Photoisomers of Azobenzene Star with a Flat Core: Theoretical Insights into Multiple States from DFT and MD Perspective,The Journal of Physical Chemistry B

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Photoisomers of Azobenzene Star with a Flat Core: Theoretical Insights into Multiple States from DFT and MD Perspective
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2017-09-08 00:00:00 , DOI: 10.1021/acs.jpcb.7b07350
Markus Koch _{1,

2} , Marina Saphiannikova _{1,

3} , Svetlana Santer ₄ , Olga Guskova _{1,

3}

Affiliation

This study focuses on comparing physical properties of photoisomers of an azobenzene star with benzene-1,3,5-tricarboxamide core. Three azobenzene arms of the molecule undergo a reversible trans–cis isomerization upon UV–vis light illumination giving rise to multiple states from the planar all-trans one, via two mixed states to the kinked all-cis isomer. Employing density functional theory, we characterize the structural and photophysical properties of each state indicating a role the planar core plays in the coupling between azobenzene chromophores. To characterize the light-triggered switching of solvophilicity/solvophobicity of the star, the difference in solvation free energy is calculated for the transfer of an azobenzene star from its gas phase to implicit or explicit solvents. For the latter case, classical all-atom molecular dynamics simulations of aqueous solutions of azobenzene star are performed employing the polymer consistent force field to shed light on the thermodynamics of explicit hydration as a function of the isomerization state and on the structuring of water around the star. From the analysis of two contributions to the free energy of hydration, the nonpolar van der Waals and the electrostatic terms, it is concluded that isomerization specificity largely determines the polarity of the molecule and the solute–solvent electrostatic interactions. This convertible hydrophilicity/hydrophobicity together with readjustable occupied volume and the surface area accessible to water, affects the self-assembly/disassembly of the azobenzene star with a flat core triggered by light.

中文翻译：

具有扁平核的偶氮苯星的光异构体：从DFT和MD角度对多种状态的理论见解

这项研究的重点是比较偶氮苯星的光异构体与苯-1,3,5-三甲苯酰胺核的物理性质。分子的三个偶氮苯臂在紫外可见光照射下经历可逆的反式-顺式异构化，从而产生了从平面全反式到两个混合态到纠结的全顺式异构体的多种状态。利用密度泛函理论，我们表征了每种状态的结构和光物理性质，表明了平面核在偶氮苯生色团之间的偶联中所起的作用。为了表征恒星的嗜溶剂性/疏油性的光触发转换，计算了无溶剂自由能的差异，用于将偶氮苯恒星从其气相转移到隐式或显式溶剂中。对于后一种情况，使用聚合物一致的力场对偶氮苯星的水溶液进行经典的全原子分子动力学模拟，以阐明显着水合的热力学与异构化状态的关系，以及星周围水的结构。通过对水合自由能的两个贡献（非极性范德华力和静电项）的分析，可以得出结论，异构化特异性在很大程度上决定了分子的极性以及溶质-溶剂的静电相互作用。这种可转换的亲水性/疏水性以及可调节的占据体积和水可接触的表面积影响光触发的具有扁平核的偶氮苯星的自组装/分解。

更新日期：2017-09-08

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