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首页> 外文期刊>The Journal of Chemical Physics >Temperature-induced dynamical conformational disorder in 4-vinyl benzoic acid molecular crystals: A molecular simulation study - art. no. 094508
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Temperature-induced dynamical conformational disorder in 4-vinyl benzoic acid molecular crystals: A molecular simulation study - art. no. 094508

机译：温度诱导的4-乙烯基苯甲酸分子晶体中的动态构象障碍：分子模拟研究-艺术。没有。 094508

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摘要

Extensive molecular simulations are carried out as a function of temperature to understand and quantify the conformational disorder in molecular crystals of 4-vinyl benzoic acid. The conformational disorder is found to be dynamic and associated with a flip-flop motion of vinyl groups. The population of minor conformer is less than 3% up to 300 K and is 13.2% at 350 K and these results are consistent with the experimental observations. At still higher temperatures, the population of minor conformer increases up to 25%. The evolution of structure at both molecular and unit-cell level of the molecular crystal as a function of temperature has been characterized by various quantities such as radial distribution functions, average cell parameters, volume, and interaction energies. The van't Hoff plot shows a nonlinear behavior at lower temperatures as it has been reported recently by Ogawa and co-workers in the case of stilbene, azobenzene [J. Am. Chem. Soc. 126, 3539 (2004)], and N-(4-methylbenzylidene)-4-methylaniline [Acta Crystallogr, Sect. B. Struct. Sci. B60, 589 (2004)] molecular crystals. A set of rigid body simulations were also carried out to quantify the effect of conformational disorder on structural quantities such as unit-cell volume and interaction energy. The anomalous shrinkage of vinyl C=C bond length as a function of temperature has been explained by combining the results of simulations and a set of constrained optimizations using ab initio electronic structure calculations for various molecular structures differing in torsional angle. (C) 2005 American Institute of Physics.
机译：根据温度进行广泛的分子模拟，以了解和量化4-乙烯基苯甲酸分子晶体中的构象紊乱。发现构象障碍是动态的，并且与乙烯基的触发器运动有关。直到300 K时，次要构象子的总数不到3％，而在350 K时为13.2％，这些结果与实验观察结果一致。在更高的温度下，次要构象种群增加了25％。分子晶体在分子和单位晶胞水平上的结构随温度的变化已经通过各种量来表征，例如径向分布函数，平均晶胞参数，体积和相互作用能。 Vangawa Hoff图显示了低温下的非线性行为，这是Ogawa及其同事最近在二苯乙烯，偶氮苯的案例中报道的[J.上午。化学Soc。 126，3539（2004）]和N-（4-甲基亚苄基）-4-甲基苯胺[Acta Crystallogr，Sect。 B.结构。科学B60，589（2004）]分子晶体。还进行了一组刚体模拟，以量化构象紊乱对结构量（如单位细胞体积和相互作用能）的影响。乙烯基C = C键长随温度的异常收缩已通过结合模拟结果和一组使用从头算电子结构计算得出的针对扭角不同的分子结构的约束优化进行了解释。 （C）2005美国物理研究所。

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