Kara Zaitri Lamia, Mekelleche Sidi Mohamed
Laboratory of Applied Thermodynamics and Molecular Modeling, Department of Chemistry, Faculty of Science, University of Tlemcen, PB 119, 13000, Tlemcen, Algeria.
J Mol Model. 2021 Apr 26;27(5):136. doi: 10.1007/s00894-021-04764-7.
A theoretical analysis of a series of imidazole-based Y-shaped chromophores, D1-D8, is performed in order to investigate their non(linear) optical, fluorescence, and charge-transport properties. The calculations have been carried out employing DFT and TD-DFT methods at CAM-B3LYP and M06-2X levels of theory. FMO analysis reveals that in ground state, the highest occupied molecular orbital is localized on the 4,5-dimethylanilino donor moiety and imidazole core while the lowest unoccupied molecular orbital spreads on π-linker and nitro acceptor moieties. Vertical absorption and fluorescence transitions are characterized as intramolecular charge transfer and maximum absorption and fluorescence wavelengths show that by changing the π-bridge to the imidazole C2, we can tune fluorescence color from cyan to orange. Calculated (hyper)polarizabilities show that elongation of π-linker by polarizable subunits, such as double bonds or heteroaromatic rings, increases significantly the nonlinear response and shifts the charge-transfer band bathochromically. Calculated reorganization energies indicate that the studied compounds are hole-transporting materials rather than electron-transporters. Interestingly, D7 and D8, with higher hyperpolarizabilities, are predicted to be potent candidates for NLO-devices while D5 and D8 molecules are expected to be promising candidates for luminescent materials and good hole-transport materials for organic light-emitting diodes.
为了研究一系列基于咪唑的 Y 形发色团 D1-D8 的非线性光学、荧光和电荷传输特性，进行了理论分析。计算采用了密度泛函理论（DFT）和含时密度泛函理论（TD-DFT）方法，理论水平为 CAM-B3LYP 和 M06-2X。前线分子轨道（FMO）分析表明，在基态下，最高占据分子轨道定域在 4,5-二甲基苯胺供体部分和咪唑核心上，而最低未占据分子轨道分布在 π 连接体和硝基受体部分。垂直吸收和荧光跃迁被表征为分子内电荷转移，最大吸收和荧光波长表明，通过将 π 桥连接到咪唑 C2 上，我们可以将荧光颜色从青色调至橙色。计算得到的（超）极化率表明，通过可极化亚基（如双键或杂芳环）延长 π 连接体，可显著增加非线性响应，并使电荷转移带发生红移。计算得到的重组能表明，所研究的化合物是空穴传输材料而非电子传输体。有趣的是，具有较高超极化率的 D7 和 D8 预计是 NLO 器件的有力候选者，而 D5 和 D8 分子有望成为发光材料的有前途的候选者以及有机发光二极管的良好空穴传输材料。
