Juliana C. Biazzotto

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 fluorinated metalloporphyrinosilica imprinted with templates through sol-gel process

Abstract We present the synthesis of a hybrid material containing fluorinated iron porphyrins through hydrolysis and polycondensation of iron porphyrin bearing a trifluorosilyl function with tetraethoxysilane in the presence of nitrogen bases acting as template molecules. The presence of metalloporphyrin Soret band is detected in the ultraviolet–visible absorption spectra of all metalloporphyrinosilica-templates. Thermogravimetric analysis and electron paramagnetic resonance of the materials also confirm the presence of metalloporphyrin in a silica network. Electron spectroscopy imaging was that of a non-crystalline microstructure. The iron and silicon distribution are homogeneous for the elements in all particle sites. The iron porphyrinosilicas-template were active as catalysts for cyclooctene epoxidation using iodozylbenzene as oxygen donor. In general, the epoxidation yield is larger for iron porphyrinosilicas-template than for manganese porphyrinosilicas-template. The manganese porphyrinosilicas-template had a smaller activity due to their manganese oxidation state. The largest catalytic yield were obtained with the iron porphyrinosilica-pyridine (85%).

Nitric oxide photorelease from a trinuclear ruthenium nitrosyl complex and its in vitro cytotoxicity against melanoma cells

In vitro cytotoxicity study of the [Ru3O(CH3COO)6(4-pic)2(NO)]PF6 triruthenium nitrosyl cluster (compound 1, 4-pic=4-methylpyridine) against B16F10 melanoma cell line was evaluated in the presence and absence of visible light irradiation. The nitrosyl cluster 1 showed a significant tumoricidal activity when irradiated at λ=532 nm, reducing cell viability up to 90% at a concentration of 62.5 μM. However, cell death of 60% is also observed in the dark which can be assigned to the NO release mediated by a redox reaction of the cluster in cell medium. This possibility was confirmed by amperometric detection of NO after the addition of ascorbic acid to compound 1 in phosphate buffer. A control experiment was performed with the solvated cluster [Ru3O(CH3COO)6(4-pic)2(CH3OH)]PF6 (compound 2) and no significant lowering of cell viability was observed. These results suggest that the nitrosyl cluster acts as a pro-drug, delivering NO, which is the actual active species.

Synthesis of manganese porphyrinosilica imprinted with templates using the sol-gel process

Abstract The optimized conditions for the preparation of a new manganese porphyrinosilica-template material are reported. The manganese porphyrinosilica-template was prepared by the sol–gel process, by the reaction of –SO 2 Cl groups present in the phenyl rings of MnTDC(SO 2 Cl)PPCl with 3-aminopropyltriethoxysilane. The reaction produces a precursor porphyrinopropylsilyl species, which were then polymerized with tetraethoxysilane. The presence of manganese porphyrin on xerogel is confirmed by ultraviolet visible absorption spectroscopy and thermogravimetric analysis (TGA). The prepared materials have surface areas between 19 and 674 m 2 g −1 . Electron spectroscopy imaging of the materials show that manganese distribution in the xerogel is uniform. Both manganese(III) porphyrinosilica-template and a similar iron(III) porphyrinosilica-template can catalyze the epoxidation of cyclooctene using iodozylbenzene as oxygen donor. The metalloporphyrinosilica-template presents catalytic activity similar to that of metaloporphyrin in solution.

Electrochemical properties and dissolved oxygen reduction study on an iron(III)-tetra(o-ureaphenyl)porphyrinosilica matrix surface

Electrochemical reduction of dioxygen on an iron(III)-tetra-o-ureaphenylporphyrino-silica matrix surface ((o)-FeTUPPS) obtained by attachment of the iron porphyrin tetraurea to a silica matrix through the sol-gel process was studied. Cyclic voltammetry and chronoamperometry techniques using as working electrode a carbon paste electrode modified with (o)-FeTUPPS, showed that (o)-FeTUPPS catalyzed O2 reduction at −0.34 V vs SCE in 0.5 mol.L−1KCl solution at pH 6. The electrode showed a linear and reproducible response to O2 concentrations in the range ca. 0.5 and 11 mg.L−1 and was chemically stable under various oxidation-reduction cycles. From rotating disk experiments it was concluded that dissolved O2 was reduced at the electrode surface to H2O2 in a two-electron process.

Ironporphyrins trapped sol–gel glasses: a chemometric approach

Abstract The optimised conditions for preparation of ironporphyrin (FeP)-template trapped silica obtained by the sol–gel process are analysed by fractional factorial design. The FeP iron 5,10,15,20-tetrakis(pentafluorophenyl)-porphyrin (FeTFPPCl), iron 5,10,15,20-tetrakis(2,6-dichlorophenyl-3-sulphonatophenyl)-porphyrin (FeTDCSPP(Na)4Cl), iron 5,10,15,20-tetrakis-p-carboxyphenylporphyrin (FeTCPP(Na)4Cl) and iron 5,10,15,20-tetrakis-p-methylpyridilporphyrin (FeTMPyP(Cl)5) were used. Pyridine or 4-phenylimidazole was used as template. Scanning electron microscopy (SEM) shows that the use of different porphyrins and conditions in the preparation of xerogel produce different product morphologies. The prepared materials have surface areas, between 300 and 1000 m2/g. The electron paramagnetic resonance spectra of trapped materials have characteristic signal of FeIII high spin, the presence of porphyrin species in a rhombic symmetry and porphyrin aggregates were also observed.

Synthesis and properties of urea porphyrinosilica

Abstract The synthesis of a hybrid network consisting of alternating porphyrin as optical active agent and siloxane units (porphyrinosilica) can be achieved by sol–gel process. Due to several applications of these hybrids, we search for new methods to prepare them. A porphyrinosilica with a urea linker was synthesized through the reaction of NH2 groups present in the phenyl rings of mesotetrakis p-aminophenyl porphyrin (TAMPPH2) with 3-isocyanatopropyltriethoxysilane (IPTES) followed by condensation with tetraethoxysilane (TEOS). The polymerization reactions were carried out in ethanol or dimethylformamide using acidic or basic catalysis. The formation of urea bonds was confirmed by infrared spectroscopy. The absorption and luminescence spectra confirmed the presence of porphyrin in the network and were also established by thermal analysis. Nuclear magnetic resonance 29Si data for the porphyrinosilica addressed the degree of condensation and the extent of network formation.

Iron(III)-tetra-o-ureaphenylporphyrinosilica obtained by a sol–gel process: a study of EPR, surface area and catalytic activity

Abstract The properties, morphology and catalytic activity of an iron(III)-tetra-o-ureaphenylporphyrinosilica (FePS), obtained using two nitrogenous bases as catalysts in the sol–gel process, are reported. Electron paramagnetic resonance spectra have components due to FeIII high spin, a component at g∼4.3 due to porphyrins species in rhombic symmetry and a component in the region of 0.2 to 0.3 T attributed to Fe–Fe coupling. The solid samples have surface areas 645 and 723 cm2/g, the adsorption isotherms of the solids are type II and the hysteresis loop is type H1. The solids have porosity classified between meso- and macro- porous containing pores with regular morphology and cylindrical and/or polyhedral geometry. Scanning electron microscopy detects an amorphous material composed of aggregates and granules. The matrix effect on the catalytic activity of the FePS, in the Z-cyclooctene oxidation, using iodosylbenzene (PhIO) as oxygen donor was verified. In the repeat-use experiment with FeP:PhIO molar ratio of 1:2000, the total turnover number was 670 for FePS-py, while for the corresponding homogeneous system it was 342.

Gold nanoparticle modifies nitric oxide release and vasodilation in rat aorta

Nitric oxide (NO) plays an important role on several biological functions. Recently, it has been reported the possibility of modifying the NO release profile from the NO donors through its coupling to gold nanoparticles (AuNPs). Thus, AuNPs were synthesized and they were exposed to the NO donor ruthenium complex Cis-[Ru(bpy)2(NO)(4PySH)].(PF6)3 termed (Ru-4PySH)—forming AuNPs-{Ru-4PySH}n cluster. Our results indicate that AuNPs do not modify the maximum effect (ME) and potency (pD2) in the vasodilation induced by Ru-4PySH. Both complexes induce similar vascular relaxation in concentration-dependent way. However, the NO released from the complex AuNPs-{Ru-4PySH}n is lower than Ru-4PySH. Both complexes release only NO0 specie, but AuNPs-{Ru-4PySH}n releases NO in constant way and exclusively in the extracellular medium. In time-course, Ru-4Py-SH was faster than AuNPs-{Ru-4PySH}n in inducing the maximum vasodilation. Inhibition of soluble guanylyl cyclase (sGC) abolished the vasodilation induced by Ru-4PYSH, but not by AuNPs-{Ru-4PySH}n. Non-selective potassium (K+) channel blocker TEA had no effect on the vasodilation induced by AuNPs-{Ru-4PySH}n, but it reduced the potency to Ru-4PySH. In conclusion, our results suggest that AuNPs can reduce the permeability of NO donor Ru-4PySH due to AuNPs-{Ru-4PySH}n cluster formation. AuNPs reduce NO release, but they do not impair the vasodilator effect induced by the NO donor. Ru-4PySH induces vasodilation by sGC and K+ channels activation, while AuNPs-{Ru-4PySH}n activates mainly sGC. Taken together, these findings represent a new pharmacological strategy to control the NO release which could activate selective biological targets.

Nitric Oxide Sensors obtained through the entrapment of iron complexes in sol-gel matrix

Abstract : Iron(III)-diethyldithiocarbamate (Fe3DETC) or iron(III)-tetra-pentafluorophenyl porphyrin (FeTFPP) was entrapped within a silica matrix by the sol-gel process. The obtained sol-gel materials SGFeDETC and SGFeTFPP were investigated as sensors for nitric oxide (NO). UV/Vis spectra of the SGFeTFPP present a Soret band at 410 nm similar to that found in the solution. The binding of gaseous NO resulted in a red shift in the Soret absorption band (410 to 419 nm) of the FeTFPP in the matrix unlike FeTFPP:NO in solution. In the case of SGFeDETC, after addition of sodium dithionite solution and bubbling NO we have good evidence that the complex is formed. The EPR spectrum of the SGFeDETC:NO in solid form exhibited a signal similar to that found in a solution of FeDETC:NO at 77K. The UV/Vis spectrum of SGFeDETC:NO shows a band at 367 nm also found in FeDETC:NO solutions. It is observed that the FeDETC:NO is more stable entrapped in the sol-gel than in aqueous solution. In the former the EPR signal decreases by a factor of 4 after one week, in the latter in 2 days the EPR signal cannot be observed anymore.