Inspiring mechanochemical interconversions of halogen-bonded cocrystals by periodic DFT calculations Lavanya Kumar a , Katarina Leko b , Vinko Nemec b , Nikola Bregović b , Dominik Cinčić b and Mihails Arhangelskis *a a Faculty of Chemistry, University of Warsaw, Poland, b Faculty of Science, Department of Chemistry, University of Zagreb, Croatia Design and synthesis of new type of multicomponent molecular crystals (cocrystals), as a means to target materials with desired properties, relies on detailed understanding of non-covalent interactions such as hydrogen bonding, halogen bonding and π-π stacking. In particular, halogen bonding, as an interaction arising from the positive region of electrostatic potential (σ-hole) on the halogen atom and a negative region of electrostatic potential on the acceptor species, including π-systems lighter acceptor atoms (N, O, S), and, more recently, heavier elements such as As and Sb, offers a method for building unprecedented supramolecular architectures 1 and yield materials with unusual luminescent, optical behavior 2 , and pharmaceutical bioavailability 3 . Reliable design of halogen-bonded cocrystals with desired properties relies on good understanding of the effects controlling halogen bond formation, insights into which can be gained from theoretical calculations 4 . In this presentation I will describe, mechanochemical synthesis and interconversion of a series of halogen-bonded cocrystals inspired by previously conducted periodic density-functional theory (DFT) calculations. Here we have chosen co-crystals sharing either an identical donor or acceptor and experimentally introduced the co-former to a co-crystal system. This results in a competition between two cocrystals, to be decided based on the relative thermodynamic stability of the respective materials. By conducting the calculations prior to experiment, we can judge the likelihood of solid-state transformations occurring. Subsequently, by observing the experimental outcomes and comparing them with theoretical predictions, we can refine the computational models for future use. One excellent way of validating the theoretical thermodynamic predictions from periodic DFT is via dissolution calorimetry measurements, which will be presented herein, as one of an early benchmarks of this sort for the study of halogen-bonded materials. In all cases examined herein, reactions which DFT predicted to be thermodynamically favorable, occurred under a variety of experimental conditions, including ball milling with several liquid additives (LAG) 5 , as well as slurry experiments. Reactions with strongly positive calculated enthalpies (i.e. unfavorable) were found not to occur under any of the experimental conditions. This work demonstrates how periodic DFT calculations can help us design experiments with halogen-bonded materials References 1. Catalano, L.; Germann, L. S.; Julien, P. A.; Arhangelskis, M.; Halasz, I.; Užarević, K.; Etter, M.; Dinnebier, R. E.; Ursini, M.; Cametti, M.; Martí-Rujas, J.; Friščić, T.; Metrangolo, P.; Resnati, G.; Terraneo, G.. Chem 2021 , 7 (1), 146–154. 2. Wolters, L. P.; Schyman, P.; Pavan, M. J.; Jorgensen, W. L.; Bickelhaupt, F. M.; Kozuch, S. Wiley Interdiscip. Rev. Comput. Mol. Sci. 2014 , 4 (6). 3. Lu, Y.; Shi, T.; Wang, Y.; Yang, H.; Yan, X.; Luo, X.; Jiang, H.; Zhu, W. J. Med. Chem. 2009 , 52 (9), 2854–2862. 4. Arhangelskis, M.; Topić, F.; Hindle, P.; Tran, R.; Morris, A. J.; Cinčić, D.; Friščić, T. Chem. Commun. 2020 , 56 (59), 8293– 8296. 5. Friščić, T.; Fábián, L. CrystEngComm 2009 , 11 (5), 743–745.
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