# Influence of Halogen and Its Position on Crystal Packing: Proposals for Molecular-Level Crystallization Mechanisms of Isomeric Halogenated Benzoximes

## TL;DR

This paper explores how halogen atoms and their positions affect the crystal structures of benzoximes, revealing molecular-level crystallization mechanisms.

## Contribution

The study proposes a new crystallization mechanism for isomeric halogenated benzoximes based on nonclassical nucleation theory.

## Key findings

- Strongest interactions form 1D supramolecular chains (O–H···N or π···π).
- 2D layers are stabilized by C–H···H–C, C–H···X, and C–H···O interactions.
- 3D crystal growth is driven by X···X and C···X interactions.

## Abstract

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.