A Systematic Comparison of Second-Order Polarization Propagator Approximation and Equation-of-Motion Coupled Cluster Singles and Doubles C-C, C-N, N-N, C-H, and N-H Spin-Spin Coupling Constants

Ab initio one-, two-, and three-bond C-C, C-N, and N-N spin-spin coupling constants, and one-bond C-H and N-H coupling constants have been computed using two different theoretical methods, SOPPA/(qzp,qz2p) and EOM-CCSD/(qzp,qz2p). Both EOM-CCSD (equation-of-motion coupled cluster singles and doubles) and SOPPA (second-order polarization propagator approximation) coupling constants correlate linearly with experimental data. In the great majority of cases, the computed EOM-CCSD C-C, C-N, N-N, and N-H coupling constants are in better agreement with experimental data than SOPPA values, although both levels of theory provide reasonable estimates of these Couplings. EOM-CCSD Consistently underestimates one-bond C-H coupling constants by about 10 Hz, and SOPPA values of (1)J(C-H) are in better agreement with experimental data. The performance of SOPPA Supports it, use in future studies Of Coupling constants involving C, N, and H in larger chemical and biological systems.