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

The gas-phase ground-state dissociation energy D0(So) 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 Do(Si) 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 So 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. [ABSTRACT FROM AUTHOR]