Electron-transfer fluorescence quenching processes in coaggregates betweenexcited N-alkylcarbazoles as electron donors and 2,4-dinitrophenyl carboxylates or pentafluorophenyl carboxylates as accepters

Electron-transfer processes facilitated by hydrophobic-lipophilic interacti on (HLI) between excited N-alkylcarbazoles (1-n, pr = 4, 8, 12, IG) as elec tron donors and 2,4-dintrophenyl carboxylates (Zn, n = 4, 8, 12, le) or pen tafluorophenyl carboxylates (3-n, n = 4, 8, 12, Tb) as electron acceptors h ave been investigated by means of fluorescence spectroscopy in aqueous or a quiorgano binary mixtures. The fluorescence quenching of -n * by Zn or -n i ndicates that preassociation precedes the electron transfer. The extent of HLI-driven coaggregation of the acceptor and the donor may be assessed from the B value of the equation I-0/I = A + B [Q]. The chain-length effect and possibly also a chain-fold-ability effect, as well as the solvent aggregat ing power (SAgP) effect have been observed, Comparison of the quenching con stants (B) for 1-n*/2-n combinations and 1-n* / 3-n combinations, shows tha t the order of Increasing B values fur the quenching processes is 3-n < 2-n .