Double Jahn–Teller Distortion in AuGe Complexes Leading to a Dual Blue–Orange Emission

The tetrahedral Au I complexes [Au(GeCl 3 )L 3 ] (L=PMe 3  ( 1 ), PMe 2 Ph ( 2 ), PMePh 2  ( 3 ), PPh 3  ( 4 )) were synthesized by in situ treatment of the [Au(GeCl 3 )(tht)] complex with three equivalents of the corresponding tertiary phosphine. The crystal structures of complexes  1 and 3 have been determined through X‐ray diffraction studies and show [GeCl 3 ] − fragments bonded to the corresponding [Au(PR 3 ) 3 ] + units through covalent bonds, leading to a tetrahedral coordination environment for gold. Complexes  3 and 4 show dual phosphorescence in the solid state at 77 K and, in the case of complex  4 , an interesting room‐temperature mechanochromism effect is observed. Correlated MP2, SCS‐MP2, SCS‐CC2, and ONIOM MP2/UFF calculations suggest the existence of two largely distorted and thermally connected triplet excited states (T 1 and T 2 ) for a model system of complex  4 . The AuP 3 + moiety can be distorted in two different planes leading to the two triplet excited states T 1 and T 2 , leaving the GeCl 3 − unit almost unaltered. The emissions of these phosphorescent Au I Ge II complexes is mainly ascribed to a metal (gold)‐centered ( 3 MC) transition with some contribution from the [GeCl 3 ] − fragments.