An NQR study of thermally activated molecular motion in 4-nitrobenzene sulphonyl chloride

A study of the temperature dependence of the 35Cl, NQR frequency and spin-lattice relaxation time in 4-nitrobenzene sulphonyl chloride is reported. The data indicate the existence of four crystalline phases. The observed behaviour of T1 in two of the phases is explained in terms of molecular librations, modulation effects due to the reorientation of NO2 groups, and reorientations between unequal potential wells of SO2SI groups. Values of the activation energies of these motions in both phases are estimated and compared with those obtained in 2-nitrobenzene sulphonyl chloride.