Time-dependent density functional study of excimers and exciplexes of organic molecules
Time-dependent density functional study of excimers and exciplexes of organic molecules
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DOI：
10.1016/j.chemphys.2007.08.005
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发表时间：
2008-01-29
期刊：
影响因子：
2.3
通讯作者：
Grimme, Stefan
中科院分区：
文献类型：
--
作者：
Huenerbein, Robert;Grimme, Stefan
采用含时密度泛函理论（TD-DFT）研究了芘和苯的有机激基聚合物以及苯乙烯与三甲基胺的激基复合物。该方法的性能首先以惰性气体准分子为基准。采用混合泛函BH-LYP和半局域B-LYP GGA方法计算了Ne-2和Kr-2低激发态的势能曲线。为了包括色散（货车德瓦耳斯）效应，应用先前开发的R-6型校正（DFT-D）。TD-DFT/BH-LYP结果与CC 2或更早的MRD-CI处理的结果非常一致，而纯GGA则失败得很惨。然后，该方法用于充分优化有机络合物在其基态和激发态。苯和芘准分子以及苯乙烯和三甲胺的有机激基复合物的激发态离解能（D-0）分别为0.6，1.2和0.8 eV。对于后者，理论值和实验值在20%以内吻合。对于芘和苯的准分子，已在溶液中测量，偏差较大，但在预期的溶剂效应的范围内。在芘激基缔合物的情况下，TD-DFT/BH-LYP计算的低位激基缔合物态的阶数与简单激子耦合模型预测的结果一致。与基态相比，所有激发复合物的分子间距离显着减小（0.07-0.4埃）以及发生重排的原因（有利的轨道相互作用和电荷转移）进行了讨论。(C)2007 Elsevier B. V.保留所有权利。
Organic excimers of pyrene and benzene and an exciplex of styrene with trimethylamine are studied by time-dependent density functional theory (TD-DFT). The performance of the method was first benchmarked on noble gas excimers. Potential curves for low-lying excited states of Ne-2 and Kr-2 are computed using the hybrid functional BH-LYP and the semi-local B-LYP GGA functional. In order to include dispersion (van der Waals) effects, a previously developed R-6 type correction (DFT-D) was applied. The TD-DFT/BH-LYP results are in good agreement with those from CC2 or older MRD-CI treatments while pure GGAs fail miserably. The approach is then used to fully optimise the organic complexes in their ground and excited states. Excited state dissociation energies (D-0) of 0.6, 1.2 and 0.8 eV are obtained for benzene and pyrene excimers and the organic exciplex of styrene and trimethylamine, respectively. For the latter system, the theoretical and experimental values agree to each other within 20%. For the excimers of pyrene and benzene, which have been measured in solution, the deviations are larger but within the range of expected solvent effects. In the case of the pyrene excimer, the TD-DFT/BH-LYP computed order of the low-lying excimer states is in agreement with that predicted by the simple exciton coupling model. The significant decrease of inter-molecular distances for all excited complexes compared to the ground state (0.07-0.4 angstrom) and the reasons for occurring rearrangements (favourable orbital interactions and charge transfer) are discussed. (C) 2007 Elsevier B.V. All rights reserved.