Electrochemistry of iron(III) complexes with salicylaldehyde thiosemicarbazone and its S-methyl derivative

Abstract

A detailed electrochemical study of Fe(III) chelate complexes with salicylaldehyde thiosemicarbazone (H2L1) and its S-methyl derivative (H2L2), of general formulae Fe(HL)Cl2, [Fe(HL)2]Cl, Fe(HL)L and Li[FeL2] was carried out at a glassy carbon electrode in a DMF + LiCl system. Both the cation and anion of the supporting electrolyte affect the behaviour of the complexes significantly: Li+ by forming ion pairs with the reduced bis(ligand) anions and Cl- via replacement of HL- in corresponding complexes. In addition, H+ plays an important role in both the heterogeneous and homogeneous processes. While all complex species are reduced in a one-electron process, those containing the L2- form can also be oxidized. The H2L1 complexes are more easily reduced/oxidized than the analogous H2L2 complexes. Chemical reactions associated with electron transfer processes make the overall behaviour of the compounds rather complex. All heterogeneous and homogeneous reactions are presented in a common reaction scheme, and the overall mechanism is discussed. © 1986.