Nuclear relaxation and molecular motion of liquid thiazole and isothiazole

Nuclear relaxation rates of 13C and 14N have been measured as a function of temperature for neat thiazole and isothiazole. Nuclear Overhauser enhancements, also measured as a function of temperature, were used to separate dipolar and spin rotational contributions to 13C relaxation. 13CH dipolar relaxation rates were combined with quadrupolar 14N relaxation rates to determine the angle between the rotational axes and the principal inertial axes, and the rotational correlation times for motion about each rotational axis. The accuracy of the results were discussed, especially with respect to the 14N coupling parameters. The viscosity has been measured for thiazole and isothiazole as a function of temperature. The temperature and viscosity dependence of the rotational correlation times is compared with those of other planar molecules.