Design, Synthesis and Functionalization of Luminescent Alkynylgold(i) Complexes with [Pi]-Conjugated Ligands: From Photophysics to Supramolecular Assembly

This dissertation, "Design, Synthesis and Functionalization of Luminescent Alkynylgold(I) Complexes With [pi]-conjugated Ligands: From Photophysics to Supramolecular Assembly" by Yau-hin, Hong, 康祐軒, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of the thesis entitled DESIGN, SYNTHESIS AND FUNCTIONALIZATION OF LUMINESCENT ALKYNYLGOLD(I) COMPLEXES WITH π-CONJUGATED LIGANDS  FROM PHOTOPHYSICS TO SUPRAMOLECULAR ASSEMBLY Submitted by HONG Yau Hin for the Degree of Doctor of Philosophy at The University of Hong Kong in July 2015 A library of polynuclear thiophene-based alkynylgold(I) complexes with N-heterocyclic carbenes (NHCs) and triphenylphosphine as the peripheral ligands, [R{(C≡C)Au(NHC)} ] (R = benzo[1,2-b:4,5-b']dithiophene, n = 2, 4; benzo[1,2- b:3,4-b':5,6-b'']trithiophene, n = 3; dithieno[3,2-b:2',3'-d]thiophene, n = 2; dithieno[3,2-e:2',3'-g](dibenzo[b, d]-thiophene), n = 2; 4-hexyl-4H-dithieno[3,2- b:2',3'-d]pyrrole, n = 4) and [R'{(C≡C)Au(PPh )}] (R' = benzo[1,2-b:4,5- 3 2 b']dithiophene), has been synthesized and characterized. The X-ray crystal structure of [BDT{(C≡C)Au(IHex)} -2,6] (BDT = benzo[1,2-b:4,5-b']dithiophene, IHex = 1,3-dihexylimidazol-2-ylidene) has been determined by X-ray crystallography. This class of complexes showed dual emissive behaviour and exhibited broad vibronic-structured emission bands in degassed dichloromethane solution at ambient temperature. As demonstrated by the temperature-dependent UV-vis absorption spectroscopy, some of the alkynylgold(I) complexes were shown to self-assemble in THFwater mixtures through a cooperative growth mechanism. Variation of the alkyl chain length on the NHC ligands not only has a significant effect on the morphologies of the aggregates, but also on the thermodynamic parameters of the self-assembly processes as revealed by the nucleationelongation model. Apart from the thiophene-based sulfur heterocycle-containing alkynylgold(I) system, a series of N-alkyl substituted triindole-based nitrogen heterocycle-containing trinuclear alkynylgold(I) complexes with isocyanide and NHCs as the peripheral ligands, [(TATI){(C≡C)Au(C≡N-R)}] (TATI = trialkyltriindole; R = 2,6-dimethoxyphenyl, 2,6-dimethylphenyl), and [(TATI){(C≡C)Au(NHC)}], has been prepared and characterized. The photophysical properties of the trinuclear alkynylgold(I) complexes have been examined. Their self-assembly properties have also been explored using TEM, SEM, DLS, H NMR spectroscopy, solvent-dependent and variable-temperature UV-vis absorption experiments. Some of the complexes have been demonstrated to possess spherical nanostructures in their THFwater dispersions. The self-assembly was believed to be mediated by the ππ stacking interactions of the central triindole moiety and governed by a cooperative growth mechanism. In addition, a novel class of amphiphilic phosphole-based phosphorus heterocycle-containing alkynylgold(I) complexes, [Au(C≡C-R){Ph-DBP(O)-  ] O(CH ) SO }]K (DBP = 5H-dibenzophosphole; R = phenyl, naphthyl, 2 3 3 phenanthrenyl, pyrenyl, perylenyl, 4-methoxyphenyl, 4-chlorophenyl) was designed and synthesized. The photophysical properties of this class of complexes have been studied. Some of the complexes were shown to display sheet-like nanostructures in aqueous DMSO solution. The self-assembly process was found to be governed by an isodesmic mechanism and mediated by hydrophobichydrophobic interactions between the alkynyl units. It has been shown that modulation of t