Half-sandwich triazolato Rh(III) compound of pyridylbenzimidazole ligand with cell selective toxicity towards Cryptococcus neoformans

Recently, screening attempts for potential antimicrobial drugs based on metal-based compounds have shown an unpredictably high hit rate for some classes of organometallic compounds (9.9%) compared to some organic compounds (0.87%) submitted to the same assays. Herein, we report the influence of the axial ligand (X = Cl and triazolate^COOC2H5,CF3) on the antimicrobial activity of [Rh₂(X)₂(η⁵-C₅Me₅)₂L]²⁺ (L = 1,1′-(Hexane-1,6-diyl)bis[2-(pyridin-2-yl)1H-benzimidazole]) against some bacterial and fungal pathogens as well as healthy cells. The compatibility with red blood cells was also examined. The stability of the compounds in presence of a model lysozyme protein was followed to gather insight into the activation profiles. Triazolate compound was prepared under a mild reaction via catalyst-free [3+2] cycloaddition reaction of azide analogue with 4,4,4-trifluoro-2-butynoic acid ethyl ester. While triazolate complex exhibited higher antifungal activity (MIC = 4.8–9.7 μM) against C. neoformans than Fluconazole (MIC = 26.1 μM), the chloro analogue dispalyed no activity towards the same microorganism.