Role of functionalities in structural analogues urocanic acid and l -histidine, toward the formation of anhydrous and hydrated molecular salts

Ganduri, R and Swain, D and Cherukuvada, S and Guru Row, TN (2019) Role of functionalities in structural analogues urocanic acid and l -histidine, toward the formation of anhydrous and hydrated molecular salts. In: Crystal Growth and Design, 19 (3). pp. 1845-1852.

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Abstract

Cocrystallization of structural analogues urocanic acid and l-histidine with mono-, di-, and trisubstituted hydroxy benzoic acids has been carried out to gain insights into the formation of anhydrous and hydrated molecular salts. Urocanic acid generated anhydrous molecular salts with 2-hydroxy, 3,5-dihydroxy, and 2,4,6-trihydroxybenzoic acids, whereas 2,3-dihydroxy, 3,4-dihydroxy, and 3,4,5-trihydroxybenzoic acids resulted in hydrated salts. Cocrystallization experiments of anhydrous l-histidine with 2,3-dihydroxy, 3,4-dihydroxy, 3,5-dihydroxy, 3,4,5-trihydroxy, and 2,4,6-trihydroxybenzoic acids resulted in hydrated molecular salts. However, l-histidine 2-hydroxybenzoic acid formed an anhydrous molecular salt. In this context, the hitherto elusive structure of native urocanic acid (anhydrous form) has been determined. The rationale for the formation of hydrated and anhydrous salts is evaluated in terms of the hydroxyl substituents on benzoic acids and the presence of additional amino group in l-histidine. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) proved the presence or absence of hydration, whereas Fourier-transform infrared (FT-IR) experiments confirmed proton transfer suggesting the formation of molecular salts for those combinations that did not produce good quality single crystals for diffraction. © 2019 American Chemical Society.

Item Type:	Journal Article
Publication:	Crystal Growth and Design
Publisher:	American Chemical Society
Additional Information:	Copyright for this article belongs to American Chemical Society.
Keywords:	Amino acids; Differential scanning calorimetry; Gravimetric analysis; Hydration; Quality control; Salts; Single crystals; Thermogravimetric analysis, Anhydrous salts; Cocrystallization; Fourier transform infrared; Hydroxyl substituents; Molecular salts; Structural analogue; Thermal gravimetric analyses (TGA); Urocanic acid, Benzoic acid
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	08 Apr 2019 11:49
Last Modified:	08 Apr 2019 11:49
URI:	http://eprints.iisc.ac.in/id/eprint/62025

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