| 초록 |
Two isomeric N-heterocyclic (NHC) carbene Ir(III) complexes, f-Ir-(dbfmi)3 (1) and m-Ir-(dbfmi)3 (2), were isolated and their systematic investigation on photophysical and electrochemical properties was carried out. The origin of phosphorescent emissions differs depending on the configurations of the two isomers. Both isomers, (1) and (2), showed efficient emission with quantum yields of 68% and 53%, respectively, due to unusual properties of the NHC ligand; –that is, the complexes possess a strong metal–ligand bond that destabilizes the nonradiative metal centred ligand-field states. Depending on their configurations, the two isomers showed slightly different excited states. Even though both isomers possess a largely 3LC character mixed with the 3MLCT character in their excited states, (2) showed higher 3MLCT character as evidenced by the solvent polarity dependence emission spectra and emission lifetime. DFT calculations clearly support this different photophysical property. |
