Intensely Luminescent Homoleptic Alkynyl Decanuclear Gold(I) Clusters and Their Cationic Octanuclear Phosphine Derivatives

Treatment of Au­(SC4H8)Cl with a
stoichiometric amount of hydroxyaliphatic alkyne in the presence of
NEt3 results in high-yield self-assembly of homoleptic
clusters (AuC2R)10 (R = 9-fluorenol (1), diphenylmethanol (2), 2,6-dimethyl-4-heptanol (3), 3-methyl-2-butanol (4), 4-methyl-2-pentanol
(4), 1-cyclohexanol (6), 2-borneol (7)). The molecular compounds contain an unprecedented catenane
metal core with two interlocked 5-membered rings. Reactions of the
decanuclear clusters 1–7 with gold–diphosphine
complex [Au2(1,4-PPh2–C6H4–PPh2)2]2+ lead to
octanuclear cationic derivatives [Au8(C2R)6(PPh2–C6H4–PPh2)2]2+ (8–14), which consist of planar tetranuclear units {Au4(C2R)4} coupled with two fragments [AuPPh2–C6H4–PPh2(AuC2R)]+. The titled complexes were characterized by
NMR and ESI-MS spectroscopy, and the structures of 1, 13, and 14 were determined by single-crystal
X-ray diffraction analysis. The luminescence behavior of both AuI10 and AuI8 families has
been studied, revealing efficient room-temperature phosphorescence
in solution and in the solid state, with the maximum quantum yield
approaching 100% (2 in solution). DFT computational studies
showed that in both AuI10 and AuI8 clusters metal-centered Au → Au charge transfer
transitions mixed with some π-alkynyl MLCT character play a
dominant role in the observed phosphorescence.