Trigonal to T-Shape Jahn-Teller distortion upon photoexcitation of luminescent 3-coordinate Au(I) complexes
The remarkably rich photophysical properties are among the most intriguing attributes of monovalent gold compounds. Three-coordinate gold(I) complexes are generally the only species that luminesce as monomers without the presence of Au…Au interactions. The luminescence of [Au(PR3)3]+ complexes was reported to be phosphorescence from a triplet excited state that is observed in the visible region and exhibits a large Stokes’ shift (typically 10,000 cm-1). My work employs a multitude of theoretical methodologies, varying from DFT to QM/MM with progressively larger basis sets, to study the nature of the optimized ground and excited states of [Au(PR3)3]+ models with different R groups. The results illustrate that the independently optimized triplet excited state exhibits a Jahn-Teller distortion from trigonal planar towards T-shaped, suggesting a different excited state geometry distinct from the ground state structure and providing a reasonable explanation for the experimentally-determined large Stokes’ shifts. The calculations also suggest that a ground-state d9 [Au(PR3)3]2+ species should also exhibit the same Jahn-Teller distorted T-shaped geometry.