The Role of Weak C-H•••X (X = O, π) Interactions in Three 1-Hydroxy-2-naphthoic Acid Cocrystals with N-Containing Heteroaromatics: Structural Characterization and Synthon Cooperation

Herein, three novel cocrystals of 1-hydroxy-2-naphthoic acid: tetramethylpyrazine, 1-hydroxy-2-naphthoic acid:1,10-phenanthroline, and 1-hydroxy-2-naphthoic acid:1,4-bis(imidazol-1-ylmethyl)benzene (L2) were obtained by crystallization in methanol-water mixed solvent via a slow evaporation method. The cocrystalline products 1-3 were carried out by a range of techniques, including single-crystal X-ray diffraction, Fourier transform-infrared spectroscopy, elemental analysis, and thermogravimetric testing. We analyzed the crystal structures of the cocrystals 1-3 and found that weak interactions C-H center dot center dot center dot X (X = O or pi) were of great importance in the process of self-assembly as well as strong and conventional hydrogen bonds (N-H center dot center dot center dot O, O-H center dot center dot center dot N, O-H center dot center dot center dot O), leading to a stable and diverse multidimensional supramolecular architecture. It is worth noting that a series of ring motifs with different sizes were explored in the crystal structures of the above complexes, such as R-2(2)(5), R-2(2)(7), R-2(2)(8), R-3(2)(13), R-4(2)(16), R-4(4)(16), R-4(4)(22), and so on. The classical and robust supramolecular synthon intermolecular bond between acid and pyridine (acid center dot center dot center dot pyridine) heterosynthon R-2(2)(7), commonly found in organic solids containing carboxylic acids with other N-containing heteroaromatics, was further demonstrated to be involved in the construction of the hydrogen-bond networks of cocrystal 1. The thermogravimetric technique used in this study proved that the mass losses of these three cocrystals were closely related to the strength of the hydrogen bonds in the package fraction.