1
|
Ikeda T, Tanaka Y, Hashimoto R, Furutani T, Yamawaki M, Suzuki H, Yoshimi Y. Double difunctionalization of vinyl ether tethered nucleophile with electron-deficient alkene in two-molecule photoredox system. Photochem Photobiol Sci 2024; 23:1417-1423. [PMID: 38703275 DOI: 10.1007/s43630-024-00588-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Accepted: 04/24/2024] [Indexed: 05/06/2024]
Abstract
Double difunctionalization of a vinyl ether tethered hydroxy or carbamoyl group with electron-deficient alkenes such as acrylonitrile or acrylic esters was achieved by visible-light irradiation in a two-molecule photoredox system. Use of anhydrous acetonitrile solution as a solvent promoted both dimerization of the radical cation of electron-rich alkene with electron-rich alkene and intramolecular nucleophilic addition to generate an electron-rich radical that was added to electron-deficient alkene to furnish the double difunctionalized product. A variety of electronically differentiated rich and deficient alkenes were used in the photoreaction; a simple construction of a complex carbon framework containing acetal from simple alkenes was successful under mild conditions.
Collapse
Affiliation(s)
- Takumi Ikeda
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui, 910-8507, Japan
| | - Yosuke Tanaka
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui, 910-8507, Japan
| | - Ryoga Hashimoto
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui, 910-8507, Japan
| | - Toshiki Furutani
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui, 910-8507, Japan
- Department of Chemistry and Biology, National Institute of Technology, Fukui College, Genshi-cho, Fukui, 916-8507, Japan
| | - Mugen Yamawaki
- Department of Chemistry and Biology, National Institute of Technology, Fukui College, Genshi-cho, Fukui, 916-8507, Japan
| | - Hirotsugu Suzuki
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui, 910-8507, Japan
| | - Yasuharu Yoshimi
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui, 910-8507, Japan.
| |
Collapse
|
2
|
Zhang T, Huang H. Photocatalyzed Aminomethylation of Alkyl Halides Enabled by Sterically Hindered N-Substituents. Angew Chem Int Ed Engl 2023; 62:e202310114. [PMID: 37721856 DOI: 10.1002/anie.202310114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Revised: 09/16/2023] [Accepted: 09/18/2023] [Indexed: 09/20/2023]
Abstract
The catalytic C(sp3 )-C(sp3 ) coupling of alkyl halides and tertiary amines offers a promising tool for the rapid decoration of amine skeletons. However, this approach has not been well established, partially due to the challenges in precisely distinguishing and controlling the reactivity of amine-coupling partners and their product homologues. Herein, we developed a metal-free photocatalytic system for the aminomethylation of alkyl halides through radical-involved C(sp3 )-C(sp3 ) bond formation, allowing for the synthesis of sterically congested tertiary amines that are of interest in organic synthesis but not easily prepared by other methods. Mechanistic studies disclosed that sterically hindered N-substituents are key to activate the amine coupling partners by tuning their redox potentials to drive the reaction forward.
Collapse
Affiliation(s)
- Tianze Zhang
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Chemistry, University of Science and Technology of China, Hefei, 230026, P. R. China
| | - Hanmin Huang
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Chemistry, University of Science and Technology of China, Hefei, 230026, P. R. China
- Key Laboratory of Green and Precise Synthetic Chemistry and Applications, Ministry of Education, Huaibei Normal University, Huaibei, 235000, P. R. China
| |
Collapse
|
3
|
Polyansky DE, Manbeck GF, Ertem MZ. Combined Effects of Hemicolligation and Ion Pairing on Reduction Potentials of Biphenyl Radical Cations. J Phys Chem A 2023; 127:7918-7927. [PMID: 37721794 DOI: 10.1021/acs.jpca.3c03817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2023]
Abstract
Formal reduction potentials of highly oxidizing and short-lived radical cations of substituted biphenyls generated by pulse radiolysis in 1,2-dichloroethane (DCE) were measured using a redox equilibrium ladder method. The effect of halide ion-radical interactions on reduction potentials of biphenyls was examined by utilizing the ability of DCE to release Cl- in the vicinity of the radical cation. The Hammett correlation of measured potentials across a range of over 700 mV shows saturation at high Hammett sigma values. This effect has been explained by both ion-pairing and hemicolligation interactions between biphenyl radical cations and Cl- and appears to modulate reduction potentials by as much as 400 mV. This finding offers a convenient way to manipulate the energetics of electron transfer involving organic redox species.
Collapse
Affiliation(s)
- Dmitry E Polyansky
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
| | - Gerald F Manbeck
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
| | - Mehmed Z Ertem
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
| |
Collapse
|
4
|
Abstract
The quest to find milder and more sustainable methods to generate highly reactive, carbon-centred intermediates has led to a resurgence of interest in radical chemistry. In particular, carboxylic acids are seen as attractive radical precursors due their availability, low cost, diversity, and sustainability. Moreover, the corresponding nucleophilic carbon-radical can be easily accessed through a favourable radical decarboxylation process, extruding CO2 as a traceless by-product. This review summarizes the recent progress on using carboxylic acids directly as convenient radical precursors for the formation of carbon-carbon bonds via the 1,4-radical conjugate addition (Giese) reaction.
Collapse
Affiliation(s)
- David M Kitcatt
- Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK.
| | - Simon Nicolle
- GlaxoSmithKline, Gunnels Wood Rd, Stevenage SG1 2NY, UK
| | - Ai-Lan Lee
- Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK.
| |
Collapse
|
5
|
Feinberg EC, Dinnocenzo JP. Mechanism and Selectivity of Aryltrimethylgermane Cation Radical Fragmentations. J Org Chem 2020; 85:8639-8644. [PMID: 32530642 DOI: 10.1021/acs.joc.0c01032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Aryltrimethylgermane cation radicals were generated by nanosecond transient absorption spectroscopy. Transient kinetics experiments show that the aryltrimethylgermane cation radicals react with added nucleophiles in reactions that are first-order in both the cation radicals and the nucleophiles. Preparative photo-oxidation experiments demonstrate that the intermediate cation radicals react with nucleophiles, resulting in aryl-Ge or Me-Ge nucleophile-assisted fragmentations. The aryltrimethylgermane cation radicals were found to react more slowly than analogous stannane cation radicals; however, loss of the thermodynamically disfavored aryl radicals remains competitive with methyl radical loss.
Collapse
Affiliation(s)
- Elizabeth C Feinberg
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Joseph P Dinnocenzo
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| |
Collapse
|
6
|
Kubosaki S, Takeuchi H, Iwata Y, Tanaka Y, Osaka K, Yamawaki M, Morita T, Yoshimi Y. Visible- and UV-Light-Induced Decarboxylative Radical Reactions of Benzoic Acids Using Organic Photoredox Catalysts. J Org Chem 2020; 85:5362-5369. [DOI: 10.1021/acs.joc.0c00055] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Suzuka Kubosaki
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Haruka Takeuchi
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Yutaka Iwata
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Yosuke Tanaka
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Kazuyuki Osaka
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Mugen Yamawaki
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Toshio Morita
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Yasuharu Yoshimi
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| |
Collapse
|
7
|
Morris W, Lorance ED, Gould IR. Understanding the Solvent Contribution to Chemical Reaction Barriers. J Phys Chem A 2019; 123:10490-10499. [PMID: 31724860 DOI: 10.1021/acs.jpca.9b06310] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Absolute rate theories attempt to predict the rate constants of reactions from basic principles and independent data. For the contribution of solvent to a reaction rate constant, this requires connecting absolute rate data to fundamental solvent properties such as dielectric constant and refractive index. We have explored this connection for the unimolecular fragmentation reaction of a pinacol radical cation. The rate constants for fragmentation were measured as a function of temperature in 12 different solvents with dielectric constants from 4.7 to 36.2, and the free energies of activation for bond fragmentation in each solvent determined using transition state theory. Using the solvent effects on electron-transfer reactions as a starting point, Marcus theory was used to model the solvent effect on the reaction activation energies. The solvent contribution to both the activation free energy and the overall reaction energy is best described using the Born model rather than the Pekar solvation model. The solvent reorganization energies for bond fragmentation are substantially larger than solvent reorganization energies for electron transfer, presumably because of the requirement to translate the solvent molecules in the course of bond breaking.
Collapse
Affiliation(s)
- William Morris
- School of Molecular Sciences , Arizona State University , Tempe , Arizona 85287 , United States
| | - Edward D Lorance
- Department of Chemistry , Vanguard University , Costa Mesa , California 92626 , United States
| | - Ian R Gould
- School of Molecular Sciences , Arizona State University , Tempe , Arizona 85287 , United States
| |
Collapse
|
8
|
Buzzetti L, Crisenza GEM, Melchiorre P. Mechanistic Studies in Photocatalysis. Angew Chem Int Ed Engl 2019; 58:3730-3747. [DOI: 10.1002/anie.201809984] [Citation(s) in RCA: 357] [Impact Index Per Article: 71.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Indexed: 12/18/2022]
Affiliation(s)
- Luca Buzzetti
- ICIQ—Institute of Chemical Research of Catalonia the Barcelona Institute of Science and Technology Avenida Països Catalans 16 43007 Tarragona Spain
| | - Giacomo E. M. Crisenza
- ICIQ—Institute of Chemical Research of Catalonia the Barcelona Institute of Science and Technology Avenida Països Catalans 16 43007 Tarragona Spain
| | - Paolo Melchiorre
- ICIQ—Institute of Chemical Research of Catalonia the Barcelona Institute of Science and Technology Avenida Països Catalans 16 43007 Tarragona Spain
- ICREA—Catalan Institution for Research and Advanced Studies Passeig Lluís Companys 23 08010 Barcelona Spain
- IIT—Istituto Italiano di TecnologiaLaboratory of Asymmetric Catalysis and Photochemistry Via Morego 30 16163 Genoa Italy
| |
Collapse
|
9
|
Buzzetti L, Crisenza GEM, Melchiorre P. Mechanistische Studien in der Photokatalyse. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201809984] [Citation(s) in RCA: 95] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Luca Buzzetti
- ICIQ—Institute of Chemical Research of Catalonia the Barcelona Institute of Science and Technology Avenida Països Catalans 16 43007 Tarragona Spanien
| | - Giacomo E. M. Crisenza
- ICIQ—Institute of Chemical Research of Catalonia the Barcelona Institute of Science and Technology Avenida Països Catalans 16 43007 Tarragona Spanien
| | - Paolo Melchiorre
- ICIQ—Institute of Chemical Research of Catalonia the Barcelona Institute of Science and Technology Avenida Països Catalans 16 43007 Tarragona Spanien
- ICREA—Catalan Institution for Research and Advanced Studies Passeig Lluís Companys 23 08010 Barcelona Spanien
- IIT—Istituto Italiano di TecnologiaLaboratory of Asymmetric Catalysis and Photochemistry Via Morego 30 16163 Genoa Italy
| |
Collapse
|
10
|
Kammer LM, Lipp B, Opatz T. Photoredox Alkenylation of Carboxylic Acids and Peptides: Synthesis of Covalent Enzyme Inhibitors. J Org Chem 2018; 84:2379-2392. [DOI: 10.1021/acs.joc.8b02759] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
|
11
|
Lenczewski MS, de Lijser HJP, Turner DM, Dinnocenzo JP. Stereochemistry of Nucleophilic Substitutions on Benzyl-silane and -germane Cation Radicals: Application of the Endocyclic Restriction Test. J Org Chem 2017; 82:12112-12118. [PMID: 29094591 DOI: 10.1021/acs.joc.7b01892] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Benzyltrialkylgermane cation radicals were generated and spectroscopically characterized by nanosecond transient absorption spectroscopy. The germane cation radicals were found to rapidly react with nucleophiles (e.g., alcohols) in reactions that were first-order in cation radical and first-order in nucleophile. The geometries of the transition states for nucleophilic substitutions on benzyl-silane and -germane cation radicals were investigated by using the endocyclic restriction test. Cation radicals containing tethered nucleophiles that required endocyclic transition states with small angles between the bond being formed to the nucleophilic atom and the bond to the leaving group reacted ∼250 times more slowly than cation radicals with tethered nucleophiles where a large bond angle can be accommodated. The results are consistent with the nucleophile-assisted fragmentations proceeding through an inversion transition state.
Collapse
Affiliation(s)
- Mary S Lenczewski
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States
| | - H J Peter de Lijser
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States
| | - David M Turner
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States
| | - Joseph P Dinnocenzo
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States
| |
Collapse
|
12
|
Affiliation(s)
- Joseph P. Dinnocenzo
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Paul B. Merkel
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Samir Farid
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| |
Collapse
|
13
|
Dinnocenzo JP, Feinberg EC, Farid S. Multiple Intermolecular Exciplexes in Highly Polar Solvents. J Phys Chem A 2017; 121:3662-3670. [PMID: 28475349 DOI: 10.1021/acs.jpca.7b01461] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Exciplexes of 2,6,9,10-tetracyanoanthracene (TCA) with alkylbenzenes were investigated in solvents ranging from cyclohexane to acetonitrile. Plots of the reduced emission maxima or the average emission frequency (hνav) versus redox potential differences (Eredox) were linear with a slope of ∼1 in all solvents, which is consistent with the highly ionic character of the exciplexes. The exciplex spectra were analyzed in terms of the energy gap between the exciplex minimum and the AD pair (ΔG), the energy difference between ΔG and Eredox (δEx), and the total reorganization energy (Σλ). A plot of (Eredox - hνav), equivalent to (Σλ - δEx), versus a solvent polarity function showed a linear dependency for the low-to-moderate polarity solvents, whereas highly polar solvents deviated significantly. δEx showed a smooth linear dependency for all solvents. Thus, the deviation of the polar solvents is due to a larger-than-expected Σλ. Additionally, the full width at half-maximum (fwhm) of the emission spectra in polar solvents deviates significantly from the extrapolated trend in less-polar solvents. The deviations of Σλ and fwhm in highly polar solvents can plausibly be explained by composite emissions from two exciplex structures, with the donor overlapping with the inner or outer ring of TCA.
Collapse
Affiliation(s)
- Joseph P Dinnocenzo
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States
| | - Elizabeth C. Feinberg
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States
| | - Samir Farid
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States
| |
Collapse
|
14
|
Matsui Y, Ikeda T, Takahashi Y, Kamata M, Akagi M, Ohya Y, Fujino R, Namai H, Ohta E, Ogaki T, Miyashi T, Tero‐Kubota S, Mizuno K, Ikeda H. Electron‐Transfer Reactions Triggered by Uncharged or Cationic Photosensitizer: Methodology for Generation of
o
‐Quinodimethane and Analysis of Back Electron‐Transfer Process. ASIAN J ORG CHEM 2017. [DOI: 10.1002/ajoc.201600570] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Yasunori Matsui
- Department of Applied Chemistry Graduate School of Engineering Osaka Prefecture University Sakai Osaka 599–8531 Japan
- The Research Institute for Molecular Electronic Devices (RIMED) Osaka Prefecture University Sakai Osaka 599–8531 Japan
| | - Teruyo Ikeda
- Department of Chemistry Graduate School of Science Tohoku University Sendai 980–8578 Japan
| | - Yasutake Takahashi
- Division of Chemistry Graduate School of Medicine and Pharmaceutical Sciences University of Toyama Toyama 930-0194 Japan
| | - Masaki Kamata
- Department of Chemistry Faculty of Education Niigata University Igarashi Niigata 950–2181 Japan
| | - Megumi Akagi
- Department of Chemistry Graduate School of Science Tohoku University Sendai 980–8578 Japan
| | - Yukako Ohya
- Department of Chemistry Graduate School of Science Tohoku University Sendai 980–8578 Japan
| | - Ryota Fujino
- Department of Chemistry Faculty of Education Niigata University Igarashi Niigata 950–2181 Japan
| | - Hayato Namai
- Department of Chemistry Graduate School of Science Tohoku University Sendai 980–8578 Japan
| | - Eisuke Ohta
- Department of Applied Chemistry Graduate School of Engineering Osaka Prefecture University Sakai Osaka 599–8531 Japan
- The Research Institute for Molecular Electronic Devices (RIMED) Osaka Prefecture University Sakai Osaka 599–8531 Japan
| | - Takuya Ogaki
- Department of Applied Chemistry Graduate School of Engineering Osaka Prefecture University Sakai Osaka 599–8531 Japan
- The Research Institute for Molecular Electronic Devices (RIMED) Osaka Prefecture University Sakai Osaka 599–8531 Japan
| | - Tsutomu Miyashi
- Department of Chemistry Graduate School of Science Tohoku University Sendai 980–8578 Japan
| | - Shozo Tero‐Kubota
- Institute of Multidisciplinary Research for Advanced Materials Tohoku University Sendai 980–8577 Japan
| | - Kazuhiko Mizuno
- Department of Applied Chemistry Graduate School of Engineering Osaka Prefecture University Sakai Osaka 599–8531 Japan
| | - Hiroshi Ikeda
- Department of Applied Chemistry Graduate School of Engineering The Research Institute for Molecular Electronic Devices (RIMED) Osaka Prefecture University Sakai Osaka 599–8531 Japan
| |
Collapse
|
15
|
Capaldo L, Buzzetti L, Merli D, Fagnoni M, Ravelli D. Smooth Photocatalyzed Benzylation of Electrophilic Olefins via Decarboxylation of Arylacetic Acids. J Org Chem 2016; 81:7102-9. [DOI: 10.1021/acs.joc.6b00984] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Luca Capaldo
- PhotoGreen Lab, Department
of Chemistry, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy
| | - Luca Buzzetti
- PhotoGreen Lab, Department
of Chemistry, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy
| | - Daniele Merli
- PhotoGreen Lab, Department
of Chemistry, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy
| | - Maurizio Fagnoni
- PhotoGreen Lab, Department
of Chemistry, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy
| | - Davide Ravelli
- PhotoGreen Lab, Department
of Chemistry, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy
| |
Collapse
|
16
|
Cao R, Saracini C, Ginsbach JW, Kieber-Emmons MT, Siegler MA, Solomon EI, Fukuzumi S, Karlin KD. Peroxo and Superoxo Moieties Bound to Copper Ion: Electron-Transfer Equilibrium with a Small Reorganization Energy. J Am Chem Soc 2016; 138:7055-66. [PMID: 27228314 DOI: 10.1021/jacs.6b02404] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Oxygenation of [Cu2(UN-O(-))(DMF)](2+) (1), a structurally characterized dicopper Robin-Day class I mixed-valent Cu(II)Cu(I) complex, with UN-O(-) as a binucleating ligand and where dimethylformamide (DMF) binds to the Cu(II) ion, leads to a superoxo-dicopper(II) species [Cu(II)2(UN-O(-))(O2(•-))](2+) (2). The formation kinetics provide that kon = 9 × 10(-2) M(-1) s(-1) (-80 °C), ΔH(‡) = 31.1 kJ mol(-1) and ΔS(‡) = -99.4 J K(-1) mol(-1) (from -60 to -90 °C data). Complex 2 can be reversibly reduced to the peroxide species [Cu(II)2(UN-O(-))(O2(2-))](+) (3), using varying outer-sphere ferrocene or ferrocenium redox reagents. A Nernstian analysis could be performed by utilizing a monodiphenylamine substituted ferrocenium salt to oxidize 3, leading to an equilibrium mixture with Ket = 5.3 (-80 °C); a standard reduction potential for the superoxo-peroxo pair is calculated to be E° = +130 mV vs SCE. A literature survey shows that this value falls into the range of biologically relevant redox reagents, e.g., cytochrome c and an organic solvent solubilized ascorbate anion. Using mixed-isotope resonance Raman (rRaman) spectroscopic characterization, accompanied by DFT calculations, it is shown that the superoxo complex consists of a mixture of μ-1,2- (2(1,2)) and μ-1,1- (2(1,1)) isomers, which are in rapid equilibrium. The electron transfer process involves only the μ-1,2-superoxo complex [Cu(II)2(UN-O(-))(μ-1,2-O2(•-))](2+) (2(1,2)) and μ-1,2-peroxo structures [Cu(II)2(UN-O(-))(O2(2-))](+) (3) having a small bond reorganization energy of 0.4 eV (λin). A stopped-flow kinetic study results reveal an outer-sphere electron transfer process with a total reorganization energy (λ) of 1.1 eV between 2(1,2) and 3 calculated in the context of Marcus theory.
Collapse
Affiliation(s)
- Rui Cao
- Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States
| | - Claudio Saracini
- Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States.,Department of Chemistry and Nano Science, Ewha Womans University , Seoul 120-750, Korea
| | - Jake W Ginsbach
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | | | - Maxime A Siegler
- Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Shunichi Fukuzumi
- Faculty of Science and Engineering, ALCA, SENTAN, Japan Science and Technology Agency (JST), Meijo University , Nagoya, Aichi 468-0073, Japan.,Department of Chemistry and Nano Science, Ewha Womans University , Seoul 120-750, Korea
| | - Kenneth D Karlin
- Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States
| |
Collapse
|
17
|
Pitts CR, Ling B, Snyder JA, Bragg AE, Lectka T. Aminofluorination of Cyclopropanes: A Multifold Approach through a Common, Catalytically Generated Intermediate. J Am Chem Soc 2016; 138:6598-609. [DOI: 10.1021/jacs.6b02838] [Citation(s) in RCA: 114] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Cody Ross Pitts
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Bill Ling
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Joshua A. Snyder
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Arthur E. Bragg
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Thomas Lectka
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| |
Collapse
|
18
|
Luo P, Dinnocenzo JP. Mechanism and Unusual Fragmentation Selectivities of Aryltrialkylstannane Cation Radicals. J Org Chem 2015; 80:9240-6. [PMID: 26332071 DOI: 10.1021/acs.joc.5b01690] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Aryltrialkylstannane cation radicals were generated and characterized by nanosecond transient absorption spectroscopy. Kinetics show the fragmentations of the stannane cation radicals occur by a bimolecular, nucleophile-assisted mechanism (S(N)2). Consistent with this hypothesis, steric effects on both the nucleophile and the stannane cation radicals were observed. Steady-state, preparative photooxidation experiments show that aryltrimethylstannane cation radicals have an unusual preference for loss of aryl radicals over methyl radicals and that the selectivity for aryl vs methyl radical loss is dependent on the identity of the nucleophile. The preference for loss of aryl radicals is rationalized by a hypothesis based on Bent's rules.
Collapse
Affiliation(s)
- Pu Luo
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States
| | - Joseph P Dinnocenzo
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States
| |
Collapse
|
19
|
Cruz H, Bourdelande JL, Gallardo I, Guirado G. Combining Nanosecond and Millisecond Time Scale Techniques: Determination of Thermodynamic and Kinetic data of Primary Alkyl Amine Cation Radicals. J Phys Chem A 2015; 119:620-33. [DOI: 10.1021/jp5109366] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Hugo Cruz
- Departament de Química, Univeristat Autònoma de Barcelona, 08193-Bellaterra, Barcelona, Spain
| | - Jose Luis Bourdelande
- Departament de Química, Univeristat Autònoma de Barcelona, 08193-Bellaterra, Barcelona, Spain
| | - Iluminada Gallardo
- Departament de Química, Univeristat Autònoma de Barcelona, 08193-Bellaterra, Barcelona, Spain
| | - Gonzalo Guirado
- Departament de Química, Univeristat Autònoma de Barcelona, 08193-Bellaterra, Barcelona, Spain
| |
Collapse
|
20
|
Schroeder CA, Pluhařová E, Seidel R, Schroeder WP, Faubel M, Slavíček P, Winter B, Jungwirth P, Bradforth SE. Oxidation half-reaction of aqueous nucleosides and nucleotides via photoelectron spectroscopy augmented by ab initio calculations. J Am Chem Soc 2014; 137:201-9. [PMID: 25551179 DOI: 10.1021/ja508149e] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Oxidative damage to DNA and hole transport between nucleobases in oxidized DNA are important processes in lesion formation for which surprisingly poor thermodynamic data exist, the relative ease of oxidizing the four nucleobases being one such example. Theoretical simulations of radiation damage and charge transport in DNA depend on accurate values for vertical ionization energies (VIEs), reorganization energies, and standard reduction potentials. Liquid-jet photoelectron spectroscopy can be used to directly study the oxidation half-reaction. The VIEs of nucleic acid building blocks are measured in their native buffered aqueous environment. The experimental investigation of purine and pyrimidine nucleotides, nucleosides, pentose sugars, and inorganic phosphate demonstrates that photoelectron spectra of nucleotides arise as a spectral sum over their individual chemical components; that is, the electronic interactions between each component are effectively screened from one another by water. Electronic structure theory affords the assignment of the lowest energy photoelectron band in all investigated nucleosides and nucleotides to a single ionizing transition centered solely on the nucleobase. Thus, combining the measured VIEs with theoretically determined reorganization energies allows for the spectroscopic determination of the one-electron redox potentials that have been difficult to establish via electrochemistry.
Collapse
Affiliation(s)
- Christi A Schroeder
- Department of Chemistry, University of Southern California , Los Angeles, California 90089-0482, United States
| | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Transition from Charge-Transfer to Largely Locally Excited Exciplexes, from Structureless to Vibrationally Structured Emissions. Photochem Photobiol 2014; 91:624-36. [DOI: 10.1111/php.12380] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 10/08/2014] [Indexed: 01/02/2023]
|
22
|
Luo P, Feinberg EC, Guirado G, Farid S, Dinnocenzo JP. Accurate Oxidation Potentials of 40 Benzene and Biphenyl Derivatives with Heteroatom Substituents. J Org Chem 2014; 79:9297-304. [DOI: 10.1021/jo501761c] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Pu Luo
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Elizabeth C. Feinberg
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Gonzalo Guirado
- Departament de Química (Quimica-Fisica), Universitat Autònoma de Barcelona, Edifi C, 08193 Bellaterra, Barcelona, Spain
| | - Samir Farid
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Joseph P. Dinnocenzo
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| |
Collapse
|
23
|
Carlotti B, Del Giacco T, Elisei F. Competition of C–H and C–O fragmentation in substituted p-methoxybenzyl ether radical cations generated by photosensitized oxidation. Photochem Photobiol Sci 2013. [DOI: 10.1039/c2pp25335f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
24
|
Luo P, Dinnocenzo JP, Merkel PB, Young RH, Farid S. Bimolecular electron transfers that deviate from the Sandros-Boltzmann dependence on free energy: steric effect. J Org Chem 2012; 77:1632-9. [PMID: 22283183 DOI: 10.1021/jo202385f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
As we reported recently, endergonic to mildly exergonic electron transfer between neutral aromatics (benzenes and biphenyls) and their radical cations in acetonitrile follows a Sandros-Boltzmann (SB) dependency on the reaction free energy (ΔG); i.e., the rate constant is proportional to 1/[1 + exp(ΔG/RT)]. We now report deviations from this dependency when one reactant is sterically crowded: 1,4-di-tert-butylbenzene (C1), 1,3,5-tri-tert-butylbenzene (C2), or hexaethylbenzene (C3). Obvious deviation from SB behavior is observed with C1. Stronger deviation is observed with the more crowded C2 and C3, where steric hindrance increases the interplanar separation at contact by ~1 Å, significantly decreasing the π orbital overlap. Consequently, electron transfer (k(et)) within the contact pair becomes slower than diffusional separation (k(-d)), causing deviation from the SB dependency, especially near ΔG = 0. Fitting the data to a standard electron-transfer theory gives small matrix elements (~5-7 meV) and reasonable reorganization energies. A small systematic difference between reactions of C3 with benzenes vs biphenyls is rationalized in terms of small differences in the electron-transfer parameters that are consistent with previous data. The influence of solvent viscosity on the competition between k(et) and k(-d) was investigated by comparing reactions in acetonitrile and propylene carbonate.
Collapse
Affiliation(s)
- Pu Luo
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | | | | | | | | |
Collapse
|
25
|
Roth HD, Sauers RR. Radical cations and triplet states of 1,2-disubstituted cyclopropanes: comparison of potential surfaces. Photochem Photobiol Sci 2012; 11:931-7. [DOI: 10.1039/c1pp05334e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
26
|
Farid S, Dinnocenzo JP, Merkel PB, Young RH, Shukla D, Guirado G. Reexamination of the Rehm-Weller data set reveals electron transfer quenching that follows a Sandros-Boltzmann dependence on free energy. J Am Chem Soc 2011; 133:11580-7. [PMID: 21736293 DOI: 10.1021/ja2024367] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In a landmark publication over 40 years ago, Rehm and Weller (RW) showed that the electron transfer quenching constants for excited-state molecules in acetonitrile could be correlated with the excited-state energies and the redox potentials of the electron donors and acceptors. The correlation was interpreted in terms of electron transfer between the molecules in the encounter pair (A*/D ⇌ A(•-)/D(•+) for acceptor A and donor D) and expressed by a semiempirical formula relating the quenching constant, k(q), to the free energy of reaction, ΔG. We have reinvestigated the mechanism for many Rehm and Weller reactions in the endergonic or weakly exergonic regions. We find they are not simple electron transfer processes. Rather, they involve exciplexes as the dominant, kinetically and spectroscopically observable intermediate. Thus, the Rehm-Weller formula rests on an incorrect mechanism. We have remeasured k(q) for many of these reactions and also reevaluated the ΔG values using accurately determined redox potentials and revised excitation energies. We found significant discrepancies in both ΔG and k(q), including A*/D pairs at high endergonicity that did not exhibit any quenching. The revised data were found to obey the Sandros-Boltzmann (SB) equation k(q) = k(lim)/[1 + exp[(ΔG + s)/RT]]. This behavior is attributed to rapid interconversion among the encounter pairs and the exciplex (A*/D ⇌ exciplex ⇌ A(•-)/D(•+)). The quantity k(lim) represents approximately the diffusion-limited rate constant, and s the free energy difference between the radical ion encounter pair and the free radical ions (A(•-)/D(•+) vs A(•-) + D(•+)). The shift relative to ΔG for the overall reaction is positive, s = 0.06 eV, rather than the negative value of -0.06 eV assumed by RW. The positive value of s involves the poorer solvation of A(•-)/D(•+) relative to the free A(•-) + D(•+), which opposes the Coulombic stabilization of A(•-)/D(•+). The SB equation does not involve the microscopic rate constants for interconversion among the encounter pairs and the exciplex. Data that fit this equation contain no information about such rate constants except that they are faster than dissociation of the encounter pairs to (re-)form the corresponding free species (A* + D or A(•-) + D(•+)). All of the present conclusions agree with our recent results for quenching of excited cyanoaromatic acceptors by aromatic donors, with the two data sets showing indistinguishable dependencies of k(q) on ΔG.
Collapse
Affiliation(s)
- Samir Farid
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
| | | | | | | | | | | |
Collapse
|
27
|
Rijksen B, van Lagen B, Zuilhof H. Mimicking the Silicon Surface: Reactivity of Silyl Radical Cations toward Nucleophiles. J Am Chem Soc 2011; 133:4998-5008. [DOI: 10.1021/ja110844e] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Bart Rijksen
- Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB Wageningen, The Netherlands
| | - Barend van Lagen
- Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB Wageningen, The Netherlands
| | - Han Zuilhof
- Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB Wageningen, The Netherlands
| |
Collapse
|
28
|
Farid S, Dinnocenzo JP, Merkel PB, Young RH, Shukla D. Bimolecular electron transfers that follow a Sandros-Boltzmann dependence on free energy. J Am Chem Soc 2011; 133:4791-801. [PMID: 21384880 DOI: 10.1021/ja104536j] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Rate constants (k) for exergonic and endergonic electron-transfer reactions of equilibrating radical cations (A(•+) + B ⇌ A + B(•+)) in acetonitrile could be fit well by a simple Sandros-Boltzmann (SB) function of the reaction free energy (ΔG) having a plateau with a limiting rate constant k(lim) in the exergonic region, followed, near the thermoneutral point, by a steep drop in log k vs ΔG with a slope of 1/RT. Similar behavior was observed for another charge shift reaction, the electron-transfer quenching of excited pyrylium cations (P(+)*) by neutral donors (P(+)* + D → P(•) + D(•+)). In this case, SB dependence was observed when the logarithm of the quenching constant (log k(q)) was plotted vs ΔG + s, where the shift term, s, equals +0.08 eV and ΔG is the free energy change for the net reaction (E(redox) - E(excit)). The shift term is attributed to partial desolvation of the radical cation in the product encounter pair (P(•)/D(•+)), which raises its free energy relative to the free species. Remarkably, electron-transfer quenching of neutral reactants (A* + D → A(•-) + D(•+)) using excited cyanoaromatic acceptors and aromatic hydrocarbon donors was also found to follow an SB dependence of log k(q) on ΔG, with a positive s, +0.06 eV. This positive shift contrasts with the long-accepted prediction of a negative value, -0.06 eV, for the free energy of an A(•-)/D(•+) encounter pair relative to the free radical ions. That prediction incorporated only a Coulombic stabilization of the A(•-)/D(•+) encounter pair relative to the free radical ions. In contrast, the results presented here show that the positive value of s indicates a decrease in solvent stabilization of the A(•-)/D(•+) encounter pair, which outweighs Coulombic stabilization in acetonitrile. These quenching reactions are proposed to proceed via rapidly interconverting encounter pairs with an exciplex as intermediate, A*/D ⇌ exciplex ⇌ A(•-)/D(•+). Weak exciplex fluorescence was observed in each case. For several reactions in the endergonic region, rate constants for the reversible formation and decay of the exciplexes were determined using time-correlated single-photon counting. The quenching constants derived from the transient kinetics agreed well with those from the conventional Stern-Volmer plots. For excited-state electron-transfer processes, caution is required in correlating quenching constants vs reaction free energies when ΔG exceeds ∼+0.1 eV. Beyond this point, additional exciplex deactivation pathways-fluorescence, intersystem crossing, and nonradiative decay-are likely to dominate, resulting in a change in mechanism.
Collapse
Affiliation(s)
- Samir Farid
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
| | | | | | | | | |
Collapse
|
29
|
Guirado G, Haze O, Dinnocenzo JP. Generation and Characterization of 1,2-Diaryl-1,1,2,2-tetramethyldisilane Cation Radicals. J Org Chem 2010; 75:3326-31. [DOI: 10.1021/jo100358y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gonzalo Guirado
- Department of Chemistry and the Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627-0216
| | - Olesya Haze
- Department of Chemistry and the Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627-0216
| | - Joseph P. Dinnocenzo
- Department of Chemistry and the Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627-0216
| |
Collapse
|
30
|
Merkel PB, Luo P, Dinnocenzo JP, Farid S. Accurate Oxidation Potentials of Benzene and Biphenyl Derivatives via Electron-Transfer Equilibria and Transient Kinetics. J Org Chem 2009; 74:5163-73. [DOI: 10.1021/jo9011267] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Paul B. Merkel
- Department of Chemistry and the Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627-0216
| | - Pu Luo
- Department of Chemistry and the Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627-0216
| | - Joseph P. Dinnocenzo
- Department of Chemistry and the Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627-0216
| | - Samir Farid
- Department of Chemistry and the Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627-0216
| |
Collapse
|
31
|
CHENG X, ZHAO Y, LI F, ZHANG D. A Theoretical Investigation on the Reaction Mechanism of the C 9H 12+·Side-chain Decomposition. CHINESE J CHEM 2009. [DOI: 10.1002/cjoc.200990108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
32
|
Wang Y, Haze O, Dinnocenzo JP, Farid S, Farid RS, Gould IR. Bonded Exciplex Formation: Electronic and Stereoelectronic Effects. J Phys Chem A 2008; 112:13088-94. [DOI: 10.1021/jp8041445] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Yingsheng Wang
- Department of Chemistry and Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627, Schrödinger, Inc., 120 West 45th Street, 29th Floor, New York, New York 10036, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287
| | - Olesya Haze
- Department of Chemistry and Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627, Schrödinger, Inc., 120 West 45th Street, 29th Floor, New York, New York 10036, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287
| | - Joseph P. Dinnocenzo
- Department of Chemistry and Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627, Schrödinger, Inc., 120 West 45th Street, 29th Floor, New York, New York 10036, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287
| | - Samir Farid
- Department of Chemistry and Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627, Schrödinger, Inc., 120 West 45th Street, 29th Floor, New York, New York 10036, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287
| | - Ramy S. Farid
- Department of Chemistry and Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627, Schrödinger, Inc., 120 West 45th Street, 29th Floor, New York, New York 10036, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287
| | - Ian R. Gould
- Department of Chemistry and Center for Photoinduced Charge Transfer, University of Rochester, Rochester, New York 14627, Schrödinger, Inc., 120 West 45th Street, 29th Floor, New York, New York 10036, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287
| |
Collapse
|
33
|
Bietti M, Capone A. One-electron oxidation of 2-(4-methoxyphenyl)-2-methylpropanoic and 1-(4-methoxyphenyl)cyclopropanecarboxylic acids in aqueous solution. the involvement of radical cations and the influence of structural effects and pH on the side-chain fragmentation reactivity. J Org Chem 2008; 73:618-29. [PMID: 18076187 DOI: 10.1021/jo702104j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A product and time-resolved kinetic study on the one-electron oxidation of 2-(4-methoxyphenyl)-2-methylpropanoic acid (2), 1-(4-methoxyphenyl)cyclopropanecarboxylic acid (3), and of the corresponding methyl esters (substrates 4 and 5, respectively) has been carried out in aqueous solution. With 2, no direct evidence for the formation of an intermediate radical cation 2*+ but only of the decarboxylated 4-methoxycumyl radical has been obtained, indicating either that 2*+ is not formed or that its decarboxylation is too fast to allow detection under the experimental conditions employed (k > 1 x 10(7) s(-1)). With 3, oxidation leads to the formation of the corresponding radical cation 3*+ or radical zwitterion -3*+ depending on pH. At pH 1.0 and 6.7, 3*+ and -3*+ have been observed to undergo decarboxylation as the exclusive side-chain fragmentation pathway with rate constants k = 4.6 x 10(3) and 2.3 x 10(4) s(-1), respectively. With methyl esters 4 and 5, direct evidence for the formation of the corresponding radical cations 4*+ and 5*+ has been obtained. Both radical cations have been observed to display a very low reactivity and an upper limit for their decay rate constants has been determined as k < 10(3) s(-1). Comparison between the one-electron oxidation reactions of 2 and 3 shows that the replacement of the C(CH3)2 moiety with a cyclopropyl group determines a decrease in decarboxylation rate constant of more than 3 orders of magnitude. This large difference in reactivity has been qualitatively explained in terms of three main contributions: substrate oxidation potential, stability of the carbon-centered radical formed after decarboxylation, and stereoelectronic effects. In basic solution, -3*+ and 5*+ have been observed to react with -OH in a process that is assigned to the -OH-induced ring-opening of the cyclopropane ring, and the corresponding second-order rate constants (k-OH) have been obtained. With -3*+, competition between decarboxylation and -OH-induced cyclopropane ring-opening is observed at pH >or=10, with the latter process that becomes the major fragmentation pathway around pH 12.
Collapse
Affiliation(s)
- Massimo Bietti
- Dipartimento di Scienze e Tecnologie Chimiche, Università Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Rome, Italy.
| | | |
Collapse
|
34
|
Del Giacco T, Faltoni A, Elisei F. Anomalous reactivity of radical cations produced by photosensitized oxidation of 4-methoxybenzyl alcohol derivatives: role of the sensitizer. Phys Chem Chem Phys 2008; 10:200-10. [DOI: 10.1039/b711541e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
35
|
Merkel PB, Dinnocenzo JP. Thermodynamic energies of donor and acceptor triplet states. J Photochem Photobiol A Chem 2008. [DOI: 10.1016/j.jphotochem.2007.06.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
36
|
Wang Y, Haze O, Dinnocenzo JP, Farid S, Farid RS, Gould IR. Bonded Exciplexes. A New Concept in Photochemical Reactions. J Org Chem 2007; 72:6970-81. [PMID: 17676917 DOI: 10.1021/jo071157d] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Charge-transfer quenching of the singlet excited states of cyanoaromatic electron acceptors by pyridine is characterized by a driving force dependence that resembles those of conventional electron-transfer reactions, except that a plot of the log of the quenching rate constants versus the free energy of electron transfer is displaced toward the endothermic region by 0.5-0.8 eV. Specifically, the reactions with pyridine display rapid quenching when conventional electron transfer is highly endothermic. As an example, the rate constant for quenching of the excited dicyanoanthracene is 3.5 x 10(9) M(-1)s(-1), even though formation of a conventional radical ion pair, A*-D*+, is endothermic by approximately 0.6 eV. No long-lived radical ions or exciplex intermediates can be detected on the picosecond to microsecond time scale. Instead, the reactions are proposed to proceed via formation of a previously undescribed, short-lived charge-transfer intermediate we call a "bonded exciplex", A- -D+. The bonded exciplex can be formally thought of as resulting from bond formation between the unpaired electrons of the radical ions A*- and D*+. The covalent bonding interaction significantly lowers the energy of the charge-transfer state. As a result of this interaction, the energy decreases with decreasing separation distance, and near van der Waals contact, the A- -D+ bonded state mixes with the repulsive excited state of the acceptor, allowing efficient reaction to form A- -D+ even when formation of a radical ion pair A*-D*+ is thermodynamically forbidden. Evidence for the bonded exciplex intermediate comes from studies of steric and Coulombic effects on the quenching rate constants and from extensive DFT computations that clearly show a curve crossing between the ground state and the low-energy bonded exciplex state.
Collapse
Affiliation(s)
- Yingsheng Wang
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | | | | | | | | | | |
Collapse
|
37
|
Bonesi SM, Manet I, Freccero M, Fagnoni M, Albini A. Photosensitized oxidation of sulfides: discriminating between the singlet-oxygen mechanism and electron transfer involving superoxide anion or molecular oxygen. Chemistry 2007; 12:4844-57. [PMID: 16598801 DOI: 10.1002/chem.200501144] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The oxidation of diethyl and diphenyl sulfide photosensitized by dicyanoanthracene (DCA), N-methylquinolinium tetrafluoroborate (NMQ(+)), and triphenylpyrylium tetrafluoroborate (TPP(+)) has been explored by steady-state and laser flash photolysis studies in acetonitrile, methanol, and 1,2-dichloroethane. In the Et(2)S/DCA system sulfide-enhanced intersystem crossing leads to generation of (1)O(2), which eventually gives the sulfoxide via a persulfoxide; this mechanism plays no role with Ph(2)S, though enhanced formation of (3)DCA has been demonstrated. In all other cases an electron-transfer (ET) mechanism is involved. Electron-transfer sulfoxidation occurs with efficiency essentially independent of the sulfide structure, is subject to quenching by benzoquinone, and does not lead to Ph(2)SO cooxidation. Formation of the radical cations R(2)S(*+) has been assessed by flash photolysis (medium-dependent yield, dichloroethane>>CH(3)CN>CH(3)OH) and confirmed by quenching with 1,4-dimethoxybenzene. Electron-transfer oxidations occur both when the superoxide anion is generated by the reduced sensitizer (DCA(*-), NMQ(*)) and when this is not the case (TPP(*)). Although it is possible that different mechanisms operate with different ET sensitizers, a plausible unitary mechanism can be proposed. This considers that reaction between R(2)S(*+) and O(2)(*-) mainly involves back electron transfer, whereas sulfoxidation results primarily from the reaction of the sulfide radical cation with molecular oxygen. Calculations indeed show that the initially formed fleeting complex RS(2)(+)...O-O(*) adds to a sulfide molecule and gives strongly stabilized R(2)S-O(*)-(+)O-SR(2) via an accessible transition state. This intermediate gives the sulfoxide, probably via a radical cation chain path. This mechanism explains the larger scope of ET sulfoxidation with respect to the singlet-oxygen process.
Collapse
Affiliation(s)
- Sergio M Bonesi
- CHIDECAR-CONICET, Dep. Quim. Org., Fac. Cien. Ex. Nat. Universidad de Buenos Aires, Ciudad Universidaria, 1428 Buenos Aires, Argentina
| | | | | | | | | |
Collapse
|
38
|
Crespo-Hernandez CE, Close DM, Gorb L, Leszczynski J. Determination of Redox Potentials for the Watson−Crick Base Pairs, DNA Nucleosides, and Relevant Nucleoside Analogues. J Phys Chem B 2007; 111:5386-95. [PMID: 17447808 DOI: 10.1021/jp0684224] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Redox potentials for the DNA nucleobases and nucleosides, various relevant nucleoside analogues, Watson-Crick base pairs, and seven organic dyes are presented based on DFT/B3LYP/6-31++G(d,p) and B3YLP/6-311+G(2df,p)//B3LYP/6-31+G* levels of calculations. The values are determined from an experimentally calibrated set of equations that correlate the vertical ionization (electron affinity) energy of 20 organic molecules with their experimental reversible oxidation (reduction) potential. Our results are in good agreement with those estimated experimentally for the DNA nucleosides in acetonitrile solutions (Seidel et al. J. Phys. Chem. 1996, 100, 5541). We have found that nucleosides with anti conformation exhibit lower oxidation potentials than the corresponding syn conformers. The lowering in the oxidation potential is due to the formation of an intramolecular hydrogen bonding interaction between the 5'-OH group of the sugar and the N3 of the purine bases or C2=O of the pyrimidine bases in the syn conformation. Pairing of adenine or guanine with its complementary pyrimidine base decreases its oxidation potential by 0.15 or 0.28 V, respectively. The calculated energy difference between the oxidation potential for the G.C base pair and that of the guanine base is in good agreement with the experimental value estimated recently (0.34 V: Caruso, T.; et al. J. Am. Chem. Soc. 2005, 127, 15040). The complete and consistent set of reversible redox values determined in this work for the DNA constituents is expected to be of considerable value to those studying charge and electronic energy transfer in DNA.
Collapse
Affiliation(s)
- Carlos E Crespo-Hernandez
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
| | | | | | | |
Collapse
|
39
|
Bourdelande JL, Gallardo I, Guirado G. Inductive vs solvation effects in primary alkyl amines: determination of the standard potentials. J Am Chem Soc 2007; 129:2817-21. [PMID: 17298061 DOI: 10.1021/ja0656245] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The determination of the standard potential of alkyl primary amines is reported for the first time using the nanosecond equilibrium method. The versatility and accuracy of the method demonstrates that it is not only an alternative to the classical and modern electrochemical methods, but also a powerful tool for quantifying inductive and/or solvation effects in a related family of compounds. Two different trends were observed depending on alkyl chain length. For "short-chain" alkyl primary amines, where the solvation around the amino group is expected to be the same, the standard potential value appears to follow a linear relationship with the number of carbon atoms, which indicates that the methylene group (-CH2-) causes an inductive effect that is responsible for the stabilization of the amine cation radical. Meanwhile, the E(o) rises slightly to a constant potential value 1.500 V for "long-chain" unbranched alkyl primary amines. This interesting result can be explained by a steric inhibition of solvation around the amino group due to a fold of the long alkyl chain following a solvent exclusion mechanism.
Collapse
Affiliation(s)
- José Luis Bourdelande
- ConDepartament de Química, Universitat Autonoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain
| | | | | |
Collapse
|
40
|
Gould IR, Wosinska ZM, Farid S. Kinetic Determinations of Accurate Relative Oxidation Potentials of Amines with Reactive Radical Cations†. Photochem Photobiol 2006; 82:104-9. [PMID: 16489849 DOI: 10.1562/2005-06-14-ra-571] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Accurate oxidation potentials for organic compounds are critical for the evaluation of thermodynamic and kinetic properties of their radical cations. Except when using a specialized apparatus, electrochemical oxidation of molecules with reactive radical cations is usually an irreversible process, providing peak potentials, E(p), rather than thermodynamically meaningful oxidation potentials, E(ox). In a previous study on amines with radical cations that underwent rapid decarboxylation, we estimated E(ox) by correcting the E(p) from cyclic voltammetry with rate constants for decarboxylation obtained using laser flash photolysis. Here we use redox equilibration experiments to determine accurate relative oxidation potentials for the same amines. We also describe an extension of these experiments to show how relative oxidation potentials can be obtained in the absence of equilibrium, from a complete kinetic analysis of the reversible redox kinetics. The results provide support for the previous cyclic voltammetry/laser flash photolysis method for determining oxidation potentials.
Collapse
Affiliation(s)
- Ian R Gould
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA.
| | | | | |
Collapse
|
41
|
Dombrowski GW, Dinnocenzo JP, Zielinski PA, Farid S, Wosinska ZM, Gould IR. Efficient Unimolecular Deprotonation of Aniline Radical Cations. J Org Chem 2005; 70:3791-800. [PMID: 15876062 DOI: 10.1021/jo047813g] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[reaction: see text] Deprotonation of the radical cations of aromatic amines, such as anilines, generally occurs much more slowly than other fragmentation reactions. Here we report a stereoelectronic effect involving twisting of the anilino group out of the plane of the benzene ring that results in a significantly increased rate of reactivity toward deprotonation. Quantitative studies of the rate constants for deprotonation as a function of aniline radical cation pKa (Brønsted plots) demonstrate that the effect is not simply due to a change in the reaction thermodynamics. By combining this stereoelectronic effect with covalent attachment of carboxylate as a base, aniline radical cations that undergo unimolecular deprotonation with rate constants as high as 10(8) s(-1), even in unfavorable protic media, are described.
Collapse
Affiliation(s)
- Gary W Dombrowski
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, USA
| | | | | | | | | | | |
Collapse
|