13C, 14N and 2H magnetic relaxation and anisotropic molecular reorientation of nitrobenzene

Abstract

Magnetic relaxation rates of 13C and 14N have been measured for neat nitrobenzene and several 50% (v/v) solutions thereof. Using known values of the 14N quandrupole coupling constant and asymmetry parameter and the 13CH bond distances we have determined the three reorientational correlation times and the orientation of the 14N quadrupole coupling tensor. The correlation times are compared with those previously obtained for nitrobenzene from a combination of depolarized Rayleigh scattering ad 13C relaxation data. Knowledge of the principal components of the rotational diffusion tensor permits determination of the quadrupole coupling constant for the ortho deuterons in nitrobenzene- d 5 and the unambiguous assignment to molecular axes of previously determined components of the chemical shift tensor for 15N in nitrobenzene 15N. In addition, the implications of our assignment of the 14N quadrupole coupling tensor components for earlier studies of the alignment of nitrobenzene by electric fields and in a liquid crystal are discussed.