Details
| Original language | English |
|---|---|
| Pages (from-to) | 375-395 |
| Number of pages | 21 |
| Journal | Chemical physics |
| Volume | 293 |
| Issue number | 3 |
| Publication status | Published - 15 Sept 2003 |
| Externally published | Yes |
Abstract
The thermal expansion of the spin crossover system [Fe(pybzim) 3](ClO4)2 · H2O (pybzim = 2-(2′-pyridyl)benzimidazole) has been determined from powder X-ray data between 50 and 250 K; the wavelength of the synchrotron source was 1.21888(1) Å. The unit cell parameters of the triclinic crystal system were a = 12.091 Å, b = 12.225 Å, c = 14.083 Å, α = 77.70°, β = 80.35°, Yγ = 74.35°, and V = 1944.9 Å3 at 250 K. In addition to the linear thermal expansion of the unit cell volume, an extra expansion due to the low-spin (LS) to high-spin (HS) transition is observed. The V(T) function shows a sudden increase comparable with the step in the effective magnetic moment at the transition region (140 K). A similar behavior is obtained on the basis of the infrared spectra. The absorption bands corresponding to the metal-ligand stretching modes change their intensities upon heating: the bands corresponding to the low-spin molecules (at ca. 409, 430, 443, and 460 cm-1) disappear in the gain of the high-spin bands (at 259 and 285 cm-1). The variable-temperature data obtained by different techniques (powder diffraction, EXAFS, IR spectra, Mössbauer spectra, magnetic susceptibility, DSC) have been transformed to a common basis - the temperature dependence of the high-spin mole fraction xHS(T). The application of the Ising-like (two-level) model of the spin crossover led to the thermodynamic data ΔH = 2.6 kJ mol-1 and ΔS = 19 J K-1 mol-1 as well as to the cooperativeness J/kæ 110 K (subtracted from the susceptibility data) that characterizes the abruptness of the spin crossover in the solid state.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- General Physics and Astronomy
- Chemistry(all)
- Physical and Theoretical Chemistry
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In: Chemical physics, Vol. 293, No. 3, 15.09.2003, p. 375-395.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Spin crossover in iron(II) tris(2-(2′-pyridyl)benzimidazole) complex monitored by variable temperature methods
T2 - Synchrotron powder diffraction, DSC, IR spectra, mössbauer spectra, and magnetic susceptibility
AU - Boča, R.
AU - Boča, M.
AU - Ehrenberg, H.
AU - Fuess, H.
AU - Linert, W.
AU - Renz, F.
AU - Svoboda, I.
N1 - Funding Information: Thanks are to the grant agencies (VEGA: 1/9252/02, APVT: 20-009902, Slovakia; DAAD and DFG, Germany) for financial support. The authors are thankful to Dr. Rüdiger Werner (TU Darmstadt, Germany), Dr. Martina Vrbová and Ing. Rastislav Jaroščiak (STU Bratislava, Slovakia) for help in taking and analyzing some experimental data.
PY - 2003/9/15
Y1 - 2003/9/15
N2 - The thermal expansion of the spin crossover system [Fe(pybzim) 3](ClO4)2 · H2O (pybzim = 2-(2′-pyridyl)benzimidazole) has been determined from powder X-ray data between 50 and 250 K; the wavelength of the synchrotron source was 1.21888(1) Å. The unit cell parameters of the triclinic crystal system were a = 12.091 Å, b = 12.225 Å, c = 14.083 Å, α = 77.70°, β = 80.35°, Yγ = 74.35°, and V = 1944.9 Å3 at 250 K. In addition to the linear thermal expansion of the unit cell volume, an extra expansion due to the low-spin (LS) to high-spin (HS) transition is observed. The V(T) function shows a sudden increase comparable with the step in the effective magnetic moment at the transition region (140 K). A similar behavior is obtained on the basis of the infrared spectra. The absorption bands corresponding to the metal-ligand stretching modes change their intensities upon heating: the bands corresponding to the low-spin molecules (at ca. 409, 430, 443, and 460 cm-1) disappear in the gain of the high-spin bands (at 259 and 285 cm-1). The variable-temperature data obtained by different techniques (powder diffraction, EXAFS, IR spectra, Mössbauer spectra, magnetic susceptibility, DSC) have been transformed to a common basis - the temperature dependence of the high-spin mole fraction xHS(T). The application of the Ising-like (two-level) model of the spin crossover led to the thermodynamic data ΔH = 2.6 kJ mol-1 and ΔS = 19 J K-1 mol-1 as well as to the cooperativeness J/kæ 110 K (subtracted from the susceptibility data) that characterizes the abruptness of the spin crossover in the solid state.
AB - The thermal expansion of the spin crossover system [Fe(pybzim) 3](ClO4)2 · H2O (pybzim = 2-(2′-pyridyl)benzimidazole) has been determined from powder X-ray data between 50 and 250 K; the wavelength of the synchrotron source was 1.21888(1) Å. The unit cell parameters of the triclinic crystal system were a = 12.091 Å, b = 12.225 Å, c = 14.083 Å, α = 77.70°, β = 80.35°, Yγ = 74.35°, and V = 1944.9 Å3 at 250 K. In addition to the linear thermal expansion of the unit cell volume, an extra expansion due to the low-spin (LS) to high-spin (HS) transition is observed. The V(T) function shows a sudden increase comparable with the step in the effective magnetic moment at the transition region (140 K). A similar behavior is obtained on the basis of the infrared spectra. The absorption bands corresponding to the metal-ligand stretching modes change their intensities upon heating: the bands corresponding to the low-spin molecules (at ca. 409, 430, 443, and 460 cm-1) disappear in the gain of the high-spin bands (at 259 and 285 cm-1). The variable-temperature data obtained by different techniques (powder diffraction, EXAFS, IR spectra, Mössbauer spectra, magnetic susceptibility, DSC) have been transformed to a common basis - the temperature dependence of the high-spin mole fraction xHS(T). The application of the Ising-like (two-level) model of the spin crossover led to the thermodynamic data ΔH = 2.6 kJ mol-1 and ΔS = 19 J K-1 mol-1 as well as to the cooperativeness J/kæ 110 K (subtracted from the susceptibility data) that characterizes the abruptness of the spin crossover in the solid state.
UR - http://www.scopus.com/inward/record.url?scp=0042830493&partnerID=8YFLogxK
U2 - 10.1016/S0301-0104(03)00375-6
DO - 10.1016/S0301-0104(03)00375-6
M3 - Article
AN - SCOPUS:0042830493
VL - 293
SP - 375
EP - 395
JO - Chemical physics
JF - Chemical physics
SN - 0301-0104
IS - 3
ER -