Ralf Haiges - Structural and Photophysical Studies of Phosphorescent Three-Coordinate Copper(I) Complexes Supported by an N-Heterocyclic Carbene Ligand.

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      Publication Details (including relevant citation   information): Krylova, Valentina A., Djurovich, Peter   I., Aronson, Jacob W., Haiges, Ralf, Whited, Matthew T.,   Thompson, Mark E., Organometallics,   2012, 31 (22), pp 7983-7993

      Abstract: A series of four neutral luminescent   three-coordinate Cu(I) complexes (IPr)Cu(N-N), where IPr is a   monodentate N-heterocyclic carbene (NHC) ligand (IPr =   1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and N-N denotes   monoanionic pyridylazolate ligands, have been synthesized and   characterized. A monomeric, three-coordinate geometry, best   described as distorted trigonal planar, has been established by   single-crystal x-ray analyses for three of the derivs. In   contrast to the previously reported (IPr)Cu(N-N) complexes, the   compds. described here display a perpendicular orientation   between the chelating N-N ligands and the imidazolylidene ring of   the carbene ligand. The geometrical preferences revealed by x-ray   crystallog. correlate well with the NMR data. The conformational   behavior of the complexes, investigated by variable-temp. 1H NMR   spectroscopy, indicate free rotation about the CNHC-Cu bond in   soln. The complexes display broad, featureless luminescence at   both room temp. and 77 K, with emission maxima that vary between   555 and 632 nm depending on sample conditions. Luminescence   quantum efficiencies of the complexes in soln. (Φ ≤ 17%) increase   markedly in the solid state (Φ ≤ 62%). On the basis of   time-dependent d. functional theory (TD-DFT) calcns. and the   exptl. data, luminescence is assigned to phosphorescence from a   metal-to-ligand charge-transfer (MLCT) triplet state admixed with   ligand-centered (LC) character. [on SciFinder(R)]

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