Yuuki Ono

Mössbauer study of the reaction of laser-evaporated iron atoms with nitrogen molecules in low-temperature argon matrices

Reaction products of laser-evaporated iron atoms with nitrogen molecules were investigated using a low-temperature matrix isolation technique. The products observed in the Mössbauer spectra were FeNNN, Fe(NN), and Fe(NN)2, isolated in argon matrices. Yields of the species changed, depending on the concentration of nitrogen in the matrix. A product assigned to Fe(NN)6 was obtained in a pure nitrogen matrix. Infrared spectra and molecular orbital calculations of the products support these findings.

Spin transition and its photo-induced effect in spin crossover complex film based on [Fe(II)(trz)3]

We have synthesized the [Fe(II)(Htrz) 3 ] complex film by using ion-exchange film (Nafion) as counter anion. From the analysis of Fe Kedge EXAFS spectra, we could prove the existence of one-dimensional Fe chain structure, [Fe(II)(Htrz) 3 ] n on Nafion film. [Fe(II)(Htrz) 3 ]-Nafion showed a spin crossover phenomenon around room temperature. Moreover, the LIESST(Light Induced Spin State Trapping) effect was observed at 4.2 K.

Search on Multi-Functional Properties of Spin-Crossover System

We have investigated the spin-crossover behavior for one-dimensional complexes [Fe(trz) 3 (RSO 3 ) 2 (trz= triazole) and two-dimensional mixed-valence complexes (C n H 2n+1 ) 4 N[Fe II Fe III (dto) 3 ](dto=C 2 O 2 S 2 ). For the case of [Fe(4-NH 2 trz) 3 ](RSO 3 ) 2 , we have controlled Tc and the thermal hysteresis width of spin transition by using the isomerization of counter anion or the fastener effect between the alkyl chains of counter anions C n H 2n+1 SO 3 − . Moreover, we have synthesized a [Fe(Htrz) 3 ] film by using an ion-exchange film having SO 3 − , which shows the spin transition around room temperature. For the case of (C n H 2n+1 ) 4 N[Fe II Fe III (dto) 3 ](n=3,4), we have found a charge transfer phase transition between Fe II and Fe III around 120 K.

Mössbauer and infrared investigation of reactions of laser-evaporated iron atoms with ethylene

Reactions of laser-evaporated iron atoms with ethylene molecules were investigated. The reaction products were trapped in a low-temperature matrix observed by Mössbauer and infrared spectroscopies. Fe(C2H4) was produced at low ethylene concentration, and Fe(C2H4)2 was obtained as the major product at higher ethylene concentration. The assignments were confirmed through molecular orbital calculations.

Origin of charge transfer phase transition and ferromagnetism in (CnH2n+1)4N[FeIIFeIII (dto)3] (dto=C2O2S2)

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 coupled with spin and charge around 120 K, where the charge transfer between the Fe and Fe III sites occurs reversibly, and shows the ferromagnetic transition at 6.5 K. We have investigated the transport and magnetic properties for the single crystal of (n-C 3 H 7 ) 4 N[Fe II Fe III (dto) 3 ]. Both of the intra- and interlayer resistivity showed an anomalous drop due to the charge transfer phase transition. The anisotropy of the magnetization implied that the spins in the ferromagnetic ordered state were aligned parallel to the layer of [Fe II Fe III (dto) 3 ]∞.

Linkage-isomerization and charge-transfer in the formation of iron mixed valence complexes, (n-C3H7)4N[FeIIFeIII(dto)3] (dto = C2O2S2) and (n-C4H9)4N[FeIIFeIII(mto)3] (mto = C2O3S)

In iron mixed-valence complex, (n-C3H7)4N[FeIIFeIII(dto)3] (dto = C2O2S2), the linkage isomerisation and charge-transfer between FeII FeIII occur in the precipitation process. We succeeded the suppression of linkage-isomerization and charge-transfer in the formation process of (n-C3H7)4N[FeIIFeIII(dto)3] by the synthesis on low temperature condition and the selection of solvent. Moreover, we have found that the charge transfer occurs in the formation of (n-C4H9)4N[FeIIFeIII(mto)3] (mto = C2O3S) without linkage-isomerization.

Study on Chemical Bond and Electronic State of New Gold Mixed Valence Complexes Cs2 [AuIX2] [AuIIIY4] (X, Y = Cl, Br, I) by Means of 197Au Mössbauer Spectroscopy

Cs2[AuIX2][AuIIIX4] (X = Cl, Br, I) is known for a perovskite-type gold mixed-valence system. We have synthesized new gold mixed valence complexes, Cs2[AuIX2][AuIIIX4] (X, Y = Cl, Br, I), which was proved by means of Raman spectroscopy. From the analysis of 197Au Mossbauer spectra, it was elucidated that the charge transfer between \( A{{u}^{I}}(5{{d}_{{{{x}^{2}} - {{y}^{2}}}}}) \) and \( A{{u}^{{III}}}(5{{d}_{{{{x}^{2}} - {{y}^{2}}}}}) \) becomes to be predominant in the order of Y = Cl < Br < I for Cs2[AuIX2][AuIIIY4] (X, Y = Cl, Br, I).

Study on the Molecular Magnetism in Mixed Valence Iron Complexes, M[Fe II Fe III (mto) 3 ](M=( n -C n H 2n+1 ) 4 N, mto=monothiooxalato (C 2 O 3 S))

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= m 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 m 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

New-type Phase Transition Coupled with Spin and Charge in Iron Mixed-Valence System

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