Pyridylbenzimidazole based Re(i)(CO)3 complexes: Antimicrobial activity, spectroscopic and density functional theory calculations

Abstract

fac-[ReBr(CO)3(L1,2)] L1 = 1-ethyl-2-(pyridin-2-yl)benzimidazole (1) and L2 = 1-[(pyridin-2-yl) benzimidazole]-propyl-sulfonic acid (2), fac-[Re2Br2(CO)6L3] (3) L3 = 1,1′-(hexane-1,6-diyl)bis[2-(pyridin-2-yl)1H-benzimidazole] and fac-[ReBr(CO)3(L4,5-κ2N1N2)] (L4 = 2,6-bis(benzimidazol-2′-yl)pyridine (4) and L5 = 2,6-bis(1-ethyl-benzimidazol-2′-yl)pyridine (5) were synthesized and fully characterized using different spectrocopic and analytical tools. The spectrocopic data showed coordination of L1-3 to fac-ReBr(CO)3via the benzimidazole and pyridine N-atoms. For 4 and 5, the absence of a two-fold axis of symmetry for L4,5 in the 1H NMR spectra reflect the κ2N1,N2 mode of coordination. The electronic properties of 1-5 were investigated by time-dependent density functional theory calculations in the singlet and triplet states. The ligands and their Re(i) complexes were assessed for their potential antimicrobial activity. Compound 5 was screened against non-malignant cell line (noncancerous human embryonic kidney cell line (HEK293)) as well as evaluated for its blood compatibility.