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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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Alexander E, Lee B, Pham D, Garcia-Rodriguez S, Gryczynski Z, Gryczynski I. Photophysical properties of DAPI in PVA films. Possibility of room temperature phosphorescence. Anal Biochem 2024; 689:115498. [PMID: 38423238 DOI: 10.1016/j.ab.2024.115498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 02/09/2024] [Accepted: 02/26/2024] [Indexed: 03/02/2024]
Abstract
We studied the spectral properties of 4'-6-diamidino-2-phenylindole (DAPI) in poly (vinyl alcohol) (PVA) films. Absorption and fluorescence spectra, emission and excitation spectra, quantum yield, and fluorescence lifetime have been characterized. An efficient room temperature phosphorescence (RTP) of DAPI has been observed with UV and blue light excitations. A few hundred millisecond phosphorescence lifetime enables a gated detection with sufficient background reduction. We found the phosphorescent Quantum Yield of DAPI in PVA Film to be 0.0009.
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Affiliation(s)
- Emma Alexander
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76129, USA.
| | - Bong Lee
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76129, USA
| | - Danh Pham
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76129, USA
| | | | - Zygmunt Gryczynski
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76129, USA
| | - Ignacy Gryczynski
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76129, USA
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Alexander E, Ceresa L, Pham D, Gryczynski Z, Gryczynski I. Effect of annealing on the room temperature luminescence of coumarin 106 in PVA films. Methods Appl Fluoresc 2023; 12:015005. [PMID: 37879322 DOI: 10.1088/2050-6120/ad06dc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 10/25/2023] [Indexed: 10/27/2023]
Abstract
We studied the effect of annealing on the luminescence of Coumarin 106 (C106) in poly (vinyl alcohol) films (PVA films). The samples and reference polymer films were treated at temperatures between 100 °C and 150 °C (212 F and 302 F) for various times. After cooling and smoothing, the samples and references were measured at room temperature. We observed that the PVA polymer (reference films) changes its optical properties with annealing at higher temperatures, affecting the baselines in absorption and the backgrounds in emission measurements. This requires precise background subtractions and control of the signal-to-noise ratio. Whereas the fluorescence intensity of C106 in PVA films modestly decreases with annealing, the phosphorescence depends dramatically and progressively increases by many folds. The fluorescence quantum yields and lifetimes decrease with the annealing, which suggests an increase in the non-radiative processes in the singlet excited state S1. The increase in the phosphorescence intensities results from increased intersystem crossing (ISC), which also decreases fluorescence. We also studied the effect of annealing on phosphorescence with the directly excited triplet state of C106. In this case, two processes are affected by annealing, S0→T1absorption and T1→S0phosphorescence. The long-wavelength excitation (475 nm) avoids PVA polymer excitation. The phosphorescence lifetime decreases with annealing while the phosphorescence intensity increases. These changes suggest that the radiative rate of T1→ S0increases with annealing.
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Affiliation(s)
- Emma Alexander
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76129, United States of America
| | - Luca Ceresa
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76129, United States of America
| | - Danh Pham
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76129, United States of America
| | - Zygmunt Gryczynski
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76129, United States of America
| | - Ignacy Gryczynski
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76129, United States of America
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Chavez J, Ceresa L, Kitchner E, Pham D, Gryczynski Z, Gryczynski I. Room temperature phosphorescence of 2-aminopyridine with direct triplet state excitation. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 295:122640. [PMID: 36958243 DOI: 10.1016/j.saa.2023.122640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Revised: 03/05/2023] [Accepted: 03/14/2023] [Indexed: 06/18/2023]
Abstract
Phosphorescence emission at room temperature has been observed from 2-Aminopyridyne (2APi) embedded in poly (vinyl alcohol) (PVA) films. The gated emission with UV excitation at 305 nm results in a residual delayed fluorescence at around 350 nm and a broad phosphorescence spectrum with a maximum of around 500 nm. The phosphorescence excitation spectrum of 2APi - doped PVA film differs from the absorption spectrum in the long-wavelength part, showing a band at about 400-450 nm. The phosphorescence spectrum measured with a blue (420 nm) excitation closely resembles the spectrum measured with 305 nm excitation. Whereas the phosphorescence anisotropy measured with UV excitation is low and negative, with the blue excitation, the anisotropy is high and positive. The phosphorescence lifetimes (a fraction of a millisecond) are similar for UV and blue excitations. Both phosphorescence emissions with either UV or blue excitation strongly depend on temperature.
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Affiliation(s)
- Jose Chavez
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, United States.
| | - Luca Ceresa
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, United States
| | - Emma Kitchner
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, United States
| | - Danh Pham
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, United States
| | - Zygmunt Gryczynski
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, United States
| | - Ignacy Gryczynski
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, United States
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Chavez JL, Ceresa L, Reeks JM, Strzhemechny Y, Kimball J, Kitchner E, Gryczynski Z, Gryczynski I. Direct Excitation of Tryptophan Phosphorescence. A New Method for Triplet States Investigation. Methods Appl Fluoresc 2022; 10. [PMID: 35042210 DOI: 10.1088/2050-6120/ac4c9a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 01/18/2022] [Indexed: 11/12/2022]
Abstract
We studied room temperature phosphorescence of tryptophan (TRP) embedded in poly (vinyl alcohol) films. With UV (285 nm) excitation, the phosphorescence spectrum of tryptophan appears at about 460 nm. We also observed the TRP phosphorescence with blue light excitation at 410 nm, well outside of the S0→S1 absorption. This excitation reaches the triplet state of tryptophan directly without the involvement of the singlet excited state. The phosphorescence lifetime of tryptophan is in the sub-millisecond range. The long-wavelength direct excitation to the triplet state results in high phosphorescence anisotropy which can be useful in macromolecule dynamics study via time-resolved phosphorescence.
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Affiliation(s)
- Jose Luis Chavez
- Department of Physics & Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, 76129, UNITED STATES
| | - Luca Ceresa
- Department of Physics and Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, Texas, 76129, UNITED STATES
| | - John M Reeks
- Department of Physics & Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, 76129, UNITED STATES
| | - Yuri Strzhemechny
- Department of Physics and Astronomy, Texas Christian University, College of Science & Engineering, TCU Box 298840, Fort Worth, TX 76129, USA, Fort Worth, Texas, 76129, UNITED STATES
| | - Joe Kimball
- Department of Physics and Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, Texas, 76129, UNITED STATES
| | - Emma Kitchner
- Department of Physics and Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, Texas, 76129, UNITED STATES
| | - Zygmunt Gryczynski
- Department of Physics and Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, Texas, 76129, UNITED STATES
| | - Ignacy Gryczynski
- Department of Physics & Astronomy, Texas Christian University, 2995 S. University Dr., Fort Worth, 76129, UNITED STATES
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Yu D, To WP, Liu Y, Wu LL, You T, Ling J, Che CM. Direct photo-induced reductive Heck cyclization of indoles for the efficient preparation of polycyclic indolinyl compounds. Chem Sci 2021; 12:14050-14058. [PMID: 34760188 PMCID: PMC8565399 DOI: 10.1039/d1sc04258k] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 09/16/2021] [Indexed: 12/15/2022] Open
Abstract
The photo-induced cleavage of C(sp2)-Cl bonds is an appealing synthetic tool in organic synthesis, but usually requires the use of high UV light, photocatalysts and/or photosensitizers. Herein is described a direct photo-induced chloroarene activation with UVA/blue LEDs that can be used in the reductive Heck cyclization of indoles and without the use of a photocatalyst or photosensitizer. The indole compounds examined display room-temperature phosphorescence. The photochemical reaction tolerates a panel of functional groups including esters, alcohols, amides, cyano and alkenes (27 examples, 50-88% yields), and can be used to prepare polycyclic compounds and perform the functionalization of natural product analogues in moderate to good yields. Mechanistic experiments, including time-resolved absorption spectroscopy, are supportive of photo-induced electron transfer between the indole substrate and DIPEA, with the formation of radical intermediates in the photo-induced dearomatization reaction.
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Affiliation(s)
- Daohong Yu
- Department of Chemistry, Southern University of Science and Technology Shenzhen Guangdong 518055 China
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong Pokfulam Road Hong Kong China
- Key Laboratory of Organo-Pharmaceutical Chemistry of Jiangxi Province, Gannan Normal University Ganzhou 341000 China
| | - Wai-Pong To
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong Pokfulam Road Hong Kong China
| | - Yungen Liu
- Department of Chemistry, Southern University of Science and Technology Shenzhen Guangdong 518055 China
| | - Liang-Liang Wu
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong Pokfulam Road Hong Kong China
| | - Tingjie You
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong Pokfulam Road Hong Kong China
| | - Jesse Ling
- Laboratory for Synthetic Chemistry and Chemical Biology Limited Units 1503-1511, 15/F, Building 17W, Hong Kong Science Park New Territories Hong Kong China
| | - Chi-Ming Che
- Department of Chemistry, Southern University of Science and Technology Shenzhen Guangdong 518055 China
- State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong Pokfulam Road Hong Kong China
- HKU Shenzhen Institute of Research and Innovation Shenzhen Guangdong 518057 China
- Laboratory for Synthetic Chemistry and Chemical Biology Limited Units 1503-1511, 15/F, Building 17W, Hong Kong Science Park New Territories Hong Kong China
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Ceresa L, Kimball J, Chavez J, Kitchner E, Nurekeyev Z, Doan H, Borejdo J, Gryczynski I, Gryczynski Z. On the origin and correction for inner filter effects in fluorescence. Part II: secondary inner filter effect -the proper use of front-face configuration for highly absorbing and scattering samples. Methods Appl Fluoresc 2021; 9. [PMID: 34032610 DOI: 10.1088/2050-6120/ac0243] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 05/17/2021] [Indexed: 11/12/2022]
Abstract
Fluorescence is an established technology for studying molecular processes and molecular interactions. More recently fluorescence became a leading method for detection, sensing, medical diagnostics, biotechnology, imaging, DNA analysis, and gene expression. Consequently, precise and accurate measurements in various conditions have become more critical for proper result interpretations. Previously, in Part 1, we discussed inner filter effect type I, which is a consequence of the instrumental geometrical sensitivity factor and absorption of the excitation. In this part, we analyze inner filter effect type II and discuss the practical consequences for fluorescence measurements in samples of high optical density (absorbance/scattering). We consider both the standard square and front-face experimental configurations, discuss experimental approaches to limit/mitigate the effect and discuss methods for correcting and interpreting experimental results.
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Affiliation(s)
- Luca Ceresa
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76109, United States of America
| | - Joseph Kimball
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76109, United States of America
| | - Jose Chavez
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76109, United States of America
| | - Emma Kitchner
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76109, United States of America
| | - Zhangatay Nurekeyev
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76109, United States of America
| | - Hung Doan
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76109, United States of America
| | - Julian Borejdo
- Department of Microbiology, Immunology, and Genetics, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX, 76107, United States of America
| | - Ignacy Gryczynski
- Department of Microbiology, Immunology, and Genetics, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX, 76107, United States of America
| | - Zygmunt Gryczynski
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76109, United States of America
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Weigl P, Schadt D, Weißheit S, Thiele CM, Walther T, Blochowicz T. Triplet state solvation dynamics: extending the accessible timescale by using indole as local probe. Phys Chem Chem Phys 2021; 23:683-693. [PMID: 33336668 DOI: 10.1039/d0cp05240j] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Triplet state solvation dynamics (TSD) is a truly local measurement technique, where a dye molecule is dissolved as a probe at low concentration in a solvent. Depending on the dye molecule, local information on mechanical or dielectric solvation can be obtained. So far, this method has mainly been used to investigate topics such as fundamentals of glassy dynamics and confinement effects. Based on the procedure presented in [P. Weigl et al., Z. Phys. Chem., 2018, 232, 1017-1039] in the present contribution two new TSD probes, namely indole and its derivative cbz-tryptophan, are identified and characterized in detail. In particular, their longer phosphorescence lifetime allows for a significant extension of the timescale of local mechanical and dipolar solvation measurements. In combination with previously used dyes a measurement window of up to five orders of magnitude in time can be covered. Furthermore, we show that in cbz-tryptophan the indole unit is the phosphorescence center, while the rest of the molecule only slightly contributes to the solvation response function. The detailed understanding of these two new TSD probes presented in this work, will allow in depth investigations of solvation and the corresponding dynamics also for biologically relevant systems in the future.
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Affiliation(s)
- Peter Weigl
- Institute for Condensed Matter Physics, Technical University of Darmstadt, 64289 Darmstadt, Germany.
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