American Chemical Society
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Luminescent μ-Ethynediyl and μ-Butadiynediyl Binuclear Gold(I) Complexes:  Observation of 3(ππ*) Emissions from Bridging Cn2- Units

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journal contribution
posted on 2001-05-03, 00:00 authored by Chi-Ming Che, Hsiu-Yi Chao, Vincent M. Miskowski, Yanqin Li, Kung-Kai Cheung
The synthesis and X-ray structural and spectroscopic characterization for LAuC⋮CAuL·4CHCl3 and LAuC⋮C−C⋮CAuL·2CH2Cl2 (1·4CHCl3 and 2·2CH2Cl2, respectively; L = PCy3, tricyclohexylphosphine) are reported. The bridging Cn2- units are structurally characterized as acetylene or diacetylene units, with C⋮C distances of 1.19(1) and 1.199(8) Å for 1·4CHCl3 and 2·2CH2Cl2, respectively. An important consequence of bonding to Au(I) for the Cn2- moieties is that the lowest-energy electronic excited states, which are essentially acetylenic 3(ππ*) in nature, acquire sufficient allowedness via Au spin−orbit coupling to appear prominently in both electronic absorption and emission spectra. The origin lines for both complexes are well-defined and are observed at 331 and 413 nm for 1 and 2, respectively. Sharp vibronic progressions corresponding to v(C⋮C) are observed in both emission and absorption spectra. The acetylenic 3(ππ*) excited state of 2 has a long lifetime (τ0 = 10.8 μs) in dichloromethane at room temperature and is a powerful reductant (E°[Au2+/Au2*] ≤ −1.85 V vs SSCE).