RUI: Bimolecular Collisions in Ionic Liquid

The primary goal of the proposed research is to study the bimolecular collisions between solute molecules in ionic liquids (ILs) employing nitroxide spin probes. Recently, we have developed a new spin probe electron paramagnetic resonance (EPR) Heisenberg spin exchange (HSE) technique that can separate the effects of dipole-dipole and spin exchange interactions on the EPR spectra in viscous media. This method can now measure the bimolecular collisions of neutral and charged nitroxide spin probes in viscous liquids such as ILs, which has not been possible before. Using the same technique, one may also measure the rotational correlation time of the nitoxides. Ionic liquids are a new class of solvents which are being explored as green substitutes for volatile organic solvents, and whose physicochemical properties can be fine-tuned by modifying their chemical structure. The effective use of ILs as solvents often requires a detailed knowledge of the physicochemical properties, as well as the encounter and re-encounter rates of solutes in ILs; however, experimental data for many properties are scarce.