LUMINESCENT ORGANOMETALLIC GOLD(I) COMPLEXES - STRUCTURE AND PHOTOPHYSICAL PROPERTIES OF ALKYL-ETHYNYLENE, ARYL-ETHYNYLENE AND MU-ETHYNYLENE GOLD(I) COMPLEXES

The complexes [Au(PPh3)Ph] 1, [Au2(dppm)Me2] 2, [Au2(dppm)Ph2] 3 and [{Au(P(C6H4OMe-p)3]}2-(mu-C=C)] 4 were prepared by literature methods. The structures of 1-3 have been established by X-ray crystallography: 1, triclinic, space group P1BAR, a = 8.524(2), b = 15.227(2), c = 15.525 angstrom, alpha = 91.07(1), beta = 92.06(1), gamma = 94.28(1)degrees; 2, monoclinic, space group P2(1)/n, a = 12.201 (3) b = 13.014(5), c = 16.329(4) angstrom, beta = 94.11 (2)degrees; 3, monoclinic, space group C2/c, a = 16.688(3), b = 10.468(1), c = 17.8992) angstrom, beta = 97.70(1)degrees. The intramolecular Au ... Au distances in 2 and 3 are 3.251(1) and 3.154(1) angstrom respectively. Extended-Huckel molecular orbital calculations showed that the highest occupied molecular orbital of 3 is a combination of d(sigma*) and d(delta*), whereas its lowest unoccupied molecular orbital is the pi* of the co-ordinated phenyl group. The UV/VIS absorption spectra of 2 and 3 show intense absorptions at around 290-300 nm, which are assigned as Au (d(sigma*), d(delta*)) --> pi*(Ph, dppm) in nature. Both 2 and 3 show luminescence in fluid solution at room temperature. The emission properties of 3 have been examined in detail. Complex 4 shows a well resolved vibronic structured emission at 400-600 nm in dichloromethane at room temperature, arising from the 3[pipi*] excited state of C-2(2-).