Charge-Transfer Interaction and Chemical Reaction. II. Interaction of s-Triaminobenzene with Several Electron Acceptors

The charge-transfer interaction was studied for systems including s-triaminobenzene as electron donor. The formation of 1 : 1 stable outer (π,π) complexes at room temperature was observed for the systems including s-trinitrobenzene, trininitrotoluene and tetracyanobenzene as electron acceptors. From the analysis of the observed absorption intensities and peak positions of charge-transfer bands, the equilibrium constants of these complexes were determined and the ionization potential of s-triaminobenzene was estimated to be 7.3–7.4 eV. Chloranil was found to form a stable outer (π,π) complex with s-triaminobenzene only at low temperature, and to be led to a substitution reaction by raising the temperature. The spectrum of the reaction intermediate, the inner (σ) complex of s-triaminobenzene with chloranil, was observed at ∼500 mμ. A tentative reaction mechanism was proposed.