Fan Jianzhong, Liu Huanling, Wang Yan, Xie Zhen, Lin Zongwei, Pang Kunwei
Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, Jinan 250014, China.
Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, Jinan 250014, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2024 Nov 5;320:124626. doi: 10.1016/j.saa.2024.124626. Epub 2024 Jun 8.
Stimulus-responsive organic room temperature phosphorescence (RTP) materials exhibit variations in their luminescent characteristics (lifetime and efficiency) upon exposure to external stimuli, including force, heat, light and acid-base conditions, the development of stimulus-responsive RTP molecules becomes imperative. However, the inner responsive mechanism is unclear, theoretical investigations to reveal the relationship among hydrostatic pressures, molecular structures and photophysical properties are highly desired. Herein, taking the Se-containing RTP molecule (SeAN) as a model, based on the dispersion corrected density functional theory (DFT-D), the combined quantum mechanics and molecular dynamics (QM/MM) method and thermal vibration correlation function (TVCF) theory, the influences of hydrostatic pressure on molecular structures, transition properties as well as lifetimes and efficiencies of RTP molecule are theoretically studied. Results show that extended lifetime and enhanced efficiency are observed at 2 Gpa compared with molecule at normal pressure, and this is related with the small reorganization energy and large oscillator strength. Moreover, due to the small energy gap (0.34 eV) and remarkable spin-orbit coupling (SOC) constant (8.56 cm) between first singlet excited state and triplet state, fast intersystem crossing (ISC) process is determined for molecule at 6 Gpa. Furthermore, the intermolecular interactions are visualized using independent gradient model based on Hirshfeld partition (IGMH) and the changes of molecular packing modes, SOC values, lifetimes and efficiencies with pressures are detected. These results reveal the relationship between molecular structures and RTP properties. Our work provides theoretical insights into the hydrostatic pressure response mechanism and could promote the development new efficient stimulus-responsive molecules.
刺激响应型有机室温磷光（RTP）材料在受到包括力、热、光和酸碱条件在内的外部刺激时，其发光特性（寿命和效率）会发生变化，因此开发刺激响应型RTP分子变得势在必行。然而，其内部响应机制尚不清楚，非常需要进行理论研究以揭示静水压力、分子结构和光物理性质之间的关系。在此，以含硒RTP分子（SeAN）为模型，基于色散校正密度泛函理论（DFT-D）、量子力学与分子动力学相结合的方法（QM/MM）以及热振动相关函数（TVCF）理论，从理论上研究了静水压力对RTP分子的分子结构、跃迁性质以及寿命和效率的影响。结果表明，与常压下的分子相比，在2 GPa时观察到寿命延长和效率提高，这与较小的重组能和较大的振子强度有关。此外，由于第一单重激发态和三重态之间的能隙较小（0.34 eV）以及显著的自旋轨道耦合（SOC）常数（8.56 cm），确定了6 GPa时分子的快速系间窜越（ISC）过程。此外，使用基于 Hirshfeld 划分的独立梯度模型（IGMH）可视化分子间相互作用，并检测分子堆积模式、SOC值、寿命和效率随压力的变化。这些结果揭示了分子结构与RTP性质之间的关系。我们的工作为静水压力响应机制提供了理论见解，并可能促进新型高效刺激响应分子的开发。
