Electrostatic terms in the interaction of chiral molecules

Abstract

In a model in which molecular interactions are analysed in three components (i) short-range ‘contact’ interactions, (ii) dispersion interactions and (iii) ectrostatic interactions between permanent moments, attention is drawn in this paper to the electrostatic terms. Discrimination (energy difference between laevo-laevo and laevo-dextro interactions) occurs both in the limit of nearly free rotation of the coupled molecules, and in that of locked molecules in a fixed average relative orientation. Electrostatic discrimination in the freely rotating systems has a leading term in the inverse seventeenth power of the separation and can be disregarded. In locked situations values of tens to hundreds of joules per mole are possible with realistic moment values. Where the interacting systems owe their chirality to the helicity of sources on a lattice, or to helical polymers, there may be much larger discriminations. Reference is also made to hypothetical systems in which chirality depends on permanent magnetic and electric dipoles.