Syntheses, characterization and structures of 2-(2-pyridyl)-4-methylcarboxyquinoline ligand and bis(2,2′-bipyridine)-2-(2-pyridyl)-4-methylcarboxyquinoline ruthenium (II) hexafluorophosphate

Abstract

The synthesis, characterization and X-ray single crystal structure of a 2-(2-pyridyl)-4-methylcarboxyquinoline diimine ligand (pqme) and its corresponding bis(2,2′-bipyridine)-2-(2-pyridyl)-4-methylcarboxyquinoline ruthenium (II) hexafluorophosphate Ru(bpy) 2(pqme)(PF 6) 2 complex is described. 1H, 1H– 1H COSY, 1H– 1H TOCSY, 13C NMR, FT-IR, elemental and mass spectrometric analyses were used to characterize the products and fully ascertain their structures. The complex exhibited two well-resolved MLCT transitions in the visible region and a ligand-based transition in the UV region. The cyclic voltammogram of the complex showed a reversible Ru(III)/Ru(II) couple and three well-defined ligand-based reductions. X-ray diffraction analyses provided further insight as to the conformations and geometry of both products. A trans conformation is shown in the solid state as expected for the 2-(2-pyridyl)-4-methylcarboxyquinoline ligand, and a distorted octahedral geometry for the bis(2,2′-bipyridyl)-2-(2-pyridyl)-4-methylcarboxyquinoline ruthenium (II) hexafluorophosphate complex due to α hydrogens of the opposing N–N ligands have been revealed.