Dynamics of interspecies hydrogen bonding of a fluorinated alcohol and a nitroxide free radical

Abstract

The combined use of (1) the magnetic field dependence of solvent nuclear relaxation times induced by paramagnetic solutes and (2) the dynamic nuclear polarization of the same solvent nuclei is reported in a study of the dynamics of interactions between trifluoroethanol and 4-oxo-2,2,6,6-tetramethyl piperidino-oxy free radical. The -OH proton behavior is dominated by dipolar coupling with the spin-label unpaired electron that is characterized by rotational diffusion of the complex with a correlation time of 5×10 -11 s and an interaction distance of 2.6 Å. The interaction with the -CH2 protons and -CF3 fluorine nuclei is weaker, dominated by dipolar coupling with the free radical, and characterized by a shorter correlation time. © 1981 American Institute of Physics.