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International Journal of Photoenergy
Volume 2009, Article ID 413915, 10 pages
http://dx.doi.org/10.1155/2009/413915
Research Article

A Singlet Oxygen Photogeneration and Luminescence Study of Unsymmetrically Substituted Mesoporphyrinic Compounds

1Centro de Química-Física Molecular (CQFM) and Instituto de Nanociencias e Nanotecnologias (IN), Instituto Superior Técnico, Universidade Técnica de Lisboa, Avenida Rovisco Pais, 1049-001 Lisbon, Portugal
2Department of Physical Chemistry, Faculty of Chemistry, University of Bucharest, 4-12 Regina Elisabeta Bulevardul, 030018 Bucharest, Romania
3Department of Inorganic Chemistry, Faculty of Pharmacy, “Carol Davila” University of Medicine and Pharmacy, Bucharest, 6 Traian Vuia Street, Sector 1, Bucharest, Romania
4Institute of Physical Chemistry “I.G. Murgulescu” of the Romanian Academy, 202 Spl. Independentei, 060021 Bucharest-12, Romania

Received 6 June 2008; Revised 26 September 2008; Accepted 9 March 2009

Academic Editor: Mohamed Sabry Abdel-Mottaleb

Copyright © 2009 Anabela Sousa Oliveira et al. 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.

Abstract

This paper deals with a series of new unsymmetrically substituted mesoporphyrins: 5-(2-hydroxyphenyl)-10,15,20-tris-phenyl-21,23-H-porphyrin (TPPO), 5-(3-hydroxyphenyl)-10,15,20-tris-phenyl-21,23-H-porphyrin (TPPO), 5-(4-hydroxyphenyl)-10,15,20-tris-phenyl-21,23-H-porphyrin (TPPO), 5-(2-hydroxyphenyl)-10,15,20-tris-butyl-21,23-H-porphyrin (TBPO), and their parent nonsubstituted compounds, respectively, 5,10,15,20-tetrakis-phenyl-21,23-H-porphyrin (TPP) and 5,10,15,20-tetrakis-butyl-21,23-H-porphyrin (TBP). Several photophysical studies were carried out to access the influence of the unsymmetrical substitution at the porphyrinic macrocycle on porthyrin's photophysical properties, especially porthyrin's efficiency as singlet oxygen sensitizers. The quantum yields of singlet oxygen generation were determined in benzene ((TPP) = 0.66  0.05; (TPPO) = 0.69  0.04; (TPPO) = 0.62  0.04; (TPPO) = 0.73  0.03; (TBP) = 0.76  0.03; (TBPO) = 0.73  0.02) using the 5,10,15,20-tetraphenyl-21,23-H-porphine ((TPP) = 0.66) and Phenazine ((Phz) = 0.83) as reference compounds. Their fluorescence quantum yields were found to be ((TPPO) = 0.10  0.04; (TPPO) = 0.09  0.03; (TPPO) = 0.13  0.02; (TBP) = 0.08  0.03 and (TBPO) = 0.08  0.02 using 5,10,15,20-tetraphenyl-21,23-H-porphine as reference (TPP) = 0.13). Singlet state lifetimes were also determined in the same solvent. All the porphyrins presented very similar fluorescence lifetimes (mean values of (with , air equilibrated) = 9.6  0.3 nanoseconds and (without , argon purged) = 10.1  0.6 nanoseconds, resp.). The phosphorescence emission was found to be negligible for this series of unsymmetrically substituted mesoporphyrins, but an E-type, thermally activated, delayed fluorescence process was proved to occur at room temperature.