Electrochemical behaviour of Tris(β-diketonato)iron(III) complexes: A DFT and experimental study

A combined experimental and theoretical study on the electrochemical behaviour of a series of tris (beta-diketonato) iron(III) complexes is reported. The experimental cyclic voltammetric data showed the reversible reduction and reoxidation of Fe-III/Fe-II. A diffusion coefficient of 5.6 x 10(-6) cm(2) s(-1) was obtained for tris(acetonato) iron(III) in acetonitrile. Linear relationships and trends obtained between the formal reduction potential of Fe-III/Fe-II in tris(beta-diketonato) iron(III) complexes and those electronic parameters describing the electron donating ability of the beta-diketonato ligand, such as the Gordy scale group electronegativities, and the Hammett meta substituent constants of the side groups R-1 and R-2 on the beta-diketonato ligand ((RCOCHCOR2)-C-1)-, the Lever electronic parameters and the pK(a) of the free beta-diketone ligand, are presented. The experimental formal reduction potential relates linearly to the density functional theory calculated electron affinity, as well as to the energy of the lowest unoccupied molecular orbital of the tris(beta-diketonato) iron(III) complexes. (C) 2014 Elsevier Ltd. All rights reserved.