Double Photoinduced Jahn-Teller Distortion of Tetrahedral AuISnII Complexes

Tetrahedral AuI complexes [L3Au(SnCl3)] (L=PMe3 (1), PMe2Ph (2), PMePh2 (3), and PPh3 (4)) were prepared by treatment of the [(tht)Au(SnCl3)] (tht=tetrahydrothiophene) complex with three equivalents of the corresponding tertiary phosphine. The crystal structures of complexes 1–4 have been determined through X‐ray diffraction studies showing, in all cases, [SnCl3]− fragments covalently bonded to the corresponding [Au(PR3)3]+ units, which leads to a tetrahedral coordination environment for gold. Complexes 3 and 4 show phosphorescence in the solid state at room temperature and 77 K that is largely redshifted relative to the free [Au(PR3)3]+ and [SnCl3]− counterparts. Correlated MP2, SCS‐MP2, and ONIOM MP2/UFF calculations suggest a largely distorted lower triplet excited state (T1) for each model system. The AuP3+ moiety is distorted leading to a T‐shape, whereas the SnCl3− unit is left almost unaltered. Molecular orbital and population analysis suggest that the emission of these tetrahedral AuI complexes arises from a 3MC transition slightly perturbed by the SnCl3− fragment. Golden rules: Complexes [L3Au(SnCl3)] (L=PMe3 (1), PMe2Ph (2), PMePh2 (3), and PPh3 (4)) display tetrahedral environments for gold. Compounds 3 and 4 display low‐energy phosphorescence in the solid state. The structural distortion of the lowest triplet excited state T1 for models of these compounds was analyzed. The large structural distortion of the T1 state arises from a first‐order Jahn–Teller effect at the gold center and a second‐order Jahn–Teller effect at the tin center (see figure).