- Dehydrogenation versus oxygenation in two-electron and four-electron reduction of dioxygen by 9-alky-10-methyl-9,10-dihydroacridines catalyzed by monomeric cobalt porphyrins and cofacial dicobalt porphyrins in the presence of perchloric acid
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Dehydrogenation of 10-methyl-9,10-dihydroacridine (AcrH2) by dioxygen (O2) proceeds efficiently, accompanied by the two-electron and four-electron reduction of O2 to produce H2O 2 and H2O,
- Fukuzumi, Shunichi,Okamoto, Ken,Tokuda, Yoshihiro,Gros, Claude P.,Guilard, Roger
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- Acid-Catalyzed Photoreduction of Dialkyl Sulfoxides by an Acid-Stable NADH Analogue
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Photoreduction of dialkyl sulfoxides (R2SO) by an acid-stable NADH analogue, 10-methyl-9,10-dihydroacridine (AcrH2), proceeds in the presence of perchloric acid in acetonitrile containing H2O (0.50 M) to yield 10-methylacridinium ion (AcrH(1+)) and the corresponding dialkyl sulfides (R2S).No photoreduction of R2SO by AcrH2 has occurred in the absence of perchloric acid.In the presence of perchloric acid the protonation of dialkyl sulfoxides occurs to increase the oxidizing ability of the sulfoxides significantly, when the singlet excited state (1AcrH2*) is quenched efficiently by the protonated sulfoxides (R2SOH(1+)).The 1AcrH2* is also quenched by HClO4.The dependence of quantum yields on indicates that the photoreduction of R2SO by AcrH2 proceeds via electron transfer from 1AcrH2* to R2SOH(1+), followed by the hydrogen transfer from AcrH2(*1+) to R2SOH*, accompanied by the concominant dehydration to yield AcrH(1+) and R2S.
- Fukuzumi, Shunichi,Tokuda, Yoshihiro
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- Effective thermal oxidation of isopropanol by an NAD+ model
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The reaction of 10-methylacridinium cation (MA+) with isopropanol in the parent alcohol medium under dark, oxygen-free, and refluxing conditions gave hydride transfer product 10-methyl-9,10-dihydroacridine (MAH). The kinetics of the alcoholic oxidation reaction, including the kinetic isotope effect and the kinetic temperature effect, were determined. Hydride transfer is involved in the rate-determining step.
- Lu, Yun,Endicott, Donald,Kuester, William
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- Nonconventional versus conventional application of pseudo-first-order kinetics to fundamental organic reactions
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Three new analysis procedures for pseudo-first-order kinetics are introduced and applied to eight different fundamental organic reactions. The reactions belong to the following classes: nitroalkane proton transfer, formal hydride ion transfers from NADH model compounds, and SN2 reactions of alkyl halides with ionic and neutral nucleophiles. The three methods consist of (1) half-life dependence of kapp, (2) sequential linear pseudo-first-order correlation, and (3) revised instantaneous rate constant analysis. Each of the three procedures is capable of distinguishing between one- and multistep mechanisms, and the combination of the three procedures provides a powerful strategy for differentiating between the two mechanistic possibilities. The data from the eight reactions chosen as examples clearly show how the procedures work in practice.
- Parker, Vernon D.,Hao, Weifang,Li, Zhao,Scow, Russell
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experimental part
p. 2 - 12
(2012/03/22)
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- Hydride, hydrogen, proton, and electron affinities of imines and their reaction intermediates in acetonitrile and construction of thermodynamic characteristic graphs (TCGs) of imines as a molecule ID card
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(Chemical Equation Presented) A series of 61 imines with various typical structures were synthesized, and the thermodynamic affinities (defined as enthalpy changes or redox potentials in this work) of the imines to abstract hydride anions, hydrogen atoms, and electrons, the thermodynamic affinities of the radical anions of the imines to abstract hydrogen atoms and protons, and the thermodynamic affinities of the hydrogen adducts of the imines to abstract electrons in acetonitrile were determined by using titration calorimetry and electrochemical methods. The pure heterolytic and homolytic dissociation energies of the C=N π-bond in the imines were estimated. The polarity of the C=N double bond in the imines was examined using a linear free-energy relationship. The idea of a thermodynamic characteristic graph (TCG) of imines as an efficient Molecule ID Card was introduced. The TCG can be used to quantitatively diagnose and predict the characteristic chemical properties of imines and their various reaction intermediates as well as the reduction mechanism of the imines. The information disclosed in this work could not only supply a gap of thermodynamics for the chemistry of imines but also strongly promote the fast development of the applications of imines. 2009 American Chemical Society.
- Zhu, Xiao-Qing,Liu, Qiao-Yun,Chen, Qiang,Mei, Lian-Rui
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experimental part
p. 789 - 808
(2010/04/29)
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- Mechanistic insights into hydride-transfer and electron-transfer reactions by a manganese(IV)-oxo porphyrin complex
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Hydride transfer from dihydronicotinamide adenine dinucleotide (NADH) analogs to a manganese(IV)-oxo porphyrin complex, (TMP)MnIV(O) [TMP = 5,10,15,20-tetrakis(2,4,6-trimethylphenyl) porphyrin], occurs via disproportionation of (TMP)MnIV(O) to [(TMP)MnIII] + and [(TMP)MnV(O)]+ that acts as the actual hydride acceptor. In contrast, electron transfer from ferrocene derivatives to (TMP)MnIV(O) occurs directly to afford ferricenium ions and (TMP)MnIII(OH) products. The disproportionation rate constant of (TMP)MnIV(O) was determined by the dependence of the observed second-order rate constants on concentrations of NADH analogs to be (8.0 ± 0.6) × 106 M-1 s-1 in acetonitrile at 298 K. The disproportionation rate constant of (TMP)Mn IV(O) in hydride-transfer reactions increases linearly with increasing acid concentration, whereas the rate constant of electron transfer from ferrocene to (TMP)MnIV(O) remains constant irrespective of the acid concentration. The rate constants of electron transfer from a series of ferrocene derivatives to (TMP)MnIV(O) were evaluated in light of the Marcus theory of electron transfer to determine the reorganization energy of electron transfer by the (TMP)MnIV(O) complex.
- Fukuzumi, Shunichi,Fujioka, Naofumi,Kotani, Hiroaki,Ohkubo, Kei,Lee, Yong-Min,Nam, Wonwoo
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experimental part
p. 17127 - 17134
(2010/03/25)
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- Driving Force Dependence of Photoinduced Electron Transfer Dynamics of Intercalated Molecules in DNA
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A series of acridinium, quinolinium, and phenanthridinium ions (9-substituted-10-methylacridinium (AcrR+, R = H, PrI, and CH2Ph), 3-substituted-1-methylquinolinium (RQuH+, R = CN and Br), and 5-methylphenanthridinium (5-MePhen+) perchlorate salts) are shown to be intercalated into the DNA double helix from calf thymus. The one-electron reduction potentials (Ered0) of these intercalates have been determined in the absence and presence of DNA by both cyclic voltammetry and second harmonic ac voltammetry. The E0red values of intercalators are shifted in a positive direction by intercalation into the DNA double helix. The one-electron oxidation potential (E ox0) of ethidium bromide, which is known to be intercalated into DNA, is also shifted in a positive direction by the intercalation. The wide range of E0red values of intercalators thus determined in the presence of DNA allows us to examine the exact driving force dependence of the rates of photoinduced electron transfer from the singlet excited state of ethidium bromide to the intercalators in DNA for the first time. The resulting data were evaluated in light of the Marcus theory of electron transfer to determine the reorganization energy and the electron coupling matrix element in DNA.
- Fukuzumi, Shunichi,Nishimine, Mari,Ohkubo, Kei,Tkachenko, Nikolai V.,Lemmetyinen, Helge
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p. 12511 - 12518
(2007/10/03)
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- Mechanism of the 10-methylacridinium ion-sensitized photooxidation of N,N-dibenzylhydroxylamine and its derivatives in acetonitrile
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The 10-methylacridinium ion (MA+)-sensitized photooxidation of substituted N,N-dibenzylhydroxylamines (1) in acetonitrile occurred mainly by a superoxide ion mechanism to give N-benzylidenebenzylamine N-oxides (2) and hydrogen peroxide quantitatively. Analysis of substituent effects on the limiting quantum yield for formation of 2 showed that back electron transfer (ET) from the 10-methylacridinyl radical (MA.) to the radical cation 1+. proceeds in the Marcus 'normal region'. In addition, this back ET was found to take place in preference to one-electron reduction of O2 by MA..
- Ohba, Yasuhiro,Kubo, Kanji,Igarashi, Tetsutaro,Sakurai, Tadamitsu
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p. 491 - 493
(2007/10/03)
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- Electron-transfer oxidation of 9-substituted 10-methyl-9,10-dihydroacridines. Cleavage of the C-H vs C-C bond of the radical cations
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Electron-transfer oxidation of various 9-substituted 10-methyl-9,10-dihydroacridines (AcrHR) by Fe(ClO4)3 and [Fe(phen)3](PF6)3 (phen = 1,10-phenanthroline) results in cleavage of the C(9)-H or C(9)-C bond of AcrHR?+ depending on the substituent R. Transient electronic absorption spectra as well as electron spin resonance (ESR) spectra of AcrHR?+ have been detected by using a stopped-flow spectrophotometer and a rapid mixing flow ESR technique, respectively. The hyperfine splitting constants (hfs) are determined by comparing the observed ESR spectra with those from the computer simulation. Comparison of the hfs values with those expected from the molecular orbital calculations indicates the structural change of AcrHR?+ with the substituent R, which is reflected in the selectivity of the C-H vs C-C bond cleavage of AcrHR?+ depending on the substituent R. The decay rates of AcrHR?+ obey the mixture of first-order and second-order kinetics due to the deprotonation (or the C-C bond cleavage) and disproportionation reactions, respectively. Both the first-order and bimolecular second-order decay rate constants of AcrHR?+ are reported. The first-order decay rate constant for the deprotonation of AcrHR?+ by the C-H bond cleavage decreases with the substitution in order R = primary > secondary > tertiary alkyl groups, while the first-order decay due to the C-C bond cleavage becomes dominant with tertiary alkyl groups. The one-electron oxidation potentials of various AcrHR have been determined directly by applying fast cyclic voltammetry. The pKa values of AcrHR?+ (R = H and Me) have also been evaluated by analyzing the dependence of the first-order deprotonation rate constants on the concentrations of HClO4.
- Fukuzumi, Shonichi,Tokuda, Yoshihiro,Kitano, Toshiaki,Okamoto, Toshihiko,Otera, Junzo
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p. 8960 - 8968
(2007/10/02)
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- C(9)-C Bonds of 10-Methyl-9-alkyl-9,10-dihydroacridines Acting Like Metal-Carbon Bonds in the Reactions with Electrophiles
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The C(9)-C bonds of 10-methyl-9-alkyl-9,10-dihydroacridines (AcrHR: R = CMe2COOMe, CMe(H)COOEt, But, CHPh2) are readily cleaved by electrophiles (perchloric acid, oxygen, and iodine) in acetonitrile at 298 K, acting like metal-carbon bonds to yield the corresponding alkane, alkyl hydroperoxide, and alkyl iodide, respectively.
- Fukuzumi, Shunichi,Tokuda, Yoshihiro,Fujita, Morifumi,Otera, Junzo,Chanon, Michel,et al.
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p. 1701 - 1704
(2007/10/02)
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- Photoinduced Cleavage of the C-C Bonds of 9-Alkyl-10-methyl-9,10-dihydroacridines by Perchloric Acid
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The C-C single bonds of 9-alkyl-10-methyl-9,10-dihydroacridines are readily cleaved by perchloric acid in acetonitrile under irradiation of the absorption band of AcrHR to yield the corresponding alkane (RH) and 10-methylacridinium ion (AcrH+).
- Fukuzumi, Shunichi,Tokuda, Yoshihiro,Fujita, Morifumi
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p. 1905 - 1908
(2007/10/02)
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- Dynamics of hydride transfer between NAD+ analogues
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Primary kinetic isotope effects (KIE) for hydride transfer between 10-methylacridan and 1-benzyl-3-cyanoquinolinium perchlorate have been measured in 15 different solvents. There is a reduction of the KIE from 5.2 to about 2.9 in the more viscous, nonhydroxylic solvents. Hydroxylic solvents give the larger KIE regardless of their viscosity. These results suggest a three-step process. In the first step, the heavy atoms and solvent are reorganized to a configuration intermediate between reactants and products, while the hydride retains its original attachment. In the second stage, the hydride is transferred, probably by tunneling. In the final step the products are stabilized by further solvent and heavy-atom reorganization. For nonhydroxylic solvents, translational and rotational diffusion governs the heavy-atom reorganization steps and, therefore, determines which step is rate-limiting. Only when the heavy-atom reorganizations are fast is the second step rate-limiting and the KIE maximized. The rate constant for the tunneling process is assumed to be solvent-independent. It is of the right order of magnitude to compete with solvent relaxation. Changes in rate constant, k, and equilibrium constant, K, are modest, but there is a linear correlation between ln k and ln K, with a slope of 0.87. This slope suggests that it is the third step, rather than the first, which shares rate-limiting character with the second. There is no visible trend toward a maximum isotope effect at K = 1.
- Kreevoy, Maurice M.,Kotchevar, Ann T.
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p. 3579 - 3583
(2007/10/02)
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