Supramolecular Architecture of Two Modifications of Flavone-6,2′-dicarboxylic acid

Abstract

Two crystalline forms of flavone-6,2′-dicarboxylic acid (fla): one N,N-dimethylformamide (DMF) solvate (modification 1) and one without any solvate molecules (modification 2), have been obtained and their structures were determined by X-ray diffraction technique. Modification 1 crystallized in the orthorhombic space group Pbca; and modification 2 crystallized in the monoclinic space group P2(1)/c. In 1 and 2 fla molecules are both joined to helix chain structures via O–H···O hydrogen-bonds between carboxylic group of B ring and carbonyl oxygen atom of C ring, however, in 1 helix chains are further joined by DMF molecules; and in 2 helix chains are further linked via rich hydrogen-bonds between fla molecules, which result in different packing of modifications 1 and 2. Flavone-6,2′-dicarboxylic acid (fla) was found to exhibit two different conformations. One crystallizes from N,N-dimethylformamide in orthorhombic group Pbca and the other crystallizes from n-propanol in monoclinic group P2(1)/c without any solvent molecules.