Tuning supramolecular aurophilic structures: the effect of counterion, positive charge and solvent

The synthesis of the cationic gold(I) complexes [Au(C≡CC5H4N)(CH3-PTA)]X (X = I, 1; X = OTf, 4), [Au(C≡CC5H4N-CH3)(PTA)]X (X = I, 2; X = OTf = 5; PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane) and [Au(C≡CC5H4N-CH3)(DAPTA)]X (X = I, 3; X = OTf = 6, DAPTA = 3,7-diacetyl-1,3,7-triaza-5- phosphabicyclo[3.3.1]nonane) gives cationic complexes showing unexpected supramolecular assemblies in water going from rod-like structures (1) to vesicles (2 and 3) and square-like structures (5 and 6). These morphologies are completely different from the fibers previously obtained with their parent neutral complexes [Au(C≡C5H4N)(PTA)] and [Au(C≡C5H4N)(DAPTA)]. Nevertheless, the introduction of triflate as counterion in 1 (complex 4) gives rise to the formation of highly soluble complex in water which does not display any significant aggregation in solution. These results reveal the importance of the introduction of a positive charge on the global supramolecular assemblies and how the counterion can modify also the resulting package. Interestingly, we have also proved that the aggregation of complexes 2, 3, 5 and 6 is also affected by the solvent with direct influence on their absorption and emission properties and the global morphology of the aggregates