Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9756973 | Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy | 2005 | 7 Pages |
Abstract
The vibrational behavior of the uncoupled νOD modes and of the water librations in dittmarite-type compounds Mâ²Mâ³PO4·H2O (Mâ²Â = K+, NH4+; Mâ³Â = Mn2+, Co2+, Ni2+) is analyzed in terms of the influence of two types of metalâwater interactions (M+âH2O and M2+âH2O), the hydrogen bonding and the repulsion potential of the lattices. The M+âH2O interaction is found to be the main factor, which influences νOD. The strong K+âH2O interaction weakens in a higher degree the intramolecular OâH bonds than the corresponding M2+âH2O interactions (M2+ = Mn, Co, Ni). As a result νOD is shifted to lower wavenumbers in the potassium series than in ammonium one, irrespective of the synergetic effect of M2+, the hydrogen bond lengths and the repulsion potential of the lattices. The analysis of the spectroscopic data evidences for the dominating influence of the M2+âH2O interaction on the wagging mode. The blue shift of νwag strictly follows the increasing synergetic effect of M2+, i.e. νMâ²/Mn < νMâ²/Co < νMâ²/Ni, in all cases, irrespective of the strength of the M+âH2O interactions, the hydrogen bond lengths and the higher repulsion potential of the K-lattices. The rocking mode is insensitive to the replacement of the M2+ ions. Some relations between the spectroscopic and structural data are given.
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Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
Violeta G. Koleva,