1
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Clarke CJ, Verlet JRR. Dynamics of Anions: From Bound to Unbound States and Everything In Between. Annu Rev Phys Chem 2024; 75:89-110. [PMID: 38277700 DOI: 10.1146/annurev-physchem-090722-125031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2024]
Abstract
Gas-phase anions present an ideal playground for the exploration of excited-state dynamics. They offer control in terms of the mass, extent of solvation, internal temperature, and conformation. The application of a range of ion sources has opened the field to a vast array of anionic systems whose dynamics are important in areas ranging from biology to star formation. Here, we review recent experimental developments in the field of anion photodynamics, demonstrating the detailed insight into photodynamical and electron-capture processes that can be uncovered. We consider the electronic and nuclear ultrafast dynamics of electronically bound excited states along entire reaction coordinates; electronically unbound states showing that photochemical concepts, such as chromophores and Kasha's rule, are transferable to electron-driven chemistry; and nonvalence states that straddle the interface between bound and unbound states. Finally, we consider likely developments that are sure to keep the field of anion dynamics buoyant and impactful.
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Affiliation(s)
- Connor J Clarke
- Department of Chemistry, Durham University, Durham, United Kingdom;
| | - Jan R R Verlet
- Department of Chemistry, Durham University, Durham, United Kingdom;
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2
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Opoku E, Pawłowski F, Ortiz JV. New-generation electron-propagator methods for vertical electron detachment energies of molecular anions: benchmarks and applications to model green-fluorescent-protein chromophores. Phys Chem Chem Phys 2024; 26:9915-9930. [PMID: 38482723 DOI: 10.1039/d4cp00441h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2024]
Abstract
Ab initio electron-propagator calculations continue to be useful companions to experimental investigations of electronic structure in molecular anions. A new generation of electron-propagator methods recently has surpassed its antecedents' predictive accuracy and computational efficiency. Interpretive clarity has been conserved, for no adjustable parameters have been introduced in the preparation of molecular orbitals or in the formulation of approximate self-energies. These methods have employed the diagonal self-energy approximation wherein each Dyson orbital equals a canonical Hartree-Fock orbital times the square root of a probability factor. Numerical tests indicate that explicitly renormalized, diagonal self-energies are needed when Dyson orbitals have large valence nitrogen, oxygen or fluorine components. They also demonstrate that even greater accuracy can be realized with generalizations that do not employ the diagonal self-energy approximation in the canonical Hartree-Fock basis. Whereas the diagonal methods have fifth-power arithmetic scaling factors, the non-diagonal generalizations introduce only non-iterative sixth-power contractions. Composite models conserve the accuracy of the most demanding combinations of self-energy approximations and flexible basis sets with drastically reduced computational effort. Composite-model results on anions that resemble the chromophore of the green fluorescent protein illustrate the interpretive capabilities of explicitly renormalized self-energies. Accurate predictions on the lowest vertical electron detachment energy of each anion confirm experimental data and the utility of the diagonal self-energy approximation.
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Affiliation(s)
- Ernest Opoku
- Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849-5312, USA.
| | - Filip Pawłowski
- Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849-5312, USA.
| | - J V Ortiz
- Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849-5312, USA.
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3
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Li X, Huang Q, Zhang Y, Huang X, Wu Y, Geng F, Huang M, Luo P, Li X. Study on the Mechanism of Modified Cellulose Improve the Properties of Egg Yolk gel. Food Chem X 2023; 20:100877. [PMID: 38144820 PMCID: PMC10740026 DOI: 10.1016/j.fochx.2023.100877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Revised: 08/27/2023] [Accepted: 09/11/2023] [Indexed: 12/26/2023] Open
Abstract
Natural fiber is not suitable for modifying yolk gel as a modifier because of its large size and high compactness. In this study, two kinds of modified cellulose were selected to improve the thermal gel properties of yolk. The results showed that the two kinds of cellulose promoted the formation of ordered structure in yolk gel. The ordered gel network not only improved the texture properties and rheological properties, but also improved the water retention of yolk gel significantly. CMC and CNFC at the same concentration, the modification effect of CMC on yolk gel was better than CNFC because of its excellent dispersion. However, high concentration of CNFC (1.20-1.60%) disrupted the cross-linking and ordered structure formation of yolk protein, and the quality of gel was significantly reduced.
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Affiliation(s)
- Xin Li
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, the Key Laboratory of Environmental Pollution Monitoring and Disease Control of Ministry of Education, Guizhou Medical University, Guiyang 550025, China
| | - Qun Huang
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, the Key Laboratory of Environmental Pollution Monitoring and Disease Control of Ministry of Education, Guizhou Medical University, Guiyang 550025, China
- College of Food Science, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Institute for Egg Science and Technology, School of Food and Biological Engineering, Chengdu University, Chengdu 610106, China
- College of Food and Pharmaceutical Engineering, Guizhou Institute of Technology, Guiyang, Guizhou, China
| | - Yufeng Zhang
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, the Key Laboratory of Environmental Pollution Monitoring and Disease Control of Ministry of Education, Guizhou Medical University, Guiyang 550025, China
- College of Food Science, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Xiang Huang
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, the Key Laboratory of Environmental Pollution Monitoring and Disease Control of Ministry of Education, Guizhou Medical University, Guiyang 550025, China
- College of Food Science, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Yongyan Wu
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, the Key Laboratory of Environmental Pollution Monitoring and Disease Control of Ministry of Education, Guizhou Medical University, Guiyang 550025, China
- College of Food Science, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Fang Geng
- Institute for Egg Science and Technology, School of Food and Biological Engineering, Chengdu University, Chengdu 610106, China
| | - Mingzheng Huang
- College of Food and Pharmaceutical Engineering, Guizhou Institute of Technology, Guiyang, Guizhou, China
| | - Peng Luo
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, the Key Laboratory of Environmental Pollution Monitoring and Disease Control of Ministry of Education, Guizhou Medical University, Guiyang 550025, China
| | - Xiefei Li
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, the Key Laboratory of Environmental Pollution Monitoring and Disease Control of Ministry of Education, Guizhou Medical University, Guiyang 550025, China
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4
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Anstöter CS, Verlet JRR. A Hückel Model for the Excited-State Dynamics of a Protein Chromophore Developed Using Photoelectron Imaging. Acc Chem Res 2022; 55:1205-1213. [PMID: 35172580 PMCID: PMC9084545 DOI: 10.1021/acs.accounts.1c00780] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Chemistry can be described as the movement of nuclei within molecules and the concomitant instantaneous change in electronic structure. This idea underpins the central chemical concepts of potential energy surfaces and reaction coordinates. To experimentally capture such chemical change therefore requires methods that can probe both the nuclear and electronic structure simultaneously and on the time scale of atomic motion. In this Account, we show how time-resolved photoelectron imaging can do exactly this and how it can be used to build a detailed and intuitive understanding of the electronic structure and excited-state dynamics of chromophores. The chromophore of the photoactive yellow protein (PYP) is used as a case study. This chromophore contains a para-substituted phenolate anion, where the substituent, R, can be viewed as an acrolein derivative. It is shown that the measured photoelectron angular distribution can be directly related to the electronic structure of the para-substituted phenolate anion. By incrementally considering differing R groups, it is also shown that these photoelectron angular distributions are exquisitely sensitive to the conformational flexibility of R and that when R contains a π-system the excited states of the chromophore can be viewed as a linear combination of the π* molecular orbitals on the phenolate (πPh*) and the R substituent (πR*). Such Hückel treatment shows that the S1 state of the PYP chromophore has predominantly πR* character and that it is essentially the same as the chromophore of the green fluorescent protein (GFP). The S1 excited-state dynamics of the PYP chromophore probed by time-resolved photoelectron imaging clearly reveals both structural (nuclear) dynamics through the energy spectrum and electronic dynamics through the photoelectron angular distributions. Both motions can be accurately assigned using quantum chemical calculations, and these are consistent with the intuitive Hückel treatment presented. The photoactive protein chromophores considered here are examples of where a chemists' intuitive Hückel view for ground-state chemistry appears to be transferable to the prediction of photochemical excited-state reactivity. While elegant and insightful, such models have limitations, including nonadiabatic dynamics, which is present in a related PYP chromophore, where a fraction of the S1 state population forms a nonvalence (dipole-bound) state of the anion.
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Affiliation(s)
- Cate S. Anstöter
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Jan R. R. Verlet
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
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5
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Anstöter CS, Curchod BFE, Verlet JRR. Photo-isomerization of the isolated photoactive yellow protein chromophore: what comes before the primary step? Phys Chem Chem Phys 2022; 24:1305-1309. [PMID: 34984423 DOI: 10.1039/d1cp05259d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Photoactive proteins typically rely on structural changes in a small chromophore to initiate a biological response. While these changes often involve isomerization as the "primary step", preceding this is an ultrafast relaxation of the molecular framework caused by the sudden change in electronic structure upon photoexcitation. Here, we capture this motion for an isolated model chromophore of the photoactive yellow protein using time-resolved photoelectron imaging. It occurs in <150 fs and is apparent from a spectral shift of ∼70 meV and a change in photoelectron anisotropy. Electronic structure calculations enable the quantitative assignment of the geometric and electronic structure changes to a planar intermediate from which the primary step can then proceed.
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Affiliation(s)
- Cate S Anstöter
- Department of Chemistry, Durham University, Durham DH1 3LE, UK.
| | | | - Jan R R Verlet
- Department of Chemistry, Durham University, Durham DH1 3LE, UK.
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6
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Sanov A. Intermolecular interactions in cluster anions. INT REV PHYS CHEM 2021. [DOI: 10.1080/0144235x.2021.1983292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Andrei Sanov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ, USA
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7
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Woodhouse JL, Henley A, Lewin R, Ward JM, Hailes HC, Bochenkova AV, Fielding HH. A photoelectron imaging study of the deprotonated GFP chromophore anion and RNA fluorescent tags. Phys Chem Chem Phys 2021; 23:19911-19922. [PMID: 34474467 DOI: 10.1039/d1cp01901e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Green fluorescent protein (GFP), together with its family of variants, is the most widely used fluorescent protein for in vivo imaging. Numerous spectroscopic studies of the isolated GFP chromophore have been aimed at understanding the electronic properties of GFP. Here, we build on earlier work [A. V. Bochenkova, C. Mooney, M. A. Parkes, J. Woodhouse, L. Zhang, R. Lewin, J. M. Ward, H. Hailes, L. H. Andersen and H. H. Fielding, Chem. Sci., 2017, 8, 3154] investigating the impact of fluorine and methoxy substituents that have been employed to tune the electronic structure of the GFP chromophore for use as fluorescent RNA tags. We present photoelectron spectra following photoexcitation over a broad range of wavelengths (364-230 nm) together with photoelectron angular distributions following photoexcitation at 364 nm, which are interpreted with the aid of quantum chemistry calculations. The results support the earlier high-level quantum chemistry calculations that predicted how fluorine and methoxy substituents tune the electronic structure and we find evidence to suggest that the methoxy substituents enhance internal conversion, most likely from the 2ππ* state which has predominantly Feshbach resonance character, to the 1ππ* state.
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Affiliation(s)
- Joanne L Woodhouse
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| | - Alice Henley
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| | - Ross Lewin
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| | - John M Ward
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, Gower Street, London WC1E 6BT, UK
| | - Helen C Hailes
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| | | | - Helen H Fielding
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
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8
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Dauletyarov Y, Sanov A. Weak covalent interactions and anionic charge-sharing polymerisation in cluster environments. Phys Chem Chem Phys 2021; 23:11596-11610. [PMID: 33982051 DOI: 10.1039/d1cp01213d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We discuss the formation of weak covalent bonds leading to anionic charge-sharing dimerisation or polymerisation in microscopic cluster environments. The covalent bonding between cluster building blocks is described in terms of coherent charge sharing, conceptualised using a coupled-monomers molecular-orbital model. The model assumes first-order separability of the inter- and intra-monomer bonding structures. Combined with a Hückel-style formalism adapted to weak covalent and solvation interactions, it offers insight into the competition between the two types of forces and illuminates the properties of the inter-monomer orbitals responsible for charge-sharing dimerisation and polymerisation. Under typical conditions, the cumulative effect of solvation obstructs the polymerisation, limiting the size of covalently bound core anions.
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Affiliation(s)
- Yerbolat Dauletyarov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, USA.
| | - Andrei Sanov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, USA.
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9
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Anstöter CS, Verlet JRR. Photoelectron imaging of the SO 3 anion: vibrational resolution in photoelectron angular distributions*. Mol Phys 2021. [DOI: 10.1080/00268976.2020.1821921] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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10
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Abstract
Electron capture by the σ* LUMO of isoxazole triggers the dissociation of the O-N bond and the opening of the ring. Photodetachment of the resulting anion accesses a neutral structure, in which the O· and ·N bond fragments interact through the intact remainder of the molecular ring and via a 3 Å gap created by the bond dissociation. These through-bond and through-space interactions result in a dense manifold of diradical states, including (in the order of increasing energy) a triplet, an open-shell singlet, a closed-shell singlet, and another triplet state. We report photoelectron spectra that reflect partially resolved signatures of these states. Remarkably, the structure of the isoxazole diradical manifold is qualitatively different from that of the analogous system in oxazole. The distinct properties of the two manifolds are explained by using a coupled-fragments molecular-orbital model. Consistent with the past conclusions [Culberson et al. Phys. Chem. Chem. Phys. 2014, 16, 3964-3972], the lingering through-space interactions between the O· and ·C bond fragments in ring-open oxazole are responsible for the relative stabilization of the closed-shell singlet state, which correlates with the ground-state cyclic structure. In contrast, the placement of the N atom in the terminal position within the ring-open structure of isoxazole is the key factor leading to the near degeneracy of the π and σ* orbitals, favoring a triplet-state configuration.
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Affiliation(s)
- Adam A Wallace
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Yerbolat Dauletyarov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Andrei Sanov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
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11
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Anstöter CS, Curchod BFE, Verlet JRR. Geometric and electronic structure probed along the isomerisation coordinate of a photoactive yellow protein chromophore. Nat Commun 2020; 11:2827. [PMID: 32499507 PMCID: PMC7272410 DOI: 10.1038/s41467-020-16667-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 05/15/2020] [Indexed: 01/29/2023] Open
Abstract
Understanding the connection between the motion of the nuclei in a molecule and the rearrangement of its electrons lies at the heart of chemistry. While many experimental methods have been developed to probe either the electronic or the nuclear structure on the timescale of atomic motion, very few have been able to capture both these changes in concert. Here, we use time-resolved photoelectron imaging to probe the isomerisation coordinate on the excited state of an isolated model chromophore anion of the photoactive yellow protein. By probing both the electronic structure changes as well as nuclear dynamics, we are able to uniquely measure isomerisation about a specific bond. Our results demonstrate that the photoelectron signal dispersed in time, energy and angle combined with calculations can track the evolution of both electronic and geometric structure along the adiabatic state, which in turn defines that chemical transformation. Resolving concerted nuclear and electronic motion in real-time is a primary goal in chemistry. The authors monitor nuclear and valence electronic dynamics in the excited state single-bond isomerisation of a chromophore of photoactive yellow protein, using time-resolved photoelectron imaging and electronic structure calculations.
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Affiliation(s)
- Cate S Anstöter
- Department of Chemistry, Durham University, Durham, DH1 3LE, UK
| | | | - Jan R R Verlet
- Department of Chemistry, Durham University, Durham, DH1 3LE, UK.
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12
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Mensa-Bonsu G, Lietard A, Tozer DJ, Verlet JRR. Low energy electron impact resonances of anthracene probed by 2D photoelectron imaging of its radical anion. J Chem Phys 2020; 152:174303. [PMID: 32384861 DOI: 10.1063/5.0007470] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Electron-molecule resonances of anthracene were probed by 2D photoelectron imaging of the corresponding radical anion up to 3.7 eV in the continuum. A number of resonances were observed in both the photoelectron spectra and angular distributions, and most resonances showed clear autodetachment dynamics. The resonances were assigned using density functional theory calculations and are consistent with the available literature. Competition between direct and autodetachment, as well as signatures of internal conversion between resonances, was observed for some resonances. For the 12B2g resonance, a small fraction of population recovers the ground electronic state as evidenced by thermionic emission. Recovery of the ground electronic state offers a route of producing anions in an electron-molecule reaction; however, the energy at which this occurs suggests that anthracene anions cannot be formed in the interstellar medium by electron capture through this resonance.
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Affiliation(s)
- Golda Mensa-Bonsu
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Aude Lietard
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - David J Tozer
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Jan R R Verlet
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
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13
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Verlet JRR, Anstöter CS, Bull JN, Rogers JP. Role of Nonvalence States in the Ultrafast Dynamics of Isolated Anions. J Phys Chem A 2020; 124:3507-3519. [PMID: 32233436 PMCID: PMC7212518 DOI: 10.1021/acs.jpca.0c01260] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Nonvalence states
of neutral molecules (Rydberg states) play important
roles in nonadiabatic dynamics of excited states. In anions, such
nonadiabatic transitions between nonvalence and valence states have
been much less explored even though they are believed to play important
roles in electron capture and excited state dynamics of anions. The
aim of this Feature Article is to provide an overview of recent experimental
observations, based on time-resolved photoelectron imaging, of valence
to nonvalence and nonvalence to valence transitions in anions and
to demonstrate that such dynamics may be commonplace in the excited
state dynamics of molecular anions and cluster anions.
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Affiliation(s)
- Jan R R Verlet
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Cate S Anstöter
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - James N Bull
- School of Chemistry, Norwich Research Park, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Joshua P Rogers
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
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14
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Bull JN, Anstöter CS, Verlet JRR. Fingerprinting the Excited-State Dynamics in Methyl Ester and Methyl Ether Anions of Deprotonated para-Coumaric Acid. J Phys Chem A 2020; 124:2140-2151. [PMID: 32105474 DOI: 10.1021/acs.jpca.9b11993] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Chromophores based on the para-hydroxycinnamate moiety are widespread in the natural world, including as the photoswitching unit in photoactive yellow protein and as a sunscreen in the leaves of plants. Here, photodetachment action spectroscopy combined with frequency- and angle-resolved photoelectron imaging is used to fingerprint the excited-state dynamics over the first three bright action-absorption bands in the methyl ester anions (pCEs-) of deprotonated para-coumaric acid at a temperature of ∼300 K. The excited states associated with the action-absorption bands are classified as resonances because they are situated in the detachment continuum and are open to autodetachment. The frequency-resolved photoelectron spectrum for pCEs- indicates that all photon energies over the S1(ππ*) band lead to similar vibrational autodetachment dynamics. The S2(nπ*) band is Herzberg-Teller active and has comparable brightness to the higher lying 21(ππ*) band. The frequency-resolved photoelectron spectrum over the S2(nπ*) band indicates more efficient internal conversion to the S1(ππ*) state for photon energies resonant with the Franck-Condon modes (∼80%) compared with the Herzberg-Teller modes (∼60%). The third action-absorption band, which corresponds to excitation of the 21(ππ*) state, shows complex and photon energy-dependent dynamics, with 20-40% of photoexcited population internally converting to the S1(ππ*) state. There is also evidence for a mode-specific competition between prompt autodetachment and internal conversion on the red edge of the 21(ππ*) band. There is no evidence for recovery of the ground electronic state and statistical electron ejection (thermionic emission) following photoexcitation over any of the three action-absorption bands. The photoelectron spectra for the deprotonated methyl ether derivative (pCEt-) at photon energies over the S1(ππ*) and S2(nπ*) bands indicate diametrically opposed dynamics compared with pCEs-, namely, intense thermionic emission due to efficient recovery of the ground electronic state.
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Affiliation(s)
- James N Bull
- School of Chemistry, Norwich Research Park, University of East Anglia, Norwich NR4 7TJ, U.K
| | - Cate S Anstöter
- Department of Chemistry, Durham University, Durham DH1 3LE, U.K
| | - Jan R R Verlet
- Department of Chemistry, Durham University, Durham DH1 3LE, U.K
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15
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Zagorec-Marks W, Foreman MM, Verlet JRR, Weber JM. Cryogenic Ion Spectroscopy of the Green Fluorescent Protein Chromophore in Vacuo. J Phys Chem Lett 2019; 10:7817-7822. [PMID: 31682445 DOI: 10.1021/acs.jpclett.9b02916] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We present the spectrum of the S1 ← S0 transition of an anionic model for the chromophore of the green fluorescent protein in vacuo at cryogenic temperatures, showing previously unresolved vibrational features, and resolving the band origin at 20 930 cm-1 (477.8 nm) with unprecedented accuracy. The vibrational spectrum establishes that the molecule is in the Z isomer at low temperature. At increased temperature, the S1 ← S0 band shifts to the red, which we tentatively attribute to emergent population of the E isomer.
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Affiliation(s)
- Wyatt Zagorec-Marks
- JILA and Department of Chemistry , University of Colorado , Boulder , Colorado 80309-0440 , United States
| | - Madison M Foreman
- JILA and Department of Chemistry , University of Colorado , Boulder , Colorado 80309-0440 , United States
| | - Jan R R Verlet
- Department of Chemistry , Durham University , Durham , DH1 3LE , U.K
| | - J Mathias Weber
- JILA and Department of Chemistry , University of Colorado , Boulder , Colorado 80309-0440 , United States
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16
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Castellani ME, Anstöter CS, Verlet JRR. On the stability of a dipole-bound state in the presence of a molecule. Phys Chem Chem Phys 2019; 21:24286-24290. [PMID: 31663558 DOI: 10.1039/c9cp04942h] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Dipole-bound states (DBSs) are diffuse non-valence molecular orbitals of anions where the electron is bound by the permanent dipole moment of the neutral core. Here, an experimental study of the stability of such orbitals under the influence of a perturbing molecular alkyl chain is presented. Photodetachment action and photoelectron imaging spectroscopy of five para-substituted phenolate anions with progressively longer alkyl chains show that the DBS survives in all cases, suggesting that the perturbation of the orbital is not critical to the existence of the DBS.
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17
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Mensa-Bonsu G, Tozer DJ, Verlet JRR. Photoelectron spectroscopic study of I -·ICF 3: a frontside attack S N2 pre-reaction complex. Phys Chem Chem Phys 2019; 21:13977-13985. [PMID: 30534728 DOI: 10.1039/c8cp06593d] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photodetachment and 2D photoelectron spectra of the mass-selected I-·CF3I complex are presented together with electronic structure calculations. Calculations show that the I- is located at the iodine side of CF3I. Vertical and adiabatic detachment energies were measured at 4.03 and approximately 3.8 eV, respectively. The photoelectron spectra and molecular orbitals show a significant covalent bonding character in the cluster. The presence of electronic excited states is observed. Below threshold, iodide is generated which can be assigned to the photoexcitation of degenerate charge-transfer bands from the off-axis p-orbitals localised on iodide. Near the onset of two spin-orbit thresholds, bright excited states are seen in the experiment and calculations. Excitation of these leads to the formation of slow electrons. The spectroscopy of I-·CF3I is compared to the well-studied I-·CH3I cluster, a pre-reaction complex in the text-book I- + CH3I SN2 reaction. Despite the reversed stereodynamics (i.e. inversion of the CX3 between X = H and F) of the SN2 reaction, striking similarities are seen. Both complexes possess charge transfer excited states near their respective vertical detachment energies and exhibit vibrational structure in their photoelectron spectra. The strong binding is consistent with observations in crossed molecular beam studies and molecular dynamics simulations that suggest that iodine as a leaving group in an SN2 reaction affects the reaction dynamics.
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Tyson AL, Verlet JRR. On the Mechanism of Phenolate Photo-Oxidation in Aqueous Solution. J Phys Chem B 2019; 123:2373-2379. [PMID: 30768899 DOI: 10.1021/acs.jpcb.8b11766] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The photo-oxidation dynamics following ultraviolet (257 nm) excitation of the phenolate anion in aqueous solution is studied using broadband (550-950 nm) transient absorption spectroscopy. A clear signature from electron ejection is observed on a sub-picosecond timescale, followed by cooling dynamics and the decay of the signal to a constant offset that is assigned to the hydrated electron. The dynamics are compared to the charge-transfer-to-solvent dynamics from iodide at the same excitation wavelength and are shown to be very similar to these. This is in stark contrast to a previous study on the phenolate anion excited at 266 nm, in which electron emission was observed over longer timescales. We account for the differences using a simple Marcus picture for electron emission in which the electron tunneling rate depends sensitively on the initial excitation energy. After electron emission, a contact pair is formed which undergoes geminate recombination and dissociation to form the free hydrated electron at rates that are slightly faster than those for the iodide system. Our results show that, although the underlying chemical physics of electron emission differs between iodide and phenolate, the observed dynamics can appear very similar.
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Affiliation(s)
| | - Jan R R Verlet
- Department of Chemistry , Durham University , Durham DH1 3LE , U.K
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19
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Woodhouse JL, Henley A, Parkes MA, Fielding HH. Photoelectron Imaging and Quantum Chemistry Study of Phenolate, Difluorophenolate, and Dimethoxyphenolate Anions. J Phys Chem A 2019; 123:2709-2718. [PMID: 30848907 DOI: 10.1021/acs.jpca.8b11121] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Joanne L. Woodhouse
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AH, U.K
| | - Alice Henley
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AH, U.K
| | - Michael A. Parkes
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AH, U.K
| | - Helen H. Fielding
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AH, U.K
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20
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Rogers JP, Anstöter CS, Bull JN, Curchod BFE, Verlet JRR. Photoelectron Spectroscopy of the Hexafluorobenzene Cluster Anions: (C 6F 6) n- ( n = 1-5) and I -(C 6F 6). J Phys Chem A 2019; 123:1602-1612. [PMID: 30694676 DOI: 10.1021/acs.jpca.8b11627] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Frequency-resolved (2D) photoelectron (PE) spectra of the anionic clusters (C6F6) n-, for n = 1-5, and time-resolved PE spectra of I-C6F6 are presented using a newly built instrument and supported by electronic structure calculations. From the 2D PE spectra, the vertical detachment energy (VDE) of C6F6- was measured to be 1.60 ± 0.01 eV, and the adiabatic detachment energy (ADE) was ≤0.70 eV. The PE spectra also contain fingerprints of resonance dynamics over certain photon energy ranges, in agreement with the calculations. An action spectrum over the lowest resonance is also presented. The 2D spectra of (C6F6) n- show that the cluster can be described as C6F6-(C6F6) n-1. The VDE increases linearly (200 ± 20 meV n-1) due to the stabilizing influence on the anion of the solvating C6F6 molecules. For I-C6F6, action spectra of the absorption just below both detachment channels are presented. Time-resolved PE spectra of I-C6F6 excited at 3.10 eV and probed at 1.55 eV reveal a short-lived nonvalence state of C6F6- that coherently evolves into the valence ground state of the anion and induces vibrational motion along a specific buckling coordinate. Electronic structure calculations along the displacement of this mode show that at the extreme buckling angle the probe can access an excited state of the anion that is bound at that geometry but adiabatically unbound. Hence, slow electrons are emitted and show dynamics that predominantly probe the outer-turning point of the motion. A PE spectrum taken at t = 0 contains a vibrational structure assigned to a specific Raman- or IR-active mode of C6F6.
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Affiliation(s)
- Joshua P Rogers
- Department of Chemistry , Durham University , Durham DH1 3LE , United Kingdom
| | - Cate S Anstöter
- Department of Chemistry , Durham University , Durham DH1 3LE , United Kingdom
| | - James N Bull
- Department of Chemistry , Durham University , Durham DH1 3LE , United Kingdom
| | - Basile F E Curchod
- Department of Chemistry , Durham University , Durham DH1 3LE , United Kingdom
| | - Jan R R Verlet
- Department of Chemistry , Durham University , Durham DH1 3LE , United Kingdom
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21
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Gibbard JA, Shin AJ, Castracane E, Continetti RE. A high beam energy photoelectron-photofragment coincidence spectrometer for complex anions. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:123304. [PMID: 30599593 DOI: 10.1063/1.5074112] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 11/20/2018] [Indexed: 06/09/2023]
Abstract
A new high beam energy photoelectron-photofragment coincidence (PPC) spectrometer is described that allows acceleration of heavy anions (>100 amu) to energies in the tens of keV using a linear accelerator (LINAC). High beam energies result in more efficient detection of the neutral photofragments produced via dissociative photodetachment (DPD) of the parent anion and increase the mass range that can be studied with PPC spectroscopy. The novel experimental setup couples an electrospray ionization (ESI) source and a hexapole accumulation trap with a 10-stage LINAC to give a kinematically complete measurement of the dissociation dynamics for heavier anions. ESI dramatically increases the range of anions that can be studied by PPC spectroscopy to include multiply charged anions and larger, more complex molecular ions important in biological, atmospheric, and combustion processes. A radiofrequency buffer-gas-cooled hexapole trap is used to accumulate sufficient ion density for single-shot coincidence measurements and thermalize the anions to room temperature. The photoelectron and up to three neutral fragments resulting from DPD are recorded in coincidence using time and position sensitive detectors. This novel experimental setup is characterized by studying the photodetachment of I-, and the DPD of I 2 - and the oxalate anion C2O4H- at beam energies of 11 keV, 16 keV, and 21 keV.
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Affiliation(s)
- J A Gibbard
- Department of Chemistry and Biochemistry, University of California, 9500 Gilman Dr, La Jolla, San Diego, California 92093-0340, USA
| | - A J Shin
- Department of Chemistry and Biochemistry, University of California, 9500 Gilman Dr, La Jolla, San Diego, California 92093-0340, USA
| | - E Castracane
- Department of Chemistry and Biochemistry, University of California, 9500 Gilman Dr, La Jolla, San Diego, California 92093-0340, USA
| | - R E Continetti
- Department of Chemistry and Biochemistry, University of California, 9500 Gilman Dr, La Jolla, San Diego, California 92093-0340, USA
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22
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Parkes MA, Crellin J, Henley A, Fielding HH. A photoelectron imaging and quantum chemistry study of the deprotonated indole anion. Phys Chem Chem Phys 2018; 20:15543-15549. [PMID: 29808860 DOI: 10.1039/c8cp01902a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Indole is an important molecular motif in many biological molecules and exists in its deprotonated anionic form in the cyan fluorescent protein, an analogue of green fluorescent protein. However, the electronic structure of the deprotonated indole anion has been relatively unexplored. Here, we use a combination of anion photoelectron velocity-map imaging measurements and quantum chemistry calculations to probe the electronic structure of the deprotonated indole anion. We report vertical detachment energies (VDEs) of 2.45 ± 0.05 eV and 3.20 ± 0.05 eV, respectively. The value for D0 is in agreement with recent high-resolution measurements whereas the value for D1 is a new measurement. We find that the first electronically excited singlet state of the anion, S1(ππ*), lies above the VDE and has shape resonance character with respect to the D0 detachment continuum and Feshbach resonance character with respect to the D1 continuum.
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Affiliation(s)
- Michael A Parkes
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK.
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23
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Rogers JP, Anstöter CS, Verlet JRR. Evidence of Electron Capture of an Outgoing Photoelectron Wave by a Nonvalence State in (C 6F 6) n. J Phys Chem Lett 2018; 9:2504-2509. [PMID: 29694047 DOI: 10.1021/acs.jpclett.8b00739] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Frequency-resolved photoelectron spectra are presented for (C6F6) n- with n = 1-5 that show that C6F6- is solvated by neutral C6F6 molecules. Direct photodetachment channels of C6F6- are observed for all n, leaving the neutral in the S0 ground state or triplet states, T1 and T2. For n ≥ 2, an additional indirect electron loss channel is observed when the triplet-state channels open. This indirect emission appears to arise from the electron capture of the outgoing photoelectron s-wave by a neutral solvent molecule through an anion nonvalence state. The same process is not observed for the S0 detachment channel because the outgoing electron wave is predominantly a p-wave. Our results show that anion nonvalence states can act as electron-accepting states in cluster environments and can be viewed as precursor states for diffuse states of liquid C6F6.
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Affiliation(s)
- Joshua P Rogers
- Department of Chemistry , Durham University , Durham DH1 3LE , United Kingdom
| | - Cate S Anstöter
- Department of Chemistry , Durham University , Durham DH1 3LE , United Kingdom
| | - Jan R R Verlet
- Department of Chemistry , Durham University , Durham DH1 3LE , United Kingdom
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24
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Anstöter CS, Gartmann TE, Stanley LH, Bochenkova AV, Verlet JRR. Electronic structure of the para-dinitrobenzene radical anion: a combined 2D photoelectron imaging and computational study. Phys Chem Chem Phys 2018; 20:24019-24026. [DOI: 10.1039/c8cp04877k] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
2D photoelectron spectroscopy combined with high-level ab initio calculations provides insights into the dissociative electron attachment of para-dinitrobenzene.
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Affiliation(s)
- Cate S. Anstöter
- Department of Chemistry
- Durham University
- Durham DH1 3LE
- UK
- Department of Chemistry
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