Intermolecular Interactions of Trichloromethyl Group in the Crystal State, the Case of 2‑Trichloromethyl‑3H‑4-quinazoline Polymorphs and 1‑Methyl-2-trichloroacetylpyrrole–Hirshfeld Surface Analysis of Chlorine Halogen Bonding

Intermolecular interactions in the crystal state, a possible source of the observed polymorphism, are investigated with the use of the combined crystallographic methods, theoretical computations, and a modern approach of Hirshfeld surface analysis. Special attention is paid to a trichloromethyl group, a potential donor of halogen bonding. It is demonstrated that due to packing effects and stacking interactions, its conformation does not have to correspond to the lowest energy structure of an isolated molecule, leading to formation of different polymorphs. The analysis of Hirshfeld surfaces, in contrast to standard geometrical criterion of sum of van der Waals radii, indicates the dominant role of various chlorine intermolecular contacts into the overall molecular packing and reveals the characteristic features of the obtained fingerprint plots. These interactions, a subject of our special interest, are discussed in details in order to provide their comprehensive description by means of Hirshfeld surface analysis tools.