Crystal structures, luminescence, and DFT study of mixed-ligand Zn(II) and Cd(II) complexes with phenyl-containing benzimidazole derivatives with linker CN or NN group

Highlights: • Mixed-ligand zinc(II) and cadmium(II) complexes with benzimidazole derivatives L¹ and L² have been synthesized. • Luminescence properties of the complexes were measured. • Compounds with L¹ and L² were shown to be green and red luminophores, respectively. • DTF calculations were used for better understanding of the experimental data. The peculiarities of photoluminescence of zinc(II) and cadmium(II) compounds with benzimidazole derivatives L¹ (1-methylbenzimidazo-2-yl-methyleneaniline) and L² (1-ethyl-2-(4-methoxyphenyl)azobenzimidazole) containing electron-donating ligands Cl⁻, NO₃⁻, or [B₁₀H₁₀]^2– were studied. It was found that most compounds with L¹ are green luminophores, while compounds with L² are red luminophores. The intensity of the luminescence and the position of the emission band depending on the composition and structure of the complexes were analyzed. The use of the single-crystal X-ray diffraction data and the density functional theory (DFT) calculations made it possible to determine the general relationships between the structural and spectroscopic characteristics of the compounds.