Accuracy of DLPNO−CCSD(T) Method for Noncovalent Bond Dissociation Enthalpies from Coinage Metal Cation Complexes

​The performance of the domain based local pair-natural orbital coupled-cluster (DLPNO–CCSD(T)) method has been tested to reproduce the experimental gas phase ligand dissociation enthalpy in a series of Cu⁺, Ag⁺, and Au⁺ complexes. For 33 Cu⁺–noncovalent ligand dissociation enthalpies, all-electron calculations with the same method result in MUE below 2.2 kcal/mol, although a MSE of 1.4 kcal/mol indicates systematic underestimation of the experimental values. Inclusion of scalar relativistic effects for Cu either via effective core potential (ECP) or Douglass–Kroll–Hess Hamiltonian, reduces the MUE below 1.7 kcal/mol and the MSE to −1.0 kcal/mol. For 24 Ag⁺–noncovalent ligand dissociation enthalpies, the DLPNO–CCSD(T) method results in a mean unsigned error (MUE) below 2.1 kcal/mol and vanishing mean signed error (MSE). For 15 Au⁺–noncovalent ligand dissociation enthalpies, the DLPNO–CCSD(T) methods provides larger MUE and MSE, equal to 3.2 and 1.7 kcal/mol, which might be related to poor precision of the experimental measurements. Overall, for the combined data set of 72 coinage metal ion complexes, DLPNO–CCSD(T) results in a MUE below 2.2 kcal/mol and an almost vanishing MSE. As for a comparison with computationally cheaper density functional theory (DFT) methods, the routinely used M06 functional results in MUE and MSE equal to 3.6 and −1.7 kcal/mol. Results converge already at CC-PVTZ quality basis set, making highly accurate DLPNO–CCSD(T) estimates affordable for routine calculations (single-point) on large transition metal complexes of >100 atoms.