Abstract:
An experimental and theoretical RHF, MP2 and DFT/6-31++G** study is described of the matrix FT-IR spectra of monomer 2-aminopurine and H-bonded complexes of 2-aminopurine with water. 2-aminopurine occurs in Ar predominantly as the amino-N9H tautomer, but small amounts of the amino-N7H tautomer are also present. An approximate KT value for this tautomeric equilibrium is found to be 0.016 (RHF) and 0.015 (DFT) using the infrared intensity measurement. Four H-bonded complexes of the abundant amino-N9H form with water are detected in the experimental FT-IR spectrum by their characteristic predicted absorptions, i.e. the three closed complexes N3 ... H-O ... H-N9, N1 ... H-O ... H-NH, N3 ... H-O ... H-NH and the open complex N7 ... H-OH. From the experimental results, the proton affinity of the N7 atom in 2-aminopurine can be estimated. The dependence of the H-bond strength on the H-bond linearity is demonstrated by a correlation between the N ... H distance and the N ... H-O angle in closed N ... H-O ... H-N complexes.
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Received 10 December 2001 Published online 13 September 2002
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Ramaekers, R., Adamowicz, L. & Maes, G. Tautomery and H-bonding characteristics of 2-aminopurine: a combined experimental and theoretical study. Eur. Phys. J. D 20, 375–388 (2002). https://doi.org/10.1140/epjd/e2002-00160-9
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DOI: https://doi.org/10.1140/epjd/e2002-00160-9