Librational Modes of Water in Zinc Formate Dihydrate

Abstract

The infrared spectra of zinc formate dihydrate are presented for the region 1000 to 400 cm−1 along with the laser-excited Raman spectra. With the use of the corresponding IR and Raman spectra for the deuterated and anhydrous samples and their temperature dependence (between 300 to 90 K), two sets of bands for the in-plane bending mode of formate ion and all the three librations of water have been identified corresponding to two types of formate and water in the unit cell. The large shift of the formate ν3 mode in going from the hydrate to the deuterate has been attributed to a dynamic interaction of this mode with the close-lying H2O rocking mode.

IR and X‐Ray Powder Diffraction Studies on Ba2Me(HCOO)6. 4 H2O (Me = Co, Ni, Zn)

“…The assignments of the bands are done by analogy with those of metal formate dihydrates. (HEYNS, 1985 (a) (b), TEWARI et al, 1982TEWARI et al, , 1983.…”

“…2 the infrared spectra of the double salts in the range .of 900-400 cm-' are shown where the v3 modes of HCOO groups and the librational modes of the water molecules occur. As far as v3 is concerned, studies on Cu(HC00)2.2 H20 (HEYNS, 1985 (a)) and Zn(HC00)2 -2 H20 (TEWARI et al, 1982) have been revealed that existensive coupling occurs between v3 mode and the librations of the water molecules. The two bands in the frequency range of 760-785 cm-' are attributed to v3 modes of the formate groups.…”

“…The bands which occur in the low frequency range of 600-400 cm-' could be analyzed using the known ratio for the librational modes of H20 and D2O molecules. For example, the given ratio W(H20)/W(D2O) for the wagging modes is 1.36 in Zn(HC00)2.2H20 (TEWARI et al, 1982) and 1.35-1.39 in Cu(HC00)2 . 2 H20 (HEYNS, 1985 (b).…”

Evans holes in the infrared spectra of some transition metal formate dihydrates

“…The methods of preparation of samples and recording of ir and Raman spectra have been described elsewhere (4). The accuracy in the measurement of band positions is "4 cm-I, while the estimated half-widths and relative intensities are dependable within 20% for the OH stretching region.…”