bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclic voltammetric studies of octabutylthiophthalo-cyaninato-cobalt(II) and its self-assembled monolayer (SAM) on gold electrode
Authors: Ozoemena Kenneth , Westbroek Philippe , Nyokong Tebello
Published: July 2009

The synthesis of thiol-derivatized cobalt phthalocyanine complex, 2,3,9,10,16,17,23,24-octa (butylthiophthalocyaninatocobalt(II) ( CoOBTPc ) is described. Cyclic voltammetric data of this complex in DMF showed five quasi-reversible and reversible, diffusion-controlled redox couples, comprising both the phthalocyanine ring and central metal redox processes. The CoOBTPc complex forms a self-assembled monolayer (SAM) on gold electrode. The investigation of the integrity of this SAM, using the established cyclic voltammetric methods in aqueous alkaline solutions, gave evidence about the formation of a stable and easily reproducible monolayer. However, due to its susceptibility to destruction via oxidative and reductive desorptions, its potential application as an electrochemical sensor in alkaline pH is limited to a potential window of between −0.20 and +0.55 V vs Ag / AgCl .
Effects of diverse acid catalysts on the reaction course in the two-step one-flask synthesis of meso-tetraphenylporphyrin
Authors: Geier G. Richard , Lindsey Jonathan S.
Published: July 2009

A set of 45 acids or acid combinations was examined in the condensation of pyrrole + benzaldehyde (10 mM each in CH 2 Cl 2) leading to meso-tetraphenylporphyrin (TPP). Initial screening experiments identified suitable acid catalysts and the optimal concentration (in terms of TPP formation) for each acid. Subsequent experiments followed the time course of reactions using the best conditions identified in the screening experiments. The reaction course was followed by monitoring reactions from 1 min to 24 h for the yield of TPP (by UV-vis and HPLC), the yields of N-confused tetraphenylporphyrin and tetraphenylsapphyrin (by HPLC), the quantity of unreacted benzaldehyde (by TLC), and the oligomer composition (by laser desorption mass spectrometry). Diverse acids (Brønsted or Lewis; soluble or insoluble) were found to provide yields of TPP ranging up to ~50%. Only 10 acids gave no TPP. In addition, N-confused tetraphenylporphyrin was found to be a ubiquitous byproduct, whereas tetraphenylsapphyrin was not widely observed. MgBr 2-etherate and CuCl 2 each catalyzed porphyrinogen formation and resulted in porphyrin metalation following oxidation and neutralization of the reaction mixture, thereby providing direct, one-flask syntheses of magnesium and copper porphyrins. Observations concerning the reaction course obtained from prior studies of TFA or BF 3-etherate catalysis have been found to be quite general across a broad range of acid catalysts. Collectively, these results show that many acids have potential utility in porphyrin syntheses.
Acidolysis of intermediates used in the preparation of core-modified porphyrinic macrocycles
Authors: Chevalier Fabien , Geier G. Richard , Lindsey Jonathan S.
Published: July 2009

The stability towards acidolysis of intermediates used in the preparation of core-modified porphyrinic macrocycles was examined. Experiments were performed using analogs of 5-phenyldipyrromethane in which one of the two pyrrole rings was modified (XPM). The XPMs utilized in these studies had X = 2-furyl (OPM), 2-thienyl (SPM), 2-selenyl (SePM), or 3-pyrrolyl (NCPPM). The XPMs possess a potentially labile linkage to a heteroatom-modified ring as well as a potentially labile linkage to a pyrrole ring. The stability of the two types of linkages was examined under acid catalysis conditions commonly used in the preparation of porphyrinic macrocycles. The methodology employed enabled characterization of the stability of the XPM (GC analysis), the yield of porphyrin (UV-vis absorption), and the composition of porphyrinic species (laser-desorption mass spectrometry, LD-MS) formed upon acidolysis of the XPM. These experiments showed that (1) the linkage to the heteroatom-modified ring is fairly stable in the presence of a linkage to pyrrole, and (2) the linkage to pyrrole is much more stable in the XPMs than is the case in 5-phenyldipyrromethane. Additional experiments with analogs of 5-phenyldipyrromethane having both rings modified ( X 2 M ), where X = 2- furyl ( O 2 M ), 2- thienyl ( S 2 M ), or 2- selenyl ( Se 2 M ) confirmed that linkages to furyl, thienyl, and selenyl rings are stable towards acidolysis. Taken together, the observations concerning stability of various linkages provide a foundation for understanding the types and yields of core-modified porphyrinic macrocycles formed in reactions with reactants that are not direct precursors to the isolated products.
Synthesis and characterization of a new (phthalocyani-nato)bis(carboxylate) silicon(IV) compound with increased solubility
Authors: Sosa-Sánchez José L. , Galindo Alberto , Gnecco Dino , Bernès Sylvain , Fern George R. , Silver Jack , Sosa-Sánchezan Arturo , Enriquez Raúl G.
Published: July 2009

The synthesis and spectroscopic characterization of a new soluble silicon(IV) phthalocyanine complex is presented. The compound shows an increased solubility compared to its SiPcCl 2 precursor and this allowed solution 1 H NMR characterization. The assignment of the 1 H NMR signals for the axial ligands is greatly facilitated due to the anisotropic high ring current effects from the macrocycle. In addition, good quality crystals were grown from this more soluble material for molecular structure determination by single-crystal X-ray diffraction analysis. The molecular structure determination shows that the complex crystallizes in a non-centrosymmetric space group due to the inherent chirality of the naproxene ligands. Bond lengths and angles fit well to other analogous compounds previously reported.
Resonance Raman spectroscopy
Authors: Kitagawa Teizo
Published: July 2009

The main topics in resonance Raman spectroscopy presented at ICPP-2 in Kyoto are briefly discussed. These include: (i) coherent spectroscopy and low frequency vibrations of ligand-photodissociated heme proteins, (ii) vibrational relaxation revealed by time-resolved anti-Stokes Raman spectroscopy, (iii) electron transfer in porphyrin arrays, (iv) vibrational assignments of tetraazaporphyrins and (v) resonance Raman spectra of an NO storing protein, nitrophorin.
Electrochemistry and spectral characterization of arsenic porphyrins with σ-bonded axial ligands: X-ray crystallographic analysis of [(OEP)As(F)2]+PF6−, [(OEP)As(CH3)(OCH3)]+ClO4− and [(OEP)As(C2H5)2]+PF6−
Authors: Kadish Karl M. , Ou Zhongping , Tan Xiaoyu , Satoh Wataru , Yamamoto Yohsuke , Akiba Kin-ya
Published: July 2009

The electrochemistry of nine arsenic(V) octaethylporphyrins is reported in benzonitrile or dichloromethane containing 0.1 M tetra-n-butylammonium perchlorate as supporting electrolyte and the results compared to data for phosphorus and antimony porphyrins containing a similar set of σ-bonded and/or anionic axial ligands. The investigated compounds are divided into three groups based on the nature of the axial ligands and are represented as [( OEP ) As ( R )( R ')]+ (group I), [( OEP ) As ( R )( X )]+ (group II) and [( OEP ) As ( F )2]+ (group III) where R and R’ = CH 3 or C 2 H 5, X = OH −, OCH 3−, OC 2 H 5−, OC 3 H 7− or NHC 4 H 9− and OEP = the dianion of octaethylporphyrin. Each compound was characterized in its neutral, oxidized and reduced form by UV-visible and ESR spectroscopy. An X-ray crystallographic analysis of [( OEP ) As ( F )2]+ PF 6−, [( OEP ) As ( CH 3)( OCH 3)]+ ClO 4− and [( OEP ) As ( C 2 H 5)2]+ PF 6− is also presented.
The influence of heat-pretreatment on the gas-sensing properties of novel zinc phthalocyanine LB films
Authors: Ding Ximing , Zhu Hui , Xu Huijun , Jiang Dapeng
Published: July 2009

A novel asymmetrically substituted amphiphilic phthalocyanine, 1,4-di(2-hydroxyethoxyl)-8,9,16,17,23,24-hexapentyloxylphthalocyaninozinc ( asy - PcZn ), was synthesized. It can be deposited as well-ordered LB films. Significant structural changes of the films were observed by UV-vis absorption spectra and low-angle X-ray diffraction after the films were annealed at 150 °C. What is more interesting is that the initial conductance of the films in air decreases and the response signal to NH 3 is weaker with longer response time after annealing compared with that of the unpretreated films.
Synthesis and optical properties of novel covalent and non-covalent porphyrin dimers
Authors: Genady Afaf R. , Gabel Detlef
Published: July 2009

A new series of porphyrin dimers in different geometry have been synthesized. The reductive amination of dicarbonyl compounds, especially 2,5-hexadione and isophthaldhyde, with porphyrin monomers, α,α,α,α-5-(p-aminophenyl)-10,15,20-tris-(4-tolyl)porphyrin, α,α,α,α- and α,α,β,β-5,10,15,20-tetrakis-(o-aminophenyl)porphyrin in the presence of excess of NaBH 3 CN , afforded novel dimeric single and double bridged dimers of free base porphyrins, covalently linked through aliphatic or aromatic spacers. All the synthesized compounds were characterized by NMR, IR, UV-vis, and MS spectroscopy. Significant spectral changes occurred in the absorption spectra of these covalent porphyrin dimers comparing with that of the reference monomers, indicating strong electronic interaction between the adjacent porphyrin units. The UV-vis spectra showed the presence of another kind of non-covalent aggregation, which was observed at pH = 2.5-3 for some of these synthesized dimers. A similar behavior of association was also detected when α,β,α,β-5,10,15,20-tetrakis-(o-aminophenyl)porphyrin was measured at pH = 3.5 in acetone.
An improved chiroporphyrin shift reagent for the enantiomeric assay of amino acid derivatives by 1H NMR spectroscopy: evaluation of iodorhodium(III) tetramethylchiroporphyrin
Authors: Claeys-Bruno Magalie , Pécaut Jacques , Bardet Michel , Marchon Jean-Claude
Published: July 2009

1 H NMR spectroscopic studies of amino ester complexation indicate that iodorhodium(III) tetramethylchiroporphyrin RhI(TMCP) has a single axial site available for the coordination of amine groups, and that it retains its iodo ligand trans to the coordinated amine. This conclusion is confirmed by the X-ray structure of the 1:1 adduct of n-propylamine with RhI(TMCP). This stoichiometry of amine binding makes RhI(TMCP) a superior chiral derivatizing agent relative to CoCl ( TMCP ), which gives 1:2 adducts. It may have a strong impact in the utilization of RhI(TMCP) for the enantiomeric assay of amino acid mixtures by 1 H NMR spectroscopy. Axial exchange of the (R)- and (S)-enantiomers of aspartic acid dimethyl ester on RhI(TMCP) is moderately slow, and equilibrium is reached in a few minutes without kinetic resolution.
The effects of bulky ortho-aryl substituents in corroles, tested by X-ray crystallography of the rhodium complexes and catalysis thereby
Authors: Simkhovich Liliya , Goldberg Israel , Gross Zeev
Published: July 2009

In the present publication we report on the preparation and spectroscopic features of a penta-coordinate rhodium(III) complex of corrole with bulky ortho-phenyl substituents at the meso positions, Rh ( tdcc )( PPh 3)[ tdcc = tris (2,6- dichlorophenyl ) corrole ]. Addition of pyridine to Rh ( tdcc )( PPh 3), as well as to the closely related complex of tris(pentafluorophenyl)corrole [ Rh ( tpfc )( PPh 3)] reported earlier, leads to hexa-coordinated rhodium complexes with pyridine and PPh 3 occupying the axial positions. The structures of these two compounds were investigated by NMR and X-ray crystallography. The catalytic potency of Rh ( tdcc )( PPh 3) was found significantly lower than that of Rh ( tpfc )( PPh 3), which suggests that excess steric crowding prevents efficient carbene-transfer catalysis.
Effect of alkyl group length on the conductivity in the 2,3,7,8,12,13,17,18-octakis(alkyl-thio)tetraazaporphyrins and redox properties of the metallooctakis(hexyl-thio)tetraazaporphyrins
Authors: Yu Bin , Zhou Yanxiu , Wang Daike , Wang Zhenxing , Sugiura Kenichi , Sakata Yoshiteru , Levon Kalle
Published: July 2009

A series of 2,3,7,8,12,13,17,18-octakis(alkyl-thio)tetraazaporphyrins (H2OATTAP) with different alkyl chain lengths have been synthesized. Cyclic voltammetry and differential pulse voltammetry have been used to investigate the effect of the controlled lengths of the eight peripheral thioether tails on the redox behavior of the molecules. The electrochemical reduction of octakis(hexyl-thio)tetraazaporphyrins, MOHTTAP (where M = Cu , Ni ), was studied in 1,2-dichloroethane at a platinum electrode. The Cu derivative was oxidized in one single-electron-transfer step to yield a π-cation radical and reduced in three single-electron-transfer steps to yield a π-anion radical, dianion and trianion, respectively. For the Ni derivative, electron transfer reactions involving both the central metal atom and the macrocyclic ring were observed. Electron transfer pathways are proposed based upon voltammetric and in situ spectroelectrochemical results.
Electrochemical properties and dissolved oxygen reduction study on an iron(III)-tetra(o-ureaphenyl)porphyrinosilica matrix surface
Authors: Ribeiro Emerson S. , Gushikem Yoshitaka , Biazzotto Juliana C. , Serra Osvaldo A.
Published: July 2009

Electrochemical reduction of dioxygen on an iron(III)-tetra-o-ureaphenylporphyrino-silica matrix surface ((o)- FeTUPPS ) obtained by attachment of the iron porphyrin tetraurea to a silica matrix through the sol-gel process was studied. Cyclic voltammetry and chronoamperometry techniques using as working electrode a carbon paste electrode modified with (o)- FeTUPPS , showed that (o)- FeTUPPS catalyzed O 2 reduction at −0.34 V vs SCE in 0.5 mol.L−1 KCl solution at pH 6. The electrode showed a linear and reproducible response to O 2 concentrations in the range ca. 0.5 and 11 mg.L−1 and was chemically stable under various oxidation-reduction cycles. From rotating disk experiments it was concluded that dissolved O 2 was reduced at the electrode surface to H 2 O 2 in a two-electron process.
Selective sulfonation and deuteration of free-base corroles
Authors: Gross Zeev , Mahammed Atif
Published: July 2009

We show that, despite the 139 possible products, tris(pentafluorophenyl)corrole is sulfonated by H 2 SO 4 in quantitative yield to a 9:1 mixture of only the 2,17- and 3,17- isomers and that its deuteration by trifluoroacetic acid-d proceeds in the order of C 3,17 > C 2,18 >> C 8,12 > C 7,13. These results add confidence to the feasibility of electrophilic substitution of corroles as a synthetic tool to many novel derivatives.
Electronic states and infrared spectroscopy of Ni- and Co-phthalocyanines: neutral and oxidized forms
Authors: Toman Petr , Nešpůrek Stanislav , Yakushi Kyuya
Published: July 2009

Quantum chemical calculations reproduced the experimental infrared spectra of NiPc , NiPc ( AsF 6)0.5, CoPc , and CoPc ( AsF 6)0.5. The agreement in the changes of line intensities supports the ligand-centered oxidation in both NiPc ( AsF 6)0.5 and CoPc ( AsF 6)0.5. Whereas, electron configurations of NiPc and NiPc + as well as CoPc represent standard cases, i.e. they can be taken as a closed-shell and open-shell system, respectively, the electron configuration of CoPc + must be taken as an open-shell system (while the number of electrons is even) to get an agreement of theoretical and experimental infrared spectra.
Characterization of porphyrin supramolecular complexes using NMR diffusion spectroscopy
Authors: Johnston Martin R. , Latter Melissa J.
Published: July 2009

The usefulness of diffusion ordered NMR spectroscopy (DOSY) as a characterization technique for systems that are non-covalently associated in solution is demonstrated. This study investigated the diffusion properties of a series of porphyrin-based building blocks and host materials which culminated in the characterization of a self-assembled porphyrin-containing capsule.
Structural requirements for recognition of essential porphyrin byPorphyromonas gingivalis
Authors: Hunter Neil , Nguyen Ky-Anh , McDonald James A. , Quinn Melissa J. , Langley David B. , Crossley Maxwell J. , Collyer Charles A.
Published: July 2009

Porphyromonas gingivalis is an anaerobic Gram negative bacterium implicated in destructive infection of the tissues that support the teeth. This organism is unusual in that it cannot synthesize the porphyrin macrocycle and is therefore dependent on exogenous porphyrin for growth. Accordingly, in addition to physiologically relevant sources of heme, growth is stimulated by a number of iron-free porphyrins. Without exception, the capacity of porphyrins to support normal growth of P. gingivalis was associated with recognition by a sub-domain protein HA2 which is located within three outer-membrane proteins and which recognizes the porphyrin macrocycle in an iron-independent manner. Previous analysis in our laboratories indicated that recognition of the propanoate face of porphyrin was a distinguishing feature of the HA2 receptor. More detailed analysis indicated that derivatization of the two propionic acid substituents as their methyl esters or taurine derived N-(ethyl-2-sulfonic acid)amides abolished recognition by HA2 whereas the ethylenediamine derived N-(2-aminoethyl)amides did not affect binding by HA2 . The importance of the 2- and 4-vinyl groups of protoporphyrin IX for transport and growth was evaluated by testing compounds with hydrogen, sulfonic acid and glycol substituents at the 2- and 4-positions. While these derivatives bound HA2 with high affinity, study of protoporphyrin isomers indicated that the distribution of vinyl group substitution was important in regulating recognition by HA2 . In this report, the behaviour of mesoporphyrin IX in which the vinyl groups are replaced by ethyl groups and of chlorin E4 which contains only one propionic acid sidechain, were investigated to further define the structural requirements for recognition by HA2 . Both porphyrins were recognized by low affinity interactions. Based on these findings, a model for binding is proposed. The apparently unique mode of recognition of porphyrins by the receptor presents opportunities for specific targeting of this pathogenic organism.
The porphyrin-C60 non-bonded interaction: an ab initio MO and DFT study
Authors: Shephard Michael J. , Paddon-Row Michael N.
Published: July 2009

The non-bonded interactions between a porphyrin molecule and a C 60 molecule, in the gas-phase, has been systematically investigated using various theoretical models. These are: (1) wavefunction-based methods, Hartree-Fock SCF (HF), second-order Møller-Plesset (MP2) theory, and the localized MP2 (LMP2) theory using the diatomics in molecules (DIM-LMP2) and triatomics in molecules (TRIM-LMP2) methods; (2) density functional theory (DFT), using non-local (BLYP, PW91), hybrid (B3LYP), and local (SVWN) functionals. Of the HF and DFT methods examined, corrected for BSSE using the counterpoise (CP) method, only the SVWN method predicts a close separation (2.5 Å) between the porphyrin and the C 60 molecules, in line with close contacts observed in crystal structures of cocrystallates of porphyrins and fullerenes (2.7-3.0 Å). The MP2 and LMP2 methods also predict a close contact between the two molecules although the MP2 and TRIM-LMP2 methods overestimate the interaction giving a separation < 2.5 Å while the DIM-LMP2 method gives a satisfactory separation of 2.9 Å. The SVWN and DIM-LMP2 methods also predict a reasonable complexation energy of ca. −13 kcal/mol (SVWN and DIM-LMP2 CP-uncorrected) and −7.9 kcal/mol (SVWN CP-corrected), whereas the MP2 and TRIM-LMP2 methods probably strongly overestimate the complexation energy. The remaining methods underestimate the complexation energy. The CP-uncorrected DIM-LMP2/6-31G(d) method gave the best estimate of the porphyrin- C 60 separation (2.9 Å) with a complexation energy of −13.3 kcal/mol; however, the more cost-effective SVWN functional gives satisfactory values for these quantities with the SVWN/6-311+G(d) level providing the best estimate for the complexation energy (−16.5 kcal/mol). The porphyrin- C 60 interaction was investigated in the giant triad 1 in which a zinc porphyrin, a dimethoxynaphthalene and a C 60 fullerene are separated by two norbornylogous bridge sections of six and five bond lengths, respectively. All methods predict the existence of a compact form of the molecule in which the porphyrin and C 60 moieties are only 2.9-4.3 Å apart (contact distance). This finding is consistent with certain photophysical properties of 1.
Conformational changes in monolayers of a cationic amphiphilic porphyrin on saline subphases
Authors: O'Driscoll Benjamin M. D. , Ruggles Jeremy L. , Foran Garry J. , Lin Binhua , Gentle Ian R.
Published: July 2009

Langmuir monolayer films of the tetracationic porphyrin tetrakis(octadecyl-4-pyridinium)porphyrinatozinc(II) bromide on various salt containing subphases were analyzed using surface pressure-area isotherms and X-ray reflectivity. The use of these complementary techniques showed that the porphyrin molecules undergo changes in conformation upon compression. Two main phases were identified, one in which the porphyrin moiety is parallel to the subphase and one in which the porphyrin moiety is tilted out of the plane. The addition of different salts into the subphase brought about changes in film behaviour, which are explained in terms of a lyotropic series.
10,15-di(4-pyridyl)-5,20-di(4-tolyl)-21-thiaporphyrin as a building block for porphyrin coordination arrays
Authors: Berlicka Anna , Pacholska Ewa , Latos-Grażyński Lechosław
Published: July 2009

10,15-di(4-pyridyl)-5,20-di(4-tolyl)-21-thiaporphyrin, ( SDPyDTP ) H , was prepared by condensation of 2,5-bis(4-tolylhydroxymethyl)thiophene, pyrrole and 4-pyridinecarboxaldehyde in boiling propionic acid. The synthesis introduced two pyridyl substituents at two defined (opposite to thiophene) meso positions of the porphyrin periphery. The self-assembly of the angular 10,15-dipyridyl-21-thiaporphyrin modules with cis square-planar diphosphineplatinum(II) complex leads to a cyclic rhomboid dimer [ Pt ( DPPP )( SDPyDTP ) H ]2( OTf )4. The molecule acquires butterfly geometry. The 1 H NMR studies confirmed the π-π stacking of the pyridyl ring with the equatorial phenyl rings of the phosphine fragment. The conformational equilibrium, interchanging the phenyl ring positions and affording the mixture of seven conformers in solution, has been considered. 1 H NMR> spectroscopy was applied to identify oligomeric species, constructed by coordination of ( SDPyDTP ) H to the paramagnetic nickel(II) complex 5,10,15,20-tetra(4-tolyl)-21-thiaporphyrin, ( STTP ) Ni II Cl . ( SDPyDTP ) H acts as a mono- or bidentate ligand coordinating by meso-pyridyl substituents. Using the paramagnetically shifted resonances as an unambiguous spectroscopic probe, 1 H NMR spectroscopy readily discriminated between five- {[( STTP ) Ni II ](( SDPyDTP ) H )} and six-coordinate {[( STTP ) Ni II](( SDPyDTP ) H )2} oligomeric subunits. The applicability of 10,15-di(4-pyridyl)-5,20-di(4-tolyl)-21-thiaporphyrin as a suitable building block in construction of larger molecules was confirmed. The new route to modify the porphyrin coordination arrays, which preserves the overall architecture but modifies intrinsic chemical properties, using heteroporphyrin was demonstrated.
Phthalocyanines with eight oligo(ethylene oxide) alkoxy units: thermotropic phase behavior, aggregate formation and ion complexation with redox-active ions
Authors: Piet Dennis P. , Verheij Herman J. , Zuilhof Han , Sudhölter Ernst J. R.
Published: July 2009

The thermotropic phase behavior of phthalocyanines (Pc's) with eight oligo(ethylene oxide) alkoxy side chains has been investigated. An increase in the number of ethylene oxide units results in a decrease in the solid-to-mesophase and isotropization temperatures. The investigated compounds display a discotic hexagonally ordered ( D ho ) mesophase. The solubilization of LiI / I 2 into the polar side chains of the Pc's has been studied both in solution and in spin-coated films, and the effect on the aggregate formation is discussed. At higher temperatures, the Pc – LiI / I 2 complex is not stable and small crystallites are formed. The dark direct current conductivity of these films is reported as a function of LiI / I 2 concentration in the polar side groups of the Pc's. The observed decrease in conductivity with increasing salt concentration is related to the morphology of the material.
Laser-flash photolysis of dialkylbenzodipyridoporphyrazines
Authors: Sakamoto Keiichi , Ohno-Okumura Eiko , Kato Taku , Kawaguchi Tomomi , Cook Michael J.
Published: July 2009

In the course of a fundamental study of photosensitizers for photodynamic therapy of cancer, a non-peripheral substituted phthalocyanine analogue, zinc bis(1,4-didecylbenzo)bis(3,4-pyrido)porphyrazine and its position isomers were examined to measure their photoexcited triplet state lifetimes in poly(methyl methacrylate) film using laser-flash photolysis. The isomer mixture of zinc bis(1,4-didecylbenzo)bis(3,4-pyrido)porphyrazine showed the most intense absorption in the 660-710 nm region, and the longer triplet state lifetime. The lowest symmetry isomer of zinc bis(1,4-didecylbenzo)bis(3,4-pyrido)porphyrazine was found to have the longest triplet state lifetime when all isomers were separated. The compound is proposed to be suitable for use as a photosensitizer for photodynamic therapy of cancer.
Discotic liquid crystals of transition metal complexes 34: spectroscopic properties of bis[octakis(3,4-dialkoxy-phenoxy)phthalocyaninato]lutetium(III) complexes
Authors: Hatsusaka Kazuaki , Ohta Kazuchika
Published: July 2009

Spectroscopic properties of discotic liquid crystalline bis[octakis(3,4-dialkoxyphenoxy)-phthalocyaninato]lutetium(III) complexes, {[( C n O )2 PhO ]8 Pc }2 Lu (n = 12: 2a and n = 13: 2b), were investigated by recording electronic absorption spectra in the region of 250-2600 nm under three different conditions; solution, mixed solvent solutions, and a thin film at various temperatures. An intermolecular charge transfer (CT) band was found at about 2000-2100 nm both for the n-hexane solution and the thin film. It was established for the first time from the solvent-polarity-dependent and temperature-dependent electronic absorption spectra that the intermolecular CT band is attributable to molecular aggregation.
Construction and complexation studies of some self-assembled diporphyrin receptors
Authors: Fanti Chiara , Monti Donato , Monica Laura La , Ceccacci Francesca , Mancini Giovanna , Paolesse Roberto
Published: July 2009

A ternary self-assembling system consisting of two Zn(II) carboxyphenylporphyrins and an aliphatic diamine linker was constructed via hydrogen bonding and Coulombic interactions between the porphyrin carboxylic moieties and the amino groups of the spacer. The properties of the resulting structures, in terms of binding of several aromatic diamine guests are described. The stability and geometry of the final host-guest supramolecular architecture (i.e. cyclic or linear array) can be modulated by the nature of the spacer.
Sulfonated phthalocyanines: aggregation and singlet oxygen quantum yield in aqueous solutions
Authors: Kuznetsova Nina A. , Gretsova Nataliya S. , Derkacheva Valentina M. , Kaliya Oleg L. , Lukyanets Evgeny A.
Published: July 2009

The influence of sulfonation degree (n) and central atom nature on singlet oxygen quantum yield (ΦΔ) were studied for a series of sulfonated phthalocyanine metal complexes MPcS n mix . It was found that in DMSO, where the studied dyes exist as monomers, ΦΔ values are independent of number and position of the sulfogroups and are equal to 0.11 ± 0.02, 0.19 ± 0.03, 0.37 ± 0.05, 0.38 ± 0.05 and 0.68 ± 0.10 for the metal-free and Mg , Gd , Al and Zn complexes, correspondingly. However, in aqueous solutions, aggregation of the dyes determines their photochemical activity. Substitution in adjacent to macrocycle 3 and 6 benzene positions interferes with aggregation compared to 4 and 5 positions, presumably due to enhanced steric hindrances in the former case. In the ZnPcS n mix series (n varied from 2 to 4), as an example, the linear relationship between degree of aggregation and ΦΔ indicates that only the monomer fraction of the dye is responsible for singlet oxygen production. For less sulfonated samples the order of activity of the dyes in water is as follows: H 2 PcS n mix < M II PcS n mix < M III PcS n mix which is in contrast to their tendencies to form aggregates.
Photochemical studies of binuclear phenoxysubstituted phthalocyanines containing catecholate bridges
Authors: Seotsanyana-Mokhosi Itumeleng , Maree Suzanne , Maree M. David , Nyokong Tebello
Published: July 2009

Binuclear ZnPc complexes covalently bridged by catechol units have been synthesized and their absorption and photochemical properties examined. The complexes studied are 1,2-bis-2',9',16',23'-triphenoxyphthalocyaninatozinc benzene (6a), 1,2-bis-2'-9',16',23'-tri-4-carboxyphe-noxyphthalocyaninatozinc benzene (6b), 1,2-bis-2',9',16',23'-tri-4-nitrophenoxyphthalocyaninato- zinc benzene (6c) and 1,2-bis-2'-9',16',23'-tri-4-tert-butylphenoxyphthalocyaninatozinc benzene (6d). Larger intramolecular coupling was observed for 6b and 6c, containing the carboxyphenoxy and nitrophenoxy substituents, respectively, than for 6a and 6d. A single Q band peak was observed for the fluorescence spectra of 6b and 6c, whereas, 6a and 6d showed a split Q band. The absence of the high energy fluorescence peaks corresponding to absorbance peaks in the 640 nm region, suggests that the intramolecular coupling is broken by excitation for complexes 6b and 6c.
Preparation of novel highly conjugated bis-porphyrin bridged with a polyene linker
Authors: Blart Errol , Suzenet Franck , Quintard Jean-Paul , Odobel Fabrice
Published: July 2009

This paper describes the preparation of a bis free-base porphyrin and a bis-zinc porphyrin system in which the two 5,10,15-tris(3,5-ditertbutylphenyl)porphyrinyl units are connected in meso position by a tetraenic chain. The preparation of the dyad relies on the Wittig-Horner-Emmons reaction between diethyl 3-[5-[10,15,20-tris(3,5-ditert-butyl-phenyl)-porphyrinyl]] prop-2-enyl phosphonate and the aldehyde-1,3-diene[5-[10,15,20-tris(3,5-ditert-butyl-phenyl)-porphyrinyl]]. The two latter porphyrin derivatives were obtained via a Stille cross-coupling reaction between the corresponding tributyltin derivatives and the 5-iodo-10,15,20-tris(3,5-ditert-butyl-phenyl)-porphyrin. The UV-visible absorption and fluorescence spectra of the bis-porphyrin systems are measured and indicate that both the energy level and the lifetime of the porphyrin singlet excited state are reduced upon the attachment of the polyene chain to the porphyrin unit.
Structure-reactivity correlations in extended multi-porphyrinic architectures
Authors: Solladié Nathalie , Aubert Nicolas , Bouatra Souhaila , Bourgogne Cyril , Bregier Frédérique , Brettar Julie , Gisselbrecht Jean-Paul , Gross Maurice , Rein Régis , Sooambar Chloé , Troiani Vincent , Walther Mathieu
Published: July 2009

In addition to controlling the structure of multi-chromophoric arrays, monitoring the spatial orientation of the chromophores in artificial light harvesting devices is a challenge of growing interest. We report in this article our recent advances in this field. It is expected that a better understanding of the physicochemical properties of rigid cofacial porphyrinic tweezers and an identification of the factors governing them will be crucial for the design and the elaboration of new nano-molecules endowed with original properties. Extended multi-porphyrinic architectures, polypeptides bearing pendant porphyrins have been synthesized as linear devices, and a star-like pentaporphyrin as an arborescent array. The structure and the original conformation of the latter confer to this system an unusual duality in its physicochemical properties.
Structure and photoelectrochemical properties of ITO electrodes modified with self-assembled monolayers of meso, meso-linked porphyrin oligomers
Authors: Hasobe Taku , Imahori Hiroshi , Ohkubo Kei , Yamada Hiroko , Sato Tomoo , Nishimura Yoshinobu , Yamazaki Iwao , Fukuzumi Shunichi
Published: July 2009

A systematic series of ITO electrodes modified chemically with self-assembled monolayers (SAMs) of meso, meso-linked porphyrin oligomers have been designed to provide valuable insight into the development of artificial photosynthetic devices. Photoelectrochemical measurements were carried out in an argon-saturated 0.1 M Na 2 SO 4 aqueous solution containing methyl viologen (MV2+) as an electron acceptor or triethanolamine (TEA) as a sacrificial electron donor in a three electrode system including the modified ITO electrodes. The action spectrum of porphyrin oligomer SAMs exhibits photocurrent generation in a wide wavelength region, demonstrating the enhancement of light-harvesting properties in the visible region. The relative integrated value of the action spectrum as well as the quantum yield of photocurrent generation of the porphyrin oligomer SAMs increases with increasing the number of the porphyrins. These results clearly show that our strategy is highly promising for improving light energy conversion efficiency.
Fast self-exchange electron transfer and delocalization of unpaired electron between zinc porphyrin radical cations and zinc porphyrins
Authors: Fukuzumi Shunichi , Hasobe Taku , Endo Yoshito , Ohkubo Kei , Imahori Hiroshi
Published: July 2009

Self-exchange electron transfer rates between π-radical cations of zinc porphyrins and the neutral metalloporphyrins have been determined from the line-width broadening in the ESR spectra in different solvents at various temperatures. Fine tuning of the substituent on the porphyrin ring and the proper choice of the solvent have enabled us to observe negative activation enthalpies for the self-exchange electron transfer reactions. The observation of negative activation enthalpies indicates that the self-exchange electron transfer occurs via the charge-transfer π-complexes formed between zinc porphyrin radical cations and the neutral zinc porphyrins. The complete delocalization of the unpaired electron over two porphyrin moieties is observed in the radical cation of a zinc porphyrin dimer, 5,5'-bis(10,20-bis(3,5-di-tert-butylphenyl)porphyrinatozinc(II)). This is regarded as the extreme limit of the rapid self-exchange electron transfer between zinc porphyrin radical cation and the neutral form.
Enthalpy-entropy compensation upon syn-anti conformational switching of bis-porphyrins by amines and alcohols
Authors: Borovkov Victor V. , Hembury Guy A. , Inoue Yoshihisa
Published: July 2009

Upon interaction with amine and alcohol guests, Zn - Zn and Zn -2 H ethane-bridged bis-porphyrin hosts undergo dramatic conformational switching from a syn to an anti form. The thermodynamic parameters obtained exhibit excellent linear enthalpy-entropy correlations, which are distinctly different for amines and alcohols but essentially independent of the host structure. Analyses of the compensation plots reveal a more rigid complex structure and more extensive desolvation upon complexation with amines than for alcohols, which may be ascribed to the different nucleophilicity, binding strength, solvation and geometry.
Optical limiting properties of water-soluble phthalocyanine derivatives
Authors: Zhang Shuang , Yang Zhou , Liu Hongwei , Xi Fu , Guo Zhi-xin , Ye Cheng
Published: July 2009

The optical-limiting properties of several water-soluble phthalocyanine derivatives in aqueous solution were measured at 532 nm with 10 ns pulses. The excited state absorption cross-section σex of the derivatives were determined with the Z-scan technique. The results showed that the phthalocyanine derivatives are materials for reverse saturable absorption. It was noted that the optical limiting performance of the phthalocyanine derivatives in aqueous solutions can be controlled through the addition of alkalis. These phthalocyanine derivatives possess good solubility in water and optical limiting controllability, which give rise to their use for practical applications.
Dynamic saturable optical nonlinearities in free base tetrapyridylporphyrin
Authors: Neto Newton M. Barbosa , Boni Leonardo De , Rodrigues José J. , Misoguti Lino , Mendonça Cléber R. , Dinelli Luis R. , Batista Alzir A. , Zilio Sérgio C.
Published: July 2009

Dynamic optical nonlinearities in free base tetrapyridylporphyrin ( H 2 TPyP ) solutions were investigated at 532 nm with the Z-scan technique. We observed a reverse saturable absorption process that was found to have a fast contribution related to the singlet population and a slow accumulative contribution arising from the triplet population. The optical excitations and subsequent relaxations can be interpreted with a five-energy-level diagram that allows determination of the excited states photophysical parameters such as triplet and singlet absorption cross-sections and the intersystem crossing time.
Zinc tetranitrophthalocyanine: isomer separation and photophysical photobiological evaluation in J774A tumor cells
Authors: Lunardi Claure N. , Rotta Jeane C. G. , Tedesco Antonio C.
Published: July 2009

The synthesis of zinc tetranitrophthalocyanine ( T 4 NO 2 ZnPc ) was carried out and two structural isomers ( C 2v and C s) were separated by column chromatography and characterized by 400 MHz proton nuclear resonance spectroscopy and absorption spectroscopy. The photophysical and photobiological parameters for isomers C 2v and C s were determined in solution and in the presence of macrophage cell culture (J774A). The results obtained clearly indicated that the photophysical, photochemical and photobiological properties of the two isomers were different and each isomer showed a different biological behavior.
Photooxidation of cobalt(II)meso-tetraphenylporphyrin by p-benzoquinone and its mechanism studied by optical absorption and resonance Raman spectroscopies
Authors: Thanga H. Hming , Verma Anandi L.
Published: July 2009

Laser excitation of CoIITPP within the Soret absorption band in the presence of p-benzoquinone (p-BQ) results in oxidation of the complex. Oxidation occurs both at the metal center and the porphyrin ring depending upon the experimental conditions. Under anaerobic conditions, oxidation takes place at the metal center to produce the cobaltic species CoIII( TPP )+, while in the presence of molecular oxygen oxidation also occurs at the porphyrin ring giving CoIII( TPP )2+•cation radical as oxidation product. From the inhibiting effect of peroxy radical trapping agent on the photooxidation of CoIITPP under aerobic conditions, the two-electron oxidation is suggested to involve solvent radicals and we discuss the mechanistic details of the process in this work.
Solvent-free synthesis of phthalocyanines
Authors: Chauhan Shive M. S. , Srinivas Kandadai A. , Srivastava Pravin K. , Sahoo Bishawabhusan
Published: July 2009

Clean and efficient microwave assissted solid phase cyclocondensation of various substituted phthalic anhydrides, phthalic acids, phthalimide and phthalonitrile with urea in the presence of basic alumina forms free-base phthalocyanines in 15-79% yields with and without ammonium molybdate as a catalyst.
Novel aspects of the chemistry of 1,19-diunsubstituted a,c-biladienes
Authors: Paolesse Roberto , Froiio Antonella , Nardis Sara , Mastroianni Marco , Russo Michele , Nurco Daniel J. , Smith Kevin M.
Published: July 2009

Cyclization of a,c-biladienes in alcoholic solution gives corroles. When the same reaction is carried out in CHCl 3 a completely different outcome is observed, and the product of the reaction is the corresponding open-chain biliverdin. The critical step for the cyclization to corrole is the formation of the fully conjugated 22,24-dihydro-a,b,c-bilatriene cation, which is allowed in methanol and appears to be prevented in CHCl 3. The presence of substituents at the 10-position of the a,c-biladiene is also critical for the reaction; while a phenyl group strongly enhances the formation of corrole, in the case of alkyl groups the formation of both corrole and biliverdin is prevented. This result can reasonably be attributed to the failure to give a fully conjugated 22,24-dihydro-a,b,c-bilatriene structure for 10-alkyl substituted a,c-biladienes. Carrying out the a,c-biladiene cyclization in acidic methanol permits a new one-pot preparation of β-alkylcorroles.
Interaction of diatomic ligands with Fe(II) meso-mono-4-pyridyl-tri-phenyl-porphyrinate. Spectral evidence of self-assembly in sublimed layers
Authors: Kurtikyan Tigran S. , Ogden J. Steven , Kazaryan Robert K. , Madakyan Valery N.
Published: July 2009

The interaction of CO , NO and O2 gases with thin layers of meso-mono-4-pyridyl-tri-phenylporphyrinatoiron(II) ( FeMPyTPP ) obtained by sublimation onto low-temperature (T = 77 K ) substrates has been investigated by means of IR and UV-visible spectroscopy. In contrast to the closely-related meso-tetraphenylporphyrinatoiron(II) ( FeTPP ), the formation of two types of axial complexes has been observed. In one of these the 5th coordination site is occupied by the pyridyl group of an adjacent molecule indicating the self-assembly of Fe ( MPyTPP ) in layers with formation of coordinatively linked oligomers. The degree of oligomerisation depends on the nature of the interacting gas. Due to the specificity of the supramolecular structure, the layers are fairly stable in ambient conditions and conserve their microporosity to bind reversibly with the aforementioned ligands.
pHinfluenced metal ion coordination changes in reconstituted hemoglobin
Authors: Venkatesh Balan , Ramasamy Somasundaram , Asokan Rengasamy , Rifkind Joseph M. , Manoharan Periakaruppan T.
Published: July 2009

This paper covers a detailed analysis of the coordination changes taking place at the active sites in both Cu and Ni reconstituted hemoglobin as a function of pH . These experiments provide insight into how proteins are held in their native configuration. The EPR results of CuHb reveal that the species formed in extreme acidic condition were different from those formed at extreme basic condition. At pH 3 we see an isotropic spectrum characteristic of 4-coordinated species, while at pH 12 there is an indication of equilibrium between mixtures of species. Further support for the above coordination changes is obtained from FT-Raman of NiHb at different pH conditions. At pH 3 all the 5-coordination marker bands are lost and there is a shift in the 4-coordination marker band, while at pH 12 both 4- and 5-coordination marker bands are still seen with slight shift in their positions. In addition to this, we could see a new peak at 1633 cm−1. The coordination changes as a function of pH could be seen for both CuHb and NiHb using UV-visible spectroscopic techniques.
Functional solitare- and trans-hybrids, the synthesis, characterization, electrochemistry and reactivity of porphyrazine/phthalocyanine hybrids bearing nitro and amino functionality
Authors: Kandaz Mehmet , Michel Sarah L. J. , Hoffman Brian M.
Published: July 2009

We report here for the first time a new and improved approach to the complete synthesis and characterization of the unsymmetrical metallo- and metal-free phthalocyanine/porphyrazine (Pz/Pc) hybrids bearing peripheral nitro or amine functionality, H 2[ Pz (n- Pr )6( BzNO 2)] or H2[ Pz (n- Pr )4( BzNO 2)2], where Bz = benzo , n-Pr = n-propyl, fused on the one or two benzenoid ring which form from the reaction of two different precursors, 3,4-bis-(n-propyl)-pyroline-2,5-diimine and 6/7-nitro-1,3,3-tricholoro isoindoline, with the base-catalyzed direct condensation method. The direct condensation method used in this study enable us to skip magnesium porphyrazine ( MgPz ) stage and limits the formation of undesired hybrid compounds when compared with cross-condensation method. Centrally metallated solitare- and trans- Pz/Pc hybrids, M [ Pz (n- Pr )6( BzNO 2)] or M [ Pz (n- Pr )4( BzNO 2)2]( M = Zn (II) or Mn (II)), synthesized in this study are somewhat more soluble than the free ones. Metallo Pz/Pc hybrids were prepared by treatment of free-soitare and trans hybrids with the appropriate metal salts in anhydrous solvent mixtures. We observed that the solubility of solitare- and/or trans- Pz/Pc hybrids increases after nitro-substituted Pz/Pc hybrids are reduced to amine substituted ones. The reactivity of the NH2 group of the solitare- Zn [ Pz ( n - Pr )6( BzNH 2)] was tested by the condensation with ferrocenecarboxyaldehyde resulting in the formation of the ferrocene-substituted hybrid. The newly synthesized compounds have been characterized by elemental analaysis, FT IR, 1H NMR, UV-vis and MS spectroscopy. Electrochemical measurements of the complexes characterized in this study showed that the attachment of NO 2 and NH 2 moieties at the periphery makes a monitorable effect on redox properties of the macrocycle and metal center.
The antimicrobial properties of new synthetic porphyrins
Authors: Philippova Tatyana O. , Galkin Boris N. , Zinchenko Oksana Yu. , Rusakova Maria Yu. , Ivanitsa Vladimir A. , Zhilina Zinaida I. , Vodzinskii Sergey V. , Ishkov Yuriy V.
Published: July 2009

The antimicrobial activity of new meso-tetrakis(N-methyl-6-quinolinyl)-substituted porphyrins and meso-tetrakis(N-methyl-6-quinolinyl)-substituted chlorins is described. The dark toxicity and photosensitising potentials of free-base (TQP and TQC) and its Sn(IV)-complexes [(TQP)Sn(IV) and (TQC)Sn(IV)] were tested on Gram-positive (Staphylococus aureus), Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria and two species of yeasts (Candida albicans and Rhodotorula bogoriensis). The results described in this paper show that TQP and (TQP)Sn(IV) did not inhibit the growth of S. aureus in the dark, but efficiently photosensitize the inactivation of this Gram-positive bacteria. These porphyrins have no appreciable photosensitizing activity towards Gram-negative bacteria. However, (TQP)Sn(IV) shows high dark toxicity against E. coli and P. aeruginosa. The free-base derivatives demonstrated dark activity only in the case of P. aeruginosa. We suppose that these meso-tetrakis(N-methyl-6-quinolinyl)-substituted porphyrins can bind to the Gram-negative bacteria outer membrane receptors that transported vitamin B12. The meso-substituted chlorins TQC and (TQC)Sn(IV) have shown similar efficiency in the dark- and photoinactivation of S. aureus. They revealed a middle level of dark toxicity towards Gram-negative bacteria. The Sn(IV)-complex of chlorin in comparison with free base and metalloporphyrins are more effective in photoinactivation of Gram-negative bacteria. Yeasts, such as Candida albicans and Rhodotorula bogoriensis are more sensitive to photodynamic inactivation as bacterial cells. The effects of (TQP)Sn(IV) and (TQC)Sn(IV) are more expressed than effects of free bases.
The interaction of formylporphyrins with weak CH-acids
Authors: Ishkov Yurij V. , Zhilina Zinaida I. , Barday Ludmila P.
Published: July 2009

A series of 2(α,β-unsaturated-γ-keto)-5,10,15,20-tetraphenylporphyrins was obtained by condensation of 2-formyl-5,10,15,20-tetraphenylporphyrin with acetone, 1,4-diacetylbenzene, 2-acetylthiophene, acetylacetone and acetophenone according to the Claisen-Schmidt reaction. The condensation product with 1,4-diacetylbenzene could react similarly with another formyl derivative – quinoxalin-6-carboxaldehyde and 2-formyl-5,10,15,20-tetraphenylporphyrin. It is shown that this reaction passes through formation of iminium salt formylporphyrin in presence of free base piperidine and perchloric acid.
Quasi-line vibronic spectra of 2,3,12,13-tetramethyldibenzoporphine and their interpretation
Authors: Solovyov Konstantin N. , Arabei Serguei M. , Gladkov Lev L. , Konstantinova Vera K. , Turkova Alisa E. , Avlasevich Yuri S.
Published: July 2009

The quasi-line fluorescence and fluorescence excitation spectra of 2,3,12,13-tetrame-thyldibenzoporphine have been obtained at 77 K in n-octane and analyzed. The normal-coordinate analysis of this molecule has been performed, and the spectra have been interpreted in detail. In the Soret band region the fluorescence excitation quasi-line spectra clearly reveal two 0-0 components. The problem of the nature of the Soret band of free-base porphyrins is discussed.