Charge-Transfer Complex of p-Aminodiphenylamine with Maleic Anhydride: Spectroscopic, Electrochemical, and Physical Properties

A new charge‐transfer complex and the amide formed by the interaction between the electron donor of the p‐aminodiphenylamine and the electron acceptor of maleic anhydride are investigated by spectroscopic methods. The amidation reaction is caused by proton and charge transfer between the maleic anhydride and p‐aminodiphenylamine molecules. The Benesi–Hildebrand equation is used to determine the formation constant, the molar extinction coefficient and the standard Gibbs free energy of the complex by using UV/Vis spectroscopy. To reveal the electronic and spectroscopic properties of these molecules, theoretical computations are performed on the structures of maleic anhydride, p‐aminodiphenylamine and the conformers of their charge‐transfer complex. The charge‐transfer complex and amidation reaction mechanism are also confirmed by IR and NMR spectroscopy and HRMS. The nature of the maleic anhydride–p‐aminodiphenylamine complex is characterized by cyclic voltammetry, thermogravimetric analysis, XRD and SEM. Solid microribbons of this complex show higher thermal stability than p‐aminodiphenylamine. More complex than you think: The reaction of maleic anhydride with p‐aminodiphenylamine, and especially their charge‐transfer complex, is investigated by using 1H NMR, IR and UV/Vis spectroscopy, HPLC–ESI–QTOF‐MS, DFT calculations, cyclic voltammetry, thermogravimetric analysis, and XRD. SEM shows the formation of microribbons that have higher thermal stability than p‐aminodiphenylamine.