Polymorphism in parabanic acid-urea cocrystals governed by supramolecular synthons: a comparative analysis

Abstract

A new polymorph of parabanic acid-urea (PA-UA Form II) cocrystal has been reported. The comparative synthon formation analysis of polymorph (PA-UA Form II) is evaluated with respect to parabanic acid-urea (PA-UA Form I) cocrystal. The heterosynthon of parabanic acid generated in PA-UA Form II exhibits distinct O–H⋯N intermolecular interactions than the homosynthon of parabanic acid formed in PA-UA Form I. Further, parabanic acid synthons in both polymorphic forms exhibit a distinct pattern of interactions, resulting in an intriguingly varied tetrameric arrangement with urea. Both polymorphs are characterized by IR, PXRD, TGA, and DSC studies. Thermal studies show that Form I is more stable than Form II. The heterosynthons in both polymorphs have been examined theoretically by Hirshfeld and DFT calculations. The MEP, NCIplot, and QTAIM computational methods are used for deep intermolecular interaction analysis of diverse supramolecular synthons.