The antiviral pharmaceutical compound ribavirin has two known crystalline polymorphs, V1 and V2, under ambient conditions. The V2 form is thermodynamically favored and more readily obtained. The higher-density V1 form was obtained by high-pressure, high-temperature recrystallization in a diamond anvil cell. Recovered single crystals were compressed to 35.1 GPa and characterized by X-ray diffraction. The orthorhombic phase (P212121) is retained throughout compression, with changes in structural response near 10.9 and 26.6 GPa reflected by variations in c-axis compressibility and ribofuranosyl ring conformation. Compression proceeds from interlayer void collapse to progressive layer flattening and ultimately to intramolecular conformational adjustment once residual free volume is exhausted. The principal hydrogen-bond topology is preserved to the highest pressures investigated.
Tiwari et al. (Thu,) studied this question.
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