Proposal of Molecular‐Level Crystallization Mechanism for Halogenated Benzyl Alcohols: A Study of Isostructural Crystals

Proposals for crystallization mechanisms for halogenated benzyl alcohols at the molecular level show that strong interactions such as OH···O and π···π initiate the crystallization process, although weak interactions (CH···X, CH···C, and X···X) are crucial for stabilizing crystal packing. The study also shows how isostructural compounds, with halogen variation in equivalent positions, have different crystallization mechanisms.

Herein, crystallization mechanisms for halogenated benzyl alcohols, based on theoretical energetic and topological data of intermolecular and supramolecular interactions, are proposed. All interactions are verified and energetically classified by density functional theory and their contribution at each contact point is analyzed using quantum theory of atoms in molecules model. Weak interactions, such as CH···X, CH···C e C···X, perform a key role in stabilizing the crystal packing due to the larger contact area of these fragments and their higher occurrence, compared to strong interactions such as OH···O. The crystallization mechanisms are proposed based on the model developed by the research group. The mechanism starts with the strongest interaction (π···π) present in the first coordination sphere, which forms the first 1D supramolecular chain. From this chain, hypotheses of approximation between these chains are analyzed to determine the most stable arrangement for the formation of the supramolecular layer 2D. The process continues until the formation of a supramolecular structure (3D) with growth in its three directions through interactions X···X via σ-hole. The compounds in the ortho and para positions demonstrated isostructuralism in the equivalent positions, even with the variation of the halogen (chlorine and bromine).

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