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oai:docta.ucm.es:20.500.14352/1045492025-03-18T15:37:16Zcom_20.500.14352_14col_20.500.14352_15

00925njm 22002777a 4500 dc García de la Concepción, Juan author Flores Jiménez, Mirian author Cuccia, Louis A. author Light, Mark E. author Viedma Molero, Cristóbal author Cintas Moreno, Pedro author 2023-06-27 This paper documents and reinvestigates the solid-state and crystal structures of 4,4′-azobis-4-cyanopentanoic acid (ACPA), a water-soluble azobis-nitrile of immense utility as a radical initiator in living polymerizations and a labile mechanophore that can be embedded within long polymer chains to undergo selective scission under mechanical activation. Surprisingly, for such applications, both the commercially available reagent and their derivatives are used as “single initiators” when this azonitrile is actually a mixture of stereoisomers. Although the racemate and meso compounds were identified more than half a century ago and their enantiomers were separated by classical resolution, there have been confusing narratives dealing with their characterization, the existence of a conglomeratic phase, and fractional crystallization. Our results report on the X-ray crystal structures of all stereoisomers for the first time, along with further details on enantiodiscrimination and the always intriguing arguments accounting for the stability of homochiral versus heterochiral crystal aggregates. To this end, metadynamic (MTD) simulations on stereoisomer molecular aggregates were performed to capture the incipient nucleation events at the picosecond time scale. This analysis sheds light on the driving homochiral aggregation of ACPA enantiomers. García De La Concepción, Juan, et al. «Revisiting Homochiral versus Heterochiral Interactions through a Long Detective Story of a Useful Azobis-Nitrile and Puzzling Racemate». Crystal Growth & Design, vol. 23, n.o 8, agosto de 2023, pp. 5719-33 1528-7483 10.1021/acs.cgd.3c00372 https://hdl.handle.net/20.500.14352/104549 1528-7505 https://doi.org/10.1021/acs.cgd.3c00372 Revisiting homochiral versus heterochiral interactions through a long detective story of a useful azobis-nitrile and puzzling racemate