- Solvent Effects on Photoinduced Electron-Transfer Reactions
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Dependence of the fluorescence-quenching rate constant kq, effective quenching distance rq, and free radical yield ΦR on the free enthalphy change ΔGf of full electron transfer has been studied in dichloromethane by using anthracenecarbonitrile as electron-accepting fluorescers and amino- and methoxybenzenes as electron-donating quenchers.On the basis of the present data in dichloromethane and the previous data in acetonitrile, the solvent effects on the electron-transfer fluorescence-quenching mechanism and on the back electron-transfer reaction within the geminate radical ion pairs are elucidated.
- Niwa, Taeko,Kikuchi, Koichi,Matsusita, Noriyuki,Hayashi, Michiko,Katagiri, Tomoharu,et al.
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- Salt Effect for Accelerating Charge Separation from 9,10-Dicyanoanthracene-Stilbene Exciplex in Dichloromethane
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On radiation of 9,10-dicyanoanthracene (DCA) in the presence of cis-(CS) and trans-stilbene (TS) in dichloromethane, addition of tetrabutylammonium tetrafluoroborate efficiently accelerated production of the radical cations from CS and TS along with DCA radical anions.
- Zhang, Bao Wen,Kuriyama, Yasunao,Cao, Yi,Tokumaru, Katsumi
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- A pcu-type metal-organic framework with spindle [Zn7(OH) 8]6+ cluster as secondary building units
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The in situ solvothermal reaction of 9,10-dicyanoanthracene and ZnCl 2/NaN3 gave the complex, {[Zn7(OH) 8(DTA)3]·H2O}n (1) (DTA 2- = 9,10-ditetrazolateanthracene), which presents a pcu-type topological framework formed by DTA2- bridging unprecedented heptanuclear spindle [Zn7(OH)8]6+ clusters as SBUs, and exhibits strong luminescent emission with long lifetime. The Royal Society of Chemistry.
- Li, Jian-Rong,Tao, Ying,Yu, Qun,Bu, Xian-He
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- Facile synthesis of cyanoarenes from quinones by reductive aromatization of cyanohydrin intermediates
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A novel synthesis of cyanoarenes from quinones by using PCl3 as the reagent for reductive aromatization of cyanohydrin intermediates is reported. In situ IR spectroscopic measurements were conducted to monitor the reactions and to develop a convenient one-pot protocol. 1,4-Dicyanobenzene and 9,10-dicyanoanthracene were prepared by the new procedure.
- Gl?cklhofer, Florian,Lunzer, Markus,Fr?hlich, Johannes
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- Quantum amplified isomerization: A new concept for polymeric optical materials
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The preparation and evaluation of a new class of photoresponsive polymers are described on the basis of a process called quantum amplified isomerization (QAI). The QAI process utilizes photoinitiated, cation radical isomerization chemistry in a polymeric medium. Two classes of materials are described: one where the QAI reactant is molecularly doped in the polymer matrix and another where the reactant is part of a functionalized polymer. Quantum yield experiments demonstrate that the isomerization reaction can proceed by a chain process with modest efficiencies. Photochemical conversion experiments show that high extents of conversion of the QAI reactants are possible. The rate and extent of conversion are strongly correlated to the glass transition temperature of the polymer. For molecularly doped polymers, hypotheses to explain the high conversions based on diffusion or phase separation of the reactants were tested and excluded. Models are discussed to rationalize experimental factors that affect the quantum yields and the photochemical conversions.
- Gillmore,Neiser,McManus,Roh,Dombrowski,Brown,Dinnocenzo,Farid,Robello
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- Steric Effects in Photoinduced Electron-Transfer Reactions
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Quantum yields for formation of separated radical ions are determined for the electron-transfer reactions of singlet excited cyanoanthracene acceptors with sterically hindered alkylbenzene donors, in acetonitrile.These yields are up to 4 times larger than those for unhindered alkylbenzene donors.The yields are controlled by the competition between separation and return electron transfer in the initially formed radical-ion pairs.From studies of the dependence of the steric effect on the driving force for return electron transfer, it is concluded that the main effect of the steric hindrance is to decrease the magnitude of the electronic coupling matrix element for electron transfer, thus decreasing the return electron transfer rate and increasing the separation yield.The sterically hindered donors can be divided into two groups depending upon whether the substituents on the benzene ring have hydrogens that are capable of hyperconjugative stabilization of the positive charge in the radical cation.The electron transfer reorganization parameters are measurably different for the donors that have these substituents compared to those that lack such hydrogen atoms.
- Gould, Ian R.,Farid, Samir
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- Reductive Electrophotocatalysis: Merging Electricity and Light to Achieve Extreme Reduction Potentials
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We describe a new electrophotocatalytic strategy that harnesses the power of light and electricity to generate an excited radical anion with a reducing potential of -3.2 V vs SCE, which can be used to activate substrates with very high reduction potentials (Ered ≈ -1.9 to -2.9 V). The resultant aryl radicals can be engaged in various synthetically useful transformations to furnish arylboronate, arylstannane, and biaryl products.
- Kim, Hyunwoo,Kim, Hyungjun,Lambert, Tristan H.,Lin, Song
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supporting information
p. 2087 - 2092
(2020/02/04)
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- A Versatile One-Pot Access to Cyanoarenes from ortho- and para-Quinones: Paving the Way for Cyanated Functional Materials
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A generally applicable direct synthesis of cyanoarenes from quinones is presented. Particular emphasis is placed on the preparation of precursors and target molecules relevant for organic materials, including halogenated cyanoarenes and larger cyanated acenes. The reaction and work-up protocols are adjusted for the challenges presented by the different substrates and products. Screening results of the initial reaction optimization are given to further facilitate adaptation to other synthetic problems. The universality of the reaction is finally highlighted by successful substitution of para-quinones by an ortho-quinone as the starting material.
- Gl?cklhofer, Florian,Lunzer, Markus,St?ger, Berthold,Fr?hlich, Johannes
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supporting information
p. 5173 - 5180
(2016/04/09)
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- Preparation of (1R,1′R)-1,1′-(anthracene-9,10-diyl)bis(2,2,2-trifluoroethanamine): a chiral diamine with low basicity
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A new chiral diamine with low basicity was synthesized in enantiopure form. (1R,1′R)-1,1′-(Anthracene-9,10-diyl)bis(2,2,2-trifluoroethanamine) was obtained by means of several stereochemically controlled reactions. The structures of the title compound and several intermediates were studied.
- Estivill, Carla,Mendizabal, Julen,Virgili, Albert,Monteagudo, Eva,Flor, Teresa,Sánchez-Ferrando, Francisco,Alvarez-Larena, Angel,Piniella, Juan F.
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body text
p. 171 - 176
(2009/04/10)
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- An environmentally benign procedure for the synthesis of aryl and arylvinyl nitriles assisted by microwave in ionic liquid
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Aryl and arylvinyl nitriles have been prepared in good yields from the corresponding bromides with potassium hexacyanoferrate (II) using palladium-catalyzed reactions in ionic liquid under microwave irradiation. Georg Thieme Verlag Stuttgart.
- Li, Lian-Hua,Pan, Zhen-Liang,Duan, Xin-Hua,Liang, Yong-Min
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p. 2094 - 2098
(2008/02/05)
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- Aminosilanes as two-electron donors: A technological application of radical cation chemistry
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Aminosilanes possess the appropriate structural features for use as two-electron sensitizers in silver halide photography. Here, we describe studies of the nucleophile-assisted cleavage reactions of the C - Si bonds in their radical cations. Water is identified as a useful nucleophile. It is found that the kinetics of these reactions are best described by taking into account a radical cation - water complex. The cleavage reactions are also controlled by steric effects at silicon and by the proximity of a carboxylate group that can modify the nucleophilicity of the water. Cleavage forms an α-amino radical that can donate a second electron to 9,10-dicyanoanthracene as a solution-phase electron acceptor.
- Gould, Ian R.,Godleski, Stephen A.,Zielinski, Paul A.,Farid, Samir
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p. 777 - 788
(2007/10/03)
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- Photoinduced electron-transfer cope rearrangements of 3,6-diaryl-2,6- octadienes and 2,5-diaryl-3,4-dimethyl-1,5-hexadienes: Stereospecificity and an unexpected formation of the bicyclo[2.2.0]hexane Derivatives
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Under the 9,10-dicyanoanthracene-sensitized photoinduced electron- transfer conditions, (Z,Z)-, (E,E)-, (E,Z)-3,6-diaryl-2,6-octadiene and (d,l),(meso)-2,5-diaryl-3,4-dimethyl-1,5-hexadiene stereospecifically undergo the Cope rearrangement to give a Cope
- Ikeda, Hiroshi,Takasaki, Toshihiko,Takahashi, Yasutake,Konno, Akinori,Matsumoto, Masao,Hoshi, Yosuke,Aoki, Takashi,Suzuki, Takanori,Goodman, Joshua L.,Miyashi, Tsutomu
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p. 1640 - 1649
(2007/10/03)
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- Indirect Electrochemical Reduction of Some Peroxide Derivatives
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Indirect reduction of derivatives of tert-butyl hydroperoxide by means of aromatic radical anions in DMF results in the formation of tert-butoxy radicals, which abstract a hydrogen atom from DMF.The N,N-dimethylaminocarbonyl radical may couple with the radical anion or be reduced by it; from this competition the reduction potential of the N,N-dimethylaminocarbonyl radical is estimated to be -1.62 V (SCE).
- Kjaer, Niels Them,Lund, Henning
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p. 848 - 852
(2007/10/02)
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- Free Enthalpy Dependence of Free Radical Yield of Photoincuced Electron Transfer in Acetonitrile
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The free enthalpy dependence of the free-radical yield ΦR of the electron-transfer (ET) fluorescence quenching was studied in acetonitrile by using anthracenecarbonitriles as the electron-accepting fluorescer and 1,4-diphenyl-1,3-butadienes as the electron-donating quencher. ΦR decreases, passes through a minimum, increases with increase of ΔGf, the free enthalpy change involved in the actual ET process, and then suddenly falls when ΔGf goes beyond -0.25 eV.Switchover of the quenching mechanism was suggested for the ET fluorescence quenching: The radical pairs are exclusively produced by the full ET in the encounter state bet ween the fluorescer and the quencher when ΔGf is smaller than -0.4 eV, but in contrast through the partial ET, i.e., the exciplex formation as the primary quenching products when ΔGf is larger than -0.4 eV.
- Kikuchi, Koichi,Takahashi, Yasutake,Hoshi, Masato,Niwa, Taeko,Katagiri, Tomoharu,Miyashi, Tsutomu
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p. 2378 - 2381
(2007/10/02)
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- Efficiencies of photoinduced electron-transfer reactions: Role of the Marcus inverted region in return electron transfer within geminate radical-ion pairs
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In photoinduced electron-transfer processes the primary step is conversion of the electronic energy of an excited state into chemical energy retained in the form of a redox (geminate radical-ion) pair (A + D →hν A?-/D?+). In polar solvents, separation of the geminate pair occurs with formation of free radical ions in solution. The quantum yields of product formation, from reactions of either the free ions, or of the geminate pair, are often low, however, due to the return electron transfer reaction (A?-/D?+ → A + D), an energy-wasting step that competes with the useful reactions of the ion pair. The present study was undertaken to investigate the parameters controlling the rates of these return electron transfer reactions. Quantum yields of free radical ion formation were measured for ion pairs formed upon electron-transfer quenching of the first excited singlet states of cyanoanthracenes by simple aromatic hydrocarbon donors in aceonitrile at room temperature. The free-ion yields are determined by the competition between the rates of separation and return electron transfer. By assuming a constant rate of separation, the rates of the return electron transfer process are obtained. These highly exothermic return electron transfer reactions (-ΔG-et = 2-3 eV) were found to be strongly dependent on the reaction exothermicity. The electron-transfer rates showed a marked decrease (ca. 2 orders of magnitude in this ΔG-et range) with increasing exothermicity. This effect represents a clear example of the Marcus "inverted region". Semiquantum mechanical electron-transfer theories were used to analyze the data quantitatively. The electron-transfer rates were found also to depend upon the degree of charge delocalization within the ions of the pair, which is attributed to variations in the solvent reorganization energy and electronic coupling matrix element. Accordingly, mostly on the basis of redox potentials, one can vary the quantum yield of free-ion formation from a few percent to values approaching unity. Use of a strong donor with a strong acceptor to induce reactions based on electron transfer is likely to be inefficient because of the fast return electron transfer in the resulting low-energy ion pair. A system with the smallest possible driving force for the initial charge-separation reaction results in a high-energy, and therefore long-lived ion pair, which allows the desired processes to occur more efficiently. The use of an indirect path based on secondary electron transfer, a concept called "cosensitization", results in efficient radical-ion formation even when the direct path results in a very low quantum yield.
- Gould, Ian R.,Ege, Deniz,Moser, Jacques E.,Farid, Samir
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p. 4290 - 4301
(2007/10/02)
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- Photoadditions of Ethers, Thioethers, and Amines to 9,10-Dicyanoanthracene by Electron Transfer Pathways
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Studies were conducted to explore single electron transfer (SET) induced photoaddition reactions of 9,10-dicyanoanthracene (DCA) with a variety of n-electron donors including silicon-containing substrates (EtOCH2TMS, EtSCH2TMS, and Et2NCH2TMS).Photoadditions of EtOCH2TMS and EtSCH2TMS to DCA in MeCN occur in high yields to produce 10-substituted 9,10-dicyano-9,10-dihydroanthracenes in which the anthracenyl unit is bonded to the ether or thioether in place of the TMS substituent.The photoadducts undergo base-induced dehydrocyanation and oxidation to generate the respective 10-substituted 9-cyanoanthracenes and 10-substituted 10-cyano-9-anthrones.Photoaddition of Et2NCH2TMS to DCA in MeCN produces the corresponding dihydroanthracene adduct, which spontaneously dehydrocyanates under the reaction conditions to yield the coresponding 10-substituted 9-cyanoanthracene.This process is inefficient as compared to the O and S analogues; other products from this reaction include 9-cyano-10-aminoanthracene, 9-cyanoanthracene, and 9-cyano-10-methylanthracene.The latter product is shown to arise by secondary photoreaction of the Et2NCH2TMS-DCA anthracene adduct.Mechanism for these photoadditions involving SET from the n donors to DCAS1 followed by selective desilylation of the intermediate cation radicals and radical coupling are proposed.In contrast, photoadditions of Et2O and THF occur in high yield while that of Et2NMe to DCA is inefficient.These processes follow sequential electron-transfer-deprotonation pathways.Finally, the α-amino radical, Et2NCH2, an intermediate in the DCA + Et2NCH2TMS photoreaction, is trapped by added cyclohex-2-en-1-one and its 4,4-dimethyl analogue via routes involving conjugate radical addition.Adduct formation between these enones and Et2NCH2TMS represents a novel method for initiating radical addition processes by use of SET photosensitization.
- Hasegawa, Eietsu,Brumfield, Martha A.,Mariano, Patrick S.,Yoon, Ung-Chan
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p. 5435 - 5442
(2007/10/02)
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- Photoinduced Electron Transfer Reaction. Part 3. 9,10-Dicyanoanthracene-sensitized Photo-oxidation of Electron-rich Stilbene Oxides
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The 9,10-dicyanoanthracene (DCA)-sentisized photo-oxygenation of the electron-rich stilbene oxides (1) gives the ozonides (2) almost quantitatively.The fluorescence of DCA is quenched by (1) at a diffusion-controlled rate and the above reaction is quenched by polymethoxybenzenes which indicates that an electron transfer mechanism is involved.The quantum yield for ozonide formation varies from 0.6 for trans-2-(4-methoxyphenyl)-3-phenyloxirane (1d) to 2.4 for trans-2,3-bis(4-methoxyphenyl)-2,3-diethyloxirane (1h), suggesting a duplex reaction mechanism such as photo-oxygenation by superoxide and a Barton mechanism after the initial electron transfer from the epoxides (1) to the excited singlet state of DCA.
- Futamura, Shigeru,Kusunose, Shosaku,Ohta, Hiroyuki,Kamiya, Yoshio
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- Anomalous Reactions of Cyanide with Two Hindered Aromatic Aldehydes
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9-Anthraldehyde (1), under the conditions of a benzoin condensation, yields 9-anthracenecarbonitrile (2). 9-Cyano-10-anthraldehyde (6) has been shown to be the likely intermediate in this reaction.Mesitaldehyde (7), under similar conditions, yields 2-hydroxy-2-mesitylethanoic amide (8).
- Gore, P. H.,Gupta, S. D.,Obaji, G. A.
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p. 381 - 384
(2007/10/02)
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- Photochemical Electron-Transfer Reactions: Effect of Ring Opening of the Cyclobutane Radical Cation on the Dimerization of Phenyl Vinyl Ether
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The photosensitized electron-transfer dimerization of olefins proceeds via several reversible steps.Limited kinetic data on some of these processes have been reported.We used the dependence of the product distribution in the electron-transfer-sensitized d
- Mattes, Susan L.,Luss, Henry R.,Farid, Samir
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p. 4779 - 4781
(2007/10/02)
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- Electron-transfer Fluorescence Quenching of Radical Ions
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The radical anions of anthraquinone and 9,10-dicyanoanthracene and the radical cation of thianthrene fluoresce in oxygen-free fluid solution at room temperature.The fluorescence of the radical anions is quenched by added electron acceptors, while the fluorescence of the cation is quenched by added electron donors.The fluorescence quenching is treated in terms of an electron-transfer mechanism.The results agree with Marcus' theory and Weller's equation only if very large solvent and/or bond reorganization energies (20 - 30 kcal/mol) are introduced.
- Eriksen, Jens,Lund, Henning,Nyvad, Annette I.
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p. 459 - 466
(2007/10/02)
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- Unusual Base-induced Ring-opening Reactions of the Bis-tosylhydrazones of Dibenzobicyclooctadiene-2,3-dione and Acenaphthenequinone
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Unusual KOH-induced ring-opening reactions of the bis-tosylhydrazones of dibenzobicyclooctadiene-2,3-dione and acenaphthenequinone are described.
- Nakayama, Juzo,Segiri, Tsunehiko,Ohya, Ryuji,Hoshino, Masamatsu
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p. 791 - 792
(2007/10/02)
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