Hydrogen-Bonded One- and Two-Dimensional Hybrid Water-Chloride Motifs

The organic salt α,α′-p-xylene-N,N′-bis­(3-hydroxymethylpyridinium)
dichloride (1) has been crystallized in two hydrated
forms, namely, 1A and 1B, with two and three
water molecules as lattice guests, respectively. These supramolecular
structures were well characterized by various physicochemical techniques
such as CHN analysis, IR, thermogravimetric, differential scanning
calorimetry, NMR, powder X-ray diffraction, and single crystal X-ray
diffraction. Both hydrates are fairly stable and soluble in water
and other polar solvents. Structural analysis of 1A and 1B reveals that various hydrogen bonding interactions such
as C–H···Cl–, O–H···Cl–, and O–H···O between the cationic
organic moiety, chloride anion, and lattice water molecules play a
crucial role in stabilizing the zigzag water-chloride infinite chains
in 1A and a novel two-dimensional water-chloride [(H2O)10(Cl–)6]n network in 1B. In addition to
the above-mentioned hydrogen bonding interactions, strong electrostatic
interactions between cation and anion play an important role in assembly
of such hybrid networks. Interestingly, dehydration followed by a
rehydration process results in the recovery of [(H2O)10(Cl–)6]n water-chloride net leading to the regeneration of 1B in the case of both solvates. The structural studies of both hydrates
and their reversible inter conversion via solid–gas reactions
and recrystallization experiments provide comprehensive information
about cooperative hydrogen bonding behavior of the chosen system.