Mali K S, Dutt G B, Mukherjee T
Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
J Chem Phys. 2005 Nov 1;123(17):174504. doi: 10.1063/1.2102847.
In an attempt to understand the nature of interactions between organic solutes and room temperature ionic liquids, temperature-dependent rotational relaxation 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)--has been examined in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim+][PF6(-)]). Even with the ionic liquid, where the cation and the anion are strongly associated, the solute DPP experiences specific interactions, which is evident from its reorientation times that are 50%-60% longer in relation to DMDPP. It has been noticed that the reorientation times of both the solutes are faster in [bmim+][PF6(-)] than in glycerol, which is also a strongly associated solvent and whose viscosity is similar to the ionic liquid. This observation has been explained by taking into consideration the relative sizes of the solvents. By comparing the ratios of the reorientation times of DPP to DMDPP, in [bmim+][PF6(-)] and glycerol, it has been deduced that the strengths of the interaction between DPP-[bmim+][PF6(-)] and DPP-glycerol are the same.
为了理解有机溶质与室温离子液体之间相互作用的本质，研究了两种结构相似的非偶极溶质——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）——在1-丁基-3-甲基咪唑六氟磷酸盐（[bmim⁺][PF₆⁻]）中的温度依赖性旋转弛豫。即使在阳离子和阴离子紧密缔合的离子液体中，溶质DPP也会经历特定的相互作用，这从其重取向时间相对于DMDPP长50%-60%这一点上可以明显看出。已经注意到，两种溶质在[bmim⁺][PF₆⁻]中的重取向时间比在甘油中更快，甘油也是一种紧密缔合的溶剂，其粘度与离子液体相似。通过考虑溶剂的相对尺寸来解释这一观察结果。通过比较DPP与DMDPP在[bmim⁺][PF₆⁻]和甘油中的重取向时间之比，推断出DPP-[bmim⁺][PF₆⁻]和DPP-甘油之间相互作用的强度是相同的。
