Eur. Phys. J. D 20, 375-388 (2002)
https://doi.org/10.1140/epjd/e2002-00160-9

Tautomery and H-bonding characteristics of : a combined experimental and theoretical study^*

¹ Department of Chemistry, University of Leuven, Celestijnenlaan 200 F, 3001 Heverlee, Belgium
² Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA

Corresponding author: ^a guido.maes@chem.kuleuven.ac.be

Received: 10 December 2001
Published online: 13 September 2002

Abstract

An experimental and theoretical RHF, MP2 and DFT/6-31++G^** study is described of the matrix FT-IR spectra of monomer and complexes of with water. occurs in Ar predominantly as the amino–N9H tautomer, but small amounts of the amino–N7H tautomer are also present. An approximate K_T value for this tautomeric equilibrium is found to be 0.016 (RHF) and 0.015 (DFT) using the infrared intensity measurement. Four 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 N3H–OH–N9, N1H–OH–NH, N3H–OH–NH and the open complex N7H–OH. From the experimental results, the proton affinity of the N7 atom in can be estimated. The dependence of the strength on the linearity is demonstrated by a correlation between the NH distance and the NH–O angle in closed NH–OH–N complexes.