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Journal of Thermal Analysis and Calorimetry
Authors: Lenka Findoráková, Katarína Győryová, Jana Kovářová, V. Balek, F. Nour El-Dien, and L. Halás

Abstract  

Novel zinc(II) complex compounds of general formula Zn(C6H5COO)2·L2 (where L=caffeine (caf) and urea (u)) were synthesized and characterized by elemental analysis and IR spectroscopy. The thermal behaviour of the complexes was studied during heating in air by thermogravimetry. It was found that the thermal decomposition of the anhydrous Zn(II) benzoate compounds with bioactive ligands was initiated by the release of organic ligands at various temperatures. On further heating of the compounds up to 400°C the thermal degradation of the benzoate anions took place. Zinc oxide was found as the final product of the thermal decomposition of all zinc(II) benzoate complex compounds heated to 600°C. Results of elemental analysis, infrared spectroscopy, mass spectroscopy and thermogravimetry are presented.

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Summary Three new complex compounds of general formula Zn[5-ClC6H3-2-(OH)COO]2·L2·nH2O (where L=thiourea (tu), nicotinamide (nam), caffeine (caf), n=2-5), were prepared and characterized by chemical analysis, IR spectroscopy and their thermal properties were studied by TG/DTG, DTA methods. It was found that the thermal decomposition of hydrated compounds starts with the release of water molecules. During the thermal decomposition of anhydrous compounds the release of organic ligands take place followed by the decomposition of salicylate anion. Zinc oxide was found as the final product of the thermal decomposition performed up to 800°C. RTG powder diffraction method, IR spectra and chemical analysis were used for the determination of products of the thermal decomposition.

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Abstract  

New zinc acetate based complex compounds (of general formula Zn(CH3COO)2·1−2L·nH2O) containing one or two molecules of urea, thiourea, coffeine and phenazone were prepared namely: Zn(CH3COO)2·2.5H2O, Zn(CH3COO)2·2u·0.5H2O, Zn(CH3COO)2·tu·0.5H2O, Zn(CH3COO)2·2tu, Zn(CH3COO)2·cof·2.5H2O, Zn(CH3COO)2·2cof·3.5H2O, Zn(CH3COO)2·2phen·1.5H2O. The compounds were characterized by IR spectroscopy, chemical analysis and thermal analysis. Thermal analysis showed that no changes in crystallographic modifications of the compounds take place during (heating in nitrogen before) the thermal decompositions. The temperature interval of the stability of the prepared compounds were determined. It was found that the thermal decomposition of hydrated compounds starts by the release of water molecules. During the thermal decomposition of anhydrous compounds in nitrogen the release of organic ligands take place followed by the decomposition of the acetate anion. Zinc oxide and metallic zinc were found as final products of the thermal decomposition of the zinc acetate based complex compounds studied. Carbon dioxide and acetone were detected in the gaseous products of the decomposition of the compounds if ZnO is formed. Carbon monoxide and acetaldehyde were detected in the gaseous products of the decomposition, if metallic Zn is formed. It is supposed that ZnO and Zn resulting from Zn acetate complex compounds here studied, possess different degree of structural disorder. Annealing takes place by further heating above 600°C.

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Abstract  

Four new complex compounds were prepared by the reaction of zinc bromobutyrate and organic ligands. The general formula of the synthetized complex compounds are (2-Brbut)2ZnL and (4-Brbut)2ZnL2 nH2O (but=butyrate, L=theobromine (tbr), theophylline (tph), methyl-3-pyridyl carbamate (mpc), n=0-1). The compounds were characterized by chemical analysis and IR spectroscopy. The thermal behaviour of the zinc(II) complexes was studied by thermal analysis. Thermal decomposition in the case of hydrated compounds starts with the release of water molecules. Then molecules of organic ligands and the bromobutyrate anion are released and decomposed. CH3CH2CH=O, CO, CH2=CHCH=O, CH2O and ZnBr2 were found as gaseous products of thermal decomposition during heating up to 700°C. IR, mass spectroscopy, X-ray powder diffraction and chemical analysis were used for the determination of solid and gaseous intermediates and products of the thermal decomposition.

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Abstract  

New zinc complex compounds of general formula ZnL2,X2 {X=CI, Br; L=phenazone(phen), nicotinamide(nam)} were synthesized. The new compounds were characterized by elemental analysis, IR spectroscopy and DTA, TG/DTG methods. Thermal properties of the new compounds were investigated. It was found that nicotinamide, phenazone and ZnCl2 or ZnBr2 are released during the thermal decomposition of the compounds. Mass spectroscopy has been used for the determination of the thermal decomposition intermediate products.

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Journal of Thermal Analysis and Calorimetry
Authors: Katarína Győryová, J. Chomič, Erika Szunyogová, Lenka Piknová, V. Zeleňák, and Zuzana Vargová

Abstract  

Three new complex compounds of general formula Zn{4-ClC6H3-2-(OH)COO}2L 2nH2O (where L=thiourea (tu), nicotinamide (nam), caffeine (caf), n=2,3), were prepared and characterized by chemical analysis, IR spectroscopy and their thermal properties were studied by TG/DTG, DTA methods. It was found that the thermal decomposition of hydrated compounds starts with the release of water molecules. During the thermal decomposition of anhydrous compounds the release of organic ligands take place followed by the decomposition of salicylate anion. Zinc oxide was found as the final product of the thermal decomposition performed up to 650C. RTG powder diffraction method, IR spectra and chemical analysis were used for the determination of products of the thermal decomposition.

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Abstract  

Thermal behaviours of three zinc(II) benzoate complex compounds (two new with caffeine and urea), namely Zn(C6H5COO)2, Zn(C6H5COO)2·caf2, Zn(C6H5COO)2·u2, were characterized by using thermogravimetry (TG/DTG), differential thermal analysis (DTA), evolved gas analysis (EGA) with mass spectrometry (MS) detection and emanation thermal analysis (ETA). Temperature intervals of the stability of the compounds as well as the mechanisms of their thermal degradation were determined. From TG and DTA results it followed that the oxidative degradation of urea with CO2 or caffeine with CO2 from the investigated Zn(II) benzoate complex compounds takes place as the first step of their thermal degradation. In the second step of thermal degradation diphenylketone was release. The evolved gas analysis has been used to determine intermediate products of thermal degradation and temperature ranges of their evolution from the samples. From the emanation thermal analysis results it followed that changes in the surface area and microstructure accompanied the thermal degradation of the compounds studied and that no microstructure changes can be supposed in the resulting zinc oxide on heating from 650 up to 850 °C.

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Thermal properties of zinc butyrate complex compounds

II. Caffeine, nicotinamide and theobromine

Journal of Thermal Analysis and Calorimetry
Authors: K. Györyová, V. Balek, B. H. Behrens, A. Matuschek, and A. Kettrup

The new zinc(II) complexes of general formula Zn(CH3CH2CH2COO)2· nL (whereL = caffeine, nicotinamide, theobromine;n=1 or 2) were prepared and identified.

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Abstract  

Zinc carboxylate complexes with N-donor ligands exhibit antimicrobial and antifungal effects. The preparation and thermal properties of complex compounds Zn(isobut)2 and Zn(isobut)2L(isobut=(CH3)2CHCOO, L=papaverine — pap, phenazone — phen) are described in this paper. The newly synthesized compounds were characterized by elemental analysis, IR spectroscopy and TG/DTG, DTA methods.During the thermal treatment it was found that the release of organicligands (pap, phen) was followed by pyrolysis of zinc(II) isobutyrate. (C3H7)2CO and CO2 were found as gaseous products and zinc oxide as the final product of thermal decomposition. Gaseous and solid products of thermal decomposition were confirmed by chemical analysis, IR spectra and X-ray powder diffraction.

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