Magnetic properties of the mononuclear iron (III) complexes with biphenyl‐disubstituted Schiff base ligand: EPR and SQUID study

Abstract

The magnetic features of the mononuclear iron (III) complexes [Fe(L)2]+X− with tridentate Schiff base ligands [where L is 4‐(4‐diphenylcarboxy)‐2′‐oxysalicylidene‐N′‐ethylene‐N‐ethylene‐2′‐amine‐(carboxy‐4‐diphenyl) and X− = Cl− (1), PF6− (2) and NO3− (3) counter‐ions] have been studied by electron paramagnetic resonance (EPR) spectroscopy, SQUID (superconducting quantum interference device) magnetometry (solid), and Evans 1H nuclear magnetic resonance method (solution). EPR established that compounds (1) and (2) consist of two types high‐spin (HS, S = 5/2) centers with weak distorted and strong low‐symmetry octahedral crystal fields. The signals from low‐spin centers (LS, S = 1/2) of Fe (III) are observed in the spectra of compounds 2 and 3. SQUID revealed permanent HS behavior in (1) and mixed LS + HS in (2), (3) in wide temperature range, while solution method—only HS. Magnetic measurements allowed to estimate part of HS and LS fractions and detected antiferromagnetic exchange interactions between the neighboring Fe (III) ions in complexes.“

Azomethine Fe3+ coordination compounds containing carbazole units: Synthetic approach, spectral characterization, and magnetic studies

“…This result is consistent with the possible existence of a weak FM in AFM‐coupled Fe (III) spin chains. Previously, this behavior was observed in azomethine Fe (III) complexes 56 . Weak ferromagnetism is also confirmed by the magnetic hysteresis loop on M ( H ) in weak magnetic fields.…”

“…Previously, this behavior was observed in azomethine Fe (III) complexes. 56 Weak ferromagnetism is also confirmed by the magnetic hysteresis loop on M(H) in weak magnetic fields. And the linear increase on M(H) in strong fields is a manifestation of the AFM behavior of chains with canted spin moments.…”