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Telegina TA, Vechtomova YL, Borzova VA, Buglak AA. Tetrahydrobiopterin as a Trigger for Vitiligo: Phototransformation during UV Irradiation. Int J Mol Sci 2023; 24:13586. [PMID: 37686391 PMCID: PMC10487557 DOI: 10.3390/ijms241713586] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 08/25/2023] [Accepted: 08/30/2023] [Indexed: 09/10/2023] Open
Abstract
Vitiligo is a type of hypomelanosis. Tetrahydrobiopterin (H4Bip), the coenzyme of the initial stage of melanogenesis, appears to be a trigger for vitiligo. H4Bip is present in vitiligo in 3-5-fold excess and causes oxidative stress by triggering an autocatalytic cycle of excess hydrogen peroxide synthesis. Using quantum-chemical calculations, we have evaluated the possibility of H4Bip reactions occurring in the dark and under ultraviolet (UV) irradiation, including the formation of dihydropterin dimers. In order to simulate the oxidative stress, oxidative modification of human serum albumin (HSA) has been carried out in the presence of excessive H4Bip using the fluorescence method. The fraction of oxidized protein (FOP) has been calculated. It has been established that there is a strong oxidative modification of amino acids chromophores (tryptophan and tyrosine) in the protein (FOP 0.64). Under UV irradiation of the system (HSA + H4Bip), FOP is reduced to 0.39. Apparently, a part of H4Bip transforms into dihydropterin dimers and does not participate in the oxidative modification of the protein. The data on oxidative modification of HSA are consistent with dynamic light scattering: H4Bip promotes HSA aggregation with the formation of particles with a hydrodynamic radius Rh ≥ 2000 nm, which can become immunogenic.
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Affiliation(s)
- Taisiya A. Telegina
- Research Center of Biotechnology of the Russian Academy of Sciences, Bach Institute of Biochemistry, 119071 Moscow, Russia; (T.A.T.); (Y.L.V.); (V.A.B.)
| | - Yuliya L. Vechtomova
- Research Center of Biotechnology of the Russian Academy of Sciences, Bach Institute of Biochemistry, 119071 Moscow, Russia; (T.A.T.); (Y.L.V.); (V.A.B.)
| | - Vera A. Borzova
- Research Center of Biotechnology of the Russian Academy of Sciences, Bach Institute of Biochemistry, 119071 Moscow, Russia; (T.A.T.); (Y.L.V.); (V.A.B.)
| | - Andrey A. Buglak
- Faculty of Physics, Saint Petersburg State University, 199034 Saint Petersburg, Russia
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2
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Jarrold CC. Probing Anion-Molecule Complexes of Atmospheric Relevance Using Anion Photoelectron Detachment Spectroscopy. ACS PHYSICAL CHEMISTRY AU 2022; 3:17-29. [PMID: 36718261 PMCID: PMC9881448 DOI: 10.1021/acsphyschemau.2c00060] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 12/08/2022] [Accepted: 12/09/2022] [Indexed: 01/01/2023]
Abstract
Bimolecular reaction and collision complexes that drive atmospheric chemistry and contribute to the absorption of solar radiation are fleeting and therefore inherently challenging to study experimentally. Furthermore, primary anions in the troposphere are short lived because of a complicated web of reactions and complex formation they undergo, making details of their early fate elusive. In this perspective, the experimental approach of photodetaching mass-selected anion-molecule complexes or complex anions, which prepares neutrals in various vibronic states, is surveyed. Specifically, the application of anion photoelectron spectroscopy along with photoelectron-photofragment coincidence spectroscopy toward the study of collision complexes, complex anions in which a partial covalent bond is formed, and radical bimolecular reaction complexes, with relevance in tropospheric chemistry, will be highlighted.
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3
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Sanov A. Intermolecular interactions in cluster anions. INT REV PHYS CHEM 2021. [DOI: 10.1080/0144235x.2021.1983292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Andrei Sanov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ, USA
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4
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Hashimoto Y, Saito K, Takayanagi T, Tachikawa H. Theoretical study of the dissociative photodetachment dynamics of the hydrated superoxide anion cluster. Phys Chem Chem Phys 2021; 23:16958-16965. [PMID: 34338247 DOI: 10.1039/d1cp02379a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The dissociative photodetachment of the hydrated superoxide anion cluster, O2-·H2O + hν → O2 + H2O + e-, is theoretically investigated using path-integral and ring-polymer molecular dynamics simulation methods, which can account for nuclear quantum effects. Full-dimensional potential energy surfaces for the anionic and lowest two neutral states (triplet and singlet spin states) are constructed based on extensive density-functional theory calculations. The calculated photoelectron spectrum agrees well with the experimental spectra measured for different photodetachment laser wavelengths. The calculated photoelectron-photofragment kinetic energy correlation spectrum also agrees well with previous experimental measurements. The dissociation mechanisms, including available energy partitioning and the importance of nuclear quantum effects in photodetachment, are discussed in detail.
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Affiliation(s)
- Yu Hashimoto
- Department of Chemistry, Saitama University, Shimo-Okubo 255, Saitama City, Saitama 338-8570, Japan.
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5
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Dauletyarov Y, Sanov A. Weak covalent interactions and anionic charge-sharing polymerisation in cluster environments. Phys Chem Chem Phys 2021; 23:11596-11610. [PMID: 33982051 DOI: 10.1039/d1cp01213d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We discuss the formation of weak covalent bonds leading to anionic charge-sharing dimerisation or polymerisation in microscopic cluster environments. The covalent bonding between cluster building blocks is described in terms of coherent charge sharing, conceptualised using a coupled-monomers molecular-orbital model. The model assumes first-order separability of the inter- and intra-monomer bonding structures. Combined with a Hückel-style formalism adapted to weak covalent and solvation interactions, it offers insight into the competition between the two types of forces and illuminates the properties of the inter-monomer orbitals responsible for charge-sharing dimerisation and polymerisation. Under typical conditions, the cumulative effect of solvation obstructs the polymerisation, limiting the size of covalently bound core anions.
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Affiliation(s)
- Yerbolat Dauletyarov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, USA.
| | - Andrei Sanov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, USA.
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6
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Buglak AA, Telegina TA, Vechtomova YL, Kritsky MS. Autoxidation and photooxidation of tetrahydrobiopterin: a theoretical study. Free Radic Res 2021; 55:499-509. [PMID: 33283562 DOI: 10.1080/10715762.2020.1860213] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 11/07/2020] [Accepted: 12/02/2020] [Indexed: 01/24/2023]
Abstract
Pterins are naturally occurring pigments and enzyme cofactors widespread in living organisms. Tetrahydrobiopterin (H4Bip) is a coenzyme of aromatic amino acid hydroxylases, NO-synthases, and alkylglycerol monooxygenases. This coenzyme is prone to oxidation in the presence of molecular oxygen, a so-called autoxidation. The reactions participating in H4Bip autoxidation are well known. However, our study is an attempt to evaluate theoretically the feasibility of reactions participating in autoxidation. To do so, we have calculated the Gibbs free energy of elementary reactions between H4Bip, its derivatives, molecular oxygen, and reactive oxygen species (ROS). In the last few years, we have established the photosensitized oxidation of H4Bip experimentally. Thus, we have also evaluated the feasibility of H4Bip photooxidation reactions, which may occur according to both type-I and type-II photosensitized oxidation. We calculated Fukui indices for H4Bip and found particular atoms in the molecule that interact with nucleophiles (for example, singlet oxygen 1O2) and radicals (in particular, molecular oxygen 3O2). Therefore, we evaluated the probability of H4Bip autoxidation reactions, photooxidation reactions, and the reactivity of particular atoms in H4Bip molecule using the theoretical methods of quantum chemistry.
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Affiliation(s)
- Andrey A Buglak
- Physical Faculty, St. Petersburg State University, St. Petersburg, Russia
| | - Taisiya A Telegina
- Physical Faculty, St. Petersburg State University, St. Petersburg, Russia
- Laboratory of ecological and evolutionary biochemistry, A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Yulia L Vechtomova
- Laboratory of ecological and evolutionary biochemistry, A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Mikhail S Kritsky
- Laboratory of ecological and evolutionary biochemistry, A. N. Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, Russia
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7
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Dauletyarov Y, Wallace AA, Blackstone CC, Sanov A. Photoelectron Spectroscopy of Biacetyl and Its Cluster Anions. J Phys Chem A 2019; 123:4158-4167. [PMID: 31017789 DOI: 10.1021/acs.jpca.9b01302] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Photoelectron spectroscopy of the biacetyl (dimethylglyoxal) anion reveals the properties of the ground singlet and lowest triplet electronic states of the neutral biacetyl (BA) molecule. Due to the broad and congested nature of the singlet transition, which peaks at a vertical detachment energy VDE = 1.12(5) eV, only an upper bound of the adiabatic electron affinity of BA could be determined: EA(BA) < 0.7 eV. A narrower and more structured triplet band peaking at VDE = 3.17(2) eV reveals the adiabatic electron binding energy of the triplet to be 3.05(2) eV. These results are in good agreement with ab initio (coupled-cluster) calculations. The lowest-energy structures of the anion, singlet, and triplet states of biacetyl are characterized by different orientations of the methyl groups within the molecular frame. In the ground singlet state of neutral BA, the methyl torsion is offset by ∼60° compared to that of the anion, while in the triplet the methyl orientation is similar to that of the anion. Photoelectron spectra of the cluster anions reveal that the intermolecular interactions in the homogeneously solvated (BA) n- clusters are significantly stronger than the interactions of BA- with N2O or even of BA- with H2O. To account for these observations, π-π bonded structures of the dimer and trimer anions of biacetyl are proposed based on density-functional theory calculations. The analysis of the proposed structures indicates that the negative charge in the (BA) n- cluster anions, at least in the dimer and the trimer, is significantly delocalized between all BA moieties present and there is a significant degree of covalent bonding within the cluster.
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Affiliation(s)
- Yerbolat Dauletyarov
- Department of Chemistry and Biochemistry , The University of Arizona , Tucson , Arizona 85721 , United States
| | - Adam A Wallace
- Department of Chemistry and Biochemistry , The University of Arizona , Tucson , Arizona 85721 , United States
| | - Christopher C Blackstone
- Department of Chemistry and Biochemistry , The University of Arizona , Tucson , Arizona 85721 , United States
| | - Andrei Sanov
- Department of Chemistry and Biochemistry , The University of Arizona , Tucson , Arizona 85721 , United States
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8
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Shen BB, Lunny KG, Benitez Y, Continetti RE. Photoelectron-Photofragment Coincidence Spectroscopy With Ions Prepared in a Cryogenic Octopole Accumulation Trap: Collisional Excitation and Buffer Gas Cooling. Front Chem 2019; 7:295. [PMID: 31114785 PMCID: PMC6503059 DOI: 10.3389/fchem.2019.00295] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Accepted: 04/10/2019] [Indexed: 11/17/2022] Open
Abstract
A cryogenic octopole accumulation trap (COAT) has been coupled to a photoelectron-photofragment coincidence (PPC) spectrometer allowing for improved control over anion vibrational excitation. The anions are heated and cooled via collisions with buffer gas <17 K. Shorter trapping times (500 μs) prevent thermalization and result in anions with high internal excitation while longer trapping times (80 ms) at cryogenic temperatures thermalize the ions to the temperature of the buffer gas. The capabilities of the COAT are demonstrated using PPC spectroscopy ofO 3 - at 388 nm (Ehν = 3.20 eV). Cooling the precursor anions with COAT resulted in the elimination of the autodetachment of vibrationally excitedO 2 - produced by the photodissociationO 3 - + hν → O +O 2 - (v ≥ 4). Under heating conditions, a lower limit temperature for the anions was determined to be 1,500 K through Franck-Condon simulations of the photodetachment spectrum ofO 3 - , considering a significant fraction of the ions undergo photodissociation in competition with photodetachment. The ability to cool or heat ions by varying ion injection and trapping duration in COAT provides a new flexibility for studying the spectroscopy of cold ions as well as thermally activated processes.
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Affiliation(s)
| | | | | | - Robert E. Continetti
- Department of Chemistry and Biochemistry, University of California, San Diego, San Diego, CA, United States
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9
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Theoretical study of photoreactions between oxidized pterins and molecular oxygen. J Photochem Photobiol A Chem 2019. [DOI: 10.1016/j.jphotochem.2018.12.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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10
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Buglak AA, Kononov AI. Triplet state generation by furocoumarins revisited: a combined QSPR/DFT approach. NEW J CHEM 2018. [DOI: 10.1039/c8nj03002b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We developed a QSPR model for fast virtual screening and prediction of the efficiency of triplet state generation by furocoumarins.
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11
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Shen BB, Benitez Y, Lunny KG, Continetti RE. Internal energy dependence of the photodissociation dynamics of O3− using cryogenic photoelectron-photofragment coincidence spectroscopy. J Chem Phys 2017; 147:094307. [PMID: 28886639 DOI: 10.1063/1.4986500] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Ben B. Shen
- Department of Chemistry and Biochemistry, University of California, 9500 Gilman Drive, La Jolla, San Diego, California 92093, USA
| | - Yanice Benitez
- Department of Chemistry and Biochemistry, University of California, 9500 Gilman Drive, La Jolla, San Diego, California 92093, USA
| | - Katharine G. Lunny
- Department of Chemistry and Biochemistry, University of California, 9500 Gilman Drive, La Jolla, San Diego, California 92093, USA
| | - Robert E. Continetti
- Department of Chemistry and Biochemistry, University of California, 9500 Gilman Drive, La Jolla, San Diego, California 92093, USA
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12
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Patros KM, Mann JE, Jarrold CC. O 2-·[Polar VOC] Complexes: H-Bonding versus Charge-Dipole Interactions, and the Noninnocence of Formaldehyde. J Phys Chem A 2017; 121:5459-5467. [PMID: 28671848 DOI: 10.1021/acs.jpca.7b05124] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Anion photoelectron imaging was used to measure the photodetachment spectra of molecular complexes formed between O2- and a range of atmospherically relevant polar molecules, including species with a carbonyl group (acetone, formaldehyde) and alcohols (ethanol, propenol, butenol). Experimental spectra are analyzed using a combination of Franck-Condon simulations and electronic structure calculations. Strong charge-dipole interactions and H-bonding stabilize the complex anions relative to the neutrals, resulting in a ca. 1 eV increase in electron binding energy relative to bare O2-, an effect more pronounced in complexes with H-bonding. In addition, broken degeneracy of the O2-local πg orbitals in the complexes results in the stabilization of the low-lying excited O2 (a 1Δg)·[polar VOC] state relative to the ground O2 (X 3Σg-)·[polar VOC] state when compared to bare O2. The spectra of the O2-·[polar VOC] complexes exhibit less pronounced laser photoelectron angular distribution (PADs). The spectrum of O2-·formaldehyde is unique in terms of both spectral profile and PAD. On the basis of these experimental results in addition to computational results, the complex anion cannot be described as a distinct O2- anion partnered with an innocent solvent molecule; the molecules are more strongly coupled through charge delocalization. Overall, the results underscore how the symmetry of the O2 πg orbitals is broken by different polar partners, which may have implications for atmospheric photochemistry and models of solar radiation absorption that include collision-induced absorption.
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Affiliation(s)
- Kellyn M Patros
- Department of Chemistry, Indiana University , 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Jennifer E Mann
- Physical Electronics , 18725 Lake Drive East, Chanhassen, Minnesota, 55317, United States
| | - Caroline Chick Jarrold
- Department of Chemistry, Indiana University , 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
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Patros KM, Mann JE, Jarrold CC. Photoelectron Imaging Spectra of O 2-·VOC and O 4-·VOC Complexes. J Phys Chem A 2016; 120:7828-7838. [PMID: 27648607 DOI: 10.1021/acs.jpca.6b07107] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The anion photoelectron imaging spectra of O2-·VOC and O4-·VOC (VOC = hexane, isoprene, benzene, and benzene-d6) complexes measured using 3.49 eV photon energy, along with the results of ab initio and density functional theory results are reported and analyzed. Photodetachment of these anionic complexes accesses neutrals that model collision complexes, offering a probe of the effects of symmetry-breaking collision events on the electronic structure of normally transparent neutral molecules. The energies of O2-·VOC spectral features compared to the bare O2- indicate that photodetachment of the anion accesses a modestly repulsive region of the O2-VOC potential energy surface, with subtle VOC dependence on the relative energies of the O2 (X 3Σg-)·VOC ground state and O2 (a 1Δg)·VOC excited state. In contrast, a significantly higher intensity of the transition to the O2 (a 1Δg)·VOC excited state relative to the O2 (X 3Σg-)·VOC ground state is observed for VOC = benzene, with a less pronounced effect observed for VOC = isoprene. Similar spectral effects are observed in the O4-·benzene and O4-·isoprene PE spectra. Several explanations are considered, with involvement of a temporary anion state emerging as the most plausible.
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Affiliation(s)
- Kellyn M Patros
- Department of Chemistry, Indiana University , 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Jennifer E Mann
- Physical Electronics , 18725 Lake Drive East, Chanhassen, Minnesota 55317, United States
| | - Caroline Chick Jarrold
- Department of Chemistry, Indiana University , 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
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Dixon AR, Khuseynov D, Sanov A. Benzonitrile: Electron affinity, excited states, and anion solvation. J Chem Phys 2015; 143:134306. [DOI: 10.1063/1.4931985] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Affiliation(s)
- Andrew R. Dixon
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, USA
| | - Dmitry Khuseynov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, USA
| | - Andrei Sanov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, USA
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Mann JE, Troyer ME, Jarrold CC. Photoelectron imaging and photodissociation of ozonide in O3(-)⋅(O2)n (n = 1-4) clusters. J Chem Phys 2015; 142:124305. [PMID: 25833577 DOI: 10.1063/1.4916048] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The photoelectron images of O3 (-) and O3 (-) ⋅ (O2)n (n = 1-4) have been measured using 3.49 eV photon energy. The spectra exhibit several processes, including direct photodetachment and photodissociation with photodetachment of O(-) photofragments. Several spectra also exhibit autodetachment of vibrationally excited O2 (-) photofragments. Comparison of the bare O3 (-) photoelectron spectra to that of the complexes shows that the O3 (-) core is preserved upon clustering with several O2 molecules, though subtle changes in the Franck-Condon profile of the ground state photodetachment transition suggest some charge transfer from O3 (-) to the O2 molecules. The electron affinities of the complexes increase by less than 0.1 eV with each additional O2 molecule, which is comparable to the corresponding binding energy [K. Hiraoka, Chem. Phys. 125, 439-444 (1988)]. The relative intensity of the photofragment O(-) detachment signal to the O3 (-) ⋅ (O2)n direct detachment signal increases with cluster size. O2 (-) autodetachment signal is only observed in the O3 (-), O3 (-) ⋅ (O2)3, and O3 (-) ⋅ (O2)4 spectra, suggesting that the energy of the dissociative state also varies with the number of O2 molecules present in the cluster.
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Affiliation(s)
- Jennifer E Mann
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 40405, USA
| | - Mary E Troyer
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 40405, USA
| | - Caroline Chick Jarrold
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 40405, USA
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Khuseynov D, Dixon AR, Dokuchitz DJ, Sanov A. Photochemistry of fumaronitrile radical anion and its clusters. J Phys Chem A 2014; 118:4510-8. [PMID: 24904970 DOI: 10.1021/jp503761g] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The photodetachment and photochemistry of the radical anion of fumaronitrile (trans-1,2-dicyanoethylene) and its clusters are investigated using photoelectron imaging and photofragment spectroscopy. We report the first direct spectroscopic determination of the adiabatic electron affinity (EA) of fumaronitrile (fn) in the gas phase, EA = 1.21 ± 0.02 eV. This is significantly smaller than one-half the EA of tetracyanoethylene (TCNE). The singlet-triplet splitting in fumaronitrile is determined to be ΔES-T ≤ 2.6 eV, consistent with the known properties. An autodetachment transition is observed at 392 and 355 nm and assigned to the (2)Bu anionic resonance in the vicinity of 3.3 eV. The results are in good agreement with the predictions of the CCSD(T) and EOM-XX-CCSD(dT) (XX = IP, EE) calculations. The H2O and Ar solvation energies of fn(-) are found to be similar to the corresponding values for the anion of TCNE. In contrast, a very large (0.94 eV) photodetachment band shift, relative to fn(-), is observed for (fn)2(-). In addition, while the photofragmentation of fn(-), fn(-)·Ar, and fn(-)(H2O)1,2 yielded only the CN(-) fragment ions, the dominant anionic photofragment of (fn)2(-) is the fn(-) monomer anion. The band shift, exceeding the combined effect of two water molecules, and the fragmentation pattern, inconsistent with an intact fn(-) chromophore, rule out an electrostatically solvated fn(-)·fn structure of (fn)2(-) and favor a covalently bound dimer anion. A C2 symmetry (fn)2(-) structure, involving a covalent bond between the two fn moieties, is proposed.
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Affiliation(s)
- Dmitry Khuseynov
- Department of Chemistry and Biochemistry, The University of Arizona , P.O. Box 210041, 1306 East University Boulevard, Tucson, Arizona 85721, United States
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17
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Bandyopadhyay B, Pruitt CJM, Goebbert DJ. Communication: Photoelectron angular distributions of CH− reveal a temporary anion state. J Chem Phys 2013; 138:201101. [DOI: 10.1063/1.4808045] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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18
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Khuseynov D, Fontana MT, Sanov A. Photoelectron spectroscopy and photochemistry of tetracyanoethylene radical anion in the gas phase. Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2012.08.035] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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19
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Khuseynov D, Goebbert DJ, Sanov A. Oxygen cluster anions revisited: solvent-mediated dissociation of the core O4(-) anion. J Chem Phys 2012; 136:094312. [PMID: 22401445 DOI: 10.1063/1.3691104] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The electronic structure and photochemistry of the O(2n)(-)(H(2)O)(m), n = 1-6, m = 0-1 cluster anions is investigated at 532 nm using photoelectron imaging and photofragment mass-spectroscopy. The results indicate that both pure oxygen clusters and their hydrated counterparts with n ≥ 2 form an O(4)(-) core. Fragmentation of these clusters yields predominantly O(2)(-) and O(2)(-)·H(2)O anionic products, with the addition of O(4)(-) fragments for larger parent clusters. The fragment autodetachment patterns observed for O(6)(-) and larger O(2n)(-) species, as well as some of their hydrated counterparts, indicate that the corresponding O(2)(-) fragments are formed in excited vibrational states (v ≥ 4). Yet, surprisingly, the unsolvated O(4)(-) anion itself does not show fragment autodetachment at 532 nm. It is hypothesized that the vibrationally excited O(2)(-) is formed in the intra-cluster photodissociation of the O(4)(-) core anion via a charge-hopping electronic relaxation mechanism mediated by asymmetric solvation of the nascent photofragments: O(4)(-) → O(2)(-)(X(2)Π(g)) + O(2)(a(1)Δ(g)) → O(2)(X(3)Σ(g)(-)) + O(2)(-)(X(2)Π(g)). This process depends on the presence of solvent molecules and leads to vibrationally excited O(2)(-)(X(2)Π(g)) products.
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Affiliation(s)
- Dmitry Khuseynov
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, USA
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Sheu WS, Chiou MF. Potential Energy Surface of O2−(H2O) and Factors Controlling Water-to-O2− Binding Motifs. J Phys Chem A 2010; 115:99-104. [DOI: 10.1021/jp110264x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Wen-Shyan Sheu
- Department of Chemistry, Fu-Jen Catholic University, Taipei, Taiwan 242, Republic of China
| | - Mong-Feng Chiou
- Department of Chemistry, Fu-Jen Catholic University, Taipei, Taiwan 242, Republic of China
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Goebbert DJ, Khuseynov D, Sanov A. Photoelectron Imaging of Cyanovinylidene and Cyanoacetylene Anions. J Phys Chem A 2010; 114:2259-65. [DOI: 10.1021/jp9106102] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Daniel J. Goebbert
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - Dmitry Khuseynov
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - Andrei Sanov
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
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