Abstract
Two [PdN3L]PF6 complexes (L = 2 ,6-bis(1-ethyl-benzimidazol-2'-yl)pyridine (L-BZ) and 4-(2-pyridyl)-2,2':6',2''-terpyridine (L-PY)) underwent catalyst-free 1 ,3-dipolar cycloaddition coupling with phenyl isothiocyanate at the room temperature giving the corresponding tetrazole-thiolato complexes. H-1 NMR studies showed that the N1-isomer appeared first in the catalyst-free coupling, then gradually isomerized to the more stable tetrazole-thiolato isomer. The interconversion of N1-isomer into the S-isomer is accompanied by a decrease of the greater steric demand of the 5-membered ring. Tetrazolate complex of L-BZ displayed higher antifungal activit y (MIC <= 0.25 mu g/mL) than the chloride analogue (MIC = 0.5-1.0 mu g/mL) and the reference drug, Fluconazole (MIC = 0.125-8.0 mu g/mL) against Candida albicans and Cryptococcus neoformans. The treated non-cancerous human embryonic kidney cells (HEK293) showed no cytotoxicity and no haemolysis release at the measured concentrations of the chloride complex of L-BZ and tetrazolate comple x of L-PY.