VIBRATIONAL-SPECTRA OF HEXAAQUA COMPLEXES .5. THE WATER BENDING BANDSIN THE INFRARED-SPECTRA OF TUTON SALTS

Multiple overlapped bands forming a broad complex which extends over s everal hundreds of reciprocal centimeters appear in the water bending region of the spectra of Tuton salts whose general formula is (M2MII)- M-1(XY4)(2) . 6H(2)O. The essential characteristics of the complex per sist when one univalent cation is replaced by another, when the nature of the divalent cation is changed or when a sulfate salt is compared with an analogous selenate compound. This shows that the feature is re lated to water vibrations only and this is supported by its behaviour on deuteration. Since neither the number of components nor the spread of their frequencies can-be attributed solely to the fundamental vibra tions of different types of water molecules, anharmonic couplings of t he delta(HOH) modes with second-order transitions must be responsible for the observed spectral picture. (C) 1997 Elsevier Science B.V.