Structural Landscape of α‑Acetamidocinnamic Acid Cocrystals withBipyridine-Based Coformers: Influence of Crystal Packing on TheirThermal and Photophysical Properties

Abstract

Controlling the supramolecular synthon outcome in systems with different functionalities has been a key factor for the design of supramolecular materials, which also affected theirphysicochemical properties. In this contribution, we have analyzed the structural landscape of α-acetamidocinnamic acid (HACA) aiming to find its synthon outcome from the competitivity between its acidic and amidic groups. We prepared four multicomponent forms including one dihydrate (HACA·2H2O) and three cocrystals bearing different bipyridine coformers with formulas(HACA)2(1,2-bpe) (1), (HACA)2(4,4′-azpy) (2), and (HACA)2(4,4′-bipy)3 (3) (1,2-bpe = 1,2-bis(4-pyridyl)ethylene; 4,4′-azpy = 4,4′-azopyridine; 4,4′-bipy = 4,4′-bipyridine). First, we applied a virtual screening approach to assess the feasibility of cocrystal formation. Then, we synthesized the cocrystals, via liquid-assisted grinding (LAG) (1 and 2) or solvothermal (3) techniques, and single crystals of HACA, and their four multicomponent forms were obtained showing different synthons and crystal packings. Besides, a Cambridge Structural Database (CSD) search of the cocrystals presenting bipyridine-type coformers and molecules with acid and amide functionalities was performed, and the observed synthon occurrences as well as the possibility of synthon modification by tuning the H-donor/H-acceptor propensity of the acidic and amidic groups were shown. Finally, we measured their thermal and photophysical properties, which were correlated with their structural features.