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Crystal-to-crystal structural transformation of hydrogen-bonding molecular crystals of (imidazolium)(3-hydroxy-2-quinoxalinecarboxylate) through H2O adsorption–desorption.
- Source :
-
CrystEngComm . 8/21/2015, Vol. 17 Issue 31, p5962-5969. 8p. - Publication Year :
- 2015
-
Abstract
- The Brønsted acid–base reaction between 3-hydroxy-2-quinoxalinecarboxylic acid (Hhqxc) and imidazole (Im) in acetone–H2O yielded two 1 : 1 salts: anhydrous (HIm+)(hqxc−) (1) and hydrated (HIm+)(hqxc−)·(H2O) (2), where HIm+ and hqxc− are imidazolium and 3-hydroxy-2-quinoxalinecarboxylate, respectively. Single-crystal X-ray structural analyses and vibrational spectra were consistent with the lactam tautomer of the hqxc− anion, which formed π-dimers in both 1 and 2. Each π-dimer in crystal 1 was connected by intermolecular N–H…O hydrogen-bonding interactions to form a linear hqxc− chain, whereas the π-dimers in crystal 2 formed an intermolecular N–H…O hydrogen-bonding zigzag chain. The HIm+ cations existed in the crystalline space between the hydrogen-bonding hqxc− anionic chains. A reversible crystal-to-crystal structural transformation between crystals 1 and 2 was observed following H2O adsorption–desorption, which was confirmed by powder X-ray diffraction measurements, single-crystal X-ray structural analyses, and H2O adsorption–desorption isotherms at 323 K. The structural rearrangement of the hqxc− anions was achieved through changes in the intermolecular hydrogen-bonding interactions. The temperature- and frequency-dependent dielectric constants of crystal 2 revealed a dielectric peak at ~330 K owing to thermal fluctuations of H2O molecules within the crystal. [ABSTRACT FROM AUTHOR]
- Subjects :
- *ALLOTROPIC transition
*HYDROGEN bonding
*MOLECULAR crystals
*WATER
*SORPTION
Subjects
Details
- Language :
- English
- ISSN :
- 14668033
- Volume :
- 17
- Issue :
- 31
- Database :
- Academic Search Index
- Journal :
- CrystEngComm
- Publication Type :
- Academic Journal
- Accession number :
- 115166055
- Full Text :
- https://doi.org/10.1039/c4ce02519a