Abstract
Photodynamic therapy (PDT) is based on the accumulation of a photosensitizer, such as a porphyrin or a chlorin, in a malignant tissue after its administration. Chlorins exhibit photophysical properties similar to those of the porphyrin macrocycles, but with intensified and red-shifted Q bands, making chlorin-containing systems even better candidates for PDT. In this contribution, we report the synthesis of 5,10,15-tris(pentafluorophenyl)-20-(4-pyridyl)porphyrin, (2) and its transformation to the novel chlorin derivatives 4, (5,10,20-tris(pentafluorophenyl)-15-(4-pyridyl)-tetrahydro-1H- N-methyl-pyrrolo [3,4-b]porphyrin and 5, (5,10,15-tris(pentafluorophenyl)-20-(4-pyridyl)-tetrahydro-1H- N-methyl-pyrrolo[3,4-b]porphyrin) by 1,3-dipolar cycloaddition with an azomethine ylide. The new products have been characterized by UV-Vis, 1H NMR and FAB-MS. The photophysics, photochemical and photobleaching properties of chlorin 4 have been evaluated. Its quantum yield of photobleaching (fPb, mol Einstein-1) was 0.047±0.014. In order to demonstrate the production of 1O2 when 4 is used as a photosensitizer, uric acid tests have been carried out. The results indicate that chlorin 4 can be considered a promising photosensitizer in PDT.
Highlights
Macrocyclic tetrapyrrolic metal complexes have been investigated for a few decades on account of their catalytic properties
Our aim is to synthesize new porphyrins and employ them in cycloaddition transformations leading to novel chlorin derivatives that can be considered as potential Photodynamic therapy (PDT) candidates
We report the synthesis and structural characterization (UV-Vis spectra, FAB-MS and 1H NMR) of 5,10,15-tris(pentafluorophenyl)-20-(4-pyridyl) porphyrin, (2), and its use as a dipolarophile in a 1,3-dipolar cycloaddition with the azomethine ylide generated in situ from N-methylglycine and paraformaldehyde (Scheme 2)
Summary
Macrocyclic tetrapyrrolic metal complexes have been investigated for a few decades on account of their catalytic properties. They are capable of catalyzing a wide range of oxidation reactions: from hydroxylation of alkanes and epoxidation of alkenes to drug oxidation and DNA. Photodynamic therapy (PDT) is a form of neoplastic diseases treatment using a photosensitizer, oxygen and light. The exogenous photosensitizer localises in tumours with a high degree of selectivity after its administration. Subsequent irradiation with visible or near infrared light induces a photodynamic effect.
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