Intramolecular O−H∙∙∙O Hydrogen Bonding in Crystal Structures of Ortho-Hydroxymethyl-hydroxy (Hetero)arenes

Insight in non-covalent interactions, especially the extent of the charge transfer in variety of H-bonds (HB) and the directional reproducibility of the utterly smallest patterns (synthons) established depending on donor-acceptor propensity of functional groups and molecular structural fragments within the crystal structures determined and deposited in Cambridge Crystallography database (CCD) [1], impacts previously established skills of serendipity growing crystal toward customized crystallization procedures nowadays to be upraised to Crystal Engineering. This engineering concept enables designing new single phases of single or multicomponent crystalline functional materials with purpose. [2] On the large, macroscopic scale the solid-state structures of the bulk powders may exert improved water solubility, flowability, reactivity or phase transition in photochemical and mechanoshemical processing. The structural diversity in CCD requires the Etter’s General rule “Six-membered-ring intramolecular hydrogen bonds form in preference to intermolecular hydrogen bonds” to be additionally tested for further exploring the influence of the intramolecular HB (IMHB) to its possible participation in establishing intrermolecular HB, and hierarchy in synthons preference as a predictive tool for the mode of crystal packing. [3] The crystal structures and packing analyses based on HB motifs of the molecular salts of protonated hydroxypyridine derivative with deprotonated hydroxybenzoic acid derivatives comparable with statistical analyses on the surveyed structures deposited in CDC, selected based on IMHB fragments ortho position carboxyl–hydroxyl (carboxylate–hydroxyl) and phenyl hydroxyl–methyl hydroxy groups in phenyl and six-membered-hetero-atom-ring, respectively reveal how the nature and the position of the substituents influence the strength of the IMHBs as per the range of their distances and type of synthons in the formation of intermolecular HBs. [4] References 1.Gilli, P; Pretto, L; Bertolasi, V; Gilli G Predicting Hydrogen-Bond Strengths from Acid− Base Molecular Properties. The p K a Slide Rule: Toward the Solution of a Long-Lasting Problem Acc. Chem. Res. 2009 42 (1), 33-44 2.Braga, D. Crystal Engineering: where from? Where to? Chem.Commun., 2003, 22, 2751–2755 3.Etter, C.M Encoding and decoding hydrogen-bond patterns of organic compounds Acc. Chem. Res. 1990 23 (4), 120-126 4.Cvetkovski, A; Ferretti, V; Bertolasi, V. New pharmaceutical salts containing pyridoxine, Acta Cryst. (2017). C73, 1064–1070