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Huang G, Zhou C, Liang R, Sun S, Deng Z, Li J, Dang L, Phillips DL, Li MD. Ultrafast Time-Resolved Spectroscopic Study on the Photophysical and Photochemical Reaction Mechanisms of ortho-Methylbenzophenone in Selected Solutions. J Phys Chem B 2022; 126:9388-9398. [PMID: 36331406 DOI: 10.1021/acs.jpcb.2c06452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The photophysical and photochemical reaction pathways of ortho-methylbenzophenone (o-MeBP) in different solutions were investigated by employing femtosecond to nanosecond transient absorption and nanosecond time-resolved resonance Raman spectroscopy methods. In pure acetonitrile, neutral or pH 1 aqueous solutions, o-MeBP exhibit similar excited-state evolutions upon excitation in which o-MeBP will experience excitation to an excited state then undergo intersystem crossing and solvent arrangement followed by 1,5 hydrogen atom transfer processes to form the first singlet excited state, triplet state (n, π*), biradical intermediates, and enol form transients, respectively. However, in a pH 0 acidic solution, the protonation of o-MeBP will form the cation biradical intermediate that facilitates radical coupling to generate a benzocyclobutanol product, which causes a dramatic reduction of the lifetime of the enol form transients. In contrast, in sodium bicarbonate solution, the biradical intermediate may be quenched by the bicarbonate ion to construct a C-C bond and form the carboxylic acid that causes a fast decay of biradical intermediate. These results demonstrate that the photophysical and photochemical reaction pathways of o-MeBP are pH-dependent in aqueous solution which may be very useful for the capture of CO2 capture by photoexcitation of aromatic ketones.
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Affiliation(s)
- Guanheng Huang
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence, Shantou University, Shantou515063, China.,Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, PR China
| | - Chen Zhou
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence, Shantou University, Shantou515063, China
| | - Runhui Liang
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, PR China
| | - Shanshan Sun
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence, Shantou University, Shantou515063, China
| | - Ziqi Deng
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence, Shantou University, Shantou515063, China
| | - Jiayu Li
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence, Shantou University, Shantou515063, China
| | - Li Dang
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence, Shantou University, Shantou515063, China
| | - David Lee Phillips
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, PR China
| | - Ming-De Li
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structure Materials of Guangdong Providence, Shantou University, Shantou515063, China
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He J, Liu M, Yin L, Deng Z, Pang J, He H, Dang L, Li MD. Revealing the Photophysical and Photochemical Reaction Processes of Carprofen in Different Solutions via Ultrafast Femtosecond to Nanosecond Transient Absorption. Chem Res Toxicol 2021; 35:89-98. [PMID: 34962376 DOI: 10.1021/acs.chemrestox.1c00315] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Carprofen (CP), one kind of a nonsteroidal anti-inflammatory drug, exhibits phototoxic side effects in physiology, while its phototoxic mechanism is ambiguous. To uncover CP's photophysical and photochemical reaction processes, femtosecond to nanosecond transient absorption spectroscopies were employed to directly detect excited states and transient intermediates of CP upon UV irradiation in pure acetonitrile (MeCN), MeCN/water 1:1, and acid/alkaline buffer solutions. The transient absorption data together with DFT calculations were integrated to elucidate mechanisms for photochemical reactions of CP in different solutions. The associated photophysical and photochemical reaction pathways are dependent on various solution environments. In a pure MeCN solvent, CP is excited to a singlet state (S1) and rapidly interacts with the solvent to proceed solvent rearrangement (SR). It then undergoes vibrational cooling (VC) and proceeds intersystem crossing (ISC) to produce the lowest triplet state (3CP). 3CP finally decays to the ground state. While in a MeCN/water 1:1 solution, deprotonated S1 of CP experiences SR and VC processes, and then it is promoted to a deprotonated triplet state (3CP-). 3CP- undergoes the parallel reactions: dechlorination to a phenyl radical (2CP-) and decarboxylation to a T1 anion (3CP-(de-CO2)). Finally, both intermediates produce the radical anion species 2CP-(de-CO2). In a pH = 7.4 (MeCN/PBS 1:1) solution, 3CP- can be converted into 2CP-(de-CO2) more quickly. Interestingly, we found that the dechlorination step can be promoted in an alkaline solution. Phenyl and chlorine radicals produced in an aqueous solution may be the root cause of the drug's harmful side effects on the human body. This may be useful to guide the design of related CP drugs with minimal phototoxicity in the pharmaceutical process.
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Affiliation(s)
- Jiaxing He
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - Mingyue Liu
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - Lingfeng Yin
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - Ziqi Deng
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - Junhong Pang
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - Haoxian He
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - Li Dang
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou 515063, China
| | - 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
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Ma J, Zhang X, Phillips DL. Time-Resolved Spectroscopic Observation and Characterization of Water-Assisted Photoredox Reactions of Selected Aromatic Carbonyl Compounds. Acc Chem Res 2019; 52:726-737. [PMID: 30742408 DOI: 10.1021/acs.accounts.8b00619] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
In recent years, unusual and efficient self-photoredox reactions were detected for selected benzophenone derivatives (BPs) and anthraquinone derivatives (AQs) in aqueous environments by Wan and co-workers, where the carbonyl undergoes reduction to the corresponding alcohol and a side-chain alcohol group undergoes oxidation to the corresponding carbonyl. To unravel the photoredox reaction mechanisms of these types of BPs and AQs in aqueous environments, we have utilized a combination of time-resolved spectroscopy techniques such as femtosecond transient absorption, nanosecond transient absorption, and nanosecond time-resolved resonance Raman spectroscopy to detect and characterize the electronic absorption and vibrational spectra of the intermediates and transient species from the femtosecond to microsecond time region after they are generated in the photoredox reactions. With the assistance of density functional theory calculations to simulate the electronic absorption and Raman spectra, the structural and kinetic information on the key reactive intermediates is described. Furthermore, the reaction pathways were calculated by finding the transition states connecting with the reactant and product complexes to better understand the photoredox reaction mechanism. In this Account, we summarize some of our time-resolved spectroscopic observations and characterization of water-assisted photoredox reactions of selected BPs and AQs. In the strong hydrogen-donor solvent isopropanol, the commonly studied photoreduction reaction for aromatic carbonyls via an intermolecular hydrogen atom tranfer process was observed for BPs and AQs. The photoredox reactions for the investigated BPs and AQs in aqueous environments occur on the triplet excited-state surface. Under moderately acidic aqueous conditions, the photoredox reactions for BPs and AQs are triggered by a proton transfer (PT) pathway. In neutral aqueous solutions, AQs may also undergo proton-coupled electron transfer (PCET) leading to the photoredox reaction, while BPs generate the ketyl radical species. Both BPs and AQs prefer the photohydration reaction in high-proton-concentration aqueous solutions (pH 0). The PT and PCET processes were found to offer more possibilities for the aromatic carbonyl compounds to lead to new photochemical reactions like the unusual photoredox reactions associated with BPs and AQs described here. Clear characterization of the photophysical pathways and the photochemical reactions of representative aromatic carbonyl compounds in aqueous environments not only provides fundamental information to better understand the photochemistry of carbonyl-containing compounds but also will facilitate the development of applications of these systems, like photochemical synthesis, drugs, and photolabile protecting groups. In addition, the importance of water molecules in the photochemical reactions of interest here may also lead to further understanding of how water influences the photochemistry of related carbonyl-containing compounds in aqueous environments.
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Affiliation(s)
- Jiani Ma
- Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi’an 710127, P. R. China
| | - Xiting Zhang
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China
| | - David Lee Phillips
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China
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Ma J, Mewes JM, Harris KT, Dore TM, Phillips DL, Dreuw A. Unravelling the early photochemical behavior of (8-substituted-7-hydroxyquinolinyl)methyl acetates through electronic structure theory and ultrafast transient absorption spectroscopy. Phys Chem Chem Phys 2018; 19:1089-1096. [PMID: 27942621 DOI: 10.1039/c6cp05499d] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The photophysical processes and photochemical reactions in the ultrafast time region of (8-bromo-7-hydroxyquinolin-2-yl)methyl acetate (BHQ-OAc) in acetonitrile and neutral aqueous solutions were investigated using quantum chemical calculations and femtosecond transient absorption spectroscopy. After initial excitation into the π,π* excited state, BHQ-OAc undergoes an ultrafast intersystem crossing (ISC) into a π,π* excited triplet state on a timescale of 16 ps. The n,π* and π,π* excited singlet and triplet states involved in the photochemistry were identified by means of their characteristic excited state absorption (ESA) bands and from second order coupled-cluster (CC2) calculations. The high ISC rate of BHQ-OAc and related compounds is traced back to involvement of almost energetically degenerate n,π* excited states that enable efficient ISC that obeys El-Sayed's rules.
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Affiliation(s)
- Jiani Ma
- Key Laboratory of Synthetic and Natural Functional Molecular Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi'an, P. R. China. and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong S.A.R., P. R. China.
| | - Jan-Michael Mewes
- Interdisciplinary Center for Scientific Computing, University of Heidelberg, Im Neuenheimer Feld 205, 69120 Heidelberg, Germany.
| | - Kyle T Harris
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA
| | - Timothy M Dore
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA and New York University Abu Dhabi, PO Box 129188, Abu Dhabi, United Arab Emirates.
| | - David Lee Phillips
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong S.A.R., P. R. China.
| | - Andreas Dreuw
- Interdisciplinary Center for Scientific Computing, University of Heidelberg, Im Neuenheimer Feld 205, 69120 Heidelberg, Germany.
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Huang J, Muliawan AP, Ma J, Li MD, Chiu HK, Lan X, Deodato D, Phillips DL, Dore TM. A spectroscopic study of the excited state proton transfer processes of (8-bromo-7-hydroxyquinolin-2-yl)methyl-protected phenol in aqueous solutions. Photochem Photobiol Sci 2017; 16:575-584. [DOI: 10.1039/c6pp00377j] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Spectroscopy and DFT calculations elucidate a mechanism involving early and rapid ESPTs for the photolytic release of phenol from BHQ-OPh.
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Affiliation(s)
- Jinqing Huang
- Department of Chemistry
- The University of Hong Kong
- People's Republic of China
| | | | - Jiani Ma
- Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education
- College of Chemistry and Materials Science
- Northwest University
- Xi'an
- People's Republic of China
| | - Ming De Li
- Department of Chemistry
- The University of Hong Kong
- People's Republic of China
| | - Hoi Kei Chiu
- Department of Chemistry
- The University of Hong Kong
- People's Republic of China
| | - Xin Lan
- Department of Chemistry
- The University of Hong Kong
- People's Republic of China
| | - Davide Deodato
- New York University Abu Dhabi
- Abu Dhabi
- United Arab Emirates
| | - David Lee Phillips
- Department of Chemistry
- The University of Hong Kong
- People's Republic of China
| | - Timothy M. Dore
- New York University Abu Dhabi
- Abu Dhabi
- United Arab Emirates
- Department of Chemistry
- University of Georgia
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Zhang X, Ma J, Phillips DL. To Photoredox or Not in Neutral Aqueous Solutions for Selected Benzophenone and Anthraquinone Derivatives. J Phys Chem Lett 2016; 7:4860-4864. [PMID: 27934041 DOI: 10.1021/acs.jpclett.6b02403] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The experimental and theoretical results in neutral aqueous solutions reported here indicate that a proton-coupled electron transfer (PCET) from an alcohol C-H bond to the para-carbonyl is the initial and crucial process for the photoredox reaction of 2-(1-hydroxyethyl)-anthraquinone (HEAQ) to occur while the counterpart 3-(hydroxymethyl)-benzophenone (3-BPOH) compound displays a different PCET from an alcohol O-H bond to the carbonyl as the first step, followed by an intersystem crossing process that does not lead to the analogous photoredox, which is caused by a subtle charge-radical coupled effect between HEAQ and 3-BPOH. This can account for experimental results in the literature that HEAQ can undergo efficient photoredox but 3-BPOH does not under neutral aqueous conditions. These results have implications for the pH-dependent photochemical behavior of aromatic carbonyl compounds in aqueous media.
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Affiliation(s)
- Xiting Zhang
- Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University , Xi'an 710127, P. R. China
- Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong 999077, P. R. China
| | - Jiani Ma
- Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University , Xi'an 710127, P. R. China
| | - David Lee Phillips
- Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong 999077, P. R. China
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Ma J, Li H, Zhang X, Tang WJ, Li M, Phillips DL. Competition between "Meta Effect" Photochemical Reactions of Selected Benzophenone Compounds Having Two Different Substituents at Meta Positions. J Org Chem 2016; 81:9553-9559. [PMID: 27661756 DOI: 10.1021/acs.joc.6b00698] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recent studies conducted on some "meta effect" photochemical reactions focused on aromatic carbonyls having a substitution on one meta position of the benzophenone (BP) and anthraquinone parent compound. In this paper, two different substitutions were introduced with one at each meta position of the BP parent compound to investigate possible competition between different types of meta effect photochemistry observed in acidic solutions containing water. The photochemical pathways of 3-hydroxymethyl-3'-fluorobenzophenone (1) and 3-fluoro-3'-methylbenzophenone (2) were explored in several solvents, including acidic water-containing solutions, using time-resolved spectroscopic experiments and density functional theory computations. It is observed that 1 can undergo a photoredox reaction and 2 can undergo a meta-methyl deprotonation reaction in acidic water-containing solutions. Comparison of these results to those previously reported for the analogous BP derivatives that contain only one substituent at a meta position indicates the introduction of electron-donating (such as hydroxyl) and electron-withdrawing groups (such as F) on the meta positions of BP can influence the meta effect photochemical reactions. It was found that involvement of an electron-donating moiety facilitates the meta effect photochemical reactions by stabilizing the crucial reactive biradical intermediate associated with the meta effect photochemical reactions.
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Affiliation(s)
- Jiani Ma
- Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University , 229 Taibai N Road, Xi'an, Shaanxi, People's Republic of China
| | - Huai Li
- Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University , 229 Taibai N Road, Xi'an, Shaanxi, People's Republic of China
| | - Xiting Zhang
- Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong 11111
| | - Wen-Jian Tang
- School of Pharmacy, Anhui Medical University , Meishan Road 81, Hefei 230032, People's Republic of China
| | - Mingde Li
- Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong 11111
| | - David Lee Phillips
- Department of Chemistry, The University of Hong Kong , Pokfulam Road, Hong Kong 11111
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Huang J, Ma J, Li M, Liu M, Zhang X, Phillips DL. How Does the C–Halogen Bond Break in the Photosubstitution Reaction of 3-Fluorobenzophenone in Acidic Aqueous Solutions? J Org Chem 2015; 80:9425-36. [DOI: 10.1021/acs.joc.5b01308] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jinqing Huang
- Department
of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s Republic of China
| | - Jiani Ma
- Department
of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s Republic of China
- Key
Laboratory of Synthetic and Natural Functional Molecule Chemistry
of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi’an 710127, People’s Republic of China
| | - Mingde Li
- Department
of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s Republic of China
| | - Mingyue Liu
- Department
of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s Republic of China
| | - Xiting Zhang
- 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
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