1
|
Riedel R, Seel AG, Malko D, Miller DP, Sperling BT, Choi H, Headen TF, Zurek E, Porch A, Kucernak A, Pyper NC, Edwards PP, Barrett AGM. Superalkali-Alkalide Interactions and Ion Pairing in Low-Polarity Solvents. J Am Chem Soc 2021; 143:3934-3943. [PMID: 33660507 PMCID: PMC8028040 DOI: 10.1021/jacs.1c00115] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Indexed: 11/30/2022]
Abstract
The nature of anionic alkali metals in solution is traditionally thought to be "gaslike" and unperturbed. In contrast to this noninteracting picture, we present experimental and computational data herein that support ion pairing in alkalide solutions. Concentration dependent ionic conductivity, dielectric spectroscopy, and neutron scattering results are consistent with the presence of superalkali-alkalide ion pairs in solution, whose stability and properties have been further investigated by DFT calculations. Our temperature dependent alkali metal NMR measurements reveal that the dynamics of the alkalide species is both reversible and thermally activated suggesting a complicated exchange process for the ion paired species. The results of this study go beyond a picture of alkalides being a "gaslike" anion in solution and highlight the significance of the interaction of the alkalide with its complex countercation (superalkali).
Collapse
Affiliation(s)
- René Riedel
- Department
of Chemistry, Imperial College London, Molecular
Sciences Research Hub, White City Campus, Wood Lane, London W12
0BZ, U.K.
| | - Andrew G. Seel
- Department
of Physics and Astronomy, University College
London, Gower Street, London WC1E
6BT, U.K.
- Inorganic
Chemistry Laboratories, University of Oxford, Park Royal Road, Oxford OX1 3QR, U.K.
| | - Daniel Malko
- Department
of Chemistry, Imperial College London, Molecular
Sciences Research Hub, White City Campus, Wood Lane, London W12
0BZ, U.K.
| | - Daniel P. Miller
- Department
of Chemistry, Hofstra University, 106 Berliner Hall, Hempstead, New York 11549, United States
| | - Brendan T. Sperling
- Department
of Chemistry, Hofstra University, 106 Berliner Hall, Hempstead, New York 11549, United States
| | - Heungjae Choi
- School
of Engineering, Cardiff University, Cardiff CF24 3AA, U.K.
| | - Thomas F. Headen
- ISIS Neutron
and Muon Source, Science and Technology
Facilities Council, Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, U.K.
| | - Eva Zurek
- Department
of Chemistry, State University of New York
at Buffalo, 777 Natural Sciences Complex, Buffalo, New York 14260-3000, United States
| | - Adrian Porch
- School
of Engineering, Cardiff University, Cardiff CF24 3AA, U.K.
| | - Anthony Kucernak
- Department
of Chemistry, Imperial College London, Molecular
Sciences Research Hub, White City Campus, Wood Lane, London W12
0BZ, U.K.
| | - Nicholas C. Pyper
- University
Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, U.K.
| | - Peter P. Edwards
- Inorganic
Chemistry Laboratories, University of Oxford, Park Royal Road, Oxford OX1 3QR, U.K.
| | - Anthony G. M. Barrett
- Department
of Chemistry, Imperial College London, Molecular
Sciences Research Hub, White City Campus, Wood Lane, London W12
0BZ, U.K.
| |
Collapse
|
2
|
Koga M, Yoneda Y, Sotome H, Miyasaka H. Ionization dynamics of a phenylenediamine derivative in solutions as revealed by femtosecond simultaneous and stepwise two-photon excitation. Phys Chem Chem Phys 2019; 21:2889-2898. [PMID: 30451254 DOI: 10.1039/c8cp06530f] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Femtosecond transient absorption spectroscopy with off-resonant simultaneous and resonant stepwise two-photon excitation methods were applied to the direct observation of photoionization dynamics of a phenylenediamine derivative in n-hexane, ethanol and acetonitrile solutions. Upon the selective excitation of the solute via the off-resonant two-photon excitation to the energy level almost equivalent with the ionization potential in the gas phase, rapid appearance of the radical cation (within ca. 100-200 fs) was observed in polar and nonpolar solutions. On the other hand, in the case where the excited energy level from the ground state is 0.8 eV lower than the ionization potential in the gas phase, the radical cation appears only in polar solutions in sub-ps to ps time scales, indicating that the photoionization does not occur directly from the highly electronically excited state even in the polar solution. Comparison of the dynamics between ethanol and acetonitrile solutions strongly suggested that the solvation process of the precursor species leading to the ionization took a crucial role in the electron ejection process with lower energy in polar solutions.
Collapse
Affiliation(s)
- Masafumi Koga
- Division of Frontier Materials Science and Center for Advanced Interdisciplinary Research, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
| | | | | | | |
Collapse
|
3
|
Mak CC, Timerghazin QK, Peslherbe GH. Photoexcitation and Charge-Transfer-to-Solvent Relaxation Dynamics of the I–(CH3CN) Complex. J Phys Chem A 2013; 117:7595-605. [DOI: 10.1021/jp403586u] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Chun C. Mak
- Centre for
Research in Molecular Modeling (CERMM) and
Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, Canada
H4B 1R6
| | - Qadir K. Timerghazin
- Centre for
Research in Molecular Modeling (CERMM) and
Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, Canada
H4B 1R6
| | - Gilles H. Peslherbe
- Centre for
Research in Molecular Modeling (CERMM) and
Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, Canada
H4B 1R6
| |
Collapse
|
4
|
Fischer MK, Rossmadl H, Iglev H. Novel geminate recombination channel after indirect photoionization of water. J Chem Phys 2011; 134:214507. [PMID: 21663367 DOI: 10.1063/1.3597776] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We studied the photolysis of neat protonated and heavy water using pump-probe and pump-repump-probe spectroscopy. A novel recombination channel is reported leading to ultrafast quenching (0.7 ± 0.1 ps) of almost one third of the initial number of photo-generated electrons. The efficiency and the recombination rate of this channel are lower in heavy water, 27 ± 5% and (0.9 ± 0.1 ps)(-1), respectively. Comparison with similar data measured after photodetachment of aqueous hydroxide provides evidence for the formation of short-lived OH:e(-) (OD:e(-)) pairs after indirect photoionization of water at 9.2 eV.
Collapse
Affiliation(s)
- Martin K Fischer
- Physik-Department E 11, Technische Universität München, D-85748 Garching, Germany
| | | | | |
Collapse
|
5
|
Fischer MK, Gliserin A, Laubereau A, Iglev H. Ultrafast electron transfer processes studied by pump-repump-probe spectroscopy. JOURNAL OF BIOPHOTONICS 2011; 4:178-183. [PMID: 21287690 DOI: 10.1002/jbio.201000099] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Accepted: 10/07/2010] [Indexed: 05/30/2023]
Abstract
The photodetachment of Br(-), I(-) and OH(-) in aqueous solution is studied by 2- and 3-pulse femtosecond spectroscopy. The UV excitation leads to fast electron separation followed by formation of a donor-electron pairs. An additional repump pulse is used for secondary excitation of the intermediates. The 3-pulse technique allows distinguishing the pair-intermediate from the fully separated electron. Using this method we observe a novel geminate recombination channel of .OH with adjacent hydrated electrons. The process leads to an ultrafast quenching (0.7 ps) of almost half the initial number of radicals. The phenomenon is not observed in Br(-) and I(-). Our results demonstrate the potential of the 3-pulse spectroscopy to elucidate the mechanism of ultrafast ET reactions. Photodetachment of aqueous anions studied by two- and three pulse spectroscopy.
Collapse
Affiliation(s)
- Martin K Fischer
- Physics Department E11, Technical University Munich, Munich, Germany
| | | | | | | |
Collapse
|
6
|
Iglev H, Fischer MK, Gliserin A, Laubereau A. Ultrafast Geminate Recombination after Photodetachment of Aqueous Hydroxide. J Am Chem Soc 2010; 133:790-5. [DOI: 10.1021/ja103866s] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Hristo Iglev
- Physik-Department E11, Technische Universität München, D-85748 Garching, Germany
| | - Martin K. Fischer
- Physik-Department E11, Technische Universität München, D-85748 Garching, Germany
| | - Alexander Gliserin
- Physik-Department E11, Technische Universität München, D-85748 Garching, Germany
| | - Alfred Laubereau
- Physik-Department E11, Technische Universität München, D-85748 Garching, Germany
| |
Collapse
|
7
|
Glover WJ, Larsen RE, Schwartz BJ. First principles multielectron mixed quantum/classical simulations in the condensed phase. I. An efficient Fourier-grid method for solving the many-electron problem. J Chem Phys 2010; 132:144101. [DOI: 10.1063/1.3352564] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
8
|
Glover WJ, Larsen RE, Schwartz BJ. First principles multielectron mixed quantum/classical simulations in the condensed phase. II. The charge-transfer-to-solvent states of sodium anions in liquid tetrahydrofuran. J Chem Phys 2010; 132:144102. [DOI: 10.1063/1.3352565] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
9
|
Larsen MC, Schwartz BJ. Searching for solvent cavities via electron photodetachment: The ultrafast charge-transfer-to-solvent dynamics of sodide in a series of ether solvents. J Chem Phys 2009; 131:154506. [DOI: 10.1063/1.3245864] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
|
10
|
Maslennikova TP, Korytkova EN, Drozdova IA, Gusarov VV. Interaction of potassium chloride aqueous solution Mg3Si2O5(OH)4 with the nanotubes based on magnesium hydrosilicate. RUSS J APPL CHEM+ 2009. [DOI: 10.1134/s1070427209030021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
11
|
Fischer MK, Laubereau A, Iglev H. Femtosecond electron detachment of aqueous bromide studied by two and three pulse spectroscopy. Phys Chem Chem Phys 2009; 11:10939-44. [DOI: 10.1039/b913688f] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
12
|
Glover WJ, Larsen RE, Schwartz BJ. The roles of electronic exchange and correlation in charge-transfer-to-solvent dynamics: Many-electron nonadiabatic mixed quantum/classical simulations of photoexcited sodium anions in the condensed phase. J Chem Phys 2008; 129:164505. [DOI: 10.1063/1.2996350] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
13
|
Shoshanim O, Ruhman S. Na− photolysis in THF: Charge transfer to solvent studied from the donors perspective in <10fs detail. J Chem Phys 2008; 129:044502. [DOI: 10.1063/1.2946701] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
|
14
|
Affiliation(s)
- Xiyi Chen
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482;
| | - Stephen E. Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482;
| |
Collapse
|
15
|
Bragg AE, Schwartz BJ. The ultrafast charge-transfer-to-solvent dynamics of iodide in tetrahydrofuran. 1. Exploring the roles of solvent and solute electronic structure in condensed-phase charge-transfer reactions. J Phys Chem B 2007; 112:483-94. [PMID: 18085770 DOI: 10.1021/jp076934s] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Although they represent the simplest possible charge-transfer reactions, the charge-transfer-to-solvent (CTTS) dynamics of atomic anions exhibit considerable complexity. For example, the CTTS dynamics of iodide in water are very different from those of sodide (Na-) in tetrahydrofuran (THF), leading to the question of the relative importance of the solvent and solute electronic structures in controlling charge-transfer dynamics. In this work, we address this issue by investigating the CTTS spectroscopy and dynamics of I- in THF, allowing us to make detailed comparisons to the previously studied I-/H2O and Na-/THF CTTS systems. Since THF is weakly polar, ion pairing with the counterion can have a substantial impact on the CTTS spectroscopy and dynamics of I- in this solvent. In this study, we have isolated "counterion-free" I- in THF by complexing the Na+ counterion with 18-crown-6 ether. Ultrafast pump-probe experiments reveal that THF-solvated electrons (e-THF) appear 380 +/- 60 fs following the CTTS excitation of "free" I- in THF. The absorption kinetics are identical at all probe wavelengths, indicating that the ejected electrons appear with no significant dynamic solvation but rather with their equilibrium absorption spectrum. After their initial appearance, ejected electrons do not exhibit any additional dynamics on time scales up to approximately 1 ns, indicating that geminate recombination of e-THF with its iodine atom partner does not occur. Competitive electron scavenging measurements demonstrate that the CTTS excited state of I- in THF is quite large and has contact with scavengers that are several nanometers away from the iodide ion. The ejection time and lack of electron solvation observed for I- in THF are similar to what is observed following CTTS excitation of Na- in THF. However, the relatively slow ejection time, the complete lack of dynamic solvation, and the large ejection distance/lack of recombination dynamics are in marked contrast to the CTTS dynamics observed for I- in water, in which fast electron ejection, substantial solvation, and appreciable recombination have been observed. These differences in dynamical behavior can be understood in terms of the presence of preexisting, electropositive cavities in liquid THF that are a natural part of its liquid structure; these cavities provide a mechanism for excited electrons to relocate to places in the liquid that can be nanometers away, explaining the large ejection distance and lack of recombination following the CTTS excitation of I- in THF. We argue that the lack of dynamic solvation observed following CTTS excitation of both I- and Na- in THF is a direct consequence of the fact that little additional relaxation is required once an excited electron nonadiabatically relaxes into one of the preexisting cavities. In contrast, liquid water contains no such cavities, and CTTS excitation of I- in water leads to local electron ejection that involves substantial solvent reorganization.
Collapse
Affiliation(s)
- Arthur E Bragg
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, USA
| | | |
Collapse
|
16
|
Cavanagh MC, Larsen RE, Schwartz BJ. Watching Na Atoms Solvate into (Na+,e-) Contact Pairs: Untangling the Ultrafast Charge-Transfer-to-Solvent Dynamics of Na- in Tetrahydrofuran (THF). J Phys Chem A 2007; 111:5144-57. [PMID: 17523607 DOI: 10.1021/jp071132i] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
With the large dye molecules employed in typical studies of solvation dynamics, it is often difficult to separate the intramolecular relaxation of the dye from the relaxation associated with dynamic solvation. One way to avoid this difficulty is to study solvation dynamics using an atom as the solvation probe; because atoms have only electronic degrees of freedom, all of the observed spectroscopic dynamics must result from motions of the solvent. In this paper, we use ultrafast transient absorption spectroscopy to investigate the solvation dynamics of newly created sodium atoms that are formed following the charge transfer to solvent (CTTS) ejection of an electron from sodium anions (sodide) in liquid tetrahydrofuran (THF). Because the absorption spectra of the sodide reactant, the sodium atom, and the solvated electron products overlap, we first examined the dynamics of the ejected CTTS electron in the infrared to build a detailed model of the CTTS process that allowed us to subtract the spectroscopic contributions of the sodide bleach and the solvated electron and cleanly reveal the spectroscopy of the solvated atom. We find that the neutral sodium species created following CTTS excitation of sodide initially absorbs near 590 nm, the position of the gas-phase sodium D-line, suggesting that it only weakly interacts with the surrounding solvent. We then see a fast solvation process that causes a red-shift of the sodium atom's spectrum in approximately 230 fs, a time scale that matches well with the results of MD simulations of solvation dynamics in liquid THF. After the fast solvation is complete, the neutral sodium atoms undergo a chemical reaction that takes place in approximately 740 fs, as indicated by the observation of an isosbestic point and the creation of a species with a new spectrum. The spectrum of the species created after the reaction then red-shifts on a approximately 10-ps time scale to become the equilibrium spectrum of the THF-solvated sodium atom, which is known from radiation chemistry experiments to absorb near approximately 900 nm. There has been considerable debate as to whether this 900-nm absorbing species is better thought of as a solvated atom or a sodium cation:solvated electron contact pair, (Na+,e-). The fact that we observe the initially created neutral Na atom undergoing a chemical reaction to ultimately become the 900-nm absorbing species suggests that it is better assigned as (Na+,e-). The approximately 10-ps solvation time we observe for this species is an order of magnitude slower than any other solvation process previously observed in liquid THF, suggesting that this species interacts differently with the solvent than the large molecules that are typically used as solvation probes. Together, all of the results allow us to build the most detailed picture to date of the CTTS process of Na- in THF as well as to directly observe the solvation dynamics associated with single sodium atoms in solution.
Collapse
Affiliation(s)
- Molly C Cavanagh
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, USA
| | | | | |
Collapse
|
17
|
Bedard-Hearn MJ, Larsen RE, Schwartz BJ. Moving solvated electrons with light: Nonadiabatic mixed quantum/classical molecular dynamics simulations of the relocalization of photoexcited solvated electrons in tetrahydrofuran (THF). J Chem Phys 2006; 125:194509. [PMID: 17129125 DOI: 10.1063/1.2358131] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Motivated by recent ultrafast spectroscopic experiments [Martini et al., Science 293, 462 (2001)], which suggest that photoexcited solvated electrons in tetrahydrofuran (THF) can relocalize (that is, return to equilibrium in solvent cavities far from where they started), we performed a series of nonequilibrium, nonadiabatic, mixed quantum/classical molecular dynamics simulations that mimic one-photon excitation of the THF-solvated electron. We find that as photoexcited THF-solvated electrons relax to their ground states either by continuous mixing from the excited state or via nonadiabatic transitions, approximately 30% of them relocalize into cavities that can be over 1 nm away from where they originated, in close agreement with the experiments. A detailed investigation shows that the ability of excited THF-solvated electrons to undergo photoinduced relocalization stems from the existence of preexisting cavity traps that are an intrinsic part of the structure of liquid THF. This explains why solvated electrons can undergo photoinduced relocalization in solvents like THF but not in solvents like water, which lack the preexisting traps necessary to stabilize the excited electron in other places in the fluid. We also find that even when they do not ultimately relocalize, photoexcited solvated electrons in THF temporarily visit other sites in the fluid, explaining why the photoexcitation of THF-solvated electrons is so efficient at promoting recombination with nearby scavengers. Overall, our study shows that the defining characteristic of a liquid that permits the photoassisted relocalization of solvated electrons is the existence of nascent cavities that are attractive to an excess electron; we propose that other such liquids can be found from classical computer simulations or neutron diffraction experiments.
Collapse
Affiliation(s)
- Michael J Bedard-Hearn
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, USA
| | | | | |
Collapse
|
18
|
Smallwood CJ, Mejia CN, Glover WJ, Larsen RE, Schwartz BJ. A computationally efficient exact pseudopotential method. II. Application to the molecular pseudopotential of an excess electron interacting with tetrahydrofuran (THF). J Chem Phys 2006; 125:074103. [PMID: 16942318 DOI: 10.1063/1.2218835] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
In the preceding paper, we presented an analytic reformulation of the Phillips-Kleinman (PK) pseudopotential theory. In the PK theory, the number of explicitly treated electronic degrees of freedom in a multielectron problem is reduced by forcing the wave functions of the few electrons of interest (the valence electrons) to be orthogonal to those of the remaining electrons (the core electrons); this results in a new Schrodinger equation for the valence electrons in which the effects of the core electrons are treated implicitly via an extra term known as the pseudopotential. Although this pseudopotential must be evaluated iteratively, our reformulation of the theory allows the exact pseudopotential to be found without ever having to evaluate the potential energy operator, providing enormous computational savings. In this paper, we present a detailed computational procedure for implementing our reformulation of the PK theory, and we illustrate our procedure on the largest system for which an exact pseudopotential has been calculated, that of an excess electron interacting with a tetrahyrdrofuran (THF) molecule. We discuss the numerical stability of several approaches to the iterative solution for the pseudopotential, and find that once the core wave functions are available, the full e(-)-THF pseudopotential can be calculated in less than 3 s on a relatively modest single processor. We also comment on how the choice of basis set affects the calculated pseudopotential, and provide a prescription for correcting unphysical behavior that arises at long distances if a localized Gaussian basis set is used. Finally, we discuss the effective e(-)-THF potential in detail, and present a multisite analytic fit of the potential that is suitable for use in molecular simulation.
Collapse
Affiliation(s)
- C Jay Smallwood
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, USA
| | | | | | | | | |
Collapse
|
19
|
Shoshana O, Pérez Lustres JL, Ernsting NP, Ruhman S. Mapping CTTS dynamics of Na−in tetrahydrofurane with ultrafast multichannel pump–probe spectroscopy. Phys Chem Chem Phys 2006; 8:2599-609. [PMID: 16738713 DOI: 10.1039/b602933g] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using multichannel femtosecond spectroscopy we have followed Na- charge transfer to solvent (CTTS) dynamics in THF solution. Absorption of the primary photoproducts in the visible, resolved here for the first time, consists of an asymmetric triplet centered at 595 nm, which we assign to a metastable incompletely solvated neutral atomic sodium species. Decay of this feature within approximately 1 ps to a broad and structureless solvated neutral is accompanied by broadening and loss of spectral detail. Kinetic analysis shows that both the spectral structure and the decay of this band are independent of the excitation photon frequency in the range 400-800 nm. With different pump-probe polarizations the anisotropy in transient transmission has been charted and its variation with excitation wavelength surveyed. The anisotropies are assigned to the reactant bleach, indicating that due to solvent-induced symmetry breaking, the CTTS absorption band of Na- is made up of discreet orthogonally polarized sub bands. None of the anisotropy in transient absorption could be associated with the photoproduct triplet band even at the earliest measurable time delays. Along with the documented differences in the spatial distribution of ejected electrons across the tested excitation wavelength range, these results lead us to conclude that photoejection is extremely rapid, and that loss of correlations between the departing electron and its neutral core is faster than our time resolution of approximately 60 fs.
Collapse
Affiliation(s)
- O Shoshana
- Department of Physical Chemistry, and the Farkas Center for Light Induced Processes, the Hebrew University, Jerusalem, 91904, Israel.
| | | | | | | |
Collapse
|
20
|
Cavity size effects on charge-transfer-to-solvent precursor excited states of internal halide water clusters X−(H2O)6. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2004.09.138] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
21
|
Sauer MC, Shkrob IA, Lian R, Crowell RA, Bartels DM, Chen X, Suffern D, Bradforth SE. Electron Photodetachment from Aqueous Anions. 2. Ionic Strength Effect on Geminate Recombination Dynamics and Quantum Yield for Hydrated Electron. J Phys Chem A 2004. [DOI: 10.1021/jp047435j] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
|
22
|
Geminate recombination dynamics studied via electron reexcitation: kinetic analysis for anion CTTS photosystems. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2004.07.094] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
23
|
Crowell RA, Lian R, Shkrob IA, Bartels DM, Chen X, Bradforth SE. Ultrafast dynamics for electron photodetachment from aqueous hydroxide. J Chem Phys 2004; 120:11712-25. [PMID: 15268207 DOI: 10.1063/1.1739213] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Charge-transfer-to-solvent reactions of hydroxide induced by 200 nm monophotonic or 337 and 389 nm biphotonic excitation of this anion in aqueous solution have been studied by means of pump-probe ultrafast laser spectroscopy. Transient absorption kinetics of the hydrated electron, e(aq) (-), have been observed, from a few hundred femtoseconds out to 600 ps, and studied as function of hydroxide concentration and temperature. The geminate decay kinetics are bimodal, with a fast exponential component ( approximately 13 ps) and a slower power "tail" due to the diffusional escape of the electrons. For the biphotonic excitation, the extrapolated fraction of escaped electrons is 1.8 times higher than for the monophotonic 200 nm excitation (31% versus 17.5% at 25 degrees C, respectively), due to the broadening of the electron distribution. The biphotonic electron detachment is very inefficient; the corresponding absorption coefficient at 400 nm is <4 cm TW(-1) M(-1) (assuming unity quantum efficiency for the photodetachment). For [OH(-)] between 10 mM and 10 M, almost no concentration dependence of the time profiles of solvated electron kinetics was observed. At higher temperature, the escape fraction of the electrons increases with a slope of 3x10(-3) K(-1) and the recombination and diffusion-controlled dissociation of the close pairs become faster. Activation energies of 8.3 and 22.3 kJ/mol for these two processes were obtained. The semianalytical theory of Shushin for diffusion controlled reactions in the central force field was used to model the geminate dynamics. The implications of these results for photoionization of water are discussed.
Collapse
Affiliation(s)
- Robert A Crowell
- Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
| | | | | | | | | | | |
Collapse
|
24
|
Sauer MC, Crowell RA, Shkrob IA. Electron Photodetachment from Aqueous Anions. 1. Quantum Yields for Generation of Hydrated Electron by 193 and 248 nm Laser Photoexcitation of Miscellaneous Inorganic Anions. J Phys Chem A 2004. [DOI: 10.1021/jp049722t] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Myran C. Sauer
- Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - Robert A. Crowell
- Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - Ilya A. Shkrob
- Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439
| |
Collapse
|
25
|
Martini IB, Schwartz BJ. Elucidating the initial dynamics of electron photodetachment from atoms in liquids using variably-time-delayed resonant multiphoton ionization. J Chem Phys 2004; 121:374-9. [PMID: 15260556 DOI: 10.1063/1.1756874] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
We study the photodetachment of electrons from sodium anions in room temperature liquid tetrahydrofuran (THF) using a new type of three-pulse pump-probe spectroscopy. Our experiments use two variably-time-delayed pulses for excitation in what is essentially a resonant 1+1 two-photon ionization: By varying the arrival time of the second excitation pulse, we can directly observe how solvent motions stabilize and trap the excited electron prior to electron detachment. Moreover, by varying the arrival times of the ionization (excitation) and probe pulses, we also can determine the fate of the photoionized electrons and the distance they are ejected from their parent Na atoms. We find that as solvent reorganization proceeds, the second excitation pulse becomes less effective at achieving photoionization, and that the solvent motions that stabilize the excited electron following the first excitation pulse occur over a time of approximately 450 fs. We also find that there is no spectroscopic evidence for significant solvent relaxation after detachment of the electron is complete. In combination with the results of previous experiments and molecular dynamics simulations, the data provide new insight into the role of the solvent in solution-phase electron detachment and charge-transfer-to-solvent reactions.
Collapse
Affiliation(s)
- Ignacio B Martini
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095-1569, USA
| | | |
Collapse
|
26
|
Bedard-Hearn MJ, Larsen RE, Schwartz BJ. Understanding Nonequilibrium Solute and Solvent Motions through Molecular Projections: Computer Simulations of Solvation Dynamics in Liquid Tetrahydrofuran (THF). J Phys Chem B 2003. [DOI: 10.1021/jp035846e] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Michael J. Bedard-Hearn
- Department of Chemistry and Biochemistry, University of California, Los Angeles California, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569
| | - Ross E. Larsen
- Department of Chemistry and Biochemistry, University of California, Los Angeles California, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569
| | - Benjamin J. Schwartz
- Department of Chemistry and Biochemistry, University of California, Los Angeles California, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569
| |
Collapse
|
27
|
Barthel ER, Schwartz BJ. Mapping out the conduction band under CTTS transitions: the photodetachment quantum yield of sodide (Na−) in tetrahydrofuran. Chem Phys Lett 2003. [DOI: 10.1016/s0009-2614(03)00922-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
28
|
Bedard-Hearn MJ, Larsen RE, Schwartz BJ. Hidden Breakdown of Linear Response: Projections of Molecular Motions in Nonequilibrium Simulations of Solvation Dynamics. J Phys Chem A 2003. [DOI: 10.1021/jp034383+] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
29
|
Wang Z, Shoshana O, Hou B, Ruhman S. Solvent Induced Symmetry Breaking and Relaxation Following Charge Transfer to Solvent Excitation of Na- in Tetrahydrofuran. J Phys Chem A 2003. [DOI: 10.1021/jp014331p] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Zhaohui Wang
- Department of Physical Chemistry, and the Farkas Center for Light Induced Processes, the Hebrew University, Jerusalem 91904, Israel
| | - Ofir Shoshana
- Department of Physical Chemistry, and the Farkas Center for Light Induced Processes, the Hebrew University, Jerusalem 91904, Israel
| | - Bixue Hou
- Department of Physical Chemistry, and the Farkas Center for Light Induced Processes, the Hebrew University, Jerusalem 91904, Israel
| | - Sanford Ruhman
- Department of Physical Chemistry, and the Farkas Center for Light Induced Processes, the Hebrew University, Jerusalem 91904, Israel
| |
Collapse
|