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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Models for Quantum Effects in Electron Transfer: Co(Cp)_2~+|V(CO)_6~-
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Models for Quantum Effects in Electron Transfer: Co(Cp)_2~+|V(CO)_6~-

机译：电子转移的量子效应模型：Co（Cp）_2〜+ | V（CO）_6〜-

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We model the absolute electron transfer (ET) rate and the vibrational quantum effects on ET rate previously observed experimentally for the ion pair complex Co(Cp)_2~+|V(CO)_6~-. We find that the absolute rate and vibrational rate effects cannot be predicted by the standard ET methods. In this work we analyze new resonance Raman, absorption, and infrared spectra and combine these results with density functional (DFT) quantum calculations of structure, vibrational modes, and solvent effects to predict absolute electron-transfer rates and vibrational quantum effects for ET. Related DFT calculations on Na~+|V(CO_6~- are used to support a spectroscopic identification of the ion pair geometry. The ET is from the radical pair state reached by charge-transfer absorption of the ion pair Co(Cp)_2~+|V(CO)_6~-. The weak coupling rate model based on the golden rule model of ET predicts absolute ET rates that are 135 times too large. From our DFT calculations on Co(Cp)_2|V(CO)_6 we conclude that a small Jahn-Teller geometry change in both radicals can reduce the orbital overlap and electronic coupling in the radical pair state so that the effective coupling matrix element in much smaller than the 417 cm~(-1) inferred from the absorption spectrum. A new study of the electronic coupling versus geometry is required to test this suggestion versus the possibility that the weak coupling model is inappropriate for our molecule. The standard model, which emphasizes totally symmetric vibrations, also cannot explain prior experimental ET rates for quantum populations (v = 0, 1, 2) in the nontotally symmetric CO stretching mode. These rate effects likely involve a fast IVR conversion from totally symmetric vibrations to IR active CO stretching motions followed by ET. The vibrational quantum effect on ET probably is caused by a breakdown in the Condon approximation, where an increase in the quantum number of vibration increases the electronic coupling matrix element. The models suggest a number of new experiments to probe the mechanism of ET in weak coupled molecules.
机译：我们对离子对配合物Co（Cp）_2〜+ | V（CO）_6〜-进行了实验观察，建立了绝对电子传递（ET）速率和振动量子效应对ET速率的影响。我们发现，标准ET方法无法预测绝对速率和振动速率的影响。在这项工作中，我们分析了新的共振拉曼光谱，吸收光谱和红外光谱，并将这些结果与结构，振动模式和溶剂效应的密度泛函（DFT）量子计算相结合，以预测ET的绝对电子传输速率和振动量子效应。 Na〜+ | V（CO_6〜-）的相关DFT计算用于支持离子对几何结构的光谱识别，ET来自离子对Co（Cp）_2〜的电荷转移吸收所达到的自由基对状态。 + | V（CO）_6〜-。基于ET黄金法则模型的弱耦合率模型预测的绝对ET率太大135倍。根据我们对Co（Cp）_2 | V（CO）_6的DFT计算我们得出的结论是，两个自由基的微小Jahn-Teller几何变化都可以减少自由基对状态下的轨道重叠和电子耦合，因此有效吸收矩阵元素要比吸收光谱推断的417 cm〜（-1）小得多为了验证这一建议与弱耦合模型不适用于我们的分子的可能性之间的关系，需要对电子耦合与几何进行新的研究，标准模型强调完全对称的振动，也无法解释先前的量子种群实验ET速率（v = 0， 1、2）在非完全对称的CO拉伸模式下。这些速率效应可能涉及从完全对称振动到IR主动CO拉伸运动以及ET的快速IVR转换。对ET的振动量子效应可能是由于Condon近似值的击穿而引起的，其中，振动量子数的增加增加了电子耦合矩阵元素。该模型提出了许多新的实验来探索弱耦合分子中ET的机制。

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