Synthesis, characterization and theoretical studies of the heteroleptic Ruthenium(II) complexes of 2,6-bis(benzimidazolyl)pyridine

Four new Ruthenium(II) complexes [Ru(bbp)(pyterpy)](PF6)2 (1), [Ru(bbp)(bip)Cl]PF6 (2), [Ru(bbp)(biq)Cl]PF6 (3) and [Ru(bbp)(phen)Cl]PF6 (4) have been synthesized and characterized by spectroscopic techniques (IR, NMR and mass) and single crystal X-ray diffraction study of one of them (4) (where bbp = 2,6-bis(benzimidazolyl)pyridine, pyterpy = 4(4-pyridyl)terpyridine, phen = 1,10-phenanthroline, bip = 2-(benzimidazolyl)pyridine, biq = 2,2′-biquinoline). The electronic spectra of all the complexes show significant bathochromic shift of their lowest energy Metal to Ligand Charge Transfer band position with respect to [Ru(bpy)3]2+. The position of the MLCT band is modulated by the nature of the coligand, the 2,6-bis(benzimidazolyl)pyridine ligand being present in all the complexes. The change in the RuIII/II potential is also explained on the basis of the σ/π donor characteristic of the ligands.

Graphical abstractHeteroleptic Ruthenium complexes with benzimidazolyl ligand has been reported here. The complexes have been characterized by spectroscopic techniques and single crystal X-ray diffraction study. DFT calculations have been performed on all the ligands and the complexes. Electronic spectra of the ligands and the complexes have been correlated with the theoretical spectra obtained from TD-DFT study. Shift in the MLCT band and the Ru(II–III) oxidation potential has been explained on the basis of nature of the coligand in the complexes.Figure optionsDownload full-size imageDownload as PowerPoint slide