Tricarbonyl triazolato Re(i) compounds of pyridylbenzimidazole ligands: spectroscopic and antimicrobial activity evaluation

Catalyst-free [3+2] cycloaddition coupling between [Re_n(N₃)_n(CO)_3nL] (n = 1, L = 1-ethyl-2-(pyridin-2-yl)benzimidazole (L¹) and n = 2, L = 1,1′-(hexane-1,6-diyl)bis[2-(pyridin-2-yl)-1H-benzimidazole] (L²)) and dimethyl acetylene dicarboxylate (DMAD) afforded mono- and binuclear triazolate complexes. Spectroscopic data presented unambiguous evidence for isomerization of the kinetically formed N(1) bound triazolate isomer into the N(2) analogue. The solvatochromism properties were assessed by UV/Vis spectroscopy with the aid of time dependent density functional theory calculations. The free ligands and their tricarbonyl triazolato Re(i) complexes were screened for their potential antimicrobial activity against different bacterial and fungal pathogens.

The antimicrobial activity and solvatochromism properties of mono- and binuclear tricarbonyl triazolato Re(i) complexes of pyridylbenzimidazole, formed by catalyst-free [3+2] cycloaddition reaction, were examined.

Antimicrobial properties of half-sandwich Ir(iii) cyclopentadienyl complexes with pyridylbenzimidazole ligands

Ethyl group determined the toxicity of pyridylbenzimidazole Ir(iii) compounds and exchange of the group with sulfonate led to diminishing of the antibacterial activity. Increasing the metal content per complex, 3, gave rise to a compound with no toxicity.

DNA/lysozyme binding propensity and nuclease properties of benzimidazole/2,2'-bipyridine based binuclear ternary transition metal complexes

In the present contribution, new binuclear ternary complexes; [M2(bpy)4L](ClO4)4 (M = Co(ii) (1) and Ni(ii) (2); bpy = 2,2'-bipyridine; L = 1,1'-(hexane-1,6-diyl)bis[2-(pyridin-2-yl)1H-benzimidazole] and [Cu2(bpy)2(OH2)2L](BF4)4 (3) were synthesized, characterized and screened for their antimicrobial activity and cytotoxicity against human liver carcinoma cells (HepG-2) as well as non-malignant human embryonic kidney cells (HEK-293). The structural studies were complemented by density functional theory (DFT) calculations. DNA binding of 1-3 was spectrophotometrically studied. The DNA cleavage ability of 1-3 towards the supercoiled plasmid DNA (pBR322 DNA) was examined through gel electrophoresis. Compound 3 has the highest cytotoxic activity (IC50 = 3.5 μg mL-1) against HepG-2 among the investigated complexes and is non cytotoxic to noncancerous HEK-293. Complexes (1 and 2) exhibited toxicity to HEK-293 with IC50 values of 30.3 and 23.5 μg mL-1 in that order. While compound 1 showed antifungal activity against Cryptococcus neoformans, complex 2 exhibited its toxicity against Candida albicans.

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

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)3 via 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.