Raman and infrared spectra of NiI₂ · 6H₂O

Abstract

The polarized Raman spectra and infrared absorption spectra of NiI, * 6H,O were measured in the 50-4000 cm-' region at low temperatures. Deuterated samples were a150 studied and gave results which were useful for hterpretation purposes. Satisfactory assignments of water internal and external modes and lattice vibrations were made. Tbe vibrational analysis, on the basis of which the assignments were made, was related to the D,, factor group; however, the symmetry of the Raman-active bands, as deduced from polarized spectra, suggests that for water librations the C,, factor group provides a better basis for interpretation.

Deliquescent Chromism of Nickel(II) Iodide Thin Films

“…10,26−28 The FTIR spectrum of the clear film in Figure 3B exhibits two strong absorption bands at 3460 and 1610 cm −1 . Although these could come from nickel iodide hexahydrate; 24 these bands also correspond to the Transmissions greater than one in FTIR spectra are due to reduced reflection of the silicon substrate once the thin film is deposited. (D) TGA of a clear hydrated NiI 2 thin film.…”

“…The XRD pattern of the clear film is featureless, indicating that the layer lacks crystallinity. NiI 2 is hygroscopic, and in its bulk form, exposure to humidity changes the material from the black rhombohedral phase to crystalline penta- or hexahydrate, which has a green color. − The trace amount of hexagonal NiI 2 ·6H 2 O observed in the dark state film in Figure B is the result of brief air exposure during the sample preparation. XRD of the clear film does not show any evidence of hexagonal NiI 2 ·6H 2 O or any other crystalline hydrate phase.…”

“…There is no residual DMF or DMSO in the film that could possibly give rise to a nickel-ligand rearrangement or a change in d-splitting of nickel due to change in coordination geometry. ,− The FTIR spectrum of the clear film in Figure B exhibits two strong absorption bands at 3460 and 1610 cm –1 . Although these could come from nickel iodide hexahydrate; these bands also correspond to the stretching and bending region of condensed water. − Since there is no evidence of NiI 2 ·6H 2 O by XRD (Figure B), these bands must be due to water. TGA (Figure D) also indicates a significant amount of water in the clear film, with a H 2 O:NiI 2 molar ratio of at least 10, corresponding to a dissolved nickel iodide concentration of ∼5.5 M.…”

Single‐crystal Raman studies on nickel iodate dihydrate, Ni(IO3)2·2H2O

“…It is worth mentioning, however, that in the case of other nickel salt hydrates Raman bands in the range 400-300 cm 1 were interpreted by some authors 38,39 as Ni $ OH 2 stretching vibrations. These modes with very low intensity in the Raman experiment may be hidden by the IO 3 bending modes of Ni IO 3 2 Ð 2H 2 O.…”