Proton NMR relaxation studies on several nitroxyl-water systems

Proton spin-lattice and spin-spin relaxation times of several nitroxyl radicals in aqueous solutions have been measured between 10 kHz and 90 MHz. There are two regions where the relaxation times of the solvent water protons are frequency dependent. It is possible to extract from these experimental data structural and dynamical parameters such as the number of solvated water protons and/or their mean lifetime in the first hydration sphere around the paramagnetic center. These results were found to differ considerably from corresponding data reported in the literature which have been deduced mainly from chemical shift measurements. To whom correspondence should be addressed.