Thermoanalytical investigation and biological properties of zinc(II) 4-chloro- and 5-chlorosalicylates with N-donor ligands
New zinc(II) 4- and 5-chlorosalicylate complexes of general formula [Zn(X-sal)2(L) n (H2O) x ] (where X-sal = 4-Clsalicylate, 5-Clsalicylate; L = N,N-diethylnicotinamide, isonicotinamide, theophylline; n = 1, 2; x = 0, 1, 2, 4) were prepared. The complexes were determined by elemental analysis and characterised by infrared spectroscopy. The thermal behaviour of the complexes was studied by simultaneous TG, DTG and DTA methods under dynamic air conditions. The thermal decomposition is a multi-step process. In the first step of the thermal decomposition, water is released in hydrated compounds. The anhydrous compounds start to decompose by the release of organic ligand, followed by chlorosalicylic acid, chlorophenol and carbon monoxide. The final solid product of the thermal decomposition is zinc oxide. The volatile products of the thermal decomposition were determined by mass spectrometry. The antimicrobial activities of the complexes were evaluated against selected pathogen and probiotic bacteria, yeasts and fungi strains. Bioactivities of the tested compounds are different against bacteria, yeasts and filamentous fungi. It was found that bacteria were more sensitive to the studied zinc(II) complex compounds than yeasts or filamentous fungi.
KeywordsChlorosalicylate Zinc(II) Nicotinamide derivatives Theophylline Thermal properties Biological activity
The financial support of the Slovak Ministry of Education (VEGA project No. 1/0122/08) for this study is gratefully acknowledged.
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