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.
Kalal et al. (Thu,) studied this question.