Magnetic interaction in oxygenated alpha Fe-phthalocyanines

Abstract

Abstract. Alpha iron phthalocyanines ( -FePc) oxygenated at low temperatures were investigated with the help of 57 Fe Mössbauer spectroscopy, magnetization measurements (SQUID) and X-ray diffractometry (XRD). Mössbauer spectroscopy revealed that upon oxygenation of -FePc, new species were formed which could be associated with Fe III Pc oxygen adducts. Unexpectedly, magnetically split spectrum of oxygenated -FePc was observed below 20 K. In-field Mössbauer spectra in a 5 T external magnetic field at 5K and magnetization measurements indicate antiferromagnetic coupling in oxygenated -FePc.

57Fe Mössbauer Spectroscopy as a Tool for Study of Spin States and Magnetic Interactions in Inorganic Chemistry

“…An analysis of spectra showed that the magnitude of the internal magnetic field remained unchanged when an external magnetic field was applied. This confirms the presence of an antiferromagnetic interaction in the studied system [ 43 ]. The antiferromagnetism of this sample was also verified by measurements of its magnetic susceptibility [ 43 ].…”

“…This confirms the presence of an antiferromagnetic interaction in the studied system [ 43 ]. The antiferromagnetism of this sample was also verified by measurements of its magnetic susceptibility [ 43 ].…”

“…For all species in this series, the value of the isomer shift δ is remarkably similar, indicating that the oxidation state of metal did not change. We have for the first time succeeded in effectively oxygenating α-iron(II) phthalocyanine by an appropriate treatment with oxygen, such that all iron atoms have oxygen neighbors ( Figure 13 c) [ 43 ].…”

“…Furthermore, we found that one of the components in the Mössbauer spectrum of the oxygen-treated α-iron(II)-phthalocyanine showed a typical six-line magnetic splitting pattern, as shown in Figure 14 [ 42 , 43 ]. To investigate the origin of the spectroscopic sextet that arose simply by cooling of this sample, the effect of an applied external magnetic field on the sample’s internal magnetic field was measured.…”

“…In summary, the antiferromagnetic coupling of magnetism observed at low temperatures in the highly oxygen-loaded α-iron phthalocyanines was explained by a super-exchange interaction between the long μ-peroxo – Fe –O–O– Fe– zigzag chains connecting layers of complexes ( Figure 16 ) [ 43 ]. We realize that this model opposes data on the existing and well-known μ-oxo Fe–O–Fe dimers and polymers observed in the chemistry of porphyrins [ 44 ], phthalocyanines, and texaphyrins [ 45 ].…”