Ab initio Study on Luminescence and Aurophilicity of a Dinuclear [(AuPH 3 ) 2 (i‐mnt)] Complex (i‐mnt = isomer‐Malononitriledithiolate)

The luminescence and Au−Au aurophilicity of the model complex, [(AuPH 3 ) 2 (i‐mnt)] (i‐mnt = isomer‐malononitriledithiolate in both solid state and solution have been studied by ab initio methods. The structures of the Au I complex were fully optimized by the MP2 method for the ground state and the CIS method for the excited state. The b 3 A′ excited‐state Au−Au (2.946 Å) and the corresponding Au−Au stretching frequency (83 cm −1 ) indicate intramolecular Au−Au aurophilicity. Using [(AuPH 3 ) 2 (i‐mnt)] 2 to rationalize the solid‐state emission to the [(AuPPh 3 ) 2 (i‐mnt)] complex at 20 K we assigned the experimental emission (462 nm) to an Au−Au⇄i‐mnt charge‐transfer ( 3 MMLCT) transition from the triplet excited state to the ground state. In the 3 MMLCT emissive excited state, the Au−Au aurophilicity, including intra‐ and intermolecular Au−Au interactions, results in a ca. 120 nm red shift in emission relative to that of mononuclear PH 3 AuSH. The calculated absorption and emission in dichloromethane solution agree with the experimental results. These results, combined with our previous studies on both [Au 2 (dpm) 2 ] 2+ [dpm = bis(diphosphanyl)methane] and [Au 2 (dpm)(i‐mnt)], indicate a clear correlation between Au−Au aurophilicity and the excited‐state properties of the dinuclear Au I complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)