A two-dimensional potential function for bent hydrogen bonded systems. II-6-hydroxy-2-formylfulvene

A simple and practical method for treating the non-adiabatic proton tunneling in 6-hydroxy-2-formylfulvene was used. A two dimensional potential energy surface function, which couples OH stretching and in-plane bending modes, has been constructed for motion of hydrogen by the aid of quantum mechanical calculations at MP2/6-31G** level for a fixed skeleton geometry. This potential was used for calculation of energy levels from which a tunneling splitting of 181±14 cm−1 was obtained in an excellent agreement with the experimental value of at least 150 cm−1. The calculated barrier height for these results was about 26-27 kJ/mol. This method also assigns a broad band at about 1740 cm−1 to the OH in-plane bending mode. The calculated hydrogen bond strength was estimated to be about 80 kJ/mol.