A study of activated molecular motion in 2-nitrobenzene sulphonyl chloride by NQR

Abstract

A comprehensive chlorine nuclear quadrupole resonance study of the temperature and pressure dependences of frequency, line width and spin-lattice relaxation time in 2-nitrobenzene sulphonyl chloride is reported. The results show that each of the two substituted groups on the benzene ring contributes to the spin-lattice relaxation via a different and independent mechanism. In the high-temperature regime, the data are successfully explained assuming reorientation of the SO2Cl group between unequal potential wells and field gradient fluctuations resulting from reorientations of nearby NO2 groups. The activation energy of both motions and the fraction of the electric field gradient influenced by the motion of nitro groups have been estimated, as well as the pressure dependence of the activation enthalpy and the activation volume for these motions.

The revision of intermolecular interactions in 1,3‐dinitrobenzene crystal—the role of nitro groups in optical nonlinearity

“…The values of activation energy of reorientation were obtained according to the Arrhenius‐type relation:48, 49 where Γ denotes FWHM and a , b , c and E a are fitted to the experimental results giving E a equal to 2.86 and 8.31 kJ·mol −1 , respectively. The theoretical calculation for a free nitrobenzene molecule yielded 13 ± 4 kJ·mol −1 50, 51. The values obtained in this work were lower than the theoretical value and much lower than in other crystals containing nitro groups, like in 2‐chloro‐nitrobenzene where Perez et al 50 estimated the energy values to be 21.9 and 23.6 kJ·mol −1 , whereas Kyuntsel52 found 27.4 and 31.2 kJ·mol −1 in 2,4,6‐trinitrochlorobenzene crystal.…”

“…The theoretical calculation for a free nitrobenzene molecule yielded 13 ± 4 kJ·mol −1 50, 51. The values obtained in this work were lower than the theoretical value and much lower than in other crystals containing nitro groups, like in 2‐chloro‐nitrobenzene where Perez et al 50 estimated the energy values to be 21.9 and 23.6 kJ·mol −1 , whereas Kyuntsel52 found 27.4 and 31.2 kJ·mol −1 in 2,4,6‐trinitrochlorobenzene crystal. The increasing values of reorientation energy were connected with intermolecular forces and steric effects.…”

A new ordered phase inp-chloronitrobenzene detected by NQR studies

“…Figure 2 shows the line shape just above and below T c . Above T c , we observed a line width of about 200 kHz and below T c the line width observed was about 10 kHz (this is a typical line width in ordered molecular crystals [4]).…”