On the n(N)/n(O) interaction in adamantane cages

Abstract

The equilibrium structures of adamantane, 1-azaadamantane, adamantanone and derivatives were fully optimized at the B3LYP/6-31+G∗∗ ab initio level of theory. The NMR 13C chemical shifts were predicted by means of ab initio CSGT (continuous set of gauge transformations) calculations performed with the B3LYP/6-311+G(2d,p) DFT-HF hybrid model. The low-lying ionization energies were determined by ab initio outer valence Green function (OVGF) calculations. The results for the displacement of the resonances in the NMR spectra and for the location and splitting of the n-ionization bands in the photoelectron spectra are in good agreement with experiment. The mutual influence of the electronic interaction between the nitrogen and oxygen lone-pairs in various steric arrangements was examined by comparing the spectroscopic features of mono-, bi-, and tri-functionalized adamantane cages.