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Zinc tetraphenylporphyrin (TPP)Zn was examined as to its as to its electroreduction properties by cyclic voltammetry and spectroelectrochemistry in six nonaqueous solvents containing tetrabutylammonium perchlorate (TBAP). The porphyrin undergoes an initial one-electron reduction to give a [Formula: see text]-anion radical on the cyclic voltammetry timescale but the radical was not stable on the spectroelectrochemical timescale when utilizting chlorinated alkane solvents containing 0.1 M TBAP (CH2Cl2, 1-2,dichloroethane (C2H4Cl[Formula: see text] where chloride, generated from minute amounts of reduced solvent, formed an axially coordinated complex, (TPP)Zn[Formula: see text](Cl[Formula: see text], prior to reduction of the porphyrin. This spectroelectrochemically characterized product exhibits red-shifted Soret and Q-bands as compared to that of the neutral (TPP)Zn under the same solution conditions and analytical plots obtained from recording the spectrum as a function of potential rule out the possibility of forming the superoxide complex, (TPP)Zn[Formula: see text](O[Formula: see text], in chlorinated alkane solvents.

Six [Formula: see text],[Formula: see text]-butano substituted metalloporphyrins containing sterically hindered meso-dihalogenophenyl substituents and first-row transition metal ions were synthesized and their electrochemical and spectroelectrochemical properties were characterized in nonaqueous media. The investigated compounds have the general formula butano(Y2Ph)4PorM, where Por is a dianion of the porphyrin, M = Mn[Formula: see text]Cl, Fe[Formula: see text]Cl, Co[Formula: see text], Ni[Formula: see text], Cu[Formula: see text] or Zn[Formula: see text]and Y2Ph is a sterically hindered 2,6-F2Ph or 2,6-Cl2Ph group on each of the four meso-positions of the macrocycle. The electrochemistry of each porphyrin was examined in CH2Cl2or pyridine containing 0.1 M tetra-[Formula: see text]-butylammonium perchlorate. The first one-electron reduction is metal-centered for the manganese(III), iron(III) and cobalt(II) porphyrins to generate the Mn(II), Fe(II) and Co(I) porphyrins, but it is porphyrin ring-centered for the other examined M(II) porphyrins to give porphyrin [Formula: see text]-anion radicals under the given solution conditions. The effect of the [Formula: see text],[Formula: see text]-butano and sterically hindered meso-Y2Ph substituents on redox potentials and electron transfer mechanisms are discussed and compared to what was previously reported for butano-substituted tetraarylporphyrins without hindered meso-substituents.

Synthesis, characterization and oxygen reduction reaction (ORR) catalytic properties of bimetallic sulfides CoS/MnS/N-C catalyst was discussed. The catalyst was derived from a typical Co based zeolitic imidazolate framework (ZIF-67) and manganese aminoporphyrin. 5,15-Bis(4-aminophenyl)-10,20-bis(4-bromophenyl) porphyrin manganese oxoacetate loaded with ZIF-67 forms a porphyrin loaded ZIF-67. This product was then calcined at 800ˆ∘C and vulcanized with thioacetamide to obtain the bimetallic sulfide product CoS/MnS/N-C. The structure of CoS/MnS/N-C was further characterized by XRD, XPS, FESEM and HRTEM spectra which indicated a novel porous and hollow sphere structure. The electrocatalytic properties of the bimetallic material as well as its parent porphyrin and ZIF-67 were also compared in alkaline condition (0.1 M KOH) with a rotating disk electrode. The prepared catalyst CoS/MnS/N-C exhibits a higher catalytic performance than its precursors (PorMnOAc, ZIF-67 and PorMnOAc loaded ZIF-67) with almost four electron transfers under this condition.

A series of different metal centered 5,15-Bis(4-aminophenyl)-10,20-bis(4-bromophenyl)porphyrins (PorM) where M = H2, MnOAc, FeCl, Co or Zn were synthesized, and then encapsulated in zeolite imidazole framework-8 (ZIF-8) by typical template directed strategy to generate PorM@ZIF-8 metal organic frameworks (MOFs). These composites were characterized by UV-vis, FTIR, XRD, FESEM and HRTEM methods. Each prepared PorM@ZIF-8 MOF retained the molecular structure of porphyrin and crystal structure of ZIF-8. It is clearly shown that porphyrin centered metal ions will affect MOFs morphology. Both PorH2@ZIF-8 and PorZn@ZIF-8 gave a rhombic dodecahedron, PorMnOAc@ZIF-8 gave a truncated hexagonal prism-like structure, while no specific structures were obtained for PorFeCl@ZIF-8 and PorCo@ZIF-8 due to aggregation as characterized by FESEM spectrum. Oxygen reduction catalytic ability of ZIF-8, PorM and PorM@ZIF-8 were measured in alkaline condition (0.1 M KOH) with the number of electrons transferred being [Formula: see text] = 2.20–2.60 and generating HO[Formula: see text] as the oxygen reduction product. The catalytic property slightly increased after the porphyrin was encapsulated, due possibly to the capacity limit, inappropriate molecular distance or the direction of encapsulated porphyrin molecular.

Four tetrabutano and tetrabenzoporphyrins containing sterically hindered meso-(2,6-difluorophenyl) substituents and copper(II) or manganese(III) central metal ions were synthesized and characterized as to their electrochemical and spectroelectrochemical properties in nonaqueous media. The copper(II) derivatives exhibit the expected two one-electron reductions to give [Formula: see text]-anion radicals and dianions in CH2Cl2. Electrochemical and spectroelectrochemical data suggest that a Cu(II) phlorin anion is generated from the doubly reduced Cu(II) butanoporphyrin and it is this species which undergoes the third reduction in pyridine. The first one-electron reduction of the Mn(III) porphyrins is metal-centered to give a Mn(II) compound, while the second and third reductions are macrocycle-centered to give Mn(II) porphyrin [Formula: see text]-anion radicals and dianions in both CH2Cl2 and pyridine. A Mn(II) phlorin anion is also generated from the Mn(II) dianion on the spectroelectrochemical timescale under the given solution conditions. The [Formula: see text],[Formula: see text]-butano and benzo groups have a significant effect on the measured redox potentials. Steric hindrance of the meso-(2,6-difluorophenyl) substituents also has an effect on the potential separation between the first two oxidations of the benzoporphyrins.

In the south of China, green Tofu, comprised of a large amount of green and pollution-free cellulose, is one of most characteristic traditional foods in the local diet. Inspired by the preparation of the traditional green Tofu, we report a general protocol to fabricate biomass carbon aerogel based on extraction of cellulose from the plant leaves, freeze-drying and carbonization of cellulose. In this strategy, the plant leaves-derived celluloses were extracted from premna microphylla (PM) leaves and sisal leaves via alkalization and bleaching processes. Then, the superhydrophobic hierarchical porous carbon-X aerogel (SHPC-X aerogel) with ultralow density and excellent elastic properties were observed by carbonizing the freeze-dried celluloses. The incorporation of plant cellulose into aerogel could not only improve the specific surface areas and morphologies, but also enhance hydrophobic properties and mechanical properties of materials. When the sisal cellulose content of 200% (sisal: PM cellulose mass ratio), the SHPC-200 aerogel exhibited robust superhydrophobicity (WCA = 158°) and large specific surface areas (475.68 m2 g−1). In addition, the as-prepared SHPC-200 aerogel exhibited high absorption capacity (77.7–147.3 g g−1) for different oils and organic solvents and excellent oil recoverability, high durability, and regenerability during oil/water separation for 10 cycles. This study provides an effective strategy for fabrication of biomass carbon aerogel by using PM leaves as raw material that can be extended for the fabrication of other biomass aerogels for application in chemical separation, environmental remediation and energy storage.

The axial coordination properties of six zinc tetraarylporphyrins with seven different nitrogenous bases were examined in CH2Cl2 for derivatives containing four [Formula: see text],[Formula: see text]-fused butano or benzo groups and the equilibrium constants (log[Formula: see text] determined using spectral titration methods. The examined compounds are represented as butano(YPh)4PorZn and benzo(YPh)4PorZn, where Por is the porphyrin dianion and Y is a CH3, H or Cl substituent on the para-position of each meso-phenyl ring of the macrocycle. The initial four-coordinate butano- and benzoporphyrins will axially bind one nitrogenous base to form five-coordinate derivatives in CH2Cl2 and this leads to a 4–22 nm red-shift of the Soret and Q bands. The log[Formula: see text] values range from 1.98 to 4.69 for butano(YPh)4PorZn and from 3.42 to 5.36 for benzo(YPh)4PorZn, with the exact value depending upon the meso and [Formula: see text]-substituents of the porphyrin and the conjugate acid dissociation constants (p[Formula: see text] of the nitrogenous base.

Silver corrolates are attractive compounds from both practical and theoretical points of view. Indeed, they play a key role in peripheral functionalization reactions occurring at the macrocycle, enabling high-yield and regioselective group insertions useful to further elaborate the molecular skeleton. In parallel, the Janus innocent or noninnocent behavior of the corrole ligand in these complexes makes their description particularly challenging. Herein, we report properties for a series of silver 3,17-disubstituted triarylcorrole complexes with various functionalities (halogens or different phenylethynyl units) that deeply affect the electron density in the macrocyclic ligand, with obvious repercussions on the observed spectral characteristics. The compounds were obtained in yields of 54-92% by applying the Stille coupling reaction with the appropriate tributylethynyl stannane. Among the complexes prepared was a derivative bearing two terminal acetylenic units which opens the way to "click" reactions for new corrole-based architectures. This corrole was structurally characterized by single crystal X-ray crystallography. The addition of substituted ethynyl groups resulted in red-shifts of the electronic absorption spectra, the largest of which was observed for the compound with two β-NO2-Ph-C[triple bond, length as m-dash]C substituents. The remarkable influence of the NO2 groups on the electron density of this macrocycle was further demonstrated by electrochemical measurements, where an easier reduction of this complex derivative was observed as compared to the others. DFT calculations showed full delocalization over the entire p-nitrophenylethynyl unit of 5, largely affecting orbital distributions and the corresponding electronic absorptions. Although a variation of the β-substituents dramatically modifies the Soret- and Q-band positions towards lower energies for all the examined complexes, the saddling of the macrocycle resulting from functionalization is only moderate. The collected results suggest the description of these compounds as AgIII-corrolate3-, a metallocorrole with an innocent macrocyclic ligand.

Five meso-tetraaryl open-chain pentapyrroles were synthesized and characterized as to their electrochemistry and protonation reactions in nonaqueous media. The investigated compounds are represented as (Ar)4PPyH3 where Ar [Formula: see text],[Formula: see text]-F2Ph, [Formula: see text]-BrPh, Ph, [Formula: see text],[Formula: see text],[Formula: see text]-(OMe)3Ph or [Formula: see text]-MePh and were characterized by UV-vis and 1H NMR spectroscopy, mass spectrometry and electrochemistry. Cyclic voltammetry was used to measure redox potentials, while protonation involving the conversion of (Ar)4PPyH3 to [(Ar)4PPyH5][Formula: see text] was monitored by UV-vis absorption spectroscopy. Equilibrium constants for proton addition were calculated using the Hill equation. One of the pentapyrroles was also structurally characterized. The electrochemical data, protonation constants and crystal structure were then compared with data for previously examined pentapyrroles and analyzed as a function of the solvent properties and nature of substituents on the meso-phenyl rings of the macrocycle.

Two series of zinc tetraarylporphyrins containing four [Formula: see text],[Formula: see text]′-pyrrole fused butano or benzo groups were synthesized and characterized as to their electrochemical and spectroelectrochemical properties in nonaqueous media. The examined compounds are represented as butano(Ar)4PorZn and benzo(Ar)4PorZn, where Por is the porphyrin dianion and Ar is a [Formula: see text]-CH3Ph, Ph or [Formula: see text]-ClPh substitutent on [Formula: see text]-positions of the macrocycle. Each Zn(II) butano- and benzoporphyrin undergoes two one-electron reductions to give a [Formula: see text]-anion radical and dianion in CH2Cl2. In contrast, three reductions were observed for the benzoporphyrin derivatives in pyridine, the third of which is assigned as electron addition to a benzophlorin anion generated from the doubly reduced benzoporphyrin. Two overlapped one-electron oxidations were observed for the butanoporphyrins in CH2Cl2, a result not previously observed for any other zinc porphyrin. The electrochemically measured HOMO-LUMO gap of the benzoporphyrins ranges from 1.89 to 1.90 V in CH2Cl2 and from 1.93 to 1.95 V in pyridine. Both values are smaller than the gaps of butanoporphyrins at 2.11-2.13 V in CH2Cl2 and 2.07.2.09 V in pyridine.

Biomass carbon aerogels are emerging as attractive versatile materials have broad potential applications in various fields including energy storage, oil absorption and catalysts due to their abundance in nature, low cost and environmental friendliness. Here, we have successfully prepared a compressible, superhydrophobic and multifunctional hierarchical biomass carbon@SiO2@MnO2 aerogel (HBCSM aerogel) by using cost-effective and environmentally friendly sisal cellulose as main raw material. During this process, the cellulose@SiO2 aerogel (CS aerogel) was fabricated using sol-gel process, followed by carbonization to form biomass carbon@SiO2 aerogel (BCS aerogel). Then, the HBCSM aerogel was fabricated by in situ assembly of MnO2 nanosheets on the surface of the BCS aerogel under hydrothermal conditions. The incorporation of hierarchical SiO2@MnO2 structure into the HBCSM aerogel could not only improve the surface roughness and hydrophobic properties but also enhance the absorption capacity and mechanical durability. In addition, the HBCSM aerogel exhibits excellent superhydrophobicity with the water contact angle (WCA) of 155°. The as-prepared modified HBCSM aerogel exhibits a very large absorption capacity (60–120 g g−1) for different oils and organic solvents and the absorption capacity of the as-prepared aerogel shows a slight decrease after the repeated absorption and release of several oil and solvents for 9 cycles. This work provides a new procedure for fabrication of hybrid carbon aerogel with well-defined 3D hierarchical porous structures that may provide a new slight on the relationship between the structure and property of biomass carbon aerogel, making it a promising candidate for industrial oil-polluted water treatments and oil spill cleanup.

The hierarchical nanomaterials/biomass carbon aerogels are of great interest in various fields including oil/water separation and oil absorption based on the synergistic effects of mechanical stren...

A series of chlorin-bacteriochlorin dyads (derived from naturally occurring chlorophyll-a and bacteriochlorophyll-a), covalently connected either through the meso-aryl or β-pyrrole position (position-3) via an ester linkage have been synthesized and characterized as a new class of far-red emitting fluorescence resonance energy transfer (FRET) imaging, and heavy atom-lacking singlet oxygen-producing agents. From systematic absorption, fluorescence, electrochemical, and computational studies, the role of chlorin as an energy donor and bacteriochlorin as an energy acceptor in these wide-band-capturing dyads was established. Efficiency of FRET evaluated from spectral overlap was found to be 95 and 98 % for the meso-linked and β-pyrrole-linked dyads, respectively. Furthermore, evidence for the occurrence of FRET from singlet-excited chlorin to bacteriochlorin was secured from studies involving femtosecond transient absorption studies in toluene. The measured FRET rate constants, kFRET , were in the order of 1011 s-1 , suggesting the occurrence of ultrafast energy transfer in these dyads. Nanosecond transient absorption studies confirmed relaxation of the energy transfer product, 1 BChl*, to its triplet state, 3 Bchl*. The 3 Bchl* thus generated was capable of producing singlet oxygen with quantum yields comparable to their monomeric entities. The occurrence of efficient FRET emitting in the far-red region and the ability to produce singlet oxygen make the present series of dyads useful for photonic, imaging and therapy applications.

Four N-confused free-base tetraarylporphyrins containing an amino group on the inner carbon of the inverted pyrrole were synthesized and characterized as to their electrochemical and spectroelectrochemical properties in dichloromethane and N,N-dimethylformamide containing 0.1 M tetra-[Formula: see text]-butylammonium perchlorate as supporting electrolyte. The examined compounds are represented as (NH[Formula: see text](Ar)[Formula: see text]NcpH[Formula: see text], where “Ncp” is the N-confused porphyrin macrocycle and Ar is a [Formula: see text]-CH[Formula: see text]OPh, [Formula: see text]-CH[Formula: see text]Ph, Ph or [Formula: see text]-ClPh substituent on each meso-position of the macrocycle. Each porphyrin undergoes multiple irreversible reductions and oxidations. The first one-electron addition and first one-electron abstraction are located on the porphyrin [Formula: see text]-ring system to give [Formula: see text]-anion and [Formula: see text]-cation radicals with a HOMO–LUMO gap ranging from 1.21 to 1.34 V in CH[Formula: see text]Cl[Formula: see text] and 1.06 to 1.12 V in DMF. Both electrogenerated products are unstable and undergo a rapid chemical reaction to give new electroactive species which can be further reduced at more negative potentials or further oxidized at more positive potentials. The effects of the inner amino-substituent on the UV-vis spectra and electrochemical properties of the porphyrin are discussed, and comparisons made to data in the literature for both structurally related N-confused porphyrins containing an inner carbon NO[Formula: see text] group and derivatives without the inner substituent.

Oil-polluted water has become a worldwide problem due to ever-increasing industrial oily wastewater as well as the frequent oil spill accident. A superior oil adsorbing material capable of separating oil–water mixtures efficiently, especially with a high oil adsorption capacity and mechanical strength, is urgently desired. Here, we report a novel strategy of preparing composite foams with hierarchical porous structures for effective oil/water separation and selective oil adsorption. The composite polyurethane foam is synthetized by a facile one-step foaming technology, which uses hierarchical hollow SiO 2 @MnO 2 cubes to modify the inner structures of composite polyurethane foam. The incorporation of hierarchical hollow SiO 2 @MnO 2 cubes into the foam could not only improve the morphologies, specific surface areas and hydrophobic properties but also enhance the adsorption capacity and mechanical properties. The as-prepared composite PU foam is put into the oil/water mixture to adsorb oils, and the adsorbed oils can be recovered simply by squeezing oil from composite PU foam. The resulting composite PU foam exhibits high oil adsorption capacity, high selectivity and oil adsorption capacity for carbon tetrachloride was measured to be 31.6 g/g. Also, the composite PU foam shows excellent elasticity and the height of the composite PU foam decreased from 100% to 94% after 30 compressing–releasing cycles. Furthermore, the as-prepared composite PU foam exhibits the high reusability and durability by being reused for oil–water separation for 10 cycles without losing its hydrophobicity, which makes it a good candidate for industrial oil-polluted water treatments and oil spill cleanup.

Electrochemical and acid-base properties of four free-base triarylcorroles were examined in nonaqueous media. These compounds are represented here as (tdcc)H[Formula: see text], (tpfc)H[Formula: see text], (Br[Formula: see text]tdcc)H[Formula: see text] and (Br[Formula: see text]tpfc)H[Formula: see text], where tdcc and tpfc are the trianions of tris(2,6-dichlorophenyl)corrole and tris(pentafluorophenyl)corrole, respectively. Different spectroscopic and electrochemical properties were observed for the [Formula: see text]-brominated corroles as compared to the non-brominated derivatives, due in part to the corrole ring distortion and in part to the strong electron-withdrawing properties of the Br groups. The brominated free-base corroles are easier to deprotonate than the non-brominated corroles in solution, which was confirmed by electrochemistry and spectroelectrochemistry as well as protonation/deprotonation reactions of the compounds with acid or base in PhCN. The electrochemistry of the protonated and deprotonated corroles is presented and comparisons made with previously published data for other protonated and deprotonated free-base corroles under the same solution conditions.

Two triple-decker dinuclear sandwich dysprosium complexes, which are represented as Dy2[Pc(OC5H11)8]2[Cor(FPh)3] (1) and Dy2[Pc(OC5H11)8]2[Cor(ClPh)3] (2), were synthesized and characterized by spectroscopic and electrochemical methods in nonaqueous media. Their electronic structures were also investigated on the basis of TD-DFT calculations. The sandwich triple-decker nature with the molecular conformation of [Pc(OC5H11)8]Dy[Cor(FPh)3]Dy[Pc(OC5H11)8] for compound 1 was unambiguously revealed by single-crystal X-ray diffraction analysis and showed each dyprosium ion to be octacoordinated by the isoindole and pyrrole nitrogen atoms of an outer phthalocyanine ring and the central corrole ring, respectively. In addition, the magnetic properties of both compounds have also been characterized for exploring the functionalities of these types of triple-decker complexes.

Integrating the synergistic effect of multiple components is desirable to optimize catalytic performance of composite electrocatalysts for energy conversion and storage. Herein, the electrocatalytic hydrogen evolution reaction (HER) of a three-dimensional (3D) CuSNC@MoS2-Pt featuring Pt-doped MoS2 nanosheets grown in-situ on S, N-doped carbon substrate (CuSNC) derived from rose-like structured Cu-TCPP MOF (TCPP = 5, 10, 15, 20-tetrakis(4-carboxyphenyl)porphyrin) is investigated. Compared with single MoS2, the synergistic effects of Pt-doping, S, N-doped carbon substrate and 3D open porous structural advantages allow CuSNC@MoS2-Pt to achieve optimum alkaline HER activity with small overpotentials of 102.6, 165.6 and 199.0 mV at current densites of 10, 50 and 100 mA cm−2 respectively, and a small Tafel slope of 55.7 mV dec−1. Spectroscopic techniques and density functional theory calculations reveal that pairing of Pt-doping and S, N-doped carbon substrates in CuSNC@MoS2-Pt effectively reduce the kinetic energy barrier of water dissociation and hydrogen generation, thus improving HER activity. In addition, good hydrophilicity of CuSNC@MoS2-Pt is conducive to achieving rapid mass transport. This work provides a facile strategy for simultaneously integrating structural advantages, electrical conductivity and electronic engineering to construct advanced alkaline HER electrocatalysts.

A cobalt triphenylcorrole (CorCo) was covalently bonded to graphene oxide (GO), and the resulting product, represented as GO-CorCo, was characterized by UV–vis, FT-IR, and micro-Raman spectroscopy as well as by HRTEM, TGA, XRD, XPS, and AFM. The electrocatalytic activity of GO-CorCo toward the oxygen reduction reaction (ORR) was then examined in air-saturated 0.1 M KOH and 0.5 M H2SO4 solutions by cyclic voltammetry and linear sweep voltammetry using a rotating disk electrode and/or a rotating ring-disk electrode. An overall 4-electron reduction of O2 is obtained in alkaline media while under acidic conditions a 2-electron process is seen. The ORR results thus indicate that covalently bonded GO-CoCor can be used as a selective catalyst for either the 2- or 4-electron reduction of oxygen, the prevailing reaction depending upon the acidity of the solution.

A series of zinc[Formula: see text]-hydroxylphenylporphyrins was synthesized and characterized by spectroscopic and electrochemical methods in four different nonaqueous solvents. The investigated compounds are represented as [([Formula: see text]-HOPh)[Formula: see text](ptBuPh)[Formula: see text]P]Zn, where P represents the dianion of a porphyrin, Ph represents a phenyl group, HO and [Formula: see text]Bu are para substituents on the meso-phenyl rings of the macrocycle and [Formula: see text] = 0–4. The four utilized nonaqueous solvents were dichloromethane (CH[Formula: see text]Cl[Formula: see text], NN-dimethylformamide (DMF), dimethylsulfoxide (DMSO) and pyridine (Py) which were selected on the basis of their coordinating capabilities. The UV-visible spectra and redox potentials of each porphyrin were analyzed both as a function of Hammett substituent constants for groups at the para-positions of the meso-phenyl rings and as a function of the Gutmann solvent donor number which is related to the coordinating ability of the solvent. Each porphyrin exhibits two reductions in CH[Formula: see text]Cl[Formula: see text], DMSO and Py while three reductions are observed in DMF, the additional reaction being due to a phlorin product generated in solution after formation of the porphyrin dianion. Two or three reversible oxidations were seen in CH[Formula: see text]Cl[Formula: see text], the exact number depending upon the specific porphyrin and the presence of [Formula: see text]-OH substituents at the meso-phenyl rings of the compound. The first two oxidations were assigned as involving the conjugated macrocycle and the third is associated with oxidation of the meso-HOPh group(s).

Four methylated N-confused free-base tetraarylporphyrins, which are represented as N-CH3(Ar)4NcpH2 (Ar =CH3OPh, CH3Ph, Ph or ClPh), were synthesized and characterized in terms of their spectral and electrochemical properties in nonaqueous media. The first one-electron oxidation of each porphyrin is reversible and located at E1/2=0.51–0.71 V, whereas the first one-electron reduction is quasi-reversible and located between −0.98 and −1.11 V vs. SCE. The electrochemically measured HOMO−LUMO gap ranged from 1.62 to 1.73 V, depending upon the solvent and meso-substituents on the macrocycle, and this range of values is similar to the HOMO−LUMO gaps of both the non-methylated N-confused porphyrins, (Ar)4NcpH2 (1.60–1.68 V), and the nitrated N-confused porphyrins, NO2(Ar)4NcpH2 (1.58–1.68 V). The effect of the N-methyl group on UV/Vis spectra and reduction/oxidation potentials as well as the mechanisms of electron transfer are discussed, and comparisons made with data in the literature for both the non-methylated N-confused porphyrins and related N-confused porphyrins having the same meso-substituents and an inner nitro-substituted carbon atom.

Two meso-substituted bis-metallohexaphyrins were synthesized and characterized as to their electrochemical and spectroelectrochemical properties in nonaqueous media. The examined compounds are represented as HexaPyM2, where HexaPy represents an expanded macrocycle containing six pyrroles and M [Formula: see text] Cu(II) or Zn(II). Each hexaphyrin undergoes four reversible one-electron reductions and two irreversible oxidations in PhCN or CH2Cl2 containing 0.1 M tetrabutylammonium perchlorate. The HexaPyCu2 is much easier to reduce than the corresponding Cu porphyrin with the same meso-substituents and it is also easier to reduce than a structurally related Cu(II) tripyrrinone. All four reductions of HexaPyM2 are assigned as [Formula: see text]-ring centered electron transfers to give [HexaPyM2][Formula: see text], [HexaPyM2][Formula: see text], [HexaPyM2][Formula: see text] and [HexaPyM2][Formula: see text], respectively. The neutral HexaPyCu2 and HexaPyZn2 also exhibit two oxidations, both of which are irreversible at a scan rate of 0.10 V/s. The peak separation between the first one-electron addition and the first electron abstraction of HexaPyM2 ranges from 1.46 to 1.72 V. These non-thermodynamic HOMO–LUMO gaps are similar to the range of HOMO–LUMO gaps for previously characterized sapphyrins which contain five pyrrole ring in the macrocycle.

This review describes the known electrochemistry of corroles in nonaqueous media from 1980 until the present. The outline of the review is grouped according to the periodic table, proceeding from left to right, describing first monomeric free-base derivatives and then transition-metal compounds, followed by main-group corroles, before ending with a brief description of lanthanide and actinide corroles. Many similarities exist between the redox properties of metallocorroles and metalloporphyrins, but there are also many differences due, in part, to the different charges of the two conjugated macrocycles and the noninnocence of the corrole ligand in a variety of compounds. One part of this review will focus on describing redox behavior as a function of metal ion and axial ligands, while another will focus on how changes in structure of the macrocycle are associated with changes in redox behavior. It is hoped that this review will answer the majority of the readers' questions as to what has been electrochemically observed for corroles in the past while at the same time enabling the reader to utilize data in the literature to predict and "tune" what might be observed in future electrochemical studies of corroles that have yet to be synthesized and characterized.

Four aryl-substituted tripyrrinone copper(II) complexes were synthesized and characterized as to their electrochemical and spectroelectrochemical properties. The examined compounds are represented as (YPh)3TPO2Cu, where TPO2 is a dianion of the tripyrrinone and Y is a CH3O, CH3, H or Cl substituent on the para-position of each phenyl ring of the compound. The neutral compounds are ESR active and show a typical d9 Cu(II) signal in frozen CH2Cl2 solution. Each Cu(II) compound undergoes three reductions between −0.61 and −1.90 V and two oxidations between 1.00 and 1.24 V in CH2Cl2 containing 0.1 mol/L tetra-n-butylammonium perchlorate. The potentials for oxidation are similar to those of copper tetraarylporphyrins but the reduction potentials are positively shifted as compared to the corresponding tetraarylporphyrins. Thus, the potential difference between the first one-electron oxidation and first one-electron reduction (the HOMO-LUMO gap) of (YPh)3TPO2Cu, which ranges from 1.68 to 1.75 V, is similar to that of copper corroles (1.73–1.85 V), but smaller than the separation of 2.30–2.37 V for the copper tetraarylporphyrins under the same solution conditions.

Metalation of [14]tribenzotriphyrin(2.1.1) (TriP, 1a–d) with Re(CO)5Cl provides Re(I) tricarbonyl ReI-TriP complexes (2a–d) in 93–98% yields. The complexes were characterized by mass spectrometry, UV–Vis absorption and 1H NMR spectroscopy. Single crystal X-ray analyses reveals that 2b adopts dome-shaped conformation. The rhenium(I) ion is coordinated with three pyrrolic nitrogen atoms together with three carbonyl ligands. ReI-TriP (2a–d) complexes shown blue-shift absorption spectra which the Soret-band shifted to the region that around 390 nm. The redox properties of ReI-TriP (2a–d) were studied by cyclic voltammetry. Each compound undergoes one reversible one-electron oxidation and two reversible one-electron reductions in CH2Cl2.

Two series of β,β′-pyrrole butano- and benzo-substituted mangenese(III) tetraarylporphyrins were synthesized and characterized with regard to their spectral and electrochemical properties. The investigated compounds have the general formula butano(Ar)4PorMnCl and benzo(Ar)4PorMnCl, where Por is the dianion of the porphyrin and Ar is a p-CH3Ph, Ph or p-ClPh group on each of the four meso-positions of the macrocycle. Each manganese(III) butano- or benzoporphyrin was examined in CH2Cl2 and/or pyridine containing 0.1 M tetra-n-butylammonium perchlorate and the data then were compared to that of the parent tetraarylporphyrins having the same meso-substituents. Up to four reductions are observed for each compound, the first being metal-centered to generate a Mn(II) porphyrin, and the second and third being porphyrin ring-centered to give a Mn(II) porphyrin π-anion radical and dianion, respectively. The one-electron reduced manganese porphyrins have an ESR spectrum with signals at g⊥= 5.6–5.8 and g// = 2.0, indi...

Two A2B mono-cobalt corroles and the corresponding bis-cobalt derivatives linked by a xanthene acyl group were synthesized, characterized as to their electrochemistry and spectroelectrochemistry in nonaqueous media and then examined as catalysts for the electroreduction of O2 in 1.0 M HClO4. The investigated mono- and bis-corroles are represented as (NH2Ph)(YPh)2CorCo(PPh[Formula: see text] and [(YPh)2CorCo(PPh[Formula: see text]]2Xac, respectively, where Cor is the trianion of the corrole, Y is a CH3 or Cl substituent on the para-position of the 5- and 15-meso-phenyl rings of the macrocycle and Xac is the xanthene acyl group linking the two macrocycles in a face-to-face arrangement. The neutral compounds were characterized by cyclic voltammetry while thin-layer spectroelectrochemistry was used to elucidate UV-visible spectra of the compounds in their electrooxidized or electroreduced forms. Rotating disk and rotating ring-disk electrode measurements were also utilized to examine the electrocatalytic activity for reduction of O2 when the face-to-face corroles were adsorbed on the electrode surface in 1.0 M HClO4. The number of electrons transferred in the catalytic electroreduction of dioxygen was calculated from currents at the disk electrode using Koutecky–Levich plots. The effect of linking the two cobalt corrole macrocycles on UV-visible spectra, redox potentials and electrocatalytic activity for the reduction of dioxygen is discussed.

Three copper triarylcorroles containing a [Formula: see text]-pyrrole nitro substituent were synthesized and characterized as to their spectral and electrochemical properties in nonaqueous media. The examined compounds are represented as [Formula: see text]-NO2(YPh)3CorCu, where Cor is the trianion of a triphenylcorrole and Y is a Cl, H or CH3 substituent at the para-position of the three meso-phenyl rings of the compound. The data from absorption spectra, electrochemistry and thin-layer spectroelectrochemistry are consistent with an initial assignment of Cu[Formula: see text]-Cor[Formula: see text] in CH2Cl2, DMF and pyridine and electrogeneration of a formal Cu(II) corrole with an unreduced macrocycle, represented as Cu[Formula: see text]-Cor[Formula: see text], after the first one-electron reduction in these solvents. The doubly reduced [Formula: see text]-nitrocorrole has a sharp Soret band at 439 nm and a well-defined Q-band at 611 nm in CH2Cl2. Similar absorption spectra are seen for the three examined doubly reduced nitrocorroles in DMF and pyridine, suggesting formation of a Cu(I) species with an unreduced macrocycle which is represented as Cu[Formula: see text]-Cor[Formula: see text]. Changes in redox potentials and absorption spectra of the nitrocorroles are examined as a function of solvent and substituents on the meso-phenyl rings of the compounds and comparisons are made between spectral and electrochemical data of the newly synthesized corroles and that of structurally related tetraarylcorroles lacking a [Formula: see text]-nitro group.

Three [Formula: see text],[Formula: see text]-tetrabutano-substituted cobalt(III) triarylcorroles were synthesized and characterized by UV-vis, 1H NMR spectroscopy and mass spectrometry as well as electrochemistry and spectroelectrochemistry. The examined compounds are represented as butano-(YPh)3CorCo(PPh[Formula: see text], where Cor represents the core of the corrole and Y is a CH3, H or Cl group on the para-position of each meso-phenyl ring of the macrocycle. Each corrole undergoes two stepwise cobalt-centered reductions leading to formation of Co(II) and Co(I) derivatives in CH2Cl2 containing 0.1 M TBAP. Three reversible one-electron oxidations were observed within potential, ranging from 0.16 to 1.40 V in CH2Cl2. The first oxidation generates a mixture of Co(III) [Formula: see text]-cation radical and Co(IV), while the second oxidation is metal-centered to give the Co(IV) corrole. Each cobalt corrole was examined as a catalyst for electroreduction of O2 when coated on an edge-plane pyrrolytic graphite electrode in acidic and basic solutions. The results indicate that the cobalt tetrabutanotriarylcorroles can act as selective catalysts for the 2e reduction of molecular oxygen to give H2O2 as the final product under the given solution conditions.

A thermal reaction using a series of [14]tribenzotriphyrins(2.1.1) (TriPs, 1a–d) with Rh2(C8H12)Cl2 provides RhIII–TriP complexes (2a–d) in 40−52% yields. The complexes were characterized by mass spectrometry, UV-visible absorption and 1H NMR spectroscopy. Single crystal X-ray analysis reveals that 2b adopts a dome-shaped conformation. The rhodium(III) ion is coordinated by the three pyrrole nitrogen atoms, two chloride ions and the nitrogen atom of an acetonitrile (CH3CN) solvent molecule. The optical spectra can be assigned using Michl's perimeter model. The L and B bands of the 2a–d complexes lie at ca. 600 and 500 nm, respectively, and are markedly red shifted relative to those of 1a–d. A reversible one-electron oxidation and two reversible one-electron reductions are observed in the cyclic voltammograms of 2a–d in CH2Cl2. The redox potentials are consistent with the optical data and the relatively narrow HOMO–LUMO gaps that are predicted in DFT calculations. TD-DFT calculations have been used to assign a third intense spectral band at 375 nm to a higher energy π → π* transition of the [14]tribenzotriphyrin(2.1.1) π-system.

Metalation of 6,13,20,21-tetrakis-aryl-22H-[14]tribenzotriphyrin(2.1.1) (TriPs) with PdCl2 provides Pd(II)-TriP complexes in 45-56% yields. The complexes were characterized by mass spectrometry, and UV-visible absorption, magnetic circular dichroism, and (1)H NMR spectroscopy. A single crystal X-ray analysis reveals that the Pd(II)-TriPs adopts a deeply saddled conformation. The palladium(II) ion is coordinated by two pyrrole nitrogen atoms and two chloride ions to form the square-planar coordination environment. The redox properties of the Pd(II)-TriPs were studied by cyclic voltammetry. Each compound undergoes one irreversible and two reversible one-electron reductions. There is a marked red-shift of the main spectral bands, relative to those of the free-base TriP ligand, due to a marked relative stabilization of the LUMO upon coordination by PdCl2.

Two heteroleptic corrole–phthalocyanine europium triple-decker complexes were fabricated into organic nanostructures by the standard phase-transfer method. The investigated compounds are represented by Eu2(Pc)2[Cor(ClPh)3] (1) and Eu2[Pc(OC8H17)8]2[Cor(ClPh)3] (2), where Pc represents the dianion of phthalocyanine and Cor(ClPh)3 the trianion of 5,10,15-tri(4-chlorophenyl)corrole. Both compounds 1 and 2 show typical electronic absorption spectra for a non-aggregated molecular structure in chloroform or toluene. However, in methanol compound 1 self-assembled into belt-like nanostructures while compound 2, which possesses long OC8H17 alkoxy side chains, self-assembled into large scale sheet-like nanostructures. The third-order nonlinear optical properties of both triple-decker compounds were also investigated in toluene by the Z-scan technique and characterized as showing nonlinear reverse saturation absorption and self-defocusing behavior. A third-order nonlinear optical susceptibility, χ(3), of 3.18 × 10−10 and 3.35 × 10−10 esu was obtained for 1 and 2, respectively, thus indicating the potential application of these compounds in the field of optical devices.

Novel neo-confused octaphyrin(1.1.1.1.1.1.1.0) (1) was synthesized by oxidative ring closure of an octapyrrane bearing two terminal "confused" pyrroles. Crystal structures of its Zn(II) and Cu(II) complexes (2 and 3) show a figure-of-eight conformation with unique mononuclear coordination structures. Photophysical data and theoretical calculations suggest that the neo-confused octaphyrin 1 is a 34π electron conjugated species showing nonaromaticity. Coordination of copper and zinc ions results in the further narrowing of the HOMO-LUMO gaps.

Three series of cobalt tetraarylporphyrins were synthesized and characterized by electrochemistry and spectroelectrochemistry. The investigated compounds have the general formula (TpYPP)Co, butano(TpYPP)CoII, and benzo(TpYPP)CoII, where TpYPP represents the dianion of the meso-substituted porphyrin, Y is a CH3, H, or Cl substituent on the para position of the four phenyl rings, and butano and benzo are respectively the β- and β′-substituted groups on the four pyrrole rings of the compound. Each porphyrin undergoes one or two reductions depending upon the meso substituent and solvent utilized. Two irreversible reductions are observed for (TpYPP)CoII and butano(TpYPP)CoII in CH2Cl2 containing 0.1 M tetra-n-butylammonium perchlorate; the first leads to the formation of a highly reactive cobalt(I) porphyrin, which can then rapidly react with a solvent to give a CoIIICH2Cl as the product. Only one reversible reduction is seen for benzo(TpYPP)CoII under the same solution conditions, and the one-electron-reducti...

International audience; A series of open-chain pentapyrroles and sapphyrins with highly electron-withdrawing substituents (i.e., CN, CF3 , or CO2 Me) on the meso-phenyl rings was synthesized and characterized as to the spectral properties, protonation reactions, and electrochemistry in non-aqueous media. The investigated compounds are represented as (Ar)4 PPyH3 and (Ar)4 SapH3 where PPy and Sap correspond to the tri-anion of the open-chain pentapyrrole and sapphyrin, respectively, and Ar=p-CNPh, p-CF3 Ph, or p-CO2 MePh. UV/Vis and 1 H NMR spectroscopy as well as mass spectrometry data are given for the confirmation of the structures for the newly synthesized compounds. An X-ray structure for one of the pentapyrroles, that is, (p-CF3 Ph)4 PPyH3 (2), is also presented. The protonation processes were examined by UV/Vis absorption spectroscopy during the titration of the compounds with trifluoroacetic acid (TFA) in CH2 Cl2 . Equilibrium constants for the protonation reactions were calculated by using both the Hill equation and the mole ratio method. The protonation-initiated conversion of pentapyrroles to sapphyrins upon oxidation was also investigated. Cyclic voltammetry was used to measure the redox potentials in CH2 Cl2 , PhCN, and/or pyridine (Py). Electrochemical properties, protonation constants, and chemical reactions of the six compounds in the two series were then analyzed as a function of the solvent properties and the type of the electron-withdrawing groups on the meso-phenyl rings.

Three meso-tetraaryl substituted N -5 sapphyrins were synthesized by a facile synthetic route from the corresponding open-chain pentapyrroles in high yield using acetic acid as the solvent and catalyst. Each compound was characterized by spectroscopic and electrochemical methods and the inverted pyrrole structure was confirmed in the solid state for the first time by single crystal X-ray analysis.

We recently reported the first example of a europium triple-decker tetrapyrrole with mixed corrole and phthalocyanine macrocycles and have now extended the synthetic method to prepare a series of rare earth corrole-phthalocyanine heteroleptic triple-decker complexes, which are characterized by spectroscopic and electrochemical methods. The examined complexes are represented as M2[Pc(OC4H9)8]2[Cor(ClPh)3], where Pc = phthalocyanine, Cor = corrole, and M is Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), or Tb(III). The Y(III) derivative with OC4H9 Pc substituents was obtained in too low a yield to characterize, but for the purpose of comparison, Y2[Pc(OC5H11)8]2[Cor(ClPh)3] was synthesized and characterized in a similar manner. The molecular structure of Eu2[Pc(OC4H9)8]2[Cor(ClPh)3] was determined by single-crystal X-ray diffraction and showed the corrole to be the central macrocycle of the triple-decker unit with a phthalocyanine on each end. Each triple-decker complex undergoes up to eight reversible or quasireversible one-electron oxidations and reductions with E1/2 values being linearly related to the ionic radius of the central ions. The energy (E) of the main Q-band is also linearly related to the radius of the metal. Comparisons are made between the physicochemical properties of the newly synthesized mixed corrole-phthalocyanine complexes and previously characterized double- and triple-decker derivatives with phthalocyanine and/or porphyrin macrocycles.

Two series of copper tetraarylporphyrins containing β,β′-fused tetrabutano or tetrabenzo groups were synthesized and characterized as to their electrochemistry and spectroelectrochemistry in nonaqueous media. The examined compounds are represented as butano-(TpYPP)CuII and benzo-(TpYPP)CuII, where TpYPP is the porphyrin dianion and Y is a CH3, H or Cl substituent on the para-position of the four meso-phenyl rings of the compound. Each neutral porphyrin in the two series is ESR active and shows a typical d9 Cu(II) signal in frozen CH2Cl2 solution. Each Cu(II) porphyrin also undergoes two reversible one-electron reductions and two reversible one-electron oxidations in DMF or CH2Cl2 containing 0.1 M tetra-n-butylammonium perchlorate to give a π-anion radical and dianion upon reduction and a π-cation radical and dication upon oxidation. A third one-electron oxidation is also observed for butano-(TpYPP)Cu (Y = CH3 and H) and benzo-(TPP)Cu in PhCN and this process is assigned to the CuII/CuIII transition. The reversible half-wave potential for the first oxidation of each compound in both series is shifted negatively by about 500 mV as compared to E1/2 values for oxidation of the related copper tetraarylporphyrin without the four fused benzo or butano rings while smaller positive shifts of 60 and 300 mV are seen for reduction of the tetrabenzotetraarylporphyrins and tetrabutaotetraarylporphyrins, respectively, as compared to the same redox reactions of the related tetraarylporphyrins. The electrochemically measured HOMO–LUMO gap averages 1.76 ± 0.05 V for benzo-(TpYPP)CuII, 2.04 ± 0.06 V for butano-(TpYPP)CuII and 2.33 ± 0.03 for (TpYPP)Cu in CH2Cl2.

Three meso-substituted pyrrole-terminated tripyrrins were isolated for the first time as side products in the synthesis of triarylcorroles and characterized by spectroscopic and electrochemical techniques. The examined compounds are represented as (Ar)2TriPyH, where the TriPy is the conjugated tripyrrin monoanion and Ar a 2,6-diFPh, 2,6-diClPh or 2,4-diClPh substituent. A single crystal X-ray structure of (2,6-diFPh)2TriPyH is also presented. This is the first X-ray structure of a meso-aryl substituted tripyrrin. Each tripyrrin undergoes two reductions and three oxidations in CH2Cl2. The first one-electron addition and first one-electron abstraction lead to formation of π–anion and π–cation radicals with a potential separation between the two processes of 1.71 to 1.76 V. However, both electrogenerated products are unstable and undergo a rapid chemical reaction to give new electroactive species which are identified as the deprotonated and protonated compounds, respectively. The reaction products were characterized by spectroelectrochemistry and comparisons are made with spectroscopic data obtained during base and acid titrations in CH2Cl2.