Porphyrinic Framework Research Articles

Sorption and catalysis by robust microporous metalloporphyrin framework solids

Two isostructural metalloporphyrin framework solids have been synthesized. Both frameworks contains manganese(III) metal complexes of trans-dicarboxylateporphyrins whose peripheralcarboxylates coordinate the edges of tetrahedral Zn4O[Formula: see text] clusters; the two metalloporphyrins explored are Mn(III) and Co(II). The cubic interpenetrated frameworks have 72% free volume and 4 × 7 Å averaged size pores. The evacuated frameworks are robust and retain a structure open to the sorption of substrates with medium polarity. The manganese porphyrin framework catalyzes the hydroxylation of cyclic and linear alkanes with iodosylbenzene as oxidant in a size- and polarity-selective manner. In addition, the catalysis was found to occur within the pores, making this a rare case of porphyrin framework solid with interior catalysis.

Bulky Nature Phenanthroimidazole-Based Porphyrin Sensitizers for Dye-Sensitized Solar Cell Applications

Porphyrin-based sensitizers have attracted significant attention due to their excellent performance in dye-sensitized solar cells (DSSCs). Herein, a novel electron donor−π-bridge–electron acceptor (D−π–A) based porphyrin sensitizer having strong electron donating methyl phenanthroimidazole ring and ethynylcarboxyphenyl group at meso- position of porphyrin framework (LG11) was designed and applied as sensitizer in DSSC. To reduce the undesirable loss of open-circuit voltage (VOC) caused by dye aggregation and charge recombination effect, phenyl (LG12) or hexyl phenyl chains (LG13 and LG14) were attached to the phenanthroimidazole moiety. The introduction of a simple thiophene unit between the porphyrin and carboxylic acid anchoring group (LG14) has enabled further extension of the absorption to a longer wavelength. Compared to LG11 and LG12, hexyl phenyl-substituted LG13 and LG14 effectively reduced the dye aggregation and allowed enhancement of VOC to 460 and 650 mV. Both LG13 and LG14 sensitizers exhibit broader and redshift incident photon conversion efficiency spectra and resulted in highest JSC of 14.2 and 15.5 mA cm–2, respectively. Because of all aforesaid properties, LG13 and LG14 dyes show photovoltaic conversion efficiencies of 6.25% and 7.45%, respectively. Further, a cosensitization of LG14 with an organic molecule (HC5) to increase the absorption valley in the visible region has seen efficiency enhanced to 8.27%. This work provides a potential approach to molecular design of porphyrin sensitizers and selection of cosensitizers to build better efficient and stable DSSC system. We have adopted intensity-modulated photo voltage spectroscopy and nanosecond laser flash photolysis spectroscopy to explain the efficiency and structure relationship of these LG11-LG14 sensitizers.

A novel nitroethylene-based porphyrin as a NIR fluorescence turn-on probe for biothiols based on the Michael addition reaction

Biothiols, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play essential roles in many physiological and pathological processes. In this work, three porphyrin derivatives, XQ1, XQ2 and XQ3, were synthesized by combining the porphyrin framework with nitroethylene, bis(methoxycarbonyl)ethylene and dicyanoethylene moieties, respectively. XQ1 was almost nonfluorescent, which could be utilized as a good starting point for developing fluorescence turn-on probes. Thus, XQ1 exhibits fast fluorescence enhancement and high selectivity towards the biothiols based on the Michael addition mechanism. It also exhibits high sensitivity towards the biothiols with the detection limits of 0.65–1.1 μM. In addition, XQ1 was successfully applied to cell imaging in living A549 cells for visualizing the biothiols. The results compose a good example of designing porphyrin derivatives for detecting biothiols, with the advantages of dramatic fluorescence enhancement in the NIR wavelength range, which exhibits good cell membrane permeability and practicability in detecting both exogenous and endogenous biothiols.

Covalent Porphyrin Framework-Derived Fe2P@Fe4N-Coupled Nanoparticles Embedded in N-Doped Carbons as Efficient Trifunctional Electrocatalysts.

A new porous covalent porphyrin framework (CPF) filled with triphenylphosphine was designed and synthesized using the rigid tetrakis(p-bromophenyl)porphyrin (TBPP) and 1,3,5-benzenetriboronic acid trivalent alcohol ester as building blocks. The carbonization of this special CPF has afforded coupled Fe2P and Fe4N nanoparticles embedded in N-doped carbons (Fe2P/Fe4N@N-doped carbons). This CPF serves as an "all in one" precursor of Fe, N, P, and C. The porous property and solid skeleton of the CPF endow Fe2P/Fe4N@N-doped carbons with porous structure and a high degree of graphitization. As a result, Fe2P/Fe4N@N-doped carbons exhibited highly efficient multifunctional electrocatalytic performance for water splitting and oxygen electroreduction. Typically, Fe2P/Fe4N@C-800, obtained at a heat-treatment temperature of 800 °C, showed an ORR half-wave potential of 0.80 V in alkaline media and 0.68 V in acidic media, close to that of commercial Pt/C catalysts. Fe2P/Fe4N@C-800 also displayed efficient OER and HER activities, comparable to other phosphide and nitride electrocatalysts. The coupled Fe4N and Fe2P nanoparticles embedded in carbons exert unique catalytic efficiency for water splitting and fuel cells.

Assembling Porphyrins into Extended Network Structures by Employing Aromatic Dicarboxylates: Synthesis, Metal Exchange, and Heterogeneous Catalytic Studies.

Three new metal-organic porphyrinic framework compounds of zinc and 5,10,15,20-tetrakis(4-pyridyl)porphyrin (TPyP) have been synthesized under solvothermal conditions. The compounds [Zn5 (C40 H24 N8 )(C8 H4 O4 )2 (NO3 )6 (DMA)2 ] (DMA)3 (H2 O)8 (1; DMA=dimethylacetamide), [Zn3 (C40 H24 N8 )(C8 H4 O4 )2 (DMF)](DMF)5 (H2 O)12 (2), and [Zn3 (C40 H24 N8 )(C12 H6 O4 )2 (DMA)2 ](H2 O)7 (3) have two (1) and three dimensionally (2 and 3) extended structures. All the three structures contain porphyrinic units connected through the carboxylate linkers. The nitrates bind the metal centers and are not hydrogen bonded. The different binding modes of nitrate in the structure of 1 are observed for the first time in a porphyrin-based MOF. The openness of the structure allowed us to explore metal exchange through a room-temperature metathetic route. Compound 2 undergoes 100 % exchange with copper, whereas compound 3 exchanges 70 % with copper. The copper-exchanged compounds Cu∈2 and Cu∈3 were observed to be good heterogeneous catalysts for many important organic reactions. The chemo and regioselective enamination of β-ketoesters, preparation of propargylamine derivatives as well as regioselective cycloadditions of alkyne and azide (click reactions) have been carried out with good yields and selectivity. All the compounds have been characterized by PXRD, IR, UV/Vis, atomic absorption spectroscopy (AAS), and energy-dispersive X-ray spectroscopy (for Cu exchange).

Efficient solvent-free fixation of CO2 into cyclic carbonates catalyzed by Bi(III) porphyrin/TBAI at atmospheric pressure

A series of Bi (III) porphyrin complexes were synthesized and tested as catalysts for chemical fixation of carbon dioxide (CO2) and epoxides under solvent-free conditions in the presence of tetrabutylammonium iodide (TBAI) as co-catalyst. The influences of various factors (catalyst systems, catalyst amount, pressure, time, and temperature) on the catalytic activities have been studied systematically. The catalytic performances were strongly influenced by the substitute of porphyrin framework and axial group X−. 2a/TBAI was screened as the most active catalyst system under the optimized conditions (90°C, 1h, 2MPa). Notably, a very high turnover frequency (TOF) value (37,900h−1) for catalyst 2a was achieved via adjusting reaction factors. This binary catalytic system also exhibited good activities (up to 98%) and selectivities (>99%) for the cycloaddition reaction of many epoxides, including diepoxides, with CO2 into corresponding cyclic carbonates at atmospheric pressure (0.1MPa) within 6h. Especially, the glycidyl methacrylate, which is known to have the self-polymerization tendency at higher temperature, could be converted into its corresponding cyclic carbonate selectively with high yield of 94.8% with 2a/TBAI as catalyst at room temperature and 0.1MPa. In spite of the homogeneous property of the catalytic system, 2a/TBAI, could maintain the high performance under atmospheric pressure for 60h, or even longer. Moreover, kinetic studies gave out an inferred mechanism.

MOF-Sensitized Solar Cells Enabled by a Pillared Porphyrin Framework

Metal–organic frameworks (MOFs) are highly ordered, functionally tunable supramolecular materials with the potential to improve dye-sensitized solar cells (DSSCs). Several recent reports have indicated that photocurrent can be generated in Gratzel-type DSSC devices when MOFs are used as the sensitizer. However, the specific role(s) of the incorporated MOFs and the potential influence of residual MOF precursor species on device performance are unclear. Herein, we describe the assembly and characterization of a simplified DSSC platform in which isolated MOF crystals are used as the sensitizer in a planar device architecture. We selected a pillared porphyrin framework (PPF) as the MOF sensitizer, taking particular care to avoid contamination from light-absorbing MOF precursors. Photovoltaic and electrochemical characterization under simulated 1-sun and wavelength-selective illumination revealed photocurrent generation that is clearly ascribable to the PPF MOF. Continued refinement of highly versatile MOF str...

Water-soluble metalloporphyrinates with excellent photo-induced anticancer activity resulting from high tumor accumulation

To develop a water-soluble and tumor-targeted photosensitizer for photodynamic therapy (PDT), a porphyrin framework containing the metal ion gallium(III) was combined with platinum(II)-based groups to produce two new pentacationic metalloporphyrinates, Ga-4cisPtTPyP (5,10,15,20-tetrakis{cis-diammine-chloro-platinum(II)}(4-pyridyl)-porphyrinato gallium(III) hydroxide tetranitrate) and Ga-4transPtTPyP (5,10,15,20-tetrakis{trans-diammine-chloro-platinum(II)} (4-pyridyl)-porphyrinato gallium(III) hydroxide tetranitrate). Both complexes exhibited high singlet oxygen quantum yields (Φ∆) and remarkable photocytotoxicity with appreciable phototoxic indexes (PIs). In particular, Ga-4cisPtTPyP showed a low IC50 value (Colon 26: 0.12μM; Sarcoma 180: 0.08μM) under illumination and its PI up to 1000. With outstanding tumor accumulation (tumor/muscle ratio>9), Ga-4cisPtTPyP almost completely inhibited tumor growth over two weeks in an in vivo PDT assay. These results imply that Ga-4cisPtTPyP could be a promising anticancer agent for use in PDT.

Assembly of an indium–porphyrin framework JLU-Liu7: a mesoporous metal–organic framework with high gas adsorption and separation of light hydrocarbons

A novel mesoporous indium–porphyrin framework JLU-Liu7 with frl net has been successfully synthesized. It exhibits high performance for gas adsorption and light hydrocarbon separation.

A reduced graphene oxide/covalent cobalt porphyrin framework for efficient oxygen reduction reaction.

A reduced graphene oxide/covalent cobalt porphyrin framework has been synthesized by using pyridine-functionalized reduced graphene oxide (G-dye) as the building block. Due to the unique 3-dimensional architecture and good electronic properties of graphene, as well as the electron accepting ability of the nitrogen atoms in the G-dye, the as-synthesized CoCOF-Py-0.05rGO catalyst exhibits excellent oxygen reduction reaction (ORR) activity with superior long-term stability and methanol tolerance.

A Hexagonal Covalent Porphyrin Framework as an Efficient Support for Gold Nanoparticles toward Catalytic Reduction of 4-Nitrophenol.

A hexagonal porphyrin-based porous organic polymer, namely, CPF-1, was constructed by 3+2 ketoenamine condensation of the C2 -symmetric porphyrin diamine 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin and 1,3,5-triformylphloroglucinol. This material exhibits permanent porosity and excellent thermal and chemical stability. CPF-1 can be employed as a superior supporting substrate to immobilize Au nanoparticles (NPs) as a result of the strong interactions between Au NPs and the CPF support. An Au@CPF-1 hybrid was synthesized by an interfacial solution infiltration method with NaBH4 as reducing agent. Au NPs (5 nm) grew on CPF-1 and were distributed without aggregation. Moreover, Au@CPF-1 exhibits superior catalytic activity compared to many other reported Au-based catalysts for the reduction of 4-nitrophenol in the presence of NaBH4 . In addition, Au@CPF-1 has excellent stability and recyclability, and it can be reused for three successive reaction cycles without loss of activity. The dense distribution of phenyl rings on the channel walls of the CPF support can reasonably be regarded as the active sites that adsorb the 4-nitrophenol molecule through hydrogen-bonding and C-H⋅⋅⋅π interactions, as was confirmed by the X-ray structure of model compound DAPP-Benz.

Carbaporphyrinoid Systems.

Following immediately after the serendipitous discovery of N-confused porphyrins, remarkably diverse carbaporphyrinoid systems have been synthesized and investigated. By replacing a pyrrolic unit within the porphyrin framework with cyclopentadiene, indene, azulene, cycloheptatriene, or benzene, new families of porphyrin-like macrocycles were produced. True carbaporphyrins are fully aromatic structures, while benziporphyrins are essentially devoid of macrocyclic aromatic character, and azuliporphyrins fall midway between the two extremes. Monocarbaporphyrinoids are superior organometallic ligands and form stable complexes with copper(III), silver(III), gold(III), nickel(II), palladium(II), platinum(II), rhodium(III), iridium(III), and ruthenium(II). Unusual oxidation reactions have also been discovered, commonly leading to derivatization of the internal carbon atom. In addition, structural rearrangements have been uncovered that allow the conversion of azuliporphyrins into benzocarbaporphyrins, and benziporphyrins into carbaporphyrins. Although less well studied, many examples of dicarbaporphyrinoids have been reported, and these show equally intriguing characteristics. Furthermore, contracted and expanded carbaporphyrinoids have been investigated. Studies in this area provide fundamental insights into the aromatic properties, tautomerization, and reactivity of porphyrins and related macrocyclic systems.

ChemInform Abstract: Out of the Blue! Azuliporphyrins and Related Carbaporphyrinoid Systems

AbstractReview: 59 refs.

Frontispiece: Highly Stable Mesoporous Zirconium Porphyrinic Frameworks with Distinct Flexibility

Frontispiece: Highly Stable Mesoporous Zirconium Porphyrinic Frameworks with Distinct Flexibility

Highly Stable Mesoporous Zirconium Porphyrinic Frameworks with Distinct Flexibility.

The construction of highly stable metal-porphyrinic frameworks (MPFs) is appealing as these materials offer great opportunities for applications in artificial light-harvesting systems, gas storage, heterogeneous catalysis, etc. Herein, we report the synthesis of a novel mesoporous metal-porphyrinic framework (denoted as NUPF-1) and its catalytic properties. NUPF-1 is constructed from a new porphyrin linker and a Zr6 O8 structural building unit, possessing an unprecedented doubly interpenetrating scu net. The structure exhibits not only remarkable chemical and thermal stabilities, but also a distinct structural flexibility, which is seldom seen in metal-organic framework (MOF) materials. By the merit of high chemical stability, NUPF-1 could be easily post-metallized with [Ru3 (CO)12 ], and the resulting {NUPF-1-RuCO} is catalytically active as a heterogeneous catalyst for intermolecular C(sp(3) )-H amination. Excellent yields and good recyclability for amination of small substrates with various organic azides have been achieved.

Out of the Blue! Azuliporphyrins and Related Carbaporphyrinoid Systems.

First reported in 1997, azuliporphyrins have proven to be a truly remarkable family of porphyrin analogues. In this system, although the porphyrin framework is retained, one of the pyrrolic moieties has been replaced by an azulene unit. Azulene favors electrophilic substitution at the 1,3-positions, which are structurally analogous to the α-positions in pyrrole, and this property facilitates the construction of azulene-containing porphyrinoid systems. Azuliporphyrins were first prepared from tripyrranes and 1,3-azulenedicarbaldehyde using a "3 + 1" variant on the MacDonald reaction. Subsequently, azulenes were shown to react with acetoxymethylpyrroles under acidic conditions to generate azulitripyrranes that could be utilized in a back-to-front "3 + 1" methodology to form azuliporphyrins and related heteroporphyrinoids. In addition, the favorability of azulenes toward 1,3-substitution was applied to one-pot syntheses of tetraarylazuliporphyrins and calix[4]azulenes. Azuliporphyrins have significant diatropic character that is greatly enhanced upon protonation. They have been shown to form organometallic complexes with Ni(II), Pd(II), Pt(II), Ir(III), Rh(III), and Ru(II) and undergo selective oxidations at the internal carbon with copper(II) or silver(I) salts to afford 21-oxyazuliporphyrins. In addition, oxidative ring contractions readily occur under basic conditions in the presence of peroxides to give benzocarbaporphyrins, and this reactivity provides access to tetraarylbenzocarbaporphyrins and their organometallic derivatives. A diazulenylmethane dialdehyde has been shown to react with dipyrrylmethanes in the presence of HCl or HBr to give diazuliporphyrins that were isolated in a monoprotonated form, and metalation with palladium(II) acetate afforded a stable zwitterionic palladium(II) complex. Equally intriguing dicarbaporphyrinoids incorporating indene and azulene rings have been reported, and these systems exhibit significant aromatic character. Recent studies have demonstrated that calixazulenes form supramolecular complexes with quaternary ammonium salts and afford a 1:1 complex with C60. In addition, conjugated structures have been prepared from calixazulenes that are structurally related to quatyrin, the theoretically important hydrocarbon analogue of the porphyrins. Examples of expanded azuliporphyrinoids have also been described. These azulene-containing porphyrinoids exhibit unique and complex reactivity that compares favorably with better studied porphyrin analogue systems such as the N-confused porphyrins, and azuliporphyrin derivatives show promise in the development of new catalytic systems.

Synthesis and spectroscopic studies of axially bound tetra(phenothiazinyl)/tetra(bis(4′-tert-butylbiphenyl-4-yl)aniline)-zinc(II)porphyrin-fullero[C60 & C70]pyrrolidine donor–acceptor triads

Two zinc porphyrin based dyads, 5, 10, 15, 20-tetra-4-(2-(10H-phenothiazin-10-yl)ethoxy)phenyl porphyrinato zinc (II) and 5,10,15,20-tetra-4-(bis(4′-tert-butylbiphenyl-4-yl)amino)phenyl porphyrinato zinc(II) containing four phenothiazine or bis(4′-tert-butylbiphenyl-4-yl)aniline moieties tethered to porphyrin framework were synthesized, and systematically characterized using 1H NMR, mass, UV–visible and steady state fluorescence techniques. Excitation of 5,10,15,20-tetra-4-(bis(4′-tert-butylbiphenyl-4-yl)amino)phenyl porphyrinato zinc(II) at 335nm, resulted in quenched emission of bis(4′-tert-butylbiphenyl-4-yl)aniline moiety, when compared to pristine bis(4′-tert-butylbiphenyl-4-yl)aniline, and appearance of porphyrin emission at 618nm, due to intramolecular energy transfer from bis(4′-tert-butylbiphenyl-4-yl)aniline moiety to porphyrin. The porphyrin dyads were titrated with phenylimidazole appended fullerenes, N-Methyl-4-(1H-imidazol-1-yl)phenylfullero[C60]pyrrolidine or N-Methyl-4-(1H-imidazol-1-yl)phenylfullero[C70]pyrrolidine and supramolecular triads of the type, (PTZ or BBA)4-ZnP:(C60Im or C70Im) were formed in which, zinc porphyrin and fullerenes act as primary electron donor and acceptors, while phenothiazine or bis(4′-tert-butylbiphenyl-4-yl)aniline moieties behave as secondary electron donors in photo-induced electron transfer events. Optical absorption and 1H NMR titration studies confirmed the formation of supramolecular triads and the steady state fluorescence experiments revealed the quenching of porphyrin emission upon addition of increasing amounts of N-Methyl-4-(1H-imidazol-1-yl)phenylfullero[C60]pyrrolidine or N-Methyl-4-(1H-imidazol-1-yl)phenylfullero[C70]pyrrolidine indicating the occurrence of photo-induced electron transfer from 1ZnP⁎ to co-ordinated fullerene moieties.

Nanoporous iron(iii) porphyrin frameworks: an efficient catalyst for [4+2] cycloaddition reactions of unactivated aldehydes with a diene

The one pot conversion of several unactivated aldehydes with a diene to their corresponding [4+2] cycloaddition products has been studied using nanoporous iron(iii) porphyrin frameworks as catalysts.

Investigation of a microporous iron(iii) porphyrin framework derived cathode catalyst in PEM fuel cells

In this study, an iron(iii) porphyrin framework material was synthesized and pyrolyzed and its catalytic activity towards the oxygen reduction reaction (ORR) was evaluated using rotating disk electrode (RDE) experiments and single cell testing.

A robust indium-porphyrin framework for CO2 capture and chemical transformation.

An indium based metal-porphyrinic framework, denoted NUPF-3, was prepared based on a new amido-decorated porphyrin ligand. NUPF-3 possesses a rarely seen 4-fold interpenetrated pts framework with segmented pores and dense metalloporphyrin central sites. The structure can retain its crystallinity in commonly used solvents, as well as acidic/alkaline solutions with pH ranging from 1 to 12 for 48 h, exhibiting high chemical stability. Meanwhile, thermal analysis reveals that NUPF-3 possesses relatively high thermal stability. Owing to the presence of amido groups, structural interpenetration and a charged framework, NUPF-3 exhibits relatively high CO2 uptake. Moreover, NUPF-3 could be used as a good heterogeneous catalyst for cycloaddition of CO2 and epoxides, under relatively mild conditions, with good recyclability.