The electronic structure of protonated forms of azaindoles

The Pariser-Parr-Pople (PPP) method has been applied to protonated 4-, 5-, 6-, and 7-azaindoles, and the results are compared with published ones 1] for indole and azaindoles. These show that protonation and solvation at the N in the six-membered ring can play a major part in the chemical behavior of the azaindoles. The differences between the compounds are due to induction rather than to differences in the structure of the -system. The method of restricted configuration interaction (RCI) has been used to calculate the energies of the lowest - transitions.We are indebted to L. N. Yakhontov and M. Ya. Uritskaya for numerous discussions.