1
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Ončák M, Siu C, van der Linde C, Kit Tang W, Beyer MK. Thermally Activated vs. Photochemical Hydrogen Evolution Reactions-A Tale of Three Metals. Chemistry 2023; 29:e202203590. [PMID: 36729049 PMCID: PMC10962578 DOI: 10.1002/chem.202203590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 01/18/2023] [Accepted: 02/02/2023] [Indexed: 02/03/2023]
Abstract
Molecular processes behind hydrogen evolution reactions can be quite complex. In macroscopic electrochemical cells, it is extremely difficult to elucidate and understand their mechanism. Gas phase models, consisting of a metal ion and a small number of water molecules, provide unique opportunities to understand the reaction pathways in great detail. Hydrogen evolution in clusters consisting of a singly charged metal ion and one to on the order of 50 water molecules has been studied extensively for magnesium, aluminum and vanadium. Such clusters with around 10-20 water molecules are known to eliminate atomic or molecular hydrogen upon mild activation by room temperature black-body radiation. Irradiation with ultraviolet light, by contrast, enables hydrogen evolution already with a single water molecule. Here, we analyze and compare the reaction mechanisms for hydrogen evolution on the ground state as well as excited state potential energy surfaces. Five distinct mechanisms for evolution of atomic or molecular hydrogen are identified and characterized.
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Affiliation(s)
- Milan Ončák
- Universität InnsbruckInstitut für Ionenphysik und Angewandte PhysikTechnikerstraße 256020InnsbruckAustria
| | - Chi‐Kit Siu
- Department of ChemistryCity University of Hong Kong83 Tat Chee Avenue, Kowloon TongHong Kong SARP. R. China
| | - Christian van der Linde
- Universität InnsbruckInstitut für Ionenphysik und Angewandte PhysikTechnikerstraße 256020InnsbruckAustria
| | - Wai Kit Tang
- Institute of Research Management and Services (IPPP) Research and Innovation Management ComplexUniversity of MalayaKuala Lumpur50603Malaysia
| | - Martin K. Beyer
- Universität InnsbruckInstitut für Ionenphysik und Angewandte PhysikTechnikerstraße 256020InnsbruckAustria
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2
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Heller J, Pascher TF, van der Linde C, Ončák M, Beyer MK. Photochemical Hydrogen Evolution at Metal Centers Probed with Hydrated Aluminium Cations, Al + (H 2 O) n , n=1-10. Chemistry 2021; 27:16367-16376. [PMID: 34636449 PMCID: PMC9298212 DOI: 10.1002/chem.202103289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Indexed: 11/24/2022]
Abstract
Hydrated aluminium cations have been investigated as a photochemical model system with up to ten water molecules by UV action spectroscopy in a Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometer. Intense photodissociation was observed starting at 4.5 eV for two to eight water molecules with loss of atomic hydrogen, molecular hydrogen and water molecules. Quantum chemical calculations for n=2 reveal that solvation shifts the intense 3s–3p excitations of Al+ into the investigated photon energy range below 5.5 eV. During the photochemical relaxation, internal conversion from S1 to T2 takes place, and photochemical hydrogen formation starts on the T2 surface, which passes through a conical intersection, changing to T1. On this triplet surface, the electron that was excited to the Al 3p orbital is transferred to a coordinated water molecule, which dissociates into a hydroxide ion and a hydrogen atom. If the system remains in the triplet state, this hydrogen radical is lost directly. If the system returns to singlet multiplicity, the reaction may be reversed, with recombination with the hydroxide moiety and electron transfer back to aluminium, resulting in water evaporation. Alternatively, the hydrogen radical can attack the intact water molecule, forming molecular hydrogen and aluminium dihydroxide. Photodissociation is observed for up to n=8. Clusters with n=9 or 10 occur exclusively as HAlOH+(H2O)n‐1 and are transparent in the investigated energy range. For n=4–8, a mixture of Al+(H2O)n and HAlOH+(H2O)n‐1 is present in the experiment.
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Affiliation(s)
- Jakob Heller
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020, Innsbruck, Austria
| | - Tobias F Pascher
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020, Innsbruck, Austria
| | - Christian van der Linde
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020, Innsbruck, Austria
| | - Milan Ončák
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020, Innsbruck, Austria
| | - Martin K Beyer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020, Innsbruck, Austria
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3
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Heller J, Pascher TF, Muß D, van der Linde C, Beyer MK, Ončák M. Photochemistry and UV/vis spectroscopy of hydrated vanadium cations, V +(H 2O) n, n = 1-41, a model system for photochemical hydrogen evolution. Phys Chem Chem Phys 2021; 23:22251-22262. [PMID: 34396372 PMCID: PMC8514045 DOI: 10.1039/d1cp02382a] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 08/06/2021] [Indexed: 12/18/2022]
Abstract
Photochemical hydrogen evolution provides fascinating perspectives for light harvesting. Hydrated metal ions in the gas phase are ideal model systems to study elementary steps of this reaction on a molecular level. Here we investigate mass-selected hydrated monovalent vanadium ions, with a hydration shell ranging from 1 to 41 water molecules, by photodissociation spectroscopy. The most intense absorption bands correspond to 3d-4p transitions, which shift to the red from n = 1 to n = 4, corresponding to the evolution of a square-planar complex. Additional water molecules no longer interact directly with the metal center, and no strong systematic shift is observed in larger clusters. Evolution of atomic and molecular hydrogen competes with loss of water molecules for all V+(H2O)n, n ≤ 12. For n ≥ 15, no absorptions are observed, which indicates that the cluster ensemble is fully converted to HVOH+(H2O)n-1. For the smallest clusters, the electronic transitions are modeled using multireference methods with spin-orbit coupling. A large number of quintet and triplet states is accessible, which explains the broad features observed in the experiment. Water loss most likely occurs after a series of intersystem crossings and internal conversions to the electronic ground state or a low-lying quintet state, while hydrogen evolution is favored in low lying triplet states.
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Affiliation(s)
- Jakob Heller
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
| | - Tobias F Pascher
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
| | - Dominik Muß
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
| | - Christian van der Linde
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
| | - Martin K Beyer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
| | - Milan Ončák
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
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4
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Rittgers BM, Leicht D, Duncan MA. Cation-π Complexes of Silver Studied with Photodissociation and Velocity-Map Imaging. J Phys Chem A 2020; 124:9166-9176. [PMID: 33103909 DOI: 10.1021/acs.jpca.0c08498] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Ag+(aromatic) ion-molecule complexes of benzene, toluene, or furan are generated in the gas phase by laser vaporization in a supersonic expansion. These ions are mass selected in a time-of-flight spectrometer and studied with ultraviolet laser photodissociation and photofragment imaging. UV laser excitation results in dissociative charge transfer (DCT) for these ions, producing neutral silver atom and the respective aromatic cation as the photofragments. Velocity-map imaging and slice imaging techniques are employed to investigate the kinetic energy release in these photodissociation processes. In each case, DCT produces significant kinetic energy, and evidence is also found for excitation of the internal rovibrational degrees of freedom for the molecular cations. Analysis of the kinetic energy release together with the known ionization energies of silver and the molecular ligands provides new information on the cation-π bond energies.
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Affiliation(s)
- Brandon M Rittgers
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Daniel Leicht
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Michael A Duncan
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
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5
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Barwa E, Pascher TF, Ončák M, Linde C, Beyer MK. Aktivierung von Kohlenstoffdioxid an Metallzentren: Entwicklung des Ladungstransfers von Mg
.+
auf CO
2
in [MgCO
2
(H
2
O)
n
]
.+
,
n=
0–8. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202001292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Erik Barwa
- Institut für Ionenphysik und Angewandte PhysikUniversität Innsbruck Technikerstraße 25 6020 Innsbruck Österreich
| | - Tobias F. Pascher
- Institut für Ionenphysik und Angewandte PhysikUniversität Innsbruck Technikerstraße 25 6020 Innsbruck Österreich
| | - Milan Ončák
- Institut für Ionenphysik und Angewandte PhysikUniversität Innsbruck Technikerstraße 25 6020 Innsbruck Österreich
| | - Christian Linde
- Institut für Ionenphysik und Angewandte PhysikUniversität Innsbruck Technikerstraße 25 6020 Innsbruck Österreich
| | - Martin K. Beyer
- Institut für Ionenphysik und Angewandte PhysikUniversität Innsbruck Technikerstraße 25 6020 Innsbruck Österreich
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6
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Barwa E, Pascher TF, Ončák M, van der Linde C, Beyer MK. Carbon Dioxide Activation at Metal Centers: Evolution of Charge Transfer from Mg .+ to CO 2 in [MgCO 2 (H 2 O) n ] .+ , n=0-8. Angew Chem Int Ed Engl 2020; 59:7467-7471. [PMID: 32100953 PMCID: PMC7217156 DOI: 10.1002/anie.202001292] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Indexed: 11/06/2022]
Abstract
We investigate activation of carbon dioxide by singly charged hydrated magnesium cations Mg .+(H2O)n, through infrared multiple photon dissociation (IRMPD) spectroscopy combined with quantum chemical calculations. The spectra of [MgCO2(H2O)n].+ in the 1250–4000 cm−1 region show a sharp transition from n=2 to n=3 for the position of the CO2 antisymmetric stretching mode. This is evidence for the activation of CO2 via charge transfer from Mg .+ to CO2 for n≥3, while smaller clusters feature linear CO2 coordinated end‐on to the metal center. Starting with n=5, we see a further conformational change, with CO2.− coordination to Mg2+ gradually shifting from bidentate to monodentate, consistent with preferential hexa‐coordination of Mg2+. Our results reveal in detail how hydration promotes CO2 activation by charge transfer at metal centers.
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Affiliation(s)
- Erik Barwa
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020, Innsbruck, Austria
| | - Tobias F Pascher
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020, Innsbruck, Austria
| | - Milan Ončák
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020, Innsbruck, Austria
| | - Christian van der Linde
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020, Innsbruck, Austria
| | - Martin K Beyer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020, Innsbruck, Austria
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7
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Ariyarathna IR, Pawłowski F, Ortiz JV, Miliordos E. Aufbau Principle for Diffuse Electrons of Double-Shell Metal Ammonia Complexes: The Case of M(NH3)4@12NH3, M = Li, Be+, B2+. J Phys Chem A 2019; 124:505-512. [DOI: 10.1021/acs.jpca.9b07734] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Isuru R. Ariyarathna
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, United States
| | - Filip Pawłowski
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, United States
| | - Joseph Vincent Ortiz
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, United States
| | - Evangelos Miliordos
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, United States
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8
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Duale K, Stace AJ. The Solvation of Ca 2+ with Gas Phase Clusters of Alcohol Molecules. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:1768-1778. [PMID: 31286446 PMCID: PMC6695372 DOI: 10.1007/s13361-019-02263-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 05/10/2019] [Accepted: 05/29/2019] [Indexed: 06/09/2023]
Abstract
A comprehensive examination of how the identity of an alcohol molecule can change the behavior of a solvated, alkaline earth dication has been undertaken. The metal dication of Ca2+ has been clustered with a range of different alcohols to form [Ca(ROH)n]2+ complexes, where n lies in the range 2-20. Following collisional activation via electron capture from nitrogen gas, complexes for n in the range 2-6 exhibit a switch in reaction product as a function of n. For low values, solvated CaOH+ is the dominant fragment, but as n increases beyond 4, this is displaced by the appearance of solvated CaOR+. A separate study of unimolecular metastable decay by [Ca(ROH)n]2+ complexes found evidence of charge separation to form CaOH+(ROH)n-1 + R+. For two isomers of butanol, the n = 3 complexes were found to follow parallel, but different metastable pathways: one leading to the appearance of CaOH+ and another that resulted in proton abstraction to form ROH2+. These differences have been attributed to the precursor complexes adopting geometries where one ROH molecule occupies a secondary solvation shell. Comparisons were made with a previous study of magnesium complexes; [Mg(ROH)n]2+ show that the difference in second ionization energy Mg+ (15.09 eV) as opposed to Ca+ (11.88 eV) influences behavior. A complex between Ca2+ and 1-chloroethanol is shown to favor the formation of CaCl+ as opposed to CaOH+ as a unimolecular charge separation product, which is attributed to differences in bond energy in the precursor molecule.
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Affiliation(s)
- Khadar Duale
- School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7, 2RD, UK
- School of Biology, Chemistry and Forensic Science, Faculty of Science and Engineering, University of Wolverhampton, Wolverhampton, WV1 1SB, UK
| | - Anthony J Stace
- School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7, 2RD, UK.
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9
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Taxer T, Ončák M, Barwa E, van der Linde C, Beyer MK. Electronic spectroscopy and nanocalorimetry of hydrated magnesium ions [Mg(H 2O) n] +, n = 20-70: spontaneous formation of a hydrated electron? Faraday Discuss 2019; 217:584-600. [PMID: 30994636 PMCID: PMC6677030 DOI: 10.1039/c8fd00204e] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 12/07/2018] [Indexed: 11/26/2022]
Abstract
Hydrated singly charged magnesium ions [Mg(H2O)n]+ are thought to consist of an Mg2+ ion and a hydrated electron for n > 15. This idea is based on mass spectra, which exhibit a transition from [MgOH(H2O)n-1]+ to [Mg(H2O)n]+ around n = 15-22, black-body infrared radiative dissociation, and quantum chemical calculations. Here, we present photodissociation spectra of size-selected [Mg(H2O)n]+ in the range of n = 20-70 measured for photon energies of 1.0-5.0 eV. The spectra exhibit a broad absorption from 1.4 to 3.2 eV, with two local maxima around 1.7-1.8 eV and 2.1-2.5 eV, depending on cluster size. The spectra shift slowly from n = 20 to n = 50, but no significant change is observed for n = 50-70. Quantum chemical modeling of the spectra yields several candidates for the observed absorptions, including five- and six-fold coordinated Mg2+ with a hydrated electron in its immediate vicinity, as well as a solvent-separated Mg2+/e- pair. The photochemical behavior resembles that of the hydrated electron, with barrierless interconversion into the ground state following the excitation.
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Affiliation(s)
- Thomas Taxer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
| | - Milan Ončák
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
| | - Erik Barwa
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
| | - Christian van der Linde
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
| | - Martin K Beyer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
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10
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Hattab A, Dhaouadi Z, Malloum A, Fifen JJ, Lahmar S, Russo N, Sicilia E. Structures, binding energies, temperature effects, infrared spectroscopy of [
Mg
(
NH
3
)
n
= 1−10
]
+
clusters from DFT and MP2 investigations. J Comput Chem 2019; 40:1707-1717. [DOI: 10.1002/jcc.25825] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 02/04/2019] [Accepted: 02/06/2019] [Indexed: 11/07/2022]
Affiliation(s)
- Awatef Hattab
- Laboratoire de Spectroscopie Atomique Moléculaire et Applications, Faculté des Sciences de TunisUniversité de Tunis El Manar, Campus Universitaire 1060, Tunis Tunisie
- Faculté des Sciences de BizerteUniversité de Carthage 7023, Zarzouna Bizerte Tunisie
| | - Zoubeida Dhaouadi
- Laboratoire de Spectroscopie Atomique Moléculaire et Applications, Faculté des Sciences de TunisUniversité de Tunis El Manar, Campus Universitaire 1060, Tunis Tunisie
- Faculté des Sciences de BizerteUniversité de Carthage 7023, Zarzouna Bizerte Tunisie
| | - Alhadji Malloum
- Department of Physics, Faculty of ScienceThe University of Ngaoundere, 454, Ngaoundere Cameroon
| | - Jean Jules Fifen
- Department of Physics, Faculty of ScienceThe University of Ngaoundere, 454, Ngaoundere Cameroon
| | - Souad Lahmar
- Laboratoire de Spectroscopie Atomique Moléculaire et Applications, Faculté des Sciences de TunisUniversité de Tunis El Manar, Campus Universitaire 1060, Tunis Tunisie
| | - Nino Russo
- Dipartimento di Chimica e Tecnologie ChimicheUniversitá della Calabria, Vi P. Bucci 87036 Rende (CS) Italia
| | - Emilia Sicilia
- Dipartimento di Chimica e Tecnologie ChimicheUniversitá della Calabria, Vi P. Bucci 87036 Rende (CS) Italia
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11
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Barwa E, Ončák M, Pascher TF, Taxer T, van der Linde C, Beyer MK. CO 2/O 2 Exchange in Magnesium-Water Clusters Mg +(H 2O) n. J Phys Chem A 2019; 123:73-81. [PMID: 30516989 PMCID: PMC6331139 DOI: 10.1021/acs.jpca.8b10530] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 12/03/2018] [Indexed: 11/30/2022]
Abstract
Hydrated singly charged metal ions doped with carbon dioxide, Mg2+(CO2)-(H2O) n, in the gas phase are valuable model systems for the electrochemical activation of CO2. Here, we study these systems by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry combined with ab initio calculations. We show that the exchange reaction of CO2 with O2 proceeds fast with bare Mg+(CO2), with a rate coefficient kabs = 1.2 × 10-10 cm3 s-1, while hydrated species exhibit a lower rate in the range of kabs = (1.2-2.4) × 10-11 cm3 s-1 for this strongly exothermic reaction. Water makes the exchange reaction more exothermic but, at the same time, considerably slower. The results are rationalized with a need for proper orientation of the reactants in the hydrated system, with formation of a Mg2+(CO4)-(H2O) n intermediate while the activation energy is negligible. According to our nanocalorimetric analysis, the exchange reaction of the hydrated ion is exothermic by -1.7 ± 0.5 eV, in agreement with quantum chemical calculations.
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Affiliation(s)
- Erik Barwa
- Institut für Ionenphysik
und Angewandte Physik, Universität
Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Milan Ončák
- Institut für Ionenphysik
und Angewandte Physik, Universität
Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Tobias F. Pascher
- Institut für Ionenphysik
und Angewandte Physik, Universität
Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Thomas Taxer
- Institut für Ionenphysik
und Angewandte Physik, Universität
Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Christian van der Linde
- Institut für Ionenphysik
und Angewandte Physik, Universität
Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Martin K. Beyer
- Institut für Ionenphysik
und Angewandte Physik, Universität
Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
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12
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Ariyarathna IR, Miliordos E. Superatomic nature of alkaline earth metal–water complexes: the cases of Be(H2O)0,+4 and Mg(H2O)0,+6. Phys Chem Chem Phys 2019; 21:15861-15870. [DOI: 10.1039/c9cp01897b] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Beryllium– and magnesium–water complexes are shown to accommodate peripheral electrons around their Be2+(H2O)4 and Mg2+(H2O)6 cores in hydrogenic type orbitals.
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13
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Ončák M, Taxer T, Barwa E, van der Linde C, Beyer MK. Photochemistry and spectroscopy of small hydrated magnesium clusters Mg +(H 2O) n, n = 1-5. J Chem Phys 2018; 149:044309. [PMID: 30068190 PMCID: PMC7075709 DOI: 10.1063/1.5037401] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Hydrated singly charged magnesium ions Mg+(H2O)n, n ≤ 5, in the gas phase are ideal model systems to study photochemical hydrogen evolution since atomic hydrogen is formed over a wide range of wavelengths, with a strong cluster size dependence. Mass selected clusters are stored in the cell of an Fourier transform ion cyclotron resonance mass spectrometer at a temperature of 130 K for several seconds, which allows thermal equilibration via blackbody radiation. Tunable laser light is used for photodissociation. Strong transitions to D1–3 states (correlating with the 3s-3px,y,z transitions of Mg+) are observed for all cluster sizes, as well as a second absorption band at 4–5 eV for n = 3-5. Due to the lifted degeneracy of the 3px,y,z energy levels of Mg+, the absorptions are broad and red shifted with increasing coordination number of the Mg+ center, from 4.5 eV for n = 1 to 1.8 eV for n = 5. In all cases, H atom formation is the dominant photochemical reaction channel. Quantum chemical calculations using the full range of methods for excited state calculations reproduce the experimental spectra and explain all observed features. In particular, they show that H atom formation occurs in excited states, where the potential energy surface becomes repulsive along the O⋅⋅⋅H coordinate at relatively small distances. The loss of H2O, although thermochemically favorable, is a minor channel because, at least for the clusters n = 1-3, the conical intersection through which the system could relax to the electronic ground state is too high in energy. In some absorption bands, sequential absorption of multiple photons is required for photodissociation. For n = 1, these multiphoton spectra can be modeled on the basis of quantum chemical calculations.
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Affiliation(s)
- Milan Ončák
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Thomas Taxer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Erik Barwa
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Christian van der Linde
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Martin K Beyer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
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14
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Feng G, Liu CW, Zeng Z, Hou GL, Xu HG, Zheng WJ. Initial hydration processes of magnesium chloride: size-selected anion photoelectron spectroscopy and ab initio calculations. Phys Chem Chem Phys 2017; 19:15562-15569. [DOI: 10.1039/c7cp02965a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Separation of Cl−–Mg2+ ion pairs starts at n = 4 in MgCl2(H2O)n− anions and at n = 7 in neutral MgCl2(H2O)n.
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Affiliation(s)
- Gang Feng
- Beijing National Laboratory for Molecular Sciences
- State Key Laboratory of Molecular Reaction Dynamics
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing 100190
| | - Cheng-Wen Liu
- Beijing National Laboratory for Molecular Sciences
- College of Chemistry and Molecular Engineering
- Peking University
- Beijing 100871
- China
| | - Zhen Zeng
- Beijing National Laboratory for Molecular Sciences
- State Key Laboratory of Molecular Reaction Dynamics
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing 100190
| | - Gao-Lei Hou
- Beijing National Laboratory for Molecular Sciences
- State Key Laboratory of Molecular Reaction Dynamics
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing 100190
| | - Hong-Guang Xu
- Beijing National Laboratory for Molecular Sciences
- State Key Laboratory of Molecular Reaction Dynamics
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing 100190
| | - Wei-Jun Zheng
- Beijing National Laboratory for Molecular Sciences
- State Key Laboratory of Molecular Reaction Dynamics
- Institute of Chemistry
- Chinese Academy of Sciences
- Beijing 100190
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15
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Lam TW, Zhang H, Siu CK. Reductions of oxygen, carbon dioxide, and acetonitrile by the magnesium(II)/magnesium(I) couple in aqueous media: theoretical insights from a nano-sized water droplet. J Phys Chem A 2015; 119:2780-92. [PMID: 25738586 DOI: 10.1021/jp511490n] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Reductions of O2, CO2, and CH3CN by the half-reaction of the Mg(II)/Mg(I) couple (Mg(2+) + e(-) → Mg(+•)) confined in a nanosized water droplet ([Mg(H2O)16](•+)) have been examined theoretically by means of density functional theory based molecular dynamics methods. The present works have revealed many intriguing aspects of the reaction dynamics of the water clusters within several picoseconds or even in subpicoseconds. The reduction of O2 requires an overall doublet spin state of the system. The reductions of CO2 and CH3CN are facilitated by their bending vibrations and the electron-transfer processes complete within 0.5 ps. For all reactions studied, the radical anions, i.e., O2(•-), CO2(•-), and CH3CN(•-), are initially formed on the cluster surface. O2(•-) and CO2(•-) can integrate into the clusters due to their high hydrophilicity. They are either solvated in the second solvation shell of Mg(2+) as a solvent-separated ion pair (ssip) or directly coordinated to Mg(2+) as a contact-ion pair (cip) having the (1)η-[MgO2](•+) and (1)η-[MgOCO](•+) coordination modes. The (1)η-[MgO2](•+) core is more crowded than the (1)η-[MgOCO](•+) core. The reaction enthalpies of the formation of ssip and cip of [Mg(CO2)(H2O)16](•+) are -36 ± 4 kJ mol(-1) and -30 ± 9 kJ mol(-1), respectively, which were estimated based on the average temperature changes during the ion-molecule reaction between CO2 and [Mg(H2O)16](•+). The values for the formation of ssip and cip of [Mg(O2)(H2O)16](•+) are estimated to be -112 ± 18 kJ mol(-1) and -128 ± 28 kJ mol(-1), respectively. CH3CN(•-) undergoes protonation spontaneously to form the hydrophobic [CH3CN, H](•). Both CH3CN and [CH3CN, H](•) cannot efficiently penetrate into the clusters with activation barriers of 22 kJ mol(-1) and ∼40 kJ mol(-1), respectively. These results provide fundamental insights into the solvation dynamics of the Mg(2+)/Mg(•+) couple on the molecular level.
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Affiliation(s)
- Tim-Wai Lam
- Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong SAR, P. R. China
| | - Han Zhang
- Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong SAR, P. R. China
| | - Chi-Kit Siu
- Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong SAR, P. R. China
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16
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Lam TW, van der Linde C, Akhgarnusch A, Hao Q, Beyer MK, Siu CK. Reduction of Acetonitrile by Hydrated Magnesium Cations Mg + (H 2 O) n (n≈20-60) in the Gas Phase. Chempluschem 2013; 78:1040-1048. [PMID: 31986721 DOI: 10.1002/cplu.201300170] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Indexed: 11/09/2022]
Abstract
Ion-molecule reactions of Mg+ (H2 O)n (n≈20-60) with CH3 CN are studied by Fourier-transform ion-cyclotron resonance mass spectrometry. Collision with CH3 CN initiates the formation of MgOH+ (H2 O)n-1 together with CH3 CHN. or CH3 CNH. , which is similar to the reaction of hydrated electrons (H2 O)n - with CH3 CN. In subsequent reaction steps, three more CH3 CN molecules are taken up by the clusters, to form MgOH+ (CH3 CN)3 after a reaction delay of 60 seconds. Density functional theory (DFT) calculations at the M06/6-31++G(d,p) level of theory suggest that the bending motion of CH3 CN allows the unpaired electron that is solvated out from the Mg center to localize in a π*(CN)-like orbital of the bent CH3 CN.- , which undergoes spontaneous proton transfer to form CH3 CNH. or CH3 CHN. , with the former being kinetically more favorable. The reaction energy for a cluster with the hexacoordinated Mg center is more exothermic than that with the pentacoordinated Mg. The CH3 CNH. or CH3 CHN. is preferentially solvated on the cluster surface rather than at the first solvation shell of the Mg center. By contrast, the three additional CH3 CN molecules taken up by the resulting MgOH+ (H2 O)n clusters coordinate directly to the first solvation shell of the MgOH+ core, as revealed by DFT calculations.
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Affiliation(s)
- Tim-Wai Lam
- Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong (P. R. China), Fax: (+852) 3442-0522
| | - Christian van der Linde
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstraße 40, 24098 Kiel (Germany), Fax: (+49) 431-880-2830
| | - Amou Akhgarnusch
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstraße 40, 24098 Kiel (Germany), Fax: (+49) 431-880-2830
| | - Qiang Hao
- Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong (P. R. China), Fax: (+852) 3442-0522
| | - Martin K Beyer
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstraße 40, 24098 Kiel (Germany), Fax: (+49) 431-880-2830
| | - Chi-Kit Siu
- Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong (P. R. China), Fax: (+852) 3442-0522
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17
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Hashimoto K, Ugajin S, Yoshida S, Tazawa R, Sato A. Theoretical study of OH-breaking reactions in Na(H2O)n clusters. Chem Phys 2013. [DOI: 10.1016/j.chemphys.2013.01.035] [Citation(s) in RCA: 7] [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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18
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Intracluster ion molecule reactions following the generation of Mg+ within polar clusters. Int J Mol Sci 2011; 12:9095-107. [PMID: 22272121 PMCID: PMC3257118 DOI: 10.3390/ijms12129095] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Revised: 11/11/2011] [Accepted: 11/22/2011] [Indexed: 11/25/2022] Open
Abstract
In this work we investigated the intracluster ion molecule reactions following the generation of Mg+ within the polar clusters (water, methanol, ether and acetonitrile), using time of flight mass spectrometry. In the case of Mg+/water and Mg+/methanol, dehydrogenation reactions are observed after the addition of five molecules. However, no dehydrogenation reactions are observed in the case of Mg+/ether or Mg+/acetonitrile clusters. This confirms the role of the H atom in (O–H) in the dehydrogenation reaction, and rules out any contribution from the H atom in the CH3 group. In addition, the magic numbers in the time of flight (TOF) mass spectra of the Mg+Xn clusters (X = H2O, CH3OH, CH3OCH3 and CH3CN) have been investigated. Finally, the role of ground electronic magnesium ion Mg+(2S1/2), and excited electronic magnesium ion Mg+(2P1/2) in the dehydrogenation reaction were investigated using Ion Mobility Mass spectrometry. The results offer direct evidence confirming the absence of the electronically excited, Mg+(2P1/2).
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van der Linde C, Akhgarnusch A, Siu CK, Beyer MK. Hydrated magnesium cations Mg+(H2O)n, n ≈ 20-60, exhibit chemistry of the hydrated electron in reactions with O2 and CO2. J Phys Chem A 2011; 115:10174-80. [PMID: 21823678 DOI: 10.1021/jp206140k] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ion-molecule reactions of Mg(+)(H(2)O)(n), n ≈ 20-60, with O(2) and CO(2) are studied by Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry. O(2) and CO(2) are taken up by the clusters. Both reactions correspond to the chemistry of hydrated electrons (H(2)O)(n)(-). Density functional theory calculations predicted that the solvation structures of Mg(+)(H(2)O)(16) contain a hydrated electron that is solvated remotely from a hexa-coordinated Mg(2+). Ion-molecule reactions between Mg(+)(H(2)O)(16) and O(2) or CO(2) are calculated to be highly exothermic. Initially, a solvent-separated ion pair is formed, with the hexa-coordinated Mg(2+) ionic core being well separated from the O(2)(•-) or CO(2)(•-). Rearrangements of the solvation structure are possible and produce a contact-ion pair in which one water molecule in the first solvation shell of Mg(2+) is replaced by O(2)(•-) or CO(2)(•-).
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Affiliation(s)
- Christian van der Linde
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel, Germany
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21
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Cabanillas-Vidosa I, Rossa M, Pino GA, Ferrero JC. Unexpected size distribution of Ba(H2O)n clusters: why is the intensity of the Ba(H2O)1 cluster anomalously low? Phys Chem Chem Phys 2011; 13:13387-94. [PMID: 21701713 DOI: 10.1039/c0cp02881a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An experimental and theoretical study on the reactivity of neutral Ba atoms with water clusters has been conducted to unravel the origin of the irregular intensity pattern observed in one-photon ionization mass spectra of a Ba(H(2)O)(n)/BaOH(H(2)O)(n-1) (n = 1-4) cluster distribution, which was generated in a laser vaporization-supersonic expansion source. The most remarkable irregular feature is the finding for n = 1 of a lower intensity for the Ba(+)(H(2)O)(n) peak with respect to that of BaOH(+)(H(2)O)(n-1), which is opposite to the trend for n = 2-4. Rationalization of the data required consideration of a distinct behavior of ground-state and electronically excited state Ba atoms in inelastic and reactive Ba + (H(2)O)(n) encounters that can occur in the cluster source. Within this picture, the generation of Ba(H(2)O)(n) (n > 1) association products results from stabilizing collisions with atoms of the carrier gas, which are favored by intramolecular vibrational redistribution that operates on the corresponding collision intermediates prior to stabilization; the latter is unlikely to occur for Ba + (H(2)O) encounters. Overall, this interpretation is consistent with additional in-source laser excitation and quenching experiments, which aimed to explore qualitatively the effect of perturbing the Ba atom electronic state population distribution on the observed intensity pattern, as well as with the energetics of various possible reactions for the Ba + H(2)O system that derive from high level ab initio calculations.
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Affiliation(s)
- Iván Cabanillas-Vidosa
- Centro Láser de Ciencias Moleculares, INFIQC and Departamento de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5000IUS Córdoba, Argentina
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22
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van der Linde C, Beyer MK. The structure of gas-phase [Al·nH2O]+: hydrated monovalent aluminium Al+ (H2O)n or hydride-hydroxide HAlOH+ (H2O)(n-1)? Phys Chem Chem Phys 2011; 13:6776-8. [PMID: 21399775 DOI: 10.1039/c1cp00048a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Theoretical studies predict that [Al·nH(2)O](+) clusters are present as hydride-hydroxide species HAlOH(+)(H(2)O)(n-1) in gas-phase experiments, energetically favoured by 200 kJ mol(-1) over Al(+)(H(2)O)(n). After collisions with D(2)O, however, no H/D scrambling occurs between H(2)O and D(2)O in clusters with n > 38, indicating that large clusters are present as the higher-energy isomers Al(+)(H(2)O)(n).
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Affiliation(s)
- Christian van der Linde
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel, Germany
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23
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Duncan MA. Infrared spectroscopy to probe structure and dynamics in metal ion-molecule complexes. INT REV PHYS CHEM 2010. [DOI: 10.1080/0144235031000095201] [Citation(s) in RCA: 280] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Michael A. Duncan
- a Department of Chemistry , University of Georgia , Athens , GA , 30602-2556 , USA
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24
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Donald WA, Demireva M, Leib RD, Aiken MJ, Williams ER. Electron Hydration and Ion−Electron Pairs in Water Clusters Containing Trivalent Metal Ions. J Am Chem Soc 2010; 132:4633-40. [DOI: 10.1021/ja9079385] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- William A. Donald
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Maria Demireva
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Ryan D. Leib
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - M. Jeannette Aiken
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Evan R. Williams
- Department of Chemistry, University of California, Berkeley, California 94720-1460
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25
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Rodriguez-Cruz SE, Jockusch RA, Williams ER. Hydration energies of divalent metal ions, Ca2+ (H2O)n (N = 5-7) and Ni2+ (H2O)m (N = 6-8), obtained by blackbody infrared radiative dissociation. J Am Chem Soc 2009; 120:5842-3. [PMID: 16479268 PMCID: PMC1364451 DOI: 10.1021/ja980716i] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- S E Rodriguez-Cruz
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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26
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Fox-Beyer BS, Sun Z, Balteanu I, Balaj OP, Beyer MK. Hydrogen formation in the reaction of Zn+ (H2O)n with HCl. Phys Chem Chem Phys 2009; 7:981-5. [PMID: 19791389 DOI: 10.1039/b415583a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrated singly charged zinc cations Zn (H2O)n, n approximately 6-53, were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Black-body radiation induced dissociation results exclusively in sequential loss of individual water molecules. In the reaction of Zn+ (H2O)n with gaseous HCl, Zn is oxidized and hydrogen reduced when a second HCl molecule is taken up, leading to the formation of ZnCl+ (HCl)(H2O)n-m cluster ions and evaporation of atomic hydrogen together with m H2O molecules. The results are compared with earlier studies of Mg+ (H2O)n, for which hydrogen formation is already observed without HCl in a characteristic size region. The difference between zinc and magnesium is rationalized with the help of density functional theory calculations, which indicate a distinct difference in the thermochemistry of the reactions involved. The generally accepted hydrated electron model for hydrogen formation in Mg+ (H2O)n is modified for zinc to account for the different reactivity.
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Affiliation(s)
- Brigitte S Fox-Beyer
- Department Chemie, Physikalische Chemie 2, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching, Germany.
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27
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Tulub AA, Stefanov VE. The effect of the oxidative properties of [Mg(H2O)6] in the triplet and singlet states on the energetics of adenosine triphosphate cleavage. RUSS J INORG CHEM+ 2009. [DOI: 10.1134/s0036023609070213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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28
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Donald WA, Leib RD, O'Brien JT, Holm AIS, Williams ER. Nanocalorimetry in mass spectrometry: a route to understanding ion and electron solvation. Proc Natl Acad Sci U S A 2008; 105:18102-7. [PMID: 18687894 PMCID: PMC2587548 DOI: 10.1073/pnas.0801549105] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Indexed: 11/18/2022] Open
Abstract
A gaseous nanocalorimetry approach is used to investigate effects of hydration and ion identity on the energy resulting from ion-electron recombination. Capture of a thermally generated electron by a hydrated multivalent ion results in either loss of a H atom accompanied by water loss or exclusively loss of water. The energy resulting from electron capture by the precursor is obtained from the extent of water loss. Results for large-size-selected clusters of Co(NH(3))(6)(H(2)O)(n3)(+) and Cu(H(2)O)(n2)(+) indicate that the ion in the cluster is reduced on electron capture. The trend in the data for Co(NH(3))(6)(H(2)O)(n3)(+) over the largest sizes (n >/= 50) can be fit to that predicted by the Born solvation model. This agreement indicates that the decrease in water loss for these larger clusters is predominantly due to ion solvation that can be accounted for by using a model with bulk properties. In contrast, results for Ca(H(2)O)(n2)(+) indicate that an ion-electron pair is formed when clusters with more than approximately 20 water molecules are reduced. For clusters with n = approximately 20-47, these results suggest that the electron is located near the surface, but a structural transition to a more highly solvated electron is indicated for n = 47-62 by the constant recombination energy. These results suggest that an estimate of the adiabatic electron affinity of water could be obtained from measurements of even larger clusters in which an electron is fully solvated.
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Affiliation(s)
- William A. Donald
- Department of Chemistry, University of California, Berkeley, CA 94720-1460
| | - Ryan D. Leib
- Department of Chemistry, University of California, Berkeley, CA 94720-1460
| | - Jeremy T. O'Brien
- Department of Chemistry, University of California, Berkeley, CA 94720-1460
| | - Anne I. S. Holm
- Department of Chemistry, University of California, Berkeley, CA 94720-1460
| | - Evan R. Williams
- Department of Chemistry, University of California, Berkeley, CA 94720-1460
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29
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Tulub AA. Magnesium spin state determines the energetics of an adenosinetriphosphate molecule. Biophysics (Nagoya-shi) 2008. [DOI: 10.1134/s0006350908050096] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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30
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Chan KW, Wu Y, Liu ZF. Solvation effects on the intracluster elimination channels in M+(L)n, where M+= Mg+ and Ca+, L = CH3OH, and NH3, and n = 2-6. J Phys Chem A 2008; 112:8542-50. [PMID: 18729438 DOI: 10.1021/jp804156f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The methanol and ammonia solvated Ca (+) or Mg (+) clusters are known to go through intracluster H or CH 3 eliminations which are typically switched on just below n = 6. By first principles calculations at the B3LYP/6-311+G** level, we have identified the transition structures, activation barriers, and energy changes in these reactions for clusters with 2-6 solvent molecules. The activation barrier is crucial to explain the previously reported experimental results. While increasing number of solvent molecules stabilizes a transition structure, the increasing presence of solvent molecules in the first solvation shell makes it difficult for the metal ion to assist the bond breaking through its interaction with the departing H atom or CH 3 group. The balance of these two factors determines whether a particular elimination channel could be switched on.
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Affiliation(s)
- Ka Wai Chan
- Department of Chemistry and Centre for Scientific Modeling and Computation Chinese, University of Hong Kong, Shatin, Hong Kong, China
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31
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Chan KW, Wu Y, Liu ZF. Theoretical study on the intracluster elimination channels for Mg+(CH3OH), Ca+(CH3OH), Mg+(NH3), and Ca+(NH3). J Phys Chem A 2008; 112:8534-41. [PMID: 18729440 DOI: 10.1021/jp804155t] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The intracluster elimination reactions in solvated alkaline earth metal monocation clusters, M (+)L n , are known to be size-dependent, indicating links between chemical reactivity and the solvation environment controlled by the cluster size. For the methanol and ammonia clusters, there are a number of competing elimination channels involving the breaking of O-H, C-H, O-CH 3, or N-H bond. In this report, we focus on the four clusters with only one solvent molecule and systematically map out the reaction paths and intermediates. The interaction between the metal ion and the departing H atom or CH 3 group varies considerably, depending on the interaction between the metal ion and the remaining group. The understanding of the nature of these interactions and the evaluation of various theoretical levels in treating these reactions provide a solid base for the investigation of the solvation effects on the chemical reactivity of the larger clusters.
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Affiliation(s)
- Ka Wai Chan
- Department of Chemistry and Centre for Scientific Modeling and Computation Chinese, University of Hong Kong, Shatin, Hong Kong, China
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32
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Carnegie PD, Bandyopadhyay B, Duncan MA. Infrared spectroscopy of Cr+(H2O) and Cr2+(H2O): the role of charge in cation hydration. J Phys Chem A 2008; 112:6237-43. [PMID: 18563888 DOI: 10.1021/jp803086v] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Singly and doubly charged chromium-water ion-molecule complexes are produced by laser vaporization in a pulsed-nozzle cluster source. These species are detected and mass-selected in a specially designed time-of-flight mass spectrometer. Vibrational spectroscopy is measured for these complexes in the O-H stretching region using infrared photodissociation spectroscopy and the method of rare gas atom predissociation. Infrared excitation is not able to break the ion-water bonds in these systems, but it leads to elimination of argon, providing an efficient mechanism for detecting the spectrum. The O-H stretches for both singly and doubly charged complexes are shifted to frequencies lower than those for the free water molecule, and the intensity of the symmetric stretch band is strongly enhanced relative to the asymmetric stretch. Partially resolved rotational structure for both complexes shows that the H-O-H bond angle is greater than it is in the free water molecule. These polarization-induced effects are enhanced in the doubly charged ion relative to its singly charged analog.
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Affiliation(s)
- P D Carnegie
- Department of Chemistry, University of Georgia, Athens, Georgia 30602-2556, USA
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33
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Tulub AA, Stefanov VE. New horizons of adenosinetriphosphate energetics arising from interaction with magnesium cofactor. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2008; 37:1309-16. [PMID: 18463860 DOI: 10.1007/s00249-008-0337-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2007] [Accepted: 04/03/2008] [Indexed: 11/25/2022]
Abstract
MD DFT:B3LYP (6-31G** basis set, T = 310 K) method is used to study interactions [singlet (S) and triplet (T) reaction paths] between adenosinetriphosphate, ATP(4-), and [Mg(H(2)O)(6)](2+) in water environment, modeled with 78 water molecules. Computations reveal the appearance of low and high-energy states (stable, quasi-stable, and unstable), assigned to different spin symmetries. At the initial stage of interaction, ATP donates a part of its negative charge to the Mg complex making the Mg slightly charged. As a result, the original octahedral Mg complex loses two (S state) or four (T state) water molecules. Moving along S or T potential energy surfaces (PESs), Mg(H(2)O)(4 )or Mg(H(2)O)(2) display different ways of complexation with ATP. S path favors the formation of a stable chelate with the O1-O2 fragment of ATP triphosphate tail, whereas T path favors producing a single-bonded complex with the O2. The latter, being unstable, undergoes a further conversion into a spin-separated complex, also unstable, and two metastable S complexes, which finally arise in two stable, low-energy and high-energy, chelates. The spin-separated complex experiences rapid decomposition resulting in the production of a highly reactive adenosinemonophosphate ion-radical *AMP, early observed in the CIDNP experiment (Tulub 2006). Biological consequences of the findings are discussed.
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Affiliation(s)
- Alexander A Tulub
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
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34
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Wu B, Duncombe BJ, Stace AJ. The Solvation of Mg2+ with Gas-Phase Clusters Composed of Alcohol Molecules. J Phys Chem A 2008; 112:2182-91. [DOI: 10.1021/jp710369x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Bohan Wu
- Department of Physical Chemistry, School of Chemistry, The University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
| | - Bridgette J. Duncombe
- Department of Physical Chemistry, School of Chemistry, The University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
| | - Anthony J. Stace
- Department of Physical Chemistry, School of Chemistry, The University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
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35
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Chan KW, Wu Y, Liu ZF. Solvation and electronic structures of M+Ln, with M+ = Mg+ and Ca+, L = H2O, CH3OH, and NH3, and n = 1–6. CAN J CHEM 2007. [DOI: 10.1139/v07-103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The solvation clusters M+(L)n, with a singly charged alkaline earth cation Mg+ or Ca+ as the solute and with water, methanol, or ammonia as the solvent, are studied systematically in the size range n = 1–6, to compare the variations in the solvation interactions. For clusters with n ≤ 3, the energies and structural values are compared in details, with both the MP2 and B3LYP methods. For clusters with n ≥ 4, the solute–solvent and solvent–solvent interaction energies are calculated to explain the relative stability among various isomeric structures, and the contrast in both solvent and electron distribution among these cluster series. Thermal stabilities for these clusters are also examined by ab initio molecular dynamics simulations at finite temperature.Key words: solvation clusters, ab initio calculations, solute–solvent interactions, size-dependent effects.
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36
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Cheng P, Koyanagi GK, Bohme DK. Heavy Water Reactions with Atomic Transition-Metal and Main-Group Cations: Gas Phase Room-Temperature Kinetics and Periodicities in Reactivity. J Phys Chem A 2007; 111:8561-73. [PMID: 17696503 DOI: 10.1021/jp072661p] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Reactions of heavy water, D(2)O, have been measured with 46 atomic metal cations at room temperature in a helium bath gas at 0.35 Torr using an inductively coupled plasma/selected ion flow tube tandem mass spectrometer. The atomic cations were produced at ca. 5500 K in an ICP source and were allowed to decay radiatively and thermalize by collisions with Ar and He atoms prior to reaction. Rate coefficients and product distributions are reported for the reactions of fourth-row atomic cations from K+ to Se+, of fifth-row atomic cations from Rb+ to Te+ (excluding Tc+), and of sixth-row atomic cations from Cs+ to Bi+. Primary reaction channels were observed leading to O-atom transfer, OD transfer, and D2O addition. O-Atom transfer occurs almost exclusively (>or=90%) in the reactions with most early transition-metal cations (Sc+, Ti+, V+, Y+, Zr+, Nb+, Mo+, Hf+, Ta+, and W+) and to a minor extent (10%) with one main-group cation (As+). OD transfer is observed to occur only with three cations (Sr+, Ba+, and La+). Other cations, including most late transition and main-group cations, were observed to react with D2O exclusively and slowly by D2O addition or not at all. O-Atom transfer proceeds with rate coefficients in the range of 8.1 x 10(-13) (As+) to 9.5 x 10(-10) (Y+) cm3 molecule(-1)(s-1) and with efficiencies below 0.1 and even below 0.01 for the fourth-row atomic cations V+ (0.0032) and As+ (0.0036). These low efficiencies can be understood in terms of the change in spin required to proceed from the reactant to the product potential energy surfaces. Higher order reactions are also measured. The primary products, NbO+, TaO+, MoO+, and WO+, are observed to react further with D(2)O by O-atom transfer, and ZrO+ and HfO+ react further through OD group abstraction. Up to five D(2)O molecules were observed to add sequentially to selected M+ and MO+ as well as MO2+ cations and four to MO(2)D+. Equilibrium measurements for sequential D(2)O addition to M+ are also reported. The periodic variation in the efficiency (k/k(c)) of the first addition of D(2)O appears to be similar to the periodic variation in the standard free energy (DeltaG degrees) of hydration.
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Affiliation(s)
- Ping Cheng
- Department of Chemistry, Centre for Research in Mass Spectrometry and Centre for Research in Earth and Space Science, York University, Toronto, Ontario, Canada, M3J 1P3
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37
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Leib RD, Donald WA, Bush MF, O'Brien JT, Williams ER. Nonergodicity in electron capture dissociation investigated using hydrated ion nanocalorimetry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2007; 18:1217-31. [PMID: 17521917 PMCID: PMC2034202 DOI: 10.1016/j.jasms.2007.03.033] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Revised: 03/29/2007] [Accepted: 03/29/2007] [Indexed: 05/02/2023]
Abstract
Hydrated divalent magnesium and calcium clusters are used as nanocalorimeters to measure the internal energy deposited into size-selected clusters upon capture of a thermally generated electron. The infrared radiation emitted from the cell and vacuum chamber surfaces as well as from the heated cathode results in some activation of these clusters, but this activation is minimal. No measurable excitation due to inelastic collisions occurs with the low-energy electrons used under these conditions. Two different dissociation pathways are observed for the divalent clusters that capture an electron: loss of water molecules (Pathway I) and loss of an H atom and water molecules (Pathway II). For Ca(H(2)O)(n)(2+), Pathway I occurs exclusively for n >or= 30 whereas Pathway II occurs exclusively for n <or= 22 with a sharp transition in the branching ratio for these two processes that occurs for n approximately 24. The number of water molecules lost by both pathways increases with increasing cluster size reaching a broad maximum between n = 23 and 32, and then decreases for larger clusters. From the number of water molecules that are lost from the reduced cluster, the average and maximum possible internal energy is determined to be approximately 4.4 and 5.2 eV, respectively, for Ca(H(2)O)(30)(2+). This value is approximately the same as the calculated ionization energies of M(H(2)O)(n)(+), M = Mg and Ca, for large n indicating that the vast majority of the recombination energy is partitioned into internal modes of the ion and that the dissociation of these ions is statistical. For smaller clusters, estimates of the dissociation energies for the loss of H and of water molecules are obtained from theory. For Mg(H(2)O)(n)(2+), n = 4-6, the average internal energy deposition is estimated to be 4.2-4.6 eV. The maximum possible energy deposited into the n = 5 cluster is <7.1 eV, which is significantly less than the calculated recombination energy for this cluster. There does not appear to be a significant trend in the internal energy deposition with cluster size whereas the recombination energy is calculated to increase significantly for clusters with fewer than 10 water molecules. These, and other results, indicate that the dissociation of these smaller clusters is nonergodic.
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Affiliation(s)
- Ryan D Leib
- Department of Chemistry, University of California-Berkeley, Berkeley, California 94720-1460, USA
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38
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Mó O, Yáñez M, Salpin JY, Tortajada J. Thermochemistry, bonding, and reactivity of Ni+ and Ni2+ in the gas phase. MASS SPECTROMETRY REVIEWS 2007; 26:474-516. [PMID: 17492664 DOI: 10.1002/mas.20134] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
In this review, we present a general overview on the studies carried out on Ni(+-)- and Ni(2+)-containing systems in the gas phase since 1996. We have focused our attention in the determination of binding energies in parallel with an analysis of the structure and bonding of the complexes formed by the interaction of Ni(+) with one ligand, or in clusters where this metal ion binds several identical or different ligands. Solvation of Ni(2+) by different ligands is also discussed, together with the theoretical information available of doubly charged Ni-containing species. The final section of this review is devoted to an analysis of the gas-phase uni- and bimolecular reactivity of Ni(+) and Ni(2+) complexes.
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Affiliation(s)
- Otilia Mó
- Departamento de Química, C-9, Universidad Autónoma de Madrid, Cantoblanco, 28049-Madrid, Spain
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39
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Abstract
Studying metal ion solvation, especially hydration, in the gas phase has developed into a field that is dominated by a tight interaction between experiment and theory. Since the studied species carry charge, mass spectrometry is an indispensable tool in all experiments. Whereas gas-phase coordination chemistry and reactions of bare metal ions are reasonably well understood, systems containing a larger number of solvent molecules are still difficult to understand. This review focuses on the rich chemistry of hydrated metal ions in the gas phase, covering coordination chemistry, charge separation in multiply charged systems, as well as intracluster and ion-molecule reactions. Key ideas of metal ion solvation in the gas phase are illustrated with rare-gas solvated metal ions.
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Affiliation(s)
- Martin K Beyer
- Institut für Chemie, Sekr. C4, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
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40
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Walker NR, Walters RS, Tsai MK, Jordan KD, Duncan MA. Infrared photodissociation spectroscopy of Mg(+)(H2O)Ar(n) complexes: isomers in progressive microsolvation. J Phys Chem A 2007; 109:7057-67. [PMID: 16834068 DOI: 10.1021/jp051877t] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ion-molecule complexes of the form Mg(H2O)Ar(n)+ (n = 1-8) are produced by laser vaporization in a pulsed-nozzle cluster source. These complexes are mass-selected and studied with infrared photodissociation spectroscopy in the O-H stretch region. The spectra are interpreted with the aid of ab initio calculations on the n = 1-5 complexes, including examination of various isomeric structures. The combined spectroscopic and theoretical studies reveal the presence of multiple isomeric structures at each cluster size, as the argon atoms assemble around the Mg(+)(H2O) unit. Distinct infrared resonances are measured for argon-on-metal, argon-on-OH and argon-on-two-OH isomers.
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Affiliation(s)
- N R Walker
- Department of Chemistry, University of Georgia, Athens, Georgia 30602-2556, USA
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41
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Structures, Spectroscopies, and Reactions of Atomic Ions with Water Clusters. ADVANCES IN CHEMICAL PHYSICS 2007. [DOI: 10.1002/9780470141694.ch7] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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42
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Gao B, Liu ZF. Ionization induced relaxation in solvation structure: A comparison between Na(H2O)n and Na(NH3)n. J Chem Phys 2007; 126:084501. [PMID: 17343452 DOI: 10.1063/1.2464109] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The constant ionization potential for hydrated sodium clusters Na(H2O)n just beyond n=4, as observed in photoionization experiments, has long been a puzzle in violation of the well-known (n+1)(-1/3) rule that governs the gradual transition in properties from clusters to the bulk. Based on first principles calculations, a link is identified between this puzzle and an important process in solution: the reorganization of the solvation structure after the removal of a charged particle. Na(H2O)n is a prototypical system with a solvated electron coexisting with a solvated sodium ion, and the cluster structure is determined by a balance among three factors: solute-solvent (Na+-H2O), solvent-solvent (H2O-H2O), and electron-solvent (OH{e}HO) interactions. Upon the removal of an electron by photoionization, extensive structural reorganization is induced to reorient OH{e}HO features in the neutral Na(H2O)n for better Na+-H2O and H2O-H2O interactions in the cationic Na+(H2O)n. The large amount of energy released, often reaching 1 eV or more, indicates that experimentally measured ion signals actually come from autoionization via vertical excitation to high Rydberg states below the vertical ionization potential, which induces extensive structural reorganization and the loss of a few solvent molecules. It provides a coherent explanation for all the peculiar features in the ionization experiments, not only for Na(H2O)n but also for Li(H2O)n and Cs(H2O)n. In addition, the contrast between Na(H2O)n and Na(NH3)n experiments is accounted for by the much smaller relaxation energy for Na(NH3)n, for which the structures and energetics are also elucidated.
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Affiliation(s)
- Bing Gao
- Department of Chemistry, Chinese University of Hong Kong, Shatin, Hong Kong, China
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43
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45
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Walker NR, Walters RS, Duncan MA. Infrared photodissociation spectroscopy of V+(CO2)n and V+(CO2)nAr complexes. J Chem Phys 2006; 120:10037-45. [PMID: 15268025 DOI: 10.1063/1.1730217] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
V+(CO2)n and V+(CO2)nAr complexes are generated by laser vaporization in a pulsed supersonic expansion. The complexes are mass-selected within a reflectron time-of-flight mass spectrometer and studied by infrared resonance-enhanced (IR-REPD) photodissociation spectroscopy. Photofragmentation proceeds exclusively through loss of intact CO2 molecules from V+(CO2)n complexes or by elimination of Ar from V+(CO2)nAr mixed complexes. Vibrational resonances are identified and assigned in the region of the asymmetric stretch of free CO2 at 2349 cm(-1). A linear geometry is confirmed for V+(CO2). Small complexes have resonances that are blueshifted from the asymmetric stretch of free CO2, consistent with structures in which all ligands are bound directly to the metal ion. Fragmentation of the larger clusters terminates at the size of n=4, and a new vibrational band at 2350 cm(-1) assigned to external ligands is observed for V+(CO2)5 and larger cluster sizes. These combined observations indicate that the coordination number for CO2 molecules around V+ is exactly four. Fourfold coordination contrasts with that seen in condensed phase complexes, where a coordination number of six is typical for V+. The spectra of larger complexes provide evidence for an intracluster insertion reaction that produces a metal oxide-carbonyl species.
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Affiliation(s)
- N R Walker
- Department of Chemistry, University of Georgia, Athens, GA 30602-2556, USA
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46
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Cheng P, Koyanagi GK, Bohme DK. Gas-Phase Reactions of Atomic Lanthanide Cations with D2O: Room-Temperature Kinetics and Periodicity in Reactivity. Chemphyschem 2006; 7:1813-9. [PMID: 16810661 DOI: 10.1002/cphc.200600248] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Reactions of atomic lanthanide cations (excluding Pm+) with D2O have been surveyed in the gas phase using an inductively coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer to measure rate coefficients and product distributions in He at 0.35+/-0.01 Torr and 295+/-2 K. Primary reaction channels were observed corresponding to O-atom transfer, OD transfer and D2O addition. O-atom transfer is the predominant reaction channel and occurs exclusively with Ce+, Nd+, Sm+, Gd+, Tb+ and Lu+. OD transfer is observed exclusively with Yb+, and competes with O-atom transfer in the reactions with La+ and Pr+. Slow D2O addition is observed with early lanthanide cation Eu+ and the late lanthanide cations Dy+, Ho+, Er+ and Tm+. Higher-order sequential D2O addition of up to five D2O molecules is observed with LnO+ and LnOD+. A delay of more than 50 kcal mol(-1) is observed in the onset of efficient exothermic O-atom transfer, which suggests the presence of kinetic barriers of perhaps this magnitude in the exothermic O-atom transfer reactions of Dy+, Ho+, Er) and Tm+ with D2O. The reaction efficiency for O-atom transfer is seen to decrease as the energy required to promote an electron to make two non-f electrons available for bonding increases. The periodic trend in reaction efficiency along the lanthanide series matches the periodic trend in the electron-promotion energy required to achieve a d1s1 or d2 excited electronic configuration in the lanthanide cation, and also the periodic trends across the lanthanide row reported previously for several alcohols and phenol. An Arrhenius-like correlation is also observed for the dependence of D2O reactivity on promotion energy for early lanthanide cations, and exhibits a characteristic temperature of 2600 K.
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Affiliation(s)
- Ping Cheng
- Department of Chemistry, Centre for Research in Mass Spectrometry and Centre for Research in Earth and Space Science, York University, Toronto, Ontario M3J 1P3 Canada
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47
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Liu H, Hu Y, Yang S, Guo W, Fu Q, Wang L. Photoreactions in the gas-phase complexes of Mg(*+)-dioxanes. J Phys Chem A 2006; 110:4389-96. [PMID: 16571042 DOI: 10.1021/jp060002r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photoreactions in the gas-phase complexes Mg(*+)(1,4-dioxane) (1) and Mg(*+)(1,3-dioxane) (1M) have been examined in the wavelength region of 230-440 nm. Photoproduct assignments are facilitated with the help of deuterium substitution experiments. The main energy relaxation channel for both photoexcited complexes is the evaporation of Mg(*+). Also observed from 1 are rich photoproducts with m/z 28, 41, 54-58, 67, 69, and 88; the most abundant one at m/z 54 is designated to Mg(*+)(O=CH(2)). In marked contrast, the photolysis of 1M yields only Mg(*+)(O=CH(2)) other than Mg(*+). Density functional calculations are performed to obtain optimized geometries and potential energy surfaces of 1 and 1M. Although Mg(*+)(chair-1,4-C(4)H(8)O(2)) (1a) and Mg(*+)(boat-1,4-C(4)H(8)O(2)) (1b) are comparable in energy, the much better agreement of the experimental action spectrum of Mg(*+)(1,4-C(4)H(8)O(2)) with the calculated absorption spectrum of 1a than with that of 1b indicates the predominance of 1a in the source due to the stability of the chair-1,4-dioxane. For photoreactions, the C-O bond is found to be much more prone to rupture than the C-C bond due to the coordination of O to Mg(+) in the parent complexes. Photoreaction mechanisms are discussed in terms of two key insertion complexes, which rationalize all of the observed photoproducts.
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Affiliation(s)
- Haichuan Liu
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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48
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Walters RS, Pillai ED, Duncan MA. Solvation dynamics in Ni+ (H2O)n clusters probed with infrared spectroscopy. J Am Chem Soc 2006; 127:16599-610. [PMID: 16305249 DOI: 10.1021/ja0542587] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Infrared photodissociation spectroscopy is reported for mass-selected Ni+ (H2O)n complexes in the O-H stretching region up to cluster sizes of n = 25. These clusters fragment by the loss of one or more intact water molecules, and their excitation spectra show distinct bands in the region of the symmetric and asymmetric stretches of water. The first evidence for hydrogen bonding, indicated by a broad band strongly red-shifted from the free OH region, appears at the cluster size of n = 4. At larger cluster sizes, additional red-shifted structure evolves over a broader wavelength range in the hydrogen-bonding region. In the free OH region, the symmetric stretch gradually diminishes in intensity, while the asymmetric stretch develops into a closely spaced doublet near 3700 cm(-1). The data indicate that essentially all of the water molecules are in a hydrogen-bonded network by the size of n = 10. However, there is no evidence for the formation of clathrate structures seen recently via IR spectroscopy of protonated water clusters.
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Affiliation(s)
- Richard S Walters
- Department of Chemistry, University of Georgia, Athens, Georgia 30602-2556, USA
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49
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Velasquez J, Pillai ED, Carnegie PD, Duncan MA. IR Spectroscopy of M+(Acetone) Complexes (M = Mg, Al, Ca): Cation−Carbonyl Binding Interactions. J Phys Chem A 2006; 110:2325-30. [PMID: 16480290 DOI: 10.1021/jp0574899] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
M(+)(acetone) ion-molecule complexes (M = Mg, Al, Ca) are produced in a pulsed molecular beam by laser vaporization and studied with infrared photodissociation spectroscopy in the carbonyl stretch region. All of the spectra exhibit carbonyl stretches that are shifted significantly to lower frequencies than the free-molecule value, consistent with metal cation binding on the oxygen of the carbonyl. Density functional theory is employed to elucidate the shifts and patterns in these spectra. Doublet features are measured for the carbonyl region of Mg(+) and Ca(+) complexes, and these are assigned to Fermi resonances between the symmetric carbonyl stretch and the overtone of the symmetric carbon stretch. The carbonyl stretch red shift is greater for Al(+) than it is for the Mg(+) and Ca(+) complexes. This is attributed to the smaller size of the closed-shell Al(+), which enhances its ability to polarize the carbonyl electrons. Density functional theory correctly predicts the direction of the carbonyl stretch shift and the relative trend for the three metals.
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Gao B, Liu ZF. Size-dependent charge-separation reaction for hydrated sulfate dianion cluster, SO42−(H2O)n, with n=3–7. J Chem Phys 2005; 123:224302. [PMID: 16375471 DOI: 10.1063/1.2134698] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The decrease in the reaction rate for the charge separation in SO(4) (2-)(H(2)O)(n) with increasing cluster size is examined by first-principles calculations of the energetics, activation barriers, and thermal stability for n=3-7. The key factor governing the charge separation is the difference in the strength of solvation interaction: while interaction with water is strong for the reactant SO(4) (2-) and the product OH(-), it is relatively weak for HSO(4) (-). It gives rise to a barrier for charge separation as SO(4) (2-) is transformed into HSO(4) (-) and OH(-), although the overall reaction energy is exothermic. The barrier is high when more than two H(2)O are left to solvate HSO(4) (-), as in the case of symmetric solvation structure and in the case of large clusters. The entropy is another important factor since the potential surface is floppy and the thermal motion facilitates the symmetric distribution of H(2)O around SO(4) (2-), which leads to the gradual reduction in reaction rate and the eventual switch-off of charge separation as cluster size increases. The experimentally observed products for n=3-5 are explained by the thermally most favorable isomer at each size, obtained by ab initio molecular-dynamics simulations rather than by the isomer with the lowest energy.
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Affiliation(s)
- Bing Gao
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, Hong Kong, People's Republic of China
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