Molecular orbital theory of the hydrogen bond. V. Hydrogen bonding through the lone pair and the pi system in HF–HCN

Ab initio LCAOSCF calculations with a minimal STO‐3G basis set have been performed on dimers $\mathrm{HF–HCN}$ with HCN as the proton acceptor molecule. The equilibrium dimer has a linear $\mathrm{FH}\mathrm{···}\mathrm{NCH}$ structure which is well described by the general hybridization model for the hydrogen bond. Hydrogen bond formation through the π electron system of HCN has also been investigated. It is found that the π dimers do not correspond to equilibrium structures on the intermolecular $\mathrm{HF–HCN}$ potential surface.