Porphyrin Macrocycle Research Articles

Surface Engineering of 2D Metal-Porphyrin Metal-Organic Frameworks Z-Scheme Heterostructure for Boosting and Stable Photocatalytic Hydrogen Evolution.

How to improve the stability and activity of metal-organic frameworks is an attractive but challenging task in energy conversion and pollutant degradation of metal-organic framework materials. In this paper, a facile method is developed by fabricating titanium dioxide nanoparticles (TiO2 NPs) layer on 2D copper tetracarboxylphenyl-metalloporphyrin metal-organic frameworks with zinc ions as the linkers (ZnTCuMT-X, "Zn" represented zinc ions as the linkers, the first "T" represented tetracarboxylphenyl-metalloporphyrin (TCPP), "Cu" represented the Cu2+ coordinated into the porphyrin macrocycle, "M" represented metal-organic frameworks, the second "T" represented TiO2 NPs layer, and "X" represented the added volume of n-tetrabutyl titanate (X = 100, 200, 300 or 400)). It is found that the optimized ZnTCuMT-200 showed greatly and stably enhanced H2 generation, which is ≈28.2 times and 47.0 times as high as those of the original ZnTCuM and TiO2, respectively. Combined with the results of free radical capture, X-ray photoelectron spectra (XPS), electron spin resonance (ESR), and theoretical calculation, a direct Z-scheme electron transfer mechanism is achieved to fully explain the enhanced photocatalytic performance. It demonstrates that facilely designing Z-scheme heterostructures based on porphyrin MOFs modified with an inorganic semiconductor layer can be an advantageous strategy for enhancing the stability and activity of photocatalytic hydrogen evolution.

Detecting the saddling deformations in nickel meso-phenyl substituted porphyrins using low-frequency Raman characteristic peaks.

The out-of-plane (OOP) deformations of metalloporphyrins macrocycle are closely related to their biological functions, and Raman spectroscopy is a powerful tool for investigating OOP deformations. However, due to the interplay of electronic structure, substituents, porphyrin macrocycle in-plane (IP) and OOP deformations, it is challenging to measure the OOP deformations directly, or, establish a confirmative correlation between the frequency shifts of characteristic peaks and specific OOP deformation changes. In this work, we first selected the model porphyrin Ni-P and employed DFT calculations to explore the relationship between the ruffling and saddling deformation changes and their corresponding Raman spectral differences. Subsequently, we focused on nickel meso-tetraphenyl porphyrin (NiTPP), nickel meso-tetrachlorophenylporphyrin (NiTClP), and nickel meso-tetramethoxyphenyl porphyrin (NiTMeOP), which are structurally similar in nature, and investigated the relationship between their OOP deformations and Raman spectra bands based on both experiments and DFT calculations. The results indicate that the ruffling deformation magnitudes of the three nickel porphyrins are almost identical, while the saddling deformation magnitudes differ remarkably. The frequency change of the characteristic peak γ18 in relation to saddling deformation of the three porphyrins is 7.7cm-1/Å, which is close to that of the model porphyrin Ni-P 10.6cm-1/Å. Therefore, the characteristic peak γ18 can be used as a "reporter" for the change in saddling deformation. As such, this work demonstrates how to utilize the frequency shifts of low-frequency Raman characteristic peaks to identify the OOP deformation changes of the porphyrin macrocycle caused by variations in the external environment, thereby providing a theoretically assisted tool for revealing the reasons for their biological function variations.

Host molecules inside metal-organic frameworks: host@MOF and guest@host@MOF (Matrjoschka) materials.

The controllable encapsulation of host molecules (such as porphyrin, phthalocyanine, crown ether, calixarene or cucurbituril organic macrocycles, cages, metal-organic polyhedrons and enzymes) into the pores of metal-organic frameworks (MOFs) to form host-in-host (host@MOF) materials has attracted increasing research interest in various fields. These host@MOF materials combine the merits of MOFs as a host matrix and functional host molecules to exhibit synergistic functionalities for the formation of guest@host@MOF materials in sorption and separation, ion capture, catalysis, proton/ion conduction and biosensors. (This guest@host@MOF construction is reminiscent of Russian (Matrjoschka) dolls which are nested dolls of decreasing size placed one inside another.) In this tutorial review, the advantages of MOFs as a host matrix are presented; the encapsulation approaches and general important considerations for the preparation of host@MOF materials are introduced. The state-of-the-art examples of these materials based on different host molecules are shown, and representative applications and general characterization of these materials are discussed. This review will guide researchers attempting to design functional host@MOF and guest@host@MOF materials for various applications.

Effect of Protonation-Induced Distortions on the Spectral Properties and Electronic Structure of Octaphenylporphyrins through UV-Vis and VT-NMR Spectral, Electrochemical and Ab Initio Studies.

The extent of conformational change of the porphyrin macrocycle during the course of protonation was observed, both experimentally and theoretically. For synthesised β-substituted octaphenylporphyrin (OPP) ring systems, these macrocyclic distortions have been investigated by spectrophotometric titrations, electrochemical, variable temperature nuclear magnetic resonance (VT-NMR) and computational analysis. Protonation-induced non-planarity in a macrocyclic system is experimentally observed in a single step during spectrophotometric titration. The addition of trifluoroacetic acid (TFA) eventually formed dicationic form while tetrabutylammonium hydroxide (TBAOH) was employed for deprotonation study for titration in toluene. The progress of the protonation i. e. the addition of proton to the core of the ring was monitored by UV/Vis spectroscopy, which was also determined logβ value. The spectral changes demonstrate the conformational flexibility of these macrocyclic systems correlating with the photophysical properties. The degree of nonplanarity exhibited incremental progress in response to protonation, with a specific order observed: H2TPP<H2OPP<H2OPPBr4<H2OPPBr3NO2. VT-NMR experiments were carried out in dichloromethane over a temperature range of 193-298 K, providing dynamic behaviour of these systems. Furthermore, our study delved into the structural aspects, frontier molecular orbitals and ground state energies of H4P(CF3COO)2 and absorption bands computed at the TD-B3LYP/6-31G level of theory, anticipated a red shift in both the Soret and Q0,0 bands. This theoretical prediction aligns seamlessly with the experimental findings from spectrophotometric titrations, providing validation to our computation insights. In summary, this comprehensive study elucidates the extent of conformational changes occurring in β-substituted octaphenylporphyrin (OPP) ring systems upon protonation and deprotonation.

Trends in Methanol-Solvated Actinide Ions and Actinide Expanded Porphyrin Complexes.

Trivalent actinide expanded porphyrin complexes have been of synthetic interest since the isolation of the series of trivalent lanthanide texaphyrin complexes in 1992, however, synthesis of these actinide-based complexes has not yet been achieved. In this work, a computational study with relativistic density functional theory was performed to determine how trivalent actinide ions (Ac3+ through Lr3+) interact with Schiff base expanded porphyrin macrocycles in a methanol solvent as an alternate pathway to stabilization. A thorough analysis of structural parameters, electronic structure, stability of microsolvation environments, and relative binding energies provided insight into the most stable structures. Trends in bonding and structure for the full actinide series are reported for methanol solvated ions, which reports actinide contraction along the series for early and mid actinides. Texaphyrin incorporates the actinide ions in a planar fashion, whereas for alaskphyrin a bent structure is more favorable; this bend results in stronger interaction energies than those calculated for the texaphyrin complexes. We also show that the redox-active expanded porphyrin ligands are able to accommodate a variety of actinides through charge transfer stabilization. Based on relative binding energy and energy decomposition analysis, it was found that texaphyrin and alaskaphyrin both exhibit a strong preference for binding to Th.

Octaethyl vs Tetrabenzo Functionalized Ru Porphyrins on Ag(111): Molecular Conformation, Self-Assembly and Electronic Structure.

Metalloporphyrins on interfaces offer a rich playground for functional materials and hence have been subjected to intense scrutiny over the past decades. As the same porphyrin macrocycle on the same surface may exhibit vastly different physicochemical properties depending on the metal center and its substituents, it is vital to have a thorough structural and chemical characterization of such systems. Here, we explore the distinctions arising from coverage and macrocycle substituents on the closely related ruthenium octaethyl porphyrin and ruthenium tetrabenzo porphyrin on Ag(111). Our investigation employs a multitechnique approach in ultrahigh vacuum, combining scanning tunneling microscopy, low-energy electron diffraction, photoelectron spectroscopy, normal incidence X-ray standing wave, and near-edge X-ray absorption fine structure, supported by density functional theory. This methodology allows for a thorough examination of the nuanced differences in the self-assembly, substrate modification, molecular conformation and adsorption height.

Surface Engineering of 2D Metal-Porphyrin Metal-Organic Frameworks Z-Scheme Heterostructure for Boosting and Stable Photocatalytic Hydrogen Evolution.

How to improve the stability and activity of metal-organic frameworks is an attractive but challenging task in energy conversion and pollutant degradation of metal-organic frameworks materials. In this paper, we developed a facile method by fabricating TiO2 nanoparticles (NPs) layer on 2D copper tetracarboxylphenyl-metalloporphyrin metal-organic frameworks (MOFs) with Zn2+ as the linkers (ZnTCuMT-X, "Zn" represented Zn2+ as the linkers, the first "T" represented tetracarboxylphenyl-metalloporphyrin (TCPP), "Cu" represented the Cu2+ coordinated into the porphyrin macrocycle, "M" represented MOFs, the second "T" represented TiO2 NPs layer, and "X" represented the added volume of n-tetrabutyl titanate (X = 100, 200, 300 or 400)). It was found that the optimized ZnTCuMT-200 showed greatly and stably enhanced H2 generation, which was about 28.2 times and 47.0 times as high as those of the original metalloporphyrin MOFs and TiO2, respectively. Combined with the results of free radical capture, X-ray photoelectron spectra, electron spin resonance and theoretical calculation, a direct Z-scheme electron transfer mechanism was achieved to fully explain the enhanced photocatalytic performance. It demonstrates that facilely designing Z-scheme heterostructures based on porphyrin MOFs modified with inorganic semiconductor layer could be an advantageous strategy for enhancing the stability and activity of photocatalytic hydrogen evolution.

Ruthenium Nitrosyl Porphyrins Coordinated with Aryloxides Containing Internal Hydrogen Bonds

The synthesis, characterization, and redox behavior of aryloxide complexes containing an increasing number of internal hydrogen bonds (OEP)Ru(NO)(OArxH) (OEP = octaethylporphyrinato dianion; x = 0, 1, 2) are reported. These nitrosyl aryloxide compounds were characterized by X‐ray crystallography, IR and 1H NMR spectroscopy. The IR spectra displayed uNO frequencies in the 1823–1843 cm‐1 range with compounds possessing more internal hydrogen bonds demonstrating higher uNO frequencies due to diminished π‐backdonation to the Ru‐NO fragment. Comparison of the distinct uNH and δN‐H signals in the IR and 1H NMR spectra of the free and complexed OAr1H/OAr2H ligands support the notion of additional electron density being removed via intramolecular hydrogen bonding. Results of DFT calculations on the (porphine)Ru(NO)(OArxH) models (porphine = unsubstituted porphyrin) reveal that the HOMOs of these complexes have significant axial ligand contributions, whereas the HOMOs of the five‐coordinate [(porphine)RuNO)]+ cation resides mostly on the equatorial porphyrin macrocycle. The electrochemical results of these (OEP)Ru(NO)(OArxH) complexes in CH2Cl2 reveal first oxidations that occur at increasingly positive potentials when more internal hydrogen bonds are present. Based on the DFT and preliminary IR spectroelectrochemical results, we propose that the electrooxidations result in eventual dissociation of the axial aryloxide ligands.

Antenna effect on Zn(II) porphyrin-based molecular ensembles for the detection of 2,4-dinitrophenol through energy and electron transfer process.

Twomodular systems were synthesizedcomposed of triphenylamine (ZnTPAP) and pyrene (ZnPyP) covalently linked at meso position of the Zn(II) porphyrins. Both compounds behaved as energy transfer antenna and orthogonal units to enhance the electron donating ability of Zn(II) porphyrins. Detailed photophysical and aggregation studies reveal that an appreciable electronic interaction exists between peripheral units to the porphyrin π-system so that they behave like strong donor materials. The electrochemical and computational studies demonstrate delocalization of the frontier highest occupied molecular orbital (-5.08eV) over the triphenylamine entities (ZnTPAP) in addition to the porphyrin macrocycle. Fluorescence experiments withZnTPAP and ZnPyP in the presence ofdifferent nitro analytes at various concentrations show turn-off fluorescence behaviour and exhibit superior selectivity towards 2,4-dinitrophenol (DNP) with limit of detection (LOD) of ~ 2.3 and 9.2ppm for ZnTPAP and ZnPyP. Photoinduced electron transfer process is involvedin the static and dynamicfluorescence quenching process. A Stern-Volmer quenching association constant (Ksv) determination revealed that ZnTPAP is more sensitive than the ZnPyP. This is attributed to thestrong donating behaviour of TPA unitscaused by intermolecular interaction through metal center and strong π-π interactions with nitro analytes. The present study provides new insights into the ability to tune the affinity and selectivity of porphyrin-based sensors utilising electronic factors associated with the central Zn(II) ion. Furthermore, a smartphone-interfaced portable fluorimetric method by recognising colour variations in RGB and the luminance (L) values facilitate sensitive and real-time sensing at low concentration levels will have a significant impact on development of a new class of chemosensors.

Meso-5,15-Bis[3-(iso-propyl-idenegalacto-pyran-oxy)phen-yl]-10,20-bis-(4-methyl-phen-yl)porphyrin.

The crystal structure of a glycosyl-ated porphyrin (P_Gal2) system, C70H70N4O12, where two iso-propyl-idene protected galactose moieties are attached to the meso position of a substituted tetra-aryl porphyrin is reported. This structure reveals that the parent porphyrin is planar, with the galactose moieties positioned above and below the porphyrin macrocycle. This orientation likely prevents porphyrin-porphyrin H-type aggregation, potentially enhancing its efficiency as a photosensitizer in photodynamic therapy. Notable non-bonding C-H⋯O and C-H⋯π inter-actions among adjacent P_Gal2 systems are observed in this crystal network. Additionally, the tolyl groups of each porphyrin can engage in π-π inter-actions with the delocalized π-systems of neighboring porphyrins.

Triflate Salts as Alternative Non-Chlorinated Oxidants for the Oxidative Chemical Vapor Deposition and Electronic Engineering of Conjugated Polymers.

Oxidative chemical vapor deposition (oCVD) stands as an attractive approach for the synthesis, engineering, and integration of conjugated polymers for advanced electronic and optoelectronic applications. In oCVD, the oxidant significantly influences the conformational and optoelectronic properties of the resulting conjugated polymer thin films. In this work, triflate salts of iron(III) and copper(II) (Fe(OTf)3 and Cu(OTf)2, respectively) are investigated for the first time as suitable alternative oxidants to the widely used iron(III) chloride (FeCl3) for the oCVD of conjugated polymers. Structural and compositional characterizations of the resulting thin films evidenced the successful polymerization of cobalt(II) 5,15-diphenyl porphyrin using either Fe(OTf)3 or Cu(OTf)2. Along with an intermolecular dehydrogenative C-C coupling reaction, the occurrence of side reactions, such as the inclusion of -CF3 groups and demetalation and subsequent insertion of copper(II) in the porphyrin macrocycle when using Cu(OTf)2, were evidenced. Interestingly, the inclusion of -CF3 groups into the polymer backbone when using triflate salts results in a deepening of the frontier energy levels, while the insertion of copper(II) contributes to a reduction in the band gap energy. This work demonstrates that the careful selection of the oxidant agent in oCVD enables fine-tuning the optoelectronic properties of conjugated polymers to suit specific application requirements.

Singlet oxygen generation by nanoassemblies containing porphyrin macrocycles: Steric and screening effects, energy transfer and competing processes

In this semi-review paper, we discuss some principal aspects that should be taken into account upon quantitative analysis of the interaction with molecular oxygen O2 and the singlet oxygen (1O2 or [Formula: see text] generation by various tetrapyrrolic photosensitizers (including monomers, chemical dimers, triads, pentads and organic-inorganic nanoassemblies). In all cases, the direct experimental measurements of 1O2 emission at [Formula: see text] = 1.27 μ need to be corrected to the solvent influence (refractive indexes, molecular polarizability) on the rate constant of the radiative transition [Formula: see text] in a 1O2 molecule. For porphyrin and chlorin chemical dimers, T1 states quenching by O2 followed by 1O2 generation depends on donor-acceptor interactions between the dimer halves, and extra-ligation effects as well as the spacer flexibility. In the case of self-assembled triads and pentads containing Zn-porphyrin dimers and pyridyl substituted porphyrin free bases (H2P) as extra-ligands, quenching rate constants of H2P T1 states by O2 are smaller compared to those found for individual monomeric H2P molecules which is explained by the spatial screening influence of a strongly quenched Zn-porphyrin dimer in multiporphyrin complexes. Finally, at 293 K for nanoassemblies of two types (semiconductor quantum dots CdSe/ZnS + coordinative linked tetra-pyridyl porphyrins, and semiconductor negatively charged quantum dots AgInS/ZnS + positively charged porphyrin molecules) it was quantitatively shown that non-radiative energy transfer FRET quantum dot [Formula: see text] porphyrin (competing with electron tunneling under conditions of quantum confinement) is only responsible for the singlet oxygen 1O2 generation by nanoassemblies.

Recent Advances in Main Group Coordination Driven Porphyrins: A Comprehensive Review

AbstractThe novel and exciting class of porphyrin‐based compounds are the main group coordination‐driven porphyrins (MGCPs) with a central main group element into the porphyrin macrocycle. MGCPs have unique properties, reactivity, and potential applications in catalysis, sensing, biomedicine etc. This comprehensive review article discusses recent advances in the field of main group coordination driven porphyrins and explores some of its potential uses in solar cells, catalysis, antimicrobial, optoelectronic devices, sensing, and catalysis. The addition of main group elements to porphyrin systems has resulted in the production of entirely novel compounds that have intriguing qualities including increased stability and catalytic activity. Significant modifications in these unique compounds features are apparent through the analysis of their structural properties. It encompasses FTIR, proton NMR, electrical and optical characterisation in addition to an electrochemical analysis of those parameters. They serve as significant building blocks for the creation of cutting‐edge materials and technologies in a variety of scientific and technical disciplines because to their special qualities and adaptability. Researchers working in the domains of coordination chemistry, catalysis, and materials science will find this study to be of interest since it offers a thorough examination of current developments in main group coordination driven porphyrins and their prospective applications. Overall, main group porphyrins are used in many different fields, such as sensing, catalysis, and optoelectronic devices.

Regulating Surface Metal Abundance via Lattice-Matched Coordination for Versatile and Environmentally-Viable Sn-Pb Alloying Perovskite Solar Cells.

Narrow-bandgap Sn-Pb alloying perovskites showcased great potential in constructing multiple-junction perovskite solar cells (PSCs) with efficiencies approaching or exceeding the Shockley-Queisser limit. However, the uncontrollable surface metal abundance (Sn2+ and Pb2+ ions) hinders their efficiency and versatility in different device structures. Additionally, the undesired Pb distribution mainly at the buried interface accelerates the Pb leakage when devices are damaged. In this work, a novel strategy is presented to modulate crystallization kinetics and surface metal abundance of Sn-Pb perovskites using a cobweb-like quadrangular macrocyclic porphyrin material, which features a molecular size compatible with the perovskite lattice and robustly coordinates with Pb2+ ions, thus immobilizing them and increasing surface Pb abundance by 61%. This modulation reduces toxic Pb leakage rates by 24-fold, with only ∼23 ppb Pb in water after severely damaged PSCs are immersed in water for 150 h.This strategy can also enhance chemical homogeneity, reduce trap density, release tensile strain and optimize carrier dynamics of Sn-Pb perovskites and relevant devices. Encouragingly, the power conversion efficiency (PCEs) of 23.28% for single-junction, full-stack devices and 21.34% for hole transport layer-free Sn-Pb PSCs are achieved.Notably, the related monolithic all-perovskite tandem solar cell also achieves a PCE of 27.03% with outstanding photostability.

Macrocyclic porphyrin photocatalysts without metal chelation: A novel pathway for complete degradation of tough halophenols with longwave visible LED light source

Halophenols are toxic and persistent pollutants in water environments which poses harm to various organisms. Due to their high stability and long residence time, ultraviolet radiation, heavy metals and oxidizing agents have been largely adopted on treating these compounds. However, these treatment methods could pose toxicity or hazardous risks to the marine environment and plant operators. In this study, a water-soluble porphyrin photocatalyst was synthesized and introduced for halophenol treatment using UV-free LED white light. The porphyrin catalyst is a macrocyclic ring consisting of pyrroles linked with methine bridges, the highly conjugated ring provided the superior functionality of visible light absorption. Surprisingly, over 99 % degradation of halophenols and over 90 % dehalogenation have been achieved without metal chelation, even higher than those of transition metal porphyrins with inclusion of Fe3+, Zn2+, Cu2+, Co2+, Ni2+, and Mn2+. Ring-opening reactions were confirmed with the formation of carboxylic acids; dicarboxylic acids like acrylic acid, and malonic acid; while fumaric acid was the main product. Total organic carbon results indicated no CO2 produced during the reaction. Triplet absorbance and scavenger studies also indicated that singlet oxygen and conduction band electrons are the main radical species for halophenol degradation. The 100-fold singlet emission quenching over triplet absorption quenching indicated that the excited electrons tend to be transferred via singlet state. This concept brings along new approaches detoxifying halophenol-related wastewater without UV, metals and other additives, which is more environmentally-friendly and sheds light to the conversion of toxic materials into useful chemical precursors.

Can Porphyrin-Triphenylphosphonium Conjugates Enhance the Photosensitizer Performance Toward Bacterial Strains?

Antimicrobial photodynamic treatment (aPDT) offers an alternative option for combating microbial pathogens, and in this way, addressing the challenges of growing antimicrobial resistance. In this promising and effective approach, cationic porphyrins and related macrocycles have emerged as leading photosensitizers (PS) for aPDT. In general, their preparation occurs via N-alkylation of nitrogen-based moieties with alkyl halides, which limits the ability to fine-tune the features of porphyrin-based PS. Herein, is reported that the conjugation of porphyrin macrocycles with triphenylphosphonium units created a series of effective cationic porphyrin-based PS for aPDT. The presence of positive charges at both the porphyrin macrocycle and triphenylphosphonium moieties significantly enhances the photodynamic activity of porphyrin-based PS against both Gram-positive and Gram-negative bacterial strains. Moreover, bacterial photoinactivation is achieved with a notable reduction in irradiation time, exceeding 50%, compared to 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP), used as the reference and known as good PS. The improved capability of the porphyrin macrocycle to generate singlet oxygen combined with the enhanced membrane interaction promoted by the presence of triphenylphosphonium moieties represents a promising approach to developing porphyrin-based PS with enhanced photosensitizing activity.

Enhanced Catalytic Activity of Binuclear Oxidovanadium(IV) Bisbenzimidazole Linked Porphyrin Dimer for the Generation of Biologically Active 3,4-Dihydropyrimidinones and Their Corresponding Thiones.

Binuclear vanadyl(IV) porphyrin (V2BP), where two vanadium(IV) porphyrin macrocycles are linked through benzimidazole units at the β-positions, has been prepared and characterized with various techniques, such as UV-vis, Fourier transform-infrared, electron paramagnetic resonance, cyclic voltammetry, density functional transform calculations, and mass spectrometry. V2BP exhibits a red shift (Δλmax = 10 nm) in the Soret band as compared with unsubstituted parent vanadyl(IV) meso-tetraphenylporphyrin (VP). The synthesized binuclear vanadyl(IV) porphyrin (V2BP) has further been studied as a catalyst to explore a single-pot multicomponent Biginelli reaction producing biologically active 3,4-dihydropyrimidin-2-(1H)-one (DHPM)-based biomolecules and the corresponding thiones under solvent-free conditions and its catalytic activity has been compared with vanadyl(IV) meso-tetraphenylporphyrin (VP). Several reaction conditions, such as the amount of catalyst, time, solvent, and temperature, have been optimized to obtain the maximum yield of DHPMs or thiones. The synthesized β-functionalized V2BP porphyrin dimer manifests much higher conversion (84-95% yield) of DHPMs or the corresponding thiones under the optimized reaction conditions with high TON (4454-5037) and TOF (1113-1259 h-1) values for the one-pot multicomponent Biginelli reaction as compared to the literature. The catalyst exhibited excellent recyclability up to 10 cycles.

Chlorido-[5,10,15,20-tetra-kis-(quinoline-7-carboxamido)-porphinato]iron(III).

The title compound, [Fe(C84H52N12O4)Cl], crystallizes in space group C2/c. The central FeIII cation (site symmetry 2) is coordinated in a fivefold manner, with four pyrrole N atoms of the porphyrin core in the basal sites and one Cl atom (site symmetry 2) in the apical position, which completes a slightly distorted square-pyramidal environment. The porphyrin macrocycle shows a characteristic ruffled-shape distortion and the iron atom is displaced out of the porphyrin plane by 0.42 Å with the average Fe-N distance being 2.054 (4) Å; the Fe-Cl bond length is 2.2042 (7) Å. Inter-molecular C-H⋯N and C-H⋯O hydrogen bonds occur in the crystal structure.

Comparative genomics analysis of pheophorbide a oxygenase (PAO) genes in eight pyrus genomes and their regulatory role in multiple stress responses in Chinese pear (Pyrus bretschneideri).

Pyrus (pear) is among the most nutritious fruits and contains fibers that have great health benefits to humans. It is mostly cultivated in temperate regions globally and is highly subjected to biotic and abiotic stresses which affect its yield. Pheophorbide a oxygenase (PAO) is an essential component of the chlorophyll degradation system and contributes to the senescence of leaves. It is responsible for opening the pheophorbide a porphyrin macrocycle and forming the main fluorescent chlorophyll catabolite However, this gene family and its members have not been explored in Pyrus genomes. Here we report a pangenome-wide investigation has been conducted on eight Pyrus genomes: Cuiguan, Shanxi Duli, Zhongai 1, Nijisseiki, Yunhong No.1, d'Anjou, Bartlett v2.0, and Dangshansuli v.1.1. The phylogenetic history, their gene structure, conservation patterns of motifs, their distribution on chromosomes, and gene duplication are studied in detail which shows the intraspecific structural conservation as well as evolutionary patterns of Pyrus PAOs. Cis-elements, protein-protein interactions (PPI), and the Gene Ontology (GO) enrichment analyses show their potential biological functions. Furthermore, their expression in various tissues, fruit hardening conditions, and drought stress conditions is also studied. Based on phylogenetics, the identified PAOs were divided into four groups. The expansion of this gene family in Pyrus is caused by both tandem and segmental duplication. Moreover, positive and negative selection pressure equally directed the gene's duplication process. The Pyrus PAO genes were enriched in hormones-related, light, development, and stress-related elements. RNA-seq data analysis showed that PAOs have varied levels of expression under diseased and abiotic stress conditions. The 3D structures of PAOs are also predicted to get more insights into functional conservation. Our research can be used further to get a deeper knowledge of the PAO gene family in Pyrus and to guide future research on improving the genetic composition of Pyrus to enhance stress tolerance.

The synthesis of highly nonplanar oxidovanadium(IV) porphyrins as robust catalysts for oxidative bromination of phenols in aqueous medium

Two new complexes, oxidovanadium(IV) 2,3,5,10,12,13,15,20-octaphenyl-7,8,17,18-tetrabromoporphyrin V(IV)O(OPP)Br4 (2), and oxidovanadium(IV) 2,3,5,10,12,13,15,20-octaphenyl-7,8,17,18-tetrachloroporphyrin V(IV)O(OPP)Cl4 (3) starting from oxidovanadium(IV) 2,3,5,10,12,13,15,20-octaphenylporphyrin V(IV)O(OPP) (1) have been prepared in good yields and characterized by various spectroscopic techniques. The single-crystal and DFT-optimized structures of these porphyrins showed a highly nonplanar saddle-shape conformation of the porphyrin macrocycle. In the cyclic voltammograms, the first ring oxidation potential and the first ring reduction potential of V(IV)O(OPP)Br4 (2) and V(IV)O(OPP)Cl4 (3) showed anodic shift as compared to V(IV)O(OPP) (1), indicating the electron-deficient nature of both the porphyrins. The oxidation state of vanadium in the synthesized complexes as +4 was confirmed by EPR spectroscopy, and these porphyrins exhibited axially compressed [Formula: see text] configuration. These porphyrins were utilized as catalysts for the oxidative bromination of thymol and other phenol derivatives with excellent conversion ([Formula: see text] 99.9%), good selectivity, and high TOF value (86869 h[Formula: see text].