1
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Antalicz B, Bakker HJ. Temperature Effects and Activation Barriers in Aqueous Proton-Uptake Reactions. JACS AU 2024; 4:2995-3006. [PMID: 39211613 PMCID: PMC11350741 DOI: 10.1021/jacsau.4c00326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Revised: 07/10/2024] [Accepted: 07/11/2024] [Indexed: 09/04/2024]
Abstract
Aqueous proton transfer reactions are fundamental in biology and chemistry, yet kinetics and mechanisms of strong base-weak acid reactions are not well understood. In this work, we present a temperature-dependent reaction kinetic study of the water-soluble photobase actinoquinol, in the presence and absence of succinimide, a weak acid reaction partner. We study the temperature dependence of the reaction and connect the observed dynamics to the reaction's thermodynamics. We find that actinoquinol reacts in associated complexes with water/succinimide, creating an intermediate complex that can undergo either dissociation to create products, or reverse proton transfer within the complex to recreate the initial reactants. We find that the intermediates' formation is energetically unfavorable with both reaction partners, which impacts the net reaction rates. We also find that the net reaction rate is additionally strongly influenced by the competition between the dissociation of the intermediates and their reverse reaction.
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Affiliation(s)
- Balázs Antalicz
- 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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2
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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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3
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Gilad Barzilay Y, Yucknovsky A, Amdursky N. Light-Triggered Reversible Change in the Electronic Structure of MoO 3 Nanosheets via an Excited-State Proton Transfer Mechanism. NANO LETTERS 2024; 24:1936-1943. [PMID: 38289664 PMCID: PMC10870760 DOI: 10.1021/acs.nanolett.3c04209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 01/25/2024] [Accepted: 01/26/2024] [Indexed: 02/15/2024]
Abstract
Light is an attractive source of energy for regulating stimulus-responsive chemical systems. Here, we use light as a gating source to control the redox state, the localized surface plasmonic resonance (LSPR) peak, and the structure of molybdenum oxide (MoO3) nanosheets, which are important for various applications. However, the light excitation is not that of the MoO3 nanosheets but rather that of pyranine (HPTS) photoacids, which in turn undergo an excited-state proton transfer (ESPT) process. We show that the ESPT process from HPTS to the nanosheets and the intercalation of protons within the MoO3 nanosheets trigger the reduction of the nanosheets and the broadening of the LSPR peak, a process that is reversible, meaning that in the absence of light, the LSPR peak diminishes and the nanosheets return to their oxidized form. We further show that this reversible process is accompanied by a change in the nanosheet size and morphology.
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Affiliation(s)
- Yuval Gilad Barzilay
- Schulich Faculty of Chemistry, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Anna Yucknovsky
- 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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4
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Ghosh G, Roy DS, Ghosh R, Mukherjee D, Biswas S, Roy L, Chattopadhyay A, Das R, Pal SK. Excited-State Dynamics of a Photoacid: A Potential Probe for Recognizing Transition from Lamellar to Nonlamellar Inverted Structures of Liposome based Nanocarriers. Chemphyschem 2024; 25:e202300635. [PMID: 37936318 DOI: 10.1002/cphc.202300635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 11/04/2023] [Accepted: 11/07/2023] [Indexed: 11/09/2023]
Abstract
Liposomes of a cationic lipid dioctadecyldimethylammonium bromide (DODAB) are efficient nanocarriers of nucleic acids. Incorporation of a neutral lipid monoolein (MO) in excess (xMO >0.5) changes the lamellar organization of DODAB liposomes into non-lamellar inverted structures of DODAB/MO liposomes facilitating nucleic acid delivery to cells. Photoexcitation of 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS), a photoacid, initiates an excited state proton transfer (ESPT) reaction in its protonated form (ROH*) generating the deprotonated anionic form (RO- *). The fluorescence intensity ratio (IROH* /IRO-* ) of these two forms is governed by the ESPT dynamics, and increases with increasing MO content (xMO ) in the cationic liposomes of DODAB. Transition from lamellar organization of DODAB liposomes into non-lamellar inverted structures of DODAB/MO liposomes, due to incorporation of MO (xMO ~0.7), is manifested by a significant increase of ESPT time (τPT ) and the time constant of wobbling motion (τW ) of HPTS. Thus, the lamellar organizations of DODAB or DODAB-rich (xMO 0.2) liposomes and the non-lamellar organizations of MO-rich (xMO ~0.7) liposomes are recognized by significantly different excited state dynamics of the photoacid.
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Affiliation(s)
- Gourab Ghosh
- Dept. of Chemistry, West Bengal State University, Barasat, Kolkata, 700126, India
| | - Debanjana Singha Roy
- Dept. of Chemistry, West Bengal State University, Barasat, Kolkata, 700126, India
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata, India
| | - Ria Ghosh
- Technical Research Centre, S. N. Bose National Centre for Basic Sciences, Kolkata, India
| | - Dipanjan Mukherjee
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata, India
| | - Suman Biswas
- Dept. of Chemistry, West Bengal State University, Barasat, Kolkata, 700126, India
| | - Lopamudra Roy
- Department of Applied Optics and Photonics, University of Calcutta, 92, Acharya Prafulla Chandra Rd, Kolkata, 700009, India
| | - Arpita Chattopadhyay
- Department of Basic science and humanities, Techno International New Town, Rajarhat, Kolkata, 700156
| | - Ranjan Das
- Dept. of Chemistry, West Bengal State University, Barasat, Kolkata, 700126, India
| | - Samir Kumar Pal
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata, India
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5
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Yucknovsky A, Rich BB, Gutkin S, Ramanthrikkovil Variyam A, Shabat D, Pokroy B, Amdursky N. Application of Super Photoacids in Controlling Dynamic Processes: Light-Triggering the Self-Propulsion of Oil Droplets. J Phys Chem B 2022; 126:6331-6337. [PMID: 35959566 DOI: 10.1021/acs.jpcb.2c04020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The dynamic control of pH-responsive systems is at the heart of many natural and artificial processes. Here, we use photoacids, molecules that dissociate only in their excited state and transfer their proton to nearby proton acceptors, for the dynamic control of processes. A problem arises when there is a need to protonate highly acidic acceptors. We solve this problem using super photoacids that have an excited-state pKa of -8, thus enabling them to protonate very weak proton acceptors. The process that we target is the light-triggered self-propulsion of droplets, initiated by an excited-state proton transfer (ESPT) from a super photoacid donor to a surfactant acceptor situated on the surface of the droplet with a pKa of ∼0. We first confirm using steady-state and time-resolved spectroscopy that a super photoacid can undergo ESPT to the acidic surfactant, whereas a "regular" photoacid cannot. Next, we show self-propulsion of the droplet upon irradiating the solvated super photoacid. We further confirm the protonation of the surfactant on the surface of the droplet using transient surface tension measurements. Our system is the first example of the application of super photoacids to control dynamic processes and opens new possibilities in the field of light-triggered dynamic systems.
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Affiliation(s)
- Anna Yucknovsky
- Schulich Faculty of Chemistry, Technion─Israel Institute of Technology, Haifa 3200003, Israel
| | - Benjamin B Rich
- Department of Materials Science & Engineering, Technion─Israel Institute of Technology, Haifa 3200003, Israel
| | - Sara Gutkin
- School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel Aviv 69978, Israel
| | | | - Doron Shabat
- School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Boaz Pokroy
- Department of Materials Science & Engineering, 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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6
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Sülzner N, Geissler B, Grandjean A, Jung G, Nuernberger P. Excited‐state Proton Transfer Dynamics of a Super‐Photoacid in Acetone‐Water Mixtures. CHEMPHOTOCHEM 2022. [DOI: 10.1002/cptc.202200041] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Niklas Sülzner
- Ruhr-Universitat Bochum Lehrstuhl für Theoretische Chemie GERMANY
| | - Bastian Geissler
- Universitat Regensburg Institut für Physikalische und Theoretische Chemie GERMANY
| | | | - Gregor Jung
- Universitat des Saarlandes Biophysikalische Chemie GERMANY
| | - Patrick Nuernberger
- Universitat Regensburg Institut für Physikalische und Theoretische Chemie Universitätsstraße 31 93053 Regensburg GERMANY
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7
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Kaiser C, Halbritter T, Heckel A, Wachtveitl J. Proton-Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution. Chemistry 2021; 27:9160-9173. [PMID: 33929051 PMCID: PMC8361770 DOI: 10.1002/chem.202100168] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Indexed: 01/22/2023]
Abstract
Photoacids attract increasing scientific attention, as they are valuable tools to spatiotemporally control proton-release reactions and pH values of solutions. We present the first time-resolved spectroscopic study of the excited state and proton-release dynamics of prominent merocyanine representatives. Femtosecond transient absorption measurements of a pyridine merocyanine with two distinct protonation sites revealed dissimilar proton-release mechanisms: one site acts as a photoacid generator as its pKa value is modulated in the ground state after photoisomerization, while the other functions as an excited state photoacid which releases its proton within 1.1 ps. With a pKa drop of 8.7 units to -5.5 upon excitation, the latter phenolic site is regarded a super-photoacid. The 6-nitro derivative exhibits only a phenolic site with similar, yet slightly less photoacidic characteristics and both compounds transfer their proton to methanol and ethanol. In contrast, for the related 6,8-dinitro compound an intramolecular proton transfer to the ortho-nitro group is suggested that is involved in a rapid relaxation into the ground state.
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Affiliation(s)
- Christoph Kaiser
- Institute for Physical and Theoretical ChemistryGoethe University Frankfurt/MainMax-von-Laue-Str. 760438Frankfurt/MainGermany
| | - Thomas Halbritter
- Current address: Department of Chemistry, Science InstituteUniversity of IcelandDunhaga 3Reykjavikpostcode is missingIceland
- Institute for Organic Chemistry and Chemical BiologyGoethe University Frankfurt/MainMax-von-Laue-Str. 760438Frankfurt/MainGermany
| | - Alexander Heckel
- Institute for Organic Chemistry and Chemical BiologyGoethe University Frankfurt/MainMax-von-Laue-Str. 760438Frankfurt/MainGermany
| | - Josef Wachtveitl
- Institute for Physical and Theoretical ChemistryGoethe University Frankfurt/MainMax-von-Laue-Str. 760438Frankfurt/MainGermany
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8
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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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9
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Lee C, Chung S, Song H, Rhee YM, Lee E, Joo T. Excited State Proton Transfer of Quinone Cyanine 9: Implications on the Origin of Super‐Photoacidity. CHEMPHOTOCHEM 2020. [DOI: 10.1002/cptc.202000254] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Changmin Lee
- Department of Chemistry Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
| | - Seyoung Chung
- Department of Chemistry Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
| | - Hayoung Song
- Department of Chemistry Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
| | - Young Min Rhee
- Department of Chemistry Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141 Republic of Korea
| | - Eunsung Lee
- Department of Chemistry Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
| | - Taiha Joo
- Department of Chemistry Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
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10
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Verma P, Rosspeintner A, Dereka B, Vauthey E, Kumpulainen T. Broadband fluorescence reveals mechanistic differences in excited-state proton transfer to protic and aprotic solvents. Chem Sci 2020; 11:7963-7971. [PMID: 34094165 PMCID: PMC8163259 DOI: 10.1039/d0sc03316b] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Excited-state proton transfer (ESPT) to solvent is often explained according to the two-step Eigen-Weller model including a contact ion pair (CIP*) as an intermediate, but general applicability of the model has not been thoroughly examined. Furthermore, examples of the spectral identification of CIP* are scarce. Here, we report on a detailed investigation of ESPT to protic (H2O, D2O, MeOH and EtOH) and aprotic (DMSO) solvents utilizing a broadband fluorescence technique with sub-200 fs time resolution. The time-resolved spectra are decomposed into contributions from the protonated and deprotonated species and a clear signature of CIP* is identified in DMSO and MeOH. Interestingly, the CIP* intermediate is not observable in aqueous environment although the dynamics in all solvents are multi-exponential. Global analysis based on the Eigen-Weller model is satisfactory in all solvents, but the marked mechanistic differences between aqueous and organic solvents cast doubt on the physical validity of the rate constants obtained.
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Affiliation(s)
- Pragya Verma
- Department of Physical Chemistry, University of Geneva 30 Quai Ernest Ansermet Geneva Switzerland +41 22 379 65 18 +41 22 379 36 58
| | - Arnulf Rosspeintner
- Department of Physical Chemistry, University of Geneva 30 Quai Ernest Ansermet Geneva Switzerland +41 22 379 65 18 +41 22 379 36 58
| | - Bogdan Dereka
- Department of Physical Chemistry, University of Geneva 30 Quai Ernest Ansermet Geneva Switzerland +41 22 379 65 18 +41 22 379 36 58
| | - Eric Vauthey
- Department of Physical Chemistry, University of Geneva 30 Quai Ernest Ansermet Geneva Switzerland +41 22 379 65 18 +41 22 379 36 58
| | - Tatu Kumpulainen
- Department of Physical Chemistry, University of Geneva 30 Quai Ernest Ansermet Geneva Switzerland +41 22 379 65 18 +41 22 379 36 58
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11
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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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12
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Das AK, Druzhinin SI, Ihmels H, Müller M, Schönherr H. Colorimetric and Fluorimetric DNA Detection with a Hydroxystyryl-Quinolizinium Photoacid and Its Application for Cell Imaging. Chemistry 2019; 25:12703-12707. [PMID: 31418956 PMCID: PMC6790585 DOI: 10.1002/chem.201903017] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 08/09/2019] [Indexed: 01/09/2023]
Abstract
The combination of styryl dye properties with the acidity and strong photoacidity of the 2,2'-[(1''-hydroxy-4''-methyl-(E)-2'',6''-phenylene)]-bisquinolizinium enables the detection of DNA by distinct absorption and emission color changes and the fluorimetric detection of DNA in cells with epifluorescence and confocal fluorescence microscopy.
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Affiliation(s)
- Avijit Kumar Das
- Department of Chemistry and Biology, and Center of Micro- and Nanochemistry and Engineering (Cμ)University of SiegenAdolf-Reichwein-Str. 257068SiegenGermany
| | - Sergey I. Druzhinin
- Department of Chemistry and Biology, and Center of Micro- and Nanochemistry and Engineering (Cμ)University of SiegenAdolf-Reichwein-Str. 257068SiegenGermany
| | - Heiko Ihmels
- Department of Chemistry and Biology, and Center of Micro- and Nanochemistry and Engineering (Cμ)University of SiegenAdolf-Reichwein-Str. 257068SiegenGermany
| | - Mareike Müller
- Department of Chemistry and Biology, and Center of Micro- and Nanochemistry and Engineering (Cμ)University of SiegenAdolf-Reichwein-Str. 257068SiegenGermany
| | - Holger Schönherr
- Department of Chemistry and Biology, and Center of Micro- and Nanochemistry and Engineering (Cμ)University of SiegenAdolf-Reichwein-Str. 257068SiegenGermany
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13
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Chen C, Zhu L, Baranov MS, Tang L, Baleeva NS, Smirnov AY, Yampolsky IV, Solntsev KM, Fang C. Photoinduced Proton Transfer of GFP-Inspired Fluorescent Superphotoacids: Principles and Design. J Phys Chem B 2019; 123:3804-3821. [DOI: 10.1021/acs.jpcb.9b03201] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Cheng Chen
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Liangdong Zhu
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Mikhail S. Baranov
- Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya 16/10, Moscow 117997, Russia
- Pirogov Russian National Research Medical University, Ostrovitianov 1, Moscow 117997, Russia
| | - Longteng Tang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Nadezhda S. Baleeva
- Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya 16/10, Moscow 117997, Russia
| | - Alexander Yu. Smirnov
- Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya 16/10, Moscow 117997, Russia
| | - Ilia V. Yampolsky
- Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya 16/10, Moscow 117997, Russia
- Pirogov Russian National Research Medical University, Ostrovitianov 1, Moscow 117997, Russia
| | - Kyril M. Solntsev
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | - Chong Fang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
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14
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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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15
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Maus D, Grandjean A, Jung G. Toward Magic Photoacids: Proton Transfer in Concentrated Sulfuric Acid. J Phys Chem A 2018; 122:9025-9030. [PMID: 30359029 DOI: 10.1021/acs.jpca.8b09974] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photoacids are the most convenient way to deliver protons on demand. So far, their photoacidity allows for studying excited-state proton transfer (ESPT) only to protic or strongly basic solvent molecules. The strongest superphotoacids known so far exhibit excited-state lifetimes of their conjugate base on the order of 100 ps before recapturing the proton again. Here, we describe how we developed a new aminopyrene-based superphotoacid with an excited-state lifetime of its conjugate base of several nanoseconds. It will be shown by fluorescence titration and via Förster cycle that the excited-state acidity is as high as concentrated sulfuric acid and thus exceeding any previous photoacidity by several orders of magnitude. Its outstanding chemical stability and fluorescent properties make it suitable for time-resolved proton-transfer studies in concentrated mineral acids and organic solvents of low basicity.
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Affiliation(s)
- Daniel Maus
- Biophysical Chemistry , Saarland University , Campus B2 2, 66123 Saarbruecken , Germany
| | - Alexander Grandjean
- Biophysical Chemistry , Saarland University , Campus B2 2, 66123 Saarbruecken , Germany
| | - Gregor Jung
- Biophysical Chemistry , Saarland University , Campus B2 2, 66123 Saarbruecken , Germany
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16
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Sheng W, Nairat M, Pawlaczyk PD, Mroczka E, Farris B, Pines E, Geiger JH, Borhan B, Dantus M. Ultrafast Dynamics of a “Super” Photobase. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201806787] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Wei Sheng
- Department of Chemistry Michigan State University E. Lansing MI 48824 USA
| | - Muath Nairat
- Department of Chemistry Michigan State University E. Lansing MI 48824 USA
| | | | - Elizabeth Mroczka
- Department of Chemistry Michigan State University E. Lansing MI 48824 USA
| | - Benjamin Farris
- Department of Chemistry Michigan State University E. Lansing MI 48824 USA
| | - Ehud Pines
- Department of Chemistry Ben-Gurion University of the Negev POB 653 Beer Sheva 84105 Israel
| | - James H. Geiger
- Department of Chemistry Michigan State University E. Lansing MI 48824 USA
| | - Babak Borhan
- Department of Chemistry Michigan State University E. Lansing MI 48824 USA
| | - Marcos Dantus
- Department of Chemistry Michigan State University E. Lansing MI 48824 USA
- Department of Physics and Astronomy Michigan State University East Lansing MI 48824 USA
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17
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Sheng W, Nairat M, Pawlaczyk PD, Mroczka E, Farris B, Pines E, Geiger JH, Borhan B, Dantus M. Ultrafast Dynamics of a "Super" Photobase. Angew Chem Int Ed Engl 2018; 57:14742-14746. [PMID: 30152115 DOI: 10.1002/anie.201806787] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 07/26/2018] [Indexed: 11/08/2022]
Abstract
Molecular reactivity can change dramatically with the absorption of a photon due to the difference of the electronic configurations between the excited and ground states. Here we report on the discovery of a modular system (Schiff base formed from an aldehyde and an amine) that upon photoexcitation yields a more basic imine capable of intermolecular proton transfer from protic solvents. Ultrafast dynamics of the excited state conjugated Schiff base reveals the pathway for proton transfer, culminating in a 14-unit increase in pKa to give the excited state pKa * >20 in ethanol.
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Affiliation(s)
- Wei Sheng
- Department of Chemistry, Michigan State University, E. Lansing, MI, 48824, USA
| | - Muath Nairat
- Department of Chemistry, Michigan State University, E. Lansing, MI, 48824, USA
| | - Patrick D Pawlaczyk
- Department of Chemistry, Michigan State University, E. Lansing, MI, 48824, USA
| | - Elizabeth Mroczka
- Department of Chemistry, Michigan State University, E. Lansing, MI, 48824, USA
| | - Benjamin Farris
- Department of Chemistry, Michigan State University, E. Lansing, MI, 48824, USA
| | - Ehud Pines
- Department of Chemistry, Ben-Gurion University of the Negev, POB 653, Beer Sheva, 84105, Israel
| | - James H Geiger
- Department of Chemistry, Michigan State University, E. Lansing, MI, 48824, USA
| | - Babak Borhan
- Department of Chemistry, Michigan State University, E. Lansing, MI, 48824, USA
| | - Marcos Dantus
- Department of Chemistry, Michigan State University, E. Lansing, MI, 48824, USA.,Department of Physics and Astronomy, Michigan State University, East Lansing, MI, 48824, USA
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18
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Hunt JR, Dawlaty JM. Photodriven Deprotonation of Alcohols by a Quinoline Photobase. J Phys Chem A 2018; 122:7931-7940. [DOI: 10.1021/acs.jpca.8b06152] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Jonathan Ryan 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
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19
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Green O, Gajst O, Simkovitch R, Shabat D, Huppert D. Chloro benzoate cyanine picolinium photoacid excited-state proton transfer to water. J Photochem Photobiol A Chem 2017. [DOI: 10.1016/j.jphotochem.2017.08.056] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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20
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Kumpulainen T, Rosspeintner A, Dereka B, Vauthey E. Influence of Solvent Relaxation on Ultrafast Excited-State Proton Transfer to Solvent. J Phys Chem Lett 2017; 8:4516-4521. [PMID: 28872875 DOI: 10.1021/acs.jpclett.7b01956] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
A thorough understanding of the microscopic mechanism of excited-state proton transfer (ESPT) and the influence of the solvent environment on its dynamics are of great fundamental interest. We present here a detailed investigation of an ESPT to solvent (DMSO) using time-resolved broadband fluorescence and transient absorption spectroscopies. All excited-state species are resolved spectrally and kinetically using a global target analysis based on the two-step Eigen-Weller model. Reversibility of the initial short-range proton transfer producing excited contact ion pairs (CIP*) is observed unambiguously in fluorescence and must be explicitly considered to obtain the individual rate constants. Close inspection of the early dynamics suggests that the relative populations of the protonated form (ROH*) and CIP* are governed by solvent relaxation that influences the relative energies of the excited states. This constitutes a breakdown of the Eigen-Weller model, although the overall agreement between the data and the analysis using classical rate equations is excellent.
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Affiliation(s)
- Tatu Kumpulainen
- Department of Physical Chemistry, University of Geneva , 30 Quai Ernest Ansermet, Geneva, Switzerland
| | - Arnulf Rosspeintner
- Department of Physical Chemistry, University of Geneva , 30 Quai Ernest Ansermet, Geneva, Switzerland
| | - Bogdan Dereka
- Department of Physical Chemistry, University of Geneva , 30 Quai Ernest Ansermet, Geneva, Switzerland
| | - Eric Vauthey
- Department of Physical Chemistry, University of Geneva , 30 Quai Ernest Ansermet, Geneva, Switzerland
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21
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Kumpulainen T, Lang B, Rosspeintner A, Vauthey E. Ultrafast Elementary Photochemical Processes of Organic Molecules in Liquid Solution. Chem Rev 2016; 117:10826-10939. [DOI: 10.1021/acs.chemrev.6b00491] [Citation(s) in RCA: 249] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Tatu Kumpulainen
- Department of Physical Chemistry,
Sciences II, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Bernhard Lang
- Department of Physical Chemistry,
Sciences II, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Arnulf Rosspeintner
- Department of Physical Chemistry,
Sciences II, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Eric Vauthey
- Department of Physical Chemistry,
Sciences II, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
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22
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Phukon A, Ray S, Sahu K. Effect of Cosurfactants on the Interfacial Hydration of CTAB Quaternary Reverse Micelle Probed Using Excited State Proton Transfer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:10659-10667. [PMID: 27666561 DOI: 10.1021/acs.langmuir.6b02869] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
It has been proven previously that the negatively charged photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) resides at the interface of the cationic reverse micelle (RM) cetyltrimethylammonium bromide (CTAB)/octanol/water/cyclohexane and is a potential reporter of hydration through the excited state proton transfer (ESPT) process. However, the ESPT dynamics monitored by the pump-probe study was limited to the ultrafast timescale and hence did not report any discernible ESPT signature. Herein, we reinvestigate the ESPT behavior using fluorescence spectroscopy in the nanosecond timescale and at different values of w0 (=[water]/[surfactant]). We clearly observed distinct w0-dependent ESPT signatures analogous to conventional ternary cationic RMs implying considerable interfacial hydration. The results agree with a recent molecular simulation study, where significant penetration of water molecules into the interface was predicted for the CTAB quaternary RM. Moreover, we also found that the ESPT dynamics and the fluorescence anisotropy decay of HPTS depend differentially on the octanol/CTAB ratio (p0). The ESPT process was found to be disfavored, whereas the anisotropy decay accelerates upon the increase in p0 values. Our analysis indicates that with the increase in the octanol concentration, dehydrated regions enrich gradually at the interface. However, the increase in octanol concentration may reduce the effective electrostatic potential experienced by the probe and thus may result in faster rotational relaxation.
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Affiliation(s)
- Aparajita Phukon
- Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati 781039, Assam, India
| | - Sudipta Ray
- Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati 781039, Assam, India
| | - Kalyanasis Sahu
- Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati 781039, Assam, India
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23
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Green O, Simkovitch R, Pinto da Silva L, Esteves da Silva JCG, Shabat D, Huppert D. Excited-State Proton Transfer and Formation of the Excited Tautomer of 3-Hydroxypyridine-Dipicolinium Cyanine Dye. J Phys Chem A 2016; 120:6184-99. [DOI: 10.1021/acs.jpca.6b04666] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Ori Green
- Raymond
and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ron Simkovitch
- Raymond
and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | | | | | - Doron Shabat
- Raymond
and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Dan Huppert
- Raymond
and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
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24
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Phukon A, Ray S, Sahu K. How Does Interfacial Hydration Alter during Rod to Sphere Transition in DDAB/Water/Cyclohexane Reverse Micelles? Insights from Excited State Proton Transfer and Fluorescence Anisotropy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:6656-6665. [PMID: 27292367 DOI: 10.1021/acs.langmuir.6b01254] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
How does microscopic organization of an organized assembly alter during macroscopic structural transition? The question may be important to ascertain driving forces responsible for such transitions. Didodecyldimethylammonium bromide (DDAB)/water/cyclohexane reverse micelle is an attractive assembly that undergoes structural transition from rod to spherical shape when the amount of water loading, w0 ([water]/[surfactant]), exceeds a particular value (w0 ∼ 8). Here, we intend to investigate the effect of the morphological change upon interfacial hydration using steady-state and time-resolved fluorescence measurements. The anionic fluorophore 8-hydroxypyrene-1,3,6-trisulfonate (HPTS or pyranine) is expected to be trapped within the positively charged RM interface. The fluorophore can undergo excited-state proton transfer (ESPT) in the presence of water and, thus, is able to provide insight on the level of hydration within the interface. The ESPT process is markedly inhibited within the interface at low w0 and gradually favored with increase of w0. The time-resolved fluorescence decays could be best analyzed by assuming distribution of HPTS over two distinct interfacial regions- partly hydrated and mostly dehydrated. The relative population of the two regions varies distinctly at low w0 (<6) and high w0 (>6) regimes. Moreover, fluorescence anisotropy (steady-state and time-resolved) varies differently with respect to w0, before and after the transition point (w0 ∼ 8).
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Affiliation(s)
- Aparajita Phukon
- Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati 781039, Assam, India
| | - Sudipta Ray
- Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati 781039, Assam, India
| | - Kalyanasis Sahu
- Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati 781039, Assam, India
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25
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Driscoll EW, Hunt JR, Dawlaty JM. Photobasicity in Quinolines: Origin and Tunability via the Substituents' Hammett Parameters. J Phys Chem Lett 2016; 7:2093-2099. [PMID: 27195691 DOI: 10.1021/acs.jpclett.6b00790] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Affiliation(s)
| | - Jonathan Ryan Hunt
- University of Southern California , Los Angeles, California 90089, United States
| | - Jahan M Dawlaty
- University of Southern California , Los Angeles, California 90089, United States
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26
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Liu W, Wang Y, Tang L, Oscar BG, Zhu L, Fang C. Panoramic portrait of primary molecular events preceding excited state proton transfer in water. Chem Sci 2016; 7:5484-5494. [PMID: 30034688 PMCID: PMC6021748 DOI: 10.1039/c6sc00672h] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Accepted: 05/11/2016] [Indexed: 12/31/2022] Open
Abstract
Primary events that power ultrafast excited state proton transfer in water are revealed to involve coupled intermolecular and intramolecular motions.
Photochemistry powers numerous processes from luminescence and human vision, to light harvesting. However, the elucidation of multidimensional photochemical reaction coordinates on molecular timescales remains challenging. We developed wavelength-tunable femtosecond stimulated Raman spectroscopy to simultaneously achieve pre-resonance enhancement for transient reactant and product species of the widely used photoacid pyranine undergoing excited-state proton transfer (ESPT) reaction in solution. In the low-frequency region, the 280 cm–1 ring deformation mode following 400 nm photoexcitation exhibits pronounced intensity oscillations on the sub-picosecond timescale due to anharmonic vibrational coupling to the 180 cm–1 hydrogen-bond stretching mode only in ESPT-capable solvents, indicating a primary event of functional relevance. This leads to the contact ion pair formation on the 3 ps timescale before diffusion-controlled separation. The intermolecular 180 cm–1 mode also reveals vibrational cooling time constants, ∼500 fs and 45 ps in both H2O and D2O, which differ from ESPT time constants of ∼3/8 and 90/250 ps in H2O/D2O, respectively. Spectral results using H218O further substantiate the functional role of the intermolecular 180 cm–1 mode in modulating the distance between proton donor and acceptor and forming the transient ion pair. The direct observation of molecular structural evolution across a wide spectral region during photochemical reactions enriches our fundamental understanding of potential energy surface and holds the key to advancing energy and biological sciences with exceptional atomic and temporal precision.
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Affiliation(s)
- Weimin Liu
- Oregon State University , Department of Chemistry , 263 Linus Pauling Science Centre (lab) , 153 Gilbert Hall (office) , Corvallis , OR 97331 , USA . ; ; Tel: +1 541 737 6704
| | - Yanli Wang
- Oregon State University , Department of Chemistry , 263 Linus Pauling Science Centre (lab) , 153 Gilbert Hall (office) , Corvallis , OR 97331 , USA . ; ; Tel: +1 541 737 6704
| | - Longteng Tang
- Oregon State University , Department of Chemistry , 263 Linus Pauling Science Centre (lab) , 153 Gilbert Hall (office) , Corvallis , OR 97331 , USA . ; ; Tel: +1 541 737 6704
| | - Breland G Oscar
- Oregon State University , Department of Chemistry , 263 Linus Pauling Science Centre (lab) , 153 Gilbert Hall (office) , Corvallis , OR 97331 , USA . ; ; Tel: +1 541 737 6704
| | - Liangdong Zhu
- Oregon State University , Department of Chemistry , 263 Linus Pauling Science Centre (lab) , 153 Gilbert Hall (office) , Corvallis , OR 97331 , USA . ; ; Tel: +1 541 737 6704
| | - Chong Fang
- Oregon State University , Department of Chemistry , 263 Linus Pauling Science Centre (lab) , 153 Gilbert Hall (office) , Corvallis , OR 97331 , USA . ; ; Tel: +1 541 737 6704
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27
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Vester M, Grueter A, Finkler B, Becker R, Jung G. Biexponential photon antibunching: recombination kinetics within the Förster-cycle in DMSO. Phys Chem Chem Phys 2016; 18:10281-8. [PMID: 27020473 DOI: 10.1039/c6cp00718j] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Time-resolved experiments with pulsed-laser excitation are the standard approach to map the dynamic evolution of excited states, but ground-state kinetics remain hidden or require pump-dump-probe schemes. Here, we exploit the so-called photon antibunching, a purely quantum-optical effect related to single molecule detection to assess the rate constants for a chemical reaction in the electronic ground state. The measurement of the second-order correlation function g((2)), i.e. the evaluation of inter-photon arrival times, is applied to the reprotonation in a Förster-cycle. We find that the antibunching of three different photoacids in the aprotic solvent DMSO significantly differs from the behavior in water. The longer decay constant of the biexponential antibunching tl is linked to the bimolecular reprotonation kinetics of the fully separated ion-pair, independent of the acidic additives. The value of the corresponding bimolecular rate constant, kp = 4 × 10(9) M(-1) s(-1), indicates diffusion-controlled reprotonation. The analysis of tl also allows for the extraction of the separation yield of proton and the conjugated base after excitation and amounts to approximately 15%. The shorter time component ts is connected to the decay of the solvent-separated ion pair. The associated time constant for geminate reprotonation is approximately 3 ± 1 ns in agreement with independent tcspc experiments. These experiments verify that the transfer of quantum-optical experiments to problems in chemistry enables mechanistic conclusions which are hardly accessible by other methods.
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Affiliation(s)
- Michael Vester
- Biophysical Chemistry, Saarland University, 66123 Saarbrücken, Germany.
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28
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Park SY, Ghosh P, Park SO, Lee YM, Kwak SK, Kwon OH. Origin of ultraweak fluorescence of 8-hydroxyquinoline in water: photoinduced ultrafast proton transfer. RSC Adv 2016. [DOI: 10.1039/c5ra23802a] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Ultrafast excited-state proton transfer of 8-hydroxuquinoline to produce short-lived its tautomeric form causes immensely attenuated fluorescence in water.
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Affiliation(s)
- Sun-Young Park
- Center for Soft and Living Matter
- Institute for Basic Science (IBS)
- Ulsan 689-798
- Republic of Korea
| | - Prasun Ghosh
- Department of Chemistry
- Ulsan National Institute of Science and Technology (UNIST)
- Ulsan 689-798
- Republic of Korea
| | - Sung O. Park
- School of Energy and Chemical Engineering
- Ulsan National Institute of Science and Technology (UNIST)
- Ulsan 689-798
- Republic of Korea
| | - Young Min Lee
- Department of Chemistry
- Ulsan National Institute of Science and Technology (UNIST)
- Ulsan 689-798
- Republic of Korea
| | - Sang Kyu Kwak
- School of Energy and Chemical Engineering
- Ulsan National Institute of Science and Technology (UNIST)
- Ulsan 689-798
- Republic of Korea
| | - Oh-Hoon Kwon
- Center for Soft and Living Matter
- Institute for Basic Science (IBS)
- Ulsan 689-798
- Republic of Korea
- Department of Chemistry
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29
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Kumpulainen T, Bakker BH, Brouwer AM. Complexes of a naphthalimide photoacid with organic bases, and their excited-state dynamics in polar aprotic organic solvents. Phys Chem Chem Phys 2015. [PMID: 26204802 DOI: 10.1039/c5cp02556g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Complex formation and intermolecular excited-state proton transfer (ESPT) between a dihydroxy-1,8-naphthalimide photoacid and organic bases are investigated in polar aprotic solvents. First, quantum chemical calculations are used to explore the acid-base and spectroscopic properties and to identify energetically favorable complexes. The two hydroxyl groups of the photoacid enable stepwise formation of 1 : 1 and 1 : 2 complexes. Weak bases exhibit only hydrogen-bonding interactions whereas strong bases are able to deprotonate one of the hydroxyl groups resulting in strong negative cooperativity (K1≫ 4K2) in the formation of the 1 : 2 complex. Time-resolved fluorescence studies of the complexes provide strong indications of a three-step dissociation process. The species involved in the model are: a hydrogen-bonded complex, a hydrogen-bonded ion pair, a solvent separated ion pair, and a free ion pair.
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Affiliation(s)
- Tatu Kumpulainen
- Van't Hoff Institute for Molecular Sciences, Faculty of Science, University of Amsterdam, P. O. Box 94157, 1090 GD Amsterdam, The Netherlands.
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30
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Henrich JD, Suchyta S, Kohler B. Ultrafast Hydrolysis of a Lewis Photoacid. J Phys Chem B 2014; 119:2737-48. [DOI: 10.1021/jp510953e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Joseph D. Henrich
- Department
of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Scott Suchyta
- Department
of Chemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Bern Kohler
- Department
of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
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31
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Kumpulainen T, Bakker BH, Hilbers M, Brouwer AM. Synthesis and spectroscopic characterization of 1,8-naphthalimide derived "super" photoacids. J Phys Chem B 2014; 119:2515-24. [PMID: 25225779 DOI: 10.1021/jp508334s] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The ground- and excited-state acid-base properties of three novel naphthalimide-based “super” photoacids were studied using steady-state and time-resolved spectroscopy. The compounds exhibit pKa = 8.8-8.0 and pKa* = -1.2 to -1.9. The decrease in both ground- and excited-state pKa is achieved by attachment of an electron withdrawing group (sulfonate) on the aromatic system. All compounds are deprotonated upon excitation in alcohols and DMSO. Good correlation is established between the pKa* and the ratio of the neutral and anion emission intensities in a certain solvent. The excited-state intermolecular proton transfer to solvent (H2O and DMSO) is explained by a two-step model. In the first step, short-range proton transfer takes place, resulting in the formation of a contact ion pair. Free ion pairs are formed in the diffusion controlled second step.
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Affiliation(s)
- Tatu Kumpulainen
- Van 't Hoff Institute for Molecular Sciences, Faculty of Science, University of Amsterdam , P.O. Box 94157, 1090 GD Amsterdam, The Netherlands
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