The thermosalient phenomenon. "jumping crystals" and crystal chemistry of the anticholinergic agent oxitropium bromide

Željko Skoko, Sharona Zamir, Pance Naumov, Joel Bernstein

    Research output: Contribution to journalArticle

    Abstract

    The anticholinergic agent oxitropium bromide possesses rich crystal chemistry, most remarkably exhibiting a strong thermosalient effect ("jumping crystal" effect), a mechanical property with potential applications in organic-based actuators. The thermosalient effect, manifested in forceful jumps of up to several centimeters, was investigated by a combination of structural, microscopic, spectroscopic, and thermoanalytical techniques, providing data on which to base a proposed mechanism for the phenomenon. Direct observation of the effect in a single crystal and structure determination of both phases revealed that the jumping of the crystals is a macroscopic manifestation of a highly anisotropic change in the cell volume. The cell distortion is accompanied by a conformational change of the oxitropium cation, which triggers increased separation between the ion pairs in the lattice at nearly identical separation between the cation and the anion within each ion pair. At the molecular level, the cation acts as a molecular shuttle composed of two rigid parts (epoxy-aza-tricyclic-nonyl portion and phenyl ring) that are bridged by a flexible ester linkage. The structure of the rigid, inert aza-tricyclic portion remains practically unaffected by the temperature, suggesting a mechanism in which the large, thermally accumulated strain is transferred over the ester bridge to the phenyl ring, which rotates to trigger the phase transition. Mechanistic details of the higher temperature solid-state phenomena are also presented. The high-temperature phase can also be obtained by grinding or UV irradiation of the room-temperature phase. In addition, if it is irradiated with UV light in the presence of KBr, the high-temperature phase undergoes intramolecular photochemical rearrangement. Heating the high-temperature phase to slightly below the melting temperature results in an additional solid-state reaction that results in the conversion of the salt to a mixture of neutral compounds.

    Original languageEnglish (US)
    Pages (from-to)14191-14202
    Number of pages12
    JournalJournal of the American Chemical Society
    Volume132
    Issue number40
    DOIs
    StatePublished - Oct 13 2010

    Fingerprint

    Crystal chemistry
    Cholinergic Antagonists
    Crystals
    Temperature
    Cations
    Positive ions
    Esters
    Ions
    Solid state reactions
    Phase Transition
    Ultraviolet radiation
    Ultraviolet Rays
    Anions
    Melting point
    oxitropium
    Cell Size
    Heating
    Negative ions
    Freezing
    Actuators

    ASJC Scopus subject areas

    • Catalysis
    • Chemistry(all)
    • Biochemistry
    • Colloid and Surface Chemistry

    Cite this

    The thermosalient phenomenon. "jumping crystals" and crystal chemistry of the anticholinergic agent oxitropium bromide. / Skoko, Željko; Zamir, Sharona; Naumov, Pance; Bernstein, Joel.

    In: Journal of the American Chemical Society, Vol. 132, No. 40, 13.10.2010, p. 14191-14202.

    Research output: Contribution to journalArticle

    Skoko, Željko ; Zamir, Sharona ; Naumov, Pance ; Bernstein, Joel. / The thermosalient phenomenon. "jumping crystals" and crystal chemistry of the anticholinergic agent oxitropium bromide. In: Journal of the American Chemical Society. 2010 ; Vol. 132, No. 40. pp. 14191-14202.
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