Interaction of cationic water-soluble meso-tetrakis(4-N-methylpyridiniumyl)porphyrin (TMPyP) with ionic and nonionic micelles: aggregation and binding

The equilibrium of meso-tetrakis(4-N-methylpyridiniumyl)porphyrin (TMPyP) in aqueous solution in the presence of surfactants was studied by optical spectroscopic techniques and SAXS (small angle X-ray scattering). Anionic SDS (sodium dodecyl sulfate), zwitterionic HPS (N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate) and nonionic TRITON X-100 (t-octyl-phenoxypolyethoxyethanol), surfactants were used. TMPyP is characterized by a protonation equilibrium with a pK(a) around 1.0, associated with the diacid-free base transition, and a second pK(a) around 12.0 related with the transition between the free base and the monoanion form. Three independent species were observed for TMPyP at pH 6.0 as a function of SDS concentration: free TMPyP, TMPyP-SDS aggregates and porphyrin monomer bound to micelles. For HPS and TRITON X-100, the equilibrium of TMPyP as a function of pH is quite similar to that obtained in pure aqueous solution: no aggregation was observed, suggesting that electrostatic contribution is the major factor in the interaction between TMPyP and surfactants. SAXS data analysis demonstrated a prolate ellipsoidal shape for SDS micelles; no significant changes in shape and size were observed for SDS-TMPyP co-micelles. Moreover, the ionization coefficient, alpha, decreases with the increase of the porphyrin concentration, suggesting the ""screening"" of the anionic charge of SDS by the cationic porphyrin. These results are consistent with optical absorption, fluorescence and RLS (resonance light scattering) spectroscopies data, allowing to conclude that neutral surfactants present a smaller interaction with the cationic porphyrin as compared with an ionic surfactant. Therefore, the interaction of TMPyP with the ionic and nonionic surfactants is predominantly due to the electrostatic contribution. Copyright (c) 2008 Society of Porphyrins & Phthalocyanines.

Investigation of Ground- and Excited-State Photophysical Properties of 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphyrin with Ruthenium Outlying Complexes

The present work employs a set of complementary techniques to investigate the influence of outlying Ru(II) groups on the ground- and excited-state photophysical properties of free-base tetrapyridyl porphyrin (H(2)TPyP). Single pulse and, pulse train Z-scan techniques used M association with laser flash photolysis, absorbance and fluorescence spectroscopy, and fluorescence decay measurements, allowed us to conclude that the presence of outlying Ru(II) groups causes significant changes on both electronic structure and vibrational properties of porphyrin. Such modifications take place mainly due to the activation of. nonradiative decay channels responsible for the emission, quenching, as well as by favoring some vibrational modes in the light absorption process, It is also observed that, differently from what happens when the Ru(II) is placed at the center of the macrocycle, the peripheral groups cause an increase of the intersystem crossing processes, probably due to the structural distortion of the ring that implies a worse spin orbit coupling, responsible for the intersystem crossing mechanism.

Excited-state dynamics of meso-tetrakis(sulfonatophenyl) porphyrin J-aggregates

The excited-state dynamics of free-base meso-tetrakis(sulfonatophenyl) porphyrin J-aggregates obtained by the Z-scan technique in femto- and picosecond time scales, along with UV-Vis spectroscopy and flash photolysis is reported. Besides obtaining the S-1 state lifetime, the discrimination between internal conversion and intersystem crossing nonradiative processes from that state was also possible, and their rates and respective quantum yields were found. The aggregates present reverse saturable absorption at 532 nm for both singlet and triplet excited states. The data shown is important for several applications such as optical limiting, photodynamic therapy and others. (C) 2011 Elsevier B.V. All rights reserved.

Interaction of the meso-tetrakis (4-N-methylpyridyl) porphyrin with gel and liquid state phospholipid vesicles

The interaction of the cationic meso-tetrakis 4-N-methylpyridyl porphyrin (TMPyP) with large unilamellar vesicles (LUVs) was investigated in the present study. LUVs were formed by mixtures of the zwitterionic 1,2-dipalmitoyl-sn-glycero-phosphatidylcholine (DPPC) and anionic 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) phospholipids, at different DPPG molar percentages. All investigations were carried out above (50 degrees C) and below (25 degrees C) the main phase transition temperature of the LUVs (similar to 41 degrees C). The binding constant values, K-b, estimated from the time-resolved fluorescence study, showed a significant increase of the porphyrin affinity at higher mol% DPPG. This affinity is markedly increased when the LUVs are in the liquid crystalline state. For both situations, the increase of the K-b value was also followed by a higher porphyrin fraction bound to the LUVs. The displacement of the vesicle-bound porphyrins toward the aqueous medium, upon titration with the salt potassium chloride (KCl), was also studied. Altogether, our steady-state and frequency-domain fluorescence quenching data results indicate that the TMPyP is preferentially located at the LUVs Stern layer. This is supported by the zeta potential studies, where a partial neutralization of the LUVs surface charge, upon porphyrin titration, was observed. Dynamic light scattering (DLS) results showed that, for some phospholipid systems, this partial neutralization leads to the LUVs flocculation. (C) 2012 Elsevier Inc. All rights reserved.

Iron(III) Porphyrin Covalently Supported onto Magnetic Amino-Functionalized Nanospheres as Catalyst for Hydrocarbon and Herbicide Oxidations

This work describes the covalent immobilization of an ironporphyrin, 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin iron(III) chloride (FeTFPP), onto maghemite/silica magnetic nanospheres covered with aminofunctionalized silica. The resulting material (gamma-Fe2O3/SiO2-NHFeP) was characterized by diffuse reflectance infrared spectroscopy (DRIFTS) and UV-Vis absorption spectroscopy. The catalytic activity of this magnetic ironporphyrin was investigated in the oxidation of hydrocarbons (styrene, (Z)-cyclooctene and R-(+)-limonene) and an herbicide (simazine) by hydrogen peroxide or 3-chloroperoxybenzoic acid. Hydrocarbon and simazine oxidation reaction products were analyzed by gas chromatography (GC) and high performance liquid chromatography (HPLC), respectively. This catalytic system proved to be efficient and selective for hydrocarbon oxidation, leading to high product yields from styrene (89%), cyclooctene (71%) and R-(+) -limonene (86%). Simazine oxidation was attained with 100% selectivity for a dechlorinated product (OEAT), while several oxidation products were obtained for the same catalyst in homogeneous media. The catalyst can be easily recovered through application of an external magnetic field and washed after reaction. Catalyst reuse experiments for R-(+)-limonene oxidation have shown that the catalytic activity is kept at 90% after 10 consecutive reactions.

Sevenfold enhancement on porphyrin dye efficiency by coordination of ruthenium polypyridine complexes

Sevenfold enhancement of photoconversion efficiency was achieved by incorporation of peripheral ruthenium complexes to a porphyrin dye, generating supramolecular effects capable of playing several key roles (e.g., transferring energy to, inhibiting aggregation, and accepting the hole generated in the porphyrin center after electron injection), providing new insights for the design of better DSSC photosensitizers.

5-(1-(4-phenyl)-3-(4-nitrophenyl)triazene)-10,15,20-triphenylporphyrin: a new triazene-porphyrin dye and its spectroelectrochemical properties

The new triazene-porphyrin dye 5-(1-(4-phenyl)-3-(4-nitrophenyl)triazene)-10,15,20-triphenylporphyrin, encompassing a reactive protonated triazene moiety, was prepared starting from meso-tetraphenylporphyrin (H2TPP), first converting it to the 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin, then reducing to the 5-(4-aminophenyl)-10,15,20-tri(phenyl) porphyrin intermediate, and reacting with the diazonium salt of 4-nitroaniline; and characterized by spectroscopic and electrochemical methods. The absorption spectrum of the neutral species resembled the sum of H2TPP and of 1,3-bis(4-nitrophenyl) triazene spectrum, but the deprotonated anionic species showed more delocalized frontier orbitals, behaving as a push-pull system exhibiting triazenide-to-porphyrin charge-transfer transitions.

Iron(III) porphyrin covalently supported onto magnetic amino-functionalized nanospheres as catalyst for hydrocarbon and herbicide oxidations

This work describes the covalent immobilization of an ironporphyrin, 5,10,15,20- tetrakis(pentafluorophenyl)porphyrin iron(III) chloride (FeTFPP), onto maghemite/silica magnetic nanospheres covered with aminofunctionalized silica. The resulting material (γ-Fe2O3/SiO2-NHFeP) was characterized by diffuse reflectance infrared spectroscopy (DRIFTS) and UV-Vis absorption spectroscopy. The catalytic activity of this magnetic ironporphyrin was investigated in the oxidation of hydrocarbons (styrene, (Z)-cyclooctene and R-(+)-limonene) and an herbicide (simazine) by hydrogen peroxide or 3-chloroperoxybenzoic acid. Hydrocarbon and simazine oxidation reaction products were analyzed by gas chromatography (GC) and high performance liquid chromatography (HPLC), respectively. This catalytic system proved to be efficient and selective for hydrocarbon oxidation, leading to high product yields from styrene (89%), cyclooctene (71%) and R-(+)-limonene (86%). Simazine oxidation was attained with 100% selectivity for a dechlorinated product (OEAT), while several oxidation products were obtained for the same catalyst in homogeneous media. The catalyst can be easily recovered through application of an external magnetic field and washed after reaction. Catalyst reuse experiments for R-(+)-limonene oxidation have shown that the catalytic activity is kept at 90% after 10 consecutive reactions.

Synthesis of self-assembled tubes in direct conjugated porphyrin-gold nanohybrid solution

We report on the formation of self-assembled meso-tetrakis (p-sulfonatofenyl) porphyrin (H2 TPP'S POT. 4-''IND. 4') tubes stabilized by gold nanoparticles (NPs) in basic solution and on their spectroscopic chareterization. The role of the gold NPs in the aggregation dynamics of free-base sulfonated porphyrin (H2TPP'S POT. 4-''IND. 4') is also investigated. The direct conjugation of the gold NPs to the H2TPPS4 molecule quenches the fluorescence intensity, while absorption peaks are blue-shifted, indicating predominant H-type aggregation. It is observed that porphyrin molecules adsorbed on the surface of the gold NP interact and form tubes of maximum diameter ∼1.5 μm and length >100 μm. Steady-state and time-resolved spectroscopic techniques confirm nonradiative energy transfer from porphyrin to gold NP.

Pharmacokinetics of Photogem Using Fluorescence Spectroscopy in Dimethylhydrazine-Induced Murine Colorectal Carcinoma

This study aimed to investigate the pharmacokinetics of a hematoporphyrin derivative in colonic tumors induced by dimethylhydrazine and adjacent normal colon in Wistar rats using an in vivo fluorescence spectroscopy technique. In conventional clinical application of photodynamic therapy, the interval between photosensitizer (PS) administration and lesion illumination is often standardized without taking into account variations due to the type or localization of the tumor and intrinsic differences in the microcirculation and vascular permeability of each target organ. The analysis of the fluorescence spectra was based on the intensity of porphyrin emission band centered at around 620nm in normal colon and colon tumors. The photosensitizer fluorescence intensity rapidly grew for carcinoma and normal colon, reaching the maximum values 1 and 3 hours after PS injection, respectively. Data presented here allow us to verify that the best compromise between selectivity and drug concentration for colon carcinoma in rats took place in the interval between 1 to 4 h after PS injection.

Correlation of photodynamic activity and singlet oxygen quantum yields in two series of hydrophobic monocationic porphyrins

The photodynamic properties of eight hydrophobic monocationic methyl and ruthenium polypyridine complex derivatives of free-base and zinc(II) meso-triphenyl-monopyridylporphyrin series were evaluated and compared using HeLa cells as model. The cream-like polymeric nanocapsule formulations of marine atelocollagen/xanthan gum, prepared by the coacervation method, exhibited high phototoxicity but negligible cytotoxicity in the dark. Interestingly, the formulations of a given series presented similar photodynamic activities but the methylated free-base derivatives were significantly more phototoxic than the respective ruthenated photosensitizers, reflecting the higher photoinduced singlet oxygen quantum yields of those monocationic porphyrin dyes.

Toxicity of photodynamic therapy with LED associated to Photogem (R): An in vivo study

The aims of this study were to evaluate the effects of PhotogemA (R)-mediated photosensitization on rat palatal mucosa and the biodistribution of the photosensitizer in this tissue. A solution of PhotogemA (R) (500 or 1000 mg/l) was applied to the palatal mucosa for 30 min and the exposure time to blue LED (460 nm) was 20 min (144 J/cm(2)). At 0, 1, 3, and 7 days, palatal mucosa was photographed for macroscopic analysis. After killing, the palate was removed for microscopic analysis. Thermal mapping evaluated temperature change in the tissue during irradiation. All experimental groups revealed intact mucosa in the macroscopic analysis. Tissue alterations were observed microscopically for only four out of 80 animals subjected to PDT. Fluorescence emitted by PhotogemA (R) was identified and was limited to the epithelial layer. A temperature increase from 35 to 41A degrees C was recorded. PhotogemA (R)- mediated PDT was not toxic to the rat palatal mucosa.

Photodynamic Efficiency of Cationic meso-Porphyrins at Lipid Bilayers: Insights from Molecular Dynamics Simulations

Porphyrin derivatives have applications as photoactive drugs in photodynamic therapy. However, little is known about their interactions with phospholipid membranes at the molecular level. We employed molecular dynamics simulations to model the binding between a series of cationic meso-(N-methyl-4-pyridinium)phenylporphyrins and anionic phosphatidylglycerol lipid bilayers. This was done in the presence of molecular oxygen within the membrane. The ability of various porphyrins to cause photodamage was quantified in terms of their immersion depth and degree of exposition to a higher oxygen concentration inside the membrane. Simulations showed that the photodynamic efficiency could be improved as the number of hydrophobic phenyl substituents attached to the porphyrinic ring increased. In the specific case of porphyrins containing two hydrophobic and two charged substituents, the cis isomer was significantly more efficient than the trans. These results correlate well with previous experimental observations. They highlight the importance of both the total charge and amphiphilicity of the photosensitizer for its performance in photodynamic therapy.

Corrole isomers: intrinsic gas-phase shapes via traveling wave ion mobility mass spectrometry and dissociation chemistries via tandem mass spectrometry

Corrole and four of its isomers with subtle structural changes promoted by exchange of nitrogen and carbon atoms in the corrole ring have been studied by traveling wave ion mobility mass spectrometry and collision induced dissociation experiments. Significant differences in shapes and charge distributions for their protonated molecules were found to lead to contrasting gas phase mobilities, most particularly for corrorin, the most "confused" isomer. Accordingly, corrorin was predicted by B3LYP/6-31g(d,p) and collisional cross section calculations to display the most compact tri-dimensional structure, whereas NCC4 and corrole were found to be the most planar isomers. Better resolution between the corrole isomers was achieved using the more polarizable and massive CO2 as the drift gas. Sequential losses of HF molecules were found to dominate the dissociation chemistry of the protonated molecules of these corrole isomers, but their unique structures caused contrasting labilities towards CID, whereas NCC4 showed a peculiar and structurally diagnostic loss of NH3, allowing its prompt differentiation from the other isomers.

Electrochemically activated coordenative assembly of a triruthenium cluster metallopolymer

A general strategy for electrochemically induced assembly of coordination metallopolymers is demonstrated using the tritopic bridging [Ru-3(mu(3)-O)(CH3COO)(6)(pytpy)(3)](+) cluster complex, where pytpy is the 4'-(4-pyridyl)-2,2':6',2 ''-terpyridine ligand, and iron(III) ions. The concept of such an electrochemically induced coordinative assembly was proven exploring the large difference in the [Fe(pytpy)2 complex formation constants depending on the iron ion oxidation state. Much more stable bridging complexes are formed in the presence of Fe(II) in contrast to Fe(III) ions. The build-up of electrochemically active films on FTO electrodes was confirmed by the growth of the corresponding voltammetric peaks concomitantly with the rise of typical triruthenium cluster and [Fe(pytpy)(2)](2+) complex absorption bands. The metallopolymer was constituted by agglomerates of more or less fused tape like structures, exhibiting large voids and pinholes, as revealed by SEM and AFM images. The adhesion/deposition on FTO was improved by functionalizing the surface with TES-tpy and HOOC-tpy, which increased the surface coverage up to 80%, as estimated by impedance spectroscopy. (C) 2012 Elsevier Ltd. All rights reserved.