The cocrystallization of active pharmaceutical ingredients (APIs) is a classic example of molecular recognition between two or more compounds. Studies that seek to design these materials and others often focus on strong non-bonded contacts (e.g. hydrogen bonds) as a means to generate desired supramolecular architectures. Less well studied, but no less important to the overall molecular recognition process, are chemical features that produce less manageable motifs via ill-defined or weak contacts. Molecular shape is one such feature. This investigation exploits quasiracemates – i.e., near racemic materials – to probe the role molecular topology plays in the recognition process. A diverse set of diarylamide quasienantiomers that differ incrementally in substituent size and molecular framework has been prepared. Mixing of pairs of these quasienantiomers in the melt using video-assisted hot stage microscopy provided a robust diagnostic tool for detecting new quasiracemic crystalline phases. Data retrieved using this virtual melting-point phase method not only draws considerable attention to the role of topological features to supramolecular assemblies, but also the structural boundaries of these co-crystalline systems. This investigation synthetically explores the broad structure space towards the identification of new isostructural building blocks and highlights important molecular relationships responsible for molecular recognition that may serve in the design of new functional materials.

Molecular recognition boundaries of diarylamide quasiracemates

253rd National Meeting (2017)

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