1
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Dissanayake KC, Yuan D, Winter AH. Structure-Photoreactivity Studies of BODIPY Photocages: Limitations of the Activation Barrier for Optimizing Photoreactions. J Org Chem 2024; 89:6740-6748. [PMID: 38695507 DOI: 10.1021/acs.joc.3c02980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2024]
Abstract
BODIPY photocages are photoreactive chromophores that release covalently linked cargo upon absorption of visible light. Here, we used computations of the T1 photoheterolysis barrier to ascertain whether a computational approach could assist in a priori structure design by identifying new structures with higher quantum yields of photorelease. The electronic structure-photoreactivity relationships were elucidated for boron-substituted and core-functionalized 2-substituted BODIPY photocages as well as aryl substitutions at the meso-methyl position. Although there is a clear trend for the 2-substituted derivatives, with donor-substituted derivatives featuring both lower computed barriers and higher experimental quantum yields, no trend in the quantum yield with the computed activation barrier is found for the meso-methyl-substituted or boron-substituted derivatives. The lack of a correlation between the experimental quantum yield with the computed barrier in the latter two substitution cases is attributed to the substituents having larger effects on the rates of competing channels (internal conversion and competitive photoreactions) than on the rate of the photoheterolysis channel. Thus, although in some cases computed photoreaction barriers can aid in identifying structures with higher quantum yields, the ignored impacts of how changing the structure affects the rates of competing photophysical/photochemical channels limit the effectiveness of this single-parameter approach.
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Affiliation(s)
- Komadhie C Dissanayake
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Ding Yuan
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
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2
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Qiu Y, Du L, Cady SD, Phillips DL, Winter AH. Optical and EPR Detection of a Triplet Ground State Phenyl Nitrenium Ion. J Am Chem Soc 2024; 146:10679-10686. [PMID: 38579336 DOI: 10.1021/jacs.4c00511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2024]
Abstract
Nitrenium ions are important reactive intermediates participating in the synthetic chemistry and biological processes. Little is known about triplet phenyl nitrenium ions regarding their reactivity, lifetimes, spectroscopic features, and electronic configurations, and no ground state triplet nitrenium ion has been directly detected. In this work, m-pyrrolidinyl-phenyl hydrazine hydrochloride (1) is synthesized as the photoprecursor to photochemically generate the corresponding m-pyrrolidinyl-phenyl nitrenium ion (2), which is computed to adopt a π, π* triplet ground state. A combination of femtosecond (fs) and nanosecond (ns) transient absorption (TA) spectroscopy, cryogenic continuous-wave electronic paramagnetic resonance (CW-EPR) spectroscopy, computational analysis, and photoproduct studies was performed to elucidate the photolysis pathway of 1 and offers the first direct experimental detection of a ground state triplet phenyl nitrenium ion. Upon photoexcitation, 1 forms S1, where bond heterolysis occurs and the NH3 leaving group is extruded in 1.8 ps, generating a vibrationally hot, spin-conserving closed-shell singlet phenyl nitrenium ion (12) that undergoes vibrational cooling in 19 ps. Subsequent intersystem crossing takes place in 0.5 ns, yielding the ground state triplet phenyl nitrenium ion (32), with a lifetime of 0.8 μs. Unlike electrophilic singlet phenyl nitrenium ions, which react rapidly with nucleophiles, this triplet phenyl nitrenium reacts through sequential H atom abstractions, resulting in the eventual formation of the reduced m-pyrrolidinyl-aniline as the predominant stable photoproduct. Supporting the triplet ground state, continuous irradiation of 1 in a glassy matrix at 80 K in an EPR spectrometer forms a paramagnetic triplet species, consistent with a triplet nitrenium ion.
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Affiliation(s)
- Yunfan Qiu
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Lili Du
- Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, S.A.R 11111, P. R. China
| | - Sarah D Cady
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - David Lee Phillips
- Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, S.A.R 11111, P. R. China
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
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3
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Hasan F, Gillen JH, Jayaweera AT, McDearmon WD, Winter AH, Bejger CM. Simple Air-Stable [3]Radialene Anion Radicals as Environmentally Switchable Catholytes in Water. Chemistry 2024; 30:e202302829. [PMID: 37968900 DOI: 10.1002/chem.202302829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 10/30/2023] [Accepted: 11/12/2023] [Indexed: 11/17/2023]
Abstract
The hexacyano[3]radialene radical anion (1) is an attractive catholyte material for use in redox flow battery (RFB) applications. The substitution of cyano groups with ester moieties enhances solubility while maintaining redox reversibility and favorable redox potentials. Here we show that these ester-functionalized, hexasubstituted [3]radialene radical anions dimerize reversibly in water. The dimerization mode is dependent on the substitution pattern and can be switched in solution. Stimuli-responsive behavior is achieved by exploiting an unprecedented tristate switching mechanism, wherein the radical can be toggled between the free radical, a π-dimer, and a σ-dimer-each with dramatically different optical, magnetic, and redox properties-by changing the solvent environment, temperature, or salinity. The symmetric, triester-tricyano[3]radialene (3) forms a solvent-responsive, σ-dimer in water that converts to the radical anion with the addition of organic solvents or to a π-dimer in brine solutions. Diester-tetracyano[3]radialene (2) exists primarily as a π-dimer in aqueous solutions and a radical anion in organic solvents. The dimerization behavior of both 2 and 3 is temperature dependent in methanol solutions. Dimerization equilibrium has a direct impact on catholyte stability during galvanostatic charge-discharge cycling in static H-cells. Specifically, conditions that favor the free radical anion or π-dimer exhibit significantly enhanced cycling profiles.
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Affiliation(s)
- Fuead Hasan
- Department of Chemistry, The University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Jonathan H Gillen
- Department of Chemistry, The University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | | | - William D McDearmon
- Department of Chemistry, The University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, Ames, IA 50010, USA
| | - Christopher M Bejger
- Department of Chemistry, The University of North Carolina at Charlotte, Charlotte, NC 28223, USA
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4
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Shrestha P, Kand D, Weinstain R, Winter AH. meso-Methyl BODIPY Photocages: Mechanisms, Photochemical Properties, and Applications. J Am Chem Soc 2023; 145:17497-17514. [PMID: 37535757 DOI: 10.1021/jacs.3c01682] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/05/2023]
Abstract
meso-methyl BODIPY photocages have recently emerged as an exciting new class of photoremovable protecting groups (PPGs) that release leaving groups upon absorption of visible to near-infrared light. In this Perspective, we summarize the development of these PPGs and highlight their critical photochemical properties and applications. We discuss the absorption properties of the BODIPY PPGs, structure-photoreactivity studies, insights into the photoreaction mechanism, the scope of functional groups that can be caged, the chemical synthesis of these structures, and how substituents can alter the water solubility of the PPG and direct the PPG into specific subcellular compartments. Applications that exploit the unique optical and photochemical properties of BODIPY PPGs are also discussed, from wavelength-selective photoactivation to biological studies to photoresponsive organic materials and photomedicine.
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Affiliation(s)
- Pradeep Shrestha
- Department of Chemistry, Iowa State University, Ames, Iowa 50010, United States
| | - Dnyaneshwar Kand
- School of Plant Sciences and Food Security, Tel-Aviv University, Tel-Aviv 6997801, Israel
| | - Roy Weinstain
- School of Plant Sciences and Food Security, Tel-Aviv University, Tel-Aviv 6997801, Israel
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, Ames, Iowa 50010, United States
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5
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Kaye EG, Mirabi B, Lopez-Miranda IR, Dissanayake KC, Banerjee U, Austin M, Lautens M, Winter AH, Beharry AA. Photo-Uncaging by C(sp 3)-C(sp 3) Bond Cleavage Restores β-Lapachone Activity. J Am Chem Soc 2023. [PMID: 37265114 DOI: 10.1021/jacs.3c00398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
β-Lapachone is an ortho-naphthoquinone natural product with significant antiproliferative activity but suffers from adverse systemic toxicity. The use of photoremovable protecting groups to covalently inactivate a substrate and then enable controllable release with light in a spatiotemporal manner is an attractive prodrug strategy to limit toxicity. However, visible light-activatable photocages are nearly exclusively enabled by linkages to nucleophilic functional sites such as alcohols, amines, thiols, phosphates, and sulfonates. Herein, we report covalent inactivation of the electrophilic quinone moiety of β-lapachone via a C(sp3)-C(sp3) bond to a coumarin photocage. In contrast to β-lapachone, the designed prodrug remained intact in human whole blood and did not induce methemoglobinemia in the dark. Under light activation, the C-C bond cleaves to release the active quinone, recovering its biological activity when evaluated against the enzyme NQO1 and human cancer cells. Investigations into this report of a C(sp3)-C(sp3) photoinduced bond cleavage suggest a nontraditional, radical-based mechanism of release beginning with an initial charge-transfer excited state. Additionally, caging and release of the isomeric para-quinone, α-lapachone, are demonstrated. As such, we describe a photocaging strategy for the pair of quinones and report a unique light-induced cleavage of a C-C bond. We envision that this photocage strategy can be extended to quinones beyond β- and α-lapachone, thus expanding the chemical toolbox of photocaged compounds.
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Affiliation(s)
- Esther G Kaye
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Bijan Mirabi
- Department of Chemistry, Davenport Chemical Laboratories, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Ivonne R Lopez-Miranda
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | | | - Upasana Banerjee
- Department of Chemistry, Iowa State University, Ames, Iowa 50014, United States
| | - Madelyn Austin
- Department of Chemistry, Iowa State University, Ames, Iowa 50014, United States
| | - Mark Lautens
- Department of Chemistry, Davenport Chemical Laboratories, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, Ames, Iowa 50014, United States
| | - Andrew A Beharry
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
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6
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Digby EM, Ayan S, Shrestha P, Gehrmann EJ, Winter AH, Beharry AA. Photocaged DNA-Binding Photosensitizer Enables Photocontrol of Nuclear Entry for Dual-Targeted Photodynamic Therapy. J Med Chem 2022; 65:16679-16694. [PMID: 36480920 DOI: 10.1021/acs.jmedchem.2c01504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Photodynamic therapy (PDT) is a clinically approved cancer treatment that requires a photosensitizer (PS), light, and molecular oxygen─a combination which produces reactive oxygen species (ROS) that can induce cancer cell death. To enhance the efficacy of PDT, dual-targeted strategies have been explored where two photosensitizers are administered and localize to different subcellular organelles. To date, a single small-molecule conjugate for dual-targeted PDT with light-controlled nuclear localization has not been achieved. We designed a probe composed of a DNA-binding PS (Br-DAPI) and a photosensitizing photocage (WinterGreen). Illumination with 480 nm light removes WinterGreen from the conjugate and produces singlet oxygen mainly in the cytosol, while Br-DAPI localizes to nuclei, binds DNA, and produces ROS using one- or two-photon illumination. We observe synergistic photocytotoxicity in MCF7 breast cancer cells, and a reduction in size of three-dimensional (3D) tumor spheroids, demonstrating that nuclear/cytosolic photosensitization using a single agent can enhance PDT efficacy.
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Affiliation(s)
- Elyse M Digby
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, OntarioL5L 1C6, Canada
| | - Seylan Ayan
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, OntarioL5L 1C6, Canada
| | - Pradeep Shrestha
- Department of Chemistry, Iowa State University, Ames, Iowa50011, United States
| | | | - Arthur H Winter
- Department of Chemistry, Iowa State University, Ames, Iowa50011, United States
| | - Andrew A Beharry
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, OntarioL5L 1C6, Canada
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7
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Shrestha P, Mukhopadhyay A, Dissanayake KC, Winter AH. Efficiency of Functional Group Caging with Second-Generation Green- and Red-Light-Labile BODIPY Photoremovable Protecting Groups. J Org Chem 2022; 87:14334-14341. [PMID: 36255274 DOI: 10.1021/acs.joc.2c01781] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BODIPY-based photocages release substrates by excitation with wavelengths in the visible to near-IR regions. The recent development of more efficient BODIPY photocages spurred us to evaluate the scope and efficiency of these second-generation boron-methylated green-light and red-light-absorbing BODIPY photocages. Here, we show that these more photosensitive photocages release amine, alcohol, phenol, phosphate, halides, and carboxylic acid derivatives with much higher quantum yields than first-generation BODIPY photocages and excellent chemical yields. Chemical yields are near-quantitative for the release of all functional groups except the photorelease of amines, which react with concomitantly photogenerated singlet oxygen. In these cases, high chemical yields for photoreleased amines are restored by irradiation under an inert atmosphere. The photorelease quantum yield has a weak relationship with the leaving group pKa of the green-absorbing BODIPY photocages but little relationship with the red-absorbing derivatives, suggesting that factors other than leaving group quality impact the quantum yield. For the photorelease of alcohols, in all cases a carbonate linker (that loses CO2 upon photorelease) significantly increases both the quantum yield and the chemical yield compared to those for direct photorelease via the ether.
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Affiliation(s)
- Pradeep Shrestha
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa50010, United States
| | - Atreyee Mukhopadhyay
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa50010, United States
| | - Komadhie C Dissanayake
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa50010, United States
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa50010, United States
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8
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Juneau A, Lepage I, Sabbah SG, Winter AH, Frenette M. Mechanistic Insight into Phenol Dearomatization by Hypervalent Iodine: Direct Detection of a Phenoxenium Cation. J Org Chem 2022; 87:14274-14283. [PMID: 36215691 DOI: 10.1021/acs.joc.2c01765] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phenol dearomatization is one of several oxidation reactions enabled by hypervalent iodine reagents. However, the presence of a proposed free phenoxenium intermediate in phenol dearomatization is a matter of debate in the literature. Here, we report the unambiguous detection of a free phenoxenium intermediate in the reaction of an electron-rich phenol, 2,4,6-trimethoxyphenol, and (diacetoxyiodo)benzene using UV-vis and resonance Raman spectroscopies. In contrast, we predominantly detect single electron oxidation products of less electron-rich phenols or alkoxy-substituted aromatics in their reaction with (diacetoxyiodo)benzene using UV-vis and electron paramagnetic resonance (EPR) spectroscopies. We conclude that the often-postulated free phenoxenium intermediate, while possible with highly stabilizing substituents, is unlikely to be a general mechanistic pathway in the reaction of typical phenols with hypervalent iodine reagents. The polar solvent 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) or the use of more strongly oxidizing hypervalent iodine reagents, such as [bis(trifluoroacetoxy)iodo]benzene (PIFA) or [hydroxy(tosyloxy)iodo]benzene (HTIB), can help reduce the formation of radical byproducts and favors the formation of phenoxenium intermediates.
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Affiliation(s)
- Antoine Juneau
- Department of Chemistry, Quebec Centre for Advanced Materials and NanoQAM, Université du Québec à Montréal, Case Postale 8888, Succursale Centre-Ville, Montréal, Québec H3C 3P8, Canada
| | - Iannick Lepage
- Department of Chemistry, Quebec Centre for Advanced Materials and NanoQAM, Université du Québec à Montréal, Case Postale 8888, Succursale Centre-Ville, Montréal, Québec H3C 3P8, Canada
| | - Sami G Sabbah
- Department of Chemistry, Quebec Centre for Advanced Materials and NanoQAM, Université du Québec à Montréal, Case Postale 8888, Succursale Centre-Ville, Montréal, Québec H3C 3P8, Canada
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, Iowa 50010, United States
| | - Mathieu Frenette
- Department of Chemistry, Quebec Centre for Advanced Materials and NanoQAM, Université du Québec à Montréal, Case Postale 8888, Succursale Centre-Ville, Montréal, Québec H3C 3P8, Canada
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9
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Abstract
Protective groups that can be selectively removed under mild conditions are an essential aspect of carbohydrate chemistry. Groups that can be selectively removed by visible light are particularly attractive because carbohydrates are transparent to visible light. Here, different BODIPY protecting groups were explored for their utility during glycan synthesis. A BODIPY group bearing a boron difluoride unit is stable during glycosylations but can be cleaved with green light as illustrated by the assembly of a trisaccharide.
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Affiliation(s)
- Sabrina Leichnitz
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany. .,Institute of Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany
| | | | - Arthur H Winter
- Department of Chemistry, Iowa State University, Ames, Iowa 50014, USA.
| | - Peter H Seeberger
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany. .,Institute of Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany
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10
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Du L, Wang J, Qiu Y, Liang R, Lu P, Chen X, Phillips DL, Winter AH. Generation and direct observation of a triplet arylnitrenium ion. Nat Commun 2022; 13:3458. [PMID: 35710806 PMCID: PMC9203820 DOI: 10.1038/s41467-022-31091-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 05/31/2022] [Indexed: 11/22/2022] Open
Abstract
Nitrenium ions are important reactive intermediates in both chemistry and biology. Although singlet nitrenium ions are well-characterized by direct methods, the triplet states of nitrenium ions have never been directly detected. Here, we find that the excited state of the photoprecursor partitions between heterolysis to generate the singlet nitrenium ion and intersystem crossing (ISC) followed by a spontaneous heterolysis process to generate the triplet p-iodophenylnitrenium ion (np). The triplet nitrenium ion undergoes ISC to generate the ground singlet state, which ultimately undergoes proton and electron transfer to generate a long-lived radical cation that further generates the reduced p-iodoaniline. Ab Initio calculations were performed to map out the potential energy surfaces to better understand the excited state reactivity channels show that an energetically-accessible singlet-triplet crossing lies along the N-N stretch coordinate and that the excited triplet state is unbound and spontaneously eliminates ammonia to generate the triplet nitrenium ion. These results give a clearer picture of the photophysical properties and reactivity of two different spin states of a phenylnitrenium ion and provide the first direct glimpse of a triplet nitrenium ion. Nitrenium ions are highly electrophilic reactive intermediates of formula R−N−R+, nitrogen analogue of carbenes. Here the authors report the detection of a triplet nitrenium ion using time-resolved spectroscopic methods and ab initio computations, allowing a glimpse at the properties and behavior of this important class of intermediates.
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Affiliation(s)
- Lili Du
- School of Life Sciences, Jiangsu University, 212013, Zhenjiang, P.R. China.,Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P.R. China
| | - Juanjuan Wang
- Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Department of Chemistry, Beijing Normal University, 100875, Beijing, P.R. China
| | - Yunfan Qiu
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, IA, 50011, USA
| | - Runhui Liang
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P.R. China
| | - Penglin Lu
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P.R. China
| | - Xuebo Chen
- Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Department of Chemistry, Beijing Normal University, 100875, Beijing, P.R. China.
| | - David Lee Phillips
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P.R. China. .,Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, IA, 50011, USA.
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, IA, 50011, USA.
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11
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Contreras-García E, Lozano C, García-Iriepa C, Marazzi M, Winter AH, Torres C, Sampedro D. Controlling Antimicrobial Activity of Quinolones Using Visible/NIR Light-Activated BODIPY Photocages. Pharmaceutics 2022; 14:pharmaceutics14051070. [PMID: 35631655 PMCID: PMC9144359 DOI: 10.3390/pharmaceutics14051070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 05/03/2022] [Accepted: 05/13/2022] [Indexed: 11/26/2022] Open
Abstract
Controlling the activity of a pharmaceutical agent using light offers improved selectivity, reduction of adverse effects, and decreased environmental build-up. These benefits are especially attractive for antibiotics. Herein, we report a series of photoreleasable quinolones, which can be activated using visible/NIR light (520–800 nm). We have used BODIPY photocages with strong absorption in the visible to protect two different quinolone-based compounds and deactivate their antimicrobial properties. This activity could be recovered upon green or red light irradiation. A comprehensive computational study provides new insight into the reaction mechanism, revealing the relevance of considering explicit solvent molecules. The triplet excited state is populated and the photodissociation is assisted by the solvent. The light-controlled activity of these compounds has been assessed on a quinolone-susceptible E. coli strain. Up to a 32-fold change in the antimicrobial activity was measured.
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Affiliation(s)
- Elena Contreras-García
- Departamento de Química, Centro de Investigación en Síntesis Química (CISQ), Universidad de La Rioja, Madre de Dios 53, 26006 Logroño, Spain;
| | - Carmen Lozano
- Área Bioquímica y Biología Molecular, Universidad de La Rioja, Madre de Dios 53, 26006 Logroño, Spain; (C.L.); (C.T.)
| | - Cristina García-Iriepa
- Departamento de Química Analítica, Química Física e Ingeniería Química, Grupo de Reactividad y Estructura Molecular (RESMOL), Universidad de Alcalá, 28805 Alcalá de Henares, Spain; (C.G.-I.); (M.M.)
- Instituto de Investigación Química “Andrés M. del Río” (IQAR), Universidad de Alcalá, 28805 Alcalá de Henares, Spain
| | - Marco Marazzi
- Departamento de Química Analítica, Química Física e Ingeniería Química, Grupo de Reactividad y Estructura Molecular (RESMOL), Universidad de Alcalá, 28805 Alcalá de Henares, Spain; (C.G.-I.); (M.M.)
- Instituto de Investigación Química “Andrés M. del Río” (IQAR), Universidad de Alcalá, 28805 Alcalá de Henares, Spain
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, Ames, IA 50014, USA;
| | - Carmen Torres
- Área Bioquímica y Biología Molecular, Universidad de La Rioja, Madre de Dios 53, 26006 Logroño, Spain; (C.L.); (C.T.)
| | - Diego Sampedro
- Departamento de Química, Centro de Investigación en Síntesis Química (CISQ), Universidad de La Rioja, Madre de Dios 53, 26006 Logroño, Spain;
- Correspondence:
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12
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Abstract
Metastable radicals exist in a steady-state equilibrium in solution with dimers, which can be either σ dimers or π dimers. Here, we show that steric hindrance at the para position causes julolidine-derived dicyanomethyl radicals to form σ dimers rather than π dimers, the opposite behavior as seen in other carbon-centered radicals, where steric hindrance typically favors pimerization. The change in dimerization mode can be attributed to weaker London dispersion forces and a decreased orbital overlap in the sterically hindered dicyanomethyl radical π dimers, while the bulky groups exert relatively little effect on the energy of the σ dimer.
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Affiliation(s)
- Rui Zhang
- Department of Chemistry, Iowa State University, 1651 Gilman Hall, Ames, Iowa 50010, United States
| | - Arkady Ellern
- Department of Chemistry, Iowa State University, 1651 Gilman Hall, Ames, Iowa 50010, United States
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, 1651 Gilman Hall, Ames, Iowa 50010, United States
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13
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Zhang R, Ellern A, Winter AH. Anti-Aromaticity Relief as an Approach to Stabilize Free Radicals. Angew Chem Int Ed Engl 2021; 60:25082-25088. [PMID: 34528379 DOI: 10.1002/anie.202110870] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [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: 08/12/2021] [Revised: 09/06/2021] [Indexed: 11/07/2022]
Abstract
A new strategy to stabilize free radicals electronically is described by conjugating formally antiaromatic substituents to the free radical. With an antiaromatic substituent, the radical acts as an electron sink to allow configuration mixing of a low-energy zwitterionic state that provides antiaromaticity relief to the substituent. A combination of X-ray crystallography, VT-EPR and VT-UV/Vis spectroscopy, as well as computational analysis, was used to investigate this phenomenon. We find that this strategy of antiaromaticity relief is successful at stabilizing radicals, but only if the antiaromatic substituent is constrained to be planar by synthetically imposed conformational restraints that enable state mixing. This work leads to the counterintuitive finding that increasing the antiaromaticity of the radical substituent leads to greater radical stability, providing proof of concept for a new stereoelectronic approach for stabilizing free radicals.
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Affiliation(s)
- Rui Zhang
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA, 50010, USA
| | - Arkady Ellern
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA, 50010, USA
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA, 50010, USA
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14
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Affiliation(s)
- Rui Zhang
- Department of Chemistry Iowa State University 1605 Gilman Hall Ames IA 50010 USA
| | - Arkady Ellern
- Department of Chemistry Iowa State University 1605 Gilman Hall Ames IA 50010 USA
| | - Arthur H. Winter
- Department of Chemistry Iowa State University 1605 Gilman Hall Ames IA 50010 USA
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15
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Abstract
Selective deprotection of functional groups using different wavelengths of light is attractive for materials synthesis as well as for achieving independent photocontrol over substrates in biological systems. Here, we show that mixtures of recently developed visible light-absorbing BODIPY-derived photoremovable protecting groups (PRPGs) and a coumarin-derived PRPG can undergo wavelength-selective activation, giving independent optical control over a mixture of photocaged substrates using biologically benign long-wavelength light.
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Affiliation(s)
- Julie A Peterson
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, Iowa 50010, United States
| | - Ding Yuan
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, Iowa 50010, United States
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, Iowa 50010, United States
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16
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Shrestha P, Dissanayake KC, Gehrmann EJ, Wijesooriya CS, Mukhopadhyay A, Smith EA, Winter AH. Efficient Far-Red/Near-IR Absorbing BODIPY Photocages by Blocking Unproductive Conical Intersections. J Am Chem Soc 2020; 142:15505-15512. [PMID: 32786742 DOI: 10.1021/jacs.0c07139] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Photocages are light-sensitive chemical protecting groups that give investigators control over activation of biomolecules using targeted light irradiation. A compelling application of far-red/near-IR absorbing photocages is their potential for deep tissue activation of biomolecules and phototherapeutics. Toward this goal, we recently reported BODIPY photocages that absorb near-IR light. However, these photocages have reduced photorelease efficiencies compared to shorter-wavelength absorbing photocages, which has hindered their application. Because photochemistry is a zero-sum competition of rates, improvement of the quantum yield of a photoreaction can be achieved either by making the desired photoreaction more efficient or by hobbling competitive decay channels. This latter strategy of inhibiting unproductive decay channels was pursued to improve the release efficiency of long-wavelength absorbing BODIPY photocages by synthesizing structures that block access to unproductive singlet internal conversion conical intersections, which have recently been located for simple BODIPY structures from excited state dynamic simulations. This strategy led to the synthesis of new conformationally restrained boron-methylated BODIPY photocages that absorb light strongly around 700 nm. In the best case, a photocage was identified with an extinction coefficient of 124000 M-1 cm-1, a quantum yield of photorelease of 3.8%, and an overall quantum efficiency of 4650 M-1 cm-1 at 680 nm. This derivative has a quantum efficiency that is 50-fold higher than the best known BODIPY photocages absorbing >600 nm, validating the effectiveness of a strategy for designing efficient photoreactions by thwarting competitive excited state decay channels. Furthermore, 1,7-diaryl substitutions were found to improve the quantum yields of photorelease by excited state participation and blocking ion pair recombination by internal nucleophilic trapping. No cellular toxicity (trypan blue exclusion) was observed at 20 μM, and photoactivation was demonstrated in HeLa cells using red light.
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Affiliation(s)
- Pradeep Shrestha
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Komadhie C Dissanayake
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Elizabeth J Gehrmann
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Chamari S Wijesooriya
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Atreyee Mukhopadhyay
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Emily A Smith
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
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17
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Affiliation(s)
- Joshua P. Peterson
- Department of Chemistry, Iowa State University, 1605 Gilman
Hall, Ames, Iowa 50010, United States
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, 1605 Gilman
Hall, Ames, Iowa 50010, United States
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18
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Peterson JA, Fischer LJ, Gehrmann EJ, Shrestha P, Yuan D, Wijesooriya CS, Smith EA, Winter AH. Direct Photorelease of Alcohols from Boron-Alkylated BODIPY Photocages. J Org Chem 2020; 85:5712-5717. [DOI: 10.1021/acs.joc.0c00044] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Julie A. Peterson
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Logan J. Fischer
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Elizabeth J. Gehrmann
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Pradeep Shrestha
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Ding Yuan
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Chamari S. Wijesooriya
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Emily A. Smith
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
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19
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Qiu Y, Winter AH. Anomalous Electronic Properties of Iodous Materials: Application to High-Spin Reactive Intermediates and Conjugated Polymers. J Org Chem 2020; 85:4145-4152. [DOI: 10.1021/acs.joc.9b03289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yunfan Qiu
- Department of Chemistry, Iowa State University, 2101 Hach Hall, Ames, Iowa 50010, United States
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, 2101 Hach Hall, Ames, Iowa 50010, United States
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20
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Kand D, Liu P, Navarro MX, Fischer LJ, Rousso-Noori L, Friedmann-Morvinski D, Winter AH, Miller EW, Weinstain R. Water-Soluble BODIPY Photocages with Tunable Cellular Localization. J Am Chem Soc 2020; 142:4970-4974. [PMID: 32115942 PMCID: PMC7302507 DOI: 10.1021/jacs.9b13219] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
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Photoactivation of
bioactive molecules allows manipulation of cellular
processes with high spatiotemporal precision. The recent emergence
of visible-light excitable photoprotecting groups has the potential
to further expand the established utility of the photoactivation strategy
in biological applications by offering higher tissue penetration,
diminished phototoxicity, and compatibility with other light-dependent
techniques. Nevertheless, a critical barrier to such applications
remains the significant hydrophobicity of most visible-light excitable
photocaging groups. Here, we find that applying the conventional 2,6-sulfonation
to meso-methyl BODIPY photocages is incompatible
with their photoreaction due to an increase in the excited state barrier
for photorelease. We present a simple, remote sulfonation solution
to BODIPY photocages that imparts water solubility and provides control
over cellular permeability while retaining their favorable spectroscopic
and photoreaction properties. Peripherally disulfonated BODIPY photocages
are cell impermeable, making them useful for modulation of cell-surface
receptors, while monosulfonated BODIPY retains the ability to cross
the cellular membrane and can modulate intracellular targets. This
new approach is generalizable for controlling BODIPY localization
and was validated by sensitization of mammalian cells and neurons
by visible-light photoactivation of signaling molecules.
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Affiliation(s)
| | | | | | - Logan J Fischer
- Department of Chemistry, Iowa State University, Ames, Iowa 50010, United States
| | | | | | - Arthur H Winter
- Department of Chemistry, Iowa State University, Ames, Iowa 50010, United States
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21
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Peterson JP, Ellern A, Winter AH. Spin Delocalization, Polarization, and London Dispersion Forces Govern the Formation of Diradical Pimers. J Am Chem Soc 2020; 142:5304-5313. [DOI: 10.1021/jacs.0c00190] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Joshua P. Peterson
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Arkady Ellern
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
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22
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Toupin NP, Arora K, Shrestha P, Peterson JA, Fischer LJ, Rajagurubandara E, Podgorski I, Winter AH, Kodanko JJ. BODIPY-Caged Photoactivated Inhibitors of Cathepsin B Flip the Light Switch on Cancer Cell Apoptosis. ACS Chem Biol 2019; 14:2833-2840. [PMID: 31750642 PMCID: PMC9885843 DOI: 10.1021/acschembio.9b00711] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Acquired resistance to apoptotic agents is a long-standing challenge in cancer treatment. Cathepsin B (CTSB) is an enzyme which, among many essential functions, promotes apoptosis during cellular stress through regulation of intracellular proteolytic networks on the minute time scale. Recent data indicate that CTSB inhibition may be a promising method to steer cells away from apoptotic death toward necrosis, a mechanism of cell death that can overcome resistance to apoptotic agents, stimulate an immune response and promote antitumor immunity. Unfortunately, rapid and selective intracellular inactivation of CTSB has not been possible. However, here we report on the synthesis and characterization of photochemical and biological properties of BODIPY-caged inhibitors of CTSB that are cell permeable, highly selective and activated rapidly upon exposure to visible light. Intriguingly, these compounds display tunable photophysical and biological properties based on substituents bound directly to boron. Me2BODIPY-caged compound 8 displays the dual-action capability of light-accelerated CTSB inhibition and singlet oxygen production from a singular molecular entity. The dual-action capacity of 8 leads to a rapid necrotic response in MDA-MB-231 triple negative breast cancer cells with high phototherapeutic indexes (>30) and selectivity vs noncancerous cells that neither CTSB inhibition nor photosensitization gives alone. Our work confirms that singlet oxygen production and CTSB inactivation is highly synergistic and a promising method for killing cancer cells. Furthermore, this ability to trigger intracellular inactivation of CTSB with light provides researchers with a powerful photochemical tool for probing biochemical processes on short time scales.
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Affiliation(s)
- Nicholas P. Toupin
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States
| | - Karan Arora
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States
| | - Pradeep Shrestha
- Department of Chemistry, Iowa State University, Ames, Iowa 50014, United States
| | - Julie A. Peterson
- Department of Chemistry, Iowa State University, Ames, Iowa 50014, United States
| | - Logan J. Fischer
- Department of Chemistry, Iowa State University, Ames, Iowa 50014, United States
| | - Erandi Rajagurubandara
- Department of Pharmacology, School of Medicine, Wayne State University, Detroit, Michigan 48201, United States
| | - Izabela Podgorski
- Barbara Ann Karmanos Cancer Institute, Detroit, Michigan 48201, United States,Department of Pharmacology, School of Medicine, Wayne State University, Detroit, Michigan 48201, United States
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, Ames, Iowa 50014, United States,Corresponding Authors: .
| | - Jeremy J. Kodanko
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States,Barbara Ann Karmanos Cancer Institute, Detroit, Michigan 48201, United States,Corresponding Authors: .
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23
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Peterson J, Zhang R, Winter AH. Effect of Structure on the Spin Switching and Magnetic Bistability of Solid-State Aryl Dicyanomethyl Monoradicals and Diradicals. ACS Omega 2019; 4:13538-13542. [PMID: 31460483 PMCID: PMC6705199 DOI: 10.1021/acsomega.9b01658] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 07/29/2019] [Indexed: 06/10/2023]
Abstract
Stable organic radicals with switchable spin states have applications in medicine, biology, and material science. An emerging class of such spin-switchable radicals is based on dicyanomethyl radicals, which are typically thermally and air-stable species that form weakly bonded (closed-shell singlet) dimers at a lower temperature that rupture into electron paramagnetic resonance-active diradicals at a higher temperature. However, thus far, the study of these dicyanomethyl radicals has focused on their solution-phase behavior. An understanding of how chemical structure affects the solid-state spin switching behavior for these radicals is unknown. Here, we examine the solid-state spin crossover behavior of 6 monoradicals and 10 tethered diradicals and demonstrate that these species also undergo spin switching in the solid state. We find that the susceptibility for solid-state spin switching for the intermolecular dimers is weakly correlated to the solution-phase Gibbs free energies of dimerization, but no apparent correlations are seen between the solution-state free energies for the intramolecular dimerization and the solid-state behavior. Furthermore, intramolecular diradical dimers have greatly enhanced temperature-responsive behavior compared to their intermolecular counterparts. Crystalline and amorphous powders of the same radicals feature similar spin switching behavior, but the crystalline materials have slower bond-rupture kinetics at higher temperatures, suggesting that solid-state packing effects are an important kinetic consideration. An interesting feature of these systems is that, upon cooling down to room temperature after heating, some radicals remain trapped in the solids, indicating magnetic bistability, while others partially or fully return to the diamagnetic dimers. This work provides insights into how chemical structure affects spin crossover in the solid state for this new class of air-stable radicals, the knowledge of importance for the construction of dynamically responsive solid-state materials, and organic spin crossover polymers.
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24
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Peterson JP, Winter AH. Solvent Effects on the Stability and Delocalization of Aryl Dicyanomethyl Radicals: The Captodative Effect Revisited. J Am Chem Soc 2019; 141:12901-12906. [PMID: 31352783 DOI: 10.1021/jacs.9b06576] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The captodative effect postulates that radicals substituted with both electron donating and accepting groups enjoy a special enhanced stabilization, a model given theoretical support by simple MO and resonance arguments. A key prediction from theory is that captodative stabilization of radicals is larger in polar solvents than in nonpolar solvents or the gas phase, which can be viewed in the resonance model as solvent stabilization of charge-separated resonance forms. Yet, several experimental studies have failed to observe a solvent effect on radical stability, casting doubt on key aspects of the captodative effect. Here, we examine in detail the effect of solvent on the stability of structurally related captodative aryl dicyanomethyl radicals. An attractive feature of these radicals is that they exist as stable steady state populations of radicals in equilibrium with their dimers, allowing us to directly characterize from experiment their thermodynamic stabilities and spin delocalization in solvents of varying polarity. In contrast to the prior studies, we find that captodative radicals are indeed stabilized by polar solvents, as measured by a shift in the radical-dimer association constants by up to 100-fold toward the radical upon going from nonpolar toluene to more polar DMF. Moreover, in polar solvents, the spin is shifted onto the donor substituent and away from the benzylic carbon. Within the resonance model, these results can be explained by the increased contributions of the zwitterionic resonance structures to the overall hybrid. These results provide experimental support to a key prediction from theory that had previously been dismissed.
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Affiliation(s)
- Joshua P Peterson
- Department of Chemistry , Iowa State University , 1608 Gilman Hall , Ames , Iowa 50010 , United States
| | - Arthur H Winter
- Department of Chemistry , Iowa State University , 1608 Gilman Hall , Ames , Iowa 50010 , United States
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25
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Li MD, Wong NK, Xiao J, Zhu R, Wu L, Dai SY, Chen F, Huang G, Xu L, Bai X, Geraskina MR, Winter AH, Chen X, Liu Y, Fang W, Yang D, Phillips DL. Dynamics of Oxygen-Independent Photocleavage of Blebbistatin as a One-Photon Blue or Two-Photon Near-Infrared Light-Gated Hydroxyl Radical Photocage. J Am Chem Soc 2018; 140:15957-15968. [PMID: 30269478 DOI: 10.1021/jacs.8b10235] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Development of versatile, chemically tunable photocages for photoactivated chemotherapy (PACT) represents an excellent opportunity to address the technical drawbacks of conventional photodynamic therapy (PDT) whose oxygen-dependent nature renders it inadequate in certain therapy contexts such as hypoxic tumors. As an alternative to PDT, oxygen free mechanisms to generate cytotoxic reactive oxygen species (ROS) by visible light cleavable photocages are in demand. Here, we report the detailed mechanisms by which the small molecule blebbistatin acts as a one-photon blue light-gated or two-photon near-infrared light-gated photocage to directly release a hydroxyl radical (•OH) in the absence of oxygen. By using femtosecond transient absorption spectroscopy and chemoselective ROS fluorescent probes, we analyze the dynamics and fate of blebbistatin during photolysis under blue light. Water-dependent photochemistry reveals a critical process of water-assisted protonation and excited state intramolecular proton transfer (ESIPT) that drives the formation of short-lived intermediates, which surprisingly culminates in the release of •OH but not superoxide or singlet oxygen from blebbistatin. CASPT2//CASSCF calculations confirm that hydrogen bonding between water and blebbistatin underpins this process. We further determine that blue light enables blebbistatin to induce mitochondria-dependent apoptosis, an attribute conducive to PACT development. Our work demonstrates blebbistatin as a controllable photocage for •OH generation and provides insight into the potential development of novel PACT agents.
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Affiliation(s)
- Ming-De Li
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province , Shantou University , Shantou 515063 , China
| | - Nai-Kei Wong
- Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China.,State Key Discipline of Infectious Diseases , Shenzhen Third People's Hospital , Shenzhen 518112 , China
| | - Jia Xiao
- State Key Discipline of Infectious Diseases , Shenzhen Third People's Hospital , Shenzhen 518112 , China
| | - Ruixue Zhu
- Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China
| | - Liangliang Wu
- Department of Chemistry , Beijing Normal University , Xin-wai-da-jie 19 , Beijing 100875 , China
| | - Sheng-Yao Dai
- Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China
| | - Feng Chen
- State Key Discipline of Infectious Diseases , Shenzhen Third People's Hospital , Shenzhen 518112 , China
| | - Guanheng Huang
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province , Shantou University , Shantou 515063 , China
| | - Liang Xu
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province , Shantou University , Shantou 515063 , China
| | - Xiaoyu Bai
- Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China
| | - Margarita R Geraskina
- Department of Chemistry , Iowa State University , 2101d Hach Hall , Ames , Iowa 50011 , United States
| | - Arthur H Winter
- Department of Chemistry , Iowa State University , 2101d Hach Hall , Ames , Iowa 50011 , United States
| | - Xuebo Chen
- Department of Chemistry , Beijing Normal University , Xin-wai-da-jie 19 , Beijing 100875 , China
| | - Yingxia Liu
- State Key Discipline of Infectious Diseases , Shenzhen Third People's Hospital , Shenzhen 518112 , China
| | - Weihai Fang
- Department of Chemistry , Beijing Normal University , Xin-wai-da-jie 19 , Beijing 100875 , China
| | - Dan Yang
- Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China
| | - David Lee Phillips
- Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong , China
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26
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Zhang R, Peterson JP, Fischer LJ, Ellern A, Winter AH. Effect of Structure on the Spin–Spin Interactions of Tethered Dicyanomethyl Diradicals. J Am Chem Soc 2018; 140:14308-14313. [DOI: 10.1021/jacs.8b08628] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Rui Zhang
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Joshua P. Peterson
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Logan J. Fischer
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Arkady Ellern
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, 1608 Gilman Hall, Ames, Iowa 50010, United States
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27
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Affiliation(s)
- Paul G. Wenthold
- The Department of Chemistry and Biochemistry, Purdue University, West Lafayette, Indiana 47906, United States
| | - Arthur H. Winter
- The Department of Chemistry and Biochemistry, Iowa State University, Ames, Iowa 52101, United States
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28
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Affiliation(s)
- Paul G. Wenthold
- The Department of Chemistry and Biochemistry, Purdue University, West Lafayette, Indiana 47906, United States
| | - Arthur H. Winter
- The Department of Chemistry and Biochemistry, Iowa State University, Ames, Iowa 52101, United States
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29
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Wijesooriya CS, Peterson JA, Shrestha P, Gehrmann EJ, Winter AH, Smith EA. A Photoactivatable BODIPY Probe for Localization‐Based Super‐Resolution Cellular Imaging. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201805827] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
| | | | | | | | | | - Emily A. Smith
- Department of Chemistry Iowa State University Ames IA 50011 USA
- The Ames Laboratory US Department of Energy Ames IA 50011 USA
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30
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Wijesooriya CS, Peterson JA, Shrestha P, Gehrmann EJ, Winter AH, Smith EA. A Photoactivatable BODIPY Probe for Localization-Based Super-Resolution Cellular Imaging. Angew Chem Int Ed Engl 2018; 57:12685-12689. [PMID: 30247796 DOI: 10.1002/anie.201805827] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [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: 05/20/2018] [Revised: 07/10/2018] [Indexed: 11/07/2022]
Abstract
The synthesis and application of a photoactivatable boron-alkylated BODIPY probe for localization-based super-resolution microscopy is reported. Photoactivation and excitation of the probe is achieved by a previously unknown boron-photodealkylation reaction with a single low-power visible laser and without requiring the addition of reducing agents or oxygen scavengers in the imaging buffer. These features lead to a versatile probe for localization-based microscopy of biological systems. The probe can be easily linked to nucleophile-containing molecules to target specific cellular organelles. By attaching paclitaxel to the photoactivatable BODIPY, in vitro and in vivo super-resolution imaging of microtubules is demonstrated. This is the first example of single-molecule localization-based super-resolution microscopy using a visible-light-activated BODIPY compound as a fluorescent probe.
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Affiliation(s)
| | - Julie A Peterson
- Department of Chemistry, Iowa State University, Ames, IA, 50011, USA
| | - Pradeep Shrestha
- Department of Chemistry, Iowa State University, Ames, IA, 50011, USA
| | | | - Arthur H Winter
- Department of Chemistry, Iowa State University, Ames, IA, 50011, USA
| | - Emily A Smith
- Department of Chemistry, Iowa State University, Ames, IA, 50011, USA.,The Ames Laboratory, US Department of Energy, Ames, IA, 50011, USA
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31
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Peterson JA, Wijesooriya C, Gehrmann EJ, Mahoney KM, Goswami PP, Albright TR, Syed A, Dutton AS, Smith EA, Winter AH. Family of BODIPY Photocages Cleaved by Single Photons of Visible/Near-Infrared Light. J Am Chem Soc 2018; 140:7343-7346. [PMID: 29775298 DOI: 10.1021/jacs.8b04040] [Citation(s) in RCA: 174] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Photocages are light-sensitive chemical protecting groups that provide external control over when, where, and how much of a biological substrate is activated in cells using targeted light irradiation. Regrettably, most popular photocages (e.g., o-nitrobenzyl groups) absorb cell-damaging ultraviolet wavelengths. A challenge with achieving longer wavelength bond-breaking photochemistry is that long-wavelength-absorbing chromophores have shorter excited-state lifetimes and diminished excited-state energies. However, here we report the synthesis of a family of BODIPY-derived photocages with tunable absorptions across the visible/near-infrared that release chemical cargo under irradiation. Derivatives with appended styryl groups feature absorptions above 700 nm, yielding photocages cleaved with the highest known wavelengths of light via a direct single-photon-release mechanism. Photorelease with red light is demonstrated in living HeLa cells, Drosophila S2 cells, and bovine GM07373 cells upon ∼5 min irradiation. No cytotoxicity is observed at 20 μM photocage concentration using the trypan blue exclusion assay. Improved B-alkylated derivatives feature improved quantum efficiencies of photorelease ∼20-fold larger, on par with the popular o-nitrobenzyl photocages (εΦ = 50-100 M-1 cm-1), but absorbing red/near-IR light in the biological window instead of UV light.
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Affiliation(s)
- Julie A Peterson
- Department of Chemistry , Iowa State University , Ames , Iowa 50014 , United States
| | - Chamari Wijesooriya
- Department of Chemistry , Iowa State University , Ames , Iowa 50014 , United States
| | - Elizabeth J Gehrmann
- Department of Chemistry , Iowa State University , Ames , Iowa 50014 , United States
| | - Kaitlyn M Mahoney
- Department of Chemistry , Iowa State University , Ames , Iowa 50014 , United States
| | - Pratik P Goswami
- Department of Chemistry , Iowa State University , Ames , Iowa 50014 , United States
| | - Toshia R Albright
- Department of Chemistry , Iowa State University , Ames , Iowa 50014 , United States
| | - Aleem Syed
- Department of Chemistry , Iowa State University , Ames , Iowa 50014 , United States
| | - Andrew S Dutton
- Department of Chemistry , Iowa State University , Ames , Iowa 50014 , United States
| | - Emily A Smith
- Department of Chemistry , Iowa State University , Ames , Iowa 50014 , United States
| | - Arthur H Winter
- Department of Chemistry , Iowa State University , Ames , Iowa 50014 , United States
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Qiu Y, Fischer LJ, Dutton AS, Winter AH. Aryl Nitrenium and Oxenium Ions with Unusual High-Spin π,π* Ground States: Exploiting (Anti)Aromaticity. J Org Chem 2017; 82:13550-13556. [PMID: 29087717 DOI: 10.1021/acs.joc.7b02698] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nitrenium and oxenium ions are important reactive intermediates in synthetic and biological processes, and their ground electronic configurations are of great interest due to having distinct reactivities and properties. In general, the closed-shell singlet state of these intermediates usually react as electrophiles, while reactions of the triplet states of these ions react like typical diradicals (e.g., H atom abstractions). Nonsubstituted phenyl nitrenium ions (Ph-NH+) and phenyl oxenium ions (Ph-O+) have closed-shell singlet ground states with large singlet-triplet gaps resulting from a strong break in the degeneracy of the p orbitals on the formal nitrenium/oxenium center. Remarkably, we find computationally (CBS-QB3 and G4MP2) that azulenyl nitrenium and oxenium ions can have triplet ground states depending upon the attachment position on the azulene core. For instance, CBS-QB3 predicts that 1-azulenyl nitrenium ion and 1-azulenyl oxenium ion are singlet ground-state species with considerable singlet-triplet gaps of -47 and -45 kcal/mol to the lowest-energy triplet state, respectively. In contrast, 6-azulenyl nitrenium ion and 6-azulenyl oxenium ion have triplet ground states with a singlet-triplet gap of +7 and +10 kcal/mol, respectively. Moreover, the triplet states are π,π* states, rather than the typical n,π* states seen for many aryl nitrenium or oxenium ions. This dramatic switch in favored electronic states can be ascribed to changes in ring aromaticity/antiaromaticity, with the switch from ground-state singlet ions to triplet-favored ions resulting from both a destabilized singlet state (Hückel antiaromatic) and a stabilized triplet (Baird aromatic) state. Density functional theory (UB3LYP/6-31+G(d,p)) was used to determine substituent effects on the singlet-triplet energy gap for azulenyl nitrenium and oxenium ions, and we find that the unusual ground triplet states can be further tuned by employing electron-donating or -withdrawing groups on the azulene ring. This work demonstrates that azulenyl nitrenium and oxenium ions can have triplet π,π* ground states and provides a simple recipe for making ionic intermediates with distinct electronic configurations and consequent prediction of unique reactivity and magnetic properties from these species.
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Affiliation(s)
- Yunfan Qiu
- Department of Chemistry, Iowa State University , 2101 Hach Hall, Ames, Iowa 50010, United States
| | - Logan J Fischer
- Department of Chemistry, Iowa State University , 2101 Hach Hall, Ames, Iowa 50010, United States
| | - Andrew S Dutton
- Department of Chemistry, Iowa State University , 2101 Hach Hall, Ames, Iowa 50010, United States
| | - Arthur H Winter
- Department of Chemistry, Iowa State University , 2101 Hach Hall, Ames, Iowa 50010, United States
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Slanina T, Shrestha P, Palao E, Kand D, Peterson JA, Dutton AS, Rubinstein N, Weinstain R, Winter AH, Klán P. In Search of the Perfect Photocage: Structure-Reactivity Relationships in meso-Methyl BODIPY Photoremovable Protecting Groups. J Am Chem Soc 2017; 139:15168-15175. [PMID: 29039200 DOI: 10.1021/jacs.7b08532] [Citation(s) in RCA: 166] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A detailed investigation of the photophysical parameters and photochemical reactivity of meso-methyl BODIPY photoremovable protecting groups was accomplished through systematic variation of the leaving group (LG) and core substituents as well as substitutions at boron. Efficiencies of the LG release were evaluated using both steady-state and transient absorption spectroscopies as well as computational analyses to identify the optimal structural features. We find that the quantum yields for photorelease with this photocage are highly sensitive to substituent effects. In particular, we find that the quantum yields of photorelease are improved with derivatives with higher intersystem crossing quantum yields, which can be promoted by core heavy atoms. Moreover, release quantum yields are dramatically improved by boron alkylation, whereas alkylation in the meso-methyl position has no effect. Better LGs are released considerably more efficiently than poorer LGs. We find that these substituent effects are additive, for example, a 2,6-diiodo-B-dimethyl BODIPY photocage features quantum yields of 28% for the mediocre LG acetate and a 95% quantum yield of release for chloride. The high chemical and quantum yields combined with the outstanding absorption properties of BODIPY dyes lead to photocages with uncaging cross sections over 10 000 M-1 cm-1, values that surpass cross sections of related photocages absorbing visible light. These new photocages, which absorb strongly near the second harmonic of an Nd:YAG laser (532 nm), hold promise for manipulating and interrogating biological and material systems with the high spatiotemporal control provided by pulsed laser irradiation, while avoiding the phototoxicity problems encountered with many UV-absorbing photocages. More generally, the insights gained from this structure-reactivity relationship may aid in the development of new highly efficient photoreactions.
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Affiliation(s)
- Tomáš Slanina
- Department of Chemistry and RECETOX, Faculty of Science, Masaryk University , Kamenice 5, 625 00, Brno, Czech Republic.,Institute of Organic Chemistry and Chemical Biology, Goethe University Frankfurt , 60323 Frankfurt am Main, Germany
| | - Pradeep Shrestha
- Department of Chemistry, Iowa State University , 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Eduardo Palao
- Department of Chemistry and RECETOX, Faculty of Science, Masaryk University , Kamenice 5, 625 00, Brno, Czech Republic
| | - Dnyaneshwar Kand
- School of Plant Sciences and Food Security, Faculty of Life Sciences, Tel-Aviv University , Tel-Aviv 6997801, Israel
| | - Julie A Peterson
- Department of Chemistry, Iowa State University , 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Andrew S Dutton
- Department of Chemistry, Iowa State University , 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Naama Rubinstein
- School of Plant Sciences and Food Security, Faculty of Life Sciences, Tel-Aviv University , Tel-Aviv 6997801, Israel
| | - Roy Weinstain
- School of Plant Sciences and Food Security, Faculty of Life Sciences, Tel-Aviv University , Tel-Aviv 6997801, Israel
| | - Arthur H Winter
- Department of Chemistry, Iowa State University , 1608 Gilman Hall, Ames, Iowa 50010, United States
| | - Petr Klán
- Department of Chemistry and RECETOX, Faculty of Science, Masaryk University , Kamenice 5, 625 00, Brno, Czech Republic
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Du L, Qiu Y, Lan X, Zhu R, Phillips DL, Li MD, Dutton AS, Winter AH. Direct Detection of the Open-Shell Singlet Phenyloxenium Ion: An Atom-Centered Diradical Reacts as an Electrophile. J Am Chem Soc 2017; 139:15054-15059. [PMID: 28945081 DOI: 10.1021/jacs.7b07512] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new photoprecursor to the phenyloxenium ion, 4-methoxyphenoxypyridinium tetrafluoroborate, was investigated using trapping studies, product analysis, computational investigations, and laser flash photolysis experiments ranging from the femtosecond to the millisecond time scale. These experiments allowed us to trace the complete arc of the photophysics and photochemistry of this photoprecursor beginning with the initially populated excited states to its sequential formation of transient intermediates and ultimate formation of stable photoproducts. We find that the excited state of the photoprecursor undergoes heterolysis to generate the phenyloxenium ion in ∼2 ps but surprisingly generates the ion in its open-shell singlet diradical configuration (1A2), permitting an unexpected look at the reactivity of an atom-centered open-shell singlet diradical. The open-shell phenyloxenium ion (1A2) has a much shorter lifetime (τ ∼ 0.2 ns) in acetonitrile than the previously observed closed-shell singlet (1A1) phenyloxenium ion (τ ∼ 5 ns). Remarkably, despite possessing no empty valence orbitals, this open-shell singlet oxenium ion behaves as an even more powerful electrophile than the closed-shell singlet oxenium ion, undergoing solvent trapping by weakly nucleophilic solvents such as water and acetonitrile or externally added nucleophiles (e.g., azide) rather than engaging in typical diradical chemistry, such as H atom abstraction, which we have previously observed for a triplet oxenium ion. In acetonitrile, the open-shell singlet oxenium ion is trapped to generate ortho and para Ritter intermediates, one of which (para) is directly observed as a longer-lived species (τ ∼ 0.1 ms) in time-resolved resonance Raman experiments. The Ritter intermediates are ultimately trapped by either the 4-methoxypyridine leaving group (in the case of para addition) or trapped internally via an essentially barrierless rearrangement (in the case of ortho addition) to generate a cyclized product. The expectation that singlet diradicals react similarly to triplet or uncoupled diradicals needs to be reconsidered, as a recent study by Perrin and Reyes-Rodríguez (J. Am. Chem. Soc. 2014, 136, 15263) suggested the unsettling possibility that singlet p-benzyne could suffer nucleophilic attack to generate a naked phenyl anion. Now, this study provides direct spectroscopic observation of this phenomenon, with an atom-centered open-shell singlet diradical reacting as a powerful electrophile. To the question of whether a nucleophile can attack a singly occupied molecular orbital, the answer is apparently yes, at least if another partially occupied orbital is available to avoid violation of the rules of valence.
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Affiliation(s)
- Lili Du
- Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong, People's Republic of China
| | - Yunfan Qiu
- Department of Chemistry, Iowa State University , 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Xin Lan
- Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong, People's Republic of China
| | - Ruixue Zhu
- Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong, People's Republic of China
| | - David Lee Phillips
- Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong, People's Republic of China
| | - Ming-De Li
- Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong, People's Republic of China.,Department of Chemistry, Shantou University , Guangdong 515063, P. R. China.,Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University , Shantou 515063, P. R. China
| | - Andrew S Dutton
- Department of Chemistry, Iowa State University , 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Arthur H Winter
- Department of Chemistry, Iowa State University , 2101d Hach Hall, Ames, Iowa 50011, United States
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35
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Affiliation(s)
| | | | - Mark J. Juetten
- Department of Chemistry Iowa State University Ames IA 50011 USA
| | - Samuel A. Wood
- Department of Chemistry Iowa State University Ames IA 50011 USA
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Affiliation(s)
| | | | - Mark J. Juetten
- Department of Chemistry Iowa State University Ames IA 50011 USA
| | - Samuel A. Wood
- Department of Chemistry Iowa State University Ames IA 50011 USA
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Peterson JP, Geraskina MR, Zhang R, Winter AH. Effect of Substituents on the Bond Strength of Air-Stable Dicyanomethyl Radical Thermochromes. J Org Chem 2017; 82:6497-6501. [DOI: 10.1021/acs.joc.7b01188] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Joshua P. Peterson
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Margarita R. Geraskina
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Rui Zhang
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
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Fischer LJ, Dutton AS, Winter AH. Anomalous effect of non-alternant hydrocarbons on carbocation and carbanion electronic configurations. Chem Sci 2017; 8:4231-4241. [PMID: 29719673 PMCID: PMC5902794 DOI: 10.1039/c7sc01047h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 04/30/2017] [Indexed: 12/01/2022] Open
Abstract
Carbocations are widely viewed to be closed-shell singlet electrophiles. Here, computations show that azulenyl-substituted carbocations have triplet ground states. This triplet ground state for azulenyl carbocations stands in striking contrast to the isomeric naphthenyl carbocation, which is a normal closed-shell singlet with a large singlet-triplet gap. Furthermore, substitution of the azulenyl carbocation can substantially alter the energy gap between the different electronic configurations and can manipulate the ground state towards either the singlet or the triplet state depending on the nature and location of the substituent. A detailed investigation into the origin of this spin state reversal, including NICS calculations, structural effects, substitution patterns, orbital analysis, and detailed linear free-energy relationships allowed us to distill a set of principles that caused these azulenyl carbocations to have such low-lying diradical states. The fundamental origin of this effect mostly centers on singlet state destabilization from increasing antiaromatic character, in combination with a smaller, but important, Baird triplet state aromatic stabilization. We find that azulene is not unique, as extension of these principles allowed us to generate simple rules to predict an entire class of analogous non-alternant carbocation and carbanion structures with low-energy or ground state diradical states, including a purely hydrocarbon triplet cation with a large singlet-triplet gap of 8 kcal mol-1. Although these ions have innocuous-looking Lewis structures, these triplet diradical ions are likely to have substantially different reactivity and properties than typical closed-shell singlet ions.
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Affiliation(s)
- Logan J Fischer
- Department of Chemistry , Iowa State University , 1608 Gilman Hall , Ames , IA 50010 , USA .
| | - Andrew S Dutton
- Department of Chemistry , Iowa State University , 1608 Gilman Hall , Ames , IA 50010 , USA .
| | - Arthur H Winter
- Department of Chemistry , Iowa State University , 1608 Gilman Hall , Ames , IA 50010 , USA .
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39
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Abstract
The combination of theoretical calculations and laser flash photolysis experiments has aided in understanding the reactivity and properties of oxenium ions.
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Affiliation(s)
- Yunfan Qiu
- Department of Chemistry
- Iowa State University
- Ames
- USA
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40
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Reinig RR, Mukherjee D, Weinstein ZB, Xie W, Albright T, Baird B, Gray TS, Ellern A, Miller GJ, Winter AH, Bud'ko SL, Sadow AD. Synthesis and Oxidation Catalysis of [Tris(oxazolinyl)borato]cobalt(II) Scorpionates. Eur J Inorg Chem 2016. [DOI: 10.1002/ejic.201600237] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Regina R. Reinig
- Department of ChemistryIowa State University1605 Gilman Hall50011AmesIAUSA
- US Department of Energy Ames Lab50011AmesIAUSA
| | | | - Zachary B. Weinstein
- Department of ChemistryIowa State University1605 Gilman Hall50011AmesIAUSA
- US Department of Energy Ames Lab50011AmesIAUSA
| | - Weiwei Xie
- Department of ChemistryIowa State University1605 Gilman Hall50011AmesIAUSA
- US Department of Energy Ames Lab50011AmesIAUSA
| | - Toshia Albright
- Department of ChemistryIowa State University1605 Gilman Hall50011AmesIAUSA
| | - Benjamin Baird
- Department of ChemistryIowa State University1605 Gilman Hall50011AmesIAUSA
| | - Tristan S. Gray
- Department of ChemistryIowa State University1605 Gilman Hall50011AmesIAUSA
| | - Arkady Ellern
- Department of ChemistryIowa State University1605 Gilman Hall50011AmesIAUSA
| | - Gordon J. Miller
- Department of ChemistryIowa State University1605 Gilman Hall50011AmesIAUSA
- US Department of Energy Ames Lab50011AmesIAUSA
| | - Arthur H. Winter
- Department of ChemistryIowa State University1605 Gilman Hall50011AmesIAUSA
| | | | - Aaron D. Sadow
- Department of ChemistryIowa State University1605 Gilman Hall50011AmesIAUSA
- US Department of Energy Ames Lab50011AmesIAUSA
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41
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Li MD, Albright TR, Hanway PJ, Liu M, Lan X, Li S, Peterson J, Winter AH, Phillips DL. Direct Spectroscopic Detection and EPR Investigation of a Ground State Triplet Phenyl Oxenium Ion. J Am Chem Soc 2015. [PMID: 26198984 DOI: 10.1021/jacs.5b06302] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oxenium ions are important reactive intermediates in synthetic chemistry and enzymology, but little is known of the reactivity, lifetimes, spectroscopic signatures, and electronic configurations of these unstable species. Recent advances have allowed these short-lived ions to be directly detected in solution from laser flash photolysis of suitable photochemical precursors, but all of the studies to date have focused on aryloxenium ions having closed-shell singlet ground state configurations. To study alternative spin configurations, we synthesized a photoprecursor to the m-dimethylamino phenyloxenium ion, which is predicted by both density functional theory and MRMP2 computations to have a triplet ground state electronic configuration. A combination of femtosecond and nanosecond transient absorption spectroscopy, nanosecond time-resolved Resonance Raman spectroscopy (ns-TR(3)), cryogenic matrix EPR spectroscopy, computational analysis, and photoproduct studies allowed us to trace essentially the complete arc of the photophysics and photochemistry of this photoprecursor and permitted a first look at a triplet oxenium ion. Ultraviolet photoexcitation of this precursor populates higher singlet excited states, which after internal conversion to S1 over 800 fs are followed by bond heterolysis in ∼1 ps, generating a hot closed-shell singlet oxenium ion that undergoes vibrational cooling in ∼50 ps followed by intersystem crossing in ∼300 ps to generate the triplet ground state oxenium ion. In contrast to the rapid trapping of singlet phenyloxenium ions by nucleophiles seen in prior studies, the triplet oxenium ion reacts via sequential H atom abstractions on the microsecond time domain to ultimately yield the reduced m-dimethylaminophenol as the only detectable stable photoproduct. Band assignments were made by comparisons to computed spectra of candidate intermediates and comparisons to related known species. The triplet oxenium ion was also detected in the ns-TR(3) experiments, permitting a more clear assignment and identifying the triplet state as the π,π* triplet configuration. The triplet ground state of this ion was further supported by photolysis of the photoprecursor in an ethanol glass at ∼4 K and observing a triplet species by cryogenic EPR spectroscopy.
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Affiliation(s)
- Ming-De Li
- †Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, S.A.R., P. R. China
| | - Toshia R Albright
- ‡Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Patrick J Hanway
- ‡Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Mingyue Liu
- †Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, S.A.R., P. R. China
| | - Xin Lan
- †Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, S.A.R., P. R. China
| | - Songbo Li
- †Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, S.A.R., P. R. China
| | - Julie Peterson
- ‡Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Arthur H Winter
- ‡Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - David Lee Phillips
- †Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, S.A.R., P. R. China
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Goswami PP, Syed A, Beck CL, Albright TR, Mahoney KM, Unash R, Smith EA, Winter AH. BODIPY-derived photoremovable protecting groups unmasked with green light. J Am Chem Soc 2015; 137:3783-6. [PMID: 25751156 DOI: 10.1021/jacs.5b01297] [Citation(s) in RCA: 185] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Photoremovable protecting groups derived from meso-substituted BODIPY dyes release acetic acid with green wavelengths >500 nm. Photorelease is demonstrated in cultured S2 cells. The photocaging structures were identified by our previously proposed strategy of computationally searching for carbocations with low-energy diradical states as a possible indicator of a nearby productive conical intersection. The superior optical properties of these photocages make them promising alternatives to the popular o-nitrobenzyl photocage systems.
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Affiliation(s)
- Pratik P Goswami
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Aleem Syed
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Christie L Beck
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Toshia R Albright
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Kaitlyn M Mahoney
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Ryan Unash
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Emily A Smith
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
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43
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Affiliation(s)
- Toshia R. Albright
- Department
of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Arthur H. Winter
- Department
of Chemistry, Iowa State University, Ames, Iowa 50011, United States
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Abstract
A polymer containing viologen radical cation monomer units is shown to reversibly switch between paramagnetic and diamagnetic statesvianon-covalent host–guest interactions or temperature control in water.
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Mahoney KM, Goswami PP, Syed A, Kolker P, Shannan B, Smith EA, Winter AH. Self-Immolative Phthalate Esters Sensitive to Hydrogen Peroxide and Light. J Org Chem 2014; 79:11740-3. [DOI: 10.1021/jo501900h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Kaitlyn M. Mahoney
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50014, United States
| | - Pratik P. Goswami
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50014, United States
| | - Aleem Syed
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50014, United States
| | - Patrick Kolker
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50014, United States
| | - Brian Shannan
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50014, United States
| | - Emily A. Smith
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50014, United States
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50014, United States
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Li MD, Hanway PJ, Albright TR, Winter AH, Phillips DL. Direct Spectroscopic Observation of Closed-Shell Singlet, Open-Shell Singlet, and Triplet p-Biphenylyloxenium Ion. J Am Chem Soc 2014; 136:12364-70. [DOI: 10.1021/ja505447q] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ming-De Li
- Department
of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S.A.R., P.R. China
| | - Patrick J. Hanway
- Department
of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Toshia R. Albright
- Department
of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Arthur H. Winter
- Department
of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - David Lee Phillips
- Department
of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S.A.R., P.R. China
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47
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Affiliation(s)
- Margarita R. Geraskina
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Alexander T. Buck
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
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48
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Buck AT, Beck CL, Winter AH. Inverted Substrate Preferences for Photochemical Heterolysis Arise from Conical Intersection Control. J Am Chem Soc 2014; 136:8933-40. [DOI: 10.1021/ja501777r] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Alexander T. Buck
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Christie L. Beck
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
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Geraskina MR, Juetten MJ, Winter AH. Access to Aryl Mellitic Acid Esters through a Surprising Oxidative Esterification Reaction. J Org Chem 2014; 79:5334-7. [DOI: 10.1021/jo5005185] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Margarita R. Geraskina
- Department
of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Mark J. Juetten
- Department
of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
| | - Arthur H. Winter
- Department
of Chemistry, Iowa State University, 2101d Hach Hall, Ames, Iowa 50011, United States
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Affiliation(s)
- Christie L. Beck
- Department
of Chemistry, 2101d Hach Hall, Iowa State University, Ames, Iowa 50014, United States
| | - Arthur H. Winter
- Department
of Chemistry, 2101d Hach Hall, Iowa State University, Ames, Iowa 50014, United States
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