Benchmark interaction energies for biologically relevant noncovalent complexes containing divalent sulfur.

Molecules containing divalent sulfur can participate in significant noncovalent interactions. Computing accurate noncovalent interaction energies using ab initio quantum chemical methods requires a proper description of electron correlation effects. Coupled-cluster theory with single and double substitutions and perturbative triple substitutions, CCSD(T), using extrapolation to the complete basis set (CBS) limit has become the method of choice for computing accurate interaction energies of noncovalently bound complexes. Here, interaction energies are computed for several biologically relevant hydrogen-bonded and dispersion-bound complexes that contain divalent sulfur. Eight-point estimated CCSD(T)/CBS dissociation curves along the noncovalent interaction vector are computed for each complex. As a comparison of high-accuracy ab initio methods, interaction energies are also calculated for each complex using the correlation-consistent Composite Approach (ccCA). We find that, on average, the two methods yield energies within 0.1 kcal mol(-1) of each other. The interaction energies provided here should be useful for developing and assessing the accuracy of more approximate ab initio, density functional theory, semiempirical, and classical force field approaches.