UV Raman spectroscopic study of hydrogen bonding in gibbsite and bayerite between 93 and 453 K

Abstract

AbstractRaman spectra of bayerite and gibbsite (hydrargillite) were measured at 453, 295 and 93 K and after H D exchange at 423 K with gaseous D2O. Spectra in the O H stretching vibration region were recorded with the use of ultraviolet laser excitation, which avoided the fluorescence problem typical for these materials. Lowering the temperature led to a spectral resolution improvement with additional bands resolved in the ν(OH) spectrum of bayerite. It was established that the positions of the Raman bands are sensitive to the temperature of the sample. A spectral criterion based on different shifts of band positions with temperature was proposed as a method to distinguish between structural OH groups forming H‐bonds between hydroxide layers or in the same plane of the layer. It was found that the highest wavenumber band at 3655 cm−1 in the spectrum of bayerite does not participate in H‐bonding. A one‐to‐one correspondence between Raman spectra recorded in the ν(OH) and ν(OD) regions upon partial H D exchange with D2O is evidence that the multiplicity of spectral bands is caused by different O H···O′ distances in the hydroxide lattice rather than by vibrational coupling of H‐bonded hydroxyls. Copyright © 2001 John Wiley & Sons, Ltd.