Noncovalent Interactions in Succinic and Maleic Anhydride Derivatives

Herein, we present a study of the short contacts that several heterocycles of the same family, namely, succinic and maleic anhydrides, maleimide, and succinimide establish in their condensed phases. DFT calculations on model systems in the gas phase have allowed us to calibrate the strength of such interactions, obtaining associated energies up to 2 kcal/mol. We have performed MEP and EDA analysis to unveil their nature, which is mainly electrostatic with some London dispersion contribution. Furthermore, the origin of the interaction is the existence of a charge depletion region (a pi-hole) in the inner part of the rings. This hole interacts with a Lewis base in a precise topological way, with the contacts showing a high directionality as revealed by the analysis of hundreds of crystal structures. We believe that the description for the first time of these interactions, along with their abundance, can assist their use as a tool in crystal design.