Beryllium selenate tetrahydrate, BeSeO4ž4H2O: Crystal structure and infrared spectroscopy
- Author(s)
- Manfred Wildner, Donka Stoilova, Mitko Georgiev, V Karadjova
- Abstract
The crystal and molecular structure of the title compound, BeSeO 4ž4H2O, as determined by single crystal X-ray diffraction and infrared spectroscopy is discussed. BeSeO4ž 4H2O crystallizes in the orthorhombic space group Cmca (at 295 K: a.920(1), b.449(1), c.764(1) , V68.8 3, Z=2, wR2=0.057 for 2035 reflections and 68 variables, R1=0.022). The crystal structure is composed of isolated Be(H2O)4 and SeO4 tetrahedra which are interconnected by strong hydrogen bonds with O w?O lengths between 2.619 and 2.661 . Contrary to expectation, the cell volume and the mean Be-O and Se-O distances increase with decreasing temperature. The structure is closely related with that of acentric tetragonal BeSO4ž4H2O, but differs in pronounced polyhedral rotations and a partial rearrangement of the hydrogen bonding scheme. The infrared spectrum of BeSeO4ž4H2O in the region of the uncoupled OD modes (matrix-isolated HDO molecules) reveals that very strong hydrogen bonds are formed in the title compound, analogical to other hydrated beryllium salts due to the strong synergetic effect of the Be2+ ions. The appearance of two bands only (2327 and 2239 cm-1) corresponding to OD stretches instead of four expected is owing to both the similar O w?O hydrogen bond distances and the strong Be-OH2 and Ow?OSeO3 interactions. The water librations which couple intensively with the translatory modes of the Be2+ ions (BeO4 skeleton vibrations) are also discussed. Matrix-isolated SO42- guest ions in BeSeO4ž4H2O display a higher local symmetry (close to Td) than the crystallographic one (C 2(x), in correlation with the host ion distortion and the large unit-cell volume of the host (repulsion potential of the lattice) if the S-O stretching modes are considered. Œ 2004 Elsevier B.V. All rights reserved.
- Organisation(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- Bulgarian Academy of Sciences (BAS), Technical University of Sofia
- Journal
- Journal of Molecular Structure
- Volume
- 707
- Pages
- 123-130
- No. of pages
- 8
- ISSN
- 0022-2860
- DOI
- https://doi.org/10.1016/j.molstruc.2004.06.033
- Publication date
- 2004
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 1051 Geology, Mineralogy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/6f3757c9-d60e-47d3-a2de-063ac4cbde7f