Fe spin states and redox processes in Schiff base type complexes

Novel iron(II) Schiff base type complexes of [Fe(4-benzyl-2-hydroxy-propiophenone)2(o-phenylenediamine)], [Fe(ninhydrin)2(ethylenediamine)], [Fe(ninhydrin)2(1,2-propylenediamine)], [Fe(2,4,6-trihydroxy-benzyl-4-methoxyphenyl-ketone)2(ethylenediamine)] and [Fe(ninhydrin)2(1,3-propylenediamine)] have been prepared by reaction of the components dissolved in ethanol at refluxing temperature in inert atmosphere, and were characterized by mass spectrometry (MS), infrared spectrometry (IR), thermal analysis, atomic force microscopy (AFM), 57Fe Mössbauer spectroscopy, cyclic voltammetry and biological activity tests. Mössbauer spectroscopy revealed the dominant occurrence of high spin FeII besides minor or no low spin FeII in the complexes, and minor FeIII impurity phase. The cyclic voltammograms indicated peaks due to redox processes in certain complexes. In these cases the occurrence of low spin FeII was also observed. Low biological activity was experienced for some compounds. The thermal decomposition process of all complexes was performed by TG–DTG–DTA analysis in air atmosphere aiming to understand the mechanism of the mass change with increasing temperature. The importance of the current research is to find correlation between the Fe spin states, redox processes and biological activity.