1
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Hunt JR, Hecht J, Goolsby C, Hagihara J, Loza M, del Pozo S. Excited State Proton Transfer from Acidic Alcohols to a Quinoline Photobase Can Be Solvated by Non-Acidic Alcohol Solvents. J Phys Chem A 2024; 128:6199-6207. [PMID: 39034730 PMCID: PMC11299183 DOI: 10.1021/acs.jpca.4c02907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2024] [Revised: 06/25/2024] [Accepted: 07/11/2024] [Indexed: 07/23/2024]
Abstract
Photobases are a type of molecule that become more basic upon photoexcitation and can therefore be used to control proton transfer reactions with light. The solvation requirements for excited state proton transfer (ESPT) in photobase systems is poorly understood, which limits their applicability. Here, we investigate the solvation of the ESPT reaction using 5-methoxyquinoline (MeOQ), a well-studied photobase with an excited state pKa (pKa*) of approximately 15.1, as a model system. Previous studies have shown that, in addition to the acidic donor that donates a proton to the photoexcited MeOQ, an additional "auxiliary donor" is necessary to solvate the resulting alkoxide. We investigate whether a nonacidic hydrogen bond donor (an alcohol solvent that MeOQ cannot deprotonate in bulk) can act as the auxiliary donor for the MeOQ ESPT reaction. First, we use steady state spectroscopy, TCSPC, and electronic structure calculations to show that MeOQ can deprotonate the acidic donor 2,2,2-trifluoroethanol (TFE, pKa = 12.5) using ethanol as the auxiliary donor. We show that the degree of ESPT is largely predicted by the degree of ground state hydrogen bonding between the photobase and the acidic donor. Next, we study the deprotonation of the acidic donors TFE and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP, pKa = 9.3) with MeOQ in a variety of nonacidic alcohol solvents of varying chain length and branching. MeOQ ESPT occurs to varying extents in all solvents, suggesting that all studied nonacidic alcohols can function as auxiliary donors. We show that the concentration of the acidic donor is strongly correlated with the degree of ESPT. These results are necessary fundamental steps toward the understanding of the photobase ESPT reaction and its wide application in a variety of chemical systems.
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Affiliation(s)
- Jonathan Ryan Hunt
- Loyola Marymount University, Los Angeles, California 90045, United States
| | - Joseph Hecht
- Loyola Marymount University, Los Angeles, California 90045, United States
| | - Clara Goolsby
- Loyola Marymount University, Los Angeles, California 90045, United States
| | - Jade Hagihara
- Loyola Marymount University, Los Angeles, California 90045, United States
| | - Monique Loza
- Loyola Marymount University, Los Angeles, California 90045, United States
| | - Samantha del Pozo
- Loyola Marymount University, Los Angeles, California 90045, United States
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2
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Chen LX, Yano J. Deciphering Photoinduced Catalytic Reaction Mechanisms in Natural and Artificial Photosynthetic Systems on Multiple Temporal and Spatial Scales Using X-ray Probes. Chem Rev 2024; 124:5421-5469. [PMID: 38663009 DOI: 10.1021/acs.chemrev.3c00560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2024]
Abstract
Utilization of renewable energies for catalytically generating value-added chemicals is highly desirable in this era of rising energy demands and climate change impacts. Artificial photosynthetic systems or photocatalysts utilize light to convert abundant CO2, H2O, and O2 to fuels, such as carbohydrates and hydrogen, thus converting light energy to storable chemical resources. The emergence of intense X-ray pulses from synchrotrons, ultrafast X-ray pulses from X-ray free electron lasers, and table-top laser-driven sources over the past decades opens new frontiers in deciphering photoinduced catalytic reaction mechanisms on the multiple temporal and spatial scales. Operando X-ray spectroscopic methods offer a new set of electronic transitions in probing the oxidation states, coordinating geometry, and spin states of the metal catalytic center and photosensitizers with unprecedented energy and time resolution. Operando X-ray scattering methods enable previously elusive reaction steps to be characterized on different length scales and time scales. The methodological progress and their application examples collected in this review will offer a glimpse into the accomplishments and current state in deciphering reaction mechanisms for both natural and synthetic systems. Looking forward, there are still many challenges and opportunities at the frontier of catalytic research that will require further advancement of the characterization techniques.
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Affiliation(s)
- Lin X Chen
- Chemical Science and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Junko Yano
- Molecular Biophysics & Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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3
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Nair S, Bysewski OA, Klosterhalfen N, Sittig M, Winter A, Schubert US, Dietzek-Ivanšić B. Intramolecular Energy Transfer Competing with Light-Driven Intermolecular Proton Transfer in an Iron(II)-NHC Complex? A Query into the Role of Photobasic Ligands and MLCT States. ACS OMEGA 2024; 9:13427-13439. [PMID: 38524456 PMCID: PMC10955593 DOI: 10.1021/acsomega.3c06196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 11/15/2023] [Accepted: 11/20/2023] [Indexed: 03/26/2024]
Abstract
Inorganic photoacids and photobases comprising of photoactive transition metal complexes (TMCs) offer the ability to modulate proton transfer reactions through light irradiation, while utilizing the excellent optical properties of the latter. This provides a powerful tool for precise control over chemical reactions and processes, with implications for both fundamental science and practical applications. In this contribution, we present a novel molecular architecture amending an Fe-NHC complex with a pendant quinoline, as a prototypical photobase, as a representative earth-abundant TMC based inorganic photobase. We characterize the excited-state properties and proton-transfer dynamics using steady-state absorption and emission spectroscopy as well as pump wavelength dependent transient absorption spectroscopy in various protic solvents. The kinetics and thermodynamics of proton transfer in the quinoline moiety are influenced by both the presence of the metal center and the choice of the solvent. Furthermore, we see indications of intramolecular energy transfer from the quinoline to the MLCT state as a limiting factor for panchromatic photobasicity of the complex.
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Affiliation(s)
- Shruthi
S. Nair
- Department
Functional Interfaces, Leibniz Institute
of Photonic Technology (Leibniz-IPHT), Albert-Einstein-Strasse 9, 07745 Jena, Germany
- Institute
of Physical Chemistry, Friedrich-Schiller
University Jena, Helmholtzweg 4, 07743 Jena, Germany
| | - Oliver A. Bysewski
- Laboratory
of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstrasse 10, 07743 Jena, Germany
- Center for
Energy and Environmental Chemistry Jena (CEEC Jena), Friedrich Schiller University Jena, Philosophenweg 7a, Jena 07743, Germany
| | - Niklas Klosterhalfen
- Department
Functional Interfaces, Leibniz Institute
of Photonic Technology (Leibniz-IPHT), Albert-Einstein-Strasse 9, 07745 Jena, Germany
- Institute
of Physical Chemistry, Friedrich-Schiller
University Jena, Helmholtzweg 4, 07743 Jena, Germany
| | - Maria Sittig
- Department
Functional Interfaces, Leibniz Institute
of Photonic Technology (Leibniz-IPHT), Albert-Einstein-Strasse 9, 07745 Jena, Germany
- Institute
of Physical Chemistry, Friedrich-Schiller
University Jena, Helmholtzweg 4, 07743 Jena, Germany
| | - Andreas Winter
- Laboratory
of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstrasse 10, 07743 Jena, Germany
- Center for
Energy and Environmental Chemistry Jena (CEEC Jena), Friedrich Schiller University Jena, Philosophenweg 7a, Jena 07743, Germany
| | - Ulrich S. Schubert
- Laboratory
of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstrasse 10, 07743 Jena, Germany
- Center for
Energy and Environmental Chemistry Jena (CEEC Jena), Friedrich Schiller University Jena, Philosophenweg 7a, Jena 07743, Germany
| | - Benjamin Dietzek-Ivanšić
- Department
Functional Interfaces, Leibniz Institute
of Photonic Technology (Leibniz-IPHT), Albert-Einstein-Strasse 9, 07745 Jena, Germany
- Institute
of Physical Chemistry, Friedrich-Schiller
University Jena, Helmholtzweg 4, 07743 Jena, Germany
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4
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Mathew R, Verma P, Barak A, Adithya Lakshmanna Y. Excited-State Dynamics in 4-[4'(Dimethylamino)styryl]pyridine, a Photobase: Role of Photoinitiated Proton-Coupled Electron Transfer. J Phys Chem A 2023; 127:7419-7428. [PMID: 37647516 DOI: 10.1021/acs.jpca.3c02502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
The photoinitiated proton-coupled electron transfer (PCET) process in photoacid-based adducts is predominantly governed by the evolution of the electron-proton transfer state. However, such a process is underexplored in the case of photobases as the excited states evolve through multiple competitive channels. Here, we elucidate the excited-state dynamics of a photobase, 4-[4'-(dimethylamino)styryl]pyridine (DMASP), in the presence of hexafluoroisopropanol (HFIP) that enables PCET. Transient absorption measurements show the evolution of a protonated species in the excited state with a time constant of ∼2.5 ps. Fluorescence upconversion measurements reveal the signatures of an emissive intramolecular charge transfer state and a protonated state. The role of such states is further confirmed by time-resolved measurements in the presence of trifluoroacetic acid and computational analysis. Furthermore, the proton-abstraction dynamics of DMASP is analyzed in bulk methanol and butanol solvents. The extent of proton abstraction by DMASP is found to be higher in the presence of HFIP when compared with the normal alcohols over a time period of a few picoseconds.
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Affiliation(s)
- Reshma Mathew
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Vithura, Thiruvananthapuram 695551, India
| | - Preetika Verma
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Vithura, Thiruvananthapuram 695551, India
| | - Arvind Barak
- Department of Inorganic and Physical Chemistry, Indian Institute of Science Bangalore, Bangalore 560012, India
| | - Yapamanu Adithya Lakshmanna
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Vithura, Thiruvananthapuram 695551, India
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5
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Antalicz B, Versluis J, Bakker HJ. Observing Aqueous Proton-Uptake Reactions Triggered by Light. J Am Chem Soc 2023; 145:6682-6690. [PMID: 36940392 PMCID: PMC10064335 DOI: 10.1021/jacs.2c11441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2023]
Abstract
Proton-transfer reactions in water are essential to chemistry and biology. Earlier studies reported on aqueous proton-transfer mechanisms by observing light-triggered reactions of strong (photo)acids and weak bases. Similar studies on strong (photo)base-weak acid reactions would also be of interest because earlier theoretical works found evidence for mechanistic differences between aqueous H+ and OH- transfer. In this work, we study the reaction of actinoquinol, a water-soluble strong photobase, with the water solvent and the weak acid succinimide. We find that in aqueous solutions containing succinimide, the proton-transfer reaction proceeds via two parallel and competing reaction channels. In the first channel, actinoquinol extracts a proton from water, after which the newly generated hydroxide ion is scavenged by succinimide. In the second channel, succinimide forms a hydrogen-bonded complex with actinoquinol and the proton is transferred directly. Interestingly, we do not observe proton conduction in water-separated actinoquinol-succinimide complexes, which makes the newly studied strong base-weak acid reaction essentially different from previously studied strong acid-weak base reactions.
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Affiliation(s)
- Balázs Antalicz
- AMOLF, Ultrafast Spectroscopy, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Jan Versluis
- AMOLF, Ultrafast Spectroscopy, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Huib J Bakker
- AMOLF, Ultrafast Spectroscopy, Science Park 104, 1098 XG Amsterdam, The Netherlands
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6
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Ley C, Siedel A, Bertaux T, Croutxé-Barghorn C, Allonas X. Photochemical Processes of Superbase Generation in Xanthone Carboxylic Salts. Angew Chem Int Ed Engl 2023; 62:e202214784. [PMID: 36533332 DOI: 10.1002/anie.202214784] [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: 10/07/2022] [Revised: 12/16/2022] [Accepted: 12/16/2022] [Indexed: 12/23/2022]
Abstract
Photobase generators are species that allow the photocatalysis of various reactions, such as thiol-Michael, thiol-isocyanate, and ring-opening polymerization reactions. However, existing compounds have complex syntheses and low quantum yields. To overcome these problems, photobase generators based on the photodecarboxylation reaction were developed. We synthesized and studied the photochemistry and photophysics of two xanthone photobase, their carboxylic acid precursors, and their photoproducts to understand the photobase generation mechanism. We determined accurate quantum yields of triplet states and photobase generation. The effect of the intermediate radical preceding the base release was demonstrated. We characterized the photophysics of the photobase by femtosecond spectroscopy and showed that the photodecarboxylation process occurred from the second excited triplet state with a rate constant of 2.2×109 s-1 .
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Affiliation(s)
- Christian Ley
- Laboratoire de Photochimie et d'Ingénierie Macromoléculaire, Université de Haute Alsace, 3b rue A. Werner, 68200, Mulhouse, France
| | - Antoine Siedel
- Laboratoire de Photochimie et d'Ingénierie Macromoléculaire, Université de Haute Alsace, 3b rue A. Werner, 68200, Mulhouse, France
| | - Tony Bertaux
- Laboratoire de Photochimie et d'Ingénierie Macromoléculaire, Université de Haute Alsace, 3b rue A. Werner, 68200, Mulhouse, France
| | - Céline Croutxé-Barghorn
- Laboratoire de Photochimie et d'Ingénierie Macromoléculaire, Université de Haute Alsace, 3b rue A. Werner, 68200, Mulhouse, France
| | - Xavier Allonas
- Laboratoire de Photochimie et d'Ingénierie Macromoléculaire, Université de Haute Alsace, 3b rue A. Werner, 68200, Mulhouse, France
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7
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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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8
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Knorr J, Sülzner N, Geissler B, Spies C, Grandjean A, Kutta RJ, Jung G, Nuernberger P. Ultrafast transient absorption and solvation of a super-photoacid in acetoneous environments. PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES : OFFICIAL JOURNAL OF THE EUROPEAN PHOTOCHEMISTRY ASSOCIATION AND THE EUROPEAN SOCIETY FOR PHOTOBIOLOGY 2022; 21:2179-2192. [PMID: 36178669 DOI: 10.1007/s43630-022-00287-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 08/08/2022] [Indexed: 12/13/2022]
Abstract
The phenomenon of photoacidity, i.e., an increase in acidity by several orders of magnitude upon electronic excitation, is frequently encountered in aromatic alcohols capable of transferring a proton to a suitable acceptor. A promising new class of neutral super-photoacids based on pyranine derivatives has been shown to exhibit pronounced solvatochromic effects. To disclose the underlying mechanisms contributing to excited-state proton transfer (ESPT) and the temporal characteristics of solvation and ESPT, we scrutinize the associated ultrafast dynamics of the strongest photoacid of this class, namely tris(1,1,1,3,3,3-hexafluoropropan-2-yl)8-hydroxypyrene-1,3,6-trisulfonate, in acetoneous environment, thereby finding experimental evidence for ESPT even under these adverse conditions for proton transfer. Juxtaposing results from time-correlated single-photon counting and femtosecond transient absorption measurements combined with a complete decomposition of all signal components, i.e., absorption of ground and excited states as well as stimulated emission, we disclose dynamics of solvation, rotational diffusion, and radiative relaxation processes in acetone and identify the relevant steps of ESPT along with the associated time scales.
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Affiliation(s)
- Johannes Knorr
- Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany.,Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Paul-Gordan-Straße 6, 91052, Erlangen, Germany
| | - Niklas Sülzner
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780, Bochum, Germany.,Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Bastian Geissler
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 95053, Regensburg, Germany.,Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Christian Spies
- Biophysikalische Chemie, Universität des Saarlandes, 66123, Saarbrücken, Germany.,Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Alexander Grandjean
- Biophysikalische Chemie, Universität des Saarlandes, 66123, Saarbrücken, Germany
| | - Roger Jan Kutta
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 95053, Regensburg, Germany
| | - Gregor Jung
- Biophysikalische Chemie, Universität des Saarlandes, 66123, Saarbrücken, Germany
| | - Patrick Nuernberger
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 95053, Regensburg, Germany. .,Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany.
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9
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Abstract
Dative bonding or Lewis acid-base chemistry underpins a large number of chemical phenomena in a variety of fields, such as catalysis, metal-ligand interactions, and surface chemistry. Developing light-controlled Lewis acid-base interactions could offer a new way of controlling and understanding such phenomena. Photoinduced proton transfer, that is, excited-state Brønsted acidity and basicity, has been extensively studied and applied. Here, in direct analogy to excited-state Brønsted basicity, we show that exciting a photobasic molecule with light generates a thermodynamic drive for the transfer of a Lewis acid from a donor to a photobasic molecule. We have used the archetypal BF3 as our Lewis acid and our photoactive Lewis bases are a family of quinolines, which are known Brønsted photobases as well. We have constructed the experimental Förster cycle for this system and have verified it computationally to demonstrate that a significant drive (0.2-0.7 eV) exists for the transfer of BF3 to a photoexcited quinoline. The magnitude of this drive is similar to those reported for Brønsted photobasicity in quinolines. Computational results from TDDFT and energy decomposition analysis show that the origin of such an effect is similar to the Brønsted photoactivity of these molecules, in that they follow the Hammett parameter of substituent groups. These results suggest that photobases may be capable of controlling the chemical phenomena beyond proton transfer and may open opportunities for a new handle in photocatalysis.
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Affiliation(s)
- Matthew J Voegtle
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Jahan M Dawlaty
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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10
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Capistran BA, Yuwono SH, Moemeni M, Maity S, Vahdani A, Borhan B, Jackson JE, Piecuch P, Dantus M, Blanchard GJ. Intramolecular Relaxation Dynamics Mediated by Solvent-Solute Interactions of Substituted Fluorene Derivatives. Solute Structural Dependence. J Phys Chem B 2021; 125:12486-12499. [PMID: 34752096 DOI: 10.1021/acs.jpcb.1c06475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Several fluorene derivatives exhibit excited-state reactivity and relaxation dynamics that remain to be understood fully. We report here the spectral relaxation dynamics of two fluorene derivatives to evaluate the role of structural modification in the intramolecular relaxation dynamics and intermolecular interactions that characterize this family of chromophores. We have examined the time-resolved spectral relaxation dynamics of two compounds, NCy-FR0 and MK-FR0, in protic and aprotic solvents using steady-state and time-resolved emission spectroscopy and quantum chemical computations. Both compounds exhibit spectral relaxation characteristics similar to those seen in FR0, indicating that hydrogen bonding interactions between the chromophore and solvent protons play a significant role in determining the relaxation pathways available to three excited electronic states.
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Affiliation(s)
- Briana A Capistran
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Stephen H Yuwono
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Mehdi Moemeni
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Soham Maity
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Aria Vahdani
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Babak Borhan
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - James E Jackson
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Piotr Piecuch
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States.,Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
| | - Marcos Dantus
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States.,Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
| | - G J Blanchard
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
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11
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Capistran BA, Yuwono SH, Moemeni M, Maity S, Vahdani A, Borhan B, Jackson JE, Piecuch P, Dantus M, Blanchard GJ. Excited-State Dynamics of a Substituted Fluorene Derivative. The Central Role of Hydrogen Bonding Interactions with the Solvent. J Phys Chem B 2021; 125:12242-12253. [PMID: 34726920 DOI: 10.1021/acs.jpcb.1c06474] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Substituted fluorene structures have demonstrated unusual photochemical properties. Previous reports on the substituted fluorene Schiff base FR0-SB demonstrated super photobase behavior with a ΔpKb of ∼14 upon photoexcitation. In an effort to understand the basis for this unusual behavior, we have examined the electronic structure and relaxation dynamics of the structural precursor of FR0-SB, the aldehyde FR0, in protic and aprotic solvents using time-resolved fluorescence spectroscopy and quantum chemical calculations. The calculations show three excited singlet states in relatively close energetic proximity. The spectroscopic data are consistent with relaxation dynamics from these electronic states that depend on the presence and concentration of solvent hydroxyl functionality. These results underscore the central role of solvent hydrogen bonding to the FR0 aldehyde oxygen in mediating the relaxation dynamics within this molecule.
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Affiliation(s)
- Briana A Capistran
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Stephen H Yuwono
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Mehdi Moemeni
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Soham Maity
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Aria Vahdani
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Babak Borhan
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - James E Jackson
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Piotr Piecuch
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States.,Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
| | - Marcos Dantus
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States.,Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
| | - G J Blanchard
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
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12
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Burnstine‐Townley A, Mondal S, Agam Y, Nandi R, Amdursky N. Light‐Modulated Cationic and Anionic Transport across Protein Biopolymers**. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202111024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Alex Burnstine‐Townley
- Schulich Faculty of Chemistry Technion—Israel Institute of Technology Haifa 3200003 Israel
| | - Somen Mondal
- Schulich Faculty of Chemistry Technion—Israel Institute of Technology Haifa 3200003 Israel
| | - Yuval Agam
- Schulich Faculty of Chemistry Technion—Israel Institute of Technology Haifa 3200003 Israel
| | - Ramesh Nandi
- Schulich Faculty of Chemistry Technion—Israel Institute of Technology Haifa 3200003 Israel
| | - Nadav Amdursky
- Schulich Faculty of Chemistry Technion—Israel Institute of Technology Haifa 3200003 Israel
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13
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Burnstine-Townley A, Mondal S, Agam Y, Nandi R, Amdursky N. Light-Modulated Cationic and Anionic Transport across Protein Biopolymers*. Angew Chem Int Ed Engl 2021; 60:24676-24685. [PMID: 34492153 DOI: 10.1002/anie.202111024] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Indexed: 12/13/2022]
Abstract
Light is a convenient source of energy and the heart of light-harvesting natural systems and devices. Here, we show light-modulation of both the chemical nature and ionic charge carrier concentration within a protein-based biopolymer that was covalently functionalized with photoacids or photobases. We explore the capability of the biopolymer-tethered photoacids and photobases to undergo excited-state proton transfer and capture, respectively. Electrical measurements show that both the photoacid- and photobase-functionalized biopolymers exhibit an impressive light-modulated increase in ionic conductivity. Whereas cationic protons are the charge carriers for the photoacid-functionalized biopolymer, water-derived anionic hydroxides are the suggested charge carriers for the photobase-functionalized biopolymer. Our work introduces a versatile toolbox to photomodulate both protons and hydroxides as charge carriers in polymers, which can be of interest for a variety of applications.
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Affiliation(s)
- Alex Burnstine-Townley
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa, 3200003, Israel
| | - Somen Mondal
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa, 3200003, Israel
| | - Yuval Agam
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa, 3200003, Israel
| | - Ramesh Nandi
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa, 3200003, Israel
| | - Nadav Amdursky
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa, 3200003, Israel
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14
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Codescu MA, Weiß M, Brehm M, Kornilov O, Sebastiani D, Nibbering ETJ. Switching between Proton Vacancy and Excess Proton Transfer Pathways in the Reaction between 7-Hydroxyquinoline and Formate. J Phys Chem A 2021; 125:1845-1859. [PMID: 33651619 PMCID: PMC7957860 DOI: 10.1021/acs.jpca.0c10191] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Bifunctional or amphoteric
photoacids simultaneously present donor
(acidic) and acceptor (basic) properties making them useful tools
to analyze proton transfer reactions. In protic solvents, the proton
exchange between the acid and the base is controlled by the acidity
or basicity strength and typically occurs on two different pathways
known as protolysis and hydrolysis. We report here how the addition
of a formate base will alter the relative importance of the possible
reaction pathways of the bifunctional photoacid 7-hydroxyquinoline
(7HQ), which has been recently understood to predominantly involve
a hydroxide/methoxide transport mechanism between the basic proton-accepting
quinoline nitrogen site toward the proton-donating OH group with a
time constant of 360 ps in deuterated methanol (CD3OD).
We follow the reaction dynamics by probing the IR-active marker modes
of the different charged forms of photoexcited 7HQ, and of formic
acid (HCOOD) in CD3OD solution. A comparison of the transient
IR spectra as a function of formate concentration, and classical molecular
dynamics simulations enables us to identify distinct contributions
of “tight” (meaning “contact”) and “loose”
(i.e., “solvent-separated”) 7HQ–formate reaction
pairs in our data. Our results suggest that depending on the orientation
of the OH group with respect to the quinoline aromatic ring system,
the presence of the formate molecule in a proton relay pathway facilitates
a net proton transfer from the proton-donating OH group of 7HQ-N*
via the methanol/formate bridge toward the quinoline N site.
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Affiliation(s)
- Marius-Andrei Codescu
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max Born Strasse 2A, 12489 Berlin, Germany
| | - Moritz Weiß
- Institut für Chemie, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle Saale, Germany
| | - Martin Brehm
- Institut für Chemie, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle Saale, Germany
| | - Oleg Kornilov
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max Born Strasse 2A, 12489 Berlin, Germany
| | - Daniel Sebastiani
- Institut für Chemie, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle Saale, Germany
| | - Erik T J Nibbering
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max Born Strasse 2A, 12489 Berlin, Germany
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15
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Alamudun SF, Tanovitz K, Espinosa L, Fajardo A, Galvan J, Petit AS. Structure-Photochemical Function Relationships in the Photobasicity of Aromatic Heterocycles Containing Multiple Ring Nitrogen Atoms. J Phys Chem A 2021; 125:13-24. [PMID: 33373234 DOI: 10.1021/acs.jpca.0c07013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Photobases are compounds that become more basic when promoted to an excited electronic state. Previous experimental and computational studies have demonstrated that several quinoline and quinoline-derived compounds are strong photobases (pKa* > 14). Moreover, the strength of photobasicity was shown to depend strongly on the identity and position of the substituent group(s), with the strongest photobases having multiple electron-donating substituents on a fused benzene ring as opposed to the ring containing the photobasic nitrogen atom. These electron-donating substituents build up electron density on one side of the molecule that shifts onto the nitrogen-containing ring in the electronic transition. This shift in electron density produces an increase in negative charge on the ring nitrogen atom responsible for the photobasicity. In this paper, we expand on our previous investigation to study the effect of an additional ring nitrogen atom on photobasicity in aromatic heterocycles. In particular, we consider how the thermodynamic driving force for excited-state protonation can be tuned by changing the relative placement of the ring nitrogen atoms and varying the position and number of electron-donating substituents. In the set of 112 molecules screened, we identified 42 strong photobases with generally comparable pKa* but lower vertical excitation energies than the quinoline derivatives with only a single ring nitrogen atom. We additionally explored photobasicity in substituted azaindole and carboline derivatives, identifying 76 strongly photobasic compounds with pKa* as large as 22.6 out of the 155 compounds that we considered. Overall, this work provides new insights into the design principles necessary to develop next-generation photocatalysts that employ photobasicity.
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Affiliation(s)
- Sophya F Alamudun
- Department of Chemistry and Biochemistry, California State University-Fullerton, Fullerton, California 92834-6866, United States
| | - Kyle Tanovitz
- Department of Chemistry and Biochemistry, California State University-Fullerton, Fullerton, California 92834-6866, United States
| | - Lanette Espinosa
- Department of Chemistry and Biochemistry, California State University-Fullerton, Fullerton, California 92834-6866, United States
| | - April Fajardo
- Department of Chemistry and Biochemistry, California State University-Fullerton, Fullerton, California 92834-6866, United States
| | - John Galvan
- Department of Chemistry and Biochemistry, California State University-Fullerton, Fullerton, California 92834-6866, United States
| | - Andrew S Petit
- Department of Chemistry and Biochemistry, California State University-Fullerton, Fullerton, California 92834-6866, United States
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16
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Sittig M, Tom JC, Elter JK, Schacher FH, Dietzek B. Quinoline Photobasicity: Investigation within Water-Soluble Light-Responsive Copolymers. Chemistry 2021; 27:1072-1079. [PMID: 32986286 PMCID: PMC7839697 DOI: 10.1002/chem.202003815] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 09/14/2020] [Indexed: 01/13/2023]
Abstract
Quinoline photobases exhibit a distinctly higher pKa in their electronically excited state than in the ground state, thereby enabling light-controlled proton transfer reactions, for example, in molecular catalysis. The absorption of UV light translates to a pKa jump of approximately 10 units, as established for small-molecule photobases. This contribution presents the first synthesis of quinoline-based polymeric photobases prepared by reversible addition-fragmentation chain-transfer (RAFT) polymerization. The integration of quinolines as photobase chromophores within copolymers offers new possibilities for light-triggered proton transfer in nanostructured materials, that is, in nanoparticles, at surfaces, membranes and interfaces. To exploit the light-triggered reactivity of photobases within such materials, we first investigated how the ground- and excited-state properties of the quinoline unit changes upon polymer integration. To address this matter, we combined absorption and emission spectroscopy with time-resolved transient-absorption studies to reveal photoinduced proton-transfer dynamics in various solvents. The results yield important insights into the thermodynamic and kinetic properties of these polymeric quinoline photobases.
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Affiliation(s)
- Maria Sittig
- Department of Functional InterfacesLeibniz Institute of Photonic Technology JenaAlbert-Einstein-Strasse 907745JenaGermany
- Institute of Physical Chemistry and Abbe Center of PhotonicsFriedrich-Schiller-University JenaHelmholtzweg 407743JenaGermany
- Jena Center for Soft Matter (JCSM)Friedrich Schiller University JenaPhilosophenweg 707743JenaGermany
| | - Jessica C. Tom
- Institute of Organic Chemistry and Macromolecular Chemistry (IOMC)Friedrich Schiller University JenaHumboldtstrasse 1007743JenaGermany
- Jena Center for Soft Matter (JCSM)Friedrich Schiller University JenaPhilosophenweg 707743JenaGermany
| | - Johanna K. Elter
- Institute of Organic Chemistry and Macromolecular Chemistry (IOMC)Friedrich Schiller University JenaHumboldtstrasse 1007743JenaGermany
- Jena Center for Soft Matter (JCSM)Friedrich Schiller University JenaPhilosophenweg 707743JenaGermany
| | - Felix H. Schacher
- Institute of Organic Chemistry and Macromolecular Chemistry (IOMC)Friedrich Schiller University JenaHumboldtstrasse 1007743JenaGermany
- Jena Center for Soft Matter (JCSM)Friedrich Schiller University JenaPhilosophenweg 707743JenaGermany
| | - Benjamin Dietzek
- Department of Functional InterfacesLeibniz Institute of Photonic Technology JenaAlbert-Einstein-Strasse 907745JenaGermany
- Institute of Physical Chemistry and Abbe Center of PhotonicsFriedrich-Schiller-University JenaHelmholtzweg 407743JenaGermany
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17
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Lahiri J, Moemeni M, Kline J, Magoulas I, Yuwono SH, Laboe M, Shen J, Borhan B, Piecuch P, Jackson JE, Blanchard GJ, Dantus M. Isoenergetic two-photon excitation enhances solvent-to-solute excited-state proton transfer. J Chem Phys 2020; 153:224301. [PMID: 33317305 PMCID: PMC7725536 DOI: 10.1063/5.0020282] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 11/15/2020] [Indexed: 01/05/2023] Open
Abstract
Two-photon excitation (TPE) is an attractive means for controlling chemistry in both space and time. Since isoenergetic one- and two-photon excitations (OPE and TPE) in non-centrosymmetric molecules are allowed to reach the same excited state, it is usually assumed that they produce similar excited-state reactivity. We compare the solvent-to-solute excited-state proton transfer of the super photobase FR0-SB following isoenergetic OPE and TPE. We find up to 62% increased reactivity following TPE compared to OPE. From steady-state spectroscopy, we rule out the involvement of different excited states and find that OPE and TPE spectra are identical in non-polar solvents but not in polar ones. We propose that differences in the matrix elements that contribute to the two-photon absorption cross sections lead to the observed enhanced isoenergetic reactivity, consistent with the predictions of our high-level coupled-cluster-based computational protocol. We find that polar solvent configurations favor greater dipole moment change between ground and excited states, which enters the probability for TPE as the absolute value squared. This, in turn, causes a difference in the Franck-Condon region reached via TPE compared to OPE. We conclude that a new method has been found for controlling chemical reactivity via the matrix elements that affect two-photon cross sections, which may be of great utility for spatial and temporal precision chemistry.
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Affiliation(s)
- Jurick Lahiri
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | - Mehdi Moemeni
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | - Jessica Kline
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | - Ilias Magoulas
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | - Stephen H. Yuwono
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | - Maryann Laboe
- Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, Michigan 48824, USA
| | - Jun Shen
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | - Babak Borhan
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | - Piotr Piecuch
- Authors to whom correspondence should be addressed: , Tel.: +1-517-353-0501; , Tel.: +1-517-353-1151; , Tel.: +1-517-353-0504; , Tel.: +1-517-353-1105; and , Tel.: +1-517-353-1191
| | - James E. Jackson
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | - G. J. Blanchard
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | - Marcos Dantus
- Authors to whom correspondence should be addressed: , Tel.: +1-517-353-0501; , Tel.: +1-517-353-1151; , Tel.: +1-517-353-0504; , Tel.: +1-517-353-1105; and , Tel.: +1-517-353-1191
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18
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Photobase effect for just-in-time delivery in photocatalytic hydrogen generation. Nat Commun 2020; 11:5179. [PMID: 33056986 PMCID: PMC7560858 DOI: 10.1038/s41467-020-18583-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 08/17/2020] [Indexed: 11/09/2022] Open
Abstract
Carbon dots (CDs) are a promising nanomaterial for photocatalytic applications. However, the mechanism of the photocatalytic processes remains the subject of a debate due to the complex internal structure of the CDs, comprising crystalline and molecular units embedded in an amorphous matrix, rendering the analysis of the charge and energy transfer pathways between the constituent parts very challenging. Here we propose that the photobasic effect, that is the abstraction of a proton from water upon excitation by light, facilitates the photoexcited electron transfer to the proton. We show that the controlled inclusion in CDs of a model photobase, acridine, resembling the molecular moieties found in photocatalytically active CDs, strongly increases hydrogen generation. Ultrafast spectroscopy measurements reveal proton transfer within 30 ps of the excitation. This way, we use a model system to show that the photobasic effect may be contributing to the photocatalytic H2 generation of carbon nanomaterials and suggest that it may be tuned to achieve further improvements. The study demonstrates the critical role of the understanding the dynamics of the CDs in the design of next generation photocatalysts.
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19
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Lahiri J, Moemeni M, Magoulas I, Yuwono SH, Kline J, Borhan B, Piecuch P, Jackson JE, Blanchard GJ, Dantus M. Steric effects in light-induced solvent proton abstraction. Phys Chem Chem Phys 2020; 22:19613-19622. [PMID: 32936138 DOI: 10.1039/d0cp03037f] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The significance of solvent structural factors in the excited-state proton transfer (ESPT) reactions of Schiff bases with alcohols is reported here. We use the super photobase FR0-SB and a series of primary, secondary, and tertiary alcohol solvents to illustrate the steric issues associated with solvent to photobase proton transfer. Steady-state and time-resolved fluorescence data show that ESPT occurs readily for primary alcohols, with a probability proportional to the relative -OH concentration. For secondary alcohols, ESPT is greatly diminished, consistent with the barrier heights obtained using quantum chemistry calculations. ESPT is not observed in the tertiary alcohol. We explain ESPT using a model involving an intermediate hydrogen-bonded complex where the proton is "shared" by the Schiff base and the alcohol. The formation of this complex depends on the ability of the alcohol solvent to achieve spatial proximity to and alignment with the FR0-SB* imine lone pair stabilized by the solvent environment.
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Affiliation(s)
- Jurick Lahiri
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA.
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20
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Empel C, Jana S, Pei C, Nguyen TV, Koenigs RM. Photochemical O–H Functionalization of Aryldiazoacetates with Phenols via Proton Transfer. Org Lett 2020; 22:7225-7229. [DOI: 10.1021/acs.orglett.0c02564] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Claire Empel
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany
- School of Chemistry, University of New South Waley, Sydney 2052, Australia
| | - Sripati Jana
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany
| | - Chao Pei
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany
| | - Thanh Vinh Nguyen
- School of Chemistry, University of New South Waley, Sydney 2052, Australia
| | - Rene M. Koenigs
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany
- School of Chemistry, University of New South Waley, Sydney 2052, Australia
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21
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Alamudun SF, Tanovitz K, Fajardo A, Johnson K, Pham A, Jamshidi Araghi T, Petit AS. Structure-Photochemical Function Relationships in Nitrogen-Containing Heterocyclic Aromatic Photobases Derived from Quinoline. J Phys Chem A 2020; 124:2537-2546. [PMID: 32196344 DOI: 10.1021/acs.jpca.9b11375] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photobases are compounds that become strong bases after electronic excitation. Recent experimental studies have highlighted the photobasicity of the 5-R quinoline compounds, demonstrating a strong substituent dependence to the pKa*. In this paper, we describe our systematic study of how the thermodynamic driving force for photobasicity is tuned through substituents in four families of nitrogen-containing heterocyclic aromatics. We show that substituent position and identity both significantly impact the pKa*. We demonstrate that the substituent effects are additive and identify many disubstituted compounds with substantially greater photobasicity than the most photobasic 5-R quinoline compound identified previously. We show that the addition of a second fused benzene ring to quinoline, along with two electron-donating substituents, lowers the S0 → SPBS vertical excitation energy into the visible region while still maintaining a pKa* > 14. Overall, the structure-function relationships developed in this study provide new insights to guide the development of new photocatalysts that employ photobasicity.
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Affiliation(s)
- Sophya F Alamudun
- Department of Chemistry and Biochemistry, California State University, Fullerton, Fullerton, California 92834-6866, United States
| | - Kyle Tanovitz
- Department of Chemistry and Biochemistry, California State University, Fullerton, Fullerton, California 92834-6866, United States
| | - April Fajardo
- Department of Chemistry and Biochemistry, California State University, Fullerton, Fullerton, California 92834-6866, United States
| | - Kaitlind Johnson
- Department of Chemistry and Biochemistry, California State University, Fullerton, Fullerton, California 92834-6866, United States
| | - Andy Pham
- Department of Chemistry and Biochemistry, California State University, Fullerton, Fullerton, California 92834-6866, United States
| | - Tina Jamshidi Araghi
- Department of Chemistry and Biochemistry, California State University, Fullerton, Fullerton, California 92834-6866, United States
| | - Andrew S Petit
- Department of Chemistry and Biochemistry, California State University, Fullerton, Fullerton, California 92834-6866, United States
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22
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Photoinduzierte Protonentransferreaktionen für milde O‐H‐Funktionalisierungsreaktionen unreaktiver Alkohole. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201915161] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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23
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Jana S, Yang Z, Li F, Empel C, Ho J, Koenigs RM. Photoinduced Proton-Transfer Reactions for Mild O-H Functionalization of Unreactive Alcohols. Angew Chem Int Ed Engl 2020; 59:5562-5566. [PMID: 31880397 PMCID: PMC7154649 DOI: 10.1002/anie.201915161] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 12/26/2019] [Indexed: 12/16/2022]
Abstract
Hexafluoroisopropanol is typically considered as an unreactive solvent and not as a reagent in organic synthesis. Herein, we report on a mild and efficient photochemical reaction of aryl diazoacetates with hexafluoroisopropanol that enables, under stoichiometric reaction conditions, the synthesis of fluorinated ethers in excellent yield. Mechanistic studies indicate there is a preorganization of hexafluoroisopropanol and the diazoalkane acts as an unreactive hydrogen-bonding complex. Only after photoexcitation does this complex undergo a protonation-substitution reaction to the reaction product. Investigations on the applicability of this photochemical transformation show that a broad variety of acidic alcohols can be subjected to this transformation and thus demonstrate the feasibility of this concept for O-H functionalization reactions (54 examples, up to 98 % yield).
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Affiliation(s)
- Sripati Jana
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Zhen Yang
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Fang Li
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Claire Empel
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Junming Ho
- School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Rene M Koenigs
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
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24
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Hunt JR, Dawlaty JM. Kinetic Evidence for the Necessity of Two Proton Donor Molecules for Successful Excited State Proton Transfer by a Photobase. J Phys Chem A 2019; 123:10372-10380. [PMID: 31710812 DOI: 10.1021/acs.jpca.9b08970] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Photobases are molecules that convert light to proton transfer drive and therefore have potential applications in many areas of chemistry. Previously, we studied the photobasicity of quinolines and explored their applications. While it is possible to tether a photobase near a target proton donor, for the sake of versatility it is desirable to explore their capability to deprotonate molecules dispersed in a solution. Previous evidence suggested that in this scenario at least two proton donors were necessary for successful excited state proton transfer: one to donate a proton and the second to stabilize the photogenerated donor anion. Here we report kinetic evidence from transient absorption (TA) and time-correlated single photon counting (TCSPC) in support of this hypothesis. We used 5-methoxyquinoline as the photobase and 2,2,2-trifluoroethanol (TFE), a low pKa alcohol, as the proton donor. A constant concentration of the photobase was used for a range of proton-donor dilutions spanning several orders of magnitude in an aprotic background solvent. Absorption spectra confirm that over most of the studied range the majority of the photobase population is hydrogen bonded to at least one donor. Short-pulse TA was used to measure the faster (2-500 ps) dynamics, while TSCPC was used to measure the slower (>500 ps) dynamics. The measured proton transfer time constants varied as a function of donor concentration over a wide range. A log-log plot of the proton transfer rate constant as a function of proton-donor concentration shows two regimes: nondiffusive at high donor concentrations where multiple proton donors are near the photobase and diffusive at low donor concentrations where proton donors are more dilute. The nondiffusive regime has a slope of approximately one, suggesting that the proton transfer process is dependent on one donor molecule in addition to the donor molecule already hydrogen bonded with the photobase. The diffusive regime reasonably follows diffusion kinetics. We propose a model for how the second proton-donor molecule may interact with the photogenerated alkoxide to stabilize it. This work highlights the importance of inducing irreversible changes, in this case solvation of the alkoxide, after proton transfer. Understanding of such details is likely to be important in applications of photobases.
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Affiliation(s)
- Jonathan Ryan Hunt
- Department of Chemistry , University of Southern California , 920 Bloom Walk SSC 702 , Los Angeles , California 90089-0482 , United States
| | - Jahan M Dawlaty
- Department of Chemistry , University of Southern California , 920 Bloom Walk SSC 702 , Los Angeles , California 90089-0482 , United States
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25
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Lahiri J, Moemeni M, Kline J, Borhan B, Magoulas I, Yuwono SH, Piecuch P, Jackson JE, Dantus M, Blanchard GJ. Proton Abstraction Mediates Interactions between the Super Photobase FR0-SB and Surrounding Alcohol Solvent. J Phys Chem B 2019; 123:8448-8456. [PMID: 31532676 DOI: 10.1021/acs.jpcb.9b06580] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report on the motional and proton transfer dynamics of the super photobase FR0-SB in the series of normal alcohols C1 (methanol) through C8 (n-octanol) and ethylene glycol. Steady-state and time-resolved fluorescence data reveal that the proton abstraction dynamics of excited FR0-SB depend on the identity of the solvent and that the transfer of the proton from solvent to FR0-SB*, forming FR0-HSB+*, fundamentally alters the nature of interactions between the excited molecule and its surroundings. In its unprotonated state, solvent interactions with FR0-SB* are consistent with slip limit behavior, and in its protonated form, intermolecular interactions are consistent with a much stronger interaction of FR0-HSB+* with the deprotonated solvent RO-. We understand the excited-state population dynamics in the context of a kinetic model involving a transition state wherein FR0-HSB+* is still bound to the negatively charged alkoxide, prior to solvation of the two charged species. Data acquired in ethylene glycol confirm the hypothesis that the rotational diffusion dynamics of FR0-SB* are largely mediated by solvent viscosity while proton transfer dynamics are mediated by the lifetime of the transition state. Taken collectively, our results demonstrate that FR0-SB* extracts solvent protons efficiently and in a predictable manner, consistent with a ca. 3-fold increase in dipole moment upon photoexcitation as determined by ab initio calculations based on the equation-of-motion coupled-cluster theory.
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26
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Pozharskii AF, Ozeryanskii VA, Mikshiev VY, Chernyshev AV, Metelitsa AV, Antonov AS. Proton-induced fluorescence in modified quino[7,8-h]quinolines: dual sensing for protons and π-donors. Org Biomol Chem 2019; 17:8221-8233. [PMID: 31436774 DOI: 10.1039/c9ob01391a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The synthesis, as well as spectral, structural and photoluminescence properties of dipyrido[3,2-e:2',3'-h]acenaphthene 5 and quinazolino[7,8-h]quinazolines 6 as representatives of the bidentate -N[double bond, length as m-dash]/-N[double bond, length as m-dash] superbases, are reported. These nitrogen bases being more rigid (5) or π-extended (6) analogs of optically-mute quino[7,8-h]quinoline are both active in terms of fluorescence with quantum yields up to φ = 0.71-0.77. At the same time, their luminescence behavior is opposite to that of peri-NMe2/NMe2 naphthalene proton sponges and their hybrid NMe2/-N[double bond, length as m-dash] analogs. Although 5 and 6 exhibit visible region emission upon protonation, for the hybrid systems the fluorescence is manifested only for bases. The most remarkable observation is that the fluorescence of compound 5 can be switched on not only by means of organic or inorganic acids, but also through the formation of chelate complexes with such weak H-donors as water and primary alcohols. It was disclosed that water is present in the complex as a cluster comprising 8 interconnected H2O molecules. Overall, the studied compounds demonstrate a previously unobserved type of dual mode optical response, H-sensing (emission enhancement in 5 and 6 on protonation) and π-sensing (emission quenching in 5H+ and 6H+ on coordination with π-donors). This work seems to be an important contribution to areas such as chemosensorics, the creation of new ligands, hydrogen transfer and some other phenomena representing different types of supramolecular interactions.
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Affiliation(s)
- Alexander F Pozharskii
- Department of Organic Chemistry, Southern Federal University, Zorge str. 7, 344090 Rostov-on-Don, Russian Federation.
| | - Valery A Ozeryanskii
- Department of Organic Chemistry, Southern Federal University, Zorge str. 7, 344090 Rostov-on-Don, Russian Federation.
| | - Vladimir Y Mikshiev
- Department of Organic Chemistry, Southern Federal University, Zorge str. 7, 344090 Rostov-on-Don, Russian Federation.
| | - Anatoly V Chernyshev
- Institute of Physical and Organic Chemistry, Southern Federal University, Stachki Ave. 194/2, 344090 Rostov-on-Don, Russian Federation
| | - Anatoly V Metelitsa
- Institute of Physical and Organic Chemistry, Southern Federal University, Stachki Ave. 194/2, 344090 Rostov-on-Don, Russian Federation
| | - Alexander S Antonov
- Department of Organic Chemistry, Southern Federal University, Zorge str. 7, 344090 Rostov-on-Don, Russian Federation.
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Goldsmith ZK, Soudackov AV, Hammes-Schiffer S. Theoretical analysis of the inverted region in photoinduced proton-coupled electron transfer. Faraday Discuss 2019; 216:363-378. [PMID: 31017599 PMCID: PMC6620152 DOI: 10.1039/c8fd00240a] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Photoinduced proton-coupled electron transfer (PCET) plays a key role in a wide range of energy conversion processes, and understanding how to design systems to control the PCET rate constant is a significant challenge. Herein a theoretical formulation of PCET is utilized to identify the conditions under which photoinduced PCET may exhibit inverted region behavior. In the inverted region, the rate constant decreases as the driving force increases even though the reaction becomes more thermodynamically favorable. Photoinduced PCET will exhibit inverted region behavior when the following criteria are satisfied: (1) the overlap integrals corresponding to the ground reactant and the excited product proton vibrational wavefunctions become negligible for a low enough product vibronic state and (2) the reaction free energies associated with the lower excited product proton vibrational wavefunctions contributing significantly to the rate constant are negative with magnitudes greater than the reorganization energy. These criteria are typically not satisfied by harmonic or Morse potentials but are satisfied by more realistic asymmetric double well potentials because the proton vibrational states above the barrier correspond to more delocalized proton vibrational wavefunctions with nodal structures leading to destructive interference effects. Thus, this theoretical analysis predicts that inverted region behavior could be observed for systems with asymmetric double well potentials characteristic of hydrogen-bonded systems and that the hydrogen/deuterium kinetic isotope effect will approach unity and could even become inverse in this region due to the oscillatory nature of the highly excited vibrational wavefunctions. These insights may help guide the design of more effective energy conversion devices.
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Affiliation(s)
- Zachary K Goldsmith
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA.
| | - Alexander V Soudackov
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA.
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA.
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Roy S, Ardo S, Furche F. 5-Methoxyquinoline Photobasicity Is Mediated by Water Oxidation. J Phys Chem A 2019; 123:6645-6651. [DOI: 10.1021/acs.jpca.9b05341] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Saswata Roy
- Department of Chemistry, University of California, Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025, United States
| | - Shane Ardo
- Department of Chemistry, University of California, Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025, United States
| | - Filipp Furche
- Department of Chemistry, University of California, Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025, United States
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29
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Demianets I, Hunt JR, Dawlaty JM, Williams TJ. Optical pKa Control in a Bifunctional Iridium Complex. Organometallics 2019. [DOI: 10.1021/acs.organomet.8b00778] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ivan Demianets
- Donald P. and Katherine B. Loker Hydrocarbon Institute and Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661, United States
| | - Jonathan R. Hunt
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Jahan M. Dawlaty
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Travis J. Williams
- Donald P. and Katherine B. Loker Hydrocarbon Institute and Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661, United States
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30
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Hunt JR, Tseng C, Dawlaty JM. Donor-acceptor preassociation, excited state solvation threshold, and optical energy cost as challenges in chemical applications of photobases. Faraday Discuss 2019; 216:252-268. [PMID: 31025987 DOI: 10.1039/c8fd00215k] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Photobases are molecules with increased pKa in the excited state that can serve to transduce light energy into proton removal capability. They can be used to control chemical reactions using light, such as removing protons from a catalytic site in reactions that are rate-limited by proton transfer. We identify and explore several major challenges toward their practical applications. Two important challenges are the need for pre-association (or ground state hydrogen bonding) between the proton donor and the photobase, and the need for excited state solvation of the photogenerated products. We investigate these two challenges with the photobase 5-methoxyquinoline as the proton acceptor and a low-pKa alcohol, 2,2,2-trifluoroethanol, as the proton donor. We vary the concentration of the donor in a background non-hydrogen-bonding solvent. Using absorption spectroscopy, we have identified that the donor-acceptor concentration ratio must exceed 100 : 1 to achieve appreciable ground state hydrogen bonding. Interestingly, emission spectroscopy reveals that the onset of ground state hydrogen bonding does not guarantee successful excited state proton transfer. It takes an additional order of magnitude increase in donor-acceptor ratio to achieve that goal, revealing that it is necessary to have excess donor molecules to reach the solvation threshold for the photogenerated products. The next challenge is reducing the large ground-excited state energy gap, which often requires UV photons to drive proton transfer. We show experimental and computational data comparing the photobasicity and optical energy gap for a few N-aromatic heterocyclic photobases. In general, we find that reducing the energy gap by increasing the conjugation size necessarily reduces photobasicity, while adding substituents of varying electron-withdrawing strength allows some fine-tuning of this effect. The combination of these two factors provide a preliminary design space for creating new photobasic molecules.
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Affiliation(s)
| | - Cindy Tseng
- University of Southern California, 920 Bloom Walk, Los Angeles, USA.
| | - Jahan M Dawlaty
- University of Southern California, 920 Bloom Walk, Los Angeles, USA.
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