Investigation on the Hydrogen Bond Interaction in the Aniline-Furan Complex and Its Cation by Infrared Depletion Spectroscopy

The vibrational spectra of the NH₂-stretching modes of the aniline-furan complex and its cation in a supersonic jet have been measured by infrared depletion spectroscopic methods. Two absorption bands have been observed at 3409 and 3497 cm^-1 in the spectrum of the neutral aniline-furan complex, which is red-shifted from the corresponding bands of aniline monomer by 12 and 11cm^-1, respectively. The main intermolecular interaction of the complex has been found to be a weak hydrogen bond between the NH bond of aniline and the lone pair of the oxygen atom of furan. As for the aniline-furan cation complex, two strong absorption bands have been observed at 3315 and 3446 cm^-1 in the infrared spectrum. In this case, the main intermolecular interaction has been found to be the NH-p type hydrogen bond between one of the NH bonds and the p-electron of the aromatic ring of furan. The difference between the interactions of the neutral and the cation complexes has been discussed.

Fig. 1. Infrared depletion spectrum of aniline-furan complex measured using the resonance UV laser corresponding to the 0-0 band of the excitation spectrum.