Electron Paramagnetic Resonance Spectroscopic Investigation of the Dynamics of Spin Probe in Room Temperature Ionic Liquid

摘要

Rotational motion of the spin probe 4-hydroxyl-2,2,6,6- tetramethyl-1-piperidinyloxy (TEMPOL) in methyl imidazoium based ionic liquid was studied by Electron Paramagnetic Resonance spectroscopy (EPR). The influence of rotational tumbling of the paramagnetic spin probe on the width and shape of EPR transition was studied to calculate rotational correlation time, equilibrium radius, and rotational diffusion coefficient of spin probe in different ionic liquid media; CnmimPF6/NTf2 (n=4, 6, 8). The glass transition temperatures for CnmimNTf2 (n=4, 6) were calculated from the inflection point of τc vs T plots whereas activation energy of the rotation were calculated from the Arrhenius plots of lnD vs 1/ T(K).