Del Bene Janet E, Elguero José
Department of Chemistry, Youngstown State University, Youngstown, Ohio 44555, USA.
J Phys Chem A. 2007 Jul 19;111(28):6443-8. doi: 10.1021/jp072145z. Epub 2007 Jun 20.
Ab initio EOM-CCSD calculations have been carried out in search of acids with one-bond spin-spin coupling constants which could serve as probes of molecular basicity upon complex formation. Only 1J(F-H) and 1J(B-Li) in complexes F-H...Y and H2B-Li...Y, respectively, are able to differentiate among the protonation energies of bases containing Y. Changes in 1J(F-H) upon complex formation are related to the protonation energies of bases, but only when these energies are about 200 kcal/mol or greater. On the other hand, changes in 1J(B-Li) upon complexation are related to base protonation energies in the range between 100 and about 190 kcal/mol. Thus, these two one-bond coupling constants 1J(F-H) and 1J(B-Li) are complementary probes. For the first time, the computed NMR property of a gas-phase one-bond spin-spin coupling constant has been related to the experimental gas-phase thermodynamic property of proton affinity.
