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).