Small rotational barriers for H2O flips in phase III of [Me(H2O)6](ClO4)2 with Me=Mg, Ni, and Zn

Nöldeke, C.; Asmussen, B.; Press, W.; Büttner, Herma; Kearley, GJ

doi:10.1016/s0301-0104(03)00054-5

Cited by 14 publications

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References 13 publications

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“…Similar values of activation energy for 180° jumps of H 2 O around M–O bond were observed in [Mg(H 2 O) 6 ](ClO 4 ) 2 , where E a (180°) = 5.0 kJ mol –1 in phases I and II, and E a (180°) = 10.0 kJ mol –1 in phase III, as derived from quasielastic neutron scattering measurements . This is in good agreement with the data obtained also by Nöldeke et al . According to them, activation energies for 180°‐reorientations of H 2 O groups in phases I and II is E a (180°) = 4.1 kJ mol –1 (43 meV) for [Mg(H 2 O) 6 ](ClO 4 ) 2 , and E a (180°) = 5.9 kJmol –1 (6.1 meV) for [Ni(H 2 O) 6 ](ClO 4 ) 2 .…”

Section: Resultssupporting

confidence: 92%

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Raman light scattering, infrared absorption and DSC studies of the phase transition and vibrational and reorientational dynamics of H₂O ligands and ClO₄^– anions in [Ba(H₂O)₃](ClO₄)₂

Hetmańczyk

Migdał-Mikuli

et al. 2012

J Raman Spectroscopy

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[Ba(H2O)3](ClO4)2 between 90 and 300 K possesses two solid phases. One phase transition of the first‐order type at: TCh = 211.3 K (on heating) and TCc = 204.6 K (on cooling) was determined by differential scanning calorimetry. The entropy change value (ΔS ≈ 15 Jmol–1 K–1), associated with the observed phase transition, indicates a moderate degree of molecular dynamical disorder. Both, vibrational and reorientational motions of H2O ligands and ClO4– anions, in the high‐temperature and low‐temperature phases, were investigated by Fourier transform far‐infrared and middle‐infrared and Raman light scattering spectroscopies. The temperature dependences of the full‐width at half‐maximum values of the bands associated with ρw(H2O) mode, in both infrared (~570 cm–1) and Raman light scattering (~535 cm–1) spectra, suggest that the observed phase transition is not associated with a sudden change of a speed of the H2O reorientational motions. Ligands reorient fast, with correlation time of the order of several picoseconds, with a mean activation energy value Ea = 5.1 kJ mol–1 in both high and low temperature phases. On the other hand, measurements of temperature dependences of full‐width at half‐maximum values of the infrared band at ~460 cm–1, associated with δd(OClO)E mode, and Raman band at ~1105 cm–1, associated with νas(ClO)F2 mode, revealed the existence of a fast ClO4– reorientation in phase I and in phase II, with the Ea(I) and Ea(II) values equal to 8.0 and 6.5 kJ mol–1, respectively. These reorientational motions of ClO4– are slightly distorted at the TC. Fourier transform far‐infrared and middle‐infrared spectra with decreasing of temperature indicated characteristic changes at the vicinity of PT at TC, which suggested lowering of the crystal structure symmetry. All these experimental facts suggest that the discovered phase transition is associated with small change of H2O ligands and somewhat major change of ClO4– anions reorientational dynamics, and with insignificant change of the crystal structure, too. Copyright © 2012 John Wiley & Sons, Ltd.

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Section: Resultssupporting

confidence: 92%

“…According to them, activation energies for 180°‐reorientations of H 2 O groups in phases I and II is E a (180°) = 4.1 kJ mol –1 (43 meV) for [Mg(H 2 O) 6 ](ClO 4 ) 2 , and E a (180°) = 5.9 kJmol –1 (6.1 meV) for [Ni(H 2 O) 6 ](ClO 4 ) 2 . Rather small energy activation values suggest that the hydrogen bonds are weak …”

Section: Resultsmentioning

confidence: 99%

Raman light scattering, infrared absorption and DSC studies of the phase transition and vibrational and reorientational dynamics of H₂O ligands and ClO₄^– anions in [Ba(H₂O)₃](ClO₄)₂

Hetmańczyk

Migdał-Mikuli

et al. 2012

J Raman Spectroscopy

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“…Moreover the authors reported that the activation energy barrier (E a ≈ 60 meV = 5.8 kJ/mol) is low for a high‐temperature transition. We were not able to determine the value of activation energy from our QENS results, but the value obtained from IR band shape analysis (E a = 7.7 kJ/mol) is comparable with data reported in three sources …”

Section: Resultssupporting

confidence: 52%

“…It can be concluded that water molecules perform reorientational jumps around a twofold symmetry axis. Reorientational motion of H 2 O ligands was also observed for compounds which were similar but contained another tetrahedral anion, namely, perchlorate instead of perrhenate . These compounds exhibit more complex polymorphism and three phase transitions are registered in a temperature range of 20–350 K. However, the conclusions extracted from neutron scattering investigations are similar.…”

Section: Resultsmentioning

confidence: 69%

Dynamics of H₂O ligands and ReO₄⁻ anions at the phase transition in [Mn(H₂O)₂](ReO₄)₂ studied by complementary spectroscopic methods

Hetmańczyk

2017

J Raman Spectroscopy

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The vibrational and reorientational motions of H2O ligands and ReO4− anions in high‐ and low‐temperature phases were investigated by means of Fourier transform far‐ and mid‐infrared and Raman light‐scattering spectroscopy and neutron scattering (inelastic/quasi‐elastic incoherent neutron scattering) methods. The dynamics of H2O and ReO4− molecules in high‐ (I) and low‐temperature (II) phases was investigated by means of band shape analysis performed for Raman and IR bands. The temperature dependencies of full width at half maximum values of the Raman bands at 874 (νas(ReO)) and 943 cm−1 (νs(ReO)) exhibit changes in their behaviour in the vicinity of transformation, suggesting that the observed phase transition is connected with a change in the reorientational dynamics of ReO4−. However, anions also perform fast (τR ≈ 10−12 to 10−13 s) stochastic reorientational motions in Phase II. The estimated mean value of activation energy for ReO4− anions in the low‐temperature phase is Ea(II) = 8.1 kJmol−1. In infrared band shape analysis it was found that H2O ligands perform fast (picosecond correlation time scale) motions in both phases with a mean value of activation energies of 7.68 kJmol−1. These reorientational motions of H2O ligands do not contribute to the phase transition mechanism. Moreover, the observed phase transition was accompanied by the splitting of some bands, suggesting a reduction in crystal structure symmetry. Quasi‐elastic neutron scattering measurements furnished evidence that H2O motion in Phase I can be fairly accurately described by a simple model of 180° jumps around a twofold axis within a picosecond time scale. Additionally, infrared, Raman light‐scattering spectra were calculated using the density functional theory method for the isolated equilibrium model Mn(H2O)2(ReO4)2, and qualitative agreement with the experimental data was achieved. The theoretical vibrational spectra of the title compound were interpreted by means of potential energy distributions using the VEDA 4 program.

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“…It is convenient to analyze the quasielastic neutron scattering data in terms of an elastic incoherent structure factor EISF defined as follows [14,15]:…”

Section: Inelastic and Quasielastic Neutron Scattering Vs Temperaturementioning

confidence: 99%

Phase transition in [Ca(NH3)6](ClO4)2 studied by neutron scattering methods and far infrared spectroscopy

Hetmańczyk

Migdał-Mikuli

et al. 2011

Journal of Alloys and Compounds

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Small rotational barriers for H2O flips in phase III of [Me(H2O)6](ClO4)2 with Me=Mg, Ni, and Zn

Cited by 14 publications

References 13 publications

Raman light scattering, infrared absorption and DSC studies of the phase transition and vibrational and reorientational dynamics of H₂O ligands and ClO₄^– anions in [Ba(H₂O)₃](ClO₄)₂

Raman light scattering, infrared absorption and DSC studies of the phase transition and vibrational and reorientational dynamics of H₂O ligands and ClO₄^– anions in [Ba(H₂O)₃](ClO₄)₂

Dynamics of H₂O ligands and ReO₄⁻ anions at the phase transition in [Mn(H₂O)₂](ReO₄)₂ studied by complementary spectroscopic methods

Phase transition in [Ca(NH3)6](ClO4)2 studied by neutron scattering methods and far infrared spectroscopy

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Small rotational barriers for H2O flips in phase III of [Me(H2O)6](ClO4)2 with Me=Mg, Ni, and Zn

Cited by 14 publications

References 13 publications

Raman light scattering, infrared absorption and DSC studies of the phase transition and vibrational and reorientational dynamics of H2O ligands and ClO4– anions in [Ba(H2O)3](ClO4)2

Raman light scattering, infrared absorption and DSC studies of the phase transition and vibrational and reorientational dynamics of H2O ligands and ClO4– anions in [Ba(H2O)3](ClO4)2

Dynamics of H2O ligands and ReO4− anions at the phase transition in [Mn(H2O)2](ReO4)2 studied by complementary spectroscopic methods

Phase transition in [Ca(NH3)6](ClO4)2 studied by neutron scattering methods and far infrared spectroscopy

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Raman light scattering, infrared absorption and DSC studies of the phase transition and vibrational and reorientational dynamics of H₂O ligands and ClO₄^– anions in [Ba(H₂O)₃](ClO₄)₂

Raman light scattering, infrared absorption and DSC studies of the phase transition and vibrational and reorientational dynamics of H₂O ligands and ClO₄^– anions in [Ba(H₂O)₃](ClO₄)₂

Dynamics of H₂O ligands and ReO₄⁻ anions at the phase transition in [Mn(H₂O)₂](ReO₄)₂ studied by complementary spectroscopic methods