Metal Porphyrin Complexes Research Articles

Effective Proficiency of Manganese Porphyrins as Catalysts in Chemical Transformations: A Review

: Porphyrin ligands are well-known for their promising tendency to produce metal porphyrin complexes of great significance. Out of different metal porphyrins, manganese porphyrins are one of the most valuable metal porphyrins due to effective catalytic performance and potential in many reactions like C-H isocyanation, the cycloaddition of CO2 with epoxides, epoxidation, oxygen reduction reaction, depolymerization reactions, oxidation of aromatic alcohols, selective oxidation of cycloalkenes/ alkanes, aliphatic C-H chlorination, dehydrogenation of alcohols, dye degradation, BSA nitration and others. Hence, in this review, the authors have best tried to present an effective insight overview of these aforementioned applications with the help of some recent studies for signifying the value of manganese porphyrins as a competent catalyst.

Role of metal (Fe(III), Zn(II), and Co(III)) and porphyrin in enhancing photocatalytic performance of MTCPP/TiO2 photocatalysts

Metal-porphyrin complexes modified TiO2 photocatalyst, called MTCPP@P25, shows excellent photocatalytic activity under visible light irradiation. Metal-porphyrin is successfully utilized to broaden the photo response range of TiO2 from ultraviolet (3.2 eV) to visible light (2.43 eV to 2.65 eV) resulting in significant enhancement of photocatalytic efficiency. MTCPP@P25 exhibited the higher photocatalytic activity than bare TiO2. Additionally, introduction of different metals, like Fe, Zn, and Co into porphyrin ring can effectively adjust the photocatalytic activity of MTCPP@P25 due to the increasing the electron density of porphyrin rings. The degradation order for MB followed as FeTCPP@P25≧ZnTCPP@P25 > CoTCPP@P25. This finding demonstrated that FeTCPP@P25 and ZnTCPP@P25 possess higher photo-excited electrons under visible irradiation resulting in higher photocatalytic performance. Based on the PL and EIS analysis, FeTCPP@P25 exhibited longest lifetime and fast electron transition compared to ZnTCPP@P25. The spent FeTCPP@P25 were reusable after three cycles, the efficiency remained at approximately 80 %.

Metal-ligand delocalization of iron and cobalt porphyrin complexes in aqueous solutions probed by soft X-ray absorption spectroscopy.

Metal-ligand delocalization of metal porphyrin complexes in aqueous solutions was investigated by analyzing the electronic structure of both the metal and ligand sides using soft X-ray absorption spectroscopy (XAS) at the metal L2,3-edges and nitrogen K-edge, respectively. In the N K-edge XAS spectra of the ligands, the energies of the CN π* peaks of cobalt protoporphyrin IX (CoPPIX) are higher than iron protoporphyrin IX (FePPIX). The energy difference between the two lowest peaks in the XAS spectrum of CoPPIX is also larger than that of FePPIX. Nitrogen K-edge inner-shell calculations of metalloporphyrins with different central metals indicate that the energy differences between these peaks reflect the electronic configurations and spin multiplicities of metalloporphyrins. We also investigated the hydration structure of CoPPIX in aqueous solution by analyzing the electronic structure of the ligand and revealed that CoPPIX maintains its five-coordination geometry in aqueous solution. The present study shows high performance of N K-edge XAS of ligands for studying the coordination structures of metalloporphyrins in solutions rather than the metal L2,3-edges of central metals.

An engineered thermally tolerant apo-cytochrome scaffold for metal-less incorporation of heme derivative.

Cytochrome c552 from Thermus thermophilus is one of the hot topics for creating smart biomaterials as it possesses remarkable stability, is tolerant to multiple mutations and has therefore been recently reported for a number of functionalizations upon substitution of the original prosthetic group with an artificial prosthetic group. However, all of the substitutions were driven by the coordination through the axial ligands followed by complete reconstitution with a metal-porphyrin complex. This limits the scope of the cytochrome c for incorporating a metal-less non-natural heme species that could improve the versatility of cytochrome c for a new generation of engineered cytochrome proteins for further enhancement in their functionalities such as biocatalysts. In this connection, a new variant of Cytochrome c (rC552 C14A) from Thermus thermophilus was reported, where an easy approach to remove the original prosthetic group was achieved, followed by the incorporation of a number of metal-PPIX derivatives that ultimately led to the formation of artificial c-type cytochromes through covalent bonding. The apo-cytochrome was found to be thermally tolerant and to possess a distinctive overall structure as that of the wild type, as was evident from the corresponding CD spectra, which ultimately encouraged reconstitution with a metal-less protoporphyrin derivative for better understanding the role of axial ligands in the reconstitution process. Successful reconstitution was achieved, resulting in a new type of Cytochrome b-type artificial protein without the metal in its active site, indicating the non-involvement of the axial ligand. In order to prove the non-involvement of the axial ligand, a subsequent double mutant (C14A/M69A) was constructed, replacing the methionine at 69 position with non-coordinating alanine residue. Accordingly, the apo-C14A/M69A was prepared and found to be extremely stable as the earlier mutants and the WT showed no signs of denaturation, even at the elevated temperature of 98°C. Subsequently, heme b was successfully incorporated into the apo-C14A/M69A, which demonstrated itself as a highly thermally tolerant protein scaffold for incorporating a metal-less artificial prosthetic group in the absence of the axial ligand. Further improvement in the reconstitution process is achieved by replacing the methionine at 69 position with phenyl alanine (C14A/M69F mutant), resulting in further stabilization of heme species, possibly through non-covalent π-interactions, as corroborated by molecular docking.

Porphyrin complexes of transition metals with a large dipole moment as active components of new film electret materials

Porphyrin complexes of transition metals with a large dipole moment as active components of new film electret materials

Porphyrins: ‘‘Smart Catalysts’’ for the Synthesis of High-Added Value Compounds

The chemical industry needs to develop clean, efficient and selective procedures to synthesize high added-value fine chemicals and catalytic processes provide powerful tools to reach this goal. The key point to perform sustainable transformations is the choice of catalytic systems that show selectivity, activity and stability, resulting in high TOF (turnover frequency) and TON (turnover number), not to mention an efficient catalyst must be easily recovered and recycled. Based on these concepts, the employment of metal porphyrin complexes in catalysis is constantly growing due to the enormous potential of this class of molecules. Metal porphyrins are robust and their chemo-physical properties can easily be fine-tuned by varying their molecular structure to allow the use of these catalysts to selectively promote a large number of organic transformations.We have studied in depth the employment of metal porphyrin complexes to create new C-N and C-C bonds by using organic azides[1] and diazo compounds[2] and more recently we have focused our interest also on the synthesis of high-added value fine chemicals by using waste, such as CO2, as starting material by applying 100% atom economic procedures.[3] We will present different synthetic protocols which will also be discussed from a mechanistic point of view based on spectroscopic and theoretical studies and the identification of active intermediates. It is important to point out that mechanistic speculations are fundamental to optimize the catalytic performance of porphyrin complexes and spread out their applications in other fields of homogeneous catalysis References [1] Damiano, C.; Sonzini, P.; Caselli, A.; Gallo, E. Adv. Organom. Chem. 2021, 76, 145 [2] Damiano, C.; Sonzini, P.; Gallo, E. Chem. Soc. Rev. 2020 , 49, 4867[3] a) Sonzini, P.; Damiano, C.; Intrieri, D.; Manca, G.; Gallo, E. Adv. Synth. Catal. 2020, 362, 2961. b) Damiano, C.; Sonzini, P.; Manca, G.; Gallo, E. Eur. J. Org. Chem. 2021, 2807. c) M. Cavalleri, C. Damiano, G. Manca, E. Gallo, Chem. Eur. J. 2022, e202202729. d) P. Sonzini, N. Berthet, C. Damiano, V. Dufaud, E. Gallo J. Catalysis 2022, 414, 143–154

An Insight on the Potential of Manganese Porphyrins in Cancer Treatment

Abstract: Porphyrin ligands are recognized for their exclusive tendency to form metal porphyrin complexes of pronounced value. Such metal porphyrin complexes display their inimitable roles as catalysts in various fields viz. conversion reactions, oxidation reactions, organic synthesis, pharmaceutical areas, biological and environmental fields, and many more. Out of different metal porphyrins; manganese porphyrins are one of the appreciated metal porphyrins due to their prodigious catalytic performance and potential in cancer treatment. In this perspective, the proficient participation of manganese porphyrins in the treatment of cancer along with operative discussions on molecular pathways have been briefly but effectively assessed based on the recent scientific literatures available.

Photophysical characterization of tetrahydroxyphenyl porphyrin Zn(II) and V(IV) complexes: experimental and DFT study.

Photodynamic therapy (PDT) is a promising technique for the treatment of various diseases. In this sense, the singlet oxygen quantum yield (Φ∆) is a physical-chemical property that allows to stablish the applicability of a potential photosensitizers (PS) as a drug for PDT. In the herein report, the Φ∆ of three photosensitizers was determined: metal-free tetrahydroxyphenyl porphyrin (THPP), THPP-Zn and the THPP-V metal complexes. Their biological application was also evaluated. Therefore, the in vitro study was carried out to assess their biological activity against Escherichia coli. The metal-porphyrin complexes exhibited highest activities against the bacterial strain Escherichia coli. at the highest concentration (175μg/mL) and show better activity than the free base ligand (salts and blank solution). Results indicated a relation between Φ∆ and the inhibitory activity against Escherichia coli, thus, whereas higher is the Φ∆, higher is the inhibitory activity. The values of the Φ∆ and the inhibitory activity follows the tendency THPP-Zn > THPP > THPP-V. Furthermore, quantum chemical calculations allowed to gain deep insight into the electronic and optical properties of THPP-Zn macrocycle, which let to verify the most probable energy transfer pathway involved in the singlet oxygen generation.

Hydrogen-Bonding Secondary Coordination Sphere Effect on CO2 Reduction

Great efforts of the scientific community are focused on the development of catalysts for the reduction of carbon dioxide (CO2) to useful molecules such as carbon monoxide, formic acid, methanol, ethanol, methane, ethylene, or acetate. Various metal porphyrin complexes were synthesized and studied to develop highly active and selective catalysts. While the substituents on the porphyrin core (the primary coordination sphere) determine the reactivity of the metal, the introduction of the secondary coordination is important for the binding and activation of CO2. In this review, selected examples of iron porphyrin catalysts with a secondary coordination sphere capable of stabilizing intermediates of the CO2 reduction process by hydrogen bonding are presented.

Effect of Sub- and Supercritical Water on the Transformation of High-Molecular-Mass Components of High-Carbon Rocks from Unconventional Formations (A Review)

State-of-the-art in the field of recovering high-molecular-mass hydrocarbon components of bituminous and shale rocks by intrastratum transformation into readily recoverable forms using sub- and supercritical water is analyzed. The phase composition of water and its properties in the critical state and the transformations of a number of substances in subcritical (SBW) and supercritical (SCW) water are discussed. The substances under consideration include model polycyclic and heteroatomic compounds containing nitrogen, sulfur, and oxygen, metal porphyrin complexes, asphaltenes, oil sands, and heavy oils and organic matter (OM) of kerogen-containing shale rocks. The preventing effect of hydrogen donors and catalysts for hydrogenation and oxidative cracking on the coking in the course of transformation of heavy hydrocarbons in SCW is compared. The catalytic effect of the mineral matrix of rocks in the course of generation of oil fractions from them is analyzed in detail. The published data concerning the possibility of using SBW and SCW for the transformation of high-molecular-mass components of high-carbon dense rocks from unconventional formations demonstrate high potential of hydrothermal and supercritical fluid technologies

Metal Porphyrin Complex Combined with Polymerization and Isomerization Cyclic Amplification for a Sensitive Photoelectrochemical Assay.

5,10,15,20-Tetrakis(4-aminophenyl)-21H,23H-porphine (TPAPP) possesses good light-harvesting ability and photoelectrochemical (PEC) cathode response signal; however, the disadvantages of easy stacking and weak hydrophilicity limit its application as a signal probe in PEC biosensors. Based on these, we prepared a Fe3+ and Cu2+ co-coordinating photoactive material (TPAPP-Fe/Cu) with horseradish peroxidase (HRP)-like activity. The metal ions in the porphyrin center not only enabled the directional flow of photogenerated electrons between electron-rich porphyrin and positive metal ions within inner-/intermolecular layers but also accelerated electron transfer through a synergistic redox reaction of Fe(III)/Fe(II) and Cu(II)/Cu(I) as well as rapid generation of superoxide anion radicals (O2-•) by mimicking catalytically produced and dissolved oxygen, thereby providing the desired cathode photoactive material with extremely high photoelectric conversion efficiency. Accordingly, by combining with toehold-mediated strand displacement (TSD)-induced single cycle and polymerization and isomerization cyclic amplification (PICA), an ultrasensitive PEC biosensor was constructed for the detection of colon cancer-related miRNA-182-5p. The ultratrace target could be converted to abundant output DNA by TSD possessing the desirable amplifying ability to trigger PICA for forming long ssDNA with repetitive sequences, thus decorating substantial TPAPP-Fe/Cu-labeled DNA signal probes for producing high PEC photocurrent. Meanwhile, the Mn(III) meso-tetraphenylporphine chloride (MnPP) was embedded in dsDNA to further exhibit a sensitization effect toward TPAPP-Fe/Cu and an acceleration effect analogous to that of metal ions in the porphyrin center above. As a result, the proposed biosensor displayed a detection limit as low as 0.2 fM, facilitating the development of high-performance biosensors and showing great potential in early clinical diagnosis.

Development of Wireless Power-Transmission-Based Photodynamic Therapy for the Induction of Cell Death in Cancer Cells by Cyclometalated Iridium(III) Complexes.

Photodynamic therapy (PDT), a noninvasive method for cancer therapy, involves the generation of reactive oxygen species (ROS) by the photochemical excitation of photosensitizers (PSs) to induce cell death in cancer cells. A variety of PS including porphyrin derivatives and metal complexes such as iridium (Ir) complexes have been reported. In clinical trials, red-near infrared (NIR) light (650-900 nm) is preferred for the excitation of PSs due to its deeper penetration into tissues compared with visible light (400-500 nm). To overcome this limitation, we established a PDT system that uses cyclometalated iridium(III) (Ir(III)) complexes that are excited with blue light in the wireless power transmission (WPT) system. To achieve this, we developed a light-emitting diode (LED) light device equipped with a receiver coil that receives electricity from the transmitter coil through magnetic resonance coupling. The LEDs in the receiving device use blue light (470 nm) to irradiate a given Ir(III) complex and excite triplet oxygen (3O2) to singlet oxygen (1O2) which induces cell death in HeLa S3 cells (human cervical carcinoma cells). The results obtained in this study suggest that WPT-based PDT represents a potentially new method for the treatment of tumors by a non-battery LED, which are otherwise difficult to treat by previous PDT systems.

Recent advances in the rational designing of metalloporphyrinoid-based CO2 reduction catalysts: From molecular structural tuning to the application in catalysis

Electro and photochemical [Formula: see text] reduction ([Formula: see text]R) has emerged as a contemporary research field for tackling the fossil fuel problems and construction of a modern chemical industry. For efficient [Formula: see text]R, a catalyst is needed, and Earth-abundant Fe, Co, and Ni-based metalloporphyrinoids have appeared as promising molecular catalysts for [Formula: see text]R. Several metal complexes of porphyrins, phthalocyanines, corroles, and chlorins-type porphyrinoids have been designed and tested for this purpose. The unique advantages in the judicious tuning of the porphyrinoid structures and their susceptibility towards different functionalization reactions allow an impressive scope to explore and establish a direct structure-activity relationship of metalloporphyrinoids towards [Formula: see text]R. There have been rapid advances in this field in the last few years. For the homogeneous [Formula: see text]R, the electronic and steric aspects of the porphyrinoids are fine-controlled by installing favorable functional groups at the periphery of the porphyrinoids. On the other hand, in heterogenous [Formula: see text]R, the design principle is guided by integrating metalloporphyrinoids in composite material after mixing with carbon supports, semiconductors, or adopting reticular chemistry. All the advancements further result in the testing of excellent metalloporphyrinoids in industrially feasible [Formula: see text] electrolyzers or photoelectrochemical devices. This review focuses on the recent advances in designing principles of metalloporphyrnoids catalysts in homogeneous, heterogeneous, and [Formula: see text]R reactors.

Традиционные и новые подходы к созданию биомедицинских материалов на основе полигидроксиалканоатов c антимикробной активностью

This thematic review considers the principles of creating biomedical materials based on biopolymers and their compositions for various medical needs. The direction of creating materials with antimicrobial activity is especially emphasized using the example of polyhydroxyalkanoates. These biopolymers and composites based on them occupy leading positions in the production of medical devices. Polyhydroxyalkanoates as a class of biopolymers, as well as polyhydroxybutyrate, the most suitable representative of this class for biomedical products, were analyzed from the point of view of increasing resistance to microorganisms. Progress in this direction has been reported in recent years. The influence of the supramolecular and molecular structure of materials on the ability to biodegrade in the environment and in a living organism is considered in sufficient detail. The advantage of mixtures of biopolymers for achieving high degradation rates compared to the original polymers was noted. Promising antiseptics based on porphyrin metal complexes in combination with biopolymer nonwoven fibrous matrices have been demonstrated. Features of preclinical tests of antiseptic materials are considered. Based on this review of research papers, it can be concluded that the structural organization of a polymeric material or composite determines the level of intermolecular interactions during the formation of the material and thereby programs the complex of functional properties and the degradation mechanism under the influence of aggressive external factors.

Porphyrin(2.1.2.1) rhenium(I) complexes: Synthesis, structures, properties, and dipyrrin act as bipyridyl-like ligand

Two new rhenium(I) porphyriniod complexes (H2PY: 3,3-rhenium(I) tricarbonyl chloride-(31 E,32 Z,71 E,72 Z)-4,8-bis(perfluorophenyl)-11 H,32 H,72 H-51 λ2 ,71 λ4 -1,5(2,5),3,7(5,2)-tetrapyrrola-2,6(1,2)-dibenzenacyclooctaphane, and H2PZ: 3,3-rhenium(I) tricarbonyl acetate-(31 E,32 Z,71 E,72 Z)-4,8-bis(perfluorophenyl)-11 H,32 H,72 H-51 λ2 ,71 λ4 -1,5(2,5),3,7(5,2)-tetrapyrrola-2,6(1,2)-dibenzenacyclooctaphane) containing two different Re(I)−N π-bonding networks were prepared from the saddle-shaped porphyrin(2.1.2.1) bearing pentafluorophenyl substituents at the two meso-positions (H2Por: 31 E,32 Z,71 E,72 Z)-4,8-bis(perfluorophenyl)-11 H,32 H,51 H,72 H-1,5(2,5),3,7(5,2)-tetrapyrrola-2,6(1,2)-dibenzenacyclooctaphane). Despite the tetrapyrrolic nature of the porphyrin(2.1.2.1) scaffold, this is the first case of a pyrrole-based macrocycle which acts as a bipyridyl-like complexing ligand in the formation of an octahedral Re(I) complex. X-ray analysis and 1H NMR studies show that both Re(I) complexes (H2PY and H2PZ) consist of one octahedral Re(I) ion π-bonded to a dipyrrin unit and one protonated dipyrrin moiety linked together through o-phenylene bridges. This bonding behavior is compared to related metal complexes of porphyrin(2.1.2.1) macrocycles as well as other Re(I) porphyrins and demonstrates that the distorted conformation and, by virtue, the electronics of H2Por serve as a novel platform for examining structure property relationships which differ than those of other related planar porphyrin macrocycles.

Ultra-long cycle life organic-sodium batteries enabled by thiophene-based porphyrin in-situ electropolymerization

Organic-sodium batteries have attracted extensive attention due to the abundance of sodium resource and the molecular tunability of organic materials. However, the dissolution of organic materials in electrolytes and low electronic conductivity limit its development. Here, a porphyrin complex of [5,15-di(thiophen-2-yl) porphinato] M(II) (MTP, M = Cu, Ni) is proposed as highly stable cathode material for organic-sodium batteries. Benefiting from the multiple electron transfer of metal porphyrin complex and in-situ polymerization of thiophene groups of porphyrin complex in initial cycles, the CuTP cathode delivers a reversible capacity of 203 mAh/g at 100 mA g−1 and long-term cycling stability up to 11,000 cycles at a high current density of 5 A/g owing to the enhanced conjugated structure induced by in situ polymerization process. A specific energy density of 508 Wh kg−1 and a power density of 18 KW kg−1 are achieved for metal porphyrin-based cathode. The charge storage sites and in-situ polymerization mechanism of MTP cathode are systematically evaluated by both experimental and simulated studies. This study would provide a new strategy to address the dissolution issue of organic cathode and improve cycling stability of the organic-sodium batteries.

Efficient Reductive Defluorination of Branched PFOS by Metal-Porphyrin Complexes.

Vitamin B12 (VB12) has been reported to degrade PFOS in the presence of TiIII citrate at 70 °C. Porphyrin-based catalysts have emerged as VB12 analogues and have been successfully used in various fields of research due to their interesting structural and electronic properties. However, there is inadequate information on the use of these porphyrin-based metal complexes in the defluorination of PFOS. We have therefore explored a series of porphyrin-based metal complexes for the degradation of PFOS. CoII-5,10,15,20-tetraphenyl-21H,23H-porphyrin (CoII-TPP), CoII-5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphyrin (CoII-M-TPP), and CoIII-M-TPP exhibited efficient reductive defluorination of the branched PFOS. Within 5-8 h, these compounds achieved the same level of PFOS defluorination as VB12 achieved in 7-10 days. For branched isomers, the specific removal rate of the CoII-TPP-TiIII citrate system is 64-105 times higher than that for VB12-TiIII citrate. Moreover, the CoII-TPP-TiIII citrate system displayed efficient (51%) defluorination for the branched PFOS (br-PFOS) in 1 day even at room temperature (25 °C). The effects of the iron and cobalt metal centers, reaction pH, and several reductants (NaBH4, nanosized zerovalent zinc (nZn0), and TiIII citrate) were systematically investigated. Based on the analysis of the products and previously published reports, a new possible defluorination pathway of branched PFOS is also proposed.

Chemical, Thermal, and Radiation Resistance of an Iron Porphyrin: A Model Study of Biosignature Stability.

Metal complexes of porphyrins and porphyrin-type compounds are ubiquitous in all three domains of life, with hemes and chlorophylls being the best-known examples. Their diagenetic transformation products are found as geoporphyrins, in which the characteristic porphyrin core structure is retained and which can be up to 1.1 billion years old. Because of this, and their relative ease of detection, metalloporphyrins appear attractive as chemical biosignatures in the search for extraterrestrial life. In this study, we investigated the stability of solid chlorido(2,3,7,8,12,13,17,18-octaethylporphyrinato)iron(III) [FeCl(oep)], which served as a model for heme-like molecules and iron geoporphyrins. [FeCl(oep)] was exposed to a variety of astrobiologically relevant extreme conditions, namely: aqueous acids and bases, oxidants, heat, and radiation. Key results are: (1) the [Fe(oep)]+ core is stable over the pH range 0.0–13.5 even at 80°C; (2) the oxidizing power follows the order ClO− > H2O2 > ClO3− > HNO3 > ClO4−; (3) in an inert atmosphere, the iron porphyrin is thermally stable to near 250°C; (4) at high temperatures, carbon dioxide gas is not inert but acts as an oxidant, forming carbon monoxide; (5) a decomposition layer is formed on ultraviolet irradiation and protects the [FeCl(oep)] underneath; (6) an NaCl/NaHCO3 salt mixture has a protective effect against X-rays; and (7) no such effect is observed when [FeCl(oep)] is exposed to iron ion particle radiation. The relevance to potential iron porphyrin biosignatures on Mars, Europa, and Enceladus is discussed.

Mechanistic Studies on the Epoxidation of Alkenes by Macrocyclic Manganese Porphyrin Catalysts.

Macrocyclic metal porphyrin complexes can act as shape‐selective catalysts mimicking the action of enzymes. To achieve enzyme‐like reactivity, a mechanistic understanding of the reaction at the molecular level is needed. We report a mechanistic study of alkene epoxidation by the oxidant iodosylbenzene, mediated by an achiral and a chiral manganese(V)oxo porphyrin cage complex. Both complexes convert a great variety of alkenes into epoxides in yields varying between 20–88 %. We monitored the process of the formation of the manganese(V)oxo complexes by oxygen transfer from iodosylbenzene to manganese(III) complexes and their reactivity by ion mobility mass spectrometry. The results show that in the case of the achiral cage complex the initial iodosylbenzene adduct is formed on the inside of the cage and in the case of the chiral one on the outside of the cage. Its decomposition leads to a manganese complex with the oxo ligand on either the inside or outside of the cage. These experimental results are confirmed by DFT calculations. The oxo ligand on the outside of the cage reacts faster with a substrate molecule than the oxo ligand on the inside. The results indicate how the catalytic activity of the macrocyclic porphyrin complex can be tuned and explain why the chiral porphyrin complex does not catalyze the enantioselective epoxidation of alkenes.

Electrocatalytic CO2 Reduction: from Discrete Molecular Catalysts to Their Integrated Catalytic Materials.

Molecular catalysts (metal complexes), with molecularly defined uniform active sites and atomically precise structural tailorability allowing for regulating catalytic performance through metal- and ligand-centered engineering and elucidating reaction mechanisms via routine photoelectrochemical characterizations, have been increasingly explored for electrocatalytic CO2 reduction (ECR). However, their poor stability and low catalytic current density are undesirable for practical applications. Heterogenizing discrete molecular catalysts can potentially surmount these issues, and the resulting integrated catalysts largely share catalytical properties with their discrete molecular counterparts, which bridge the gap between heterogeneous and homogeneous catalysis and combine their advantages. This minireview surveys advances in design and regulation of molecular catalysts such as porphyrin, phthalocyanine, and bipyridine-based metal complexes and their integrated catalytic materials for selective ECR.