Empirical Relationship between Chemical Structure and Redox Properties: Mathematical Expressions Connecting Structural Features to Energies of Frontier Orbitals and Redox Potentials for Organic Molecules

Abstract

A set of mathematical expressions to predict redox potentials and frontier orbital energy levels for organic molecules as a function of structural features is proposed. This is achieved by using the principal component regression method on reduction potential (Ered), oxidation potential (Eox), highest occupied molecular orbital (HOMO), and lowest unoccupied molecular orbital (LUMO) values calculated using density functional theory (DFT) on a training set consisting of 77 547 molecules from PubChem database. The first set of expressions allows prediction of Ered, Eox, HOMO, and LUMO values using molecular fingerprints alone with R2 of ca. 0.74, 0.82, 0.92, and 0.85, respectively, which can be used for preliminary screening of molecules before performing DFT calculations. In the second set of expressions, when we include DFT-calculated HOMO and LUMO values as additional descriptors, the R2 values of Eox and Ered predictions increase to 0.91 and 0.90, respectively. This more accurate approach for redox poten...