Synthesis, Spectroscopic and Electrochemical Characterization of Ethylene Diammonium Hydrogen Phosphate: A DFT and IR Spectroscopy Study

Abstract

Organo-inorganic phosphate materials, particularly hydrogen phosphate salts with organic cations, are increasingly popular due to their structural, spectroscopic, and physicochemical properties, with hydrogen bonding enabling stable supramolecular networks across applications in materials chemistry, catalysis, pharmaceuticals, and electrochemistry. This work presents a comprehensive multidisciplinary study of ethylenediammonium hydrogen phosphate, a hybrid organic–inorganic material of growing interest due to its structural properties and potential applications (catalysis, sensors, and corrosion protection). The study combines theoretical calculations (DFT) at the B3LYP/6-31+G(d,p) level, infrared (IR) spectroscopy, and electrochemical analyses (cyclic voltammetry). The results reveal a robust structure stabilized by hydrogen-bonding networks (N–H···O and O–H···O). DFT calculations confirm the compound’s high electronic stability, evidenced by a wide HOMO–LUMO energy gap (6.50 eV) and low chemical reactivity. A strong correlation between experimental and theoretical IR spectra enables precise identification of the vibrational modes of phosphate and ammonium groups. The compound exhibits excellent ionic conductivity and promotes charge transfer, showing quasi-reversible behavior. It significantly enhances the response of glassy carbon electrodes. This comprehensive characterization validates the effectiveness of combining theoretical and experimental approaches. The demonstrated properties confirm the potential of this salt as a high-performance functional material for molecular electronics, active biology, and sensing devices.