Two‐bond NMR Spin–Spin Coupling Constants across Hydrogen Bonds

This article presents a summary of the results of ab initio equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) calculations performed on series of complexes stabilized by N–H–N, C–H–N, and F–H–N hydrogen bonds. For these complexes, the total X–Y spin–spin coupling constant across an X–H–Y hydrogen bond (2hJX–Y) is determined solely by the Fermi-contact term, which is distance dependent. Curves are presented that relate the X–Y distance to 2hJX–Y for each series. The dependence of coupling constants on the hybridization and bonding of X and Y are discussed. Relationships are noted between hydrogen bond type, X–Y distances, NMR spin–spin coupling constants, and infrared proton-stretching frequencies. The effects of zero-point motion, thermal vibrational averaging, and isotopic substitution on coupling constants are also discussed. Comparisons are made with available experimental data. Keywords: two-bond NMR spin–spin coupling constants across hydrogen bonds; hydrogen bond type; ab initio EOM-CCSD calculations; vibrational averaging; isotopic substitution