ELECTRONIC STATE OF IRON COMPLEXES IN THE INTERLAYER OF HYDROTALCITE-LIKE MATERIALS

Abstract--lnfrared and Mrssbauer spectroscopic studies were made on hydrotalcite-like materials, MgrA12(OH)~6(NO3)2-4H20, anion exchanged in aqueous olution of K3Fe(CN)6, K4Fe(CN)6'3H20, or Na2Fe(CN)~NO- 2H20. The material anion-exchanged in aqueous olution of K3Fe(CN)6 gave infrared (IR) absorption bands at 2120 and 2040 cm- ~ in the C~-N stretching region, suggesting that part of the ferrate(III) complex was reduced to ferrate(II) complex on the intercalation chiefly because pure K3Fe(III)(CN)6 and KaFe(II)(CN)6-3H20 gives bands at 2120 and 2040 cm i, respectively. On the inter-calation of Fe(CN)64-, no change in the oxidation state of iron was observed. These features were confirmed by M/~ssbauer spectroscopy. In the IR spectra of material anion-exchanged in aqueous olution of Na2Fe(CN)sNO ' 2H20, the intensity of bands due to N=-O (1940 cm-l) and C-=N stretching was much less than that observed for Na2Fe(CN)sNO. 2H20, indicating that most of N~O ligand was eliminated during the intercalation. Four bands were observed in the C~N stretching region: a band at 2143 cm-I was assigned to C- = N groups in Fe(CN)~NO2-; a band at 2120 cm- ~ was tentatively assigned to Fe(CN)~H2OZ-; bands at 2040-2050 cm I were assigned to Fe(CN)~H203-