title: Electrochemical and phosphorescent properties of new Ir(III) complexes coordinated by various bipyridine derivatives.
abstract: Four useful polypyridine iridium(III) complexes in the form of [IrCl2L2]+ were prepared and their spectroscopic and electrochemical properties as well as X-ray crystallography were investigated. The ligands used were L = 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine, 4,4'-diphenyl-2,2'-bipyridine, 1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline, and 2,2'-biquinoline. Synthetic methods were developed by a sequential ligand-replacement, which occurred in the reaction vessel using a microwave oven. All complexes showed that LUMOs are based on the pi-system contribution of the polypyridine ligand for [IrCl2(bpy)2]+, [IrCl2(dmbpy)2]+, [IrCl2(dpbpy)2]+, [IrCl2(phen)2]+, [IrCl2(dpphen)2]+ and [IrCl2(bqn)2]+. The HOMOs are also localized on the polypyridine ligand in the iridium complexes. It was found that [IrCl2L2]+ emits intense phosphorescence at room temperature. In particular, the use of dpbpy as ancillary ligands extends the lifetime (660 ns) of the 3(pi-pi*) excited states of Ir(III) polypyridine complexes. The complex [IrCl2(bqn)2]+ with electron acceptor substituents shows a large red-shift to 622 nm. It is noticed that iridium polypyridine complexes show intense emissions at various colors, such as yellow for [IrCl2(dmbpy)2]+ and red for [IrCl2(bqn)2]+ which can be applied to photosensitizers. The spectroscopic and electrochemical details are also reported herein.
authors.affiliation: Department of Chemistry, Faculty of Science, Nara Women's University, Nara 630-8506, Japan. naokazuu@dg.mbn.or.jp
authors.forename: Naokazu
authors.initials: N
authors.lastname: Yoshikawa
authors.forename: Jun
authors.initials: J
authors.lastname: Sakamoto
authors.forename: Takeko
authors.initials: T
authors.lastname: Matsumura-Inoue
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takashima
authors.forename: Keiichi
authors.initials: K
authors.lastname: Tsukahara
authors.forename: Nobuko
authors.initials: N
authors.lastname: Kanehisa
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kai