Infrared depletion spectroscopy suggests fast vibrational relaxation in the hydrogen-bonded aniline-tetrahydrofuran (C6H5-NH2 ••• OC4H8) complex

The vibrational spectrum of the 1:1 aniline-tetrahydrofuran complex, formed in a pulsed supersonic jet, has been observed in the NH stretching region using IR depletion spectroscopy cum REMPI time-of-flight MS. Two strong absorption features observed at 3370 and 3479.3 cm(-1) are assigned to the H-bonded and free N-H stretching vibrations of the complex, respectively. The vibrational frequencies and intensities of the MH stretching bands are qualitatively reproduced by ab initio MP2/6-31G (*) (*) calculations. The optimized geometry shows one of the amino hydrogens of aniline interacts with the oxygen of tetrahydrofuran, giving a binding energy of 37 KJ mol(-1) without BSSE correction. A fast vibrational relaxation occurs on vibrational excitation of the hydrogen-bonded N-H stretching mode. (C) 2000 Elsevier Science B.V. All rights reserved.