Synthesis, structure and photophysics of binuclear gold(I) and mercury(II) complexes derived from 2,5-bis(ethynylphenyl)-1,3,4-oxadiazole

The organometallic chemistry of the dialkyne ligand 2,5-bis(ethynylphenyl)-1,3,4-oxadiazole with gold(I) and mercury(II) salts has been investigated. Four new group 11 gold(I) and group 12 mercury(II) bis(alkynyl) binuclear complexes functionalized with electron-deficient oxadiazole (OXD) spacer [(PR3)AuC  C(p-C6H4)(OXD)(p-C6H4)C  CAu(PR3)] (R = Ph, 1; Me, 2) and [RHgC  C(p-C6H4)(OXD)(p-C6H4)C  CHgR] (R = Ph, 3; Me, 4) were prepared in good yields by the base-catalyzed dehydrohalogenation reaction of the corresponding metal chloride precursors with HC  C(p-C6H4)(OXD)(p-C6H4)C  CH at room temperature. We report the optical absorption and photoluminescence properties of these metallaynes. The structural properties of 1 have been studied by X-ray crystallography, in which no short-contact aurophilic interaction is observed. The influence of the heavy metal atom on the intersystem crossing rate from the S1 singlet excited state to the T1 triplet excited state in these metal alkynyl systems and the spatial extent of the lowest singlet and triplet excitons is systematically characterized. Our investigations indicate that harvesting of the organic triplet emissions by the heavy-atom effect of group 11–12 transition metals generally follows the order Au(I) > Hg(II).