A model of single-electron transport. Calculation of the thermodynamic parameters for electron capture by the bound proton of oxyacids

Electron transfer is an elementary chemical event involved in many biochemical reactions. Experiments have shown that some oxyacids participating in electron transport are capable of dissociative capture of low-energy electrons, a process indicative of the formation of a metastable anion. The present work reports the results of quantum-chemical simulations of the dissociative electron attachment to a number of oxyacids (H₃PO₄, H₂SO₄⁻, HPO₄²⁻, H₂SO₄, HSO₄⁻, B(OH)₄⁻, HCOOH) with formation of a hydrogen atom in vacuum and in the aqueous medium. Phosphate is one of the most important building units of biological molecules, whereas formic acid can serve as a model of the −COOH group in amino acids, carboxylic acids, functional sites of enzymes, etc. The electron affinity of these oxyacids in the aquatic environment is positive and exceeds the energy of hydrogen atom abstraction. The proton of the OH group captures the electron, while the aquatic environment stabilizes it in the trapped state due to its polarizability. The data obtained provide a fresh look at the phenomenon of proton-assisted electron transfer and at the use of oxyacid buffers.