The excited states interaction of safranine-O with PAMAM and DAB dendrimers in metanol

C. SUCHETTI, A. I. NOVAIRA, S. G. BERTOLOTTI AND C. M. PREVITALI

JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY

Elsevier

Año: 2009 vol. 201 p. 69 - 74

1010-6030

PAMAM and DAB dendrimers was investigated in methanol. The rate constants for the quenching of the excited singlet state depend on the number of primary amino groups in the dendrimer. The first-order rate constant for the decay of the triplet state presents a downward curvature as a function of the quencher concentration. This behavior was interpreted in terms of the reversible formation of an intermediate complex in the excited state. Froma kinetic analysis of the quenching mechanism the equilibrium constant Kexc could be extracted. The values of Kexc may be related to the proton affinity of the quencher. The results were interpreted in terms of a reversible proton transfer quenching. This was further confirmed by the transient absorption spectra obtained by laser flash photolysis. The transient absorption immediately after the triplet state quenching could be assigned to the unprotonated form of the dye. At later times the spectrum matches the semireduced form of the dye. The overall process corresponds to a one-electron reduction of the dye mediated by the deprotonated triplet state. were interpreted in terms of a reversible proton transfer quenching. This was further confirmed by the transient absorption spectra obtained by laser flash photolysis. The transient absorption immediately after the triplet state quenching could be assigned to the unprotonated form of the dye. At later times the spectrum matches the semireduced form of the dye. The overall process corresponds to a one-electron reduction of the dye mediated by the deprotonated triplet state. were interpreted in terms of a reversible proton transfer quenching. This was further confirmed by the transient absorption spectra obtained by laser flash photolysis. The transient absorption immediately after the triplet state quenching could be assigned to the unprotonated form of the dye. At later times the spectrum matches the semireduced form of the dye. The overall process corresponds to a one-electron reduction of the dye mediated by the deprotonated triplet state. exc could be extracted. The values of Kexc may be related to the proton affinity of the quencher. The results were interpreted in terms of a reversible proton transfer quenching. This was further confirmed by the transient absorption spectra obtained by laser flash photolysis. The transient absorption immediately after the triplet state quenching could be assigned to the unprotonated form of the dye. At later times the spectrum matches the semireduced form of the dye. The overall process corresponds to a one-electron reduction of the dye mediated by the deprotonated triplet state.