Synthesis, Structural Characterization and Luminescence Studies of Di- and Trinuclear Gold(I) Alkynyl-phosphine Complexes

Reactions of the polymer {AuIC2Ph}n with polyphosphine ligands [1,4-bis(2-diphenylphosphino-1H-imidazol-1-yl)-benzene (dpib), 1,3,5-tris(4-diphenylphosphinophenyl)benzene (tppb), 2,2′-bis(diphenylphosphanyl)-4,4′-bipyridine (dpbp), and 3,6-bis(diphenylphosphanyl)pyridazine (dppz)] afforded four gold(I) alkynyl-polyphosphine complexes [{AuC2Ph}2(μ-dpib)] (1), [{AuC2Ph}3(μ3-tppb)] (2), [{AuC2Ph}2(μ-dpbp)] (3), and [{AuC2Ph}2(μ-dppz)] (4) in nearly quantitative yield. The compounds obtained were characterized using elemental analysis, ESI-MS, X-ray crystallography, and polynuclear NMR spectroscopy. Intermolecular aurophilic interaction together with π–π and σ–π stacking build up the supramolecular 3D network of complex 3, whereas none of these intermolecular bondings were found in the crystal structures of compounds 1, 2, and 4. Complexes 1–4 are luminescent both in solution (CH2Cl2) and in solid state under laser irradiation (λex = 308 nm). In solution, the diphosphine complexes 1–4 display dual emission corresponding to ligand centered transitions (λem = 360–375 nm) along with weaker contribution from MLCT excited states at ca. 490 nm. The long wavelength component of the emission plays a dominant role in the solid state luminescence spectra of complexes 1, 3, and 4 (460, 544, 520 nm, respectively) whereas the triphosphine complex 2 shows dual luminescence (372 and 520 nm) with considerable contribution from ligand centered excited state.