- Tuning the interactions between electron spins in fullerene-based triad systems
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A series of six fullerene-linker-fullerene triads have been prepared by the stepwise addition of the fullerene cages to bridging moieties thus allowing the systematic variation of fullerene cage (C60 or C70) and linker (oxalate, acetate or terephthalate) and enabling precise control over the inter-fullerene separation. The fullerene triads exhibit good solubility in common organic solvents, have linear geometries and are diastereomerically pure. Cyclic voltammetric measurements demonstrate the excellent electron accepting capacity of all triads, with up to 6 electrons taken up per molecule in the potential range between -2.3 and 0.2 V (vs Fc+/Fc). No significant electronic interactions between fullerene cages are observed in the ground state indicating that the individual properties of each C60 or C 70 cage are retained within the triads. The electron-electron interactions in the electrochemically generated dianions of these triads, with one electron per fullerene cage were studied by EPR spectroscopy. The nature of electron-electron coupling observed at 77 K can be described as an equilibrium between doublet and triplet state biradicals which depends on the inter-fullerene spacing. The shorter oxalate-bridged triads exhibit stronger spin-spin coupling with triplet character, while in the longer terephthalate-bridged triads the intramolecular spin-spin coupling is significantly reduced.
- Lebedeva, Maria A.,Chamberlain, Thomas W.,Davies, E. Stephen,Thomas, Bradley E.,Schroeder, Martin,Khlobystov, Andrei N.
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Read Online
- Synthesis and application of oxalic acid monoester derivatives
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The invention relates to synthesis and application of oxalic acid monoester-containing compounds as shown in a general formula (I) which is described in the specification. The compounds represent a broad-spectrum efficient insecticidal and bactericidal agent structure type. The oxalic acid monoester-containing compounds can well control aphids, plutella xylostella and spodoptera exigua when used as novel insecticidal bactericides; the compounds can also be used for preventing and treating cucumber brown blotch, cucumber bacterial angular leaf spot, cucumber fusarium wilt, cucumber downy mildew, cucumber powdery mildew, tomato bacterial leaf spot and rice sheath blight. R in the general formula (I) is as defined in the specification.
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Paragraph 0015-0018
(2020/12/08)
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- Photoredox-catalyzed deoxyfluorination of activated alcohols with Selectfluor
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Herein we disclose a deoxyfluorination of alcohols with an electrophilic fluorine source via visible-light photoredox catalysis. This radical-mediated C–F coupling is capable of fluorinating secondary and tertiary alcohols efficiently, complementing previously reported nucleophilic deoxyfluorination protocols.
- González-Esguevillas, María,Miró, Javier,Jeffrey, Jenna L.,MacMillan, David W.C.
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supporting information
p. 4222 - 4227
(2019/06/13)
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- Meso-ester and carboxylic acid substituted BODIPYs with far-red and near-infrared emission for bioimaging applications
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A series of meso-ester-substituted BODIPY derivatives 1-6 are synthesized and characterized. In particular, dyes functionalized with oligo(ethylene glycol) ether styryl or naphthalene vinylene groups at the α positions of the BODIPY core (3-6) become partially soluble in water, and their absorptions and emissions are located in the far-red or near-infrared region. Three synthetic approaches are attempted to access the meso-carboxylic acid (COOH)-substituted BODIPYs 7 and 8 from the meso-ester-substituted BODIPYs. Two feasible synthetic routes are developed successfully, including one short route with only three steps. The meso-COOH-substituted BODIPY 7 is completely soluble in pure water, and its fluorescence maximum reaches around 650 nm with a fluorescence quantum yield of up to 15 %. Time-dependent density functional theory calculations are conducted to understand the structure-optical properties relationship, and it is revealed that the Stokes shift is dependent mainly on the geometric change from the ground state to the first excited singlet state. Furthermore, cell staining tests demonstrate that the meso-ester-substituted BODIPYs (1 and 3-6) and one of the meso-COOH-substituted BODIPYs (8) are very membrane-permeable. These features make these meso-ester- and meso-COOH-substituted BODIPY dyes attractive for bioimaging and biolabeling applications in living cells. Copyright
- Ni, Yong,Zeng, Lintao,Kang, Nam-Young,Huang, Kuo-Wei,Wang, Liang,Zeng, Zebing,Chang, Young-Tae,Wu, Jishan
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p. 2301 - 2310
(2014/03/21)
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- Catalytic phosphorus(V)-mediated nucleophilic substitution reactions: Development of a catalytic appel reaction
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Catalytic phosphorus(V)-mediated chlorination and bromination reactions of alcohols have been developed. The new reactions constitute a catalytic version of the classical Appel halogenation reaction. In these new reactions oxalyl chloride is used as a consumable stoichiometric reagent to generate the halophosphonium salts responsible for halogenation from catalytic phosphine oxides. Thus, phosphine oxides have been transformed from stoichiometric waste products into catalysts and a new concept for catalytic phosphorus-based activation and nucleophilic substitution of alcohols has been validated. The present study has focused on a full exploration of the scope and limitations of phosphine oxide catalyzed chlorination reactions as well as the development of the analogous bromination reactions. Further mechanistic studies, including density functional theory calculations on proposed intermediates of the catalytic cycle, are consistent with a catalytic cycle involving halo- and alkoxyphosphonium salts as intermediates.
- Denton, Ross M.,An, Jie,Adeniran, Beatrice,Blake, Alexander J.,Lewis, William,Poulton, Andrew M.
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experimental part
p. 6749 - 6767
(2011/10/02)
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- Fura-2FF-based calcium indicator for protein labeling
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We describe the synthesis and fluorescence properties of a Fura-2FF-based fluorescent Ca2+ indicator that can be covalently linked to SNAP-tag fusion proteins and retains its Ca2+ sensing ability after coupling to protein. The Royal
- Ruggiu, Agostina A.,Bannwarth, Michael,Johnsson, Kai
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supporting information; experimental part
p. 3398 - 3401
(2010/08/21)
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- Enantioselective rhodium-catalyzed addition of arylboronic acids to α-ketoesters
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(Chemical Figure Presented) Rhodium catalysis: The first example of a catalytic asymmetric addition of arylboronic acids to α-ketoesters was realized by using a chiral RhI-spirophosphite ligand complex in aqueous solvent to provide tertiary α-hydroxyesters in good yields with high enantioselectivities (see scheme; DCE = 1,2-dichloroethane).
- Duan, Hai-Feng,Xie, Jian-Hua,Qiao, Xiang-Chen,Wang, Li-Xin,Zhou, Qi-Lin
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supporting information; experimental part
p. 4351 - 4353
(2009/02/08)
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- Characterization of alkoxycarbonyl radicals by step-scan time-resolved infrared spectroscopy
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A series of alkoxycarbonyl radicals has been generated by laser flash photolysis (355 nm) of fluorenone oxime alkyl oxalates in carbon tetrachloride and characterized by time-resolved infrared spectroscopy using the step-scan technique. The alkoxycarbonyl radicals (v?C=O = 1802 cm-1 for R = ethyl) generally have a lifetime of several microseconds, decaying by reaction with the solvent to yield esters of chloroformic acid. In some cases, decarboxylation yielding alkyl radicals has also been observed. Thus, photolysis of fluorenone oxime tert-butyl oxalate results in the formation of tert-butoxycarbonyl radicals, which subsequently decay, mainly yielding CO2 and tert-butyl radicals. The benzyloxycarbonyl radical and the acetoneiminoxycarbonyl radical both decarboxylate too rapidly to be detected with our spectrometer (25 ns rise-time). Upon purging the solution with oxygen, the alkoxycarbonyl radicals were efficiently quenched, to yield alkoxycarbonylperoxy radicals (v?C=O = 1845 cm-1 for R = ethyl), which again had a lifetime of the order of several microseconds. A short-lived transient (v? = 1768 cm-1, τ ? 200 ns) is assigned as the carbonyloxy radical 4a on the basis of comparison with time-resolved UV/Vis data. A further product of the photolysis of fluorenone oxime oxalates can be tentatively assigned as the 9-fluorenylideneiminoxy radical 3 (v? = 1670 cm-1), which according to our DFT calculations should show a very intense v?C=N-O,as. = 1665 cm-1. Fluorenone oxime oxalates are compounds well suited as precursors for alkoxycarbonyl radicals, since they are easily synthesized as crystalline solids, show a convenient absorption at λ = 355 nm, and exhibit a high degree of thermal stability.
- Bucher, G?tz,Halupka, Martin,Kolano, Christoph,Schade, Olaf,Sander, Wolfram
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p. 545 - 552
(2007/10/03)
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- Absolute Rate Constants for Alkoxycarbonyl Radical Reactions
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PTOC oxalates (anhydrides of an oxalic acid monoester and N-hydroxypyridine-2-thione) were used in laser flash photolysis (LFP) kinetic studies. Irradiation of the PTOC oxalates gave the following alkoxycarbonyl radicals ROC(·)=O: 2a, R = PhCH2; 2b, R = (trans-2-phenylcyclopropyl)methyl; 2c, R = (2,2-diphenylcyclopropyl)methyl. Rate constants for decarboxylation of radical 2a measured by LFP were in agreement with those obtained previously by indirect kinetic methods. Rate constants for decarboxylation of radical 2c were measured by LFP over the temperature range 3-48°C; the reaction is described by log k = 12.2-9.6/2.3RT (kcal/mol). Reactions of Bu3SnH with radical 2c produced from the corresponding phenylseleno carbonate gave inconsistent kinetic results apparently due to the production of small amounts of PhSeH that reacted rapidly with 2c. An approximate rate constant at 2°C for reaction of Bu3SnH with 2c produced from the PTOC oxalate was obtained. Tin hydride reacts with the alkoxycarbonyl radical approximately 1 order of magnitude less rapidly than it reacts with alkyl radicals. Rate constants for 5-exo cychzations of simple alkoxycarbonyl radicals were estimated from previous results and the approximate rate constant for tin hydride trapping; the cyclizations are slightly faster than 5-exo cyclizations of structurally related alkyl radicals.
- Simakov, Pavel A.,Martinez, Felix N.,Horner, John H.,Newcomb, Martin
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p. 1226 - 1232
(2007/10/03)
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- Conversion of Hydroxyl Groups in Alcohols to Other Functional Groups with N-Hydroxy-2-thiopyridone, and Its Application to Dialkylamines and Thiols
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The radical decarboxylation reaction of N-alkoxyoxalyloxy-2-thiopyridone which was prepared by the reaction of alcohol, oxalyl chloride, and N-hydroxy-2-thiopyridone was studied both in the absence and presence of olefinic compounds.The same reactions with olefinic and acetylenic alcohols gave the corresponding lactone derivatives.On the other hand the unsymmetrical alkyl 2-pyridyl disulfides were obtained by the same reaction with aliphatic thiols.
- Togo, Hideo,Fujii, Misa,Yokoyama, Masataka
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