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.

本研究通过1,4-取代丁二炔的关环反应，合成了两种π共轭2,5位取代碲吩化合物：2,5-双(2-(9,9-二己基芴))碲吩(1)与2,5-二苯基碲吩(3)。针对Br₂与化合物1、3的氧化加成反应，本研究采用吸收光谱、核磁共振（NMR）、电化学测试、X射线晶体学及密度泛函理论（density functional theory, DFT）计算进行了系统研究。当Br₂加成至碲中心后，产物的吸收光谱向低能区域发生偏移。结合电化学测试与DFT计算结果可知，该光谱偏移源于最低未占轨道（lowest unoccupied orbital）能级的降低；尽管最高占据轨道（highest occupied orbital）能级同样出现下降，但其降幅相对更小。吸收光谱的这一偏移以及氧化电位的降低，可为含碲吩功能材料的改性提供可行策略。该双电子氧化加成反应在储能反应催化领域具有良好的应用前景。