Casado Juan, Ruiz Delgado M Carmen, Rey Merchán M Carmen, Hernández Víctor, López Navarrete Juan T, Pappenfus Ted M, Williams Nathaniel, Stegner William J, Johnson Jared C, Edlund Brett A, Janzen Daron E, Mann Kent R, Orduna Jesús, Villacampa Belén
Department of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, Málaga 29071, Spain.
Chemistry. 2006 Jul 17;12(21):5458-70. doi: 10.1002/chem.200501389.
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).
合成了一系列三氰基乙烯基（TCV）取代的低聚噻吩，并采用多种物理方法对其进行了研究，包括紫外/可见光谱、红外光谱和拉曼光谱、非线性光学（NLO）测量、X射线衍射和循环伏安法。通过四氰基乙烯与单锂化或双锂化低聚物的反应制备了单取代或双取代的低聚物。研究了对称和不对称取代对电子和分子性质的比较影响。与未取代的分子相比，这些低聚物的光学和电化学带隙均显著降低。密度泛函理论计算辅助了对分子电子性质的分析，计算结果与实验数据高度吻合。TCV取代影响前沿轨道的能量，特别是对最低未占分子轨道（LUMO）的稳定作用。一种单取代低聚物的X射线结构表征显示出具有良好分子间相互作用的π堆积。NLO结果与不对称样品中分子内电荷转移特征的作用一致。这些结果进一步突出了双取代化合物中构象灵活性的作用，并揭示了对称分子出人意料的非线性光学活性。关于电子结构，振动数据的解释反映了芳香形式和醌式形式之间的平衡相互作用，这种相互作用通过链长和取代模式进行了精细调节。电子和结构性质与这些材料在薄膜晶体管（TFT）中表现出的半导体性质一致。
