Wei Wei, Ren Wenhui, Jian Wei, Xia Baohui, Zhang Hongxing, Bai Fu-Quan, Li Wei
Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun, China.
School of Chemistry and Materials Science, Hunan Agricultural University, Changsha, China.
Front Chem. 2020 Sep 4;8:776. doi: 10.3389/fchem.2020.00776. eCollection 2020.
The macrocyclic molecules with terthiophene (TTH) isomers unit exhibit intriguing properties in terms of aromaticity, stability, and absorption. In this work, we theoretically designed a series of macrocyclic molecules featured with TTH and dithienothiophene (DTT) π-conjugated building units, which are used to permute pyrrole unit in porphyrin skeleton. Density functional theory and time-dependent DFT methods are used to evaluate the performance of the designed molecules. Our simulations show that molecules - exhibit excellent optoelectronic performance. Specifically, the molecule with the DTT unit is more stable than the one with TTH unit in terms of aromaticity and aromatic stabilization energy. This is because DTT unit enhances the coplanarity of the molecular material, facilitating electronic communication. Calculation of vertical electronic excitations suggests the absorption feature of these molecules is mainly contributed by the electronic excitations of higher occupied molecular orbital (HOMO) → lowest unoccupied molecular orbital (LUMO)+1 and HOMO-1 → LUMO. Judging from the key parameters determining the overall performance, stands out because of its good planarity, large HOMO-LUMO gap, and strong aromaticity among all molecules. Interestingly, molecule has the current density flow distributes around the outer section of TTH unit; in contrast, molecule with DTT unit has the current density flow located at the inner section of DTT, which is beneficial for stability and aromaticity. Second-order perturbation energies are calculated to rationalize this observation. We expect that these research results can provide valuable insights into the rational design of novel molecular materials for a variety of applications.
含有噻吩并噻吩（TTH）异构体单元的大环分子在芳香性、稳定性和吸收方面展现出有趣的性质。在本工作中，我们从理论上设计了一系列以TTH和二噻吩并噻吩（DTT）π共轭结构单元为特征的大环分子，这些结构单元用于置换卟啉骨架中的吡咯单元。采用密度泛函理论和含时密度泛函理论方法来评估所设计分子的性能。我们的模拟表明这些分子展现出优异的光电性能。具体而言，就芳香性和芳香稳定能而言，含有DTT单元的分子比含有TTH单元的分子更稳定。这是因为DTT单元增强了分子材料的共面性，有利于电子通讯。垂直电子激发的计算表明这些分子的吸收特征主要由较高占据分子轨道（HOMO）→最低未占据分子轨道（LUMO）+1和HOMO-1→LUMO的电子激发所贡献。从决定整体性能的关键参数来看， 在所有分子中因其良好的平面性、较大的HOMO-LUMO能隙和较强的芳香性而脱颖而出。有趣的是， 分子的电流密度流分布在TTH单元的外部区域；相反，含有DTT单元的 分子的电流密度流位于DTT的内部区域。这有利于稳定性和芳香性。计算二阶微扰能以合理解释这一观察结果。我们期望这些研究结果能为合理设计用于各种应用的新型分子材料提供有价值的见解。
