A Density Functional Theory (DFT) Investigation on the Structure and Spectroscopic Behavior of 2-Aminoterephthalic Acid and Its Sodium Salts

As a substitute for lithium ion batteries, Na chemistry for ion battery systems is promising materials for energy storage applications for the next generation. Herein, the structures, IR and UV-visible spectra of 2-aminoterephthalic acid (H2ATA), disodium 2-aminoterephthalate (Na2ATA), trisodium 2-aminotere-phthalate (Na3ATA) and tetrasodium 2-aminoterephthalate (Na4ATA) have been studied using density functional theory (DFT/B3LYP/6-311++G(d,p)). The theoretical geometric parameters and FTIR results showed very good agreement with the experimental results. Different conformers of Na2ATA, Na3ATA and Na4ATA showed that the binding energy per sodium in Na2ATA, Na3ATA and Na4ATA is -694.94, -543.44 and -407.46 kJ/mol, respectively. The Na3ATA and Na4ATA salts are higher in energy (151.46 and 287.48 kJ/mol, respectively) than Na2ATA, indicating the higher stability of the Na2ATA complex. The calculated binding energy, enthalpy and Gibbs free energy of Na2ATA, Na3ATA and Na4ATA revealed that the compounds are thermodynamically stable. Natural bond orbital (NBO) analysis of Na2ATA, Na3ATA and Na4ATA indicated that the major interaction occurs between the lone pair electrons of the oxygen atom and anti-bonding orbitals of carbon atoms of the two carboxylate ions. UV-visible spectrum of the free H2ATA and its sodium salts Na2ATA, Na3ATA and Na4ATA were performed using the time-dependent density functional theory (TD-DFT) method at the level of B3LYP/6-311++G(d,p). The frontier molecular orbital energetic parameters and global reactivity descriptors revealed that the Na4ATA and Na3ATA complexes exhibited a higher band gap (ΔEgap) and electronegativity (χeV) than Na2ATA.