A Luminescent Supermolecule with Gold(I) Quinoline-8-thiolate: Crystal Structure, Spectroscopic and Photophysical Properties

The trinuclear complex [(8-QNS)2Au(AuPPh3)2]·BF4 (8-QNS = quinoline-8-thiolate), with intramolecular gold(I)···gold(I) distances of 3.0952(4) and 3.0526 (3) (angstrom), is aggregated to form a novel hexanuclear supermolecule, {[(8-QNS)2Au(AuPPh3)2]}2·(BF4)2, via a close intermolecular gold(I)···gold(I) contact of 3.1135(3) (angstrom). The beautiful hexanuclear supermolecule has an inversion center, and the six metal centers can be viewed as roughly coplanar. Six gold(I) ions are embedded in an ellipse and surrounded by 4 quinoline and 12 phenyl rings. The title compound shows interesting spectroscopic and luminescence properties dependent on the solvent polarity; i.e., it emits at ca. 440 and 636 nm in CH2Cl2 and only at ca. 450 nm in CH3CN. The long-lived emission at ca. 636 nm (16.2 (mu)s) in CH2Cl2 is quenched by polar solvents such as CH3CN and CH3OH with quenching constants as 1.00 × 10^5 and 3.03 × 10^4 s^-1 M^-1, respectively, which is suggested to be related to the presence or absence of gold(I)··· gold(I) interactions due to scrambling of the [AuPPh3]+ units, isolobal to H+.