Comparative study on energetic distortions of SO42- ions matrix-isolated in compounds with kröhnkite-type chains, K2Me(CrO4)2×2H2O and Na2Me(SeO4)2×2H2O (Me = Mg, Co, Ni, Zn, Cd)
- Autor(en)
- Manfred Wildner, Donka Stoilova, Mitko Georgiev, D. Marinova
- Abstrakt
Infrared spectra of compounds with kröhnkite-type infinite octahedral-tetrahedral chains, K2Me(CrO4)2×2H2O and Na2Me(SeO4)2×2H2O (Me = Mg, Co, Ni, Zn, Cd), as well as infrared spectra of the title double salts containing matrix-isolated SO42- guest ions are presented and discussed in the regions of the X-O stretching modes.The SO42- guest ions matrix-isolated in selenate and chromate matrices exhibit four infrared bands corresponding to the four site-group components of the stretching modes in good agreement with the low site symmetry of the host ions (C1 site symmetry). The values of delta ny3 (site-group splitting) and delta ny max (the difference between the highest and the lowest wavenumbered components of the stretching modes) are used as an adequate measure for the extent of energetic distortion of the matrix-isolated SO42- guest ions.The influence of different crystal-chemical parameters (Me2+-OXO3 bond strengths, sizes of the Me2+ and Me+ ions, electronic configurations of the Me2+ ions, hydrogen bond strengths, and unit-cell volumes of the host compounds) on the extent of energetic distortion of both the host SeO42- and CrO42- ions, and the SO42- guest ions is analyzed. Correlations between the values of delta ny3 and delta ny max of the guest ions and both the degree of covalency of the respective Me2+-OXO3 bonds and the electronic configurations of the Me2+ ions have been found and will be discussed. For example, the energetic distortion of SO42- ions included in the chromate lattices decreases in the order Zn > Cd > Mg as a result of the decreasing covalency of the respective Me2+-O bonds in the same order delta ny3 have values of 73, 58 and 36 cm-1, respectively). Furthermore, the values of delta ny 3 and delta ny max are larger when the metal ions have CFSE ? 0 (crystal field stabilization energy, Co2+, Ni2+). These cations are more resistant to angular deformations of the MeO6 octahedra (i.e. changes in the O-Me-O bond angles), thus facilitating the extent of distortion of the matrix-isolated SO42- ions as compared to those having CFSE = 0 (Mg2+, Zn2+ and Cd2+). For example, delta ny3 and delta ny max of SO42- ions matrix-isolated in K2Zn(CrO4)2×2H2O have values of 73 and 163 cm-1, and 116 and 207 cm-1 in Na2Zn(SeO4)2×2H2O, whereas in the respective nickel lattices delta ny3 and delta ny max have values of 88 and 173 cm-1 (K2Ni(CrO4)2×2H2O) and 127 and 212 cm-1 (Na2Ni(SeO4)2×2H2O).The SO42- guest ions included in selenate matrices, Na2Me(SeO4)2×2H2O, are remarkably much distorted than in chromate ones, K2Me(CrO4)2×2H2O, as deduced from the values of delta ny3 and delta ny max owing to a stronger static field caused by the smaller Na+ ions as compared to that caused by the larger K+ ions. The smaller unit-cell volumes of the selenate host compounds, i.e. the higher repulsion potential at the lattice sites at which the guest ions are situated additionally favor the extent of energetic distortion of the sulfate guest ions in the selenate matrices.
- Organisation(en)
- Institut für Mineralogie und Kristallographie
- Externe Organisation(en)
- Bulgarian Academy of Sciences (BAS), University of Chemical Technology and Metallurgy
- Journal
- Solid State Sciences
- Band
- 11
- Seiten
- 2044-2050
- Anzahl der Seiten
- 7
- ISSN
- 1293-2558
- Publikationsdatum
- 2009
- Peer-reviewed
- Ja
- ÖFOS 2012
- 105113 Kristallographie
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/eec81422-9771-4c89-aedc-97fe8c1f8cbe