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 its use in future studies of coupling constants involving C, N, and H in larger chemical and biological systems.
Del Bene
Janet E
JE
Department of Chemistry, Youngstown State University, Youngstown, Ohio 44555, USA. jedelbene@ysu.edu
Alkorta
Ibon
I
Elguero
José
J