Heteroleptic cyclometalated iridium(III) complexes displaying blue phosphorescence in solution and solid state at room temperature

被引:208
作者
Yang, CH
Li, SW
Chi, Y [1 ]
Cheng, YM
Yeh, YS
Chou, PT
Lee, GH
Wang, CH
Shu, CF
机构
[1] Natl Tsing Hua Univ, Dept Chem, Hsinchu 300, Taiwan
[2] Natl Taiwan Univ, Dept Chem, Taipei 106, Taiwan
[3] Natl Taiwan Univ, Instrumentat Ctr, Taipei 106, Taiwan
[4] Natl Chiao Tung Univ, Dept Appl Chem, Hsinchu 300, Taiwan
关键词
D O I
10.1021/ic050311g
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
A series of heteroleptic Ir(III) metal complexes 1-3 bearing two N-phenyl-substituted pyrazoles and one 2-pyridyl pyrazole (or triazole) ligands were synthesized and characterized to attain highly efficient, room-temperature blue phosphorescence. The N-phenylpyrazole ligands, dfpzH = 1-(2,4-difluorophenyl)pyrazole, fpzH = 1-(4-fluorophenyl)-pyrazole, dfmpzH = 1-(2,4-difluorophenyl)-3,5-dimethylpyrazole, and fmpzH = 1-(4-fluorophenyl)-3,5-dimethylpyrazole, show a similar reaction pattern with respect to the typical cyclometalated (C boolean AND N) chelate, which utilizes its orthosubstituted phenyl segment to link with the central Ir(III) atom, while the second 2-pyridylpyrazole (or triazole) ligand, namely, fppzH = 3-(trifluoromethyl)-5-(2-pyridyl)pyrazole, fptzH = 3-(trifluoromethyl)-5-(2-pyridyl)triazole, and hptzH = 3-(heptafluoropropyl)-5-(2-pyridyl)triazole, undergoes typical anionic (N boolean AND N) chelation to complete the octahedral framework. X-ray structural analyses on complexes [(dfPZ)(2)Ir(fppz)] (1a) and [(fMPZ)(2)Ir(hptz)] (3d) were established to confirm their molecular structures. Increases of the pi pi* energy gaps of the Ir(III) metal complexes were systematically achieved with two tuning strategies. One involves the substitution for one or two fluorine atoms at the N-phenyl segment or the introduction of two electron-releasing methyl substituents at the pyrazole segment of the H(CAN) ligands. Alternatively, we have applied the more electron-accepting triazolate in place of the pyrazolate segment for the third (N boolean AND N)H ligand, Our results, on the basis of steady-state, relaxation dynamics, and theoretical approaches, lead to a conclusion that, for complexes 1-3, the weakening of iridium metal-ligand bonding strength in the T-1 state plays a crucial role for the fast radiationless deactivation. For the case of [(fMPZ)(2)Ir(hptz)] (3d), a thermal deactivation barrier of 4.8 kcal/mol was further deduced via temperature-dependent studies. The results provide a theoretical basis for future design and synthesis of the corresponding analogues suited to blue phosphorescent emitters.
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收藏
页码:7770 / 7780
页数:11
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