bluuebunny/crossref_metadata_2025 huggingface dataset:
Quenching of singlet photoexcited state of water soluble phthalocyanines and porphyrins by viologens interacting electrostatically
Authors: Kaneko Masao , Ueno Hirohito , Masuda Satoshi , Suzuki Kazuhisa , Okimi Hiroshi , Hoshino Mikio , Lapok Lukasz , Wöhrle Dieter
Published: July 2009

Quenching of photoexcited anionic and water-soluble phthalocyanines and 5,10,15,20-tetraarylporphyrins by viologens has been investigated. It was confirmed that the quenching of the singlet photoexcited state takes place, and that the mechanism is mostly a static one due to electrostatic interaction between the donor and the acceptor. The static mechanism was analyzed by curve-fitting of the relative emission intensity vs viologen concentration resulting in four kinds of mechanisms composed of static quenching accompanied partly by a dynamic one. The static mechanism was classified into two types: one mechanism is due to 1:n electrostatic interaction of the anionic sensitizer and the cationic acceptor, and other is a Perrin type for which the acceptor is incorporated into the quenching sphere around the sensitizer according to a Poisson distribution. The effect of micelles for the quenching was also studied including the effect of viologen with a long alkyl chain. The ionic micelles either incorporated or repulsed the ionic sensitizer and accepter resulting in either static quenching or prohibition of the quenching. Cationic phthalocyanines and porphyrins were also examined for the reaction with cationic viologens.
Synthesis of dipyrrin-containing architectures
Authors: Muthukumaran Kannan , Zaidi Syeda Huma H. , Yu Lianhe , Thamyongkit Patchanita , Calder Matthew E. , Sharada Duddu S. , Lindsey Jonathan S.
Published: July 2009

Dipyrrins are valuable precursors to dyes [dipyrrinatoboron difluoride, bis(dipyrrinato)-zinc(II) complexes] and serve as ligands in a variety of self-assembled materials. Six new dipyrrin-containing architectures have been synthesized. The architectures include bis(dipyrrinato) complexes containing copper(II) or palladium(II), a dipyrrin bearing a protected phosphonic acid unit, a porphyrin bearing two dipyrrins in a trans configuration, a linear diphenylethyne-linked dipyrromethane-dipyrrin building block, and a triad composed of two zinc porphyrins joined via an intervening bis(dipyrrinato)copper(II) complex. Two porphodimethenatozinc complexes were prepared and found to have Φ f ≤ 0.002 (in toluene at room temperature), which is substantially less than the analogous bis(dipyrrinato)zinc complexes. Taken together, the syntheses described herein should broaden access to dipyrrins for use as complexation motifs in supramolecular chemistry and as pigments in light-harvesting applications.
Influence of the spacer in bis-porphyrinic tweezers on the association constant for host/guest complexes
Authors: Solladié Nathalie , Bouatra Souhaila , Merkas Sonja , Rein Régis , Roeser Jéröme
Published: July 2009

Detailed complexation studies of two rigid tweezers bearing mono- or tris-anthracenic spacers is reported, along with the synthesis and characterization of two new tweezers bearing flexible nucleosidic linkers. For flexible tweezers bearing the two porphyrins at O -5' and O -3' positions of the ribose, the association constant for the complexation of DABCO increases, when compared to the association constant for the same base with a reference mono-porphyrin. The nucleoside seems to confer sufficient preorganization to this dimer to enhance the binding constant, documenting the fact that rigid dimers are not necessary for preorganization, and opening new routes to the rapid synthesis of flexible tweezers capable of complexing guests with high association constants.
Syntheses and properties of carboranylpyrroles
Authors: Clark J. Caleb , Fabre Bruno , Fronczek Frank R. , Vicente M. Graça H.
Published: July 2009

Synthetic routes to mono- and di-carboranylpyrroles (1-5) bearing the carborane groups linked either directly to the 3- and/or 4-positions of the pyrrole ring or via one or two methylene spacers are described. Several X-ray structures of key intermediates are presented and discussed. Carboranylpyrroles can be cyclotetramerized to afford carboranylporphyrins in low to moderate yields, depending on the number of carborane cages and their linkage to the pyrrole ring. The best yields of porphyrin were obtained with pyrrole 3, bearing a two carbon spacer between the carborane and pyrrole units. The electrochemical polymerization of pyrroles 2 and 3 gave functionalized conducting polymer films with increased overoxidation resistance and thermal stability compared with unsubstituted polypyrrole. Dicarboranylpyrrole 4 did not electropolymerize under a variety of experimental conditions, whereas pyrrole 5 formed only soluble oligomers.
Spectroelectrochemical behavior of N-confused dioxohexaphyrins
Authors: Mayer Ildemar , Nakamura Kiyohisa , Srinivasan Alagar , Furuta Hiroyuki , Toma Henrique E. , Araki Koiti
Published: July 2009

Doubly N -confused dioxohexaphyrins were characterized by cyclic voltammetry and spectroelectrochemistry in the -2.5 to +2.0 V vs Ag | Ag + (0.10 M, in CH3CN) range. Six reversible monoelectronic processes were found suggesting that the rich electrochemistry of porphyrin systems was preserved in that expanded macrocycle. However, the electronic and electrochemical properties of the free-base, Cu(II) and Ni(II) species were shown to be sensitive to the coordinated transition metal ions and solvent revealing a quite complex behavior, probably reflecting the higher flexibility and strong conformational effects on the energy levels and stability of those complexes.
High temperature molecular magnetism caused by π-electrons: copper phthalocyanine doped with alkaline metals
Authors: Sharoyan Eduard G. , Manukyan Aram S.
Published: July 2009

Electron spin resonance spectra of copper phthalocyanine doped with alkaline metals ( A x CuPc ) have been investigated. The temperature dependence of ESR spectra indicates ferromagnetic behavior. The Curie-Weiss temperature varies from 30 to 115 K depending on the stoichiometry x of the samples. Some particles of polycrystalline samples were attracted to a weak magnet at temperatures slightly higher than 77 K. The observed magnetism is caused by unpaired π-electrons of phthalocyanine anions on the eg doubly degenerated molecular orbital. The observed ferromagnetism can be understood within the framework of the McConnell-2 model proposed for organic ferromagnetic charge-transfer complexes. The high-temperature magnetism in A x CuPc is considered to be a result of the Zener mechanism of double exchange between phthalocyanine molecular anions of different valence.
Nucleobase (A, T, G and C) appended tri-cationic water-soluble porphyrins: synthesis, characterization, binding and photocleavage studies with DNA
Authors: Poddutoori Premaladha , Poddutoori Prashanth Kumar , Maiya Bhaskar G.
Published: July 2009

A series of nucleobase appended tri-cationic porphyrins ( AT 4, TT 4, GT 4 and CT 4) have been synthesized and their binding and cleaving ability of DNA were investigated in this present study. UV-vis, fluorescence, circular dichroism and thermal melting studies were carried out to investigate binding of the porphyrin with calf thymus DNA (CTDNA). The apparent binding constant ( K app ) and the intrinsic binding constant ( K b) values calculated from UV-vis and fluorescence titrations, respectively, were comparable to 5,10,15,20-tetra(N-methylpyridinium-4-yl) porphyrin ( H 2 T 4) or slightly more for few compounds. Circular dichroism spectra of these porphyrins with DNA show variation in their mode of binding. Among the nucleobase appended tri-cationic porphyrins, the porphyrin in GT4 and TT4 exhibit strong intercalating ability in the DNA duplex whereas the porphyrin in AT 4 and CT 4 exhibit very less ability for intercalation. The intercalating efficiency of the porphyrin in GT 4 is even stronger than that of the H 2 T 4. The steric strain exists between the tri-cationic porphyrin moiety and the DNA may decrease depending on (a) the ease to exhibit keto-enol tautomerism due to the more acidic protons in guanine and thymine, (b) extended conjugation and (c) hydrogen bonding capability of the nucleobase moieties. Photocleavage proclivities with pBR322 DNA in the presence of light reveal that AT 4, TT 4 and CT 4 show same amount of cleavage but GT 4 shows more cleaving efficiency than H 2 T 4 due to the stacked guanine moieties those are more reducing than a single guanine residue. The singlet oxygen mechanism that is responsible for the photocleavage was confirmed with various inhibitors and interestingly with Tiron (disodium salt of 1,2-dihydroxy-3,5-benzenedisulfonic acid) the photocleaving efficiency increases due to the inhibition of superoxide formation.
Synthesis and properties of a corrole with small and electron-withdrawing substitutents, 5,15-bis(trifluoromethyl)-10-pentafluorophenylcorrole
Authors: Goldschmidt Ruth , Goldberg Israel , Balazs Yael , Gross Zeev
Published: July 2009

Several methodologies for the synthesis of corroles that carry minimal-sized electron-withdrawing substituents at the meso- C atoms were investigated; of these the one based on dypyrromethane/aldehyde condensation was fruitful. The new corrole with one C 6 F 5 and two CF 3 groups, as well as its cobalt(III) complex, were fully characterized by spectroscopy and X-ray crystallography.
Synthesis and photophysical properties of a covalently bonded palladiummeso-sulfophenylporphyrin-poly(vinyl alcohol)polymer with potential applications as an oxygen sensor
Authors: Pereira Mariette M. , Ruano Francisco , Azenha M. Emília D. G. , Burrows Hugh D. , Miguel Maria G. M. , Douglas Peter , Eaton Kay
Published: July 2009

The synthesis and photochemical characterization of a covalently bonded palladium meso-sulfophenylporphyrin-poly(vinyl alcohol)polymer ( PVA - PdTPPS ), made via reaction of the chlorosulfonyl derivative of Pd meso-tetrakis-phenylporphyrin with the alcohol group of the polymer to form the sulfonate ester, is described. Absorption, emission and phosphorescence lifetime data are reported. In both the solid film and in aqueous solution phosphorescence decays in the absence of oxygen are non-monoexponential and suggest heterogeneity in the decay and oxygen quenching kinetics. As a solid film there is very little phosphorescence quenching by oxygen at moderate pressures of O2(0-30 Torr), but in aqueous solution oxygen quenches at a rate of 7.5 (±0.5) × 108M . s−1. The synthetic route described is versatile enough to be used with a variety of metalloporphyrins and polymers and this allows the possibility of extensive tuning in terms of lumophore lifetime, polarity, solubility, location in heterogeneous media, and compatibility with other polymers.
Preparation and characterization of meso-tetrakis(2,6-diaryloxyphenyl)porphyrins
Authors: Tohara Akira , Sugawara Yoko , Sato Mitsuo
Published: July 2009

A series of meso-tetrakis(2,6-diaryloxyphenyl)porphyrins was synthesized by the Lindsey method from pyrrole and 2,6-diaryloxybenzaldehydes, which were prepared by regioselective formylation of 1,3-diaryloxybenzenes. In CDCl 3 solution, 1 H NMR spectral analysis of ring current shifts arising from the porphyrin macrocycle and the attached phenyl rings indicated that meso-tetrakis(2,6-diphenoxyphenyl)porphyrin, the prototypical meso-tetrakis(2,6-diaryloxyphenyl)porphyrin, forms deep open well cavities above and below the porphyrin plane.
Synthesis and singlet oxygen production of azaphthalocyanines bearing functional derivatives of carboxylic acid
Authors: Musil Zbynek , Zimcik Petr , Miletin Miroslav , Kopecky Kamil , Link Marek , Petrik Pavel , Schwarz Jan
Published: July 2009

New metal-free, magnesium and zinc azaphthalocyanines ( AzaPc ) were prepared from 6-(3-tert-butylsulfany1-5,6-dicyanopyrazine-2-ylamino)hexanoic acid and its butylester and N,N-diethylamide. Their singlet oxygen production was measured by a dye-sensitized photooxidation of 1,3-diphenylisobenzofuran ( DPBF ) and ΦΔ values were calculated. It was found that the presence of carboxylic acid in the structure of AzaPc decreases their singlet oxygen production. Singlet oxygen activity of the newly prepared compounds (containing mixed alkylamino and alkylsulfanyl peripheral substituents) lies between purely alkylsulfanyl and alkylamino derivatives of AzaPc . This fact further supports previously proposed structure-activity relationships, where alkylsulfanyl derivatives belong to the best singlet oxygen producers while the presence of alkylamino substituents in the structure rapidly decreases their photodynamic properties.
Self-assembled, nano-structured octaalkoxy helicenocyanines
Authors: Mandal Braja K. , Sooksimuang Thanasat , Lee Chi-Hang , Wang Rong
Published: July 2009

A method to prepare a new class of helicene-fused phthalocyanine derivatives is outlined. These derivatives self-assemble into unique rod-like features, with a narrow length distribution of 750-850 nm and a uniform width of 95 ± 10 nm .
N, N', N″, N‴-tetramethyltetra-2,3-pyridinoporphyrazinato copper(II) methyl sulfate as a new and efficient catalyst for the dithioacetalization and the oxathioacetalization of carbonyl compounds
Authors: Akhlaghinia Batool , Tavakoli Sedigheh , Asadi Mozaffar , Safaei Elham
Published: July 2009

The use of N, N', N″, N‴-tetramethyltetra-2,3-pyridinoporphyrazinato copper(II) methyl sulfate as an efficient catalyst for the conversion of carbonyl compounds into their cyclic 1,3-dithioacetals and 1,3-oxathiolanes under mild reaction condithions is described.
meso-iodo- andmeso-iodovinylporphyrins via organopalladium porphyrins and the crystal structure of 5-iodo-10,20-diphenylporphyrin
Authors: Atefi Farzad , Locos Oliver B. , Senge Mathias O. , Arnold Dennis P.
Published: July 2009

The regiospecific halogen exchange reactions of various easily accessible meso-bromoporphyrins to obtain meso-iodoporphyrins, using η1-palladioporphyrins as intermediates, have been investigated. This one-pot methodology allows the isolation of meso-iodoporphyrins in excellent yields with short reaction times. Similarly meso-(2-bromoethenyl)porphyrins can be converted to their iodoethenyl analogues. These iodoporphyrins show great potential as starting materials for various palladium catalyzed reactions. The X-ray crystal structure of 5-iodo-10,20-diphenylporphyrin has been determined.
An expeditious, solvent-free synthesis ofmeso-arylporphyrins using activated charcoal as a catalyst
Authors: Vignaud Yannick , Granet Robert , Krausz Pierre
Published: July 2009

Activated charcoal treated with nitric acid was used as a solid catalyst for synthesis of meso-arylporphyrins by condensation of pyrrole with convenient arylaldehydes in a solvent-free system. The reaction took place at 200°C and porphyrins were obtained in good yields. This environment-friendly method avoids the use of detrimental solvents and toxic catalysts.
Synthesis of new meso-tetraarylporphyrins bearing cardanol and further transformation of the unsaturated chains
Authors: Guo Ying-Cen , Xiao Wen-Jing , Mele Giuseppe , Martina Francesca , Margapoti Eleonora , Mazzetto Selma E. , Vasapollo Giuseppe
Published: July 2009

This paper deals with the synthesis of a new hybrid meso-tetraarylporphyrin-cardanol with the cardanol bearing an unsaturated chain. Cardanol is a renewable, natural, widely available and relatively low-cost material obtained as a by-product of the cashew industry which provides cashew kernels for edible use. The unsaturation in the chain in the new hybrid meso-tetraarylporphyrin-cardanol leads to chemical and physico-chemical properties which are different from the saturated derivatives. The unsaturation also allows preparation of the corresponding epoxy compounds as well as self-metathesis derivatives.
Photophysical studies of supramolecular triads involving zinc naphthalocyanines and pyridylfullerenes with a second electron donor
Authors: El-Khouly Mohamed E. , Araki Yasuyuki , Ito Osamu , Gadde Suresh , Zandler Melvin E. , D'Souza Francis
Published: July 2009

Supramolecular triads composed of zinc naphthalocyanine ( ZnNc ) as an electron donor, pyridylfullerenes as primary electron acceptors, and either ferrocene ( Fc ) or N , N -dimethylaminophenyl ( DMA ) entities as second electron donors were constructed via metal-ligand axial coordination. The formation of the supramolecular triads was monitored using optical absorption methods and the measured binding constants revealed a moderately stable complex formation. The B3LYP/3-21G(*) optimized structures showed the disposition of the three entities of the triads to be in a linear fashion. The redox behavior of the different components was studied using cyclic voltammetry in o-dichlorobenzene containing (n- C 4 H 9)4 NClO 4. The donor ability evaluated from the oxidation potentials of the electron donors followed the trend: ZnNc < Fc < DMA . Efficient electron transfer from the excited singlet state of zinc naphthalocyanine to the fullerene entity was observed in all of the studied triads in o-dichlorobenzene by fluorescence quenching measurements. Clear evidence, that the charge-separation process formed the radical ions in the triads, was obtained from a nanosecond transient absorption spectral technique, indicating the contribution of the second electron donor in prolonging the charge-separated states.
Synthesis, lead lability and ring deformation of three 1,4,8,11,15,18,22,25-octasubstituted phthalocyaninato lead derivatives
Authors: Burnham Paul M. , Chambrier Isabelle , Hughes David L. , Isare Benjamin , Poynter Richard J. , Powell Annie K. , Cook Michael J.
Published: July 2009

The syntheses and attempted syntheses of some non-peripherally (1,4,8,11,15,18,22,25) octasubstituted lead phthalocyanines from their corresponding metal-free derivatives are described. Some compounds exhibited lability of the lead ion during work-up to regenerate the starting material. The results of single crystal X-ray diffraction analyses of 1,4,8,11,15,18,22,25-octahexyl-, 1,4,8,11,15,18,22,25-octa-iso-pentyl- and 1,4,8,11,15,18,22,25-octahexylsulfanyl lead phthalocyanines are reported and cast some light on the greater stability of 1,4,8,11,15,18,22,25-octahexylsulfanyl lead phthalocyanine, in terms of ease of loss of the lead ion, over the other two substituted lead phthalocyanines studied. The phthalocyanine cores of all three derivatives adopt a saddle-shaped geometry rather than the saucer-shaped conformation exhibited by unsubstituted lead phthalocyanine. The saddle-shaped conformation would appear to offer a means of relieving steric interactions between the substituents on adjacent benzene rings. That steric interactions are a feature of these molecules is perhaps reflected in the different distortions of the saddle conformations. This is greatest for compound 1,4,8,11,15,18,22,25-octa-iso-pentyl lead phthalocyanine bearing the isopentyl groups, expected to introduce the most interactions, and least for compound 1,4,8,11,15,18,22,25-octahexylsulfanyl lead phthalocyanine where S atoms rather than methylene groups are adjacent to the benzene ring. The molecules of 1,4,8,11,15,18,22,25-octahexyl- and 1,4,8,11,15,18,22,25-octahexylsulfanyl lead phthalocyanine pack together in pairs with their nearest neighbouring molecule; their lead atoms, displaced from the core and directed towards each other. The presence of the S atoms in 1,4,8,11,15,18,22,25-octahexylsulfanyl lead phthalocyanine leads to close Pb … S contacts between the molecules. Attractive Pb … S interactions in this compound may also account for the larger displacement of the Pb from the mean-plane of the four coordinated nitrogen atoms at the centre of the phthalocyanine core than is found for 1,4,8,11,15,18,22,25-octahexyl- and 1,4,8,11,15,18,22,25-octa-iso-pentyl lead phthalocyanines. The molecular packing of 1,4,8,11,15,18,22,25-octa-iso-pentyl lead phthalocyanine is more complex because of the presence of tetrahydrofuran molecules (the solvent of recrystallisation) within the crystal, offering additional interactions with the Pb atoms.
Magnetic circular dichroism spectroscopy and TD-DFT calculations of metal phthalocyanine anion and cation radical species
Authors: Mack John , Kobayashi Nagao , Stillman Martin J.
Published: July 2009

The results of INDO/s and TD-DFT calculations for neutral ZnPc (−2), unligated [ ZnPc (−1)]+ and chloride anion ligated [( Cl ) ZnPc (−1)] cation radicals, the [ ZnPc (−3)]− radical anion and [ ZnPc (−4)]2− dianion species, performed on a set of B3LYP geometry optimizations are compared with magnetic circular dichroism spectral data. The two calculation methods predict spectra that are broadly similar. The TD-DFT calculations provide a significantly closer agreement with the experimental band centers in the UV region than was previously the case with INDO/s based calculations. The assignment of several key spectral features remains problematic, however, when band polarization information derived from magnetic circular dichroism spectroscopy is taken into consideration.
Zn(quinoline)2Cl2: an efficient reagent for synthesis of zinc azaphthalocyanines with thiomorpholine- or pyrazole substituents
Authors: Mørkved Eva H. , Afseth Nils K. , Kjøsen Helge
Published: July 2009

The Zn ( quinoline )2 Cl 2 complex is found to be a convenient reagent for the direct synthesis of amino-substituted, zinc azaphthalocyanines. Octa(4-thiomorpholinyl)- and octa(1-pyrazolyl)- substituted zinc azaphthalocyanines were synthesized from pyrazines, 5,6-bis(4-thiomorpholinyl)pyrazine-2,3-dicarbonitrile and 5,6-bis(1-pyrazolyl)pyrazine-2,3-dicarbonitrile, respectively and dry Zn ( quinoline )2 Cl 2. Two zinc azaphthalocyanines, both mixtures of four constitutional isomers, were synthesized by the same method, from 6-(2-thienyl)-5-(4-thiomorpholinyl)pyrazine-2,3-dicarbonitrile and from 6-(2-thienyl)-5-(1-pyrazolyl)pyrazine-2,3-dicarbonitrile respectively. The octa(4-thiomorpholinyl)- and octa(1-pyrazolyl)-substituted zinc azaphthalocyanines and the zinc azaphthalocyanines with mixed substituents were characterized by elemental analyses, TOF-SIMS, 1 H and 13 C NMR, and UV-vis spectroscopic methods. Q-bands for octa(4-thiomorpholinyl)- and octa(1-pyrazolyl)-substituted zinc azaphthalocyanines and the zinc azaphthalocyanines with mixed substituents are found at respectively 655 and 670 nm (ɛ: 100 000-180 000 M-1.cm-1).
Synthesis and photodynamic activity of diaryl-porphyrins characterized by the presence of nitro groups
Authors: Banfi Stefano , Caruso Enrico , Fieni Emanuele , Buccafurni Loredana , Gariboldi Marzia Bruna , Ravizza Raffaella , Monti Elena
Published: July 2009

A panel of nitro substituted 5,15-diaryl-porphyrins, featuring nitro groups either on the phenyl rings or on one of the two free meso-positions, was synthesized. In the former category, compounds 5-(3-nitrophenyl)-15-phenylporphyrin, 5,15-di(3-nitrophenyl)porphyrin and 5-(4-nitrophenyl)-15-phenylporphyrin were obtained following standard procedures by reacting dipyrromethane and aromatic aldehydes. In the latter category, porphyrins 10-nitro-5,15-diphenylporphyrin, 10-nitro-5-(3-methoxyphenyl)-15-phenylporphyrin and 10-nitro-5,15-di(3-methoxyphenyl)porphyrin were generated by nitration of 5,15-diarylporphyrins with trifluoroacetic acid/sodium nitrite under particularly mild conditions. The new molecules bearing one or two nitro-groups were tested as photosensitizers during in vitro experiments on a human colon adenocarcinoma cell line (HCT116), and their effects were compared with those induced by temoporfin, porfimer sodium and by some previously published electron-rich diarylporphyrins. The results, expressed as IC50 values obtained by the MTT test following 24 h incubation with the photosensitizers and 2 h irradiation with a 500 W tungsten-halogen lamp, indicate that the presence of an electron withdrawing substituent, on a meso-position, decreases the photodynamic activity of the compound. Conversely, 5-(3-nitrophenyl)-15-phenylporphyrin, a non symmetrically substituted diarylporphyrin bearing both one electron-deficient and one lipophilic moiety, resulted in high phototoxic activity.
A macrocyclic supramolecular complex obtained from a fullerene ligand bearing two pyridine substituents and a bis-Zn(II)-porphyrin receptor
Authors: Ajamaa Fettah , Albrecht-Gary Anne-Marie , de la Cruz Juan Luis Delgado , Elhabiri Mourad , Nierengarten Jean-François , Solladié Nathalie , Trabolsi Ali , Urbani Maxence
Published: July 2009

A fullerene derivative bearing two pyridine subunits has been designed to allow assembly with a bis- Zn (II)-phorphyrin receptor with two equivalent Zn binding sites separated by about 20 Å. Owing to the complementarity between the bis- Zn (II)-porphyrin receptor and a fullerene ligand bearing two pyridine substituents, the substrate can be clicked on the ditopic receptor, thus leading to a stable non-covalent macrocyclic 1:1 complex.
Synthesis and physical properties of the succinyloxyl-bridgedmeso-tetraphenylporphyrin dimer
Authors: Cheng Xiuli , Li Ying , Chen Zhengxia , Shi Tongshun
Published: July 2009

A new succinyloxyl-bridged porphyrin dimer has been synthesized and characterized by UV-vis, IR,1H NMR spectra and mass spectra. The photovoltaic properties and charge-transfer process have been investigated by surface photovoltage spectroscopy and electric-field-induced surface photovoltage spectroscopy techniques, which reveal that the compound is a P-type semiconductor. The spectral bands correspond to the π → π* transition. Its fluorescent properties have been studied using emission spectra. The quantum yield of the S1→ S0fluorescence was 0.04 at room temperature. The electrochemical properties have been studied by cyclic voltammetry, which revealed three reversible redox processes. Thermogravimetric analysis shows that the dimer has higher stability (its decomposition commences at 260°C, and it is completely decomposed at 680°C).
Atropisomers of 5,10,15,20-tetrakis(2,6-dichloro-3-sulfamoyl-phenyl)porphyrins
Authors: Ressurreição Ana Sofia M. , Pineiro Marta , Arnaut Luis G. , Rocha Gonsalves António M. d'A.
Published: July 2009

The ratio, resolution and photophysical characterization of atropisomers of 5,10,15,20-tetrakis(2,6-dichloro-3-N-butylsulfamoylphenyl)porphyrin, 5,10,15,20-tetrakis(2,6-dichloro-3-(N-1-(L)-ethoxycarbonyl-2-methyl-propyl-sulfamoyl)phenyl)porphyrin and 5,10,15,20-tetrakis(2,6-dichloro-3-(N-1-(L)-methoxycarbonyl-3-methyl-butyl-sulfamoyl)phenyl)porphyrin are reported.
Synthesis and photophysical studies of non-covalently linked porphyrin dyads and triads
Authors: Sokkalingam Punidha , Santra Sangita , Mangalampalli Ravikanth
Published: July 2009

Non-covalent porphyrin dyads and triads containing N 3 S porphyrin and RuN 4 porphyrin subunits were synthesized by treating meso-pyridyl-21-thiaporphyrin with RuTPP(CO)(EtOH) in toluene at refluxing temperature. The dyads and triads were characterized by various spectroscopic techniques and the properties were compared with the reported dyad containing N 4 and RuN 4 porphyrin subunits. The 1 H NMR study of dyads and triads indicated that the inner NH , β-heterocycle and meso-pyridyl protons of the 21-thiaporphyrin unit experienced large upfield shifts as compared to their corresponding monomeric meso-pyridyl-21-thiaporphyrins due to the ring current effect of RuTPP(CO) subunit. The singlet state photophysical properties of N 3 S porphyrin subunit in dyads and triads showed 50-80% quenching of fluorescence as observed previously for N 4- RuN 4 dyad due to heavy ruthenium ion(s).
Aggregation and DNA binding characteristics of tetrakis(N,N',N″,N‴-tetramethyltetra-3,4-pridino)porphyrazine cobalt(II)
Authors: Khalegh Bordbar A. , Davari Manuchehr , Safaei Elham , Mirkhani Valiollah
Published: July 2009

The association behavior of tetrakis( N , N ', N ″, N ‴-tetramethyltetra-3,4-pridino)porphyrazine cobalt(II) ([ Co (II)3,4- TMTPPA ]4+) was investigated in aqueous solution at 25°C and various ionic strengths using optical absorption and resonance light scattering spectroscopies. The results show that [ Co (II)3,4- TMTPPA ]4+ does not have any affinity for aggregation due to increasing salt concentration and exists as the monomer form even in homogeneous aqueous solutions at high ionic strengths (more than 1 M concentration of NaCl ). The interaction of [ Co (II)3,4- TMTPPA ]4+ with calf thymus DNA in aqueous solution has also been studied in 5 mM phosphate buffer pH 7.2, by optical absorption and resonance light scattering spectroscopies, and thermal denaturation experiments. The appearance of hypochromicity of less than 10% and a bathochromic shift of Δλ ≤ 8 nm in the UV-vis spectra of [ Co (II)3,4- TMTPPA ]4+, an increase in the thermal melting point of DNA, and no enhancement in resonance light scattering spectra of porphyrazine due to interaction with DNA, indicates the minor outside-groove binding mode without any stack aggregate formation. The thermodynamics of the binding of [ Co (II)3,4- TMTPPA ]4+-DNA has also been studied. The binding constant (K) was obtained by analysis of optical absorption spectra of the above-mentioned complex at various DNA concentrations using SQUAD software. The value of K was estimated as 1.31 × 106 ± 1.174 M-1 at 25°C. The thermodynamic parameters were calculated by van't Hoff equation. The enthalpy and entropy changes were 48.77 ± 2.50 kJ . mol -1 and 280.77 ± 9.62 J . mol -1. K -1 at 25°C, respectively. The results indicate that the process is entropy driven suggesting that hydrophobic interactions are the main driving forces for complex formation. The increase of ionic strength due to the addition of NaCl , destabilized porphyrazine-DNA complexes, which indicates the competition of Na + ions with porphyrazine complexes for occupation of minor groove binding sites.
Oxygen concentration imaging in a single living cell using phosphorescence lifetime of Pt-porphyrin
Authors: Saito Takashi , Asakura Noriyuki , Kamachi Toshiaki , Okura Ichiro
Published: July 2009

An oxygen concentration imaging system inside a single living cell, based on the phosphorescence lifetime, under a microscope was developed. A fluorescence microscope equipped with a pulsed Nd : YAG laser (532 nm) and a CCD camera equipped with a gated imaging intensifier was used. When the cell was incubated with the phosphorescent compound, platinum tetra-(carboxyphenyl)-porphyrin ( PtTCPP ) was incorporated and localized in the cell. As the phosphorescence intensity depends not only on the concentration of a quencher such as oxygen but also on the concentration of phosphorescent molecules, the oxygen concentration was measured by the phosphorescence lifetime. To measure the oxygen concentration image, the time dependence of the phosphorescence intensity was observed under a microscope. The phosphorescence intensity decay obeyed first order kinetics and the oxygen concentration imaging in the single cell was obtained by the lifetime of a single exponential decay curve.
Low-spin organoiron(III) N-confused pyriporphyrin
Authors: Myśliborski Radomir , Rachlewicz Krystyna , Latos-Grażyński Lechosław
Published: July 2009

Oxidation of ( PyP H) Fe II Br , an iron(II) complex of 6,11,16,21-tetraaryl-3-aza-m-benziporphyrin ( N -confused pyriporphyrin, ( PyP H) H ) has been followed, in the presence of pyridine, by 1 H and 2 H NMR spectroscopy. One-electron oxidation with dioxygen, accompanied by deprotonation of a C (22) H fragment and formation of a Fe - C (22) bond, produced a low-spin, six-coordinate iron(III) complex [( PyP ) Fe III( py )2]+ as confirmed by combination of 1 H NMR, EPR and structural data. The characteristic patterns of 1 H NMR pyrrole and meso-aryl resonances resemble features assigned to the less common, low-spin ground electronic state (( d xz d yz )4( d xy )1) of iron(III) regular porphyrins. A conformational rearrangement process has been detected which involves two structures differentiated by macrocyclic ruffling. The structure of { H [( PyP ) Fe III( py )2]2}( Fe III Br 4)3· CH 2 Cl 2 has been determined by X-ray crystallography. The cationic complex involves a six-coordinate iron atom bound to the N -confused pyriporphyrin through its three nitrogens ( Fe - N (23) = 1.924(7), Fe - N (24) = 1.979(7), Fe - N (25) = 1.9343(7) Å) and the pirydyl trigonal C (22) atom ( Fe (1)- C (22) = 1.972(10) Å). The porphyrin is strongly ruffled, defining two deep grooves along C meso - C meso axes at right angles to each other. Two axial pyridine ligands are located in the prearranged equatorial ligand grooves. The iron lies in the N 3 C plane of the macrocycle defined by coordinating nitrogen and carbon atoms. In the solid, pairs of molecules are positioned along the line defined by Fe (1)- C (22) and Fe (2)- C (91) bonds. The structure demonstrates the head-to-head arrangement of two [( PyP ) Fe III( py )2]+ subunits revealing the adjacency of the two perimeter nitrogen atoms (the N (3)⋯ N (72) distance = 2.587(10) Å) linked by the N ⋯ H ⋯ N hydrogen bond.
Amphiphilic aluminium(III) and gallium(III) corroles
Authors: Sorasaenee Karn , Taqavi Pouyan , Henling Lawrence M. , Gray Harry B. , Tkachenko Elena , Mahammed Atif , Gross Zeev
Published: July 2009

The preparation and spectroscopic properties of a series of metallocorroles with polar head groups CHO and CH = C ( CN )( COOH ) are reported, as well as the X-ray crystal structure of 5,10,15-tris(pentafluorophenyl)corrolatoaluminium(III)bispyridine (triclinic space group (P-1) with unit cell parameters: a = 9.426(1) Å; b = 13.202(1) Å; c = 19.936(1) Å; α = 74.19(1)°; β = 78.47(1)°; γ = 75.75(1)°; V = 2289.57(8) Å3). Amphiphilic aluminium(III) and gallium(III) corroles exhibit electronic absorption (Soret peaks between 410 and 448 nm; Q-bands between 584 and 638 nm) and fluorescence (band maxima between 634 and 706 nm) at lower energies than their hydrophobic analogs.
Electrocatalytic reduction of oxygen with phenanthroline-strapped porphyrins
Authors: Melin Frédéric , Boudon Corinne , Lo Mamadou , Schenk Kurt J. , Bonin Michel , Ochsenbein Philippe , Gross Maurice , Weiss Jean
Published: July 2009

The electrochemical behavior of three cytochrome c oxidase models has been investigated. All the models are derived from a phenanthroline-strapped, porphyrin framework that binds zinc(II) or iron(III) chloride in the porphyrin subunit, and copper(I) in the phenanthroline site. The iron complex and the bimetallic zinc(II) copper(I) complex of the parent ligand have been characterized by X-ray diffraction. One model consists of the parent structure on which C 12 alkyl chains have been added. This soluble model achieves electrochemical 2-electron reduction of oxygen in organic solvents without the addition of an exogenous axial base, and in the presence of an organic or inorganic source of protons. The two other models comprise the parent phenanthroline-strapped porphyrin framework, on which two pendant imidazoles have been incorporated. These models adsorbed on ring-disk electrodes with an edge-oriented, pyrolytic graphite (EOPG) disk and a platinum ring, efficiently catalyze the 4-electron reduction of oxygen in dioxygen saturated water at neutral pH.
Great adaptability of the heme-cysteinate monooxygenases family to very diverse substrates and sophisticated reactions
Authors: Mansuy Daniel , Lafite Pierre
Published: July 2009

Heme-cysteinate proteins, such as cytochromes P 450( CYPs ) and nitric oxide synthases (NOSs), catalyze the monooxygenation of a huge number of substrates with very diverse structures. The ability of CYPs to oxidize a myriad of xenobiotics, in order to facilitate their elimination, plays a key role in the adaptation of aerobic organisms to their always changing chemical environment. Moreover, some members of the CYP superfamily and the NOSs are involved in the biosynthesis of key biological endogenous molecules, such as estrogens or NO, through the catalysis of highly sophisticated and regulated reactions. How can proteins using the same catalytic heme-cysteinate cofactor and mechanism of dioxygen activation oxidize such diverse and always changing substrates and catalyze different, sometimes very sophisticated reactions? Recent data on the first X-ray structures of mammalian cytochrome P 450-substrate complexes and on the mechanism of NO-synthases has permitted an understanding of this"double adaptation" of heme-cysteinate monooxygenases towards very diverse substrates and different reactions. These data show that cytochromes P 450 involved in the metabolism of xenobiotics are able to oxidize very different substrates by offering a great choice of very diverse and malleable active sites. They also show that heme-cysteinate monooxygenases are able to catalyze special, sophisticated reactions, such as the selective oxidation of L-arginine to NO, by using supplementary cofactors adapted for the required catalysis.
Advances in supramolecularly assembled nanostructures of fullerenes and porphyrins at surfaces
Authors: Yoshimoto Soichiro , Itaya Kingo
Published: July 2009

The ‘bottom-up’ strategy is an attractive and promising approach for the construction of nanoarchitectures. Supramolecular assemblies based on non-covalent interactions have been explored in an attempt to control surface properties. In this minireview, we focus on advances made in the past three years in the field of scanning tunneling microscopy (STM) on supramolecular assembly and the function of porphyrins, phthalocyanines, and fullerenes, non-covalently bound on metal single crystal surfaces. Well-defined adlayers, consisting of porphyrin and phthalocyanine for the design of supramolecular nanoarchitectures, supramolecular traps of C 60 on hydrogen bond networks, a unique approach for controlling molecular orientation by a 1:1 supramolecularly assembled film consisting of C 60 and the related derivatives and metallooctaethylporphyrins, and nanoapplications of fullerenes, either induced by tip manipulation or driven by thermal fluctuations at surfaces, were clearly visualized by STM.
Design and construction of photoinduced electron transfer systems based on [60]fullerene and porphyrin-containing [2]rotaxanes
Authors: Sasabe Hisahiro , Takata Toshikazu
Published: July 2009

This review explores recent developments of photoinduced electron transfer systems based on interlocked molecules, especially [60]fullerene ( C 60) and porphyrin-containing [2]rotaxanes. A number of synthetic methodologies for the construction of C 60-containing interlocked molecules with various photo- and electro-active moieties, such as metalloporphyrins, metallophthalocyanines, triarylamines, and ferrocenes, in addition to the photoinduced electron transfer behaviors of these interlocked molecules, are examined. A synthetic strategy for a multi-step photoinduced electron transfer system based on interlocked molecules is also discussed.
Photoinduced electron transfer in a supramolecular triad system composed of ferrocene-zinc porphyrin-pyridylnaphtha-lenediimide
Authors: Fukuzumi Shunichi , Kashiwagi Yukiyasu
Published: July 2009

A supramolecular ferrocene-zinc porphyrin-pyridylnaphthalenediimide triad is formed by coordinating the pyridine entity of pyridylnaphthalenediimide with the zinc ion of a ferrocene-zinc porphyrin dyad in benzonitrile. The fluorescence of the zinc porphyrin moiety is efficiently quenched by photoinduced electron transfer from the singlet excited state of the zinc porphyrin moiety to the naphthalenediimide moiety. This is followed by subsequent electron transfer from the ferrocene moiety to the zinc porphyrin radical cation to produce the final charge-separated state, ferricenium ion-zinc porphyrin-naphthalenediimide radical anion, which is successfully detected as a transient absorption spectrum in the laser flash photolysis. The decay of the charge-separated state obeys first-order kinetics irrespective of the initial concentration of the charge-separated state to afford a long lifetime (320 μs). This is the first example of a supramolecular triad that has a long lifetime as compared with the charge-separated state lifetime of the component dyad.
Pyrene-to-porphyrin excited singlet energy transfer in LBL-deposited LDH nanosheets
Authors: Yui Tatsuto , Kameyama Tatsuya , Sasaki Takayosi , Torimoto Tsukasa , Takagi Katsuhiko
Published: July 2009

Nano-ordered hybrid films of layered double hydroxide (LDH) nanosheets and two types of anionic dye molecules, i.e. tetrakis(4-carboxyphenyl)porphyrin (TCPP) and 1,3,6,8-pyrenetetrasulfonic acid (PTSA), were prepared by a layer-by-layer deposition (LBL) method. Photo-induced energy transfers (PET) between the PTSA and TCPP layers were investigated for two differently stacked structures of the TCPP/LDH/PTSA hybrid films, i.e. (a) PTSA/LDH multilayers independently stacked on the TCPP/LDH multilayers to form (TCPP/LDH)n/(PTSA/LDH)n and (b) TCPP/LDH and PTSA/LDH monolayers deposited alternately to form [(TCPP/LDH)/(PTSA/LDH)]n hybrid films, which were both prepared by varying the successive and alternate stacking of the (TCPP/LDH) and (PTSA/LDH) unit layers. A Foerster type resonance energy transfer is observed in the present hybrid films, where the efficiency of PET was strongly affected by changing the distance between the TCPP and PTSA molecules in the (TCPP/LDH)3/(PSS/LDH)m/(PTSA/LDH)3 hybrid films ( m = 1−10) obtained by the insertion of the photochemically inert poly(styrenesulfonic acid) (PSS) and LDH hybrid layers, i.e. the insertion of (PSS/LDH)m between the (TCPP/LDH)3 and (PTSA/LDH)3 layers.
High-accuracy Z-scan measurements of the optical nonlinearity of bis-phthalocyanines
Authors: Gnoli Andrea , Paoletti Anna Maria , Pennesi Giovanna , Rossi Gentilina , Righini Marcofabio
Published: July 2009

The usage of a modified Z-scan setup for the study of optical nonlinearities of bis-phthalocyanines is discussed. The setup leads to the selection of the pure electronic nonlinear optical response purged from other possible contributions such as molecular reorientation or thermal effects. The described experimental method is based on the capability to extract the instantaneous nonlinear response of the sample, by monitoring and managing cumulative effects and taking full advantage of the large number of probing laser pulses. This kind of approach has been applied on some sandwich-type metal bis-phthalocyanines confirming its potential for an in-depth analysis of the nonlinear response of such molecules. First results on titanium, niobium and tin bis-phthalocyanines provide information on the role of the conjugation length in their nonlinear optical response.
An improved synthesis of meso-tetraanthrylporphyrin by a kinetically controlled Lindsey reaction
Authors: Tohara Akira , Sato Mitsuo
Published: July 2009

Meso-tetraanthrylporphyrin was successfully synthesized in 3.0% yield by a kinetically controlled Lindsey method in which tetraanthrylporphyrinogen was oxidized to meso-tetraanthrylporphyrin only 1 min after the condensation of pyrrole and 9-anthraldehyde had been initiated by the addition of an acid catalyst. A longer condensation time lowered the yield of meso-tetraanthrylporphyrin and made separation and purification more difficult. The electronic spectra are also reported.
The effect of lipid composition, bilayer phase and temperature on the uptake of hematoporphyrin by liposomal membranes
Authors: Minnes Refael , Weitman Hana , Ehrenberg Benjamin
Published: July 2009

In this study we investigated, spectroscopically, the binding of hematoporphyrin (HP) to non-charged lipid vesicles as a function of temperature and the molecular structure of the phospholipid. The temperature dependence of partitioning was employed to evaluate the thermodynamic parameters of the process. We studied the binding of HP to liposomes composed of different phospholipids: natural lecithin and three chemically defined phosphatidylcholines: dimiristoyl-phosphatidylcholine (DMPC), 1-palmitoyl-2-myristoyl-phosphatidylcholine (PMPC) and 1-stearoyl-2-myristoyl-phosphatidylcholine (SMPC), at different temperatures. The last three lipids differ only in the length of the fatty acid on 1 position of the glycerol backbone. Consequently, they have different phase transition temperatures and different order parameters. For SMPC, PMPC and DMPC, we checked the effect of temperatures above and below the phase transition while for lecithin, whose phase transition temperature is well below 0 °C, only temperatures above the phase transition could be tested. A very distinct effect of the phase transition on the binding constant was observed. Below this temperature a dramatic decrease in the binding was observed as the temperature was increased. Above the phase transition, the effect of temperature declined and the changes were minor compared to the changes observed when the bilayers undergo the solid-gel phase transition. Differences in HP binding to the various bilayers were attributed to the differences in the order parameters of DMPC, PMPC, SMPC and lecithin bilayers.
A study on the self assembly of Fe(II) and dual binding of Ni(II) porphyrazines on CT-DNA
Authors: Safaei Elham , Ranjbar Bijan , Hasani Leila
Published: July 2009

Interaction of N , N ′, N ″, N ‴-tetramethyltetra-2,3-pyridinoporphyrazinatonickel(II), ([ Ni (2,3- tmtppa )]4+) and N , N ′, N ″, N ‴-tetramethyltetra-2,3-pyridinoporphyrazinatoiron(II), ([ Fe (2,3- tmtppa )]4+) with calf thymus DNA (CT-DNA) have been studied in 1mM phosphate buffer and low ionic strength (5 mM NaCl ) using several spectroscopic techniques: absorbance, fluorescence and circular dichroism. The 2:1 porphyrazine/DNA mole ratio, existence of moderate hypochromicity, moderate and progressive red shift and conservative ICD in the visible part of [ Fe (2,3- tmtppa )]4+ spectra suggested an outside binding with self-stacking mode. Analysis of the dramatic hypochromicity, small blue shift and bisignate ICD in the Q-band absorption region of [ Ni (2,3- tmtppa )]4+ spectra and 1:1 porphyrazine/DNA mole ratio possibly led us to the dual binding mode of this complex, i.e. at the minor and major grooves of DNA. The influence of the ionic strength on the porphyrazine-DNA binding confirmed this suggestion. The fluorescence quenching of DNA-ethidium bromide complex by porphyrazines was investigated. The values of quenching constants ( K sv ) and the rate constants of the quenching ( K q ) were determined by Stern-Volmer equation. The values of K sv have been obtained (2.07 ± 0.11) × 106 and (0.48 ± 0.01) × 106 M−1 for [ Fe (2,3- tmtppa )]4+ and [ Ni (2,3- tmtppa )]4+, respectively, at 27°C. The higher affinity of [ Fe (2,3- tmtppa )]4+ for the quenching of EB-DNA fluorescence with respect to Ni complex was attributed to self-stacking of the former along DNA helix and favorable energy transfer between EB+ and cationic porphyrazine. ΔG25 (the difference between the free energy of the native ( N ) and the denatured (D) form of DNA at 25°C), ΔHm and ΔSm (difference between enthalpy and entropy at Tm) were extracted from thermal curves. The decline in the melting temperature of DNA following the addition of porphyrazine complexes confirms that the substantial mode of Ni and Fe interaction is not intercalation. The thermodynamic results imply that both Ni and Fe complexes have a slight destabilizing effect on the DNA. A comparison between [ Ni ( tmtppa )]4+ and [ Fe ( tmtppa )]4+ indicates that the latter is more effective than the former.
Synthesis and mesogenic properties of β-tetrabrominated tetraalkyloxyporphyrins
Authors: Bhyrappa Puttaiah , Arunkumar Chellaiah , Varghese Babu , Rao Doddamane S. Shankar , Prasad Subbarao K.
Published: July 2009

A new class of 2,3,7,8-tetrabromo-5,10,15,20-tetrakis(4'-n-1-alkyloxyphenyl)porphyrins, H 2 T (4'- OC n P ) PBr 4 (n = 4,6,8,10,12,14,16 and 18) and their Cu(II) complexes have been synthesized regioselectively and their mesophase properties explored. The mesogenic properties of the porphyrins were examined by differential scanning calorimetry and optical microscopy. An increase in alkyl chain length of the mesogens, showed an increase in melting point temperature and lowering of their clearing point temperatures with the narrower mesophases. This has been ascribed to the decreased π-π interactions as evidenced from the crystal structure of H 2 T (4'- OC 6 P ) PBr 4· THF derivative. MT (4'- OC n P ) PBr 4 derivatives showed rectangular mesophases in contrast to discotic lamellar mesophases reported for the planar MT (4'- OC n P ) P mesogens.