Giant RS spectroscopy and structural-conformational transformations of thiamine adsorbed on the surface of a silver electrode

An investigation of giant RS spectra of a thiamine (vitamin B₁) molecule adsorbed on the surface of an anodized silver electrode from weak-concentration aqueous solutions is made. The dependences of the spectral bands sensitive to the ionic state of the adsorbed molecule on the pH and the electrode potential are discussed. It is shown that the rate constant of thiamine protonation in the adsorbed layer depends on the electrode potential and is substantially lower than the corresponding value for the solution. In conformity with the important role of short-range mechanisms of enhancement of electrochemical GRS in the excitation wavelength range investigated, models of the structural-conformational states of the molecule in the adsorbed state are constructed and a conclusion is drawn about the possibility of monitoring the acid-base equilibrium of these states for a molecular layer of thiamine under the conditions of an electrochemical cell. To whom correspondence should be addressed. Ya. Kupala Grodno State University, 22, Ozheshko Str., Grodno, 230023, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 622–626, September–October, 1999.