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Effect of the Medium on Fluorescence Parameters and Photostability of Porphyrins of Different Structure
摘要： Fluorescence and photostability against the action of UV irradiation of different porphyrins in benzene, DMF, and acetic acid media have been studied. The effect of the macroheterocycle structure on the conditions of its thermal decomposition under inert atmosphere has been investigated.
关键词： photodecomposition,nonplanar macrocycles,NH-activity,porphyrin,thermal stability
更新于2025-09-09 09:28:46
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High-Energy Charge-Separated States by Reductive Electron Transfer Followed by Electron Shift in Tetraphenylethylene – Aluminum(III) Porphyrin – Fullerene Triad
摘要： A high potential supramolecular triad (TPE-AlPor?Im-C60) composed of aluminum(III) porphyrin (AlPor), fullerene (C60), and tetraphenylethylene (TPE) has been constructed. The fullerene and tetraphenylethylene units are bound axially to opposite faces of the porphyrin plane via coordination and covalent bonds, respectively. The ground and excited-state properties of the triad and reference dyads are studied using steady-state and time-resolved spectroscopic techniques. The transient data show that photoexcitation results in charge separation (CS) from tetraphenylethylene to the excited singlet state of the porphyrin (1AlPor*), generating high-energy (2.14 eV) charge-separated state, (TPE)?+-(AlPor)?? in toluene. A subsequent electron migration from the AlPor?? to fullerene generates a second high-energy (1.78 eV) charge-separated state (TPE)?+-AlPor?Im-(C60)??. The lifetime of the charge separation persists about 25 ns. The high energy stored in the form of charge-separated states along with its reasonable lifetimes makes these donor-acceptor systems potential electron-transporting catalysts to carry out energy-demanding photochemical reactions, especially in artificial photosynthesis for conversion of solar energy into chemical energy.
关键词： high-energy charge-separated states,aluminum(III) porphyrin,tetraphenylethylene,fullerene,reductive electron transfer,electron shift,triad
更新于2025-09-09 09:28:46
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Visible-Light-Driven Conversion of CO2 to CH4 with an Organic Sensitizer and an Iron Porphyrin Catalyst
摘要： Using a phenoxazine-based organic photosensitizer and an iron porphyrin molecular catalyst, we demonstrated photochemical reduction of CO2 to CO and CH4 with turnover numbers (TONs) of 149 and 29, respectively, under visible light irradiation (λ > 435 nm) with a tertiary amine as sacrificial electron donor. This work is the first example of a molecular system using an earth-abundant metal catalyst and an organic dye to effect complete 8e-/8H+ reduction of CO2 to CH4, as opposed to typical 2e-/2H+ products of CO or formic acid. The catalytic system continuously produced methane even after prolonged irradiation up to four days. Using CO as the feedstock, the same reactive system was able to produce CH4 with 85% selectivity, 80 TON and a quantum yield of 0.47%. The redox properties of the organic photosensitizer and acidity of the proton source were shown to play a key role in driving the 8e-/8H+ processes.
关键词： methane,organic photosensitizer,CO2 reduction,iron porphyrin,visible light
更新于2025-09-09 09:28:46
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Synthesis of C-C bonded Two-dimensional Conjugated Covalent Organic Framework Films via Suzuki Polymerization on Liquid/liquid Interface
摘要： Synthesis of free standing two-dimensional (2D) conjugated covalent organic framework (COF) films linked by C-C bonds can be considered as a holy grail of synthetic chemistry. However, reactions for their synthesis are quite rare. Herein we developed a very simple and mild strategy to synthesize them via the Nobel Prize reaction (Suzuki polymerization) on water/toluene interface in a fridge. The versatility of this strategy was proved by the successful synthesis of two different 2D-COF films: a porous graphene and a porphyrin-contained 2D-COF. Both 2D-COF films have large lateral size and their crystalline domains were visualized by high resolution TEM. Based on the wide compatibility of Suzuki reaction, our breakthrough work opened a door for the synthesis of various 2D conjugated COF films. For application studies, the porous graphene exhibits a good carrier mobility which is much higher than -C=N- linked 2D COF films and a good catalytic activity for hydrogen evolution reaction which is comparable with nitrogen or phosphorus doped graphene.
关键词： porous graphene,interface,porphyrin,2D conjugated COF,Suzuki polymerization
更新于2025-09-09 09:28:46
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ECCD characterization of monotopically binding guests in host-guest complexes with a bis-(zinc porphyrin) tweezer
摘要： We have investigated the possibility to use a stiff-stilbene linked bisporphyrin tweezer with inherent helicity for Exciton-Coupled Circular Dichroism (ECCD) characterization of a series of monotopically binding amine guest molecules. CD signals were observed for a variety of monoamines at relatively low tweezer:amine (host:guest) ratios between 1:10 to 1:70. For the amines producing the most intense CD signals a binding stoichiometry of 1:2 was found. A likely explanation is the presence of guest-guest interactions in the complexes. This is supported by observing a correlation between CD signal intensity and magnitude of possible non-covalent binding between the guests, which we can divide into three groups showing no, moderate or strong response, respectively. Further support for this rationalization comes from molecular modelling.
关键词： absolute stereochemistry,molecular modelling,bis-porphyrin tweezers,monotopic binding,exciton-coupled circular dichroism
更新于2025-09-09 09:28:46
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Two-dimensional porphyrin-based covalent organic framework: A novel platform for sensitive epidermal growth factor receptor and living cancer cell detection
摘要： A porphyrin-based covalent organic framework (denoted as p-COF) was synthesized by a simple oil-bath method and exploited as a novel sensing layer for immobilizing epidermal growth factor receptor (EGFR)-targeting aptamer strands to detect trace EGFR and living michigan cancer foundation-7 (MCF-7) cells for the first time. p-COF presented a nanosheet-like structure, large cavities, rich nitrogen-bearing groups, high electrochemical activity, excellent bioaffinity, low toxicity, and good stability in aqueous solution; the microstructural features of this material enabled strong immobilization of the aptamer strands. Interactions between the aptamer strands and EGFR significantly changed the electrochemical signals of the modified electrode due to the formation of an aptamer-EGFR complex. The p-COF-based aptasensor exhibited an extremely low detection limit (LOD) of 5.64 fg?mL?1 obtained from differential pulse voltammetry and 7.54 fg?mL?1 originated from electrochemical impedance spectroscopy with a broad linear detection range of 0.05–100 pg?mL?1 of the EGFR concentration. When detecting living MCF-7 cells, the p-COF-based aptasensor showed an LOD of 61 cell?mL?1 with a linear detection range of 500 × 105 cell?mL?1. The fabricated aptasensor exhibited high selectivity, good stability, reproducibility, acceptable recyclability, and favorable applicability in human serum samples. We believe that the developed p-COF-based aptasensor is a potential candidate for the sensitive detection of target cancer markers or living cells.
关键词： Detection of epidermal growth factor receptor,Living cancer cell detection,Porphyrin-based covalent organic framework,Electrochemical aptasensor
更新于2025-09-09 09:28:46
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Photostability of oxygen-sensitive core-shell nanofibers
摘要： Core-shell electrospun nanofibers constitute a vehicle enabling novel uses for phosphorescent oxygen-sensitive molecules. In this work, we investigate compositional parameters and other factors governing fiber design appropriate to long-term sensor applications. These nanofibers contain an oxygen-sensitive palladium (II) porphyrin species within a polysulfone core; an outer polycaprolactone shell protects the core from the surrounding environment. The presence of a core-shell architecture was confirmed using advanced time-of-flight secondary ion mass spectrometry (ToF-SIMS). Although these sensors exhibit excellent photostability in the short-term, long-term exposures (up to 1,000 hr) are shown to detrimentally impact performance via photobleaching phenomenon. We also investigated higher porphyrin concentrations to determine whether the resulting sensors are predisposed to photobleaching. High porphyrin loadings (up to 10 wt%) could be successfully incorporated into the core. While increased probe content should logically enhance emission intensity, we sought to investigate the balance between a stronger signal and the potential for decreased photostability. The resulting behavior is rationalized by (1) establishing the spacing associated with a ‘perfect’ molecular dispersion and (2) invoking five distinct populations of porphyrin agglomeration. Populations that are not molecularly dispersed experience varying degrees of agglomeration-catalyzed photobleaching. The photobleaching rate increases with the extent of agglomeration and, therefore, the initial porphyrin content. Although it is demonstrated that low porphyrin loadings exhibit improved photobleaching resistance, the initial brightness is inadequate. In contrast, enhanced brightness via increased porphyrin content also leads to diminishing returns due to the apparent emergence of a self-quenched population. For a given application, selection of an appropriate porphyrin concentration is critical to achieving a compromise between initial brightness and photobleaching resistance. Detector sensitivity and anticipated duration of use must be considered when weighing the relative benefits of these attributes and selecting a specific porphyrin content.
关键词： Core-shell electrospinning,electrospun nanofiber,agglomeration,porphyrin,oxygen sensing
更新于2025-09-09 09:28:46
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Silk fibroin hydrogels for potential applications in photodynamic therapy
摘要： In this study, we prepared translucid hydrogels with different concentrations of silk fibroin, extracted from raw silk fibers, and used them as a matrix to incorporate the photosensitizer 5-(4-aminophenyl)-10,15,20-tris-(4-sulphonatophenyl) porphyrin trisodium for application in photodynamic therapy (PDT). The hydrogels obtained were characterized by rheology, spectrophotometry, and scattering techniques to elucidate the factors involved in the formation of the hydrogel, and to characterize the behavior of silk fibroin (SF) after incorporating of the porphyrin to the matrix. The rheology results demonstrated that the SF hydrogels had a shear thinning behavior. In addition, we were able to verify that the structure of the material was able to be recovered over time after shear deformation. The encapsulation of porphyrins in hydrogels leads to the formation of self-assembled peptide nanostructures that prevent porphyrin aggregation, thereby greatly increasing the generation of singlet oxygen. Also, our findings suggest that porphyrin can diffuse out of the hydrogel and permeate the outer skin layers. This evidence suggests that SF hydrogels could be used as porphyrin encapsulation and as a drug carrier for the sustained release of photosensitizers for PDT.
关键词： singlet oxygen,hydrogel,fibroin,rheology,photodynamic therapy,porphyrin
更新于2025-09-04 15:30:14
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Differential quenching of the angular momentum of the B and Q bands of a porphyrin as a result of extended ring π-conjugation
摘要： A novel porphyrin, whose p-system has been extended via the presence of two additional carbon–carbon triple bonds on opposite meso-positions and by fusion of a single naphthalene unit simultaneously bridging the third meso-position and the b-carbon of one of the pyrroles, has been synthesized in good yield. Absorption, magnetic circular dichroism, emission, and theoretical spectra are reported for the fused and unfused trans-naphthalene free base and zinc porphyrins. The fusing of one of the naphthalene moieties results in significant changes to the absorption spectrum and, very unusually, the bridged meso-b-pyrrole fusion results in quenching of the MCD Faraday pseudo-A term in the porphyrin’s B band (S2). This unique effect was interpreted as resulting from the origin of the electronic structure of the second excited state (the B state). The x and y polarizations are completely mixed by the electronic effects of the non-symmetric extended conjugation of the p ring. Analysis of the origin of the MCD signal indicates that the presence of this novel mixed polarization leads to negligible angular momentum in the important B state. To our knowledge, this is the first report in which the magnetic moment in a porphyrin’s intensely absorbing B band has been quenched while the angular momentum in the Q band, the first excited state, remains as normal. This implies that the photophysical properties of the B state are likely very different than those of the Q state, which has novel and significant implications for applications, especially in non-linear spectroscopy.
关键词： TD-DFT calculations,Extended porphyrin,Magnetic Circular Dichrosim (MCD),Q band,B band,angular momentum
更新于2025-09-04 15:30:14
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Selective Formation of Helical Tetrapyrrin‐fused Porphyrins by Oxidation of beta‐to‐beta Linked meso‐Aminoporphyrin Dimers
摘要： Oxidation of b-to-b directly linked and sulfur-bridged meso-amino NiII-porphyrin dimers with PbO2 gave helical tetrapyrrin (biliverdin analogue)-fused NiII-porphyrins. These ring cleaving reactions differ markedly from the previously reported oxidation of a b-b linked NiII-porphyrin dimer carrying one amino-group that gave an azepine-fused porphyrin dimer. The tetrapyrrin-fused NiII-porphyrins display intense NIR absorption bands reaching at 1200–1400 nm and reversible redox processes because of the highly p-conjugated networks and rigid structures. These tetrapyrrin-fused NiII-porphyrins were separated to stable enantiomers, which showed clear Cotton effects in their CD spectra with De of 102 order.
关键词： NIR absorption,aminyl radical,helical structure,p-extended porphyrin,circular dichroism
更新于2025-09-04 15:30:14