Synthesis and Characterization of New Iron Complexes Induced with y-Ray Irradiation

2005 Fiscal Year Final Research Report Summary

• Project/Area Number: 16550059
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Inorganic chemistry
• Research Institution: Tokyo Metropolitan University
• Principal Investigator: MOTOMI Katada Faculty of Urban Liberal Arts, Professor, 都市教養学部, 教授 (20094261)
• Project Period (FY): 2004 – 2005
• Keywords: induced irradiation / radiolysis / Mossbaue spectra / γ-ray / iron complexes / iron(III) oxalates / iron(III) citrate / iron(II) oxalates

Research Abstract

Materials. Fe2(C2O4)3・6H2O, [LaFe(C2O4)3]・9H2O, [bipyH][Fe(C2O4)2(H2O)2]・H2O,[phenH][Fe(C2O4)2(H2O)2] H2O, (Hpy)2[Fe2(C6H4O7)2(H2O)2], (Hbpiy)2[Fe2(C6H4O7)2(H2O)2] and (Hphen)3[Fe2(C6H4O7)3] complexes were prepared and irradiated with 60Co γ-ray. New iron(II) species were observed in these complexes. New iron(II) high-spin species of irradiated Fe2(C2O4)3.6H2O and [LaFe(C2O4)3]・9H2O were assigned to FeC2O4・2H2O by using Mossbauer spectroscopy and XRD. However, new iron(II) high-spin species of [bipyH][Fe(C2O4)2(H2O)2] H2O, [phenH][Fe(C2O4)2(H2O)2] ・H2O and iron citrate were different with FeC2O4・2H2O. It is well known in radiation chemistry that the reduction of iron atoms in trisoxalatoferrate(III) is associated with following radiolysis of oxalate anions, C2O42-→2CO2 + 2e-. In this system, formation fo Fe(II) species is explaine by the same reason.
In [bipyH][Fe(C204)2(H20)・H2O, [phenH][Fe(C2O4)2(H2O)・H2O, (Hbpiy)2[Fe2(C6H4O7)2(H2O)2] and ( Hphen)3[Fe2(C6H4O7)3] complexes, another new Fe(II) low-spin species were found with increase of irradiation dose. Its new species was assigned to Fe(bipy)33+ and Fe(phen)33+ by Mossbauer spectra. This result is explained by the reaction fo Fe2+ ion and bipyridine and phenanthroline ligands which resist radiation. Malonate iron complexe K3[Fe(C2H2O4)3]・3H2O were also observed Fe(II) high-spin species by y-ray irradiation.
In mixture of K3Fe(C2O4)3 and Co(bipy)3・Cl2 and Co(phen)3・Cl2, Fe(II) high-spin species was observed due to K3Fe(C2O4)3 itself but new Fe(II) low-spin species was not found. It suggests that the chemical bond strength of Co-bipy and Co-phen greater than those of Fe-bipy and Fe-phen. New iron species were not found in irradiated (Hphen)3[Fe(CN)6]・5H2O and (Hphen)3[Fe(CN)5NO]・2H2O. It suggest that the radiation resisting of CN ligand is stronger than those of oxalate, citrate and malonate ligands.
We obtained new iron species by y-ray irradiation of iron complexes containing oxalate, citrate, malonate.