Eugenia Fagadar-Cosma

A Novel Sensor for Monitoring of Iron(III) Ions Based on Porphyrins

Three A3B porphyrins with mixed carboxy-, phenoxy-, pyridyl-, and dimethoxy-substituent functionalization on the meso-phenyl groups were obtained by multicomponent synthesis, fully characterized and used as ionophores for preparing PVC-based membrane sensors selective to iron(III). The membranes have an ionophore:PVC:plasticizer composition ratio of 1:33:66. Sodium tetraphenylborate was used as additive (20 mol% relative to ionophore). The performance characteristics (linear concentration range, slope and selectivity) of the sensors were investigated. The best results were obtained for the membrane based on 5-(4-carboxyphenyl)-10,15,20-tris(4-phenoxyphenyl)-porphyrin plasticized with bis(2-ethylhexyl)sebacate, in a linear range from 1 × 10−7–1 × 10−1 M with a slope of 21.6 mV/decade. The electrode showed high selectivity with respect to alkaline and heavy metal ions and a response time of 20 s. The influence of pH on the sensor response was studied. The sensor was used for a period of six weeks and the utility has been tested for the quantitative determination of Fe(III) in recovered solutions from spent lithium ion batteries and for the quantitative determination of Fe(III) in tap water samples.

Combinatorial synthesis and characterization of new asymmetric porphyrins as potential photosensitizers in photodynamic therapy.

Porphyrins play a major role as active photosensitizers in noninvasive optical photodynamic therapy (PDT). In a modular approach, this paper presents a short review of the recent developments of porphyrin structures and materials with improved photosensitizing properties and then presents the synthesis and characterization of a series of new second generation asymmetrical meso-tetraphenylporphyrins varied by substituent in the meta positions of the phenyl rings with either -OH or -OCH3 groups, whereas in the para positions only with -OCH3 groups. The new series of differentially functionalized porphyrins were obtained by a combinatorial multicomponent synthesis (Adler-Longo method) by simultaneously using two different aldehydes: 3,4-dimethoxybenzaldehyde and 3-hydroxybenzaldehyde. The porphyrins were isolated, purified and characterized by HPLC, TLC, UV-vis, fluorescence, MS, 1H-NMR, and 13C-NMR analysis, accompanied by DEPT 135 experiments. Because of the fact that the medium in cancerous tissues is often more acidic than in normal tissues, the capacity of these porphyrins to exist simultaneously in aggregated and protonated forms was also investigated, in tetrahydrofuran (THF) and acid THF-water systems, underlying the changes in the photophysical behaviour. The relative fluorescence quantum yields (Phif) were calculated in comparison with meso-tetraphenylporphyrin (TPP), and the values between 0.14-0.26 were found to be promising for further trials. The series of asymmetrically substituted tetraphenylporphyrins, as the new class of supramolecular materials, are suitable for further functionalization in order to improve their photophysical properties, and they could represent interesting potential PDT photosensitizers.

Free Base Porphyrins as Ionophores for Heavy Metal Sensors

Two functionalized porphyrins: 5,10,15,20-tetrakis(3,4-dimethoxyphenyl) porphyrin (A) and 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin (B) obtained and characterized by us were used as ionophores (I) for preparing PVC-based membrane sensors selective to Ag+, Pb2+ and Cu2+. The membranes were prepared using three different plasticizers: (bis(2-ethylhexyl)sebacate (DOS), dioctylphtalate (DOP), o-nitro-phenyl octyl ether (NPOE) and potassium tetrakis(4-chlorophenyl)borate (KTClPB) as additive. The functional parameters (linear concentration range, slope and selectivity) of the sensors with membrane composition: (I:PVC:KTClPB:Plasticizer) in different ratios were investigated. The best results were obtained for the membranes in the ratio I:PVC:KTClPB:Plasticizer 10:165:5:330. The influence of pH on the sensors response was studied. The sensors were used for a period of four months and their utility has been tested on synthetic and real samples.

Syntheses, Spectroscopic and AFM Characterization of Some Manganese Porphyrins and Their Hybrid Silica Nanomaterials

The present work is concerned with the manganese complexes of 5,10,15,20-tetraphenylporphyrin and of 5,10,15,20-tetra(3-hydroxyphenyl)porphyrin, which were prepared by metallation of the corresponding porphyrin ligands, and the study of their spectroscopic and photophysical behavior under strongly acidic and alkaline conditions. The second objective was to obtain and study some new hybrid materials, with special optoelectronic and surface properties, by impregnation of silica gels obtained by one step acid and by two steps acid-base catalysis with these Mn-porphyrins. The resulting nanomaterials exhibited interesting bathochromic and hyperchromic effects of their second band in the emission spectra in comparison with the Mn-porphyrins and also they have distinct orientation of the aggregates on surfaces, as shown by AFM images, making them useful for applications in medicine, formulation of sensors and for environmental-friendly catalysts for photodegradation of organic compounds.

Manganese(III) Porphyrin-based Potentiometric Sensors for Diclofenac Assay in Pharmaceutical Preparations

Two manganese(III) porphyrins: manganese(III) tetraphenylporphyrin chloride and manganese(III)-tetrakis(3-hydroxyphenyl)porphyrin chloride were tested as ionophores for the construction of new diclofenac–selective electrodes. The electroactive material was incorporated either in PVC or a sol–gel matrix. The effect of different plasticizers and additives (anionic and cationic) on the potentiometric response was studied. The best results were obtained for the PVC membrane plasticized with dioctylphtalate and having sodium tetraphenylborate as a lipophilic anionic additive incorporated. The sensor response was linear in the concentration range 3 × 10−6 – 1 × 10−2 M with a slope of −59.7 mV/dec diclofenac, a detection limit of 1.5 × 10−6 M and very good selectivity coefficients. It was used for the determination of diclofenac in pharmaceutical preparations, by direct potentiometry. The results were compared with those obtained by the HPLC reference method and a good agreement was found between the two methods.

Synthesis, Spectroscopic and Self-Assembling Characterization of Novel Photoactive Mixed Aryl-Substituted Porphyrin

The present report is concerned with the designing, obtaining and characterization of novel light -sensitive molecules, belong- ing to second generation meso-tetraarylporphyrin derivatives. A new structure of A3B porphyrin, namely: 5-(4-pyridyl)-10,15,20-tris(4- phenoxyphenyl)-porphyrin was synthesized in fair yield by multicomponent reaction and characterized by 1 H-NMR, FT-IR, UV-vis, fluo- rescence, MS, HPLC, TLC, AFM and XRD techniques. Tailoring porphyrins by introducing a pyridyl substituent in one of the meso-aryl groups confers some degree of hydrophilicity and may cause absorption and fluorescence emission bands in the long wavelength region. Besides, as it was expected, because of the relatively rigid planar structure, due to substitution with three phenoxy substituents, this por- phyrin is characterized by a value of 0.219 for fluorescence quantum yield, a higher value in comparison with usual porphyrins. In solu- tion, by UV-vis and fluorescence spectra, the effects of pH and concentration upon H and J aggregates of the porphyrin are discussed. X- ray diffraction and atomic force microscopy investigations proved that this newly synthesized porphyrin is able to generate stable self- assembly in preferred orientations, such as multilayer of lamellar triangles, densely packed and homogeneous, with dimensions around 440 nm, finally forming pyramidal type structures. CHCl3 favors the spiral organization of the pyramids so that rings and even tubes of various diameters ranging from 1μm to 4.5 μm were formed.

Synthesis of new phosphorus-containing (co)polyesters using solid-liquid phase transfer catalysis and product characterization.

This paper is directed towards the development of safe, and thermally stable solid polymer electrolytes. Linear phosphorus-containing (co)polyesters are described, including their synthesis, thermal analysis, conductivity, and non-flammability. Polycondensation of phenylphosphonic dichloride (PPD) with poly(ethylene glycol) (PEG 12000) with and without bisphenol A (BA) was carried out using solid-liquid phase transfer catalysis. Potassium phosphate is used as base. Yields in the range of 85.0–88.0%, and inherent viscosities in the range of 0.32–0.58 dL/g were obtained. The polymers were characterized by gel permeation chromatography, FT-IR, 1H- and 31P-NMR spectroscopy and thermal analysis. Their flammability was investigated by measuring limiting oxygen index values. The polymers are flame retardants and begin to lose weight in the 190 °C–231 °C range. Solid phosphorus- containing (co)polyesters were complexed with lithium triflate and the resulting ionic conductivity was determined. Conductivities in the range of 10−7–10−8 S cm−1 were obtained.

Potentiometric detection and removal of copper using porphyrins

BackgroundCopper is an essential trace element with a great importance in industry, environment and biological systems. The great advantage of ion-selective sensors in comparison with other proposed techniques is that they are measuring the free metal ion activity which is responsible for their toxicity. Porphyrins are known to be among the best ionophores in formulation of ion-selective sensors.ResultsA symmetrically substituted meso-porphyrin, namely: 5,10,15,20-tetrakis(4-allyloxyphenyl)porphyrin (TAPP) was used in the construction of a new copper selective-sensor and was also tested for the removal of copper from waste waters. The potentiometric response characteristics (slope and selectivity) of copper-selective electrodes based on TAPP in o-nitrophenyloctylether (o-NPOE), dioctyl phtalate (DOP) and dioctyl sebacate (DOS) plasticized with poly(vinyl chloride) membranes are compared.ConclusionsThe best results were obtained for the membrane plasticized with DOP. The sensor has linear response in the range 1x10-7 – 1x10-1 M with 28.4 ± 0.4 mV/decade near-Nernstian slope towards copper ions and presents good selectivity. Due to its chelating nature, the same porphyrin was also tested for the retention of copper from synthetic copper samples, showing a maximum adsorption capacity of 280 mg/g.

Nanostructured Glasses Based on Hybrid Silica Materials Incorporating a New Asymmetrical Phenyl-Substituted Porphyrin

The new asymmetrical, phenyl substituted porphyrin structure, namely: 5,10,15-tris(3-hydroxy-phenyl)-20- (3,4-dimethoxy-phenyl)-21H,23H-porphyrin, along with the nanostructured glasses and silica-based nanoparticles embedded with this compound were synthetized and characterized as to be designated for potential use in construction of advanced optoelectronic devices or electrochemical sensors. This porphyrin was synthesized by a multicomponent Adler- Longo type reaction using two different substituted aldehydes, and next characterized by HPLC, TLC, MS, UV-vis, fluorescence spectroscopy, AFM, 1 H-NMR and 13 C-NMR analysis. The observed changes in UV-vis and emission spectra were also discussed in terms of various pH conditions. The series of novel porphyrin-silica nanomaterials have been prepared by using silica matrices obtained in two variable sol-gel processes, i.e. via the one step acid- or two steps acid- base-catalyzed hydrolysis and condensation of tetraethylorthosilicate. Especially, the hybrid monolithic glass nanomaterials obtained here via the one step acid-sol-gel procedure exhibited a high intensity of the emission spectra bands and, besides, a very sharp bathochromic shift in the red region towards 723 nm, thus making also these nanoparticles as the valuable source of potential second generation photosensitizers. In the atomic force microscopy (AFM) measurements this hybrid nanomaterials displayed the spherical and highly monodispersed particles of ultra low size (less than 70 nm and with an average height of 20 nm), controlled shape, high porosity, and superior stability as the potential water-insoluble photosensitizers.

A Sensitive A3B Porphyrin Nanomaterial for CO2 Detection

The present report deals with the tailoring, preparation and characterization of novel nanomaterials sensitive to CO2 for use in detection of this gas during space habitation missions. A new nanostructured material based on mixed substituted asymmetrical A3B porphyrin: 5-(4-pyridyl)-10,15,20-tris(3,4-dimethoxyphenyl)-porphyrin (PyTDMeOPP) was synthesized and characterized by 1H-NMR, FT-IR, UV-vis, fluorescence, MS, HPLC and AFM. Introducing one pyridyl substituent in the 5-meso-position of porphyrin macrocycle confers some degree of hydrophilicity, which may cause self-assembly properties and a better response to increased acidity. The influence of pH and nature of the solvent upon H and J aggregates of the porphyrin are discussed. Porphyrin aggregation at the air–THF interface gave a triangular type morphology, randomly distributed but uniformly oriented. When deposition was made by multiple drop-casting operations, a network of triangles of uniform size was created and a porous structure was obtained, being reorganized finally in rings. When the deposition was made from CHCl3, ring structures ranging in internal diameter from 300 nm to 1 µm, but with the same width of the corona circular of approx. 200 nm were obtained. This porphyrin-based material, capable of generating ring aggregates in both THF and CHCl3, has been proven to be sensitive to CO2 detection. The dependence between the intensity of porphyrin UV-vis absorption and the concentration of CO2 has a good correlation of 98.4%.