Structures and luminescence of mononuclear and dinuclear base-stabilized gold(I) pyrazolate complexes

The mono- and dinuclear base-stabilized gold(I) pyrazolate complexes, (PPh3)Au(μ-3,5-Ph2pz)) (1), (TPA)Au(3,5-Ph2pz), TPA=1,3,5-triaza-7-phophaadamantane (2), [(PPh3)2Au(μ-3,5-Ph2pz)]NO3 (3) and [(dppp)Au(μ-3,5-Ph2pz)]NO3, dppp=bis(diphenylphosphino)propane (4), have been synthesized and structurally characterized. The mononuclear gold(I) complexes 1 and 2 show intermolecular Au⋯Au interactions of 3.1540(6) and 3.092(6) Å, while the dinuclear gold(I) complexes 3 and 4 show an intramolecular Au⋯Au distances of 3.3519(7) and 3.109(2) Å, respectively, typical of an aurophilic attraction. Complexes 1–4 exhibit luminescence at 77 K when excited with ca. 333 nm UV light with an emission maximum at ca. 454 nm. The emission has been assigned to ligand-to-metal charge transfer, LMCT, based upon the vibronic structure that is observed.