First examples of luminescent zinc(II)-bisquinoxalinato complexes: Synthesis, spectroscopic and theoretical studies

Four novel homoleptic zinc(II) complexes were prepared in high yield from para-substituted 2,3-diphenyl-5-hydroxyquinoxaline ligands, LHn, giving [Zn(Ln)2]. Density functional theoretical calculations were performed to probe the influence of the variation in para-substitution on the ligands. The calculations suggest that ligand-centred character appears to dominate the HOMO and LUMOs. Experimental electrochemical and spectroscopic characterisation showed that the subtle variations in absorption and emission wavelengths are due to ligand-dominated transitions that are influenced by electronic nature of the para-substituted phenyl units in coordinated Ln, in both solution and the solid states.