Time-resolved electron paramagnetic resonance

BURNS c s, HEYERICK A, KEUKELEiRE D D and FOBES M D E (2001) Mechanism for formation of the light struck flavour in beer revealed by time-resolved electron paramagnetic resonance, Chem Eur J, 7, 4554-61. 

The X-ray structure of zinc naphthalocyanate has been determined with Zn—N bond lengths of 1.983(4) A.829 Pentanuclear complexes with a zinc phthalocyanine core and four ruthenium subunits linked via a terpyridyl ligand demonstrate interaction between the photoactive and the redox active components of the molecule. The absorbance and fluorescence spectra showed considerable variation with the ruthenium subunits in place.830 Tetra-t-butylphthalocyaninato zinc coordinated by nitroxide radicals form excited-state phthalocyanine complexes and have been studied by time-resolved electron paramagnetic resonance.831... 

Time-resolved electron paramagnetic resonance served to detected the short-lived triplet state of the keto tautomer (238) of 2-(2-hydroxyphenyl)benzothiazole (239) generated by excited state intramolecular proton transfer (92CC641). 

In a supramolecular approach to fullerene-porphyrin hybrids, the assembly of a rigidly connected dyad, in which a zinc tetraphenylporphyrin, Zn(TPP), is noncovalently linked to a C60 derivative via axial pyridine coordination to the metal, was reported [219-222]. Photo excitation of the dyad Zn-complex led to electron transfer with very long lifetimes of the charge-separated pairs, as revealed by optical spectroscopy and confirmed by time-resolved electron paramagnetic resonance spectroscopy. Accordingly, two different solvent-dependent pathways can be considered for the electron-transfer processes. Either the excitation of the porphyrin chromophore is followed by fast intramolecular electron transfer inside the complex, or alternatively the free porphyrin is excited undergoing intermolecular electron transfer when the acceptor molecules ap-... 

Rink T, Pfeiffer M, Oesterhelt D, Gerwert K, Steinhoff HJ. Unraveling photoexcited conformational changes of bacteriorhodopsin by time resolved electron paramagnetic resonance specttoscopy. Biophys. J. 2000 78 1519-1530. 

TA-transient absorption TRANIP = time-resolved anisotropy TRPL = time-resolved photoluminescence TRIR = time-resolved IR TR = EPR-time-resolved electron paramagnetic resonance spectroscopy. 

In all covalent electron donor-acceptor systems produced earlier, triplet states observed by EPR were formed via a spin-orbit intersystem crossing (SO-ISC) mechanism. Another possible mechanism of triplet formation is RP-ISC, mentioned above, which results from radical ion pair recombination, and which had been observed previously by time-resolved electron paramagnetic resonance spectroscopy (TREPR) only in bacterial reaction centers and in the green plant Photosystem I and II reaction centers. These two mechanisms can be differentiated by the polarization pattern of the six EPR transitions at the canonical orientations. In SO-ISC,... 

Burns, C. S., Heyerick, A., De Keukeleire, D., Forbes, M. D. E., Mechanism for Formation of the Lightstruck Flavor in Beer Revealed by Time resolved Electron Paramagnetic Resonance, Chem. Eur. J. 2001, 7, 4553 4561. 

Figure 3.18 shows the time-resolved Electron Paramagnetic Resonance (EPR) spectra of the reaction center from Rba. sphaeroides 2.4.1 at low temperatures. At 65 K, the initial spectrum (0.0 ps) can be ascribed to 3P. After its decay, two different spectral patterns ascribable to the T, species of spheroidene appear they are called 3Car(I) and 3Car(II). At higher temperatures, the contribution of 3P becomes much smaller, but those triplet species of carotenoid exhibit basically the same time-resolved spectra. 

Wagnert L, Rubin R, Berg A, Mahammed A, Gross Z, Levanon H (2010) Photoexcited triplet state properties of brominated and non-brominated Ga(III)-corroles as studied by time-resolved electron paramagnetic resonance. J Phys Chem B 114 14303-14308... 

Bordignon E, Klare JP, Holterhues J, Martell S, Krasnaberski A, Engelhard M, Steinhoff HJ (2007) Analysis of light-induced conformational changes of Natronomonas pharaonis sensory rhodopsin II by time resolved electron paramagnetic resonance spectroscopy. Photochem Photobiol 83(2) 263-272... 

Fragmentation processes have in several cases be documented through the spectral and kinetic characterization of the intermediates. Radicals have been detected upon flash photolysis of nanocrystals of a para-methoxy substituted dicumylketone analogue suspended in water, a rare event at room temperature (see Scheme 11b). This has been revealed by time-resolved electron paramagnetic resonance (TREPR). Under an externally... 

Weber, S., Kay, C.W.M., MogHng, H., Hitomi, K., and Todo, T., Photoreactivation of the flavin cofactor in Xenopus laevis (6—4) photolyase observation of a transient tyrosyl radical by time-resolved electron paramagnetic resonance, Proc. Natl. Acad. Sci. USA, 99, 1319, 2002. 

Time-resolved electron paramagnetic resonance spectroscopy history, technique, and application to supramolecular and macromolecular chemistry, 47, 1... 

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