Spontaneous in situ generation of photoemissive aurophilic oligomers in water solution based on the 2-thiocytosine ligand

Complexes [Au(S-2-thiocytosinate)(PMe(3))] (2, 2-thiocytosine = 4-amino-2-mercaptopyrimidine) and [Au(S-2-thiocytosine)(PMe(3))](CF(3)CO(2)) (3) have been prepared by the reaction of [Au(acac)(PMe(3))] (1, acac = acetylacetonate) or [Au(OCOCF(3))(PMe(3))] with 2-thiocytosine, respectively. The equimolecular mixture of complexes 1 and 3 also produces [{Au(PMe(3))}(2)(μ-S,N(1)-2-thiocytosinate)](CF(3)CO(2)) (4), which features two distinct [Au(PMe(3))](+) groups coordinated to the S and N(1) atoms of the heterocycle. Complex 4 experiences a ligand redistribution process in water solution that liberates [Au(PMe(3))(2)](CF(3)CO(2)) and a brightly coloured and luminescent species of [Au(n)(μ-S,N(1)-2-thiocytosinate)(n)] stoichiometry, presumably as a tetraauracycle (n = 4).