Versatile coordinative abilities of perhalophenyl-gold(I) fragments to Xantphos: Influence on the emissive properties

Abstract

Reaction of perhalophenylgold(I) complexes [AuR(tht)] (R = C6Cl2F3, C6Cl5; tht = tetrahydrothiophene) with different number of equivalents of Xantphos (4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene) leads to discrete complexes in which the metal atom displays very different coordination environments. Thus, the ionic complex [Au(Xantphos)2][Au(C6Cl2F3)2] (1) or the neutral [Au(C6Cl5)(Xantphos)] (2) one are obtained when a 1:1 (Au:Xantphos) stoichiometry is used. However, similar compounds [Au2R2(μ-Xantphos)] (R = C6Cl2F3 (3); C6Cl5 (4)) are synthesized when the amount of gold is increased to a 2:1 ratio. The use of diphosphine Xantphos, which can act as bridging, chelate or even as mono-dentate ligand, together with the use of different perhalophenyl groups bonded to the gold(I) centres, allows the synthesis of cationic tetracoordinate gold(I) fragments (1), mononuclear (2) or dinuclear (3–4) dicoordinated gold(I) complexes. This structural diversity in the coordination arrangements as well as the different aryl groups present in the molecules directly affect their photophysical properties, giving rise to different luminescent emission energies ranging from 470 to 580 nm, and also to a different origin for the electronic transitions related to them such as 3IL (3) to 3MLCT (4) and also a mixture of them 3MLCT/3IL (1 and 2). The experimental photophysical results obtained for these gold(I) complexes were supported by DFT and TD-DFT calculations. On the other hand, the behaviour of these complexes in solution is different, losing their emissive properties for all complexes or displaying the co-existence of different structural arrangements in the case of complexes 1 and 2, as observed through variable-temperature 31P{1H} NMR experiments.