Anderson O. Ribeiro

A phthalocyanine covalently bonded to a silica network by a sol–gel process

Abstract The preparation and properties of a phthalocyaninosilica, where the phthalocyanine is covalently bonded to an inorganic network, are described. The synthesis consists of the reaction between tetrachlorosulfonylphthalocyanine (PcSO2Cl) and 3-aminopropyltriethoxysilane (APTES) under reflux in dry dichloroethane. After that, ethanol, tetraethoxysilane, water and 1 M HCl or 1 M NH4OH were added to the reaction mixture. The properties of this new material were determined by thermal analysis (TGA/DTA), absorption, luminescence and infrared spectroscopy. The absorption spectra confirmed the presence of the phthalocyanine in the material. The emission spectra of the phthalocyanine and phthalocyaninosilica were measured to verify the structure of the phthalocyanine after its incorporation into the silica. The thermal analysis shows the presence and the retention of the thermal stability of phthalocyanine in the matrix. The resulting materials are presented as blue films and monoliths with optical quality.

Synthesis of Phthalocyanines−ALA Conjugates: Water-Soluble Compounds with Low Aggregation

Syntheses of two water-soluble phthalocyanines (Pc) containing 5-aminolevulinic acid (ALA) linked to the core structure are described. These compounds were prepared by using original functionalizations, and they present remarkable structural and photophysical features, indicating that they could be applied to photodynamic therapy (PDT).

Characterization and spectroscopic studies of Eu3+ and Tb3+ complexes with 2,2′-bipyridine-4,4′-dicarboxylic acid

This work reports on the synthesis of the ligand 2,2′-bipyridine-4,4′-dicarboxylic acid (bpc), the characterization and photophysical properties of Ln2(bpc)3·nH2O (Ln=Eu,Tb,Gd). The compounds were synthesized by the addition of LnCl3 aqueous solution to an aqueous ligand (bpc) solution (pH ∼7.0). The characteristic transitions 5Do→ 7FJ (J=0, 1, 2, 3 and 4) of the Eu3+ and 5D4→7FJ (J=6, 5, 4 and 3) of Tb3+ were observed. The lifetime measurements of the 5D0 and 5D4 excited levels (0.37 and 0.90±0.01 ms) are in agreement with three to four coordinated water molecules. The monoexponential decay curves reveal only one type of site for each ion in the complexes. The complexes were also characterized by thermogravimetric analyses and infrared spectroscopy.

A novel chlorin derivative of Meso-tris(pentafluorophenyl)-4-pyridylporphyrin: synthesis, photophysics and photochemical properties

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.

Spectroscopic study of Tb3+(beta-diketonate)3: alpha-cyclodextrin inclusion compounds in aqueous solution

In this work we describe how the inclusion of Tb3+ b-diketonate chelates into the hydrophobic cavity of a-cyclodextrin enhances the solubility of the complexes in aqueous medium and leads to changes in their photophysical properties. To this end, the complexes [Tb(ppa)3(H2O)2] and [Tb(ppa)3(phen)] (ppa=3-phenyl-2,4-pentanedione; phen = phenantroline) were synthesized and characterized, and they were then included into a-cyclodextrin pockets. This inclusion was confirmed by 1H NMR spectroscopy and the stoichiometry was determined by means of the Job method. In the excitation spectra, the maximum intensity wavelength of the inclusion compounds [Tb(ppa)3(H2O)2]: a-CD and [Tb(ppa)3(phen)]:a-CD were displaced 15 and 60 nm respectively when compared with the non-CD starting complexes. The typical Tb3+ emission bands were maintained after inclusion of the complexes into a-CD and their subsequent solubilization in aqueous medium.

New Design of Mini PTFE Vessels for Sample Preparation in Micro Scale: Determination of Cd, K, Mg and Na in Biological Sample

This paper presents a study involving the development of a new mini polytetrafluoroethylene (PTFE) vessel project for biological sample preparation in micro scale in closed system with microwave radiation for subsequent determination of Cd, K, Mg and Na by atomic spectrometry techniques. All experiments were carried out in micro quantities of samples (up to 20 mg) and reagents (300 μL of HNO3) for 5 min at 350 W. Certified reference materials of biological samples (bovine muscle and liver) were used to evaluate the accuracy of the proposed system and the results obtained were in agreement with the certified value at 95% of confidence (t-test). Relative standard deviations (RSD) were lower than 8.0% for all elements. The proposed method is not only easy and fast, but it is also based on the use of an inexpensive system for sample digestion.

Evaluation of the Concentration of Cu, Zn, Pb and Cr in Different Fish Species from the São Gonçalo Channel in Pelotas-RS, Brazil

The objective of this study was to evaluate the concentration of Cu, Zn, Cr and Pb in different species of fish collected in the estuarine and limnic regions of the São Gonçalo channel, located in the Patos-Mirim lagoon complex in the coastal plain of Rio Grande do Sul State (Southern Brazil) during 2013 (autumn, winter and spring) and 2014 (summer). Fish samples were decomposed in a digester block with a reflux system under conditions optimized using a central composite design as it follows: 250 mg of fish sample, 5 mL HNO3, 2 mL H2O2 during 2 h at 150 °C. The concentrations obtained ranged from 6.7 to 12.0 mg kg for Cu; 1.8 to 23.6 mg kg for Zn; 37 to 487 μg kg for Pb; and 40 to 1268 μg kg for Cr. The highest concentrations of Cu, Zn and Pb, were observed in fishes collected at locations in the estuarine region and Cr showed high levels, especially in the limnic region. The samples of the species Loricariichthys anus (viola) showed the highest concentrations of all analytes investigated.

Determination of Hg in Biological Samples and Ethanol Fuel by Photochemical Vapor Generation after Pre-Concentration in a Gold Trap

In this work, the photochemical vapor generation (PVG) coupled with atomic absorption spectrometry and a pre-concentration step with an Au column was used for the determination of Hg in biological samples and ethanol fuel. PVG with pre-concentration showed an up to 250-fold higher sensitivity compared to the approach without pre-concentration. The accuracy of analysis of biological samples was evaluated using certified reference materials (fish tissues), while for ethanol fuel samples, recovery tests were employed (91%). Analytical curves were linear (R > 0.99) in the studied range of 2.5 to 10 μg L for conventional PVG and 0.2 to 0.5 μg L for PVG with the pre-concentration step. For the last, the limits of detection reached for biological samples and ethanol fuel were 0.02 and 0.01 μg L, respectively. The systems presented are simple, sensitive and safe for the control of low Hg concentrations in different samples. However, only the system using pre-concentration with an Au column was capable of obtaining the reproduced signals of Hg in low concentrations of the order of 0.2 μg L.

Photophysical and Photochemical Properties and Aggregation Behavior of Phthalocyanine and Naphthalocyanine Derivatives

2 789 0.7024 HOMO → LUMO; HOMO → LUMO+1 489 0.0092 HOMO → LUMO+4 485 0.0060 HOMO → LUMO+5 477 0.0422 HOMO-2 → LUMO; HOMO-1 → LUMO 471 0.2010 HOMO-1 → LUMO+1 470 0.2334 HOMO-1 → LUMO Wavelength fitted to experimental data by a factor of 16% for ZnPc and 1 and 10% ZnNc (calculated from the difference between calculated and experimental Q-band). Fit parameters are different because DFT predicts better gap energy as larger is the conjugated system.

TiO2 spherical structures with potential application for photodynamic therapy

24h receiving the treatment. For toxicity studies, cells remained in contact with the phthalocyanine for 2 and 24h. For phototoxicity studies, cells remained in contact with the treatment for 2h, irradiated by laser (660nm, 8W/cm2) for 20min and re-incubated for 2, 6, 24 and 48h. Cells treatedwith new ruthenium phthalocyanine showedhighpercentage viability anddid not differmuch from the untreated control cells, demonstrating the low toxicity of compound.However, a decrease in percentage viabilitywas observed in PDT treated cells showing its potential as a photosensitizer. Further studies of this system are in progress.