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The apparent association constants of N,N,N',N'-tetramethyl-p-phenylenediamine complexes with polycyanobenzenes in chlorofom have been determined spectrophotometricaly. The stabilities of similar polynitrobenzene complexes have also been measured for comparison. The polycyanobenzene complexes have lower stabilities, higher excitation energies and lower extinction coefficients than those of the corresponding nitrobenzenes.

The visible absorption spectra of the solid molecular complexes of N, N, N ' , "-tetramethylp-phenylenediamine with weak electron acceptors show only a single absorption in the visible region corresponding to an intermolecular charge-transfer transition of a loose " outer " molecular complex, whereas the spectra of complexes with acceptors of relatively high electron affinity suggest that ionization by complete transfer of an electron from the donor to the acceptor molecule has occurred in the ground state.

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The slow disappearance of the charge-transfer complex and the slow increase in concentration of the Wurster free radical ion in solutions formed by dissolving 2,6-dichloro-p-benzoquinone and N,N,N',N'-tetramethyl-p-phenylenediamine in acetonitrile have been shown to be the result of the upset of equilibria between these species due to the further reaction of the semiquinone ion formed from the quinone. There is evidence that the formation of an "outer" charge-transfer complex from its components is very fast. Relaxation times of the order of 10-l2 seconds have been measured for such processes 3. The observed