Inke Jeß

Synthesis, crystal structures and thermal properties of new copper(I)halide 2-ethylpyrazine coordination polymers: the influence of solid-state kinetics on product formation

Three new copper(I) coordination polymers were prepared by the reaction of copper(I) chloride with 2-ethylpyrazine in water at room temperature or under solvothermal conditions. In poly[CuCl(μ2-2-ethylpyrazine-N,N′)] (I), “zig-zag”-like CuCl chains are present, which are connected by the 2-ethylpyrazine ligand to a three-dimensional network. In comparison in catena[Cu3Cl3(μ2-2-ethylpyrazine-N,N′)2] (II) six-membered Cu3Cl3 rings occur, which are connected to chains by the organic ligands. In poly[Cu2Cl2(μ2-2-ethylpyrazine-N,N′)] (III), CuCl double chains are found, which are linked by the ligands to form sheets. The thermal behaviour of the different compounds was investigated using simultaneous thermogravimetry, differential thermoanalysis and mass spectroscopy as well as temperature-dependent X-ray powder diffraction. Two mass steps are found upon heating compound I in a thermobalance with 1°C/min, where the first corresponds to the transformation into compound III, and the second to the loss of the remaining ligands under formation of CuCl. If the heating rate is increased to 16°C/min, compound II is formed as an intermediate in a consecutive reaction. Therefore, the product formation depends on the actual heating rate, which shows that the solid-state kinetics plays an important role in such thermal reactions.

Synthesis and thermal properties of the inorganic–organic transition metal halogenides CuCl–pyrazine and Cu2Cl2–pyrazine

The coordination polymers CuCl–pyrazine and Cu2Cl2–pyrazine were synthesised by the reaction of CuCl with pyrazine in aqueous solution under hydrothermal conditions. Using an excess of pyrazine, phase pure CuCl–pyrazine can be prepared in high yield. On lowering the pyrazine excess only a small amount of Cu2Cl2–pyrazine can be obtained as a phase mixture with CuCl–pyrazine. Phase pure Cu2Cl2–pyrazine can only be synthesised via thermal decomposition of CuCl–pyrazine. This reaction was investigated using simultaneously difference thermal analysis and thermogravimetry measurements (DTA–TG), mass spectrometry, thermomicroscopy and temperature resolved X-ray powder diffraction.

Copper(I) thiocyanate coordination polymers with dimethylpyrazine: synthesis, crystal structures, thermal and luminescence properties

Abstract The new copper(I) coordination polymers poly[(di-μ2-thiocyanato-N,S)-(μ2-2,5-dimethylpyrazine-N,N)] dicopper(I) (I) and poly[di-μ2-thiocyanato-N,S)-(μ2-2,3-dimethyl-pyrazine-N,N)] dicopper(I) (II) were prepared by the reaction of copper(I) thiocyanate with 2,3- and 2,5-dimethylpyrazine in acetonitrile. In all compounds different CuSCN sub-structures are found which are connected by the dimethylpyrazine ligands to multi-dimensional coordination networks. The thermal properties of all compounds were investigated using simultaneous differential thermoanalysis (DTA), thermogravimetry (TG) and mass spectrometry (MS) as well as temperature resolved X-ray powder diffraction. On heating, compound I and II loose all of the dimethylpyrazine ligands in an endothermic reaction and transform directly into copper(I) thiocyanate. Optical investigations show two excited states for both compounds in absorption and in luminescence measurements which are both, MC and LMCT in character.

Synthesis, crystal structure, thermal and luminescence properties of CuX(2,3-dimethylpyrazine) (X = Cl, Br, I) coordination polymers

Three new coordination polymers based on CuI and 2,3-dimethylpyrazine (2,3-dmpyz) were prepared, structurally characterized and investigated for their thermal and luminescence properties. In the ligand rich 2:3 compound [(CuI)2(2,3-dmpyz)3] (CuI)2 dimers are found, which are connected by the N-donor ligands into chains, whereas in the structure of the 1:1 intermediate [(CuI)(2,3-dmpyz)] (CuI)4 tetramers are found, which are also connected into chains. The crystal structure of the ligand deficient 2:1 compound [(CuI)2(2,3-dmpyz)] is built up of CuI double chains, which are connected by the 2,3-dmpyz ligands into layers. Thermal decomposition of results in its direct transformation into the ligand deficient compound , without the formation of the 1:1 compound as an intermediate. A similar thermal reactivity is found for compound , which transforms into on heating. Stirring of a crystalline suspension of pure or in acetonitrile, always leads to a transformation into the ligand deficient compound indicating that compound is the most stable of all the coordination polymers, whereas compounds and are metastable. The luminescence properties of the CuCl and CuI coordination polymers were investigated at 298 and 77K. It was observed that the emission maxima strongly depends on the nature of the halide atom and the composition and structure of the coordination polymers. In addition, several of these compounds show luminescence thermochromism. These results are compared with those obtained for the previously reported CuCl and CuBr(2,3-dimethylpyrazine) coordination polymers.

Synthesis, crystal structures and thermal properties of new copper(I) halide coordination polymers

Abstract The new copper(I) halide coordination polymers 3 ∞ poly[CuCl(μ-2,5-dimethylpyrazine-N,N′)] (I), 2 ∞ poly[CuBr(μ-2,5-dimethylpyrazine-N,N′)] (II) and 2 ∞ poly[Cu2X2(μ-2,5-dimethylpyrazine-N,N′)] (X=Br (III), I (IV)) were synthesized by the reaction of the copper(I) halides with 2,5-dimethylpyrazine in acetonitrile. In the crystal structure of I, helical CuCl chains are found, which are connected by the 2,5-dimethylpyrazine ligands forming a three-dimensional structure. In the structure of compound II Cu2Br2 dimers and in compounds III and IV CuX double chains (X=Br, I) occur which are connected via the ligands to sheets. The thermal properties of all compounds were investigated using simultaneously differential thermoanalysis (DTA), thermogravimetry (TG) and mass spectroscopy (MS) as well as temperature resolved X-ray powder diffraction. On heating compound I transforms into the new compound Cu2Cl2(2,5-dimethylpyrazine) (V), which forms CuCl on further heating. For compound II in the first step a transformation into the 2:1 compound III is observed, which loses again a part of the ligands forming the new copper(I) halide rich compound Cu4Br4(2,5-dimethylpyrazine) (VI). A halide rich compound Cu4I4(2,5-dimethylpyrazine) (VII) which is presumably isotypic to VI is also observed during the thermal decomposition of IV. On further heating both 4:1 compounds transform directly to CuBr and CuI.

SYNTHESIS, CRYSTAL STRUCTURES, AND OPTICAL PROPERTIES OF NEW QUATERNARY METAL CHALCOGENIDES OF GROUP 5 : CS2AGVS4, K2AGVSE4, RB2AGVSE4, RB2AGNBS4, AND CS2AGNBSE4

The new quaternary compounds Cs2AgVS4, K2AgVSe4, Rb2AgVSe4, Rb2AgNbS4, and Cs2AgNbSe4 were prepared using the reactive flux method. In this structure type infinite chains of edge-sharing AgQ4- and MVQ4-tetrahedra are running parallel to the crystallographic a-axis. The chains are separated by alkali cations. A linear relationship between the size of the alkali cation A+ and the Q–Q interchain distances was found. These compounds are isostructural with the analogous quaternary copper chalcogenides. The optical properties were studied by collecting UV/Vis transmission and reflectance spectra which allowed to derive the optical band gaps. The colours of the vanadium compounds range from black to dark violet with optical band gaps between 1.7 and 1.8 eV. In addition, the behaviour of the samples was studied using polarized light. Under these experimental conditions the niobium compound Rb2AgNbS4 changes its colour from green to red when the direction of the polarization plane is changed by 90°. Synthese, Kristallstruktur und optische Eigenschaften von neuen quaternaren Metallchalkogeniden der 5. Gruppe: Cs2AgVS4, K2AgVSe4, Rb2AgVSe4, Rb2AgNbS4 und Cs2AgNbSe4 Die neuen Verbindungen Cs2AgVS4, K2AgVSe4, Rb2AgVSe4, Rb2AgNbS4 und Cs2AgNbSe4 wurden mit der „reactive flux”-Methode hergestellt. Ihre Strukturen bestehen aus unendlichen Ketten, die aus kantenverknupften AgQ4- und MVQ4-Tetraedern aufgebaut sind und parallel zur kristallographischen a-Achse verlaufen. Die Ketten werden durch Alkalikationen voneinander getrennt. Es wurde ein linearer Zusammenhang zwischen der Grose des Alkalikations A+ und dem kurzesten Q–Q Interkettenabstand gefunden. Die Verbindungen sind isostrukturell zu den analogen Kupferchalkogeniden. Die optischen Bandlucken konnten aus den UV/Vis Transmissions- und Reflexionsspektren abgeschatzt werden. Die Vanadiumverbindungen sind dunkelviolett bis schwarz mit optischen Bandlucken zwischen 1.7 und 1.8 eV. Zusatzlich wurde das Verhalten der Kristalle unter polarisiertem Licht untersucht. Die Farbe der Niobverbindung Rb2AgNbS4 wechselt unter polarisiertem Licht von grun nach rot, wenn die Richtung der Polarisationsebene um 90° gedreht wird.

Structural, Thermodynamic, and Kinetic Aspectsof the Trimorphism of Hydrocortisone

Hydrocortisone was investigated for polymorphism and pseudopolymorphism and three different polymorphic modifications (I-III) and one 2-propanol solvate were found. Forms I and III crystallize in the orthorhombic space group P2(1)2(1)2(1), whereas form II and the 2-propanol solvate crystallize monoclinic in space group P2(1). In all the modifications the molecules are connected by intermolecular O--H...O hydrogen bonding. In the 2-propanol solvate, channels are formed in which the solvent molecules are embedded. Solvent-mediated conversion experiments reveal that the commercially available form I represents the thermodynamically most stable modification at room temperature, whereas forms II and III are metastable. On heating, form III transforms into form II in an endothermic reaction, which shows that an enantiotropic relationship exists between these forms. Form I exhibits the highest melting point and the highest heat of fusion and thus represents the thermodynamically most stable form over the whole temperature range. DSC measurements indicate that form I behaves monotropic to forms II and III. Desolvation of the 2-propanol solvate at higher temperatures results in a transformation into form II, whereas the removal of 2-propanol at room temperature and in vacuum reduced pressure leads to the formation of form III.

Research ArticlesStructural, Thermodynamic, and Kinetic Aspectsof the Trimorphism of Hydrocortisone

Hydrocortisone was investigated for polymorphism and pseudopolymorphism and three different polymorphic modifications (I-III) and one 2-propanol solvate were found. Forms I and III crystallize in the orthorhombic space group P2(1)2(1)2(1), whereas form II and the 2-propanol solvate crystallize monoclinic in space group P2(1). In all the modifications the molecules are connected by intermolecular O--H...O hydrogen bonding. In the 2-propanol solvate, channels are formed in which the solvent molecules are embedded. Solvent-mediated conversion experiments reveal that the commercially available form I represents the thermodynamically most stable modification at room temperature, whereas forms II and III are metastable. On heating, form III transforms into form II in an endothermic reaction, which shows that an enantiotropic relationship exists between these forms. Form I exhibits the highest melting point and the highest heat of fusion and thus represents the thermodynamically most stable form over the whole temperature range. DSC measurements indicate that form I behaves monotropic to forms II and III. Desolvation of the 2-propanol solvate at higher temperatures results in a transformation into form II, whereas the removal of 2-propanol at room temperature and in vacuum reduced pressure leads to the formation of form III.

(CH3NH3)2Sb2S4, a New Thioantimonate(III) with Building Groups Stabilized by Hydrogen Bonds

(CH3NH3)2Sb2S4 has been isolated from the reaction of antimony with sulfur in the presence of manganese in an ethanolic solution of methylamine under solvothermal conditions. Two pyramidal SbS3 units are linked via common S-S edges to give dimeric Sb2S42- anions, which are joined via secondary Sb···S contacts of 3.074(2) and 2.975(2) Å forming infinite 1∞ [SbS2]-2n chains consisting of edge-linked ψ-SbS4 trigonal bipyramids. The cis configuration of the Sb2S42- anions in the title compound is observed for the first time. A specific hydrogenbonding pattern between the amino-hydrogen and the sulfur atoms stabilizes this configuration and gives rise to anionic layers separated by the methyl groups.

The superstructure of KCuCe2Se6 due to ordering of copper cations

Abstract The quaternary compound KCuCe2Se6 was obtained as black needlelike crystals by reacting a mixture of K2Se, Cu, Ce and Se in a 2:1:1:8 ratio at 450 °C. The compound crystallizes in the orthorhombic space group Fddd with a = 8.5907(5), b = 11.3962(8) and c = 44.490(3) A which is a superstructure of the already published structure of KCuCe2Se6 which was described in space group Immm. The Ce3+ ions are in bicapped distorted trigonal prismatic coordination of Se atoms and the Cu+ ions are in tetrahedral environment. The prisms are connected via triangular faces forming rods parallel to the crystallographic a axis. These rods are joined by one capping Se atom and one Se center of the triangular faces thus leading to the formation of anionic layers [CuCe2Se6]nnȒ within the ab plane. The Cu+ ions occupy only one half of the tetrahedral sites in an ordered fashion in contrast to the statistical occupation reported for the substructure. The charge balancing K+ ions are located between the anionic layers.