SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Phthalocyanine

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In contrast to pristine zinc phthalocyanine (1), zinc phthalocyanine based oPPV-oligomers (2-4) of different chain lengths interact tightly and reversibly with graphite, affording stable and finely dispersed suspensions of mono- to few-layer graphene-nanographene (NG)-that are photoactive. The p-type character of the oPPV backbones and the increasing length of the oPPV backbones facilitate the overall π-π interactions with the graphene layers. In NG/2, NG/3, and NG/4 hybrids, strong electronic coupling between the individual components gives rise to charge transfer from the photoexcited zinc phthalocyanines to NG to form hundreds of picoseconds lived charge transfer states. The resulting features, namely photo- and redoxactivity, serve as incentives to construct and to test novel solar cells. Solar cells made out of NG/4 feature stable and repeatable photocurrent generation during several ‘on-off’ cycles of illumination with monochromatic IPCE values of around 1%.

Concepts: Photoelectric effect, Cadmium, Solar cell, Photovoltaics, Length, Photovoltaic module, Band gap, Phthalocyanine

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A biosorbent was developed by simple dried Agaricus bisporus (SDAB) and effectively used for the biosorption of cationic dyes, Crystal Violet and Brilliant Green.

Concepts: Dye, Dyes, Pigment, Mushroom, Triarylmethane dyes, Agaricus bisporus, Phthalocyanine

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Purified laccase from Trametes polyzona WR710-1 was used as biocatalyst for bisphenol A biodegradation and decolorization of synthetic dyes. Degradation of bisphenol A by laccase with or without redox mediator, 1-hydroxybenzotriazole (HBT) was studied. The quantitative analysis by HPLC showed that bisphenol A rapidly oxidized by laccase with HBT. Bisphenol A was completely removed within 3 h and 4-isopropenylphenol was found as the oxidative degradation product from bisphenol A when identified by GC-MS. All synthetic dyes used in this experiment, Bromophenol Blue, Remazol Brilliant Blue R, Methyl Orange, Relative Black 5, Congo Red, and Acridine Orange were decolorized by Trametes laccase and the percentage of decolorization increased when 2 mM HBT was added in the reaction mixture. This is the first report showing that laccase from T. polyzona is an affective enzyme having high potential for environmental detoxification, bisphenol A degradation and synthetic dye decolorization.

Concepts: Enzyme, Redox, Nicotinamide adenine dinucleotide, Dye, Triarylmethane dyes, Azo dyes, Acridine, Phthalocyanine

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Porphyrins, phthalocyanines and subphthalocyanines are three attractive classes of chromophores with intriguing properties making them suitable for the design of artificial photosynthetic systems. The assembly of these components by a supramolecular approach is of particular interest as it provides a facile means to build multi-chromophoric arrays with various architectures and tuneable photophysical properties. In this paper, we show the formation of mixed host-guest supramolecular complexes that consist of a β-cyclodextrin-conjugated subphthalocyanine, a tetrasulfonated porphyrin and a series of silicon(iv) phthalocyanines substituted axially with two β-cyclodextrins via different spacers. We found that the three components form supramolecular complexes held by host-guest interactions in aqueous solution. Upon excitation of the subphthalocyanine part of the complex, the excitation energy is delivered to the phthalocyanine unit via excitation energy transfer and the porphyrin chromophore acts as an energy transfer bridge enabling this process. It was shown that photo-induced charge transfer also takes place. A sequential electron transfer process from the porphyrin unit to the phthalocyanine moiety and subsequently from the subphthalocyanine moiety to the porphyrin unit takes place, and the probability of this process is controlled by the linker between β-cyclodextrin and phthalocyanine. The lifetime of the charge-separated state was found to be 1.7 ns by transient absorption spectroscopy.

Concepts: Electron, Metabolism, Electromagnetic radiation, Chemistry, Supramolecular chemistry, Porphyrin, Macrocycle, Phthalocyanine

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A novel approach to axially induce chirality on silicon phthalocyanines via a microwave-assisted route is reported. CD analysis provides spectroscopic evidence that chirality is transferred onto both Soret and Q-bands of the phthalocyanine core. A chiral naphthalenediimide ligand was found to induce the largest Cotton effect on the macrocycle absorptions.

Concepts: Amine, Chirality, Circular dichroism, Porphyrin, Phthalocyanine

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Synthetic dyes or colorants are key chemicals for various industries producing textiles, food, cosmetics, pharmaceutics, printer inks, leather, and plastics. Nowadays, the textile industry is the major consumer of dyes. The mass of synthetic colorants used by this industry is estimated at the level of 1 ÷ 3 × 105 tons, in comparison with the total annual consumption of around 7 × 105 tons worldwide. Synthetic dyes are relatively easy to detect but difficult to eliminate from wastewater and surface water ecosystems because of their aromatic chemical structure. It should be highlighted that the relatively high stability of synthetic dyes leads to health and ecological concerns due to their toxic, mutagenic, and carcinogenic nature. Currently, removal of such chemicals from wastewater involves various techniques, including flocculation/coagulation, precipitation, photocatalytic degradation, biological oxidation, ion exchange, adsorption, and membrane filtration. In this review, a number of classical and modern technologies for synthetic dye removal from industry-originated wastewater were summarized and discussed. There is an increasing interest in the application of waste organic materials (e.g., compounds extracted from orange bagasse, fungus biosorbent, or green algal biomasses) as effective, low-cost, and ecologically friendly sorbents. Moreover, a number of dye removal processes are based on newly discovered carbon nanomaterials (carbon nanotubes and graphene as well as their derivatives).

Concepts: Water, Ecology, Carbon, Chemical compound, Dye, Dyes, Pigment, Phthalocyanine

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Tetrabenzotriazacorroles (Tbcs) are a family of molecules related to phthalocyanines but have the unique ability to intensely absorb both blue and red light. Here, we report the synthesis of four novel silicon tetrabenzotriazacorrole derivatives (SiTbcs) with varying sized axial ligands. SiTbcs are formed starting from bis(hydroxy) silicon phthalocyanine ((OH)2-SiPc) via a simple in situ axial functionalization and reductive chemical process using magnesium metal and the respective chlorosilane in pyridine. Systematic probing of the reaction conditions revealed that the reaction is acid-promoted and that the formation of the Tbc macrocycle occurs at temperatures as low as 40 °C. Results imply this chemistry can be extended to SiTbcs with any axial ligands using pyridine hydrochloride as an acid source. Single crystals of all compounds were grown and showed significant π-π interactions between the macrocycles in the solid state. Optical, electrochemical, and thermal characterization of these materials is also described. The SiTbcs exhibit interesting highly oxidative electrochemistry as well as high thermal stability and tunable phase transition behavior.

Concepts: Iron, Chemical reaction, Electrochemistry, Chemistry, Solid, Porphyrin, Macrocycle, Phthalocyanine

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Energy transfer and interchange are central to fabricating white-light-emitting organic materials. However, increasing the efficiency of light-energy transfer remains a considerable challenge due to the occurrence of “crosstalk”. In this work, by exploiting the unique photophysical properties of cucurbiturils triggered host-guest interactions, the two complementary luminescent colors blue and yellow for white-light emission were independently obtained from a single fluorophore dye rather than energy transfer. Further study suggested that the rigid cavity of cucurbiturils efficiently prevented aggregation of the dye and improved its thermal stability in the solid state by providing a regular nano-sized fence for each encapsulated dye molecule. As a result, a novel macrocycle-assisted supramolecular approach for obtaining solid, white-light emitting organic materials with low cost, high efficiency, and easy scale-up was successfully demonstrated.

Concepts: Light, Chemistry, Interaction, Organic compound, Organic matter, Phthalocyanine, Complementary color

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Phthalocyanines are aromatic macrocyclic compounds, which are structurally related to porphyrins. In clinical practice phthalocyanines are used in fluorescence imaging and photodynamic therapy of cancer and non-cancer lesions. Certain forms of the substituted polycationic metallophthalocyanines have been previously shown to be active in photodynamic inactivation of both Gram-negative and Gram-positive bacteria, one of them is zinc octakis(cholinyl)phthalocyanine (ZnPcChol8+). However, the molecular details of how these compounds translocate across bacterial membranes still remain unclear. In the present work we have developed a coarse-grained (CG) molecular model of ZnPcChol8+within the framework of the popular MARTINI CG force field. The obtained model was used to probe the solvation behavior of phthalocyanine molecules, which agreed with experimental results. Subsequently, it was used to investigate the molecular details of interactions between phthalocyanines and membranes of various composition. The results demonstrate that ZnPcChol8+has high affinity to both the inner and the outer model membranes of Gram-negative bacteria, while this species does not show noticeable affinity to the POPC membrane. Furthermore, we found out that the process of ZnPcChol8+penetration towards the center of the outer bacterial membrane is energetically favorable and leads to its overall disturbance and formation of the aqueous pore. Such intra-membrane localization of ZnPcChol8+suggests their twofold cytotoxic effect on bacterial cells: (1) via induction of lipid peroxidation by enhanced production of reactive oxygen species (i.e., photodynamic toxicity); (2) via rendering the bacterial membrane more permeable for additional Pc molecules as well as other compounds. We also found that the kinetics of penetration depends on the presence of phospholipid defects in the LPS leaflet of the outer membrane and the type of counterions, which stabilize it. Thus, the results of our simulations provide a detailed molecular view of ZnPcChol8+“self-promoted uptake”, the pathway previously proposed for some small molecules crossing the outer bacterial membrane.

Concepts: Oxygen, Bacteria, Antioxidant, Bacterial cell structure, Gram-negative bacteria, Porphyrin, Gram-positive bacteria, Phthalocyanine

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The inherent tendency of proteins to convert from their native states into amyloid aggregates is associated with a range of human disorders, including Alzheimer’s and Parkinson’s diseases. In that sense, the use of small molecules as probes for the structural and toxic mechanism related to amyloid aggregation has become an active area of research. Compared with other compounds, the structural and molecular basis behind the inhibitory interaction of phthalocyanine tetrasulfonate (PcTS) with proteins such as αS and tau has been well established, contributing to a better understanding of the amyloid aggregation process in these proteins. We present here the structural characterization of the binding of PcTS and its Cu(II) and Zn(II)-loaded forms to the amyloid β-peptide (Aβ) and the impact of these interactions on the peptide amyloid fibril assembly. Elucidation of the PcTS binding modes to Aβ40revealed the involvement of specific aromatic and hydrophobic interactions in the formation of the Aβ40-PcTS complex, ascribed to a binding mode in which the planarity and hydrophobicity of the aromatic ring system in the phthalocyanine act as main structural determinants for the interaction. Our results demonstrated that formation of the Aβ40-PcTS complex does not interfere with the progression of the peptide toward the formation of amyloid fibrils. On the other hand, conjugation of Zn(II) but not Cu(II) at the center of the PcTS macrocyclic ring modified substantially the binding profile of this phthalocyanine to Aβ40and became crucial to reverse the effects of metal-free PcTS on the fibril assembly of the peptide. Overall, our results provide a firm basis to understand the structural rules directing phthalocyanine-protein interactions and their implications on the amyloid fibril assembly of the target proteins; in particular, our results contradict the hypothesis that PcTS might have similar mechanisms of action in slowing the formation of a variety of pathological aggregates.

Concepts: Protein, Hydrophobe, Hydrophobic effect, Amyloid, Determinant, Fluorocarbon, Hydrophobicity scales, Phthalocyanine