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首页> 外文期刊>Chemistry: A European journal >Optical, redox, and NLO properties of tricyanovinyl oligothiophenes: Comparisons between symmetric and asymmetric substitution patterns
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Optical, redox, and NLO properties of tricyanovinyl oligothiophenes: Comparisons between symmetric and asymmetric substitution patterns

机译：三氰基乙烯基寡噻吩的光学，氧化还原和NLO性质：对称和不对称取代模式之间的比较

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摘要

A series of tricyanovinyl (TCV)-substituted oligothiophenes was synthesized and investigated with a number of physical methods including UV/Vis, IR, and Raman spectroscopy, nonlinear optical (NLO) measurements, X-ray diffraction, and cyclic voltammetry. Mono- or disubstituted oligomers were prepared by the reaction of tetracyanoethylene with mono- or dilithiated oligomers. The comparative effects of the symmetric and asymmetric substitutions in the electronic and molecular properties have been addressed. These oligomers display dramatic reductions in both their optical and electrochemical band gaps in comparison with unsubstituted molecules. The analysis of the electronic properties of the molecules was assisted by density functional theory calculations, which are in excellent agreement with the experimental data. TCV substitution influences the energies of the frontier orbitals, especially with respect to the stabilization of LUMO orbitals. X-ray structural characterization of a monosubstituted oligomer exhibits pi-stacking with favorable intermolecular interactions. NLO results agree with the role of the intramolecular charge-transfer feature in the asymmetric samples. These results furthermore exalt the role of conformational flexibility in the disubstituted compounds and reveal an unexpected nonlinear optical activity for symmetric molecules. Regarding the electronic structure, the interpretation of the vibrational data reflects the balanced interplay between aromatic and quinoid forms, finely tuned by the chain length and substitution pattern. The electronic and structural properties are consistent with the semiconducting properties exhibited by these materials in thin film transistors (TFTs).
机译：合成了一系列三氰基乙烯基（TCV）取代的寡噻吩，并通过许多物理方法进行了研究，包括UV / Vis，IR和拉曼光谱，非线性光学（NLO）测量，X射线衍射和循环伏安法。通过使四氰基乙烯与单或二锂化的低聚物反应来制备单或二取代的低聚物。已经解决了对称和不对称取代在电子和分子性质方面的比较作用。与未取代的分子相比，这些低聚物的光学带隙和电化学带隙均显着降低。分子的电子特性分析由密度泛函理论计算辅助，与实验数据非常吻合。 TCV替代会影响边界轨道的能量，特别是在LUMO轨道的稳定方面。单取代低聚物的X射线结构表征显示pi堆积，且分子间相互作用良好。 NLO结果与不对称样品中分子内电荷转移特征的作用一致。这些结果进一步提高了构象柔韧性在双取代化合物中的作用，并揭示了对称分子意外的非线性光学活性。关于电子结构，振动数据的解释反映了芳香族和醌型之间的平衡相互作用，并通过链长和取代模式对其进行了微调。电子和结构特性与这些材料在薄膜晶体管（TFT）中表现出的半导体特性一致。

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