Meso-tetraphenyl Porphyrin Research Articles

Ultra-low power carbon nanotube/porphyrin synaptic arrays for persistent photoconductivity and neuromorphic computing

Developing devices with a wide-temperature range persistent photoconductivity (PPC) and ultra-low power consumption remains a significant challenge for optical synaptic devices used in neuromorphic computing. By harnessing the PPC properties in materials, it can achieve optical storage and neuromorphic computing, surpassing the von Neuman architecture-based systems. However, previous research implemented PPC required additional gate voltages and low temperatures, which need additional energy consumption and PPC cannot be achieved across a wide temperature range. Here, we fabricated a simple heterojunctions using zinc(II)-meso-tetraphenyl porphyrin (ZnTPP) and single-walled carbon nanotubes (SWCNTs). By leveraging the strong binding energy at the heterojunction interface and the unique band structure, the heterojunction achieved PPC over an exceptionally wide temperature range (77 K-400 K). Remarkably, it demonstrated nonvolatile storage for up to 2×104 s, without additional gate voltage. The minimum energy consumption for each synaptic event is as low as 6.5 aJ. Furthermore, we successfully demonstrate the feasibility to manufacture a flexible wafer-scale array utilizing this heterojunction. We applied it to autonomous driving under extreme temperatures and achieved as a high impressive accuracy rate as 94.5%. This tunable and stable wide-temperature PPC capability holds promise for ultra-low-power neuromorphic computing.

Electroreduction mechanisms of meso-Tetraphenylphlorin cation in strongly acidic media of benzonitrile

In nonaqueous media free-base porphyrins are easily protonated by strong proton donors to form the diprotonated porphyrins. The two-electron reduction of these species leads to phlorin cation species. To investigate the electroreduction products that follow the formation of these species, we evaluate the effect of increasing amounts of HClO4 on the electroreduction mechanism of the phlorin cation of meso-tetraphenyl porphyrin. We demonstrate that the phlorin cation undergoes a reversible protonation reaction to form a porphodimethene, which is further reduced to yield the chlorin-phlorin cation, a 4-electron reduced phlorin macrocycle with a hydrogenated pyrrolic Cβ = Cβ double bond. This undergoes further protonation and a 2-electron reduction to form a phlorin macrocycle, the bacteriochlorin-phlorin cation, wherein two pyrrole rings are hydrogenated. All these reduction processes occur at similar potential values, yet we managed to selectively form the 2-, 4- or 6- electron reduced product by a strict control of the number of protons in the medium. To the best of our knowledge, this is the first report of the electrochemical reduction of Cβ = Cβ bonds of pyrrolic rings. Thus, a new pathway for the electrochemical reduction of porphyrins is proposed.

The Performance Evaluation of Meso-Tetraphenyl Porphyrin and Azo Dyes as Photosensitizers in Dye-sensitized Solar Cells.

The photovoltaic properties of five different mono-azo function and meso-tetraphenyl porphyrin dyes have been investigated by computational DFT/TDDFT calculations and measurement of the J-V properties of their cells. The photovoltaic efficiency of the cells based on these dyes were determined by both experimental and theoretical methods. The efficiency-to-cost ratios of the azo-dye cells showed that they could be cheaper substitutes to porphyrin-based cells. Eriochrome blue black (EBB) and eriochrome black T (EBT) cells were shown to possess the best photovoltaic properties by the two methods employed (theory and experiment). The presence of two naphthol moieties at both ends of their -N = N- group has been adduced as possible reason for their relatively outstanding performance. The extremely low efficiency-to-cost ratio obtained for cell-POR suggests that the use of porphyrin as sensitizer may not be as economically viable as some azo dyes. MTO, EBB and EBT were found to be the most cost-effective among the investigated dyes. The porphyrin's low performance may have been amplified by the absence of an effective anchor group in its molecular structure.

Modulation of optical oxygen sensitivity of H2(TPP) by using Eu3+, Gd3+ and Yb3+ ions doped silicate-based bioactive glass powders immersed in simulated body fluid

Improving the performance of optical oxygen sensors can be accomplished by adding additives to the composition comprising an oxygen-sensitive probe encapsulated in a polymeric matrix. In this study, to advance the oxygen sensing ability, free meso-tetraphenyl porphyrin (H2(TPP)) was chosen as a luminophore. The sol-gel based 13–93 bioactive glass powders (BG) co-doped with ytterbium (Yb3+), gadolinium (Gd3+), and europium (Eu3+) and immersed in simulated body fluids (SBF) were also used as additives. After being immersed in SBF, bioactive glasses containing Eu3+, Gd3+, and Yb3+ were found to be able to convert hydroxyapatite corresponding to in vitro bioactivity tests. The optimum additive concentration for all glass samples is 3 wt%, based on photoluminescence-based properties. The luminescence dye was incorporated into poly(trimethylsilylpropyne) [poly(TMSP)] matrices in the form of a thin film along with bioactive glass additives to improve oxygen sensitivity. Emission-based intensity values of all porphyrin complexes have been followed as a signal drop during oxygen sensing measurements. The H2(TPP) along with the additive of BG:Eu3+ showed a 6.88 fold of I0/I ratio compared to the undoped and Gd3+ and Yb3+-doped BG forms in terms of the relative signal change. Large Stoke's shift (Ksv) values, high luminescence abilities, and linear spectral response make them promising candidates as oxygen sensing agents. It was concluded that prepared bioactive glass powders are suitable to use as additive materials for improving the oxygen sensitivity of meso-tetraphenyl porphyrin dye.

Anchoring porphyrin self-assembled dye sensitized solar cells: synthesis and photovoltaic application

Anchoring porphyrin, ZnPAc, featuring cyanoacetic acid group has been synthesized for application in a dye-sensitized solar cell. Capping layer dyes zinc meso-tetraphenyl porphyrin (ZnTPP) with anchoring porphyrin ZnPAc through axial coordination bonds of Zn-to-ligand self-assembles solar cell devices. With the introduction of cyanoacetic acid anchor, the higher electrons are effectively injected into the TiO2 semiconductor surface. Thus, the ZnTPP-ZnPAc-based device has more short-circuit current (JSC ) compared with our previously reported ZnTPP-ZnPA-based solar cell. The ZnPA and ZnPAc porphyrin anchoring dyes maintain a broad absorption spectrum and also improve electron injection and lower charge recombination compared to our previous reports on organic molecule anchored dye W3. Hence, the ZnTPP-ZnPAc self-assembled dye has higher power conversion efficiency. The assembled modes were also verified by transmission electron microscopy (TEM). To understand ZnTPP-ZnPAc for photovoltaic performance trends, we have carried out charge extraction, transient photovoltage decay and electrochemical impedance spectroscopy analysis.

A Green Blue LED-Driven Two-Liquid-Phase One-Pot Procedure for the Synthesis of Estrogen-Related Quinol Prodrugs.

Quinol derivatives of estrogens are effective pro-drugs in steroid replacement therapy. Here, we report that these compounds can be synthesized in one-pot conditions and high yield by blue LED-driven photo-oxygenation of parent estrogens. The oxidation was performed in buffer and eco-certified 2-methyltetrahydrofuran as the two-liquid-phase reaction solvent, and in the presence of meso-tetraphenyl porphyrin as the photosensitizer. Two steroidal prodrugs 10β, 17β-dihydroxyestra-1,4-dien-3-one (DHED) and 10β-Hydroxyestra-1,4-diene-3,17-dione (HEDD) were obtained with high yield and selectivity.

The effect of alkoxyl groups on the photoproperties of meta-octasubstituted tetraphenyl porphyrins

• . Installing substituent groups with different lengths/sizes and conformations at the meta-octa-substituted position of meso-tetraphenyl porphyrin. • . H 2 T(OHE) 2 PP with longer and branched alkoxyl chains effectively suppressed aggregation-caused quenching effect. • . H 2 T(OH) 2 PP in solid state shows the naked-eye visible fluorescence, making its practical applications possible. The emission of most organic fluorescent molecules in aggregation states decays or fades, as interpreted by the aggregation-caused quenching (ACQ) effect, because the excited state energy is depleted via nonradiative channels when chromophores stack together. However, most fluorescent materials are utilized in the solid state, and hence it is vital to tune the chromophore stacking mode for modulating the photoluminescence properties. In this work, the meso-tetraphenyl porphyrin was taken as the parent chromophore unit to investigate the substituent-group effect on the luminescence properties of porphyrin-based complexes. The selected substituent groups (-OH, -OMe and 2-ethylhexyloxy) with different lengths/sizes and conformations were installed at the meta-octa-substituted position of meso-tetraphenyl porphyrin. The distance of porphyrin chromophores was regulated by the substituent chain. It was found that in the solid or aggregate state, porphyrin with longer and branched alkoxyl chains effectively suppressed the π-π stacking interaction, maintained the photoluminescence property of the porphyrin chromophore as in its dilute solution and overcame the ACQ effect. In contrast, porphyrin with a shorter alkoxyl chain, for example, the methoxyl group, affords a weak emission property in the solid state, and the substituent hydroxyl group leads to the complete quenching of the emission in the solid-state due to the close stacking of porphyrin rings.

Unveiling the robustness of porphyrin crystalline nanowires toward aggressive chemicals

One of the keys for the development of porphyrin-based devices implies that their functionality must be robust and stable against external environmental factors. While the research has been mostly focused on the supramolecular aggregate interactions with target chemicals, the robustness of organic nanostructures in contaminating and even aggressive environments has not been diffusely investigated yet. The results here presented show that crystalline nanowires of meso-tetraphenyl porphyrin (H2TPP) and meso-tetraphenyl porphyrin-Zn(II) (ZnTPP) are insensitive to the exposure to a series of purposely chosen analytes (alcohols, alkanes and amines). Our finding suggests possible applications of the nanowires in organic-based devices (overwhelming the well-known intrinsic weakness of organic electronics), related to material stability through an appropriate material design and the opportunity offered by organic epitaxy.

Synthesis of novel bis(cyano) meso-tetraphenylporphyrinato-chromium(III), [K(2 2 2)] [CrIII(TPP)(CN)2] 2.(C7H6O2) (III), and (Chloro) meso-tetraphenylporphyrinato-chromium(III), [CrIII(TPP)Cl] (II): Spectroscopic, physico-chemical, and decolorization properties

The design of metalloporphyrins has attracted the attention of scientists owing to their valuable properties. In this work, the synthesis of meso-tetraphenyl porphyrin H2TPP (I), meso-tetraphenylporphyrinato-chromium(III) complex [CrIII(TPP)Cl] (II), and bis(cyano) meso-tetraphenylporphyrinato-chromium(III) complex [K(222)] [CrIII(TPP)(CN)2] 2.(C7H6O2) (III) was described. The physicochemical properties of (ll)-(IIII) were investigated. X-ray molecular structure of (III) displayed that the crystal lattice of the six-coordinated chromium (III) coordination compound, was made by two-dimensional chain pairs parallel to the [010] direction sustained by C__H…Cg and Cg…Cg π inter and intra-molecular interactions. Hirshfeld surface analysis allowed us to understand the intermolecular contacts, where the fingerprint plot provided the information about the percentage contribution. UV–vis data showed a red-shift for the chromium complex and slightly blue-shift after coordination with cyano axial ligand. The Eg-op value suggested that (I)-(III) compounds are semi-conductor. The complex (II) efficiently and promptly degraded calmagite dye solution at a yield of 100% (calmagite = 40 mg/L, pH = 6, time = 10 min, catalyst dose = 3 mg, H2O2 dose = 4 mL/L, and T = 20 °C).

Determination of the binding mechanism of cobalt(II) meso-tetraphenyl porphyrin with plant-esterase

Abstract Plant-esterase (EC 3.1.1.X) has received much attention because plant esterase and acetylcholinesterase (AChE) share a similar sensitivity towards organophosphorus (OP) pesticides detection with the same inhibition mechanism. To improve the analytical performance, tetraphenyl metal porphyrin, as an indicator was introduced to combine with plant-esterase. The time of reach equilibrium in PBS solution was shortened after adding plant-esterase by assaying the intensify change of the porphyrin spectrum. Meanwhile, intensify of porphyrin spectrum with plant-esterase was increased compared with that of only the porphyrin spectrum in solution. Tetraphenyl metal porphyrin, such as cobalt(II) meso-tetraphenyl porphyrin, is a mixed reversible inhibitor of plant-esterase from kinetic parameters. The combination ratio of plant-esterase and porphyrin is 2:1. On the other hand, the interaction between CoTPPCl and plant-esterase is the strongest among all tested tetraphenyl metal porphyrin. And the mixed system (CoTPPCl-plant-esterase) showed the best sensitivity towards the tested pesticide. All these results indicated that a complex system composed of tetraphenyl metal porphyrin and plant-esterase was fit for detecting pesticides. They make meaningful guidance on the further design of sensing material in monitoring pesticides.

Use of low frequency Raman bands to identify non-planar deformation of Ni(II) meso-tetraphenylporphyrin induced by axial ligands

It is important to identify non-planar deformations of porphyrin macrocycle in metallo-porphyrin proteins due to their functional relevance. The relationship between non-planar deformations of porphyrin macrocycle and low frequency Raman spectral bands of Ni(II) meso-tetraphenyl porphyrin (NiTPP), with different coordination numbers, was studied by density functional theory (DFT), normal coordinate structural decomposition method and Raman experiments. The results show that the crystal of four-coordinate NiTPP has two major kinds of non-planar deformations: ruffling and saddling. The non-planar deformations of ruffling and saddling for NiTPP are 1.473 Å and 0.493 Å determined by DFT calculation. The ruffling and saddling deformations can be identified by using the low frequency Raman characteristic peaks (γ12, γ13) and (γ16, γ17), respectively. When four-coordinate NiTPP is transformed to the six-coordinate bis(pyrrolidine) NiTPP (NiTPP(Pyr)2), the large non-planar distortion of the porphyrin macrocycle almost disappears, with the non-planar deformation of saddling only about 0.213 Å estimated by DFT calculation. Experimentally, we can make use of the characteristic peaks of low frequency Raman spectra to identify the saddling deformation beyond 0.25 Å.

Preparation of meso-tetraphenyl porphyrin modified defect-rich BiOCl with enhanced visible-light photocatalytic activity for antibiotic degradation and mechanism insight

The exploration of effective photocatalysts used in wastewater treatment containing antibiotics is of significant importance for addressing the universal environment problems. In this work, the meso-tetraphenyl porphyrin (TPP) with conjugated macrocyclic π-electrons structure was successfully combined with defect-rich BiOCl to form ultrathin sheet-like TPP/defect-rich BiOCl composite as visible-light-responsive photocatalyst. The morphologies, crystal structures, chemical constitutions, optical and photo-electrochemical properties of the as-obtained photocatalyst were determined. The TPP/defect-rich BiOCl composite showed enhanced photocatalytic ability for the degradation of colorless antibiotic TC, CIP and ENR under visible light irradiation compared to defect-rich BiOCl. The effect of different TPP contents on the photodegradation activity was also investigated, and 2 wt% TPP/defect-rich BiOCl exhibited the optimal photocatalytic ability. According to the radicals trapping experiments and electron spin resonance (ESR), the hole (h+), superoxide radical (O2•−) and hydroxyl radical (•OH) contributed to the process of organic pollutant photo-degradation. The good recyclability of the photocatalyst was verified through cyclic measurements. Furthermore, a possible photodegradation mechanism was raised to clarify the effective separation and migration process of photo-induced charge carriers.

Synthesis and electronic properties of meso-tetra(3,4,5-trimethoxy)phenyl-porphyrin and -tetrabenzoporphyrin and their phosphorus complexes

meso-Tetra(3,4,5-trimethoxy)phenyl-porphyrin and -tetrabenzoporphyrin and their phosphorus complexes were synthesized and their electronic absorption and magnetic circular dichroism (MCD) spectra discussed based on TD-DFT molecular orbital (MO) calculations. Nucleus-independent chemical shift (NICS) and anisotropy of the induced current density (ACID) calculations were also carried out for metal-free (and phosphorus) tetrabenzoporphyrins in order to discuss the aromaticity and flow of electrons in the molecule.

Polyethersulfone Mats Functionalized with Porphyrin for Removal of Para-nitroaniline from Aqueous Solution.

The dispersion of para-nitroaniline (p-NA) in water poses a threat to the environment and human health. Therefore, the development of functional adsorbents to remove this harmful compound is crucial to the implementation of wastewater purification strategies, and electrospun mats represent a versatile and cost-effective class of materials that are useful for this application. In the present study, we tested the ability of some polyethersulfone (PES) nanofibers containing adsorbed porphyrin molecules to remove p-NA from water. The functional mats in this study were obtained by two different approaches based on fiber impregnation or doping. In particular, meso-tetraphenyl porphyrin (H2TPP) or zinc(II) meso-tetraphenyl porphyrin (ZnTPP) were immobilized on the surface of PES fiber mats by dip-coating or added to the PES electrospun solution to obtain porphyrin-doped PES mats. The presence of porphyrins on the fiber surfaces was confirmed by UV–Vis spectroscopy, fluorescence measurements, and XPS analysis. p-NA removal from water solutions was spectrophotometrically detected and evaluated.

Chitosan Nanoparticles as a Potential Drug Delivery System for Photodynamic Therapy of Cancer

Objective: Chitosan nanoparticles (CS-NP) can imbibe water insoluble anticancer agents into its hydrophobic multicores. In the present study, chitosan nanoparticles, a nanoscale drug carrier system is investigated for its potential as a drug delivery system for porphyrin based photodynamic therapy. Methods: Zinc meso tetra phenyl porphyrin (ZnmTPP) encapsulated CS-NP was prepared by ionic gelation method. The synthesized nanoparticles were characterized using dynamic light scattering studies, zeta potential analysis and AFM analysis. Results: Freshly prepared chitosan nanoparticles had an average hydrodynamic diameter of 175 nm and are nearly spherical in shape as per light scattering measurements and atomic force imaging respectively. As nanoscale drug carriers, (ZnmTPP) encapsulated chitosan nanoparticles exhibited high encapsulation efficiency and controlled release pattern. The encapsulated photosensitizer exhibited efficient singlet oxygen generation upon photo irradiation, retaining the photosensitization capacity of encapsulated hydrophobic ZnmTPP. The in vitro phototoxicities of free and nano-encapsulated ZnmTPP, studied using MTT assay in DLA cell lines demonstrate a concentration dependent response of photosensitizer in free and CS-nano formulations.

Control of post-growth processes for the selection of metallo-tetraphenylporphyrin nanowires.

Controlling self-organization of small organic molecules in nanostructures with a desired shape and size is one of the main challenges in organic nanoelectronics. Here, a strategy for selectively growing uniaxially aligned nanowires of meso-tetraphenyl porphyrin-Zn(ii) (ZnTPP) is presented. ZnTPP is deposited on an organic single crystal, namely potassium hydrogen phthalate, by organic molecular beam epitaxy. The films typically display a rather rich surface morphology, characterized by the presence of nanowires and other nm-sized aggregates, most of them unstable over time. Post-growth processes occurring via quasi-Ostwald ripening both in air and in vacuum demonstrate an aging protocol in vacuum as a tool for the selection of ZnTPP nanowires, whose morphology and uniaxial orientation are demonstrated to be led by organic epitaxy. The ability of growing ZnTPP nanowires with a unique crystal structure and precise orientation gives the chance to observe the intrinsic optical anisotropy of the triclinic polymorph of ZnTPP crystal and establishes the role of intermolecular interactions, providing new perspectives in the study of the intrinsic physical properties of ZnTPP crystals.

Preparation of Single Substituted Phenyl Porphyrins Form <i>Meso</i>-Tetraphenyl Porphyrin-Synthetic Example from Symmetric Porphyrin into Asymmetric Porphyrins

Two asymmetric porphyrins, 5-(4-chloromethylphenyl)-10, 15, 20-triphenyl porphyrin and 5-(4-formylphenyl)-10, 15, 20-triphenyl porphyrin, were successfully prepared by the symmetric meso-tetraphenyl porphyrin and relative molecular configurations and properties were characterized by spectral determinations. This work presented an example for synthesis of asymmetric porphyrin derivatives from the symmetric porphyrin. Both asymmetric porphyrins are reactive in molecular assembly, the concerned reactions including alkylation with Grignard reagents, etherification with alcohols, aldol condensation and Mannich reaction for modification and enhancing their functionality. In this work, the reaction conditions were improved, synthetic strategy and route were confirmed.

Cobaltocenium substituents as electron acceptors in photosynthetic model dyads

Cobaltocenium carboxylic acid hexafluorophosphate has been attached to a zinc(II) meso-tetraphenyl porphyrin chromophore via an amide linkage. Optical and electrochemical studies reveal that the metallocene and the porphyrin interact only negligibly in the ground state of the dyad. Photoinduced charge-shift from the zinc porphyrin to the cobaltocenium substituent to give the zinc porphyrin radical cation and the cobaltocene occurs upon exciting the porphyrin with light. Steady state emission, time-resolved fluorescence and transient absorption pump–probe spectroscopy in addition to density functional theory calculations suggest that the charge shift to the cobaltocenium substituent can occur from several excited states of the porphyrin, namely from the S2, S1 and T1 states. The triplet states of the cobaltocenium substituent (3E1g) and the triplet state of the zinc porphyrin (T1) are higher in energy than the charge-shifted state. This energy sequence of states of the dyad is beneficial for photoinduced charge-shift reactions.

Influence of the metal sites of M-N-C (M = Co, Fe, Mn) catalysts derived from metalloporphyrins in ethylbenzene oxidation

Transition metal catalysts M-N-C (M = Co, Fe, Mn) were synthesized by a template-free method by heating meso-tetraphenyl porphyrins (i.e. CoTPP, FeTPPCl, MnTPPCl) precursors. The catalysts were characterized by N2 adsorption-desorption, thermogravimetry, high-resolution transmission electron microscopy, and Raman and X-ray photoelectron spectroscopy. The selective oxidation of ethylbenzene with molecular oxygen under a solvent-free condition was carried out to explore the catalytic performance of the M-N-Cs, which exhibited different catalytic performance. That was ascribed to the difference in M (Co, Fe, Mn) and different graphitization degree forming during the heating process, in which M (Co, Fe, Mn) might have different catalytic activity on the formation of the M-N-C catalyst. All the M-N-C composites had remarkable recyclability in the selective oxidation of ethylbenzene.

Photo-Isomerization of Prolycopene in Chloroplast Occurs through the Triplet State: Implications on Carotenoid Biosynthesis

The carotenoid lycopene in photosynthetic organisms forms the critical precursor to the biosynthesis of reaction center carotenoids beta-carotene and lutein. In plants and cyanobacteria, a redox-controlled flavoenzyme carotenoid isomerase (CRTISO) catalyzes the four-step geometric isomerization of 7,9,9′,7′-tetra-cis-lycopene (prolycopene) to all-trans-lycopene. In chloroplasts, the functional loss of CRTISO has been shown to be rescued by a light-mediated isomerization pathway. In order to address the chloroplast-specificity and compare the efficiency of the photoisomerization reaction against redox-controlled enzyme catalysis, we need to track the excited state dynamics of prolycopene, and evaluate the nature of electronic states that lead to the photoisomerization. Using broadband femtosecond transient absorption spectroscopy, we observe ∼610 fs rise of the triplet state from the photoexcited S2 with a quantum yield of ∼0.19. The triplet state mediates the first C=C bond isomerization at symmetric 9 or 9′ position on the tetra-cis backbone to yield the tri-cis-lycopene with 15% quantum yield. However, direct sensitization of the photoreactive triplet state via meso-tetraphenyl porphyrin sensitizer under steady state illumination leads to all-trans-lycopene with 58% quantum efficiency. Our work implies that long-lived chlorophyll triplets activate the efficient isomerization of prolycopene in chloroplasts in absence of CRTISO activity. In presence of CRTISO, the role of redox equivalents in dark isomerization of prolycopene, and the light induced signaling mechanisms for the regulation of carotenoid biosynthesis will be discussed.