Characterization of Pseudopolymorphs of a Hydroxybenzoic Acid Derivative

Hydroxybenzoic acid is used in many applications, including medicine and polymer synthesis. The
synthesis, self-assembly, and characterization of three pseudopolymorphs of a derivative of a widely used
4-hydroxybenzoic acid (1) are described in detail. In this investigation, we have incorporated hydrophobic (biphenyl
groups) and hydrophilic (-OH and -CO2H) groups on an aromatic ring to influence the self-assembly in the solid
lattice. Compound 1 crystallizes into three crystalline forms:  (i) monoclinic from a solution of DMSO (1A), (ii) triclinic
from a 1:1 solution of DMSO/hot ethyl acetate (1B), and (iii) triclinic from pyridine solution (1C). The formation of
these pseudopolymorphs and the structural similarities in their packing motifs can be rationalized through a few
multipoint solute−solvent interactions. In all three structures, the crystallographic aspects pertaining to the influence
of solvent molecules towards the formation of hydrogen bonded network structures are described. In addition to the
strong hydrogen bonds, intermolecular C−H···O, C−H···π, and π···π interactions were found to stabilize the crystal
structures.