Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
J Phys Chem B. 2010 Jul 15;114(27):8971-7. doi: 10.1021/jp1039282.
Rotational dynamics of two organic solutes, rhodamine 110 (R110) and 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DMDPP), has been investigated as a function of temperature in a series of 1-alkyl-3-methylimidazolium ionic liquids (alkyl = ethyl, butyl, hexyl, and 2-hydroxyethyl) containing tris(pentafluoroethyl)trifluorophosphate (FAP) anion. The present study has been essentially undertaken to examine the influence of specific interactions on the rotation of cationic (R110) and neutral (DMDPP) solutes in this new class of ionic liquids. Analysis of the results using the Stokes-Einstein-Debye hydrodynamic theory indicates that the rotational dynamics of R110 is closer to the stick boundary condition whereas the dynamics of DMDPP is described by the slip boundary condition. The observed slow dynamics of R110 has been rationalized on the basis of specific interactions between the cationic solute and the FAP anion of the ionic liquid. It has also been noticed that the rotational dynamics of DMDPP is slower by 30% in 1-(2-hydroxyethyl)-3-methylimidazolium FAP compared to that observed in its ethyl counterpart, which is assimilated in terms of hydrogen bonding interactions between the carbonyl groups of the solute and the hydroxyl group of the imidazolium cation.
两种有机溶质，若丹明 110（R110）和 2,5-二甲基-1,4-二氧代-3,6-二苯基吡咯[3,4-c]吡咯（DMDPP）在一系列 1-烷基-3-甲基咪唑鎓离子液体（烷基=乙基、丁基、己基和 2-羟乙基）中，随温度的变化，其旋转动力学已被研究。本研究的主要目的是考察特定相互作用对阳离子（R110）和中性（DMDPP）溶质在这种新型离子液体中的旋转的影响。使用斯托克斯-爱因斯坦-德拜流体力学理论对结果进行分析表明，R110 的旋转动力学更接近棒状边界条件，而 DMDPP 的动力学则由滑移边界条件描述。基于阳离子溶质与离子液体的 FAP 阴离子之间的特定相互作用，对 R110 的观察到的缓慢动力学进行了合理化。还注意到，与在其乙基对应物中观察到的相比，DMDPP 在 1-（2-羟乙基）-3-甲基咪唑鎓 FAP 中的旋转动力学慢 30%，这可以用溶质的羰基与咪唑鎓阳离子的羟基之间的氢键相互作用来解释。
