Synthesis, characterization, and DFT calculations of iridium(III) complexes with tolylterpyridine

Chemistry, Nara Women's University* Department of Chemistry, Nara University of Education** Department of Applied Chemistry, Graduate School of Engineering, Osaka University***
Naokazu Yoshikawa* Shinichi Yamabe** Hiroshi Takashima* Keiichi Tsukahara* Nobuko Kanehisa*** Yasushi Kai***

Three polypyridine iridium(III) complexes in the form of [IrCl(L)(tterpy )]2+ were newly prepared (L=phen (1), dpphen(2), and dmbpy(3)). Reference complexes [IrCl(bpy)(tterpy )]2+ (4) and [Ir(L)2] 3+ (L= tterpy (5) and terpy (6)) were also prepared. They were synthesized by using a microwave oven and were characterized by ESI MS, UV-vis spectroscopy, and cyclic voltammograms(CV). Abbreviations of the ligands are phen = 1,10-phenanthroline, dpphen = 4,7-diphenyl-1,10-phenanthroline, bpy = 2,2'-bipyridine, dmbpy = 4,4'-dimethyl-2,2'-bipyridine, tterpy = 4'-(4-tolyl)-2,2':6',2h-terpyridine and terpy= 2,2':6',2h-terpyridine. The X-ray structures of the two complexes, 5, and 6 were also obtained. In CV, all the [IrCl(L)(tterpy )] 2+ complexes showed that the first reduction occurred at around -1.27 V, which was attributed to the reduction of tterpy ligand in [IrCl(L)(tterpy )] 2+ . The electronic properties of 3, 5, and 6 complexes were studied using the B3LYP functional. Optimized geometries were compared to the experimentally observed structures. Excited triplet and singlet states were examined using time-dependent density functional theory (TDDFT). The calculated energies of the lowest triplet state and lowest singlet state in the two complexes were in good agreement with experimental absorption spectra. All complexes in the form of [IrCl(L)(tterpy )] 2+ showed that LUMOs were localized on the tterpy ligand. It was found that [IrCl(L)(tterpy )] 2+ emited an intense phosphorescence at room temperature. The spectroscopic and electrochemical results were discussed correlatively.