Structure, binding energy, and intermolecular modes for the aniline/ammonia van der Waals clusters

Aniline(ammonia)n, n=1,2,3, formed in a supersonic jet are investigated spectroscopically, using two-color mass resolved excitation spectroscopy (MRES), hole burning spectroscopy (HB), and by model potential energy calculations. The large shift in the cluster origin (ca. 875 cm−1 for n=1) with respect to the aniline bare molecule origin, and the extent (about 1500 cm−1 for the one-to-one cluster) of the aniline cluster spectra indicate strong interactions between the solute and solvent molecules in both S0 and S1 electronic states. A Lennard-Jones–Coulomb 6-12-1 potential is used to model the intermolecular interactions and predict minimum energy cluster geometries, binding energies, and van der Waals modes. Comparison between experimental results and calculations shows the importance of hydrogen bonding interactions for cluster properties. A minimum energy structure for the cluster is proposed based upon this comparison.