NH stretching bands of the hydrogen-bonded C6H5NH2•••N(C2H5)3 cluster

The vibrational spectrum of the 1:1 aniline-triethylamine cluster, formed in a supersonic jet, has been observed in the NH stretching region using infrared depletion spectroscopy combined with REMPI/TOF mass spectrometry. The two absorption bands observed at 3328 and 3466 cm(-1) are assigned to the hydrogen-bonded and free NH stretching vibrations of the cluster, respectively. The former band is enhanced, broadened and largely red-shifted from the aniline monomer bands, while the latter appears at the middle of the symmetric and antisymmetric bands of the monomer. The vibrational frequencies and intensities of the NH stretching bands are qualitatively reproduced by ab initio calculations at the MP2 level with the 6-31G** basis set. The calculated geometry is the typical hydrogen-bonded one, where one of the amino hydrogens of aniline interacts with the nitrogen of triethylamine. (C) 1998 Elsevier Science B.V. All rights reserved.