Pushing technique boundaries to probe conformational polymorphism

Ward, Martin R. and Taylor, Christopher R. and Mulvee, Matthew T. and Lampronti, Giulio I. and Belenguer, Ana M. and Steed, Jonathan W. and Day, Graeme M. and Oswald, Iain D. H. (2023) Pushing technique boundaries to probe conformational polymorphism. Crystal Growth and Design, 23 (10). pp. 7217-7230. ISSN 1528-7483 (https://doi.org/10.1021/acs.cgd.3c00641)

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Abstract

We present an extensive exploration of the solid-form landscape of chlorpropamide (CPA) using a combined experimental–computational approach at the frontiers of both fields. We have obtained new conformational polymorphs of CPA, placing them into context with known forms using flexible-molecule crystal structure prediction. We highlight the formation of a new polymorph (ζ-CPA) via spray-drying experiments despite its notable metastability (14 kJ/mol) relative to the thermodynamic α-form, and we identify and resolve the ball-milled η-form isolated in 2019. Additionally, we employ impurity- and gel-assisted crystallization to control polymorphism and the formation of novel multicomponent forms. We, thus, demonstrate the power of this collaborative screening approach to observe, rationalize, and control the formation of new metastable forms.

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