Crystal-to-crystal structural transformation of hydrogen-bonding molecular crystals of (imidazolium)(3-hydroxy-2-quinoxalinecarboxylate) through H2O adsorption-desorption

Yuya Yoshii, K. Sakai, N. Hoshino, T. Takeda, S. Noro, T. Nakamura, T. Akutagawa

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    11 Citations (Scopus)


    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.

    Original languageEnglish
    Pages (from-to)5962-5969
    Number of pages8
    Issue number31
    Publication statusPublished - 2015 Aug 21

    ASJC Scopus subject areas

    • Chemistry(all)
    • Materials Science(all)
    • Condensed Matter Physics


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