Nechipadappu, S.K.Trivedi, D.R.2026-02-052017Journal of Molecular Structure, 2017, 1141, , pp. 64-74222860https://doi.org/10.1016/j.molstruc.2017.03.086https://idr.nitk.ac.in/handle/123456789/25548Salts of common anti-inflammatory drugs mefenamic acid (MFA), tolfenamic acid (TFA) and naproxen (NPX) with various pyridine derivatives (4-amino pyridine (4AP), 4-dimethylaminopyridine (DMAP) and 2-amino pyridine (2AP)) were synthesized by crystal engineering approach based on the pK<inf>a</inf> values of API's and the salt former. All the salts were characterized systematically by various spectroscopic methods including FT-IR and 1H NMR and the crystal structure was determined by single-crystal X-ray diffraction techniques (SCXRD). DMAP salt of NPX and 2AP salts of MFA and TFA were not obtained in the salt screening experiments. All the molecular salts exhibited 1:1 molecular stoichiometry in the asymmetric unit and except NPX-2AP salt, all the molecular salts included a water molecule in the crystal lattice. Physicochemical and structural properties between drug-drug molecular salts of MFA-4AP, TFA-4AP and NPX-4AP have been evaluated and it was found that these molecular salts were found to be stable for a time period of six months at ambient condition and further hydration of molecular salts were not observed even at accelerated humid conditions (?75% RH). It was found that 4AP salts of MFA and TFA and DMAP salts of MFA and TFA are isostructural. © 2017 Elsevier B.V.Crystal engineeringCrystal structureMoleculesPyridineSingle crystalsSpectroscopic analysisSynthesis (chemical)X ray diffraction4-dimethylaminopyridineAnti-inflammatory drugsCo-crystalsHygroscopicityIsostructuralityPhysico-chemical characterizationSingle crystal x-ray diffractionVarious spectroscopic methodsSalts