On the preparation of metalloporphyrins

The third-order nonlinear optical responses of zinc porphyrin oligomers: Cycles vs linear chains

Porphyrins are widely used as potential nonlinear optical (NLO) materials because of their highly delocalized π electrons and feasible synthesis and functionalization with broad biological applications. A variety of linear and cyclic porphyrin derivatives have been synthesized, and the correlation between their structures and NLO properties awaits being disclosed. In this work, the electronic structures and third-order NLO properties of linear and cyclic butadiyne-linked zinc porphyrin oligomers have been studied by quantum chemical methods and sum-over-states model. The static second hyperpolarizability (<γ0>) increases exponentially with the number of zinc porphyrin units ([<γ0>n] = 0.67[<γ0>1]n2.63, n = 2 ∼ 6) in linear π-conjugated oligomers, and the <γ0> of the linear hexamer is about 74 times that of the monomer. Such enhancement of <γ0> in linear oligomers originates from closely-lying frontier molecular orbitals available for low energy electron excitations and strong charge transfer-based excitations across porphyrins. The <γ0>s of cyclic porphyrins are lower than that of the linear hexamer, though the interaction between the ring and the ligand enhances the <γ0> of some cyclic zinc porphyrin complexes. The large two-photon absorption cross sections confer on these zinc porphyrin derivatives excellent candidates for two-photon absorption applications.

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.

Vibrational properties of heme-nitrosoalkane complexes in comparison with those of their HNO analogs, and reactivity studies towards nitric oxide and Lewis acids

C-Nitroso compounds (RNO, R = alkyl and aryl) are byproducts of drug metabolism and bind to heme proteins, and their heme-RNO adducts are isoelectronic to ferrous nitroxyl (NO-/HNO) complexes. Importantly, heme-HNO compounds are key intermediates in the reduction of NO to N2O and nitrite to ammonium in the nitrogen cycle. Ferrous heme-RNO complexes act as stable analogs of these species, potentially allowing for the investigation of the vibrational and electronic properties of unstable heme-HNO intermediates. In this paper, a series of six-coordinate ferrous heme-RNO complexes (where R = iPr and Ph) were prepared using the TPP2- and 3,5-Me-BAFP2- co-ligands, and tetrahydrofuran, pyridine, and 1-methylimidazole as the axial ligands (bound trans to RNO). These complexes were characterized using different spectroscopic methods and X-ray crystallography. The complex [Fe(TPP)(THF)(iPrNO)] was further utilized for nuclear resonance vibrational spectroscopy (NRVS), allowing for the detailed assignment of the Fe-N(R)O vibrations of a heme-RNO complex for the first time. The vibrational properties of these species were then correlated with those of their HNO analogs, using DFT calculations. Our studies support previous findings that RNO ligands in ferrous heme complexes do not elicit a significant trans effect. In addition, the complexes are air-stable, and do not show any reactivity of their RNO ligands towards NO. So although ferrous heme-RNO complexes are suitable structural and electronic models for their HNO analogs, they are unsuitable to model the reactivity of heme-HNO complexes. We further investigated the reaction of our heme-RNO complexes with different Lewis acids. Here, [Fe(TPP)(THF)(iPrNO)] was found to be unreactive towards Lewis acids. In contrast, [Fe(3,5-Me-BAFP)(iPrNO)2] is reactive towards all of the Lewis acids investigated here, but in most cases the iron center is simply oxidized, resulting in the loss of the iPrNO ligand. In the case of the Lewis acid B2(pin)2, the reduced product [Fe(3,5-Me-BAFP)(iPrNH2)(iPrNO)] was identified by X-ray crystallography.

A Porphyrin-Faced Zn8L6 Cage for Selective Oxidation of C(sp3)-H Bonds and Sulfides

Catalytic oxidation of benzyl C-H bonds and sulfides from fuel oils stands as an attractive proposition in the quest for clean energy, yet their simultaneous oxidation with a singular, economically friendly catalyst is not well established. In this work, the combination of a cobalt(II) porphyrin ligand with 2-pyridinecarboxaldehyde and ZnII yielded a Zn8L6 cage (Co cube). The three-dimensional conjugated structure effectively enhances energy transfer efficiency, enabling the Co cube to show a good ability to activate oxygen under light conditions for photooxidation. Moreover, this catalytic system demonstrates high selectivity for the photocatalytic oxidation of C(sp3)-H bonds and sulfides, employing the Co cube as a single component catalyst, molecular oxygen as the oxidant, and activating oxygen into 1O2 under mild reaction conditions. This provides significant insights for organic synthesis and future design of photocatalysts with complex molecular components.

Porphyrin-Based Hole-Transporting Materials for Perovskite Solar Cells: Boosting Performance with Smart Synthesis

Perovskite solar cells (PSCs) are becoming a promising and revolutionary advancement within the photovoltaic field globally. Continuous improvement in efficiency, straightforward processing methods, and use of lightweight and cost-effective materials represent superior features, among other notable aspects. Still, long-term stability and durability are issues to address to facilitate widespread commercial adoption and practical application prospects. Research has focused on overcoming these challenges, and charge transport materials play a critical role in determining charge dynamics, photovoltaic performance, and device stability. Conventional hole-transporting materials (HTMs), spiro-OMeTAD and PTAA, contribute to remarkable power conversion efficiencies owing to high thin-film quality and matched energy alignment. However, they often show a high material cost, low carrier mobility, and poor stability, which greatly limit their practical applications. Now, this review outlines recent advances in synthetic approaches to porphyrin-based HTMs to tune the charge dynamics by optimizing their molecular structures and properties. The main structural features comprise porphyrins of A4-type, trans A2B2-type, and photosynthetic pigment analogues. Strategies include well-established routes to provide the required macrocycles, such as condensation of pyrrole or dipyrromethanes with suitable aldehydes, metalation of the porphyrin inner core, and postfunctionalization of peripheral positions. These functionalizations involve conventional procedures (e.g., halogenation, esterification, transesterification, nucleophilic oxidation, reduction, and nucleophilic substitution) as well as metal-catalyzed ones such as Suzuki-Miyaura, Sonogashira, Buchwald-Hartwig, and Ullmann cross-coupling reactions. As HTMs can also protect the perovskite layer from the external environment, porphyrin structures play a pivotal role in chemical, mechanical, and environmental stability, with their high hydrophobicity ability as the most significant parameter. The impact of porphyrins on the hole hopping of other HTMs while acting as an additive or an interlayer, passivating defects, and improving charge transport is also highlighted to provide real insights into ways to develop efficient and stable porphyrin-based materials for PSCs. This perspective aims to guide the scientific community in the design of new porphyrin molecules to place PSCs as an outperformer in photovoltaic technologies.

Customizable Porphyrin Platform Enables Folate Receptor PET Imaging Using Copper-64

Folate receptors including folate receptor α (FRα) are overexpressed in up to 90% of ovarian cancers. Ovarian cancers overexpressing FRα often exhibit high degrees of drug resistance and poor outcomes. A porphyrin chassis has been developed that is readily customizable according to the desired targeting properties. Thus, compound O5 includes a free base porphyrin, two water-solubilizing groups that project above and below the macrocycle plane, and a folate targeting moiety. Compound O5 was synthesized (>95% purity) and exhibited aqueous solubility of at least 0.48 mM (1 mg/mL). Radiolabeling of O5 with 64Cu in HEPES buffer at 37 °C gave a molar activity of 1000 μCi/μg (88 MBq/nmol). [64Cu]Cu-O5 was stable in human serum for 24 h. Cell uptake studies showed 535 ± 12% bound/mg [64Cu]Cu-O5 in FRα-positive IGROV1 cells when incubated at 0.04 nM. Subcellular fractionation showed that most radioactivity was associated with the cytoplasmic (39.4 ± 2.7%) and chromatin-bound nuclear (53.0 ± 4.2%) fractions. In mice bearing IGROV1 xenografts, PET imaging studies showed clear tumor uptake of [64Cu]Cu-O5 from 1 to 24 h post injection with a low degree of liver uptake. The tumor standardized uptake value at 24 h post injection was 0.34 ± 0.16 versus 0.06 ± 0.07 in the blocking group. In summary, [64Cu]Cu-O5 was synthesized at high molar activity, was stable in serum, exhibited high binding to FRα-overexpressing cells with high nuclear translocation, and gave uptake that was clearly visible in mouse tumor xenografts.

Making and Breaking Helical Open-Chain Oligopyrroles

Closed-chain oligopyrroles such as porphyrins or corroles have been well-established in literature and experience a steadily strong interest by several fields of science. However, their open-chain derivatives are comparatively underrepresented, despite their intriguing properties and promising applications. Here, we aim to review typical synthetic routes, as well as point towards several emergent properties, marking them as interesting candidates for various fields of study. The review focuses on two traditional methods (each starting from highly symmetric metalloporphyrins) and then expands its scope towards more recent variations before moving on to more exotic and recent highlights that have yet to be included into the canon. Key chemical reactivities (ring closure, substitution and fragmentation) are then followed by notable physicochemical properties, placing special emphasis on potential uses in molecular electronics and sensors.

Porphyrin Metal-organic Framework Sensors for Chemical and Biological Sensing

Porphyrins and porphyrin derivatives have been intensively explored for a number of applications such as sensing, catalysis, adsorption, and photocatalysis due to their outstanding photophysical properties. Their usage in sensing applications, however, is limited by intrinsic defects such as physiological instability and self-quenching. To reduce self-quenching susceptibility, researchers have developed porphyrin metal-organic frameworks (MOFs). Metal-organic frameworks (MOFs), a unique type of hybrid porous coordination polymers comprised of metal ions linked by organic linkers, are gaining popularity. Porphyrin molecules can be integrated into MOFs or employed as organic linkers in the production of MOFs. Porphyrin-based MOFs are a separate branch of the huge MOF family that combines the distinguishing qualities of porphyrins (e.g., fluorescent nature) and MOFs (e.g., high surface area, high porosity) to enable sensing applications with higher sensitivity, specificity, and extended target range. The key synthesis techniques for porphyrin-based MOFs, such as porphyrin@MOFs, porphyrinic MOFs, and composite porphyrinic MOFs, are outlined in this review article. This review article focuses on current advances and breakthroughs in the field of porphyrin-based MOFs for detecting a variety of targets (for example, metal ions, anions, explosives, biomolecules, pH, and toxins). Finally, the issues and potential future uses of this class of emerging materials for sensing applications are reviewed.

Molecularly imprinted polymer hydrogel sheets with metalloporphyrin-incorporated molecular recognition sites for protein capture

Metalloporphyrins are often found in nature as coordination recognition sites within biological process, and synthetically offer the potential for use in therapeutic, catalytic and diagnostic applications. While porphyrin containing biological recognition elements have stability limitations, molecularly imprinted polymers bearing these structures offer an alternative with excellent robustness and the ability to work in extreme conditions. In this work, we synthesised a polymerizable porphyrin and metalloporphyrin and have incorporated these as co-monomers within a hydrogel thin-sheet MIP for the specific recognition of bovine haemoglobin (BHb). The hydrogels were evaluated using Scatchard analysis, with Kd values of 10.13 × 10-7, 5.30 × 10-7, and 3.40 × 10-7 M, for the control MIP, porphyrin incorporated MIP and the iron-porphyrin incorporated MIP, respectively. The MIPs also observed good selectivity towards the target protein with 73.8%, 77.4%, and 81.2% rebinding of the BHb target for the control MIP, porphyrin incorporated MIP and the iron-porphyrin incorporated MIP, respectively, compared with the non-imprinted (NIP) counterparts. Specificity was determined against a non-target protein, Bovine Serum Albumin (BSA). The results indicate that the introduction of the metalloporphyrin as a functional co-monomer is significantly beneficial to the recognition of a MIP, further enhancing MIP capabilities at targeting proteins.

Stabilization of a Heme-HNO Model Complex Using a Bulky Bis-Picket Fence Porphyrin and Reactivity Studies with NO

Nitroxyl, HNO/NO-, the one-electron reduced form of NO, is suggested to take part in distinct signaling pathways in mammals and is also a key intermediate in various heme-catalyzed NOx interconversions in the nitrogen cycle. Cytochrome P450nor (Cyt P450nor) is a heme-containing enzyme that performs NO reduction to N2O in fungal denitrification. The reactive intermediate in this enzyme, termed "Intermediate I", is proposed to be an Fe-NHO/Fe-NHOH type species, but it is difficult to study its electronic structure and exact protonation state due to its instability. Here, we utilize a bulky bis-picket fence porphyrin to obtain the first stable heme-HNO model complex, [Fe(3,5-Me-BAFP)(MI)(NHO)], as a model for Intermediate I, and more generally HNO adducts of heme proteins. Due to the steric hindrance of the bis-picket fence porphyrin, [Fe(3,5-Me-BAFP)(MI)(NHO)] is stable (τ1/2 = 56 min at -30 °C), can be isolated as a solid, and is available for thorough spectroscopic characterization. In particular, we were able to solve a conundrum in the literature and provide the first full vibrational characterization of a heme-HNO complex using IR and nuclear resonance vibrational spectroscopy (NRVS). Reactivity studies of [Fe(3,5-Me-BAFP)(MI)(NHO)] with NO gas show a 91 ± 10% yield for N2O formation, demonstrating that heme-HNO complexes are catalytically competent intermediates for NO reduction to N2O in Cyt P450nor. The implications of these results for the mechanism of Cyt P450nor are further discussed.

Deciphering Structural and Dynamical Properties of Hydrated Cobalt Porphyrins via Ab Initio Quantum Mechanical Charge Field Molecular Dynamics Simulation

The present study successfully implemented the ab initio quantum mechanical charge field molecular dynamics (QMCF MD) formalism for the investigation of structural and dynamical properties of hydrated cobalt-porphyrin complexes. Considering the significance of cobalt ions in biological systems (for instance, vitamin B12), which reportedly incorporate cobalt ions in a d6, low spin, +3 state chelated in the corrin ring, an analog of porphyrin, the current study is focused on cobalt in the oxidation states +2 and +3 bound to the parent porphyrin lead structures embedded in an aqueous solution. These cobalt-porphyrin complexes were investigated in terms of their structural and dynamical properties at the quantum chemical level. The structural attributes of these hydrated complexes revealed the contrasting features of the water binding to these solutes, including a detailed evaluation of the associated dynamics. The study also yielded notable findings in regard to the respective electronic configurations vs coordination, which suggested that Co(II)-POR possesses a 5-fold square pyramidal coordination geometry in an aqueous solution containing the metal ion coordinating to four nitrogen atoms of the porphyrin ring and one axial water as the fifth ligand. On the other hand, high-spin Co(III)-POR was hypothesized to be more stable due to the smaller size-to-charge ratio of the cobalt ion, but the high-spin complex demonstrated unstable structural and dynamical behavior. However, the corresponding properties of the hydrated Co(III)_LS-POR revealed a stable structure in an aqueous solution, thus suggesting the Co(III) ion to be in a low-spin state when bound to the porphyrin ring. Moreover, the structural and dynamical data were augmented by computing the free energy of water binding to the cobalt ions and the solvent-accessible surface area, which provide further information on thermochemical properties of the metal-water interaction and the hydrogen bonding potential of the porphyrin ring in these hydrated systems.

Sulfonamide Porphyrins as Potent Photosensitizers against Multidrug-Resistant Staphylococcus aureus (MRSA): The Role of Co-Adjuvants

Sulfonamides are a conventional class of antibiotics that are well-suited to combat infections. However, their overuse leads to antimicrobial resistance. Porphyrins and analogs have demonstrated excellent photosensitizing properties and have been used as antimicrobial agents to photoinactivate microorganisms, including multiresistant Staphylococcus aureus (MRSA) strains. It is well recognized that the combination of different therapeutic agents might improve the biological outcome. In this present work, a novel meso-arylporphyrin and its Zn(II) complex functionalized with sulfonamide groups were synthesized and characterized and the antibacterial activity towards MRSA with and without the presence of the adjuvant KI was evaluated. For comparison, the studies were also extended to the corresponding sulfonated porphyrin TPP(SO₃H)₄. Photodynamic studies revealed that all porphyrin derivatives were effective in photoinactivating MRSA (>99.9% of reduction) at a concentration of 5.0 μM upon white light radiation with an irradiance of 25 mW cm^-2 and a total light dose of 15 J cm^-2. The combination of the porphyrin photosensitizers with the co-adjuvant KI during the photodynamic treatment proved to be very promising allowing a significant reduction in the treatment time and photosensitizer concentration by six times and at least five times, respectively. The combined effect observed for TPP(SO₂NHEt)₄ and ZnTPP(SO₂NHEt)₄ with KI seems to be due to the formation of reactive iodine radicals. In the photodynamic studies with TPP(SO₃H)₄ plus KI, the cooperative action was mainly due to the formation of free iodine (I₂).

Hybrid Materials Based on Imidazo[4,5-b]porphyrins for Catalytic Oxidation of Sulfides

Heterogenized metalloporphyrin catalysts for oxidation reactions are extensively explored to improve chemical production. In this work, manganese meso-tetraarylporphyrins were immobilized on hydrated mesoporous titanium dioxide (SBET = 705 m2 g−1) through carboxylate or phosphonate anchoring groups separated from the macrocycle by the 2-arylimidazole linker fused across one of the pyrrolic rings of the macrocycle. The element composition of two mesoporous hybrid materials thus obtained were investigated and the integrity of the immobilized complexes was shown by different physicochemical methods. Finally, the catalytic efficiency of the more stable material Mn(TMPIP)/TiO2 with the phosphonate anchor was evaluated in the selective oxidation of sulfides to sulfoxides by molecular oxygen in the presence of isobutyraldehyde (IBA). The heterogenized complex has shown excellent catalytic activity exhibiting a turnover (TON) of ~1100 in a single catalytic run of the sulfoxidation of thioanisole. The catalyst was successfully reused in seven consecutive catalytic cycles.

Biocompatibility and Antimicrobial Activity of Electrospun Fibrous Materials Based on PHB and Modified with Hemin

The effect of the hemin (Hmi) on the structure and properties of nanocomposite electrospun materials based on poly-3-hydroxybutyrate (PHB) is discussed in the article. The additive significantly affected the morphology of fibers allowed to produce more elastic material and provided high antimicrobial activity. The article considers also the impact of the hemin on the biocompatibility of the nonwoven material based on PHB and the prospects for wound healing.

μ-Oxo-bis[(octacosafluoro-meso-tetraphenylporphyrinato)iron(iii)] - synthesis, crystal structure, and catalytic activity in oxidation reactions

We describe the synthesis and X-ray crystal structure of μ-oxo-bis[(octacosafluoro-meso-tetraphenylporphyrinato)iron(iii)] [(FeTPPF₂₈)₂O]. This novel iron complex is an efficient catalyst for oxidative biaryl coupling reactions of diarylamines and carbazoles. The asymmetric oxidative coupling in the presence of an axially chiral biaryl phosphoric acid as co-catalyst provides the 2,2'-bis(arylamino)-1,1'-biaryl in 96% ee. The Wacker-type oxidation of alkenes to the corresponding ketones with (FeTPPF₂₈)₂O as catalyst in the presence of phenylsilane proceeds at room temperature with air as the terminal oxidant. For internal and aliphatic alkenes increased ketone/alcohol product ratios were obtained.

Switchable Nanozyme Activity of Porphyrins Intercalated in Layered Gadolinium Hydroxide

In this study, organo-inorganic nanohybrids LHGd-MTSPP with enzyme-like activity were prepared by in situ intercalation of anionic 5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin and its complexes with Zn(II) and Pd(II) (MTSPP, M = 2H, Zn(II) and Pd(II)) into gadolinium layered hydroxide (LHGd). The combination of powder XRD, CHNS analysis, FT-IR, EDX, and TG confirmed the layered structure of the reaction products. The basal interplanar distances in LHGd-MTSPP samples were 22.3-22.6 Å, corresponding to the size of an intercalated tetrapyrrole molecule. According to SEM data, LHGd-MTSPP hybrids consisted of individual lamellar nanoparticles 20-50 nm in thickness. The enzyme-like activity of individual constituents, LHGd-Cl and sulfoporphyrins TSPP, ZnTSPP and PdTSPP, and hybrid LHGd-MTSPP materials, was studied by chemiluminescence analysis using the ABAP/luminol system in phosphate buffer solution. All the individual porphyrins exhibited dose-dependent antioxidant properties with respect to alkylperoxyl radicals at pH 7.4. The intercalation of free base TSPP porphyrin into the LHGd preserved the radical scavenging properties of the product. Conversely, in LHGd-MTSPP samples containing Zn(II) and Pd(II) complexes, the antioxidant properties of the porphyrins changed to dose-dependent prooxidant activity. Thus, an efficient approach to the design and synthesis of advanced LHGd-MTSPP materials with switchable enzyme-like activity was developed.

Kinetics of chromium(V)-oxo and chromium(IV)-oxo porphyrins: Reactivity and mechanism for sulfoxidation reactions

In this work, chromium(IV)-oxo porphyrins [Cr^IV(Por)(O)] (2) (Por = porphyrin) were produced either by oxidation of [Cr^III(Por)Cl] (1) with iodobenzene diacetate or visible light photolysis of porphyrin‑chromium(III) chlorates. Subsequent oxidation of 2 with silver perchlorate gave chromium(V)-oxo porphyrins [Cr^V(Por)(O)](ClO₄) (3) in three porphyrin ligands, including 5,10,15,20-tetramesitylporphyrin(TMP, a), 5,10,15,20-tetrakis(2,6-difluorophenyl)porphyrin(TDFPP, b), and 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TPFPP, c). Complexes 2 and 3 reacted with thioanisoles to produce the corresponding sulfoxides, and their kinetics of sulfoxidation reactions with a series of aryl methyl sulfides(thioanisoles) were studied in organic solutions. Chromium(V)-oxo porphyrins are several orders of magnitudes more reactive than chromium(IV)-oxo species, and representative second-order rate constants (k_ox) for the oxidation of thioansole are (0.40 ± 0.01) M^-1 s^-1 (3a), and (2.82 ± 0.20) × 10² M^-1 s^-1 (3b), and (2.20 ± 0.01) × 10³ M^-1 s^-1 (3c). The order of reactivity for 2 and 3 follows TPFPP > TDFPP > TMP, in agreement with the electrophilic nature of metal-oxo complexes. Hammett analyses indicate significant charge transfer in the transition states for oxidation of para-substituted thioanisoles by [Cr^V(Por)(O)]⁺. The ρ⁺ constants are -1.69 for 3a, -2.63 for 3b, and - 2.89 for 3c, respectively, mirror values found previously for related metal-oxo species. A mechanism involving the electrophilic attack of the Cr^V-oxo at sulfides to form a sulfur cation intermediate in the rate-determining step is suggested. Competition studies with chromium(III) porphyrin chloride and PhI(OAc)₂ gave relative rate constants for oxidations of competing thioanisoles that closely match ratios of absolute rate constants from chromium(V)-oxo species, which are true oxidants under catalytic conditions.

Molecular Catalyst Synthesis Strategies to Prepare Atomically Dispersed Fe-N-C Heterogeneous Catalysts

We report a strategy to integrate atomically dispersed iron within a heterogeneous nitrogen-doped carbon (N-C) support, inspired by routes for metalation of molecular macrocyclic iron complexes. The N-C support, derived from pyrolysis of a ZIF-8 metal-organic framework, is metalated via solution-phase reaction with FeCl₂ and tributyl amine, as a Brønsted base, at 150 °C. Fe active sites are characterized by ⁵⁷Fe Mössbauer spectroscopy and aberration-corrected scanning transmission electron microscopy. The site density can be increased by selective removal of Zn²⁺ ions from the N-C support prior to metalation, resembling the transmetalation strategy commonly employed for the preparation of molecular Fe-macrocycles. The utility of this approach is validated by the higher catalytic rates (per total Fe) of these materials relative to established Fe-N-C catalysts, benchmarked using an aerobic oxidation reaction.

A Feature of the Crystalline and Amorphous Structure of Ultra Thin Fibers Based on Poly(3-hydroxybutyrate) (PHB) Containing Minor Concentrations of Hemin and a Complex of Tetraphenylporphyrin with Iron

Comprehensive studies combining X-ray diffraction analysis, thermophysical, dynamic measurements by probe method and scanning electron microscopy have been carried out. The peculiarity of the crystalline and amorphous structure of ultra-thin fibers based on poly(3-hydroxybutyrate) (PHB) containing minor concentrations (0–5%) of a gene and a tetraphenylporphyrin (TFP) complex with iron (in the form of FeCl) are considered. When these complexes are added to the PHB fibers, the morphology of the fibers change: a sharp change in the crystallinity and molecular mobility in the amorphous regions of PHB is observed. When adding a gel to the fibers of PHB, a significant decrease in the degree of crystallinity, melting enthalpy, and correlation time can be observed. The reverse pattern is observed in a system with the addition of FeCl-TFP—there is a significant increase in the degree of crystallinity, melting enthalpy and correlation time. Exposure of PHB fibers with gemin in an aqueous medium at 70 °C leads to a decrease in the enthalpy of melting in modified fibers—to an increase in this parameter. The molecular mobility of chains in amorphous regions of PHB/gemin fibers increases at the same time, a nonlinear dependence of changes in molecular dynamics is observed in PHB/FeCl-TFP fibers. Ozonolysis has a complex effect on the amorphous structure of the studied systems. The obtained fibrous materials have bactericidal properties and should be used in the creation of new therapeutic systems of antibacterial and antitumor action.

Synthesis of a Rare Water-Soluble Silver(II)/Porphyrin and Its Multifunctional Therapeutic Effect on Methicillin-Resistant Staphylococcus aureus

Porphyrin derivatives are popular photodynamic therapy (PDT) agents; however, their typical insolubility in water has made it challenging to separate cells of organisms in a liquid water environment. Herein, a novel water-soluble 5,10,15,20-tetrakis(4-methoxyphenyl-3-sulfonatophenyl) porphyrin (TMPPS) was synthesized with 95% yield by modifying the traditional sulfonation route. The reaction of TMPPS with AgNO₃ afforded AgTMPPS an unusual Ag(II) oxidation state (97% yield). The free base and Ag(II) complex were characterized by matrix-assisted laser desorption ionization-mass spectroscopy, and ¹H nuclear magnetic resonance, Fourier-transform infrared, UV-vis, fluorescence, and X-ray photolectron spectroscopies. Upon 460 nm laser irradiation, AgTMPPS generated a large amount of ¹O₂, whereas no ⦁OH was detected. Antibacterial experiments on methicillin-resistant Staphylococcus aureus (MRSA) revealed that the combined action of Ag^Ⅱ ions and PDT could endow AgTMPPS with a 100% bactericidal ratio for highly concentrated MRSA (10⁸ CFU/mL) at a very low dosage (4 μM) under laser irradiation at 360 J/cm². Another PDT response was demonstrated by photocatalytically oxidizing 1,4-dihydronicotinamide adenine dinucleotide to NAD⁺ with AgTMPPS. The structural features of the TMPPS and AgTMPPS molecules were investigated by density functional theory quantum chemical calculations to demonstrate the efficient chemical and photodynamical effects of AgTMPPS for non-invasive antibacterial therapy.

Nonplanar porphyrins: synthesis, properties, and unique functionalities

Porphyrins are variously substituted tetrapyrrolic macrocycles, with wide-ranging biological and chemical applications derived from metal chelation in the core and the 18π aromatic surface. Under suitable conditions, the porphyrin framework can deform significantly from regular planar shape, owing to steric overload on the porphyrin periphery or steric repulsion in the core, among other structure modulation strategies. Adopting this nonplanar porphyrin architecture allows guest molecules to interact directly with an exposed core, with guest-responsive and photoactive electronic states of the porphyrin allowing energy, information, atom and electron transfer within and between these species. This functionality can be incorporated and tuned by decoration of functional groups and electronic modifications, with individual deformation profiles adapted to specific key sensing and catalysis applications. Nonplanar porphyrins are assisting breakthroughs in molecular recognition, organo- and photoredox catalysis; simultaneously bio-inspired and distinctly synthetic, these molecules offer a new dimension in shape-responsive host-guest chemistry. In this review, we have summarized the synthetic methods and design aspects of nonplanar porphyrin formation, key properties, structure and functionality of the nonplanar aromatic framework, and the scope and utility of this emerging class towards outstanding scientific, industrial and environmental issues.

Photodynamic activity of novel cationic porphyrins conjugated to graphene quantum dots against Staphylococcus aureus

Novel 5-(pyridyl)-10-15-20-tris(4-bromophenyl) porphyrin (complex 1), indium metal derivative (complex 2), and quaternized derivative (complex 3) were synthesized and conjugated to graphene quantum dots (GQDs). The conjugation of the porphyrins to GQDs was through [Formula: see text]-[Formula: see text] stacking. Herein, the [Formula: see text]-[Formula: see text] stacking approach was used to avoid covalent conjugation which might compromise the intrinsic chemical and physical properties. The photodynamic activities of the proposed nanomaterials were assessed towards Staphylococcus aureus cell obliteration. The photophysical properties of the prepared complexes were also studied prior to the application. Moreover, a decrease in fluorescence lifetimes was observed upon metalation of complex 1. As anticipated, singlet oxygen quantum yield ([Formula: see text] increased notably upon heavy metal (indium) insertion and upon composite formation. Antimicrobial photodynamic therapy comparative studies were done on quaternized and unquaternized indium porphyrins conjugated to GQDs. Complex 3-GQDs exhibited the highest antibacterial activities compared to other complexes, and this was attributed to the high [Formula: see text] which plays an imperative role in photodynamic therapy applications.

Stepwise Oxidative C-C Coupling and/or C-N Fusion of Zn(II) meso-Pyridin-2-ylthio-porphyrins

The synthesis and characterization of zinc(II) meso-pyridin-2-ylthio-porphyrins are presented in this manuscript. The (electro)chemical oxidation of [5-(pyridin-2-ylthio)-10,20-bis(p-tolyl)-15-phenylporphyrinato] zinc(II) or [5,15-bis(pyridin-2-ylthio)-10,20-bis(p-tolyl)porphyrinato] zinc(II) leads to the formation of one or two C-N bond(s) by intramolecular nucleophilic attack of the peripheral thiopyridinyl fragment(s) on the neighboring β-pyrrolic position(s) (C-N fusion reaction). In addition, the chemical oxidation of [5-(pyridin-2-ylthio)-10,20-bis(p-tolyl)porphyrinato] zinc(II), i.e., bearing one free meso position, mainly affords the meso,meso-dimer. Further stepwise electrochemical oxidation selectively produces the mono and bis C-N fused meso,meso-dimer. The resulting pyridinium derivatives exhibit important changes in their physicochemical properties (NMR, UV-vis, CV) as compared to their initial unfused precursors. Also, the X-ray crystallographic structures of three unfused monomers, one unfused meso,meso-dimer, and two C-N fused monomers are presented.

Metal Complexes of Porphyrinoids Containing Nonpyrrolic Heterocycles

The replacement of one or more pyrrolic building block(s) of a porphyrin by a nonpyrrolic heterocycle leads to the formation of so-called pyrrole-modified porphyrins (PMPs), porphyrinoids of broad structural variability. The wide range of coordination environments (type, number, charge, and architecture of the donor atoms) that the pyrrole-modified frameworks provide to the central metal ions, the frequent presence of donor atoms at their periphery, and their often observed nonplanarity or conformational flexibility distinguish the complexes of the PMPs clearly from those of the traditional square-planar, dianionic, N₄-coordinating (hydro)porphyrins. Their different coordination properties suggest their utilization in areas beyond which regular metalloporphyrins are suitable. Following a general introduction to the synthetic methodologies available to generate pyrrole-modified porphyrins, their general structure, history, coordination chemistry, and optical properties, this Review highlights the chemical, electronic (optical), and structural differences of specific classes of metalloporphyrinoids containing nonpyrrolic heterocycles. The focus is on macrocycles with similar "tetrapyrrolic" architectures as porphyrins, thusly excluding the majority of expanded porphyrins. We highlight the relevance and application of these metal complexes in biological and technical fields as chemosensors, catalysts, photochemotherapeutics, or imaging agents. This Review provides an introduction to the field of metallo-PMPs as well as a comprehensive snapshot of the current state of the art of their synthesis, structures, and properties. It also aims to provide encouragement for the further study of these intriguing and structurally versatile metalloporphyrinoids.

Metallic Effects on p-Hydroxyphenyl Porphyrin Thin-Film-Based Planar Optical Waveguide Gas Sensor: Experimental and Computational Studies

Metal effects on the gas sensing behavior of metal complexes of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (THPP) thin film was investigated in terms of detecting NO₂ gas by the planar optical waveguide. For this purpose, several THPP and metal complexes were synthesized with different central metal ions: Co(II), Ni(II), Cu(II), and Zn(II). Planar optical gas sensors were fabricated with the metalloporphyrins deposited on K⁺ ion-exchanged soda-lime glass substrate with the spin coating method serving as host matrices for gas interaction. All of the THPP complex’s films were fully characterized by UV-Vis, IR and XPS spectroscopy, and the laser light source wavelength was selected at 520 and 670 nm. The results of the planar optical waveguide sensor show that the Zn–THPP complex exhibits the strongest response with the lowest detectable gas concentration of NO₂ gas for both 520 nm and 670 nm. The Ni–THPP and Co–THPP complexes display good efficiency in the detection of NO₂, while, on the other hand, Cu–THPP shows a very low interaction with NO₂ gas, with only 50 ppm and 200 ppm detectable gas concentration for 520 nm and 670 nm, respectively. In addition, molecular dynamic simulations and quantum mechanical calculations were performed, proving to be coherent with the experimental results.

CO2 to CO Electroreduction, Electrocatalytic H2 Evolution, and Catalytic Degradation of Organic Dyes Using a Co(II) meso-Tetraarylporphyrin

The meso-tetrakis(4-(trifluoromethyl)phenyl)porphyrinato cobalt(II) complex [Co(TMFPP)] was synthesised in 93% yield. The compound was studied by 1H NMR, UV-visible absorption, and photoluminescence spectroscopy. The optical band gap Eg was calculated to 2.15 eV using the Tauc plot method and a semiconducting character is suggested. Cyclic voltammetry showed two fully reversible reduction waves at E1/2 = -0.91 V and E1/2 = -2.05 V vs. SCE and reversible oxidations at 0.30 V and 0.98 V representing both metal-centred (Co(0)/Co(I)/Co(II)/Co(III)) and porphyrin-centred (Por2-/Por-) processes. [Co(TMFPP)] is a very active catalyst for the electrochemical formation of H2 from DMF/acetic acid, with a Faradaic Efficiency (FE) of 85%, and also catalysed the reduction of CO2 to CO with a FE of 90%. Moreover, the two triarylmethane dyes crystal violet and malachite green were decomposed using H2O2 and [Co(TMFPP)] as catalyst with an efficiency of more than 85% in one batch.

([2.2.2]Cryptand)potassium (4-methyl-benzene-thiol-ato)[5,10,15,20-tetra-kis-(4-chloro-phen-yl)porphyr-inato]manganate(II) tetra-hydro-furan disolvate

Single crystals of the title compound, [K(C18H36N2O6)][Mn(C44H24Cl4N4)(C7H7S)]·2C4H8O, were obtained by the solvent evaporation method. The MnII cation is coordinated by four pyrrole N atoms (Np) of the porphyrin ring and one S atom of the apical 4-methyl-benzene-thiol-ate ligand with the average Mn-Np and the apical Mn-S bond lengths being 2.160 (9) and 2.4642 (8) Å, respectively. Two tetra-hydro-furan solvent mol-ecules and a potassium cation chelated inside a [2.2.2]cryptand (4,7,13,16,21,24-hexa-oxa-1,10-di-aza-bicyclo[8.8.8]hexa-cosa-ne) are also present.

The Comparison of Advanced Electrospun Materials Based on Poly(-3-hydroxybutyrate) with Natural and Synthetic Additives

The comparison of the effect of porphyrins of natural and synthetic origin containing the same metal atom on the structure and properties of the semi-crystalline polymer matrix is of current concern. A large number of modifying additives and biodegradable polymers for biomedical purposes, composed of poly(-3-hydroxybutyrate)-porphyrin, are of particular interest because of the combination of their unique properties. The objective of this work are electrospun fibrous material based on poly(-3-hydroxybutyrate) (PHB), hemin (Hmi), and tetraphenylporphyrin with iron (Fe(TPP)Cl). The structure of these new materials was investigated by methods such as optical and scanning electron microscopy, X-ray diffraction analysis, Electron paramagnetic resonance method, and Differential scanning calorimetry. The properties of the electrospun materials were analyzed by mechanical and biological tests, and the wetting contact angle was measured. In this work, it was found that even small concentrations of porphyrin can increase the antimicrobial properties by 12 times, improve the physical and mechanical properties by at least 3.5 times, and vary hydrophobicity by at least 5%. At the same time, additives similar in the structure had an oppositely directed effect on the supramolecular structure, the composition of the crystalline, and the amorphous phases. The article considers assumptions about the nature of such differences due to the influence of Hmi and Fe(TPP)Cl) on the macromolecular and fibrous structure of PHB.

A New Analytical Method to Quantify Ammonia in Freshwater with a Bulk Acoustic Wave Sensor

A new method to analyse ammonia in freshwater, based on a piezoelectric quartz crystal coated with the metalloporphyrin chloro[5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato] manganese(III) is presented. A 9 MHz quartz crystal coated on both faces with an amount of porphyrin produced a frequency decrease of 21.4 kHz, which allowed ammonia in a 10.00 mL sample to be quantified in concentrations between 5 and 70 µg L^-1, with a sensitivity of 0.60 Hz L µg^-1, over a period of at least eight months. The proposed method has several advantages over the officially recommended indophenol spectrophotometric method: sample volume was reduced by a factor of 2.5, toxic reagents (phenol and sodium nitroprusside) were eliminated, analysing turbid samples presented no difficulty, and there was not only a significant time saving in solution preparation, but also in sample analysis time, which was reduced from 1 h to 2 min. No statistically significant differences (α = 0.05) were found both in the mean and precision of the results obtained for ammonia in water samples collected from domestic wells, analysed by this new method and by the indophenol spectrophotometric method. Furthermore, the proposed method would allow the individual quantification, with similar sensitivity, of amines and ammonia within a single analytical run.

Functionalization of Gold Nanoparticles with Ru-Porphyrin and Their Selectivity in the Oligomerization of Alkynes

Gold nanoparticles (AuNPs) were functionalized by ruthenium porphyrins through a sulfur/gold covalent bond using a three-steps reaction. The catalyst was characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) in order to control the binding of ruthenium porphyrin on AuNPs’ surface. The catalyst was tested and compared with an analog system not bound to AuNPs in the oligomerization reaction using 1-phenylacetylene as the substrate.

Dioxygen Reactivity of Copper(I)/Manganese(II)-Porphyrin Assemblies: Mechanistic Studies and Cooperative Activation of O2

The oxidation of transition metals such as manganese and copper by dioxygen (O₂) is of great interest to chemists and biochemists for fundamental and practical reasons. In this report, the O₂ reactivities of 1:1 and 1:2 mixtures of [(TPP)Mn^II] (1; TPP: Tetraphenylporphyrin) and [(tmpa)Cu^I(MeCN)]⁺ (2; TMPA: Tris(2-pyridylmethyl)amine) in 2-methyltetrahydrofuran (MeTHF) are described. Variable-temperature (-110 °C to room temperature) absorption spectroscopic measurements support that, at low temperature, oxygenation of the (TPP)Mn/Cu mixtures leads to rapid formation of a cupric superoxo intermediate, [(tmpa)Cu^II(O₂^•-)]⁺ (3), independent of the presence of the manganese porphyrin complex (1). Complex 3 subsequently reacts with 1 to form a heterobinuclear μ-peroxo species, [(tmpa)Cu^II-(O₂^2-)-Mn^III(TPP)]⁺ (4; λ_max = 443 nm), which thermally converts to a μ-oxo complex, [(tmpa)Cu^II-O-Mn^III(TPP)]⁺ (5; λ_max = 434 and 466 nm), confirmed by electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy. In the 1:2 (TPP)Mn/Cu mixture, 4 is subsequently attacked by a second equivalent of 3, giving a bis-μ-peroxo species, i.e., [(tmpa)Cu^II-(O₂^2-)-Mn^IV(TPP)-(O₂^2-)-Cu^II(tmpa)]²⁺ (7; λ_max = 420 nm and δ_pyrrolic = -44.90 ppm). The final decomposition product of the (TPP)Mn/Cu/O₂ chemistry in MeTHF is [(TPP)Mn^III(MeTHF)₂]⁺ (6), whose X-ray structure is also presented and compared to literature analogs.

Dendronized Porphyrins: Molecular Design and Synthesis

Abstract:

In this review, we report different methods and strategies to synthesize flexible and rigid dendronized porphyrins. We will focus on porphyrin dendrimers that have been reported in the last 10 years. Particularly, in our research group, we have designed and synthesized different series of dendronized porphyrins (free base and metallated) with pyrene units at the periphery and Fréchet-type dendritic arms. The Lindsey methodology has allowed the synthesis of meso-substituted porphyrins with various substitution patterns, such as symmetric, dissymmetric, or unsymmetric. Porphyrin dendrimers have been prepared by different synthetic methodologies; one of the most reported being the convergent method, where the dendrons are first prepared and further linked to a meso-substituted functionalized porphyrin unit, which will constitute the core of the dendrimer. Another interesting synthetic approach is the use of a reactive dendron bearing a terminal aldehyde functional group to form the final porphyrin core. In this way, a two-armed dendronized dissymmetric porphyrin core can be prepared from a dendritic precursor and a dipyrromethene derivative. This strategy is very convenient to prepare low-generation dendritic porphyrins. The divergent approach is another well-known methodology for porphyrin dendrimer synthesis, mostly used for the obtainment of high-generation dendrimers. Click chemistry reaction has been advantageous for the development of more complex porphyrin dendritic structures. This reaction presents important advantages, such as high yields and mild reaction conditions which permit the assembly of different multiporphyrin dendritic structures. In the constructs presented in this review, the emission of the porphyrin moiety has been observed, leading to potential applications in artificial photosynthesis, sensing, nanomedicine, and biological sciences.

A new porphyrinic vanadium-based MOF constructed from infinite V(OH)O4 chains: syntheses, characterization and photoabsorption properties

A new porphyrinic vanadium-based metal–organic framework (MOF), namely V-MOF-10 [V2(OH)2(H2TCPP)], constructed from {V(OH)O4}∞ chains and 4-tetracarboxyphenylporphyrin linkers, was synthesized by a solvothermal procedure.

A Sn(iv) porphyrin with mitochondria targeting properties for enhanced photodynamic activity against MCF-7 cells

A Sn(iv) porphyrin with a mitochondria targeting triphenylphosphonium moiety has a high ΦΔ value (ca. 0.72) and does not aggregate in aqueous solution. The dye exhibits favorable photodynamic activity against MCF-7 cells with an IC50 value of 2.9 μM.

Perspectives on Ligand Properties of N-Heterocyclic Carbenes in Iron Porphyrin Complexes

There has been considerable research interest in the ligand nature of N-heterocyclic carbenes (NHCs). In this work, two six-coordinate NHC iron porphyrin complexes [Fe^II(TTP)(1,3-Me₂Imd)₂] (TTP = tetratolylporphyrin, 1,3-Me₂Imd = 1,3-dimethylimidazol-2-ylidene) and [Fe^III(TDCPP)(1,3-Me₂Imd)₂]ClO₄ (TDCPP = 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin) are reported. Single-crystal X-ray characterizations demonstrate that both complexes have strongly ruffled conformations and relatively perpendicular ligand orientations which are forced by the sterically bulky 1,3-Me₂Imd NHC ligands. Multitemperature (4.2-300 K) and high magnetic field (0-9 T) Mössbauer and low-temperature (4.0 K) EPR spectroscopies definitely confirmed the low-spin states of [Fe^II(TTP)(1,3-Me₂Imd)₂] (S = 0) and [Fe^III(TDCPP)(1,3-Me₂Imd)₂]ClO₄ (S = 1/2). The similarity of 1,3-Me₂Imd and imidazole, as well as the well-established correlations between the ligand nature and spectroscopic characteristics of [Fe^II,III(Porph)(L)₂]^0,+ (Porph: porphyrin; L: planar base ligand) species, allowed direct comparisons between the pair of ligands which revealed for the first time that NHC has a stronger π-acceptor ability than imidazoles, in addition to its very strong σ-donation.

Effect of the Hemin Molecular Complexes on the Structure and Properties of the Composite Electrospun Materials Based on Poly(3-hydroxybutyrate)

The creation of innovative fibrous materials based on biodegradable semicrystalline polymers and modifying additives is an urgent scientific problem. In particular, the development of biomedical materials based on molecular complexes and biopolymers with controlled properties is of great interest. The paper suggests an approach to modifying the structure and properties of the composite materials based on poly(3-hydroxybutyrate) (PHB) obtained by the electrospinning method using molecular complexes of hemin. The introduction of 1-5 wt. % of hemin has a significant effect on the supramolecular structure, morphology and properties of PHB-based fibers. Changes in the supramolecular structure intensified with the increasing hemin concentration. On the one hand, a decrease in the fraction of the crystalline phase by 8-10% was observed. At the same time, there is a decrease in the density of the amorphous phase by 15-70%. Moreover, the addition of hemin leads to an improvement in the strength characteristics of the material: the elongation at break increased by 1.5 times, and in the tensile strength, it increased by 3 times. The antimicrobial activity of the hemin-containing composite materials against Escherichia coli and Staphylococcus aureus was confirmed. The obtained materials are proposed to be used in the creation of composite systems for regenerative medicine.