Publication Type |
Journal Article |
Title |
Photoinduced electron-transfer in supramolecular complex of zinc porphyrin with poly(amido amine) dendrimer donor |
Authors |
Pedro M. R. Paulo Sílvia M. B. Costa |
Groups |
MPPM |
Journal |
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY |
Year |
2012 |
Month |
April |
Volume |
234 |
Number |
0 |
Pages |
66-74 |
Abstract |
We report on electron-transfer reactions triggered by photoexcitation of zinc meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (ZnTMPyP4+) complexed with poly(amido amine) dendrimers (PAMAMs). In aqueous medium, cationic ZnTMPyP4+ associates to negatively charged PAMAMs with a binding constant of 1.3 x 10(5) M-1 determined for generation 2.5 dendrimer. Electron-transfer from tertiary amines of the PAMAMs to excited singlet-state of ZnTMPyP4+ induces weak fluorescence quenching without appreciable effect on the porphyrin s photostability in the presence of oxygen. However, under deaerated conditions ZnTMPyP4+ is efficiently reduced to a chlorin, and further on to tetrahydroporphyrin. when exposed to light. A mechanism is proposed for the successive photoreduction of ZnTMPyP4+ based on the spectral identification of reaction intermediates and products. The addition of methyl viologen (Mv(2+)) inhibits this process by acting as an electron acceptor towards the radical ion ZnTMPyP circle,3+ that is formed in the primary electron-transfer step. Laser flash photolysis technique provided insight on electron-transfer reactions between the triplet state of ZnTMPyP4+ and methyl viologen. (c) 2012 Elsevier B.V. All rights reserved. |
DOI |
http://dx.doi.org/10.1016/j.jphotochem.2011.12.021 |
ISBN |
|
Publisher |
|
Book Title |
|
ISSN |
1010-6030 |
EISSN |
|
Conference Name |
|
Bibtex ID |
ISI:000303367600010 |
Observations |
|