Structure of the aniline–benzene and aniline–cyclohexane clusters based on infrared depletion spectroscopy

The vibrational spectra of jet-cooled aniline–benzene and aniline–cyclohexane clusters have been investigated using infrared depletion spectroscopy combined with REMPI–TOF mass spectrometry. The symmetric and antisymmetric NH2 stretching bands are red-shifted by 28.4 and 40.9 cm−1 in aniline–benzene and by 1.6 and 1.2 cm−1 in aniline–cyclohexane, from those of the aniline monomer. The spectrum of aniline–benzene suggests a face-to-face structure with NH2–π hydrogen bonds. This structure is supported by ab initio calculations at the MP2 level, which also reproduce the observed red-shifts. The small red-shifts in aniline–cyclohexane indicate no direct interaction of the amino hydrogens with cyclohexane.