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#### Spectroscopic, magnetochemical, and crystallographic study of cesium iron phosphate hexahydrate: Characterization of the electronic structure of the iron(II) hexa-aqua cation in a quasicubic environment

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##### Citation

Carver, G., Dobe, C., Jensen, T. B., Tregenna-Piggott, P. L. W., Janssen, S., Bill, E., et al. (2006).
Spectroscopic, magnetochemical, and crystallographic study of cesium iron phosphate hexahydrate: Characterization of the electronic
structure of the iron(II) hexa-aqua cation in a quasicubic environment.* Inorganic Chemistry,*
*45*(12), 4695-4705.

Cite as: https://hdl.handle.net/21.11116/0000-000F-012F-C

##### Abstract

Spectroscopic, magnetochemical, and crystallographic data are presented

for CsFe(H2O)(6)PO4, a member of a little-known isomorphous series of

salts that facilitates the study of hexa-aqua ions in a quasicubic

environment. Above 120 K, the deviations from cubic symmetry are

minimal, as shown by the first example of an iron(II) Mossbauer

spectrum that exhibits no measurable quadrupole splitting. Two

crystallographically distinct [Fe(OH2)(6)](2+) complexes are identified

from inelastic neutron-scattering (INS) experiments conducted between 2

and 15 K. The data are modeled with the ligand-field Hamiltonian, (H)

over cap = lambda(L) over cap(S) over cap + beta B(k (L) over cap +2

(S) over cap)+Delta(tet){(L) over cap (2)(z)-(1/3)L(L+1)} + Delta(rhom)

{(L) over cap (2)(x)-(L) over cap (2)(y)}, operating in the ground-term

T-5(2g) (O-h) basis. An excellent reproduction of INS, Mossbauer,

HF-EPR, and magnetochemical data are obtained in the 2 and 15 K

temperature regimes with the following parameters: I) - 80 cm(-1); k =

0.8; site A Delta(tet) = 183 cm(-1), Delta(rhom) = 19 cm(-1); site B

Delta(tet) = 181 cm(-1), Delta(rhom) = 12 cm(-1). The corresponding

zero-field-splitting (ZFS) parameters of the conventional S = 2 spin

Hamiltonian are as follows: site A D = 12.02 cm(-1), E = 2.123 cm(-1);

site B D = 12.15 cm(-1), E = 1.37 cm(-1). A theoretical analysis of the

variation of the energies of the low-lying states with respect to

displacements along selected normal coordinates of the

[Fe(OH2)(6)](2+), shows the zero-field splitting to be extremely

sensitive to small structural perturbations of the complex. The

expressions derived are discussed in the context of spin-Hamiltonian

parameters reported for the [Fe(OH2)(6)](2+) cation in different

crystalline environments.

for CsFe(H2O)(6)PO4, a member of a little-known isomorphous series of

salts that facilitates the study of hexa-aqua ions in a quasicubic

environment. Above 120 K, the deviations from cubic symmetry are

minimal, as shown by the first example of an iron(II) Mossbauer

spectrum that exhibits no measurable quadrupole splitting. Two

crystallographically distinct [Fe(OH2)(6)](2+) complexes are identified

from inelastic neutron-scattering (INS) experiments conducted between 2

and 15 K. The data are modeled with the ligand-field Hamiltonian, (H)

over cap = lambda(L) over cap(S) over cap + beta B(k (L) over cap +2

(S) over cap)+Delta(tet){(L) over cap (2)(z)-(1/3)L(L+1)} + Delta(rhom)

{(L) over cap (2)(x)-(L) over cap (2)(y)}, operating in the ground-term

T-5(2g) (O-h) basis. An excellent reproduction of INS, Mossbauer,

HF-EPR, and magnetochemical data are obtained in the 2 and 15 K

temperature regimes with the following parameters: I) - 80 cm(-1); k =

0.8; site A Delta(tet) = 183 cm(-1), Delta(rhom) = 19 cm(-1); site B

Delta(tet) = 181 cm(-1), Delta(rhom) = 12 cm(-1). The corresponding

zero-field-splitting (ZFS) parameters of the conventional S = 2 spin

Hamiltonian are as follows: site A D = 12.02 cm(-1), E = 2.123 cm(-1);

site B D = 12.15 cm(-1), E = 1.37 cm(-1). A theoretical analysis of the

variation of the energies of the low-lying states with respect to

displacements along selected normal coordinates of the

[Fe(OH2)(6)](2+), shows the zero-field splitting to be extremely

sensitive to small structural perturbations of the complex. The

expressions derived are discussed in the context of spin-Hamiltonian

parameters reported for the [Fe(OH2)(6)](2+) cation in different

crystalline environments.