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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Predicting the localized/delocalized character of mixed-valence diquinone radical anions. Toward the right answer for the right reason
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Predicting the localized/delocalized character of mixed-valence diquinone radical anions. Toward the right answer for the right reason

机译：预测混合价二醌自由基阴离子的局部/离域特征。寻求正确答案的正确理由

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摘要

The Robin-Day class II/III mixed-valence character is established quantum-chemically for a series of mixed-valence diquinone radical anions. Particular emphasis is placed on the radical anion of tetrathiafulvalenedibenzoquinone, Q-TTF-Q, which has recently been used to evaluate constrained density functional approaches (CDFT) and new range hybrid functionals. Using a computational protocol based on hybrid functionals with 35-42% exact-exchange admixture and inclusion of solvent models during the structure optimization, it is demonstrated that a) Q-TTF-Q ?-, 1, and the related diquinone radical anions 2-4 are all delocalized class III species in the gas phase and in nonpolar solvents, in contrast to previous assumptions; b) 1,4,5,8-anthracenetetraone radical anion, 2, remains class III in polar aprotic solvents, c) systems 1, 3 and 4 become class II, providing excellent agreement between computed and experimental intervalence charge-transfer excitations, thermal electron-transfer (ET) barriers and ESR hyperfine couplings. The direct conductor-like screening model for real solvents (D-COSMO-RS) allows the inclusion of specific hydrogen-bonding effects without the computational effort of molecular dynamics simulations and provides increased ET barriers, as well as a predicted incipient symmetry breaking for 2, due to hydrogen bonding in alcohol solvents. For the first time D-COSMO-RS optimizations in solvent mixtures have been evaluated. As previous computational studies of Q-TTF-Q ?- neglected solvent effects during structure optimizations and obtained charge localization in gas-phase optimizations by CDFT or by exaggerated exact-exchange admixtures, they provided at best the right answer for the wrong reason.
机译：Robin-day II / III类混合价特性是通过量子化学方法建立的，用于一系列混合价二醌自由基阴离子。尤其强调四硫富瓦烯二苯醌的自由基阴离子Q-TTF-Q，该自由基阴离子最近已用于评估约束密度泛函方法（CDFT）和新的混合功能泛函。在结构优化过程中，使用基于具有35-42％精确交换掺和物并包含溶剂模型的混合功能的计算协议，证明了a）Q-TTF-Qα-，1和相关的二醌自由基阴离子2与以前的假设相反，-4在气相和非极性溶剂中均为离域的III类物质; b）1,4,5,8-蒽四酮自由基阴离子2在极性非质子溶剂中仍为III类; c）系统1、3和4变为II类，在计算和实验间隔电荷转移激发，热之间提供了极好的一致性电子传输（ET）势垒和ESR超精细耦合。实际溶剂的直接导体样筛选模型（D-COSMO-RS）允许包含特定的氢键效应，而无需分子动力学模拟的计算工作，并提供增加的ET势垒，以及预测的初始对称性破坏2 ，是由于在醇类溶剂中存在氢键。首次评估了溶剂混合物中的D-COSMO-RS优化。由于先前对Q-TTF-Q-的计算研究忽略了结构优化过程中的溶剂效应，并通过CDFT或夸大的精确交换混合物在气相优化中获得了电荷局部化，因此，由于错误的原因，它们充其量只能提供正确的答案。

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