1
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Guo Y, Ge L, Phillips DL, Ma J, Fang Y. Different Reaction Mechanisms Triggered by the Meta Effect: Photoinduced Generation of Quinone Methides from Hydroxybiphenyl Derivatives. J Phys Chem Lett 2024; 15:8569-8576. [PMID: 39140706 DOI: 10.1021/acs.jpclett.4c01875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/15/2024]
Abstract
A series of sterically congested quinone methides (QMs) exhibit photoinduced antiproliferative activity against some human cancer cell lines. To elucidate the structure-reactivity relationship and details of mechanisms of the photogeneration of sterically congested QMs, we chose phenylphenol derivatives 1-3 as QM precursors and investigated their photodehydration processes in aqueous solutions using ultrafast spectroscopy and theoretical computations. We found that meta derivatives 1 and 2 undergo water-mediated excited-state proton transfer (ESPT) from the phenol OH, followed by expulsion of the OH- to form QMs. By comparison, para derivative 3 proceeds via water-mediated ESPT from H2O to benzyl alcohol coupled with dehydration as the first step, delivering a cation intermediate, which further deprotonates to yield QM. Such results would help chemists understand more about the meta effects in photochemistry and about ESPT and would help synthetic chemists design sterically congested QM precursors with extraordinary reactivities and expand applications of QMs in biological and medical systems.
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Affiliation(s)
- Yan Guo
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China
| | - Lingfeng Ge
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China
| | - David Lee Phillips
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong S.A.R. 999077, P. R. China
| | - Jiani Ma
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China
| | - Yu Fang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China
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2
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Asghar A, Lipfert D, Kerpen K, Schmidt TC. Elucidating the inhibitory effects of natural organic matter on the photodegradation of organic micropollutants: Atrazine as a probe compound. CHEMOSPHERE 2024; 352:141390. [PMID: 38325617 DOI: 10.1016/j.chemosphere.2024.141390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 02/02/2024] [Accepted: 02/03/2024] [Indexed: 02/09/2024]
Abstract
Natural organic matter (NOM) is a complex mixture of heterogeneous compounds with varying functional groups and molecular sizes. Understanding the impact of NOM on the generation of photochemically produced reactive intermediates (PPRIs) and their potential inhibitory effects on photolysis has remained challenging due to the variations in the reactivities and concentrations of these functional groups. To address this gap, tannic acid (TA), gallic acid (GA), catechin (CAT), and tryptophan (Trp), were chosen as potential substitutes for NOM. Their effects on the photochemical transformation process were evaluated and compared with the widely used Suwannee River NOM (SRNOM). Atrazine (ATZ) was selected as a probe organic micropollutant (OMP). In this investigation, a significantly higher concentration of HO• was observed compared to O21, and the triplet excited state ( NOM*3). The findings suggest that the substituted phenols, particularly those with carboxylate-substitutions, played a substantial role in HO• formation, while electron-rich moieties acted as antioxidants, consuming NOM*3. Hydroxyl, carboxylic, and amino acid were the active groups for O21 formation. However, the inhibitory effects induced by the NOM surrogates were significant and mainly attributed to the direct photolysis inhibition caused by the inner filter effect. The scope of this work was further extended to include SRNOM, where similar trends with less pronounced formation of PPRIs and inner filter effects were observed. Therefore, this study sheds some light on the role of the functional groups in NOM during photochemical transformations of OMPs, thereby deepening our understanding of their fate in aqueous systems.
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Affiliation(s)
- Anam Asghar
- Instrumental Analytical Chemistry, Faculty of Chemistry, University of Duisburg-Essen, Universitätsstraße 5, Essen, Germany.
| | - Daniel Lipfert
- Instrumental Analytical Chemistry, Faculty of Chemistry, University of Duisburg-Essen, Universitätsstraße 5, Essen, Germany
| | - Klaus Kerpen
- Instrumental Analytical Chemistry, Faculty of Chemistry, University of Duisburg-Essen, Universitätsstraße 5, Essen, Germany
| | - Torsten C Schmidt
- Instrumental Analytical Chemistry, Faculty of Chemistry, University of Duisburg-Essen, Universitätsstraße 5, Essen, Germany; Centre for Water and Environmental Research (ZWU), Universitätsstraße 5, 45141, Essen, Germany; IWW Water Centre, Moritzstraße 26, 45476, Mülheim an der Ruhr, Germany
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3
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Photodehydration mechanisms of quinone methide formation from 2-naphthol derivatives. J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2022.114171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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4
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Tomilin OB, Boyarkina OV, Tanaseichuk BS. One-Electron Transfer during Dimerization of Phenoxyl Radicals. RUSSIAN JOURNAL OF ORGANIC CHEMISTRY 2022. [DOI: 10.1134/s1070428022050013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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5
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Cink RB, Zhou Y, Du L, Rahman MS, Phillips DL, Simpson MC, Seed AJ, Sampson P, Brasch NE. Mechanistic Insights into Rapid Generation of Nitroxyl from a Photocaged N-Hydroxysulfonamide Incorporating the (6-Hydroxynaphthalen-2-yl)methyl Chromophore. J Org Chem 2021; 86:8056-8068. [PMID: 34107217 DOI: 10.1021/acs.joc.1c00457] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
HNO is a highly reactive molecule that shows promise in treating heart failure. Molecules that rapidly release HNO with precise spatial and temporal control are needed to investigate the biology of this signaling molecule. (Hydroxynaphthalen-2-yl)methyl-photocaged N-hydroxysulfonamides are a new class of photoactive HNO generators. Recently, it was shown that a (6-hydroxynaphthalen-2-yl)methyl (6,2-HNM)-photocaged derivative of N-hydroxysulfonamide incorporating the trifluoromethanesulfonamidoxy group (1) quantitatively generates HNO. Mechanistic studies have now been carried out on this system and reveal that the ground state protonation state plays a key role in whether concerted heterolytic C-O/N-S bond cleavage to release HNO occurs versus undesired O-N bond cleavage. N-Deprotonation of 1 can be achieved by adding an aqueous buffer or a carboxylate salt to an aprotic solvent. Evidence is presented for C-O/N-S bond heterolysis occurring directly from the singlet excited state of the N-deprotonated parent molecule on the picosecond time scale, using femtosecond time-resolved transient absorption spectroscopy, to give a carbocation and 1NO-. This is consistent with the observation of significant fluorescence quenching when HNO is generated. The carbocation intermediate reacts rapidly with nucleophiles including water, MeOH, or even (H)NO in the absence of a molecule that reacts rapidly with (H)NO to give an oxime.
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Affiliation(s)
- Ruth B Cink
- School of Science, Auckland University of Technology, Private Bag 92006, Auckland 1142, New Zealand.,The Photon Factory, School of Chemical Sciences and Department of Physics, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.,The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6012, New Zealand.,The Dodd-Walls Centre for Quantum and Photonic Technologies, Dunedin 9054, New Zealand
| | - Yang Zhou
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
| | - Lili Du
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR 99077, P. R. China
| | - Mohammad S Rahman
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
| | - David Lee Phillips
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR 99077, P. R. China
| | - M Cather Simpson
- The Photon Factory, School of Chemical Sciences and Department of Physics, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.,The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6012, New Zealand.,The Dodd-Walls Centre for Quantum and Photonic Technologies, Dunedin 9054, New Zealand
| | - Alexander J Seed
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
| | - Paul Sampson
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
| | - Nicola E Brasch
- School of Science, Auckland University of Technology, Private Bag 92006, Auckland 1142, New Zealand.,The Dodd-Walls Centre for Quantum and Photonic Technologies, Dunedin 9054, New Zealand.,The Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, New Zealand
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6
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Dutta Choudhury S, Mohanty J. Photoinduced electron transfer in host-guest interactions of lumichrome with p-sulfonatocalix[6]arene. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2020.114955] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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7
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Siano G, Crespi S, Bonesi SM. Direct Irradiation of Phenol and Para-Substituted Phenols with a Laser Pulse (266 nm) in Homogeneous and Micro-heterogeneous Media. A Time-Resolved Spectroscopy Study. J Org Chem 2020; 85:14012-14025. [PMID: 33063512 DOI: 10.1021/acs.joc.0c02031] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Direct irradiation of para-substituted phenols under N2 atmosphere in homogeneous (cyclohexane, acetonitrile, and methanol) and micellar (SDS) solution was investigated by means of time-resolved spectroscopy. After a laser pulse (266 nm), two transient species were formed, viz. the para-substituted phenol radical-cations and the corresponding phenoxy radicals. The radical-cations showed a broad absorption band located between 390 and 460 nm, while the phenoxy radicals showed two characteristic bands centered at 320 nm and 400-410 nm. The deprotonation rate constant of radical-cations (kH) of 105 s-1 and the reaction rate constant of the phenoxy radicals (kR) in the order of 109-1010 M-1·s-1 have been derived. The kH rate constants gave good linear Hammett correlation with positive slope indicating that electron-withdrawing substituents enhance the radical-cation acidity. The binding constants (Kb) of the para-substituted phenols with the surfactant were also measured, and NOESY experiments showed that phenols were located in the hydrophobic core of the micelle. Finally, computational calculations provided the predicted absorption spectra of the transients and nice linear correlations were obtained between the theoretical and experimental energy of the lower absorption band of these species.
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Affiliation(s)
- Gastón Siano
- Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Quı́mica Orgánica, C1428EGA Buenos Aires, Argentina.,CONICET - Universidad de Buenos Aires. Centro de Investigaciones en Hidratos de Carbono (CIHIDECAR). C1428EGA Buenos Aires, Argentina
| | - Stefano Crespi
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - Sergio M Bonesi
- Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Quı́mica Orgánica, C1428EGA Buenos Aires, Argentina.,CONICET - Universidad de Buenos Aires. Centro de Investigaciones en Hidratos de Carbono (CIHIDECAR). C1428EGA Buenos Aires, Argentina.,Dipartimento di Chimica, Sezione Chimica Organica, University of Pavia, v.le Taramelli 12, 27100 Pavia, Italy
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8
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Mondal P, McDonald AR. Phenol Oxidation by a Nickel(III)-Fluoride Complex: Exploring the Influence of the Proton Accepting Ligand in PCET Oxidation. Chemistry 2020; 26:10083-10089. [PMID: 32567726 DOI: 10.1002/chem.202002135] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/15/2020] [Indexed: 11/05/2022]
Abstract
In order to gain insight into the influence of the H+ -accepting terminal ligand in high-valent oxidant mediated proton coupled electron transfer (PCET) reactions, the reactivity of a high valent nickel-fluoride complex [NiIII (F)(L)] (2, L=N,N'-(2,6-dimethylphenyl)-2,6-pyridinecarboxamidate) with substituted phenols was explored. Analysis of kinetic data from these reactions (Evans-Polanyi, Hammett, and Marcus plots, and KIE measurements) and the formed products show that 2 reacted with electron rich phenols through a hydrogen atom transfer (HAT, or concerted PCET) mechanism and with electron poor phenols through a stepwise proton transfer/electron transfer (PT/ET) reaction mechanism. The analogous complexes [NiIII (Z)(L)] (Z=Cl, OCO2 H, O2 CCH3 , ONO2 ) reacted with all phenols through a HAT mechanism. We explore the reason for a change in mechanism with the highly basic fluoride ligand in 2. Complex 2 was also found to react one to two orders of magnitude faster than the corresponding analogous [NiIII (Z)(L)] complexes. This was ascribed to a high bond dissociation free energy value associated with H-F (135 kcal mol-1 ), which is postulated to be the product formed from PCET oxidation by 2 and is believed to be the driving force for the reaction. Our findings show that high-valent metal-fluoride complexes represent a class of highly reactive PCET oxidants.
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Affiliation(s)
- Prasenjit Mondal
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin, 2, Ireland
| | - Aidan R McDonald
- School of Chemistry, Trinity College Dublin, The University of Dublin, College Green, Dublin, 2, Ireland
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9
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Colasson B, Credi A, Ventura B. Photoinduced Electron Transfer Involving a Naphthalimide Chromophore in Switchable and Flexible [2]Rotaxanes. Chemistry 2019; 26:534-542. [PMID: 31638287 DOI: 10.1002/chem.201904155] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Indexed: 11/10/2022]
Abstract
The interlocking of ring and axle molecular components in rotaxanes provides a way to combine chromophoric, electron-donor and electron-acceptor moieties in the same molecular entity, in order to reproduce the features of photosynthetic reaction centers. To this aim, the photoinduced electron transfer processes involving a 1,8-naphthalimide chromophore, embedded in several rotaxane-based dyads, were investigated by steady-state and time-resolved absorption and luminescence spectroscopic experiments in the 300 fs-10 ns time window. Different rotaxanes built around the dialkylammonium/ dibenzo[24]crown-8 ether supramolecular motif were designed and synthesized to decipher the relevance of key structural factors, such as the chemical deactivation of the ammonium-crown ether recognition, the presence of a secondary site for the ring along the axle, and the covalent functionalization of the macrocycle with a phenothiazine electron donor. Indeed, the conformational freedom of these compounds gives rise to a rich dynamic behavior induced by light and may provide opportunities for investigating and understanding phenomena that take place in complex (bio)molecular architectures.
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Affiliation(s)
- Benoit Colasson
- Université de Paris, UMR 8601, LCBPT, CNRS, 45 rue des Saints-Pères, 75006, Paris, France.,Photochemical Nanosciences Laboratory, Dipartimento di Chimica "G. Ciamician", Università di Bologna, via Selmi 2, 40126, Bologna, Italy
| | - Alberto Credi
- Dipartimento di Scienze e Tecnologie Agro-alimentari, Università di Bologna, viale Fanin 50, 40127, Bologna, Italy.,CLAN-Center for Light Activated Nanostructures, Università di Bologna and Consiglio Nazionale delle Ricerche, via P. Gobetti 101, 40129, Bologna, Italy.,Istituto ISOF-CNR, via P. Gobetti 101, 40129, Bologna, Italy
| | - Barbara Ventura
- Istituto ISOF-CNR, via P. Gobetti 101, 40129, Bologna, Italy
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10
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Dozova N, Lacombat F, Bou-Nader C, Hamdane D, Plaza P. Ultrafast photoinduced flavin dynamics in the unusual active site of the tRNA methyltransferase TrmFO. Phys Chem Chem Phys 2019; 21:8743-8756. [PMID: 30968076 DOI: 10.1039/c8cp06072j] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Flavoproteins often stabilize their flavin coenzyme by stacking interactions involving the isoalloxazine moiety of the flavin and an aromatic residue from the apoprotein. The bacterial FAD and folate-dependent tRNA methyltransferase TrmFO has the unique property of stabilizing its FAD coenzyme by an unusual H-bond-assisted π-π stacking interaction, involving a conserved tyrosine (Y346 in Bacillus subtilis TrmFO, BsTrmFO), the isoalloxazine of FAD and the backbone of a catalytic cysteine (C53). Here, the interaction between FAD and Y346 has been investigated by measuring the photoinduced flavin dynamics of BsTrmFO in the wild-type (WT) protein, C53A and several Y346 mutants by ultrafast transient absorption spectroscopy. In C53A, the excited FAD very rapidly (0.43 ps) abstracts an electron from Y346, yielding the FAD˙-/Y346OH˙+ radical pair, while relaxation of the local environment (1.3 ps) of the excited flavin produces a slight Stokes shift of its stimulated emission band. The radical pair then decays via charge recombination, mostly in 3-4 ps, without any deprotonation of the Y346OH˙+ radical. Presumably, the H-bond between Y346 and the amide group of C53 increases the pKa of Y346OH˙+ and slows down its deprotonation. The dynamics of WT BsTrmFO shows additional slow decay components (43 and 700 ps), absent in the C53A mutant, assigned to excited FADox populations not undergoing fast photoreduction. Their presence is likely due to a more flexible structure of the WT protein, favored by the presence of C53. Interestingly, mutations of Y346 canceling its electron donating character lead to multiple slower quenching channels in the ps-ns regime. These channels are proposed to be due to electron abstraction either (i) from the adenine moiety of FAD, a distribution of the isoalloxazine-adenine distance in the absence of Y346 explaining the multiexponential decay, or (ii) from the W286 residue, possibly accounting for one of the decays. This work supports the idea that H-bond-assisted π-π stacking controls TrmFO's active site dynamics, required for competent orientation of the reactive centers during catalysis.
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Affiliation(s)
- Nadia Dozova
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France.
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11
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Ossola R, Schmitt M, Erickson PR, McNeill K. Furan Carboxamides as Model Compounds To Study the Competition between Two Modes of Indirect Photochemistry. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:9594-9603. [PMID: 31335132 DOI: 10.1021/acs.est.9b02895] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Singlet oxygen (1O2) and triplet chromophoric dissolved organic matter (3CDOM*) are photochemically produced reactive intermediates responsible for the photodegradation of several micropollutants in the sunlit surface waters. However, elucidating the mechanism of reactions involving both 1O2 and 3CDOM* can be complicated by the deeply interconnected nature of these two reactive species. In this work, we synthesized a series of model compounds inspired by the chemical structure of fenfuram, a fungicide used in the 1980s, and used them to investigate structure-reactivity relationships in photodegradation reactions involving 1O2 and 3CDOM*. A combination of steady-state and time-resolved approaches was employed to successfully predict the extent of 1O2-induced degradation. Conversely, the prediction of triplet-induced reactivity was complicated by the presence of repair mechanisms whose extent and relative importance were difficult to predict. The results of our work indicate that bimolecular rate constants measured via time-resolved techniques alone are not sufficient to accurately predict environmental half-lives, as intrinsic differences in the reaction mechanism can amplify the importance of secondary degradation pathways.
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Affiliation(s)
- Rachele Ossola
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), Department of Environmental Systems Science , ETH Zurich , 8092 Zurich , Switzerland
| | - Markus Schmitt
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), Department of Environmental Systems Science , ETH Zurich , 8092 Zurich , Switzerland
| | - Paul R Erickson
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), Department of Environmental Systems Science , ETH Zurich , 8092 Zurich , Switzerland
| | - Kristopher McNeill
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), Department of Environmental Systems Science , ETH Zurich , 8092 Zurich , Switzerland
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12
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Sambol M, Ester K, Landgraf S, Mihaljević B, Cindrić M, Kralj M, Basarić N. Competing photochemical reactions of bis-naphthols and their photoinduced antiproliferative activity. Photochem Photobiol Sci 2019; 18:1197-1211. [PMID: 30820496 DOI: 10.1039/c8pp00532j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The photophysical properties and photochemical reactivities of a series of bis-naphthols 4a-4e and bis-anthrols 5a and 5e were investigated by preparative irradiation in CH3OH, fluorescence spectroscopy and laser flash photolysis (LFP). Methanolysis taking place via photodehydration (bis-naphthols: ΦR = 0.04-0.05) is in competition with symmetry breaking charge separation (SB-CS). The SB-CS gave rise to radical ions that were detected for 4a and 4e by LFP. Photodehydration gave quinone methides (QMs) that were also detected by LFP (λmax = 350 nm, τ ≈ 1-2 ms). In the aqueous solvent, excited state proton transfer (ESPT) competes with the abovementioned processes, giving rise to naphtholates, but the process is inefficient and can only be observed in the buffered aqueous solution at pH > 7. Since the dehydration of bis-naphthols delivers QMs, their potential antiproliferative activity was investigated by an MTT test on three human cancer cell lines (NCI-H1299, lung carcinoma; MCF-7, breast adenocarcinoma; and SUM159, pleomorphic breast carcinoma). Cells were treated with 4 or 5 with or without irradiation (350 nm). An enhancement of the activity (up to 10-fold) was observed upon irradiation, which may be associated with QM formation. However, these QMs do not cross-link DNA. The activity is most likely associated with the alkylation of proteins present in the cell cytoplasm, as evidenced by photoinduced alkylation of bovine and human serum albumins by 4a.
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Affiliation(s)
- Matija Sambol
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
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13
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Parada GA, Goldsmith ZK, Kolmar S, Pettersson Rimgard B, Mercado BQ, Hammarström L, Hammes-Schiffer S, Mayer JM. Concerted proton-electron transfer reactions in the Marcus inverted region. Science 2019; 364:471-475. [PMID: 30975771 PMCID: PMC6681808 DOI: 10.1126/science.aaw4675] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/28/2019] [Indexed: 11/02/2022]
Abstract
Electron transfer reactions slow down when they become very thermodynamically favorable, a counterintuitive interplay of kinetics and thermodynamics termed the inverted region in Marcus theory. Here we report inverted region behavior for proton-coupled electron transfer (PCET). Photochemical studies of anthracene-phenol-pyridine triads give rate constants for PCET charge recombination that are slower for the more thermodynamically favorable reactions. Photoexcitation forms an anthracene excited state that undergoes PCET to create a charge-separated state. The rate constants for return charge recombination show an inverted dependence on the driving force upon changing pyridine substituents and the solvent. Calculations using vibronically nonadiabatic PCET theory yield rate constants for simultaneous tunneling of the electron and proton that account for the results.
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Affiliation(s)
| | | | - Scott Kolmar
- Department of Chemistry, Yale University, New Haven, CT, USA
| | | | | | - Leif Hammarström
- Department of Chemistry - Ångström Laboratory, Uppsala University, Uppsala, Sweden.
| | | | - James M Mayer
- Department of Chemistry, Yale University, New Haven, CT, USA.
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14
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Siano G, Crespi S, Mella M, Bonesi SM. Selectivity in the Photo-Fries Rearrangement of Some Aryl Benzoates in Green and Sustainable Media. Preparative and Mechanistic Studies. J Org Chem 2019; 84:4338-4352. [DOI: 10.1021/acs.joc.9b00334] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gastón Siano
- Departamento de Química Orgánica, CIHIDECAR − CONICET, Facultad de Ciencias Exactas y Naturales, University of Buenos Aires, 3er Piso, Pabellón 2, Ciudad Universitaria, Buenos Aires 1428, Argentina
| | - Stefano Crespi
- Dipartimento di Chimica, University of Pavia, Sezione Chimica Organica, v.le Taramelli 12, 27100 Pavia, Italy
| | - Mariella Mella
- Dipartimento di Chimica, University of Pavia, Sezione Chimica Organica, v.le Taramelli 12, 27100 Pavia, Italy
| | - Sergio M. Bonesi
- Departamento de Química Orgánica, CIHIDECAR − CONICET, Facultad de Ciencias Exactas y Naturales, University of Buenos Aires, 3er Piso, Pabellón 2, Ciudad Universitaria, Buenos Aires 1428, Argentina
- Dipartimento di Chimica, University of Pavia, Sezione Chimica Organica, v.le Taramelli 12, 27100 Pavia, Italy
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15
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Sohora M, Vazdar M, Sović I, Mlinarić-Majerski K, Basarić N. Photocyclization of Tetra- and Pentapeptides Containing Adamantylphthalimide and Phenylalanines: Reaction Efficiency and Diastereoselectivity. J Org Chem 2018; 83:14905-14922. [PMID: 30460849 DOI: 10.1021/acs.joc.8b01785] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
A series of tetrapeptides and pentapeptides was synthesized bearing a phthalimide chromophore at the N-terminus. The C-terminus of the peptides was strategically substituted with an amino acid, Phe, Phe(OMe), or Phe(OMe)2 characterized by different oxidation potentials. The photochemical reactivity of the peptides was investigated by preparative irradiation and isolation of photoproducts, as well as with laser flash photolysis. Upon photoexcitation, the peptides undergo photoinduced electron transfer (PET) and decarboxylation, followed by diastereoselective cyclization with the retention of configuration for tetrapeptides or inversion of configuration for pentapeptides. Molecular dynamics (MD) simulations and NOE experiments enabled assignment of the stereochemistry of the cyclic peptides. MD simulations of the linear peptides disclosed conformational reasons for the observed diastereoselectivity, being due to the peptide backbone spatial orientation imposed by the Phe amino acids. The photochemical efficiency for the decarboxylation and cyclization is not dependent on the peptide length, but it depends on the oxidation potential of the amino acid at the C-terminus. The results described herein are particularly important for the rational design of efficient photochemical reactions for the preparation of cyclic peptides with the desired selectivity.
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Affiliation(s)
- Margareta Sohora
- Department of Organic Chemistry and Biochemistry , Rud̵er Bošković Institute , Bijenička cesta 54 , 10000 Zagreb , Croatia
| | - Mario Vazdar
- Department of Organic Chemistry and Biochemistry , Rud̵er Bošković Institute , Bijenička cesta 54 , 10000 Zagreb , Croatia
| | - Irena Sović
- Department of Organic Chemistry and Biochemistry , Rud̵er Bošković Institute , Bijenička cesta 54 , 10000 Zagreb , Croatia
| | - Kata Mlinarić-Majerski
- Department of Organic Chemistry and Biochemistry , Rud̵er Bošković Institute , Bijenička cesta 54 , 10000 Zagreb , Croatia
| | - Nikola Basarić
- Department of Organic Chemistry and Biochemistry , Rud̵er Bošković Institute , Bijenička cesta 54 , 10000 Zagreb , Croatia
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16
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Investigation of IRGANOX®1076 as a dosimeter for clinical X-ray, electron and proton beams and its EPR angular response. Radiat Phys Chem Oxf Engl 1993 2017. [DOI: 10.1016/j.radphyschem.2017.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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17
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Nag L, Sournia P, Myllykallio H, Liebl U, Vos MH. Identification of the TyrOH •+ Radical Cation in the Flavoenzyme TrmFO. J Am Chem Soc 2017; 139:11500-11505. [PMID: 28745052 DOI: 10.1021/jacs.7b04586] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Tyrosine (TyrOH) and tryptophan radicals play important roles as intermediates in biochemical charge-transfer reactions. Tryptophanyl radicals have been observed both in their protonated cation form and in their unprotonated neutral form, but to date, tyrosyl radicals have only been observed in their unprotonated form. With a genetically modified form of the flavoenzyme TrmFO as a suitable model system and using ultrafast fluorescence and absorption spectroscopy, we characterize its protonated precursor TyrOH•+, and we show this species to have a distinct visible absorption band and a transition moment that we suggest to lie close to the phenol symmetry axis. TyrOH•+ is formed in ∼1 ps by electron transfer to excited flavin and decays in ∼3 ps by charge recombination. These findings imply that TyrOH oxidation does not necessarily induce its concerted deprotonation. Our results will allow disentangling of photoproduct states in flavoproteins in often-encountered complex situations and more generally are important for understanding redox chains relying on tyrosyl intermediates.
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Affiliation(s)
- Lipsa Nag
- LOB, Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay , Palaiseau 91128 Cedex, France
| | - Pierre Sournia
- LOB, Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay , Palaiseau 91128 Cedex, France
| | - Hannu Myllykallio
- LOB, Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay , Palaiseau 91128 Cedex, France
| | - Ursula Liebl
- LOB, Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay , Palaiseau 91128 Cedex, France
| | - Marten H Vos
- LOB, Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay , Palaiseau 91128 Cedex, France
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18
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More NY, Jeganmohan M. Oxidative Cross-Coupling of Substituted Phenols with Unactivated Aromatics. European J Org Chem 2017. [DOI: 10.1002/ejoc.201700666] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Nagnath Yadav More
- Department of Chemistry; Indian Institute of Science Education and Research; 411021 Pune India
| | - Masilamani Jeganmohan
- Department of Chemistry; Indian Institute of Science Education and Research; 411021 Pune India
- Department of Chemistry; Indian Institute of Technology Madras; 600036 Chennai Tamil Nadu India
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19
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Barsotti F, Bartels-Rausch T, De Laurentiis E, Ammann M, Brigante M, Mailhot G, Maurino V, Minero C, Vione D. Photochemical Formation of Nitrite and Nitrous Acid (HONO) upon Irradiation of Nitrophenols in Aqueous Solution and in Viscous Secondary Organic Aerosol Proxy. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:7486-7495. [PMID: 28581723 DOI: 10.1021/acs.est.7b01397] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Irradiated nitrophenols can produce nitrite and nitrous acid (HONO) in bulk aqueous solutions and in viscous aqueous films, simulating the conditions of a high-solute-strength aqueous aerosol, with comparable quantum yields in solution and viscous films (10-5-10-4 in the case of 4-nitrophenol) and overall reaction yields up to 0.3 in solution. The process is particularly important for the para-nitrophenols, possibly because their less sterically hindered nitro groups can be released more easily as nitrite and HONO. The nitrophenols giving the highest photoproduction rates of nitrite and HONO (most notably, 4-nitrophenol and 2-methyl-4-nitrophenol) could significantly contribute to the occurrence of nitrite in aqueous phases in contact with the atmosphere. Interestingly, dew-water evaporation has shown potential to contribute to the gas-phase HONO levels during the morning, which accounts for the possible importance of the studied process.
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Affiliation(s)
- Francesco Barsotti
- Dipartimento di Chimica, Università di Torino , Via Pietro Giuria 5, 10125 Torino, Italy
| | | | - Elisa De Laurentiis
- Dipartimento di Chimica, Università di Torino , Via Pietro Giuria 5, 10125 Torino, Italy
| | - Markus Ammann
- Laboratory of Environmental Chemistry, Paul Scherrer Institute , 5232 Villigen, Switzerland
| | - Marcello Brigante
- Université Clermont Auvergne , CNRS, Sigma Clermont, Institut de Chimie de Clermont-Ferrand, F-63000 Clermont-Ferrand, France
| | - Gilles Mailhot
- Université Clermont Auvergne , CNRS, Sigma Clermont, Institut de Chimie de Clermont-Ferrand, F-63000 Clermont-Ferrand, France
| | - Valter Maurino
- Dipartimento di Chimica, Università di Torino , Via Pietro Giuria 5, 10125 Torino, Italy
| | - Claudio Minero
- Dipartimento di Chimica, Università di Torino , Via Pietro Giuria 5, 10125 Torino, Italy
| | - Davide Vione
- Dipartimento di Chimica, Università di Torino , Via Pietro Giuria 5, 10125 Torino, Italy
- Centro Interdipartimentale NatRisk, Università di Torino , Largo Paolo Braccini 2, 10095 Grugliasco, Torino, Italy
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20
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Škalamera Đ, Mlinarić-Majerski K, Martin Kleiner I, Kralj M, Oake J, Wan P, Bohne C, Basarić N. Photochemical Formation of Anthracene Quinone Methide Derivatives. J Org Chem 2017; 82:6006-6021. [PMID: 28534631 DOI: 10.1021/acs.joc.6b02735] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Anthrols 2-7 were synthesized and their photochemical reactivity investigated by irradiations in aq CH3OH. Upon excitation with visible light (λ > 400 nm) in methanolic solutions, they undergo photodehydration or photodeamination and deliver methyl ethers, most probably via quinone methides (QMs), with methanolysis quantum efficiencies ΦR = 0.02-0.3. Photophysical properties of 2-7 were determined by steady-state fluorescence and time-correlated single photon counting. Generally, anthrols 2-7 are highly fluorescent in aprotic solvents (ΦF = 0.5-0.9), whereas in aqueous solutions the fluorescence is quenched due to excited-state proton transfer (ESPT) to solvent. The exception is amine 4 that undergoes excited-state intramolecular proton transfer (ESIPT) in neat CH3CN where photodeamination is probably coupled to ESIPT. Photodehydration may take place via ESIPT (or ESPT) that is coupled to dehydration or via a hitherto undisclosed pathway that involves photoionization and deprotonation of radical cation, followed by homolytic cleavage of the alcohol OH group from the phenoxyl radical. QMs were detected by laser flash photolysis and their reactivity with nucleophiles investigated. Biological investigation of 2-5 on human cancer cell lines showed enhancement of antiproliferative effect upon exposure of cells to irradiation by visible light, probably due to formation of electrophilic species such as QMs.
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Affiliation(s)
| | | | | | | | - Jessy Oake
- Department of Chemistry, University of Victoria , Box 1700 STN CSC, Victoria BC V8W 2Y2, Canada
| | - Peter Wan
- Department of Chemistry, University of Victoria , Box 1700 STN CSC, Victoria BC V8W 2Y2, Canada
| | - Cornelia Bohne
- Department of Chemistry, University of Victoria , Box 1700 STN CSC, Victoria BC V8W 2Y2, Canada
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21
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Uzelac L, Škalamera Đ, Mlinarić-Majerski K, Basarić N, Kralj M. Selective photocytotoxicity of anthrols on cancer stem-like cells: The effect of quinone methides or reactive oxygen species. Eur J Med Chem 2017. [PMID: 28633106 DOI: 10.1016/j.ejmech.2017.05.063] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cancer stem cells (CSCs) are a subpopulation of cancer cells that share properties of embryonic stem cells like pluripotency and self-renewal and show increased resistance to chemo- and radiotherapy. Targeting CSC, rather than cancer cells in general, is a novel and promising strategy for cancer treatment. Novel therapeutic approaches, such as photodynamic therapy (PDT) have been investigated. A promising group of phototherapeutic agents are reactive intermediates - quinone methides (QMs). This study describes preparation of QM precursor, 2-hydroxy-3-hydroxymethylanthracene (2) and a detailed photochemical and photobiological investigation on similar anthracene derivatives 3 and 4. Upon photoexcitation with near visible light at λ > 400 nm 1 and 2 give QMs, that were detected by laser flash photolysis and their reactivity with nucleophiles has been demonstrated in the preparative irradiation experiments where the corresponding adducts were isolated and characterized. 3 and 4 cannot undergo photodehydration and deliver QM, but lead to the formation of phenoxyl radical and singlet oxygen, respectively. The activity of 1-4 was tested on a panel of human tumor cell lines, while special attention was devoted to demonstrate their potential selectivity towards the cells with CSC-like properties (HMLEshEcad). Upon the irradiation of cell lines treated with 1-4, an enhancement of antiproliferative activity was demonstrated, but the DNA was not the target molecule. Confocal microscopy revealed that these compounds entered the cell and, upon irradiation, reacted with cellular membranes. Our experiments demonstrated moderate selectivity of 2 and 4 towards CSC-like cells, while necrosis was shown to be a dominant cell death mechanism. Especially interesting was the selectivity of 4 that produced higher levels of ROS in CSC-like cells, which forms the basis for further research on cancer phototherapy, as well as for the elucidation of the underlying mechanism of the observed CSC selectivity based on oxidative stress activation.
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Affiliation(s)
- Lidija Uzelac
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia
| | - Đani Škalamera
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia
| | - Kata Mlinarić-Majerski
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia
| | - Nikola Basarić
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
| | - Marijeta Kralj
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
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22
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Synthesis and photochemical reactivity of phthalimidoadamantane–tyrosine conjugates. RESEARCH ON CHEMICAL INTERMEDIATES 2017. [DOI: 10.1007/s11164-017-2927-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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23
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More NY, Jeganmohan M. Solvent-controlled selective synthesis of biphenols and quinones via oxidative coupling of phenols. Chem Commun (Camb) 2017; 53:9616-9619. [DOI: 10.1039/c7cc04829g] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
A regioselective synthesis of unsymmetrical and symmetrical biphenols and binaphtholsviaoxidative coupling of phenols or naphthols in the presence of K2S2O8in CF3COOH under ambient conditions is described.
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Affiliation(s)
- Nagnath Yadav More
- Department of Chemistry
- Indian Institute of Science Education and Research
- Pune 411021
- India
| | - Masilamani Jeganmohan
- Department of Chemistry
- Indian Institute of Science Education and Research
- Pune 411021
- India
- Department of Chemistry
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24
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Martin MV, Mignone RA, Rosso JA, David Gara P, Pis Diez R, Borsarelli CD, Mártire DO. Transient spectroscopic characterization and theoretical modeling of fulvic acid radicals formed by UV-A radiation. J Photochem Photobiol A Chem 2017. [DOI: 10.1016/j.jphotochem.2016.10.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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25
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Verma S, Aute S, Das A, Ghosh HN. Proton-Coupled Electron Transfer in a Hydrogen-Bonded Charge-Transfer Complex. J Phys Chem B 2016; 120:10780-10785. [DOI: 10.1021/acs.jpcb.6b06032] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sandeep Verma
- Radiation
and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
| | - Sunil Aute
- CSIR-National Chemical Laboratory, Pune 411008, India
| | - Amitava Das
- CSIR-National Chemical Laboratory, Pune 411008, India
- CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar 364002, India
| | - Hirendra N. Ghosh
- Radiation
and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
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26
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Direct observation of light-driven, concerted electron-proton transfer. Proc Natl Acad Sci U S A 2016; 113:11106-11109. [PMID: 27660239 DOI: 10.1073/pnas.1611496113] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The phenols 4-methylphenol, 4-methoxyphenol, and N-acetyl-tyrosine form hydrogen-bonded adducts with N-methyl-4, 4'-bipyridinium cation (MQ+) in aqueous solution as evidenced by the appearance of low-energy, low-absorptivity features in UV-visible spectra. They are assigned to the known examples of optically induced, concerted electron-proton transfer, photoEPT. The results of ultrafast transient absorption measurements on the assembly MeOPhO-H---MQ+ are consistent with concerted EPT by the instantaneous appearance of spectral features for MeOPhO·---H-MQ+ in the transient spectra at the first observation time of 0.1 ps. The transient decays to MeOPhO-H---MQ+ in 2.5 ps, accompanied by the appearance of oscillations in the decay traces with a period of ∼1 ps, consistent with a vibrational coherence and relaxation from a higher υ(N-H) vibrational level or levels on the timescale for back EPT.
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27
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Zabik NL, Virca CN, McCormick TM, Martic-Milne S. Selective Electrochemical versus Chemical Oxidation of Bulky Phenol. J Phys Chem B 2016; 120:8914-24. [PMID: 27454828 DOI: 10.1021/acs.jpcb.6b06135] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The electrochemical oxidation of selected tert-butylated phenols 2,6-di-tert-butyl-4-methylphenol (1), 2,6-di-tert-butylphenol (2), 2,4,6-tri-tert-butylphenol (3), 2-tert-butylphenol (4), and 4-tert-butylphenol (5) was studied in an aprotic environment using cyclic voltammetry, square-wave voltammetry, and UV-vis spectroscopy. All compounds exhibited irreversible oxidation of the corresponding phenol or phenolate ion. Compound 2 was selectively electrochemically oxidized, while other phenol analogues underwent mostly chemical oxidation. The electrochemical oxidation of 2 produced a highly absorbing product, 3,5,3',5'-tetra-tert-butyl-4,4'-diphenoquinone, which was characterized by X-ray crystal diffraction. The electrochemical oxidation was monitored as a function of electrochemical parameters and concentration. Experimental and theoretical data indicated that the steric hindrance, phenoxyl radical stability, and hydrogen bonding influenced the outcome of the electrochemical oxidation. The absence of the substituent at the para position and the presence of the bulky substituents at ortho positions were structural and electrostatic requirements for the selective electrochemical oxidation.
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Affiliation(s)
- Nicole L Zabik
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
| | - Carolyn N Virca
- Department of Chemistry, Portland State University , Portland, Oregon 97201, United States
| | - Theresa M McCormick
- Department of Chemistry, Portland State University , Portland, Oregon 97201, United States
| | - Sanela Martic-Milne
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
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28
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Karunakaran V, Das S. Direct Observation of Cascade of Photoinduced Ultrafast Intramolecular Charge Transfer Dynamics in Diphenyl Acetylene Derivatives: Via Solvation and Intramolecular Relaxation. J Phys Chem B 2016; 120:7016-23. [DOI: 10.1021/acs.jpcb.6b05264] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Venugopal Karunakaran
- Photosciences
and Photonics Section, Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram 695 019, Kerala, India
- Academy of Scientific and Innovative Research (AcSIR), New Delhi 110 001, India
| | - Suresh Das
- Photosciences
and Photonics Section, Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram 695 019, Kerala, India
- Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560 064, India
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29
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Pagba CV, McCaslin TG, Chi SH, Perry JW, Barry BA. Proton-Coupled Electron Transfer and a Tyrosine-Histidine Pair in a Photosystem II-Inspired β-Hairpin Maquette: Kinetics on the Picosecond Time Scale. J Phys Chem B 2016; 120:1259-72. [PMID: 26886811 DOI: 10.1021/acs.jpcb.6b00560] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photosystem II (PSII) and ribonucleotide reductase employ oxidation and reduction of the tyrosine aromatic ring in radical transport pathways. Tyrosine-based reactions involve either proton-coupled electron transfer (PCET) or electron transfer (ET) alone, depending on the pH and the pKa of tyrosine's phenolic oxygen. In PSII, a subset of the PCET reactions are mediated by a tyrosine-histidine redox-driven proton relay, YD-His189. Peptide A is a PSII-inspired β-hairpin, which contains a single tyrosine (Y5) and histidine (H14). Previous electrochemical characterization indicated that Peptide A conducts a net PCET reaction between Y5 and H14, which have a cross-strand π-π interaction. The kinetic impact of H14 has not yet been explored. Here, we address this question through time-resolved absorption spectroscopy and 280-nm photolysis, which generates a neutral tyrosyl radical. The formation and decay of the neutral tyrosyl radical at 410 nm were monitored in Peptide A and its variant, Peptide C, in which H14 is replaced by cyclohexylalanine (Cha14). Significantly, both electron transfer (ET, pL 11, L = lyonium) and PCET (pL 9) were accelerated in Peptide A and C, compared to model tyrosinate or tyrosine at the same pL. Increased electronic coupling, mediated by the peptide backbone, can account for this rate acceleration. Deuterium exchange gave no significant solvent isotope effect in the peptides. At pL 9, but not at pL 11, the reaction rate decreased when H14 was mutated to Cha14. This decrease in rate is attributed to an increase in reorganization energy in the Cha14 mutant. The Y5-H14 mechanism in Peptide A is reminiscent of proton- and electron-transfer events involving YD-H189 in PSII. These results document a mechanism by which proton donors and acceptors can regulate the rate of PCET reactions.
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Affiliation(s)
- Cynthia V Pagba
- School of Chemistry and Biochemistry, the Petit Institute for Bioengineering and Bioscience, and the ‡Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Tyler G McCaslin
- School of Chemistry and Biochemistry, the Petit Institute for Bioengineering and Bioscience, and the ‡Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - San-Hui Chi
- School of Chemistry and Biochemistry, the Petit Institute for Bioengineering and Bioscience, and the ‡Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Joseph W Perry
- School of Chemistry and Biochemistry, the Petit Institute for Bioengineering and Bioscience, and the ‡Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Bridgette A Barry
- School of Chemistry and Biochemistry, the Petit Institute for Bioengineering and Bioscience, and the ‡Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
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30
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Oliver TAA, Zhang Y, Roy A, Ashfold MNR, Bradforth SE. Exploring Autoionization and Photoinduced Proton-Coupled Electron Transfer Pathways of Phenol in Aqueous Solution. J Phys Chem Lett 2015; 6:4159-4164. [PMID: 26722792 DOI: 10.1021/acs.jpclett.5b01861] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The excited state dynamics of phenol in water have been investigated using transient absorption spectroscopy. Solvated electrons and vibrationally cold phenoxyl radicals are observed upon 200 and 267 nm excitation, but with formation time scales that differ by more than 4 orders of magnitude. The impact of these findings is assessed in terms of the relative importance of autoionization versus proton-coupled electron transfer mechanisms in this computationally tractable model system.
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Affiliation(s)
- Thomas A A Oliver
- School of Chemistry, University of Bristol , Bristol, BS8 1TS, United Kingdom
| | - Yuyuan Zhang
- University of Southern California , Los Angeles, California 90089, United States
| | - Anirban Roy
- University of Southern California , Los Angeles, California 90089, United States
| | - Michael N R Ashfold
- School of Chemistry, University of Bristol , Bristol, BS8 1TS, United Kingdom
| | - Stephen E Bradforth
- University of Southern California , Los Angeles, California 90089, United States
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31
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Vargas R, Borrás C, Méndez D, Mostany J, Scharifker BR. Electrochemical oxygen transfer reactions: electrode materials, surface processes, kinetic models, linear free energy correlations, and perspectives. J Solid State Electrochem 2015. [DOI: 10.1007/s10008-015-2984-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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32
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Tseng MY, Hung HY, Sung K. Electron-Withdrawing β-Substituent, Ring-Strain, and Ortho Effects on Reactivity, Selectivity, and Stability of o-Alkoxybenzyl Carbocations. J Phys Chem A 2015; 119:3905-12. [DOI: 10.1021/acs.jpca.5b02234] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Meng-Yun Tseng
- Department of Chemistry, National Cheng Kung University, Tainan, Taiwan
| | - Hsin-Yi Hung
- Department of Chemistry, National Cheng Kung University, Tainan, Taiwan
| | - Kuangsen Sung
- Department of Chemistry, National Cheng Kung University, Tainan, Taiwan
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33
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34
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An T, Fang H, Li G, Wang S, Yao S. Experimental and theoretical insights into photochemical transformation kinetics and mechanisms of aqueous propylparaben and risk assessment of its degradation products. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2014; 33:1809-1816. [PMID: 24796535 DOI: 10.1002/etc.2632] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 04/04/2014] [Accepted: 04/29/2014] [Indexed: 06/03/2023]
Abstract
The kinetics and mechanisms of ultraviolet photochemical transformation of propylparaben (PPB) were studied. Specific kinetics scavenging experiments coupled with quantum yield determinations were used to distinguish the roles of various reactive species induced by self-sensitized and direct photolysis reactions, and the excited triplet state of PPB ((3) PPB*) was identified as the most important species to initiate the photochemical degradation of PPB in aquatic environments. The computational results of time-resolved absorption spectra proved that (3) PPB* is a highly reactive electron acceptor, and a head-to-tail hydrogen transfer mechanism probably occurs through electron coupled with proton transfer. Physical quenching by, or chemical reaction of (3) PPB* with, O2 was confirmed as a key step affecting the initial PPB transformation pathways and degradation mechanisms. The transformation products were identified and the toxicity evolutions of PPB solutions during photochemical degradation under aerobic and anaerobic conditions were compared. The results indicate that anaerobic conditions are more likely than aerobic conditions to lead to the elimination and detoxification of PPB but less likely to lead to PPB mineralization.
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Affiliation(s)
- Taicheng An
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, People's Republic of China
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35
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Škalamera Đ, Mlinarić-Majerski K, Martin-Kleiner I, Kralj M, Wan P, Basarić N. Near-visible light generation of a quinone methide from 3-hydroxymethyl-2-anthrol. J Org Chem 2014; 79:4390-7. [PMID: 24758707 DOI: 10.1021/jo500290y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Excitation of 2-hydroxy-3-(diphenylhydroxymethyl)anthracene (7) to S1 initiates photodehydration, giving the corresponding quinone methide (QM) that was detected by laser flash photolysis (LFP) in 2,2,2-trifluoroethanol (λ = 580 nm, τ = 690 ± 10 ns). The QM decays by protonation, giving a cation (λ = 520 nm, τ = 84 ± 3 μs), which subsequently reacts with nucleophiles. The rate constants in the reactions with nucleophiles were determined by LFP, whereas the adducts were isolated via preparative photolyses. The photogeneration of QMs in the anthrol series is important for potential use in biological systems since the chromophore absorbs at wavelengths > 400 nm. Antiproliferative investigations conducted with 2-anthrol derivative 7 on three human cancer cell lines showed higher activity for irradiated cells.
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Affiliation(s)
- Đani Škalamera
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute , Bijenička cesta 54, 10 000 Zagreb, Croatia
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36
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Fang H, Gao Y, Li G, An J, Wong PK, Fu H, Yao S, Nie X, An T. Advanced oxidation kinetics and mechanism of preservative propylparaben degradation in aqueous suspension of TiO2 and risk assessment of its degradation products. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:2704-12. [PMID: 23432079 DOI: 10.1021/es304898r] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The absolute kinetic rate constants of propylparaben (PPB) in water with different free radicals were investigated, and it was found that both hydroxyl radicals (HO(•)) and hydrated electrons could rapidly react with PPB. The advanced oxidation kinetics and mechanisms of PPB were investigated using photocatalytic process as a model technology, and the degradation was found to be a pseudo-first-order model. Oxidative species, particularly HO(•), were the most important reactive oxygen species mediating photocatalytic degradation of PPB, and PPB degradation was found to be significantly affected by pH because it was controlled by the radical reaction mechanism and was postulated to occur primarily via HO(•)-addition or H-abstraction reactions on the basis of pulse radiolysis measurements and observed reaction products. To investigate potential risk of PPB to humans and aqueous organisms, the estrogenic assays and bioassays were performed using 100 μM PPB solution degraded by photocatalysis at specific intervals. The estrogenic activity decreased as PPB was degraded, while the acute toxicity at three trophic levels first increased slowly and then decreased rapidly as the total organic carbon decreased during photocatalytic degradation.
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Affiliation(s)
- Hansun Fang
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
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37
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Herzog W, Bronner C, Löffler S, He B, Kratzert D, Stalke D, Hauser A, Wenger OS. Electron Transfer between Hydrogen-Bonded Pyridylphenols and a Photoexcited Rhenium(I) Complex. Chemphyschem 2013; 14:1168-76. [DOI: 10.1002/cphc.201201069] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Indexed: 12/22/2022]
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38
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Škalamera Đ, Mlinarić-Majerski K, Uzelac L, Kralj M, Wan P, Basarić N. Photosolvolysis of bulky (4-hydroxyphenyl)naphthalene derivatives. Photochem Photobiol Sci 2013; 12:2043-56. [DOI: 10.1039/c3pp50190f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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39
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Marković Z, Amić D, Milenković D, Dimitrić-Marković JM, Marković S. Examination of the chemical behavior of the quercetin radical cation towards some bases. Phys Chem Chem Phys 2013; 15:7370-8. [DOI: 10.1039/c3cp44605k] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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40
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De Laurentiis E, Maurino V, Minero C, Vione D, Mailhot G, Brigante M. Could triplet-sensitised transformation of phenolic compounds represent a source of fulvic-like substances in natural waters? CHEMOSPHERE 2013; 90:881-884. [PMID: 23036323 DOI: 10.1016/j.chemosphere.2012.09.031] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/05/2012] [Accepted: 09/08/2012] [Indexed: 06/01/2023]
Abstract
Here we show that fluorescent compounds that could be classified as "M-like" (marine-like) fulvic acids are formed upon phototransformation of phenol by a triplet sensitiser (anthraquinone-2-sulphonate, AQ2S). The relevant process most likely involves phenol oxidation to phenoxyl radical by triplet AQ2S, followed by dimerisation of phenoxyl radicals into phenoxyphenols and dihydroxybiphenyls. It might be the first step of an oligomerization process that bears resemblance with the expected formation pathways of humic-like substances (HULIS) in the atmosphere. Such a process could account for the formation in surface waters of compounds having similar fluorescence properties as "M-like" fulvic acids. Presently it is thought that such species are formed upon photo-fragmentation of larger humic and fulvic acids ("top-down" pathway), and we propose that an opposite, "bottom-up" pathway could also be operational.
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Affiliation(s)
- Elisa De Laurentiis
- Università degli Studi di Torino, Dipartimento di Chimica, Via P. Giuria 5, 10125 Torino, Italy
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41
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Yurkova MP, Pozdnyakov IP, Plyusnin VF, Grivin VP, Bazhin NM, Kruppa AI, Maksimova TA. A mechanistic study of the photodegradation of herbicide 2,4,5-trichlorophenoxyacetic acid in aqueous solution. Photochem Photobiol Sci 2013; 12:684-9. [DOI: 10.1039/c2pp25204j] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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42
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Zhang L, Muchall HM, Peslherbe GH. Substituent effects in the absorption spectra of phenol radical species: origin of the redshift caused by 3,5-dimethoxyl substitution. Photochem Photobiol 2012; 89:536-44. [PMID: 23216064 DOI: 10.1111/php.12028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 11/07/2012] [Indexed: 12/31/2022]
Abstract
The ground-state equilibrium geometries, electronic structures and vertical excitation energies of methyl- and methoxyl-substituted phenol radical cations and phenoxyl radicals have been investigated using time-dependent density-functional theory (namely TD-B3LYP) and complete-active-space second-order perturbation theory (CASPT2). The "anomalous" large redshifts of the absorption maxima of the phenol radical species observed in the ultraviolet-visible spectral region upon di-meta-methoxyl substitution are reproduced by the calculations. Furthermore, these "anomalous" shifts which were unexplained to date can be rationalized on the basis of a qualitative molecular orbital perturbation analysis.
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Affiliation(s)
- Lei Zhang
- Centre for Research in Molecular Modeling and Department of Chemistry and Biochemistry, Concordia University, Montreal, QC, Canada
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43
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El-Agamey A, Fukuzumi S. The Remarkable Effect of the Manganese Ion with Dioxygen on the Stability of π-Conjugated Radical Cations. Chemistry 2012; 18:14660-70. [DOI: 10.1002/chem.201201328] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Indexed: 11/05/2022]
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44
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Basarić N, Došlić N, Ivković J, Wang YH, Veljković J, Mlinarić-Majerski K, Wan P. Excited State Intramolecular Proton Transfer (ESIPT) from Phenol to Carbon in Selected Phenylnaphthols and Naphthylphenols. J Org Chem 2012; 78:1811-23. [DOI: 10.1021/jo301456y] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Nikola Basarić
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta
54, 10000 Zagreb, Croatia
| | - Nađa Došlić
- Department of Physical Chemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb,
Croatia
| | - Jakov Ivković
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta
54, 10000 Zagreb, Croatia
| | - Yu-Hsuan Wang
- Department of Chemistry, University of Victoria, Box 3065 Stn CSC, Victoria
BC, V8W 3 V6, Canada
| | - Jelena Veljković
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta
54, 10000 Zagreb, Croatia
| | - Kata Mlinarić-Majerski
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta
54, 10000 Zagreb, Croatia
| | - Peter Wan
- Department of Chemistry, University of Victoria, Box 3065 Stn CSC, Victoria
BC, V8W 3 V6, Canada
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45
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Kuss-Petermann M, Wolf H, Stalke D, Wenger OS. Influence of Donor–Acceptor Distance Variation on Photoinduced Electron and Proton Transfer in Rhenium(I)–Phenol Dyads. J Am Chem Soc 2012; 134:12844-54. [DOI: 10.1021/ja3053046] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Martin Kuss-Petermann
- Institut
für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
| | - Hilke Wolf
- Institut
für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
| | - Dietmar Stalke
- Institut
für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
| | - Oliver S. Wenger
- Institut
für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
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46
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Bronner C, Wenger OS. Proton-Coupled Electron Transfer between 4-Cyanophenol and Photoexcited Rhenium(I) Complexes with Different Protonatable Sites. Inorg Chem 2012; 51:8275-83. [DOI: 10.1021/ic300834c] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Catherine Bronner
- Georg-August-Universität, Institut für Anorganische Chemie, Tammannstrasse 4, D-37077
Göttingen, Germany
| | - Oliver S. Wenger
- Georg-August-Universität, Institut für Anorganische Chemie, Tammannstrasse 4, D-37077
Göttingen, Germany
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47
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Basarić N, Došlić N, Ivković J, Wang YH, Mališ M, Wan P. Very Efficient Generation of Quinone Methides through Excited State Intramolecular Proton Transfer to a Carbon Atom. Chemistry 2012; 18:10617-23. [DOI: 10.1002/chem.201201144] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Indexed: 11/09/2022]
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48
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Morisawa Y, Higashi N, Takaba K, Kariyama N, Goto T, Ikehata A, Ozaki Y. Development of a time-resolved attenuated total reflectance spectrometer in far-ultraviolet region. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:073103. [PMID: 22852667 DOI: 10.1063/1.4732846] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A far-ultraviolet transient absorption spectrometer based on time-resolved attenuated total reflectance (ATR) has been developed and tested for aqueous solutions of phenol and tryptophan in the region 170-185 nm. In this region, a stable tunable laser was not available, and therefore, white light from a laser-driven Xe lamp source was used. The time resolution, which was determined by the time response of a continuous light detector, was 40 ns. A new ATR cell where a sample liquid is exchanged continuously by a flow system was designed to reduce efficiently the stray light from the excitation light. We have tested the performance of the instrument by using aqueous solutions of phenol and tryptophan, whose photochemistry is already well known. Phenol and tryptophan have very strong absorptions due to a π-π∗ transition near 180 nm. Even for dilute solutions (10(-3) mol dm(-3)), we could observe decreases in their concentrations due to photochemistry that occurred upon their irradiation with a fourth harmonic generation laser pulse produced by an Nd:YAG laser. The sensitivity of the spectrometer was about 10(-4) abs, which corresponded to a concentration variation of 10(-3) mol dm(-3) for phenol and tryptophan.
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Affiliation(s)
- Yusuke Morisawa
- Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
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49
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Li DD, Han RM, Liang R, Chen CH, Lai W, Zhang JP, Skibsted LH. Hydroxyl radical reaction with trans-resveratrol: initial carbon radical adduct formation followed by rearrangement to phenoxyl radical. J Phys Chem B 2012; 116:7154-61. [PMID: 22650146 DOI: 10.1021/jp3033337] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In the reaction between trans-resveratrol (resveratrol) and the hydroxyl radical, kinetic product control leads to a short-lived hydroxyl radical adduct with an absorption maximum at 420 nm and a lifetime of 0.21 ± 0.01 μs (anaerobic acetonitrile at 25 °C) as shown by laser flash photolysis using N-hydroxypyridine-2(1H)-thione (N-HPT) as a "photo-Fenton" reagent. The transient spectra of the radical adduct are in agreement with density functional theory (DFT) calculations showing an absorption maximum at 442 or 422 nm for C2 and C6 hydroxyl adducts, respectively, and showing the lowest energy for the transition state leading to the C2 adduct compared to other radical products. From this initial product, the relative long-lived 4'-phenoxyl radical of resveratrol (τ = 9.9 ± 0.9 μs) with an absorption maximum at 390 nm is formed in a process with a time constant (τ = 0.21 ± 0.01 μs) similar to the decay constant for the C2 hydroxyl adduct (or a C2/C6 hydroxyl adduct mixture) and in agreement with thermodynamics identifying this product as the most stable resveratrol radical. The hydroxyl radical adduct to phenoxyl radical conversion with concomitant water dissociation has a rate constant of 5 × 10(6) s(-1) and may occur by intramolecular hydrogen atom transfer or by stepwise proton-assisted electron transfer. Photolysis of N-HPT also leads to a thiyl radical which adds to resveratrol in a parallel reaction forming a sulfur radical adduct with a lifetime of 0.28 ± 0.04 μs and an absorption maximum at 483 nm.
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Affiliation(s)
- Dan-Dan Li
- Department of Chemistry, Renmin University of China, Beijing 100872, PR China
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50
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Veljković J, Uzelac L, Molčanov K, Mlinarić-Majerski K, Kralj M, Wan P, Basarić N. Sterically congested adamantylnaphthalene quinone methides. J Org Chem 2012; 77:4596-610. [PMID: 22533612 DOI: 10.1021/jo3002479] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Five new (2-adamantyl)naphthol derivatives (5-9, quinone methide precursors, QMP) were synthesized and their photochemical reactivity was investigated by preparative photolyses, fluorescence spectroscopy, and laser flash photolysis (LFP). Excitation of QMP 5 to S(1) leads to efficient excited state intramolecular proton transfer (ESIPT) coupled with dehydration, giving quinone methide QM5 which was characterized by LFP (in CH(3)CN-H(2)O, λ(max) = 370 nm, τ = 0.19 ms). On irradiation of QMP 5 in CH(3)OH-H(2)O (4:1), the quantum yield of methanolysis is Φ = 0.70. Excitation of naphthols QMP 6-8 to S(1) in CH(3)CN leads to photoionization and formation of naphthoxyl radicals. In a protic solvent, QMP 6-8 undergo solvent-assisted PT giving QM6 or zwitterion QM8 that react with nucleophiles delivering adducts, but with a significantly lower quantum efficiency. QMP 9 in a protic solvent undergoes two competitive processes, photosolvolysis via QM9 and solvent-assisted PT to carbon atom of the naphthalene giving zwitterion. QM9 has been characterized by LFP (in CH(3)CN-H(2)O, λ(max) > 600 nm, τ = 0.9 ms). In addition to photogenerated QMs, two stable naphthalene QMs, QM10 and QM11 were synthesized thermally and characterized by X-ray crystallography. QM10 and QM11 do not react with H(2)O but undergo acid-catalyzed fragmentation or rearrangement. Antiproliferative activity of 5-9 was investigated on three human cancer cell lines. Exposure of MCF-7 cells treated with 5 to 300 nm irradiation leads to an enhanced antiproliferative effect, in accordance with the activity being due to the formation of QM5.
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Affiliation(s)
- Jelena Veljković
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia
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