Raman and FTIR spectra of [Cu(H2O)6](BrO3)2 and [Al(H2O)6](BrO3)3 · 3H2O

Abstract

Raman and FTIR spectra of [Cu(H2O)6](BrO3)2 and [Al(H2O)6](BrO3)3 x 3H2O are recorded and analyzed. The observed bands are assigned on the basis of BrO3- and H2O vibrations. Additional bands obtained in the region of v3 and v1 modes in [Cu(H2O)6](BrO3)2 are due to the lifting of degeneracy of v3 modes, since the BrO3- ion occupies a site of lower symmetry. The appearance v1 mode of BrO3- anion at a lower wavenumber (771 cm(-1)) is attributed to the attachment of hydrogen to the BrO3- anion. The presence of three inequivalent bromate groups in the [Al(H2O)6](BrO3)3 x 3H2O structure is confirmed. The lifting of degeneracy of v4 mode indicates that the symmetry of BrO3- anion is lowered in the above crystal from C3v to C1. The appearance of additional bands in the stretching and bonding mode regions of water indicates the presence of hydrogen bonds of different strengths in both the crystals. Temperature dependent Raman spectra of single crystal [Cu(H2O)6](BrO3)2 are recorded in the range 77-523 K for various temperatures. A small structural rearrangement takes place in BrO3- ion in the crystal at 391 K. Hydrogen bounds in the crystal are rearranging themselves leading to the loss of one water molecule at 485 K. This is preceded by the reorientation of BrO3- ions causing a phase transition at 447 K. Changes in intensities and wavenumbers of the bands and the narrowing down of the bands at 77 K are attributed to the settling down of protons into ordered positions in the crystal.

X-Ray Crysatllographic and Vibrational Spectroscopic Studies of Thorium Bromate Hydrate

“…These bands correspond to ν 1 -ν 3 modes of BrO 3− anion. These spectral band positions are in the same region as reported previously in the literature which is having comparable Br-O distance [21][22][23][24][25]. downward shift is attributed to the presence of hydrogen bonding, which is attached to water molecules.…”

“…downward shift is attributed to the presence of hydrogen bonding, which is attached to water molecules. Symmetric bending mode ν 2 is observed at 429 cm −1 as a weak band in the Raman spectrum similar to that in the case of [Cu (H 2 O) 6 ] (BrO 3 ) 2 (Table 2) [25]. The degeneracy of the ν 4 mode of anion is lifted in the 3 BrO  Raman spectrum and two bands are observed at 371 and at 383 cm −1 (Figure 3).…”

“…Therefore, this almost equally energetic upward and downward pulling of O atoms causes the intense OH bending modes to appear without any shift in wavenumber values with respect to its free state value (1595-ν 2 H 2 O). The appearance of additional bands in the OH stretching regions and broad spectral profile of both bending and stretching regions confirms the existence of hydrogen bonds of different strengths in the crystal [24,25]. The bands observed below 250 cm −1 are mostly of lattice modes and are assigned in Table 2.…”

Direct Solvothermal Synthesis of Phase-Pure Colloidal NiO Nanocrystals

“…For the nonaminated nickel carboxylate complex Ni­(DA) 2 (H 2 O) 2 , the COO – stretch is broad and there is an additional broad feature at ∼1590 to 1570 cm –1 corresponding to the OH scissoring mode of water molecules bound to the nickel center (shaded green box). , The FTIR spectrum of Ni­(DA) 2 (DAm) 1.83 (H 2 O) 0.17 ·0.83H 2 O also contains this feature corresponding to coordinated water, but the FTIR spectrum of Ni­(DA) 2 (DAm) 2.17 ·2H 2 O does not, which indicates that this product does not contain water within the coordination sphere of the nickel. Although elemental analysis indicates that water is present in the Ni­(DA) 2 (DAm) 2.17 ·2H 2 O compound, the absence of the broad FTIR feature at 1560 cm –1 implies that this water is not coordinated to nickel, but rather these complexes are crystallohydrates, which contain water molecules in the crystal structure that do not interact covalently with the metal center . These crystallohydrate water molecules have an OH scissoring mode at ∼1610 cm –1 (indicated by the blue dashed line) , and are tabulated in the molecular formula as “· x H 2 O” (e.g., Ni­(DA) 2 (DAm) 2.17 ·2 H 2 O).…”

Photochemical CO2 Splitting by Metal-to-Metal Charge-Transfer Excitation in Mesoporous ZrCu(I)-MCM-41 Silicate Sieve

“…The concurrent intensity loss of the Cu(I)−O−Zr mode at 643 cm -1 (Figure d) confirms that the carbon dioxide photoreduction is accompanied by the oxidation of Cu(I) linked to the Zr center. Photoreduction of C 18 O 2 leads to growth of H 2 18 O at 1594 cm -1 (Figure ), indicating that the oxygen atom of water stems from CO 2 . When the CO 2 photoreduction was attempted in TiCu(I)-MCM-41, whose MMCT absorption is much more intense, no significant CO growth was detected.…”