TY - JOUR
T1 - Photophysics and photochemistry of porphyrin core PAMAM dendrimers. Excited states interaction with quinones
AU - Militello, M. Paula
AU - Arbeloa, Ernesto M.
AU - Hernández Ramírez, Raquel E.
AU - Lijanova, Irina V.
AU - Montejano, Hernán A.
AU - Previtali, Carlos M.
AU - Bertolotti, Sonia G.
N1 - Publisher Copyright:
© 2019
PY - 2020/2/1
Y1 - 2020/2/1
N2 - Quenching of excited states of the meso-substituted tetraphenyl porphyrins with PAMAM branches, and one with PAMAM generation 1 peripherally-modified with thiazole groups by p-benzoquinones, were studied in DMF solution. Fluorescence lifetime measurements evidence a static component in the quenching process. The dynamic quenching rate constants were close to the diffusional limit except for the case of duroquinone. Apparent association constants of the porphyrin compounds with the quinones were determined by comparison of static and dynamic measurements of fluorescence quenching. The ground state interaction is very weak with the exception of tetrachlorobenzoquinone. The triplet state decay kinetics and the transient absorption spectra in the presence of the quinones were determined by laser flash photolysis. Triplet quenching rate constants were lower than those of singlet quenching. An electron transfer mechanism was proposed to explain the results. The long-time transient absorption spectra were assigned to the radical cation of the dyes. Relative radical yields were determined and a dependence on the side chains and the quencher was observed.
AB - Quenching of excited states of the meso-substituted tetraphenyl porphyrins with PAMAM branches, and one with PAMAM generation 1 peripherally-modified with thiazole groups by p-benzoquinones, were studied in DMF solution. Fluorescence lifetime measurements evidence a static component in the quenching process. The dynamic quenching rate constants were close to the diffusional limit except for the case of duroquinone. Apparent association constants of the porphyrin compounds with the quinones were determined by comparison of static and dynamic measurements of fluorescence quenching. The ground state interaction is very weak with the exception of tetrachlorobenzoquinone. The triplet state decay kinetics and the transient absorption spectra in the presence of the quinones were determined by laser flash photolysis. Triplet quenching rate constants were lower than those of singlet quenching. An electron transfer mechanism was proposed to explain the results. The long-time transient absorption spectra were assigned to the radical cation of the dyes. Relative radical yields were determined and a dependence on the side chains and the quencher was observed.
KW - Laser flash photolysis
KW - PAMAM dendrimers
KW - Porphyrin-based dendrimers
KW - Quinones
KW - Triplet quenching
UR - http://www.scopus.com/inward/record.url?scp=85074348233&partnerID=8YFLogxK
U2 - 10.1016/j.jphotochem.2019.112167
DO - 10.1016/j.jphotochem.2019.112167
M3 - Artículo
SN - 1010-6030
VL - 388
JO - Journal of Photochemistry and Photobiology A: Chemistry
JF - Journal of Photochemistry and Photobiology A: Chemistry
M1 - 112167
ER -