Electronic configuration and spectra of the neutral and protonated forms of triphenylamine

Abstract

The π-electron system of the triphenylamine molecule is disturbed by the protonation of the nitrogen atom, and consequently three phenyl groups become the equivalent chromophores, which is clearly seen in the absorption and luminescence spectra, comparing them with the corresponding spectra of benzene. The dissociation constant in aqueous sulfuric acid (pKa =-3.94) and 20% ethanol-aqueous sulfuric acid (pKa =-4.86) in the ground state were determined spectrophotometricaly. Förster's cycle, applied to absorption spectra, gave the dissociation constant in the excited state, which has a lower value (ΔpKa =-13.3) than the ones in the ground state. © 1984.