P 58 Phosphorescence vs Fluorescence in Cyclometalated Platinum(II) and Iridium(III) Complexes of (Oligo)thienylpyridines / D. N. Kozhevnikov, V. N. Kozhevnikov, M. Z. Shafikov, A. M. Prokhorov, D. W. Bruce, J. A. Gareth Williams // Inorganic Chemistry . - 2011. - Vol. 50, № 8. - С. 3804-3815 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): OLIGOTHIENYLPYRIDINES -- LIGANDS -- LUMINESCENCE PROPERTIES Аннотация: Two newly prepared oligothienylpyridines, 5-(2-pyridyl)-5?-dodecyl-2,2?-bithiophene, HL2, and 5-(2-pyridyl)-5??-dodecyl-2,2?:5?,2??-ter-thiophene, HL3, bind to platinum(II) and iridium(III) as NC-coordinating ligands, cyclometallating at position C4 in the thiophene ring adjacent to the pyridine, leaving a chain of either one or two pendent thiophenes. The synthesis of complexes of the form [PtLn(acac)] and [Ir(Ln)2(acac)] (n = 2 or 3) is described. The absorption and luminescence properties of these four new complexes are compared with the behavior of the known complexes [PtL1(acac)] and [Ir(L1)2(acac)] {HL1 = 2-(2-thienyl)pyridine}, and the profound differences in behavior are interpreted with the aid of time-dependent density functional theory (TD-DFT) calculations. Whereas [PtL1(acac)] displays solely intense phosphorescence from a triplet state of mixed ??*/MLCT character, the phosphorescence of [PtL2(acac)] and [PtL3(acac)] is weak, strongly red shifted, and accompanied by higher-energy fluorescence. TD-DFT reveals that this difference is probably due to the metal character in the lowest-energy excited states being strongly attenuated upon introduction of the additional thienyl rings, such that the spin?orbit coupling effect of the metal in promoting intersystem crossing is reduced. A similar pattern of behavior is observed for the iridium complexes, except that the changeover to dual emission is delayed to the terthiophene complex [Ir(L3)2(acac)], reflecting the higher degree of metal character in the frontier orbitals of the iridium complexes than their platinum counterparts.?? \\\\Expert2\\nbo\\Inorganic Chemistry\\2011, v.50, p.3804.pdf |