Abstract
We measured accurate intermolecular dissociation energies D0 of the supersonic jet-cooled complexes of 1-naphthol (1NpOH) with the noble gases Ne, Ar, Kr, and Xe and with N2, using the stimulated-emission pumping resonant two-photon ionization method. The ground-state values D0(S0) for the 1NpOH⋅S complexes with S= Ar, Kr, Xe, and N2 were bracketed to be within ±3.5%; they are 5.67 ± 0.05 kJ/mol for S = Ar, 7.34 ± 0.07 kJ/mol for S = Kr, 10.8 ± 0.28 kJ/mol for S = Xe, 6.67 ± 0.08 kJ/mol for isomer 1 of the 1NpOH⋅N2 complex, and 6.62 ± 0.22 kJ/mol for the corresponding isomer 2. For S = Ne, the upper limit is D0 < 3.36 kJ/mol. The dissociation energies increase by 1%-5% upon S0 → S1 excitation of the complexes. Three dispersion-corrected density functional theory (DFT-D) methods (B97-D3, B3LYP-D3, and ωB97X-D) predict that the most stable form of these complexes involves dispersive binding to the naphthalene "face." A more weakly bound edge isomer is predicted in which the S moiety is H-bonded to the OH group of 1NpOH; however, no edge isomers were observed experimentally. The B97-D3 calculated dissociation energies D0(S0) of the face complexes with Ar, Kr, and N2 agree with the experimental values within <5%, but the D0(S0) for Xe is 12% too low. The B3LYP-D3 and ωB97X-D calculated D0(S0) values exhibit larger deviations to both larger and smaller dissociation energies. For comparison to 1-naphthol, we calculated the D0(S0) of the carbazole complexes with S = Ne, Ar, Kr, Xe, and N2 using the same DFT-D methods. The respective experimental values have been previously determined to be within <2%. Again, the B97-D3 results are in the best overall agreement with experiment.
Highlights
Intermolecular London dispersion forces are weak when viewed on a per-atom basis and act at a longer range (3-10 Å) than chemical bonds, but they are ubiquitous and are always attractive.1,2 They play a major role in the formation of molecular solids, liquids, and solutions and are important for understanding their structures, lattice energies, phonon spectra, melting points, enthalpies, and many other properties.3–12 Synthetic chemists have recognized that dispersion interactions can be employed as control elements for reactivity and catalysis, in particular, for larger molecules, for which the dispersion energy contributions accumulate.11the accurate treatment of intermolecular dispersion interactions between polyatomic molecules has proven to be remarkably challenging
Three dispersion-corrected density functional theory (DFT-D) methods (B97-D3, B3LYP-D3, and ωB97X-D) predict that the most stable form of these complexes involves dispersive binding to the naphthalene “face.” A more weakly bound edge isomer is predicted in which the S moiety is H-bonded to the OH group of 1NpOH; no edge isomers were observed experimentally
The B97-D3 calculated dissociation energies D0(S0) of the face complexes with Ar, Kr, and N2 agree with the experimental values within
Summary
Intermolecular London dispersion forces are weak when viewed on a per-atom basis and act at a longer range (3-10 Å) than chemical bonds, but they are ubiquitous and are always attractive. They play a major role in the formation of molecular solids, liquids, and solutions and are important for understanding their structures, lattice energies, phonon spectra, melting points, enthalpies, and many other properties. Synthetic chemists have recognized that dispersion interactions can be employed as control elements for reactivity and catalysis, in particular, for larger molecules, for which the dispersion energy contributions accumulate.11the accurate treatment of intermolecular dispersion interactions between polyatomic molecules has proven to be remarkably challenging. Intermolecular London dispersion forces are weak when viewed on a per-atom basis and act at a longer range (3-10 Å) than chemical bonds, but they are ubiquitous and are always attractive.. Intermolecular London dispersion forces are weak when viewed on a per-atom basis and act at a longer range (3-10 Å) than chemical bonds, but they are ubiquitous and are always attractive.1,2 They play a major role in the formation of molecular solids, liquids, and solutions and are important for understanding their structures, lattice energies, phonon spectra, melting points, enthalpies, and many other properties.. Synthetic chemists have recognized that dispersion interactions can be employed as control elements for reactivity and catalysis, in particular, for larger molecules, for which the dispersion energy contributions accumulate..
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