The aurophilic attraction as interpreted by local correlation methods

The nature of the aurophilic interaction is studied by applying local second-order Mo/ller–Plesset perturbation theory (LMP2) on model dimers of X–Au–PH32 (X=H, Cl) type. The possibility to decompose the correlation contribution of the interaction energy in the dimer (A–B) into different excitation classes reveals that the dispersion contribution (A→A′,B→B′) is accompanied by an almost equally important ionic component (A→A′,B→A′), at shorter distances. Double excitations where at least one electron originates from the gold 5d orbitals account for almost 90% of the attraction. Relativistic effects amount to 28% of the binding energy and can be traced to arise almost exclusively from the relativistic expansion of gold d-shells.