Synthesis of luminescent coumarin-substituted phosphinoamide-bridged polynuclear gold( i ) metallacycles and reactivity studies

Herein, we present the first report of coumarin-based phosphinoamine ligands [CoumPNH] and their gold(I) complexes. The deprotonation and chloride abstraction from phosphinoamine gold(I) complexes [(CoumPNH)AuICl] led to the unexpected formation of polynuclear gold(I) metallacycles. The size of the cycles depends on the steric bulk of the phosphine groups. The gold(I) metallacycles feature only weak intramolecular aurophilic interactions and do not exhibit intermolecular interactions. Additionally, these metallacycles show significant luminescent properties. Quantum chemical calculations support the photophysical properties of the complexes. Notably, these compounds are the first polynuclear cyclic rings bridged by phosphinoamide ligands. Moreover, the reactivity of the cyclic compounds was explored in this study.