The small impact of various partial charge distributions in ground and excited state on the computational Stokes shift of 1-methyl-6-oxyquinolinium betaine in diverse water models
The small impact of various partial charge distributions in ground and excited state on the computational Stokes shift of 1-methyl-6-oxyquinolinium betaine in diverse water models
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DOI：
10.1063/1.4966147
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发表时间：
2016-10-28
影响因子：
4.4
通讯作者：
Schroeder, Christian
中科院分区：
文献类型：
--
作者：
Heid, Esther;Harringer, Sophia;Schroeder, Christian
通过分子动力学计算机模拟，研究了1-甲基-6-氧基喹啉甜菜碱分子基态和第一激发态的量子力学部分电荷分布对含时Stokes位移的影响。此外，还研究了所采用的溶剂模型--非极化的SPC、TIP4P和TIP4P/2005以及极化的SWM4水模型--对体系溶剂化动力学的影响。使用不同的泛函和计算方法影响溶质的部分电荷分布和偶极矩的大小，但不影响偶极矩的取向。基于计算的电荷分布的模拟显示了几乎相同的驰豫行为。用偶极近似整个溶质分子得到相同的驰豫行为，但溶剂化能较低，这表明斯托克斯位移的时间尺度与溶质的特性无关。然而，SPC和TIP4P水模型表现出太快的动力学，这可以归因于扩散系数太大和粘度太低。SWM4和TIP4P/2005模型的扩散系数和粘度与实验值吻合较好，相应的松弛行为与实验值相当。此外，我们发现，为了定量描述应用系统的斯托克斯位移，至少必须考虑溶质周围的两个溶剂化壳层。由AIP出版公司出版。
The influence of the partial charge distribution obtained from quantum mechanics of the solute 1-methyl-6-oxyquinolinium betaine in the ground- and first excited state on the time-dependent Stokes shift is studied via molecular dynamics computer simulation. Furthermore, the effect of the employed solvent model-here the non-polarizable SPC, TIP4P and TIP4P/2005 and the polarizable SWM4 water model - on the solvation dynamics of the system is investigated. The use of different functionals and calculation methods influences the partial charge distribution and the magnitude of the dipole moment of the solute, but not the orientation of the dipole moment. Simulations based on the calculated charge distributions show nearly the same relaxation behavior. Approximating the whole solute molecule by a dipole results in the same relaxation behavior, but lower solvation energies, indicating that the time scale of the Stokes shift does not depend on peculiarities of the solute. However, the SPC and TIP4P water models show too fast dynamics which can be ascribed to a too large diffusion coefficient and too low viscosity. The calculated diffusion coefficient and viscosity for the SWM4 and TIP4P/2005 models coincide well with experimental values and the corresponding relaxation behavior is comparable to experimental values. Furthermore we found that for a quantitative description of the Stokes shift of the applied system at least two solvation shells around the solute have to be taken into account. Published by AIP Publishing.