Faculty of Electrical Engineering, Czestochowa University of Technology, Al. Armii Krajowej 17, 42-200 Czestochowa, Poland.
J Phys Chem A. 2012 Mar 22;116(11):3048-55. doi: 10.1021/jp300305j. Epub 2012 Mar 14.
Long-range-corrected (LC) DFT/TDDFT methods may provide adequate description of ground and excited state properties; however, accuracy of such an approach depends much on a range separation (exchange screening) representing adjustable model parameter. Its relation to a size or specific of molecular systems has been explored in numerous studies, whereas the effect of solvent environment is usually ignored during the evaluation of state properties. To benchmark and assess the quality of the LC-DFT/TDDFT formalism, we report the optical absorption and fluorescence emission energies of organic heterocyclic isomers, DPIPQ and PTNA, calculated by LC-BLYP DFT/TDDFT method in the polarizable continuum (PCM) approach. The calculations are compared with the optical absorption and fluorescence spectra measured in organic solvents of different polarity. Despite a considerable structural difference, both dyes exhibit quite similar range separations being somewhat different for the optical absorption and fluorescence emission processes. Properly parametrized LC-BLYP xc-potential well reproduces basic features of the optical absorption spectra including the electronic transitions to higher excited states. The DFT/TDDFT/PCM analysis correctly predicts the solvation trends although solvatochromic shifts of the electronic transition energies appear to be evidently underestimated in most cases, especially for the fluorescence emission. Considering the discrepancy between the experiment and theory, evaluated state dipole moments and solvation corrections to the exchange screening are analyzed. The results of the present study emphasize the importance of a solvent-dependent range separation in DFT/TDDFT/PCM calculations for investigating excited state properties.
长程校正（LC）DFT/TDDFT 方法可能提供对基态和激发态性质的充分描述；然而，这种方法的准确性在很大程度上取决于代表可调模型参数的范围分离（交换筛选）。已经有许多研究探讨了它与分子系统的大小或特定性质的关系，而在评估状态性质时，通常忽略溶剂环境的影响。为了基准测试和评估 LC-DFT/TDDFT 形式的质量，我们报告了通过 LC-BLYP DFT/TDDFT 方法在极化连续体（PCM）方法中计算的有机杂环异构体 DPIPQ 和 PTNA 的光吸收和荧光发射能。将计算结果与在不同极性有机溶剂中测量的光吸收和荧光光谱进行比较。尽管结构差异相当大，但两种染料都表现出相当相似的范围分离，对于光吸收和荧光发射过程略有不同。适当参数化的 LC-BLYP xc 势阱再现了光吸收光谱的基本特征，包括向更高激发态的电子跃迁。DFT/TDDFT/PCM 分析正确预测了溶剂化趋势，尽管在大多数情况下，电子跃迁能量的溶剂化位移似乎明显低估，特别是对于荧光发射。考虑到实验与理论之间的差异，评估了状态偶极矩和对交换筛选的溶剂化修正。本研究的结果强调了在研究激发态性质时，DFT/TDDFT/PCM 计算中溶剂依赖性范围分离的重要性。
