IN-SITU INFRARED SPECTROSCOPIC STUDIES OF THYMINE ADSORPTION ON A AU(111) ELECTRODE

We have investigated the adsorption of thymine on Au(111) with in-situ infrared spectroscopy. Using IR spectroscopy we have been able to pro be the structure and bonding of the 'chemisorbed' thymine phase. IR ba nds in the 1800-1550 cm(-1) region, which have a major contribution fr om stretching vibrations of the carbonyl groups of thymine, exhibit la rge spectral shifts between thymine in aqueous solution and the chemis orbed phase. By contrast, 'physisorbed' thymine shows no IR bands in t he spectral region studied, which is consistent with a flat-lying adso rbate. In-situ IR spectroscopy provides compelling evidence for the or ientational change of adsorbed thymine occurring concomitantly with th e most pronounced anodic current peak in the voltammogram. We have com pared the in-situ IR spectra for chemisorbed thymine with IR spectra o f metal co-ordination complexes of thymine and uracil. These compariso ns provide evidence that chemisorbed thymine bonds to the Au(111) surf ace through both carbonyl functionalities and a deprotonated N3. (C) 1 998 Elsevier Science S.A. All rights reserved.