A theoretical structural analysis of the factors that affect 1JNH, 1hJNH and 2hJNN in N–H···N hydrogen‐bonded complexes

Calculations of ¹ J_NH, ^1h J_NH and ^2h J_NN spin–spin coupling constants of 27 complexes presenting N–H·N hydrogen bonds have allowed to analyze these through hydrogen‐bond coupling as a function of the hybridization of both nitrogen atoms and the charge (+1, 0, ? 1) of the complex. The main conclusions are that the hybridization of N atom of the hydrogen bond donor is much more important than that of the hydrogen bond acceptor. Positive and negative charges (cationic and anionic complexes) exert opposite effects while the effect of the transition states ‘proton‐in‐the‐middle’ is considerable. Copyright © 2008 John Wiley & Sons, Ltd.