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Intramolecular Energy Transfer (intramolecular + energy_transfer)

Distribution by Scientific Domains

Chemistry	55%
Polymers and Materials Science	44%

Selected Abstracts

A Triphenylamine Dye Model for the Study of Intramolecular Energy Transfer and Charge Transfer in Dye-Sensitized Solar Cells,

ADVANCED FUNCTIONAL MATERIALS, Issue 21 2008
Haining Tian
Abstract A novel dye (2TPA-R), containing two triphenylamine (TPA) units connected by a vinyl group and rhodanine-3-acetic acid as the electron acceptor, is designed and synthesized successfully to reveal the working principles of organic dye in dye-sensitized solar cells (DSSCs). 2TPA and TPA-R, which consist of two TPA units connected by vinyl and a TPA unit linked with rhodanine-3-acetic acid, respectively, are also synthesized as references to study the intramolecular energy transfer (EnT) and charge transfer (ICT) processes of 2TPA-R in CH2Cl2 solution and on a TiO2 surface. The results suggest that the intramolecular EnT and ICT processes show a positive effect on the performance of DSSCs. However, the flexible structure and less-adsorbed amount of dye on TiO2 may make it difficult to improve the efficiency of DSSCs. This study on intramolecular EnT and ICT processes acts as a guide for the design and synthesis of efficient organic dyes in the future. [source]

Reversible Luminescent Switching in a [Eu(SiW10MoO39)2]13, -Agarose Composite Film by Photosensitive Intramolecular Energy Transfer

ADVANCED MATERIALS, Issue 17 2009
Zhongliang Wang
Transparent, flexible, self-supporting EuSiWMo/agarose composite films are fabricated by a combination of hydrogel chemistry and a casting technique, and present reversible, high-contrast luminescence photoswitching modulated by inorganic photochromic components through intramolecular resonance-energy transfer. Two-dimensional recording employing the luminescence as read-out signals is accomplished in this novel recording medium. [source]

A Mechanically Interlocked [3]Rotaxane as a Light-Harvesting Antenna: Synthesis, Characterization, and Intramolecular Energy Transfer

CHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2009
Jie-Yu Wang
Abstract Mimicking photosynthesis: The concept of light-harvesting by using a mechanically interlocked [3]rotaxane is developed through synthesis and characterization. Our results provide a new candidate for light-harvesting systems and also open up the possibility of creating intelligent or controllable energy-collecting machines (see figure). A mechanically interlocked light-harvesting system [3]rotaxane A has been synthesized in high yield through Cu(I)-catalyzed azide,alkyne cycloaddition; the hexyl-substituted truxene units are introduced into the wheels as donors and an oligo(para -phenylenevinylene) (OPV) unit into the axis as the acceptor. The structure and the purity of [3]rotaxane A were confirmed by 1H and 13C,NMR spectroscopy and ESI HRMS. The azide,alkyne cycloaddition is demonstrated to be an efficient stoppering method in the synthesis of the rotaxane containing dibenzo[24]crown-8 and dibenzyl ammonium units. Detailed steady-state UV/Vis absorption, photoluminescent, and time-resolved fluorescence spectroscopy were performed to investigate the photophysical properties of [3]rotaxane A and its reference compounds in solution and as thin films. Even in dilute solution, efficient energy transfer from the truxene-functionalized wheels to the OPV-based axis, through the dibenzo[24]crown-8 and dibenzyl ammonium interaction, is observed in [3]rotaxane A. The unique topology of [3]rotaxane A not only efficiently promotes the intramolecular energy-transfer process, but also prevents intermolecular aggregation in the solid state. The new antenna system opens up the possibility of controllable light-harvesting molecular machines or other optoelectronic devices on the nanometer scale. [source]

Intramolecular Energy Transfer in Pyrene,Bodipy Molecular Dyads and Triads

CHEMISTRY - A EUROPEAN JOURNAL, Issue 24 2005
Raymond Ziessel Dr.
Abstract Molecules bearing a 4,4-difluoro-8-(aryl)-1,3,5,7-tetramethyl-2,6-diethyl-4-bora-3a,4a-diaza- s -indacene (bodipy) core and 1-pyrenyl-1-phenyl-4-(1-ethynylpyrene), or 1-phenyl-4-[1-ethynyl-(6-ethynylpyrene)pyrene] units were constructed in a step-by-step procedure based on palladium(0)-promoted cross-coupling reactions with the required preconstructed modules. X-ray structures of single crystals reveal a twisted arrangement of the two chromophores. In one case, an almost perfect orthogonal arrangement is found. These dyes are strongly luminescent in solution and display rich electrochemistry in which all redox processes of the bodipy and pyrene fragments are clearly resolved. The absorption spectra indicate that the bodipy and pyrene chromophores are spectrally isolated, thereby inducing a large "virtual" Stokes shift. The latter is realised by efficient transfer of intramolecular excitation energy by the Förster dipole,dipole mechanism. The rate of energy transfer depends on the structure of the dual-dye system and decreases as the centre-to-centre separation increases. The energy transfer efficiency, however, exceeds 90,% in all cases. The linkage of two pyrene residues by an ethyne group leads to a decrease in the energy-transfer efficiency, with the two polycycles acting as a single chromophore. The directly linked bodipy,pyrene dual dye binds to DNA and operates as an efficient solar concentrator when dispersed in plastic. De nouvelles molécules comprenant un c,ur 4,4-difluoro-8-(aryl)-1,3,5,7-tetramethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indacene (appelé bodipy) et des fragments 1-pyrènyl, 1-phényl-4-(1-éthynylpyrène), ou 1-phényl-4-[1-éthynyl-(6-éthynylpyrène)pyrène] ont été synthétisées par le biais de couplage croisés entre des modules pré-construits. Ces réactions ont été catalysées par du palladium sous-ligandé dans des conditions anaérobiques. Dans deux cas typiques la structure moléculaire déterminée par diffraction aux rayons X sur monocristal révèle un arrangement quasi perpendiculaire des deux sous-unités bodipy et pyrène. L'ensemble des composés sont très fluorescents en solution et dévoilent une voltammétrie cyclique riche en signaux réversibles. L'ensemble des processus d'oxydation et de réduction localisés sur les sous-unité pyrène et bodipy sont bien résolus. De plus ces deux fragments sont spectroscopiquement différenciées ce qui permet d'obtenir des déplacements de Stokes important lorsque la partie pyrène est excitée et que la fluorescence de la partie bodipy est observée. Le processus responsable de ce phénomène est un transfert d'énergie ayant lieu par résonance (mécanisme dit de Förster par interaction dipôle-dipôle). La vitesse de ce transfert d'énergie dépends de la structure moléculaire et décroît en augmentant la distance ente les deux chromophores. L'efficacité de ce transfert est supérieur à 90,% dans l'ensemble des cas étudiés. Cependant la connexion par une liaison triple des motifs bodipy et pyrène diminue l'efficacité de ce transfert. La molécule comportant un pyrène directement connecté au bodipy se lie fortement à l'ADN et se comporte comme un concentrateur de photons lorsque dispersé dans des plastiques rigides. [source]

Synthesis and Luminescent Properties of Novel Europium(III) Heterocyclic ,-Diketone Complexes with Lewis Bases: Structural Analysis Using the Sparkle/AM1 Model

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2005
Rani Pavithran
Abstract Tris(,-diketonato)europium(III) complexes of general formula [Eu(TPI)3·L], with chelating ligands such as 3-phenyl-4-(4-toluoyl)-5-isoxazolone (HTPI) and adduct-forming reagents [L = H2O, tri- n -octylphosphane oxide (TOPO), triphenylphosphane oxide (TPhPO), 1,10-phenanthroline], have been synthesized and characterized by elemental analysis and FT-IR, 1H NMR, and photoluminescence spectroscopy. The coordination geometries of the complexes were calculated using the Sparkle/AM1 (Sparkle model for the calculation of lanthanide complexes within the Austin model 1) model. The ligand,Eu3+ energy-transfer rates were calculated using a model of intramolecular energy transfer in lanthanide coordination complexes reported in the literature. The room-temperature PL spectra of the europium(III) complexes are composed of the typical Eu3+ red emission, assigned to transitions between the first excited state (5D0) and the multiplet (7F0,4). The results clearly show that the substitution of water molecules by TOPO leads to greatly enhanced quantum yields (i.e., 1.3,% vs. 49.5,%) and longer 5D0 lifetimes (220 vs. 980 ,s). This can be ascribed to a more efficient ligand-to-metal energy transfer and a less efficient nonradiative 5D0 relaxation process. The theoretical quantum yields are in good agreement with the experimental quantum yields, which highlights that the present theoretical approach can be a powerful tool for the a priori design of highly luminescent lanthanide complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

A Triphenylamine Dye Model for the Study of Intramolecular Energy Transfer and Charge Transfer in Dye-Sensitized Solar Cells,

Facile fabrication of novel Eu-containing copolymer and luminescent properties

POLYMER ENGINEERING & SCIENCE, Issue 7 2009
Ziqun Huang
A new Eu-containing copolymer was successfully fabricated through two steps. First, the Eu-containing monomer was synthesized from 4-Vinylbenzoic acid and europium ion (Eu3+) complex, which rare-earth ions connect with the ligand by covalent bands. Next, the copolymer was obtained by free-radical copolymerization of Eu-containing monomer with methyl methacrylate using 2, 2,-azobis(isobutyronitrile) (AIBN) as initiator at low temperature. Infrared spectroscopy, gel permeation chromatography and scanning electron microscopy were applied to characterize the structure of the polymer. UV-visible absorption/photoluminescence spectra and fluorescence spectra were taken to valuate the photophysical properties of the obtained Eu-containing copolymer. The experimental result shows that the strong luminescence of europium ions substantiates optimum energy match and effective intramolecular energy transfer between the triplet state energy of coordination complex and the emissive energy level of the rare-earth ions. A study of the dependence of emission intensities of the Eu-containing nanoparticles on the Eu content showed that the emission intensities increased nearly linearly with increasing Eu content. In addition, no significant emission concentration quenching phenomenon was observed at the Eu content of 0,4.61 mol%. The hybrid material systems can be expected to have potential applications in light conversion materials. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source]

Conjugated Polyelectrolytes for Protein Assays and for the Manipulation of the Catalytic Activity of Enzymes

CHEMISTRY - AN ASIAN JOURNAL, Issue 8-9 2008
Lingling An
Abstract A new method has been developed to discriminate between proteins with different isoelectric points by using fluorescent conjugated polyelectrolytes. Charged water-soluble polyfluorenes that contain 2,1,3-benzothiadiazole (BT) units demonstrate intramolecular energy transfer from the fluorene units to the BT sites when oppositely charged proteins are added to the mixture. This results in a shift in emission color from blue to green and a change in the emission intensity of conjugated polyelectrolytes, which makes it possible to assay proteins. The formation of conjugated polyelectrolyte/enzyme complexes by electrostatic interactions can be utilized to manipulate the activity of enzymes by means of local alteration of enzyme charge density. The oppositely charged substrate binds to conjugated polyelectrolyte and reduces the distance between the enzyme and the substrate, leading to an increase in the cleavage reaction rate. The new method has three important features: 1),it offers a convenient "mix-and-detect" continuous approach for protein assays and rapid detection of enzyme activity; 2),the use of water-soluble conjugated polyelectrolytes imparts the sensor with a high sensitivity; 3),this method does not require fluorescent labels on the targets, which should significantly reduce the cost. [source]

Monitoring Protein Interactions in the Living Cell Through the Fluorescence Decays of the Cyan Fluorescent Protein

CHEMPHYSCHEM, Issue 7 2006
Regis Grailhe Dr.
Abstract Using fluorescence lifetime microspectroscopy and imaging techniques, we have studied the fluorescence of cyan fluorescent protein (CFP) transiently expressed in HEK-293 cells, in the presence or absence of its fluorescence resonance energy transfer (FRET) partner, yellow fluorescent protein (YFP). When the two proteins are attached through a 27-amino-acid linker, a 33,% average efficiency of intramolecular energy transfer is accurately determined inside the cell. Additionally, we observe a systematic quenching of the CFP fluorescence with increasing levels of protein expression. This quenching cannot be accounted for by formation of the previously described dimer of GFP-related proteins, since its magnitude is unchanged when the fluorescent proteins carry the mutation A206K shown to dissociate this dimer in vitro. Even when the intracellular protein concentration largely exceeds the in vitro dissociation constant of the dimer, self-association remains undetectable, either between free proteins or intramolecularly within the CFP,YFP construct. Instead, the detailed concentration effects are satisfactorily accounted for by a model of intermolecular, concentration-dependent energy transfer, arising from molecular proximity and crowding. In the case of CFP alone, we suggest that self-quenching could result from a pseudo-homo FRET mechanism between different, spectrally shifted emissive forms of the protein. These phenomena require careful consideration in intracellular FRET studies. [source]