Recent Advances in Multicolor Emission and Color Tuning of Heteroleptic Iridium Complexes

摘要: We review recent advances in the spectroscopic properties of heteroleptic Ir(N^C)2(LX)-type iridium complexes, which are known as color-tuning materials. Most Ir complexes give single emission, accordance with Kasha’s rule. Dual however, has been observed from a Ir(N^C)2(LX) complex, depending on choice N^C moiety and LX ligands. For example, Ir(dfppy)2(pq), Ir(ppy)2(dpq-3F), Ir(ppy)2(pq), Ir(pq)2(tpy) (dfppy=2-(2,4-difluorophenyl)pyridine, pq=2-phenylquinoline, ppy=2-phenylpyridine, dpq-3F=2-(3-fluorophenyl)-4-phenylquinoline, tpy=2-p-tolylpyridine). Recently, triple emission was Ir(ppy)2(BTZ)-type two ppy ligands (N^C)2 one 2-(2-hydroxyphenyl)benzothiazole (BTZ) ligand, while quadruple Ir(ppy)2Q-type quinolinolato (Q) ligand. These multiple emissions cover spectral range blue to red, leading white emission. Of four bands Ir(ppy)2Q, UV violet attributed singlet states IrQ Ir(ppy), respectively, green red triplet Ir(ppy) IrQ. The appearance each (or Ir(BTZ)) components is understood by reduced Forster energy transfer between due an orientation factor nearly zero, that is, orthogonality ligand planes, both fluorescence phosphorescence inefficient intersystem crossing upper state lower state.