Predicting and Understanding the Signs of One- and Two-Bond Spin-Spin Coupling Constants across X-H-Y Hydrogen Bonds

One-bond X-H (¹J_X-H) and H-Y (^1hJ_H-Y) and two-bond X-Y (^2hJ_X-Y) spin-spin coupling constants across X-H-Y hydrogen bonds have been calculated for a variety of hydrogen-bonded complexes formed from the second period elements ¹³C, ¹⁵N, ¹⁷0, and ¹⁹F. These calculations, carried out using the ab initio equation-of-motion coupled cluster singles and doubles (EOM-CCSD) method, have led to generalizations concerning the signs of the one- and two-bond reduced coupling constants (¹K_X-H, ^lhK_H-Y, and ^2hK_X-Y). These generalizations make possible the prediction of the signs of the corresponding spin-spin coupling constants (J) measured experimentally, taking into account the magnetogyric ratios of the pair of coupled atoms. Insight into the signs of the reduced coupling constants can be gained through the newly-proposed Nuclear Magnetic Resonance Triplet Wavefunction Model (NMRTWM).