The Spin Transition of an Iron(III) Complex Intercalated in a MnPS₃Layered Magnet. Occurrence of a Hysteresis Effect on Removal of Lattice Solvent

Abstract

A cationic iron(III) complex [FeIII(5-OMe-sal2trien]+ (where [H2(5-OMe-sal)2trien] was derived from triethylenetetramine and substituted salicylaldehyde), designed to undergo spin crossover, has been inserted in the layered MnPS3 host lattice. The magnetic properties of the resulting intercalation compound [Fe(5-OMe-sal2trien)]0.28Mn0.86PS3·nH2O have been characterized by 57Fe Mössbauer spectrometry and SQUID measurements. The untreated compound exhibits a sluggish thermal spin crossover over the range 200−300 K, but without hysteresis. Removing the co-intercalated water molecules from the compound dramatically affects its behavior and confers a broad hysteresis loop to the transition. The appearance of cooperativity is discussed in terms of elastic interactions and specific arrangement of the ferric complexes. Further interest arises from the spontaneous magnetization acquired by the intercalation compound below 36 K. The static internal magnetic field experienced by the iron sites affects the Mössbauer spectrum of the low-spin form of the inserted complex below T c.

Spin crossover iron(III) complexes

“…[72]. Intercalation of a SCO iron(III) complex, [Fe(5-OMe-sal 2 trien)] + , into the MnPS 3 host lattice yielded [Fe(5-OMe-sal 2 trien)] 0.28 Mn 0.86 PS 3 ·nH 2 O [73]. This material exhibited thermal SCO of the guest molecules and ferrimagnetic ordering of the host lattice.…”

The Role of Molecular Vibrations in the Spin Crossover Phenomenon

“…However, the thermal dependence of the isomer shift only depends on m eff , and finally enables lattice and bond strength effects to be disentangled. Recent results [41,42] suggest that the bond strength effect plays the prominent role at the spin-transition temperature. A typical ratio m eff (LS) /m eff (HS)~1 .2 would explain as well the Lamb-Mössbauer factor change usually observed upon SCO.…”

A Comparative Investigation of Spin Crossover in Bulk Materials, Lamellar CdPS3 Layers, and Polyelectrolytes in a Series of Ferric Complexes: [FeIII((X-sal)2trien)]Y

“…For the intercalated compound we observe a quasifrozen low-spin state, because the host ± guest interactions are strong, favoring the stabilization of the LS state, as observed in other series. [10,13] Finally, for the polymeric samples different curves are observed after the first thermal treatment (heating to 350 K). In the case of the PSS compound, a small irreversible increase of the high-spin content (around 10 %) is detected after heating to temperatures between 293 and 423 K. This change appears reproducible in further temperature cycles.…”