Triphosphine-supported bimetallic Au-I-M-I (M = Ag, Cu) alkynyl clusters

The reactions of gold acetylides (AuC2R)(n) with triphosphine ligands PPh2(CH2)(n)-PPh-(CH2)(2)-PPh2 (n = 1, dpmp; 2, dpep) in the presence of M+ ions (M = Cu, Ag) lead to an assembly of the heterometallic clusters, the composition of which is determined by the steric bulkiness of the alkynyl groups and the flexibility of the phosphine motifs. For R = Ph, an unprecedented hexanuclear complex [Au5Cu(C2R)(4)(dpmp)(2)](2+) (1) was isolated, while for the aliphatic alkynes (R = 1-cyclohexanolyl, 2-borneolyl, 2,6-dimethyl-4-heptanolyl) a family of compounds based on a tetrametallic framework was prepared, [Au3Cu(C2R)(3)(dpmp)](+) (2, R = 1-cyclohexanolyl), [Au3M(C2R)(3)(dpep)](2) (+2) (3, M = Cu, R = 1-cyclohexanolyl; 4, M = Cu, R = 2-borneolyl; 5, M = Ag, R = 2-borneolyl), and [Au3Ag(C2R)(3)(dpep)](+) (6, R = 2,6-dimethyl-4-heptanolyl). Clusters 1, 2, and 4-6 were studied by X-ray crystallography. The NMR spectroscopic investigations showed that 1 and 3-5 are stereochemically non-rigid in solution and reversibly undergo possible dissociation (3) or isomerization (4, 5) processes. All the title complexes exhibit room temperature luminescence in the solid state in the spectral region from 414 to 566 nm, showing a dependence of emission energy on the structure and composition of the metal core. Computational studies with density functional methods were carried out to rationalize the dynamic and photophysical behavior of these compounds.