Comments on the paper “planar dynamic Jahn-Teller effect in nitrocomplexes”

Harrowfield, B.V.

doi:10.1016/0038-1098(76)90635-9

Cited by 10 publications

(4 citation statements)

References 5 publications

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“…The values g || ) 2.060 and g ⊥ ) 2.288 observed for (ND 4 ) 2 [Cu(D 2 O) 6 ](SO 4 ) 2 at 0.5 kbar indicate a rather large orbital contribution to g || , however, which contradicts such a supposition (see below). The situation seems to be similar to that reported for γ-Cs 2 PbCu-(NO 2 ) 6 (g || ) 2.06, g ⊥ ) 2.15) 39 and (3-chloroanilinium) 8 [CuCl 6 ]-Cl 4 (g || ) 2.06, g ⊥ ) 2.19). 40 For these latter compounds, it was initially assumed that the copper(II) complex has a tetragonally compressed octahedral geometry, 39,40 but in both cases it was subsequently shown 41,42 that at the local level, an orthorhombically distorted tetragonally elongated geometry occurs.…”

Section: Resultssupporting

confidence: 86%

“…The situation seems to be similar to that reported for γ-Cs 2 PbCu-(NO 2 ) 6 (g || ) 2.06, g ⊥ ) 2.15) 39 and (3-chloroanilinium) 8 [CuCl 6 ]-Cl 4 (g || ) 2.06, g ⊥ ) 2.19). 40 For these latter compounds, it was initially assumed that the copper(II) complex has a tetragonally compressed octahedral geometry, 39,40 but in both cases it was subsequently shown 41,42 that at the local level, an orthorhombically distorted tetragonally elongated geometry occurs. The corresponding ground state potential surface would be one in which the two minima are energetically equivalentsa situation approximately intermediate between those depicted in Figure 3.…”

Section: Resultssupporting

confidence: 86%

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Pressure Dependence of the Crystal Structures and EPR Spectra of Potassium Hexaaquacopper(II) Sulfate and Deuterated Ammonium Hexaaquacopper(II) Sulfate

et al. 1996

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The crystal structures of (ND4)2[Cu(D2O)6](SO4)2 at 295 K, determined by X-ray diffraction at pressures of 1 bar, ∼1.5 kbar and ∼3.0 kbar, are reported. Between 1 bar and 1.5 kbar, the crystal structure changes to one almost identical to that of the corresponding hydrogenous compound at 1 bar. The structural change involves a 90° switch in the direction of the long bonds of the Cu(D2O)6 2+ ion, accompanied by a change in the hydrogen-bonding interactions of the ammonium cations. Comparison of these two structures with those at ∼15 K shows that at room temperature, for both the high (H) and low (L) pressure phases, the Cu complexes are in thermal equilibrium with the other structural isomer. Though one of these is energetically preferred in the H and the other in the L phase, the variation of the powder EPR spectrum with pressure indicates a continuous transition between both within ∼1 kbar and suggests that at ∼0.5 kbar the two orientations of the copper complex are similar in energy. However, the underlying thermally induced equilibrium is little affected by pressure, and this is also the case for the Cu(H2O)6 2+ ion in Cu2+-doped K2[Zn(H2O)6](SO4)2. The crystal structure of K2[Cu(H2O)6](SO4)2 at 15 K and 1.4 kbar, determined by time-of-flight neutron diffraction, is similar to that at 295 K and 1 bar, except for indications that here also a thermal population of the higher energy form in which the directions of the long and intermediate Cu−O bonds interchange occurs at 295 K. The powder EPR spectrum of the potassium salt at 295 K shows little change between 1 bar and 11 kbar.

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Section: Resultssupporting

confidence: 86%

Section: Resultssupporting

confidence: 86%

Pressure Dependence of the Crystal Structures and EPR Spectra of Potassium Hexaaquacopper(II) Sulfate and Deuterated Ammonium Hexaaquacopper(II) Sulfate

et al. 1996

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“…Here, the interactions between neighboring complexes are not cushioned by hydrogen-bonding effects, so the cooperative interactions are probably stronger than those in the Tutton salts, though considerably weaker than those in continuous lattices involving bridging ligands. In the γ phase of K 2 Pb[Cu(NO 2 ) 6 ], which is the stable form below 273 K, it is now known that the Cu(NO 2 ) 6 4- ions have a tetragonally elongated octahedral geometry, with the long and one pair of short Cu−N bonds arranged in a two-dimensional antiferrodistortive packing arrangement (originally, the X-ray and EPR data were misinterpreted as indicating a ferrodistortive arrangement of tetragonally compressed octahedra). Above 280 K, a sharp phase transition to the α cubic phase occurs.…”

Section: Resultsmentioning

confidence: 99%

Cooperative Jahn−Teller Interactions in Dynamic Copper(II) Complexes. Temperature Dependence of the Crystal Structure and EPR Spectrum of Deuterated Ammonium Copper(II) Sulfate Hexahydrate

et al. 1999

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The crystal structure of the deuterated Tutton salt (ND 4 ) 2 [Cu(D 2 O) 6 ](SO 4 ) 2 determined by X-ray diffraction at several temperatures between 100 and 321 K is reported. The intermediate and longest Cu-O bond lengths of the Jahn-Teller distorted octahedral Cu(D 2 O) 6 2+ ion progressively converge as the temperature is raised above ∼200 K, and this is accompanied by a partial rotation of the ammonium and sulfate groups. The g-values derived from the EPR spectrum of the compound exhibit similar behavior, as do those of ∼1% Cu 2+ doped into the isomorphous zinc(II) compound. The temperature dependence of the g-values of Cu 2+ -doped (ND 4 ) 2 [Zn(D 2 O) 6 ](SO 4 ) 2 may be interpreted satisfactorily by a model which assumes a Boltzmann thermal distribution between two energy states which differ solely in the orientation of the Cu(D 2 O) 6 2+ ion in the lattice. However, such a model does not satisfactorily explain the behavior of pure (ND 4 ) 2 [Cu(D 2 O) 6 ](SO 4 ) 2 , and it is suggested that this is due to cooperative interactions. A new model, in which the probable energy state of each complex is estimated after taking into account the likely orientations of its neighbors in the lattice, is described. Application of this model suggests that the thermal behavior is dominated by the cooperative interactions between complexes, these being transmitted via the hydrogen-bonding network. Comparisons are drawn with the cooperative interactions observed in more strongly coupled Jahn-Teller systems and in compounds for which the structural changes are associated with equilibria between two spin states.

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“…Crystal Structure of the Usual R2Pb[Cu(N02)6 J Type ComplexesAs for the structure o f the lowest tem p eratu re phase o f K 2P b [C u (N 0 2)6], H arrow field et al[7,8] assum ed a ferrodistortive o rd er in w hich all the [ C u ( N 0 2)6]4~ o ctah ed ra are tetragonally com pressed along [001] axis. O n th e o th er hand, R einen et al [ 9 -1 1 ] proposed an altern ativ e m odel from their ESR results w hich have been explained by an an ti ferrodistortive ord ered system consisting o f tw o crystallographically n o n eq u iv alen t [C u (N 0 2)6]4_ octa h ed ra elongated along [ 100] and [010] crystal axes.…”

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confidence: 99%

An ESR Study of Structural Phase Transitions of(NH₄)₂Pb[Cu(NO₂)₆]

Asaji

Prabhumirashi

Nakamura

1986

Zeitschrift Für Naturforschung A

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The structural changes o f (N H 4) 2P b [C u (N 0 2)6] crystals during the phase transitions at 316, 287, and 95 K were studied by means o f a single crystal ESR technique. Anisotropic g values [9 > 9±) were obtained in the lowest temperature phase IV, whereas the ESR spectra recorded in the intermediate phases III and II, in which the crystal is known to be tetragonally compressed along the c axis, could be interpreted by use o f effective g values [g ( c) < g (_L c)]. In the highest temperature phase I an isotropic g value was obtained. The phases I, II, and III o f the present complex can be assumed to be very similar to the corresponding phases observed above ~ 250 K for the com pounds R2P b [C u (N 0 2) 6] with R = K, Rb, Cs, and Tl. However, the lowest temperature phase transition transforms the phase III with an antiferrodistortive order o f the elongated [C u (N 0 2)6]4_ octahedra into the phase IV with a ferrodistortive one. This occurs only for the complex with R = N H 4 and is very unusual. The results o f the 14N N Q R experiments already reported for the phases III and IV could be well explained by the present newly proposed model.

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Comments on the paper “planar dynamic Jahn-Teller effect in nitrocomplexes”

Cited by 10 publications

References 5 publications

Pressure Dependence of the Crystal Structures and EPR Spectra of Potassium Hexaaquacopper(II) Sulfate and Deuterated Ammonium Hexaaquacopper(II) Sulfate

Pressure Dependence of the Crystal Structures and EPR Spectra of Potassium Hexaaquacopper(II) Sulfate and Deuterated Ammonium Hexaaquacopper(II) Sulfate

Cooperative Jahn−Teller Interactions in Dynamic Copper(II) Complexes. Temperature Dependence of the Crystal Structure and EPR Spectrum of Deuterated Ammonium Copper(II) Sulfate Hexahydrate

An ESR Study of Structural Phase Transitions of(NH₄)₂Pb[Cu(NO₂)₆]

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Comments on the paper “planar dynamic Jahn-Teller effect in nitrocomplexes”

Cited by 10 publications

References 5 publications

Pressure Dependence of the Crystal Structures and EPR Spectra of Potassium Hexaaquacopper(II) Sulfate and Deuterated Ammonium Hexaaquacopper(II) Sulfate

Pressure Dependence of the Crystal Structures and EPR Spectra of Potassium Hexaaquacopper(II) Sulfate and Deuterated Ammonium Hexaaquacopper(II) Sulfate

Cooperative Jahn−Teller Interactions in Dynamic Copper(II) Complexes. Temperature Dependence of the Crystal Structure and EPR Spectrum of Deuterated Ammonium Copper(II) Sulfate Hexahydrate

An ESR Study of Structural Phase Transitions of(NH4)2Pb[Cu(NO2)6]

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An ESR Study of Structural Phase Transitions of(NH₄)₂Pb[Cu(NO₂)₆]