Investigation of supramolecular synthons of p-hydroxybenzoic acid (PHBA): Comparison of its hydrate, co-crystal and salt

• Three different kinds of supramolecular syntheses of PHBA have been carried out and characterized.
• The hydrogen bonding motif in the solid state has been investigated by vibrational spectroscopy.
• The intermolecular contacts of crystal structure have been revealed by Hirshfeld surfaces.

An investigation of supramolecular synthons of p-hydroxybenzoic acid (PHBA) has been carried out in this work. Three different kinds of compounds derived from PHBA (hydrate (1), co-crystal (2) and salt (3)) have been synthesized and characterized by single-crystal X-ray diffraction, infrared spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA). A thorough structural investigation revealed the different supramolecular synthons patterns of the three compounds: hydrate (1)—displays 1-D supramolecular sheet completed by water molecules; co-crystal (2)—displays square grid structure completed by hetero-dimeric unit; and salt (3)—forms hetero-dimeric unit and displays infinite zigzag striped structure. We further prepared Hirshfeld surfaces for compounds 1–3 as well as PHBA, accompanied by vibrational spectroscopy, for the in-depth studies of intermolecular interactions in their solid-state forms.