Electron transfer reaction and demetalation of phthalocyaninesReportar como inadecuado

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International Journal of Photoenergy - Volume 2 2000, Issue 1, Pages 9-15

Laboratoire des Matériaux Moléculaires, C.N.R.S., 2–8, rue Henri Dunant, Thiais 94320, France

Copyright © 2000 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


An electron-transfer reaction takes place in the ground state between phthalocyanines aselectron-donors and pyrylium cations as electron-acceptors in polar solvents, reaction which leads to thephthalocyanine radical-cations as evidenced by its absorption spectra identical to the one of the speciesformed by electrochemical oxidation.

The fluorescence emission of the phthalocyanines is quenched by electron-acceptors principally quinones.The free energy change ΔGCT of the electron-transfer reaction has been evaluated for each electron acceptorwith a solvation energy of 0.14 eV in the case of dimethylformamide and 1.2 eV in that of dichloromethane.The rate constant of the quenching of the phthalocyanines singlet excited state by a series of electronacceptorsis found to be of the order of 1.2−1.5×1010L⋅mol-1s-1.

Metalated phthalocyanines are demetalated in the dark by hydroxy-anthraquinones with a rate constantof the order of 10−2L⋅mol-1s-1 at 292K and which increases up to 7×10−2L⋅mol-1s-1 at 349 K withtemperature. The activation energy of the demetalation reaction has been determined to be ca 30 kJ⋅mol-1 for 1,4-dihydroxyanthraquinone and 35 kJ⋅mol-1 for 1,2,4-trihydroxyanthraquinone.

Autor: Jean Kossanyi and Driss Chahraoui

Fuente: https://www.hindawi.com/


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