RESEARCH ARTICLE

 

Redox potentials of ligands and complexes - a DFT approach

 

 

Karel G. von Eschwege^*; Jeanet Conradie^*

Department of Chemistry, University of the Free State, Bloemfontein, 9300, South Africa

 

 

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ABSTRACT

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 (x_R), electrophilicity index (ω), LUMO energy (E_LUMO) and HOMO energy (E_HOMO) - obtained from calculated electronic energies of neutral, anionic and cationic molecules, are compared. Observed E⁰,E_pa or E_pc gave excellent correlations in the linear relationships between E_pc and E_LUMO (R² > 0.99), and E_pa and E_HOMO (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

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Full text available only in pdf format.

 

Acknowledgement

The National Research Foundation of South Africa and the Central Research Fund of the University of the Free State, Bloemfontein, is gratefully acknowledged.

 

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Received 9 September 2011
Revised 18 October 2011
Accepted 4 November 2011

 

 

Submitted by invitation to celebrate 2011 the 'International Year of Chemistry'.
* To whom correspondence should be addressed. E-mail: veschwkg@ufs.ac.za; conradj@ufs.ac.za