SciCombinator

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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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An unprecedented Fe2Pc3metallo-organic helicate has been assembled using a bidentate phthalocyanine (Pc) ligand, 2-formylpyridine and Fe(OTf)2. This giant helicate has proved itself as a host for large redox-active guests such as fullerene and naphthalenediimide derivatives. Photoactivated electronic interactions between components occur in the host-guest complex.

Concepts: Ligand, Denticity, EDTA, Coordination chemistry, Porphyrin, Phthalocyanine

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A porphyrin-based octahedrally ligated complex with high-spin iron(iii) was designed, and the resulting electrically conducting crystal TPP[FeIII(tbp)Br2]2 (TPP = tetraphenylphosphonium and tbp = tetrabenzoporphyrin) was synthesised. Although TPP[Fe(tbp)Br2]2 was isostructural to the reported TPP[Fe(Mc)L2]2 systems (Mc = macrocyclic ligands such as phthalocyanine (Pc) or tbp; and L = CN, Cl, or Br), the bond lengths between Fe and ligands in the [Fe(tbp)Br2] unit were evidently longer than those in the other units, because of the different spin states of Fe: high-spin in TPP[Fe(tbp)Br2]2 and low-spin in others. The magnetic anisotropy observed in the low-spin state vanished when the Fe is in the high-spin state. Based on reports for Pc-based systems, the negative magnetoresistance (MR) effect for TPP[Fe(tbp)Br2]2 was expected to be smaller than that for TPP[Fe(tbp)(CN)2]2. However, the former showed a giant negative MR effect similar to or larger than the latter, suggesting that the nature of iron is a crucial factor for the electrical properties of porphyrin-based materials.

Concepts: Electron, Carbon, Coordination chemistry, Heme, Units of measurement, Porphyrin, Macrocycle, Phthalocyanine

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Dye sensitizers play an important role in dye-sensitized solar cells (DSSCs). As a promising strategy for the design of novel porphyrin sensitizers, the asymmetric modification of the porphyrin ring to meso-link porphyrin sensitizer has emerged in recent years, which can improve the light-harvesting properties and enhance the electron distribution. In this work, in order to reveal the essence of the effect of unsymmetrical substitution on the performance of β-link porphyrin dyes in DSSCs, four kinds of common β-link porphyrin dyes with different structures are calculated by using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The electronic structures and optical properties of these studied dyes in dimethylformamide (DMF) are also investigated. The key parameters of the short-circuit current density (Jsc), including light harvesting efficiency (LHE), electron injection driving force (ΔGinject), and intra-molecular charge transfer (ICT) are discussed in detail. In addition, the periodic DFT calculations in the dye-TiO2 systems are also employed to investigate the geometrical and electronic injection process of the different connection types of these studied dyes adsorbed on the periodic TiO2 model with an exposed anatase (101) surface. We expect the present study would deepen the understanding of the alternative function of unsymmetrical substitution and may contribute to future DSSC design.

Concepts: Electron, Electric charge, Density functional theory, Solar cell, Titanium dioxide, Dye-sensitized solar cell, Time-dependent density functional theory, Phthalocyanine

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Four organic sensitizers incorporating a cross-conjugated cyclopenta[2,1-b:3,4-b']dithiophene (CPDT) π-bridge have been synthesized. As a result of molecular engineering, broad high energy bands and red shifted absorption maxima and onset is observed relative to a benchmark analogue (C218) using a non-cross-conjugated CPDT π-bridge. The use of a cross-conjugated bridge allows a new strategy for tuning dye energetics and introduction of increased absorption uniformity by adding additional high-energy absorption bands. These dyes show solar-to-electric conversion up to 800 nm with one derivative exceeding the performance of C218 under identical conditions.

Concepts: Electron, Photon, Dye, Dyes, Phthalocyanine

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1-Aminopyrene and 1-naphthylamine-5-sulfonic acid were converted to the putrescine (1,4-diaminobutane)-substituted derivatives (dyes 1 and 2). The diaminobutyl anchor serves as a common binding motive for cation-receptor macrocycles such as cucurbit[n]urils (n = 6-8) and p-sulfonatocalix[4]arene. When protonated, they are prone to undergo a rapid deprotonation in their excited state to result in fluorescence from the unprotonated form (Förster cycle). The deprotonation can be suppressed by complexation with cation-receptor macrocycles, which allows the fluorescence of the locally excited (protonated) state to be dramatically enhanced (factor 12 for dye 1 and 83 for dye 2). This host-retarded excited-dye deprotonation is a direct consequence of the previously established complexation-induced pKa shifts which dyes undergo upon binding to a macrocyclic host. The data set allows also a systematic comparison of complexation-induced pKa shifts in the ground and excited state of a dye. The trends are comparable, which suggests that structural factors, that is, the geometry of the host-guest complexes, determine the magnitude of the shifts. In regard to the magnitude of the absolute pKa shifts on the size of the macrocycles, we observe for dye 2 that the complexation-induced pKa shifts on the size of the macrocycles, we observe for dye 2 that the complexation-induced pKa shifts decrease as the portal becomes larger for the CBn series.

Concepts: Acid, Absolute, Atom, Acetic acid, Dye, Dyes, Deprotonation, Phthalocyanine

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The molecular doping of graphene with π-stacked conjugated molecules has been widely studied during the last 10 years, both experimentally or using first-principle calculations, mainly with strongly acceptor or donor molecules. Macrocyclic metal complexes have been far less studied and their behavior on graphene is less clear-cut. The present density functional theory study of cobalt porphyrin and phthalocyanine adsorbed on monolayer or bilayer graphene allows to compare the outcomes of two models, either a finite-sized flake of graphene or an infinite 2D material using periodic calculations. The electronic structures yielded by both models are compared, with a focus on the density of states around the Fermi level. Apart from the crucial choice of calculation conditions, this investigation also shows that unlike strongly donating or accepting organic dopants, these macrocycles do not induce a significant doping of the graphene sheet and that a finite size model of graphene flake may be confidently used for most modeling purposes. © 2017 Wiley Periodicals, Inc.

Concepts: Condensed matter physics, Chemistry, Computational chemistry, Density functional theory, Model, Porphyrin, Macrocycle, Phthalocyanine