Evolution of lowest singlet and triplet excited states with transition metals in group 10–12 metallaynes containing biphenyl spacer

A new series of thermally stable group 10 platinum(II) and group 12 mercury(II) poly-yne polymers containing biphenyl spacer trans-[–Pt(PBu3)2Ctriple bond; length of mdashC(p-C6H4)2Ctriple bond; length of mdashC–]n and [single bondHgCtriple bond; length of mdashC(p-C6H4)2Ctriple bond; length of mdashC–]n were prepared in good yields by Hagihara’s dehydrohalogenation reaction of the corresponding metal chloride precursors with 4,4′-diethynylbiphenyl HCtriple bond; length of mdashC(p-C6H4)2Ctriple bond; length of mdashCH at room temperature. We report the optical spectroscopy of these polymetallaynes and compare the results with their bimetallic model complexes trans-[Pt(Ph)(PEt3)2Ctriple bond; length of mdashC(p-C6H4)2Ctriple bond; length of mdashCPt(Ph)(PEt3)2] and [MeHgCtriple bond; length of mdashC(p-C6H4)2Ctriple bond; length of mdashCHgMe] as well as the group 11 gold(I) counterpart [(PPh3)AuCtriple bond; length of mdashC(p-C6H4)2Ctriple bond; length of mdashCAu(PPh3)]. The structural properties of all model complexes have been studied by X-ray crystallography. The influence of the heavy metal atom in these metal alkynyl systems on the intersystem crossing rate and the spatial extent of lowest singlet and triplet excitons is systematically characterized. Our investigations indicate that the organic triplet emissions can be harvested by the heavy-atom effect of group 10–12 transition metals (viz., Pt, Au, and Hg) which enables efficient intersystem crossing from the S1 singlet excited state to the T1 triplet excited state.