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Armstrong DA, Huie RE, Koppenol WH, Lymar SV, Merényi G, Neta P, Ruscic B, Stanbury DM, Steenken S, Wardman P. Standard electrode potentials involving radicals in aqueous solution: inorganic radicals (IUPAC Technical Report). PURE APPL CHEM 2015. [DOI: 10.1515/pac-2014-0502] [Citation(s) in RCA: 241] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractRecommendations are made for standard potentials involving select inorganic radicals in aqueous solution at 25 °C. These recommendations are based on a critical and thorough literature review and also by performing derivations from various literature reports. The recommended data are summarized in tables of standard potentials, Gibbs energies of formation, radical pKa’s, and hemicolligation equilibrium constants. In all cases, current best estimates of the uncertainties are provided. An extensive set of Data Sheets is appended that provide original literature references, summarize the experimental results, and describe the decisions and procedures leading to each of the recommendations.
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Grampp G, Shohoji MCBL, Herold BJ, Steenken S. Solvent Induced Intramolecular Electron Exchange Kinetics in 1,3-Isodisubstituted Aromatic Radical Anions II. Activation Parameters. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/bbpc.199000067] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Latif N, O'Neill P, Schulte-Frohlinde D, Steenken S. Two Routes in the Formation of Hydrogen Halides from OH Adducts of Halogenated Anisoles in Aqueous Solution. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/bbpc.197800088] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Adam B, Bill E, Bothe E, Goerdt B, Haselhorst G, Hildenbrand K, Sokolowski A, Steenken S, Weyhermüller T, Wieghardt K. Phenoxyl radical complexes of gallium, scandium, iron and manganese. Chemistry 2013; 3:308-19. [PMID: 24022963 DOI: 10.1002/chem.19970030221] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/1996] [Indexed: 11/11/2022]
Abstract
The hexadentate macrocyclic ligands 1,4,7-tris(3,5-dimethyl-2-hydroxybenzyl)-1,4,7-triazacyclononane (L CH 3H3 ), 1,4,7-tris(3,5-di-tert-butyl-2-hydroxybenzyl)-1,4,7-triazacyclononane (L(Bu) H3 ) and 1,4,7-tris(3-tert-butyl-5-methoxy-2-hydroxybenzyl)-1,4,7-triazacyclononane (L OCH 3-H3 ) form very stable octahedral neutral complexes LM(III) with trivalent (or tetravalent) metal ions (Ga(III) , Sc(III) , Fe(III) , Mn(III) , Mn(IV) ). The following complexes have been synthesized: [L(Bu) M], where M = Ga (1), Sc (2), Fe (3); [L(Bu) Mn(IV) ]PF6 (4'); [L OCH 3M], where M = Ga (1 a), Sc (2 a), Fe (3 a); [L OCH 3Mn(IV) ]PF6 (4 a'); [L CH 3M], where M = Sc (2 b), Fe (3 b), Mn(III) (4 b); [L CH 3Mn(IV) ]2 (ClO4 )3 (H3 O)(H2 O)3 (4 b'). An electrochemical study has shown that complexes 1, 2, 3, 1 a, 2 a and 3 a each display three reversible, ligand-centred, one-electron oxidation steps. The salts [L OCH 3Fe(III) ]ClO4 and [L OCH 3Ga(III) ]ClO4 , have been isolated as stable crystalline materials. Electronic and EPR spectra prove that these oxidations produce species containing one, two or three coordinated phenoxyl radicals. The Mössbauer spectra of 3 a and [3 a](+) show conclusively that both compounds contain high-spin iron(III) central ions. Temperature-dependent magnetic susceptibility measurements reveal that 3 a has an S = 5/2 and [3a](+) an S = 2 ground state. The latter is attained through intramolecular antiferromagnetic exchange coupling between a high-spin iron(III) (S1 = 5/2) and a phenoxyl radical (S2 = 1/2) (H = - 2JS1 S2 ; J = - 80 cm(-1) ). The manganese complexes undergo metal- and ligand-centred redox processes, which were elucidated by spectroelectrochemistry; a phenoxyl radical Mn(IV) complex [Mn(IV) L OCH 3](2+) is accessible.
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Affiliation(s)
- B Adam
- Max-Planck-Institut für Strahlenchemie, Stiftstrasse 34-36 D-45470 Mülheim an der Ruhr (Germany), Fax: Int. code +(208)306-3952, e-mail:
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Steenken S, Reynisson J. DFT calculations on the deprotonation site of the one-electron oxidised guanine-cytosine base pair. Phys Chem Chem Phys 2010; 12:9088-93. [PMID: 20532316 DOI: 10.1039/c002528c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
As calculated by the density functional theory (DFT), the acidity of cytosine's exocyclic amine group (C-N(4)H2) in the base pair G-C is considerably increased upon its one-electron oxidation. The proton affinity (PA) of the amine moiety is lowered by ionisation of G-C (which yields G(*+)-C) from -348.1 to -269.1 kcal mol(-1). The PA is further decreased by 7.6 kcal mol(-1) as a result of the ensuing proton transfer from G(*+) to C to yield the spin-charge separated base pair G(-H)(*)-C(+H)(+). Under these conditions and taking the hydration energy of H(+) into account, the overall proton transfer from the C-N(4)H2 group to the aqueous phase in the major groove is exothermic by -2.4 kcal mol(-1). This proton transfer to water from the initially present DNA radical cation constitutes separation of charge from spin and thus reduces positive charge transfer in double stranded DNA.
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Affiliation(s)
- Steen Steenken
- Department of Chemistry & Auckland Bioengineering Institute, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
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O'Neill P, Steenken S. Pulse Radiolysis and Electron Spin Resonance Studies on the Formation of Phenoxyl Radicals by Reaction of OH Radicals with Methoxylated Phenols and Hydroxybenzoic Acids. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/bbpc.19770810603] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Abstract
The electron affinity and the subsequent proton affinity of the electron adducts of 2-aminopurine (abbreviated 2AP) and adenine (A) are calculated with density functional theory (DFT). According to these calculations 2AP*- and A*- have similar thermochemical parameters leading to the conclusion that their reaction pathways should be close to analogous. Using the pulse radiolysis technique 2AP*- is formed by reaction with the hydrated electron (e(-)aq) and the resulting transient absorption spectrum is assigned to 2AP(NH)*. Additionally, it was found, employing the laser flash photolysis technique, that the excited singlet state of 2AP is incapable of oxidizing guanine in the aqueous phase. However, the one-electron oxidized 2AP (2AP*+) has sufficient energy to ionize guanine according to the DFT results in agreement with experimental data from the literature.
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Candeias LP, O'Neill P, Jones GD, Steenken S. Ionization of Polynucleotides and DNA in Aqueous Solution by 193nm Pulsed Laser Light: Identification of Base-derived Radicals. Int J Radiat Biol 2009; 61:15-20. [PMID: 1345926 DOI: 10.1080/09553009214550571] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- L P Candeias
- Max-Planck-Institut für Strahlenchemie, Mülheim, Germany
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Gurzadyan GG, Reynisson J, Steenken S. Photoionization versus photoheterolysis of all-trans-retinol. The effects of solvent and laser radiation intensity. Phys Chem Chem Phys 2006; 9:288-98. [PMID: 17186072 DOI: 10.1039/b609165m] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The time-resolved formation of the retinyl carbocation from all-trans-retinol and all-trans-retinol acetate was studied by use of picosecond flash photolysis. From both precursors, the retinyl cation is produced by heterolytic C-O bond cleavage in solvents of medium polarity (acetonitrile, tetrahydrofuran, propanol with Reichardt polarity parameter ET(N) approximately 0.5) and high polarity (EtOH, MeOH, TFE, HFIP, ET(N) > 0.6) during the laser pulse (< or =5 ps) where its lifetime is >10 ns. The absorption maximum of the cation at early times (t < 100 ps) is at lambda = 590-600 nm; it shifts to shorter wavelengths (Deltalambda = 5-10 nm) within 1-10 ns. This spectral shift is suggested to be due to contact ion pair --> solvent-separated ion pair --> free-ion transformation. The quantum yield of cation formation phi(cat) is independent of excitation wavelength (213, 266 or 355 nm). Photoheterolysis proceeds via a one-quantum process. In chlorinated solvents, i.e. n-BuCl, 1,2-dichloroethane, chloroform or CCl(4), formation of the retinol radical cation (which is characterized by a peak at 610 nm and further absorption maxima at approximately 840 and approximately 940 nm) by intermolecular electron transfer to the solvent molecules was detected. The radical cation lifetime in all these solvents is 1.5-2 ns, except for CCl(4) where it is 0.25 ns. The formation of the radical cation or cation was not detected in the low polarity solvents: cyclohexane, hexane, dioxane and p-xylene. However, in solvents of medium and high polarity, at high radiation intensities the radical cation may form in addition to the cation (as a result of two-quantum ionization). DFT calculations confirm our experimental results. The rate of retinol S(1) depopulation (k = 0.3-1 x 10(9) s(-1)) is almost independent of the solvent polarity in the range from cyclohexane to methanol. In highly polar solvents (ET(N) > 0.9) the rate increases to (0.5-5) x 10(10) s(-1).
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Affiliation(s)
- Gagik G Gurzadyan
- Max-Planck-Institut für Bioanorganische Chemie (formerly Max-Planck-Institut für Strahlenchemie), D-45413, Mülheim, Germany.
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Canle López M, Fernández MI, Rodríguez S, Santaballa JA, Steenken S, Vulliet E. Mechanisms of Direct and TiO2-Photocatalysed UV Degradation of Phenylurea Herbicides. Chemphyschem 2005; 6:2064-74. [PMID: 16158459 DOI: 10.1002/cphc.200500004] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Phenylurea herbicides undergo low-yield (phi(PI) <15 %) monophotonic photoionisation upon 193-nm laser flash excitation. The so-formed radical cations (phenylurea.+) are highly acidic (-1.5 < pKa <0.5) and deprotonate readily to yield the corresponding neutral radical (phenylurea.). Pulse radiolysis experiments allowed limitation of the reduction potential of phenylurea.+ within 2.22 V versus the normal hydrogen electrode (NHE) < E degrees (phenylurea.+/phenylurea) < 2.43 V versus NHE. The main photoproducts of UVC (lambda=193 nm) photodegradation of phenylureas correspond to a photo-Fries rearrangement. One-electron reduction with e-(aq) yields the corresponding radical anions (phenylurea.-), for which 4.3< pKa < 5.33. The rate constants for reaction with e-(aq) show that in photocatalysis the generation of phenylurea.- and O2.- on the surface of the photocatalyst may be competitive. High reactivity toward e-(aq) is predicted from linear free-energy relationships (LFER) for phenylureas bearing electron-withdrawing groups. Reaction with HO. takes place mainly via addition to the aromatic ring and/or H. abstraction from a saturated carbon atom (98 %), rather than one-electron oxidation (2 %). High reactivity toward oxidation by HO. is predicted from LFER for phenylureas bearing electron-donating groups. Adsorption studies for TiO2 in its polymorphic forms of rutile and anatase, as well as with the commercial mixture Degussa P-25, show photocatalysis is independent of the specific area of the catalyst. A variety of compounds are generated during the photocatalytic degradation of Diuron, while only two hydroxychloro derivatives are observed upon prolonged direct 365 nm irradiation. The photocatalytic degradation proceeds mainly by oxidation of the Me group of the side chain, hydroxylation of the aromatic ring, and dechlorination. The photoproducts of photocatalytic degradation differ from one polymorphic form of TiO2 to another.
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Affiliation(s)
- Moisés Canle López
- Grupo de Reactividade Química e Fotorreactividade, Departamento de Química Física e Enxeñería Química I, Universidade da Coruña, Rúa Alejandro de la Sota 1, 15008A Coruña, Galicia, Spain.
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Gaebert C, Mattay J, Toubartz M, Steenken S, Müller B, Bally T. Radical Cations of Phenyl-Substituted Aziridines: What Are the Conditions for Ring Opening? Chemistry 2005; 11:1294-304. [PMID: 15635685 DOI: 10.1002/chem.200400557] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Radical cations were generated from different phenyl-substituted aziridines by pulse radiolysis in aqueous solution containing TlOH.+, N3. or SO4.- as oxidants or in n-butyl chloride, by 60Co gamma radiolysis in Freon matrices at 77 K, and in some cases by flash photolysis in aqueous solution. Depending on the substitution pattern of the aziridines, two different types of radical cations are formed: if the N atom carries a phenyl ring, the aziridine appears to retain its structure after oxidation and the resulting radical cation shows an intense band at 440-480 nm, similar to that of the radical cation of dimethylaniline. Conversely, if the N atom carries an alkyl substituent while a phenyl ring is attached to a C-atom of the aziridine, oxidation results in spontaneous ring opening to yield azomethine ylide radical cations which have broad absorptions in the 500-800 nm range. In aqueous solution the two types of radical cations are quenched by O2 with different rates, whereas in n-butyl chloride, the ring-closed aziridine radical cations are not quenchable by O2. The results of quantum chemical calculations confirm the assignment of these species and allow to rationalize the different effects that phenyl rings have if they are attached in different positions of aziridines. In the pulse radiolysis experiments in aqueous solution, the primary oxidants can also be observed, whereas in n-butyl chloride a transient at 325 nm remains unidentified. In the laser flash experiments, both types of radical cations were also observed.
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Affiliation(s)
- Carsten Gaebert
- Fakultät für Chemie, Universität Bielefeld, 33501 Bielefeld, Germany
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Gaebert C, Siegner C, Mattay J, Toubartz M, Steenken S. Formation of radical cations of aziridines generated by laser flash photolysis. Photochem Photobiol Sci 2004; 3:990-1. [PMID: 15570384 DOI: 10.1039/b410464a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The radical cations of 1-butyl-trans-2,3-diphenyl aziridine (1), 1-butyl-2-phenyl aziridine (2), 1,2-diphenyl aziridine (3) and 1-(p-methoxyphenyl)-2-phenyl aziridine (4) were generated upon laser flash photolysis in aqueous and aqueous acetonitrile solutions by direct photoionisation as indicated by the broad absorption band of the solvated electron above 550 nm as well.
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Affiliation(s)
- Carsten Gaebert
- Organische Chemie I, Universitat Bielefeld, Universitatsstrasse 25, D-33615, Bielefeld, Germany
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Reynisson J, Steenken S. Hydrogen bonding between histidine and lignin model compounds or redox mediators as calculated with the DFT method. Effects on the ease of oxidation. Org Biomol Chem 2004; 2:578-84. [PMID: 14770237 DOI: 10.1039/b314991a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using the Density Functional Theory method, the effect of hydrogen bonding between imidazole (IM) and ten benzyl alcohol derivatives (BA) on the ionization potentials of the latter is calculated. IM is used as a model for histidine, which is found in the reaction sites of laccases and lignin peroxidases, and the BA-derivatives serve as lignin model compounds. A marked decrease ([similar]15 kcal mol(-1)) is found for the IP's of the BA-derivatives when paired with IM. This should facilitate the one-electron oxidation of BA in the reaction site of the enzyme. The same effect is found for the known redox mediators violuric acid, 1-hydroxybenzotriazole and N-hydroxyacetanilide which are assumed to enter the reaction site of the enzymes. Furthermore, upon one-electron oxidation the strength of the H-bond from BA to IM is considerably increased and in the case of the mediators this effect is so pronounced that the relevant proton shifts from them to IM. If this occurs in the active site of the enzyme then the oxidized redox mediators are released into the aqueous phase in their neutral form rather than as radical cations (deprotonation of the radical cations). The oxidation power of the neutral radical mediators, however, is too low to initialize oxidation of lignin. A more likely reaction pathway is oxidation of the substrates via hydrogen abstraction. The pertinent bond dissociation energies are similar for the BA-derivatives and the redox mediators, which in principle allows the reaction to occur.
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Affiliation(s)
- Jóhannes Reynisson
- Max-Planck-Institut für Strahlenchemie, D-45413, Mülheim, Germany. Johannes
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Siemeling U, Vor der Brüggen J, Vorfeld U, Neumann B, Stammler A, Stammler HG, Brockhinke A, Plessow R, Zanello P, Laschi F, Fabrizi de Biani F, Fontani M, Steenken S, Stapper M, Gurzadyan G. Ferrocenyl-functionalised terpyridines and their transition-metal complexes: syntheses, structures and spectroscopic and electrochemical properties. Chemistry 2003; 9:2819-33. [PMID: 12866548 DOI: 10.1002/chem.200204412] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Terpyridine ligands of the type Fc'-X-tpy (Fc'=ferrocenyl or octamethylferrocenyl, X=rigid spacer, tpy'=4'-substituted 2,2':6',2''-terpyridine) were prepared, crystallographically characterised and used for the synthesis of di- and trinuclear bis(terpyridine) complexes of RuII, FeII and ZnII. Donor-sensitiser dyads and triads based on RuII were thoroughly investigated by (spectro)electrochemistry, UV/Vis, transient absorption and luminescence spectroscopy, and an energy level scheme was derived on the basis of the data collected. Intramolecular quenching of the photoexcited RuII complexes by the redox-active Fc' groups can occur reductively and by energy transfer. Both the redox potential of the donor Fc' and the nature of the spacer X have a decisive influence on excited-state lifetimes and emission properties of the complexes. Some of the compounds show room-temperature luminescence, which is unprecedented for ferrocenyl-functionalised compounds of this kind.
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Azenha MEDG, Burrows HD, Canle M, Coimbra R, Fernández MI, García MV, Rodrigues AE, Santaballa JA, Steenken S. On the kinetics and energetics of one-electron oxidation of 1,3,5-triazines. Chem Commun (Camb) 2003:112-3. [PMID: 12610991 DOI: 10.1039/b210119j] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
One-electron oxidation of 1,3,5-triazines is observed with both excited uranyl ion (*UO2(2+)) and sulfate radical anion (SO4.-) in aqueous solution, but not with Tl2+, indicating that the standard reduction potentials E degree of 1,3,5-triazine radical cations are = 2.3 +/- 0.1 V vs. NHE, consistent with theoretical calculations; this suggests that if triazines inhibit electron transfer during photosynthesis, they would need to act on the reductive part of the electron transport chain.
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Affiliation(s)
- M E D G Azenha
- Departamento de Química, Universidade de Coimbra, 3004-535 Coimbra, Portugal
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Steenken S, Sies H. Editors' Note. Free Radic Res 2003; 37:1043. [DOI: 10.1080/10715760310001600372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Reynisson J, Steenken S. DNA-base radicals. Their base pairing abilities as calculated by DFTElectronic supplementary information (ESI) available: Single-point energies, zero-point energies and BSSE corrections for guanine, 7,8-dihydro-8-oxoguanine, their radicals and base pairs. See http://www.rsc.org/suppdata/cp/b2/b204842f/. Phys Chem Chem Phys 2002. [DOI: 10.1039/b204842f] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
The photodegradation of pesticides is reviewed, with particular reference to the studies that describe the mechanisms of the processes involved, the nature of reactive intermediates and final products. Potential use of photochemical processes in advanced oxidation methods for water treatment is also discussed. Processes considered include direct photolysis leading to homolysis or heterolysis of the pesticide, photosensitized photodegradation by singlet oxygen and a variety of metal complexes, photolysis in heterogeneous media and degradation by reaction with intermediates generated by photolytic or radiolytic means.
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Affiliation(s)
- H D Burrows
- Departamento de Química, Universidade de Coimbra, 3004-535 Coimbra, Portugal.
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Gurzadyan GG, Steenken S. Photoionization of β-carotene via electron transfer from excited states to chlorinated hydrocarbon solvents. A picosecond transient absorption study. Phys Chem Chem Phys 2002. [DOI: 10.1039/b201765b] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Vieira AJSC, Steenken S. Pattern of hydroxyl radical reaction with N6,N6,9-trimethyladenine: dehydroxylation and ring opening of isomeric hydroxyl adducts. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100176a056] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Das PK, Encinas MV, Steenken S, Scaiano JC. Reaction of tert-butoxy radicals with phenols. Comparison with the reactions of carbonyl triplets. J Am Chem Soc 2002. [DOI: 10.1021/ja00404a030] [Citation(s) in RCA: 160] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Haas A, Schlosser K, Steenken S. Carbon-carbon bond homolysis in hexakis(trifluoromethylmercapto)ethane at room temperature. Thermodynamic, kinetic, and electron spin resonance results. J Am Chem Soc 2002. [DOI: 10.1021/ja00515a021] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Trampe G, Mattay J, Steenken S. Ionization of 1,3-dioxoles in aqueous solution by 248-nm laser flash photolysis: characterization of the radical cations. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100357a026] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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O'Neill P, Steenken S, Schulte-Frohlinde D. Formation of radical zwitterions from methoxylated benzoic acids. 2. Hydroxyl adducts as precursors. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100516a008] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Candeias LP, Steenken S. Ionization of purine nucleosides and nucleotides and their components by 193-nm laser photolysis in aqueous solution: model studies for oxidative damage of DNA. J Am Chem Soc 2002. [DOI: 10.1021/ja00028a043] [Citation(s) in RCA: 172] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Jovanovic SV, Steenken S. Substituent effects on the spectral, acid-base, and redox properties of indolyl radicals: a pulse radiolysis study. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100195a029] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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McClelland RA, Kanagasabapathy VM, Banait NS, Steenken S. Reactivities of diarylmethyl and triarylmethyl cations with primary amines in aqueous acetonitrile solutions. The importance of amine hydration. J Am Chem Soc 2002. [DOI: 10.1021/ja00031a041] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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O'Neill P, Steenken S, Schulte-Frohlinde D. Formation of radical cations of methoxylated benzenes by reaction with hydroxyl radicals, thallium(2+), silver(2+), and peroxysulfate (SO4.-) in aqueous solution. Optical and conductometric pulse radiolysis and in situ radiolysis electron spin resonance study. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100592a013] [Citation(s) in RCA: 217] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Steenken S. Purine bases, nucleosides, and nucleotides: aqueous solution redox chemistry and transformation reactions of their radical cations and e- and OH adducts. Chem Rev 2002. [DOI: 10.1021/cr00093a003] [Citation(s) in RCA: 1011] [Impact Index Per Article: 46.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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34
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Candeias LP, Steenken S. Electron adducts of adenine nucleosides and nucleotides in aqueous solution: protonation at two carbon sites (C2 and C8) and intra- and intermolecular catalysis by phosphate. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100181a074] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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35
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Jagannadham V, Steenken S. One-electron reduction of nitrobenzenes by .alpha.-hydroxyalkyl radicals via addition/elimination. An example of an organic inner-sphere electron-transfer reaction. J Am Chem Soc 2002. [DOI: 10.1021/ja00334a015] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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36
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Steenken S, Schuchmann HP, Von Sonntag C. Fragmentation of .alpha.-alkoxyalkyl radicals. Electron paramagnetic resonance study. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100574a020] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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37
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Neta P, Huie RE, Mosseri S, Shastri LV, Mittal JP, Maruthamuthu P, Steenken S. Rate constants for reduction of substituted methylperoxyl radicals by ascorbate ions and N,N,N',N'-tetramethyl-p-phenylenediamine. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100347a045] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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38
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Jovanovic SV, Hara Y, Steenken S, Simic MG. Antioxidant Potential of Gallocatechins. A Pulse Radiolysis and Laser Photolysis Study. J Am Chem Soc 2002. [DOI: 10.1021/ja00144a014] [Citation(s) in RCA: 225] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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39
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Faria JL, Steenken S. Photoionization (.lambda. = 248 or 308 nm) of triphenylmethyl radical in aqueous solution. Formation of triphenylmethyl carbocation. J Am Chem Soc 2002. [DOI: 10.1021/ja00159a076] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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40
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Steenken S, O'Neill P. Oxidative demethoxylation of methoxylated phenols and hydroxybenzoic acids by the hydroxyl radical. An in situ electron spin resonance, conductometric pulse radiolysis and product analysis study. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100521a002] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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41
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Schlosser K, Steenken S. Reversible nitrogen-nitrogen bond homolysis in tetrakis(trifluoromethylthio)hydrazine at room temperature. Electron spin resonance, thermodynamic, and kinetic results. J Am Chem Soc 2002. [DOI: 10.1021/ja00344a015] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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42
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McClelland RA, Banait N, Steenken S. Electrophilic reactions of xanthylium carbocations produced by flash photolysis of 9-xanthenols. J Am Chem Soc 2002. [DOI: 10.1021/ja00190a030] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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43
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McClelland RA, Kanagasabapathy VM, Banait NS, Steenken S. Reactivities of triarylmethyl and diarylmethyl cations with azide ion investigated by laser flash photolysis. Diffusion-controlled reactions. J Am Chem Soc 2002. [DOI: 10.1021/ja00003a040] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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44
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Faria JL, Steenken S. Photoionization of diarylmethyl radicals in acetonitrile and alcohol-water: laser flash production of diarylcarbenium ions. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100111a034] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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45
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Steenken S, Raghavan NV. Oxidation of methoxyhydroxycyclohexadienyl radicals by quinones. The influence of the isomeric structure of the radical on the rate constant for electron transfer. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100487a009] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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46
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Jagannadham V, Steenken S. Reactivity of .alpha.-heteroatom-substituted alkyl radicals with nitrobenzenes in aqueous solution: an entropy controlled electron transfer/addition mechanism. J Am Chem Soc 2002. [DOI: 10.1021/ja00215a031] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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47
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Steenken S, O'Neill P. Selectivity of addition of the hydroxyl radical to ring positions of pyridine and pyridine mono- and dicarboxylic acids. An electron spin resonance investigation. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100492a026] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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48
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Faria JL, Steenken S. Photochemistry of 2,3-dimethyl-2,3-diphenylbutane: carbon-carbon homolysis and protonation-induced side-chain fragmentation. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100205a049] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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49
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Steenken S, Buschek J, McClelland RA. Radiation-chemical production and lifetimes of trialkoxymethyl carbocations in aqueous solution. J Am Chem Soc 2002. [DOI: 10.1021/ja00271a004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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50
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Vieira AJSC, Steenken S. Pattern of hydroxy radical reaction with adenine and its nucleosides and nucleotides. Characterization of two types of isomeric hydroxy adduct and their unimolecular transformation reactions. J Am Chem Soc 2002. [DOI: 10.1021/ja00175a036] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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