Solid-State Synthesis of New Diimide Compounds: A Two-Step Reaction Followed by X-ray Powder Diffraction

Using X-ray powder diffraction, it has been possible to follow the two-step mechanism of the formation in the solid state of new diimide compounds. By mixing and heating together the α-dicarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid (H4-BCTA), with primary aromatic amines, such as R-NH2, where R = pyrazin-2-yl, pyridin-4-yl, and 2-chloro-pyridin-4-yl, three new pyromellitdiimides (R-IMID) were obtained in an economical manner (i.e., quantitative yield, fast and solventless syntheses). The initial mixing and heating of the acid and amine lead to the formation of the intermediate hydrogen-bonded organic salts. Hydrogen transport from the acid to the amine was shown to have taken place. Further heating led to the formation of the diimides as the result of a condensation reaction. All the compounds were characterized by X-ray powder diffraction (XRPD) techniques.