• On the issues of resolving a low melting combination as a definite eutectic or an elusive cocrystal: A critical evaluation

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    • Keywords


      Cocrystal; eutectic; supramolecular compatibility; heteronuclear seeding; phase diagram

    • Abstract


      Cocrystals and eutectics are different yet related crystalline multi-component adducts with diverseapplications in pharmaceutical and materials fields. Recently, they were shown to be alternate products ofcocrystallization experiments. Whereas a cocrystal shows distinct diffraction, spectroscopic and thermal signaturesas compared to parent components, the hallmark of a eutectic is its low melting nature. However, incertain cases, there can be a problem when one resorts to design a cocrystal and assess its formation vis-àvisa eutectic. In the absence of a gold standard method to make a cocrystal, it is often difficult to judge howexhaustive should the cocrystallization trials be to ensure the accomplishment of a desired/putative cocrystal.Further, a cocrystal can manifest with intermolecular interactions and/or crystal structure similar to that of itsparent compounds such that the conventional diffraction and spectroscopic techniques will be of little help toconclusively infer the formation of cocrystal in the lack of single crystals. Such situations combined with lowmelting behavior of a combination brings the complication of resolving the combination as a cocrystal or eutecticsince now both the adducts share common features. Based on the curious case of Caffeine–Benzoic acidcombination, this study aims to unfold the intricate issues related to the design, formation and characterizationof cocrystals and eutectics for a way forward. The utility of heteronuclear seeding methodology in establishinga given combination as a cocrystal-forming one or a eutectic-forming one in four known systems is appraised.

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  • Journal of Chemical Sciences | News

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