Direct Electron Transfer between Glucose Oxidase and Multi-walled Carbon Nanotubes

The direct dedrochemical behavior between the glucose oxfdase ( GOD ) and the multi-wailed carbon nauotubes (MWNTs) has been studied. Two pairs of cyclic voltammetric peaks corresponding to the two different processes, i. e. mass-transportand surface reaction of GOD are observed on this MWNTs. The formal potentials with E^o‘=-0.45Vand E^o‘=-0.55V were obtained respectively.The GOD film was observed on the carbon nanotube by the TEM.     

Photoinduced Electron Transfer Reaction between N,N-Dimethylaniline and 7,7-Dichloronorcarane

OxidativedealkylationoftertiarytaineshasattractedconsiderableattentionduetoitsrelevancetoenzymahcN-dealkylationandasamodelreactionofcytochromeP-450oxidation_1.IthasbeenreportedthattheoxidativedemethylationofN,N-dimethylaniline(DMA)couldbeaccomplishedchendcally_2,electrochemically_3andphotochemically_4.Ingeneral,anelectronacceptivesensitizerorinitiatormustbeusedtoinitiatethephotochemicalreaction,andthereactionproductsandmechanismsdependonthesensitizerorinitiatorused.Forinstance,whendicyanona…     

The Electron Transfer Reaction between p-Nitrobenzoates and β-N，N-Dimethylaminonaphthalene

A few of p-nitrobenzoates were synthesized,and the electron transfer of them with β-N,N-dimethylaminonaphthalene (DMAN) in methanol solution was studied.Steady-state fluorescence results showed the cyclodextrin moicty in p-nitrobenzoyl-β-cyclodextrin would block the electron transfer pathway from DMAN compared with other electron acceptors,thus ,reduced the electron transfer efficiency.     

The Electron Transfer Reaction between ρ-Nitrobenzoates and β-N, N-Dimethylaminonaphthalene

Photoinduced electron-transfer (PET) reactions are fundamentally important in biology and technology1,2. Because of the complexity of PET in biological systems, many simple compounds were synthesized to look into its detailed mechanism3. In previous papers, we reported the electron transfer reaction in the supramolecular systems assembled by mono-6-p-nitrobenzoyl-b-cyclodextrin 6 and naphthalene derivatives in aqueous solution4. In the present paper the intermolecular electron transfer from …     

Evidence for a Proton-Coupled Electron Transfer Mechanism in a Biomimetic System for Monoamine Oxidase B Catalysis

Mechanistic studies with 5-ethyl-3-methyllumiflavinium (Fl⁺) perchlorate, a biomimetic model for flavoenzyme monoamine oxidase B (MAO-B) catalysis, and the tertiary, allyl amine 1-methyl-4-(1-methyl-1 H-pyrrol-2-yl)-1,2,3,6-tetrahydropyridine (MMTP) reveal that proton-coupled electron transfer (PCET) may be an important pathway for MAO catalysis. The first step involves a single-electron transfer (SET) leading to the free radicals Fl^. and MMTP^., the latter produced by deprotonation of the initially formed and highly acidic MMTP^.+. Molecular oxygen (O₂) is found to play a hitherto unrecognized role in the early steps of the oxidation. MMTP and several structurally similar tertiary amines are the only tertiary amines oxidized by MAO, and their structural/electronic properties provide the key to understanding this behavior. A general hypothesis about the role of SET in MAO catalysis, and the recognition that PCET occurs with appropriately substituted substrates is presented.     

Nucleophilic Substitution Reaction of p-Dinitrobenzene by a Carbanion: Evidence for Electron Transfer Mechanism

ＩｎｔｒｏｄｕｃｔｉｏｎＳｉｎｇｌｅｅｌｅｃｔｒｏｎｔｒａｎｓｆｅｒｉｎａｒｏｍａｔｉｃｎｕｃｌｅｏｐｈｉｌｉｃｓｕｂ ｓｔｉｔｕｔｉｏｎｈａｓａｔｔｒａｃｔｅｄｍｕｃｈａｔｔｅｎｔｉｏｎｉｎｒｅｃｅｎｔｙｅａｒｓ .Ｉｎａｄｄｉｔｉｏｎｔｏｔｈｅｗｅｌｌ ｋｎｏｗｎＳＲＮ1ｍｅｃｈａｎｉｓｍｒｅｐｏｒｔｅｄｂｙＢｕｎｎｅｔｔ,1ｍａｎｙｏｔｈｅｒａｃｔｉｖａｔｅｄａｒｏｍａｔｉｃｓｙｓｔｅｍｓ ,ｉ .ｅ .,ｎｉｔｒｏａｒｙｌｈａｌｉｄｅｓ ,ｄｉｎｉｔｒｏｂｅｎｚｅｎｅｓ ,ｅｔｃ .,ｈａｖｅｂｅｅｎｒｅ ｐ…     

DFT Calculations for Electron Transfer Bond-breakingReaction of CH_3-X

Bond-breaking in electron tansfer (ET) reaction is a powerful synthetic tool to provide alkyl radicals. The reaction RX + e( ? R( + X( in gas-phase yields directly the alkyl radical and the halide ion. Although ab initio calculation has been performed to this kind of reaction for CH3-X1-3, density functional theory (DFT) has not been invoked so far. DFT is gaining popularity recently as a cost-effective procedure for studying physical properties of molecules. The activation energy ((G#) …     

Strongly Bound π-Hole Tetrel Bonded Complexes between H2SiO and Substituted Pyridines. Influence of Substituents

Ab initio calculation at the MP2/aug-cc-pVTZ level has been performed on the π-hole based N^…Si tetrel bonded complexes between substituted pyridines and H₂SiO. The primary aim of the study is to find out the effect of substitution on the strength and nature of this tetrel bond, and its similarity/difference with the N^…C tetrel bond. Correlation between the strength of the N^…Si bond and several molecular properties of the Lewis acid (H₂SiO) and base (pyridines) are explored. The properties of the tetrel bond are analyzed using AIM, NBO, and symmetry-adapted perturbation theory calculations. The complexes are characterized with short N^…Si intermolecular distances and high binding energies ranging between −142.72 and −115.37 kJ/mol. The high value of deformation energy indicates significant geometrical distortion of the monomer units. The AIM and NBO analysis reveal significant coordinate covalent bond character of the N⋅⋅⋅Si π-hole bond. Sharp differences are also noticed in the orbital interactions present in the N⋅⋅⋅Si and N⋅⋅⋅C tetrel bonds.     

Internal Reorganization Energy Contributed by Torsional Motion in Electron Transfer Reaction between Biphenyl and Biphenyl Anion Radical

ＩｎｔｒｏｄｕｃｔｉｏｎＥｌｅｃｔｒｏｎｔｒａｎｓｆｅｒ (ＥＴ)ｒｅａｃｔｉｏｎｓａｒｅｆｏｕｎｄｔｏｂｅａｎｅｌｅｍｅｎｔａｌｓｔｅｐｉｎｍａｎｙｂｉｏｌｏｇｉｃａｌｐｒｏｃｅｓｓｅｓｉｎｄｅｅｄ .1 6ＩｔｈａｓｂｅｅｎｂｅｌｉｅｖｅｄｔｈａｔｔｈｅｅｘｐｅｒｉｍｅｎｔａｌｍｅａｓｕｒｅｍｅｎｔｏｆＥＴｒｅａｃｔｉｏｎｓｂｅｔｗｅｅｎｂｉｐｈｅｎｙｌ (Ｂｐ)ａｎｄａｓｅｒｉｅｓｏｆｏｒ ｇａｎｉｃｓｙｓｔｅｍｓ ,ｄｅｓｉｇｎｅｄｂｙＭｉｌｌｅｒｅｔａｌ.,ｉｓｔｈｅｆｉｒｓｔｓｕｃ ｃｅｓｓｆｕｌｅ…     

Synthesis and Structures of Stable PtII and PtIV Alkylidenes: Evidence for π-Bonding and Relativistic Stabilization

Isolable cationic Pt^II and Pt^IV alkylidenes, proposed intermediates in catalytic organic transformations, are reported. The bonding in these species was probed by experimental, structural, spectroscopic, electrochemical and computational methods, providing direct evidence for π-bonding, the often-theorized relativistic stabilization of these species, and the influence of oxidation state.     

Chemical interactions between 2-mercaptobenzazoles and π-acceptors

Summary 2-Mercaptobenzazoles (1a–c) interact with several -acceptors such as tetracyanoethylene (TCNE) 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,3,5,6-tetrachloro-1,4-benzoquinone (CHL) dicyanomethyleneindane-1,3-dione (CNIND), 2,3-dicyano-1,4-naphthoquinone (DCNQ), 9-dicyanomethylene-2,4,7-trinitrofluorene (DTF), and 2,3-dichloro-1,4-naphthoquinone (DCHNQ)via the formation of charge-transfer (CT) complexes to yield various heterocyclic compounds.

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Chemische Wechselwirkungen zwischen 2-Mercaptobenzazolen und -Akzeptoren

Zusammenfassung Die 2-Mercaptobenzazole1a–c reagieren mit verschiedenen -Akzeptoren wie Tetracyanoethylen (TCNE), 2,3-Dichlor-5,6-dicyano-1,4-benzochinon (DDQ), 2,3,5,6-Tetrachlor-1,4-benzochinon (CHL), Dicyanomethylenindan-1,3-dion (CNIND), 2,3-Dicyano-1,4-naphthochinon (DCNQ), 9-Dicyanomethylen-2,4,7-trinitrofluoren (DTF) und 2,3-Dichlor-1,4-naphthochinon (DCHNQ) unter Ausbildung von charge transfer — Komplexen (CT) zu heterocyclischen Verbindungen.

     

On the Acidity and Lithiation-Functionalization of Thiophenes: Revisited for their Use in the Synthesis of Thiophene-Based Novel π-Systems

When lithium diisopropylamide is used for lithiation and functionalization of thiophenes, whose acidity is here measured to be pKa = 35-36 in THF-Hex (5:3), the equilibrated nature of lithiation is to be taken into consideration.     

Coupling Titanium and Chromium Catalysis in a Reaction Network for the Reprogramming of [BH4]− as Electron Transfer and Hydrogen Atom Transfer Reagent for Radical Chemistry

We describe a unique catalytic system with an efficient coupling of Ti- and Cr-catalysis in a reaction network that allows the use of [BH₄]⁻ as stoichiometric hydrogen atom and electron donor in catalytic radical chemistry. The key feature is a relay hydrogen atom transfer from [BH₄]⁻ to Cr generating the active catalysts under mild conditions. This enables epoxide reductions, regiodivergent epoxide opening and radical cyclizations that are not possible with cooperative catalysis with radicals or by epoxide reductions via Meinwald rearrangement and ensuing carbonyl reduction. No typical S_N2-type reactivity of [BH₄]⁻ salts is observed.     

Where Does the Electron Go? Stable and Metastable Peptide Cation Radicals Formed by Electron Transfer

Electron transfer to doubly and triply charged heptapeptide ions containing polar residues Arg, Lys, and Asp in combination with nonpolar Gly, Ala, and Pro or Leu generates stable and metastable charge-reduced ions, (M + 2H)^+●, in addition to standard electron-transfer dissociation (ETD) fragment ions. The metastable (M + 2H)^+● ions spontaneously dissociate upon resonant ejection from the linear ion trap, giving irregularly shaped peaks with offset m/z values. The fractions of stable and metastable (M + 2H)^+● ions and their mass shifts depend on the presence of Pro-4 and Leu-4 residues in the peptides, with the Pro-4 sequences giving larger fractions of the stable ions while showing smaller mass shifts for the metastables. Conversion of the Asp and C-terminal carboxyl groups to methyl esters further lowers the charge-reduced ion stability. Collisional activation and photodissociation at 355 nm of mass-selected (M + 2H)^+● results in different dissociations that give sequence specific MS³ spectra. With a single exception of charge-reduced (LKGLADR + 2H)^+●, the MS³ spectra do not produce ETD sequence fragments of the c and z type. Hence, these (M + 2H)^+● ions are covalent radicals, not ion–molecule complexes, undergoing dramatically different dissociations in the ground and excited electronic states. The increased stability of the Pro-4 containing (M + 2H)^+● ions is attributed to radicals formed by opening of the Pro ring and undergoing further stabilization by hydrogen atom migrations. UV–VIS photodissociation action spectroscopy and time-dependent density functional theory calculations are used in a case in point study of the stable (LKGPADR + 2H)^+● ion produced by ETD. In contrast to singly-reduced peptide ions, doubly reduced (M + 3H)⁺ ions are stable only when formed from the Pro-4 precursors and show all characteristics of even electron ions regarding no photon absorption at 355 nm or ion-molecule reactions, and exhibiting proton driven collision induced dissociations.

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Photoinduced Electron Transfer （PET） between C60 and Amines in Micells Solution—A Kinetic ESR Study

As indicated by kinetic ESR measurements, the key fctor to affect electron recombination in the process of PET between C60 and amines is the space between donor and C60. To increase solubility of C60 in water, it was incorporated into micelle of surfactants.     

Molecular complex formation between crown ether and π-acceptors

A spectrophotometric study was made of the formation of charge-transfer complexes between benzo- 18-crown-6 ether and some π-acceptors in methylene chloride at 25°C. The spectroscopic data indicate that the PhOCH₂CH₂ group is responsible for the complexation with π-acceptors. The benzo-18-crown-6 ether—2,3-dichloro-5,6-dicyanobenzoquinone and benzo-l8-crown-6 ether—tetracyanoethylene complexes were isolated in a crystalline form and characterised. Job's method shows that the stoichiometric ratio of the complexes is 1:1. The effect of KCl salt on the formation and stability of the complexes is discussed.     

Photoinduced Electron Transfer (PET) between C_(60) and Amines in Micelle Solution A Kinetic ESR Study

Fullerene chemistry has been one of the most exciting research subjects in the recent decade1,2. However, the predominant hydrophobic character and the spherical carbon allotrope of C60 hinder its solubility in an aqueous solution. In order to efficiently slow down charge recombination in the PET system containing C60, water was selected as optimal polar media to stabilize charge separation state. Accordingly, solubility of fullerene in water had to be achieved by incorporating it into th…     

Theoretical Study on the Kinetics of Electron Transfer for Bond—breaking Reaction

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Electron Capture Dissociation of Disulfide, Sulfur–Selenium, and Diselenide Bound Peptides

To examine the electron capture dissociation (ECD) behavior of disulfide (S?CS), sulfur?Cselenium (S?CSe), and diselenide (Se?CSe) bonds-containing peptides, a series of free cysteine (Cys) and selenocysteine (Sec) containing peptides were reacted to form interchain S?CS, S?CSe, and Se?CSe bonds, and then studied using ECD with Fourier transform ion cyclotron mass spectrometry (FTICR MS). These results demonstrate that the radical has higher tendency to stay at selenium rather than sulfur after the cleavage of Se?CS bonds by ECD. In addition, ?CSH (?C33), ?CS (?C32), and ?CS + H (?C31) small neutral losses were all observed from the cleavage of C?CS bonds of a disulfide bound peptide. Similar, but minor, fragments were also detected in S?CSe bound peptides. In contrast, the cleavage of C?CSe bonds of the Se?CSe species mainly forms fragments with neutral loss of ?CSe + H (?C78.90868), and the radical tends to stay on the selenium of its corresponding complementary pair. Although the electron affinities of S atom (2.07?eV) and Se atom (2.02?eV) are very close; they have very different reactivity towards electrons. The replacement of sulfur with selenium greatly increases the electron affinities of S?CSe and Se?CSe bonds comparing to S?CS bonds (with an increase of electron affinity by about 0.20?eV by replacing a sulfur with a selenium) (Int J Quantum Chem 110:513-523, 2010), which in turn leads to different ECD fragmentation behavior and mechanisms. Our results are in good agreement with previously published ab initio calculations on Se?CSe compounds by other groups.