Vibrational behavior of matrix-isolated ions in Tutton compounds IV. Infrared spectroscopic study of NH4+ and SO42- ions included in nickel sulfates and selenates
✍ Scribed by D. Marinova; M. Georgiev; D. Stoilova
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 172 KB
- Volume
- 45
- Category
- Article
- ISSN
- 0232-1300
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✦ Synopsis
Ni(SO 4 ) 2 ⋅6H 2 O, (NH 4 ) 2 Ni(SO 4 ) 2 ⋅6H 2 O, K 2 Ni(SeO 4 ) 2 ⋅6H 2 O, (NH 4 ) 2 Ni(SeO 4 ) 2 ⋅6H 2 O, crystal matrix infrared spectroscopy. Infrared spectra of K 2 Ni(SeO 4 ) 2 ⋅6H 2 O and (NH 4 ) 2 Ni(SeO 4 ) 2 ⋅6H 2 O containing SO 4 2-ions and those of K 2 Ni(SO 4 ) 2 ⋅6H 2 O and K 2 Ni(SeO 4 ) 2 ⋅6H 2 O containing NH 4 + ions are presented and discussed in the region of ν 3 and ν 1 of the sulfate ions and in the region of ν 4 of the NH 4 + ions, respectively. The SO 4 2-ions matrixisolated in the selenate matrices (approximately 1 mol%) exhibit three bands for ν 3 and one band for ν 1 in agreement with the low site symmetry C 1 of the host selenate ions. The NH 4 + guest ions included in the potassium sulfate matrix are characterized also with three bands for ν 4 . However, the ammonium ions in (NH 4 ) 2 Ni(SeO 4 ) 2 ⋅6H 2 O as well as those included in K 2 Ni(SeO 4 ) 2 ⋅6H 2 O display four infrared bands corresponding to ν 4 due probably to some kind of disorder of the ammonium ions. The extent of energetic distortion of the isomorphously included sulfate ions as deduced from the values of Δν 3 and Δν max is commented.
The spectroscopic experiments reveal that the SO 4 2-guest ions are weaker distorted in the selenate matrices as compared to the same ions in the neat sulfates due to the larger unit-cell volumes of the selenate compounds. The band positions of the water librations in the host potassium compounds are affected by the included ammonium cations. The formation of hydrogen bonds between the NH 4 + guest ions and the XO 4 2-host ions leads to a decrease in the proton acceptor capabilities of the anions and as a result the hydrogen bonds weaken on going from the neat potassium compounds to the mixed crystals.