Intermolecular dissociation energies of hydrogen-bonded 1-naphthol complexes

Area of Science:

• Physical Chemistry
• Supramolecular Chemistry
• Computational Chemistry

Background:

• Understanding intermolecular forces is crucial for chemical processes.
• 1-naphthol (1NpOH) serves as a model for studying hydrogen bonding interactions.
• Solvent properties significantly influence the stability of molecular complexes.

Purpose of the Study:

• To measure intermolecular dissociation energies (D0) of 1-naphthol complexes with furan, thiophene, 2,5-dimethylfuran, and tetrahydrofuran.
• To investigate the relationship between dissociation energies and solvent properties, particularly polarizability.
• To compare experimental results with theoretical predictions from various density functional theory methods.

Main Methods:

• Supersonic cooling of 1-naphthol complexes.
• Stimulated-emission pumping resonant two-photon ionization (SEP-R2PI) for energy measurement.
• Dispersion-corrected density functional theory (DFT) calculations (B97-D3, B3LYP-D3, ωB97X-D).

Main Results:

• Experimental D0 values were determined for furan (21.8 ± 0.3 kJ/mol), thiophene (26.6 ± 0.6 kJ/mol), 2,5-dimethylfuran (36.5 ± 2.3 kJ/mol), and tetrahydrofuran (37.6 ± 1.3 kJ/mol).
• Non-classically H-bonded complexes showed a linear increase in D0 with solvent polarizability.
• Classically H-bonded complexes exhibited a more rapid increase at low polarizability, saturating at higher values.
• DFT methods generally agreed well with experimental D0 values, with B3LYP-D3 showing the lowest mean absolute deviation.

Conclusions:

• The study successfully quantified dissociation energies for 1NpOH complexes with specific solvents.
• A clear distinction in binding behavior was observed between non-classical (π-electron) and classical (O-atom) hydrogen bonds.
• DFT calculations, particularly B3LYP-D3, provide reliable predictions for these intermolecular interactions.