Geometrically confined diffused energy transfers from metal to ligand : Carbazole and naphthalene substituents effect of deep-blue phosphorescent isomer of homoleptic <em>N</em>-heterocyclic carbene (NHC) based Ir(III) complexes
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초록
내용
We investigated the intraligand energy transfer (IET) mechanism on new N-heterocyclic carbene (NHC) Ir(III) complexes with 1-phenyl-3-methyl-imidazolin-2-ylidene (pmi) ligands, which have naphthalene (Np) or carbazole (Cz) group, resulting to Ir(Nppmi)3, and Ir(Czpmi)3. Ir complexes showed dual emission: one is the fluorescence originated from Np/Cz, and the other is the phosphorescence of cored Ir complexes. At 77 K, all Ir(Nppmi)3 and Ir(Czpmi)3 showed intense phosphorescence originated from excited triplet Np/Cz species. The fast IET dynamics was confirmed by the time-resolved transient absorption (TA) spectroscopic technique. The relative energy levels calculated by DFT showed that the excited states of NHC Ir complexes lay at higher energy states compared to those of peripheral Np/Cz.