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)1 H -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.