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TEMPO Radicals (tempo + radical)

Distribution by Scientific Domains
Chemistry71%
Polymers and Materials Science28%

Selected Abstracts

Synthesis and Catalytic Activity of a Fluorous-Tagged TEMPO Radical.

CHEMINFORM, Issue 36 2004
Gianluca Pozzi
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

The Effect of Persistent TEMPO Radicals on the Gilch Polymerization

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 1 2007
Jens Wiesecke
Abstract The mechanism of the Gilch polymerization leading to poly(p -phenylene vinylenes) is still a matter of controversial discussion. Similar to some other research groups, we strongly favor a basically radical process. Moreover, we believe it is initiated by spontaneously formed diradicals. Here, we describe further experimental evidence which clearly supports the assumed initiation step: it is shown how the polymerization process is affected quantitatively when different amounts of 2,2,6,6-tetramethylpiperidine- N -oxyl (TEMPO) are added as a scavenger. In full agreement with our expectations, the chain growth is either retarded or completely prevented, depending on the respective molar ratio of monomer and scavenger. [source]

Aerobic Oxidation of Alcohols to Carbonyl Compounds Mediated by Poly(ethylene glycol)-Supported TEMPO Radicals.

CHEMINFORM, Issue 14 2006
Maurizio Benaglia
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Deactivation reactions in the modeled 2,2,6,6-tetramethyl-1-piperidinyloxy-mediated free-radical polymerization of styrene: A comparative study with the 2,2,6,6-tetramethyl-1-piperidinyloxy/acrylonitrile system

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2007
Andrzej Kaim
Abstract The competitiveness of the combination and disproportionation reactions between a 1-phenylpropyl radical, standing for a growing polystyryl macroradical, and a 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) radical in the nitroxide-mediated free-radical polymerization of styrene was quantitatively evaluated by the study of the transition geometry and the potential energy profiles for the competing reactions with the use of quantum-mechanical calculations at the density functional theory (DFT) UB3-LYP/6-311+G(3df, 2p)//(unrestricted) Austin Model 1 level of theory. The search for transition geometries resulted in six and two transition structures for the radical combination and disproportionation reactions, respectively. The former transition structures, mainly differing in the out-of-plane angle of the NO bond in the transition structure TEMPO molecule, were correlated with the activation energy, which was determined to be in the range of 8.4,19.4 kcal mol,1 from a single-point calculation at the DFT UB3-LYP/6-311+G(3df, 2p)//unrestricted Austin Model 1 level. The calculated activation energy for the disproportionation reaction was less favorable by a value of more than 30 kcal mol,1 in comparison with that for the combination reaction. The approximate barrier difference for the TEMPO addition and disproportionation reaction was slightly smaller for the styrene polymerization system than for the acrylonitrile polymerization system, thus indicating that a ,-proton abstraction through a TEMPO radical from the polymer backbone could diminish control over the radical polymerization of styrene with the nitroxide even more than in the latter system. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 232,241, 2007 [source]

Organic biradical compounds with a mesogenic core and long alkoxy groups: preparation, structures and magnetic properties

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2006
Shin'ichi Nakatsuji
Abstract Series of organic biradical compounds 3a,3h consisting of a mesogenic core (biphenyl, naphthalene, azobenzene and azoxybenzene) and long alkoxy groups with PROXYL or TEMPO radicals were prepared. The TEMPO derivatives (3b, 3d, 3f, and 3h) were found to show fairly large antiferromagnetic interactions (J,=,,34,,,,45,K) being well expressed by singlet-triplet model irrespective of the mesogenic cores and the behavior is understandable by taking a hand-in-hand like assembled structure into consideration. On the other hand, only weak antiferromagnetic interactions with Curie,Weiss behavior were observed in all of the PROXYL derivatives (3a, 3c, 3e, and 3d) affording a sharp contrast with the TEMPO-based biradicals. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Water-proton relaxivity of hyperbranched polymers carrying TEMPO radicals

MAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2009
Hiroyuki Hayashi
Abstract High water-soluble hyperbranched poly(styrene) (HPS) polymers carrying stable 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO) radicals, HPS-N-TEMPO, HPS-Im-TEMPO, and HPS-Im-(TEMPO)2, were prepared in ca. 60% introducing yield. HPS-N-TEMPO and HPS-Im-TEMPO were determined to be nearly spherical shapes of the diameter of 2.4 ± 0.6 and 2.2 ± 0.6 nm, respectively, by transmission electron microscope (TEM) images. The values of water-proton relaxivity, r1, at 25 MHz, 0.59 T, and 25 °C were 6.0, 5.2, and 14 mM,1 sec,1 for HPS-N-TEMPO, HPS-Im-TEMPO, and HPS-Im-(TEMPO)2, respectively. The spin-lattice relaxation time (T1)-weighted images in phantom were also observed. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Synthesis and Properties of DNA Complexes Containing 2,2,6,6-Tetramethyl-1-piperidinoxy (TEMPO) Moieties as Organic Radical Battery Materials

CHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2008
Jinqing Qu Dr.
Abstract We report here the first example of organic radical battery with DNA. Though there is a growing interest in DNA/cationic-lipid complexes as promising gene delivery vehicles, few efforts have been focused on the use of such complexes as advanced materials for organic optoelectronic applications. The present article describes how substitution of the sodium counter cation of DNA with cationic amphiphilic lipid(1,4) provided novel DNA,lipid complexes that contain TEMPO radicals, in which the actual mole ratio of phosphate to lipid was 1:0.84 to 1:0.16. All the TEMPO-containing DNA,lipid complexes displayed reversible two-stage charge/discharge processes, the discharge capacities of which were 40.5,60.0,A,h,kg,1. In particular, the capacity of a DNA,lipid(3)-based cell reached 60.0,A,h,kg,1, which corresponds to 192,% relative to its theoretical value for the single-electron one-stage process, indicating a two-electron process. [source]