Structural and antimicrobial studies on a tricarbonyl rhenium(i) complex with the 6,7-dimethyl-2-(pyridin-2-yl)quinoxaline ligand

Abstract

A new tricarbonyl rhenium(I) complex featuring 6,7-dimethyl-2-(pyridin-2-yl)quinoxaline (1) was synthesized and characterized using spectroscopic and crystallographic techniques, supported by density functional theory (DFT) calculations. Ligand 1 acts as a bidentate N,N′-donor, coordinating through the pyridyl and quinoxaline nitrogen atoms to form a fac-[ReCl(CO)₃(1)] (2) complex. Single-crystal X-ray diffraction analysis revealed an octahedral geometry around the Re(I) centre, with the three carbonyl ligands adopting a facial arrangement. Hirshfeld surface analysis indicated that weak C–H⋯Cl interactions play a significant role in crystal packing stabilization. DFT and time-dependent DFT (TDDFT) calculations confirmed the observed experimental geometry and provided insights into the metal–ligand bonding, charge distribution, and electronic transitions. The combined results highlight the structural and electronic features that contribute to the stability and potential bioactivity of this rhenium(I) tricarbonyl complex. The antimicrobial assay indicated that the rhenium metal complex (2) was superior to the ligand (1) in activity against six different microbial species, but inferior to the standard antimicrobial agents.