35 Cl Quadrupole resonance in chloranil molecular complexes at high pressure

A high-pressure study of the 35Cl quadrupole resonance frequency in five molecular complexes of chloranil has revealed very small values of the pressure coefficient (∂νQ/∂p)T at 273 K–in two of the complexes this quantity is actually negative. It is shown that the values of this coefficient, the mean frequency differences between the complexes, and the crystal splittings can all be understood in terms of a crystal-field polarization of the chlorine non-bonding 3py electrons in the molecular plane.