Search results for "Acceptor"
showing 10 items of 394 documents
Dendron to central core S1-S1 and S2-S(n) (n1) energy transfers in artificial special pairs containing dendrimers with limited numbers of conformatio…
2013
Two dendrimers consisting of a cofacial free-base bisporphyrin held by a biphenylene spacer and function- alized with 4-benzeneoxomethane (5-(4-benzene)tri-10,15,20-(4-n-octyl- benzene)zinc(II)porphyrin) using either five or six of the six available meso-positions, have been synthesized and characterized as models for the an- tenna effect in Photosystems I and II. The presence of the short linkers, -CH2O-, and long C8H17 soluble side chains substantially reduces the number of conformers (foldamers) compared with classic dendrimers built with longer flexible chains. This simpli- fication assists in their spectroscopic and photophysical analysis, notably with respect to fluorescence resonance…
Intramolecular electronic excitation energy transfer in donor∕acceptor dyads studied by time and frequency resolved single molecule spectroscopy
2008
Electronic excitation energy transfer has been studied by single molecule spectroscopy in donor/acceptor dyads composed of a perylenediimide donor and a terrylenediimide acceptor linked by oligo(phenylene) bridges of two different lengths. For the shorter bridge (three phenylene units) energy is transferred almost quantitatively from the donor to the acceptor, while for the longer bridge (seven phenylene units) energy transfer is less efficient as indicated by the occurrence of donor and acceptor emission. To determine energy transfer rates and efficiencies at the single molecule level, several methods have been employed. These comprise time-correlated single photon counting techniques at r…
Facilitated SLM extraction of peptides with D2EHPA as a carrier
2004
Abstract The extraction of short peptides through a supported liquid membrane containing di-2-(ethylhexyl)phosphoric acid (D2EHPA) as a carrier was investigated. The extraction was carried out from the aqueous donor phase with pH 3 to amore acidic acceptor phase. The proton gradient between the donor and the acceptor phase was the main driving force of the mass transfer in this system. The influence of various parameters such as diluent of the carrier, pH of the donor and acceptor phase, peptide structure and concentration on the extraction efficiency was presented.
A theory ofnonverticaltriplet energy transfer in terms of accurate potential energy surfaces: The transfer reaction from π,π* triplet donors to 1,3,5…
2004
Triplet energy transfer (TET) from aromatic donors to 1,3,5,7-cyclooctatetraene (COT) is an extreme case of "nonvertical" behavior, where the transfer rate for low-energy donors is considerably faster than that predicted for a thermally activated (Arrhenius) process. To explain the anomalous TET of COT and other molecules, a new theoretical model based on transition state theory for nonadiabatic processes is proposed here, which makes use of the adiabatic potential energy surfaces (PES) of reactants and products, as computed from high-level quantum mechanical methods, and a nonadiabatic transfer rate constant. It is shown that the rate of transfer depends on a geometrical distortion paramet…
Discotic Twin and Triple Molecules with Charge-Transfer Interactions in Langmuir−Blodgett Films
1996
X-ray and atomic force microscopy observations reveal features of the surface morphology of Langmuir-Blodgett (LB) films from discotic donor-acceptor molecules with strong core-to-core interactions caused by a charge-transfer (CT) complexation. The compounds are designed to be twin and triple molecules composed of chemically connected donor (triphenylene) and acceptor (trinitrofluorenone) fragments which display liquid crystalline structure in the bulk state. The LB films from these compounds possess edge-on orientation of molecules within monolayers with a smooth surface on a submicron scale but with substantial macroscopic imperfections. These imperfections are represented by the micron s…
A new method of anomeric protection and activation based on the conversion of glycosyl azides into glycosyl fluorides
1993
Glycosyl azides provide reliable anomeric protection stable to conditions for hydrolytic removal of ester groups, for reductive opening or release of acetalic diol protection, for the introduction of ether-type protection, and for glycosylation processes. The utility of this anomeric protection is further enhanced as glycosyl azides may be converted into glycosyl fluorides, which can be activated for glycosylation reactions. To this end, glycosyl azides have been subjected to 1,3-dipolar cycloaddition with di-tert-butyl acetylenedicarboxylate. On treatment with hydrogen fluoride-pyridine complex the N-glycosyl triazole derivatives directly give glycosyl fluorides.
Chiral donor–π-acceptor azobenzene dyes
2009
Abstract Four chiral donor–π-acceptor azobenzene dye conjugates were synthesized and characterized. Chiral moieties, namely (S)-(+)-2-(6-methoxy-2-naphthyl)propionic acid (naproxen) and (S)-2-aminopropionic acid ( l -alanine), were attached to either the donor end or the acceptor site of the azo compound using ester or amide bonds, respectively. The structures of the molecules were verified using 1H NMR, 13C NMR and ESI TOF mass spectrometry; spectral properties were evaluated with UV–vis and CD spectrometry whilst thermal stability was determined by TGA. The compounds displayed a broad absorption maximum in the visible region between 433 and 483 nm. All compounds showed relatively high the…
PHOSPHORORGANISCHE VERBINDUNGEN 1081DIE SYNTHESE FLUORESZIERENDER UND CHEMOSELEKTIVER REAGENTIEN ZUM GEZIELTEN NACHWEIS UND SCHUTZ BIOLOGISCH WICHTIG…
1984
Abstract Compounds of type A are fluorescent, if the donator groups, like NMe2, OMe, SMe and PR2, and the acceptor groups, like R′P(O)X, SO2R′ and CO2R′, are linked to different nuclei of the naphthalin ring system.
Cellular imaging using BODIPY-, pyrene- and phthalocyanine-based conjugates
2017
International audience; Fluorescent Probes aimed at absorbing in the blue/green region of the spectrum and emitting in the green/red have been synthesized (as the form of dyads-pentads), studied by spectrofluorimetry, and used for cellular imaging. The synthesis of phthalocyanine-pyrene 1 was achieved by cyclotetramerization of pyrenyldicyanobenzene, whereas phthalocyanine-BODIPY 2c was synthesized by Sonogashira coupling between tetraiodophthalocyanine and meso-alkynylBODIPY. The standard four-steps BODIPY synthesis was applied to the BODIPY-pyrene dyad 3 starting from pyrenecarbaldehyde and dimethylpyrrole. H-1, C-13, F-19, (BNMR)-B-11, ICP, MS, and UV/Vis spectroscopic analyses demonstra…
Design of neutral Lewis superacids of group 13 elements.
2011
A general approach toward superstrong neutral Lewis acids, featuring both the pyramidalization of acceptor molecules and the introduction of electron-withdrawing substituents, is proposed and examined theoretically. Complexes of group 13 element derivatives with ammonia at the B3LYP and MP2 levels of theory with def2-TZVPP basis set are considered as examples. Pyramidalization of the acceptor molecule significantly increases its Lewis acidity (by 50-60 kJ mol(-1) for aluminum and gallium compounds and by 120-130 kJ mol(-1) for boron compounds). An additional increase of the complex stability of 55-75 kJ mol(-1) may be achieved by fluorination. The combined increase of the bond dissociation …