Molecular Electrostatic Potential as a Predictor of Supramolecular Synthons in Non‐Hydrogen‐Bonded Systems: Application to Heavier p‐Block Systems.

We show that the αi and βj parameters developed by Hunter to describe the hydrogen‐bond donor and acceptor properties of particular functional groups can be successfully applied to understand favourable intermolecular interactions between molecules containing heavier p‐block elements, notwithstanding the increasing dispersion terms associated with these elements. Although dispersion is an important contribution to the dimerisation enthalpy of dithiadiazolyls, we show that many aspects of the crystal packing of dimers can successfully be interpreted through such an electrostatic analysis. This approach is exemplified through analysis of the crystal structures of a series of fluoro‐ and trifluoromethyl‐substituted 1,2,3,5‐dithiadiazolyl radicals. Comparison of fluoro‐ and trifluoromethyl‐substituted aryl dithiadiazolyls reveals that the trifluoromethyl group has a pronounced electron‐withdrawing effect, enhancing the electrostatic contribution, but also adding steric bulk. The possible intermolecular interactions between these molecules are close in energy, resulting in structural diversity and at least one case of polymorphism. Despite neglecting the significant favourable dimerisation enthalpy in the analysis of the electrostatic potential, this approach provides a very clear rationalisation of many aspects of the observed crystal structures.|||||| [ABSTRACT FROM AUTHOR]