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Molecular Design of Luminescence Ion Probes for Various Cations Based on Weak Gold(I)···Gold(I) Interactions in Dinuclear Gold(I) Complexes

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posted on 15.11.2004, 00:00 by Chi-Kwan Li, Xiao-Xia Lu, Keith Man-Chung Wong, Chui-Ling Chan, Nianyong Zhu, Vivian Wing-Wah Yam
A series of luminescent dinuclear gold(I) complexes with different crown ether pendants, [Au2(P∧P)(S-B15C5)2] [S-B15C5 = 4‘-mercaptobenzo-15-crown-5, PP = bis(dicyclohexylphosphino)methane (dcpm) (1), bis(diphenylphosphino)methane (dppm) (2)] and [Au2(PP)(S-B18C6)2] [S-B18C6 = 4‘-mercaptobenzo-18-crown-6, PP = dcpm (3), dppm (4)], and their related crown-free complexes, [Au2(PP)(SC6H3(OMe)2-3,4)2] [PP = dcpm (5), dppm (6)], were synthesized. The low-energy emission of the mercaptocrown ether-containing gold(I) complexes are tentatively assigned as originated from states derived from a S → Au ligand-to-metal charge transfer (LMCT) transition. The crown ether-containing gold(I) complexes showed specific binding abilities toward various metal cations according to the ring size of the crown pendants. Spectroscopic evidence was provided for the metal-ion-induced switching on of the gold···gold interactions upon the binding of particular metal ions in a sandwich binding mode.