The electrostatic model of field gradients at nuclei: an application to hydrogen-bonded dimers of C_s symmetry

Abstract

An electrostatic description of the effect of a proton acceptor B on the field gradient at the Cl nucleus in hydrogen-bonded complexes B···HCl of C_s symmetry is used to predict the change in the quadrupole coupling tensor of the HCl molecule due to B and the influence of this change on the nonlinearity of the hydrogen bond as determined from the quadrupole coupling in its rotational spectrum. It is found that a distributed tensor approach to the response of the HCl electron density provides more rapid convergence of the perturbation expansion. However, it is noted that the physical interpretation of these distributed quantities in terms of charge flow and polarization should be viewed with caution. For complexes of the form B···HCl, the effect of the field of B on the quadrupole coupling is found to be small, justifying its neglect by Legon et al. in recent experimental investigations of the nonlinear hydrogen bonds in these complexes.