The effects of changes in the electronic environment of the 2-aminopyridine–argon van der Waals complex

The first excited neutral and ground cationic states of the 2-aminopyridine–argon van der Waals complex have been studied using a combination of (1 + 1′) REMPI and ZEKE spectroscopy, supported by ab initio molecular orbital calculations. In addition to an updated ionisation energy of 65 265 ± 3 cm−1, an analysis of the intermolecular vibrational structure observed in both REMPI and ZEKE spectra supports an assignment to a π-bound complex. The pyramidal conformation of the amino group in the electronic ground state allows for the possibility of anti and syn π-bound conformers: this is discussed in the context of the related molecule, aniline–Ar.