UNUSUAL SPECTRAL SHIFTS OF BIS(4-AMINOPHENYL)ETHER

Absorption and fluorescence spectra of Bis(4-aminophenyl)ether (DADPE) have been studied in different solvents and at various acid concentra tions. The results are compared with the spectral data of 4-Aminodiphe nyl ether (ADPE). The fluorescence spectra of DADPE are blue shifted r elative to that of ADPE in polar and hydrogen-bonding solvents. A smal l, but unusual, red shift is observed in the fluorescence spectrum of the monocation relative to that of DADPE in water. These observations reveal that the effect of two amino groups in polar solvents is less t han that of one amino group in the excited singlet state. The abnormal ly red-shifted fluorescence with a peak at around 422 nm at pH 3.5 is due to a dication-solvent exciplex. The formation of the dication-solv ent exciplex leads to an excited state equilibria quite different from that in the ground state.