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We have synthesized and investigated the physical properties of a new mixed valence iron complex, ( n -C 3 H 7 ) 4 N[Fe II Fe III (mto) 3 ] (mto=C 2 O 3 S). This complex behaves as a ferrimagnet with T N =38 K and θ=-117 K. From the analysis of the Mössbauer spectrum of ( n -C 3 H 7 ) 4 N[Fe II Fe III (mto) 3 ] at 298 K, the spin state of Fe II was determined to be the high spin state (S=2), but it was difficult to determine the spin state of Fe III . So that, in order to elucidate the spin state of Fe III , we have investigated ESR spectra, and confirmed the coexistence of high spin state (S=5/2) and low spin state (S=1/2) for the Fe III sites. Moreover, we have synthesized ( n -C 4 H 9 ) 4 N[Fe II Fe III (mto) 3 ]. This complex shows the ferrimagnetic phase transition at 41 K, and Weiss constant is -76 K. In our previous paper, we have reported that mixed-valence complex ( n -C 3 H 7 ) 4 N[Fe II Fe III (dto) 3 ] (dto=C 2 O 2 S 2 ) shows a new type of phase transition connected with charge transfer phase transition and spin-crossover transition around 120 K. In the title complexes, the charge transfer phase transition was not observed. mixed valence complex charge transfer phase transition monothiooxalato [ABSTRACT FROM AUTHOR]

We have investigated the physical properties of (n-C n H 2n+1 ) 4 N[Fe II Fe III (dto) 3 ](dto = C 2 O 2 S 2 ) by means of 57 Fe Mössbauer spectroscopy, magnetic susceptibility, and ESR. From the analysis of 57 Fe Mössbauer spectra and ESR signal, we have discovered a new type of first order phase transition around 120 K for (n-C n H 2n+1 ) 4 N[Fe II Fe III (dto) 3 ](n = 3, 4), where the charge transfer transition between Fe II and Fe III occurs reversibly. In the higher temperature phase, the Fe III ( S = 1/2) and Fe II ( S = 2) sites are coordinated by six S atoms and six O atoms, respectively. In the lower temperature phase, on the other hand, the Fe III ( S = 5/2) and Fe II ( S = 0) sites are coordinated by six O atoms and six S atoms, respectively. Moreover, we have found the ferromagnetic phase transition in this system. The ferromagnetic order is induced by the charge transfer interaction between the Fe III ( S = 5/2) and Fe II ( S = 0) sites. spin crossover ferromagnetism charge transfer phase transition mixed valence [ABSTRACT FROM AUTHOR]

This article reports on an unusual single-chain magnet (SCM) formed by a twisted arrangement of ions with easy-plane magnetic anisotropy. The attention of nanoscientists is currently directed toward the behaviors of nanomagnets, such as single-molecule magnets and SCMs, since they show unique physical properties, such as quantum tunneling of magnetization and quantum phase interference, that are not observed in bulk magnets. An alternating Fe²/Fe³ mixed valence single-chain magnet was prepared using the complexed ligand. This twisting easy plane system is unique in that it exhibits easy-axis anisotropy over the whole chain, giving rise to stow magnetization reversal despite single ion anisotropy of the constituent Fe² ions with easy-plane.