The 2-aminopyridine•2-pyridone complex (2AP•2PY) is linked by antiparallel N-H···O=C and N-H···N hydrogen bonds, providing a model for the Watson-Crick hydrogen bond configuration of the adenine•thymine and adenine•uracil nucleobase pairs.
Mass-selected S₁←S₀ vibronic spectra of the supersonically cooled 2AP•2PY base pair analogue were measured by laser resonant two-photon ionization and emission spectroscopies.

This work was carried out by Andreas Müller and Francis Talbot in the group of Prof. Samuel Leutwyler.

References:

• A. Müller, F. Talbot, S. Leutwyler;
  "Hydrogen bond vibrations of 2-aminopyridine·2-pyridone, a Watson-Crick analogue of adenine·uracil."
  J. Am. Chem. Soc., 124, 14486-14494, (2002); doi:10.1021/ja0209969.