Linking Diffusion-Viscosity Decoupling and Jump Dynamics in a Hydroxyl-Functionalized Ionic Liquid: Realization of Microheterogeneous Nature of the Medium.

Analysis of time-resolved fluorescence anisotropy data in light of the Stokes-Einstein-Debye hydrodynamic description reveals significant decoupling of rotational motion of the solute and the viscosity of the medium for a hydroxyl-functionalized ionic liquid (IL). This behavior and NMR experiments indicate that the hydroxyl-functionalized IL is more heterogeneous than other structurally similar ILs. Considering that recent theoretical investigations have demonstrated that the jump dynamics and hydrogen-bond fluctuations are closely related in viscous media, in such a case the hydrodynamic description can provide inconsistent results, and the present inapplicability of the hydrodynamics description in explaining solute rotation in a viscous hydroxyl-functionalized IL perhaps provides experimental support to the role of orientational jumps and hydrogen bond formation in that event.