DE102009041959A1 - New metal compounds, useful as a phosphor in a light emitting diode, and as an adsorbent or absorbent material in a sensor - Google Patents

Abstract

Metal compounds (I), are new. Metal compounds of formula ([AE 1-xRE x(L) m(LH) y].zIK) (I), are new. AE : alkaline metal(s); RE : rare earth metals comprising Sc, Y, La, Ce, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and/or Lu; LH : five-membered nitrogen heterocycle of formula (II); either R1-R3 : H, 1-6C-alkyl or phenyl; or R2CR3 : fused six membered aryl ring; L : anion of LH; m : 2-3; IK : intercalated molecule; x : 0.01-1; y : 0-4; and z : 0-10. An independent claim is included for the preparation of (I). [Image].

Description

The present invention relates to coordination polymers of alkaline earth metals and rare earth metals having nitrogen heterocyclic ligands characterized by excellent luminescence properties including high quantum yields and finely tunable fluorescence wavelengths, and high fluorescence quenching temperatures. The compounds according to the invention are therefore suitable, for example, as phosphors, or can be used in sensor applications.

The emission spectrum of coordination polymers is usually determined by organic chromophores or by the presence of metal ions, especially by rare earth metals. Most known coordination compounds of rare earth metals having luminescent properties are carboxylates, as in e.g. B. from Chen et al., Angew. Chem. Int. Ed., 2009, 48, 500 described, or β-diketonate complexes such. B. from MH Baker et al., Polyhedron 2009, 28, 188 described. As a coordination polymer of a rare earth metal with imidazole ligands, [Tb (Im) ₃ ] .NH _{3 has been} described ( K. Müller-Buschbaum, S. Gomez-Torres, P. Larsen, C. Wickleder, Chem. Mater., 2007, 19, 655 ). This compound has luminescence properties only to a small extent with small quantum yields.

However, the quantum yield of known coordination polymers with luminescence properties is too low to be able to use such compounds as efficient phosphors. High quantum yields have so far only been achieved with high-temperature phosphors, such as (oxo) nitridosilicates ( R. Mueller-Mach, W. Schnick et al., Phys. Stat. Sol., 2005, 202, 1727 ). An adjustment or shift of the emission wavelengths with the aid of a change in the stoichiometric composition of a predetermined connection structure (also referred to as "tuning") is not or only to a limited extent possible with previously known coordination polymers. For inorganic high-temperature phosphors, a wavelength shift at different doping concentrations was observed ( V. Bachmann, W. Schnick et al., Chem. Mater., 2009, 21, 316 ). However, in these phosphors, at higher doping concentrations, the quantum yield is reduced by concentration quenching.

Finally, known coordination polymers with oxygen-rich ligands such as carboxylates show a reduced temperature stability, and the thermal decomposition starts at temperatures as low as 200 ° C. ( X. Li et al., Inorg: Chem. Commun., 2008, 11, 869 ). Only a few types of compounds are still stable at temperatures above 400 ° C ( A. Lan et al., Angew. Chem. 2009, 121, 1 ; Chen et al., Angew. Chem. Int. Ed., 2009, 48, 500 ).

Coordination polymers of alkaline earth metals with N-heterocyclic ligands as described herein have not heretofore been known in the art. Alkaline earth imidazole compounds are in the form of substituted borates ( BH Hamilton et al., Inorg. Chem., 2003, 42, 3076 ), Imidazoledicarboxylates ( W. Starosta et al. J. Coord. Chem., 2006, 59, 557 , or magnesium acetate-imidazole clusters ( NP Stadie, R. Sanchez-Smith, TL Groy, Acta Crystallogr. Sect. E: Struct. Rep. Online, 2007, 63, 2153 ) known. None of these alkaline earth imidazole compounds is doped with or known by rare earth ions, or exhibits rare earth luminescence properties. As regards rare earth imidazole compounds, [Pr (Im) ₃ (ImH)] .sub.imH shows a three-dimensional, non-doped network without luminescent properties, as in (FIG. K. Müller-Buschbaum, Z. Naturforsch., 2006, 61b, 792 ).

Against the background described, the object of the present invention was to provide coordination polymers with better luminescence properties and good stability.

wobei R¹ ausgewählt ist aus H, C₁-C₆-Alkyl und Phenyl und R² und R³ unabhängig voneinander ausgewählt sind aus H, C₁-C₆-Alkyl und Phenyl oder zusammen mit den Kohlenstoffatomen, an die sie gebunden sind, einen annelierten sechsgliedrigen aromatischen Ring bilden,
L ein Anion einer Verbindung LH darstellt,
m gleich 2 bis 3 ist,
IK ein interkaliertes Molekül darstellt,
und x, y und z wie folgt definiert sind:
0,01 ≤ x ≤ 1
0 ≤ y ≤ 4 und
0 ≤ z ≤ 10.This problem has been solved with the aid of compounds of the formula (I), [AE _1-x RE _x (L) _m (LH) _y ] zIK (I), in which
AE is selected from alkaline earth metals or their mixtures,
RE is selected from the rare earth metals Sc, Y, La, Ce, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm,
Yb and Lu or their mixtures,
LH independently at each occurrence in the formula represents a five-membered nitrogen heterocycle of formula (II):

wherein R ^{1 is} selected from H, C ₁ -C ₆ alkyl and phenyl and R ² and R ^{3 are} independently selected from H, C ₁ -C ₆ alkyl and phenyl or together with the carbon atoms to which they are attached , form a fused six-membered aromatic ring,
L represents an anion of a compound LH,
m is 2 to 3,
IK represents an intercalated molecule,
and x, y and z are defined as follows:
0.01 ≤ x ≤ 1
0 ≤ y ≤ 4 and
0≤z≤10.

The compounds according to the invention are distinguished by excellent luminescence properties and can therefore be used as phosphors. Other possible applications are, for example, in the field of sensor technology, where the compounds disclosed here can be used as sorption materials.

Finally, synthetic methods are disclosed by means of which the compounds according to the invention can be prepared in high yields.

1 shows normalized fluorescence spectra (photoluminescence, emission spectra) of compounds of the formula [AE _1-x RE _x (Im) ₂ (ImH) _y ] .zImH, for AE = Sr, RE = Eu, Im = imidazolate anion, ImH = imidazole , x = 0.05-1.0, y = 0, and z = 0. The excitation was carried out at a wavelength of 366 nm. For comparison, the normalized emission spectrum of BaMgAl ₁₀ O ₁₇ : Eu, Mn is mapped.

2 shows the simultaneous thermal analysis (DTA / TG) of the compound [AE _1-x RE _x (Im) ₂ (ImH) _y ] .zImH, for AE = Sr, RE = Eu, Im = imidazolate anion, ImH = imidazole, x = 0.95, y = 0, and z = 0, between 20 ° C and 650 ° C with a heating rate of 10 ° C / min.

3 shows the crystal structure of 3 / ∞ [Sr (Im) ₂ ]: Eu _0.05 with the view along [100], determined by single-crystal structure analysis.

4 shows the crystal structure of 3 / ∞ [Sr (Im) ₂ ]: Eu _0.03 with the view along [001].

The compounds of the formula (I) are coordination polymers, ie polymers which are structured by covalent and ionic bonds as well as coordinative bonds between metal atoms and / or ions (here the elements AE and RE) and anionic and / or charge-neutral Ligands (here L or LH). In particular, a linking of the constituent units of the polymer takes place with the aid of the nitrogen heterocycles of the formula (II). They act as bridging ligands coordinated to two metal centers. Exemplary are such structures in 3 and 4 played.

By coordinating the metal centers with a sufficient number of ligands, three-dimensional spatial networks, which are also referred to as organometallic framework structures or MOFs ("metal organic frameworks"), are preferably formed. The coordination sphere of each individual metal center in the compounds according to the invention preferably comprises at least 4, more preferably at least 6 metal-ligand coordinations. It is clear to the person skilled in the art that this may exclude metal centers which are located at interfaces of the compound according to the invention.

According to common practice, especially in the field of phosphors, formula (I) indicates the composition of a constituent unit of the compounds of the invention.

It is clear to the person skilled in the art that a large number of these formal constituent units are linked in the compound according to the invention. Alternatively, this fact is represented by spellings such as " [Constructional unit] ", wherein the chemical composition of the constituent unit is indicated in the square brackets, and the indices" 3 "and" ∞ "indicate the presence of a three-dimensional spatial network structure.

A common notation in the field of phosphors, which is also used in the context of the present invention, in particular for concrete compounds, first indicates the composition of the constituent unit, followed by the specification of the doping element and the amount thereof used. So is the formula 3 / ∞ [Sr (Im) ₂ ]: Eu _0.03 assume that Sr accounts for 97 mol% of the total metal content and Eu accounts for 3 mol%. This corresponds to the formula 3 / ∞ [Sr _0.97 Eu _0.03 (Im) ₂ ].

In formula (I), AE represents an alkaline earth metal, i. H. Be, Mg, Ca, Sr, Ba or a mixture of two or more thereof, the term "mixture" being understood here to mean that in the compounds according to the invention different alkaline earth metals are present as coordination centers. If mixtures are used, they are preferably binary. In general, compounds containing an alkaline earth metal are preferred. As alkaline earth metals, Mg, Ca, Sr or Ba are preferable, especially Ca, Sr, Ba, especially Sr.

RE stands for a rare earth metal or a mixture of two or more of these metals, the term "mixture" being understood here to mean that different rare earth metals are present as coordination centers in the compounds according to the invention. In general, compounds containing one or two rare earth metals are preferred. The rare earth metals are selected from the chemical elements Sc, Y, La, Ce, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, preferably Ce, Nd, Sm, Eu, Yb. Ce and Eu are particularly preferred, especially Eu.

wobei R¹ ausgewählt ist aus H, C₁-C₆-Alkyl und Phenyl und R² und R³ unabhängig voneinander ausgewählt sind aus H, C₁-C₆-Alkyl und Phenyl oder zusammen mit den Kohlenstoffatomen, an die sie gebunden sind, einen annelierten sechsgliedrigen aromatischen Ring bilden. R¹ steht bevorzugt für H. R² und R³ stehen bevorzugt für H, Methyl, Ethyl oder für einen annelierten aromatischen Ring, besonders bevorzugt für H, Methyl oder Ethyl und insbesondere für H.LH stands for the five-membered nitrogen heterocycle of the formula (II) which is present in the compound according to the invention as ligand of the metal centers AE or RE.

wherein R ^{1 is} selected from H, C ₁ -C ₆ alkyl and phenyl and R ² and R ^{3 are} independently selected from H, C ₁ -C ₆ alkyl and phenyl or together with the carbon atoms to which they are attached , form a fused six-membered aromatic ring. R ¹ is preferably H. R ² and R ³ are preferably H, methyl, ethyl or a fused aromatic ring, particularly preferably H, methyl or ethyl and in particular H.

wobei R¹, R² und R³ so definiert sind wie für Formel (II).L represents an anion that forms formally by removing a proton, typically the ring-bonded proton, from the LH compounds. Incidentally, L is defined as LH including the preferred embodiments. As a rule, L is therefore a compound of the formula (IIa):

wherein R ¹ , R ² and R ^{3 are} as defined for formula (II).

The compound according to the invention may contain identical and different ligands L, and identical and different ligands LH. Preference is given to the case in which only one type of ligand L and / or only one type of ligand LH is present. If both L and LH are present, the anionic ligands L can be derived from the ligand LH which is present in the relevant compound according to the invention or from another ligand LH insofar as it satisfies the above definition. Preferably, L and LH are the same heterocyclic compound, ie, preferably, the only difference between L and LH is the absence of the proton in L. Based on the above definition of L or LH, respectively for the metals AE and RE in the compounds according to the invention an advantageous coordination by nitrogen atoms and aromatic systems, preferably by nitrogen atoms.

The intercalated molecule IK is an optional component of the compound of the invention. These are generally small molecules which are incorporated in the framework structure of the compound of the formula (I) without formation of a chemical bond between the metals AE and RE or the ligands L and LH on the one hand and the molecule IK on the other hand. As a rule, the molecules IK can be removed without destroying the structure of the compound (I) (for example by supplying heat energy or by applying a vacuum) and, if appropriate, replaced by other molecules.

For example, IK can be selected from the same compounds that are also listed for LH, from compounds that are gaseous at 20 ° C and 1013.25 hPa, for example, NH ₃ , CO, CO ₂ , N ₂ , O ₂ , SO ₂ , H ₂ , or from salts, for. As alkali or alkaline earth metal salts, such as NaCl or KBr and their ions. A compound of the formula (I) may contain molecules of a single type or several different types, for example 2 or 3.

When using an excess of the heterocyclic compound LH over the stoichiometric composition [AE _1-x RE _x (L) _m (LH) _y ] to be achieved, molecules of the heterocyclic compound LH can already be incorporated into the framework during the synthesis of the compound according to the invention, ie For example, IK may match the LH used in the same connection. Are formed in the preparation of the compound of the formula (I) decomposition products, for. As NH ₃ , they may additionally or alternatively be incorporated as molecules IK in the synthesis.

m is 2 to 3. Preferably, for m, the integer values are 2 or 3, but values that are not integer may also be assumed, e.g. For example, 2≤m <3.

x satisfies the inequality: 0.01 ≦ x ≦ 1. Preferably, 0.01 ≦ x ≦ 0.99, and more preferably 0.01 ≦ x ≦ 0.95. Lower upper limits for x, z. B. x ≤ 0.9 or x ≤ 0.7 can be maintained, but are not essential, since no concentration quenching of the luminescence was observed for the compounds of the invention even at high levels of rare earth metals. Furthermore, x is preferably 0.02 or larger.

The variable y satisfies the inequality 0 ≦ y ≦ 3. Preferably, y ≦ 3, especially y ≦ 2, very particularly y = 0.

The variable z fulfills the inequality 0 ≦ z ≦ 10. As the molecular size of the intercalated compound (s) increases and / or the size of the pores decreases, which can be affected by the metal (s) used as described below, the upper limit of z can be set to values of 5, 3 or 1 sink. Compounds without intercalated molecules (i.e., z = 0) may be advantageous, e.g. B. in applications where a sorption of certain substances in the compounds of the invention is to take place. However, compounds with higher values of z, which arise after incorporation of the sorbate, are also included. For pure phosphor applications, compounds are often advantageous in which z is not higher than 1, in particular not higher than 0.3, and particularly preferably 0 in order to exclude the possibility of fluorescence quenching by intercalated substances.

The sum of m and y is preferably not greater than 5.

In a particularly preferred embodiment, the compounds according to the invention are compounds of the formula (III): [AE _1-x RE _x (Im) _m (ImH) _y ] * zIK (III), where Im is an imidazololate anion and ImH is imidazole. The remaining variables of the formula, including their preferred embodiments, are defined as well as for formula (I). In particular, in formula (III) IK is also imidazole. AE is preferably Sr or Ba, more preferably Sr, and RE is preferably Ce or Eu, more preferably Eu.

The compounds according to the invention exhibit photoluminescence and exhibit excellent luminescence properties with high quantum yields, finely tunable fluorescence wavelengths and high temperatures for fluorescence quenching.

Through the use of different rare earth metals or their mixtures different emission wavelengths can be generated, which can cover the entire visible spectral range. Strong emission with high quantum efficiencies of more than 70% is also achieved by efficient excitation via the ligand L / LH, where the quantum yield indicates the ratio between the number of absorbed and emitted photons. A particular advantage of the compounds according to the invention lies in the fact that the quantum yields do not decrease by concentration quenching at higher doping concentrations. Therefore, the change in doping concentration can be used to shift and adjust the excitation wavelength of the materials, as in FIG 1 shown. In the context of the invention, the doping concentration is the proportion of the rare earth metals in the total metal content of the compound according to the invention, as may be indicated by the variable x, for example.

In addition, the compounds of the present invention are stable at temperatures up to 400 ° C or convert into equivalent or better-bearing high temperature forms, preferably into multi-dimensional networks, more preferably 3D networks. These often decompose only at temperatures above 500 ° C, preferably above 600 ° C. 2 shows in this regard the results of the thermal analysis of a compound of the invention. Decomposition can only be observed at a temperature well above 500 ° C.

The compounds according to the invention can preferably be prepared by means of solvent-free, solid-state chemical synthesis methods, as described, for example, in US Pat. B. for rare earth metal complexes in K. Müller-Buschbaum, Z. Anorg. Gen. Chem. 2005, 631, 811 . K. Müller Buschbaum et al., Chem. Mater., 2007, 19, 655 or K. Müller-Buschbaum, Z. Naturforsch., 2006, 61b, 792 are described. Syntheses from the melt or solvothermal reactions under pressure, in which the heated over the boiling point ligand as in the melt is the only reactant, allow access to the preferred compounds here with pure nitrogen coordination. The preferred method for preparing the compounds of the invention is carried out in a high temperature reaction with respect to L and LH, wherein the selected alkaline earth metal AE or the mixture of selected alkaline earth metals AE and the selected rare earth element RE or the mixture of selected rare earth elements RE solvent-free and with the exclusion of oxygen in the Melt the ligand LH oxidized. The reaction temperature is usually 90-350 ° C, and should be above the melting point of LH. Preferably, the temperature is below 200 ° C, more preferably below 150 ° C. The compounds of the invention can thus be obtained in yields> 90%.

Because of their excellent luminescence properties, the compounds according to the invention are suitable as phosphors in a large number of illumination devices, in particular in LEDs. Such devices usually have at least one element that stimulates a stimulating radiation such. B. emitted light, and a layer of at least one phosphor. As an element for the emission of stimulating radiation can, for. B. a semiconductor element (eg., In LEDs, a device for generating a vacuum discharge, a device for generating a cathode ray or an element having thermoluminescence properties.) The compounds of the invention can, for example, as a phosphor in a vacuum fluorescent display (VFD), field emission display (FED, plasma display (PD), or cathode ray tube), and are particularly suitable for use with LEDs, including LEDs that emit warm white light, making them ideal for residential lighting.

The compounds of the invention can be used individually or as a combination of several compounds as a phosphor. Of course, a combination with non-inventive phosphors known in the art for setting a desired emission spectral range is also possible.

Another advantageous field of application is in sensor technology, since the compounds according to the invention have both luminescence properties and typical properties of network structures which can store compounds in their structural framework. By using metal atoms of different sizes, it is possible within the scope of the invention to tailor coordination polymers with differently sized pores for incorporating sorbates of different sizes. By sorption / incorporation of compounds into the network of the compounds according to the invention there is a change in the luminescence properties of the compounds of the invention, such as the shift of the fluorescence spectrum and / or a fluorescence quenching, by their observation, the absorption process can be detected qualitatively as well as quantitatively. As a result, the compounds according to the invention are suitable individually or as a combination of several compounds as absorbing or adsorbing materials, in particular in a sensor.

Examples

The following examples merely serve to further illustrate the invention and accordingly do not limit it.

The structure determination and characterization of the compounds according to the invention was carried out by single-crystal structure analysis using X-radiation, powder diffractometry, thermal analysis, energy dispersive X-ray spectroscopy, electron microscopy, microanalysis, fluorescence spectroscopy, infrared spectroscopy and Raman spectroscopy.

Preparation, preparation and analysis of the compounds according to the invention were carried out under inert conditions. For this purpose, an argon glove box was used as a rule. Outside work was carried out using Schlenk techniques on a vacuum protective gas system. To prepare the compounds according to the invention, the starting materials were charged in the glove box in one side ablated DURAN ^® ampoules evacuated to a vacuum protective gas conditioning and heat-sealed by means of a natural gas-oxygen torch. The ampoules prepared in this way were then subjected to a defined temperature program in corundum tubular ovens with induction heating.

To illustrate the invention, three synthetic examples which cover the range of the composition of the compounds according to the invention, [AE _1-x RE _x (L) _m (LH) _y ] zIK, follow.

Synthesis of 3 / ∞ (Sr (Im) ₂ ]: Eu _0.05

Strontium metal (83.2 mg, 0.95 mmol, Sigma Aldrich, 99.99%) and europium metal (7.6 mg, 0:05 mmol, Smart Elements, 99.99%) were introduced into a Duran ^® -Ampulle. This was then filled together with imidazole (204.2 mg, 3 mmol, Acros Organics, 99%) in a DURAN ^® -Ampulle. This was melted off under vacuum, the reaction mixture was reacted for 24 h at 150 ° C in a tube furnace and cooled to RT for a further 30 min. Excess imidazole was removed in a two-chamber DURAN ^® -Ampulle at 130 ° C. The product was obtained as a crystalline pale yellow solid.

In this way doping levels between 0-100 mol% for europium can be realized. For the production of reaction ampoules, DURAN ^® glass tubes (about 1 = 19 cm, ø = 1.0 cm) were melted on one side with the help of a natural gas oxygen burner and tapered in the middle. For the production of two-chamber ampoules, the glass tubes were chosen correspondingly longer (about 1 = 25 cm) and provided with two tapers, so that the melting of the first taper resulted in an ampoule with two separate chambers.

For the homogenization of the components RE and AE, in the course of a doping either the dissolution in liquid ammonia or a melting of the metals are recommended. This is especially useful for accurate RE to AE ratios.
Yield: 212 mg (94%). C, H, N analysis: calc. (%) For Sr _0.95 Eu _0.05 C ₆ H ₆ N ₄ : C 32.03, H 2.69, N 24.90; Found: C 32.10, H 3.03, N 24.93. EDX: (atom%) Sr 6.29, Eu 0.32, N 25.81.

Synthesis of 1 / ∞ [Mg (Im) ₂ (ImH) ₃ ]

Magnesium metal (24.3 mg, 1 mmol, Merck-Schuchardt, 99%) and imidazole (136.2 mg, 2 mmol, Acros Organics, 99%) were introduced into a Duran ^® -Ampulle. This was melted off under vacuum, the reaction mixture was reacted for 42 h at 90 ° C in a tube furnace and cooled to RT for a further 30 min. Excess imidazole was removed in a two-chamber DURAN ^® -Ampulle at 90 ° C. Commercially available magnesium turnings (Sigma Merck-Schuchardt, 99%) may preferably be treated with dilute hydrochloric acid in a Schlenk frit under an argon atmosphere, freed from MgCl ₂ formed in this case with dry acetone and dried in vacuo to remove the passivation layer. The magnesium thus prepared can be processed as described above.

Magnesium can in this way with different doping levels z. B. 0-50 mol% Yb be provided. Ytterbium metal is processed for this purpose as described above for europium.

The product 1 / ∞ [Mg (Im) ₂ (ImH) ₃ ] was obtained in the form of colorless, rod-shaped crystals. Yield: 132 mg (91%, in terms of ImH). C, H, N analysis: calc. (%) For MgC ₁₅ H ₁₈ N ₁₀ : C, 49.68, H, 5.00, N, 38.62; Found: C 49.62, H 5.83, N 38.68. EDX: (atom%) Mg 2.05, N 22.72.

Synthesis of 3 / ∞ [Ce (Im) ₃ (ImH)] · ImH

Cerium metal (46.2 mg, 0.33 mmol, Smart Elements, 99.9%) and imidazole (68.1 mg, 1 mmol, Acros Organics, 99%) were introduced into a Duran ^® -Ampulle. This was melted off under vacuum, the reaction mixture was heated in a tube furnace within 26 h at 150 ° C and held for 336 h at this temperature. It was then cooled to 80 ° C. in 350 h and to RT for a further 10 h. Excess imidazole was removed in a two-chamber DURAN ^® -Ampulle at 90 ° C.

The product 3 / ∞ [Ce (Im) ₃ (ImH)] · ImH was obtained in the form of colorless, diamond-shaped crystals. Yield: 84 mg (88%, relative to ImH). C, H, N analysis: calc. (%) For CeC ₁₅ H ₁₈ N ₁₀ : C, 37.73, H, 3.59, N, 29.33; Found: C 37.38, H 4.16, N 29.35.

The compounds according to the invention show considerable quantum yields, preferably> 60%, in particular> 80%, very particularly> 95%, as for the in 1 shown doping series of 3 / ∞ [Sr _1-Eu Eu _0.03-1.0 (Im) ₂ ]. In particular, no concentration quenching is observed. In the case of the compounds according to the invention, the quantum yield decreases only slightly as the number of luminous centers increases; in particular, it does not fall off. More particularly, as for the above-mentioned doping series, an increase in the quantum yield can be observed with increasing number of luminous centers.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• Chen et al., Angew. Chem. Int. Ed., 2009, 48, 500 [0002]
• MH Baker et al., Polyhedron 2009, 28, 188 [0002]
• K. Muller-Buschbaum, S. Gomez-Torres, P. Larsen, C. Wickleder, Chem. Mater., 2007, 19, 655 [0002]
• R. Mueller-Mach, W. Schnick et al., Phys. Stat. Sol., 2005, 202, 1727 [0003]
• V. Bachmann, W. Schnick et al., Chem. Mater., 2009, 21, 316 [0003]
• X. Li et al., Inorg: Chem. Commun., 2008, 11, 869 [0004]
• A. Lan et al., Angew. Chem. 2009, 121, 1 [0004]
• Chen et al., Angew. Chem. Int. Ed., 2009, 48, 500 [0004]
• BH Hamilton et al., Inorg. Chem., 2003, 42, 3076 [0005]
• W. Starosta et al. J. Coord. Chem., 2006, 59, 557 [0005]
• NP Stadie, R. Sanchez-Smith, TL Groy, Acta Crystallogr. Sect. E: Struct. Rep. Online, 2007, 63, 2153 [0005]
• K. Müller-Buschbaum, Z. Naturforsch., 2006, 61b, 792 [0005]
• K. Müller-Buschbaum, Z. Anorg. Gen. Chem. 2005, 631, 811 [0036]
• K. Müller Buschbaum et al., Chem. Mater., 2007, 19, 655 [0036]
• K. Müller-Buschbaum, Z. Naturforsch., 2006, 61b, 792 [0036]

Claims (16)

Compound of the formula (I) [AE _1-x RE _x (L) _m (LH) _y ] zIK (I), where AE is selected from alkaline earth metals or their mixtures, RE is selected from the rare earth metals Sc, Y, La, Ce, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu or their mixtures, LH independently at each occurrence in the formula represents a five-membered nitrogen heterocycle of formula (II):

wherein R ^{1 is} selected from H, C ₁ -C ₆ alkyl and phenyl and R ² and R ^{3 are} independently selected from H, C ₁ -C ₆ alkyl and phenyl or together with the carbon atoms to which they are attached , form an annulated six-membered aromatic ring, L is an anion of a compound LH, m is 2 to 3, IK is an intercalated molecule, and x, y and z are defined as follows: 0.01 ≤ x ≤ 1 0 ≤ y ≤ 4 and 0 ≤ z ≤ 10. A compound according to claim 1 wherein in both LH and LR ^{1 is} selected from H, methyl, ethyl and phenyl and R ² and R ^{3 are} independently selected from H, methyl, ethyl and phenyl. A compound according to claim 1 or 2, wherein LH is imidazole and L is an imidazolate anion. A compound according to any one of claims 1 to 3, wherein AE is selected from Ca, Sr and Ba. A compound according to claim 4, wherein AE is strontium. A compound according to any one of claims 1 to 5, wherein RE is selected from Ce, Nd, Sm, Eu and Yb. A compound according to claim 6, wherein RE is europium. A compound according to any one of claims 1 to 7, wherein m is 2 or 3. A compound according to any one of claims 1 to 8, wherein 0.01 ≤ x ≤ 0.99. A compound according to any one of claims 1 to 9, wherein y is 0 or 1. A compound according to any one of claims 1 to 10, wherein z is 0. Use of a compound according to any one of claims 1 to 11 as a phosphor. Use according to claim 12 as a phosphor in a light-emitting diode. Use of a compound according to any one of claims 1 to 11 as an adsorbing or absorbing material. Use according to claim 14 as adsorbing or absorbing material in a sensor. A process for the preparation of a compound according to any one of claims 1 to 11, wherein AE and RE are oxidized in a solvent-free high temperature reaction in the melt of a compound LH.

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