PHOTOOXIDATION OF 2-MERCAPTOETHANOL BY VARIOUS WATER-SOLUBLE PHTHALOCYANINES IN AQUEOUS ALKALINE SOLUTION UNDER IRRADIATION WITH VISIBLE LIGHT

β-Cyclodextrin-conjugated phthalocyanines as water-soluble and recyclable sensitisers for photocatalytic applications

Two zinc(ii) phthalocyanines substituted with two and four permethylated β-cyclodextrin moieties at the α positions have been synthesised and immobilised on the surface of adamantane-modified silica nanoparticles through host-guest interactions. These molecular and supramolecular systems can catalyse the photooxygenation of 1-naphthol and 2-furoic acid in organic and aqueous media with high conversion efficiency and reaction yield, and photodegradation of 2-chlorophenol in water. Having a higher photostability and recyclability, the supramolecular nanosystems are particularly promising for these photocatalytic applications.

Photo-assisted oxidation of thiols to disulfides using cobalt “Nanorust” under visible light

A pyrolyzed cobalt based heterogeneous catalyst was found to be a more effective catalyst than the heterogenized CoPc@CeO₂ for oxidation of thiols to disulfides under visible light.

FeCl3-diorganyl dichalcogenides promoted cyclization of 2-organochalcogen-3-alkynylthiophenes: synthesis of chalcogenophene[2,3-b]thiophenes

We report here our results on the FeCl3-diorganyl dichalcogenides intramolecular cyclization of 2-organochalcogen-3-alkynylthiophenes. The cyclization reaction proceeded cleanly under mild reaction conditions giving the (S)-Se-, (S)-S- and (S)-Te-heterocycles in good yields. In addition, the obtained chalcogenophenes were readily transformed into more complex products using the palladium cross-coupling reaction with boronic acids. Conversely, using a metal-halogen exchange reaction with n-BuLi, the chalcogenophenes produced the lithium-intermediate which was trapped with aldehyde furnishing the desired secondary alcohol in good yield.

Singlet Oxygen Quantum Yields of Different Photosensitizers in Polar Solvents and Micellar Solutions

The singlet oxygen luminescence method and the photochemical methods using 1,3-diphenylisobenzofuran ( DPBF ) or bilirubin ditaurate ( BDT ) as chemical quenchers were employed to determine the single oxygen quantum yields (ΦΔ) of different phthalocyanines and tris(2,2″-bipyridyl)ruthenium(II) dichloride in dimethylformamide ( DMF ) or aqueous micellar solution of 0.1 M CTAC (cetyltrimethylammonium chloride). Additionally, a perylenetetracarboxylic acid diimide derivative was examined in DMF . In a series of tetrasulfonated phthalocyanines ( PTS ) the following order was found: ZnPTS > GaPTS > AlPTS ≈ H 2 PTS > CoPTS . In general, the singlet oxygen quantum yields are higher in DMF than in 0.1 M CTAC/H 2 O . The results obtained with the photochemical systems are comparable with those obtained by the photophysical method.

The photochemical DPBF method results in absolute values of ΦΔ. However, in micellar solution, chain reactions occur when DPBF is used as chemical quencher in the photo-oxidative process. This problem can be overcome by adding sodium thiosulphate which is able to destroy the endoperoxide initially formed. BDT can be used as quencher in different solvents to determine ΦΔ relative to a photosensitizer with known singlet oxygen quantum yield in the respective solvent.

In comparison to the chemical methods the luminescence method exhibits the advantage that side reactions of the quencher are excluded. But normally the ΦΔ values obtained are relative to a reference, since absolute determinations need much larger efforts.

Singlet Oxygen Quantum Yields of Different Photosensitizers in Polar Solvents and Micellar Solutions

The singlet oxygen luminescence method and the photochemical methods using 1,3-diphenylisobenzofuran ( DPBF ) or bilirubin ditaurate ( BDT ) as chemical quenchers were employed to determine the single oxygen quantum yields (ΦΔ) of different phthalocyanines and tris(2,2″-bipyridyl)ruthenium(II) dichloride in dimethylformamide ( DMF ) or aqueous micellar solution of 0.1 M CTAC (cetyltrimethylammonium chloride). Additionally, a perylenetetracarboxylic acid diimide derivative was examined in DMF . In a series of tetrasulfonated phthalocyanines ( PTS ) the following order was found: ZnPTS > GaPTS > AlPTS ≈ H 2 PTS > CoPTS . In general, the singlet oxygen quantum yields are higher in DMF than in 0.1 M CTAC/H 2 O . The results obtained with the photochemical systems are comparable with those obtained by the photophysical method.

The photochemical DPBF method results in absolute values of ΦΔ. However, in micellar solution, chain reactions occur when DPBF is used as chemical quencher in the photo-oxidative process. This problem can be overcome by adding sodium thiosulphate which is able to destroy the endoperoxide initially formed. BDT can be used as quencher in different solvents to determine ΦΔ relative to a photosensitizer with known singlet oxygen quantum yield in the respective solvent.

In comparison to the chemical methods the luminescence method exhibits the advantage that side reactions of the quencher are excluded. But normally the ΦΔ values obtained are relative to a reference, since absolute determinations need much larger efforts.

Porphyrins, phthalocyanines and related systems in polymer phases

Macrocyclic ring systems in polymer phases described in this overview are part of the field of macromolecular metal complexes. In this review, first, examples of porphyrins in protein environments being active in biological systems are given. These biological sites are essential to understand the functions of artificial systems. Then a classification and examples of synthetic macromolecular metal complexes based on porphyrins, phthalocyanines and related systems are described.

Incorporation of Differently Substituted Phthalocyanines into the Mesoporous Molecular Sieve Si-MCM-41

Substituted phthalocyanine Zn complexes exhibiting negative, positive or no charge are incorporated in the mesopores of Si -MCM-41 materials during hydrothermal synthesis in the presence of cetyltrimethylammonium chloride. The nature of the intermolecular interaction between the surfactant micelle and the capped chromophores determines (i) the resistance of the dye towards hydrolytic degradation during the synthesis and (ii) its stability of anchoring towards extraction with ethanol in the composite material. Loadings up to 2 × 10−5 mol/g molecular sieve are achieved, corresponding to an average distance between the encapsulated dye molecules between 2 and 3 nm. The UV-vis spectra reveal the non-aggregated state of the chromophores, pointing to a uniform distribution and a perfect separation by the surfactant molecules.

Efficient Near-IR Sensitization of Nanocrystalline TiO2 Films by Zinc and Aluminum Phthalocyanines

Several zinc(II) and aluminum(III) phthalocyanines substituted by carboxylic acid and sulfonic acid groups were anchored to nanocrystalline TiO 2 films. By irradiation with visible light the photovoltaic behavior of the electrodes containing LiI / LiI 3/propylene carbonate electrolyte was measured. Most efficient results were found using zinc(II) 2,9,16,23-tetracarboxyphthalocyanine, with a current conversion efficiency at 700 nm approaching 45%. It is shown that electron injection into TiO 2 occurs from the excited singlet state of the phthalocyanine derivatives. High stability of the cell performance under continuous irradiation was found.

Synthesis of a Monofunctional Phthalocyanine on Silica

Silica of different surface area and grain size modified by aminopropyl groups reacted with 4-(3,4-dicyanophenoxy)benzoic acid chloride. The reaction of these benzamidophenoxydicarbonitrile modified silica gels with 4-(4-tert-butyl-phenoxy)-1,2-benzenedicarbonitrile in the presence of a zinc(II) salt results in covalently bonded phthalocyanine zinc(II) complexes with a loading between 1.8 × 10−5 and 1.7 × 10−6 mol g −1 silica. UV/vis reflectance spectra show that the phthalocyanines on the surface exist in a monomeric state. Cleavage at the amide bond between the silica and the phthalocyanine led to the corresponding monocarboxylic acid phthalocyanine derivative.

Photo-oxidative Stability and its Correlation with Semi-empirical MO Calculations of Various Tetraazaporphyrin Derivatives in Solution

The photo-oxidative stability of various annelated and substituted tetraazaporphyrin derivatives were investigated in N , N -dimethylformamide by irradiation in the presence of air. First-order rate constants were calculated. In addition, the positions of the HOMO and LUMO energy levels of the compounds were calculated using a commercially available program. A linear correlation between the experimental values of the rate constants and the theoretical values of the HOMO position exists. The method described allows one to predict the photo-oxidative stability by calculating their HOMO levels, which is very important for the use of macrocyclic metal complexes in photo-oxidation reactions in solution. From the calculated triplet energies it is considered that the macrocyclic metal complexes can convert by photoinduced energy transfer triplet oxygen to singlet oxygen. Experimentally, tetraazaporphyrin derivatives show high quantum yields of singlet oxygen formation under irradiation. No correlations of the quantum yields with the position of the HOMOs or with the rate constants of decomposition was observed.

Synthesis and catalytic properties of a novel phthalocyanine covalently grafted onto silica

The iron complex of 2(3),9(10),16(17),23(24)-tetra[1,5-di(3-triethoxysilyl-propyl)biuryl]phthalocyanine (1) was prepared by reacting iron tetraaminophthalocyanine with 3-(triethoxysilyl)propyl isocyanate. This complex was directly grafted onto silica to give a supported catalyst without preliminary modification of silica support. This supported catalyst was successfully applied in clean catalytic oxidations by using molecular oxygen in combination with isobutyraldehyde. Cyclooctene, cyclohexene and styrene were oxidized to corresponding epoxides with 90, 78 and 74% yields, respectively. 2,3,6-Trimethylphenol was selectively oxidized to 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol.

Synthesis of charged triazatetrabenzcorroles, phthalocyanines and tetrapyridylporphyrin, and their activities in the co-sensitized photooxidation of 2-mercaptoethanol

Water soluble zwitterionic, as well as cationic and anionic triazatetrabenzcorroles (TBC), phthalocyanines (Pc) and a porphyrin (P) were synthesized and their sensitizer properties investigated. Monomerization of the sensitizers, including their mixtures, in the presence of a detergent was used as a basis for studying the fundamental effect of co-sensitization upon a known model reaction, viz. the photooxidation of 2-mercaptoethanol in aqueous alkaline solutions. Compared to single-component sensitizers, a remarkable improvement of the photocatalytic activity is observed in the case of co-sensitization employing molecules that absorb in different Q and Soret regions.

Hybrid thin films of ZnO with porphyrins and phthalocyanines prepared by one-step electrodeposition

Hybrid thin films of crystalline zinc oxide and the zinc complex of 5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin (ZnTPPS) have been prepared by cathodic electrodeposition from different aqueous zinc salt solutions. Films from a solution containing zinc nitrate and the porphyrin derivate show a rough surface and porosity, whereas films prepared from an oxygen-saturated zinc chloride solution were very smooth. The presence of the porphyrin derivative in the deposition solution has a clear influence on the morphology of the hybrid films compared with pure zinc oxide films. In aqueous zinc nitrate solution the addition of the porphyrin derivative hinders the growth of zinc oxide. In contrast, the addition of the dye to the oxygen-saturated zinc chloride solution leads to an increase of the growth rate of ZnO /porphyrin hybrid films. An increased spectral absorbance was reached when two dyes (zinc complex of tetrasulfonated phthalocyanine and porphyrin) were added to the zinc nitrate solution since the electrodeposited hybrid thin films contained both dyes. UV-vis spectra revealed the presence of both macrocyclic metal complexes in the ZnO films.

Synthesis of new carboran-based phthalocyanines and study of their activities in the photooxidation of citronellol

The synthesis and characterization of novel phthalocyanines containing o-carborane groups are described. These new tetrasubstituted phthalocyanines are of interest for the use in cancer therapy. The activities of the carboranyl substituted phthalocyanines were evaluated by the photooxidation of (S)-(−)-citronellol to give a high oxygen consumption comparable to the photosensitizers tetrasulfophthalocyanine zinc complexes.

Quenching of singlet photoexcited state of water soluble phthalocyanines and porphyrins by viologens interacting electrostatically

Quenching of photoexcited anionic and water-soluble phthalocyanines and 5,10,15,20-tetraarylporphyrins by viologens has been investigated. It was confirmed that the quenching of the singlet photoexcited state takes place, and that the mechanism is mostly a static one due to electrostatic interaction between the donor and the acceptor. The static mechanism was analyzed by curve-fitting of the relative emission intensity vs viologen concentration resulting in four kinds of mechanisms composed of static quenching accompanied partly by a dynamic one. The static mechanism was classified into two types: one mechanism is due to 1:n electrostatic interaction of the anionic sensitizer and the cationic acceptor, and other is a Perrin type for which the acceptor is incorporated into the quenching sphere around the sensitizer according to a Poisson distribution. The effect of micelles for the quenching was also studied including the effect of viologen with a long alkyl chain. The ionic micelles either incorporated or repulsed the ionic sensitizer and accepter resulting in either static quenching or prohibition of the quenching. Cationic phthalocyanines and porphyrins were also examined for the reaction with cationic viologens.

Immobilization of cationic zinc(II) complexes of phthalocyanine and unsymmetrical porphyrazine in mesoporous MCM-41 silica, and photo-catalytic activity of the composites

Cationic 2,9,16,23-tetrakis(3- N , N , N -trimethylaminoethyloxy)phthalocyaninatozinc(II) and 20,21-bis(4- N , N , N -trimethylaminophenyl)-4,5,9,10,14,15-hexakis(4-t-butylphenyl)porphyrazinatozinc(II) were immobilized in MCM-41 silica by the use of an electrostatic interaction with the deprotonated silanol groups of MCM-41. From nitrogen adsorption isotherms, specific surface areas were estimated as 1031 and 702 m2.g−1 for MCM-41 and the composite of 2,9,16,23-tetrakis(3- N , N , N -trimethylaminoethyloxy)phthalocyaninatozinc(II), respectively. From pore-size distribution curves, the maximum pore diameter of MCM-41 and the composite were also estimated as 3.24 and 3.10 nm, respectively. These results revealed that 2,9,16,23-tetrakis(3- N , N , N -trimethylaminoethyloxy)phthalocyaninatozinc(II) was immobilized in the mesopores of MCM-41. While 2,9,16,23-tetrakis(3- N , N , N -trimethylaminoethyloxy)phthalocyaninatozinc(II) formed a dimer with increase in the amount of the complex in the composite, 20,21-bis(4- N , N , N -trimethylaminophenyl)-4,5,9,10,14,15-hexakis(4-t-butylphenyl)porphyrazinatozinc(II) only slightly formed a dimer in the composite, due to steric hindrance of its peripheral substituents. 1,3-diphenylisobenzofuran was photo-oxidized using the composites as the sensitizer in aerated acetonitrile. The reaction proceeded with singlet dioxygen generated by visible-light irradiation of the sensitizers. While the initial reaction rate with the composite of 20,21-bis(4- N , N , N -trimethylaminophenyl)-4,5,9,10,14,15-hexakis(4-t-butylphenyl)porphyrazinatozinc(II) increased in proportion to the increase in the amount of the complex, the initial reaction rate with the composite of 2,9,16,23-tetrakis(3- N , N , N -trimethylaminoethyloxy)phthalocyaninatozinc(II) at first increased, but subsequently decreased due to the formation of the photo-inactive dimer.

Synthesis of new side-chain phthalocyanine methacrylate monomers for ophthalmosurgery in ophthalmology

Convenient synthesis of new methacryloyloxy-substituted phthalocyanines for polymerization reactions, i.e. copper(II) 2,9,16,23-tetra(methacryloxyethoxycarbonyl)phthalocyanine and copper 2,9,16-tris(tert-butyl)-23-(methacryloxyethoxycarbonyl)phthalocyanine, consisting of just a few steps, has been developed. The copolymerization with a dimethacrylate derivative was investigated. The substituted phthalocyanines are interesting materials for ophthalmosurgery in ophthalmology (contact vision correction of eye lenses).

Efficient oxidations and photooxidations with molecular oxygen using metal phthalocyanines as catalysts and photocatalysts

Metal phthalocyanines can be very efficient as catalysts and photocatalysts in oxidation reactions using molecular oxygen as oxidant. Different types of soluble low molecular weight or oligomeric and insoluble heterogeneous catalysts and photocatalysts were developed. The heterogeneous metal phthalocyanines exist either impregnated on SiO 2, Al 2 O 3, charcoal and TiO 2 or covalently and coordinatively bound on SiO 2 and organic polymers or ionically bound on an organic ion exchanger. The catalytic oxidations of toxic sulfide and thiol derivative are studied. In addition, toxic phenols were employed as substrates for the photooxidation. Heterogeneous catalysts can exhibit higher activities then low molecular weight phthalocyanines. These systems exhibit a good stability for re-use. Photooxidations are more efficient than oxidations. A Si(IV) phthalocyanine derivative on a polymer ion exchanger is most active and stable. Also some examples for photooxidations in the direction of photochemical synthesis are given.

Photo-catalytic activity of cationic zinc(II) complexes of phthalocyanine and porphyrazine derivatives loaded on the surface of silica gel

Cationic 2,9,16,23-tetra(3-N,N,N-trimethylaminoethyloxy)phthalocyaninatozinc(II) (complex 1) and 22,23-di(4-N,N,N-trimethylaminophenyl)benzo[b]-7,8,12,13,17,18-hexa(4-t-butylphenyl) porphyrazinatozinc(II) (complex 2) were loaded on the surface of silica gel by use of an electrostatic interaction with deprotonated silanol groups of silica gel. While complex 1 formed its dimer with increase in the amount of the complex in the composite, complex 2 hardly formed the dimer in the composite due to the steric hindrance of its peripheral substituents. 1,3-diphenylisobenzofuran was photo-oxidized using the composites as the sensitizer in aerated methanol. The reaction proceeded with singlet dioxygen generated by the visible-light irradiation upon the sensitizer. While the initial reaction rate with the composite of complex 2 steadily increased in accordance with increase in the amount of the complex, that with the composite of complex 1 at first increased, but subsequently decreased due to the formation of the photo-inactive dimer. Bilirubinditaurate was also photo-oxidized using the composites as the sensitizer in an aerated aqueous solution. The reaction proceeded with superoxide instead of singlet dioxygen. The relationship between the initial reaction rate and the amount of the complex was similar to that in methanol.

A novel cationic triazatetrabenzcorrole: selective detection of mercury(II) by nucleic acid-induced aggregation

In the present work, a novel water-soluble cationic triazatetrabenzcorrole compound was synthesised. Its aggregation and fluorescence quenching properties are demonstrated by serval methods, such as UV-vis and fluorescence spectroscopic studies and naked-eye visualization. Unlike the traditional Hg(2+) sensor based on thymine-Hg(2+)-thymine, we use a novel approach, exploiting the high affinity of Hg(2+) for sulfur in phosphorothioate DNA. Based on the S-Hg(2+)-S pairs, we designed the phosphorothioate DNA T4G4-S3 as an Hg(2+) sensor, which can detect Hg(2+) sensitively and selectively in aqueous solution. And this sensing system is fairly fast and convenient.

Photodynamic activity of water-soluble phthalocyanine zinc(II) complexes against pathogenic microorganisms

Photodynamic activity of tetrakis-(3-methylpyridyloxy)- and tetrakis-(4-sulfophenoxy)-phthalocyanine zinc(II) toward the gram-positive Staphylococcus aureus, the gram-negative Pseudomonas aeruginosa, and the fungi Candida albicans was studied. The drug uptake dependency with an inverse behavior to the cell density was observed. The cationic photosensitizer completely inactivated S. aureus and C. albicans, and with 4 log10 P. aeruginosa. The photoinactivation at mild experimental conditions, such as drug dose of 1.5 microM and fluence of 50 mW cm(-2) for 10 min irradiation time, was shown.

Phthalocyanines: old dyes, new materials. Putting color in nanotechnology

Phthalocyanines are versatile building blocks for fabricating materials at the nanometer scale. These colored macrocycles exhibit fascinating physical properties which arise from their delocalized pi-electronic structure. This article describes why these molecules are targets for different scientific purposes and technological applications.