bluuebunny/crossref_metadata_2025 huggingface dataset:
A novel route to 4-chloro-5-alkyl-phthalonitrile and phthalocyanines derived from it
Authors: Dinçer Hatice Akin , Gül Ahmet , Koçak Makbule Burkut
Published: July 2009

A new route to the synthesis of 4-chloro-5-alkyl-phthalonitrile derivatives was shown by the displacement reaction of 4,5-dichloro-phthalonitrile and diethylmalonate, a CH -acidic precursor, in the presence of K 2 CO 3. Cyclotetramerization of 1-chloro-3,4-dicyano-6-(1,1-dicarbethoxy-methyl)benzene and the metal salt without any solvent gave the corresponding metallophthalocyanines ( M = Co , Cu or Pd ). Transesterification occurred when the reaction was carried out in hexanol in the presence of DBU to obtain the metal-free derivative. Treatment of 1-chloro-3,4-dicyano-6-(1,1-dicarbethoxy-methyl)benzene with sodium ethoxide at ambient temperature and further acidification resulted in 2,9,16,23-tetra(carboxymethyl)-3,10,17,24-tetrachloro-phthalocyaninatopalladium(II) with partial decarboxylation. Its electronic spectrum in aqueous solution indicated no appreciable change over a pH range from 7 to 12.
Synthesis of metallophthalocyanines using microwave irradiation under solvent free and reflux conditions
Authors: Safari Nasser , Jamaat Parisa R. , Pirouzmand Mahtab , Shaabani Ahmad
Published: July 2009

Metal substituted octachloro-, hexadecachloro- and tetranitrophthalocyanine were synthesized by exposure to microwave irradiation under solvent free and reflux conditions and the products were purified by a new route.
Physical properties of electrically conducting and stable molecular neutral radical solid [Co(2,3-Nc)(CN)2]CH3CN (2,3-Nc = 2,3-naphthalocyanine)
Authors: Naito Toshio , Matsumura Naoko , Inabe Tamotsu , Matsuda Masaki , Tajima Hiroyuki
Published: July 2009

Solid state properties of dicyano(2,3-naphthalocyaninato)cobalt(III) neutral radical crystal, [ Co (2,3- Nc )( CN )2] CH 3 CN , were characterized by measurements of the resistivity under high pressure and under uniaxial strain, thermoelectric power, magnetic susceptibility, ESR and polarized reflectance spectra. The title compound exhibited thermally activated-type electrical conductivity along the c-axis. The room temperature (RT) resistivity ρRT along the c-axis and activation energy Ea rapidly decreased with increasing pressure. The temperature-dependent thermoelectric power S was that of a typical one-dimensional (1D) semiconductor. However the high absolute value of S suggested that this electronic system should be strongly correlated. Although the electrical resistivity exhibited monotonous temperature-dependence, the magnetic susceptibility clearly indicated a Peierls-type transition and marked fluctuation from RT. Both Peierls-type transitions and fluctuations are characteristic phenomena to 1D conductors. Furthermore ESR spectra manifested that the Peierls-type transition occurred at 100 K. The inconsistency between the electrical behavior (without a phase-transition) and magnetic behavior (with a phase-transition) indicates separation of the degrees of freedom in spin and charge (spin-charge separation) of this material. Spin-charge separation is a theoretically predicted phenomenon peculiar to the 1D conductors with strong correlation. The reflectance spectra were quantitatively explained by a 1D Hubbard model, and manifested the existence of a structural fluctuation of this material from RT. Based on these observed physical properties it is concluded that [ Co (2,3- Nc )( CN )2] CH 3 CN is a strongly correlated 1D semiconductor with a Mott(Hubbard) type energy gap and characterised with a fluctuation and spin-charge separation.
Multisubstituted phthalonitriles for phthalocyanine synthesis
Authors: Wang Jianghong , Khanamiryan Ashot Kh. , Leznoff Clifford C.
Published: July 2009

3,4,5,6-tetrafluorophthalonitrile and 3,4,5,6-tetrachlorophthalonitrile were used as substrates with various phenoxides to prepare 3,4,6-trihalo-5-p-substitutedphenoxyphthalonitriles, containing four substituents other than hydrogen, by nucleophilic aromatic substitution reactions. Subsequent reactions with unsymmetrical catechols gave tetrasubstitutedphthalonitriles, having four different substituents. In one instance, attempts to displace the last remaining fluoro group by an octanoxide nucleophile led to substitution of a p-methylphenoxy group, showing that phenoxy substituents are also labile in nucleophilic aromatic substitution reactions on phthalonitriles. Alternatively, 4,5-dimethoxyphthalonitrile or 4,5-dineopentoxyphthalonitrile underwent electrophilic aromatic substitution reactions with dibromoisocyanuric acid to give their respective 3,6-dibromophthalonitriles. Coupling of these bromophthalonitriles with tri(n-butyl)phenylylethynyltin and tri(n-butyl)vinyltin in the presence of a nickel catalyst gave 4,5-dimethoxy-3,6-bisphenylethy nylphthalonitrile, 3-bromo-4,5-dimethoxy-6-phenylethynylphthalonitrile, 4,5-dineopentoxy-3,6-bisphenylethynylphthalonitrile, 3-bromo-4,5-dineopentoxy-6-phenylethynylphthalonitrile, 4,5-dimethoxy-3,6-vinylphthalonitrile and 3-bromo-4,5-dimethoxy-6-vinylphthalonitrile. Reductions in the coupling steps sometimes led to 4,5-dimethoxy-3-phenylethynylphthalonitrile and 4,5-dimethoxy-3-vinylphthalonitrile.
Complete assignment of the 1H and 13C NMR spectra and conformational analysis of bonellin dimethyl ester
Authors: Hynninen Paavo H. , Helaja Juho , Montforts Franz-Peter , Müller Claudia M.
Published: July 2009

The use of a high-field NMR instrument (ν(1 H ) = 500 MHz ) and 2-dimensional NMR techniques (HMQC, HMBC, ROESY) enabled us to fully assign the 1 H and 13 C chemical shifts of bonellin dimethyl ester. The β-pyrrolic proton of C -3 appeared as a broad singlet at δ = 8.93, whereas that of C -8 gave a quartet with δ = 8.69 and 4J H - H = |1.28| Hz . The C -21 methyl protons appeared as a doublet with δ = 3.55 and 4J H - H = |1.07| Hz , while the C -71 methyl protons afforded a doublet with δ = 3.51 and 4J H - H = |1.28| Hz . These results suggest that the β-pyrrolic carbons of ring A belong to the aromatic 18 π-electron [18]diazaannulene delocalization pathway, whereas those of ring B remain outside the aromatic pathway. The broadening of the C -3 β-pyrrolic proton signal can be attributed to the allylic 3- CH - 21- CH 3 coupling and the 3- CH - 21- NH coupling. At 330 K, the tautomeric exchange 21- NH a ⇌ 23- NH b is fast and only one broad signal at δ = -2.49 is seen for these protons. The ROESY spectrum showed clear correlation signals between the 182- CH 3 and 171- CH 2 protons, the 182- CH 3 and 174- CH 3 protons, as well as between the 181- CH 3 and 17- CH protons. These results are compatible with the previous assignment that the absolute configuration at C-17 is S. Application of spin simulation enabled us to determine the chemical shifts and the 3J H - H coupling constants of the 17-propionate side-chain. The 3J H - H -values were used to calculate the populations for the 171-17 and 172-171 rotamers. A relatively high population value of 0.41 was found for the 171-17 g--rotamer, whose methoxycarbonylmethyl group points to the C -15 methine-bridge. This was interpreted as explaining the high tendency of bonellin to form anhydrobonellin. The rotational freedoms in the 13-propionate side-chain were studied by measuring the 1 H NMR spectra of the side-chain at temperatures between 300 and 195 K. At 300 K, the 131- and 132- CH 2 proton signals appeared as deceptively simple triplets, which at 195 K were split into complex multiplets. At 195 K, the signal arising from the 131- CH 2 protons exhibited more splitting, which indicates that these protons have less rotational freedom than the 132- CH 2 protons.
The photophysical and metal coordination properties of the N-CH3 substituted porphyrins: H(N-CH3) TPP vs H(N-CH3)OEP
Authors: Sazanovich Igor V. , Berezin Dmitry B. , van Hoek Arie , Panarin Andrei Yu. , Bolotin Vladimir L. , Semeykin Alexander S. , Chirvony Vladimir S.
Published: July 2009

The effect of N -methyl substitution on photophysical and metal coordination properties of the respective derivatives of octaethylporphyrin ( H 2 OEP ) and tetraphenylporphyrin ( H 2 TPP ) was studied by means of steady-state and time-resolved optical spectroscopies combined with semi-empirical quantum-chemical calculations and coordination chemistry methods. In case of H 2 TPP , the insertion of the methyl substituent into the center of the porphyrin macrocycle leads to noticeable nonplanar distortions of the molecule and is accompanied by changes of its photophysical and physicochemical properties towards those manifested by “classical” nonplanar porphyrins. Contrasting to that, N -methyl substituted H 2 OEP does not undergo significant nonplanar distortions and possesses photophysical characteristics mainly similar to unsubstituted H 2 OEP , except for the long-wavelength shift of the absorption and emission bands. The Zn coordination/ Zn complex dissociation and macrocycle thermal stability parameters were also determined for both N -methyl substituted and parent unsubstituted macrocycles, which correlate well with a higher degree of nonplanarity of the N -methyl substituted H 2 TPP as compared to H 2 OEP . Basing on the results of this study the conclusion postulated is that N -methyl substitution has a different effect on the photophysical and coordination properties of H 2 TPP vs. H 2 OEP .
Phthalocyanine-phthalocyanine salt crystal: a unique assembly design
Authors: Ohtsuka Yoshikazu , Naito Toshio , Inabe Tamotsu
Published: July 2009

A unique salt composed of cationic and anionic phthalocyanine complexes has been prepared and structurally characterized. The cationic component is di(pyridine)(phthalocyaninato)cobalt(III) and the anionic one is dicyano(phthalocyaninato)cobalt(III). They arrange alternately in the crystal, forming a two-dimensional sheet with partial π–π overlaps.
The effect of cyclic voltammetry on the crystalline order of PdPc thin films
Authors: Gaffo Luciana , Brasil Maria J. S. P. , Cerdeira Fernando , Giles Carlos , Moreira Wania C.
Published: July 2009

The degree of crystalline order of evaporated and cast palladium phthalocyanine films was investigated before and after they were submitted to a voltammetric process. X-ray diffraction and UV-vis spectroscopy measurements demonstrated that the electrochemical treatment improves the crystalline quality of the films. The X-ray results revealed an increase of the average size of the crystallites composing the films as well as a decrease in the spacing between the lattice planes in the direction perpendicular to the surface of the film. Optical measurements showed that the electrochemical treatment also introduces an appreciable degree of in-plane ordering. These improvements of crystalline order are observed in both types of films, cast and evaporated, which indicates that the ordering is a direct consequence of the electrochemical treatment and not of the method used for the film deposition.
Copper-induced fluoroalkylation of porphyrins: solvent-dependent synthesis of fluoroalkyl chlorins and porphyrins from fluoroalkyl iodides
Authors: Jin Li-Mei , Chen Liang , Guo Can-Cheng , Chen Qing-Yun
Published: July 2009

Treatment of copper(II) or nickel(II) porphyrins with fluoroalkyl iodides ( R f I ) in the presence of copper powder in dioxane, diglyme(DG) or tetrahydrofuran ( THF ) at 70-90°C gave β-fluoroalkyl chlorins in moderate yields. Unexpectedly, when dimethylsulphoxide ( DMSO ), hexamethylphosphoric triamide ( HMPA ) or N , N -dimethylformamide ( DMF ) was used as the solvent, with chlorobenzene as a co-solvent, the β-fluoroalkylporphyrins were obtained. In the first three solvents the reaction can be completely suppressed by p-dinitrobenzene (p- DNB ) or hydroquione ( HQ ), but not at all in the last three solvents. Apparently, a single electron-transfer mechanism may be involved in the formation of β-fluoroalkyl chlorins while fluoroalkylcopper intermediates may play a role in the production of β-fluoroalkylporphyrins. The metallofluoroalkylchlorins can be converted quantitatively to 2-hydoxyl-3-fluoroalkylchlorins by air/ SiO 2 or air/ Al 2 O 3. Additionally, the metallofluoroalkylchlorins and metallofluoroalkylporphyrins can be converted into the corresponding free-base chlorins and porphyrins, respectively, with H 2 SO 4. On the other hand, the metallohydoxyfluoroalkylchlorins under the same conditions afforded β-fluoroalkylporphyrins. Metallohydroxyfluoroalkylchlorins were readily also etherified to the corresponding metallomethoxyfluoroalkylchlorins with dimethyl sulfate ( Me 2 SO 4).
Microwave assisted synthesis of substituted metallophthalocyanines and their catalytic activity in epoxidation reaction
Authors: Bahadoran Farzad , Dialameh Solmaz
Published: July 2009

Substituted iron and cobalt phthalocyanines are easily prepared by microwave irradiation of the starting materials under solvent free condition, which reduced reaction time considerably. The synthesized metallophthalocyanines (octachloro-, tetranitro-, tetracarboxy- or polyphthalocyanine) are used as epoxidation catalysts of cyclooctene in homogeneous and heterogeneous conditions by iodosylbenzene as an oxidant. Their catalytic activities have shown that the electron withdrawing groups on the phthalocyanine ring have a very small effect on stability of the catalyst during the reactions.
An intermolecular quinone shuttle based on porphyrin-quinone recognition
Authors: Tanaka Kiyoshi , Taguchi Kazuto , Iwata Satoru , Obara Hirohito
Published: July 2009

The large difference in the binding affinity of tetramethoxy-p-benzoquinone between 5,15-cis-bis(ureidophenyl)porphyrin and its zinc-porphyrin analogue enables construction of a reversible system in which tetramethoxy-p-benzoquinone moves between 5,15-cis-bis(ureidophenyl)porphyrin and the zinc-porphyrin as a quinone shuttle and a nitrate ion works as a chemical switch.
Chloroquine-iron(III) tetra-arylporphyrin interactions and their effect on chloroquine oxidations catalyzed by iron(III) tetra-arylporphyrins
Authors: dos Santos Ádamo César M. A. , Lindsay Smith John R. , Assis Marilda D.
Published: July 2009

This paper reports a UV-Vis spectroscopic study on the interactions of chloroquine with anionic, cationic and neutral tetra-arylporphyrins and their iron(III) complexes in aqueous buffer and in methanolic solution. This study reveals that in water at pH 6.4 cooperative ion-pair and π-π interactions lead to complex formation between the anionic porphyrin species and chloroquine. In methanolic solution no π-π complexation is observed. The neutral and cationic porphyrins and metalloporphyrins do not form complexes with chloroquine. On the basis of these results, the iron(III) porphyrins have been used as catalysts for the oxidation of chloroquine by iodosylbenzene. The main oxidation product in all systems is monodesethylchloroquine. The anionic iron(III) porphyrins are the most active catalysts; in aqueous solution they are selective for oxidative deethylation whereas in methanol they also give five other oxidation products. The cationic and neutral iron(III) porphyrins are poor or inactive catalysts for chloroquine oxidation by iodosylbenzene. The effect of iron(III) porphyrin/chloroquine interactions on the yields and selectivity of the oxidation is discussed.
Synthesis of asymmetricallymeso-substituted porphyrins bearing amino groups as potential cationic photodynamic agents
Authors: Caminos Daniel A. , Durantini Edgardo N.
Published: July 2009

Novel asymmetrically meso-substituted porphyrins bearing amino groups have been synthesized as precursors of cationic photodynamic agents. The amphiphilic character of these porphyrins was increased by the presence of a high lipophilic trifluoromethyl group. Different patterns of porphyrin structures were obtained from meso-4-[(3- N , N -dimethylaminopropoxy)phenyl] dipyrromethane 1, which was formed by the condensation of 4-(3- N , N -dimethylaminopropoxy) benzaldehyde with a large excess of pyrrole. This reaction takes place at high temperature with a yield of 59%. This reaction was also attempted under acid-catalyzed condensation at room temperature. However, under these conditions, the amino group reduces the catalyst and the reaction does not take place. To obtain porphyrins, dipyrromethane 1 was condensed with aldehydes in the presence of trifluoroacetic acid ( TFA ) under different conditions. First, 1 reacted with 4-(3- N , N -dimethylaminopropoxy)benzaldehyde in dichloromethane catalyzed by TFA (∼4 times TFA /1 molar ratio) to obtain 6.2% of 5,10,15,20-tetrakis(4-[3- N , N -dimethylaminopropoxy]phenyl)porphyrin ( A4-porphyrin). Under similar conditions, reaction of 1 with 4-(trifluoromethyl)benzaldehyde produces 5,15-di(4-[3- N , N -dimethylaminopropoxy]phenyl)-10,20-di(4-trifluoromethylphenyl)porphyrin ( A2B2- porphyrin ) with a 4.8% yield. This procedure also yields a mixture of porphyrins, which were formed due to acidolysis of 1. When a minor amount of TFA was used in acetonitrile, the yield of A2B2-porphyrin was very poor (∼0.4%). On the other hand, condensation of 1 with 4-trifluoromethylbenzaldehyde and 4-(3- N , N -dimethylaminopropoxy)benzaldehyde catalyzed by TFA (∼2 times TFA /1 molar ratio) in acetonitrile yields 9.3% of 5-(4-trifluoromethylphenyl)-10,15,20-tris(4-[3- N , N -dimethylaminopropoxy]phenyl)porphyrin ( A3B-porphyrin ). A2B2and A4porphyrins were also isolated with 6.0 and 2.0%, respectively. Finally, exhaustive methylation of amino porphyrins produces cationic sensitizers (>94% yield). Absorption and fluorescence spectroscopic studies of these sensitizers were compared in N , N -dimethylformamide. In these porphyrins, the cationic centers are isolated from the porphyrin ring by a propoxy bridge. Thus, the cationic charges have minimal influence on the photophysical properties of the sensitizers. In addition, this chain provides a higher mobility of the charge, which could facilitate interaction with the outer membrane of the Gram-negative bacteria. These amphiphilic cationic porphyrins are promising photosensitizers with potential applications in bacterial inactivation by photodynamic therapy.
Photooxidation of metallophthalocyanines: the effects of singlet oxygen and PcM-O2 complex formation
Authors: Kuznetsova Nina A. , Okunchikov Vyacheslav V. , Derkacheva Valentina M. , Kaliya Oleg L. , Lukyanets Evgeny A.
Published: July 2009

The importance of singlet oxygen mechanism in photooxidation of phthalocyanine chromophore has been studied for promising singlet oxygen sensitizers: metal-free tetra-tert-butyl phthalocyanine and its Zn , Mg or Al complexes. It has been found that involvement of singlet oxygen in phthalocyanine photodegradation is dependent on the presence and character of the central metal atom, being the most prominent for the metal-free compound and almost negligible for the Al complex. The interaction of dioxygen with metal centers results in a sharp increase of phthalocyanine photooxidation rate.
Manganese(III) and manganese(IV) corroles: synthesis, spectroscopic, electrochemical and X-ray structural characterization
Authors: Ou Zhongping , Erben Christoph , Autret Marie , Will Stefan , Rosen Daniel , Lex Johann , Vogel Emanuel , Kadish Karl M.
Published: July 2009

The synthesis, spectroscopic characterization and electrochemistry of four Mn(III) and Mn(IV) octaethylcorroles are reported and the potentials of the Mn(III) / Mn(IV) and Mn(IV) / Mn(III) processes examined as a function of the axial ligand. The investigated compounds are represented as ( OEC ) Mn , ( OEC ) MnCl , ( OEC ) Mn ( py ) and ( OEC ) Mn ( C 6 H 5) where OEC is the trianion of octaethylcorrole. The first one-electron oxidation of ( OEC ) Mn III and ( OEC ) Mn III ( py ) in PhCN or pyridine containing 0.1 M TBAP leads to the facile formation of a Mn(IV) species while the first one-electron reduction of ( OEC ) Mn IV Cl and ( OEC ) Mn IV ( C 6 H 5) in the same two solvents leads to the Mn(III) corrole. All other redox reactions occur at the corrole macrocycle to give π-cation radicals or π-anion radicals and there is no evidence for electrogeneration of a compound with a Mn(II) oxidation state as is the case for manganese(III) porphyrins which are all easily reduced to the Mn(II) state in nonaqueous media. The products of each Mn(III)/Mn(IV) redox reaction were characterized by UV-visible and/or ESR spectroscopy and the structures of ( OEC ) MnCl , ( OEC ) Mn ( py ) and ( OEC ) Mn ( C 6 H 5) were determined by single-crystal X-ray diffraction.
Meso-tetrakis(3',5'-di-substituted-phenyl)porphyrins: structural, electrochemical redox and axial ligation properties
Authors: Sankar Muniappan , Bhyrappa Puttaiah , Varghese Babu , Praneeth K. K. , Vaijayanthimala G.
Published: July 2009

A family of meta octa-substituted 5,10,15,20-tetraphenylporphyrin derivatives and their metal ( Cu(II) and Zn(II) ) complexes were examined by electrochemical studies. These functionalized MTPPs exhibited a dramatic anodic shift (>200 mV ) in their first ring redox potentials relative to the para-phenyl substituted-MTPP(X) complexes and follow a fairly linear relationship with the Hammett parameter of the substituents. The extent of Lewis acidity of the core Zn(II) center in these porphyrins was probed by axial ligation of bases of varying pK a values. The increase in K eq values of the electron deficient Zn(II) porphyrins are as high as an order of magnitude and increase with anodic shift of the electrochemical redox potentials of the porphyrin. A crystal structure of the Zn(II) octa(carboxyethylester phenyl)porphyrin shows six-coordination geometry with the coordination through peripheral ester groups to form a supramolecular two-dimensional layer structure while the ZnT (3',5'- DMP ) P complex exhibited a five-coordinate structure.
Synthesis, characterization and ESR spectroscopy of novel s-triazine bearing three oxygen-linked lutetium bisphthalocyanine sandwich complexes
Authors: Ceyhan Tanju , Korkmaz Mustafa , Erbil Mehmet K. , Bekaroğlu Özer
Published: July 2009

The conversion of compound 1 [2,4,6-tris(2-oxaphthalonitrile)-s-triazine] into its isoindoline derivative of 2,4,6-tris[2-oxa(1,3-hexaimino isoindoline)]-s-triazine 2 was accomplished by bubbling ammonia gas through a solution in methanol in the presence of sodium methoxide. The cyclization of two different isoindoline derivatives namely, compound 2 and 4,5-bis(hexylthio)-1,2-diimino-isoindoline 3 with lutetium(III) acetate, [ Lu ( OAc )3] in refluxed DMF by the method of statistically mixed condensation gave trimeric trilutetium phthalocyanine [( LuOAc )3( Pc )3]4. [ Lu 3( Pc )6]5 has been synthesized in situ by the reaction of phthalocyanine 4 and three equivalents of dilithium octakis-hexylsulfanyl phthalocyanine in amyl alcohol.
Oxidation states of manganese porphyrins in water solutions
Authors: Ramirez-Gutierrez Oscar , Claret Josep , Ribo Josep M.
Published: July 2009

The Mn oxidation state of two water soluble Mn porphyrins, MnTMPyP and MnTPPS 4, was studied as a function of the aqua or hydroxo ligands of the Mn atom. In NaOH solutions, long-lived O = Mn(IV) species were detected in the presence of O 2. Conversely, the dihydroxo Mn(III) porphyrin reduces spontaneously to the Mn(II) species in the absence of O 2. In alkaline solutions, these Mn porphyrins were able to electrocatalyze the 4-electron reduction of O 2 to H 2 O on a vitreous carbon electrode.
p-nitrobenzamide substituted phosphorus(V) porphyrins: synthesis and interactions with DNA
Authors: Gajewski Mariusz P. , Czuchajowski Leszek
Published: July 2009

Four new phosphorus(V) porphyrins were designed and synthesized. The compounds were diaxially substituted with 4-nitrobenzamide. The axial ligands were attached to the P(V) center of the porphyrins through methylene linkers of different lengths. DNA titrations showed the expected porphyrin binding. When exposed to 532 nm laser light, which corresponds to the porphyrin Q band, the photosensitizers induced DNA nicking. Inhibition of the nicking by sodium azide suggested participation of singlet oxygen in the process. Photoexcitation with 305 nm laser light, which corresponds to absorption of 4-nitrobenzamide, also resulted in DNA damage. Due to the lack of electronic communication between the axial ligands and the porphyrin, the desired pathway of DNA cleavage was chosen by selecting a proper wavelength of the light used for photoexcitation. The activities of the porphyrins in photoinduced DNA nicking were very similar in both experiments: irradiation with 305 and 532 nm light, and were inversely correlated with the length of the linkers.
Photophysical properties of a water-soluble adjacently substituted bisnaphthalophthalocyanine
Authors: Seotsanyana-Mokhosi Itumeleng , Nyokong Tebello
Published: July 2009

Spectral properties of a water soluble metal free tetracarboxyphenoxy bisnaphthalophthalocyanine (3) were studied in water and organic solvents. It was found that in protic solvents, complex 3 was highly aggregated. The surfactant, Triton X100, and bovine serum albumin (BSA) do not effect disaggregation while cetyl trimethylammonium chloride (CTAC) caused the molecule to disaggregate. The fluorescence quantum yields were higher in the presence of CTAC. Studying the interaction of BSA with complex 3 using fluorometry revealed that BSA is highly quenched by the latter. A 1:1 stoichiometric binding ratio between BSA and the Pc was found. Triplet quantum yields in water containing CTAC were higher than in organic solvents.
Synthesis, electrochemical and spectroelectrochemical studies of octaphenylthio-substituted phthalocyanines
Authors: Matemadombo Fungisai , David Maree M. , Ozoemena Kenneth I. , Westbroek Philippe , Nyokong Tebello
Published: July 2009

Cobalt (4) and iron (5) phenylthio-substituted phthalocyanines ( MPc ( SR )8) have been synthesized and characterized. Cyclic square wave voltammetry in dimethylformamide containing tetrabutylammonium perchlorate revealed five and six redox processes, respectively, for complexes 4 and 5. The complexes are easier to reduce compared to the corresponding unsubstituted MPc and to butylthio substituted derivatives. The first oxidation and reduction occurs on the metal for both complexes. Spectroelectrochemistry (in dimethylformamide containing tetrabutylammonium perchlorate) was employed to assign the cyclic voltammetry peaks, and gave spectra characteristic of Fe I Pc for reduction of 5 and Co I Pc for the reduction of 4. The spectrum of the former is particularly of importance since such species have not received much attention in the literature.
Preparation and spectroscopic properties of the (cyanato-N) and (oxalato) iron(III) “picket fence” porphyrins: Structure of the (cyanato-N)(α,α,α,α-tetrakis(o-pivalamidophenyl)porphinato)iron(III) complex
Authors: Belkhiria Mohamed Salah , Dhifet Mondher , Nasri Habib
Published: July 2009

The reaction of the iron(III) aqua triflato picket fence porphyrin starting material with NaOCN and K2C2O4salts, solubilized by the crown ether 18- C -6 in organic solvents, yields respectively the iron(III) porphyrin species [ FeIII( TpivPP )( NCO )] and [ FeIII( TpivPP )( ox )]−. These compounds have been characterized by UV-vis, IR, and1H NMR spectroscopies. Proton NMR data for the isolated products are in accordance with high-spin ( S = 5/2) ferric porphyrin derivatives. The X-ray molecular structure of the (cyanato-N)(α,α,α,α-tertakis(o-pivalamidophenyl)porphinato)iron(III), has been determined. This structure, which is the first one reported of an iron-cyanato species, confirms the spin-state of the cyanato derivative. The iron atom is pentacoordinated by the four nitrogen atoms of the pyrrole rings and the nitrogen atom of the NCO−group. It lies at 0.540(1) Å out of the porphinato plane and 0.486(1) Å out of the four nitrogen plane of the porphyrin ring. The Fe – N ( NCO ) bond length is 1.970(2) Å and the Fe - N - C ( NCO ) bond angle is 169.9(3)°.
Studies on the oxidation of 2,6-di-tert-butylphenol by molecular oxygen catalyzed by cobalt(II) tetraarylporphyrins bound to cationic latex
Authors: Hassanein Mahmoud T. , Gerges Shady S. , Abdo Mohamed A. , El-Khalafy Sahar H.
Published: July 2009

A cationic latex has been prepared by emulsion copolymerization of styrene and divinylbenzene with 2 mol.% of quaternary ammonium ion surfactant monomer. The catalytic activity of cobalt(II) sulfonated tetraarylporphrins 1-5 supported on the cationic latex 6 was investigated in the autoxidation of 2,6-di-tert-butylphenol in water. All colloidal catalysts showed good catalytic activity in the autoxidation of 2,6-di-tert-butylphenol. Reaction products were identified as 2,6-di-tert-butyl-1,4-benzoquinone and the oxidative coupling product as 3,3',5,5'-tetra-tert-butyl-4,4'-diphenoquinone. The rate of autoxidation reaction catalyzed by 5 supported on cationic latex was found to increase with increasing pH in the range 7.0-10.0. At constant concentration of cobalt(II) porphyrin 5 in the reaction mixture, the rate as a function of the weight of the latex showed a maximum. The rate of autoxidation increased with increasing partial pressure of dioxygen in the range between 0.2 and 1.0 atm. 5,10,15,20-tetrakis(2,4,6-trimethyl-3,5-disulfonatopheny)porphyrinatocobalt(II) bound to the cationic latex was found to be the most reactive catalyst and the latex supported 5,10,15,20-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphyrinatocobalt(II) showed the highest stability.
Artificial photosynthetic antenna-reaction center complexes based on a hexaphenylbenzene core
Authors: Terazono Yuichi , Liddell Paul A. , Garg Vikas , Kodis Gerdenis , Brune Alicia , Hambourger Michael , Moore Ana L. , Moore Thomas A. , Gust Devens
Published: July 2009

A hexaphenylbenzene scaffold has been used to organize the components of artificial photosynthetic antennas and antenna-reaction center mimics that feature bis(phenylethynyl)anthracene antenna moieties and porphyrin-fullerene charge-separation units. The five bis(phenylethynyl)anthracene chromophores absorb in the spectral region around 430-480 nm, where porphyrins have low extinction coefficients but solar irradiance is maximal. The hexaphenylbenzene core was built up by the well-known Diels-Alder reaction of diarylacetylenes with substituted tetraphenylcyclopentadienones. The latter were in turn prepared by condensation of substituted benzils and dibenzyl ketones, allowing flexibility in the design of the substitution pattern on the core. The spacing between the various chromophores is suitable for rapid singlet-singlet energy transfer among antenna moieties and the porphyrin, and the relatively rigid structure of the hexaphenylbenzene limits conformational heterogeneity that could reduce the efficiency of energy and electron transfer. NMR studies reveal a high barrier to rotation of the porphyirn plane relative to the hexaphenylbenzene.
Photodynamic effects of Radachlorin® on cervical cancer model
Authors: Kwak Sun-Young , Lim Dae-Seog , Bae Su-Mi , Kim Yong-Wook , Lee Joon-Mo , Namkoong Sung-Eun , Han Sei-Jun , Kim Jong-Ki , Lee Chang-Hee , Chun Heung-Jae , Ahn Woong-Shick
Published: July 2009

Photodynamic therapy (PDT) has been reported to be effective for treating various tumors and induce apoptosis in many tumor cells. In this study, we examined a biological significance of PDT with a chlorin-based photosensitizer, Radachlorin®, in a cervical cancer model, TC-1 cells. When TC-1 cells were exposed to varied doses of Radachlorin® with light irradiation (6.25 J/cm2), PDT induced a dose-dependent growth inhibition of TC-1 cells. All of these cells were significantly damaged after light irradiation and categorized to be early and late apoptosis, as determined by annexin V staining. Radachlorin® localized primarily into the Golgi apparatus of cells in 12 h of the treatment, and weak fluorescence intensity was also detected in mitochondria. On the other hand, in the in vivo experiments, following light irradiation (100 J/cm2), retarded tumor growth was significant in mice treated with Radachlorin®, as compared to the control group. Taken together, we propose that PDT after the application of Radachlorin® may induce the Golgi apparatus-mediated apoptosis of cervical cancer cells in vitro, and also be effective in the mice system.
Zwitterionic vs porphyrin free-base structures in 4-phenylsulfonic acid meso-substituted porphyrins
Authors: Escudero Carlos , El-Hachemi Zoubir , Crusats Joaquim , Ribó Josep M.
Published: July 2009

The 5,10,15,20-tetrakis(4-sulfophenyl)porphyrin (TPPS4) and 5-phenyl-10,15,20-tris(4-sulfophenyl)porphyrin (TPPS3)] were obtained for the first time as the pure sulfonic acid derivatives and characterized for their constitutional structure in the solid state and in water solution. The zwitterionic species in water solutions, above a critical micellar concentration, are stabilized by side-to-side homoassociation to J-aggregates (B-band: 490 nm), but in solids they only give the J-aggregates when water is present in enough amount. Severe dried solids show a zwitterionic species, stabilized by side-to-side interactions, that probably corresponds to the dimer (B-band: 455 nm). The monomeric zwitterion (B-band: 434 nm) is detected in dilute water solutions and its acid/base properties (concentration pK a (1/2) ≈ 5.0) are not significantly different from those of the acidified solutions of their sodium sulfonate derivatives. However, pure water solutions of TPPS n , in contrast to those of their sodium salts, show important interactions with hydrophilic surfaces: e.g. TPPS4 adsorbs on fused quartz forming a monolayer of the free-base porphyrin together with its counter cations. Dilution of the title porphyrins in a solid matrix (e.g. KBr ) leads to a free-base porphyrin species with a red-shifted B-band (424 nm) that points to a side-to-side homoassociation, which is in contrast with the typical π-stacked aggregates of the corresponding alkaline metal sulfonato salts.
Unique electrochemical behavior of tantalum(V) phthalocyanine
Authors: Tau Prudence , Nyokong Tebello
Published: July 2009

The electrochemical and spectroscopic behavior of tantalum(V) phthalocyanine are presented. The NMR spectra is consistent with the lack of symmetry of the complex. Cyclic (CV) and square wave (SWV) voltammetries, and spectroelectrochemistry, were employed in the study of the complex. Two one-electron reductions and a simultaneous 4-electron reduction were observed. Reduction occurs first at the metal to form a Ta (IV) species, followed by ring based processes.
Catalysis of metalloporphyrins for selective hydroxylation of phenol by H2O2
Authors: Zeng Hai-Qiang , Jiang Quan , Zhu Yun-Fei , Yan Xu-Hui , Liang Xue-Bo , Hu Hai-Yang , Liu Qiang , Lin Wei-ying , Guo Can-Cheng
Published: July 2009

Liquid phase catalytic selective hydroxylation of phenol to catechol and hydroquinone was carried out in the presence of metalloporphyrins using hydrogen peroxide as oxidant and water as solvent. Five kinds of metal tetra(p-chlorophenyl)porphrin ( T (p- Cl ) PPMCl , M = Fe , Co , Mn , Cu , Zn ) were studied. It was found that T (p- Cl ) PPFeCl had high catalytic activity and diphenol selectivity for the hydroxylation of phenol to catechol and hydroquinone. The influence of various reaction parameters, namely, reaction temperature, solvent, ratio of substrate and oxidant, substrate concentration, the amount of catalyst, reaction time and pH value were investigated systematically. When water was used as solvent (10 mL), the optimum conditions were following: pH = 7, the concentration of phenol was 0.3 g/mL, the molar ratio of phenol and H 2 O 2 was 1/2, the molar ratio of catalyst and phenol was 7/100000, the reaction temperature was 65°C and the reaction time was 1.5 h. Under above optimum conditions, the phenol conversion was up to 55.1%, and the selectivity of diphenol was almost up to 99.9%, the molar turnover numbers of the catalyst was about 7500. A possible mechanism was also proposed.
Binding of 1-methylimidazole to heme determined by factor analysis
Authors: Lopez Marco A. , Ybarra Cynthia D.
Published: July 2009

We report the binding of 1-methylimidazole to ferric octaethylporphyrin chloride in methylene chloride. Factor analysis of a series of UV-vis titration spectra indicated there were three species in solution. These species are postulated as being the ferric porphyrin chloride species, the ferric porphyrin(1-MeIm)chloride species, and the ferric (1-MeIm)2chloride species. A coupled nonlinear least squares analysis of absorbance changes at two wavelengths yielded estimates of the binding constants. The binding constants for the first and second 1-MeIm are K 1 = 278 ± 7 M -1 and K 2 = 161 ± 25 M -1. It is suggested that displacing the chloride ion is the reason for having K 2 < K 1.
Characterization of electrodes chemically modified withMn(III)porphyrin/polypyrrole films as catalytic surfaces for an azo dye
Authors: Barros Valéria P. , Zanoni Maria Valnice B. , Assis Marilda das D.
Published: July 2009

In this study we describe the electrochemical behavior of 5,10,15,20-tetrakis(2'-aminophenylporphyrin)manganese(III) chloride supported on a glassy carbon electrode, as well as the electrochemical preparation and characterization of thin films based on pyrrole-3-carboxylic acid. The electrocatalytic action of the electrode modified with the Mn(III) porphyrin toward an azo dye was tested, and the characteristic strong interaction between the incorporated metalloporphyrin and RR120 dye was verified.
Optical changes induced in Zn porphyrin solutions and LB films by exposure to amines
Authors: Dunbar Alan D. F. , Richardson Tim H. , McNaughton Alex J. , Cadby Ashley , Hutchinson Jordan , Hunter Chris A.
Published: July 2009

The 5,10,15,20-tetrakis[3,4-bis(2-ethylhexyloxy)phenyl]-21 H ,23 H -porphinato zinc(II) ( ZnEHO ) is highly stable and exhibits a colorful absorption spectrum in the visible range. Exposure of a chloroform solution of ZnEHO to amines is shown to induce changes in the characteristic optical spectrum owing to charge transfer between the amine and the delocalized π-electron system within the highly conjugated molecule. Solid state Langmuir Blodgett (LB) films containing only ZnEHO are compared to films containing a mixture of ZnEHO and calix[8]arene. The transparent calix[8]arene does not change the optical response but aids the diffusion of the amine gas into the LB films. Atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM) images demonstrate the topological and compositional differences between the samples. The response of the LB films of ZnEHO and calix[8]arene to a variety of different amines demonstrates that this is a good material system for use as an amine sensor.
Porphyrin-rhodanine dyads for dye sensitized solar cells
Authors: Giribabu Lingamallu , Kumar Ch. Vijay , Reddy P. Yella
Published: July 2009

A series of four new porphyrin-rhodanine dyads were synthesized having the rhodanine acetic acid group either at the meso- or the pyrrole-β position of a free-base/zinc porphyrin. These dyads were fully characterized by UV-visible, 1 H NMR, MALDI-MS and fluorescence spectroscopies and cyclic voltammetry. Both the Soret and Q-bands were red-shifted in the case of pyrrole-β substituted dyads. The redox potentials of all four dyads were altered in comparison with their individual constituents. The dyads were tested in dye sensitized solar cells and the zinc metalated dyads gave a better performance in comparison with the corresponding free-base dyads.
Catalytic dehalogenation enhanced by appending dendritic ligands on cobalt porphyrins
Authors: Imaoka Takane , Takatsuka Toshio , Yamamoto Kimhisa
Published: July 2009

The dehalogenation activities of cobalt porphyrin catalysts with dendritic phenylazomethine units on the meso-positions were studied. Tetrachloroethylene was used as a substrate. By applying samarium iodide as a reducing agent, the tetrachloroethylene conversion into trichloroethylene and dichloroethylene was observed in the presence of the cobalt porphyrin catalyst. The turnover frequency was 1.70 min−1 when a cobalt porphyrin connected with dendritic phenylazomethines (3 generations) was employed as the catalyst. While the turnover frequency was almost the same as that for a non-dendritic porphyrin catalyst (1.57 min−1 by cobalt tetraphenylporphyrin), a significant increase in the turnover frequency was observed when samarium (3.43 min−1) or terbium trifluoromethane sulfonate (8.57 min−1) binds to the phenylazomethine units of the dendrimer. Because these metal ions ( Sm 3+ or Tb 3+) are positioned in a space between the encapsulated catalytic center and the solvent phase, they can act as electron mediators that relay electrons from the reducing agent (samarium iodide) to the catalytic center (cobalt porphyrin). This facile electron transfer would provide an enhancement in the catalytic activity for the tetrachloroethylene reduction leading to dehalogenation.
Development of phthalocyanines for photodynamic therapy
Authors: Ogura Shun-ichiro , Tabata Kenji , Fukushima Kaoru , Kamachi Toshiaki , Okura Ichiro
Published: July 2009

Photodynamic therapy is a method for treating several diseases, most notably cancer. Recent synthetic activity has created a number of phthalocyanines for potential use as photodynamic therapy photosensitizers. In this mini-review article, the background and the concepts in the development of new phthalocyanines are introduced.
Synthesis and liquid crystal behavior of bis[3,4,12,13,21,22,30,31-octa(dodecylthio)-2,3-naphthalocyaninato] rare earth complexes
Authors: Zhang Ying , Pan Na , Xue Qingbin , Bai Ming , Jiang Jianzhuang
Published: July 2009

A series of novel bis[3,4,12,13,21,22,30,31-octa(dodecylthio)-2,3-naphthalocyaninato] rare earth(III) complexes M [ Nc ( SC 12 H 25)8]2( M = Nd , Eu , Gd , Tb , Y , Ho , Er ) have been prepared by tetramerization of 2,3-bis(dodecylthio)-6,7-dicyanonaphthalene with M ( acac )3·n H 2 O in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in refluxing n-octanol. These sandwich double-decker complexes were characterized by elemental analysis and various spectroscopic methods including UV-vis, near IR, IR, and mass spectroscopies. Their liquid crystal behavior was studied by polarized optical microscope (POM), differential scanning calorimeter (DSC), and X-ray diffraction. These alkylthio-substituted bis(2,3-naphthalocyaninato) rare earth complexes yield a hexagonal columnar liquid crystal whose stable temperature range is between 42 and 243°C. The stable temperature domain of the mesophase shows a trend to be dependent on the central rare earth ionic size. In contrast, the molecular packing of these complexes as revealed by X-ray diffraction was found to be almost independent of the ionic size of the central rare earth.
Immobilization of cationic zinc(II) complexes of phthalocyanine and unsymmetrical porphyrazine in mesoporous MCM-41 silica, and photo-catalytic activity of the composites
Authors: Kasuga Kuninobu , Imai Makoto , Irie Hiroyuki , Tanaka Hidekazu , Ikeue Takashi , Handa Makoto , Wada Shusaku , Sugimori Tamotsu
Published: July 2009

Cationic 2,9,16,23-tetrakis(3- N , N , N -trimethylaminoethyloxy)phthalocyaninatozinc(II) and 20,21-bis(4- N , N , N -trimethylaminophenyl)-4,5,9,10,14,15-hexakis(4-t-butylphenyl)porphyrazinatozinc(II) were immobilized in MCM-41 silica by the use of an electrostatic interaction with the deprotonated silanol groups of MCM-41. From nitrogen adsorption isotherms, specific surface areas were estimated as 1031 and 702 m2.g−1 for MCM-41 and the composite of 2,9,16,23-tetrakis(3- N , N , N -trimethylaminoethyloxy)phthalocyaninatozinc(II), respectively. From pore-size distribution curves, the maximum pore diameter of MCM-41 and the composite were also estimated as 3.24 and 3.10 nm, respectively. These results revealed that 2,9,16,23-tetrakis(3- N , N , N -trimethylaminoethyloxy)phthalocyaninatozinc(II) was immobilized in the mesopores of MCM-41. While 2,9,16,23-tetrakis(3- N , N , N -trimethylaminoethyloxy)phthalocyaninatozinc(II) formed a dimer with increase in the amount of the complex in the composite, 20,21-bis(4- N , N , N -trimethylaminophenyl)-4,5,9,10,14,15-hexakis(4-t-butylphenyl)porphyrazinatozinc(II) only slightly formed a dimer in the composite, due to steric hindrance of its peripheral substituents. 1,3-diphenylisobenzofuran was photo-oxidized using the composites as the sensitizer in aerated acetonitrile. The reaction proceeded with singlet dioxygen generated by visible-light irradiation of the sensitizers. While the initial reaction rate with the composite of 20,21-bis(4- N , N , N -trimethylaminophenyl)-4,5,9,10,14,15-hexakis(4-t-butylphenyl)porphyrazinatozinc(II) increased in proportion to the increase in the amount of the complex, the initial reaction rate with the composite of 2,9,16,23-tetrakis(3- N , N , N -trimethylaminoethyloxy)phthalocyaninatozinc(II) at first increased, but subsequently decreased due to the formation of the photo-inactive dimer.
Surface electrochemistry of N,N',N″,N‴-tetramethyl-tetra-3,4-pyridinoporphyrazinocobalt(II)
Authors: Chen Junsheng , Zhang Jiujun , Tse Yu-Hong , Janda Pavel , Christendat Dharamdat , Lever A. B. P.
Published: July 2009

The complex N,N',N″,N‴ -tetramethyl-tetra-3,4-pyridinoporphyrazinocobalt(II) ([ Co II TMPz [4+])4+ adsorbed on a graphite electrode undergoes spontaneous reduction, forming a surface containing Co I. Five reversible surface peaks are observed at low pH, two of which are two-electron concerted processes. At high pH, one of these two-electron processes splits into two one-electron waves. Both oxidation and reduction of the central metal can be observed, along with successive reduction steps involving the porphyrazine ligand. Notable is the marked shift to positive potentials of these processes, relative to unsubstituted cobalt phthalocyanine, due to the positive charge localized on the porphyrazine. The electrocatalytic activity of this complex modified electrode toward the reduction of hydrogen peroxide is also reported. We demonstrate that a series of different surfaces exist which are obtained by variation of pH and polarization potential and that these surfaces possess differing electrocatalytic activity. Surfaces inactive to hydrogen peroxide can exist at potentials more negative than active surfaces even though the driving force for peroxide reduction will be greater for the former.