bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of catenation on the acidity constants of porphyrin [2]catenanes
Authors: Gunter Maxwell J. , Farquhar Sandra M. , Jeynes Tyrone P.
Published: July 2009

The acidity constants ( pK a3 and pK a4) of a series of porphyrins and their corresponding [2]catenanes where the porphyrin is over-arched with a hydroquinol or naphthoquinol polyether strap and mechanically linked to a bipyridinium macrocycle cyclobis-paraquat(4,4'-biphenylene), are calculated from acid-base titration data. As the length of the strap decreases from tetraethylene through triethylene to diethylene, the pK a values decrease, and the separation between pK a3 and pK a4 increases. In the diethylene glycol strapped derivatives, only the monocation is accessible above pH = 0. The trend in values reflects the ease of protonation which becomes increasingly difficult as the coulombic repulsions between the protonated porphyrin and the tetracationic macrocycle becomes more severe, as a consequence of enforced proximity of the two charged centres. On protonation, any electronic interactions between the interlinked subunits is replaced by strong electrostatic repulsions. This is alleviated by a 90° rotation of the tetracation and a movement away from the porphyrin; such a reorientation is possible only in the longer strapped derivatives, and is prevented in the “tight” analogues.
Microporous porphyrin assemblies: Interaction of NO2 gas with sublimed layers of meso-mono-4-pyridyl-tri-phenylporphyrinatocobalt(II)
Authors: Kurtikyan Tigran S. , Mardyukov Arthur N. , Kazaryan Robert K. , Goodwin John A.
Published: July 2009

The interaction of NO 2 (15 NO 2) gas with sublimed layers of meso-mono-4-pyridyl-triphenylporphyrinatocobalt(II) (CoMPyTPP) has been investigated by means of IR and UV-visible spectroscopies. These studies have led to the characterisation of two nitro-complexes: (1) the five-coordinated nitro complex similar to that observed earlier for the closely-related meso-tetraphenylporphyrinatocobalt(II) (CoTPP), and (2) the six-coordinated complex, in which the fifth coordination site is occupied by the pyridyl group of an adjacent molecule. Upon storage of the films, the concentration of six-coordinate complexes increases at the expense of the five-coordinate. These experimental observations indicate the self-assembly of CoMPyTPP in layers with formation of coordinatively linked oligomers. Due to the specificity of the supramolecular structure, the layers conserve their microporosity upon storage and reveal the oxo-transfer activity relative to appropriate oxygen acceptors.
Spectroscopic studies of peroxo/hydroperoxo derivatives of heme proteins and model compounds
Authors: Ibrahim Mohammed , Kincaid James R.
Published: July 2009

The spectroscopic characterization of peroxo- and hydroperoxo- intermediates of heme proteins and enzymes has long interested scientists studying the structure and function of these important biochemical systems. Until very recently, little progress had been made in studying these fleeting intermediates by vibrational spectroscopic methods. In this brief review, recent studies reporting the Resonance Raman and Infrared spectra of such intermediates and pertinent model compounds are reviewed and compared to corresponding studies utilizing electronic absorption and electron paramagnetic resonance spectrometric methods.
Phenyl biliverdin isomers obtained by chemical oxidation of iron(III) complex of 5-phenyl protoporphyrin IX
Authors: Niemevz Fernando , Buldain Graciela Y.
Published: July 2009

Oxidative cleavage of synthetic 5-phenyl protohemin IX in pyridine solution in the presence of ascorbic acid (coupled oxidation), followed by esterification of the products with boron trifluoride-methanol rendered mainly three isomeric biliverdins. These were identified by MS and 1D and 2D1H NMR as 15-phenyl biliverdin IXβ (1), 10-phenyl biliverdin IXγ (2) and 5-phenyl biliverdin IXδ (3) dimethyl esters. The fact that biliverdin IXα dimethyl ester derivative is not obtained indicates that oxidation fails to occur in the α-meso-carbon bearing the phenyl group.
Porphyrazines with oligo(ethylene oxide) thio alkoxy chains: Synthesis, aggregation, photophysics, and complexation with redox-active ions
Authors: Piet Dennis P. , Veldhuis Harald , Zuilhof Han , Sudhölter Ernst J. R.
Published: July 2009

A series of new porphyrazines with oligo(ethylene oxide) thioalkoxy side chains has been synthesized. Study of the phase transitions reveals the absence of liquid crystallinity. Due to the ethylene oxide moieties, the solubility in a variety of solvents is dramatically increased. This allowed the first study of solvent effects on the photophysical properties (absorption and emission) in water and chloroform. The complexation of the porphyrazines with the redox couple LiI / I 2 has been studied. No effect on the aggregate formation has been observed in solution, while in a film incorporation of an increased amount of LiI / I 2 leads to a disturbance of the aggregates. At temperatures up to 100°C the porphyrazine - LiI / I 2 complexes are stable in the liquid phase, but from 115°C onwards, small crystallites of LiI are formed in the isotropic liquid.
Spectroelectrochemical and ESR studies of highly substituted copper corroles
Authors: Ou Zhongping , Shao Jianguo , Zhao Hui , Ohkubo Kei , Wasbotten Ingar H. , Fukuzumi Shunichi , Ghosh Abhik , Kadish Karl M.
Published: July 2009

Electrochemical and spectroelectrochemical studies are presented for nine copper corroles with electron-withdrawing or electron-donating substituents on the three meso-phenyl rings of the compounds or on the eight β-pyrrole positions of the macrocycle. Up to three reversible oxidations can be seen for each Cu (III) corrole in CH 2 Cl 2 containing 0.1 M TBAP. Unlike the case of ( OEC ) Cu , no dimer is electrochemically detected upon the first oxidation of these compounds at room temperature. However, a dimer forms at low temperature (< -50°C) for compounds having strong electron-donating groups. Two reductions are observed for all nine corroles at low temperature in CH 2 Cl 2, 0.1 M TBAP, but only one reduction is detected at room temperature for four of these compounds which have weak electron-withdrawing or electron-donating groups. The neutral, reduced or oxidized Cu corroles were also characterized by thin-layer UV-visible spectroelectrochemistry and ESR. The resulting data indicates that eight of the nine neutral complexes contain a Cu (III) center while only one complex, [ Br 8( C 6 F 5)3 Cor ] Cu , exists in its Cu (II) form in CH 2 Cl 2 containing 0.2 M TBAP.
Cellular localization and photodynamic effect of chlorine6-monoclonal antibody conjugate
Authors: Ogura Shun-ichiro , Kamachi Toshiaki , Okura Ichiro
Published: July 2009

Chlorin e6(Ce6) was conjugated with anti-tumor monoclonal antibody ( IgG ) to increase its binding affinity for tumors. Ce 6 was activated by N -hydroxysulfosuccinimide and conjugated with IgG via peptide bonds, and Ce 6 molecules were conjugated with IgG ( IgG - Ce 6) and their binding affinities to tumor cells were investigated. Intracellular localization of IgG - Ce 6 was observed, and IgG - Ce 6 was accumulated in tumor cells much higher than Ce 6, indicating that the IgG - Ce 6 has specific binding affinity to tumor cells. The effective photocytotoxicity of the cells with IgG - Ce 6 is caused by the high accumulation of IgG - Ce 6 in tumor cells.
A novel synthesis of 5,15-trimethylammonium substituted porphyrins and their evaluation as potential antimicrobial photosensitizers
Authors: Nistri Daniele , Dei Donata , Chiti Giacomo , Cocchi Annalisa , Fantetti Lia , Roncucci Gabrio
Published: July 2009

The MacDonald's [2 + 2] condensation of unsubstituted dipyrromethane and 3- or 4-hydroxyalkoxybenzoaldehydes afforded 5,15-meso-hydroxyalkoxyphenylporphyrins. The hydroxyl groups on the side chains were then transformed to tertiary amines via synthesis of the mesylate and substitution with the appropriate amines or aminoalcohols. Methylation of such products afforded a series of cationic porphyrins which have been tested in vitro as photodynamic agents against microorganisms, showing high antimicrobial activity.
A synthetic approach towards novel octa-substituted zinc(II) phthalocyanines with different solubility and photophysical properties
Authors: Strassert Cristian A. , Rodriguez Myriam E. , Dicelio Lelia E. , Awruch Josefina
Published: July 2009

The synthesis and behavior in homogeneous solutions of 2,3,9,10,16,17,23,24-octakis(3-phthalimidopropyloxy)phthalocyaninatozinc(II) (5) and 2,3,9,10,16,17,23,24-octakis(3-aminopropyloxy)phthalocyaninatozinc(II) (6) are reported.
Synthesis and redox properties of a [meso-tris(4-nitrophenyl) corrolato]Mn(III) complex
Authors: Fryxelius Jacob , Eilers Gerriet , Feyziyev Yashar , Magnuson Ann , Sun Licheng , Lomoth Reiner
Published: July 2009

The Mn complexated corrole [ T (4- NO 2 P ) Corr ] Mn ( py ) (3) has been prepared ( py = pyridine ) where [ T (4- NO 2 P ) Corr ] is the trianion of the electron-poor 5,10,15-tris(4-nitrophenyl)corrole (1). The preparation of 3 includes a new synthetic method to form the corrole ligand 1 in a two-step synthesis. The Mn(III) complex gives a parallel mode EPR signal centered around g = 8.2 with six distinct hyperfine lines ( A || = 139 × 10-4 cm -1). Electrochemically 3 undergoes one reversible oxidation ( E 1/2 = 0.12 V vs Fc) and two reversible reductions ( E 1/2 = -1.45, -1.61 V). The oxidation is metal-centered and the product has been characterized by EPR spectroscopy as an S = 3/2 Mn(IV) species with no indication for oxidation of the macrocycle. The reductions of complex 3 are ligand based, and at the potential of the second reduction step a stable nitrogen centered radical with g = 2.0055 is generated. Chemical oxidation of 3 by iodosobenzene yields a Mn(IV) complex and epoxidation of cis-stilbene is not catalyzed by the Mn complex.
Solution STM images of porphyrins on HOPG reveal that subtle differences in molecular structure dramatically alter packing geometry
Authors: Zou Zhi-Qiang , Wei Lingyun , Chen F. , Liu Zhiming , Thamyongkit Patchanita , Loewe Robert S. , Lindsey Jonathan S. , Mohideen U. , Bocian David F.
Published: July 2009

Solution STM images are reported for free-base octaethylporphyrin ( H 2 OEP ) and the Cu ( II ) and Zn ( II ) chelates ( CuOEP and ZnOEP ) on HOPG in 1,2-dichlorobenzene solution under ambient conditions. H 2 OEP and CuOEP each form a quasi-square lattice, whereas ZnOEP forms a quasi-hexagonal lattice on the surface. The binary mixture of any two of the porphyrins forms a well-ordered two-layer structure on the HOPG surface, with one species occupying the bridge sites of the array of the other species. All of the mixed adlayers exhibit a quasi-hexagonal lattice with a higher packing density than the single-component adlayers. Collectively, these observations indicate that the structure of the adlayers is controlled by a complex interplay of substrate-molecule and molecule-molecule interactions.
Effect of tetrapyrrole-based photosensitizers on spin trapping by 5,5-dymethyl-1-pyrroline N-oxide
Authors: Németh András , Mamasheva Zuchra , Jemnitz Katalin , Vidóczy Tamás , Jakus Judit
Published: July 2009

Kinetics of the effect of three different tetrapyrrole-based photosenzitizers, pheophorbide a, meso-tetrahydroxyphenyl chlorin, and 3,7-bis(2-carboxyethyl)-2,8,12,17-tetramethyl-13,18-bis[(5-propoxycarbonyl-3-4-dihidroxy-phenyloxy) ethyl] porphyrin, on spin trapping with of 5,5-dymethyl-1-pyrroline N -oxide (DMPO) – a method widely applied in photodynamic therapy research – was investigated in the chemical model system of initiated oxidation of ethylbenzene. Spin adducts were measured by ESR spectroscopy, and kinetics of the consumption of the spin trap and accumulation of main products of oxidation (acetophenon, 1-phenyl-ethanol and 1-phenyl-ethyl-hydroperoxide) were followed using high performance liquid chromatography. The ESR spectrum of the non-illuminated system corresponded to an adduct formed between the spin trap and α–phenylethyl peroxyl radical, while under illumination, the spectrum indicated competitive formation of another adduct. Based on analysis of the corresponding g factor and hyperfine coupling constant values of the latter adduct ( g = 2.00587, αN = 13.57 G , αH = 2.27 G ), the nitrone ring has presumably been split up and an adduct was formed between α-phenylethyl radical and 4-methyl-4-nitrosopentanoic acid – a product of the oxidation of the parent spin trap by singlet oxygen. Computer modeling based on detailed reaction mechanism and fitted to the measured data confirmed this assumption. The rate constants gave values of 2.3 × 105 M −1. s −1 for the formation of the adduct and 1.0 × 104 M −1. s −1 for its decay by interaction with free radicals offering a more detailed quantitative understanding of spin trapping in the presence of tetrapyrrole photosensitizers under illumination.
A new procedure for the synthesis of water-soluble tri-cationic and -anionic phthalocyanines
Authors: Sharman Wesley M. , van Lier Johan E.
Published: July 2009

A series of water-soluble tri-anionic and -cationic substituted phthalocyanines has been synthesized via iodinated boron subphthalocyanines. The latter were opened with differently substituted diiminoisoindolines via the Kobayashi ring expansion reaction followed by metal insertion to exclusively yield the asymmetrically 3:1 substituted iodinated zinc phthalocyanines. These iodinated phthalocyanines readily underwent palladium-catalyzed coupling reactions with terminal alkynes such as 5-hexynoic acid and 10-undecynoic acid to give anionic phthalocyanines, or with 2-ethynylpyridine and 3-ethynylpyridine followed by N -methylation to give cationic phthalocyanines. These novel asymmetrically substituted charged phthalocyanines could have interesting properties as photosensitizers for photodynamic therapy.
Syntheses of boronic-acid-appended metalloporphyrins as potential colorimetric sensors for sugars and carbohydrates
Authors: Zhang Chen , Suslick Kenneth S.
Published: July 2009

Boronic-acid-based dyes have been widely studied in the past decade as potential sensors for sugars and carbohydrates, owing to the strong interaction of boronic acid and diols. In this work, two boronic-acid-appended metalloporphyrins were synthesized by new routes and tested as potential sugar and carbohydrate sensors. Boronic acid substituents were attached either to a β-pyrrolic position ((2-dihydroxylboryl-5,10,15,20-tetraphenylporphyrinato)zinc(II), 1) or to the meso-position ((10-dihydroxylboryl-5,15-diphenylporphyrinato)zinc(II), 2) of the porphyrin core. These complexes were tested as potential carbohydrate sensors; unfortunately, no UV-vis or fluorescence spectra changes were observed with the addition of glucose or fructose. Molecular orbital calculations confirm little electronic conjugation between the porphyrin π-system and the boronic acid substituents in either pyrrolic or meso-positions.
The reaction of [bispyridinotetrakis(t-butyl)phthalocyaninato]iron(II) with dioxygen to give μ-oxo-bis[tetrakis(t-butyl)phthalocyaninato]iron(III)
Authors: Monacelli Fabrizio , Viola Elisa
Published: July 2009

The reaction of [bispyridinotetrakis(t-butyl)phthalocyaninato]iron(II), ( py )2 FePc t, with dioxygen in CH 2 Cl 2, gives almost quantitatively the oxo-bridged μ-oxo-bis[tetrakis(t-butyl)phthalocyaninato]iron(III) as the final, stable product. The reaction order with respect to the starting complex changes within a run. For t = 0, the rate is proportional to the ratio [Formula: see text] (Equation 1) where y0 is the initial absorbance of the solution and a1 and a2 are linear functions of [O2]. For t > 0, the instantaneous rate is instead described by the equation Rate = b [O2][A]/([A]0 - [A]) (Equation 2), where A is ( py )2 FePc t and the coefficient b is again proportional to [ O 2]. A mechanism is proposed implying the presence of trace amounts of ( py )(S) FePc t (S = axially bound CH 2 Cl 2) in equilibrium with ( py )2 FePc t. Both species are able to generate the transient pentacoordinate ( py ) FePc t that may react with py and S, giving back the hexacoordinate precursors, or with dioxygen, giving ultimately the μ-oxo complex. At t = 0, the species ( py )(S) FePc t, expected to be much more labile than ( py )2 FePc t, is at its maximum concentration and is assumed to give the prevaling contribution to the instantaneous rate. As the reaction proceeds, and free pyridine accumulates in the solution, the concentration of ( py )(S) FePc t decreases rapidly and the transient ( py ) FePc t is produced essentially by the bispyridino complex. This fact and the still growing concentration of free pyridine account for the Equation 2. Finally, when the py concentration is buffered by addition of small amounts of base, the reaction attains a simple first order law. Present data further support the iron(III) formulation of the final μ-oxo product and are inconsistent with the iron(II) hypothesis put forward by some authors.
Effect of air-absorbed oxygen and moisture on the chemical stability of photoexcitedMg,ZnandEuphthalocyanines in dimethylformamide
Authors: Słota Rudolf , Dyrda Gabriela , Hnatejko Zbigniew , Karolczak Jerzy , Stryła Zdzisław
Published: July 2009

Absorption of oxygen and moisture from air by MPc-DMF systems was studied and related to the molecular stability demonstrated by phthalocyanine complexes (unsubstituted MPc's : MgPc , ZnPc and EuPc2; Pc = phthalocyanine ligand, C32H16N8) subjected to UV irradiation. A lower stability of air-exposed dimethylformamide solutions is observed and is due to a specific affinity for molecular oxygen revealed by the Pc macrocycle. SEM results proved oxygen molecules fixed to the phthalocyanine solids by forces strong enough to sustain desorption under vacuum. Absorption curves determined for MPc-DMF systems also indicate oxygen accommodated by the phthalocyanine moiety. This explains the predominantly oxygen-mediated photolysis, as well as the very short fluorescence lifetimes of metal phthalocyanines. The effect of air-absorbed moisture on the photostability is much less pronounced and practically insignificant for concentrations of H2O lower than 1%. An apparent stabilizing effect of water was observed and elucidated basing on kinetic considerations. The degradation rate of the photoexcited phthalocyanine moiety in air-exposed solutions depends on individual chemical properties and the molecular structure of the complex. EuPc2proved very stable whereas the photostability of ZnPc and MgPc gradually decreased in the course of time.
The features of cerium coordination chemistry in the complexes with tetra-15-crown-5-phthalocyanine
Authors: Birin Kirill P. , Gorbunova Yuliya G. , Tsivadze Aslan Yu.
Published: July 2009

For the first time, using a method of direct interaction of crownphthalocyanine and cerium(III) acetate in the presence of strong organic base, a sandwich-type double-decker cerium(IV) bis[tetra-(15-crown-5)-phthalocyaninate] [ Ce 4+( R 4 Pc 2−)2]0 ( R 4 Pc 2− = [4,5,4',5',4″,5″,4‴,5‴-tetrakis-(1,4,7,10,13-pentaoxapentadecamethylene)-phthalocyaninate-anion]) is synthesized with 60% yield. The composition and structure of the obtained complex are confirmed using spectral methods. UV-vis, IR and 1 H NMR spectroscopy and MALDI-TOF mass-spectrometry were used for characterization of the complex. It has been shown, that a particular feature of cerium ion in the complex with tetra-15-crown-5-phthalocyanine is the stability of oxidation state +4, unlike other lanthanide ions. The Ce(IV) complex has been obtained despite using a Ce(III) salt in synthesis. It has been found that the introduction of crown ether substituents in the phthalocyanine molecule results in a decreased stability of the compound to oxidation in comparison with unsubstituted and tert-butylsubstituted cerium phthalocyaninates.
Nitric acid promoted formation of an N-confused porphyrin-derived porphodimethene and a violinoid
Authors: Hung Chen-Hsiung , Liaw Chia-Chi , Chin Wei-Ming , Chang Gao-Fong , Chuang Chuan-Hung
Published: July 2009

The nitration of free-base N -confused porphyrin led to a novel 5,10-meso-dihydroxy- N -confused porphodimethene and an open-ring N -confused violinoid. The results support nitration occurring first, followed by nucleophilic addition of a hydroxyl group and a parallel reaction of oxygenolysis to cause the ring-opening. The nitro group substituted at the inner carbon of the inverted pyrrole ring is located on both the porphodimethene and violinoid. In the case of the porphodimethene, two dihydroxyl groups with υ( OH ) at 3404 cm−1 are arranged in a syn conformation at the same side with the nitro group. The violinoid exhibits υ( C = O ) at 1659 cm−1. NMR and structure determination suggest that oxygenolysis occurs selectively at the C=C bond between the α-pyrrole and meso carbon closest to the amino NH of the inverted pyrrole ring. The single crystal structure of porphodimethene gave a 50% disorder between the peripheral nitrogen and carbon atom on the inverted pyrrole ring, while a dimeric structure assembled through hydrogen bonding interactions was observed in the crystal lattice of the violinoid.
Electrostatic self-assembly layer-by-layer film fabrication using a polycation and a phthalocyanine dye anion
Authors: Son Young-A , Park Young-Min , Kim Byung-Soon
Published: July 2009

A multi-layer film has been fabricated, using poly(diallyldimethylammonium chloride) ( PDDAC ) and a copper phthalocyanine ( CuPc ) dye, held together by electrostatic forces and layer-by-layer self-assembly attractions. The result of the multi-layer fabrication was characterized by UV-vis absorbance measurements and Atomic Force Microscopy (AFM). UV-vis absorption spectra of the multi-layer films increased linearly at 676 nm, which indicated that the fabrication proceeded regularly. The AFM images show that the surface of the self-assembled multi-layer was thickly covered with PDDAC / CuPc and relatively uniform.
Multi-layer preparation of phthalocyanine dye and diazonium resin using a self-assembly fabrication method
Authors: Park Young-Min , Kim Byung-Soon , Son Young-A
Published: July 2009

By using the electrostatic self-assembly technique, arranged multi-layer thin films composed of diazonium resin as the polycation and phthalocyanine as the anion, were alternately fabricated on a glass slide. The obtained multi-layers were characterized by UV-vis spectroscopy and Atomic Force Microscopy (AFM). The growth of multi-layers formed by the sequential alternative adsorption of diazonium resin and phthalocyanine was observed and determined. The results of UV-vis absorption show that the deposition process is progressive and uniform. In addition, AFM images of the self-assembled multi-layer films reveal that the surface of the films is relatively uniform.
Photoinduced electron-transfer processes between phthalocyanines and perylene derivatives
Authors: Kitazume Koji , Chen Yu , Itou Mitsunari , Araki Yasuyuki , Uchida Satoshi , Ito Osamu
Published: July 2009

Photoinduced electron-transfer processes between phthalocyanines ( H2Pc and ZnPc ) as electron donors and perylene derivatives as electron acceptors have been studied using a time-resolved, nanosecond transient absorption method in benzonitrile. The observed findings show that intermolecular electron transfer takes place via the excited triplet states of ZnPc and H2Pc , as confirmed by the characteristic transient absorption bands in the near-IR region. The visible light excitation of the mixtures of H2Pc and the perylene derivatives adsorbed onto TiO2gave a relatively high photovoltaic efficiency.
Corrole-sensitized TiO2 solar cells
Authors: Walker Don , Chappel Shlomit , Mahammed Atif , Brunschwig Bruce S. , Winkler Jay R. , Gray Harry B. , Zaban Arie , Gross Zeev
Published: July 2009

We are investigating the properties of corrole-sensitized TiO 2 solar cells. The TiO 2-adsorbed free base and Ga III corroles display cell efficiencies under AM 1.5 illumination that are about half that of a standard N 3-sensitized cell ( N 3 = cis-bis(4,4'-dicarboxy-2,2'-bipyridine)dithiocyanato ruthenium(II)), while that of the Sn IV-based cell is much lower. The properties of the corrole- TiO 2 solar cells, along with results obtained with electrodes of lower conduction band energies clearly reveal that the reducing power of the singlet excited states of the free base and Ga III corrole, but not of the Sn IV derivative, is sufficiently high for efficient injection into the TiO 2 conduction band.
Resonance Raman spectra of highly reduced iron porphycenes
Authors: Gulam Rabbani M. , Neya Saburo , Teraoka Junji
Published: July 2009

The redox behavior of iron porphycenes using the sodium mirror contact technique is reported. The resonance Raman spectra are obtained for each redox state, in order to explore the vibrational characteristics of these species in different redox states. The observed resonance Raman behavior of Fe II porphycene anion radical and its dianion is interpreted using the vibrational analysis of free-base porphycene anion radical and dianion. For the first time, a species generated in the fourth reduction step, is confirmed by UV-vis spectroscopy and is assigned to Fe I porphycene π dianion. The dependence of resonance enhancements of Raman bands for the Fe I porphycene π dianion on excitation laser reveals structural distortion along the NC a C a N or C b C a C a C b segments of the pyrrole-pyrrole direct connection in the excited electronic state.
Guanine-specific DNA oxidation photosensitized by the tetraphenylporphyrinP(V) complex
Authors: Hirakawa Kazutaka , Kawanishi Shosuke , Segawa Hiroshi , Hirano Toru
Published: July 2009

Porphyrins have been studied as photosensitizers in photodynamic therapy. DNA is one of the most important targets of the sensitizer. In the present study, we have examined the photosensitized DNA damage caused by dihydroxo P ( V ) tetraphenylporphyrin ( P ( V ) TPP ), a cationic water-soluble porphyrin. P ( V ) TPP photosensitized guanine-specific damage to the DNA fragment. P ( V ) TPP induced severe photodamage to single-stranded rather than to double-stranded DNA. High performance liquid chromatography measurements confirmed the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-G), an oxidized product of 2'-deoxyguanosine, and showed that the content of 8-oxo-G in single-stranded DNA is larger than that in double-stranded DNA. The effects of reactive oxygen scavengers on DNA damage suggested the involvement of singlet oxygen (1O2). Photosensitized1O2formation was confirmed by near-infrared emission measurements. The results showed that1O2formation mainly contributes to the mechanism of DNA photodamage by P ( V ) TPP . Absorption spectrum measurements showed the interaction between P ( V ) TPP and DNA. This interaction is expected to enhance the1O2-mediated DNA damage since the lifetime of1O2in a cell is very short. On the other hand, P ( V ) TPP induced DNA damage at the consecutive guanines in double-stranded DNA. Because the consecutive guanines act as a hole trap, this DNA-damaging pattern suggests the partial involvement of photo-induced electron transfer. The fluorescence of P ( V ) TPP was quenched by DNA, supporting the electron transfer mechanism. However, DNA damage by electron transfer was not a main mechanism possibly due to reverse electron transfer. In conclusion, P ( V ) TPP binds to DNA and induces guanine-specific, photo-oxidation mainly via1O2generation.
Role of positive charge of lysine residue on cytochrome c3for electrostatic interaction with hydrogenase
Authors: Iida Shin , Asakura Noriyuki , Tabata Kenji , Okura Ichiro , Kamachi Toshiaki
Published: July 2009

Cytochrome c3from Desulfovibrio vulgaris (Miyazaki) is an electron transfer protein containing four hemes per molecule. Its physiological electron transfer partner is the hydrogenase which catalyzes reversible oxidation of hydrogen. The complex formation between cytochrome c3and hydrogenase is caused by electrostatic interaction, because cytochrome c3is a basic protein and hydrogenase is an acidic protein. As cytochrome c3has 20 lysine residues among 108 amino acids, the positive charges of some lysine residues may play an important role in the interaction with hydrogenase. To clarify the role of positive charge of lysine residue, the positive charge was changed to neutral or negative charge using chemical modification and site-directed mutagenesis. When the positive charges around heme IV were changed, the hydrogen evolution rate with hydrogenase decreased. The affinity between hydrogenase and mutated cytochrome c3(K57Q, K57E, K72Q, K94Q, K94E) were not affected. On the other hand, the affinity of K72E cytochrome c3for hydrogenase was very low. These results suggest that the positive charge around heme IV plays an important role in the electrostatic interaction with hydrogenase in hydrogen evolution.
Carbon nanotubes and porphyrins: an exciting combination for optoelectronic devices
Authors: Langa Fernando , José Gómez-Escalonilla M. , de la Cruz Pilar
Published: July 2009

Hybrids between carbon nanotubes and porphyrins, either covalently or non-covalently linked, have been the target of numerous groups with the aim of studying their properties and searching for potential applications. The state of the art in the field of carbon nanotubes and porphyrins is reviewed here.
Syntheses and nonlinear absorption properties of conjugated porphyrin supramolecules
Authors: Ogawa Kazuya , Hara Chihiro , Kobuke Yoshiaki
Published: July 2009

Self-assemblies consisting of acetylene-linked bisporphyrins with a 4-nitrophenylethynyl substituent and with a phenylethynyl substituent were synthesized. The Q-band of the phenylethynyl-substituted compound appears at 762 nm whereas that of the 4-nitrophenylethynyl-substituted one was red-shifted to 784 nm and intensified. This may be attributed to the participation of the nitro group in the π-electronic communication system. HOMOs and LUMOs were calculated for these compounds using an INDO/S-CI method. The effective two-photon absorption cross-section values of these self-assemblies were measured by using a nanosecond open aperture Z-scan method. The maximum effective two-photon absorption cross-section values of 4-nitrophenylethynyl- and phenylethynyl-substituted bisporphyrins were obtained as 1.2 × 105 GM and 8.1 × 104 GM , respectively, at 890 nm. A 1.5 enhancement factor was obtained by introducing nitro groups, which was similar to the value previously reported for ferrocene- and fullerene-connected supramolecular porphyrin.
Synthesis and photophysical properties of water-soluble dendrimers bearing a phthalocyanine core
Authors: Nishida Masakazu , Momotake Atsuya , Shinohara Yoshihiro , Nishimura Yoshinobu , Arai Tatsuo
Published: July 2009

Aggregation behaviors of phthalocyanine derivatives which have a dendritic structure were examined in an aqueous solution. We prepared the first- and second-generation dendrimers (WG1-PC and WG2-PC), having water-soluble substituents as a peripheral group, to be resolved in water. From spectroscopic measurement, WG2-PC acted in a monomeric manner, even in an aqueous solution, in contrast to WG1-PC, which exhibited spectra attributed to aggregation. This implies that a higher generation of water-soluble dendrimers can prevent a phthalocyanine core from forming an aggregation. The introduction of the second-generation dendrons to an aggregatable core may be effective to avoid self-aggregation and an undesirable deactivation process.
Strong reverse saturable absorptive effect of an ultrathin film containing octacarboxylic cobalt phthalocyanine and polyethylenimine
Authors: He Chunying , Wu Yiqun , Shi Guang , Jiang Li , Duan Wubiao , Song Yinglin , Chang Qing
Published: July 2009

A novel nanoscopic composite film with alternating layers consisting of anionic octacarboxylic cobalt phthalocyanine [ CoPc ( COONa )8] and cationic polyethylenimine (PEI) has been fabricated by an electrostatic, layer-by-layer, self-assembly technique. UV-vis spectroscopy revealed consecutive regular deposition of CoPc ( COONa )8/ PEI onto a quartz slide. The film's delicate nanostructure was characterized by atomic force microscopy and small angle X-ray diffraction. Third-order nonlinear properties of the film performed using Z-scan measurements with 21 ps laser pulses at the incidence wavelength of 532 nm showed rather strong, nonlinear reverse saturable absorption.
Aerobic liquid-phase oxidation of p-xylene over metalloporphyrins
Authors: Jiang Quan , Hu Hai-Yang , Guo Can-Cheng , Liu Qiang , Song Jian-Xin , Li Qing-Hong
Published: July 2009

The five metalloporphyrins ( T (p- Cl ) PPM , M = Fe , Mn , Co , Cu , Zn ) with different metal nuclei were synthesized, and their catalytic aerobic liquid-phase oxidations of p-xylene into p-toluic acid, p-toluic aldehyde and terephthalic acid using a low concentration of acetic acid as solvent without any halide additives, were studied. The p-xylene conversions and the oxidation product distributions were found to be affected by the structures and concentration of the metalloporphyrins as well as the reaction parameters such as time, temperature and air pressure. The formation of some intermediate oxidation products in the oxidation process also influenced the reaction conversions and the product distribution. Among the metalloporphyrins used, tetrakis(p-chlorophenylporphinato)manganese chloride ( T (p- Cl ) PPMnCl ) was the most efficient catalyst for the oxidation of p-xylene. Under the conditions of 180 °C and 2.0 MPa, 44% conversion of p-xylene and 85% selectivity of p-toluic acid were obtained. Based on the results obtained, a preliminary mechanism of the oxidation of p-xylene over metalloporphyrins was proposed.
The observation of room temperature delayed fluorescence in various non-peripherally substituted phthalocyanines
Authors: Swarts Jannie C. , David Maree M.
Published: July 2009

The first observation of direct room temperature delayed fluorescence from non-peripherally substituted phthalocyanines is reported. The quantum yields of delayed fluorescence and delayed fluorescence lifetimes were determined and are discussed. The normal fluorescence quantum yields and photodegradative quantum yields of these compounds were also determined.
Electrochemically induced orientation of copper phthalocyanine thin films
Authors: Gaffo Luciana , Rinaldi Andrelson W. , Santos Marcos J. L. , Girotto Emerson M.
Published: July 2009

The dependence of the electrochromic and organizational behaviors of copper phthalocyanine ( CuPc ) evaporated thin films on oxidation level have been investigated. UV-vis experiments with CuPc thin film obtained before cyclic voltammetry display two Q bands in the region between 600 and 700 nm, which correspond to the α form of CuPc . The FTIR spectra show an improved molecular orientation of CuPc molecules, obtained after the electrochemical process. Molecules in the film in the oxidized state (1.27 V) display a plane parallel to the film surface, indicating a flat-on molecular orientation. Spectrum changes observed after one complete voltammetric cycle (between −0.5 and 1.5 V) show an evolution from a mixed molecular organization to an edge-on organization.
Vibrational analysis of Ni(II) complex with 4,12-ditolyl-16,24-diphenyl-3-thiaporphyrin (SDTDPPNi(II)Cl) and its isotopic labeled (61Ni(II), −d6, and −d10) derivatives
Authors: Podstawka Edyta , Fościak Mateusz , Chmielewski Piotr , Proniewicz Leonard M.
Published: July 2009

This work presents complete vibrational analysis of a chloride complex of Ni (II) 4,12-ditolyl-16,24-diphenyl-3-thiaporphyrin ( SDTDPPNi (II) Cl ) and its isotopic derivatives (61 Ni (II), − d 6, and −d 10). Five-coordinate SDTDPPNi (II) Cl , SDTDPP 61 Ni (II) Cl , ( SDTDPP - d 6) Ni (II) Cl , and ( SDTDPP - d 10) Ni (II) Cl were investigated by Fourier-Transform infrared (FT-IR), resonance Raman (RR), and electronic absorption (UV-vis) methods. Because the methyl groups of tolyl rings at the para-position have negligible influence on geometry and vibrational spectra of SDTDPPNi (II) Cl , they can be treated as point groups. Thus, geometry optimization and vibrational frequencies were calculated for the 4,12,16,24-tetraphenyl-3-thiaporphyrin ( STPPNi (II) Cl ) model molecule and its isotopically labeled analogs using Gaussian'03. Moreover, charge distributions (General Atomic Polar Tensor – GAPT) and geometrical aromaticity indexes (Bird's I 5 and Harmonic Oscillator Model of Aromaticity – HOMA) were calculated. All theoretical calculations were performed at the B3LYP level with the LANL2DZ basis set. As is shown, the experimental FT-IR and RR spectra for each compound are reproduced well by the corresponding theoretical spectra.
Resonance Raman and absorption properties of Zn(II) and Ni(II) polynitroporphyrins and their chemical reduction products
Authors: Terekhov Sergei N. , Sinyakov Gennadii N. , Lobko Evgeni E. , Battiony Pierrette , Turpin Pierre-Yves , Chirvony Vladimir S.
Published: July 2009

Electron-deficient metallocomplexes of dodeca- and octanitroporphyrins produced by the introduction of 8 β-nitro substituents or 8 β-nitro and a meta-nitro substituent on each meso-aryl ring of Zn (II) and Ni (II) [meso-tetra-(2,6-dichlorophenyl)porphyrin] (Zn8, Ni8 and Zn12, Ni12, respectively) and their air-stable reduced species have been characterized by steady-state absorption and Soret-excited resonance Raman spectroscopies. One-electron reduced species of the metallocomplexes were produced by three different procedures (in deprotonated tetrahydrofuran in air ambient, in tetralhydrofuran with the addition of piperidine in air ambient, and in contact with a sodium mirror under vacuum) and demonstrated similar absorption and RR spectra. It is concluded on the basis of the RR spectra that the one-electron reduction products of the studied polynitrosubstituted metalloporphyrins are π–anion radicals in character.
MnII/O2-oxidation products of α,ω-dimethyldipyrrins
Authors: Bröring Martin , Penno Dirk , Krüger Robin
Published: July 2009

A α,ω-dimethyldipyrrin with and without a meso-situated phenyl substituent has been investigated as the substrate in the oxidation reaction with the Mn II/ O 2 system. While for the meso-phenyldipyrrin, the expected, though impure and sensitive diformyl derivative is formed, the reaction of the meso unsubstituted dipyrrin leads to a novel tripyrrolic species, the α-(vinylpyrrolyl)dipyrrin, as the only isolable product. The new tripyrrole displays positive solvatochromic behavior and has been investigated with respect to this property.
Zinc phthalocyanine-nicotinamide complexes: evidence of their formation by using spectral studies
Authors: Del Sole Roberta , Lazzoi M. Rosaria , De Luca Agnese , Vasapollo Giuseppe
Published: July 2009

Spectral studies and job plot analyses which provide evidence of the formation of complexes of zinc phthalocyanines or zinc naphthalocyanines and nicotinamide or its positional isomers, known as isonicotinamide and picolinamide, are reported. Nicotinamide, isonicotinamide and picolinamide contain the amide group in a different position in the ring and these molecules can coordinate the metal of phthalocyanines through their nitrogen pyridinic atom, or their amide group, to form complexes. FT-IR and NMR spectroscopic studies, as well as job plot analyses in chloroform, have been performed. To validate the formation of complexes, some of them have been isolated, fully characterized and their binding properties and thermal stability have also been investigated.
Effects of substituted metal-free porphyrins in apo-horseradish peroxidase
Authors: Rad A. Molaei , Moosavi-Movahedi A. Akbar , Ghourchian Hedayatollah , Safari Nasser , Hong Jun , Moosavi-Movahedi Zinab , Nazari Khodadad , Saboury A. Akbar , Jamaat P. Rajabali
Published: July 2009

The peroxidase-like catalytic activities of some synthetic porphyrins following substitution in apo-horseradish peroxidase (apo-HRP) were studied by UV-vis and fluorescence spectrophotometries in buffer potassium phosphate solution at pH 7. The insertion of these synthetic porphyrins in apo-HRP is very difficult, due to steric hindrances between coordinated metals in porphyrins and the side-chains of amino acids in native protein. However, because of planar coordination following insertion in an active site of apo-HRP tetrapyridylporphyrin(TPyP), a metal-free porphyrin, adsorbs free metal ions from the environment and shows higher peroxidase-like catalytic activity than other new synthetic porphyrins. The results indicate that the metal-free porphyrins with optimum Reinheitzahl (RZ) show higher catalytic activity relative to others. The fluorescence emission of TPyP only, and of apo-HRP-TPyP, displayed significantly different wavelengths for the maximum aromatic fluorescence intensity. The λmaxfor apo-HRP-TPyP was around 447 nm, while for TPyP, alone, it increased to 463 nm, which showed that the aromatic groups' surroundings changed upon substitution of porphyrins in a low polar environment.
Discotic liquid crystals of transition metal complexes 39: columnar mesomorphism and homeotropic alignment speed of sandwich-type of double-deckers and triple-deckers based on phthalocyaninato lutetium metal complexes
Authors: Mukai Hidetomo , Hatsusaka Kazuaki , Ohta Kazuchika
Published: July 2009

A series of sandwich-type metal complexes, bis[2,3,9,10,16,17,23,24-octakis(3,4-dialkoxyphenoxy)phthalocyaninato]lutetium(III) ({[( C n O )2 PhO ]8 Pc }2 Lu (n = 8−16): double-deckers (2)), were synthesized. As the by-product, tris[2,3,9,10,16,17,23,24-octakis(3,4-diakoxyphenoxy)phthalocyaninato]dilutetium(III) ({[( C n O )2 PhO ]8 Pc }3 Lu 2 (n = 8, 9, 11, 12, 14, 16): triple-deckers (3)) were successfully separated. The mesomorphic properties of these double-deckers (2) and triple-deckers (3) were investigated using a polarization microscope, differential scanning calorimetry and temperature-dependent X-ray diffraction techniques. The double-deckers (2) showed Colh , Cub and Coltet mesophases for n ≥ 10. On the other hand, the triple-deckers (3) showed only a Colr mesophase for n = 8, only a Coltet mesophase for n = 14, and both Colr and Coltet mesophases for n = 9, 11, 12 and 16. For the Coltet mesophase, both the double-deckers (2) and the triple-deckers (3) exhibited spontaneous homeotropic alignment in a large area. In comparison with the homeotropic alignment of these present lutetium complexes 2, 3 and the previous copper complexes, 2,3,9,10,16,17,23,24-octakis(3,4-dialkoxyphenoxy)phthalocyaninato copper(II) ([( C n O )2 PhO ]8 PcCu (n = 9-14): single-decker (1)), the alignment was fast, slow and fast, respectively, in the order of the single-deckers (1), double-deckers (2) and triple-deckers (3). Very interestingly, the complexes 1 and 3 which have flat Pc macrocycles gave fast alignment, whereas the complexes, 2, which have non-flat Pc macrocycles, gave slow alignment. Thus, it was revealed for the first time that the flatness of discotic liquid crystalline molecules influences the speed of homeotropic alignment.
Conformation and π-conjugation of olefin-bridged acceptor on the pyrrole β-carbon of nickel tetraphenylporphyrins: implicit evidence from linear and nonlinear optical properties
Authors: Yeh Hsiu-Chih , Chen Chin-Ti , Yu Jenwei , Tsai Pei-Chang , Wang Juen-Kai
Published: July 2009

This paper has scrutinized, both experimentally and theoretically, the conformation of an olefinic substituent on the pyrrole β-carbon of tetraphenylporphyrin. Compelling evidences collected from linear optical absorption and NOESY 1H NMR experiment strongly suggest that, in solution, it is highly possible for the olefinic acceptor on pyrrole β-carbon to have a coplanar or near coplanar conformation with the pyrrole of the porphyrin core. This conformation ensures effective π-conjugation between the pyrrole ring and its olefinic substituent which is reflected in the linear absorption spectroscopy as the red-shifting of both Soret and Q-bands and possibly the splitting of the absorption Soret band. The intensified long wavelength absorption Q-band of the porphyrin is also consistent with the proposed π-conjugation. Regarding nonlinear optical absorption, an active nonlinear optical (NLO) response has been observed for these porphyrins, indicative of efficient electronic coupling (resonance interaction) between the electronic acceptor and porphyrin macrocyclic ring, compatible with a coplanar or near coplanar conformation in order to achieve π-conjugation. Such conformation of the peripherally appended olefinic acceptor has been further confirmed by INDO/1 Hamiltonian in the ZINDO computational calculations. The INDO/S electron density calculation further reveals that the range of intramolecular charge-transfer (ICT) does not encompass the whole porphyrin core but is mostly confined to the pyrrole ring attached to the olefin-linked acceptor. Furthermore, ICT characteristics were found to be more heavily involved in the Soret absorption band than Q-band. Our analysis of the porphyrin π-conjugation is consistent with modest solvatochromic behavior and the moderate NLO activity of the porphyrins compared with NLO chromophores with many less π-electrons.
Rational oxidation of cyclohexane to cyclohexanol, cyclohexanone and adipic acid with air over metalloporphyrin and cobalt salt
Authors: Hu Bo-Yu , Yuan Yong-Jun , Xiao Jiang , Guo Can-Cheng , Liu Qiang , Tan Ze , Li Qin-Hong
Published: July 2009

A systematic study on the effect of a catalyst on the aerobic oxidation of cyclohexane was carried out using cobalt isooctanoate, metalloporphyrin p- ClTPPCo and [p- ClTPPFe ]2 O as catalysts. The results showed that the metalloporphyrin-catalyzed system performed better than the traditional cobalt salt ( Co isooctanoate) in terms of both the reaction conversion and the selectivity of cyclohexanol and cyclohexanone (KA oil). More importantly, we discovered that bisironporphyrin complex, which was traditionally considered to be either non-active or not-so-active for hydrocarbon oxidation, excelled at 155°C, achieving high selectivity for KA oil (80%) and good reaction conversion (13.8%). This result is in sharp contrast to earlier results by others. Meanwhile, the production of adipic acid was also increased and good selectivity of adipic acid among the by-products was also obtained. Our study suggested that [p- ClTPPFe ]2 O catalyzed aerobic oxidation could be used to produce adipic acid in addition to KA oil. Some mechanistic rationales were proposed to explain the superior performance of the [p- ClTPPFe ]2 O catalyst based on its unique structural and chemical properties.
Interaction of NO2 gas with sublimed microporous layers of iron(II)-meso-mono-4-pyridyl-tri-aryl-porphyrins: Two different reaction pathways
Authors: Hovhannisyan Astghik A. , Kurtikyan Tigran S. , Kazaryan Robert K. , Goodwin John A.
Published: July 2009

Sublimed layers of Fe II MPyTPP and Fe II MPyTTP ( MPyTPP and MPyTTP are meso-mono-4-pyridyl-triphenyl- and meso-mono-4-pyridyl-tri-p-tolyl-porphyrin dianions, respectively) consist of coordination oligomers that are formed by binding of pyridyl nitrogen atoms with the iron centers of the adjacent molecules in the film. Fourier transform infrared (FT-IR) spectroscopy including experiments with the 15 NO 2 isotopomer demonstrates that the reaction of low pressure NO 2 gas with these layers leads to the formation of two types of complexes: six-coordinate nitro-complexes, in which the fifth site is occupied by the pyridyl group of the neighboring molecule in the layer and five-coordinate nitrito-complexes that terminate the oligomers. Further addition of NO 2 increments leads to the preferential oxidation of these nitrito ligands to bidentate nitrato ligands. These layers conserve their porosity upon standing and allow study of the oxo-transfer reactivity from coordinated nitro-groups to appropriate oxygen acceptors.