bluuebunny/crossref_metadata_2025 huggingface dataset:
Probabilistic Torsional Vibration Analysis of a Marine Diesel Engine Shafting System: The Level Crossing Problem
Authors: Nikolaidis Efstratios , Perakis Anastassios N. , Parsons Michael G.
Published: July 2009

A probabilistic approach to the torsional vibration problem of a marine diesel engine shafting system has been developed. In this analysis, the shafting shear stress is found to be a Gaussian, harmonizable cyclostationary process with a harmonic series representation consisting of two complex conjugate components. In this paper, the level crossing problem for this stress process is studied. Two methods for estimating the probability that the stress exceeds a specified threshold at least once over a given time interval are presented. In the first method, a local maximum of the process is approximated by the value of the corresponding envelope at the time of occurrence of this maximum. A Markov-type condition is assumed to hold for the local maxima. The second method assumes that the maximum of the process over a reasonable number of cycles is approximately equal to that of the envelope process. The envelope crossings are assumed to constitute a Poisson process. The two methods are applied to estimate the upcrossing probability in various cases. The results of both approaches are found to be in good agreement with those from Monte Carlo simulation.
Triple Combination of Oseltamivir, Amantadine, and Ribavirin Displays Synergistic Activity against Multiple Influenza Virus Strains In Vitro
Authors: Nguyen Jack T. , Hoopes Justin D. , Smee Donald F. , Prichard Mark N. , Driebe Elizabeth M. , Engelthaler David M. , Le Minh H. , Keim Paul S. , Spence R. Paul , Went Gregory T.
Published: July 2009

The recurring emergence of influenza virus strains that are resistant to available antiviral medications has become a global health concern, especially in light of the potential for a new influenza virus pandemic. Currently, virtually all circulating strains of influenza A virus in the United States are resistant to either of the two major classes of anti-influenza drugs (adamantanes and neuraminidase inhibitors). Thus, new therapeutic approaches that can be rapidly deployed and that will address the issue of recurring resistance should be developed. We have tested double and triple combinations of the approved anti-influenza drugs oseltamivir and amantadine together with ribavirin against three influenza virus strains using cytopathic effect inhibition assays in MDCK cells. We selected A/New Caledonia/20/99 (H1N1) and A/Sydney/05/97 (H3N2) as representatives of the wild-type versions of the predominant circulating seasonal influenza virus strains and A/Duck/MN/1525/81 (H5N1) as a representative of avian influenza virus strains. Dose-response curves were generated for all drug combinations, and the degree of drug interaction was quantified using a model that calculates the synergy (or antagonism) between the drugs in double and triple combinations. This report demonstrates that a triple combination of antivirals was highly synergistic against influenza A virus. Importantly, the synergy of the triple combination was 2- to 13-fold greater than the synergy of any double combination depending on the influenza virus subtype. These data support the investigation of a novel combination of oseltamivir, amantadine, and ribavirin as an effective treatment for both seasonal and pandemic influenza virus, allowing the efficient use of the existing drug supplies.
Paradoxical Effect of Isoniazid on the Activity of Rifampin-Pyrazinamide Combination in a Mouse Model of Tuberculosis
Authors: Almeida Deepak , Nuermberger Eric , Tasneen Rokeya , Rosenthal Ian , Tyagi Sandeep , Williams Kathy , Peloquin Charles , Grosset Jacques
Published: July 2009

To investigate the antagonism between isoniazid (INH) and rifampin (rifampicin) (RIF)-pyrazinamide (PZA) combination observed in
Mycobacterium tuberculosis
-infected mice, extensive pharmacokinetic studies of INH were performed and followed by experiments to assess the impact of increasing doses of INH on the antimicrobial activity of RIF-PZA combination. INH at 6.25 mg/kg of body weight produced a maximum concentration of drug in serum (
C
max
) value of 4 μg/ml and an area under the concentration-time curve from 0 to 24 h (AUC
0-24
) value of 4.9 μg·h/ml, the former being close to the
C
max
value observed after the standard 5-mg/kg dose in humans. INH at 25 mg/kg produced a
C
max
value of 22 μg/ml and an AUC
0-24
value of 29 μg·h/ml, the latter being close to the AUC observed after a 5-mg/kg dose of INH in humans with the slow acetylation phenotype. Beginning 2 weeks after aerosol infection with
M. tuberculosis
, mice were treated for 8 weeks with INH at twofold-increasing doses, ranging from 1.56 to 50 mg/kg, either alone or in combination with RIF-PZA. Given alone, INH exhibited dose-dependent activity. Combined with RIF-PZA, INH exhibited dose-dependent antagonism of RIF-PZA activity. To determine the individual components of RIF-PZA combination with which INH was antagonistic, mice were treated for 8 weeks with RIF alone, PZA alone, RIF-PZA, and INH at 3.125, 12.5, or 50 mg/kg either alone or combined with RIF or PZA. Addition of INH to RIF had additive activity, whereas addition of INH to PZA resulted in a negative interaction. Finally, a 10-mg/kg dose of INH in mice may best represent the 5-mg/kg dose in humans and decrease the antagonism of INH with RIF-PZA.
Furanone at Subinhibitory Concentrations Enhances Staphylococcal Biofilm Formation by
luxS
Repression
Authors: Kuehl Richard , Al-Bataineh Sameer , Gordon Oliver , Luginbuehl Reto , Otto Michael , Textor Marcus , Landmann Regine
Published: July 2009

Brominated furanones from marine algae inhibit multicellular behaviors of gram-negative bacteria such as biofilm formation and quorum sensing (QS) without affecting their growth. The interaction of furanone with QS in gram-positive bacteria is unknown. Staphylococci have two QS systems,
agr
and
luxS
, which lower biofilm formation by two different pathways, RNAIII upregulation and bacterial detachment, and polysaccharide intercellular adhesin (PIA) reduction, respectively. We synthesized natural furanone compound 2 [(5
Z
)-4-bromo-5-(bromomethylene)-3-butyl-2(5
H
)-furanone] from
Delisea pulchra
and three analogues to investigate their effect on biofilm formation in gram-positive bacteria. Compound 2, but not the analogues, enhanced the biofilms of
Staphylococcus epidermidis
1457 and 047 and of
S. aureus
Newman at concentrations between 1.25 and 20 μM. We show the growth inhibition of
S. epidermidis
and
S. aureus
by free furanone and demonstrate bactericidal activity. An induction of biofilm occurred at concentrations of 10 to 20% of the MIC and correlated with an increase in PIA. The biofilm effect was
agr
independent. It was due to interference with
luxS
, as shown by reduced
luxS
expression in the presence of compound 2 and independence of the strong biofilm formation in a
luxS
mutant upon furanone addition. Poly(
l
-lysine)-grafted/poly(ethylene glycol)-grafted furanone was ineffective on biofilm and not bactericidal, indicating the necessity for free furanone. Free furanone was similarly toxic for murine fibroblasts as for staphylococci, excluding a therapeutic application of this compound. In summary, we observed a biofilm enhancement by furanone in staphylococci at subinhibitory concentrations, which was manifested by an increase in PIA and dependent on
luxS
.
INVESTIGATIONS OF FIBER NONLINEARITIES IN LONG-HAUL OPTICAL WDM TRANSMISSION SYSTEMS
Authors: KAUR GURMEET , SINGH M. L. , PATTERH M. S.
Published: July 2009

Wavelength division multiplexing (WDM) has been emerging as an effective technique for making use of the full bandwidth offered by optical fiber. To achieve long-haul transmission, erbium-doped fiber amplifiers (EDFAs) are employed to compensate for signal attenuation without using optoelectronic/electro-optic conversions. Transmission in these systems is limited by fiber nonlinearities and amplified spontaneous emission noise from amplifiers. In this paper, the long-haul optical WDM system with EDFAs is investigated theoretically. The noise and bit error rate (BER) characteristics of the system with optical amplifiers are calculated and the dependence of the BER on interamplifier separation and input power is shown.
LASER INDUCED ABSORPTION SPECTRA PROPERTIES OF ETHYL RED DOPED FILM AND ITS POTENTIAL APPLICATIONS FOR OPTICAL SWITCH BASED ON TWO BEAMS MUTUAL MODULATION
Authors: HAO ZHAOFENG , LU WENQIANG , ZHANG CHUNGPING , TIAN JIANGUO , CHEN GUIYING , XU TANG , QI SHENGWEN
Published: July 2009

Azo dye ethyl red (ER) doped methyl methacrylate polymer (PMMA) films were prepared by the sol-gel process and the spin coating method. The samples were 3% ER by weight and 33 μm thick. The absorption spectra of the samples, illuminated by He-Cd laser (441.6 nm, CW) and YAG laser (532 nm, CW) were measured and the change of nonlinear refractive index distribution curve of the ER-doped PMMA thin film induced by 532 nm laser was simulated using the Kramers–Kronig relation. Additionally, the transmission intensity mutual modulations of the two beams were studied. Our results suggest that ethyl red (ER) has potential applications in all-optical devices.
Flexible dizinc diporphyrin systems as selective receptors for ditopic amine ligands
Authors: La Monica Laura , Monti Donato
Published: July 2009

Zinc (II) diporphyrin systems, characterised by the presence of flexible oligooxaethylene spacers of different lengths, have been synthesised and the binding properties toward a series of aliphatic and aromatic diamine derivatives characterised by different structural and coordination properties, investigated. The results obtained, compared to that for a rigid diporphyrin cleft, point out that the observed degree of selectivity is dependent both on the length of the spacer and on the nature of the nitrogen ligands.
Specific visible spectral changes induced by guanine binding to cytosine-derivatized porphyrin
Authors: Harmon H. James
Published: July 2009

The interaction of the free nucleic acid bases adenine, cytosine, and thymidine with meso-tri(4-sulfonatophenyl) meso 4-phenyl porphyrin cytosine amide (TPSC) trisodium salt at pH 5.9, 7.4, and 9.3 results is a decrease in the absorbance of the Soret (B-band) at 413 nm of TPSC. A decrease in Soret band absorbance is observed with guanine below pH 8; at higher pH values a new absorbance band at 424 nm is observed. The appearance of the band is consistent with hydrogen bonding between the cytosine-functionalized porphyrin and guanine and the resulting perturbation of the electron orbitals of the porphyrin.
Structure versus electrical behavior in films of homoassociates of diprotonated meso-tetrakis(4-sulfonato-phenyl)porphyrin
Authors: Rubires Raimon , Müller Carlos , Campos Lourdes , El-Hachemi Zoubir , Pakhomov Georgi L. , Ribó Josep M.
Published: July 2009

The gel-like films obtained from the homoassociation of diprotonated meso-tetrakis(4-sulfonatophenyl)porphyrin show structural changes depending on their water content, which is determined by the affinity for water of the ionic species segregated from the homoassociation process. These materials, in which NaCl or H 2 SO 4 are segregated, were studied and their electrochemical behavior at several water contents was examined. The behavior of humid films was clearly different from dry films. The pH2O value, which determines the separation between the dry and humid behavior, depends on the type of the ionic species segregated in the homoassociation. This is briefly discussed in relation to the design of humidity sensors.
Synthesis and biological evaluation of polyamine-porphyrin conjugates as potential agents in photodynamic therapy (PDT)
Authors: Lamarche François , Sol Vincent , Huang Yi-Ming , Granet Robert , Guilloton Michel , Krausz Pierre
Published: July 2009

A new class of porphyrins bearing natural polyamines has been designed in order to target the photosensitizers towards malignant cells. We report here the synthesis of spermidine and spermine porphyrins. The photocytotoxicity of these compounds against K562 human chronic myelogenous leukemia cells has been evaluated and compared to Photofrin II®.
Near-infrared sensitization solar cell with the electrode of aluminium phthalocyanine adsorbed on nanocrystalline titanium dioxide film
Authors: Komori Tasuku , Amao Yutaka
Published: July 2009

The dye-sensitized solar cell using visible and near-infrared sensitization of nanocrystalline TiO 2 films by aluminium phthalocyanine, aluminium 2,9,16,23-tetraphenoxy-29H, 31H-phthalocyanine hydroxide (AlTPPc), was developed and its photoelectrochemical properties were investigated. The short-circuit photocurrent (ISC) was 0.026 mA cm-2, the open-circuit photovoltage ( V OC) was 186 mV, and the fill factor (FF) of solar cell using AlTPPc adsorbed on nanocrystalline TiO 2 film electrode was estimated to be 40.4%, respectively. By using AlTPPc adsorbed on nanocrystalline TiO 2 film electrode, photovoltage and photocurrent were higher compared with that of only nanocrystalline TiO 2 film electrode and were maintained under near-infrared irradiation. Thus, the solar cell using the near-infrared sensitization by AlTPPc adsorbed on nanocrystalline TiO 2 film electrode was developed.
Ruthenium phthalocyanines with axial carboxylate ligands: Synthesis and function in solar cells based on nanocrystalline TiO2
Authors: Yanagisawa Masaru , Korodi Ferenc , He Jianjun , Sun Licheng , Sundström Villy , Åkermark Björn
Published: July 2009

The synthesis and characterization of phthalocyaninato-ruthenium ( PcRu ) complexes with potential functional axial ligands are described. The solubility of these PcRu complexes was much improved compared to their parent phthalocyanines without Ru , enabling purification by normal flash column chromatography and also NMR measurements in common solvents (e. g. DMSO - d 6 and CDCl 3). Adsorption of these phthalocyanine dyes onto the surface of a semiconductor through the carboxyl group(s) in the axial ligands prevents to some extent formation of H-aggregates, which is typical for phthalocyanines. It also prevents stacking of the dye molecules on the surface. The photovoltaic behavior of sandwich solar cells based on nanostructured TiO 2 films sensitized by these PcRu complexes was studied under irradiation with visible light. For a solar cell based on bis(4-carboxypyridine)-phthalocyaninato ruthenium(II) (1) sensitized nanoporous-nanocrystalline TiO 2, a monochromatic incident photon-to-current conversion efficiency (IPCE) of 21% was obtained at 640 nm. The overall conversion efficiency (η) was 0.61%, which is one of the best results for a solar cell based on a phthalocyanine dye. For a cell based on (4-carboxypyridine)-(4-(2-ethoxy)ethyloxycarbo-nylpyridine)-2,3,9,10,16,17,23,24-octa(n-pentyloxy)-phthalocyaninato ruthenium(II) (5) sensitized TiO 2, a IPCE of 6.6% at 640 nm and η of 0.58% were obtained.
Excited state dynamics in phthalocyanines studied using degenerate four wave mixing with incoherent light
Authors: Rao S. Venugopal , Rao D. Narayana
Published: July 2009

We present our experimental results on the measurements of excited state dynamics in phthalocyanines ( Pc , CuPc , FePc , and ZnPc ) using degenerate four wave mixing with incoherent light (DFWM-IL). Three different timescales were observed, for all samples, in the phase conjugate signal recorded as a function of delay in probe beam in the standard backward geometry. The fastest component (< 170 fs) is associated to the phase relaxation in the S n states and the slowest components (∼3-5 ps and 35-55 ps) to the vibration and population relaxation times from the S1 state. The present results are compared with those obtained with shorter pulses and various techniques for similar molecules. The consequences of such short lifetimes are also discussed in view of the strong optical limiting properties of these molecules.
Recent developments in the coordination chemistry of porphyrin complexes containing non-metallic and semi-metallic elements
Authors: Brothers Penelope J.
Published: July 2009

Recent advances in the chemistry of main group porphyrin complexes are surveyed. New, unprecedented structural types for porphyrin complexes which have been revealed from the recent reports of boron and tellurium porphyrins are described. Advances in the preparation and reactivity of Group 14 (silicon and tin) and Group 15 porphyrin complexes are discussed. A systematic variation in the out-of-plane distortion (ruffling) of light element Group 14 and 15 porphyrin complexes has become apparent now that a significant number of structurally characterized examples are at hand.
From studies on artemisinin derivatives to trioxaquines
Authors: Meunier Bernard
Published: July 2009

Heme, resulting from hemoglobin digestion by the malaria parasite is one of the main target of antimalarial drugs like chloroquine and artemisinin. This later molecule contains a trioxane which is activated by the reduced form of heme to generate a strong alkylating agent able to react with heme itself. Taking advantage of these studies, we prepared new antimalarial drugs, trioxaquines, containing a trioxane motif covalently linked to an aminoquinoline.
Synthetic advances in phthalocyanine chemistry
Authors: de la Torre Gema , Torres Tomás
Published: July 2009

A brief overview is presented on the status of the synthesis of unsymmetric phthalocyanines and related compounds. The main aim of this paper is to describe the key problems and the interest in synthesizing new functionalized unsymmetric phthalocyanine systems. Some phthalocyanine homologues and analogues like subphthalocyanines and expanded phthalocyanines are also treated.
Electron transfer in electron donor-acceptor ensembles containing porphyrins and metalloporphyrins
Authors: Guldi Dirk M. , Fukuzumi Shunichi
Published: July 2009

Recent advances in electron transfer chemistry of electron donor-acceptor ensembles reported containing porphyrins and metalloporphyrins reported in ICPP-2 are reviewed briefly by focusing on the fundamental aspects of electron transfer reactions.
Some reactions of dimeric silicon phthalocyanines under alkaline conditions
Authors: Myakov Viktor N. , Lopatin M. A. , Kurskii Yu. A.
Published: July 2009

Reactions of bis(hydroxy)- and bis(trimethylsiloxy)diphthalocyaninato silicon with KOH were studied in o-xylene or oligosiloxane in the presence of crown ether 15-cr-5 in vacuo at 190-200 °C by the means of electronic, EPR and 1 H NMR spectroscopy. Under gradual removing of H 2 O , consecutive formation of paramagnetic silicon diphthalocyanine monoanions (λ max 580 nm ), and diamagnetic silicon diphthalocyanine dianions (λ max 550 nm ) have been observed. The dianions react with H 2 O to regenerate silicon diphthalocyanine monoanions and then the starting silicon diphthalocyanine. Reaction of the dianion with O 2 results in a decomposition of silicon diphthalocyanine. 1 H NMR spectra of silicon diphthalocyanine dianion have proven the absence of a ring current in the π-electron system of the dianion.
Syntheses, characterization and properties of soluble and liquid phenanthralocyanines
Authors: Maya Eva M. , Snow Arthur W. , Shirk James S. , Flom Steven R. , Pong Richard G. S. , Callahan John H.
Published: July 2009

Phenanthralocyanine compounds with cumylphenoxy, nonylphenoxy and oligodimethylsiloxane phenoxy peripheral substitution were synthesized by nucleophilic aromatic substitution reaction between 3,6-difluoro-9,10-dicyanophenanthrene and the corresponding phenolic precursor. Structural characterization includes IR, NMR, UV-vis and mass spectroscopies. The nonylphenoxy and oligodimethylsiloxane phenoxy phenanthralocyanines were soluble in common organic solvents, and the siloxane product was an isotropic liquid. Compared with the phthalocyanine analog, the Q bands of the Pb , H 2 and Cu phenanthralocyanine were slightly red shifted and variably broadened (small for the Pb compound but large for the H 2 and Cu compounds). The nominal red shift is a consequence of an angular annelation of the benzene rings to the phthalocyanine system. Aggregation was not detected in toluene solution, and the Q band broadening was attributed to a distortion of the tetraazaporphyrin ring to a nonplanar conformation. The siloxane substituted lead phenanthralocyanine neat liquid was evaluated as an optical limiter material. As a neat film a substantial broadening and weakening of the Q band results in a broad visible transmission window and a relatively neutral light olive hue. Upon excitation, there is a rapid decay of the initially excited state so the initial optical limiting is predominately due to a thermorefractive effect rather than a nonlinear absorption.
Synthesis of unsymmetrical 5,15-diarylporphyrins
Authors: Mamardashvili Nugzar Zh. , Golubchikov Oleg A. , Mamardashvili Galina M. , Dehaen Wim
Published: July 2009

A new, unsymmetrically substituted 5,15-diarylporphyrin has been synthesized following a stepwise approach. The tetrapyrrolic precursor for the porphyrin is a 10-aryl substituted a,c-biladiene dihydrobromide. The preparation of the starting pyrrolic compounds has been optimized with respect to the previously reported methods.
Synthesis, characterization and catalytic behavior of iron porphyrins immobilized in layered double hydroxides
Authors: Halma Matilte , Wypych Fernando , Drechsel Sueli M. , Nakagaki Shirley
Published: July 2009

We report the synthesis, characterization and catalytic behavior of iron(III) porphyrins immobilized in layered double hydroxides (LDH). A combination of EPR, UV-visible spectroscopy and powder X-ray diffraction (PXRD) was used to characterize the products. Three different procedures were used to perform the immobilization of iron porphyrin: a) adsorption into the LDH powder, b) co-precipitation and c) rehydration of calcined LDH. Several different porphyrins ( Fe ( TSPP ), Fe ( TCPP ), Fe ( TPP ) and Fe ( TDFSPP )) were employed in the study. After characterization, the isolated powders were investigated in the oxidation reaction of cyclohexane by iodosylbenzene and hydrogen peroxide in heterogeneous catalysis in comparison to homogeneous media. Some of these immobilized compounds were very good catalysts for this oxidation reaction, stimulating the future investigation of other substrates.
Phosphorescent labeling reagents of platinum(II) and palladium(II) coproporphyrin-II: Preparation and performance characteristics
Authors: Koskelin Mirva M. , Soini Aleksi E. , Meltola Niko J. , Ponomarev Gelii V.
Published: July 2009

Synthesis of monofunctional derivatives of platinum(II) and palladium(II) coproporphyrin-II with the isothiocyanato reactive group is presented. The compounds exhibit strong phosphorescence at room temperature in deoxygenated aqueous solutions and they enable facile covalent labeling of proteins and other biomolecules under slightly alkaline conditions. The performance of the compounds as phosphorescent labeling reagents is studied and the results are considered in relation to the results for the respective labeling reagent of coproporphyrin-I isomer. The results show that the derivatives of coproporphyrin-II exhibit similar reactivity and emission efficiency to that of the derivatives of coproporphyrin-I isomers. Thus, the coproporphyrin-II derivatives serve as alternative labels to coproporphyrin-I in the design of sensitive bioassays based on phosphorescence and time-resolved fluorescence detection.
Excited states of analogue models of M-bacteriochlorophylls (M = Mg, Zn) in the photosynthetic reaction center: a time-dependent density functional theory study
Authors: Yamaguchi Yoichi
Published: July 2009

Using time-dependent density functional theory (TDDFT), the excited states of the analogue model Mg -bacteriochlorophyll b - imidazole ( BChl -Im) dimer (P) for a special pair in the photosynthetic reaction center (RC) of Rhodopseudomonas (Rps.) viridis were examined. The calculated low-lying excited states and optimal geometries are in good agreement with experimental data. The order of the lowest unoccupied molecular orbital (LUMO) energies of P, the monomeric "accessory" BChl -Im (B), and bacteriopheophytin b ( H ) indicates the possibility of the light-induced electron transfer from P to H via B. The Im ligand of B destabilizes Goutermann's four-orbitals of BChl by 0.3-0.4 eV. With no energetic difference in the LUMOs between H and BChl , the Im ligands of P and B play an important role in providing a greater energetic gradient to the LUMOs along with the pathway for the excited-electron transfer in RC, resulting in the reduced reverse electron transfer from H to P (via B). Thus it is expected that the asymmetric Mg -Im interactions will directly affect the pathway of the excited-electron transfer. Using the deformed heterodimer (P') formed by the BChl halves with and without Im as the primary donor model, its cation radical P'+ was calculated as to whether the experimental asymmetric spin-density distribution can reproduce. The excited states of the analogue model Zn - BChl -Im dimer for a special pair in RC of the recently discovered Acidiphilium rubrum were also examined for a comparison with P.
Reaction of 5-nitro-octaethylporphyrins with nucleophiles
Authors: Crossley Maxwell J. , King Lionel G. , Pyke Simon M. , Tansey Charles W.
Published: July 2009

An investigation of the reactions of metallo-5-nitro-2,3,7,8,12,13,17,18-octaethylporphyrins with Grignard reagents, benzyl oxide, phenoxide and benzenethiolate nucleophiles shows that, except for benzenethiolate reactions, they are less efficient than related reactions of metallo-2-nitro-5,10,15,20-tetraarylporphyrins. Treatment of free-base and nickel(II) 5-nitro-octaethylporphyrin with the “soft” nucleophile benzenethiolate in DMF affords the corresponding 5-phenylthioporphyrins in 61 and 72% yield, respectively, by ipso-substitution of the nitro group. In contrast, with methylmagnesium iodide and benzyl oxide, “hard” nucleophiles, attack is at the diagonally opposite 15-position of the ring to give 15-substituted 5-nitroporphyrin while with phenoxide and more substituted Grignard reagents, electron-transfer reactions lead to denitration to (metallo)-octaethylporphyrin or reduction to the corresponding 5-aminoporphyrin. The lower efficiency of the latter reactions, compared to those on 2-nitro-tetraarylporphyrin analogues, is a consequence of two factors, higher energies being required for initial nucleophilic attack as macrocyclic aromaticity is lost in intermediates and the susceptibility of the resultant “non-aromatic” intermediates to further attack.
The synthesis of specifically metallated heterobimetallic dimeric porphyrins
Authors: Belcher Warwick J. , Burrell Anthony K. , Officer David L. , Reid David C. W. , Scott Sonya M.
Published: July 2009

A series of conjugated mixed metal heteroporphyrin dimers has been prepared using Wittig chemistry. They can be synthesized from a double Wittig reaction between porphyrin phosphonium salts and phthalaldehydes, or from stepwise Wittig reactions. This allows both symmetrical and unsymmetrical dimers to be prepared with complete control of porphyrin metallation.
Synthesis, structure and properties of ferrocene functionalized porphyrins
Authors: Hodgson Michael C. , Burrell Anthony K. , Boyd Peter D. W. , Brothers Penelope J. , Rickard Clifton E. F.
Published: July 2009

A series of free-base and metallated mixed ferrocenamido- and pivalamidophenylporphy-rins have been prepared from the α,α′,α″,α‴ isomer of 5,10,15,20-tetra(o-aminophenyl)porphyrin. The X-ray crystal structure of the iron(III) α,α′,α″,α‴-5,10,15,20-tetrakis(o-ferrocenamidophenyl)-porphyrin bromide has been determined and compared with related structures of cobalt(III) α,α′,α″,α‴-5,10,15,20-tetrakis(o-pivalamidophenyl)porphyrin bromide pyridine and the free base α,α′,α″,α‴-5,10,15,20-tetrakis(o-pivalamidophenyl)porphyrin. In both metalloporphyrins the coordinated axial bromides are contained in the cavity formed by the appended pickets with all the amide N - H bonds directed toward the anion.
Porphyrin-based supermolecules and supramolecular arrays
Authors: Langford Steven J. , Lau Vei-Lin , Lee Marcia A. P. , Lygris Emmanuel
Published: July 2009

This article reviews our recent work in constructing discrete multiporphyrin assemblies and supramolecular arrays through the application of two organising principles - crown ethers and tin(IV)porphyrin phenolates. The role of the crown ethers is illustrated by two examples: (a) the cation-induced control of the reduction potentials within a model 18 C 6 bearing naphthalene and naphthoquinone chromophores antipodally displaced on the crown ether in the presence of alkali metal cations and (b) in the complexation of dialkylammonium salt within the cavity of a 24 C 8 bischlorin system. Tin(IV)porphyrin phenolates provide a means of efficiently constructing multiporphyrin assemblies without the use of covalent bond formation. Their potential is illustrated through the formation of discrete trimers, using a “one pot” self-assembly strategy, as well as the generation of supramolecular arrays with sieve like networks.
Inter-porphyrin coupling: how strong should it be for molecular electronics applications?
Authors: Reimers Jeffrey R. , Hush Noel S. , Crossley Maxwell J.
Published: July 2009

Porphyrins and phthalocyanines have now been assembled in a multitude of different architectures, each of which may be identified with a different scenario of the coupling acting between the porphyrins. The synthetic flexibility of these compounds makes possible the design of particular molecules for specific applications in molecular electronics, both in naturally occurring and synthetic devices. Here, we form an overview of these features and focus on the coupling strength, considering what values are appropriate for different molecular electronics applications. In particular, we focus on model compounds that have been prepared as mimics of naturally occurring photosynthetic functional units, oligoporphyrins molecular wires, and stacked systems in which small changes in geometry can affect significant changes in the inter-porphyrin coupling and hence produce dramatic changes in device properties.
Novel routes to substituted 5,10,15-triarylcorroles
Authors: Paolesse Roberto , Marini Alessia , Nardis Sara , Froiio Antonella , Mandoj Federica , Nurco Daniel J. , Prodi Luca , Montalti Marco , Smith Kevin M.
Published: July 2009

A one-pot procedure that allows the preparation of 5,10,15-triarylcorroles directly from the condensation of pyrrole and benzaldehydes, avoiding the concomitant formation of the corresponding tetraarylporphyrins, has been developed. This approach is general and allows the preparation of sterically hindered corroles from 2,6-disubstituted benzaldehydes, where the Rothemund approach failed. The first examples of fully substituted corrole free bases were prepared following this approach, but in this case corroles were obtained as a mixture with the corresponding dodecasubstituted porphyrins. Unsymmetrically substituted ABC corroles were obtained from the condensation of two different dipyrromethanes. A [2+12] biladiene-like approach afforded 10-(4-methylphenyl)-5,15-diphenylcorrole, along with a significant amount of tetraphenylporphyrin from the self-tetramerization of the starting pyrryl carbinol. An X-ray structure of 5,10,15-triphenylcorrole shows deviations from planarity that are attributed to the steric hindrance between the three hydrogen atoms present in the core of the corrole. Luminescence spectra of 5,10,15-triarylcorroles (where aryl = Ph , 3- NO 2- Ph or 4- NO 2- Ph ) show intense emission bands that, in the case of the nitro derivatives, are strongly dependent upon the solvent.
Synthesis of a diporphyrin dyad bearing electron-donor and electron-withdrawing substituents with potential use in the spectral sensitization of semiconductor solar cells
Authors: Milanesio M. Elisa , Gervaldo Miguel , Otero Luis A. , Sereno Leonides , Silber Juana J. , Durantini Edgardo N.
Published: July 2009

A new dyad 9( ZnP - P ) has been synthesized linking 5,15-bis(4-carboxyphenyl)-10,20-bis(4-nitrophenyl) porphyrin 4( P ) and Zn(II) 5-(4-aminophenyl)-10,15,20-tris(4-methoxylphenyl) porphyrin 8 (ZnP) by an amide bond. The structural moieties of dyad 9( ZnP-P ) present both different singlet state energy and redox properties. Dyad 9 was designed to improve the intramolecular electron transfer capacity. The ZnP moiety bears electron-donating methoxy groups and a zinc ion, while the other porphyrin structure, P , is substituted by electron-withdrawing nitro groups. On the other hand, structure P bears a carboxylic acid group, which is able to benefit from the orientation of dyad 9 adsorbed on the SnO 2 electrode. Absorption spectroscopic studies indicated only a very weak interaction between the chromophores in the ground state. The fluorescence analysis shows that both porphyrin moieties in dyad 9 are strongly quenched and that the quenching increases in a polar solvent. The ZnP moiety acts like an antenna for porphyrin P , but, singlet-singlet energy transfer is not complete. Thermodynamically, dyad 9 presents a high capacity to form the photoinduced charge-separated state, ZnP ·+- P ·-. Dyad 9 sensitizes the SnO 2 electrode and the photocurrent action spectrum closely matches the absorption spectrum, which confirms that light absorption by dyad is the initial step in the charge transfer mechanism. The photocurrent efficiency of dyad 9 is considerably higher than those of porphyrin monomers used as models of ZnP and P structures. Two processes may be contributing to enhance the charge injection efficiency in dyad 9; one involves an antenna effect that produces energy transfer from ZnP to P and the other includes electron transfer from the ZnP moiety to the photooxidizable free-base P . This dyad design, with P in direct contact with the substrate through the free carboxylic acid group, is a promising architecture of organic material for spectral sensitization of semiconductor solar cells.
Unique molecular structure and properties of novel purple intermediates of phthalocyanine derivative
Authors: Maeda Fumiihiro , Uno Kenjiro , Ohta Kazuchika , Sugibayashi Makiko , Nakamura Naotake , Matsuse Takehiro , Kimura Mutsumi
Published: July 2009

When long alkylthio-substituted phthalocyaninato copper(II) complexes, ( C n S )8 PcCu , were rapidly prepared in an α-diol by using our developed see-through microwave reactor and/or a conventional hot stirrer, novel purple intermediates were selectively obtained instead of the expected green complex, ( C n S )8 PcCu , for some specific combinations of the reaction solvent and metal salt. The reaction conditions to obtain the purple intermediates were established and the unique molecular structure was clarified for a buthylthio-substituted intermediate by X-ray single crystal structure analysis.
Synthesis and study of a calixpyrrole-texaphyrin chimera: A new oligopyrrolic chloride anion receptor
Authors: Sessler Jonathan L. , Cho Won-Seob , Dudek Stephen P. , Hicks Lindsay , Lynch Vincent M. , Huggins Michael T.
Published: July 2009

Reported here is the synthesis and characterization of a new class of macrocycle that represents a hybrid between texaphyrin and calixpyrrole. These polypyrrolic macrocycles were prepared in one step by the acid-catalyzed condensation between diformyl dipyrromethanes and o-phenylenediamines in high yields. The X-ray crystal structure of one of these new “chimeras” was solved. It reveals that the diprotonated Schiff-base macrocycle has a V-shape in which one chloride anion is bound. Isothermal titration calorimetry (ITC) studies served to confirm the ability of the hybrid macrocycles to bind chloride anion in acetonitrile solution. These compounds may be useful as easy-to-make anion receptors.
Meso tetrakis ortho-, meta-, and para-N-alkylpyridiniopor-phyrins: kinetics of copper(II) and zinc(II) incorporation and zinc porphyrin demetalation
Authors: Hambright Peter , Batinić-Haberle Ines , Spasojević Ivan
Published: July 2009

The relative reactivities of the tetrakis( N -alkylpyridinium- X - yl )-porphyrins where X = 4 (alkyl = methyl, ethyl, n -propyl) , X = 3 (methyl) , and X = 2 (methyl, ethyl, n -propyl, n -butyl, n -hexyl, n -octyl) were studied in aqueous solution. From the ionic strength dependence of the metalation rate constants, the effective charge of a particular cationic porphyrin was usually larger when copper(II) rather than zinc(II) was the reactant. The kinetics of ZnOH + incorporation and the acid catalyzed removal of zinc from the porphyrins in 1.0 M HCl were also studied. In general, the more basic 4- (para-) and 3- (meta-) isomers were the most reactive, followed by the less basic 2- (ortho-) methyl to n -butyl derivatives, with the lipophilic ortho n -hexyl and n -octyl porphyrins the least reactive.
Synthesis, spectroscopy and electrochemistry of a new phthalonitrile derivative with substituted PDT-TTF unit
Authors: Hu Yingyu , Shen Yongjia , Xu Xu , Li Xiaohong , Li Yongfang
Published: July 2009

A phthalonitrile derivative with a substituted propylenedithio-tetrathiafulvalene (PDT-TTF) unit was synthesized and characterized. 1 H NMR spectra disclosed an unexpected ring expansion reaction, by which the title compound was formed. Its crystal structure was determined by single crystal X-ray diffraction. The cyclic voltammogram and differential pulse voltammogram of the title compound showed two couples of redox peaks arising from TTF, one additional irreversible oxidation peak and one irreversible reduction peak.
Superoxide induced cyclizations of metallo-2,2'-bidipyrrins
Authors: Bröring Martin , Hell Christian , Brandt Carsten D. , Tejero Esther Cónsul
Published: July 2009

The reaction of the open-chain tetrapyrrolic ligand 2,2'-bidipyrrin with molecular dioxygen in the presence of a catalytic amount of manganese(II)-acetate was found to produce 10,10'-diformyl-2,2'-bidipyrrin with a remarkable selectivity. To identify the active oxidant in this transformation, 2,2'-bidipyrrin was treated with potassium superoxide, sodium peroxide and manganese(III) acetate, respectively, in dry DMF. While superoxide produces the dialdehyde in high yield, the treatment with peroxide or manganese(III) acetate leads to decomposition only. Nickel(II)-, palladium(II)- and copper(II)-2,2'-bidipyrrin were found to undergo macrocyclization reactions when treated with potassium superoxide in dry DMF at room temperature. While the respective 10-oxocorrolates are formed from the nickel(II)- and palladium(II)-2,2'-bidipyrrins, the copper(II) chelate reacts very slowly and yields copper(III) corrole in low yield. The results strongly point to superoxide as the active oxidant in a recently found new synthesis of corroles.
Electrochemical investigations of tripyrrin complexes
Authors: Bley-Escrich Jordi , Prikhodovski Serguei , Brandt Carsten D. , Bröring Martin , Gisselbrecht Jean-Paul
Published: July 2009

Electrochemical investigations on divalent transition metal complexes with a conjugated linear tripyrrole ligand, namely 3,4,8,9,13,14-hexaethyl-2,15-dimethyltripyrrin (HTrpy) are reported. This tripyrrin ligand behaves as a tridentate monoanionic ligand and forms a series of neutral metal complexes of the type TrpyMX, where M = Zn ( II ), Cu ( II ), Ni ( II ) Co ( II ) or Pd ( II ) and X is a chloride anion ( Cl -). The studied nickel, cobalt and zinc complexes undergo respectively three and two ligand-centered reversible one-electron reductions and a reversible ligand-centered one-electron oxidation. Only irreversible electron transfers are observed for TrpyPdCl , due to the instability of the reduced complex. TrpyCoCl does not undergo any metal-centered electron transfer which is unexpected compared to related complexes. The copper(II) complex shows an additional reduction step occurring on the metal, generating a stable copper(I) complex. A comparison of the redox behavior of tripyrrin complexes with porphyrins and linear tetrapyrrolic complexes, namely bidipyrrins, clearly indicates that the observed redox behavior of tripyrrin complexes is mainly metal dependent. The observed HOMO-LUMO gap in the studied series of tripyrrins is rather small (about 1.70 V) compared to porphyrins (2.25 V), but it is close to bidipyrrins (1.60 V).
Electrochemical and spectroscopic investigation of neutral, oxidized and reduced double-decker lutetium(III) phthalocyanines
Authors: Yilmaz Ismail , Nakanishi Takashi , Gürek Aysegül , Kadish Karl M.
Published: July 2009

The double-decker lutetium(III) phthalocyanine [( C 6 H 13 S )8 Pc ]2 Lu was investigated by electrochemical and spectroelectrochemical methods and comparisons made to previously investigated [( C 12 H 25 S )4 Pc ]2 Lu and ( Pc )2 Lu under the some experimental conditions. All three compounds undergo a single reversible one-electron oxidation and up to four reversible one-electron reductions in CH 2 Cl 2 containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). The octa- and tetra substituted phthalocyanine derivatives exhibit one oxidation and three or four reductions in solution while five reductions can be detected for the two compounds in a gel-like cast film membrane of tetraoctylphosphonium bromide (4 C 8 P + Br −) at a basal plane pyrolytic graphite electrode which was immersed in aqueous 0.5 M KCl . The half-wave potentials of these SR substituted complexes in CH 2 Cl 2 are negatively shifted by 210-490 mV from E1/2 values for the same compounds in the aqueous 4 C 8P+ Br − matrix and five reductions of these compounds are observed under the latter experimental conditions. The UV-visible spectra of the compounds were measured in five different oxidation states and ESR spectra were also characterized for the neutral and doubly reduced complexes. As was expected, [( Pc )2 Lu ]−,{[( C 6 H 13 S )8 Pc ]2 Lu }− and {[( C 12 H 25 S )4 Pc ]2 Lu }− are ESR silent while electrogenerated [( Pc )2 Lu ]2−, {[( C 6 H 13 S )8 Pc ]2 Lu }2− and {[( C 12 H 25 S )4 Pc ]2 Lu }2− show broad strong signals at g = 2.0046, 2.0041 and 2.0034 with linewidths of 13.9, 16.1 and 12.9, respectively. These signals are indicative of organic free radicals where the unpaired electrons of the dianion are delocalized over two macrocycles.
Vectorial photoinduced electron transfer of phytochlorin-fullerene systems in Langmuir-Blodgett films
Authors: Tkachenko Nikolai V. , Vehmanen Visa , Efimov Alexander , Alekseev Alexander S. , Lemmetyinen Helge
Published: July 2009

Molecular systems capable of photoinduced vectorial electron transfer (ET) were assembled using the Langmuir-Blodgett technique. The active part of the systems consisted of phytochlorin-fullerene donor-acceptor layers and polythiophene secondary donor layers. Such structures can promote multi-step inter-layer ET in a direction determined by the film architecture. Transient photovoltage and photocurrent were studied and ET rates and efficiencies were determined. The primary intramolecular charge separated state was formed upon photoexcitation in less than 1 ns and it recombined in approximately 50 ns. Addition of the polythiophene layer at the side of the phytochlorin moieties increased the distance of charge transfer and the lifetime of the charge separated state by promoting spontaneous interlayer electron transfer from the polymer to the phytochlorin cation.
Tripodal and/or picket porphyrins to mimic the cytochrome c oxidase activity
Authors: Didier Amandine , Ricard David , L'Her Maurice , Boitrel Bernard
Published: July 2009

The efficiency of different series of tris-(2-aminoethyl)amine TREN-capped porphyrins as catalysts for the electroreduction of dioxygen has been studied after adsorption of the molecules at the surface of a graphite electrode. The influence of two structural features have been explored: the relative position of the two metals in the iron-copper bimetallic complexes and the nature of the benzyl groups of the tripod itself. These compounds have also been compared with picket porphyrins bearing aromatic amino functions, e.g. quinoline. The conclusions obtained in the case of TREN-capped catalysts cannot be extended to those bearing aromatic pickets.
A practical approach to the study of photoactive self-assembled porphyrin systems
Authors: Flamigni Lucia , Talarico Anna Maria , Ventura Barbara
Published: July 2009

An overview of simple methods for the determination, by UV-vis spectroscopy, of association constants of porphyrin based, self-assembling components is presented. Sources of ambiguity and errors are outlined in order to provide non-specialists with basic information. A few cases of self-assembled structures based on porphyrins and displaying photoinduced energy and electron transfer processes are reviewed and evidence is given that a correct determination and interpretation of the association phenomena are of key importance for the interpretation of the photoinduced processes within the array.
Charge mobility in discotic liquid crystalline porphyrins and phthalocyanines measured by PR-TRMC
Authors: Warman John M. , Kroeze Jessica E. , Schouten Pieter G. , van de Craats Anick M.
Published: July 2009

The pulse-radiolysis time-resolved microwave conductivity technique, “PR-TRMC”, has been used to determine the charge carrier mobility within columnar stacks of mesomorphic discotic porphyrins and phthalocyanines. The influences of temperature, morphology and variations in the primary molecular structure are demonstrated and discussed. Both the mesomorphic and conductive properties are shown to be dramatically influenced by subtle changes in the peripheral alkyl chain structure or the core-to-chain coupling element. Mobilities close to 1 cm2.V−1.s−1 are found in crystalline solids, and well in excess of 0.1 cm2.V−1.s−1 in columnar, liquid crystalline phases. These values which are even larger than those determined by PR-TRMC for conjugated polymers and similar to values found for electrons and holes in organic single crystals.
Layer-by-layer assembly of porphyrin-fullerene dyads
Authors: Zilbermann Israel , Anderson Gregory A. , Guldi Dirk M. , Yamada Hiroko , Imahori Hiroshi , Fukuzumi Shunichi
Published: July 2009

The fabrication of high quality, robust and photoactive ITO electrodes is reported. Electrostatic and van-der-Waals interactions have been used for the step-by-step deposition of layers containing a fullerene-porphyrin dyad as the active layer.
Synthesis and crystal structure of a “double picket fence” 5,10,15,20-tetrakis-(2',6'-diacrylamido-4'-tert-butylphenyl)Zn porphyrin
Authors: Rose Eric , Etheve-Quelquejeu Mélanie , Andrioletti Bruno
Published: July 2009

Metalation of 5,10,15,20-tetrakis-(2',6'-diacrylamido-4'-tert-butylphenyl)porphyrin with Zn ( OAc )2·2 H 2 O afforded the expected Zn derivative whose X-ray crystal structure reveals a Zn atom hexacoordinated by the four pyrrolic nitrogen atoms and two molecules of H 2 O .
Photogeneration of charges in poly(N-vinylcarbazole) doped with lutetium bisphthalocyanines and lutetium bisnaphthalocyanines
Authors: Galmiche Laurent , Guyon François , Pondaven Annig , Moisan Jean-Yves , L'Her Maurice
Published: July 2009

Lutetium bisphthalocyanines and bisnaphthalocyanines, sandwich complexes having interesting electronic properties were studied as electron-acceptors associated with the donor polyvinylcarbazole ( PVCz ) in single-layer photoconductors. It is known, from their redox properties, that these lanthanide complexes are potential electron-acceptors as well as electron-donors; moreover, they strongly absorb light from the near-UV to the near-IR. The xerographic spectra recorded between 400 and 900 nm show that the polymeric phases doped with the lutetium bisphthalocyanines are photoconductive. These new photoconducting phases are active in the near IR domain which is promising with regard to their potential applications.
π-Conjugated multiporphyrin box via self-assembly of an ethynylene-bridged zinc porphyrin dimer
Authors: Tsuda Akihiko , Hu Haifeng , Watanabe Reiko , Aida Takuzo
Published: July 2009

An ethynylene-bridged zinc porphyrin dimer bearing metal-coordinating groups, such as bis[{5-(4-pyridyl)-15-(3,5-didodecyloxyphenyl)porphyrinato}zinc] Z2, self-assembles in CHCl 3 to form a rectangular-shaped supramolecular nano box, in which all the Z2 units preferentially adopt a planar conformation with a syn-parallel geometry as for the pyridyl groups.