Study on the ferromagnetic state in iron mixed-valence complexes, A[FeIIFeIII(dto)3] (A = (n-CnH2n + 1)4N; dto = C2S2O2) by means of Mössbauer spectroscopy

We have investigated the ferromagnetic states for (n-C_nH_2n?+?1)₄N[Fe^IIFe^III(dto)₃] (n = 3–6; dto = C₂O₂S₂) by means of ⁵⁷Fe Mössbauer spectroscopy. The major component of the spin configuration in the ferromagnetic states for n = 3 and 4 is the low-temperature phase (LTP) with the Fe^III (S = 5/2) and Fe^II (S = 0) states. The high-temperature phase (HTP) of n = 4 remains by more than 20%, which is consistent with two ferromagnetic transitions (T_C = 7 & 13 K). Moreover, it was revealed that the Mössbauer spectra in the ferromagnetic states for n = 5 and 6 correspond to the HTP consisting of the Fe^II (S = 2) and Fe^III (S = 1/2) states.     

Study of the structure and electronic state of thiolate-protected gold clusters by means of 197Au Mössbauer spectroscopy

We have investigated the structures and electronic states of a series of glutathionate-protected Au clusters, Au _n (SG) _m with n = 10 ? ～55, using ¹⁹⁷Au Mössbauer spectroscopy, which allows us to probe the local environment of the constituent Au atoms via isomer shift (IS) and quadrupole splitting (QS). The spectral profile abruptly changes on going from Au₂₂(SG)₁₇ to Au₂₅(SG)₁₈, then it smoothly changes to that of Au～₅₅(SG)_m. However, the spectral profile dramatically changes on going from Au～₅₅(SG)_m to the dodecanethiolate-protected Au cluster with average diameter of 2 nm. The ¹⁹⁷Au Mössbauer spectra of glutathionate-protected Au clusters and dodecanethiolate-protected Au clusters were successfully analyzed on the basis of the structure and electronic state of Au₂₅(SG)₁₈.     

Study on charge transfer interaction and valence state of layered perovskite-type mixed valence complex [NH3(CH2) n NH3]2[(AuII2)(AuIIII4)(I3)2] (n = 7, 8), by means of 197Au Mössbauer spectroscopy

Cs₂[Au^I X ₂][Au^III X ₄](X = Cl, Br, and I) is well known for the three-dimensional perovskite-type gold mixed valence system. Recently, layered perovskite-type gold mixed valence complexes, [NH₃(CH₂) _n NH₃]₂[(Au^II₂)(Au^IIII₄)(I₃)₂] (n = 7 and 8), have been synthesized. We have investigated the relationship between the structural dimensionality and the Au^I–Au^III charge transfer interaction for Cs₂[Au^II₂][Au^IIII₄] and [NH₃(CH₂) _n NH₃]₂[(Au^II₂)(Au^IIII₄)(I₃)₂] (n = 7 and 8) by means of ¹⁹⁷Au Mössbauer spectroscopy.     

Mechanism of the NO2 conversion to NO2- in an alkaline solution.

The reaction of NO2 and NaOH aqueous solution at room temperature was studied for elucidating the behavior of gaseous NO2 in an alkaline solution. Experimental runs related to NO2 absorption have been carried out in various pH solutions. The nitrite and nitrate ions formed in these absorption solutions were quantitatively analyzed. In the case of pH 5-12, both of the nitrite and nitrate ions were formed simultaneously. On the other hand, only the nitrite ion was formed when the pH of the absorption solution was higher than 13. In this paper, a new reaction mechanism was proposed to explain the selective formation of nitrite ion in the 10 M alkaline solution. In order to confirm the new reaction mechanism, H2(18)O was used as part of the absorption solution for detecting oxygen gas production. The amounts of reaction products: (18)O(18)O, (18)O(16)O and (16)O(16)O, were quantitatively determined. It was confirmed that the new reaction proceeds mainly in the 10 M alkaline solution.     

Rare transition event with self-consistent theory of large-amplitude collective motion

A numerical simulation method, based on Dang et al.’s self-consistent theory of large-amplitude collective motion, for rare transition events is presented. The method provides a one-dimensional pathway without knowledge of the final configuration, which includes a dynamical effect caused by not only a potential but also kinetic term. Although it is difficult to apply the molecular dynamics simulation to a narrow-gate potential, the method presented is applicable to the case. A toy model with a high-energy barrier and/or the narrow gate shows that while the Dang et al. treatment is unstable for a changing of model parameters, our method stable for it.     

Electronic Properties of Low-Dimensional Ternary Copper Chal-Cogenides A-Cu-X (A˭Na,K, Rb,Cs; X˭S,Se)

Abstract

Electronic properties of Na₃Cu₄S₄, K₃Cu₈S₆, Rb₃Cu₈S₆, Rb₃Cu₈Se₆, KCu₃S₂, and CsCu₃S₂ are discussed on the basis of the measurements of resistivity and thermopower.     

Three‐Step Spin State Transition and Hysteretic Proton Transfer in the Crystal of an Iron(II) Hydrazone Complex

A proton–electron coupling system, exhibiting unique bistability or multistability of the protonated state, is an attractive target for developing new switchable materials based on proton dynamics. Herein, we present an iron(II) hydrazone crystalline compound, which displays the stepwise transition and bistability of proton transfer at the crystal level. These phenomena are realized through the coupling with spin transition. Although the multi‐step transition with hysteresis has been observed in various systems, the corresponding behavior of proton transfer has not been reported in crystalline systems; thus, the described iron(II) complex is the first example. Furthermore, because proton transfer occurs only in one of the two ligands and π electrons redistribute in it, the dipole moment of the iron(II) complexes changes with the proton transfer, wherein the total dipole moment in the crystal was canceled out owing to the antiferroelectric‐like arrangement.