Mössbauer study of novel iron(II) complexes with oximes in low spin and high spin states

New iron(II) dioximato complexes [Fe(DioxH)2L2] (DioxH: methyl-ethyl-glyoxime, dimethyl-glyoxime, and benzyl-methyl-glyoxime) without and with axially coordinated ligands L (L: 4-dimethyl-amino-pyridine; 3-OH-aniline; 2-imidazolidone; 4-nitrobenzyl-pyridine; 2-amino-pyridine) have been synthesized by reaction of the components dissolved in ethanol at room temperature in inert atmosphere, and were studied by 57Fe Mössbauer spectroscopy. Characteristic isomer shift and quadrupole splitting values of the individual new compounds were determined. It was suggested that iron is in the iron(II) low spin state in all compounds having axially coordinated ligands; however, the high spin iron(II) state is characteristic when no axial ligands are bound to the iron center. Low spin state complexes could be categorized into two groups on the basis of isomer shifts. The difference in the isomer shift was explained on the basis of the type of ligating nitrogens.