Hydrogen Bond Hierarchy: Persistent Phenol···Chloride Hydrogen Bonds in the Presence of Carboxylic Acid Moieties

Crystal engineering strategies have been delineated during the past decade for the design of multi-component molecular crystals (molecular cocrystals, MCCs). However, the same depth of understanding has not yet been established for cocrystals that are comprised of at least one ionic compound (ionic cocrystals, ICCs). We address this long known but understudied class of cocrystals through the use of organic cation chloride salts as cocrystal formers with carboxylic acids and phenols. Such ICCs are of particular interest for both fundamental and applied reasons. With respect to the former, carefully selected molecular cocrystal formers (coformers) enable systematic study of the hierarchy of hydrogen bonds. With respect to the latter, chloride anions, phenol groups, and carboxylic acid moieties are prevalent in biologically active drug substances and nutraceuticals. In this contribution, we evaluated the propensity to form chloride···carboxylic acid vs chloride···phenol hydrogen bonds (supramolecular heteros...