Multicomponent solids of diclofenac with pyridine based coformers

The present study reports nine crystalline forms of diclofenac acid which include cocrystals, salts, salt-cocrystals and salt hydrates with pyridines and amines based coformers utilizing acid … pyridine synthon. All the solids were successfully prepared and structurally characterized through PXRD, ATR, DSC and single crystal XRD. The crystal structures were analyzed and discussed in terms of acid … pyridine heterosynthon. The conformation of diclofenac acid in the multicomponent solids reported in this paper is compared with its polymorphs. The structural chemistry of diclofenac acid (DIC) is discussed based on carboxylic acid … pyridine synthon in terms of DIC-coformer dimer or DIC-coformer-DIC trimers. The influence of pKa in dictating the final solid is also discussed. [Display omitted] •Acid … Pyridine is a robust supramolecular synthon to design multicomponent solids.•Conformational flexibility and supramolecular aggregation are the key factors to decide stoichiometry of final solids.•ΔpKa influence the nature of multicomponent solids.•ATR is a reliable technique to distinguish between a cocrystal and a salt.