A preorganized hydrogen bond network and its effect on anion stability

Rigid tricyclic locked in all axial 1,3,5-cyclohexanetriol derivatives with 0-3 trifluoromethyl groups were synthesized and photoelectron spectra of their conjugate bases and chloride anion clusters are reported along with density functional computations. The resulting vertical and adiabatic detachment energies span 4.07-5.50 eV (VDE) and 3.75-5.00 (ADE) for the former ions and 5.60-6.23 eV (VDE) and 5.36-6.00 eV (ADE) for the latter species. These results provide measures of the anion stabilization due to the hydrogen bond network and inductive effects. The latter mechanism is found to be transmitted through space via hydrogen bonds, and the presence of three ring skeleton oxygen atoms and up to three trifluoromethyl groups enhance the ADEs by 1.61-2.88 eV for the conjugate bases and 1.01-1.60 eV for the chloride anion clusters. Computations indicate that the most favorable structures of the latter complexes have two hydrogen bonds to the chloride anion and one bifurcated interaction between the remote OH substituent and the two hydroxyl groups that directly bind to Cl ^-.