'Vertical' and 'Adiabatic' Proton Affinity

摘要

The protonation of some Bronsted bases is accompanied by a significant structural reorganization leading to a decrease in the rate of the processes of addition and detachment of the mobile protons. Such cases are considered as a combination of high thermodynamic basicity with low nucleophilicity [1] or with low kinetic basicity [2]. However, by analogy with the "vertical" ionization potential, which characterizes the process of the instantaneous removal of an electron, and the "adiabatic" ionization potential, which takes into account the difference between the equilibrium structural parameters of the cation and the parent molecule, it is possible to distinguish the "vertical" and "adiabatic" proton affinity (VPA and APA). In this report the quantum chemical method PBEO using the cc-pVTZ orbitals for the nitrogen and mobile hydrogen and the cc-pVDZ orbitals for the carbon and for hydrogen atoms strongly bound to carbon and Gaussian-03 software [3] were applied to calculate the VPA and APA values for the quinuclidine and l,8-bis(dimethylamino)naphthalene molecules.