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Kim SF, Schwarz H, Jurczyk J, Nebgen BR, Hendricks H, Park H, Radosevich A, Zuerch MW, Harper K, Lux MC, Yeung CS, Sarpong R. Mechanistic Investigation, Wavelength-Dependent Reactivity, and Expanded Reactivity of N-Aryl Azacycle Photomediated Ring Contractions. J Am Chem Soc 2024; 146:5580-5596. [PMID: 38347659 DOI: 10.1021/jacs.3c13982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
Under mild blue-light irradiation, α-acylated saturated heterocycles undergo a photomediated one-atom ring contraction that extrudes a heteroatom from the cyclic core. However, for nitrogenous heterocycles, this powerful skeletal edit has been limited to substrates bearing electron-withdrawing substituents on nitrogen. Moreover, the mechanism and wavelength-dependent efficiency of this transformation have remained unclear. In this work, we increased the electron richness of nitrogen in saturated azacycles to improve light absorption and strengthen critical intramolecular hydrogen bonding while enabling the direct installation of the photoreactive handle. As a result, a broadly expanded substrate scope, including underexplored electron-rich substrates and previously unsuccessful heterocycles, has now been achieved. The significantly improved yields and diastereoselectivities have facilitated reaction rate, kinetic isotope effect (KIE), and quenching studies, in addition to the determination of quantum yields. Guided by these studies, we propose a revised ET/PT mechanism for the ring contraction, which is additionally corroborated by computational characterization of the lowest-energy excited states of α-acylated substrates through time-dependent DFT. The efficiency of the ring contraction at wavelengths longer than those strongly absorbed by the substrates was investigated through wavelength-dependent rate measurements, which revealed a red shift of the photochemical action plot relative to substrate absorbance. The elucidated mechanistic and photophysical details effectively rationalize empirical observations, including additive effects, that were previously poorly understood. Our findings not only demonstrate enhanced synthetic utility of the photomediated ring contraction and shed light on mechanistic details but may also offer valuable guidance for understanding wavelength-dependent reactivity for related photochemical systems.
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Affiliation(s)
- Sojung F Kim
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Henrik Schwarz
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Justin Jurczyk
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Bailey R Nebgen
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
- Lawrence Berkeley National Laboratory, Materials Sciences Division, Berkeley, California 94720, United States
| | - Hailey Hendricks
- Department of Discovery Chemistry, Merck & Co., Inc., Boston, Massachusetts 02115, United States
| | - Hojoon Park
- Department of Process Research and Development, Merck & Co., Inc., Boston, Massachusetts 02115, United States
| | - Andrew Radosevich
- Small Molecule Therapeutics & Platform Technologies, Abbvie Inc., North Chicago, Illinois 60064, United States
| | - Michael W Zuerch
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
- Lawrence Berkeley National Laboratory, Materials Sciences Division, Berkeley, California 94720, United States
| | - Kaid Harper
- Process Chemistry, Abbvie Inc., North Chicago, Illinois 60064, United States
| | - Michaelyn C Lux
- Department of Discovery Chemistry, Merck & Co., Inc., Boston, Massachusetts 02115, United States
| | - Charles S Yeung
- Department of Discovery Chemistry, Merck & Co., Inc., Boston, Massachusetts 02115, United States
| | - Richmond Sarpong
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
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Xu C, Xu F, Chen X, Li Z, Luan Z, Wang X, Guo Q, Yang X. Wavelength-Dependent Water Oxidation on Rutile TiO 2(110). J Phys Chem Lett 2021; 12:1066-1072. [PMID: 33470822 DOI: 10.1021/acs.jpclett.0c03726] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Understanding the microscopic mechanism of water photocatalysis on TiO2 is of great value in energy chemistry and catalysis. To date, it is still unclear how water photocatalysis occurs after the initial light absorption. Here we report the investigation of the photoinduced water dissociation and desorption on a R-TiO2(110) surface, at different wavelengths (from 250 to 330 nm), using temperature-programmed desorption and time-of-flight techniques. Primary photooxidation products, gas phase OH radicals and surface H atoms, were clearly observed at wavelengths of ≤290 nm. As the laser wavelength decreases from 290 to 250 nm, the relative yield of H2O oxidation increases significantly. Likewise, photoinduced H2O desorption was also observed in the range of 320-250 nm, and the relative yield of H2O desorption also increases with a decrease in wavelength. The strong wavelength-dependent H2O photooxidation and photodesorption suggest that the energy of charge carriers is important in these two processes. More importantly, the result raises doubt about the widely accepted photocatalysis model of TiO2 in which the excess energy of charge carriers is useless for photocatalysis. In addition, the H2O photooxidation is more likely initiated by nonthermalized holes and is accomplished on the ground state potential energy surface via a non-adiabatic decay process.
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Affiliation(s)
- Chenbiao Xu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Zhongshan Road 457, Dalian 116023, Liaoning, P. R. China
| | - Fei Xu
- Center for Advanced Chemical Physics and Department of Chemical Physics, School of Chemistry and Materials Science, University of Science and Technology of China, Jinzhai Road 96, Hefei 230026, Anhui, P. R. China
| | - Xiao Chen
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China
| | - Zhenxing Li
- Center for Advanced Chemical Physics and Department of Chemical Physics, School of Chemistry and Materials Science, University of Science and Technology of China, Jinzhai Road 96, Hefei 230026, Anhui, P. R. China
| | - Zhiwen Luan
- Center for Advanced Chemical Physics and Department of Chemical Physics, School of Chemistry and Materials Science, University of Science and Technology of China, Jinzhai Road 96, Hefei 230026, Anhui, P. R. China
| | - Xingan Wang
- Center for Advanced Chemical Physics and Department of Chemical Physics, School of Chemistry and Materials Science, University of Science and Technology of China, Jinzhai Road 96, Hefei 230026, Anhui, P. R. China
| | - Qing Guo
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China
| | - Xueming Yang
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Zhongshan Road 457, Dalian 116023, Liaoning, P. R. China
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3
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Guo Q, Zhou C, Ma Z, Yang X. Fundamentals of TiO 2 Photocatalysis: Concepts, Mechanisms, and Challenges. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1901997. [PMID: 31423680 DOI: 10.1002/adma.201901997] [Citation(s) in RCA: 450] [Impact Index Per Article: 90.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 07/23/2019] [Indexed: 05/27/2023]
Abstract
Photocatalysis has been widely applied in various areas, such as solar cells, water splitting, and pollutant degradation. Therefore, the photochemical mechanisms and basic principles of photocatalysis, especially TiO2 photocatalysis, have been extensively investigated by various surface science methods in the last decade, aiming to provide important information for TiO2 photocatalysis under real environmental conditions. Recent progress that provides fundamental insights into TiO2 photocatalysis at a molecular level is highlighted. Insights into the structures of TiO2 and the basic principles of TiO2 photocatalysis are discussed first, which provides the basic concepts of TiO2 photocatalysis. Following this, details of the photochemistry of three important molecules (oxygen, water, methanol) on the model TiO2 surfaces are presented, in an attempt to unravel the relationship between charge/energy transfer and bond breaking/forming in TiO2 photocatalysis. Lastly, challenges and opportunities of the mechanistic studies of TiO2 photocatalysis at the molecular level are discussed briefly, as well as possible photocatalysis models.
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Affiliation(s)
- Qing Guo
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, Liaoning, 116023, China
- Department of Chemistry, Southern University of Science and Technology, 1088 Xueyuan Avenue, Shenzhen, 518055, China
| | - Chuanyao Zhou
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, Liaoning, 116023, China
| | - Zhibo Ma
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, Liaoning, 116023, China
| | - Xueming Yang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, Liaoning, 116023, China
- Department of Chemistry, Southern University of Science and Technology, 1088 Xueyuan Avenue, Shenzhen, 518055, China
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Wang ZQ, Hao QQ, Zhou CY, Dai DX, Yang XM. Excitation Wavelength Dependence of Photocatalyzed Oxidation of Methanol on TiO2(110). CHINESE J CHEM PHYS 2015. [DOI: 10.1063/1674-0068/28/cjcp1507147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Xu C, Yang W, Ren Z, Dai D, Guo Q, Minton TK, Yang X. Strong Photon Energy Dependence of the Photocatalytic Dissociation Rate of Methanol on TiO2(110). J Am Chem Soc 2013; 135:19039-45. [DOI: 10.1021/ja4114598] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Chengbiao Xu
- State
Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China
| | - Wenshao Yang
- State
Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China
| | - Zefeng Ren
- International
Center for Quantum Materials, Peking University, 5 Yiheyuan Road, Beijing 100871, P. R. China
| | - Dongxu Dai
- State
Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China
| | - Qing Guo
- State
Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China
| | - Timothy K. Minton
- State
Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China
- Department
of Chemistry and Biochemistry, Montana State University, PO Box 173400, Bozeman, Montana 59717, United States
| | - Xueming Yang
- State
Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China
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6
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The Adsorption, Thermal Desorption and Photochemistry of Methyl Iodide on an Ag-Covered TiO2(110) Surface. J CHIN CHEM SOC-TAIP 2013. [DOI: 10.1002/jccs.200600106] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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7
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Kershis MD, Wilson DP, White MG. Dynamics of acetone photooxidation on TiO2(110): State-resolved measurements of methyl photoproducts. J Chem Phys 2013; 138:204703. [DOI: 10.1063/1.4805065] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Henderson MA, Lyubinetsky I. Molecular-Level Insights into Photocatalysis from Scanning Probe Microscopy Studies on TiO2(110). Chem Rev 2013; 113:4428-55. [DOI: 10.1021/cr300315m] [Citation(s) in RCA: 204] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Michael A. Henderson
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999,
MS K8-87 Richland, Washington 99352, United States
| | - Igor Lyubinetsky
- Environmental Molecular Sciences
Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, MS K8-93 Richland, Washington 99352, United States
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9
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DeSimone AJ, Olanrewaju BO, Grieves GA, Orlando TM. Photodissociation of methyl iodide adsorbed on low-temperature amorphous ice surfaces. J Chem Phys 2013; 138:084703. [DOI: 10.1063/1.4790585] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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10
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White JM, Henderson MA. Thermal and Photochemistry of tert-Butyl Iodide on Rutile TiO2(110). J Phys Chem B 2005; 109:14990-5000. [PMID: 16852898 DOI: 10.1021/jp0517448] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The thermal and photochemistry of tert-butyl iodide (t-buI) dosed at 100 K on rutile TiO2(110) has been studied using isothermal and temperature programmed desorption mass spectrometry. Nondissociative adsorption and desorption dominate the thermal behavior with dose-dependent t-buI desorption peaks at nominally 220 and 150 K. Ultraviolet photochemistry occurs readily, but the behavior of submonolayers and multilayers differ qualitatively. Ejection of t-buI and i-C4H8 dominate during submonolayer photolysis at 100 K. Multilayer photolysis results are also dominated by ejection during irradiation, but the t-buI component is strongly suppressed, and the maximum rates of i-C4H8 and HI ejection did not occur at the outset. A mechanistic model capturing the observations involves both direct and substrate-mediated electronic excitation of t-buI. According to this model, ejection of t-buI occurs only from transient substrate-mediated formation of anionic t-buI. For either excitation path, the C-I dissociation probability is significant, and the excited tert-butyl product rearranges readily to form i-C4H8 that is ejected. For any local region where there is multilayer coverage, products formed at the adsorbate-vacuum interface are ejected promptly, but products formed within the multilayer are trapped. Thus, ejection of t-buI is suppressed, and trapped primary photodissociation products, tert-butyl and I, react to either reform t-buI or rearrange to i-C4H8 and HI. The latter two products remain trapped and are subsequently induced to desorb by acquisition of momentum from collisions with subsequently formed translationally excited photodissociation products.
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Affiliation(s)
- J M White
- Institute for Interfacial Catalysis and Interfacial Chemistry and Engineering Group, P.O. Box 999, MS K8-93, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
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11
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Henderson MA. Photooxidation of Acetone on TiO2(110): Conversion to Acetate via Methyl Radical Ejection. J Phys Chem B 2005; 109:12062-70. [PMID: 16852488 DOI: 10.1021/jp0507546] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
It is generally held that radicals form and participate in heterogeneous photocatalytic processes on oxide surfaces, although understanding the mechanistic origins and fates of such species is difficult. In this study, photodesorption and thermal desorption techniques show that acetone is converted into acetate on the surface of TiO2(110) in a two-step process that involves, first, a thermal reaction between acetone and coadsorbed oxygen to make a surface acetone-oxygen complex, followed second by a photocatalytic reaction that ejects a methyl radical from the surface and converts the acetone-oxygen complex into acetate. Designation of the photodesorption species to methyl radicals was confirmed using isotopically labeled acetone. The yield of photodesorbed methyl radicals correlates well with the amount of acetone depleted and with the yield of acetate left on the surface, both gauged using postirradiation temperature programmed desorption (TPD). The thermal reaction between adsorbed acetone and oxygen to form the acetone-oxygen complex exhibits an approximate activation barrier of about 10 kJ/mol. A prerequisite to this reaction is the presence of surface Ti3+ sites that enable O2 adsorption. Creation of these sites by vacuum reduction of the surface prior to acetone and oxygen coadsorption results in an initial spike in the acetone photooxidation rate, but replenishment of these sites by photolytic means (i.e., by trapping excited electrons at the surface) appears to be a slow step in a sustained reaction. Evidence in this study for the ejection of organic radicals from the surface during photooxidation catalysis on TiO2 provides support for mechanistic pathways that involve both adsorbed and nonadsorbed species.
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Affiliation(s)
- Michael A Henderson
- Interfacial Chemistry and Engineering Group, Pacific Northwest National Laboratory, P.O. Box 999, MS K8-93, Richland, Washington 99352, USA.
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