Binding Energies of Aromatic 1:1 Hetero‐Clusters in a Supersonic Jet

Abstract

Methods used to experimentally estimate the binding energies of van der Waals clusters containing an aromatic molecule are surveyed. These include microwave and infrared absorption spectroscopies, single and two photon ionization, dispersed fluorescence, and stimulated emission pumping. The problems encountered in the application of these methods are briefly discussed, and prospects for the firm establishment of the binding energies are assessed. Although the present database is too small for firm conclusions, methods based on dispersed fluorescence (i.e., probing the excited state surface) tend to yield lower values for argon adducts than those based on ionization, probing the ground state, or ionic surfaces. A mechanism that may account for this tendency is proposed, and further experiments are proposed to test it.

Dual Emission of 4-(1H-Pyrrol-1-yl)benzonitrile Clusters with Acetonitrile in a Supersonic Jet and Its Absence in Phenylpyrrole Clusters

“…This is due to the added electrostatic interaction that is stronger than the dispersion forces holding together the neutral clusters. In contrast, bond dissociation energies of the LE states of clusters are usually quite close to those of the ground-state ones. ,− It is also evident that the ionization potential of clusters is usually lower than that of the bare molecule by 0.2 to 0.7 eV (5 to 16 kcal/mol). Therefore, multiphoton excitation of clusters near the 0,0 band of the bare monomer can lead to ionization of the cluster, depositing a large energy excess in the cluster ion compared to van der Waals binding energies.…”

Experimental and Theoretical Determination of Dissociation Energies of Dispersion-Dominated Aromatic Molecular Complexes

“…The research on noncovalently bonded gas-phase complexes has been summarized in several reviews. Most reviews have focused on H-bonded systems. − Exceptions are the reviews of Topp (1993), who reports on structures and vibrational predissociation dynamics of complexes of small molecules with chromophores such as perylene or 2,5-diphenylfuran determined by fluorescence spectroscopy, and Kendler and Haas (1997), discussing the binding energies of vdW complexes with Ar. In 2015, Hobza and co-workers published a thorough comparison study between theoretical and experimental dissociation energies of 11 hydrogen bonded and 11 dispersive bonded complexes, finding an average disagreement of 6% .…”