Ab initio study on luminescence and aurophilicity of a dinuclear [(AuPH3)2(i-nmt)] complex (i-mnt = isomer-malononitriledithiolate)

The luminescence and Au-Au aurophilicity of the model complex, [(AuPH3)(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 Angstrom) and the corresponding Au-Au stretching frequency (83 cm(-1)) indicate intramolecular Au-Au aurophilicity. Using [(AuPH3)2(i-mnt)12 to rationalize the solid-state emission to the [(AuPPh3)(2)(i-mnt)] complex at 20 K we assigned the experimental emission (462 nm) to an Au-Au-->imnt charge-transfer ((MMLCT)-M-3) transition from the triplet excited state to the ground state. In the (MMLCT)-M-3 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 PH3AuSH. 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-1 complexes. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).