Copper(II) and Zinc(II) Coordination Compounds with 4-(Pyridin-2-yl)methyleneamino-1,2,4-triazole: Synthesis, Crystal Structure, Thermal Stability, and Antimicrobial Activity

The reaction of copper(II) chloride with azomethine ligand 4-(pyridin-2-yl)methyleneamino-1,2,4-triazole (L) yielded crystals of a 1D coordination polymer [Cu(L)Cl2]n (1), in whose structure metal atoms are bound by L molecules due to nitrogen atoms of imine, pyridyl, and triazole moieties. In contrast to this process, the reaction of zinc(II) chloride with L resulted in the formation of mononuclear complex [Zn(L)2Cl2]<middle dot>H2O (2), containing L molecules coordinated to the metal center in a monodentate mode due to triazole nitrogen atoms. The structures of the coordination compounds obtained were determined by single-crystal X-ray diffraction. The antimicrobial activity of 1 and 2 was assessed against the bacteria Escherichia coli, Staphylococcus aureus, Streptococcus spp., the fungi Candida albicans, Candida glabrata, Aspergillus fumigatus, Rhizopus oryzae, and the protozoa Colpoda steinii. Compound 1 showed high antiprotozoal activity, as well as significant antifungal activity against C. glabrata, and complex 2 demonstrated high bacteriostatic activity against Streptococcus spp. Thermal stability of 1 and 2 was studied by simultaneous thermal analysis under an argon atmosphere.