Intermolecular interactions in polymorphs of the cyclic trimeric perfluoro-ortho-phenylene mercury from geometric, energetic and AIM viewpoints: DFT study and Hirshfeld surface analysis

Abstract

Macrocyclic polydentate Lewis acids are of ongoing interest owing to their ability for molecular recognition of anions; however, deep understanding of the nature of supramolecular bonding in their crystals is still lacking. To solve this problem, we have analysed four polymorphic modifications A–D of cyclic trimeric perfluoro-ortho-phenylene mercury (1) by quantum chemical calculations of intermolecular pair interactions energy. In all polymorphs, the main structural motif is stacked columns, which are further connected to a three-dimensional structure with either ladder-shape interactions between parallel macrocycles or T-shape interactions between nearly perpendicular macrocycles. Both arrangements contribute almost equally to the stabilization of the crystal structure. According to DFT computational study of isolated dimers that correspond to the most energetically favourable molecular pairs, and topological analysis of electron density distribution, the stabilization of these dimers is governed by Hg···C and C···C interactions. Significant contribution also comes from F···C and Hg···F interactions, while the role of mercurophilic interactions and F···F contacts seems negligible. Statistical analysis of crystal structures of host–guest complexes of the macrocycle 1 using Voronoi polyhedra and Hirshfeld surfaces showed the same types of intermolecular interactions to be responsible for stabilization of its polymorphs and co-crystals.