Narrow Results

A new copper deuteroporphyrin functionalized by two pyrrole groups has been synthesized. This complex was isolated and characterized by ¹HNMR, UV-visible spectroscopy, mass spectrometry and electrochemistry. This functionalization has allowed the preparation of the first example of metallodeuteroporphyrin film by oxidative electropolymerization. The redox properties of the resulting modified electrode have been investigated by cyclic voltammetry. The voltammograms display the regular electroactivity of copper deuteroporphyrin as well as that related to the polypyrrole skeleton. Owing to its cross-linked structure this polymeric film exhibits a relatively good electrochemical stability. In addition, it appears that the electropolymerization yield is markedly better than those previously reported for pyrrole-substituted copper tetraphenylporphyrin. Preliminary experiments have demonstrated the possibility to use this kind of electrode material in aqueous media.

A stepwise synthesis method was used to encapsulate tetrachloro-tetramethyl porphyrin in NaCoX molecular sieve supercages. Characterization of the encapsulated porphyrin was carried out by UV-vis and IR Spectroscopy, DTA, SEM and EPR. A comparison was made of the activities of tetrachloro-tetramethyl porphyrin, its Co(II) complex, NaCoX molecular sieve and the encapsulated porphyrin as catalysts in the oxidation reactions of styrene and p-cresol. The stability and catalytic capability of the metalloporphyrin were increased after combination of the porphyrin with the molecular sieve. In addition, this new type of catalyst, tetrachloro-tetramethyl porphyrin encapsulated in NaCoX molecular sieve supercages, not only possesses the advantages of both the porphyrin and the molecular sieve, but also makes up for their respective deficiencies. In this study, another method called sealing–melting was also used to encapsulate the Zn(II) complex of meso-tetraphenyl-tetrabenzoporphyrin into NaY molecular sieve supercages. The catalytic capabilities of the free Zn(II) complex of meso-tetraphenyl-tetrabenzoporphyrin, the Zn(II) complex encapsulated in NaY molecular sieve supercages and the NaY molecular sieve itself in the oxidation of styrene by hydrogen peroxide were also studied. The experimental results again confirmed that both the stability and catalytic capability of the metalloporphyrin encapsulated in molecular sieve supercages are increased.

Polymer-bound cobalt(II) porphyrins were studied for their dioxygen—binding capacity. Tetra—aminoporphyrins were anchored on a divinylbenzene (DVB)-crosslinked chloromethyl polystyrene network. The crosslinked, solid polymers were swelled in chloroform and the swollen polymers were used for the entire studies. Ortho-, meta- and para-substituted porphyrin systems were developed by adjusting the bonding position with the help of suitably substituted aminoporphyrins. The products were characterized by chemical and spectroscopic methods. Cobalt(II) complexes of polymeric porphyrins were synthesized and characterized by electronic and ESR spectral methods. The spectra gave evidence for the systematic variation of electronic properties in ortho, meta and para compounds and for the dioxygen-binding capacity of cobalt complexes. These results are discussed.

A series of new fluoropolymer, poly(styrene-co-trifluoroethylmethacrylate) (poly-Sty_n-co-TFEM_m), with different composition ratios of Sty and TFEM units, is synthesized and applied to the matrix of an optical oxygen sensing probe using phosphorescence quenching of metalloporphyrins, platinum and palladium octaethylporphyrin (PtOEP and PdOEP), by oxygen. The phosphorescence intensity of PtOEP and PdOEP in poly-Sty_n-co-TFEM_m film decreased with increase of oxygen concentration. The ratio I₀/I₁₀₀ is used as a sensitivity of the sensing film, where I₀ and I₁₀₀ represent the detected phosphorescence intensities from a film exposed to 100% argon and 100% oxygen, respectively. For PtOEP in poly-Sty_n-co-TFEM_m film, I₀/I₁₀₀ ratios are more than 20.6 and large Stern–Volmer constants greater than 0.49%^-1 are obtained compared with PtOEP in PS film. For PdOEP in poly-Sty_n-co-TFEM_m film, on the other hand, large I₀/I₁₀₀ values greater than 188.7 are obtained. In both cases for PtOEP and PdOEP, I₀/I₁₀₀ values increased with increase of the number of TFEM units in poly-Sty_n-co-TFEM_m. The response times of PtOEP and PdOEP immobilized in poly-Sty₁-co-TFEM_2.50 films are 5.5 and 3.0 s on going from argon to oxygen and 90.0 and 143 s from oxygen to argon, respectively. These results show that PtOEP and PdOEP immobilized in poly-Sty_n-co-TFEM_m films are highly sensitive devices for oxygen.

A new dyad 9(ZnP-P) has been synthesized linking 5,15-bis(4-carboxyphenyl)-10,20-bis(4-nitrophenyl) porphyrin 4(P) and Zn(II) 5-(4-aminophenyl)-10,15,20-tris(4-methoxylphenyl) porphyrin 8(ZnP) by an amide bond. The structural moieties of dyad 9(ZnP-P) present both different singlet state energy and redox properties. Dyad 9 was designed to improve the intramolecular electron transfer capacity. The ZnP moiety bears electron-donating methoxy groups and a zinc ion, while the other porphyrin structure, P, is substituted by electron-withdrawing nitro groups. On the other hand, structure P bears a carboxylic acid group, which is able to benefit from the orientation of dyad 9 adsorbed on the SnO₂ electrode. Absorption spectroscopic studies indicated only a very weak interaction between the chromophores in the ground state. The fluorescence analysis shows that both porphyrin moieties in dyad 9 are strongly quenched and that the quenching increases in a polar solvent. The ZnP moiety acts like an antenna for porphyrin P, but, singlet-singlet energy transfer is not complete. Thermodynamically, dyad 9 presents a high capacity to form the photoinduced charge-separated state, ZnP^·+-P^·-. Dyad 9 sensitizes the SnO₂ electrode and the photocurrent action spectrum closely matches the absorption spectrum, which confirms that light absorption by dyad is the initial step in the charge transfer mechanism. The photocurrent efficiency of dyad 9 is considerably higher than those of porphyrin monomers used as models of ZnP and P structures. Two processes may be contributing to enhance the charge injection efficiency in dyad 9; one involves an antenna effect that produces energy transfer from ZnP to P and the other includes electron transfer from the ZnP moiety to the photooxidizable free-base P. This dyad design, with P in direct contact with the substrate through the free carboxylic acid group, is a promising architecture of organic material for spectral sensitization of semiconductor solar cells.

Two iron complexes of a porphyrin dimer molecule were synthesized and studied at the air-water interface and in Langumir-Blodgett (LB) films. Surface pressure-area isotherm and UV-vis absorption spectroscopic studies revealed an interesting molecular switching behavior between the two iron porphyrin complexes under basic or acidic conditions. Such a reversible structural transition does not only occur in solution phase, but readily takes place in the deposited Langmuir-Blodgett films. Domains with strip or disk-like shapes were formed in the Langmuir films of the metalloporphyrin complexes when barbituric acid was added into the subphase, an indication of supramolecular network formation between the metalloporphyrin dimer and barbituric acid molecules. Magnetic property studies of the Langmuir-Blodgett films of the iron porphyrin complexes by magnetic force microscopy provide further insights into relationships between the magnetic response and molecular structures of the metalloporphyrin LB films.

Toluene oxidation with molecular oxygen as the sole oxidant, and μ-oxo-bis[tetraphenylporphinatoiron(III)] as the catalyst, are reported. Under the reaction conditions of 438 K and 0.8 MPa, the molar total yields for the products benzaldehyde and benzyl alcohol and the turnover number of the catalyst are 4.35% and 21,830 (based on the metal ion), respectively. Compared with the reaction catalyzed by the corresponding monometalloporphyrin TPPFe^IIICl, the total yields of the oxidation products and the catalyst turnover number by the dimeric iron porphyrin were almost twice those by the former. A possible reaction mechanism of the toluene oxidation by μ-oxo-bis[tetraphenylporphinatoiron(III)] is proposed.

This review explores recent developments of photoinduced electron transfer systems based on interlocked molecules, especially [60]fullerene (C₆₀) and porphyrin-containing [2]rotaxanes. A number of synthetic methodologies for the construction of C₆₀-containing interlocked molecules with various photo- and electro-active moieties, such as metalloporphyrins, metallophthalocyanines, triarylamines, and ferrocenes, in addition to the photoinduced electron transfer behaviors of these interlocked molecules, are examined. A synthetic strategy for a multi-step photoinduced electron transfer system based on interlocked molecules is also discussed.

The synthesis of a Zn(II) porphyrin-fullerene dyad in which the two chromophore units are tethered by a conformationally-flexible linker, is described. The synthesis is highlighted by the use of a cross metathesis strategy to prepare the linker between the chromophores. Photoexcitation of the Zn(II) porphyrin unit of the dyad in tetrahydrofuran leads to substantial (77%) quenching of porphyrin fluorescence. The multiple exponentials fluorescence decay kinetics observed are attributed to different rates of electron transfer from photoexcited porphyrin to fullerene in the various conformers present. A charge-separated state with a 330 ns lifetime is observed by transient spectroscopy.

Efficient selective oxidation of ketones to lactones by molecular oxygen with benzaldehyde as an oxygen acceptor, in the presence of metalloporphyrins, has been reported. Iron(III) meso-tetraphenylporphyrin chloride (Fe(TPP)Cl) showed excellent activity and selectivity for oxidation of cyclohexanones under mild conditions. Moreover, different factors influencing ketones oxidation, e.g. catalyst, solvent, temperature and additive, have been investigated. The turnover number (TON) of the Fe(TPP)Cl catalyst could reach up to 71000 in a large scale oxidation of cyclohexanone. A plausible mechanism of ketone oxidation by molecular oxygen in the presence of metalloporphyrins and benzaldehyde was proposed.

Tetrapyrrolic compounds such as porphyrins are known to be prospective chemotherapeutics and photosensitizers for cancer treatment and diagnosis. In this work, water-soluble, meso-substituted cationic pyridyl-porphyrins and their metallocomplexes bearing various central metal atoms (Ag, Zn, Co, and Fe) in the porphine ring and various functional groups (allyl, oxyethyl, butyl, and methallyl) at the nitrogen atom in the pyridine ring were synthesized and characterized by ¹H and ¹³C NMR and UV-visible spectroscopy. Cytotoxic and photodynamic activities of new porphyrins and their metal derivatives were investigated in vitro (KCL-22 cancer cell line of human chronic myeloid leukemia). The cytotoxicity of porphyrins was shown to be dependent on the presence and type of the central metal atom in the porphine ring. Ag-derivatives were more cytotoxic than Co−, Zn−, and Fe− metallocomplexes. The porphyrins bearing allyl-functional groups were evidenced to be more cytotoxic than those which included butyl-, oxyethyl-, and methallyl-groups. The change of nitrogen position in the pyridine ring of Ag-metalloporphyrins from 3(3-N-pyridylporphyrins) to 4(4-N-pyridylporphyrins) induced an increase in the cytotoxic activity of metallocomplexes. All synthesized Ag-metalloporphyrins, except, the oxyethyl-containing one were more cytotoxic than cisplatin. Allyl containing free porphyrin and its Zn-metallocomplex had higher phototoxicity than Ag−, Co−, and Fe-metalloporphyrins. The results obtained can be useful for further investigation of new porphyrins as potential chemotherapeutics and photosensitizers.

Inorganic nanoparticles combined with conducting polymers provide interesting physical properties. This research describes the aniline polymerization taking place on the nanoparticles surface by catalytic oxidative polymerization with metalloporphyrin and metallophthalocyanine. In this way, the core-shell structure of the polyaniline/TiO₂ nanocomposites was obtained. The comparison of results demonstrates that porphyrin is a better catalyst than phthalocyanine for synthesis of nanocomposite. The morphology and composition of the nanocomposites were characterized by techniques such as SEM and FT-IR spectroscopy. TGA analysis showed that the nanocomposites, synthesized with iron(III) tetrasulfonated tetraphenyl porphyrin and iron(II) tetrasulfonated phthalocyanines, contained 10% and 5% conducting polyaniline (by mass), respectively. Eventually, the voltammograms revealed that these nanocomposites were electroactive and there was a linear relationship between the anodic and cathodic peak current values and scan rates.

Manganese tetraphenylporphyrin supported on nano-TiO₂ has been synthesized and structurally characterized. It has been shown to have excellent catalytic activity for the aerobic oxidation of α-pinene. Experimental results showed that this much-enhanced activity could arise from possible co-catalysis between metalloporphyrin and the nano-TiO₂ support. The catalyst can be reused several times with minor loss to its catalytic activity.

Oxygen-monitoring techniques are applied to various fields, such as chemicals, deep sea environment, fluid dynamics, clinical analysis and environmental monitoring. Recently, a variety of devices and sensors based on phosphorescence or photoexcited state quenching of porphyrin molecules have been developed to measure oxygen concentration on the solid surface. Many optical oxygen sensors are composed of porphyrins (platinum(II), palladium(II), zinc(II), metal-free, etc.) dispersed in oxygen-permeable polymer film or directly immobilized onto solid surface via chemical or physical adsorption. Oxygen-sensing systems are classified into four types: (1) phosphorescence intensity change, (2) phosphorescence lifetime change, (3) change of lifetime of photoexcited triplet state, and (4) intensity change of absorption of photoexcited triplet state. In this review, the properties of various optical oxygen-sensing devices using porphyrins and sensing system are introduced.

Cobalt tetra(para-chlorophenyl)porphyrin (CoTCPP) and zinc tetraphenyl porphyrin (ZnTPP) were linked on the side chains of the copolymer of 4-vinylpyridine (4VP) and styrene (St), P(4VP-co-St), via axial coordination reactions, respectively, and the metalloporphyrin-functionalized macromolecules, CoTCPP-P(4VP-co-St) and ZnTPP-P(4VP-co-St), were prepared. Their chemical structures were characterized by FTIR and ¹H NMR. The spectral properties of the two macromolecular axial coordination complexes were mainly studied, and their photophysical behavior were discussed in depth. The experimental results show that the metalloporphyrin-functionalized macromolecules, CoTCPP-P(4VP-co-St) and ZnTPP-P(4VP-co-St), can be prepared favorably through axial coordination reaction with the side pyridine groups of the copolymer P(4VP-co-St) as ligands. The two complexes have characteristic spectra similar to that of the small molecular metalloporphyrins, CoTCPP and ZnTPP, respectively. At the same time, they also display the characteristic spectroscopic property of axial coordination complexes: the electronic adsorption spectra of CoTCPP-P(4VP-co-St) and ZnTPP-P(4VP-co-St) red-shifted obviously as compared to that of CoTCPP and ZnTPP, and the fluorescence emission of ZnTPP-P(4VP-co-St) blue-shifted apparently with respect to that of ZnTPP. For CoTCPP-P(4VP-co-St) and ZnTPP-P(4VP-co-St), some polymer effects were found: (1) the bonding degree of the small molecular metalloporphyrin, CoTCPP or ZnTPP, on the side chains of the copolymer P(4VP-co-St) has a limit value because of the steric hindrance and there is a bonding degree difference between the actual value and the theoretical value; (2) for ZnTPP-P(4VP-co-St), slight energy transfer between adjacent ZnTPP units on an identical macromolecule occurs, leading to slight static quench of the fluorescence emission as the bonding density of ZnTPP units on the side chains of the copolymer P(4VP-co-St) reaches a certain value.

Porphine is the parent compound of a family of biologically and chemically relevant compounds called porphyrins. The potential of these compounds is enormous and it would be advantageous to use the porphine (porphyrin) unit as a building block for the synthesis of diverse porphyrin complexes with a wide range of applications. However, despite first being synthesized over 70 years ago, porphine has not been utilized to its full extent due to low yield syntheses and poor solubility. Recent advances have now overcome many of these problems. The purpose of this review is to illustrate the advances made in porphine chemistry to illustrate the inherent potential of this simple compound.

In this work, novel magnetic nanocomposite-bonded metalloporphyrins were synthesized by an effective silanation approach between 3-aminopropyltriethoxysilane derivatized metalloporphyrins and silica-coated magnetic Fe₃O₄ nanoparticles. The initial metalloporphyrin derivatives were synthesized by the amidation reaction of metalloporphyrin acyl chloride with 3-aminopropyltriethoxysilane. After the metalloporphyrin derivatives were adsorbed on the surface of silica-coated magnetic Fe₃O₄ nanoparticles, the solid mixture was heated under vacuum at 110 °C for 3 h and then thoroughly washed with chloroform. The obtained magnetic nanocomposite-bonded metalloporphyrins were characterized by elemental analyzer, low-temperature N₂ adsorption (BET method), transmission electron microscopy, UV-vis spectroscopy, and infrared spectroscopy. Interestingly, using this particular silanation method, metalloporphyrins could be quantitative-immobilized in magnetic nanocomposites by controlling the input ratio of metalloporphyrins and silica-coated magnetic Fe₃O₄ nanoparticles. The excellent catalytic activity and recyclability of the magnetic nanocomposite-bonded metalloporphyrins were demonstrated in the cyclohexane oxidation with iodosylbenzene.

A simple, highly efficient and green procedure for the condensation of aryl and alkyl 1,2-diamines with α-diketones in the presence of catalytic amounts of metalloporphyrins at room temperature is described. Using this method, quinoxaline derivatives as biologically interesting compounds are produced in high to excellent yields and short reaction times. In this report, the effects of central metal in porphyrin core and substituents on tetraphenylporphyrin skeleton have been studied.

Organic nanoparticles of metalloporphyrins can be a versatile catalyst for the selective oxidation of alkenes and other hydrocarbons. The catalytic activity of the metalloporphyrin depends on the nature of the central metal atom, peripheral groups, and the architecture of the porphyrin macrocycle. Herein, we report the catalytic activity of organic nanoparticles of 5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)porphyrinato manganese(III), Mn(III)TPPF₂₀, for the oxidation of cyclohexene using molecular oxygen as an oxidant in aqueous solvent under ambient conditions. While the solvated metalloporphyrins catalytically oxidize alkenes to the corresponding epoxide with a modest turn-over numbers, ca. 30 nm organic nanoparticles of Mn(III)TPPF₂₀ have enhanced catalytic activity with up to a two-fold greater turn-over number and yields only allylic oxidation products. The activity of organic nanoparticles is slow compared to the solvated metalloporphyrins. These organic nanoparticles catalytic systems facilitate a greener reaction since ca. 89% of the reaction medium is water, molecular oxygen is used in place of man-made oxidants, and the ambient reaction conditions require less energy. This organic nanoparticle catalytic system also avoids using halogenated solvents commonly used in solution phase reactions. The enhanced catalytic activity of these organic nanoparticles is unexpected because the metalloporphyrins in the nanoaggregates are in the close proximity and the turn-over number should diminish by self-oxidative degradation.

Porphyrin and phthalocyanine macrocycles with ionic substituents can form mixed assemblies with interesting electronic properties for potential application on the development of new devices. This paper reports the synthesis, isolation and purification of heteroaggregate formed by cobalt(II) 4,4′,4″,4‴-tetrasulfophthalocyanine (CoTsPc) and cobalt(II) tetrakis(N-methyl-4-pyridyl)porphyrin (CoTMPyP), followed by its spectroscopic characterization. Spectroscopic titration, performed with a CoTsPc water/acetone solution, allowed the use of Job's method for determination of the heteroaggregates stoichiometry. The Job's plot revealed the formation of only one predominant heterocomplex in solution, containing two CoTsPc molecules in terminal positions and a central CoTMPyP one. For the first time, a method for isolation and purification of a mixed ionic array has been reported in the literature. The triad's electronic spectrum is quite different from the sum of the macrocycles isolated spectra, due to the overlap of their electronic densities and a charge transfer process between CoTsPc and CoTMPyP.