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101.
Sayanti Chatterjee Tapan Kanti Paine 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(32):9470-9474
Many iron‐containing enzymes involve metal–oxygen oxidants to carry out O2‐dependent transformation reactions. However, the selective oxidation of C H and CC bonds by biomimetic complexes using O2 remains a major challenge in bioinspired catalysis. The reactivity of iron–oxygen oxidants generated from an FeII–benzilate complex of a facial N3 ligand were thus investigated. The complex reacted with O2 to form a nucleophilic oxidant, whereas an electrophilic oxidant, intercepted by external substrates, was generated in the presence of a Lewis acid. Based on the mechanistic studies, a nucleophilic FeII–hydroperoxo species is proposed to form from the benzilate complex, which undergoes heterolytic O O bond cleavage in the presence of a Lewis acid to generate an FeIV–oxo–hydroxo oxidant. The electrophilic iron–oxygen oxidant selectively oxidizes sulfides to sulfoxides, alkenes to cis‐diols, and it hydroxylates the C H bonds of alkanes, including that of cyclohexane. 相似文献
102.
Olefin cis‐Dihydroxylation and Aliphatic CH Bond Oxygenation by a Dioxygen‐Derived Electrophilic Iron–Oxygen Oxidant
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Sayanti Chatterjee Dr. Tapan Kanti Paine 《Angewandte Chemie (International ed. in English)》2015,54(32):9338-9342
Many iron‐containing enzymes involve metal–oxygen oxidants to carry out O2‐dependent transformation reactions. However, the selective oxidation of C? H and C?C bonds by biomimetic complexes using O2 remains a major challenge in bioinspired catalysis. The reactivity of iron–oxygen oxidants generated from an FeII–benzilate complex of a facial N3 ligand were thus investigated. The complex reacted with O2 to form a nucleophilic oxidant, whereas an electrophilic oxidant, intercepted by external substrates, was generated in the presence of a Lewis acid. Based on the mechanistic studies, a nucleophilic FeII–hydroperoxo species is proposed to form from the benzilate complex, which undergoes heterolytic O? O bond cleavage in the presence of a Lewis acid to generate an FeIV–oxo–hydroxo oxidant. The electrophilic iron–oxygen oxidant selectively oxidizes sulfides to sulfoxides, alkenes to cis‐diols, and it hydroxylates the C? H bonds of alkanes, including that of cyclohexane. 相似文献
103.
Mitrali Biswas Sanchaita Dey Abhishek Das Prof. Dr. Tapan Kanti Paine Dr. Sanjib Panda Prof. Dr. Goutam Kumar Lahiri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(63):e202202088
The unexplored ‘actor’ behavior of redox-active bis(aldimine) congener, p-phenylene-bis(picoline)aldimine (L1), towards dioxygen activation and subsequent functionalization of its backbone was demonstrated on coordination with {Ru(acac)2} (acac= acetylacetonate). Reaction under aerobic condition led to the one-pot generation of dinuclear complexes with unperturbed L1, imino-carboxamido (L2−), and bis(carboxamido) (L32−)-bridged isovalent {RuII(μ-L1)RuII}, 1/ {RuIII(μ-L32−)RuIII}, 3 and mixed-valent {RuII(μ-L2−)RuIII}, 2 . Authentication of the complexes along with the redox non-innocence behavior of their bridge have been validated through structure, spectroelectrochemistry and DFT calculations. Kinetic and isotope labelling experiments together with DFT analyzed transition states justified the consideration of redox shuttling at metal/L1 interface for 3O2 activation despite of the closed shell configuration of 1 (S=0) to give carboxamido derived 2 / 3 . 相似文献
104.
Dr. Martin R. L. Paine Dr. Berwyck L. J. Poad Gert B. Eijkel Dr. David L. Marshall Prof. Stephen J. Blanksby Prof. Dr. Ron M. A. Heeren Dr. Shane R. Ellis 《Angewandte Chemie (International ed. in English)》2018,57(33):10530-10534
Mass spectrometry imaging (MSI) enables the spatial distributions of molecules possessing different mass‐to‐charge ratios to be mapped within complex environments revealing regional changes at the molecular level. Even at high mass resolving power, however, these images often reflect the summed distribution of multiple isomeric molecules, each potentially possessing a unique distribution coinciding with distinct biological function(s) and metabolic origin. Herein, this chemical ambiguity is addressed through an innovative combination of ozone‐induced dissociation reactions with MSI, enabling the differential imaging of isomeric lipid molecules directly from biological tissues. For the first time, we demonstrate both double bond‐ and sn‐positional isomeric lipids exhibit distinct spatial locations within tissue. This MSI approach enables researchers to unravel local lipid molecular complexity based on both exact elemental composition and isomeric structure directly from tissues. 相似文献
105.
R. E. Lothrop S. I. Gertler H. A. Schuette R. J. Pauly und H. S. Paine 《Fresenius' Journal of Analytical Chemistry》1935,102(1-2):56-58
Ohne Zusammenfassung 相似文献
106.
The strengths of selected resonances in the range Ep = 0.5–2.0 MeV in the (p, γ) reactions on Mg, 30Si, 34S, 37C1, 39K and 40Ca have been found relative to the Ep = 632 and 992 keV resonances in 27Al(p, γ)28Si by relative yield measurements. Targets were made from mixtures or chemical compounds such that each contained at least two of the isotopes of interest and their chemical composition was determined by Rutherford back-scattering of α-particles. Absolute measurements were conducted on the selected resonances in 27A1(p, γ)28Si and 30Si(p, γ)31P by semi-thick target and thin target techniques with the target thickness, needed for the latter technique, found by Rutherford back-scattering of protons. Absolute strengths for all of the resonances treated, together with one from each of 23Na, 31P and 35Cl, reported in a previous paper, were deduced by normalizing to the absolute measurements on the Al(p, γ)28Si resonances. 相似文献
107.
Summary The error in the estimate of thekth eigenvalue of a regular Sturm-Liouville problem obtained by Numerov's method with mesh lengthh isO(k
6
h
4). We show that a simple correction technique of Paine, de Hoog and Anderssen reduces the error to one ofO(k
3
h
4). Numerical examples demonstrate the usefulness of this correction even for low values ofk. 相似文献
108.
109.
Zhiyu Wang Anthony J. Paine Alfred Rudin 《Journal of polymer science. Part A, Polymer chemistry》1995,33(10):1597-1606
It is well known that the amount of surfactant must be carefully controlled during starve-fed emulsion polymerization processes. Too little surfactant leads to emulsion instability and coagulation, while too much surfactant leads to secondary particle formation. Although these relationships are qualitatively understood in the art, there is little quantitative basis to guide the synthetic chemist, especially in multistep starve-fed emulsion polymerization processes to make larger supermicron particles. We have developed a method, which will be described in a companion article, to control the surfactant level by monitoring the surface tension during polymerization. In order to quantitatively predict how much surfactant to add at any given time, one needs to know in advance the adsorption characteristics of the soap. Further complicating the matter is the formation of “in situ” or oligomeric surfactant during polymerization with aqueous initiators such as ammonium persulfate. This work demonstrates how to prepare surface-active oligomers and how to make latex particles using them as surfactant. First, we established the mass balance for the initiator-derived sulfate groups in seed latexes by conductometric, potentiometric, and iodometric titrations. Based on the characterization of seed latexes, a method for determining the effective sulfate concentration has been developed. When surface-active oligomers were used as the only surfactant, we obtained a series of monodisperse, supermicron copolymer latex particles with diameters up to 3.22 μm. This is a similar result to that obtained with a commercially made anionic surfactant. © 1995 John Wiley & Sons, Inc. 相似文献
110.
Cowpea mosaic virus (CPMV) is a robust, icosahedrally symmetric platform successfully used for attaching a variety of molecular substrates including proteins, fluorescent labels, and metals. The symmetric distribution and high local concentration of the attached molecules generates novel properties for the 30 nm particles. We report new CPMV reagent particles generated by systematic replacement of surface lysines with arginine residues. The relative reactivity of each lysine on the native particle was determined, and the two most reactive lysine residues were then created as single attachment sites by replacing all other lysines with arginine residues. Structural analysis of gold derivatization not only corroborated the specific reactivity of these unique lysine residues but also demonstrated their dramatically different presentation environment. Combined with site-directed cystine mutations, it is now possible to uniquely double label CPMV, expanding its use as an addressable nanoblock. 相似文献