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. Th e 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 = ferro cenyl) 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 bondin g in the central P-Au-C=C unit, the Au-P and Au-C distances being in t he ranges 2.274(4)-2.289(5) and 1.983(8)-2.002(6) Angstrom, respective ly. Although none of the compounds have short Au...Au contacts, compou nds 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 c entre of the ethyne bond. In 2, two pairs of CHCl3 molecules are locat ed around the C=C bond, with 2.5 Angstrom between the proton and the c entre 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 inter actions, The first structural determination of naphthylphosphines resu lted in estimates of their steric requirements. The UV-visible spectra of CH2Cl2 solutions of the ethynediyl compounds exhibit intense absor ption bands at ca. 300 nm assignable to intraligand transitions. Excit ation of solid sample or fluid solution of complex 1 at lambda > 330 n m resulted in intense long-lived luminescence. Excitation of a solutio n of 2 at 350 and 380 nm led to different types of photoluminescence.