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 (1)J(F-H) and (1)J(B-Li) in complexes F-H center dot center dot center dot Y and H2B-Li center dot center dot center dot Y, respectively, are able to differentiate among the protonation energies of bases containing Y. Changes in (1)J(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 (1)J(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 (1)J(F-H) and (1)J(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.