New ruthenium(II) bipyridine complex bearing 2-aminophenylbenzimidazole: Synthesis, spectral characterization and optical properties

The new bipyridine-based ruthenium(II) complex [Ru(bpy)₂(Hapbim)]²⁺ (bpy being 2,2′-bipyridine, and Hapbim is 2-aminophenylbenzimidazole) was synthesized and characterized. On the basis of elemental analysis, spectroscopic techniques (FTIR, ¹H NMR, UV-Visible), magnetic, conductivity and thermal analysis measurements, it was found that the Hapbim ligand coordinates to Ru(II) kernel in a neutral bidentate fashion through cyclic azomethine N of benzimidazole moiety along with the terminal nitrogen of the amino group forming six-membered chelate ring. Thin films of the Ru(II)-complex were prepared using thermal evaporation technique. The thin film structure was characterized using FTIR and X-Ray diffraction techniques. FTIR analysis revealed that the complex is chemically stable under both thermal evaporation and thermal annealing. The optical properties were studied by spectrophotometric measurements. The optical constants of the complex were calculated and it is found to have 1.5 eV band gap. Also, the effect of thermal annealing on the optical properties of the complex is studied. Annealing of the complex thin films increased the values of the dispersion parameters and decreased the value of the band gap.