Differences of Structures and Electronic Properties in the Triplet States between Dibromo and Dichloro Mononuclear Polypyridine Iridium(III) Complexes

作者：Yoshikawa Naokazu^*; Yamabe Shinichi; Kanehisa Nobuko; Inoue Tsuyoshi; Takashima Hiroshi; Tsukahara Keiichi

来源：Bulletin of the Chemical Society of Japan, 2011, 84(12): 1347-1354.

DOI：10.1246/bcsj.20110098

Emission and electronic properties of eight iridium(III)-centered polypyridine complexes were studied systematically. A crystal structure of [IrBr2(phen)(2)]PF6 was obtained by X-ray diffraction study, where phen is 1,10-phenanthroline. Those in the triplet states were also determined by DFT calculations to investigate the source of emission spectra. Two triplet structures of [IrX2(bpy)(2)](+) and [IrX2(bpy)(2)](+) and the transition state of interconversion were obtained with X- = Cl- and Br-. Here, bpy is 2,2'-bipyridine. For the chloro complexes, two triplet species have nonequivalent bpy and phen ligands through pseudo-Jahn-Teller geometric distortion. The dichloro complexes with asymmetric spin density distributions were found to correspond to stronger emission spectra than those for the dibromo compounds. Energies (E's) corresponding to the observed emission wavelengths (E-em's) are in good agreement with the theoretical S-0-T-1, energy differences (Delta E's). For [IrBr2(bpy)(2)](+), E-em = 2.29eV and Delta E= 2.26 eV. For [IrCl2(bpy)(2)](+), E-em = 2.29 eV and Delta E= 2.33 eV. For [IrBr2(phen)(2)](+), E-em = 2.26 eV and Delta E= 2.28 eV. For [IrCl2(bpy)(2)](+), E-em = 2.28 eV and Delta E= 2.34 eV. For all the four complexes, 1A, 1B, 3A, and 3B, DFT calculations indicate lr-N bond rupture. T-c with a small S-0-T-1 energy-gap would undergo nonradiative relaxation. T, indicates a triplet state which is a five-coordinate species with triplet metal-centered character. Coexistence of the triplet state species are discussed in terms of their electronic structures.

• 出版日期2011-12-15