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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Exploring Non-Condon Effects in a Covalent Tetracene Dimer: How Important Are Vibrations in Determining the Electronic Coupling for Singlet Fission?
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Exploring Non-Condon Effects in a Covalent Tetracene Dimer: How Important Are Vibrations in Determining the Electronic Coupling for Singlet Fission?

机译：探索共价四烯二聚体中的非密码子效应：振动在确定单线态裂变的电子耦合中有多重要？

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摘要

Singlet fission (SF) offers opportunities for wavelength-selective processing of solar photons with an end goal of achieving higher efficiency inexpensive photovoltaic or solar-fuels-producing devices. In order to evaluate new molecular design strategies and for theoretical exploration of dynamics, it is important to put in place tools for efficient calculation of the electronic coupling between single-exciton reactant and multiexciton product states. For maximum utility, the couplings should be calculated at multiple nuclear geometries (rather than assumed constant everywhere, i.e., the Condon approximation) and we must be able to evaluate couplings for covalently linked multichromophore systems. With these requirements in mind, here we discuss the simplest methodology possible for rapid calculation of diabatic one-electron coupling matrix elementsbased on Boys localization and rediagonalization of molecular orbitals. We focus on a covalent species called BT1 that juxtaposes two tetracene units in a partially cofacial geometry via a norbornyl bridge. In BT1, at the equilibrium C-2v structure, the nonhorizontal couplings between HOMOs and LUMOs (t(HL) and t(LH)) vanish by symmetry. We then explore the impact of molecular vibrations through the calculation of tAB coupling gradients along 183 normal modes of motion. Rules are established for the types of motions (irreducible representations in the C-2v point group) that turn on tHL and tLH values as well as for the patterns that emerge in constructive versus destructive interference of pathways to the SF product. For the best modes, calculated electronic coupling magnitudes for SF (at root-mean-squared deviation in position at 298 K), are within a factor of 2 of that seen for noncovalent tetracene dimers relevant to the molecular crystal. An overall effective electronic coupling is also given, based on the Stuchebrukhov formalism for non-Condon electron transfer rates.
机译：单峰裂变（SF）为太阳能光子的波长选择处理提供了机会，最终目标是实现更高效率的廉价光伏或太阳能燃料生产设备。为了评估新的分子设计策略和动力学的理论探索，重要的是放置工具以有效计算单激子反应物与多激子产物状态之间的电子耦合。为了最大程度地发挥效用，应该在多个核几何形状（而不是假设的各处都假设恒定，即康登近似）下计算耦合，并且我们必须能够评估共价连接的多发色团系统的耦合。考虑到这些要求，在此我们讨论基于Boys定位和分子轨道的对角线化来快速计算非绝热单电子耦合矩阵元素的最简单方法。我们专注于共价物种BT1，该物种通过降冰片基桥在部分界面几何结构中并置两个并四苯单元。在BT1中，在平衡C-2v结构下，HOMO和LUMO之间的非水平耦合（t（HL）和t（LH））通过对称性消失。然后，我们通过计算沿183个正常运动模式的tAB耦合梯度来探索分子振动的影响。为打开tHL和tLH值的运动类型（C-2v点组中的不可简化表示）以及针对SF产品的路径的建设性与破坏性干扰中出现的模式建立了规则。对于最佳模式，SF的计算电子耦合强度（在298 K处的位置的均方根偏差）在与与分子晶体相关的非共价并四苯二聚体所见电子耦合强度的2倍以内。基于Stuchebrukhov形式主义的非孔顿电子传输速率，还给出了一个整体有效的电子耦合。

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