Systematic Comparison of Second-Order Polarization Propagator Approximation (SOPPA) and Equation-of-Motion Coupled Cluster Singles and Doubles (EOM-CCSD) Spin-Spin Coupling Constants for Molecules with C, N, and O Double and Triple Bonds and Selected F-Substituted Derivatives.

Abstract

Ab initio EOM-CCSD and SOPPA calculations with the Ahlrichs (qzp,qz2p) basis set have been carried out to evaluate one-, two-, and three-bond spin-spin coupling constants for molecules HmXYHn and HmXYHn for X, Y = (13)C, (15)N, and (17)O, and selected (19)F-substituted derivatives. In the great majority of cases, EOM-CCSD one-bond C-C, C-N, C-O, C-F, N-N, N-O, and N-F coupling constants and three-bond F-F coupling constants are smaller in absolute value than the corresponding SOPPA coupling constants, with the EOM-CCSD values in better agreement with experimental data. SOPPA tends to significantly overestimate the absolute values of large one- and three-bond couplings involving fluorine. The majority of two-bond SOPPA coupling constants are in better agreement with experiment than EOM-CCSD, although differences between EOM-CCSD and experimental values are not dramatic. A statistical analysis of thirty EOM-CCSD and SOPPA coupling constants versus experimental coupling constants demonstrates that better agreement with experiment is found when EOM-CCSD is the computational method.