Synthesis of a new ionic spin probe for investigation of polar and non-polar solvents

A synthesis is described for the new ionic spin probe potassium-(18-crown-6)-4-sulfonatooxy-2,2,6,6-tetramethyl-piperidine-1-yloxyl. This new spin probe shows an improved solubility in both polar and non-polar solvents in comparison with the potassium-4-sulfonatooxy-2,2,6,6-tetramethylpiperidine-1-yloxyl. Furthermore, the solubility of potassium-(18-crown-6)-4-sulfonatooxy-2,2,6,6-tetramethyl-piperidine-1-yloxyl is also improved in ionic liquids relative to the potassium salt comprising no crown ether moiety. The spin probe potassium-(18-crown-6)-4-sulfonatooxy-2,2,6,6-tetramethyl-piperidine-1-yloxyl is highly suitable for investigation of both less polar and highly polar environments.