Synthesis, Properties, and Complex Formation of Antimony- and Bismuth-Bridged Bipyridyls

Antimony- and bismuth-bridged bipyridyls (dipyridinostibole and dipyridinobismole; DPySb and DPyBi) were prepared by the reactions of dilithiobipyridyl with dibromophenylstibine and diiodophenylbismuthine. X-ray diffraction studies of the crystal structures revealed a high planarity of the heterole ring. Cyclic voltammograms obtained in acetonitrile indicated enhanced electron affinity in comparison to a bridge-free bipyridyl. These compounds showed weak fluorescence at room temperature and visible phosphorescence at 77 K with emission maxima and lifetimes of λmax = 453 nm and τ = 1.03 ms for DPySb and λmax = 454 nm and τ = 0.26 ms for DPyBi, respectively. Solid-state phosphorescence was also observed from these dipyridinoheteroles at 77 K. Their copper complexes were prepared by interaction with Cu2I2(PPh3)3, which produced red phosphorescence in the solid state at room temperature.