Synthesis, structural characterization, and initial electroluminescent properties of bis-cycloiridiated complexes of 2-(3,5-bis(trifluoromethyl)phenyl)-4-methylpyridine
作者:Alex S. Ionkin、Ying Wang、William J. Marshall、Viacheslav A. Petrov
DOI:10.1016/j.jorganchem.2007.06.026
日期:2007.10
A series of bis-cyclometalated Ir(III) complexes (8-10, 12, 15, 17, 19, 21, 23, 25, 28, 29 and 33) bearing two chromophoric N boolean AND C cyclometalated ligands derived from 2-(3,5-bis(trifluoromethyl)phenyl)-4-methylpyridine (1) and a third nonchromophoric ligand has been synthesized. A palladium-catalyzed cross-coupling reaction between 2-chloro-4-methylpyridine (2) and 3,5-bis(trifluoromethyl)phenylboronic acid (3) was used to prepare 2-(3,5-bis(trifluoromethyl)phenyl)-4-methylpyridine (1). Cyclometalation of (1) by IrCl3 was carried out in (MeO)(3)P = O, with the formation of chloro-bridged dimer [N boolean AND C](2)Ir(mu-Cl)(2)Ir[C boolean AND N](2) (8). Reaction of (8) with lithium 2,4-pentanedionate, lithium 2,2,6,6-tetramethyl-heptane-3,5-dionate (13), dipivaloyltrimethylsilylphosphine (14), 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octadione (16), 1,1,1,3,3,3-hexafluoro-2-pyridin-2-yl-propan-2-ol (18), 1,1,1,3,3,3-hexafluoro-2-pyrazol-1-ylmethyl-propan-2-ol (20), 2-diphenylphosphanylethanol (22), and 1-diphenylphosphanylpropan-2-ol (24), afforded octahedral iridium complexes 9, 12, 15, 17, 19, 21, 23 and 25, respectively. Complex 10, which contains three different ligands (L-1 = N boolean AND C of 1; L-2 = N boolean AND C of 4,4'-dimethyl-[2,2']bipyridinyl 4; L-3 = O boolean AND O of 2,4-pentanedione), and complex 11, which contains no cyclometalated ligands (L-1 = 4; L-2 = L-3 = Cl; L-4 = O boolean AND O of 2,4-pentanedione) were also isolated as minor products in a one-pot reaction between a 94:5 mixture of I and 4, IrCl3 and lithium 2,4-pentanedionate. Reaction of 8 with diphenylphosphanylmethanol (27) in 1,2-dichloroethane unexpectedly led to complexes 28 and 29. The reactions of 8 with benzoylformic acid resulted in the formation of hydroxyl-bridged dimer [N boolean AND C](2)Ir(mu-OH)(2)Ir[C boolean AND N](2) (33). According to X-ray analyses, Ir-to-Ir distances in the crystal cell increase from 6.86 angstrom for 10 to 13.31 angstrom for 33. The angle theta, which represents the twisting of two cyclometalated C-Ir-N planes relative to each other, varies from 97.5 degrees for 21 to 90.76 for complex 28. OLED devices were fabricated from several Ir complexes and preliminary results are discussed. (C) 2007 Elsevier B.V. All rights reserved.