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PHOTOPHYSICAL PROPERTIES OF PORPHYRIN‐CHLORIN SYSTEMS IN THE PRESENCE OF SURFACTANTS
Author(s) -
Cubeddu Rinaldo,
Keir William F.,
Ramponi Roberta,
Truscott T. George
Publication year - 1987
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1987.tb04824.x
Subject(s) - porphyrin , chlorin , photochemistry , photosensitizer , moiety , chemistry , fluorescence , chromophore , photodynamic therapy , absorption (acoustics) , critical micelle concentration , molecule , micelle , stereochemistry , organic chemistry , materials science , physics , quantum mechanics , aqueous solution , composite material
Abstract The therapeutic efficacy of PDT is related to the capability of the photosensitizer to absorb light at a wavelength that can penetrate into tissues. We have synthesized two systems, a haematoporphyrin‐chlorin (HPC) and a dihaematoporphyrin ether or ester (DHE) with the terminal ring converted to a chlorin (DHEC). The presence of the chlorin moiety provides an extra band at ˜ 660 nm with a relative amplitude from 5 to 10 times larger than that of the porphyrin at 630 nm. Since both HPC and DHEC strongly aggregate in buffer, we have studied their photophysical properties in the presence of cationic surfactants at different concentrations below and above the critical micelle concentrations. Absorption spectra were measured together with emission spectra and fluorescence decays at different observation wavelengths under excitation at 364 nm. The results were compared with those obtained for DHE in the same environmental conditions. As for DHE, the presence of micelles disaggregate both compounds, resulting in a large increase in the relative emission intensity at ˜ 670 nm due to the presence of the chlorin moiety. The fluorescence decays could be fitted by two or three exponential components indicating the presence of more than one molecular species and/ or conformations. On the basis of our measurements the chlorin molecule does not seem to modify appreciably the photophysical properties of the porphyrin molecules but does superimpose its absorption and emission spectrum onto that of the porphyrin. This result may be of relevance in the possible use of these compounds in PDT.