Computational Electrochemistry Study of 16 Isoindole-4,7-diones as Candidates for Organic Cathode Materials

Abstract

Prediction of the redox behavior of electroactive molecules enables screening of a variety of compounds and can serve as a guideline in the search for organic molecules for use as cathode materials in, for example, Li ion batteries. In this study, we present a computational strategy, based on density functional theory, to calculate redox potentials and acid dissociation constants for a series of 16 isoindole-4,7-dione (IID) derivatives. The calculations take all possible electron and proton transfers into account, and the results were found to correlate very well with electrochemical and spectroscopic measurements. The possibility of polymerizing the IID derivatives was also assessed computationally, as polymerization serves as a straightforward route to immobilize the active material. Three of the considered IIDs (5,6-dicyano-2-methyl-isoindole-4,7-dione, 5,6-dihydroxy-2-methyl-isoindole-4,7-dione, and 2-methyl-5-(trifluoromethyl)-isoindole-4,7-dione) are predicted to be particularly interesting for making polymers for organic cathodes because these are calculated to have high redox potentials and high specific capacities and to be readily polymerizable. The presented strategy is general and can be applied in the prediction of the electrochemical behavior of quinones as well as other systems involving proton and electron transfers.

Quinone pendant group kinetics in poly(pyrrol-3-ylhydroquinone)

“…DFT calculations predict that the Semiquinone (SQ) state of PPyHQ is stable with respect to disproportionation at pH < 1, giving rise to two one-electron steps rather than one two-electron step. The polymer is not chemically stable at pH < 1, however (possibly due to the reactivity of the SQ state) [18,19], and the majority of the analyses were therefore carried out at pH 2. The PPy doping onset potential at 0.0 V is unaffected by pH and is relatively constant with scan rate (m) [17].…”

“…A DFT method that has been described previously [18,19] was used to calculate redox potentials and pK a values for the various electron and proton transfers involved in the quinone redox reaction. The monomer was used as a model for the polymer, as the polymer chain has been found to have only a small effect on the pendant group redox chemistry [17].…”

Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

“…Similarly, there have been few other studies, in which redox potentials for a number of quinone derivatives (isoindole-4,7-diones-(IIDs)) in ACN solvent were calculated with respect to the SHE reference potential (4.44 eV) and the MUE was determined to be 0.03 eV. The calculated reduction potentials of the IIDs compounds showed a linear correlation to the Hammett constant values of the ring substituents [104,105]. In addition, two-electron redox potentials for eight substituted quinones in acetonitrile solvent were also accurately calculated by using the B3LYP method including the PCM solvation model for solvation effects [40].…”

Determination of HOMO levels of organic dyes in solid-state electrochemistry

“…The peak at ∼+0.65 V is ascribed to the overoxidation which leads to the irreversible damage to the chemical structure of the dyes because reduction peak disappears as the potential scans backward from +0.8 to −0.4 V (see Fig. 2a for reference); the organic dye loses its electrochemical activity [36][37][38]. In order to avoid the negative effect of the irreversible overoxidation on the electrochemical behaviors of dyes, the following electrochemical investigations were conducted carefully before the occurrence of overoxidation.…”