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

Abstract

Tetrahedral AuI complexes [L3 Au(SnCl3 )] (L=PMe3 (1), PMe2 Ph (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 3 MC transition slightly perturbed by the SnCl3 - fragment.