水溶液中一种离子菁J-聚集体引起相反电荷离子菁形成J-聚集体的影响因素

水溶液中的聚电解质可引起离子菁生成聚集体,考虑到离子菁J-聚集体与聚电解质的一些相似性,我们研究了其对相反电荷离子菁J-聚集体生成的引发作用。本文分析了离子菁J-聚集体引起相反电荷离子菁生成J-聚集体的影响因素,讨论了引发聚集与被引发聚集的离子菁的电性、它们本身的结构之间的相互关系及外加无机盐对引发聚集效应产生的影响。     

Exciton-coupled charge-transfer dynamics in a porphyrin J-aggregate/TiO(2) complex

Exciton-coupled charge-transfer (CT) dynamics in TiO(2) nanoparticles (NP) sensitized with porphyrin J-aggregates has been studied by femtosecond time-resolved transient absorption spectroscopy. J-aggregates of 5,10,15-triphenyl-20-(3,4-dihydroxyphenyl) porphyrin (TPPcat) form CT complexes on TiO(2) NP surfaces. Catechol-mediated strong CT coupling between J-aggregate and TiO(2) NP facilitates interfacial exciton dissociation for electron injection into the conduction band of the TiO(2) nanoparticle in pulse width limited time (<80 fs). Here, the electron-transfer (<80 fs) process dominates over the intrinsic exciton-relaxation process (J-aggregates: ca. 200 fs) on account of exciton-coupled CT interaction. The parent hole on J-aggregates is delocalized through J-aggregate excitonic coherence. As a result, holes immobilized on J-aggregates are spatially less accessible to electrons injected into TiO(2) , and thus the back electron transfer (BET) process is slower than that of the monomer/TiO(2) system. The J-aggregate/porphyrin system shows exciton spectral and temporal properties for better charge separation in strongly coupled composite systems.     

Photodriven Charge Separation and Transport in Self‐Assembled Zinc Tetrabenzotetraphenylporphyrin and Perylenediimide Charge Conduits

Zinc tetrabenzotetraphenyl porphyrin (ZnTBTPP) covalently attached to four perylenediimide (PDI) acceptors self‐assembles into a π‐stacked, segregated columnar structure, as indicated by small‐ and wide‐angle X‐ray scattering. Photoexcitation of ZnTBTPP rapidly produces a long‐lived electron–hole pair having a 26 Å average separation distance, which is much longer than if the pair is confined within the covalent monomer. This implies that the charges are mobile within their respective segregated ZnTBTPP and PDI charge conduits.     

Metalloporphyrin heterodimers,molecular bilayer fibers and monolayer leaflets

Amphiphilic metalloporphyrins assemble in water to form supramolecular fibers, which have been characterized by transmission electron microscopy. Loose octopus porphyrin fibers can be doped with hydrophobic electron acceptors, metalloporphyrin monomolecular sheets are crystalline. Charge separation occurs in amino porphyrin fibers without added electron acceptors. Bolaamphiphilic porphyrins with four pyridinyl or methyl pyridinium groups in β-pyrrolic positions have been synthesized. The regioisomer mixture is very soluble in water (≌ 0.1 M) and is ideally suited to form heterodimers with negatively charged ms-tetrasubstituted porphyrins. Bimetallic porphyrinate pairs are described. The zinc complex is stable down to pH 1.0. Regioisomer II forms well-defined molecular monolayer leaflets in bulk water at pH 2.5. The surface structure of such monolayers is discussed. It consists of a large cationic plane and hydrophobic edges. Possible applications are discussed shortly.     

Superimposed saddle and ruffled distortions of the porphyrin in iodo(pyridine‐N)(5,10,15,20‐tetraphenylporphyrinato‐κ4N)rhodium(III) toluene solvate

In the title compound, [RhI(C₄₄H₂₈N₄)(C₅H₅N)]·C₇H₈, the porphyrin ring experiences significant distortion from planarity (a saddle conformation with a superimposed ruffling), as a result of steric interactions with the 2,6‐H atoms of the axial pyridine ligand. This also leads to a slight lengthening of the Rh–pyridine bond [Rh—N 2.102 (7) Å] relative to those seen in other pyridine adducts of six‐coordinate Rh^III. The metric parameters of the porphyrin core are comparable with those of related metalloporphyrin derivatives. No significant intermolecular interactions are observed between the metalloporphyrin and disordered solvate species.     

Preparation of PMMA Electrospun Fibers Bearing Porphyrin Pendants and Photocatalytic Degradation of Organic Dyes

Porphyrins have a large π–π conjugation force between molecules, and they are easy to aggregate in solution, which affects the photoelectric properties of porphyrins. Connecting porphyrins to polymer links through covalent bonds not only retains the mechanical properties and thermal stability of polymer materials, but also has the photoelectric properties and catalytic properties of porphyrins, which improves the availability of materials. In this study, first, a porphyrin ligand with double bonds in the side chain was designed and the corresponding copper and zinc complexes were synthesized by adjusting the metal ions in the center of the pyrrole ring. Then, the metalloporphyrin complexes were copolymerized with methyl methacrylate (MMA), and two metalloporphyrin/PMMA copolymers were obtained: CPTPPCu/PMMA and CPTPPZn/PMMA. The structure of the compounds was characterized by IR, ¹H NMR, MS, and UV-Vis spectra. Metalloporphyrin/PMMA copolymers were prepared into electrospun fiber materials by electrospinning. The morphology of the composites was studied by SEM, and the thermal stability and optical properties of electrospun fibers were studied by TGA and FL. The catalytic activity of electrospun fiber materials for the degradation of organic dyes was studied. The results showed that the efficiency of the metalloporphyrin/PMMA copolymer in photocatalytic degradation of methylene blue (MB) was better than that of the PMMA electrospun fiber blended with metalloporphyrin.     

Self-organized monolayer assemblies of octopusporphyrins: photoinduced electron transfer and O 2 coordination in aqueous media

Bolaamphiphilic tetraresorcinolporphyrins with eight long side chains (octopusporphyrins) and their metal complexes form monolayered assemblies in bulk aqueous solution. The nano-structure, the photoinduced electron transfers and the O₂ coordination of these octopusporphyrin assemblies are described. In the micellar fibers of 1a and 1b, a unique spherical arrangement of eight methyl groups on both sides of the porphyrin ring plane provides hydrophobic porphyrin centers which align in a string of pearls. Exciton calculations indicated a tilt stacking porphyrins arrangement with a separation of 11 Å. These fibers fluoresced strongly; electron transfer reaction was therefore observed between the porphyrin center and hydrophobic quenchers as well as hydrophilic quenchers. The fibers were also active as photocatalysts in the reduction of dimethylviologen by triethanolamine. Octopusporphyrins with different metal centers can also produce fibrous aggregates, for example, H₂P/Zn(II)P and Zn(II)P/Fe(III)P couples. The fluorescence quenching of Zn(II)P in the Zn(II)P/Fe(III)P hybrid fibers can be ascribed to the intermolecular electron transfer within the fibers. In H₂P/Zn(II)P couple, excitation energy transfer from excited Zn¹*P to H₂P occurred after photoexcitation. Octopusporphyrin with four dialkylglycerophosphocholine groups on both sides of the ring plane ( 2b ) forms spherical unilamellar vesicles. Based on cryomicroscopy, a white line was observed with a diameter of 15 Å in the middle of the membrane which are obviously a porphyrin layer with low molecular packing. The octopusheme ( 2c ) vesicles prepared in a similar manner with 20-fold excess molar coexistence of 1-dodecyl-2-methylimidazole (DMIm) can bind and release oxygen reversibly at 25°C. Moreover, water-soluble octopusporphyrin ( 3a ) produced fluorescent and non-fluorescent monolayer assemblies by anion exchange of the head groups, e.g. 3a with sodium perchlorate showed planar sheets. An exciton calculation is consistent with a two-dimensional arrangement with porphyrin separations of 25.6 and 17.4 Å in the x- and y-directions, respectively. External addition of negatively charged electron acceptors, naphtoquinone sulfonate and anthraquinone sulfonate, led to partial quenching of the fluorescence of the central porphyrin layer. The results have been evaluated using equations derived for this special quenching. © 1998 John Wiley & Sons, Ltd.     

TRANSFER OF EXCITATION ENERGY BETWEEN PORPHYRIN CENTERS OF A COVALENTLY-LINKED DIMER*

Abstract— Three covalently-linked porphyrin hybrid dimers were synthesized, each containing a metallotetraarylporphyrin [Zn(II), Cu(II), or Ni(II)], and a free base tetraarylporphyrin. Transfer of singlet excitation energy from the metalloporphyrin center to the free base porphyrin center was determined by measuring fluorescence properties. The Zn hybrid dimer displayed excellent intramolecular transfer of energy ( 85%) from the excited singlet state of the Zn(II) chromophore to the free base chromophore. No evidence for such transfer of the excited singlet state energy was found in the Ni(II) or Cu(II) analogues. From our experimental data, the fluorescence quantum yield of the Zn hybrid dimer was the same as for the free base monomer porphyrin (0.11; Seybold and Gouterman, 1969). Thus, the covalent attachment of another fluorescent porphyrin center effectively doubled the antenna size without decreasing the quantum yield even though the fluorescence quantum yield of the Zn(II) containing monomer was substantially less (0.03, according to Seybold and Gouterman, 1969) than that of the free base porphyrin. The donor-acceptor distance and the rate constant for energy transfer were calculated using the Forster equation. Assuming random orientation, a donor-acceptor distance of 15 Å was calculated with an associated rate constant (k_ci) for energy transfer of 1.9 ± 10₉ s_–1.     

Supramolecular Assembly of Functionalized Metalloporphyrins. Porous Crystalline Networks of Zinc-Tetra(4-Carboxyphenyl)Porphyrin

Abstract

Two crystalline compounds based on the Zn-tetra (4-carboxyphenyl)porphyrin building block have been prepared and structurally analysed by x-ray diffraction in order to ellucidate the characteristic supramolecular aggregation modes of this functionalized metalloporphyrin moiety. Crystals of the 1:1 complex with sec-phenethyl alcohol (1) are monoclinic, space group I2/a (No. 15), a = 14.420(1), b = 24.678(2), c = 33.688(2) Å, β = 90.03(2)°, D_c = 1.082 g/cm³, Z = 8, R = 0.080 for 3053 data. Those of the 1:3 complex with dimethylsulphoxide (2) are monoclinic, space group P2₁/n (No. 14), a = 14.881(1), b = 8.986(2), c = 37.550(3) Å, β = 94.21(1)°, D_c = 1.444 g/cm³, Z = 4, R = 0.093 for 4200 data. The two compounds consist of nearly square-pyramidal five-coordinate metalloporphyrin species, molecules of the sec-phenethyl alcohol (in 1) and dimethylsulphoxide (in 2) linking to the metal center at the axial site. In 2, two additional molecules of dimethylsulphoxide associate through H-bonds to the terminal carboxylic substituents of the porphyrin framework. Incorporation of the carboxylic functionality into the tetraarylporphyrin unit leads to the formation of hollow hydrogen-bonded lattices in both crystals. Uniquely structured two-dimensional networks of the porphyrin building blocks with very large cavities (approximately 16 × 21 Å) are formed in 1. These networks mutually interpenetrate each other in order to fill the empty voids, yielding a spectacular ‘concatenated’ arrangement.

One-dimensional polymeric patterns with smaller cavities (6.5 × 10 Å) are built in 2 by the interacting molecular components. In the condensed crystalline environment each such cavity is occupied by two dimethylsulphoxide molecules of adjacent chains. This study is part of an ongoing evaluation of the utility of functionalized metalloporphyrin building blocks in the designed construction of hollow lattices (with varying degree of rigidity and pore size) in molecular based solids. Correlation of current results to previous findings is also discussed.     

A five‐coordinate ruthenium(II)–porphyrin–carbene complex: [bis(3‐trifluoromethylphenyl)methylene‐κC](5,10,15,20‐tetra‐p‐tolylporphyrinato‐κ4N)ruthenium(II)

The stable title tri­fluoro­methyl‐substituted carbenyl metalloporphyrin, [Ru(C₁₅H₈F₆)(C₄₈H₃₆N₄)], has a five‐coordinate Ru atom which is displaced from the porphyrin N₄ plane towards the axial carbene ligand by 0.230 (3) Å. The Ru—C(carbene) bond coincides with a crystallographic twofold axis and its length of 1.841 (6) Å is notably shorter than the value of 1.868 (3) Å in the pyridine adduct.     

Formation of mixed J-aggregates of cyanine dyes stimulated by Eu<Superscript>+3</Superscript> cations

The block mechanism of the formation of J-aggregates from the dimers of various dyes in an aqueous solution under the action of the multiply charged Eu⁺³ cation was considered for the first time. It was shown that the structure and the position of the absorption maximum of the mixed J-aggregates are determined by the length of the dye chromophore moiety. It was concluded that the mixed J-aggregates are of interest as nanosized optical elements with varying optical and electronic properties depending on the structure of cyanines used.     

Synthesis of non-covalent BODIPY–metalloporphyrin dyads and triads

Boron-dipyrromethenes (BODIPY) containing oxypyridine substituents at 3- and 3,5-positions and metalloporphyrins (Zn(II), Ru(II)) were used to synthesize four non-covalent BODIPY–metalloporphyrin dyads and four BODIPY–metalloporphyrin triads assembled using metal–pyridine ‘N’ interaction. The formation of BODIPY–metalloporphyrin assemblies was confirmed by 1D and 2D NMR methods and X-ray crystal structure obtained for one of the BODIPY–metalloporphyrin dyad. In ¹H NMR, the signals of oxypyridine group(s) of BODIPY unit showed significant upfield shifts supporting the coordination of oxypyridine group of BODIPY unit to metalloporphyrin unit. The NMR study also indicated that Zn(II) porphyrin forms relatively weak BODIPY–Zn(II) porphyrin conjugates, whereas Ru(II) porphyrin forms strong BODIPY–Ru(II) porphyrin conjugates. The X-ray structure solved for BODIPY–Zn(II)porphyrin dyad revealed that the Zn(II) porphyrin coordinated to the BODIPY unit obliquely and the angle between the Zn(II) porphyrin and the pyridyl ring is 70°. The absorption properties of stable BODIPY–Ru(II) porphyrin conjugates showed the overlapping absorption features of both the components and the fluorescence studies indicated that the BODIPY unit emission was significantly quenched on coordination with RuTPP(CO) unit. The electrochemical studies exhibited the features of both BODIPY and metalloporphyrin units in dyads and traids.     

The nmr spectra of porphyrins—15: Self-aggregation in zinc(II) protoporphyrin-IX dimethyl ester

Complex formation in Zn(II) protoporphyrin-IX dimethyl ester has been studied by proton and ¹³C NMR spectroscopy. The large concentration dependence of the spectra has been studied by the technique of porphyrin/axial ligand titration, which together with selective decoupling and regiospecific deuterium labelling allows the assignment of all the peripheral proton and ¹³C nuclei in both the monomeric and aggregated species. Titration of the metalloporphyrin with various basic ligands (pyrrolidine, pyridine, lutidine) showed that dissociation of the aggregate was complete for a 1:1 porphyrin/added base ratio. The concentration dependence of the spectra was then analyzed to give the monomer and monomer-dimer shifts for all the assigned nuclei. Analysis of the monomer-dimer shifts in terms of the ring current model gives good agreement with a dimer geometry in which the inter-ring separation is ca. 4.5 Å and there is a smaller lateral displacement of the porphyrin rings. The dimer geometry is such that rings A and B of one porphyrin molecule are situated over rings C and D of the other. These results confirm our earlier suggestions of intermolecular metal-to-porphyrin binding in these metalloporphyrins, and further suggest that charge-transfer interactions may also be present in appropriate cases. The discrepancy between the absolute values of the observed and calculated monomer-dimer shifts, which was formerly attributed to multiple aggregation, is now suggested to be due to ensemble-averaging in the dimer structure.     

J-Aggregates Formed by NaCl Treatment of Aza-Coating Heptamethine Cyanines and Their Application to Monitoring Salt Stress of Plants and Promoting Photothermal Therapy of Tumors

The cationic nature of heptamethine cyanines gives them the capacity to form aggregates with salts by electrostatic interactions. In this work, NaCl promoted J-aggregate formation of aza-coating heptamethine cyanines is explored. NaCl can induce the N-benzyloxycarbonyl Cy-CO₂Bz to assemble into a J-aggregate having an absorption at 890 nm. Its excellent fluorescence response to NaCl implies that it has great potential for use as a probe for tracing salt stress in plants. Moreover, NaCl also promotes formation of J-aggregates from the N-ethyloxycarbonyl Cy-CO₂Et . The aggregate shows an intense absorption at 910 nm compared to the monomer which absorbs at 766 nm. Its J-aggregated form can serve as a photothermal agent. And the photothermal conversion efficiency is increased from 29.37 % to 57.59 %. This effort leads to the development of two applications of new cyanine J-aggregates including one for tracing salt stress of plants and the other for promoting photothermal therapy of tumors.     

Light‐Driven Charge Separation in Isoxazolidine–Perylene Bisimide Dyads

A series of arrays for light‐driven charge separation is presented, in which perylene tetracarboxylic bisimide is the light‐absorbing chromophore and electron acceptor, whereas isoxazolidines are colourless electron donors, the electron‐releasing properties of which are increased with respect to the amino group by means of the α‐effect. Charge separation (CS) in toluene over a distance ranging from ≈10 to ≈16 Å, with efficiencies of ≈95 to ≈50 % and CS lifetimes from 300 ps to 15 ns, are demonstrated. In dichloromethane the charge recombination reaction is faster than charge separation, preventing accumulation of the CS state. The effects of solvent polarity and molecular structure are discussed in the frame of current theories.     

Gold nanoparticle enhanced charge transfer in thin film assemblies of porphyrin-fullerene dyads

Photoinduced vectorial electron transfer in a molecularly organized porphyrin-fullerene (PF) dyad film is enhanced by the interlayer charge transfer from the porphyrin moiety of the dyad to an octanethiol protected (dcore approximately 2 nm) gold nanoparticle (AuNP) film. By using the time-resolved Maxwell displacement charge (TRMDC) method, the charge separation distance was found to increase by 5 times in a multilayer film structure where the gold nanoparticles face the porphyrin moiety of the dyad, that is, AuNP|PF, compared to the case of the PF layer alone. Films were assembled by the Langmuir-Blodgett (LB) method using octadecylamine (ODA) as the matrix compound. Atomic force microscopy (AFM) images of the monolayers revealed that AuNPs are arranged into continuous, islandlike structures and PF dyads form clusters. The porphyrin reference layer was assembled with the AuNP layer to gain insight on the interaction mechanism between porphyrin and gold nanoparticles. Interlayer electron transfer was also observed between the AuNPs and porphyrin reference, but the efficiency is lower than that in the AuNP|PF film. Fluorescence emission of the reference porphyrin is slightly quenched, and fluorescence decay becomes faster in the presence of AuNPs. The proposed mechanism for the electron transfer in the AuNP|PF film is thus the primary electron transfer from the porphyrin to the fullerene followed by a secondary hole transfer from the porphyrin to the AuNPs, resulting in an increased charge separation distance and enhanced photovoltage.     

Dibromo[5,10,15,20‐tetrakis(4‐methoxyphenyl)porphyrinato‐κ4N]platinum(IV) chloroform acetonitrile solvate

In the title compound, [PtBr₂(C₄₈H₃₆N₄O₄)]·0.896CHCl₃·0.569CH₃CN, the centrosymmetric metal complex is octahedral, with the porphyrin ring essentially planar and the Br atoms occupying axial positions. The two independent methoxy­phenyl substituents are tilted at angles of 89.0 and 67.0° with respect to the porphyrin plane. The Pt—N distances are 2.035 (4) and 2.036 (4) Å and the Pt—Br distance is 2.4666 (6) Å. Chloro­form and aceto­nitrile solvent mol­ecules, exhibiting substantial disorder, occupy positions between the porphyrin mol­ecules. This is the first crystal and molecular structure of a Pt^IV–porphyrin complex to be reported.     

The interaction of 2-hydroquinone-5,10,15,20-tetra(p-hydroxyphenyl)porphyrin with surfactants: solubilization and J-aggregates

J-aggregates of 2-hydroquinone-5,10,15,20-tetra(p-hydroxyphenyl)porphyrin (HQTHPP) induced by N-lauroyl sarcosine (SKL) in aqueous neutral solutions have been studied by optical absorption, fluorescence, and resonance light-scattering spectroscopies. As SKL concentration increases, the spectra evolve to reveal the presence of four independent species with relative concentration. The most important species is J-aggregates. The J-aggregates have two strong exciton bands corresponding to the B-band and Q-bands of HQTHPP monomers, and are found to be stable when the surfactant concentration is below 8.0 mmol/L. But above 8.0 mmol/L, the J-aggregates dissolve gradually into another species: porphyrin monomers. The total fluorescence of HQTHPP is quenched due to the aggregate formation. A strong and sharply peaked resonance light-scattering signal (>1800 counts/s, centered at 490 nm) is observed just slightly to the red of the J-aggregate absorption maximum. In the case of cetyltrimethyl-ammonium bromide, increasing surfactant concentrations have only shown to favor solubilization of porphyrin monomers. Evidently, the nature of polar headgroups of surfactants influences the tendency of THPP to aggregate.     

Synthesis and structural studies of early transition metalloporphyrin complexes. 1. X-ray structures of meso-5,10,15,20 tetratolyl hafnium(IV) μ-dioxo dimer complex and meso-5,10,15,20 tetratolyl porphyrin vanadium(IV) oxo complex

Abstract

(TTP) hafnium dichloride, 1, where TTP = meso-5,10,15,20 tetratolyl porphyrin dianion, has been synthesized and spectroscopically characterized as a precursor to 2. Hydrolysis of 1 gives (TTP) hafnium μ-dioxo dimer, 2. (TTP) vanadium oxo complex, 3, can be obtained by hydrolysis of the corresponding chloro complex. Compound 2 has been characterized by spectroscopic and single crystal X-ray diffraction analyses. [(TTP)HfO]₂-toluene crystalizes in the space group C2/c, a = 31.906(6) Å, b = 16.864(3) Å, c = 19.180(4) Å, β = 117.52(3)°, V = 9152(3) ų, d_calcd = 1.369 g/cm³, Z = 8, 6029 unique observed reflections, final R = 0.077. The Hf atom is 1.02 Å from the plane of the porphyrin ring; Hf-O bond lengths are 2.1 Å. The hafnium atoms are 3.06(1) Å from each other and the average Hf-O-Hf angle is 94°. The porphyrin rings are 5.4° from being parallel and the distance between the centers of the porphyrin rings is ～ 5.1 Å. TTPVO·mesitylene, 3, crystallizes from mesitylene in the space group P1, a = 8.365(2), b = 10.320(3), c = 14.380(5) Å, α = 91.91(3), β = 91.44(3), γ = 108.26(2)°, V = 1177.2(6) ų, d_calcd = 1.27 g/cm³, Z = 1, 1851 observed unique reflections, final R = 0.069. The average V - N distance = 2.016 Å. The coordination geometry around the vanadium is distorted C_4V. The V = O group is disordered about the center of inversion. The vanadium atom resides 0.57 Å above the plane of the nitrogens. The (ring center) -V = O angle is 165.9° while the V = O vector is essentially colinear with the vector normal to the plane of nitrogens.     

The first phosphite complex of a metalloporphyrin

(Di­phenyl phosphite‐κO)(5,10,15,20‐tetra­phenyl­porphyrinato‐κ⁴N)­manganese(III) hexa­fluoro­antimonate(V), [Mn(C₄₄H₂₈N₄)(C₁₂H₁₁O₃P)](SbF₆), is the first example of a structurally characterized di­aryl or di­alkyl phosphite complex of a metal–porphyrin ion. The axial phosphite ligand binds to the Mn^III ion via the P=O O atom, affording a nominally five‐coordinate complex with an Mn—O distance of 2.120 (4) Å. The mean porphyrin Mn—N distance is 2.000 (4) Å and the Mn^III ion is displaced from the 24‐atom porphyrin mean plane by 0.1548 (13) Å towards the axial O atom. The porphyrin adopts a marked saddle conformation, with a small domed component. The saddle distortion of the porphyrin ligand reflects the tight back‐to‐back dimers formed in the lattice by pairs of neighboring cations. The `non‐covalent' dimers in the lattice exhibit an unusual (weak) η²‐type coordination of a pyrrole C=C bond from a neighboring mol­ecule, with Mn^III⃛C distances of 3.697 (5) and 3.537 (5) Å.