Solvation and Rotational Diffusion of Solutes in Room Temperature Ionic Liquids as Studied by EPR Spectroscopy with Nitroxide Spin Probing Method

Abstract

In this article, we briefly introduced our studies on solvation and rotational diffusion of solutes in room temperature ionic liquids (RTILs) by electron paramagnetic resonance with nitroxide spin probing method. Most of the rotational correlation times for the nitroxide radicals are within the range calculated on the basis of Stokes–Einstein–Debye hydrodynamic theory with stick and slip boundary conditions or Gierer–Wirtz theory except for smaller solutes in some RTILs with smaller BF₄ and PF₆ anions. In RTILs with 1-butyl-3-methylimidazolium as cation and BF₄ or PF₆ as anion, nitroxide radicals undergo rotational diffusion like supercooled liquids and nitroxide radical with smaller volume rotationally slips.