Structural characterization of dinuclear gold(I) diphosphine complexes with anion-triggered luminescence

Abstract

Dinuclear and mononuclear gold(I) complexes containing the xantphos ligand (xantphos = 9,9′-dimethyl-4,5-bis(diphenylphosphino)-xanthene), [Au2(xantphos)2](X)2 with X = BF4 (1), PF6 (2) and SbF6 (3 and 4) and Au(xantphos)(SCN) (5), were characterized by X-ray structural analysis. Two type of colourless crystals (3 and 4) crystallized together from the same solution of [Au2(xantphos)2](SbF6)2. The [Au2(xantphos)2]2+ cations have almost the same molecular structure with two xantphos ligands coordinated to two gold(I) centres with short aurophilic interaction of 2.803 (1), 2.825 (2), 2.817 (3) and 2.837 A (4), respectively. The [Au2(xantphos)2]2+ cation is in a somewhat distorted figure-eight conformation in 1–3, whereas in 4, it has and ideal figure-eight conformation with a twofold axis passing through the Au···Au bond. The molecular packing is primarily governed by C–H···F hydrogen bonding interactions between the [Au2(xantphos)2]2+ cations and fluorinated BF4 −, PF6 − and SbF6 − anions. In 5, the gold(I) centre is in a trigonal-planar geometry, and it is coordinated to two phosphorous atom of the xantphos ligand and one sulphur atom of the SCN− anion. Different anions cause some conformational changes and alter the molecular packing of these crystalline structures. These variations in the solid-state structures alter the luminescent properties of the dinuclear and mononuclear gold(I) xantphos complexes. Dinuclear complexes 1, 2 and 4 exhibit intense yellow luminescence, while compound 3 and mononuclear 5 produces green emission when irradiated with a 365-nm UV lamp at room temperature.