Polymorphism in secondary squaramides: on the importance of π-interactions involving the four membered ring

Abstract

We report the crystal structures of four new squaric acid derivatives, i.e. three polymorphs of 3,4-bis((2-(dimethylamino)ethyl)amino)cyclobut-3-ene-1,2-dione (1a–c) and a cocrystal with resorcinol. A DFT study has been also carried out to investigate the supramolecular assemblies.