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Chang KH, Peng YC, Su KH, Lin YH, Liu JC, Liu YH, Hsu CH, Yang HC, Chou PT. Long-range hydrogen-bond relay catalyses the excited-state proton transfer reaction. Chem Sci 2023; 14:7237-7247. [PMID: 37416704 PMCID: PMC10321479 DOI: 10.1039/d3sc01441j] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Accepted: 05/25/2023] [Indexed: 07/08/2023] Open
Abstract
Solvent (e.g., water)-catalyzed proton transfer (SCPT) via the relay of hydrogen (H)-bonds plays a key role in proton migration. In this study, a new class of 1H-pyrrolo[3,2-g]quinolines (PyrQs) and their derivatives were synthesized, with sufficient separation of the pyrrolic proton donating and pyridinic proton accepting sites to probe excited-state SCPT. There was dual fluorescence for all PyrQs in methanol, i.e., normal (PyrQ) and tautomer 8H-pyrrolo[3,2-g]quinoline (8H-PyrQ) emissions. The fluorescence dynamics unveiled a precursor (PyrQ) and successor (8H-PyrQ) relationship and the correlation of an increasing overall excited-state SCPT rate (kSCPT) upon increasing the N(8)-site basicity. kSCPT can be expressed by the coupling reaction kSCPT = Keq × kPT, where kPT denotes the intrinsic proton tunneling rate in the relay and Keq denotes the pre-equilibrium between randomly and cyclically H-bonded solvated PyrQs. Molecular dynamics (MD) simulation defined the cyclic PyrQs and analyzed the H-bond and molecular arrangement over time, which showed the cyclic PyrQs incorporating ≧3 methanol molecules. These cyclic H-bonded PyrQs are endowed with a relay-like proton transfer rate, kPT. MD simulation estimated an upper-limited Keq value of 0.02-0.03 for all studied PyrQs. When there was little change in Keq, the distinct kSCPT values for PyrQs were at different kPT values, which increased as the N(8) basicity increased, which was induced by the C(3)-substituent. kSCPT was subject to a deuterium isotope effect, where the kSCPT of 1.35 × 1010 s-1 for PyrQ-D in CH3OD was 1.68 times slower than that (2.27 × 1010 s-1) of PyrQ in CH3OH. MD simulation provided a similar Keq for PyrQ and PyrQ-D, leading to different proton tunneling rates (kPT) between PyrQ and PyrQ-D.
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Affiliation(s)
- Kai-Hsin Chang
- Department of Chemistry, National Taiwan University Taipei 10617 Taiwan ROC
| | - Yu-Chiang Peng
- Department of Chemistry, National Taiwan University Taipei 10617 Taiwan ROC
| | - Kuan-Hsuan Su
- Department of Chemistry, Fu Jen Catholic University New Taipei City 24205 Taiwan ROC
| | - Yi-Hsien Lin
- Department of Chemistry, Fu Jen Catholic University New Taipei City 24205 Taiwan ROC
| | - Jiun-Chi Liu
- Department of Chemistry, National Taiwan University Taipei 10617 Taiwan ROC
| | - Ying-Hsuan Liu
- Department of Chemistry, National Taiwan University Taipei 10617 Taiwan ROC
| | - Chao-Hsien Hsu
- Department of Chemistry, National Taiwan University Taipei 10617 Taiwan ROC
| | - Hsiao-Ching Yang
- Department of Chemistry, Fu Jen Catholic University New Taipei City 24205 Taiwan ROC
| | - Pi-Tai Chou
- Department of Chemistry, National Taiwan University Taipei 10617 Taiwan ROC
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Liu J, Feng RR, Zhou L, Gai F, Zhang W. Photoenhancement of the C≡N Stretching Vibration Intensity of Aromatic Nitriles. J Phys Chem Lett 2022; 13:9745-9751. [PMID: 36222647 DOI: 10.1021/acs.jpclett.2c02418] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The C≡N stretching vibration is a versatile infrared (IR) reporter that is useful for a wide range of applications. Aiming to further expand its spectroscopic utility, herein, we show that, using 4-cyanoindole and 4-cyano-7-azaindole as examples, photoexcitation can significantly shift the frequency (νCN) and enhance the molar extinction coefficient (εCN) of this vibrational mode of aromatic nitriles and that, for these indole derivatives, the enhancement factor can reach 13. Moreover, we find that while solvent relaxation at the excited electronic state(s) always leads to an increase in εCN, its effect on νCN depends on the solute and the solvent. Taken together, these results demonstrate that solvent relaxation can differently affect the local environment of the nitrile group and its conjugation with the indole ring and, more importantly, that the C≡N stretching vibration can serve as a sensitive IR probe of charge and electron transfer processes in which an aromatic nitrile is involved.
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Affiliation(s)
- Jingsong Liu
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Ran-Ran Feng
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Liang Zhou
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Feng Gai
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Wenkai Zhang
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
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Chung KY, Chen YH, Chen YT, Hsu YH, Shen JY, Chen CL, Chen YA, Chou PT. The Excited-State Triple Proton Transfer Reaction of 2,6-Diazaindoles and 2,6-Diazatryptophan in Aqueous Solution. J Am Chem Soc 2017; 139:6396-6402. [DOI: 10.1021/jacs.7b01672] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Kun-You Chung
- Department of Chemistry and
Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan, R.O.C
| | - Yi-Han Chen
- Department of Chemistry and
Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan, R.O.C
| | - Yi-Ting Chen
- Department of Chemistry and
Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan, R.O.C
| | - Yen-Hao Hsu
- Department of Chemistry and
Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan, R.O.C
| | - Jiun-Yi Shen
- Department of Chemistry and
Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan, R.O.C
| | - Chi-Lin Chen
- Department of Chemistry and
Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan, R.O.C
| | - Yi-An Chen
- Department of Chemistry and
Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan, R.O.C
| | - Pi-Tai Chou
- Department of Chemistry and
Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan, R.O.C
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Hsieh CC, Chou PT, Shih CW, Chuang WT, Chung MW, Lee J, Joo T. Comprehensive Studies on an Overall Proton Transfer Cycle of the ortho-Green Fluorescent Protein Chromophore. J Am Chem Soc 2011; 133:2932-43. [DOI: 10.1021/ja107945m] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Cheng-Chih Hsieh
- Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan, R.O.C
| | - Pi-Tai Chou
- Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan, R.O.C
| | - Chun-Wei Shih
- Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan, R.O.C
| | - Wei-Ti Chuang
- Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan, R.O.C
| | - Min-Wen Chung
- Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan, R.O.C
| | - Junghwa Lee
- Department of Chemistry, Pohang University of Science and Technology, Pohang, 790-784, South Korea
| | - Taiha Joo
- Department of Chemistry, Pohang University of Science and Technology, Pohang, 790-784, South Korea
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Hsieh CC, Jiang CM, Chou PT. Recent experimental advances on excited-state intramolecular proton coupled electron transfer reaction. Acc Chem Res 2010; 43:1364-74. [PMID: 20954751 DOI: 10.1021/ar1000499] [Citation(s) in RCA: 256] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Proton-coupled electron transfer reactions form the basis of many important chemical processes including much of the energy conversion that occurs within living cells. However, much of the physical chemistry that underlies these reaction mechanisms remains poorly understood. In this Account, we report on recent progress in the understanding of excited-state intramolecular proton-coupled electron transfer (PCET) reactions. The strategic design and synthesis of various types of PCET molecules, along with steady-state and femtosecond time-resolved spectroscopy, have uncovered the mechanisms of several excited-state PCET reactions in solution. These experimental advancements correlate well with current theoretical models, in which the proton has quantum motion with a high probability of tunneling. In addition, the rate of proton transfer is commonly incorporated within the rate of rearrangement of solvent molecules. As a result, the reaction activation free energy is essentially governed by the solvent reorganization because the charge redistribution is considered based on a solvent polarity-induced barrier instead of the height of the proton migration barrier. In accord with this theoretical basis, we can rationalize the observation that the proton transfer for many excited-state PCET systems occurs during the solvent relaxation time scale of 1-10 ps: the highly exergonic reaction takes place before the system reaches its equilibrium polarization. Also, we have used various derivatives of proton transfer molecules, especially those of 3-hydroxyflavone to clearly demonstrate how researchers can tune the dynamics of excited-state PCET through changes in the magnitude or direction of the dipole vector within the reaction. Subsequently, using 2-(2'-hydroxyphenyl)benzoxazole as the parent model, we then report on methods for the development of an ideal system for probing PCET reaction. Because future biomedical applications of such systems will likely occur in aqueous environments, we discuss various 7-azaindole analogues, for which proton transfer requires the assistance of protic solvent molecules. These results provide a unique contrast to the ubiquitous studies on the dynamic solvent effects of PCET molecules that undergo intrinsic intramolecular proton motion.
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Affiliation(s)
- Cheng-Chih Hsieh
- Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan, Republic of China
| | - Chang-Ming Jiang
- Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan, Republic of China
| | - Pi-Tai Chou
- Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan, Republic of China
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Lin CC, Chen CL, Chung MW, Chen YJ, Chou PT. Effects of Multibranching on 3-Hydroxyflavone-Based Chromophores and the Excited-State Intramolecular Proton Transfer Dynamics. J Phys Chem A 2010; 114:10412-20. [DOI: 10.1021/jp105542z] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Chao-Chen Lin
- Department of Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan, R.O.C
| | - Chyi-Lin Chen
- Department of Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan, R.O.C
| | - Min-Wen Chung
- Department of Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan, R.O.C
| | - Yi-Ju Chen
- Department of Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan, R.O.C
| | - Pi-Tai Chou
- Department of Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan, R.O.C
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Huang GJ, Yang JS. The N-Arylamino Conjugation Effect in the Photochemistry of Fluorescent Protein Chromophores and Aminostilbenes. Chem Asian J 2010; 5:2075-85. [DOI: 10.1002/asia.201000209] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Lin CW, Chou PT, Liao YH, Lin YC, Chen CT, Chen YC, Lai CH, Chen BS, Liu YH, Wang CC, Ho ML. Photoisomerization of a maleonitrile-type salen Schiff base and its application in fine-tuning infinite coordination polymers. Chemistry 2010; 16:3770-82. [PMID: 20162646 DOI: 10.1002/chem.200902500] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Strategically designed salen ligand 2,3-bis[4-(di-p-tolylamino)-2-hydroxybenzylideneamino]maleonitrile (1), which has pronounced excited-state charge-transfer properties, shows a previously unrecognized form of photoisomerization. On electronic excitation (denoted by an asterisk), 1Z*-->1E isomerization takes place by rotation about the C2--C3 bond, which takes on single-bond character due to the charge-transfer reaction. The isomerization takes place nonadiabatically from the excited-state (1Z) to the ground-state (1E) potential-energy surface in the singlet manifold; 1Z and 1E are neither thermally inconvertible at ambient temperature (25-30 degrees C), nor does photoinduced reverse 1E*-->1Z (or 1Z*) isomerization occur. Isomers 1Z and 1E show very different coordination chemistry towards a Zn(II) precursor. More prominent coordination chemistry is evidenced by a derivative of 1 bearing a carboxyl group, namely, N,N'-dicyanoethenebis(salicylideneimine)dicarboxylic acid (2). Applying 2Z and its photoinduced isomer 2E as building blocks, we then demonstrate remarkable differences in morphology (sphere- and needlelike nanostructure, respectively) of their infinite coordination polymers with Zn(II).
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Affiliation(s)
- Chun-Wei Lin
- Department of Chemistry, National Taiwan University, Taipei, Taiwan
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Organic Dyes with Excited-State Transformations (Electron, Charge, and Proton Transfers). SPRINGER SERIES ON FLUORESCENCE 2010. [DOI: 10.1007/978-3-642-04702-2_7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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