Junaid, Bushiri M; Nayar, V U(Elsevier, March 15, 2002)
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Abstract:
Raman and FTIR spectra of [Cu(H2O)6](BrO3)2 and [Al(H2O)6](BrO3)3 · 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
3 and 1 modes in [Cu(H2O)6](BrO3)2 are due to the lifting of degeneracy of 3 modes, since the BrO3
− ion occupies
a site of lower symmetry. The appearance 1 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 · 3H2O structure is confirmed. The lifting of degeneracy of 4 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
Junaid, Bushiri M; Jayasree, R S; Fakhfakh, M; Nayar, V U(Elsevier, 2002)
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Abstract:
Raman and infrared spectra of Tl2NbO2PO4, Tl3NaNb4O9(PO4)2 and TlNbOP2O7 are reported. The observed bands are assigned in
terms of vibrations of NbO6 octahedra and PO4 tetrahedra in the first two compounds and in terms of NbO6 octahedra and P2O7
4−
anion in the third compound. The NbO6 octahedra in all the title compounds are found to be corner-shared and distorted. The higher
wavenumber values of the ν1 (NbO6) mode and other stretching modes indicate that the NbO6 octahedra in them are distorted in the order
TlNbOP2O7 > Tl2NbO2PO4 > Tl3NaNb4O9(PO4)2. The splitting of the ν3 (PO4) mode indicates that PO4 tetrahedra is distorted more
in Tl2NbO2PO4 than in Tl3NaNb4O9(PO4)2. The symmetry of P2O7
4− anion in TlNbOP2O7 is lowered. Bands indicate that the P–O–P
bridge in the above compound has a bent P–O–P bridge configuration