Abstract
This work deals with the preparation of pyridine-3-carbohydrazide (isoniazid, inh) cocrystals with two α-hydroxycarboxylic acids. The interaction of glycolic acid (H2ga) or d,l-mandelic acid (H2ma) resulted in the formation of cocrystals or salts of composition (inh)·(H2ga) (1) and [Hinh]+[Hma]–·(H2ma) (2) when reacted with isoniazid. An N′-(propan-2-ylidene)isonicotinic hydrazide hemihydrate, (pinh)·1/2(H2O) (3), was also prepared by condensation of isoniazid with acetone in the presence of glycolic acid. These prepared compounds were well characterized by elemental analysis, and spectroscopic methods, and their three-dimensional molecular structure was determined by single crystal X-ray crystallography. Hydrogen bonds involving the carboxylic acid occur consistently with the pyridine ring N atom of the isoniazid and its derivatives. The remaining hydrogen-bonding sites on the isoniazid backbone vary based on the steric influences of the derivative group. These are contrasted in each of the molecular systems. Finally, Hirshfeld surface analysis and Density-functional theory (DFT) calculations (including NCIplot and QTAIM analyses) have been performed to further characterize and rationalize the non-covalent interactions.
Highlights
As an important part of supramolecular chemistry, crystal engineering has been the subject of continuous research in solid and materials science for many years, and cocrystals have been a research area for more than 150 years, used in many industries, such as pharmaceuticals, textiles, paper, chemical, photographic processing, propelling and electronics, among others [1]
Co-crystals containing heterocyclic nitrogen bases have been studied extensively, especially those with mono- and di-carboxylic acids as co-formers, and it can be concluded that the interaction between a carboxylic acid and a pyridine is a supramolecular synthon of frequent use in crystal engineering that may exist as a cocrystal (CO2 H· · · N) or as salt (CO2 − · · · HN+ ) [5,6,7,8,9]
The three crystals were obtained from the crystallization of solutions prepared by reacting the isoniazid with glycolic or mandelic acids in a molar ratio 1:1
Summary
As an important part of supramolecular chemistry, crystal engineering has been the subject of continuous research in solid and materials science for many years, and cocrystals have been a research area for more than 150 years, used in many industries, such as pharmaceuticals, textiles, paper, chemical, photographic processing, propelling and electronics, among others [1]. Rapid development in this field has revealed the use of a variety of organic components with specific functional groups to create supramolecular arrays through the coordination of metals or non-covalent forces, presenting interesting structures and useful properties. Few studies are known of cocrystals with carboxylic acids
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