Original scientific paper

Mechanism of Photoredox Reactions of Iron(III) Complexes Containing Salen-type Ligands

Jozef Šima ; Department of Inorganic Chemistry, Slovak Technical University, Radlinskeho 9, SK-812 37 Bratislava, Slovakia

Abstract

A mechanism of photoredox processes occurring in irradiated methanolic Solutions of trans-[Fe(R-salen)(CH₃OH)F], where (R-salen)2- are tetradentate open-chain Schiff base N,N'-ethylenebis(5-R-salicyl-ideneiminato) N₂O₂-ligands (R = F, I, CH₃, CF₃, OCH₃, NO₂), has been investigated and proposed. The complexes are redox stable in the dark. The photoreduction of FeIII to FeII induced by ultraviolet irradiation of the complexes is associated with the radical •CH₂OH formation, which is subsequently transformed to formaldehyde CH₂O, the mole ratio of FeII and CH₂O approaching 2:1. The efficiency of the photoredox process is strongly wavelength dependent and influenced by the peripheral R groups of the tetradentate ligands. Electrode potentials E_1/2(FeIII/II) correlate with Hammett constants of the R substituents. When compared with analogous halogeno trans-[Fe(R-salen)(CH₃OH)X] complexes, significant stabilization of FeIII by F- ligands in the photochemical reduction is observed.

Keywords

iron(III) complexes; fluoro complexes; Schiff base ligands; photoredox processes; electrode potentials; mechanism of photo-processes

Hrčak ID:

131868

URI

https://hrcak.srce.hr/131868

Publication date:

1.8.2001.

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