Coordination chemistry of pyrazine derivatives analogues of PZA: design, synthesis, characterization and biological activity†
Ru(III) complexes with pyrazine derivatives: 2,3-bis(2-pyridyl)pyrazine (DPP), pyrazine-2-amidoxime (PAOX), pyrazine-2-thiocarboxamide (PTCA) and 2-amino-5-bromo-3-(methylamino)pyrazine (ABMAP) have been prepared. Characterization of the compounds was acquired using UV-Vis and FT-IR spectroscopy, elemental analysis, conductivity and electrochemical measurements as well as thermogravimetric studies. The ligand field parameters, Δ0 (splitting parameter), B (Racah parameter of interelectronic repulsion) and β (nephelauxetic ratio) were calculated. The stabilities of the Ru(III) complexes have also been confirmed by spectrophotometric titration methods in acetonitrile and water solutions. The data showed that the examined compounds are stable both in solution and solid states, which was also confirmed by the values of their stability constants found. Moreover, the molecular structures of the complexes have been optimized using AM1 and PM3 methods and this supported octahedral geometry around the Ru(III) ion. The minimum inhibitory (MIC) and minimum bactericidal concentration (MBC) for synthesized complexes were studied against two Gram (+) bacteria, two Gram (−) bacteria and fungi – three reference strains of Candida albicans. The results show that [RuCl(PAOX)2(OH2)]Cl2 display antifungal activity.