Benchmark Experimental Gas-Phase Intermolecular Dissociation Energies by the SEP-R2PI Method

The gas-phase ground-state dissociation energy D₀(S₀) of an isolated and cold bimolecular complex is a fundamental measure of the intermolecular interaction strength between its constituents. Accurate D₀ values are important for the understanding of intermolecular bonding, for benchmarking high-level theoretical calculations, and for the parameterization of dispersion-corrected density functionals or force-field models that are used in fields ranging from crystallography to biochemistry. We review experimental measurements of the gas-phase D₀(S₀) and D₀(S₁) values of 55 different M⋅S complexes, where M is a (hetero)aromatic molecule and S is a closed-shell solvent atom or molecule. The experiments employ the triply resonant SEP-R2PI laser method, which involves M-centered (S₀ → S₁) electronic excitation, followed by S₁ → S₀ stimulated emission spanning a range of S₀ state vibrational levels. At sufficiently high vibrational energy, vibrational predissociation of the M⋅S complex occurs. A total of 49 dissociation energies were bracketed to within ≤1.0 kJ/mol, providing a large experimental database of accurate noncovalent interactions.