EXCITED STATE PROTOTROPIC EQUILIBRIA OF SOME QUINOLINOLS

The prototropic equilibrium constants for the first excited singlet states of the cation-zwitterion equilibria of a series of quinolinols and 5-isoquinolinol have been determined by fluorescence as well as absorption measurements. The results obtained by the two methods are not in good agreement and the reasons for this are discussed. Hückel MO calculations have been carried out on the molecules studied. The protonation energies and the one electron charge densities on the oxygen atoms can be qualitatively correlated with the excited state equilibrium constants. © 1968.