Search

In view of the ever‐growing demand for efficient triplet photosensitizers and photoactive components of various optoelectronic devices, we herein report the synthesis and properties of hexaiodo‐subphthalocyanines (I6SubPcs). The improved five‐step route to 4,5‐diiodophthalonitrile, which serves as precursor for the synthesis of the I6SubPcs, is reported. The improved synthesis merely required one chromatographic separation to afford the high‐purity target product. Highly desirable photophysical and photochemical properties were induced in the I6SubPcs due to the presence of six heavy iodine atoms. In particular, high values of the singlet‐oxygen quantum yields (ΦΔ) ranging from 0.83 to 0.9 were measured. The I6SubPcs investigated proved to be phosphorescent at 77 K in 2‐MeTHF with emission band maxima (λP) located at λ=957 and 970 nm. The excited‐triplet‐state energies (ET) were estimated to be approximately 1.30 eV, whereas the triplet lifetimes (τT) were found to be 27.7 and 30.1 μs. The CV/DPV measurements indicated that both I6SubPcs exhibited one irreversible oxidation and one quasi‐reversible reduction. The spectroelectrochemical measurements pointed to a relative stability and reversibility of the electrochemically formed anion radical, that is, I6SubPc.−, and an instability of the species formed upon one‐electron oxidation, that is, I6SubPc.+. Estimation of EHOMO gave a value of approximately −5.8 eV whereas ELUMO was found to be located at around −3.8 eV. Heavy atoms: Highly desirable photophysical/photochemical properties were induced in subphthalocyanine by iodination of the peripheral aromatic rings. In particular, exceptionally high singlet oxygen quantum yields were obtained for this compound which place this subphthalocyanine among the best photosensitizers described thus far and recommend it as photocatalysts and photosensitizers for biomedical applications. [ABSTRACT FROM AUTHOR]

A series of novel iodinated NO2-substituted aza-BODIPYs have been synthesized and characterized. Highly desirable photophysical and photochemical properties were induced in NO2-substituted aza-BODIPYs by iodination of the pyrrole rings. In particular, high values of singlet oxygen quantum yields ( ΦΔ) ranging from 0.79 to 0.85 were measured. The photooxygenation process proceeds via a Type II mechanism under the experimental conditions applied. The compounds studied exhibited an absorption band within the so-called 'therapeutic window', with λmax located between 645 nm to 672 nm. They were non-fluorescent at room temperature with excited singlet-state lifetimes within the picosecond range as measured by femtosecond transient absorption. Nanosecond laser flash photolysis experiments revealed T1→T n absorption spanning from ca. 400 nm to ca. 500 nm and allowed determination of the triplet-state lifetimes. The estimated triplet lifetimes ( τT) in deaerated acetonitrile ranged between 2.74 μs and 3.50 μs. As estimated by CV/DPV measurements, all iodinated aza-BODIPYs studied exhibited one irreversible oxidation and two quasi-reversible reductions processes. Estimation of the EHOMO gave the value of −6.06 to −6.26 eV while the ELUMO was found to be located at ca. −4.6 eV. Thermogravimetric (TGA) analysis revealed that iodinated aza-BODIPYs were stable up to approximately 300 °C. All compounds studied exhibit high photostability in toluene solution. [ABSTRACT FROM AUTHOR]

The review presents recent developments in the synthesis of polymeric photosensitizers and hybrid photocatalysts of various physicochemical and photochemical properties and their possible application for the degradation of water pollutants. The mechanisms of their action were presented. Photoactive amphiphilic polymers are selective and mild reagents acting as singlet oxygen generators or via photoinduced electron transfer. They can function independently as nano/micro heterogeneous photosensitizers or as components of the hybrid systems. The hybrid materials are usually dispersed in water and are involved in the generation of very reactive oxygen species, mostly superoxide and hydroxyl radical ions, which can oxidize organic compounds present in water. These systems are generally more photostable than photoactive polymers therefore they may function as photocatalysts. Polymeric and hybrid photocatalysts are especially well-suited for removal of chemical compounds which, although present at low concentrations in water resources, are dangerous due to their bioaccumulation in the food chain and often cannot be removed with the use of currently available technologies. Both photoactive polymeric and hybrid materials can be easily removed from the aqueous media thus the secondary contamination is avoided. [ABSTRACT FROM AUTHOR]

The thermoresponsive hydrogel microspheres were obtained by copolymerization of N-isopropylacrylamide (NIPAM) and 2-hydroxyethyl methacrylate (HEMA) crosslinked with N,N'-methylenebisacrylamide (BIS). The hydrogel was then functionalized using 1-naphthyl glycidyl ether (NGE) to attach naphthyl chromophores, which absorb UV light and act as photosensitizers. The ability of the functionalized microspheres to photosensitize dechlorination reactions was confirmed using pentachlorophenol (PCP) as a model compound. [ABSTRACT FROM AUTHOR]

Novel water-soluble polymeric photosensitizers based on a natural polymer, naphthalene-modified hydroxyethylcellulose (HENC), were obtained and used for the photooxidation of cyanide. The reaction leads to the formation of cyanate. The process occurs via photoinduced electron transfer from CN− to the naphthalene or naphthoquinone polymeric chromophores. The kinetics of the reaction depend on the degree of substitution of HENC, its concentration, and pH of the solution. The polymers can be easily removed after reaction as prolonged irradiation leads to their photodegradation. [ABSTRACT FROM AUTHOR]

Abstract: The photosensitized oxidation of parathion-ethyl (PTE) pesticide in the aqueous solution of anthracene substituted dextran (DXA) was investigated. The phototransformation of PTE was found to be significantly enhanced in the presence of DXA. The suggested mechanisms of reactions involve photoinduced electron transfer process as a primary photophysical step. DXA polymer plays a role of environmentally friendly photosensitizer since after the reaction it undergoes decomposition. [Copyright &y& Elsevier]

Abstract: A new type of hybrid photosensitizers was obtained by efficient adsorption of a photoactive polymer by an organically modified nanoclay. The polymer bore naphthyl and rose bengal chromophores, which absorbed light both in the ultraviolet and visible spectral region. Adsorption of the polymer on nanoclay prevented aggregation of chromophores. The obtained hybrid photosensitizer efficiently adsorbs hydrophobic compounds. It was also found to be an efficient photosensitizer in singlet oxygen generation. The hybrid photosensitizers combine the advantages of both component systems, i.e. possibility to attach a wide range of chromophores to the polymeric chain and resulting ability to photosensitize reactions, on one hand, and the ability to adsorb hydrophobic pollutants and easy separation from water characteristic of nanoclays, on the other. [ABSTRACT FROM AUTHOR]

Phthalocyanines are promising photosensitizers for photodynamic therapy (PDT). A novel zinc 1,8(11),15(18),22(25)-tetraiodo-3,10(9),17(16),24(23)-tetra- tert -butylphthalocyanine has been synthesized and characterized. The synthesis of iodinated phthalocyanine was achieved through templated cyclotetramerization of 6- tert -butyl-4-iodo-1,3-diiminoisoindoline around zinc ions (Zn 2+ ). A six step route leading to 6- tert -butyl-4-iodo-1,3-diiminoisoindoline was proposed. The synthesis started with a regiospecific iodination of 4- tert -butyl- o -xylene to 5- tert -butyl-2,3-dimethyl-iodobenzene, followed by oxidation of the methyl groups to phthalic acid, conversion of phthalic acid to phthalimide, hydrolysis of phthalimide to phthalamide, conversion of phthalamide to phthalonitrile, followed by conversion of phthalonitrile to a more reactive 6- tert -butyl-4-iodo-1,3-diiminoisoindoline. Highly desirable photophysical and photochemical properties were induced in zinc phthalocyanine by iodination of the aromatic rings, while the presence of tert -butyl groups rendered the compound non-aggregating in solution. The photosensitizer studied exhibits absorption band within the so-called “therapeutic window”, with λ max at 689 nm and very high molar absorption coefficient of 295 000 [M −1  cm −1 ] in DMF. Transient absorption experiment revealed T 1  → T n absorption spanning from ca. 400 nm to ca. 600 nm and allowed determination of the excited triplet state lifetime ( τ T ). The estimated τ T in THF equaled 3.3 μs. The phosphorescence maximum was found to be located at λ P 1103 nm and the excited triplet state energy ( E T ) equaled 1.12 eV in 2-methyltetrahydrofuran at 77 K. The photosensitizer studied is characterized by a high value of singlet oxygen quantum yield (Φ Δ ) of ca. 0.76 and the photooxygenation process proceeds via Type II mechanism under the experimental conditions applied. The photodegradation studies revealed that the iodinated phthalocyanine was moderately stable in the presence of oxygen with quantum yield of photodegradation (Φ d ) equaled 4.01 × 10 −4 . Moderate photostability of photosensitizer is advantageous from a PDT point of view where rapid breakdown and fast clearance from the patient’s system is necessary to avoid prolonged skin photosensitivity following treatment. [ABSTRACT FROM AUTHOR]

The paper describes the studies on the photodecomposition of 4-n-nonylphenol (NP), a widely used pesticide and endocrine disrupting agent. For this purpose a new hybrid photosensitizer (RB-HNT) was obtained composed of Rose Bengal (RB) incorporated into the halloysite nanotubes (HNT). The photosensitizer was characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), confocal microscopy, as well as UV–Vis and fluorescence spectroscopies. The results confirmed that the crystalline structure of HNTs was preserved after modification with RB. The obtained hybrid material efficiently adsorbs hydrophobic compounds. It was also found to be an efficient photosensitizer for singlet oxygen generation. RB-HNT combines the advantages of both of its components, i.e., the ability to adsorb hydrophobic pollutants, which is characteristic for HNT, and photocatalytic properties of RB. Photooxidation kinetics of n-nonylphenol in the presence of RB-HNT and in the aqueous solution of RB were followed spectrophotometrically and compared. The photooxidation in the presence of Bengal Rose followed the first order kinetics, while in the presence of sensitizer (RB-HNT) observed zero-order kinetics. Furthermore the pesticide oxidation by the hybrid catalyst was found to be more efficient. The products formed after various irradiation times were identified by the GCMS analysis and the photodegradation pathway has been proposed. [ABSTRACT FROM AUTHOR]

Highlights: [•] The hybrid photosensitizer was obtained using pegylated porphyrin and a nanoclay. [•] The pegylated porphyrin intercalated into the nanoclay. [•] The photosensitizer generated singlet oxygen which could oxidize phenol. [•] The efficiency of phenol photooxidation depended on pH. [•] The photosensitizer could be reused. [Copyright &y& Elsevier]

Highlights: [•] Mg tetraiodophthalocyanine is described with the purpose of applying it as a photosensitizer to eradicate cancerous cells. [•] Magnesium phthalocyanine produces singlet oxygen and other reactive oxygen species with an excellent quantum yield of 0.95. [•] It possesses the ability to penetrate lipid membranes of liposomes with binding constant equal K b =40.5±6.4 (mg/mL)−1. [•] Limited photostability of the dye is advantageous for the PDT to promote rapid breakdown and clearance after treatment. [ABSTRACT FROM AUTHOR]

Abstract: We report the intercalation of a perfluoroalkyl perfluoro phthalocyanine zinc complex (F64PcZn) in bentonite (Ben) to generate a hybrid photosensitizer (F64PcZn∈Ben) and demonstrate its ability to degrade a model azo dye, Acid Orange 7 (AO7), in aqueous solution using visible light. The F64PcZn photosensitizer is active both in the presence and in the absence of O2, via the photogeneration of singlet oxygen or via a photoinduced electron transfer from the azo dye, respectively. Both F64PcZn and F64PcZn∈Ben exhibit high photochemical stability. The heterogeneous system can be used cyclically by the removal and reutilization of the photocatalytic hybrid, thus highlighting possible technological applications. [Copyright &y& Elsevier]

Abstract: Photosensitizing properties of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (p-THPP) functionalized by covalent attachment of one chain of poly(ethylene glycol) (PEG) with a molecular weight of 350, 2000, or 5000Da (p-THPP-PEG350, p-THPP-PEG2000, p-THPP-PEG5000) were studied in vitro. Dark and photo cytotoxicity of these photosensitizers delivered in solution or embedded in liposomes were evaluated on two cell lines: a human colorectal carcinoma cell line (HCT 116) and a prostate cancer cell line (DU 145), and compared with these treated with free p-THPP. The attachment of PEG chains results in the pronounced reduction of the dark cytotoxicity of the parent porphyrin. Cell viability tests have demonstrated that the phototoxicity of pegylated porphyrins is dependent on the length of PEG chain and p-THPP-PEG2000 exhibited the highest photodynamic efficacy for both cell lines. The encapsulation into liposomes did not improve the PDT effect. However, the liposomal formulation of p-THPP-PEG2000 showed a greater tendency to induce apoptosis in both cell lines than the parent or pegylated porphyrin delivered in solution. The colocalization of p-THPP, p-THPP-PEG2000 and p-THPP-PEG2000 enclosed in liposomes with fluorescent markers for lysosomes, mitochondria, endoplasmatic reticulum (ER) and Golgi apparatus (GA) was determined in the HCT 116 line. The p-THPP exhibited ubiquitous intracellular distribution with a preference for membranes: mitochondria, ER, GA, lysosomes and plasma membrane. Fluorescence of p-THPP-PEG2000 was observed within the cytoplasm, with a stronger signal detected in membranous organelle: mitochondria, ER, GA and lysosomes. In contrast, p-THPP-PEG2000 delivered in liposomes gave a distinct lysosomal pattern of localization. [Copyright &y& Elsevier]

Natural or synthetic porphyrins are being used as photosensitizersin photodiagnosis (PD) and photodynamic therapy (PDT) of malignanciesand some other diseases. Understanding the interactions between porphyrinsand cell membranes is therefore important to rationalize the uptakeof photosensitizers and their passive transport through cell membranes.In this study, we consider the properties of hematoporphyrin (Hp),a well-known photosensitizer for PD and PDT, in the presence of a1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine(POPC) bilayer that we use as a model system for protein-free cellmembranes. For this purpose, we employed 200 ns atomic-scale moleculardynamics (MD) simulations for five systems containing the neutral(Hp0) or the dianionic form (Hp2–) ofHp and the POPC bilayer. MD simulations allowed one to estimate theposition, orientation, and dynamics of Hp molecules inside the membrane.The dye molecules were found to reside in the phospholipid headgrouparea close to the carbonyl groups of the POPC acyl chains. Their orientationswere dependent on the protonation state of two propionic groups. Hp2–was found to have a lower affinity to enter the membranethan the neutral form. The dianions, being in the aqueous phase, formedstable dimers with a strictly determined geometry. Our results fullysupported the experimental data and provide a more detailed molecular-leveldescription of the interactions of photosensitizers with lipid membranes. [ABSTRACT FROM AUTHOR]

Abstract: Two photosensitizing systems: (1) tetrakis(4-hydroxyphenyl)porphyrin (p-THPP) encapsulated in sterically stabilized liposomes (SSL) and (2) p-THPP functionalized by covalent attachment of poly(ethylene glycol) (p-THPP–PEG2000) were studied in vitro. The dark and photo cytotoxicity of these systems were evaluated on two cell lines: HCT 116, a human colorectal carcinoma cell line, and DU 145, a prostate cancer cell line and compared with these determined for free p-THPP. It was demonstrated that both encapsulation in liposomes as well as attachment of PEG chain result in pronounced reduction of the dark cytotoxicity of the parent porphyrin. The liposomal formulation showed higher than p-THPP–PEG2000 photocytotoxicity towards both cell lines used in the studies. [Copyright &y& Elsevier]