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

Abstract

Abstract A combined experimental and theoretical study on the electrochemical behaviour of a series of tris(β-diketonato) iron(III) complexes is reported. The experimental cyclic voltammetric data showed the reversible reduction and reoxidation of FeIII/FeII. A diffusion coefficient of 5.6 × 10-6 cm2 s-1 was obtained for tris(acetonato) iron(III) in acetonitrile. Linear relationships and trends obtained between the formal reduction potential of FeIII/FeII in tris(β-diketonato) iron(III) complexes and those electronic parameters describing the electron donating ability of the β-diketonato ligand, such as the Gordy scale group electronegativities, and the Hammett meta substituent constants of the side groups R1 and R2 on the β-diketonato ligand (R1COCHCOR2)−, the Lever electronic parameters and the pKa of the free β-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(β-diketonato) iron(III) complexes.