bluuebunny/crossref_metadata_2025 huggingface dataset:
Reactions between iron porphyrins and tetrahydropterins
Authors: Mansuy Daniel , Mathieu Delphine , Battioni Pierrette , Boucher Jean-Luc
Published: July 2009

Data from the last few years have revealed a novel biological role of the tetrahydrobiopterin ( H4B ) cofactor, in one-electron transfers to the heme of the active site of NO-synthases (NOSs) with intermediate formation of a H4B -derived radical. These electron transfers play a key role in the catalytic cycles of the two steps catalyzed by NOS, the Nω-hydroxylation of L-arginine, and the three-electron oxidation of Nω-hydroxyarginine to L-citrulline and NO. Recent experiments performed between various tetrahydropterins and iron porphyrins have shown that the one-electron transfer from tetrahydropterins, such as the natural cofactors H4B and tetrahydrofolate or the synthetic 6,7-dimethyltetrahydropterin (diMeH4P), to Fe(III) porphyrins of sufficiently high redox potentials (> about -100 mV versus NHE for the Fe(III)/Fe(II) couple) is a very general reaction that occurs with formation of a tetrahydropterin-derived radical. Reaction of diMeH4P with a stable porphyrin Fe(II)-O2complex leads to a diMeH4P-derived radical and a transient Fe(III)-OOH complex, mimicking the reaction between H4B and heme Fe(II)-O2in the NOS catalytic cycle. Tetrahydropterins such as diMeH4P also reduce hemeproteins Fe(III) of sufficiently high redox potentials, such as cytochromes c and b5or metmyoglobin, to the corresponding hemeproteins Fe(II) .
Molecular engineering of cytochrome P450 and myoglobin for selective oxygenations
Authors: Ueno Takafumi , Ohki Takahiro , Watanabe Yoshihito
Published: July 2009

Aspects of protein engineering of cytochrome P450 (P450) and myoglobin ( Mb ) to construct selective oxygenation catalysts have been described. Heme enzymes are known as biocatalysts for various oxidations but the design of substrate specificity has still remained one of the significant challenges because of dynamic nature of enzyme-substrate interactions. In particular, P450s are the most interesting targets among the heme enzymes because they are able to catalyze many types of monooxygenations such as hydroxylation, epoxidation, and sulfoxidation with high selectivity. Thus, many researchers have made efforts to convert the selectivity for natural substrates into that for unnatural substrates by several protein engineering approaches. On the other hand, we have reported a rational design of Mb to convert its oxygen carrier function into that of peroxidase or peroxygenase. The Mb mutants prepared in our work afford oxo-ferryl porphyrin radical cation (compound I) as observable species in Mb for the first time. Furthermore, some of the mutants we have constructed are useful for enantioselective oxygenations by oxygen transfer from the Mb -compound I to substrates.
Correlation between subcellular localization and photodynamic efficacy
Authors: Kessel David
Published: July 2009

A variety of agents have now been identified that can selectively sensitize neoplastic cells and other tissues to light. This review classifies a group of photosensitizers according to their initial affinity for specific sub-cellular organelles in vitro, and describes the consequences of each major localization site with regard to direct tumor cell kill. Considerations pertinent to determinants of efficacy in animal models and in clinical applications are also pointed out. One consequence of photodynamic therapy leading to cell death involves photodamage to anti-apoptotic members of the Bcl-2. These proteins are located on the endoplasmic reticulum and mitochondrial membranes. Direct mitochondrial photodamage can also initiate apoptosis. Agents that target lysosomes can bring about apoptotic death via an indirect route, but this does not appear to limit their usefulness. Agents that target the plasma membrane can re-localize to the cytosol during irradiation and cause photodamage to elements of the apoptotic process, resulting in necrosis. Implications of these findings are discussed.
Efficient oxidations and photooxidations with molecular oxygen using metal phthalocyanines as catalysts and photocatalysts
Authors: Wöhrle Dieter , Suvorova Olga , Gerdes Robert , Bartels Oliver , Lapok Lukasz , Baziakina Natalia , Makarov Serguei , Slodek Aneta
Published: July 2009

Metal phthalocyanines can be very efficient as catalysts and photocatalysts in oxidation reactions using molecular oxygen as oxidant. Different types of soluble low molecular weight or oligomeric and insoluble heterogeneous catalysts and photocatalysts were developed. The heterogeneous metal phthalocyanines exist either impregnated on SiO 2, Al 2 O 3, charcoal and TiO 2 or covalently and coordinatively bound on SiO 2 and organic polymers or ionically bound on an organic ion exchanger. The catalytic oxidations of toxic sulfide and thiol derivative are studied. In addition, toxic phenols were employed as substrates for the photooxidation. Heterogeneous catalysts can exhibit higher activities then low molecular weight phthalocyanines. These systems exhibit a good stability for re-use. Photooxidations are more efficient than oxidations. A Si(IV) phthalocyanine derivative on a polymer ion exchanger is most active and stable. Also some examples for photooxidations in the direction of photochemical synthesis are given.
Synthesis, optical spectroscopy and electrochemistry of a D-σ-A compound derived from magnesium phthalocyanine
Authors: Hu Yingyu , Lai Guoqiao , Shen Yongjia , Li Yongfang
Published: July 2009

A magnesium phthalocyanine substituted with four EDT-TTF units on the non-peripheral sites was synthesized and characterized. The target compound and its intermediates have been identified by NMR, MS, EA, UV-vis and mp. The molecular weight of the target molecule cannot be detected in mass spectra. UV-vis spectra indicate that a dimer forms in chloroform but not in dichloromethane. The redox behavior of the target molecule in the solutions of various concentrations and at different scan rates have been discussed.
Hydrogen bonding and crystal packing favor a nonplanarCo(III)porphyrin conformation and unusually weak axial ligation in [Co(TPP)(benzylamine)2](SCN): A crystallographic and density functional theory investigation
Authors: Munro Orde Q. , Pearson Nicole
Published: July 2009

The single crystal X-ray structure of [ Co ( TPP )( BzNH2)2]( SCN ), compound 2, where TPP = 5,10,15,20-tetraphenylporphyrin dianion and BzNH2= benzylamine, reveals that the SCN-ion is hydrogen-bonded to one of the coordinated amino group hydrogen atoms via its sulfur atom. Furthermore, the N – H ⋯ SCN interaction is balanced by a stronger N – H ⋯ NCS hydrogen bonding interaction for the trans BzNH2ligand as a result of the multiple hydrogen bond accepting character of the thiocyanate ion. Analysis of the crystal packing shows that these two hydrogen bonds play a major role in fixing unusual orientations for the axial ligands relative to the porphyrin ring in this system. This, in turn, leads to the formation of a nonplanar porphyrin core conformation that is a mixture of ruffle- and saddle-type distortions. The intricate hydrogen bonding between the cations and anions in 2 results in an unusually long mean Co – Naminecoordination distance of 2.033(4) Å, some 0.05 Å longer than previously observed for other bis(primary amine) complexes of Co(III) porphyrins with comparable porphyrin ligands. Density functional theory (DFT) calculations at the B3LYP/LACVP* level of theory have been used to gauge the perturbation of the electronic structure of the [ Co ( TPP )( BzNH2)2]+cation caused by the N – H ⋯ SCN and N – H ⋯ NCS hydrogen-bonded SCN-ions. The calculations show that partial mixing of the anion MOs with those of the porphyrin cation lead to changes in the electron populations of the 3d orbitals of up to 0.42 e as well as more nearly tetragonal electronic symmetry for the Co(III) ion as a result of adjustments of the relative energies of the MOs with predominantly 3d character.
Recent advances in the chemistry of corroles and core-modified corroles
Authors: Gryko Daniel T. , Fox Joseph P. , Goldberg David P.
Published: July 2009

The aim of this review is to highlight recent progress in the chemistry of corroles and core-modified corroles. Emphasis is put on the synthetic and coordination aspects of corroles with meso substituents and corrolazines.
Synthesis and characterization of novel liquid and liquid crystalline phthalocyanines
Authors: Durmuş Mahmut , Lebrun Colette , Ahsen Vefa
Published: July 2009

Peripheral and non-peripheral tetra(13,17-dioxanonacosane-15-hydroxy) substituted metal free-, Ni (II) and Zn (II) phthalocyanines have been synthesized from the corresponding phthalonitrile derivatives in the presence of the anhydrous metal salt ( NiCl 2 and Zn ( OOCCH 3)2) or a strong organic base. The new compounds have been characterised by elemental analyses, IR, NMR, mass spectra and electronic spectroscopy. The mesogenic properties of these new materials were studied by differential scanning calorimetry (DSC), optical polarised microscopy and X-ray investigations. The effects of peripheral or non-peripheral substitution of (13,17-dioxanonacosane-15-hydroxy) to the phthalocyanine ring are also investigated. It is found out that non-peripheral substituted phthalocyanine derivatives (4a-c) are liquid at room temperature whereas, peripheral substituted phthalocyanine derivatives (7a-c) exhibit ordered discotic hexagonal columnar mesophases ( Col h) at room temperature.
N,N',N″,N‴-tetramethyltetra-2,3-pyridinoporphyrazinato copper(II) as a new catalyst in solvent-free tetrahydropyranylation (THP) of alcohols and phenols
Authors: Akhlaghinia Batool , Asadi Mozaffar , Safaeib Elham , Heydarpoor Mozhgan
Published: July 2009

Alcohols and phenols are tetrahydropyranylated in the presence of N , N ', N ″, N ‴-tetramethyltetra-2,3-pyridinoporphyrazinato copper(II) in good to excellent yields under solvent-free conditions.
Hydrophobicity parameters (Log P) of glycoconjugated porphyrins for photodynamic therapy evaluated by reversed phase HPLC
Authors: Hirohara Shiho , Obata Makoto , Ogura Shun-ichiro , Okura Ichiro , Higashida Suguru , Ohtsuki Chikara , Ogata Shin-ichi , Nishikawa Yoshiko , Takenaka Makiko , Ono Hiroshi , Mikata Yuji , Yano Shigenobu
Published: July 2009

Photodynamic therapy (PDT) is one of the most effective treatments for cancer. We synthesized and characterized a series of 16 glycoconjugated porphyrins using a modification of the Lindsey method in the presence of Zn ( OAc )2·2 H 2 O as a template. The Zn 2+ ion template strategy improved the yield about 3-fold in the case of meta-substituted tetraphenylporphyrins, and free-base porphyrins were obtaind almost quantitatively by demetalation with 4 M HCl . The hydrophobicity parameter (Log P) of these porphyrins was evaluated by reversed phase high-performance liquid chromatography (RP-HPLC). The Log P values ranged from +4.8 to +7.8, so that most of the compounds are amphiphilic. The effect of the glycopyranosyl unit on the hydrophobicity of these compounds is discussed on the basis of the Log P value.
A multitechnique investigation of the second order NLO response of a 10,20-diphenylporphyrinato nickel(II) complex carrying a phenylethynyl based push-pull system in the 5- and 15-positions
Authors: Pizzotti Maddalena , Annoni Elisabetta , Ugo Renato , Bruni Silvia , Quici Silvio , Fantucci Piercarlo , Bruschi Maurizio , Zerbi Giuseppe , Zoppo Mirella Del
Published: July 2009

A multitechnique investigation of the determination of the order of magnitude of the second and third order NLO response of [5-[(4-dimethylaminophenyl)ethynyl]-15-[(4-nitrophenyl)ethynyl]-10,20-diphenylporphyrinato]nickel(II) (1) is reported with the aim to produce self consistent evidence for a significant NLO response of this kind of push-pull porphyrin chromophore. The experimental multitechnique approach is based on the EFISH technique, working with a non-resonant incident wavelength of 1.907 μm, on the solvatochromic method and finally on a vibrational method, avoiding any fluorescence or resonance interference. A theoretical MNDO-TDHF evaluation of the zero-frequency quadratic and cubic hyperpolarizabilities of an ab initio optimized planar structure is also reported. The order of magnitude of the quadratic hyperpolarizability of (1) at zero frequency (β0), was found to be significantly lower than that reported for the corresponding Cu (II) or Zn (II) complexes with the same push-pull porphyrin chromophore.
Electrochemical and spectral properties of tris[tetra(15-crown-5)phthalocyaninato]dilutetium(III)
Authors: Zhukov Igor V. , Lapkina Lyudmila A. , Gorbunova Yuliya G. , Larchenko Vladimir E. , Tsivadze Aslan Yu.
Published: July 2009

Tris[tetra(15-crown-5)phthalocyaninato]dilutetium(III) ( R 4 Pc )3 Lu 2, whose structure had been confirmed earlier by X-ray analysis, was further examined by physicochemical studies. The redox properties of this complex were investigated by cyclic voltammetry. The spectroelectrochemical study of this compound has been performed for the first time. Based on the results obtained and analysis of literature data, an electrochemical criterion related to double- and triple-decker structure of lanthanide phthalocyanines has been proposed. IR and 1 H NMR data are also reported.
Molecular recognition of chiral porphyrins with amino acid esters
Authors: Ruan Wen J. , Zhao Xiao J. , Han Hua , Nan Jing , Zhu Zhi A. , Wang Jian G. , Ma Yi
Published: July 2009

Association constants between α,α,α,β- ZnT (o- BocTyr ) TAPP (1), α,α,α,β- ZnT (o- BocAla )- TAPP (2), and a series of amino acid esters were determined in chloroform by means of titrations monitored by UV-vis spectra. Association constants increased in the order K( AlaOMe ) < K( ValOMe ) < K( LeuOMe ), showing the same preference for the electronic effect of bulky amino acid esters. For the guest SerOMe and ThrOMe , the association constants of two hosts showed different orders; the order of 1 is K( SerOMe ) < K( ThrOMe ), and that of 2 is the reverse. The host 2 shows a D -/ L -selectivity of 6.9 for leucine methyl ester at 293 K in CHCl 3, which is the highest enantioselectivity achieved in our study. The host-guest system was studied by 1 H NMR spectra. On association, every proton experiences a small upfield shift. The intensity of circular dichroism (CD) spectra of 1 in the presence of optically active guests were reduced as compared with that of free 1, while that of 2 with optically active guests was of the induced split type. Molecular modeling of the host-guest systems were studied by simulated annealing on the basis of the Tripos force field. The minimal energies of the complexes were calculated, and the results show that the recognition behavior of hosts 1 and 2 toward amino acid esters is very different. The change of the interaction energy of 2 with guest molecules is larger than that of 1.
N-H tautomerization in triaryl corroles
Authors: Ding Tang , Harvey John D. , Ziegler Christopher J.
Published: July 2009

Two high resolution single X-ray crystal structures of meso-substituted free-base corroles are presented: 5,10,15-triphenylcorrole (1) and 5,10,15-tris(pentafluorophenyl)corrole (2). The internal NH protons are clearly assignable to different nitrogens, which represents the two tautomer limits of corrole.
Effects of metal and porphyrin structure on the yield and chemoselectivity of naphthalene oxidation: a comparative study for manganese and iron
Authors: Khavasi Hamid Reza , Safari Nasser
Published: July 2009

Oxidation of naphthalene was performed with various manganese and iron porphyrins as catalysts and metachloroperbenzoic acid, tert-butylhydroperoxide, and hydrogenperoxide as oxidants, in the presence of imidazole as cocatalyst. With m-CPBA, in low concentration of catalyst, iron porphyrin shows a higher catalytic activity than manganese porphyrin, while a greater amount of manganese porphyrin is needed for having a good catalyst. In the presence of excess amount of H 2 O 2 oxidant in CH 3 OH solvent, manganese porphyrin acts better than iron porphyrin; however with the same oxidant and in aprotic solvent such as CH 3 CN : CH 2 Cl 2 again iron shows a higher activity than manganese. Moreover, the effects of metalloporphyrin concentration on the selectivity, activity and stability of catalyst were studied in H 2 O 2-catalytic oxidation.
Langmuir and Langmuir-Blodgett film preparation and study of a metalloporphyrin dimer molecule
Authors: Ni Yuhua , Huo Qun
Published: July 2009

Two iron complexes of a porphyrin dimer molecule were synthesized and studied at the air-water interface and in Langumir-Blodgett (LB) films. Surface pressure-area isotherm and UV-vis absorption spectroscopic studies revealed an interesting molecular switching behavior between the two iron porphyrin complexes under basic or acidic conditions. Such a reversible structural transition does not only occur in solution phase, but readily takes place in the deposited Langmuir-Blodgett films. Domains with strip or disk-like shapes were formed in the Langmuir films of the metalloporphyrin complexes when barbituric acid was added into the subphase, an indication of supramolecular network formation between the metalloporphyrin dimer and barbituric acid molecules. Magnetic property studies of the Langmuir-Blodgett films of the iron porphyrin complexes by magnetic force microscopy provide further insights into relationships between the magnetic response and molecular structures of the metalloporphyrin LB films.
Synthesis, photophysicochemical studies of adjacently tetrasubstituted binaphthalo-phthalocyanines
Authors: Seotsanyana-Mokhosi Itumeleng , Chen Ji-Yao , Nyokong Tebello
Published: July 2009

Adjacent binaphthalo-phthalocyanines tetra-substituted with phenoxy (4a), 4-carboxyphenoxy (4b) and 4-t-butylphenoxy (4c) groups, as well as the di-substituted 4-carboxyphenoxy (5b) have been synthesized and characterized. The photophysical and photochemical behavior of 4a-c, were compared with those of the corresponding di-substituted derivatives, (5a-c). The secondary substituents on the phenoxy ring have an influence on the aggregation of the molecules and hence on their photophysical properties. All of the complexes exhibit a relatively good conversion of energy from the triplet-excited state to the singlet oxygen. The less aggregated molecule (4c), has the highest singlet oxygen quantum yield. For all the molecules, fluorescence yields are low and they all have relatively shorter triplet lifetimes compared with the unsubstituted zinc phthalocyanine. Increasing the number of ring substituents on these rigid MPc complexes (from complexes 5 to 4) showed a general increase in the triplet state lifetimes and singlet oxygen quantum yields, and a decrease in stability.
Effect of Photofrin II as a radio-sensitizing agent in two different oesophageal carcinoma cell lines
Authors: Schaffer Moshe , Kulka Ulrike , Ertl-Wagner Birgit , Schaffer Pamela M. , Friso Elisabetta , Hell Roswita , Jori Giulio , Hofstetter Alfons , Dühmke Eckhart
Published: July 2009

Background and Purpose: In spite of major advances in cancer treatment, the prognosis of patients with oesophageal carcinoma remains poor. Squamous cell carcinoma and adenocarcinoma account for 95% of all oesophageal tumors, although other histological subtypes are occasionally seen. We aimed to evaluate whether Photofrin II can enhance the effect of ionizing radiation on oesophageal cancer in an in vitro tumor model. Material and Methods: A human oesophageal squamous cancer cell line (OE-21) and a human oesophageal adenocarcinoma cell line (OE-33) were evaluated with and without incubation with Photofrin II. Cells were irradiated using doses ranging from 0 to 8 Gy. The response rate of the cells to irradiation was evaluated by a tetrazolium-based colorimetric assay, similar to the MTT test, with the aim to determine the efficiency of Photofrin II as a radiation sensitizer in comparison to irradiation alone. Results: The OE-21 cell line demonstrated a significantly reduced cellular survival rate, when irradiated in the presence of Photofrin, as compared to a control group irradiated in the absence of Photofrin II. For the OE-33 cell line, no significant differences were found between the group treated with Photofrin II and the control group. Conclusion: Our results demonstrate in an in vitro model that Photofrin II may act as a radio-sensitizer in squamous cell oesophageal cancer, but not in oesophageal adenocarcinoma.
Multistate molecular information storage using S-acetylthio-derivatized dyads of triple-decker sandwich coordination compounds
Authors: Lysenko Andrey B. , Malinovskii Vladimir L. , Padmaja Kisari , Wei Lingyun , Diers James R. , Bocian David F. , Lindsey Jonathan S.
Published: July 2009

An approach toward molecular information storage employs redox-active molecules attached to an electroactive surface. The chief advantages of such molecular capacitors include higher charge density and more versatile synthetic design than is afforded by typical semiconductor charge-storage materials. An architecture containing two triple-decker sandwich coordination complexes and an S-acetylthiomethyl-terminated tether has been designed for multibit storage. Each triple decker is composed of two phthalocyanines, one porphyrin, and two europium atoms. The oxidation potentials of each triple decker are tuned through the use of different substituents on the phthalocyanines (t-butyl, methyl, H ) and porphyrins (pentyl, p-tolyl). Interleaving of the four cationic oxidation states of each triple decker potentially affords eight distinct oxidation states. Two dyads were examined in solution and in self-assembled monolayers (SAMs) on a Au surface. One dyad exhibited eight distinct states in solution and in the SAM, thus constituting a molecular octal counter. The potentials ranged from −0.1-+1.3 V in solution and +0.1-+1.6 V in the SAM. Taken together, this approach provides a viable means of achieving multibit information storage at relatively low potential.
Comparison of chemical properties of iron, cobalt, and nickel porphyrins, corrins, and hydrocorphins
Authors: Jensen Kasper P. , Ryde Ulf
Published: July 2009

Density functional calculations have been used to compare the geometric, electronic, and functional properties of the three important tetrapyrrole systems in biology, heme, coenzyme B 12, and coenzyme F430, formed from iron porphyrin ( Por ), cobalt corrin ( Cor ), and nickel hydrocorphin ( Hcor ). The results show that the flexibility of the ring systems follows the trend Hcor > Cor > Por and that the size of the central cavity follows the trend Cor < Por < Hcor . Therefore, low-spin Co I, Co II, and Co III fit well into the Cor ring, whereas Por seems to be more ideal for the higher spin states of iron, and the cavity in Hcor is tailored for the larger Ni ion, especially in the high-spin Ni II state. This is confirmed by the thermodynamic stabilities of the various combinations of metals and ring systems. Reduction potentials indicate that the +I and +III states are less stable for Ni than for the other metal ions. Moreover, Ni – C bonds are appreciably less stable than Co - C bonds. However, it is still possible that a Ni – CH 3 bond is formed in F 430 by a heterolytic methyl transfer reaction, provided that the donor is appropriate, e.g. if coenzyme M is protonated. This can be facilitated by the adjacent SO 3− group in this coenzyme and by the axial glutamine ligand, which stabilizes the Ni III state. Our results also show that a Ni III– CH 3 complex is readily hydrolysed to form a methane molecule and that the Ni III hydrolysis product can oxidize coenzyme B and M to a heterodisulphide in the reaction mechanism of methyl coenzyme M reductase.
A very fast and easy procedure for the synthesis of metallophthalocyanines
Authors: Shaabani Ahmad , Rezayan Ali Hossein
Published: July 2009

The mixture of phthalonitrile and metal salt in 1,1,3,3-N,N,N',N'-tetramethylguanidinium trifluoroacetate as an ionic liquid without using any other reagents or solvents converted to the metallophthalocyanine under conventional heating conditions in relatively good yields at 130°C after less than 1 h. The ionic liquid can be recovered conveniently and reused efficiently.
Synthesis and characterization of highly soluble hexadecachloro- and hexadecafluorophthalocyanine ruthenium(II) complexes
Authors: Christendat Dharamdat , David Mary-Ann , Morin Sylvie , Lever A. B. P. , Kadish Karl M. , Shao Jianguo
Published: July 2009

A new synthesis is reported for hexadecafluorophthalocyanineruthenium(II), F16Pc (2-) RuIIand hexadecachlorophthalocyanineruthenium(II), Cl16Pc (2-) RuII, is reported for the first time. These paramagnetic species, which contain no axial ligand, are quite reasonably soluble in a range of common organic solvents. We report and discuss electronic and vibrational (infrared and resonance Raman) spectroscopic, MALDI-TOF and magnetic data. In addition we report electrochemical data and use spectroelectrochemical methods to obtain the electronic spectra of these species in the phthalocyanine(1-), (3-) and (4-) oxidation states.
Crystallographic evidence for structural diversity in cationic (tripyrrinato)cobalt(II) complexes
Authors: Bröring Martin , Brandt Carsten D. , Köhler Silke , Sieber Maximilian
Published: July 2009

Cobalt(II) complexes of tripyrrin ligands can be transformed into cations by anion exchange using NaBAr F , a salt of a weakly coordinating anion. The complete characterization of these highly sensitive cations (probably solvate complexes) could not be achieved, but the coordination to donor ligands like nitriles or trialkylphosphanes stabilizes the cations sufficiently for the isolation of some single crystals. As the structural analyses of these donor-stabilized cobalt(II) tripyrrins reveal, either four- or five coordinate structures are formed depending on the type and size of ligand used.
A supramolecular Star Wars Tie Fighter Ship: electron transfer in a self-assembled triad composed of two zinc naphthalocyanines and a fullerene
Authors: D'Souza Francis , Gadde Suresh , El-Khouly Mohamed E. , Zandler Melvin E. , Araki Yasuyaki , Ito Osamu
Published: July 2009

Photoactive supramolecules composed of electron donor and electron acceptor entities are important for light energy harvesting applications. In the present study, a Star Wars Tie Fighter Ship shaped supramolecular triad was constructed by self-assembling two zinc naphthalocyanines to a fulleropyrrolidine bearing two pyridine entities using an axial coordination approach. Optical absorption and emission studies revealed stable complex formation, and the experimentally determined free-energy change revealed the possibility of electron transfer from singlet excited zinc naphthalocyanine to the fulleropyrrolidine. The picosecond time-resolved emission technique was utilized to evaluate the kinetics of charge separation while nanosecond transient absorption spectral studies provided evidence for electron transfer quenching. The measured charge-separation rate, k CS and quantum yield, Φ CS were found to be 5.7 × 109 s −1 and 0.93 in toluene, respectively, indicating an efficient process within the supramolecular triad. The charge recombination rate (k CR ) of the supramolecular ion-pair calculated from the nanosecond transient absorption technique was found to be 3.5 × 107 s −1 yielding a lifetime for the radical ion-pair (τ RIP ) of about 30 ns. Changing the solvent from the noncoordinating toluene to the coordinating benzonitrile or THF destroyed the supramolecular structure, and under these experimental conditions, only intermolecular electron transfer from the triplet excited zinc naphthalocyanine to fulleropyrrolidine could be observed. Under these conditions, the measured electron transfer rates, k et , T inter , were found to be 2.6 × 107 M −1. s −1 in benzonitrile and 1.2 × 107 M −1. s −1 in THF, respectively.
A non-planar, hexadeca-substituted, metal-free phthalocyanine
Authors: McKeown Neil B. , Li Hong , Helliwell Madeleine
Published: July 2009

The readily prepared 2,3,9,10,16,17,23,24-octamethyl-1,4,8,11,15,18,22,25-octaoctyloxyphthalocyanine (Pc 1) adopts a non-planar conformation in the crystalline state as indicated by a dihedral angle of 27.2° formed between isoindole subunits on opposite sides of the core. The ring distortion can be attributed to a combination of steric congestion of the side-chains and the stabilization of the saddle-shaped conformation via pairing of molecules to give the so-called 'overlap effect'. The ring distortion is compared to that found in other metal-free phthalocyanines. Pc 1 adsorbs strongly in the near-IR region, is highly soluble and gives robust spin-coated films of excellent optical clarity.
A comparative study of microwave versus conventional synthesis of lead phthalocyanine complexes
Authors: Narayana Achar B. , Manjappa Mohan Kumar T. , Sannegowda Lokesh K.
Published: July 2009

Lead(II) phthalocyanine (PbPc); lead(II) tetranitrophthalocyanine (PbTNP) and lead(II) tetraaminophthalocyanine (PbTAP) were synthesized in pure state by microwave irradiation and conventional heating methods. The procedures for their synthesis by the microwave technique are standardized and reported for the first time. PbPc and PbTNP were synthesized in dry conditions and PbTAP complex was synthesized in aqueous medium. All the compounds are obtained in very high yield (~90%). The synthesized complexes are characterized with respect to elemental analysis, UV-visible, IR-spectroscopy and X-ray diffraction study. The microwave methods are advantageous over the conventional method of synthesis with respect to higher yield, rapidity and simplicity.
Microwave assisted axial ligand substitution of titanium phthalocyanines
Authors: Maree Suzanne E.
Published: July 2009

The synthesis of various axially substituted titanium phthalocyanines in high yield using microwave irradiation without an added solvent is reported. The times of reaction, as expected, are short and generally less than 10 minutes. The products were obtained in high purity after chromatography.
Effect of aggregation of a cationic phthalocyanine in micelles and in the presence of human serum albumin
Authors: Rodriguez Myriam E. , Fernández Daniel A. , Awruch Josefina , Braslavsky Silvia E. , Dicelio Lelia E.
Published: July 2009

The photophysical properties of tetrakis(1,1-dimethyl-2-trimethylammonium)ethylphthalocyaninato zinc(II) tetraiodide (I) – a water-soluble cationic phthalocyanine – are presented in the presence of human serum albumin (HSA) and in micelles of sodium dodecylsulfate ( SDS ) and hexadecyltrimethylammonium chloride ( CTAC ). Spectrophotometric measurements showed that the surfactants SDS and CTAC induce monomerization of I, although the latter less efficiently than the former. This effect is less pronounced in the presence of HSA. The strength of this effect is evaluated through dimerization constants, which are Kd = (5 ± 1) × 105 m−1 in SDS , (1.5 ± 0.5) × 106 M −1 in CTAC , and (1.8 ± 0.9) × 106 M −1 in HSA. Fluorescence experiments confirm that aggregation of I drops as the concentration of surfactant is raised. Triplet quantum yields also decreased upon aggregation and were Φ T = 0.59, 0.16, and < 0.01 in SDS , CTAC , and HSA, respectively. These results indicate that the affinity of I for the environment is not just due to ionic interactions; hydrophobic interactions play an equally important role.
Synthesis, photochemical and photophysical properties of novel unsymmetrically substituted zinc(II) phthalocyanines
Authors: Al-Raqa Shaya Y.
Published: July 2009

The synthesis of three novel unsymmetrical free base, zinc(II) phthalocyanine derivatives obtained from 3,6-di-(thiophen-3-yl)phthalonitrile and 3,6-didecylphthalonitrile are described. The synthesis of novel 3,6-substituted phthalonitriles bearing heteroaromatic derivatives were achieved through Suzuki-coupling reaction by treatment of 3,6-di(trifluoromethanesulfonyloxy)phthalonitriles and heteroaromatic boronic acids. Two of the newly synthesized complexes showed a high efficiency against a model biological substrate, such as N-acetyl-L-tryptophanamide NATA, and shows a high singlet oxygen quantum yield.
Synthetic methodology towards novel polyphenylated naphthalocyanines
Authors: Lee Chi-Hang , Sooksimuang Thanasat , Mandal Braja K.
Published: July 2009

Phenylated phthalocyanines and naphthalocyanines have rarely been explored, due to their low solubilities and high aggregation tendencies. We describe here a novel route for the synthesis of a polyphenylated (sixteen phenyl groups) naphthalocyanine via a Diels-Alder reaction. The phenyl substituents, which are orthogonal to the macrocyclic plane, lead to improved solubility and minimal intermolecular aggregation.
Phthalocyanines as photodynamic agents for the inactivation of microbial pathogens
Authors: Dei Donata , Chiti Giacomo , De Filippis Maria P. , Fantetti Lia , Giuliani Francesco , Giuntini Francesca , Soncin Marina , Jori Giulio , Roncucci Gabrio
Published: July 2009

A variety of 1,8(11),15(18),22(25)- and 2,9(10),16(17),23(24)-tetra-substituted and 2,3,9,10,16,17,23,24-octa-susbtituted Zn (II) phthalocyanines, bearing dialkylaminophenoxy and trialkylammoniumphenoxy groups, have been synthetized, characterized and tested as photosensitizers against S. aureus, E. coli and C. albicans. All phthalocyanines exhibited intense absorption bands in the phototherapeutically useful 670-700 nm region, with a molar extinction coefficient of the order of 105 M-1.cm-1. All derivatives bearing positive charges showed a good photosensitizing efficiency (causing a greater than 4 log reduction in cell survival), as well as a high quantum yield for generation of singlet oxygen. Variations of the chemical structure appeared to strongly affect both the physicochemical properties and the phototoxic activities against microorganisms.
Partially oxidized porphyrazines
Authors: Nazli Ayhan , Gonca Ergün , Gül Ahmet
Published: July 2009

Magnesium porphyrazinate substituted with eight (1-naphthyl) groups on the peripheral positions has been synthesized by cyclotetramerization of 3,4-(1-naphthyl)pyrroline-2,5-diimine, 4-(1-naphthyl)pyrroline-2,5-diimine in the presence of magnesium butanolate. Its demetalation by treatment with trifluoroacetic acid, resulted in a partially oxidized product, namely, octakis(1-naphthyl)-2-seco-porphyrazine-2,3-dione. Further reaction of this product with copper(II) acetate, zinc(II) acetate and cobalt(II) acetate led to the metallo derivatives, [octakis(1-naphthyl)-2-seco-2,3-dioxoporphyrazinato]M(II) ( M = Cu , Zn or Co ). These new compounds have been characterized by elemental analysis, together with FT-IR, 1 H NMR, UV-vis and mass spectral data.
A facile synthesis of stilbene-linked porphyrin dimers via the Wittig reaction
Authors: Jiang Xuliang , Wu Jian , Lu Yuanyuan
Published: July 2009

A facile synthesis of free-base and metalated stilbene-linked porphyrin dimers via the Wittig reaction is reported. 5-(4-chloromethylphenyl)-10,15,20-triphenyl porphyrin was prepared by direct chloromethylation of meso-tetraphenylporphyrin as the useful precursor for both the porphyrin-derived Wittig reagent and the monoformylporphyrin. It was found that the stilbene-linked porphyrin dimers were formed with a remarkable sterochemical preference in the cis-form. Their absorption and emission spectra were measured.
Vapor pressure measurements and thermodynamics of some volatile phthalocyanines
Authors: Semyannikov Petr , Basova Tamara , Trubin Sergei , Kol'tsov Evgeny , Igumenov Igor
Published: July 2009

Mass spectrometric studies of the composition of the gaseous phase for solid compounds of hexadecafluorinated phthalocyanines MPcF 16, M = Cu , Zn , VO and their unsubstituted MPc analogs were performed in a temperature range up to 600°C. It has been shown that phthalocyanines sublime into the form of monomers without thermal decomposition. The vapor pressure of these phthalocyanines was determined as a function of temperature by the Knudsen effusion method, in which the rate of effusion of the equilibrium vapor through a small orifice was measured. The thermodynamic parameters of the sublimation process for phthalocyanines were calculated.
Synthesis and photophysical properties of octa-substituted phthalocyaninato oxotitanium(IV) derivatives
Authors: Tau Prudence , Nyokong Tebello
Published: July 2009

The synthesis, spectral and photophysical properties including fluorescence quenching of the following octa-substituted oxotitanium phthalocyanines are reported: 2,3,9,10,16,17,23,24-octaphenoxyphthalocyaninato titanium(IV) oxide, 2,3,9,10,16,17,23,24-[octakis(4-t-butylphenoxyphthalocyaninato)]titanium(IV) oxide, 2,3,9,10,16,17,23,24-{octakis[(4-benzyloxy)phenoxy]phthalocyaninato}titanium(IV) oxide and 2,3,9,10,16,17,23,24-octaphenylthiophthalocyaninato titanium(IV) oxide. The complexes are characterized by1H NMR, IR and UV-vis spectroscopies. Their photophysical properties are presented where moderate fluorescence quantum yields (0.14-0.19) and lifetimes were determined. Varied triplet quantum yields were obtained and the triplet lifetimes (40-100 μs) were short.
Synthesis, spectroscopy and photochemistry of dyads and triads with porphyrins and bis(terpyridine)ruthenium(II) complex
Authors: Poddutoori Prashanth Kumar , Poddutoori Premaladha , Maiya Bhaskar G.
Published: July 2009

A bis(terpyridine)ruthenium(II) complex ([Ru]2+) was covalently connected via a floppy - OCH 2 CH 2 O - spacer to the free-base porphyrin (H) or zinc(II) porphyrin (Zn) or both, to obtain dyads ([HRu]2+, [ZnRu]2+) and triads ([HRuH]2+, [ZnRuH]2+, [ZnRuZn]2+). These compounds have been fully characterized by MALDI, UV-vis, 1 H NMR (1D and 1 H -1 H COSY) spectroscopies, and also by the cyclic and differential pulse voltammetric techniques. Absorption spectroscopy of these newly synthesized compounds shows that significant exciton coupling exists in non-polar solvents (cyclohexane and toluene) between the porphyrin ring and the bis(terpyridine)ruthenium(II) complex. Upon excitation within the Soret band of [HRu]2+/[HRuH]2+, free-base porphyrin fluorescence was found to be strongly quenched in non-polar and weakly quenched in polar solvents, probably due to ‘singlet-triplet’ energy transfer from the free-base porphyrin to the [Ru]2+ complex. Whereas, in [ZnRu]2+/[ZnRuZn]2+, zinc(II) porphyrin fluorescence was quantitatively and reasonably quenched in non-polar and polar solvents, respectively by mainly electron transfer from the zinc(II) porphyrin to the [Ru]2+ complex. The solvent plays a crucial role in the photophysical properties of these compounds, since the energy of the triplet metal-to-ligand charge-transfer (3MLCT) excited state is influenced by the polarity of the medium. Finally, [ZnRuH]2+ exhibits the combined fluorescence properties of [HRu]2+ and [ZnRu]2+ but the observed additional quenching in non-polar solvents for the zinc(II) porphyrin component is explained by energy transfer from the zinc(II) porphyrin to the free-base porphyrin and/or the bis(terpyridine)ruthenium(II) complex.
Discotic liquid crystals of transition metal complexes, part 36: syntheses and mesomorphic properties of very large discotic liquid crystals based on triphenylenocyanine and 1,4-diazatriphenylenocyanine
Authors: Ichihara Masahiro , Miida Masakazu , Mohr Bernhard , Ohta Kazuchika
Published: July 2009

Two series of very large discotic complexes of tetrakis (2,3,6,7-tetraalkoxy)triphenylenocyaninato copper(II) (abbreviated as ( C n O )16 TcCu ; n = 8, 10, 12 and 14) and tetrakis(2,3,6,7-tetraalkoxy)-1,4-diazatriphenylenocyaninato copper(II) (abbreviated as ( C n O )16 TzCu ; n = 8, 10, 12 and 14), were synthesized to investigate their mesomorphic properties by differential scanning calorimetry, thermogravimetry analysis, polarizing optical microscope observation and temperature-dependent X-ray studies. The results show that each of the ( C n O )16 TcCu derivatives exhibits two or three disordered rectangular columnar ( Col rd ) mesophases from room temperature to the decomposition temperature at ca. 330-340°C under nitrogen gas. However, each of the ( C n O )16 TzCu complexes exhibits only one ordered tetragonal columnar ( Col tet.o ) mesophase in an extremely wide temperature region from room temperature to the decomposition temperature at ca 300°C and ca. 340-350°C under the atmosphere and nitrogen gas, respectively. It is very interesting that the Col tet.o mesophase of ( C n O )16 TzCu for n = 10, 12 and 14 shows remarkable spontaneous homeotropic alignment in a large area, without disclinations and polydomains, in the temperature range from room temperature to the decomposition temperature. As far as we know, these discotic liquid crystals are the first examples to show homeotropic alignment at room temperature. Furthermore, the difference between the mesomorphic properties of ( C n O )16 TcCu and ( C n O )16 TzCu originated only from the additional eight nitrogen atoms in the central core in ( C n O )16 TzCu .
The reaction of porphyrins with α,β-acetylenic ketone/ester (Morita-Baylis-Hillman) promoted by MgI2 and subsequent Sonogashira coupling reactions
Authors: Ahmed Naseem , Ali Hasrat , van Lier Johan E.
Published: July 2009

The stereoselective synthesis of (Z)-β-iodovinyl ketones/esters of Morita-Baylis-Hillman (MBH) porphyrin adducts has been achieved with a tandem formation of C - C and C - I bonds in a three-component reaction. The reaction is promoted by MgI 2 as a Lewis acid, as well as an iodine source for a Michael-type addition. The MBH adducts are efficiently oxidized to the corresponding ketones with Dess-Martin periodinane (DMP). These scaffolds are further used in a palladium-catalyzed Sonogashira carbon-carbon coupling reaction to obtain highly extended porphyrin systems.
Thin insulating polymer films as dielectric layers for phthalocyanine-based organic field effect transistors
Authors: Kelting Christian , Michaelis Wilfried , Hirth Andreas , Wöhrle Dieter , Schlettwein Derck
Published: July 2009

Films of organic polymers were prepared and investigated as insulating layers in contact with phthalocyanines as organic semiconductors for use in organic field effect transistors. The polymer films were obtained either by a high-vacuum technique based on the thermal decomposition of polymers and polymerization of the fragments on a substrate, by the spin-coating of polymer solutions or by the cross-linking of spin-coated precursors. Poly(vinylchloride), poly(vinylidenefluoride), poly(acrylonitrile), poly(methylmethacrylate), poly( N -vinylpyrrolidone), poly(styrene), poly(4-vinylpyridine), poly( N -vinylcarbazole) and a polyimide were used as polymers. The film growth was studied by mass spectrometry and infrared spectroscopy. Electrochemical measurements by cyclic voltammetry served to analyze the properties of the polymer films. The morphology was determined by atomic force microscopy. Interactions of the films with phthalocyaninatozinc ( PcZn ) was analyzed for co-evaporated PcZn in the polymer films, to probe the chemical compatibility of the methods. Subsequently, evaporated PcZn or hexadecafluorophthalocyaninato-oxo-vanadium ( F 16 PcVO ) thin films were studied in detail by UV-vis spectroscopy and by electrical measurements to investigate interface formation, intermolecular coupling and electrical conduction in such films. The applicability of the different polymers as dielectric layers in organic field effect transistors, with phthalocyanines as the active semiconductor thin films, is discussed, based on their dielectric behavior and observed growth characteristics.
Rapid and efficient synthesis of metal-free phthalocyanine derivatives
Authors: Shaabani Ahmad , Maleki Ali
Published: July 2009

Metal-free phthalocyanine derivatives have been synthesized in very short times with high yields in the presence of 1,1,3,3-tetramethylguanidinium trifluoroacetate (TMGT) as an ionic liquid or tetrabutylammonium bromide (TBAB) as a phase transfer reagent under both classical heating conditions and using microwave irradiation. The best results were obtained with ionic liquid. Both the ionic liquid and phase transfer reagent can be recycled for subsequent reactions and reused without appreciable loss of efficiency.
Triazole-annulated phthalocyanines and benzoporphyrazines
Authors: Vagin Sergei I. , Hanack Michael
Published: July 2009

The application of mono-triazole-annulated phthalocyanine and benzoporphyrazine complexes for the functional unsymmetrical modification of the macrocycle's periphery is discussed. The peculiarities of the synthesis of some metal complexes with aryloxy-substituted mono-triazole-annulated Pc are described. Alkylation by ω-alkenylbromide of the triazole ring in accordingly prepared novel mono-triazole-annulated phthalocyaninato nickel, as well as in mono-benzotriazole-annulated porphyrazinato zinc, is studied. The terminal double bond in the formed derivatives could be successfully converted into acetylsulfanyl function only in the case of phthalocyaninato nickel complex due to the instability of porphyrazinato zinc under the reaction conditions.
Chemical and electrochemical oxidation of N-alkyl cyclo[n]pyrroles
Authors: Sessler Jonathan L. , Lee Jeong Tae , Ou Zhonping , Köhler Thomas , Hargrove Amanda E. , Cho Won-Seob , Lynch Vincent , Kadish Karl M.
Published: July 2009

Cyclo[n]pyrroles ( n = 6, 7, and 8), are expanded porphyrins that lack bridging meso carbon atoms. They adopt conformations that are near-planar and show features that are consistent with global aromaticity. In previous work, involving studies of cyclo[8]pyrroles, it was found that, in contrast to what is true for porphyrins, reductive per- N -alkylation led to the formation of non-planar products that displayed few signs of extended conjugation. These octa- N -alkylated species could be reoxidized electrochemically to produce dicationic, octa- N -substituted analogues of the starting aromatic cyclo[8]pyrroles. We have now extended this study to cyclo[6]pyrrole, and have found that reductive per- N -methylation can be readily effected using methyl iodide. However, in contrast to what is true in the case of cyclo[8]pyrroles, efforts to obtain the fully N -ethylated or N -benzylated products proved unsuccessful. Moreover, in the case of the hexa- N -methylated cyclo[6]-pyrrole product no viable chemical means of oxidizing it to the putative aromatic dication could be found. However, evidence for the formation of such species was obtained by electrochemical means. The differences between cyclo[6]- and cyclo[8]pyrrole highlight the effect of ring size in mediating the redox and reactivity chemistry within what is otherwise a closely matched pair of porphyrin analogues.
Intramolecular photoinduced processes of newly synthesized dual zinc porphyrin-fullerene triad with flexible linkers
Authors: El-Khouly Mohamed E. , Hasegawa Jun , Momotake Atsuya , Sasaki Mikio , Araki Yasuyuki , Ito Osamu , Arai Tatsuo
Published: July 2009

Zinc porphyrin-fullerene-zinc porphyrin triad, in which two zinc porphyrin ( ZnP ) moieties and a fullerene ( C 60) moiety are linked by flexible bonds and which is intended to be a working model of the photosynthetic antenna-reaction centre, has been newly synthesized. Its photophysical properties have been investigated by both time-resolved emission and transient absorption techniques. Excitation of the zinc porphyrin moiety of the triad induced charge separation, generating the radical ion pair, in which the electron localizes on the C 60 moiety and the hole localizes on the zinc porphyrin moiety. In polar solvents, the charge-separated states decayed with lifetimes of 300-600 ns returning to the ground state. Compared with ZnP - C 60 dyad, ZnP - C 60- ZnP triad showed longer lifetimes for the radical ion pair due to the conformation of the two ZnP moieties. The effects of the coordinating reagents on the zinc atom have been studied, with the expectation of conformational change of the two ZnP moieties with respect to C 60.