Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.
School of Natural Sciences, University of California Merced, 5200 N. Lake Road, Merced, California 95343, USA.
J Chem Phys. 2018 Mar 14;148(10):104108. doi: 10.1063/1.5017285.
An ab initio study of the effects of implicit and explicit hosts on the excited state properties of pentacene and its nitrogen-based derivatives has been performed using ground state density functional theory (DFT), time-dependent DFT, and ΔSCF. We observe a significant solvatochromic redshift in the excitation energy of the lowest singlet state (S) of pentacene from inclusion in a p-terphenyl host compared to vacuum; for an explicit host consisting of six nearest neighbour p-terphenyls, we obtain a redshift of 65 meV while a conductor-like polarisable continuum model (CPCM) yields a 78 meV redshift. Comparison is made between the excitonic properties of pentacene and four of its nitrogen-based analogs, 1,8-, 2,9-, 5,12-, and 6,13-diazapentacene with the latter found to be the most distinct due to local distortions in the ground state electronic structure. We observe that a CPCM is insufficient to fully understand the impact of the host due to the presence of a mild charge-transfer (CT) coupling between the chromophore and neighbouring p-terphenyls, a phenomenon which can only be captured using an explicit model. The strength of this CT interaction increases as the nitrogens are brought closer to the central acene ring of pentacene.
我们使用基态密度泛函理论（DFT）、含时密度泛函理论（TD-DFT）和ΔSCF 对隐式和显式主体对并五苯及其含氮衍生物激发态性质的影响进行了从头计算研究。与真空相比，我们观察到并五苯在包含在三联苯主体中时，最低单线态（S）的激发能量发生了明显的溶剂化红移；对于由六个最近邻三联苯组成的显式主体，我们得到了 65 meV 的红移，而导体相似极化连续体模型（CPCM）得到了 78 meV 的红移。我们比较了并五苯和其四个含氮类似物（1,8-、2,9-、5,12-和 6,13-二氮杂并五苯）的激子性质，后一种化合物由于在基态电子结构中存在局部扭曲，因此表现出最明显的区别。我们观察到，由于发色团和相邻三联苯之间存在轻微的电荷转移（CT）耦合，CPCM 不足以完全理解主体的影响，这种现象只能通过显式模型来捕捉。随着氮原子越来越靠近并五苯的中心芳烃环，这种 CT 相互作用的强度增加。
