Amplified Triplet Emission of Organic Periphery Groups by Exothermic Triplet-Triplet Energy Transfer from the MLCT State of an Core Complex to the LC State of Geometrically Confined Carbazole/Naphthyl Tethers.

To investigate the excited-state properties of metal-organic bichromophores, including energy transfer mechanisms, a series of new homoleptic -heterocyclic carbene (NHC)-based iridium(III) complexes were prepared by incorporating a peripheral naphthalene (Np) (: and ) or carbazole (Cz) (: , , and ) unit to the phenyl moiety of the phenylimidazole (pmi) ligand. Through a series of photophysical analyses and femtosecond time-resolved absorption (fs-TA) spectroscopy, it was discovered that the phosphorescence of the Ir core, (), was considerably quenched, while intense phosphorescence peaks arising from the excited triplet Np (Np*)/Cz (Cz*) species were primarily observed at room temperature (r.t.