SPIN-DENSITIES AND POLYMERIZABILITIES OF ANILINE DERIVATIVES DEDUCED FROM DENSITY-FUNCTIONAL CALCULATIONS

A theoretical study of the electronic structure of some aniline deriva tives is performed, aimed at a microscopic explanation of the observed polymerizability of these compounds. Monomers with methyl and methoxy substituents located at various positions on the benzenoid ring are c onsidered using the density functional theory program deMon-KS. The ca lculations indicate that the distribution of the net radical cation sp in among the atoms (atomic spin populations) is very sensitive to the nature and the position of the substituents. In fact this distribution reflects specifics of the electronic structure of these monomers rela ted to their polymerizability. It is shown that polymerization is favo red when the net spin population on the nitrogen atom is similar to th at on the ring carbon atom at the para position. On the contrary, in t he species that do not polymerize, these two atoms have substantially different spin populations. A possible explanation of this result is d iscussed in terms of chemical reactivity based on the softness-hardnes s concept.