Tellurophenes with Delocalized π-Systems and Their Extended Valence Adducts

The π-conjugated 2,5-substituted tellurophene compounds 2,5-bis­(2-(9,9-dihexylfluorene))­tellurophene (1) and 2,5-diphenyltellurophene (3) were synthesized through ring closing reactions of 1,4-substituted butadiyne. The oxidative addition of Br₂ to tellurophene compounds 1 and 3 was studied through absorption spectroscopy, NMR, electrochemistry, X-ray crystallography, and density functional theory (DFT) calculations. When Br₂ adds to the tellurium center the absorption spectrum shifts to a lower energy. From electrochemistry and DFT calculations we show that this is caused by lowering the lowest unoccupied orbital. The highest occupied orbital is also lowered, but to a lesser extent. This shift in absorption spectrum and lowering of the oxidation potential can provide a method to modify tellurophene containing materials. The two-electron oxidative addition is promising for catalyzing energy storage reactions.