Effect of Pressure on the Thermal Expansionof Mixed-Valence Compound CeNi

Intramolecular electron transfer (ET) in mixed valence (MV) oxo-centered [FeiiFeiii2O(carboxylate)6(ligand)3]·solvent complexes is highly dependent on temperature, on the nature of the ligands, and on the presence of crystal solvent molecules [1]. Whereas the effects of temperature, crystal solvent, and ligand variation on the details of the ET have been explored thoroughly, the effect of pressure is less well described [2]. The effect of pressure on the ET in MV Fe3O(cyanoacetate)6(water)3has been investigated with single crystal X-ray diffraction and Mössbauer spectroscopy. Previous multi-temperature studies have shown that at room temperature the ET between the three Fe sites is fast and the observed structure of the Fe3core is a perfectly equilateral triangle [3]. Cooling the complex below 130 K induces a phase transition as the ET slows down. Below 120 K the Fe3core is distorted due to the localization of the itinerant electron on one of the three Fe sites in the triangle (the complex is then in the valence trapped state). The valence trapping is complete within a temperature interval of just 10 K. The abruptness of the transition has been attributed to the extended hydrogen bond network involving water ligands and cyano groups, promoting intermolecular cooperative effects. The high-pressure X-ray diffraction data show that there is a 900flip of half the cyano groups at 3.5 GPa, which dramatically changes the hydrogen bond network. At a slightly higher pressure, a phase transition is found to occur. The five single crystals investigated all broke into minor fragments at the transition; however triclinic unit cells, similar to the low temperature unit cell, could be indexed from selected spots. Additional evidence that the complex is valence trapped comes from high pressure Mössbauer spectra measured above the phase transition (4 GPa). The relationship between valence trapping and the structural changes will in this work be highlighted using void space and Hirshfeld surface analysis.

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Structure of the mixed-valence compound dipotassium tribromo(pyridine)platinate(II) pentabromo(pyridine)platinate(IV) dihydrate

Acta Crystallographica Section B ◽

10.1107/s0567740882007560 ◽

1982 ◽

Vol 38 (7) ◽

pp. 1901-1906 ◽

Cited By ~ 3

Author(s):

A. L. Beauchamp ◽

D. Layek ◽

T. Theophanides

Keyword(s):

Mixed Valence ◽

Mixed Valence Compound

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Crystal structure and properties of a new mixed-valence compound LiMn2TeO6 and the survey of the LiMM′XO6 family (X = Sb or Te)

Solid State Sciences ◽

10.1016/j.solidstatesciences.2011.08.019 ◽

2011 ◽

Vol 13 (11) ◽

pp. 1931-1937 ◽

Cited By ~ 6

Author(s):

A.A. Pospelov ◽

V.B. Nalbandyan ◽

E.I. Serikova ◽

B.S. Medvedev ◽

M.A. Evstigneeva ◽

...

Keyword(s):

Crystal Structure ◽

Mixed Valence ◽

Structure And Properties ◽

Mixed Valence Compound

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Die neuen Oxobismutate(III) Cs6Bi4O9, K9Bi5O13 und A2Bi4O7 (A = Rb, Cs) / The New Oxobismutates(III) Cs6Bi4O9, K9Bi5O13 and A2Bi4O7 (A = Rb, Cs)

Zeitschrift für Naturforschung B ◽

10.1515/znb-2002-1003 ◽

2002 ◽

Vol 57 (10) ◽

pp. 1090-1100

Author(s):

Franziska Emmerling ◽

Caroline Röhr

Keyword(s):

Single Crystal ◽

Crystal Structures ◽

Alkali Metals ◽

Mixed Valence ◽

Three Dimensional ◽

X Ray Diffraction ◽

X Ray ◽

Trigonal Bipyramidal ◽

Mixed Valence Compound

AbstractThe title compounds were synthesized at a temperature of 700 °C via oxidation of elemental Bi with the hyperoxides AO2 or via reaction of the elemental alkali metals A with Bi2O3. Their crystal structures have been determined by single crystal x-ray diffraction. They are dominated by two possible surroundings of Bi by O, the ψ-trigonal-bipyramidal three (B) and the ψ-tetrahedral four (T) coordination. Cs6Bi4O9 (triclinic, spacegroup P1̄, a = 813.82(12), b = 991.60(14), c = 1213.83(18) pm, α = 103.658(2), β = 93.694(3), γ = 91.662(3)°, Z = 2) contains centrosymmetric chain segmentes [Bi8O18]12- with six three- (T) and two four-coordinated (B) Bi(III) centers. K9Bi5O13 (monoclinic, spacegroup P21/c, a = 1510.98(14), b = 567.59(5), c = 2685.6(2) pm, β = 111.190(2)°, Z = 4) is a mixed valence compound with isolated [BivO4]3- tetrahedra and chains [BiIII4O9]6- of two T and two B coordinated Bi. In the compounds A2Bi4O7 (A = Rb/Cs: monoclinic, C2/c, a = 2037.0(3) / 2130.6(12), b = 1285.5(2) / 1301.9(7), c = 1566.6(2) / 1605.6(9) pm, β = 94.783(3) / 95.725(9)°, Z = 8) ribbons [Bi4O6O2/2]2- are formed, which are condensed to form a three-dimensional framework.

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