Porphyrin Skeleton Research Articles

Alkali Metal Ion Tuning of a Crown Ether‐Appended Porphyrin for Electrocatalytic CO2 Reduction

Iron‐porphyrin systems are among the best catalysts to reduce selectively CO2 to CO. Electronic modification of the porphyrin skeleton by substituents can enhance the catalytic efficiency of the complexes. In this work, we modified the iron porphyrin complex with crown‐ether auxiliaries and tested the effect of complexation with alkali metals on their electrocatalytic properties for CO2 reduction. The presence of Na+ or K+ resulted in a positive shift of the onset potential by 210 mV while not compromising the catalytic current. This effect was maintained after the immobilization at the vulcanized carbon support, and the catalyst showed the Faradaic efficiency above 90% for CO2 to CO reduction in aqueous solution of NaHCO3 or KHCO3 in a wide range of overpotentials. Hence, host‐guest chemistry at the periphery of the CO2 reduction catalysts can tune the electronic properties of the catalysts and thereby increase the catalytic efficiency.

Bimetallic synergy significantly enhances the photocatalytic performance of lanthanide porphyrin-based MOFs: Efficient photocatalytic oxidation of benzyl alcohol and benzylamine under mild conditions in air

Metal-organic frameworks as photocatalysts for the conversion of light energy into chemical energy applied to organic conversion is an efficient and sustainable strategy. Lanthanide organometallic frameworks perform poorly in photocatalytic organic reactions owing to their high electron and hole complexation rates. Inspired by the synergistic effect of biomacromolecule porphyrin as a photosensitizer with bimetallic pairs that can boost electron transport efficiency. We synthesized a series of lanthanide porphyrin mechanism MOFs (Nd PMOFs, Co–Nd PMOFs, Ni–Nd PMOFs). These PMOFs are endowed with a novel three-dimensional structure. It is noteworthy that Ni in the middle of the porphyrin ring enhances the photocatalytic performance of Ni–Nd PMOFs. The reasons can be attributed to the introduced Ni and the coordinated Nd elements, which interact synergistically with the porphyrin skeleton. This interaction results in a good photoresponse and promotes an efficient separation of photogenerated electrons and holes. The photocatalytic performance of Ni–Nd PMOFs was tested under mild conditions (12 W visible light, air) using the photocatalytic oxidation of benzyl alcohol and the oxidative coupling of benzylamine as model reactions. The conversion rate for benzyl alcohol was 90 % with a selectivity 94 %, and the conversion rate for benzylamine was 85 % with a selectivity 83 %. The photocatalytic oxidation performance of Ni–Nd PMOFs has been found to be excellent for a wide range of reactions and substrates, indicating that it is a promising photocatalyst. To some extent, the presentation of this work expands the possibilities of lanthanide metal frameworks for photocatalytic organic transformations and sheds new light on the multidirectional applications of lanthanide metal–organic frameworks.

Preparation of a Water-Soluble Glycopolymer Bearing Porphyrin Skeletons and Its Biological Properties.

A known tetraphenyl porphyrin (TPP) having an amino functional group [5-(4-aminophenyl)-10,15,20-(triphenyl)porphyrin] was converted into the corresponding monomer by means of condensation with acryloyl chloride. Simple radical polymerization of the porphyrin monomer and a glycosyl monomer in the presence of acrylamide as a regulator monomer in order to avoid steric interference gave a water-soluble glycopolymer bearing porphyrin moieties. Spectroscopic analyses suggested incorporation of porphyrin moieties in the glycopolymer. The physical properties of the water-soluble glycopolymer bearing porphyrin moieties were examined in aqueous media, and the results also indicated the incorporation of TPP moieties in the polymer. Uptake of the polymer into HeLa cells was observed, and the cytotoxicity of the polymer was confirmed by microscopic analyses. The glycopolymer bearing porphyrin moieties is promising not only for photodynamic therapy but also as an anti-cancer reagent.

Reaction mechanism of nanomedicine based on porphyrin skeleton and its application prospects.

Research on porphyrin-based photosensitizing drugs is becoming increasingly popular. They possess unique diagnostic capabilities and therapeutic effects that have gained wide recognition in oncology drug development. In recent years, the rapid growth of nanotechnology has brought great hope for nanopharmaceutical formulations. By combining porphyrins with various nanomaterials, people have improved the properties of porphyrin compounds, making drug delivery easier. Porphyrin-based nanoparticles can enhance the effect of photodynamic therapy for cancer treatment, providing opportunities for achieving complex targeting strategies and versatility with promising applications in drug carriers, tumor imaging, and treatment. This paper reviews recent porphyrin nanodrugs, including inorganic-organic hybrid nanoparticles, nanomicelles, self-assembled nanoparticles, and combination therapeutic nanodrugs, and their actions and effects on cancer cells when performing photodynamic therapy. It also discusses the drawbacks as well as the prospects for development.

Porphyrin-Conjugated Microporous Polymer Nanospheres as Electrocatalysts for Nitrobenzene Detection and Oxygen Evolution Reaction

Using pyrrole and terephthalaldehyde as raw materials, porphyrin-conjugated microporous polymer (CMP) without metal centers in the porphyrin ring was synthesized directly via the one-step method. The polymer was carbonized at different temperatures to obtain a series of carbonaceous nanospheres C-CMP-x (x is the pyrolysis temperature), of which C-CMP-900 is a multifunctional electrochemical catalyst with excellent performance. Compared to the uncarbonized polymer, C-CMP-900 is more sensitive and efficient for the reduction of nitrobenzene and exhibits a lower limit of detection. There was a significant improvement in the performance of nitrobenzene reduction over nonmetallic catalysts described in the literature. Moreover, the catalyst also shows excellent oxygen evolution reaction (OER) electrocatalytic activity, with lower overpotential than commercial RuO2. Even after long cycling tests, the catalyst maintained good activity. The catalyst, with an ultralow detection limit for nitrobenzene reduction and excellent OER activity, may be attributed to its high specific surface area and special porous carbon structure based on the porphyrin skeleton.

A biocompatible pure organic porous nanocage for enhanced photodynamic therapy.

Porphyrin-based photosensitizers have been widely utilized in photodynamic therapy (PDT), but they suffer from deteriorating fluorescence and reactive oxygen species (ROS) due to their close π-π stacking. Herein, a biocompatible pure organic porphyrin nanocage (Py-Cage) with enhanced both type I and type II ROS generation is reported for PDT. The porphyrin skeleton within the Py-Cage is spatially separated by four biphenyls to avoid the close π-π stacking within the nanocage. The Py-Cage showed a large cavity and high porosity with a Brunauer-Emmett-Teller surface area of over 300 m2 g-1, facilitating a close contact between the Py-Cage and oxygen, as well as the fast release of ROS to the surrounding microenvironment. The Py-Cage shows superb ROS generation performance over its precursors and commercial ones such as Chlorin E6 and Rose Bengal. Intriguingly, the cationic π-conjugated Py-Cage also shows promising type I ROS (superoxide and hydroxyl radicals) generation that is more promising for hypoxic tumor treatment. Both in vitro cell and in vivo animal experiments further confirm the excellent antitumor activity of the Py-Cage. As compared to conventional metal coordination approaches to improve PDT efficacy of porphyrin derivatives, the pure organic porous Py-Cage demonstrates excellent biocompatibility, which is further verified in both mice and rats. This work of an organic porous nanocage shall provide a new paradigm for the design of novel, biocompatible and effective photosensitizers for PDT.

Does the Red Shift in UV-Vis Spectra Really Provide a Sensing Option for Detection of N-Nitrosamines Using Metalloporphyrins?

N-nitrosamines are widespread cancerogenic compounds in human environment, including water, tobacco products, food, and medicinal products. Their presence in pharmaceuticals has recently led to several recalls of important medicines from the market, and strict controls and tight limits of N-nitrosamines are now required. Analytical determination of N-nitrosamines is expensive, laborious, and time-inefficient making development of simpler and faster techniques for their detection crucial. Several reports published in the previous decade have demonstrated that cobalt porphyrin-based chemosensors selectively bind N-nitrosamines, which produces a red shift of characteristic Soret band in UV-Vis spectra. In this study, a thorough re-evaluation of metalloporphyrin/N-nitrosamine adducts was performed using various characterization methods. Herein, we demonstrate that while N-nitrosamines can interact directly with cobalt-based porphyrin complexes, the red shift in UV-Vis spectra is not selectively assured and might also result from the interaction between impurities in N-nitrosamines and porphyrin skeleton or interaction of other functional groups within the N-nitrosamine structure and the metal ion within the porphyrin. We show that pyridine nitrogen is the interacting atom in tobacco-specific N-nitrosamines (TSNAs), as pyridine itself is an active ligand and not the N-nitrosamine moiety. When using Co(II) porphyrins as chemosensors, acidic and basic impurities in dialkyl N-nitrosamines (e.g., formic acid, dimethylamine) are also UV-Vis spectra red shift-producing species. Treatment of these N-nitrosamines with K2CO3 prevents the observed UV-Vis phenomena. These results imply that cobalt-based metalloporphyrins cannot be considered as selective chemosensors for UV-Vis detection of N-nitrosamine moiety-containing species. Therefore, special caution in interpretation of UV-Vis red shift for chemical sensors is suggested.

High-Surface-Area Metalloporphyrin-Based Porous Ionic Polymers by the Direct Condensation Strategy for Enhanced CO2 Capture and Catalytic Conversion into Cyclic Carbonates.

Metalloporphyrin-based porous organic polymers (POPs) that behave as advanced biomimetic nanoreactors have drawn continuous attention for heterogeneous CO2 catalysis in the past decades. Inspired by the double activation model of epoxides, the design and synthesis of metalloporphyrin-based porous ionic polymers (PIPs) are considered as one of the most promising approaches for converting CO2 to cyclic carbonates under cocatalyst- and solvent-free conditions. To overcome the obstacle of poor reaction activity of ionic monomers or highly irregular stacking architecture, in this paper, we have proposed and demonstrated a modular bottom-up approach for constructing a series of high-surface-area metalloporphyrin-based PIPs in high yields by the direct condensation strategy, thus boosting the close contact of multiple active sites and achieving the enhanced CO2 capture and catalytic conversion into cyclic carbonates with high turnover frequencies under mild conditions. These recyclable aluminum-porphyrin-based PIPs are featured with high surface areas, prominent CO2 adsorptive capacities, rigid porphyrin skeletons, and flexible ionic pendants, as well as the matched amounts and spatial positions of metal centers and ionic sites, in which is demonstrated to be one of the quite competitive catalysts. Therefore, this strategy of introducing ionic components into the porphyrin frameworks as flexible side chains rather than main chains and adjusting the reactivity ratios of comonomers by structure-oriented methods, provides feasible guidance for the multifunctionalization of metalloporphyrin-based POPs, thereby increasing the accessibility of multiple active sites and improving their synergistic catalytic behavior.

Cycloaddition of epoxides and CO2 catalyzed by C2v-symmetric cobaltoporphyrins: Structural effects and a kinetic study

a series of different substituents-modified C2v-symmetric cobaltoporphyrin complexes have been designed, synthesized and applied as efficient catalysts in conjunction with tetrabutylammonium iodide (TBAI) for the cycloaddition of epoxides and carbon dioxide. The porphyrin skeleton architectures with steric and electronic variation would deeply affect their catalytic performance. [5,15-Di(4-methoxyphenyl)porphyrin]cobalt(III) chloride (c-1) is the most effective catalyst under optimal reaction conditions. Foundational kinetic study results catalyzed by catalysts c-1, c-2, c-3 and c-4 reveal that the catalytic performance of electron-donating group-modified cobaltoporphyrin is better than it of electron-withdrawing group-modified ones, and high steric hindrance has a minor negative impact to its catalytic performance.

Two Rhodium(III) Ions Confined in a [18]Porphyrin Frame: 5,10,15,20-Tetraaryl-21,23-Dirhodaporphyrin.

Tetraaryl‐21,23‐dirhodaporphyrin and a series of related monorhodaporphyrins have been obtained by tellurium‐to‐rhodium exchange in a reaction of tetraaryl‐21,23‐ditelluraporphyrin with [RhCl(CO)2]2. These organometallic metallaporphyrins contain rhodium(III) centers embedded in rhodacyclopentadiene rings, incorporated within the porphyrin frames. The skeletons of 21,23‐dirhodaporphyrin and 21‐rhoda‐23‐telluraporphyrin are strongly deformed in‐plane from the rectangular shape typical for porphyrins, due to rhodium(III) coordination preferences, the large size of the two core atoms, and the porphyrin skeleton constrains. These two metallaporphyrins exhibit fluxional behavior, as studied by 1H NMR and DFT, involving the in‐plane motion and the switch of the rhodium center(s) between two nitrogen donors. A side product detected in the reaction mixture, 21‐oxa‐23‐rhodaporphyrin, results from tellurium‐to‐oxygen exchange, occurring in parallel to the tellurium‐to‐rhodium exchange. The reaction paths and mechanisms have been analyzed. The title 21,23‐dirhodaporphyrin contains a bridged bimetallic unit, Rh2Cl2, in the center of the macrocycle, with two rhodium(III) ions lying approximately in the plane of the porphyrinoid skeleton. The geometry of the implanted Rh2Cl2 unit is affected by macrocyclic constrains.

New Strategy for Synthesis of Bis-Pocket Metalloporphyrins Enabling Regioselective Catalytic Oxidation of Alkanes

Abstract Cytochrome P450 selectively hydroxylates the ω and ω-1 positions of fatty acids. Among synthetic oxidizing catalysts, Suslick’s bis-pocket porphyrin Mn or Fe complex achieved ω oxidation for the first time, but the yield in the preparation of the catalyst was poor due to steric hindrance, and in addition, the catalyst turnover number in the oxidation reaction was low. We have devised a new synthetic strategy involving the introduction of eight bulky aryl groups at the 2,6-positions of the meso-phenyl groups after construction of the porphyrin skeleton. This strategy greatly improved the yield in synthesis of the catalyst, and a number of derivatives of bis-pocket porphyrin and their metal complexes were prepared. These Ru complexes show unique ω-1 selectivity and provide a much higher turnover number in the oxidation of linear alkane with 2,6-dichloropyridine N-oxide, as compared to the reaction catalyzed by conventional Ru porphyrins.

Porphyrin-based Ti-MOFs conferred with single-atom Pt for enhanced photocatalytic hydrogen evolution and NO removal

A robust and efficient titanium metal–organic framework (TMF-Pt) with a single-atom Pt embedded PtII tetrakis(4-carboxyphenyl)porphyrins (PtTCPP) as linking groups and Ti-oxo molecular clusters as metal nodes was successfully fabricated for the first time, which have been confirmed by aberration-correction scanning transmission electron microscopy (HAADF-STEM) and synchrotron-radiation-based X-ray absorption fine-structure spectroscopy (XAFS), and was applied to photocatalytic hydrogen production and NO removal. It was worth noting that the TMF-Pt exhibited an extremely high hydrogen evolution activity (15456 µmol·g−1·h−1) and NO removal rate (70.3%) in comparison with most of the reported MOFs-based photocatalysts, which could be ascribed to the very high atom-utilization efficiency of single-atom Pt along with a high charge carriers separation efficiency and the Ti-oxo clusters as an alternative to the very famous TiO2 photocatalyst. The results provided us with a novel strategy that introducing single-atom Pt into the center of the porphyrin skeleton could integrate the broad light-harvesting porphyrin unite with the very high atom-utilization efficiency single-atom Pt to further improve the photocatalytic performance ultimately.

Structural, photophysical, electrochemical and spintronic study of first-row metal Tetrakis(meso-triphenylamine)-porphyrin complexes: A combined experimental and theoretical study

Different metal ions in the center of 3d-metalloporphyrins have subtle influences on their structural, photophysical, electrochemical, and spintronic properties. A new series of symmetrically meso-substituted porphyrins with six first row transition metals, namely TPA-MPs (M = 2H, Mn, Fe, Co, Ni, Cu, and Zn) have been synthesized and characterized by various spectroscopic techniques. The electrostatic potential energy surface (ESP) calculated by density functional theory (DFT) exhibits the concentrated positive electrostatic potential on the substituted triphenylamine group, while the negative electrostatic potential localized on the porphyrin ring varies depending on metal ions. All compounds were crystallographically characterized and showed a coplanar porphyrin macrocyclic ring except for TPA-MnP and TPA-ZnP, which are distorted due to their occupied axial sites by Cl− and H2O, respectively. Furthermore, the X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) confirmed the valence states of the metal ions in the TPA-MPs. Electronic spectra revealed a gradual bathochromic shift following the order of TPA-CoP < TPA-CuP < TPA-P = TPA-NiP < TPA-FeP < TPA-ZnP < TPA-MnP by appending different metal ions in the porphyrin skeleton. TPA-MnP exhibited the most significant bathochromic shift (Δλmax = 49 nm) in the Soret band compared to TPA-P. The electrochemical redox potentials of the TPA-MPs decrease with the stepwise filling of d orbitals of the central metal ions from 0.86 to 0.81 V and the completely filled 3d orbital of Zn endows TPA-ZnP with the lowest oxidation onset. Meanwhile, TPA-MnP and TPA-FeP exhibited dramatically reduced HOMO-LUMO gaps of 1.78 eV and 1.58 eV, respectively, compared to other TPA-MPs. The excellent thermal stability, panchromatic absorption in the whole visible range, and suitable energy levels of TPA-MPs indicate huge potential in the application as dyes.

A versatile method for surface functionalization and hydrophobization of gold nanoparticles

A convenient, one-step, approach for surface modification with hydrophobic thiol or its dye-derivative of hydrophilic citrate-capped Au nanoparticles (Cit–AuNPs) is demonstrated. This method depended on the solubility of both Cit–AuNP and thiol or its derivative in the reaction solvent. We investigated a variety of solvents for Cit–AuNPs with 15–75 nm sizes and a capping molecule, octadecanethiol (ODT) or a disulfide derivative of hydrophobic porphyrin (PC10S)2. As to ODT, surface immobilization of Cit–AuNPs with ODT was successful in 2-propanol, while N,N-dimethylformamide was best in the case of (PC10S)2. In both cases, surface modified AuNPs were redispersible even after storing under dried powder conditions. Two-dimensional monoparticle films of surface-modified AuNPs by the Langmuir–Blodgett method with ethylene glycol as subphase could be formed and exhibit surface-enhanced Raman scattering. Spectra from the porphyrin skeleton were certainly observed, with the maximum photoluminescence enhancement of 15-fold, around 50-nm size. As to AuNP with 17-nm diameter, mixed monolayer assemblies of (PC10S)2 and octanethiol with different concentration ratios were fabricated and spectroscopic enhancement effects due to localized surface plasmon resonance were investigated.

Triazine and Porphyrin-Based Cross-Linked Conjugated Polymers: Protonation-Assisted Dissolution and Thermoelectric Properties

As two pivotal functional segments, triazine and porphyrin can be coupled to form a highly cross-linked conjugated polymer. Although the obtained conjugated polymers are almost insoluble in most so...

Chemistry inside a Porphyrin Skeleton: Platinacyclopentadiene from Tellurophene.

Platinum(II) binds to 21,23-ditelluraporphyrin forming a side-on complex, which can be easily transformed into an aromatic metallaporphyrin, that is, 21-platina-23-telluraporphyrin, with a platinacyclopentadiene unit built in the porphyrin skeleton in place of one pyrrole ring. The central platinum(II) ion with a CCNTe square-planar coordination sphere can be oxidized to platinum(IV) by chlorine, bromine, methyl iodide or allyl chloride to yield octahedral complexes. All platinatelluraporphyrins show dynamic behavior involving the platinum ion coordination sphere fluxionality and the porphyrin skeleton deformation, both in-plane and out-of-plane, as demonstrated by 1 H NMR spectroscopy.

Stability, Aromaticity, and Photophysical Behaviors of Macrocyclic Molecules: A Theoretical Analysis.

The macrocyclic molecules with terthiophene (TTH) isomers unit exhibit intriguing properties in terms of aromaticity, stability, and absorption. In this work, we theoretically designed a series of macrocyclic molecules featured with TTH and dithienothiophene (DTT) π-conjugated building units, which are used to permute pyrrole unit in porphyrin skeleton. Density functional theory and time-dependent DFT methods are used to evaluate the performance of the designed molecules. Our simulations show that molecules 1–3 exhibit excellent optoelectronic performance. Specifically, the molecule with the DTT unit is more stable than the one with TTH unit in terms of aromaticity and aromatic stabilization energy. This is because DTT unit enhances the coplanarity of the molecular material, facilitating electronic communication. Calculation of vertical electronic excitations suggests the absorption feature of these molecules is mainly contributed by the electronic excitations of higher occupied molecular orbital (HOMO) → lowest unoccupied molecular orbital (LUMO)+1 and HOMO-1 → LUMO. Judging from the key parameters determining the overall performance, 3 stands out because of its good planarity, large HOMO–LUMO gap, and strong aromaticity among all molecules. Interestingly, molecule 1 has the current density flow distributes around the outer section of TTH unit; in contrast, molecule 3 with DTT unit has the current density flow located at the inner section of DTT, which is beneficial for stability and aromaticity. Second-order perturbation energies are calculated to rationalize this observation. We expect that these research results can provide valuable insights into the rational design of novel molecular materials for a variety of applications.

MACROCYCLE RING AND PERIPHERAL GROUP SIZES-DEPENDENT VAPOR SENSING PROPERTY OF COPPER PHTHALOCYANINE THIN FILMS

Spin-coated thin films of copper phthalocyanine (CuPc) were fabricated using different rotation speeds from 250 rpm to 1250 rpm. The structural characterization of these films was analyzed using UV-vis spectroscopy and atomic force microscopy (AFM). Gas sensing properties of these spun thin films were investigated against different volatile organic compounds such as chloroform, dichloromethane and toluene using surface plasmon resonance (SPR) technique. CuPc thin films were found to be highly sensitive to chloroform and dichloromethane vapor with fast response and recovery times. These measurements clearly indicated that the CuPc molecule is a promising material for the development of the room temperature vapor sensing applications with sensitivities between [Formula: see text] and [Formula: see text] percent response ppm[Formula: see text]. Three different functional groups of CuPc structures coded as CuPc I, II and III were investigated which differ from each other in their chemical structures in terms of their microcycle ring groups and peripheral groups, all attached to the same free base porphyrin skeleton. The number of microcycle ring groups and peripheral groups were found to be efficient on the gas sensing properties. The calculated refractive index and extinction coefficients using SPR curves were [Formula: see text] for CuPc I thin film, [Formula: see text] for CuPc II thin film and [Formula: see text] for CuPc III thin film, respectively. For different substrate rotation speeds, the thin film thicknesses vary between 2[Formula: see text]nm and 6[Formula: see text]nm for CuPc I and CuPc III thin films whereas it ranges between 4[Formula: see text]nm and 9[Formula: see text]nm for CuPc II thin film.

How does the porphyrin-like vacancy affect the spectral properties of graphene quantum dots? A theoretical study

By processing graphene quantum dot, an ideal semiconductor material with suitable band gap and higher electron mobility can be obtained. Thus, it has a broad prospect in the application of photoelectric response materials. Here, a graphene defect with porphyrin-like structure is selected to achieve the controlable light absorption. The double five-membered-ring parallel vacancy are based on self-healing properties of popular graphene defects. Aimed to separate exciton and hole more effectively and achieve higher photoelectric conversion efficiency, the occupied orbital and unoccupied orbital of the quantum dot with objected defect structure is taken as orderly dispersion to form an obvious charge separation state under the demonstration with first principles calculation. Most importantly, a real time real space charge separation is calculated by time-dependent ab-initio quantum dynamics based on numerical atomic basis sets. The result shows the specific graphene defects can form an efficient pure graphene photoelectric response medium like porphyrin skeleton, and the vacancy will induce to adjust and control the specific wavelength of the response light and charge separated state manipulably with odevity of number of peripheral carbon rings by the calculation of ultrafast process.

A promising anticancer drug: a photosensitizer based on the porphyrin skeleton.

Photodynamic therapy (PDT) is a minimally invasive combination of treatments that treat tumors and other diseases by using photosensitizers, light and oxygen to produce cytotoxic reactive oxygen species (ROS) inducing tumor cell apoptosis. Photosensitizers are the key part of PDT for clinical application and experimental research, and most of them are porphyrin compounds at present. Due to their unique affinity for tumor tissues, porphyrins are not only excellent photosensitizers, but also good carriers to transport other active drugs into tumor tissues, which can exert synergistic anticancer effects of PDT and chemotherapy. This article reviews the clinical development of porphyrin photosensitizers and the research status of porphyrin containing bioactive groups. Finally, future perspectives and the current challenges of photosensitizers based on the porphyrin skeleton are discussed.