REACTION ENTROPY FOR THE ELECTROREDUCTION OF 2-PHENYL-3-ARYLIMINO-3H-INDOLES IN VARIOUS APROTIC-SOLVENTS

The entropy and free energy of the one-electron reduction of some 2-phenyl-3-arylimino-3H-indole derivatives in dimethylformamide, acetonitrile and dimethylsulphoxide have been determined using a non-isothermal cell arrangement. The observed correlation between the values of ΔrXXX and the solvent acceptor number reveals that the electroreduction process is affected principally by the degree of structuring of the solvent, while the contribution of the substituents arising from the spin density of radical anions, as evaluated by the Hückel-Mc-Lachlan molecular orbital method, is negligible. © 1990.