Infrared spectroscopic study of SO42- ions included in K2 Me(CrO4)×22H2O (Me =Mg, Cd) and crystal structure of K2Cd(CrO4)×22H2O
- Author(s)
- Manfred Wildner, Mitko Georgiev, Donka Stoilova
- Abstract
The crystal structure of K2Cd(CrO4)22H2O was detd. from single crystal X-ray diffraction data. It crystallizes triclinic (space group P 1 , a = 5.896(1) .ANG., b = 6.446(1) .ANG., c = 7.596(1) .ANG., .alpha. = 109.09(1), .beta. = 96.80(1), .gamma. = 109.29(1), V = 249.1 .ANG.3, Z = 1, R 1 = 0.023 for 2672 F o > 4.sigma.(F o) and 79 variables), isotypic with the resp. Mg-analog. The structure is build up from CdO4(H2O)2 and CrO4 groups forming kroehnkite-type octahedral-tetrahedral chains which are linked by alkali cations and hydrogen bonds to layers and further to a three-dimensional framework. Vibrational spectra (IR and Raman) of K2Mg(CrO4)22H2O and K2Cd(CrO4)22H2O as well as IR spectra of SO 4 2 - guest ions included in the chromate matrixes are presented and discussed with respect to the Cr-O and S-O stretching modes, resp. The Raman spectra of the chromate compds. reveal that the sym. stretching modes .nu. 1 of the CrO4 tetrahedra appear at higher frequencies than the lowest wavenumbered components of the asym. stretches .nu. 3. The uncoupled OD modes of matrix-isolated HDO mols. (isotopically dil. samples) shows that stronger hydrogen bonds are formed in K2Cd(CrO4)22H2O as compared to those formed in K2Mg(CrO4)22H2O owing to both the shorter hydrogen bond lengths OwO in the former compd. and the covalent character of the Cd-OH2 bonds, irresp. of the larger Cd-OH2 bond distances than the resp. Mg-OH2 bonds. The SO 4 2 - guest ions matrix-isolated in K2Mg(CrO4)22H2O and K2Cd(CrO4)22H2O exhibit three IR bands corresponding to the asym. stretching and bending modes .nu. 3 and .nu. 4, resp. Bands of small intensities corresponding to the sym. stretches .nu. 1 are also obsd. in the IR spectra. All these observations are in good agreement with the low site symmetry of the CrO 4 2 - host ions (C 1 site symmetry). The spectroscopic expts. reveals: (i) The SO 4 2 - guest ions undergo a slightly stronger energetic distortion in the cadmium compd.
- Organisation(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- Technical University of Sofia, Bulgarian Academy of Sciences (BAS)
- Journal
- Journal of Molecular Structure
- Volume
- 889
- Pages
- 12-19
- No. of pages
- 8
- ISSN
- 0022-2860
- Publication date
- 2008
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105113 Crystallography, 1030 Physics, Astronomy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/c8469a9e-d848-4d4a-9f1e-83bbf717b2ca