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

Complexes [Au(S-2-thiocytosinate)(PMe3)] (2, 2-thiocytosine = 4-amino-2-mercaptopyrimidine) and [Au(S-2-thiocytosine)(PMe3)](CF3CO2) (3) have been prepared by the reaction of [Au(acac)(PMe3)] (1, acac = acetylacetonate) or [Au(OCOCF3)(PMe3)] with 2-thiocytosine, respectively. The equimolecular mixture of complexes 1 and 3 also produces RAu(PMe3)}(2)(mu-S,N-1-2-thiocytosinate)](CF3CO2) (4), which features two distinct [Au(PMe3)](+) 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(PMe3)(2)](CF3CO2) and a brightly coloured and luminescent species of [Au-n(mu-S,N-1-2-thiocytosinate)(n)] stoichiometry, presumably as a tetraauracycle (n = 4).