South African Journal of Chemistry
On-line version ISSN 1996-840X
Print version ISSN 0379-4350
A review of the limited literature concerned with theoretical ways to predict experimentally measured redox potentials of ligands and complexes is presented. Electrochemical and related DFT studies involving series of para-substituted nitrobenzenes and β-diketone bidentate ligands are discussed. New studies involving ferrocenes and bimetallic complexes (containing both rhodium and iron) are additionally reported. Correlations of redox potentials with calculated descriptors; electron affinity (EA), group electronegativity (xR), electrophilicity index (ω), LUMO energy (ELUMO) and HOMO energy (EHOMO) - obtained from calculated electronic energies of neutral, anionic and cationic molecules, are compared. Observed E0,Epa or Epc gave excellent correlations in the linear relationships between Epc and ELUMO (R2 > 0.99), and Epa and EHOMO (R2 > 0.92). Close correlation with the HOMO-1 energy was also found with the ferrocene-based second oxidation in the Rh complex.
Keywords : Oxidation; reduction; predict; electron affinity; electrophilicity index; electronegativity; LUMO energy; HOMO energy.