Zhang Xiaoyu, Zhang Qingfang, Zhang Yujian, Ren Qiuhe, Yuan Hengyi
School of Mechanical and Vehicular Engineering, Jilin Engineering Normal University, Changchun, China.
Research Center of Advanced Biological Manufacture, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China.
J Mol Model. 2025 Jul 26;31(8):219. doi: 10.1007/s00894-025-06442-4.
In this work, the molecular properties of the novel semi-aliphatic polyimide derivative with incorporating bulky -CF side groups (3H-6F) in gas, chloroform and acetonitrile have been studied by DFT and TDDFT methods. The optimal reaction path could be found to regulate the occurrence of excited-state intramolecular proton transfer (ESIPT) reaction. In S state, the strength of O1-H2···O3 hydrogen bond increases significantly and contributes to the ESIPT reaction providing the driving force. We calculated the infrared (IR) vibrational spectrum to analyze the movement of O1-H2 bond expansion vibration and then studied the variations of hydrogen bonding strength. In addition, from the rearrangement of frontier molecular orbital (MOs), the electron density distribution should be also an extremely important positive factor in ESIPT process. According to potential energy curves (PECs), ESIPT reaction occurs after the molecule absorbs the photon to reach the first excited state, and the hydrogen atom of the O1-H2 bond combines with the adjacent O3 atom to form an isomer. After the completion of the ESIPT reaction process, the S state returns to S state with recovering the original structure. The barrier size and photoexcitation characteristics in different surroundings are also compared, based on which we present that the increase of solvent polarity promotes occurrence of ESIPT reaction process for 3H-6F fluorophore.
All molecular structures have been optimized using DFT and TDDFT method with B3LYP/6-311 + + G(d,p) level by Gaussian 16 software. Vertical excitation simulations were based on TDDFT method with analyzing charge redistributions. Using Multiwfn 3.8 software, the core-valence bifurcation indexes were performed. Further, potential energy surfaces have been constructed, based on which the transition state configurations were found at the same level.
在本研究中，通过密度泛函理论（DFT）和含时密度泛函理论（TDDFT）方法，研究了含有庞大-CF侧基的新型半脂肪族聚酰亚胺衍生物（3H-6F）在气态、氯仿和乙腈中的分子性质。可以找到最佳反应路径来调控激发态分子内质子转移（ESIPT）反应的发生。在S态下，O1-H2···O3氢键强度显著增加，并为ESIPT反应提供驱动力。我们计算了红外（IR）振动光谱以分析O1-H2键伸缩振动的运动，进而研究氢键强度的变化。此外，从前沿分子轨道（MOs）的重排来看，电子密度分布在ESIPT过程中也应是一个极其重要的积极因素。根据势能曲线（PECs），分子吸收光子达到第一激发态后发生ESIPT反应，O1-H2键的氢原子与相邻的O3原子结合形成异构体。ESIPT反应过程完成后，S态恢复到S态并恢复原始结构。还比较了不同环境中的势垒大小和光激发特性，据此我们提出溶剂极性的增加促进了3H-6F荧光团的ESIPT反应过程。
所有分子结构均使用高斯16软件，采用B3LYP/6-311++G(d,p)水平的DFT和TDDFT方法进行了优化。垂直激发模拟基于TDDFT方法并分析电荷重新分布。使用Multiwfn 3.8软件进行了芯价分叉指数计算。此外，构建了势能面，并在同一水平上找到了过渡态构型。
