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Artigos de revistas sobre o tema "Triplet aryl cations"

Autor: Grafiati

Publicado: 8 de fevereiro de 2025

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1

Kemp, Terence J. "The Aryl Cation – the Trapping and Characterisation of a Hyper-Reactive Species". Progress in Reaction Kinetics and Mechanism 28, n.º 1 (março de 2003): 11–34. http://dx.doi.org/10.3184/007967403103165431.

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The article traces the development of the epr and optical spectroscopic characterisation and progressive theoretical understanding of the aryl cation, starting from the initial cryogenic epr study of 2,5-dialkoxyl-4-morpholinophenyl cation, which defined unambiguously its triplet state character, through simple MO, ab initio and DFT calculations on substituted aryl cations, to picosecond laser photolysis studies in fluorinated solvents, noting especially the early and vital contribution of Martyn Symons.

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2

Fasani, Elissa, Angelo Albini, Mariella Mella, Michela Rampi e Federico Barberis Negra. "Light and drugs: the photochemistry of fluoroquinolone antibiotics". International Journal of Photoenergy 1, n.º 1 (1999): 7–11. http://dx.doi.org/10.1155/s1110662x99000021.

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Light-related adverse side-effects of drugs are now an important source of concern. In order that the mechanism underlying to such effects is recognised, an in-depth photochemical study must be carried out. The case of some fluoroquinolone antibiotics (norfloxacin, enoxacin, lomefloxacin) is discussed as a representative example. These drugs undergo heterolytic fragmentation of the C—F bond leading to aryl cations. Quantum yields in neutral water range from 0.001 to 0.5 depending on the charge transfer degree of theππ*state. Lower values are obtained at both acidic and basic pH. There is indication that the excited state involved in most of this reactions is a relatively long-lived triplet. The aryl cations undergo intra- or intermolecular reactions, and are presumably involved in the reported photo-toxic effect.

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3

Laali, Kenneth K., Golam Rasul, G. K. Surya Prakash e George A. Olah. "DFT Study of Substituted and Benzannelated Aryl Cations: Substituent Dependency of Singlet/Triplet Ratio1a". Journal of Organic Chemistry 67, n.º 9 (maio de 2002): 2913–18. http://dx.doi.org/10.1021/jo020084p.

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4

Bondarchuk, Sergey V., Boris F. Minaev e Alexander Yu Fesak. "Theoretical study of the triplet state aryl cations recombination: A possible route to unusually stable doubly charged biphenyl cations". International Journal of Quantum Chemistry 113, n.º 24 (4 de julho de 2013): 2580–88. http://dx.doi.org/10.1002/qua.24509.

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5

Dulov, Dmitry A., Alexey V. Bogdanov, Sergey G. Dorofeev e Tatiana V. Magdesieva. "N,N′-Diaryldihydrophenazines as a Sustainable and Cost-Effective Alternative to Precious Metal Complexes in the Photoredox-Catalyzed Alkylation of Aryl Alkyl Ketones". Molecules 28, n.º 1 (27 de dezembro de 2022): 221. http://dx.doi.org/10.3390/molecules28010221.

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An inexpensive and highly efficient metal-free alternative to commonly used Ru- and Ir-based catalysts was proposed. It was shown that the new 2,7-di-tert-butyl-5,10-bis(4-trifluoromethylphenyl)-5,10-dihydrophenazine outcompeted the iridium phenylpyridyl complex in photoredox activity in the alkylation of silyl enol ethers yielding aryl alkyl ketones. The reaction occurred under visible light irradiation at room temperature and was also applicable to drug derivatives (ibuprofen and naproxen). In-depth photophysical, electrochemical, and quantum chemical studies showed that the aforementioned N,N-diaryldihydrophenazine exhibited enhanced properties that were essential for the photoredox catalysis (a long-lived triplet excited state, strong reducing ability, high stability of the radical cations formed in single-electron-transfer event, and chemical inertness of the catalyst with respect to reactants). Importantly, the substituted N,N′-diaryldihydrophenazines could be obtained directly from diaryl amines; a facile, easily handled and scaled-up one-pot synthetic procedure was elaborated.

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6

Milanesi, Silvia, Maurizio Fagnoni e Angelo Albini. "(Sensitized) Photolysis of Diazonium Salts as a Mild General Method for the Generation of Aryl Cations. Chemoselectivity of the Singlet and Triplet 4-Substituted Phenyl Cations". Journal of Organic Chemistry 70, n.º 2 (janeiro de 2005): 603–10. http://dx.doi.org/10.1021/jo048413w.

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7

Winter, Arthur H., Daniel E. Falvey, Christopher J. Cramer e Benjamin F. Gherman. "Benzylic Cations with Triplet Ground States: Computational Studies of Aryl Carbenium Ions, Silylenium Ions, Nitrenium Ions, and Oxenium Ions Substituted with Meta π Donors". Journal of the American Chemical Society 129, n.º 33 (agosto de 2007): 10113–19. http://dx.doi.org/10.1021/ja070143m.

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8

Chen, Kai, Man Sing Cheung, Zhenyang Lin e Pengfei Li. "Metal-free borylation of electron-rich aryl (pseudo)halides under continuous-flow photolytic conditions". Organic Chemistry Frontiers 3, n.º 7 (2016): 875–79. http://dx.doi.org/10.1039/c6qo00109b.

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9

Fleming, S. A., L. Renault, E. C. Grundy e J. A. Pincock. "The photochemistry of ring-substituted cinnamyl acetates". Canadian Journal of Chemistry 84, n.º 9 (1 de setembro de 2006): 1146–54. http://dx.doi.org/10.1139/v06-140.

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The photochemistry of the (E)-cinnamyl acetates ((E)-1-aryl-3-propenyl acetates, 8a–8e) with substituents H, 4-CH3O, 3-CH3O, 4-CF3, and 3-CF3, respectively, was examined in both cyclohexane and methanol solvents. Alkene isomerization (E to Z) occurred more efficiently than other reactions and evidence is presented that this process occurs from the excited triplet state. In a slower process, 1,3-migration of the acetoxy group led to the rearranged 3-aryl-3-propenyl acetate isomers (9a–9e) as the major pathway, particularly in cylohexane. In methanol, the isomeric ethers 3-aryl-3-methoxypropene (14) and 1-aryl-3-methoxypropene (15) were formed by reaction of methanol with the photochemically generated cation. The combined yield of 14 and 15 (95% and 5%, respectively) was quantitative for the 4-methoxyphenyl compound (8b). Independent irradiations of the isomers 9a–9c demonstrated that the ethers 14 and 15 were primary photoproducts from 8 and not secondary photoproducts from 9. Fluorescence quantum yields and excited singlet state lifetimes indicated that the reactions, other than the E to Z isomerization, are from the excited singlet state.Key words: cinnamyl acetates, photochemistry, E/Z isomerization, photocleavage, fluorescence.

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10

Ambroz, Hanna B., Terence J. Kemp, Nelson M. Pinhal, Grazyna K. Przybytniak e J. Barrie Raynor. "A powder endor study of a σ, π-triplet aryl cation 3Ar+". Chemical Physics Letters 160, n.º 4 (agosto de 1989): 396–400. http://dx.doi.org/10.1016/0009-2614(89)87617-1.

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11

Yuan, Jin-Wei, Guang-Chao Huang, Li-Li Wang, Xin-Yuan Wang, Liang-Ru Yang, Shou-Ren Zhang, Pu Mao, Yong-Mei Xiao e Ling-Bo Qu. "Chalcogenative spirocyclization of N-aryl propiolamides with diselenides/disulfides promoted by Selectfluor". Zeitschrift für Naturforschung B 77, n.º 1 (6 de dezembro de 2021): 75–85. http://dx.doi.org/10.1515/znb-2021-0154.

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Abstract A practical and efficient synthetic route to construct a variety of 3-arylselenenyl/3-arylthio spiro[4.5]trienones was developed using Selectfluor reagent as a mild oxidant. This reaction proceeds via a sequence of electrophilic cation addition, spirocyclization and dearomatization, then offers an approach to introduce Se/S-centered cation into the C–C triple bonds. The utility of this protocol were justified by the excellent compatibility of a wide range of functional groups, good yields and scalability under mild reaction conditions.

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12

Kuck, Dietmar, Linda C. Salameh, Kenneth I. Onwuka e Matthias C. Letzel. "Unidirectional Triple Hydrogen Rearrangement in the Radical Cations of Electron-Rich 3-Aryl-1-Propanols: Further Evidence and Limitation". European Journal of Mass Spectrometry 20, n.º 1 (fevereiro de 2014): 51–61. http://dx.doi.org/10.1255/ejms.1239.

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13

Yagyu, Takeyoshi, Kohtaro Osakada e Maurice Brookhart. "Single and Multiple Insertion of Carbon−Carbon Triple Bonds into the Palladium−Aryl Bond of Cationic and Neutral Arylpalladium Complexes with a 2,2‘-Bipyridine Ligand". Organometallics 19, n.º 11 (maio de 2000): 2125–29. http://dx.doi.org/10.1021/om0000360.

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14

Li, Xin‐Long, Yue‐Bo Wang, Ying Wang, Rong‐Zhen Zhang, Rui‐Zhi Dong, Hui Liu, ShengSheng Yu, Ning Han e Ling‐Bao Xing. "Construction of supramolecular dimer based on benzothiazole derivative through host–guest interaction for photocatalysis". Carbon Neutralization, 16 de novembro de 2023. http://dx.doi.org/10.1002/cnl2.98.

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AbstractIn recent years, the development of photocatalysts based on noncovalent strategies has shown an important role in medical and organic materials. Herein, an organic fluorescent dye benzothiazole derivative (2‐(N,N‐diethylanilin‐4‐yl)‐4,6‐bis(3‐methylpyrazol‐1‐yl)‐1,3,5‐triazine [MPBT]) was designed and synthesized. It was encapsulated in the cavity of cucurbit[8]uril (CB[8]) to form a supramolecular dimer through host–guest interaction, which converted the dye into a highly efficient photocatalyst. With the formation of 2MPBT‐CB[8] supramolecular dimer, the emergence of host‐enhanced charge transfer interactions could significantly facilitate singlet to triplet through intersystem crossing. At the same time, the alternating structure of 2MPBT‐CB[8] facilitated the triplet states for further energy transfer and electron transfer. In addition, the electron transfer process with electron donor generated cationic free radical and photocatalyst negative ion free radical (), which in turn reacted with oxygen (O2) to form superoxide anion radical (). The generated could be used to catalyze the oxidative hydroxylation of aryl boronic acid. Therefore, the 2MPBT‐CB[8] had become a highly efficient photocatalyst for the oxidative hydroxylation of aryl boronic acid. This strategy of supramolecular dimerization provides a new strategy for the development of new photocatalysts based on noncovalent interactions.

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15

Sun, Wei, Luke Wilding-Steele, Richard C. D. Brown e David C. Harrowven. "Aryl–aryl cross-coupling reactions without reagents or catalysts: photocyclization of ortho-iodoaryl ethers and related compounds via triplet aryl cation intermediates". Chemical Communications, 2023. http://dx.doi.org/10.1039/d3cc03271j.

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16

Nakanishi, Kazuki, Leonardo I. Lugo-Fuentes, Jun Manabe, Ronghao Guo, Soichi Kikkawa, Seiji Yamazoe, Kenji Komaguchi et al. "Redox Activity of IrIII Complexes with Multidentate Ligands Based on Dipyrido‐annulated N‐Heterocyclic Carbenes: Access to High Valent and High Spin State with Carbon Donors". Chemistry – A European Journal, 8 de agosto de 2023. http://dx.doi.org/10.1002/chem.202302303.

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Synthetic strategies to access high‐valent iridium complexes usually require use of π donating ligands bearing electronegative atoms (e.g. amide or oxide) or σ donating electropositive atoms (e.g. boryl or hydride). Besides the η5‐(methyl)cyclopentadienyl derivatives, high‐valent η1 carbon‐ligated iridium complexes are challenging to synthesize. To meet this challenge, this work reports the oxidation behavior of an all‐carbon‐ligated anionic bis(CCC‐pincer) IrIII complex. Being both σ and π donating, the diaryl dipyrido‐annulated N‐heterocyclic carbene (dpa‐NHC) IrIII complex allowed a stepwise 4e– oxidation sequence. The first 2e– oxidation led to an oxidative coupling of two adjacent aryl groups, resulting in formation of a cationic chiral IrIII complex bearing a CCCC‐tetradentate ligand. A further 2e– oxidation allowed isolation of a high‐valent tricationic complex with a triplet ground state. These results close a synthetic gap for carbon‐ligated iridium complexes and demonstrate the electronic tuning potential of organic π ligands for unusual electronic properties.

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17

Zuo, Honghua, Hendrik F. T. Klare, Elisabeth Irran e Martin Oestreich. "Electrophilic Activation of S–Si Reagents by Silylium Ions for Their Regio‐ and Diastereoselective Addition Across C–C Multiple Bonds". Angewandte Chemie, 7 de fevereiro de 2024. http://dx.doi.org/10.1002/ange.202401599.

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A regioselective silylium‐ion‐promoted thiosilylation of internal C–C triple bonds with control over the double bond geometry is described. Both a C(sp2)–S and a C(sp2)–Si bond are formed with a trans relationship in this two‐component reaction of an alkyne and a thiosilane. The resulting orthogonally functionalized C–C double bond can be chemoselectively defunctionalized or further processed by cross‐coupling reactions with the alkene configuration retained. The procedure is also applicable to the regio‐ and diastereoselective thiosilylation of terminal allenes to arrive at allylic thioethers containing a vinylsilane unit. These reactions involve the electrophilic activation of the S–Si reagent, both a silylated thiophenol and even alkylthiol derivative, by an in‐situ‐generated carbocation intermediate. The catalytic cycle is maintained by a bissilylated aryl‐ or alkylsulfonium ion as a shuttle for the cationic silicon electrophile. Its independent preparation and structural characterization by X‐ray diffraction are also reported.

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18

Zuo, Honghua, Hendrik F. T. Klare, Elisabeth Irran e Martin Oestreich. "Electrophilic Activation of S–Si Reagents by Silylium Ions for Their Regio‐ and Diastereoselective Addition Across C–C Multiple Bonds". Angewandte Chemie International Edition, 7 de fevereiro de 2024. http://dx.doi.org/10.1002/anie.202401599.

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A regioselective silylium‐ion‐promoted thiosilylation of internal C–C triple bonds with control over the double bond geometry is described. Both a C(sp2)–S and a C(sp2)–Si bond are formed with a trans relationship in this two‐component reaction of an alkyne and a thiosilane. The resulting orthogonally functionalized C–C double bond can be chemoselectively defunctionalized or further processed by cross‐coupling reactions with the alkene configuration retained. The procedure is also applicable to the regio‐ and diastereoselective thiosilylation of terminal allenes to arrive at allylic thioethers containing a vinylsilane unit. These reactions involve the electrophilic activation of the S–Si reagent, both a silylated thiophenol and even alkylthiol derivative, by an in‐situ‐generated carbocation intermediate. The catalytic cycle is maintained by a bissilylated aryl‐ or alkylsulfonium ion as a shuttle for the cationic silicon electrophile. Its independent preparation and structural characterization by X‐ray diffraction are also reported.

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19

Zheng, Shanchang, Nan Ning, Yani Hua e Zhan Gao. "A novel side‐chain type double‐cation grafted poly (binaphthyl triphenyl piperidine) membranes for anion exchange membrane fuel cells". ChemNanoMat, 9 de abril de 2024. http://dx.doi.org/10.1002/cnma.202300542.

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Recent advancements in anion exchange membrane fuel cells (AEMFCs) have been primarily driven by improvements in anion exchange membranes (AEMs). Aryl ether bond‐free membranes have emerged as a promising avenue for enhancing the performance of AEMs. In this study, a novel side‐chain polymer, PBTP‐s‐x, possesses double cationic groups, aiming at further enhancing overall performance for AEMs. The use of a twisted stereospecific backbone structure of polymerized binaphthyl and triple biphenyl monomer and grafted side chains of piperidine cationic groups not only improves the microphase separation structure of the membrane, but also improves the alkali resistance. Notably, the PBTP‐s‐100 AEMs exhibit exceptional OH‐ conductivity, reaching up to 138.21 mS cm‐1, and show outstanding mechanical properties with a tensile strength of up to 28 MPa. Additionally, PBTP‐s‐100 displays excellent durability, proved by the NMR spectral consistency and over 80% ion conductivity retention in 1 M NaOH at 60°C for 4 weeks. And PBTP‐s‐100 exhibits a higher Lowest Unoccupied Molecular Orbital (LUMO) and a larger energy gap for LOMO and Highest Occupied Molecular Orbital (HOMO) by density functional theory calculation, which indicates it possesses sterling alkaline stability. These findings highlight the potential of PBTP‐s‐100 as a highly performing polymer structure suitable for AEM.

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