Antimicrobial activities of two 1-D, 2-D, and 3-D mononuclear Mn (II) and dinuclear Bi (III) complexes: X-ray structures, spectroscopic, electrostatic potential, Hirshfeld surface analysis, and time-dependent/density functional theory studies

Two mononuclear and dinuclear octahedral complexes, [Mn(L-1)(2)Cl-2] (1) and [Bi-2(L-2)(2)Cl-8] (2) (L-1 = 2-(2-pyridyl)-4-methyl-1,2-dihydroquinazoline-N-3-oxide, L-2 = 2-(3-pyridyl)-4-methyl-1,2-dihydroquinazoline-N-3-oxide) were prepared by natural volatilization method. The ligands and both complexes were compared with spectroscopic methods, as well as characterized by elemental analysis. The photoluminescence behaviors of both complexes in different solvents were also investigated. The coordination possibility of ligands toward Mn (II)/Bi (III) was verified using X-ray crystallography, and it revealed that the ratio of ligand to metal was 2:1 in 1, whereas 1:1 in 2. The adjacent molecules of six-coordinated complex 1 constituted an infinite 1-D chain, 2-D network, and ladder-like 3-D supramolecular frameworks. Most strikingly, hexa-coordinated complex 2 with dinuclear structure formed an infinite 1-D chain, 2-D layered and meter-shaped 3-D supramolecular skeleton. Density functional theory (DFT) calculation was used to optimize the geometry of complexes, compute the electrostatic potential diagrams, and evaluate the HOMO-LUMO energy gap. The electronic transition simulated through time-dependent (TD)-DFT level of calculation rationalized the experimental data. The antibacterial properties of all compounds were evaluated against Gram-positive and Gram-negative bacterial strains. In addition, the Hirshfeld surface was utilized to quantify some hydrogen bonding interactions and their contributions.

Automated summary

This article investigates the preparation of mononuclear and dinuclear octahedral complexes with two different ligands using the natural volatilization method. The spectroscopic properties, photoluminescence behaviors, and coordination possibilities of the complexes are characterized. The structures and properties of the complexes are studied using X-ray crystallography and density functional theory. The antibacterial properties and hydrogen bonding interactions are also evaluated.