Light-emitting materials from cyclometalated heteroleptic iridium(III) complexes--A physicochemical study.

Phosphorescent studies of 2-arylimidazole heteroleptic cyclometalated iridium(III) complexes with picolinic acid as the ancillary ligand were made. The observed experimental data reveal that these complexes possess dominantly (3)MLCT and (3)π-π* excited states and the solvent shift of these complexes is interpreted by Reichardt-Dimroth and Marcus solvent functions. The results are consistent with prior assignments on the absorption band to a metal-to-ligand charge transfer excited state associated with chelating ligand. Emission kinetic studies exploited that the radiative transition (k(r)) increases with increasing λ(em).