Supramolecular Assemblies of 2-hydroxy-3-naphthoic Acid and N-Heterocycles via Various Strong Hydrogen Bonds and Weak X•••π (X= C–H, π) Interactions

The analysis of weak interactions, including hydrogen bonds and aromatic stacking interactions, and primary hydrogen bonded synthons in the crystals of 2-hydroxy-3-naphthoic acid with various N-containing cocrystal formers (coformers) is presented. Molecular complexes of 2-hydroxy-3-naphthoic acid with 3-hydroxy pyridine 1, 2-amino-4,6-dimethoxy pyrimidine 2, 2-amino-4,6-dimethyl pyrimidine 3, 1-phenyl piperazine 4, cyclohexylamine 5, dicyclohexylamine 6, 1,10-phenanthroline 7 have been obtained as single crystals using a slow solvent evaporation approach, and investigated utilizing X-ray diffraction techniques. Single crystal X-ray diffraction studies show total proton transfer from 2-hydroxy-3-naphthoic acid to the coformer in crystals 1–6 and partial proton transfer in 7. Crystals 1, 2, 3, 5 and 7 exhibit 3-D supramolecular networks extended by various hydrogen bonds, C–H⋯π and π⋯π stacking; while crystals 4 and 6 exhibit 2-D supramolecular structures via hydrogen bonds. In every crystal structure, hydrogen bonds (N–H⋯O, O–H⋯N, C–H⋯O, etc.) and aromatic stacking interactions (C–H⋯π, π⋯π stacking, etc.) direct the packing modes of molecular crystals together. Some classical supramolecular synthons, such as R22(8) and R44(12), usually observed in organic solids of carboxylic acids with other N-heterocycles, are again shown to be involved in constructing most of these hydrogen bonding networks. Moreover, these multicomponent samples are characterized by infrared and thermogravimetric analyses. Thermogravimetric analysis of mass loss for the seven compounds has been shown to correlate with the strength of the hydrogen bonds in the packing fraction.