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

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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 = 13C, 15N, and 17O, and selected 19F-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.

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