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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical Calculations of Band Gaps in the Aromatic Structures of Polythieno[3,4-b]benzene and Polythieno[3,4-b]pyrazine
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Theoretical Calculations of Band Gaps in the Aromatic Structures of Polythieno[3,4-b]benzene and Polythieno[3,4-b]pyrazine

机译：聚噻吩并[3,4-b]吡嗪和聚噻吩并[3,4-b]吡嗪芳香结构中带隙的理论计算

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摘要

Band gaps in polythiophene (T) and the related polymers with a fused benzene ring (TB, polythieno[3,4-b]-benzene) or a fused pyrazine ring (TN,polythieno[3,4-b]pyrazine)have been computed using a variety of methods. Geometries of oligomers up to octamers 9AM10 and up to tetramers (B3LYP/6-31G~*) have been optimized, while excitation energies have been computed using ZINDO (INDO/S), configuraiton interaction singles (CIS), and time-dependent density functional theory (TDDFT). Band gaps have been extrapolated from excitation energies. T oligomers are found to have nonplanar geometries, though the planar form is only slightly less stable. TB oligomers are found to be nonplanar due to steric repulsion between a hydrogen on the fused benzene ring adn the thiophene sulfur, while TN oligomers are predicted to be planar. As a result, the band gap in the TN polymer is predicted to be smaller than in the TB polymer. The aromatic/quinoid character of the TB oligomer units is discussed. Extrapolation of DFT HOMO-LUMO energies also gives reasonable band gap predictions.
机译：在聚噻吩（T）和具有稠合苯环（TB，聚噻吩并[3,4-b]-苯）或稠合吡嗪环（TN，聚噻吩并[3,4-b]吡嗪）的相关聚合物中已经实现了带隙使用多种方法进行计算。优化了八聚体（9AM10）和四聚体（B3LYP / 6-31G〜*）的低聚物的几何形状，同时使用ZINDO（INDO / S），组态相互作用单（CIS）和随时间变化的密度计算了激发能功能理论（TDDFT）。带隙已从激发能推断出来。发现低聚物具有非平面的几何形状，尽管平面形式仅稍微不稳定。由于稠合苯环上的氢与噻吩硫之间的空间排斥，发现TB低聚物是非平面的，而TN低聚物则被认为是平面的。结果，预计TN聚合物中的带隙小于TB聚合物中的带隙。讨论了TB低聚物单元的芳族/醌型特征。 DFT HOMO-LUMO能量的外推法也给出了合理的带隙预测。

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