Maurya Rajan, Naithani Sudhanshu, Bandyopadhyay Dibyendu, Choudhury Niharendu, Dutt G B
Atma Ram Sanatan Dharma College , Dhaula Kuan, New Delhi 110 021, India.
School of Physical Sciences, Doon University , Dehradun 248 001, India.
J Phys Chem B. 2017 Dec 7;121(48):10965-10973. doi: 10.1021/acs.jpcb.7b09888. Epub 2017 Nov 21.
Fluorescence anisotropy measurements and molecular dynamics (MD) simulations have been performed to understand the specific interactions of two structurally similar nondipolar solutes, 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DMDPP) and 1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP), with neat 1-butyl-3-methylimidazolium dicyanamide ([BMIM][N(CN)]) and also in the presence of glucose. It has been observed that the measured reorientation times of DMDPP in neat [BMIM][N(CN)] follow the predictions of the Stokes-Einstein-Debye hydrodynamic theory with slip boundary condition. Addition of glucose (0.075 and 0.15 mole fraction) has no bearing on the rotational diffusion of the solute apart from the viscosity related effects. In contrast, the reorientation times of DPP in neat [BMIM][N(CN)] obey stick boundary condition as the hydrogen bond donating solute experiences specific interactions with the dicyanamide anion. No influence of the additive can be noticed on the rotational diffusion of DPP at 0.075 mole fraction of glucose. However, at 0.15 mole fraction of glucose, the reorientation times of the solute at a given viscosity and temperature decrease by 15-40% compared to those obtained in the neat ionic liquid. MD simulations indicate that each DPP molecule hydrogen bonds with two dicyanamide anions in neat ionic liquid. The simulations also reveal that, at 0.15 mole fraction of glucose, the concentration of anions hydrogen bonded to glucose increases significantly; therefore, the percentage of solute molecules that can form hydrogen bonds with two dicyanamide anions decreases to 84, which leads to faster rotation of DPP.
已进行荧光各向异性测量和分子动力学（MD）模拟，以了解两种结构相似的非偶极溶质，即2,5 - 二甲基 - 1,4 - 二氧代 - 3,6 - 二苯基吡咯并[3,4 - c]吡咯（DMDPP）和1,4 - 二氧代 - 3,6 - 二苯基吡咯并[3,4 - c]吡咯（DPP），与纯1 - 丁基 - 3 - 甲基咪唑二氰胺（[BMIM][N(CN)]）以及在有葡萄糖存在时的特定相互作用。据观察，在纯[BMIM][N(CN)]中，DMDPP的测量重取向时间遵循具有滑移边界条件的斯托克斯 - 爱因斯坦 - 德拜流体动力学理论的预测。除了与粘度相关的影响外，添加葡萄糖（0.075和0.15摩尔分数）对溶质的旋转扩散没有影响。相比之下，在纯[BMIM][N(CN)]中，DPP的重取向时间遵循黏附边界条件，因为供氢溶质与二氰胺阴离子发生特定相互作用。在葡萄糖摩尔分数为0.075时，添加剂对DPP的旋转扩散没有影响。然而，在葡萄糖摩尔分数为0.15时，与在纯离子液体中获得的结果相比，在给定粘度和温度下溶质的重取向时间减少了15 - 40％。MD模拟表明，在纯离子液体中，每个DPP分子与两个二氰胺阴离子形成氢键。模拟还表明，在葡萄糖摩尔分数为0.15时，与葡萄糖形成氢键的阴离子浓度显著增加；因此，能够与两个二氰胺阴离子形成氢键的溶质分子百分比降至84％，这导致DPP旋转加快。
