Influence of Halogen and Its Position on Crystal Packing: Proposals for Molecular-Level Crystallization Mechanisms of...

A thorough understanding of the crystallization process is crucial for several fields that depend on meticulous control of the formation of crystalline solids. Therefore, the elucidation of crystallization mechanisms at the molecular level is fundamental to understanding the influence of interactions on the formation of organized solid structures. We propose a crystallization mechanism for isomeric halogenated benzoximes with distinct crystal morphologies based on nonclassical nucleation theory. The results were supported by computational tools that calculate theoretical energetic and topological data for intermolecular and supramolecular interactions. The interactions were verified and energetically classified by density functional theory (DFT) and their contribution per contact point was analyzed using Quantum Theory of Atoms in Molecules (QTAIM) topological Analysis. The crystallization mechanisms were proposed based on the model developed by our research group, in which the strongest interactions of the first coordination sphere (O-H···N or π···π) form one-dimensional (1D) supramolecular chains. From this chain, hypotheses of approximation between chains were analyzed to determine the most stable arrangement for the formation of the two-dimensional supramolecular layer (2D, mainly C-H···H-C, C-H···X, and C-H···O). Following this same evaluation, it was determined that three-dimensional (3D) growth is completed by the X···X (halogen··halogen) and C···X interactions. This work studies the influence of different halogen substituents, in addition to the influence of their positions in the benzene ring, and investigates the possibility of isostructurality and the crystallization mechanism of isomeric benzoximes, expanding the understanding of how small structural variations impact crystal packing.