Nuclear Quadrupole Resonance Studies on Molecular Complexes *

NQR studies o f a number of molecular complexes with p-chloronitrobenzene and o-chloronitrobenzene as acceptors and different hydrocarbons as donors were carried out. A linear relationship between the NQR shift and the ionization potentials o f the donors is obtained. Maksyutin’s idea o f a positive shift with respect to acceptors having a quadrupolar nucleus is shown to hold in those systems. Townes and Dailey’s method was applied to calculate the change in the ionicity of the C -C l bond on complexation to account for the a-electronic contributions in the systems.