Search Results

You are looking at 1 - 5 of 5 items for

  • Author or Editor: S. Hayami x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

We report the temperature dependence of Mössbauer spectra of a mixed-valence dinuclear Fe(II) Fe(III) complex, [Fe2(bpmp)(Ph(CH2)2COO−)2](BF4)2 1, where Hbpmp represents 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methylphenol. Two quadrupole doublets observed at 78 K approach each other as the temperature is increased. The two high-energy components of a doublet due to Fe(II) and of that due to Fe(III) become broad in the temperature range from 78 to 230 K and then become narrow above 260 K. The temperature dependence of the spectra was interpreted by assuming of intramolecular electron exchanges between two energetically inequivalent vibronic states FeA(II)FeB(III) and FeA(III)FeB(II) where one of them is slightly more stable than the other.

Restricted access

Abstract  

Mixed-valence μ-phenolate-bis(μ-carboxylate) diiron(II, III) complex [Fe2(bpmp)(ppa)2](BF4)2 (1) is prepared. The temperature dependence of the Mössbauer spectra of the complex 1 is measured. The Mössbauer parameters of the complex 1 show the unusual increase of isomer shift and quadrupole splitting with an increase in temperature. The spectra are explained by the dynamic electronic states in which the valence states of two iron atoms in a molecule are 2.2 and 2.8 on the Mössbauer time scale at 293 K. The single crystal X-ray structure of the complex 1 is determined at 133 K. The complex 1 crystallizes in the triclinic space group
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\bar P$$ \end{document}
1. Two iron atoms in the complex 1 are crystallographycally inequivalent.
Restricted access

Summary  

Iron(III) spin-crossover complexes [Fe(pap)2]ClO4 . H2O (1), [Fe(pap)2]BF4 . H2O (2), [Fe(pap)2]PF6 . CH3OH (3), [Fe(CH3-pap)2]ClO4 . H2O (4), [Fe0.5Al0.5(pap)2]ClO4 . CH3OH (5) and [Fe0.25Al0.75(pap)2] ClO4 . CH3OH (6)were prepared andthe spin transition behaviors of the complexes have been studied from magnetic susceptibility and Mössbauer spectroscopy measurements. The magnetic properties of light-induced metastable state are measured using Hg-Xe light source. T 1/2is temperature at which the populations of the high-spin and low-spin species are fifty-fifty. Metastable HS is produced by light irradiation at 5 K. T(LIESST) is the temperature at which the populations of the metastable high-spin species decrease to one half and cooperativity factor Cis defined as the parameter which presents the strength of cooperativity. The value of T(LIESST) decreases as T 1/2increases and the plots of T(LIESST) vs. Cshow linear correlation. The effect of cooperativity of the complexes on the relaxations in solid was confirmed for the iron(III) complexes.

Restricted access

Abstract  

A barium-iron(III) [BaFe(cr-salen)(py)2](ClO4)3 (1) was prepared and an iron(III) complex [Fe(cr-salen)(py)2]ClO4 (2) complex was obtained by removing Ba2+ ion from the barium-iron(III) complexes with guanidinium sulfate. These complexes are in the high-spin state both in the solid state and in acetonitrile. Single crystals of [BaFe(cr-salen)(MeOH)2]2O(ClO4)4·2MeOH (3) were obtained by slow evaporation of a solution of (2) and Ba(ClO4)2, and the single crystal X-ray structure of (3) was determined: Crystal data for [BaFe(cr-salen)(MeOH)2]4O2(ClO4)4·2MeOH: C25H36N2O17.5Cl2BaFe, are: space group C2/c, Z=8, a=24.79(7) Å, b=16.11(6) Å, c=17.24(6) Å, V=6753(36) Å3, R=0.133, Rw=0.154. The structure of the complex has a one order polymeric chain. An iron atom is located in a cavity of square pyramidal geometry and bridged by an oxygen atom of μ-oxo. A barium ion is sitted in a quasi-crownether ring and bridged by two perchlorate anions.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors:
S. Hayami
,
T. Kawahara
,
G. Juhász
,
K. Kawamura
,
K. Uehashi
,
O. Sato
, and
Y. Maeda

Abstract  

The magnetic properties of the spin-crossover compound, [Fe(qsal)2]NCSe·2DMSO (N-(8-quinolyl)-salicyladimine) (1), have been measured. We have discovered that the compound 1 exhibits a wide "thermal hysteresis loop" of 115 K (T1/2 = 324 K and T1/2 = 209 K) in the first cycle. Thermogravimetric analysis shows that solvent molecules of the compound 1 are removed at around 324 K. This means that the hysteresis loop observed for the first cycle is only an apparent one. Following the first loop, the compound 1 shows a spin-crossover in warming mode. The spin transition occurs at T1/2 = 285 K and T1/2 = 209 K and the hysteresis width can be estimated to be 76 K, which is one of the largest values reported so far for spin-crossover compounds. It is thought that the cooperativity produced in the compound mainly arises from the intermolecular interactions between the quinoline and the phenyl rings.

Restricted access