Predominance of bridging coordination in luminescent 1,1′-biisoquinoline silver(I) derivatives

A series of di- and polynuclear silver(I) complexes of stoichiometry [Ag(biisoq)2]nXn and [AgX(biisoq)] (biisoq = 1,1′-biisoquinoline, X = CF3SO3, BF4), or [(μ-biisoq)n(AgXL)2] (n = 1, 2; L = PPh3, PMePh2; X = CF3SO3, ClO4) have been prepared. During crystallization experiments to obtain single crystals the compounds can coordinate solvent or water giving the corresponding derivatives. Seven X-ray diffraction structures have been solved. Different roles of the biisoquinoline ligand are found, but all the structures have in common that it always acts as bridging ligand. Compound [(μ-biisoq){Ag(OSO2CF3)(PPh3)}{Ag(OH2)(PPh3)}](CF3SO3) (3a) shows a single biisoquinoline bridge and tricoordinated silver centres, whilst derivatives [(μ-biisoq)2{Ag(acetone)(PPh3)}2](ClO4)2 (8a), [(μ-biisoq)2{Ag(OClO3)(PMePh2)}2] (9), and [(μ-biisoq)2{Ag(OSO2CF3)(PMePh2)}2] (10) display double biisoquinoline bridging ligands and tetracoordinated silver centres, with intramolecular silver–silver distances in the range 3.684–4.434 Å. Compounds [(μ-biisoq)2{Ag(OSO2CF3)(acetone)}2]·2acetone (6a), [(μ-biisoq)2{Ag(OSO2CF3)(acetone)}2] (6b), and [(μ-biisoq)Ag(OH2)2(μ-biisoq)Ag]n(CF3SO3)2n (6c), correspond either to a biisoquinoline-double bridged dimer with short intramolecular argentophilic silver–silver distances of 3.0737(6) Å (6a) or 3.1358(6) Å (6b), or to an infinite biisoquinoline-single bridged 1D polymer (6c). In these complexes, the silver centres are either linear 2-coordinate or distorted tetrahedral 4-coordinate. The silver coordination sphere is completed by the anion and in some cases by solvent (acetone, water). Complexes [Ag(biisoq)2]nXn (X = SO3CF3 (1); BF4 (2)) are oligomeric with bridging biisoquinoline, at least in solution. All the derivatives are luminescent at room temperature in the solid state with emission maxima in the range 397–519 nm; they emit at 77 K from 366 to 523 nm. They also emit in CH2Cl2 at 298 K in the range 376–490 nm, whilst they are luminescent at 77 K in the range 376–402 nm.