COMPLEXATION OF ALIPHATIC-AMINES WITH CARBAZOLE IN THE S-0, AND S-1 STATES - SOLVENT EFFECT ON THE DEACTIVATION OF THE EXCITED COMPLEX

A study of the H-bonding interaction between carbazole, in its ground- and first excited singlet state, with aliphatic and alicyclic amines i n different solvents is reported. In the ground state, the complexatio n equilibrium constants (K-g) correlate with the hydrogen affinity of the amines not with their gas-phase basicity or their ionization poten tials, The same trend was observed for the fluorescence quenching rate constants (k(q)): this indicates that the same type of interaction is operative in both states, Concomitant to the quenching of carbazole f luorescence, a new, red-shifted emission grows up. The nature of this emission depends on the solvent: in alcohols the decay is biexponentia l and the new emission is that of the carbazole anion, In polar aproti c solvents, like acetonitrile, a three-exponential function describes the fluorescence decay, indicating that two radiative channels are ope rative for the deactivation of the excited carbazole amine couple. (C) 1997 Elsevier Science B.V.