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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Solvation Dynamics in Dipolar-Quadrupolar Mixtures: A Computer Simulation Study of Dipole Creation in Mixtures of Acetonitrile and Benzene
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Solvation Dynamics in Dipolar-Quadrupolar Mixtures: A Computer Simulation Study of Dipole Creation in Mixtures of Acetonitrile and Benzene

机译：偶极-四极混合物中的溶剂化动力学：乙腈和苯混合物中偶极产生的计算机模拟研究

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摘要

We present here the results of molecular dynamics simulation of solvation dynamics (SD) in benzene, acetonitrile, and their mixtures corresponding to three sets of acetonitrile mole fractions, x_(ac) = 0.20, 0.50, and 0.75, at temperature and densities appropriate for ambient conditions. The change in solute-solvent interactions triggered by solute electronic S_0 → S_1 excitation is represented as dipole creation in a benzene-like solute. We find that both solvent components are active participants in the SD event, with electrostatic interactions of the dipolar solute with quadrupolar benzene molecules making an important contribution to the solvation mechanism and the steady-state Stokes shift in the fluorescence spectrum. Our model solute is preferentially solvated by acetonitrile in its S_1 state and the enhancement in the local acetonitrile concentration contributes significantly to the solvation time scale, especially in the benzene-rich mixture, where this process becomes considerably slower than the solvation coordinate relaxation in either solvent, in agreement with experimental findings. We investigate the contributions to SD from concentration fluctuations by monitoring the time evolution in the solvation structure. We find that in many respects the way that these fluctuations contribute to SD in benzene-acetonitrile mixtures resembles their contributions to the SD mechanism in mixtures of dipolar molecules.
机译：我们在此介绍在适当温度和密度下，苯，乙腈及其混合物中对应于三组乙腈摩尔分数x_（ac）= 0.20、0.50和0.75的溶剂化动力学（SD）的分子动力学模拟结果环境条件。由溶质电子S_0→S_1激发触发的溶质-溶剂相互作用的变化表示为苯样溶质中的偶极子生成。我们发现两种溶剂组分都是SD事件的积极参与者，偶极溶质与四极苯分子的静电相互作用对溶剂化机理和荧光光谱中的稳态斯托克斯位移起了重要作用。我们的模型溶质优先被处于S_1状态的乙腈溶解，并且局部乙腈浓度的提高显着地影响了溶解时间范围，尤其是在富苯混合物中，该过程比在任何一种溶剂中的溶解坐标松弛都慢，与实验结果一致。我们通过监测溶剂化结构的时间演变来研究浓度波动对SD的贡献。我们发现，在许多方面，这些波动对苯乙腈混合物中SD的贡献方式类似于它们对偶极分子混合物中SD机理的贡献。

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