Luminescent Copper(I) Halide Butterfly Dimers Coordinated to [Au(CH3imCH2py)2]BF4 and [Au(CH3imCH2quin)2]BF4

The coordination chemistry of copper(I) halides to the homoleptic, N-heterocyclic carbene Au(I) complexes [Au(CH(3)imCH(2)quin)(2)]BF4 and Au(CH(3)imCH(2)py)(2)]BF4 was explored. The reaction of CuX (X = Cl, Br, I) with either [Au(CH(3)imCH(2)quin)(2)]BF4 or [Au(CH(3)imCH(2)py)(2)]BF4 produces trimetallic complexes containing Cu2X2-butterfly copper clusters coordinated to the two imine moieties. The triangular arrangement of the metals places the gold(I) center in close proximity (similar to 2.5-2.6 angstrom) to the centroid of the Cu-Cu vector The Cu-Cu separations vary as a function of bridging halide with the shortest Cu-Cu separations of similar to 2.5 angstrom found in the iodo-complexes and the longest separations of 2.9 angstrom found in the bridging chloride complexes. In all six complexes the Au-Cu separations range from similar to 2.8 to 3.0 angstrom. In the absence of halides, the dimetallic complex [AuCu(CH(3)imCH(2)py)(2)(NCCH3)(2)](BF4)(2), containing a long Au-Cu distance of similar to 4.72 angstrom is formed. Additionally, as the byproduct of the reaction of CuBr with [Au(CH(3)imCH(2)quin)(2)]BF4 the deep-red, dimetallic compound, AuCuBr2(CH(3)imCH(2)quin)(2), was isolated in very low yield. All of these complexes were studied by NMR spectroscopy, mass spectrometry, and the copper containing species were additionally characterized by X-ray crystallography, In solution the copper centers dissociate from the gold complexes, but as shown by XANES and EXAFS spectroscopy, at low temperature the Cu-Cu linkage is broken, and the individual copper(I) halides reposition themselves to opposite sides of the gold complex while remaining coordinated to one imine moiety. In the solid state all of the complexes are photoluminescent, though the nature of the excited state was not determined.