The β-phosphorus hyperfine coupling constant in nitroxide: part 3: titration of water by electron paramagnetic resonance

Recently, we showed that the phosphorus hyperfine coupling constant aPβ of persistent cyclic nitroxides decreased with the normalized polarity Reichardt's constant ENT. Thus, we investigated the changes in aPβ in binary mixtures of solvents. The sensitivity of aPβ to the solvent was high enough to allow us to perform water titration in THF, 1,4-dioxane, and acetonitrile by EPR. Accuracies of a few percent were achieved.