Determination of the intermolecular dissociation energies in the dispersion-bound N2 and Xe complexes of 2-(2′-pyridyl)benzimidazole and 1-naphthol

Abstract

In this article, the strength of intermolecular dispersion interactions was measured by employing resonant two-photon ionization (R2PI) spectroscopy using jet-cooled 1 : 1 complexes of 2-(2′-pyridyl)benzimidazole (PBI) and 1-naphthol (NpOH) with N₂ and Xe. In this spectroscopic measurement scheme, the disappearance of the Franck–Condon active vibrational modes in the S₁ ← S₀ electronic transitions of a complex was considered as the measure of excited state predissociation of the binary complex. The excited state dissociation energies of D₀(S₁) for PBI·N₂ and PBI·Xe were determined as 484 ± 15 and 852 ± 43 cm⁻¹, and the corresponding ground state dissociation energies D₀(S₀) were 512 ± 15 and 779 ± 43 cm⁻¹. Additionally, we have measured the dissociation energy D₀(S₁) of the NpOH·N₂ complex as 582 ± 35 cm⁻¹ for both the isomers, NpOH·N₂-I1 and NpOH·N₂-I2, in their respective excited states. The corresponding ground-state dissociation energies D₀(S₀) were 568 ± 35 cm⁻¹ and 554 ± 35 cm⁻¹. In the case of NpOH·Xe, the D₀(S₁) and D₀(S₀) values were obtained as 895 ± 54 and 860 ± 54 cm⁻¹. The above data provide reliable benchmarks for evaluating the accuracy of the computational methods. This work advances a fundamental understanding of dispersion-bound complexes and emphasizes the importance of such weak interactions in stabilizing molecular assemblies and influencing their photophysical properties.