluster complexes. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Figure 1
Crystal structures of L-1 (a) and D-1 (b). Color code: C, grey; N, blue; O, red; Dy, green. All disordered pyrrolidine rings show only one of two sets, and all H atoms and solvent molecules are omitted for clarity. Full article ">Figure 2
Plot of χMT vs. T of L-1 (Hdc = 1000 Oe). Full article ">Figure 3
Plots of χ″ vs. T for L-1 (Hdc = 0 Oe). Full article ">Figure 4
CD spectra of L-1 and D-1 in DMF solution (c = 0.2 gL−1; H = 0 T) (above) and UV-vis spectra of L-1 and D-1 in DMF solution (c = 0.2 gL−1; H = 0 T) (below). Full article ">Figure 5
CD spectra of L-1 and D-1 in DMF solution under an NS (+1.6 T) or SN (−1.6 T) field (c = 0.2 gL−1; optical path = 5 mm). Full article ">Figure 6
SHG spectra of crystalline samples of L-1 and KDP under excitation at λ = 1550 nm (Tint = 0.5 s). Full article ">Scheme 1
Synthesis pathway of the new hydrazone Schiff base ligand H2LSchiff. Full article ">

18 pages, 5147 KiB

Open AccessArticle

Electrocatalytic Properties of Quasi-2D Oxides LaSrMn_0.5M_0.5O₄ (M = Co, Ni, Cu, and Zn) for Hydrogen and Oxygen Evolution Reactions

by Kinithi M. K. Wickramaratne and Farshid Ramezanipour

Molecules 2024, 29(13), 3107; https://doi.org/10.3390/molecules29133107 - 29 Jun 2024

Viewed by 854

Abstract

Designing cost-effective and highly efficient electrocatalysts for water splitting is a significant challenge. We have systematically investigated a series of quasi-2D oxides, LaSrMn_0.5M_0.5O₄ (M = Co, Ni, Cu, Zn), to enhance the electrocatalytic properties of the two half-reactions [...] Read more.

Designing cost-effective and highly efficient electrocatalysts for water splitting is a significant challenge. We have systematically investigated a series of quasi-2D oxides, LaSrMn_0.5M_0.5O₄ (M = Co, Ni, Cu, Zn), to enhance the electrocatalytic properties of the two half-reactions of water-splitting, namely oxygen and hydrogen evolution reactions (OER and HER). The four materials are isostructural, as confirmed by Rietveld refinements with X-ray diffraction. The oxygen contents and metal valence states were determined by iodometric titrations and X-ray photoelectron spectroscopy. Electrical conductivity measurements in a wide range of temperatures revealed semiconducting behavior for all four materials. Electrocatalytic properties were studied for both half-reactions of water-splitting, namely, oxygen-evolution and hydrogen-evolution reactions (OER and HER). For the four materials, the trends in both OER and HER were the same, which also matched the trend in electrical conductivities. Among them, LaSrMn_0.5Co_0.5O₄ showed the best bifunctional electrocatalytic activity for both OER and HER, which may be attributed to its higher electrical conductivity and favorable electron configuration. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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12 pages, 2030 KiB

Open AccessArticle

Ab Initio Electronic, Magnetic, and Optical Properties of Fe Phthalocyanine on Cr₂O₃(0001)

by Marco Marino, Elena Molteni, Simona Achilli, Giovanni Onida and Guido Fratesi

Molecules 2024, 29(12), 2889; https://doi.org/10.3390/molecules29122889 - 18 Jun 2024

Viewed by 736

Abstract

The organic molecules adsorbed on antiferromagnetic surfaces can produce interesting interface states, characterized by charge transfer mechanisms, hybridization of molecular-substrate orbitals, as well as magnetic couplings. Here, we apply an ab initio approach to study the adsorption of Fe phthalocyanine on stoichiometric Cr [...] Read more.

The organic molecules adsorbed on antiferromagnetic surfaces can produce interesting interface states, characterized by charge transfer mechanisms, hybridization of molecular-substrate orbitals, as well as magnetic couplings. Here, we apply an ab initio approach to study the adsorption of Fe phthalocyanine on stoichiometric Cr₂O₃(0001). The molecule binds via a bidentate configuration forming bonds between two opposite imide N atoms and two protruding Cr ones, making this preferred over the various possible adsorption structures. In addition to the local modifications at these sites, the electronic structure of the molecule is weakly influenced. The magnetic structure of the surface Cr atoms shows a moderate influence of molecule adsorption, not limited to the atoms in the close proximity of the molecule. Upon optical excitation at the onset, electron density moves toward the molecule, enhancing the ground state charge transfer. We investigate this movement of charge as a mechanism at the base of light-induced modifications of the magnetic structure at the interface. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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11 pages, 981 KiB

Open AccessArticle

Cobalt(III)–Macrocyclic Scaffolds with Anti-Cancer Stem Cell Activity

by Jiaxin Fang, Philipp Gerschel, Kuldip Singh, Ulf-Peter Apfel and Kogularamanan Suntharalingam

Molecules 2024, 29(12), 2743; https://doi.org/10.3390/molecules29122743 - 8 Jun 2024

Viewed by 975

Abstract

Cobalt(III) compounds with tetradentate ligands have been widely employed to deliver cytotoxic and imaging agents into cells. A large body of work has focused on using cobalt(III)–cyclam scaffolds for this purpose. Here, we investigate the cytotoxic properties of cobalt(III) complexes containing 14-membered macrocycles [...] Read more.

Cobalt(III) compounds with tetradentate ligands have been widely employed to deliver cytotoxic and imaging agents into cells. A large body of work has focused on using cobalt(III)–cyclam scaffolds for this purpose. Here, we investigate the cytotoxic properties of cobalt(III) complexes containing 14-membered macrocycles related to cyclam. A breast cancer stem cell (CSC) in vitro model was used to gauge efficacy. Specifically, [Co(1,4,7,11-tetraazacyclotetradecane)Cl₂]⁺ (1) and [Co(1-oxa-4,8,12-triazacyclotetradecane)Cl₂]⁺ (2) were synthesised and characterised, and their breast CSC activity was determined. The cobalt(III) complexes 1 and 2 displayed micromolar potency towards bulk breast cancer cells and breast CSCs grown in monolayers. Notably, 1 and 2 displayed selective potency towards breast CSCs over bulk breast cancer cells (up to 4.5-fold), which was similar to salinomycin (an established breast CSC-selective agent). The cobalt(III) complexes 1 and 2 were also able to inhibit mammosphere formation at low micromolar doses (with respect to size and number). The mammopshere inhibitory effect of 2 was similar to that of salinomycin. Our studies show that cobalt(III) complexes with 1,4,7,11-tetraazacyclotetradecane and 1-oxa-4,8,12-triazacyclotetradecane macrocycles could be useful starting points for the development of new cobalt-based delivery systems that can transport cytotoxic and imaging agents into breast CSCs. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Figure 1
(A) Reaction scheme for the preparation of [Co(1,4,7,11-tetraazacyclotetradecane)Cl2]Cl (1). The X-ray structure of 1 is also shown. Thermal ellipsoids are drawn at 50% probability. C atoms are shown in grey, N in dark blue, Cl in green, and Co in cobalt blue. The H atoms, co-crystallising solvent molecules, and the counter-anion have been omitted for clarity. (B) Reaction scheme for the preparation of [Co(1-oxa-4,8,12-triazacyclotetradecane)Cl2]½CoCl4 (2). The X-ray structure of 2 is also shown. Thermal ellipsoids are drawn at 50% probability. C atoms are shown in grey, N in dark blue, Cl in green, O in red, and Co in cobalt blue. The H atoms and the counter-anion have been omitted for clarity. Full article ">Figure 2
(A) Representative dose–response curves for the treatment of HMLER, HMLER-shEcad, and BEAS-2B cells with 1 after 72 h incubation; and (B) representative dose–response curves for the treatment of HMLER, HMLER-shEcad, and BEAS-2B cells with 2 after 72 h incubation. Full article ">Figure 3
(A) Quantification of mammosphere formation with HMLER-shEcad cells untreated and treated with 1, 2, 3, salinomycin or cisplatin (at 2 µM, 5 days). Error bars represent standard deviations; and (B) representative bright-field images (×10) of HMLER-shEcad mammospheres in the absence and presence of 1, 2 or 3 (at 2 µM, 5 days). Full article ">

12 pages, 3444 KiB

Open AccessArticle

Bimetallic Perthiocarbonate Complexes of Cobalt: Synthesis, Structure and Bonding

by Alaka Nanda Pradhan, Shivankan Mishra, Urminder Kaur, Bikram Keshari Rout, Jean-François Halet and Sundargopal Ghosh

Molecules 2024, 29(11), 2688; https://doi.org/10.3390/molecules29112688 - 6 Jun 2024

Viewed by 1049

Abstract

The syntheses and structural elucidation of bimetallic thiolate complexes of early and late transition metals are described. Thermolysis of the bimetallic hydridoborate species [{Cp*CoPh}{µ-TePh}{µ-TeBH₃-ĸ²Te,H}{Cp*Co}] (Cp* = ɳ⁵-C₅Me₅) ( [...] Read more.

The syntheses and structural elucidation of bimetallic thiolate complexes of early and late transition metals are described. Thermolysis of the bimetallic hydridoborate species [{Cp*CoPh}{µ-TePh}{µ-TeBH₃-ĸ²Te,H}{Cp*Co}] (Cp* = ɳ⁵-C₅Me₅) (1) in the presence of CS₂ afforded the bimetallic perthiocarbonate complex [(Cp*Co)₂(μ-CS₄-κ¹S:κ²S′)(μ-S₂-κ²S″:κ¹S‴)] (2) and the dithiolene complex [(Cp*Co)(μ-C₃S₅-κ¹S,S′] (3). Complex 2 contains a four-membered metallaheterocycle (Co₂S₂) comprising a perthiocarbonate [CS₄]²⁻ unit and a disulfide [S₂]²⁻ unit, attached opposite to each other. Complex 2 was characterized by employing different multinuclear NMR, infrared spectroscopy, mass spectrometry, and single-crystal X-ray diffraction studies. Preliminary studies show that [Cp*VCl₂]₃ (4) with an intermediate generated from CS₂ and [LiBH₄·THF] yielded thiolate species, albeit different from the cobalt system. Furthermore, a computational analysis was performed to provide insight into the bonding of this bimetallic perthiocarbonate complex. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Full article ">Figure 1
Molecular structure and labeling diagram of 2. Selected bond lengths (Å) and bond angles (°): Co1–S4 2.200(3), Co1–S3 2.264(4), S5–S6 2.043(14), Co2–S5 2.202(4), Co2–S6 2.258(15), Co1···Co2 3.332, C41–S1 1.663(10), C41–S2 1.724(12), C41–S3 1.722(10), S2–S4 2.080(4), S3–C41–S2 119.3(6), Co1–S4–Co2 95.97(12), S4–Co1–S5 83.08(13), S5–Co2–S6 54.5(4), Co2–S5–Co1 96.91(13), S5–S6–Co2 61.4(4). Full article ">Figure 2
(a) HOMO-12, (b) HOMO-17, and (c) HOMO-26 of 2. Contour isodensity values for isosurface are ±0.045 (e/bohr3)1/2. (d,e), Laplacian maps of the electron density distribution computed for 2 in the Co2–S5–S6 plane and the S1–S2–S3 plane, respectively. Full article ">Figure 3
UV–vis spectrum of 2 in CH2Cl2. Full article ">Figure 4
Cyclic voltammogram (CV) recorded for complex 2 in DMF at 298 K. Full article ">Chart 1
Different binding modes of CS2-based ligands (A–F) in transition metal complexes. Full article ">Scheme 1
Synthesis of the perthiocarbonate (2) and dithiolene (3) complexes of cobalt. Full article ">

12 pages, 5726 KiB

Open AccessArticle

Gallium Trichloride Fluid: Dimer Dissociation Mechanism, Local Structure, and Atomic Dynamics

by Maxim Khomenko, Anton Sokolov, Andrey Tverjanovich, Maria Bokova, Mohammad Kassem, Takeshi Usuki and Eugene Bychkov

Molecules 2024, 29(6), 1358; https://doi.org/10.3390/molecules29061358 - 19 Mar 2024

Viewed by 1131

Abstract

Molten gallium trichloride emerges as a promising solvent for oxidative metal recycling. The use of supercritical fluid enhances the performance and kinetics of metal dissolution due to significantly lower viscosity in the reaction media. Additionally, the dual molecular nature of gallium trichloride, existing [...] Read more.

Molten gallium trichloride emerges as a promising solvent for oxidative metal recycling. The use of supercritical fluid enhances the performance and kinetics of metal dissolution due to significantly lower viscosity in the reaction media. Additionally, the dual molecular nature of gallium trichloride, existing as edge-sharing ES-Ga₂Cl₆ dimers at low temperatures and high pressure, or flat trigonal GaCl₃ monomers in the vicinity of the critical point and low pressures, creates the possibility to tailor the chemical geometry to a particular metallic species. Nevertheless, the mechanism of dimer dissociation, local structure, and atomic dynamics in supercritical gallium trichloride fluids are not known. Using first-principles molecular dynamics, validated by comparison with our high-energy X-ray diffraction results, we illustrate the elementary steps in dimer dissociation. These include the formation of intermediate corner-sharing CS-Ga₂Cl₆ dimers, the partial disproportionation of GaCl₃ monomers at high temperatures and low pressures, changes in the local environment of molecular entities, and unusual atomic dynamics in supercritical fluids. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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10 pages, 2445 KiB

Open AccessArticle

Synthesis of Alkenylgold(I) Complexes Relevant to Catalytic Carboxylative Cyclization of Unsaturated Amines and Alcohols

by Shun Hase, Kyohei Yamashita and Yoshihito Kayaki

Molecules 2024, 29(6), 1331; https://doi.org/10.3390/molecules29061331 - 16 Mar 2024

Viewed by 1241

Abstract

The carboxylation of unsaturated amine and alcohol compounds, including 4-benzylamino-1-phenyl-1-butyne (homopropargylamine), 2-butyne-1-ol (propargylic alcohol), and 2,3-butadiene-1-ol (allenylmethyl alcohol), using the hydroxidogold(I) complex, AuOH(IPr) [IPr = 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene], produces corresponding alkenylgold(I) complexes with a cyclic urethane or carbonate framework in high yields. The reaction takes [...] Read more.

The carboxylation of unsaturated amine and alcohol compounds, including 4-benzylamino-1-phenyl-1-butyne (homopropargylamine), 2-butyne-1-ol (propargylic alcohol), and 2,3-butadiene-1-ol (allenylmethyl alcohol), using the hydroxidogold(I) complex, AuOH(IPr) [IPr = 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene], produces corresponding alkenylgold(I) complexes with a cyclic urethane or carbonate framework in high yields. The reaction takes place in aprotic THF at room temperature under the atmospheric pressure of CO₂ in the absence of base additives. The products were characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography. The functionalized alkenyl complexes prepared from the alkynes can be protonated by treatment with an equimolar amount of acetic acid to afford five- or six-membered carboxylation products, whereas the related alkenyl complex derived from allenylmethyl alcohol decomposed to recover the starting allene via ring-opening decarboxylation. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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18 pages, 3579 KiB

Open AccessArticle

Metal Complexes Containing Homoleptic Diorganoselenium(II) Ligands: Synthesis, Characterization and Investigation of Optical Properties

by Darius Dumitraș, Emese Gal, Cristian Silvestru and Alexandra Pop

Molecules 2024, 29(4), 792; https://doi.org/10.3390/molecules29040792 - 8 Feb 2024

Viewed by 1265

Abstract

[(Z)-2′-{2-C₆H₅-(4H)-oxazol-5-one}CHC₆H₄]₂Se (5, L¹) and [(Z)-4′-{2-C₆H₅-(4H)-oxazol-5-one}CHC₆H₄]₂Se (6, L [...] Read more.

[(Z)-2′-{2-C₆H₅-(4H)-oxazol-5-one}CHC₆H₄]₂Se (5, L¹) and [(Z)-4′-{2-C₆H₅-(4H)-oxazol-5-one}CHC₆H₄]₂Se (6, L²) were prepared, structurally characterized and used as ligands to obtain new metal complexes of types [MX(Lⁿ)] [L¹: M = Ag, X = OTf (7); M = Au, X = Cl (13); L²: M = Ag, X = OTf (8); M = Au, X = Cl (14)], [(MX)₂(Lⁿ)] [M = Ag, X = OTf, L¹ (9); L² (10)], [ZnCl₂(Lⁿ)] [L¹ (15); L² (16)] and [Ag(Lⁿ)][PF₆] [L¹ (11); L² (12)]. The silver complexes 7 and 8 were ionic species (1:1 electrolytes) in a MeCN solution, while in the solid state, the triflate fragments were bonded to the silver cations. Similarly, the 2:1 complexes 9 and 10 were found to behave as 1:2 electrolytes in a MeCN solution, but single-crystal X-ray diffraction demonstrated that compound 9 showed the formation of a dimer in the solid state: a tetranuclear [Ag(OTf)]₄ built through bridging triflate ligands was coordinated by two bridging organoselenium ligands through the nitrogen from the oxazolone ring and the selenium atoms in a 1κN:2κSe fashion. Supramolecular architectures supported by intermolecular C−H∙∙∙π, C−H∙∙∙O, Cl∙∙∙H and F∙∙∙H interactions were observed in compounds 4, 5 and 9. The compounds exhibited similar photophysical properties, with a bathochromic shift in the UV-Vis spectra caused by the position of the oxazolone ring on the phenyl ring attached to the selenium atoms. Full article

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15 pages, 2985 KiB

Open AccessArticle

New Stable Gallium(III) and Indium(III) Complexes with Thiosemicarbazone Ligands: A Biological Evaluation

by Lorenzo Verderi, Mirco Scaccaglia, Martina Rega, Cristina Bacci, Silvana Pinelli, Giorgio Pelosi and Franco Bisceglie

Molecules 2024, 29(2), 497; https://doi.org/10.3390/molecules29020497 - 19 Jan 2024

Cited by 1 | Viewed by 2076

Abstract

The aim of this work is to explore a new library of coordination compounds for medicinal applications. Gallium is known for its various applications in this field. Presently, indium is not particularly important in medicine, but it shares a lot of chemical traits [...] Read more.

The aim of this work is to explore a new library of coordination compounds for medicinal applications. Gallium is known for its various applications in this field. Presently, indium is not particularly important in medicine, but it shares a lot of chemical traits with its above-mentioned lighter companion, gallium, and is also used in radio imaging. These metals are combined with thiosemicarbazones, ligating compounds increasingly known for their biological and pharmaceutical applications. In particular, the few ligands chosen to interact with these hard metal ions share the ideal affinity for a high charge density. Therefore, in this work we describe the synthesis and the characterization of the resulting coordination compounds. The yields of the reactions vary from a minimum of 21% to a maximum of 82%, using a fast and easy procedure. Nuclear Magnetic Resonance (NMR) and Infra Red (IR) spectroscopy, mass spectrometry, elemental analysis, and X-ray Diffraction (XRD) confirm the formation of stable compounds in all cases and a ligand-to-metal 2:1 stoichiometry with both cations. In addition, we further investigated their chemical and biological characteristics, via UV-visible titrations, stability tests, and cytotoxicity and antibiotic assays. The results confirm a strong stability in all explored conditions, which suggests that these compounds are more suitable for radio imaging applications rather than for antitumoral or antimicrobic ones. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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16 pages, 3688 KiB

Open AccessArticle

Aluminium 8-Hydroxyquinolinate N-Oxide as a Precursor to Heterometallic Aluminium–Lanthanide Complexes

by Elisa Gallo, Luca Bellucci, Silvia Carlotto, Gregorio Bottaro, Luca Babetto, Luca Giordano, Fabio Marchetti, Simona Samaritani, Lidia Armelao and Luca Labella

Molecules 2024, 29(2), 451; https://doi.org/10.3390/molecules29020451 - 17 Jan 2024

Cited by 2 | Viewed by 2058

Abstract

A reaction in anhydrous toluene between the formally unsaturated fragment [Ln(hfac)₃] (Ln³⁺ = Eu³⁺, Gd³⁺ and Er³⁺; Hhfac = hexafluoroacetylacetone) and [Al(qNO)₃] (HqNO = 8-hydroxyquinoline N-oxide), here prepared for the first time [...] Read more.

A reaction in anhydrous toluene between the formally unsaturated fragment [Ln(hfac)₃] (Ln³⁺ = Eu³⁺, Gd³⁺ and Er³⁺; Hhfac = hexafluoroacetylacetone) and [Al(qNO)₃] (HqNO = 8-hydroxyquinoline N-oxide), here prepared for the first time from [Al(O^tBu)₃] and HqNO, affords the dinuclear heterometallic compounds [Ln(hfac)₃Al(qNO)₃] (Ln³⁺ = Eu³⁺, Gd³⁺ and Er³⁺) in high yields. The molecular structures of these new compounds revealed a dinuclear species with three phenolic oxygen atoms bridging the two metal atoms. While the europium and gadolinium complexes show the coordination number (CN) 9 for the lanthanide centre, in the complex featuring the smaller erbium ion, only two oxygens bridge the two metal atoms for a resulting CN of 8. The reaction of [Eu(hfac)₃] with [Alq₃] (Hq = 8-hydroxyquinoline) in the same conditions yields a heterometallic product of composition [Eu(hfac)₃Alq₃]. A recrystallization attempt from hot heptane in air produced single crystals of two different morphologies and compositions: [Eu₂(hfac)₆Al₂q₄(OH)₂] and [Eu₂(hfac)₆(µ-Hq)₂]. The latter compound can be directly prepared from [Eu(hfac)₃] and Hq at room temperature. Quantum mechanical calculations confirm (i) the higher stability of [Eu(hfac)₃Al(qNO)₃] vs. the corresponding [Eu(hfac)₃Alq₃] and (ii) the preference of the Er complexes for the CN 8, justifying the different behaviour in terms of the Lewis acidity of the metal centre. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Full article ">Figure 1
Molecular structure of the two independent molecules of [Eu2(hfac)6Al2q4(OH)2] (light green, europium; pink, aluminium; grey, carbon; red, oxygen; blue, nitrogen; yellow, fluorine). Full article ">Figure 2
Polyhedral representation of [Eu2(hfac)6Al2q4(OH)2], 2 (light green, europium; pink, aluminium; grey, carbon; red, oxygen; blue, nitrogen; yellow, fluorine). Full article ">Figure 3
Molecular structure of [Eu2(hfac)6(µ-Hq)2], 3 (light green, europium; pink, aluminium; grey, carbon; red, oxygen; blue, nitrogen; yellow, fluorine). Full article ">Figure 4
(Left) molecular structure of [Eu(hfac)3Al(qNO)3], 5; (Right) projection along an approximated ternary axis. Lattice toluene has been omitted for clarity, (light green, europium; pink, aluminium; grey, carbon; red, oxygen; blue, nitrogen; yellow, fluorine). Full article ">Figure 5
ATR-IR of [Er(hfac)3Al(qNO)3] (orange) and [Eu(hfac)3Al(qNO)3] (blue). Full article ">Figure 6
Molecular structure of [Er(hfac)3Al(qNO)3], 7, with a polyhedral representation on the right, (green, erbium; pink, aluminium; grey, carbon; red, oxygen; blue, nitrogen; yellow, fluorine). Full article ">Scheme 1
8-hydroxyquinoline (Hq) and the aluminium complex [Alq3]. Full article ">Scheme 2
8-hydroxyquinoline N-oxide (HqNO). Full article ">Scheme 3
Hydrolytic path for decomposition of [Eu(hfac)3Alq3], 1. Full article ">

19 pages, 3055 KiB

Open AccessArticle

Photocatalytic Reduction of CO₂ into CO with Cyclometalated Pt(II) Complexes of N^C^N Pincer Dipyridylbenzene Ligands: A DFT Study

by Antonia Sarantou and Athanassios Tsipis

Molecules 2024, 29(2), 403; https://doi.org/10.3390/molecules29020403 - 14 Jan 2024

Viewed by 1481

Abstract

In this work, density functional theory (DFT) calculations were employed to study the photocatalytic reduction of CO₂ into CO using a series of Pt(II) square planar complexes with the general formula [Pt(5-R-dpb)Cl] (dpb = 1,3-di(2-pyridyl)benzene anion, R = H, N,N [...] Read more.

In this work, density functional theory (DFT) calculations were employed to study the photocatalytic reduction of CO₂ into CO using a series of Pt(II) square planar complexes with the general formula [Pt(5-R-dpb)Cl] (dpb = 1,3-di(2-pyridyl)benzene anion, R = H, N,N-dimethylaniline,T thiophene, diazaborinine). The CO₂-into-CO conversion process is thought to proceed via two main steps, namely the photocatalytic/reduction step and the main catalytic step. The simulated absorption spectra exhibit strong bands in the range 280–460 nm of the UV-Vis region. Reductive quenching of the T₁ state of the complexes under study is expected to be favorable since the calculated excited state redox potentials for the reaction with sacrificial electron donors are highly positive. The redox potentials reveal that the reductive quenching of the T₁ state, important to the overall process, could be modulated by suitable changes in the N^C^N pincer ligands. The CO₂ fixation and activation by the three coordinated Pt(II) catalytically active species are predicted to be favorable, with the Pt–CO₂ bond dissociation energies D₀ in the range of −36.9–−10.3 kcal/mol. The nature of the Pt–CO₂ bond of the Pt(II) square planar intermediates is complex, with covalent, hyperconjugative and H-bonding interactions prevailing over the repulsive electrostatic interactions. The main catalytic cycle is estimated to be a favorable exergonic process. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Figure 1
Proposed calculated mechanism for the CO2-into-CO photocatalytic reduction by the [Pt(5-R-dpb)Cl], 1–5 Pt(II) complexes. Full article ">Figure 2
Optimized geometries of 1 in (a) S0 ground state, (b) in T1 excited state and (c) of One-Electron-Reduced form, 1_OER, calculated at the PBE0-GD3BJ/Def2-TZVP level, in DCM solvent. Full article ">Figure 3
Simulated absorption spectra of 1–4 in DCM at the TDDFT/PBE0/Def2-TZVP level. Full article ">Figure 4
NTO pairs for the most significant electronic transitions of the simulated absorption spectra of 1 (hole h+ on the left, electron e− on the right). Full article ">Figure 5
(a) Optimized geometry of 1_ImC, (b) 3D surface plot of HOMO, (c) BCPs (orange spheres) and (d) 3D surface of RDG function. Full article ">Figure 6
3D isosurface plots of (a) σ(Pt–C) BD NBO and (b) of donor and acceptor NBOs participating in the Pt–C hyperconjugative interactions. Full article ">Figure 7
Free energy, ΔG (in kcal/mol), reaction profiles of 1–4 in DCM solvent calculated at the PBE0-GD3BJ/Def2-TZVP level (numbers in blue for 1, in green for 2, in orange for 3 and in red for 4). Full article ">Scheme 1
The molecular structures of Pt(II) complexes under study. Full article ">Scheme 2
Born–Haber cycle for calculation of ground-state reduction potentials E0red (above), Latimer diagram for the calculation of T1 excited state reduction potentials E0*red (middle) and Born–Haber cycle for calculation of sacrificial electron donor D (=TEOA or TEA) reduction potentials (below). Full article ">Scheme 3
Orbital interaction diagram for the formation of 1_ImC (Complex) from fragments [Pt(dpb)]− (Fragm. 1) and CO2 (Fragm. 2). Full article ">Scheme 4
(a) SOMOβ of 1_T1 species (left) and SOMO of 1_OER (right) and (b) LUMO of 1_ImF (left) and SOMOβ of 1_G (right). Full article ">

13 pages, 3248 KiB

Open AccessArticle

{Gd^III₇} and {Gd^III₁₄} Cluster Formation Based on a Rhodamine 6G Ligand with a Magnetocaloric Effect

by Lin Miao, Cai-Ming Liu and Hui-Zhong Kou

Molecules 2024, 29(2), 389; https://doi.org/10.3390/molecules29020389 - 12 Jan 2024

Cited by 2 | Viewed by 1128

Abstract

Heptanuclear {Gd^III₇} (complex 1) and tetradecanuclear {Gd^III₁₄} (complex 2) were synthesized using the rhodamine 6G ligand HL (rhodamine 6G salicylaldehyde hydrazone) and characterized. Complex 1 has a rare disc-shaped structure, where the central Gd ion [...] Read more.

Heptanuclear {Gd^III₇} (complex 1) and tetradecanuclear {Gd^III₁₄} (complex 2) were synthesized using the rhodamine 6G ligand HL (rhodamine 6G salicylaldehyde hydrazone) and characterized. Complex 1 has a rare disc-shaped structure, where the central Gd ion is connected to the six peripheral Gd^III ions via CH₃O⁻/μ₃-OH⁻ bridges. Complex 2 has an unexpected three-layer double sandwich structure with a rare μ₆-O²⁻ ion in the center of the cluster. Magnetic studies revealed that complex 1 exhibits a magnetic entropy change of 17.4 J kg⁻¹ K⁻¹ at 3 K and 5 T. On the other hand, complex 2 shows a higher magnetic entropy change of 22.3 J kg⁻¹ K⁻¹ at 2 K and 5 T. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Figure 1
Transformation of ring-opened and ring-closed form of rhodamine-6G-type ligands and their reactions. Full article ">Figure 2
UV-Vis (a) and fluorescent spectra (λex = 354 nm) (b) for the ligand HL and the reaction mixture containing HL and Gd(NO3)3 with different amounts of Et3N in MeOH. Full article ">Figure 3
(a) The structure of the {GdIII7} cation for complex 1. Hydrogen atoms and solvents have been omitted for clarity. (b) The core skeleton graph of complex 1. Color code: GdIII green; O red; N blue; C gray. Full article ">Figure 4
Schematic diagram of two different coordination modes of ring-closed rhodamine ligands L−. (a) Tridentate chelating mode; (b) phenolic oxygen bridging mode. Full article ">Figure 5
(a) The structure of complex 2. Hydrogen atoms and solvents have been omitted for clarity. (b) The core skeleton of complex 2. Color code: GdIII green; O red; N blue; C gray. Full article ">Figure 6
Temperature dependence of χMT for {Gd7} and {Gd14} under a 1000 Oe magnetic field in the range of 2–300 K. Full article ">Figure 7
Experimental −ΔSm values of 1 (a) and 2 (b) for multiple temperatures and magnetic fields calculated from magnetization data. Full article ">

13 pages, 1490 KiB

Open AccessArticle

Cd²⁺-Selective Fluorescence Enhancement of Bisquinoline Derivatives with 2-Aminoethanol Skeleton

by Yuji Mikata, Aya Tsuruta, Hinata Koike, Sunao Shoji and Hideo Konno

Molecules 2024, 29(2), 369; https://doi.org/10.3390/molecules29020369 - 11 Jan 2024

Cited by 1 | Viewed by 1060

Abstract

The development of fluorescent Cd²⁺ sensors requires strict selectivity over Zn²⁺ because of the high availability of Zn²⁺ in the natural environment. In this paper, bisquinoline-based fluorescent sensors with a 2-aminoethanol backbone were investigated. The weak coordination ability of quinoline [...] Read more.

The development of fluorescent Cd²⁺ sensors requires strict selectivity over Zn²⁺ because of the high availability of Zn²⁺ in the natural environment. In this paper, bisquinoline-based fluorescent sensors with a 2-aminoethanol backbone were investigated. The weak coordination ability of quinoline compared to well-studied pyridine is suitable for Cd²⁺ selectivity rather than Zn²⁺. In the presence of 3 equiv. of metal ions, TriMeO-N,O-BQMAE (N,O-bis(5,6,7-trimethoxy-2-quinolylmethyl)-2-methylaminoethanol (3)), as well as its N,N-isomer TriMeO-N,N-BQMAE (N,N-bis(5,6,7-trimethoxy-2-quinolylmethyl)-2-methoxyethylamine (6)), exhibits Cd²⁺-selective fluorescence enhancement over Zn²⁺ in DMF-HEPES buffer (1:1, 50 mM HEPES, 0.1 M KCl, pH = 7.5) (I_Zn/I_Cd = 26–34%), which has similar selectivity in comparison to the corresponding ethylenediamine derivative TriMeOBQDMEN (N,N’-bis(5,6,7-trimethoxy-2-quinolylmethyl)-N,N’-dimethylethylenediamine) under the same experimental condition (I_Zn/I_Cd = 24%). The fluorescence mechanisms of N,O- and N,N-isomers of BQMAE are quite different, judging from the fluorescence lifetimes of their metal complexes. The Cd²⁺ complex with TriMeO-N,O-BQMAE (3) exhibits a long fluorescence lifetime similar to that of TriMeOBQDMEN via intramolecular excimer emission, whereas the Cd²⁺ complex with TriMeO-N,N-BQMAE (6) exhibits a short lifetime from monomer emission. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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13 pages, 2415 KiB

Open AccessArticle

A Pair of Multifunctional Cu(II)–Dy(III) Enantiomers with Zero–Field Single–Molecule Magnet Behaviors, Proton Conduction Properties and Magneto–Optical Faraday Effects

by Shui-Dong Zhu, Yu-Lin Zhou, Fang Liu, Yu Lei, Sui-Jun Liu, He-Rui Wen, Bin Shi, Shi-Yong Zhang, Cai-Ming Liu and Ying-Bing Lu

Molecules 2023, 28(22), 7506; https://doi.org/10.3390/molecules28227506 - 9 Nov 2023

Cited by 2 | Viewed by 1479

Abstract

Multifunctional materials with a coexistence of proton conduction properties, single–molecule magnet (SMM) behaviors and magneto–optical Faraday effects have rarely been reported. Herein, a new pair of Cu(II)–Dy(III) enantiomers, [DyCu₂(RR/SS–H₂L)₂(H₂O)₄(NO₃) [...] Read more.

Multifunctional materials with a coexistence of proton conduction properties, single–molecule magnet (SMM) behaviors and magneto–optical Faraday effects have rarely been reported. Herein, a new pair of Cu(II)–Dy(III) enantiomers, [DyCu₂(RR/SS–H₂L)₂(H₂O)₄(NO₃)₂]·(NO₃)·(H₂O) (R–1 and S–1) (H₄L = [RR/SS] –N,N′–bis [3–hydroxysalicylidene] –1,2–cyclohexanediamine), has been designed and prepared using homochiral Schiff–base ligands. R–1 and S–1 contain linear Cu(II)–Dy(III)–Cu(II) trinuclear units and possess 1D stacking channels within their supramolecular networks. R–1 and S–1 display chiral optical activity and strong magneto–optical Faraday effects. Moreover, R–1 shows a zero–field SMM behavior. In addition, R–1 demonstrates humidity– and temperature–dependent proton conductivity with optimal values of 1.34 × 10⁻⁴ S·cm⁻¹ under 50 °C and 98% relative humidity (RH), which is related to a 1D extended H–bonded chain constructed by water molecules, nitrate and phenol groups of the RR–H₂L ligand. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Full article ">Figure 1
The enantiomeric structures of R–1 and S–1. The coordinated water molecules, coordinated nitrate oxygen atoms and the H atoms are omitted for clarity. Symmetric code: B: 1 − x, y, 2 − z. Full article ">Figure 2
The 1D H–bonding chain and the potential proton transport pathway of R–1. Full article ">Figure 3
CD spectra of R−1 and S−1 in CH3CN solution (c = 1.6 × 10−5 molL−1; H = 0 and ±1.0 T; optical path = 1 mm) in the range of (a) 200–750 nm; and partially enlarged view of (b) 200–265 nm, (c) 265–450 nm and (d) MCD spectra of enantiomers R–1 and S–1 in a CH3CN solution (c = 1.6 × 10−5 molL−1) at room temperature; and partially enlarged view of CD spectra of (e) R–1 and (f) R–1 in the range of 260–450 nm. Full article ">Figure 4
Temperature dependence of the in−phase (a) and out−of−phase (b) components of the ac magnetic susceptibility for R–1 in zero–dc fields with an oscillation of 2.5 Oe. Full article ">Figure 5
(a) Nyquist plot for R−1 at 25 °C under different RH levels; (b) plot of proton conductivity for R−1 vs. RH at 25 °C; (c) Nyquist plot for R−1 at different temperatures under 100% RH; (d) Plots of ln(σT) vs. 1000/T for R−1 under 100% RH. Full article ">

14 pages, 1573 KiB

Open AccessArticle

Antimicrobial Activity of Manganese(I) Tricarbonyl Complexes Bearing 1,2,3-Triazole Ligands

by Sofia Friães, Cândida Trigueiros, Clara S. B. Gomes, Alexandra R. Fernandes, Oscar A. Lenis-Rojas, Marta Martins and Beatriz Royo

Molecules 2023, 28(21), 7453; https://doi.org/10.3390/molecules28217453 - 6 Nov 2023

Cited by 2 | Viewed by 2194

Abstract

Background. Antimicrobial resistance is one of the most pressing health issues of our time. The increase in the number of antibiotic-resistant bacteria allied to the lack of new antibiotics has contributed to the current crisis. It has been predicted that if this situation [...] Read more.

Background. Antimicrobial resistance is one of the most pressing health issues of our time. The increase in the number of antibiotic-resistant bacteria allied to the lack of new antibiotics has contributed to the current crisis. It has been predicted that if this situation is not dealt with, we will be facing 10 million deaths due to multidrug resistant infections per year by 2050, surpassing cancer-related deaths. This alarming scenario has refocused attention into researching alternative drugs to treat multidrug-resistant infections. Aims. In this study, the antimicrobial activities of four manganese complexes containing 1,2,3,-triazole and clotrimazole ligands have been evaluated. It is known that azole antibiotics coordinated to manganese tricarbonyl complexes display interesting antimicrobial activities against several microbes. In this work, the effect of the introduction of 1,2,3,-triazole-derived ligands in the [Mn(CO)₃(clotrimazole)] fragment has been investigated against one Gram-positive bacterium and five Gram-negative bacteria. Methods. The initial antimicrobial activity of the above-mentioned complexes was assessed by determining the minimum inhibitory and bactericidal concentrations using the broth microdilution method. Growth curves in the presence and absence of the complexes were performed to determine the effects of these complexes on the growth of the selected bacteria. A possible impact on cellular viability was determined by conducting the MTS assay on human monocytes. Results. Three of the Mn complexes investigated (4–6) had good antimicrobial activities against all the bacteria tested, with values ranging from 1.79 to 61.95 µM with minimal toxicity. Conclusions. Due to the increased problem of antibiotic resistance and a lack of new antibacterial drugs with no toxicity, these results are exciting and show that these types of complexes can be an avenue to pursue in the future. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Full article ">Figure 1
ORTEP representation of complex 3. Hydrogen atoms and co-crystalised solvent molecules are omitted for clarity. Selected bond lengths: Mn1–Br1 2.5366(3) Å, Mn1–N1 2.0195(16) Å, Mn1–N4 2.0780(16) Å, 1.8075(19) Å, and < Mn1–CCO < 1.812(2) Å. Selected bond angles: N1–Mn1–N4 78.30(6)°, N1–Mn1–C16 173.01(7)°, N4–Mn1–C17 170.99(8)°, and Br1–Mn1–C16 178.98(7)°. Full article ">Figure 2
Selected metal complexes reported in the literature as antimicrobial drugs. Full article ">Figure 3
Growth kinetics of S. aureus ATCC25923, E. coli ATCC 25922, and Salmonella typhimurium 14028S in the presence of 4. Effects of the complexes on the growth of selected bacteria when these were cultured in MH broth. The results correspond to the average of three independent experiments ± standard deviation (SD). Full article ">Figure 4
Effect of the complexes on the cellular viability of human monocytes (THP-1 cell line). Human monocytes were exposed to the complexes for 24 h at 37 °C with 5% CO2. The assay was performed for all the complexes using concentrations ranging from ¼ MBC to 4× MBC for each compound. The results presented correspond to the average of two independent experiments ± standard deviation (SD); the percentage was compared to controls from two independent biological replicates. Full article ">Scheme 1
Synthesis of Mn(I) tricarbonyl complexes 1–6. Full article ">

15 pages, 2590 KiB

Open AccessArticle

A Norbornadiene-Based Molecular System for the Storage of Solar–Thermal Energy in an Aqueous Solution: Study of the Heat-Release Process Triggered by a Co(II)-Complex

by Franco Castro, Jorge S. Gancheff, Juan C. Ramos, Gustavo Seoane, Carla Bazzicalupi, Antonio Bianchi, Francesca Ridi and Matteo Savastano

Molecules 2023, 28(21), 7270; https://doi.org/10.3390/molecules28217270 - 25 Oct 2023

Cited by 2 | Viewed by 2586

Abstract

It is urgent yet challenging to develop new environmentally friendly and cost-effective sources of energy. Molecular solar thermal (MOST) systems for energy capture and storage are a promising option. With this in mind, we have prepared a new water-soluble (pH > 6) norbornadiene [...] Read more.

It is urgent yet challenging to develop new environmentally friendly and cost-effective sources of energy. Molecular solar thermal (MOST) systems for energy capture and storage are a promising option. With this in mind, we have prepared a new water-soluble (pH > 6) norbornadiene derivative (HNBD1) whose MOST properties are reported here. HNBD1 shows a better matching to the solar spectrum compared to unmodified norbornadiene, with an onset absorbance of λ_onset = 364 nm. The corresponding quadricyclane photoisomer (HQC1) is quantitatively generated through the light irradiation of HNBD1. In an alkaline aqueous solution, the MOST system consists of the NBD1⁻/QC1⁻ pair of deprotonated species. QC1⁻ is very stable toward thermal back-conversion to NBD1⁻; it is absolutely stable at 298 K for three months and shows a marked resistance to temperature increase (half-life t_½ = 587 h at 371 K). Yet, it rapidly (t_½ = 11 min) releases the stored energy in the presence of the Co(II) porphyrin catalyst Co-TPPC (ΔH_storage = 65(2) kJ∙mol⁻¹). Under the explored conditions, Co-TPPC maintains its catalytic activity for at least 200 turnovers. These results are very promising for the creation of MOST systems that work in water, a very interesting solvent for environmental sustainability, and offer a strong incentive to continue research towards this goal. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Full article ">Figure 1
(a) NBD and QC structures. (b) Schematic representation of a MOST-based plant for domestic use. (c) Photochemical and thermodynamic functioning of MOST molecules. Full article ">Figure 2
HNBD1, HQC1 and Co-TPPC structures. Full article ">Figure 3
UV-Vis spectra of HNBD1 and HQC1 recorded at different pH values in the range 2.0–11.0. [HNBD1] = [HQC1] = 1.1 × 10−4 M; 298 K, 0.1 M NaCl; Spectra in the pH range 6.0–11.0 are identical. Color code: red, spectra recorded at pH 2; blue, spectra recorded in the pH range 6.0–11.0. Full article ">Figure 4
pH dependence of the λonset for HNBD1/NBD1−. Full article ">Figure 5
DSC thermogram recorded for HQC1 with a rate of temperature increase of 2 °C∙min−1. Full article ">Figure 6
(a) 1H-NMR spectra (D2O, pH 11, 298 K, 400 MHz) showing the evolution with time of the catalyzed back-conversion of QC1− to NBD1−. Spectrum 1 corresponds to QC1− without catalysts, spectrum 2 was recorded after catalyst addition and mixing (230 s), and then the reaction was left to freely progress; spectrum 18 corresponds to 3086 s total time. (b) Left: variation of the integral of the 1H-NMR signal of QC1− at 2.5 ppm with time and fitting of the corresponding logarithmic curve. Right: Fitting details and parameters. Full article ">Figure 7
Schematic procedure for the synthesis of HNBD1. Full article ">

26 pages, 9014 KiB

Open AccessArticle

Effects of Ferrocene and Ferrocenium on MCF-7 Breast Cancer Cells and Interconnection with Regulated Cell Death Pathways

by Cristina Favaron, Elisabetta Gabano, Ilaria Zanellato, Ludovica Gaiaschi, Claudio Casali, Maria Grazia Bottone and Mauro Ravera

Molecules 2023, 28(18), 6469; https://doi.org/10.3390/molecules28186469 - 6 Sep 2023

Cited by 2 | Viewed by 2140

Abstract

The effects of ferrocene (Fc) and ferrocenium (Fc⁺) induced in triple negative human breast cancer MCF-7 cells were explored by immunofluorescence, flow cytometry, and transmission electron microscopy analysis. The different abilities of Fc and Fc⁺ to produce [...] Read more.

The effects of ferrocene (Fc) and ferrocenium (Fc⁺) induced in triple negative human breast cancer MCF-7 cells were explored by immunofluorescence, flow cytometry, and transmission electron microscopy analysis. The different abilities of Fc and Fc⁺ to produce reactive oxygen species and induce oxidative stress were clearly observed by activating apoptosis and morphological changes after treatment, but also after tests performed on the model organism D. discoideum, particularly in the case of Fc⁺. The induction of ferroptosis, an iron-dependent form of regulated cell death driven by an overload of lipid peroxides in cellular membranes, occurred after 2 h of treatment with Fc⁺ but not Fc. However, the more stable Fc showed its effects by activating necroptosis after a longer-lasting treatment. The differences observed in terms of cell death mechanisms and timing may be due to rapid interconversion between the two oxidative forms of internalized iron species (from Fe²⁺ to Fe³⁺ and vice versa). Potential limitations include the fact that iron metabolism and mitophagy have not been investigated. However, the ability of both Fc and Fc⁺ to trigger different and interregulated types of cell death makes them suitable to potentially overcome the shortcomings of traditional apoptosis-mediated anticancer therapies. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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13 pages, 7623 KiB

Open AccessArticle

The Preparation of a Challenging Superconductor Nb₃Al by Exploiting Nano Effect

by Chengkai Luan, Xiyue Cheng, Xiuping Gao, Jürgen Köhler and Shuiquan Deng

Molecules 2023, 28(18), 6455; https://doi.org/10.3390/molecules28186455 - 6 Sep 2023

Viewed by 1487

Abstract

The Nb₃Al superconductor with excellent physical and working properties is one of the most promising materials in high-magnetic-field applications. However, it is difficult to prepare high-quality Nb₃Al with a desired superconducting transition temperature (T_c) because of [...] Read more.

The Nb₃Al superconductor with excellent physical and working properties is one of the most promising materials in high-magnetic-field applications. However, it is difficult to prepare high-quality Nb₃Al with a desired superconducting transition temperature (T_c) because of its narrow phase formation area at high temperatures (>1940 °C). This work reports a method to prepare stoichiometric Nb₃Al powder samples at a relatively low temperature (1400 °C) by exploiting the nano effect of Nb particles with pretreatment of Nb powder under H₂/Ar atmosphere. The obtained Nb₃Al samples exhibit high T_c’s of ~16.8K. Based on density functional theory (DFT) calculations and statistical mechanics analysis, the crucial role of quantum effect in leading to the success of the preparation method was studied. A new measure of surface energy (MSE) of a model particle is introduced to study its size and face dependence. A rapid convergence of the MSE with respect to the size indicates a quick approach to the solid limit, while the face dependence of MSE reveals a liquid-like behavior. The surface effect and quantum fluctuation of the Nb_n clusters explain the success of the preparation method. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Full article ">Figure 1
Powder XRD patterns of Nbp samples (a) treated at various temperatures for 3 h; (b) treated under various temperatures for 3 h with 2θ from 37° to 39°; (c) sintered under 380 °C with reaction time (1 h~5 h). SEM image of (d) Nb raw material and T-3 h (T = (e) 321 °C; (f) 380 °C). Full article ">Figure 2
XRD patterns of Nb3Al samples (a) prepared at different temperatures for 10 h and (b) at 1400 °C for 10 h with different Nbp:Al ratios; (c) indexing pattern of the sample (1400 °C-10 h-Nbp:Al = 3.0:1) together with an SEM image of the sample as inset. Full article ">Figure 3
(a) Temperature dependence of the magnetization curves for samples sintered at 1400 °C for 10 h with different r (Nbp:Al); (b) the Tc–r curves for samples sintered at 1400 °C for 10 h (the inset shows M-T curve for the sample with r = 3.0). Full article ">Figure 4
Structure of Nb units used for calculations of surface energies: (a) Chain model along [010] direction; (b) Cubic model expanded along <100> equivalent directions; (c) Rhombic dodecahedron model expanded along <110> directions; (d) Octahedron model expanded along <111> directions. Full article ">Figure 5
(a) The four curves showing the relation between MSE and the number of atoms in each type of model; (b) The curves of total surface area vs. number of atoms for the four types of models. Full article ">

12 pages, 3362 KiB

Open AccessArticle

Terbium and Europium Chlorocyananilate-Based 2D Coordination Polymers

by Mariangela Oggianu, Alexandre Abhervé, Daniela Marongiu, Francesco Quochi, José Ramón Galán-Mascarós, Federica Bertolotti, Norberto Masciocchi, Narcis Avarvari and Maria Laura Mercuri

Molecules 2023, 28(18), 6453; https://doi.org/10.3390/molecules28186453 - 6 Sep 2023

Cited by 4 | Viewed by 1390

Abstract

Two-dimensional layered coordination polymers based on the hetero-substituted 3-chloro-6-cyano-2,5-dihydroxybenzoquinone ligands, hereafter ClCNAn²⁻ anilate, and Ln^III ions (Tb and Eu) are reported. Compounds 1 and 2, formulated as Ln₂(ClCNAn)₃(DMSO)₆ (Ln^III = Tb, 1; Eu, [...] Read more.

Two-dimensional layered coordination polymers based on the hetero-substituted 3-chloro-6-cyano-2,5-dihydroxybenzoquinone ligands, hereafter ClCNAn²⁻ anilate, and Ln^III ions (Tb and Eu) are reported. Compounds 1 and 2, formulated as Ln₂(ClCNAn)₃(DMSO)₆ (Ln^III = Tb, 1; Eu, 2), and their related intermediates 1′ and 2′, formulated as Ln₂(ClCNAn)₃(H₂O)_x·yH₂O (x + y likely = 12, Ln = Tb, 1′; and Eu, 2′), were prepared by a conventional one-pot reaction (the latter) and recrystallized from DMSO solvent (the former). Polyhydrated intermediates 1′ and 2′ show very similar XRPD patterns, while, despite their common stoichiometry, 1 and 2 are not isostructural. Compound 1 consists of a 2D coordination framework of 3,6 topology, where [Tb(DMSO)₃]^III moieties are bridged by three bis-chelating ClCNAn²⁻ ligands, forming distorted hexagons. Ultrathin nanosheets of 1 were obtained by exfoliation via the liquid-assisted sonication method and characterized by atomic force microscopy, confirming the 2D nature of 1. The crystal structure of 2, still showing the presence of 2D sheets with a “hexagonal” mesh and a common (3,6) connectivity, is based onto flat, non-corrugated slabs. Indeed, at a larger scale, the different “rectangular tiles” show clear roofing in 1, which is totally absent in 2. The magnetic behavior of 1 very likely indicates depopulation of the highest crystal-field levels, as expected for Tb^III compounds. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Graphical abstract
Full article ">Figure 1
Schematic representation of the synthesis of compounds 1 and 2, via the intermediacy of 1′ and 2′. Full article ">Figure 2
XRPD raw data (blue line) and Le Bail fits (red line) for polycrystalline 1′ (a) and 2′ (b) species. Difference plot and tick markers are shown in black at the bottom. Full article ">Figure 3
(a) Full coordination environment around TbIII; (b) sketch of the distorted tricapped trigonal prismatic geometry around TbIII (hydrogen and disordered C,S ghosts removed for clarity); (c) view of one pseudo-rectangular cavity in ac plane; (d) view of three consecutive layers stacking parallel to the (a–c) vector. Color code: Tb—dark green; O—red; C—gray; S—yellow; Cl—green; N—blue. Full article ">Figure 4
(a) The interdigitation of symmetry-related (and heavily corrugated) 2D layers of compound 1. The orientation of the crystal axes (not to scale) is also shown (bottom left). The double arrow addresses the length of the a–c vector (18 Å) corresponding to two corrugated layers; (b) AFM characterization of drop-casted nanosheets of 1: topographic image and, in the inset, cross-sectional height profiles, showing that flat or terraced nanosheets are formed, with ca. 9 Å steps. Full article ">Figure 5
Sketches of the main structural features of 1 CP. (a) A fragment of the CP, showing the local environment of the EuIII ions; (b,c) the brick-wall connectivity of a flat slab in 2, viewed down the axis normal to the CP extension, and from the side, respectively; (d) the overall crystal packing viewed down the a axis, showing that slabs, interacting only through weak van der Waals contacts mostly attributed to the DMSO ligands, stack along b with a ca. 9.7 Å periodicity. Full article ">Figure 6
(a) Plot of the χmT product as a function of temperature for 1. (b) In-phase (χ′) and out-of-phase (χ″) dynamic susceptibility for 1 at different frequencies as a function of temperature. Full article ">Figure 7
Final Rietveld refinement plot for species 2. Observed data in blue; calculated data in red. The difference plot (in black) and tick markers for peak positions are shown at the bottom. Full article ">Chart 1
Potassium chlorocyananilate (left) and coordination mode of the ligand (right). Full article ">

13 pages, 2159 KiB

Open AccessArticle

The Anti-Breast Cancer Stem Cell Potency of Copper(I)-Non-Steroidal Anti-Inflammatory Drug Complexes

by Alice Johnson, Xiao Feng, Kuldip Singh, Fabrizio Ortu and Kogularamanan Suntharalingam

Molecules 2023, 28(17), 6401; https://doi.org/10.3390/molecules28176401 - 1 Sep 2023

Cited by 3 | Viewed by 1635

Abstract

Cancer stem cells (CSCs) are thought to be partly responsible for metastasis and cancer relapse. Currently, there are no effective therapeutic options that can remove CSCs at clinically safe doses. Here, we report the synthesis, characterisation, and anti-breast CSC properties of a series [...] Read more.

Cancer stem cells (CSCs) are thought to be partly responsible for metastasis and cancer relapse. Currently, there are no effective therapeutic options that can remove CSCs at clinically safe doses. Here, we report the synthesis, characterisation, and anti-breast CSC properties of a series of copper(I) complexes, comprising of non-steroidal anti-inflammatory drugs (NSAIDs) and triphenylphosphine ligands (1–3). The copper(I) complexes are able to reduce the viability of breast CSCs grown in two- and three-dimensional cultures at micromolar concentrations. The potency of the copper(I) complexes towards breast CSCs was similar to salinomycin (an established anti-breast CSC agent) and cisplatin (a clinically used metallopharmaceutical). Cell-based studies showed that the copper(I) complexes are readily, and similarly, internalised by breast CSCs. The copper(I) complexes significantly increase the intracellular reactive oxygen species (ROS) levels in breast CSCs, and their ROS generation profile with respect to time is dependent on the NSAID component present. The generation of intracellular ROS by the copper(I) complexes could be part of the underlying mechanism by which they evoke breast CSC death. As far as we are aware, this is the first study to explore the anti-breast CSC properties of copper(I) complexes. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Figure 1
X-ray structures of the copper(I) complexes (A) 2 and (B) 3, comprising triphenylphosphine and naproxen or salicylate, respectively. Ellipsoids are shown at 50% probability. C atoms are in grey, P in purple, O in red, and Cu in blue. H atoms and disorder components have been omitted for clarity. Full article ">Figure 2
Copper content (ng of Cu/ 106 cells) in HMLER-shEcad cells treated with 1–3 (5 µM for 24 h). Full article ">Figure 3
(A) Quantification of mammosphere formation with HMLER-shEcad cells, untreated, and treated with 1–3, cisplatin, or salinomycin at 0.5 µM for 5 days. Error bars = SD. (B) Representative bright-field images (×10) of the mammospheres, in the absence and presence of 1–3, at 0.5 µM for 5 days. Full article ">Figure 4
Normalised ROS activity in untreated HMLER-shEcad cells (control) and HMLER-shEcad cells treated with 3 (2 × IC50 value, 0.5–24 h). Full article ">Scheme 1
Reaction scheme for the preparation of copper(I) complexes containing triphenylphosphine ligands and diclofenac, naproxen, or salicylate moieties (1–3). Full article ">

16 pages, 16575 KiB

Open AccessArticle

Aldiminium Cations as Countercations to Discrete Main Group Fluoroanions

by Evelin Gruden and Gašper Tavčar

Molecules 2023, 28(17), 6270; https://doi.org/10.3390/molecules28176270 - 27 Aug 2023

Viewed by 1212

Abstract

The reactions of group 14 tetrafluorides (SiF₄, GeF₄, and SnF₄) and group 15 pentafluorides (PF₅, AsF₅, and SbF₅) with the CAAC-based trifluoride reagent [^MeCAACH][F(HF)₂] led to the [...] Read more.

The reactions of group 14 tetrafluorides (SiF₄, GeF₄, and SnF₄) and group 15 pentafluorides (PF₅, AsF₅, and SbF₅) with the CAAC-based trifluoride reagent [^MeCAACH][F(HF)₂] led to the isolation of salts containing discrete 5- or 6-coordinated fluoroanions. The syntheses of [^MeCAACH][SiF₅], [^MeCAACH][GeF₅], [^MeCAACH][(THF)SnF₅], and the structurally related [^MeCAACH][(dioxane)SnF₅], [^MeCAACH][PF₆], [^MeCAACH][AsF₆], and [^MeCAACH][SbF₆] are effective, selective and in high yield. All compounds were characterized by X-ray single-crystal structure analysis, NMR and Raman spectroscopy. It is worth noting that the synthesized [^MeCAACH][GeF₅] is a rare example of a structurally characterized compound with discrete [GeF₅]⁻ anion, while [^MeCAACH][(THF)SnF₅] and [^MeCAACH][(dioxane)SnF₅] represent the first compounds with discrete octahedrally coordinated tin fluoride anions with incorporated solvent molecules. Finally, the aldiminium-based cation [^MeCAACH]⁺ proved to be suitable for the stabilization of rare discrete main group fluoride anions. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Full article ">Figure 1
Structure of the asymmetric unit of (a) [MeCAACH][SiF5] and (b) [MeCAACH][GeF5]. The ellipsoids are drawn at 50% probability. The positions of the fluorine atoms in both anions are disordered. For clarity, only the fluorine atoms in domain A are shown and all hydrogen atoms except those on the aldiminium ring are omitted. Full article ">Figure 2
Crystal structure of (a) [MeCAACH][(THF)SnF5] and (b) [MeCAACH][(dioxane)SnF5]. The ellipsoids are drawn at 50% probability. For clarity, all hydrogen atoms except those on the heterocyclic ring are omitted. Full article ">Figure 3
Structure of the asymmetric units of (a) [MeCAACH][PF6] and (b) [MeCAACH][AsF6]. The ellipsoids are drawn at 50% probability. For clarity, all hydrogen atoms except those on the heterocyclic ring are omitted. Full article ">Figure 4
Structure of the asymmetric unit of [MeCAACH][BF4]. The ellipsoids are drawn at 50% probability. The positions of the fluorine atoms in the anion are disordered. For clarity, only the fluorine atoms in domain A are shown and all hydrogen atoms except those on the heterocyclic ring are omitted. Full article ">Figure 5
Crystal structures of (a) [MeCAACH][Cl] and (b) [MeCAACH][OTf]. The ellipsoids are drawn at 50% probability. For clarity, all hydrogen atoms except those on the heterocyclic ring are omitted. Full article ">Scheme 1
Synthesis of [MeCAACH][SiF5] and [MeCAACH][GeF5]. Full article ">Scheme 2
Synthesis of [MeCAACH][(THF)SnF5]. Full article ">Scheme 3
Synthesis of [MeCAACH][PF6] and [MeCAACH][AsF6]. Full article ">Scheme 4
Synthesis of [MeCAACH][SbF6]. Full article ">Scheme 5
Synthesis of [MeCAACH][BF4]. Full article ">

12 pages, 3578 KiB

Open AccessArticle

Observation of Two-Step Spin Transition in Graphene Oxide-Based Hybrids with Iron(II) 4-amino-1,2,4-triazole Spin Crossover Nanoparticles

by Nikolia Lalioti, Alexander Charitos, John Parthenios, Ondrej Malina, Michaela Polaskova, Martin Petr and Vassilis Tangoulis

Molecules 2023, 28(15), 5816; https://doi.org/10.3390/molecules28155816 - 2 Aug 2023

Cited by 2 | Viewed by 1385

Abstract

A novel experimental protocol based on a reverse micellar method is presented for the synthesis of graphene oxide (GO)-based hybrids with spin crossover nanoparticles (SCO NPs) of the 1D iron(II) coordination polymer with the formula [Fe(NH₂trz)₃](Br₂). By [...] Read more.

A novel experimental protocol based on a reverse micellar method is presented for the synthesis of graphene oxide (GO)-based hybrids with spin crossover nanoparticles (SCO NPs) of the 1D iron(II) coordination polymer with the formula [Fe(NH₂trz)₃](Br₂). By introducing different quantities of 0.5% and 1.0% of GO (according to iron(II)) into the aqueous phase, two hybrids, NP4 and NP5, were synthesized, respectively. The morphological homogeneity of the NPs on the surface of the GO flakes is greatly improved in comparison to the pristine [Fe(NH₂trz)₃](Br₂) NPs. From the magnetic point of view and at a low magnetic sweep rate of 1 K/min, a two-step hysteretic behavior is observed for NP4 and NP5, where the onset of the low-temperature second step appeared at 40% and 30% of the HS fraction, respectively. For faster sweep rates of 5–10 K/min, the two steps from the cooling branch are progressively smeared out, and the critical temperatures observed are T_1/2

↑

= 343 K and T_1/2

↓

= 288 K, with a thermal width of 55 K for both NP4 and NP5. A Raman laser power-assisted protocol was used to monitor the thermal tolerance of the hybrids, while XPS analysis revealed electronic interactions between the SCO NPs and the GO flakes. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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Figure 1
TEM images of the GO-decorated NP5. The highlighted regions are shown in the enlarged images guided by the arrows. The Gaussian distribution of sizes is also shown in the figure. Full article ">Figure 2
XPS spectra of Fe2p for NP4, NP5, and pristine [Fe(NH2trz)3](Br)2 NPs (SCO). Full article ">Figure 3
Sweep rate-dependent magnetic susceptibility measurements (third thermal cycle) carried out at 1 K/min (red solid line and spheres), 5 K/min (brown solid line and spheres), and 10 K/min (blue solid line and spheres) for (a) NP4 and (b) NP5 (see text for details). Full article ">Figure 4
Comparison of HS Raman spectra (blue line) and LS Raman spectra (red line) in the range of 150–500 cm−1 and 850–1700 cm−1 of NP4 (a,d), NP5 (b,e), and pristine [Fe(NH2trz)3]Br2 NPs (c,f), respectively. The experimental conditions of spectra are the following: (a) LS spectra: laser power 84 μW, exposure time 150 s. (b) HS spectra: laser power 340 μW, exposure time 150 s. A percentage of the LS state is depicted in a low-intensity band at 248 cm−1 (presented with an asterisk), denoting the increased thermal tolerance of the hybrids. Full article ">Figure 5
Comparison of HS/LS Raman spectra of NP5 (blue line) and pristine [Fe(NH2trz)3]Br2 NPs SCO (red line), with GO (orange line) in the range of 1100–1700 cm−1. Full article ">

31 pages, 94288 KiB

Open AccessArticle

Syntheses, Structures, and Corrosion Inhibition of Various Alkali Metal Carboxylate Complexes

by Vidushi P. Vithana, Zhifang Guo, Glen B. Deacon and Peter C. Junk

Molecules 2023, 28(14), 5515; https://doi.org/10.3390/molecules28145515 - 19 Jul 2023

Viewed by 1882

Abstract

Complexes of the alkali metals Li-Cs with 3-thiophenecarboxylate (3tpc), 2-methyl-3-furoate (2m3fur), 3-furoate (3fur), 4-hydroxycinnamate (4hocin), and 4-hydroxybenzoate (4hob) ions were prepared via neutralisation reactions, and the structures of [Li₂(3tpc)₂]_n (1Li); [K₂(3tpc)₂]_n [...] Read more.

Complexes of the alkali metals Li-Cs with 3-thiophenecarboxylate (3tpc), 2-methyl-3-furoate (2m3fur), 3-furoate (3fur), 4-hydroxycinnamate (4hocin), and 4-hydroxybenzoate (4hob) ions were prepared via neutralisation reactions, and the structures of [Li₂(3tpc)₂]_n (1Li); [K₂(3tpc)₂]_n (1K); [Rb(3tpc)(H₂O)]_n (1Rb); [Cs{H(3tpc)₂}]_n (1Cs); [Li₂(2m3fur)₂(H₂O)₃] (2Li); [K₂(2m3fur)₂(H₂O)]_n (2K); [Li(3fur)]_n(3Li); [K(4hocin](H₂O)₃]_n (4K); [Rb{H(4hocin)₂}]_n.nH₂O (4Rb); [Cs(4hocin)(H₂O)]_n (4Cs); [Li(4hob)]_n (5Li); [K(4hob)(H₂O)₃]_n (5K); [Rb(4hob)(H₂O)]_n (5Rb); and [Cs(4hob)(H₂O)]_n (5Cs) were determined via X-ray crystallography. Bulk products were also characterised via XPD, IR, and TGA measurements. No sodium derivatives could be obtained as crystallographically suitable single crystals. All were obtained as coordination polymers with a wide variety of carboxylate-binding modes, except for dinuclear 2Li. Under conditions that normally gave coordinated carboxylate ions, the ligation of hydrogen dicarboxylate ions was observed in 1Cs and 4Rb, with short H-bonds and short O…O distances associated with the acidic hydrogen. The alkali-metal carboxylates showed corrosion inhibitor properties inferior to those of the corresponding rare-earth carboxylates. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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17 pages, 15144 KiB

Open AccessArticle

Ge–Cu-Complexes Ph(pyO)Ge(μ²-pyO)₂CuCl and PhGe(μ²-pyO)₄CuCl—Representatives of Cu(I)→Ge(IV) and Cu(II)→Ge(IV) Dative Bond Systems

by Jörg Wagler and Robert Gericke

Molecules 2023, 28(14), 5442; https://doi.org/10.3390/molecules28145442 - 16 Jul 2023

Cited by 1 | Viewed by 1432

Abstract

Phenylgermaniumpyridine-2-olate PhGe(pyO)₃ (compound 1Ge) and CuCl react with the formation of the heteronuclear complex Ph(pyO)Ge(μ²-pyO)₂CuCl (2Ge’) rather than forming the expected compound PhGe(μ²-pyO)₃CuCl (2Ge). Single-point calculations (at the B2T-PLYP [...] Read more.

Phenylgermaniumpyridine-2-olate PhGe(pyO)₃ (compound 1Ge) and CuCl react with the formation of the heteronuclear complex Ph(pyO)Ge(μ²-pyO)₂CuCl (2Ge’) rather than forming the expected compound PhGe(μ²-pyO)₃CuCl (2Ge). Single-point calculations (at the B2T-PLYP level) of the optimized molecular structures confirmed the relative stability of isomer 2Ge’ over 2Ge and, for the related silicon congeners, the relative stability of 2Si over 2Si’. Decomposition of a solution of 2Ge’ upon access to air provided access to some crystals of the copper(II) compound PhGe(μ²-pyO)₄CuCl (3Ge). Compounds 2Ge’ and 3Ge were characterized by single-crystal X-ray diffraction analyses, and the Ge–Cu bonds in these compounds were analyzed with the aid of quantum chemical calculations, e.g., Natural Bond Orbital analyses (NBO), Non-Covalent Interactions descriptor (NCI), and topology of the electron density at bond critical point using Quantum Theory of Atoms-In-Molecules (QTAIM) in conjunction with the related silicon compounds PhSi(μ²-pyO)₃CuCl (2Si), PhSi(μ²-pyO)₄CuCl (3Si), as well as the potential isomers Ph(pyO)Si(μ²-pyO)₂CuCl (2Si’) and PhGe(μ²-pyO)₃CuCl (2Ge). Pronounced Cu→Ge (over Cu→Si) lone pair donation was found for the Cu(I) compounds, whereas in Cu(II) compounds 3Si and 3Ge, this σ-donation is less pronounced and only marginally enhanced in 3Ge over 3Si. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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38 pages, 19100 KiB

Open AccessReview

Polyanion Condensation in Inorganic and Hybrid Fluoridometallates (IV) of Octahedrally Coordinated Ti, Zr, Hf, V, Cr, W, Mn, Ge, Sn, and Pb

by Zoran Mazej

Molecules 2024, 29(6), 1361; https://doi.org/10.3390/molecules29061361 - 19 Mar 2024

Viewed by 1089

Abstract

In fluorides, the M⁴⁺ cations of M = Ti, V, Cr, Mn, Ge, Sn, and Pb favour the octahedral coordination of six F ligands. Some examples of M⁴⁺ with larger cations (M = Zr, Hf, W) in octahedral coordination are also [...] Read more.

In fluorides, the M⁴⁺ cations of M = Ti, V, Cr, Mn, Ge, Sn, and Pb favour the octahedral coordination of six F ligands. Some examples of M⁴⁺ with larger cations (M = Zr, Hf, W) in octahedral coordination are also known. If not enough F ligands are available to have isolated M^IVF₆ octahedra, they must share their F ligands. The crystal structures of such fluoride metalates (IV) show the variety of possible structural motifs of the zero-dimensional oligomeric anions [M₂F₁₁]³⁻ (M = Ti, Cr), [M₃F₁₅]³⁻ (M = Zr, Hf), [M₃F₁₆]⁴⁻ (M = Ge), [M₄F₁₈]²⁻ (M = Ti, W), [M₄F₁₉]³⁻ (M = Ti), [M₄F₂₀]⁴⁻ (M = Ti), [M₅F₂₃]³⁻ (M = Ti), [M₆F₂₇]³⁻ (M = Ti), [M₆F₂₈]⁴⁻ (M = Ti), [M₈F₃₆]⁴⁻ (M = Ti, Mn), [M₁₀F₄₅]⁵⁻ (M = Ti) to one-dimensional chains ([MF₅]⁻)_∞ (M = V, Ti, Cr, Ge, Sn, Pb), double chains ([M₂F₉]⁻)_∞ (M = Ti, Mn), columns ([M₃F₁₃]⁻)_∞ (M = Ti), ([M₄F₁₉]³⁻)_∞ (M = Ti), ([M₇F₃₀]²⁻)_∞ (M = Ti), ([M₉F₃₈]²⁻)_∞) (M = Ti), two-dimensional layers ([M₂F₉]⁻)_∞ (M = Cr), ([M₈F₃₃]⁻)_∞ (M = Ti), and three-dimensional ([M₆F₂₇]³⁻)_∞ (M = Ti) architectures. A discrete monomeric [M₂F₉]⁻ anion with two M^IVF₆ octahedra sharing a common face has not yet been experimentally demonstrated, while two examples containing discrete dimeric [M₂F₁₀]²⁻ anions (M = Ti) with two M^IVF₆ octahedra sharing an edge are still in question. Full article

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18 pages, 7634 KiB

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Biomedical Applications of Sulfonylcalix[4]arene-Based Metal–Organic Supercontainers

by Ya-Wen Fan, Meng-Xue Shi, Zhenqiang Wang, Feng-Rong Dai and Zhong-Ning Chen

Molecules 2024, 29(6), 1220; https://doi.org/10.3390/molecules29061220 - 8 Mar 2024

Cited by 1 | Viewed by 1524

Abstract

Coordination cages sustained by metal–ligand interactions feature polyhedral architectures and well-defined hollow structures, which have attracted significant attention in recent years due to a variety of structure-guided promising applications. Sulfonylcalix[4]arenes-based coordination cages, termed metal–organic supercontainers (MOSCs), that possess unique multi-pore architectures containing an [...] Read more.

Coordination cages sustained by metal–ligand interactions feature polyhedral architectures and well-defined hollow structures, which have attracted significant attention in recent years due to a variety of structure-guided promising applications. Sulfonylcalix[4]arenes-based coordination cages, termed metal–organic supercontainers (MOSCs), that possess unique multi-pore architectures containing an endo cavity and multiple exo cavities, are emerging as a new family of coordination cages. The well-defined built-in multiple binding domains of MOSCs allow the efficient encapsulation of guest molecules, especially for drug delivery. Here, we critically discuss the design strategy, and, most importantly, the recent advances in research surrounding cavity-specified host–guest chemistry and biomedical applications of MOSCs. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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18 pages, 8970 KiB

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Recent Progress on Perovskite-Based Electrocatalysts for Efficient CO₂ Reduction

by Tong Wu, Lihua Zhang, Yinbo Zhan, Yilin Dong, Zheng Tan, Bowei Zhou, Fei Wei, Dongliang Zhang and Xia Long

Molecules 2023, 28(24), 8154; https://doi.org/10.3390/molecules28248154 - 18 Dec 2023

Cited by 1 | Viewed by 2460

Abstract

An efficient carbon dioxide reduction reaction (CO₂RR), which reduces CO₂ to low-carbon fuels and high-value chemicals, is a promising approach for realizing the goal of carbon neutrality, for which effective but low-cost catalysts are critically important. Recently, many inorganic perovskite-based [...] Read more.

An efficient carbon dioxide reduction reaction (CO₂RR), which reduces CO₂ to low-carbon fuels and high-value chemicals, is a promising approach for realizing the goal of carbon neutrality, for which effective but low-cost catalysts are critically important. Recently, many inorganic perovskite-based materials with tunable chemical compositions have been applied in the electrochemical CO₂RR, which exhibited advanced catalytic performance. Therefore, a timely review of this progress, which has not been reported to date, is imperative. Herein, the physicochemical characteristics, fabrication methods and applications of inorganic perovskites and their derivatives in electrochemical CO₂RR are systematically reviewed, with emphasis on the structural evolution and product selectivity of these electrocatalysts. What is more, the current challenges and future directions of perovskite-based materials regarding efficient CO₂RR are proposed, to shed light on the further development of this prospective research area. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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16 pages, 4824 KiB

Open AccessReview

Chiral Metal Halide Perovskites: Focus on Lead-Free Materials and Structure-Property Correlations

by Clarissa Coccia, Marco Moroni and Lorenzo Malavasi

Molecules 2023, 28(16), 6166; https://doi.org/10.3390/molecules28166166 - 21 Aug 2023

Cited by 4 | Viewed by 3111

Abstract

Hybrid organic–inorganic perovskites (HOIPs) are promising materials in several fields related to electronics, offering long carrier-diffusion lengths, high absorption coefficients, tunable band gaps, and long spin lifetimes. Recently, chiral perovskites have attracted huge interest thanks to the possibility of further widening the applications [...] Read more.

Hybrid organic–inorganic perovskites (HOIPs) are promising materials in several fields related to electronics, offering long carrier-diffusion lengths, high absorption coefficients, tunable band gaps, and long spin lifetimes. Recently, chiral perovskites have attracted huge interest thanks to the possibility of further widening the applications of HOIPs. Chiral materials, being intrinsically non-centrosymmetric, display several attractive physicochemical properties, including circular dichroism, circularly polarized photoluminescence, nonlinear optics, ferroelectricity, and spin-related effects. Recent studies have shown that chirality can be transferred from the chiral organic ligands into the inorganic perovskite framework, resulting in materials combining the advantages of both chirality and perovskite superior optoelectronic characteristics. As for HOIPs for photovoltaics, strong interest is currently devoted towards the development of lead-free chiral perovskites to overcome any toxicity issue. While considering the basic and general features of chiral HOIPs, this review mainly focuses on lead-free materials. It highlights the first attempts to understand the correlation between the crystal structure characteristics and the chirality-induced functional properties in lead and lead-free chiral perovskites. Full article

(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)

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