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

fac-[ReBr(CO)(3)(L(1,2))] L(1) = 1-ethyl-2-(pyridin-2-yl)benzimidazole (1) and L(2) = 1-[(pyridin-2-yl) benzimidazole]-propyl-sulfonic acid (2), fac-[Re(2)Br(2)(CO)(6)L(3)] (3) L(3) = 1,1′-(hexane-1,6-diyl)bis[2-(pyridin-2-yl)1H-benzimidazole] and fac-[ReBr(CO)(3)(L(4,5)-κ(2)N(1)N(2))] (L(4) = 2,6-bis(benzimidazol-2′-yl)pyridine (4) and L(5) = 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 L(1–3) to fac-ReBr(CO)(3)via the benzimidazole and pyridine N-atoms. For 4 and 5, the absence of a two-fold axis of symmetry for L(4,5) in the (1)H NMR spectra reflect the κ(2)N(1),N(2) 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.