Comprehensive ab initio studies of nuclear magnetic resonance shielding and coupling constants in XH⋯O hydrogen-bonded complexes of simple organic molecules

Abstract

The influence of hydrogen-bond formation on the scalar spin–spin coupling constants and NMR shielding constants in CH2O–H2O, C2H2–H2O, CH3OH–H2O, and (HCOOH)2 complexes has been calculated using correlated MO (MCSCF and MP2) methods. The hydrogen-bond transmitted spin–spin coupling constants are also reported. The iso- and anisotropic H1 shielding constants are found to be the most general parameters of the hydrogen bond. The changes in J1(XH) coupling in the proton donor also correlate with the XH⋯Y hydrogen bond strength. A similar correlation is found in the intermolecular J1h(HY) and J2h(XY) couplings. These couplings are substantial and dominated by the Fermi-contact term in contrast to the longer-range hydrogen-bond transmitted couplings where the noncontact terms prevail.