SYNTHESIS, STRUCTURAL CHARACTERIZATION AND PHOTOPHYSICAL PROPERTIES OF ETHYNE GOLD(I) COMPLEXES

A series of closely related ethynyl-gold(I) complexes was synthesized by reaction of Au(PR(3))Cl with an alkaline solution of the ethyne. The molecular structures of the ethynediyl-digold complexes NpPh(2)P-Au-C=C-Au-PNpPh(2).2CHCl(3) (1) (Np = naphthyl), Np(2)PhP-Au-C=C-Au-PNp(2)Ph.6CHCl(3) (2) and Fc(2)PhP-Au-C=C-Au-PFc(2)Ph.4EtOH (3) (Fc = ferrocenyl) and the phenylethynyl-gold complex Fc(2)PhP-Au-C=C-Ph (4) were determined by single-crystal X-ray diffraction measurements. Variation of the phosphines does not have a significant influence on the bonding in the central P-Au-C=C unit, the Au-P and Au-C distances being in the ranges 2.274(4)-2.289(5) and 1.983(8)-2.002(6) Angstrom, respectively. Although none of the compounds have short Au...Au contacts, compounds 1 and 2 do show novel C-H...pi interactions between the proton of CHCl3 and the pi-electron system of the C=C bond. In 1, pairs of CHCl3 molecules are located with their protons 2.4 Angstrom from the centre of the C=C bond with the C-H bond directed orthogonally towards the centre of the ethyne bond. In 2, two pairs of CHCl3 molecules are located around the C=C bond, with 2.5 Angstrom between the proton and the centre of the triple bond, resulting in a pseudo-octahedral arrangement around C=C. In addition to the C-H...pi interactions, the structures of 1 and 2 also show a range of intermolecular aromatic-aromatic interactions, The first structural determination of naphthylphosphines resulted in estimates of their steric requirements. The UV-visible spectra of CH2Cl2 solutions of the ethynediyl compounds exhibit intense absorption bands at ca. 300 nm assignable to intraligand transitions. Excitation of solid sample or fluid solution of complex 1 at lambda > 330 nm resulted in intense long-lived luminescence. Excitation of a solution of 2 at 350 and 380 nm led to different types of photoluminescence.