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Porphyrin Units (porphyrin + unit)
Selected AbstractsSynthesis of Triazole-Bridged Unsymmetrical Porphyrin Dyads and Porphyrin,Ferrocene ConjugatesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2010Vijayendra S. Shetti Abstract A simple method has been used to synthesize four porphyrin azides with cores such as N4, N3S, N2SO and N2S2 in 60,90,% yields by treating the corresponding aminoporphyrins with tert -butyl nitrite (tBuONO) and azidotrimethylsilane (TMSN3) in THF/CH3CN under mild reaction conditions. The hitherto unknown aminoporphyrins with heteroatom cores were synthesized from their corresponding nitroporphyrins by standard SnCl2/HCl reduction. The azidoporphyrins were used to synthesize six triazole-bridged unsymmetrical porphyrin dyads containing two different types of porphyrin sub-units as well as five triazole-bridged porphyrin,ferrocene conjugates under CuI -catalyzed "click" reaction conditions. Various CuI -catalyzed reaction conditions were studied and the best yields of triazole-bridged dyads and conjugates were obtained with CuI/DIPEA in THF/CH3CN at room temperature for overnight. The unsymmetrical porphyrin dyads and porphyrin,ferrocene conjugates were characterized by various spectroscopic and electrochemical techniques. In unsymmetrical porphyrin dyads, the NMR, absorption and electrochemical studies indicate a weak interaction between the two porphyrin sub-units. However, preliminary photophysical studies support an efficient singlet-singlet energy transfer from one porphyrin unit to another in five unsymmetrical dyads reported here. In porphyrin,ferrocene conjugates, the fluorescence of porphyrin was quenched significantly due to photo-induced electron transfer from ferrocene to porphyrin. [source] Covalent Functionalization of Carbon Nanohorns with Porphyrins: Nanohybrid Formation and Photoinduced Electron and Energy Transfer,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2007G. Pagona Abstract The covalent attachment of carbon nanohorns (CNHs) to ,-5-(2-aminophenyl)-,-15-(2-nitrophenyl)-10,20-bis(2,4,6-trimethyl-phenyl)-porphyrin (H2P) via an amide bond is accomplished. The resulting CNH,H2P nanohybrids form a stable inklike solution. High-resolution transmission electron microscopy (HRTEM) images demonstrate that the original dahlia-flowerlike superstructure of the CNHs is preserved in the CNH,H2P nanohybrids. Steady-state and time-resolved fluorescence studies show efficient quenching of the excited singlet state of H2P, suggesting that both electron and energy transfer occur from the singlet excited state of H2P to CNHs, depending on the polarity of the solvent. In the case of electron transfer, photoexcitation of H2P results in the reduction of the nanohorns and the simultaneous oxidation of the porphyrin unit. The formation of a charge-separated state, CNH,,,H2P,+, has been corroborated with the help of an electron mediator, hexyl-viologen dication (HV2+), in polar solvents. Moreover, the charge-separated CNH,,,H2P,+ states have been identified by transient absorption spectroscopy. [source] Noncovalent Assembly of Picket-Fence Porphyrins on Nitrogen-Doped Carbon Nanotubes for Highly Efficient Catalysis and BiosensingCHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2010Wenwen Tu Abstract A water-insoluble picket-fence porphyrin was first assembled on nitrogen-doped multiwalled carbon nanotubes (CNx MWNTs) through FeN coordination for highly efficient catalysis and biosensing. Scanning electron micrographs, Raman spectra, X-ray photoelectron spectra, UV/Vis absorption spectra, and electrochemical impedance spectra were employed to characterize this novel nanocomposite. By using electrochemical methods on the porphyrin at low potential in neutral aqueous solution, the presence of CNx MWNTs led to the direct formation of a high-valent iron(IV),porphyrin unit, which produced excellent catalytic activity toward the oxidation of sulfite ions. By using sulfite ions, a widely used versatile additive and preservative in the food and beverage industries, as a model, a highly sensitive amperometric biosensor was proposed. The biosensor showed a linear range of four orders of magnitude from 8.0×10,7 to 4.9×10,3,mol,L,1 and a detection limit of 3.5×10,7,mol,L,1 due to the highly efficient catalysis of the nanocomposite. The designed platform and method had good analytical performance and could be successfully applied in the determination of sulfite ions in beverages. The direct noncovalent assembly of porphyrin on CNx MWNTs provided a facile way to design novel biofunctional materials for biosensing and photovoltaic devices. [source] Synthesis, Characterization, and Photophysical Properties of Some Heterodimetallic Bisporphyrins of Ytterbium and Transition Metals , Enhancement and Lifetime Extension of Yb3+ Emission by Transition-Metal Porphyrin SensitizationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2007Feng-Lei Jiang Abstract A series of d-f heterodimetallic bisporphyrin complexes (YbZn, YbPd, and YbPt), in which a YbIII porphyrinate moiety is linked to a transition-metal porphyrinate moiety by a flexible three-carbon chain, were synthesized. They were fully characterized by high-resolution mass spectrometry, 1H and 31P NMR spectroscopy, electronic absorption, andfluorescence methods. Variable-temperature near-infrared photoluminescence studies showed that the transition-metal porphyrinate moiety would enhance the ytterbium(III) emission centered at about 998 nm and extend its emission lifetime. YbPd and YbPt showed large two-photon absorption cross-section values because of the interaction between the porphyrin units, which caused a loss of centrosymmetry. Optical limiting investigation demonstrated that [Yb(TPP)(LOMe)] and YbPt have comparable performance to C60 by virtue of their heavy-metal effect. Our results indicate that these bisporphyrin dimetallic complexes will find valuable applications in the field of nonlinear optics. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Fabrication of Organized Porphyrin-Nanotube-Attached Heat-Sensitive Polyelectrolyte Capsules,ADVANCED FUNCTIONAL MATERIALS, Issue 16 2006S. Sadasivan Abstract A facile method of connecting fluorescent meso -tetrakis(4-sulfonatophenyl)porphine tetranion nanotubes to polyelectrolyte capsules is developed. Heat-sensitive robust polyelectrolyte capsules consisting of poly(diallyldimethylammonium chloride) and poly(styrene sulfonate) multilayers have been fabricated using the conventional layer-by-layer technique. Supramolecular aggregation of porphyrin monomers to nanotubes is induced in the microenvironment of the capsules by sequential addition of salt and acid. Scanning electron microscopy, transmission electron microscopy, and atomic force microscopy images reveal satellite-like structures consisting of a central capsule core with porphyrin nanotubes emerging radially from the capsule walls. The growth and the distribution of the porphyrin units have been monitored by UV-vis spectroscopy, fluorescence spectroscopy, and confocal laser scanning microscopy. Changing the temperature alters the dimensions and the arrangement of the nanotubes on the capsule walls. Such an attachment of porphyrin tubes onto robust functional capsules should help in developing an artificial light-harvesting system. [source] Uncharged Water-Soluble Metal-Bis-Porphyrins Like Molecular Tweezers for Amino AcidsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 15 2007Emilio Scamporrino Abstract Some new water-soluble bis-porphyrins, constituted of two porphyrin units spaced by means of aliphatic bridges of different lengths, were synthesized and characterized by MALDI-TOF mass spectrometry, 1H NMR and UV-vis spectroscopy. The hydrosolubility of these uncharged compounds was guaranteed from the presence of six long PEG chains bound on the peripheral positions of the two porphyrins. Cobalt and zinc derivatives were also prepared. In the case of Co-bis-porphyrin, the appearance of induced circular dichroism (ICD) signals in water solution confirmed the formation of stable complexes with some amino acids, in which the bis-porphyrin behaves like molecular tweezers. [source] Square-grid coordination networks of (5,10,15,20-tetra-4-pyridylporphyrinato)zinc(II) in its clathrate with two guest molecules of 1,2-dichlorobenzene: supramolecular isomerism of the porphyrin self-assemblyACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2009Rajesh Koner The title compound, (5,10,15,20-tetra-4-pyridylporphyrinato)zinc(II) 1,2-dichlorobenzene disolvate, [Zn(C40H24N8)]·2C6H4Cl2, contains a clathrate-type structure. It is composed of two-dimensional square-grid coordination networks of the self-assembled porphyrin moiety, which are stacked one on top of the other in a parallel manner. The interporphyrin cavities of the overlapping networks combine into channel voids accommodated by the dichlorobenzene solvent. Molecules of the porphyrin complex are located on crystallographic inversion centres. The observed two-dimensional assembly mode of the porphyrin units represents a supramolecular isomer of the unique three-dimensional coordination frameworks of the same porphyrin building block observed earlier. The significance of this study lies in the discovery of an additional supramolecular isomer of the rarely observed structures of metalloporphyrins self-assembled directly into extended coordination polymers without the use of external ligand or metal ion auxiliaries. [source] DABCO-Mediated Self-Assembly of Zinc Porphyrin,Perylene Bisimide Monodisperse Multichromophoric Nanoparticles,CHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2010Peter Osswald Dr. Line up! Fourfold zinc porphyrin functionalized perylene bisimide has afforded well-defined supramolecular particles by intramolecular cofacial bridging of zinc porphyrin units through the ditopic ligand DABCO as revealed by UV/Vis and NMR spectroscopy and AFM studies (see figure). [source] Porphyrin-Functionalized Dendrimers: Synthesis and Application as Recyclable Photocatalysts in a Nanofiltration Membrane ReactorCHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2005Suhas A. Chavan Dr. Abstract The convergent synthesis of a series of porphyrin-functionalized pyrimidine dendrimers has been accomplished by a procedure involving the nucleophilic aromatic substitution (NAS) as a key reaction step. The resulting dendritic porphyrin catalysts show high activity in the light-induced generation of singlet oxygen (1O2) from ground-state oxygen. These materials are synthetically useful photosensitizers for the oxidation of various olefinic compounds to the corresponding allylic hydroperoxides. Catalytic activities and regio- and stereoselectivities of the dendritic photosensitizers are comparable to those observed for mononuclear porphyrin catalysts. Recycling of the dendrimer-enlarged homogeneous photocatalysts was possible by solvent-resistant nanofiltration (SRNF) by using an oxidatively stable membrane consisting of a polysiloxane polymer and ultrastable Y zeolite as inorganic filler. Moreover, this membrane technology provides a safe way to isolate the hydroperoxide products under very mild conditions. The membrane showed high retention for the macromolecular catalysts, even in chlorinated solvents, but some oxidative degradation of the porphyrin units of the dendrimer was observed over multiple catalytic runs. [source] | |||||||||||||