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Wang Y, Ye Z, Han T, Du Y, Xue J. Transient spectroscopic insights into nitroindole's T 1 state: Elucidating its intermediates and unique photochemical properties. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2024; 319:124555. [PMID: 38823242 DOI: 10.1016/j.saa.2024.124555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Revised: 05/25/2024] [Accepted: 05/28/2024] [Indexed: 06/03/2024]
Abstract
Indoles are notable for their distinct photophysical and photochemical properties, making them useful indicators in biological systems and promising candidates for a variety of pharmaceutical applications. While some indoles exhibit room temperature phosphorescence, such a phenomenon has not been observed in nitroindoles. Typically, adding of a nitro group into aromatic compounds promotes ultrafast intersystem crossing and increases the formation quantum yield of the lowest excited triplet (T1). Therefore, understanding the reactivity of nitroindoles' T1 states is imperative. This study investigated the physical properties and chemical reactivities of the T1 state of 6-nitroindole (3HN-6NO2) in both polar aprotic and protic solvents, using transient absorption spectroscopy. Our results demonstrate the basicity and acidity of 3HN-6NO2, emphasizing its potential for protonation and dissociation in mildly acidic and basic conditions, respectively. Furthermore, 3HN-6NO2 has a high oxidizing capacity, participating in electron transfer reactions and proton-coupled electron transfer to produce radicals. Interestingly, in protic solvents like alcohols, 3HN-6NO2 dissociates at the -NH group and forms N-H…O hydrogen-bonded complexes with the nitro group. By identifying transient absorption spectra of intermediates and quantifying kinetic reaction rate constants, we illuminate the unique properties of the T1 state nitroindoles, enriching our understanding of their photophysical and photochemical behaviors. The results of this study have significant implications for their potential application in both biological systems and materials science.
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Affiliation(s)
- Yangxin Wang
- School of Chemistry and Chemical Engineering, Key Laboratory of Surface & Interface Science of Polymer Materials, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Zhao Ye
- School of Chemistry and Chemical Engineering, Key Laboratory of Surface & Interface Science of Polymer Materials, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Ting Han
- School of Chemistry and Chemical Engineering, Key Laboratory of Surface & Interface Science of Polymer Materials, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Yong Du
- Centre for THz Research, China Jiliang University, Hangzhou, 310018, China
| | - Jiadan Xue
- School of Chemistry and Chemical Engineering, Key Laboratory of Surface & Interface Science of Polymer Materials, Zhejiang Sci-Tech University, Hangzhou 310018, China.
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Wu Y, Wang Y, Guan H, Du Y, Zheng X, Xue J. Effect of electron-donating substitution on the triplet state reactivities of 1-nitronaphthalene. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 286:121997. [PMID: 36308824 DOI: 10.1016/j.saa.2022.121997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 09/23/2022] [Accepted: 10/13/2022] [Indexed: 06/16/2023]
Abstract
Nitro-polycyclic aromatic hydrocarbons (nitro-PAHs), often found in polluted air, are carcinogenic and mutagenic. The nitro group increases the spin-orbit coupling and results in the lowest excited triplet (T1) on the picosecond time scale with a high yield. The electron-donating substituents have a significant influence on the photophysics and photochemistry of nitro-PAHs. We used transient absorption spectroscopy and kinetic analysis to investigate the reactivities of the T1 state 1-methoxy-4-nitronaphthalene (3MeO-NN) and 1-methyl-4-nitronaphthalene (3Me-NN). The results show that the methoxy and methyl substitutions have a minor effect on their hydrogen abstraction and electron accepting abilities. The main distinction is their reaction rates towards protons. The second order rate constant of 3MeO-NN towards protons is three orders of magnitude greater than that of 3Me-NN, indicating that 3MeO-NN has a stronger hydrogen bond accepting ability. The kinetic analysis reveals that the dimer of 2,2,2-trifluoroethanol participates in the reaction with 3MeO-NN. These results suggest that the formation of the hydrogen-bonded complex is responsible for the unusually short lifetime of 3MeO-NN in methanol solution and the lack of hydrogen abstraction radicals during the decay of 3MeO-NN in methanol.
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Affiliation(s)
- Yu Wu
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Yangxin Wang
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Huaiyu Guan
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Yong Du
- Centre for THz Research, Jiliang University, Hangzhou 310018, China
| | - Xuming Zheng
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Jiadan Xue
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China; Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China.
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Mazumder A, Sebastian E, Hariharan M. Solvent dielectric delimited nitro–nitrito photorearrangement in a perylenediimide derivative. Chem Sci 2022; 13:8860-8870. [PMID: 35975155 PMCID: PMC9350666 DOI: 10.1039/d2sc02979k] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Accepted: 07/04/2022] [Indexed: 12/04/2022] Open
Abstract
The discovery of vibrant excited-state dynamics and distinctive photochemistry has established nitrated polycyclic aromatic hydrocarbons as an exhilarating class of organic compounds. Herein, we report the atypical photorearrangement of nitro-perylenediimide (NO2-PDI) to nitrito-perylenediimide (ONO-PDI), triggered by visible-light excitation and giving rise to linkage isomers in the polar aprotic solvent acetonitrile. ONO-PDI has been isolated and unambiguously characterized using standard spectroscopic, spectrometric, and elemental composition techniques. Although nitritoaromatic compounds are conventionally considered to be crucial intermediates in the photodissociation of nitroaromatics, experimental evidence for this has not been observed heretofore. Ultrafast transient absorption spectroscopy combined with computational investigations revealed the prominence of a conformationally relaxed singlet excited-state (SCR1) of NO2-PDI in the photoisomerization pathway. Theoretical transition state (TS) analysis indicated the presence of a six-membered cyclic TS, which is pivotal in connecting the SCR1 state to the photoproduct state. This article addresses prevailing knowledge gaps in the field of organic linkage isomers and provides a comprehensive understanding of the unprecedented photoisomerization mechanism operating in the case of NO2-PDI. The unprecedented photorearrangement of nitro-perylenediimide (NO2-PDI) to nitrito-perylenediimide (ONO-PDI) is shown to occur through a cyclic six-membered transition state triggered by visible-light excitation.![]()
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Affiliation(s)
- Aniruddha Mazumder
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Maruthamala P.O., Vithura, Thiruvananthapuram, Kerala, India 695551
| | - Ebin Sebastian
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Maruthamala P.O., Vithura, Thiruvananthapuram, Kerala, India 695551
| | - Mahesh Hariharan
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Maruthamala P.O., Vithura, Thiruvananthapuram, Kerala, India 695551
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Anticancer and Immunomodulatory Benefits of Taro ( Colocasia esculenta) Corms, an Underexploited Tuber Crop. Int J Mol Sci 2020; 22:ijms22010265. [PMID: 33383887 PMCID: PMC7795958 DOI: 10.3390/ijms22010265] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 12/21/2020] [Accepted: 12/21/2020] [Indexed: 12/20/2022] Open
Abstract
Taro corms contain valuable bioactive molecules effective against cancer and cancer-related risk factors, such as carcinogens and biological agents, several pathophysiological conditions, including oxidative stress and inflammation, while controlling metabolic dysfunctions and boosting the immunological response. Such broad effects are achieved by the taro health-influencing compounds displaying antitumoral, antimutagenic, immunomodulatory, anti-inflammatory, antioxidant, anti-hyperglycemic, and anti-hyperlipidemic activities. Taro bioactivities are attributed to the combination of tarin, taro-4-I polysaccharide, taro polysaccharides 1 and 2 (TPS-1 and TPS-2), A-1/B-2 α-amylase inhibitors, monogalactosyldiacylglycerols (MGDGs), digalactosyldiacylglycerols (DGDGs), polyphenols, and nonphenolic antioxidants. Most of these compounds have been purified and successfully challenged in vitro and in vivo, proving their involvement in the aforementioned activities. Although these health-promoting effects have been recognized since ancient times, as well as other valuable features of taro for food profit, such as hypo-allergenicity, gluten-free, and carbohydrates with medium-glycemic index, taro crop remains underexploited. The popularization of taro intake should be considered a dietary intervention strategy to be applied to improve the overall health status of the organism and as supportive therapy to manage tumorigenesis.
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Long J, Ye Z, Du Y, Zheng XM, Xue JD. Direct observation of transient species generated from protonation and deprotonation of the lowest triplet of p-nitrophenylphenol. CHINESE J CHEM PHYS 2020. [DOI: 10.1063/1674-0068/cjcp2006107] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Jing Long
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Zhao Ye
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Yong Du
- Centre for THz Research, China Jiliang University, Hangzhou 310018, China
| | - Xu-ming Zheng
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Jia-dan Xue
- Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
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Zhang F, Zhang D, Du Y, Jin P, Zhao Y, Zheng X, Xue J. Direct observation of stepwise intermolecular proton and hydrogen transfer between alcohols and the triplet state of 4-nitro-1-naphthol. Phys Chem Chem Phys 2018; 20:11876-11881. [PMID: 29662995 DOI: 10.1039/c8cp00484f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Solvent assisted excited state intramolecular proton or hydrogen transfer has received much attention in bi-functional molecules with hydrogen donating and hydrogen accepting groups. As a typical photoacid, 1-naphthol exhibits photo-stable behavior in methanol; whether this would be disrupted by a bonded hydrogen accepting group contained in the molecule is still not assured. We present nanosecond transient absorption measurements relating to kinetics and the characteristic absorption of key intermediates upon the excitation of 4-nitro-1-naphthol in alcoholic solutions, and also transient resonance Raman spectroscopy studies combined with theoretical calculations to identify the structures of these intermediates, and we reveal the reaction mechanism to be stepwise deprotonation, hydrogen abstraction and protonation. These results demonstrate that alcohol assisted intramolecular proton or hydrogen transfer cannot occur in this system, but that the solvent cluster plays an important role during such stepwise reactions.
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Affiliation(s)
- Fengjin Zhang
- Department of Chemsitry, Zhejiang Sci-Tech University, Hangzhou, 310018, China
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Zhang D, Jin P, Yang M, Du Y, Zheng X, Xue J. Intermolecular Hydrogen Abstraction from Hydroxy Group and Alkyl by T 1(ππ*) of 1-Chloro-4-nitronaphthalene. J Phys Chem A 2018; 122:1831-1837. [PMID: 29432008 DOI: 10.1021/acs.jpca.7b11146] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nanosecond transient absorption and theoretical calculations have been used to investigate the intermolecular hydrogen abstractions from alcohols and 1-naphthol by the lowest excited triplet (T1) of 1-chloro-4-nitronaphthalene upon excitation of the compound in organic solvents. The hydrogen abstraction of T1 from hydroxy group of 1-naphthol takes place through an electron transfer followed by a proton transfer through hydrogen bonding interaction with rate constants of ∼109 M-1 s-1. Hydrogen-bonding is crucial in this process, indicated by the observation of a half reduction for T1 yield when increasing the concentration of 1-naphthol. The hydrogen abstraction in this way can be decelerated by increasing solvent polarity and hydrogen-bonding donor ability. The T1 of 1-chloro-4-nitronaphthalene can undergo one-step H atom abstraction from alkyl hydrogen in alcoholic solvents, with rate constants of ∼104 M-1 s-1, and produce radical intermediates with the absorption maximum at 368 nm. DFT calculation results indicate both oxygens of the nitro group are active sites for hydrogen abstraction, and the difference of activation barriers for formation of two radical isomers is only 1.0 kcal/mol.
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Affiliation(s)
- Di Zhang
- Department of Chemsitry, Zhejiang Sci-Tech University , Hangzhou 310018, China
| | - Peipei Jin
- Department of Chemsitry, Zhejiang Sci-Tech University , Hangzhou 310018, China
| | - Meng Yang
- Department of Chemsitry, Zhejiang Sci-Tech University , Hangzhou 310018, China
| | - Yong Du
- Center for THz Research, China Jiliang University , Hangzhou 310018, China
| | - Xuming Zheng
- Department of Chemsitry, Zhejiang Sci-Tech University , Hangzhou 310018, China
| | - Jiadan Xue
- Department of Chemsitry, Zhejiang Sci-Tech University , Hangzhou 310018, China
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