Cation and hydrogen bonding effects on the self-association and luminescence of the dicyanoaurate ion, [Au(CN)2]-

The colorless salts [C5H10NH2][AuI(CN)2], [C4H8NH2][AuI(CN)2], [Ph2NNH3][AuI(CN)2]·H2O and [(n-C3H7)4N][AuI(CN)2]·H2O have been prepared by evaporation of aqueous solutions of potassium dicyanoaurate and the chloride salt of the appropriate cation. Hydrogen bonding between the cations and the cyano groups of the anions facilitates the formation of structures with strong aurophilic interactions between the anions. Thus, the [Au(CN)2]- ions self-associate in the three salts [C5H10NH2][AuI(CN)2](Au...Au 3.0969(3) (angstrom)), [C4H8NH2][AuI(CN)2](Au1(angstrom)Au2 3.0795(4) (angstrom)), [Ph2NNH3][AuI(CN)2]·H2O (Au...Au 3.0866(4) (angstrom)), while in [(n-C3H7)4N][AuI(CN)2]·H2O, which lacks N-H units, the gold ions are widely dispersed. The crystals of [C5H10NH2][AuI(CN) 2], [C4H8NH2][AuI(CN)2] and [Ph2NNH3][AuI(CN)2]·H2O each show strong blue luminescence at room temperature, while [(n-C3H7) 4N][AuI(CN)2]·H2O is non-luminescent.