Structural characterization and antimicrobial activity of 1,3-bis(2-benzimidazyl)-2-thiapropane ligand and its Pd(II) and Zn(II) halide complexes

Abstract

1,3-Bis(2-benzimidazyl)-2-thiapropane(L) forms 5-coordinate square pyramidal and 4-coordinate tetrahedral, monometallic complexes with PdCl2 and ZnX2 (X=Cl, Br, I), respectively. In the palladium complex, the ligand acts as a chelating tridentate, through two of the nitrogen atoms in the imidazole ring and the sulfur atom of the bridging group together with two chloride ions forming a rare five coordinate complex. In the zinc halide complexes, the ligand acts as chelating bidentate, via two of the nitrogen atoms combined with two halide ions giving common tetrahedral complexes. The ligand and its complexes are characterized by analytical data and spectroscopic methods such as FT-Raman, FT-IR (mid-IR, far-IR), 1H and 13C NMR. Their antimicrobial activities are evaluated by the minimal inhibitory concentration (MIC) against 10 bacteria, each with multiple, fresh clinical isolates (10–15), and the results are compared with those of ampicillin, ciprofloxacin, cefazolin, ofloxacin, and piperacillin antibacterial agents. The compound’s antifungal activities are reported on Candida albicans, Candida utilis, and Cryptococcus neoformans yeasts, each with multiple isolates (10), and the results are referenced with amphotericin-B, fluconazole and flucytosine antifungal agents. In most cases, the compounds show broad-spectrum (Gram+ and Gram–) activities that are either, more active, or equipotent to, the antibiotic and antifungal agents in the comparison tests.