Showing papers on "Porphyrin published in 2014"
TL;DR: A molecularly engineered porphyrin dye is reported, coded SM315, which features the prototypical structure of a donor-π-bridge-acceptor and both maximizes electrolyte compatibility and improves light-harvesting properties.
Abstract: A dye that both maximizes electrolyte compatibility and improves light-harvesting properties has been designed for dye-sensitized solar cells. In cells based on the cobalt(II)/(III) redox mediator, use of the dye resulted in a power-conversion efficiency of 13%, revealing the great potential of porphyrin dyes for future solar cell applications.
3,940 citations
TL;DR: The role of heme in more active enzymatic chemical transformation began to be appreciated just after the discovery by Mason1 and Hayaishi2 that O2 O atoms can be enzymatically incorporated into organic substrates which represented the seminal discovery of oxygenases.
Abstract: Metalloporphyrins are widely used throughout the biosphere and of these heme (iron protoporphyrin IX, Fig. 1) is one of the most abundant and widely used. Heme shuttles electrons between proteins as in mitochondrial respiration or transports and stores O2 as with the globins. The role of heme in more active enzymatic chemical transformation began to be appreciated just after the discovery by Mason1 and Hayaishi2 that O2 O atoms can be enzymatically incorporated into organic substrates which represented the seminal discovery of oxygenases. While the enzymes used in these studies did not contain heme, it was not too long before heme-containing oxygenases also were discovered. In 1958 Klingenberg3 and Garfinkel4 found an unusual pigment in microsomes that when reduced in the presence of CO generated a spectrum with a peak at 450 nm instead of the expected 420 nm peak. Hence the name P450 was born. In 1964 Omura and Sato5,6 showed that this “pigment” is actually a protein and the function of this strange heme protein became clear in a seminal study by Estabrook et al.7 that demonstrated the involvement of the 450 nm pigment in steroid hydroxylation. Thus by the mid-1960s it was established that heme plays an active role in biology by somehow catalyzing the hydroxylation of organic substrates. While these discoveries certainly mark the beginning of modern approaches to studying heme enzyme oxygenases, the enzymatic role of heme dates much earlier to 1903 when horseradish peroxidase (HRP) was described.8 Indeed, owing to the ease of purification and stability of the various intermediates, HRP dominated heme enzyme studies until P450 was discovered.
Figure 1
Structure of iron protoporphyrin IX.
Heme enzymes can catalyze both reductive and oxidative chemistry but here we focus on those that catalyze oxidation reactions, and especially those for which crystal structures are available. There are two broad classes of heme enzyme oxidants: oxygenases that use O2 to oxidize, usually oxygenate, substrates and peroxidases that use H2O2 to oxidize, but not normally oxygenate, substrates. Of the two oxidants molecular oxygen is the most unusual because even though the oxidation of nearly all biological molecules by O2 is a thermodynamically favorable process, O2 is not a reactive molecule. The reason, of course, is that there is a large kinetic barrier to these reactions owing to O2 being a paramagnetic molecule so the reaction between a majority of biological molecules that have paired spins is a spin forbidden process. Overcoming this barrier is why Nature recruited transition metals and heme into enzyme active sites. As shown in Fig. 2, heme oxygenases bind O2 and store the O2 oxidizing equivalents in the iron, porphyrin, and/or amino acid side chains for further selective oxidation of substrates. Peroxidases use H2O2 as the oxidant and while not having the O2 spin barrier, H2O2 presents its own problems. The reaction between H2O2 and transition metals generates toxic hydroxyl radicals in the well known Fenton chemistry9 which would be highly destructive to enzyme active sites. As illustrated in Fig. 2, all heme oxidases are at some point in the catalytic cycle peroxidases. Molecular oxygen must first be reduced by two electrons to the peroxide level before the interesting chemistry starts: cleavage of the O-O bond. This bond can cleave either homolytically, which gives two hydroxyl radicals, or heterolytically to effectively give H2O and a naked O atom with only 6 valence electrons. Since the release of hydroxyl radicals in the active site must, in most cases, be avoided Nature has engineered heme enzyme active sites to ensure that the heterolytic pathway dominates.
Figure 2
Oxygen and peroxide activation by heme enzymes. Oxygenases like P450 must have the iron reduced to ferrous (Fe(II) or Fe2+) before O2 can bind. The oxy complex is best described as ferric-superoxide, Fe(III)-OO−. A second electron transfer results ...
The list of heme enzymes is substantial and thus it is necessary to be selective on which to discuss in detail. It may appear that a disproportionate amount of space is devoted to peroxidases and P450s. This is true and admittedly reflects the author’s own interests and area of expertise. Additionally, however, peroxidases are the most extensively studied heme enzymes and have provided fundamental insights into the chemistry and structure shared by many other enzymes. The other enzymes to be discussed were selected owing to both subtle variations on common themes and novel features that Nature selected for specific biological function.
954 citations
TL;DR: The importance of introducing the phenyl group as a spacer between the BTD and the zinc porphyrin in achieving high power-conversion efficiencies is shown.
Abstract: Porphyrins have drawn much attention as sensitizers owing to the large absorption coefficients of their Soret and Q bands in the visible region. In a donor and acceptor zinc porphyrin we applied a new strategy of introducing 2,1,3-benzothiadiazole (BTD) as a pi-conjugated linker between the anchoring group and the porphyrin chromophore to broaden the absorption spectra to fill the valley between the Soret and Q bands. With this novel approach, we observed 12.75% power-conversion efficiency under simulated one-sun illumination (AM1.5G, 100 mW cm(-2)). In this study, we showed the importance of introducing the phenyl group as a spacer between the BTD and the zinc porphyrin in achieving high power-conversion efficiencies. Time-resolved fluorescence, transient-photocurrent-decay, and transient-photovoltage-decay measurements were employed to determine the electron-injection dynamics and the lifetime of the photogenerated charge carriers.
424 citations
TL;DR: A cobalt-nitrogen-doped porous carbon that exhibits a ribbon-shape morphology, high surface area, mesoporous structure, and high nitrogen and cobalt content is fabricated for high-performance self-supported oxygen reduction electrocatalytsts through template-free pyrolysis of cobalt porphyrin-based conjugated mesoporus polymer frameworks.
Abstract: A cobalt-nitrogen-doped porous carbon that exhibits a ribbon-shape morphology, high surface area, mesoporous structure, and high nitrogen and cobalt content is fabricated for high-performance self-supported oxygen reduction electrocatalytsts through template-free pyrolysis of cobalt porphyrin-based conjugated mesoporous polymer frameworks.
412 citations
TL;DR: Based on the excellent catalyst 1d, MgII porphyrin 1o with eight tetraalkylammonium bromide groups, which showed even higher catalytic activity (turnover number, 138,000; turnover frequency, 19,000 h–1) and the catalytic mechanism was studied.
Abstract: We prepared bifunctional MgII porphyrin catalysts 1 for the solvent-free synthesis of cyclic carbonates from epoxides and CO2. The activities of 1d, 1h, and 1i, which have Br–, Cl–, and I– counteranions, respectively, increased in the order 1i < 1h < 1d. Catalysts 1d and 1j–m, which bear four tetraalkylammonium bromide groups with different alkyl chain lengths, showed comparable but slightly different activities. Based on the excellent catalyst 1d, we synthesized MgII porphyrin 1o with eight tetraalkylammonium bromide groups, which showed even higher catalytic activity (turnover number, 138,000; turnover frequency, 19,000 h–1). The catalytic mechanism was studied by using 1d. The yields were nearly constant at initial CO2 pressures in the 1–6 MPa range, suggesting that CO2 was not involved in the rate-determining step in this pressure range. No reaction proceeded in supercritical CO2, probably because the epoxide (into which the catalyst dissolved) dissolved in and was diluted by the supercritical CO2. Ex...
370 citations
TL;DR: Detailed physical measurements, density functional theory calculations, and photovoltaic characterizations disclosed that the energy level alignment, the molecular orbital profile, and dye aggregation all played very important roles on the interface electron transfer and charge recombination kinetics.
Abstract: Porphyrin-based dyes recently have become good candidates for dye-sensitized solar cells (DSCs). However, the bottleneck is how to further improve their light-harvesting ability. In this work, N-annulated perylene (NP) was used to functionalize the Zn-porphyrin, and four "push-pull"-type NP-substituted and fused porphyrin dyes with intense absorption in the visible and even in the near-infrared (NIR) region were synthesized. Co(II/III)-based DSC device characterizations revealed that dyes WW-5 and WW-6, in which an ethynylene spacer is incorporated between the NP and porphyrin core, showed pantochromatic photon-to-current conversion efficiency action spectra in the visible and NIR region, with a further red-shift of about 90 and 60 nm, respectively, compared to the benchmark molecule YD2-o-C8. As a result, the short-circuit current density was largely increased, and the devices displayed power conversion efficiencies as high as 10.3% and 10.5%, respectively, which is comparable to that of the YD2-o-C8 cell (η = 10.5%) under the same conditions. On the other hand, the dye WW-3 in which the NP unit is directly attached to the porphyrin core showed a moderate power conversion efficiency (η = 5.6%) due to the inefficient π-conjugation, and the NP-fused dye WW-4 exhibited even poorer performance due to its low-lying LUMO energy level and nondisjointed HOMO/LUMO profile. Our detailed physical measurements (optical and electrochemical), density functional theory calculations, and photovoltaic characterizations disclosed that the energy level alignment, the molecular orbital profile, and dye aggregation all played very important roles on the interface electron transfer and charge recombination kinetics.
270 citations
TL;DR: This work provides an effective combined strategy of molecular design and cosensitization for developing efficient dye-sensitized solar cells (DSSCs) and carbazole has been demonstrated to be a promising donor for porphyrin sensitizers.
Abstract: Porphyrin dyes containing the carbazole electron donor have been designed and optimized by wrapping the porphyrin framework, introducing an additional ethynylene bridge to extend the wavelength range of light absorption, and further suppression of the dye aggregation by introducing additional alkoxy chains. Application of a cosensitization approach results in improved current density (Jsc) and open-circuit voltage (Voc) values, thus achieving the highest cell efficiency of 10.45 %. This work provides an effective combined strategy of molecular design and cosensitization for developing efficient dye-sensitized solar cells (DSSCs). In addition, carbazole has been demonstrated to be a promising donor for porphyrin sensitizers.
225 citations
TL;DR: In this article, a porphyrin small molecule with less bulky substituents at the periphery has been synthesized as a donor material, which exhibits a power conversion efficiency of up to 723% under AM 15 G irradiation (100 mW cm−2) for the solution-processed bulk heterojunction solar cells with PC61BM as the acceptor material.
Abstract: A porphyrin small molecule with less bulky substituents at the porphyrin periphery has been synthesized as a donor material, which exhibits a power conversion efficiency of up to 723% under AM 15 G irradiation (100 mW cm−2) for the solution-processed bulk heterojunction solar cells with PC61BM as the acceptor material
194 citations
TL;DR: The synthesis of such novel platinum-porphyrin conjugates as well as their photophysical characterization and in vitro light-induced anticancer properties imply that tetraplatinated porphyrin complexes are worthy of exploration as novel PDT anticancer agents in vivo.
Abstract: Despite the extensive use of porphyrins in photodynamic therapy (PDT), tetraplatinated porphyrins have so far not been studied for their anticancer properties. Herein, we report the synthesis of such novel platinum–porphyrin conjugates as well as their photophysical characterization and in vitro light-induced anticancer properties. These conjugates showed only minor cytotoxicity in the dark, but IC50 values down to 19 nM upon irradiation with light at 420 nm.These values correspond to an excellent phototoxic index (PI=IC50 in the dark/IC50 in light), which reached 5000 in a cisplatin-resistant cell line. After incubation with HeLa cells, nuclear Pt concentrations were 30 times higher than with cisplatin. All of these favorable characteristics imply that tetraplatinated porphyrin complexes are worthy of exploration as novel PDT anticancer agents in vivo.
186 citations
TL;DR: Time-resolved photoluminescence measurements show a decrease in average porphyrin emission lifetime upon BPMTC insertion, consistent with an ET-based mechanism, and portend the possible utilization of photochromic ligands to direct chromophore behavior in large light-harvesting ensembles.
Abstract: In this paper, a photochromic diarylethene-based derivative that is coordinatively immobilized within an extended porphyrin framework is shown to maintain its photoswitchable behavior and to direct the photophysical properties of the host. In particular, emission of a framework composed of bis(5-pyridyl-2-methyl-3-thienyl)cyclopentene (BPMTC) and tetrakis(4-carboxyphenyl)porphyrin (H4TCPP) ligands anchored by Zn2+ ions can be altered as a function of incident light. We attribute the observed cyclic fluorescence behavior of the synthesized porphyrin–BPMTC array to activation of energy transfer (ET) pathways through BPMTC photoisomerization. Time-resolved photoluminescence measurements show a decrease in average porphyrin emission lifetime upon BPMTC insertion, consistent with an ET-based mechanism. These studies portend the possible utilization of photochromic ligands to direct chromophore behavior in large light-harvesting ensembles.
173 citations
TL;DR: The hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER).
Abstract: The hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER). We now show improved HER activity of Ni compared with Co hangman porphyrins. Cyclic voltammogram data and simulations, together with computational studies using density functional theory, implicate a shift in electrokinetic zone between Co and Ni hangman porphyrins due to a change in the PCET mechanism. Unlike the Co hangman porphyrin, the Ni hangman porphyrin does not require reduction to the formally metal(0) species before protonation by weak acids in acetonitrile. We conclude that protonation likely occurs at the Ni(I) state followed by reduction, in a stepwise proton transfer–electron transfer pathway. Spectroelectrochemical and computational studies reveal that upon reduction of the Ni(II) compound, the first electron is transferred to a metal-based orbital, whereas the second electron is transferred to a molecular orbital on the porphyrin ring.
TL;DR: An anionic indium porphyrin framework (UNLPF-10) consisting of rare Williams β-tetrakaidecahedral cages was constructed using an octatopic ligand linked with 4-connected [In(COO)4](-) SBUs, resulting in a controllable framework charge density and photocatalytic activity toward the selective oxygenation of sulfides.
Abstract: An anionic indium porphyrin framework (UNLPF-10) consisting of rare Williams β-tetrakaidecahedral cages was constructed using an octatopic ligand linked with 4-connected [In(COO)4]− SBUs. Remarkably, the extent of indium metalation of porphyrin macrocycles in UNLPF-10 can be facilely tuned in situ depending on the M/L ratio during synthesis, resulting in a controllable framework charge density and photocatalytic activity toward the selective oxygenation of sulfides.
TL;DR: In this article, a new porphyrin sensitizer, LD31, was designed based on a donor-πacceptor structure, in which an ethynyl-anthracenyl moiety was inserted between the dioctylaminophenyl group and the porphin core in order to extend the π-conjugation of the dye for improved light harvesting ability.
Abstract: A new porphyrin sensitizer, LD31, was designed based on a donor–π–acceptor structure, in which an ethynyl-anthracenyl moiety was inserted between the dioctylaminophenyl group and the porphyrin core in order to extend the π-conjugation of the dye for improved light-harvesting ability. The device made of LD31 exhibited panchromatic spectral features covering the whole visible region and further extending over 800 nm. When combined with an organic dye (AN-4), the performance of the LD31/AN-4 co-sensitized device attained JSC/mA cm−2 = 20.3, VOC/mV = 704, FF = 0.72, and the overall efficiency of power conversion η = 10.3%.
TL;DR: In this paper, a triazine-functionalized porphyrin-based porous organic polymer, TPOP-1, was used for one-pot bottom-up synthesis involving extended aromatic electrophilic substitution on to a pyrrole.
Abstract: One-pot bottom-up synthesis involving extended aromatic electrophilic substitution on to a pyrrole has been employed for the design of a novel triazine-functionalized porphyrin-based porous organic polymer, TPOP-1. Hydrothermal treatment of 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)tris(oxy)tribenzaldehyde and pyrrole in glacial acetic acid in the presence of FeCl3 leads to the formation of TPOP-1, which is a highly porous and robust material, and which exhibits a high surface area and bimodal pore sizes ranging from large micropores to mesopores. The presence of porphyrin and triazine functionality within the network structure enables formation of electron-donating basic N-sites at the surface of the porous organic framework and thus favors the adsorption of Lewis acidic CO2 molecules and decoration of the material by palladium nanoparticles at its surface to form Pd-TPOP-1. TPOP-1 showed good CO2 storage capacity (6.2 mmol g−1 or 27.3 wt% at 3 bar/273 K), suggesting its potential application in environmental clean-up. Moreover, this post Pd-functionalized material forms fine colloidal suspensions in organic solvent and exhibits high catalytic activity for Sonogashira cross-coupling of aryl halides with aryl alkynes under mild reaction conditions.
TL;DR: Mannose-functionalized pSiNPs can be vectorized to MCF-7 human breast cancer cells through a mannose receptor-mediated endocytosis mechanism to provide a 3-fold enhancement of the 2-photon PDT effect.
Abstract: Porous silicon nanoparticles (pSiNPs) act as a sensitizer for the 2-photon excitation of a pendant porphyrin using NIR laser light, for imaging and photodynamic therapy. Mannose-functionalized pSiNPs can be vectorized to MCF-7 human breast cancer cells through a mannose receptor-mediated endocytosis mechanism to provide a 3-fold enhancement of the 2-photon PDT effect.
TL;DR: In this article, the authors provide a summary of some of the most important developments and approaches that are used in order to improve the light collection efficiency of DSSCs based on porphyrin hybrid derivatives.
Abstract: In the design of new chromophores, with high efficiency, chemical stability and low cost materials for dye sensitized solar cells, porphyrin macrocycles could play a very important role. Their successful use in nature during photosynthesis must be the inspiration for new artificial antenna systems. Porphyrins offer an excellent platform for building such multi-chromophoric systems to self-assemble because of the availability of several substituent sites and their intrinsic spectroscopic properties. Specifically, their high absorption ability in the visible region can be extended, and electron donor and anchoring groups with high chemical affinity to the cell should be part of the new design. This review provides a summary of some of the most important developments and approaches that are used in order to improve the light collection efficiency of DSSCs based on porphyrin hybrid derivatives. For this reason we have attempted to describe the developments in the DSSCs of various porphyrin dyes with different anchoring groups linked through either meso or β-positions. Also, the influence of the anchoring groups in the cell performance is discussed. Studies containing chromophores other than porphyrin derivatives are not included in this work.
TL;DR: The synthesis of hierarchical structured nanocrystals are reported through an interfacial self-assembly driven microemulsion (μ-emulsion) process and exhibit collective optical properties resulting from the coupling of molecular tin porphyrin and photocatalytic activities in the reduction of platinum nanoparticles and networks and in photodegradation of methyl orange pollutants.
Abstract: We report the synthesis of hierarchical structured nanocrystals through an interfacial self-assembly driven microemulsion (μ-emulsion) process. An optically active macrocyclic building block Sn (IV) meso-tetraphenylporphine dichloride (tin porphyrin) is used to initiate noncovalent self-assembly confined within μ-emulsion droplets. In-situ studies of dynamic light scattering, UV–vis spectroscopy, and electron microscopy, as well as optical imaging of reaction processes suggest an evaporation-induced nucleation and growth self-assembly mechanism. The resulted nanocrystals exhibit uniform shapes and sizes from ten to a hundred nanometers. Because of the spatial ordering of tin porphyrin, the hierarchical nanocrystals exhibit collective optical properties resulting from the coupling of molecular tin porphyrin and photocatalytic activities in the reduction of platinum nanoparticles and networks and in photodegradation of methyl orange (MO) pollutants.
TL;DR: A water stable zirconium-porphyrin MOF (PCN-222) was synthesized according to the reported method and found to produce a distinct reversible colorimetric and fluorescent "turn-off-turn-on" pH response.
TL;DR: Spectroscopic investigation of the system by stationary and time-resolved techniques enables a complete characterization of the photoinduced dynamics.
TL;DR: In this paper, a two-electron reduction of carbon dioxide to carbon monoxide, catalyzed by a newly synthesized metal complex dyad composed of a zinc porphyrin as a light-harvesting sensitizer and a rhenium bipyridyl complex as a catalytic moiety for the reduction, was attained for the first time on the p-type semiconductor NiO without any sacrificial electron donor.
TL;DR: Using the synthetic approaches and reactivity profiles presented, eventually almost any substituted porphyrin system can be prepared for applications in a variety of areas, including in catalysis, electron transport, model biological systems and therapeutics.
Abstract: Porphyrin macrocycles have been the subject of intense study in the last century because they are widely distributed in nature, usually as metal complexes of either iron or magnesium As such, they serve as the prosthetic groups in a wide variety of primary metabolites, such as hemoglobins, myoglobins, cytochromes, catalases, peroxidases, chlorophylls, and bacteriochlorophylls; these compounds have multiple applications in materials science, biology and medicine This article describes current methodology for preparation of simple, symmetrical model porphyrins, as well as more complex protocols for preparation of unsymmetrically substituted porphyrin macrocycles similar to those found in nature The basic chemical reactivity of porphyrins and metalloporphyrin is also described, including electrophilic and nucleophilic reactions, oxidations, reductions, and metal-mediated cross-coupling reactions Using the synthetic approaches and reactivity profiles presented, eventually almost any substituted porphyrin system can be prepared for applications in a variety of areas, including in catalysis, electron transport, model biological systems and therapeutics
TL;DR: The fabrication of theranostic porphyrin dyad nanoparticles (TPD NPs) for magnetic resonance imaging (MRI)-guided PDT cancer therapy, where the inner metal free poralin functions as a photosensitizer for PDT while the outer Mn-porphyrin serve as an MRI contrast agent.
TL;DR: In this paper, a visible light-induced living radical polymerization of a wide scope of acrylates mediated by organocobalt porphyrins was developed, where photostimulus was used to control the initiation steps and regulate chain growth by reversibly activating the Co-C bond.
Abstract: Visible light induced living radical polymerization of a wide scope of acrylates mediated by organocobalt porphyrins was developed. The photocleavage of the Co–C bond of organocobalt porphyrin produced carbon centered radicals, which initiated polymerization, and porphyrin cobalt(II), a persistent metal-centered radical. The organocobalt porphyrins were highly sensitive to external visible light irradiation so that photostimulus was used to control the initiation steps and regulate chain growth by reversibly activating the Co–C bond. Polymerization occurred spontaneously under irradiation and stopped promptly once shutting down light source. The scope of monomers was successfully extended from acrylamides to various hydrophobic and hydrophilic acrylates via the control of the light intensity. The structure of polyacrylate obtained was confirmed by 2D NMR, 13C NMR, GPC, and MALDI-TOF-MS. One of the unique features of this neat visible light induced polymerization process is that organocobalt porphyrins pla...
TL;DR: In this paper, a review describes selected examples of covalently linked porphyrin tweezer receptors extracted from the extensive literature generated in this area during the last 20 years and the relationship that exists between the magnitude of the binding constant of 1:1 complexes involving ditopically bound ligands and the conformational features of the spacers is assessed in detail.
TL;DR: This is the first example of a water soluble porphyrin acting as a photosensitizer for cobaloxime catalysed H2 production.
TL;DR: This facile fabrication of the p-THPP/rGO nanohybrid film makes it available for high-performance optoelectronic applications, as well as for device integration, and exhibits enhanced visible-light photocatalytic activity compared to each moiety of the hybrid.
Abstract: Organic nanostructures in terms of porphyrin building blocks have shown great potential in visible-light photocatalytic applications because of their optical, electrical, and catalytic properties. Graphenes are known to provide a high-quality two-dimensional (2D) support for inorganic semiconductor nanostructures to increase the adsorption capability of the photocatalysts and an electron-transfer medium with attractive potential to enhance photogenerated charge separation. A combination of porphyrin nanostructures with graphene sheets, particularly in the form of free-standing films, is highly desirable due to its photocatalysing feasibility and convenience. Toward this aim, we demonstrate a facile method to integrate porphyrin (meso-tetra(p-hydroxyphenyl)porphyrin, p-THPP) nanoparticles (NPs) into macroscopic graphene (reduced graphene oxide, rGO) films through vacuum filtration of the co-colloids of graphene oxide (GO) and p-THPP nanoparticles (NPs) followed by gaseous reduction. The obtained p-THPP/rGO nanohybrid film exhibits enhanced visible-light photocatalytic activity compared to each moiety of the hybrid, and this photocatalyst can be easily separated and recycled for successive use with excellent stability. The results show that this facile fabrication of the p-THPP/rGO nanohybrid film makes it available for high-performance optoelectronic applications, as well as for device integration.
TL;DR: The synthesis of surfactant-assisted different morphologies of meso-tetra(4-carboxyphenyl)porphyrin assemblies (spherical to flower shaped) are demonstrated, which could pave the way for designing new optical based materials for the applications in photocatalytic, photovoltaic, and light harvesting system.
Abstract: In this report, we have demonstrated the synthesis of surfactant-assisted different morphologies of meso-tetra(4-carboxyphenyl)porphyrin assemblies (spherical to flower shaped). These nano/micro assemblies are well characterized by scanning electron microscopy and X-ray diffraction. The formation of assemblies is driven by noncovalent interactions such as hydrophobic–hydrophobic and aromatic π–π stacking between the molecules. The steady state and time-resolved spectroscopic investigation reveal that different assemblies are formed by virtue of special supramolecular organizations. The photocatalytic activities of different assemblies have been demonstrated with an organic pollutant Rhodamine B dye under the visible light irradiation. Such porphyrin based assemblies could pave the way for designing new optical based materials for the applications in photocatalytic, photovoltaic, and light harvesting system.
TL;DR: In this paper, facile preparation of porous conjugated polymers (CPOP-11 and CPOP-12) using porphyrin or Fe(II)-porphyrin as core structures through this approach is reported.
TL;DR: A potential reaction sequence for light-driven H2-formation is formulated, where the reductive quenching of 1 forms the initial reaction step and reduced forms of 1 serve as hydride transfer agents to the H2 evolution catalyst.
Abstract: The water-soluble tin(IV) porphyrin dichlorido-5,10,15,20-tetrakis(p-carboxyphenyl)-porphyrinato-tin(IV) (SnTPPC, 1) was synthesised as a mimic of biological chlorophyll photosensitisers. In natural photosynthesis, chlorophyll pigments start the multi-electron transfer processes resulting in water-oxidation and NADP+-reduction. The photochemical properties of compound 1 were characterised by measuring absorption and fluorescence spectra. Electrochemical measurements in water revealed well-suited redox potentials of 1 for both proton-reduction to H2 as well as water-oxidation to O2. The tin(IV) porphyrin was then used as a photosensitiser in model systems for light-induced proton-reduction in aqueous solution, where an optimization of the experimental conditions was carried out to achieve reaction rates comparable to those found for [Ru(bipy)3]2+, a standard dye in artificial photosynthesis. By employing UV/Vis-spectroelectrochemistry, we found that the porphyrin ligand of 1 is redox non-innocent in water. A complex set of reduction reactions of the porphyrin macrocycle occurs during photocatalytic experiments involving the ligand's chlorin form as a key intermediate. On the basis of these results, a potential reaction sequence for light-driven H2-formation is formulated, where the reductive quenching of 1 forms the initial reaction step and reduced forms of 1 serve as hydride transfer agents to the H2 evolution catalyst. The spectroscopic, electrochemical and catalytic properties of SnTPPC make this compound class an attractive, affordable and easily accessible choice for photosensitisers in artificial photosynthetic systems. Finally, the detected complicated redox reactions of the porphyrin ring in water offer a possible explanation of why the chlorophylls of P680 or P700 are carefully wrapped in a water-free part of the PSII and PSI proteins.
TL;DR: A series of new porphyrins (LWP1−4) for dye-sensitized solar cells (DSSCs) were prepared by attaching pyrene or a 4-dimethylaminophenyl group in combination with anthracene as discussed by the authors.
Abstract: A series of new porphyrins (LWP1–4) for dye-sensitized solar cells (DSSCs) were prepared by attaching pyrene or a 4-dimethylaminophenyl group in combination with anthracene to modify the porphyrin core. Fundamental studies showed that incorporation of these moieties renders feasible tuning of spectral and redox properties of the porphyrins. Significantly, DSSCs adopting the LWP1 dye exhibit energy conversion up to 800 nm without compromising the overall efficiency. This achievement is attributed to the collective effects of the broadened and red-shifted IPCE spectra, elevated energy levels at the excited states of the dyes, suitable dye soaking processes, and suitable electron-donating substituents.