Heteroatom Incorporation Effect in σ- and π-Electron Systems: The sEDA(II) and pEDA(II) Descriptors

2012-03-16T00:00:00Z (GMT) by Andrzej Mazurek Jan Cz. Dobrowolski
The effect of heteroatom or heteroatomic group incorporation into unsaturated five- and six-membered cyclic systems was studied by means of DFT/B3LYP/aug-cc-pVDZ calculations. Two descriptors of the incorporation effect, sEDA­(II) and pEDA­(II), reflecting the influence of the incorporated atom or group on the population of the σ and π valence electrons, were constructed on the basis of natural bond orbital analysis. The sEDA­(II) and pEDA­(II) descriptors were shown to be linearly independent; the former correlated very well with electronegativity scales, whereas the latter correlated with NICS(1)ZZ and HOMACC aromaticity indices. The two descriptors seem to be universal tools for analyzing different chemical and physicochemical effects occurring in unsaturated heterocyclic systems.