The photobleaching of the free and encapsulated metallic phthalocyanine and its effect on the photooxidation of simple molecules

Fanchiotti, Brenda Gomes; Machado, Marcella Piffer Zamprogno; De Paula, Letícia Camilato; Durmuş, Mahmut; Da Silva, André Romero

Title: The photobleaching of the free and encapsulated metallic phthalocyanine and its effect on the photooxidation of simple molecules
Creator: Fanchiotti, Brenda Gomes
Creator: Machado, Marcella Piffer Zamprogno
Creator: De Paula, Letícia Camilato
Creator: Durmuş, Mahmut
Creator: Nyokong, Tebello
Creator: Da Silva, Gonçalves
Creator: Da Silva, André Romero
Subject: To be catalogued
Date Issued: 2016
Date: 2016
Type: text
Type: article
Identifier: http://hdl.handle.net/10962/239687
Identifier: vital:50755
Identifier: xlink:href="https://doi.org/10.1016/j.jphotobiol.2016.10.007"
Description: The photobleaching of an unsubstituted phthalocyanine (gallium(III) phthalocyanine chloride (GaPc)) and a substituted phthalocyanine (1,4-(tetrakis[4-(benzyloxy)phenoxy]phthalocyaninato) indium(III) chloride (InTBPPc)) was monitored for the free photosensitizers and for the phthalocyanines encapsulated into nanoparticles of PEGylated poly(D,L-lactide-co-glycolide) (PLGA-PEG). Phosphate-buffered solutions (PBS) and organic solutions of the free GaPc or the free InTBPPc, and suspensions of each encapsulated photosensitizer (2–15 μmol/L) were irradiated using a laser diode of 665 nm with a power of 1–104 mW and a light dose of 7.5 J/cm2. The relative absorbance (RA) of the free GaPc dissolved in 1-methyl-2-pyrrolidone (MP) decreased 8.4 times when the laser power increased from 1 mW to 104 mW. However, the free or encapsulated GaPc did not suffer the photobleaching in PBS solution. The RA values decreased 2.4 times and 22.2 times for the free InTBPPc dissolved in PBS solution and in dimethylformamide (DMF), respectively, but the encapsulated InTBPPc was only photobleached when the laser power was 104 mW at 8 μmol/L. The increase of the free GaPc concentration favored the photobleaching in MP until 8 μmol/L while the increase from 2 μmol/L to 5 μmol/L reduced the photodegradation in PBS solution. However, the photobleaching of the free InTBPPc in DMF or in PBS solution, and of each encapsulated photosensitizer was not influenced by increasing the concentration. The influence of the photobleaching on the capability of the free and encapsulated GaPc and InTBPPc to photooxidate the simple molecules was investigated monitoring the fluorescence of dimethylanthracene (DMA) and the tryptophan (Trp). Free InTBPPc was 2.0 and 1.8 times faster to photooxidate the DMA and Trp than it was the free GaPc, but the encapsulated GaPc was 3.4 times more efficient to photooxidize the Trp than it was the encapsulated InTBPPc due to the photodegradation suffered by the encapsulated InTBPPc. The participation of the singlet oxygen was confirmed with the sodium azide in the photobleaching of all free and encapsulated photosensitizer, and in the photooxidation of the DMA and Trp. The asymmetry of InTBPPc increased the solubility of the free compound, decreasing the aggregation state of the photosensitizer and favoring the photobleaching process. The encapsulation shows capability in decreasing the photobleaching of both photosensitizers but the confocal micrographs showed that the increase of the solubility favored the InTBPPc photobleaching during the acquisition of optical cross section. A novel low-symmetry A3B-type phthalocyanine annelated with a pyrazino[2,3-f]phenanthroline ring system and substituted with six solubilizing diisopropylphenoxy-groups (1) was synthesized by metalfree DBU-promoted cross-condensation of diiminoisoindolines derived from 4,5- bis(diisopropylphenoxy)phthalonitrile and pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile. The use of these particular precursors affords A3B phthalocyanine in 15% yield, while cross-condensation of the corresponding dinitriles yields only trace amounts of the target compound. Comparative studies of the A3B-type phthalocyanine and its symmetrical octa(diisopropylphenoxy)-substituted counterpart 2 reveal striking differences in the Q band regions of their UVevisible absorption (UVeVis) spectra, which could be readily rationalized through a comparison with calculated TD-DFT spectra. Since 1 can have two NH-tautomers with equivalent and non-equivalent NH-groups, and DFT calculations predict that the former tautomer is only 2.3 kcal/mol more stable than the latter one, a comprehensive analysis of 13C NMR spectra was carried out through the application of 1 He13C HMBC and HSQC techniques. It demonstrated that only the tautomer with equivalent NH-groups is present in solution.
Format: computer
Format: online resource
Format: application/pdf
Format: 1 online resource (14 pages)
Format: pdf
Publisher: Elsevier
Language: English
Relation: Journal of Photobiology and Photochemistry B: Biology
Relation: Fanchiotti, B.G., Machado, M.P.Z., de Paula, L.C., Durmuş, M., Nyokong, T., da Silva Gonçalves, A. and da Silva, A.R., 2016. The photobleaching of the free and encapsulated metallic phthalocyanine and its effect on the photooxidation of simple molecules. Journal of Photochemistry and Photobiology B: Biology, 165, pp.10-23
Relation: Journal of Photobiology and Photochemistry B: Biology volume 165 p. 10 2016 1011-1344
Rights: Publisher
Rights: Use of this resource is governed by the terms and conditions of the Elsevier Terms and Conditions Statement (https://www.elsevier.com/legal/elsevier-website-terms-and-conditions)
Rights: Closed Access

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RU DST/NRF SARChI for Medicinal Chemistry and Nanotechnology

Nyokong, Tebello (Distinguished Professor)

RU Department of Chemistry

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