Sulfonate–Pyridinium Ionic Cocrystal Solvates: Improved Material and Antimicrobial Properties

Abstract

Organic cocrystals are attracting the attention of researchers from diverse fields and are the focus of interdisciplinary research. Cocrystals provide a convenient opportunity to realize the property tuning of precursors through an easy and green approach. We extend the scope of sulfonate−pyridinium supramolecular synthons to design ionic cocrystals/molecular salts based on a functionalized sulfonated Schiff base with bipyridyl (1) and bipyridyl ethane (2). The resultant products have been characterized, and their optical properties, including the vaporfluorochromism, have been reported. Structural characterization validates the existence of products in high Z′ ionic form and proton transfer between crystal formers. Hirshfeld studies have been carried out to understand the role and evaluate the contribution of intermolecular interactions toward molecular packing. Improved thermal stability and aqueous solubility, plausibly arising due to their ionic nature, are observed for 1 and 2. A remarkable increase in the aqueous solubility of the Schiff base precursor by a margin of nearly 325 and 400% is observed in the new solid forms 1 and 2, respectively. Cell toxicity studies validate the bioviability of the crystal forms. Improved aqueous solubility and lower cell toxicity studies of 1 and 2 prompted us to investigate them further for their antimicrobial studies, and their antibacterial and antifungal studies are reported.