Structure, spectroscopic, thermal properties and catalytic activity of iron(III)-Schiff base complexes

Iron(III) complexes of the Schiff bases: [FeLCl3] (L = 3-(1H-imidazole-1-yl)-N-[(1E)-1H-pyrrol-2-ylmethylene]propan-1-amine, L1; 3-(1H-imidazole-1-yl)-N-[(1E)-(3-methyl-2-thienyl) methylene]propan-1-amine, L2; 1-(3-{[(1E)-1H-pyrrol-ylmethylene] amino} propyl)pyrrolidin-2-one, L3; 1-(3-{[(1E)-2-furylmethylene]amino} propyl)pyrrolidin-2-one, L4 have been prepared and characterized by NMR, Mass, FTIR, UV–Vis spectroscopy, elemental analysis, conductance in non-aqueous solvent, and magnetic measurements. The analytical data showed that the Schiff bases act as tridentate ligands towards trivalent iron via azomethine, imidazole, pyrrole, pyrrolidin nitrogen, furan oxygen and thiophene sulfur. Thermal characterizations of the complexes have been studied in nitrogen atmosphere by simultaneous thermogravimetry and differential thermal analysis, TG-DTA. Two-step decompositions were observed until 800 °C by TG-DTA, involving first release of water until 200 °C. Finally, the organic portion of the complex was burnt out slowly accompanied by a sharp endothermic heat effect; meanwhile iron oxide is formed rapidly. The results suggested that the azomethines are tridentating chelates by N3, N2S and N2O donor atoms. A high spin octahedral geometry is assigned to the Iron(III) ion in all four complexes. It has been found that iron(III)-Schiff base complexes activate the epoxidation of cis-1, 2-diphenylethylene by NaOCl. The epoxide conversion cis-1, 2-diphenylethylene and the ratio of the cis:trans epoxides vary depending on the structure of the Schiff bases.

Graphical abstractIron(III) complexes of some tridentate Schiff bases have been prepared and characterized. Thermal characterizations and catalytic activity of the complexes have been studied. The complexes catalyzed the epoxidation of cis-1,2-diphenylethylene by NaOCl. The epoxide conversion and the ratio of the cis:trans isomer vary depending on the structure of the complexes.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Fe(III)complexes of some tetradentate ligands were prepared. ► Spectroscopic characterizations of the samples were supported with thermal methods. ► Catalytic activity of the iron(III) complexes in epoxidation reactions were observed.