Mössbauer Spectroscopy of Intercalation Compounds

Herber, Rolfe H.; Eckert, Hellmut

doi:10.1007/978-1-4613-2431-7_6

Cited by 9 publications

(9 citation statements)

References 118 publications

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“…As is already known [20], for four coordination with oxygen ligands a value for IS of 1 mm/s is expected at temperatures below 77 K, whereas sixcoordination leads to IS > 1.2 mm/s. This is explained with shorter bond lengths in four-coordination mode with respect to six-coordination one, which would increase the s-density at Fe nucleus and hence reduce the isomer shift.…”

Section: Experimental Datasupporting

confidence: 62%

A Mössbauer study on iron(II) complex of 2-acetyl-1,3-indandione ⎼ spin-crossover or structural changes

2014

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KEYWORDSAn air stable Fe(II) complex of a cyclic β-triketone, 2-acetyl-1,3-indandione (2AID) was obtained in two different ways and studied by Mössbauer spectroscopy. The Mössbauer data at room temperature point to six-coordinated, high spin Fe(II) complex. The temperaturedependent measurements indicate a phase transition in going from 293 to 77 K. Further lowering the temperature, however, do not cause the expected changes for spin-crossover transition. This data provoked application of quantum chemical methods to determine the origin of the observed appearance of spectral component attributable to low spin Fe(II) complex at 77 K. Based on the results from the theoretical calculations of the Mössbauer parameters of several different geometries and spin states of the Fe complexes of 2AID it was possible to conclude that the obtained Fe(II) complex has a pseudo-octahedral geometry. The experimentally observed temperature-dependence of the Mössbauer spectra is attributed to changes of the axial Fe-O bonds, rather than to spin transition. Discussion is given on the role of the type of the axial ligands for conditioning a spin-crossover process, as suggestion for experimental modelling of novel target materials with desired magnetic properties.

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Section: Experimental Datasupporting

confidence: 62%

A Mössbauer study on iron(II) complex of 2-acetyl-1,3-indandione ⎼ spin-crossover or structural changes

2014

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“…A better analogy seems to exist between interstitially doped P-rhombohedra1 boron and certain types of intercalation compounds, where depending on the specific electronic structures in some cases a complete charge transfer from the guest metal atoms to the host structures is proved [27]. Therefore the high degree of charge transfer between the Fe atoms and the boron framework determined in Table 4 seems to be largely realistic.…”

Section: Relation To the Electronic Propertiesmentioning

confidence: 94%

Ionization of Interstitial Iron Atoms in β‐Rhombohedral Boron

Kuhlmann

Werheit

Pelloth³

et al. 1995

Physica Status Solidi (b)

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Mössbauer spectra of β‐rhombohedral boron with interstitially distributed iron atoms up to 3.33 at% are presented. Taking into account that the six D sites in the unit cell are saturated by two Fe atoms, the distribution of the Fe atoms on A and D sites proved to be simply statistical. At lower Fe contents single iron atoms on A sites are ionized to Fe3+, while towards higher Fe contents a rapidly increasing share of Fe2+ ions is found. On D sites the ionization of single Fe atoms is 2+, but it changes to 3+, when two Fe atoms are accommodated in the D sites of one unit cell. The isomer shift of the Mössbauer doublets yields an estimation of the electron transfer to the boron framework. Transition from p‐ to n‐type takes place, when six electrons per unit cell are transferred from the iron ions to the boron framework. This number corresponds to the sum of the unoccupied sites in the upper valence band and the possible electron traps generated by an electron–phonon interaction in the B12 icosahedra.

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“…This conclusion is further supported by the temperature dependence of the isomer shift, δ, and the Mo ¨ssbauer spectral absorption area. 36,37 The observed effective recoil-free masses, M eff , reported in Table 2 are typical of the high covalency expected of the iron-ligand bonds found in these com-Figure 5. 13 pounds.…”

Section: Resultsmentioning

confidence: 70%

Solid State Dynamics of Tricarbonyl(η-1,5-cyclohexadienylium)iron Tetrafluoroborate and Tricarbonyl(η-1,5-cycloheptadienylium)iron Tetrafluoroborate

et al. 1996

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The dynamic behavior of [(C(6)H(7))Fe(CO)(3)]BF(4) (I) and [(C(7)H(9))Fe(CO)(3)]BF(4) (II) in the solid state has been investigated principally by NMR spectroscopy. High-resolution variable-temperature (1)H and (13)C NMR spectra indicate that both complexes have a solid state phase transition above which there is rapid reorientation of the cyclodienylium rings and fast exchange of the carbonyl groups. The transition occurs between 253 and 263 K for I and between 329 and 341 K for II. The presence of the phase transition is confirmed by differential scanning calorimetry (DSC). (57)Fe Mössbauer spectroscopy supports the notion that complex I is highly mobile at room temperature, while II is relatively static. The activation energy for the cyclodienylium group rotation in the high-temperature phase of I is estimated from (1)H spin-lattice relaxation time measurements to be 17.5 kJ mol(-)(1). Static (13)C NMR measurements of the solid complexes in the high-temperature phase indicate that the (13)C chemical shift anisotropies are only 20-30 ppm. This is significantly less than that expected to result from motion of individual groups and thus suggests that rotation of the whole molecule is involved. A single-crystal X-ray structural determination of complex II, at 295 K, showed that the complex is tetragonal (space group P4(1), a = 10.610(1) Å, c = 21.761(3) Å, V = 2449.7(5) Å(3), rho(calc) = 1.734 g cm(-)(3)), with eight cycloheptadienyl cations and eight tetrafluoroborate anions per unit cell. In addition, powder X-ray diffraction studies of both I and II confirm that at low temperatures both complexes have a tetragonal unit cell, which transforms to a cubic unit cell above the phase transition. The powder patterns, recorded above the phase transition, support the proposal that the complexes are undergoing whole-molecule tumbling in their dynamic regimes.

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Mössbauer Spectroscopy of Intercalation Compounds

Cited by 9 publications

References 118 publications

A Mössbauer study on iron(II) complex of 2-acetyl-1,3-indandione ⎼ spin-crossover or structural changes

A Mössbauer study on iron(II) complex of 2-acetyl-1,3-indandione ⎼ spin-crossover or structural changes

Ionization of Interstitial Iron Atoms in β‐Rhombohedral Boron

Solid State Dynamics of Tricarbonyl(η-1,5-cyclohexadienylium)iron Tetrafluoroborate and Tricarbonyl(η-1,5-cycloheptadienylium)iron Tetrafluoroborate

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