New iridium complexes with cyclometalated 2-arylimidazole ligands as highly efficient saturated green emitters

Phosphorescence studies of a series of heteroleptic cyclometalated iridium(III) complexes have been carried out. From the photoluminescent properties, it was found that these complexes possess dominantly 3MLCT and 3π–π* excited states. The solvent shifts are interpreted in terms of Reichardt–Dimroth solvent ET parameters and Marcus theory. 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 reveal that kr increases with increasing λem and linear correlation between ln(knr) and energy gap. The effect of Eg and ΔQe on knr is discussed in detail.

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► These iridium(III) complexes possess dominantly 3MLCT and 3π–π* excited states.
► The solvent shifts are interpreted in terms of Reichardt–Dimroth solvent ET parameters and Marcus theory.
► Emission kinetic studies reveal that kr increases with increasing λem and linear correlation between ln(knr) and energy gap.
► The radiative and the non-radiative rate constants are calculated from the phosphorescence yield and lifetime.