1
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Wild U, Hübner O, Meiners P, Kaifer E, Enders M, Himmel HJ. Intramolecular Through-Space Double-Electron Transfer Between A Pair of Redox-Active Guanidine Units Aligned by Dithiolate Bridges. Chemistry 2023; 29:e202302418. [PMID: 37606189 DOI: 10.1002/chem.202302418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 08/22/2023] [Accepted: 08/22/2023] [Indexed: 08/23/2023]
Abstract
Using unconventional synthesis protocols, two redox-active triguanidine units are connected by a dithiolate bridge, aligning the two redox-active units in close proximity. The reduced, neutral and the tetracationic redox states with two dicationic triguanidine units are isolated and fully characterized. Then, the dicationic redox states are prepared by mixing the neutral and tetracationic molecules. At low temperatures, the dications are diamagnetic (singlet ground state) with two different triguanidine units (neutral and dicationic). At room temperature, the triplet state with two radical monocationic triguanidine units is populated. At low temperature (210 K), chemical exchange by intramolecular through-space electron-transfer between the two triguanidine units is evidenced by EXSY NMR spectroscopy. Intramolecular through-space transfer of two electrons from the neutral to the dicationic triguanidine unit is accompanied by migration of the counterions in opposite direction. The rate of double-electron transfer critically depends on the bridge. No electron-transfer is measured in the absence of a bridge (in a mixture of one dicationic and one neutral triguanidine), and relatively slow electron transfer if the bridge does not allow the two triguanidine units to approach each other close enough. The results give detailed, quantitative insight into the factors that influence intramolecular through-space double-electron-transfer processes.
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Affiliation(s)
- Ute Wild
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Olaf Hübner
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Paul Meiners
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Elisabeth Kaifer
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Markus Enders
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Hans-Jörg Himmel
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
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2
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Duff L, Meakin H, Richardson A, Greener AJ, Smith GWA, Ocaña I, Chechik V, James MJ. Denitrative Hydroxylation of Unactivated Nitroarenes. Chemistry 2023; 29:e202203807. [PMID: 36594445 DOI: 10.1002/chem.202203807] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Accepted: 12/17/2022] [Indexed: 01/04/2023]
Abstract
A one-step method for the conversion of nitroarenes into phenols under operationally simple, transition-metal-free conditions is described. This denitrative functionalization protocol provides a concise and economical alternative to conventional three-step synthetic sequences. Experimental and computational studies suggest that nitroarenes may be substituted by an electron-catalysed radical-nucleophilic substitution (SRN 1) chain mechanism.
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Affiliation(s)
- Lee Duff
- Department of Chemistry, University of York Heslington, York, YO10 5DD, UK
| | - Harry Meakin
- Department of Chemistry, University of York Heslington, York, YO10 5DD, UK
| | - Adam Richardson
- Department of Chemistry, University of York Heslington, York, YO10 5DD, UK
| | - Andrew J Greener
- Department of Chemistry, University of York Heslington, York, YO10 5DD, UK
| | - George W A Smith
- Department of Chemistry, University of York Heslington, York, YO10 5DD, UK
| | - Ivan Ocaña
- Department of Chemistry, University of York Heslington, York, YO10 5DD, UK
| | - Victor Chechik
- Department of Chemistry, University of York Heslington, York, YO10 5DD, UK
| | - Michael J James
- Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK
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3
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Bakhshandeh A, Frydel D, Levin Y. Reactive Monte Carlo simulations for charge regulation of colloidal particles. J Chem Phys 2022; 156:014108. [PMID: 34998334 DOI: 10.1063/5.0077956] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
We use a reactive Monte Carlo simulation method and the primitive model of electrolyte to study acid-base equilibrium that controls charge regulation in colloidal systems. The simulations are performed in a semi-grand canonical ensemble in which colloidal suspension is in contact with a reservoir of salt and strong acid. The interior of colloidal particles is modeled as a low dielectric medium, different from the surrounding water. The effective colloidal charge is calculated for different numbers of surface acidic groups, pH, salt concentrations, and types of electrolyte. In the case of potassium chloride, the titration curves are compared with the experimental measurements obtained using potentiometric titration. A good agreement is found between simulations and experiments. In the case of lithium chloride, the specific ionic adsorption is taken into account through the partial dehydration of lithium ion.
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Affiliation(s)
- Amin Bakhshandeh
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970 Porto Alegre, RS, Brazil
| | - Derek Frydel
- Department of Chemistry, Universidad Técnica Federico Santa María, Campus San Joaquin, 7820275 Santiago, Chile
| | - Yan Levin
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970 Porto Alegre, RS, Brazil
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4
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Shin M, Seo S, Park IH, Lee E, Habata Y, Lee SS. Metallosupramolecules of pillar[5]-bis-trithiacrown including a mercury(ii) iodide ion-triplet complex. Chem Commun (Camb) 2020; 56:10135-10138. [PMID: 32766638 DOI: 10.1039/d0cc03902k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A combination of pillar[5]-bis-trithiacrown (L) and mercury(ii) halides afforded a monomer complex (Cl--form), a 1-D coordination polymer (Br--form) and a supramolecular ion-triplet complex [(I·Hg·I)@L] (I--form). In the ion-triplet complex, the host encapsulates the (I--Hg2+-I-) entity via Hg2+π and C-HI- interactions, reflecting geometrical complementarity.
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Affiliation(s)
- Mingyeong Shin
- Department of Chemistry and Research Institute of Natural Science, Gyeongsang National University, Jinju 52828, South Korea.
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5
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Zhou Z, Fu L, Hu Y, Wang X, Wei Z, Narita A, Müllen K, Petrukhina MA. Compressing Double [7]Helicene by Successive Charging with Electrons. Angew Chem Int Ed Engl 2020; 59:15923-15927. [DOI: 10.1002/anie.202005852] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 05/22/2020] [Indexed: 12/24/2022]
Affiliation(s)
- Zheng Zhou
- Department of Chemistry University at Albany State University of New York 1400 Washington Ave Albany NY 12222 USA
| | - Lin Fu
- State Key Laboratory of Elemento-Organic Chemistry College of Chemistry Nankai University Weijin Road 94 Tianjin 300071 China
| | - Yunbin Hu
- Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
- Department of Organic and Polymer Chemistry College of Chemistry and Chemical Engineering Central South University 932 Lushan S Rd Changsha Hunan 410083 China
| | - Xiao‐Ye Wang
- State Key Laboratory of Elemento-Organic Chemistry College of Chemistry Nankai University Weijin Road 94 Tianjin 300071 China
- Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
| | - Zheng Wei
- Department of Chemistry University at Albany State University of New York 1400 Washington Ave Albany NY 12222 USA
| | - Akimutsu Narita
- Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
| | - Klaus Müllen
- Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
| | - Marina A. Petrukhina
- Department of Chemistry University at Albany State University of New York 1400 Washington Ave Albany NY 12222 USA
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6
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Zhou Z, Fu L, Hu Y, Wang X, Wei Z, Narita A, Müllen K, Petrukhina MA. Compressing Double [7]Helicene by Successive Charging with Electrons. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202005852] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Zheng Zhou
- Department of Chemistry University at Albany State University of New York 1400 Washington Ave Albany NY 12222 USA
| | - Lin Fu
- State Key Laboratory of Elemento-Organic Chemistry College of Chemistry Nankai University Weijin Road 94 Tianjin 300071 China
| | - Yunbin Hu
- Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
- Department of Organic and Polymer Chemistry College of Chemistry and Chemical Engineering Central South University 932 Lushan S Rd Changsha Hunan 410083 China
| | - Xiao‐Ye Wang
- State Key Laboratory of Elemento-Organic Chemistry College of Chemistry Nankai University Weijin Road 94 Tianjin 300071 China
- Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
| | - Zheng Wei
- Department of Chemistry University at Albany State University of New York 1400 Washington Ave Albany NY 12222 USA
| | - Akimutsu Narita
- Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
| | - Klaus Müllen
- Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
| | - Marina A. Petrukhina
- Department of Chemistry University at Albany State University of New York 1400 Washington Ave Albany NY 12222 USA
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7
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Mukherji A, Kancharla PK. C–H···Anion Interactions Assisted Addition of Water to Glycals by Sterically Hindered 2,4,6-Tri-tert-butylpyridinium Hydrochloride. Org Lett 2020; 22:2191-2195. [DOI: 10.1021/acs.orglett.0c00348] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Ananya Mukherji
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Pavan K. Kancharla
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
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8
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Yu B, Montgomery Pettitt B, Iwahara J. Experimental Evidence of Solvent-Separated Ion Pairs as Metastable States in Electrostatic Interactions of Biological Macromolecules. J Phys Chem Lett 2019; 10:7937-7941. [PMID: 31809050 PMCID: PMC6936746 DOI: 10.1021/acs.jpclett.9b03084] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Electrostatic interactions via ion pairs are vital for biological macromolecules. Regarding the free energy of each ion pair as a function of the interionic distance, continuum electrostatic models predict a single energy minimum corresponding to the contact ion-pair (CIP) state, whereas atomically detailed theoretical hydration studies predict multiple energy minima corresponding to the CIP and solvent-separated ion-pair (SIP) states. Through a statistical analysis of high-resolution crystal structures, we present experimental evidence of the SIP as a metastable state. The histogram of interionic distances between protein side-chain NH3+ and DNA phosphate groups clearly shows two major peaks corresponding to the CIP and SIP states. The statistical data are consistent with the probability distribution of the CIP-SIP equilibria previously obtained with molecular dynamics simulations. Spatial distributions of NH3+ ions and water molecules around phosphates reveal preferential sites for CIP and SIP formations and show how the ions compete with water molecules.
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9
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Phosphorescence quenching of neutral and cationic iridium(III) complexes by molecular oxygen and aromatic electron acceptors. J Photochem Photobiol A Chem 2016. [DOI: 10.1016/j.jphotochem.2016.03.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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10
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Zandarashvili L, Esadze A, Iwahara J. NMR studies on the dynamics of hydrogen bonds and ion pairs involving lysine side chains of proteins. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2016; 93:37-80. [PMID: 24018322 DOI: 10.1016/b978-0-12-416596-0.00002-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Hydrogen bonds and ion pairs involving side chains play vital roles in protein functions such as molecular recognition and catalysis. Despite the wealth of structural information about hydrogen bonds and ion pairs at functionally crucial sites on proteins, the dynamics of these fundamental chemical interactions are not well understood largely due to the lack of suitable experimental tools in the past. NMR spectroscopy is a powerful tool for investigations of protein dynamics, but the vast majority of NMR methods had been applicable only to the backbone or methyl groups. Recently, a substantial progress has been made in the research on the dynamics of hydrogen bonds and ion pairs involving lysine side-chain NH3+ groups. Together with computational/theoretical approaches, the new NMR methods provide unique insights into the dynamics of hydrogen bonds and ion pairs involving lysine side chains. Here, the methodology and its applications are reviewed.
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Affiliation(s)
- Levani Zandarashvili
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas, USA
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11
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Hack J, Grills DC, Miller JR, Mani T. Identification of Ion-Pair Structures in Solution by Vibrational Stark Effects. J Phys Chem B 2016; 120:1149-57. [PMID: 26807492 DOI: 10.1021/acs.jpcb.5b11893] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ion pairing is a fundamental consideration in many areas of chemistry and has implications in a wide range of sciences and technologies that include batteries and organic photovoltaics. Ions in solution are known to inhabit multiple possible states, including free ions (FI), contact ion pairs (CIP), and solvent-separated ion pairs (SSIP). However, in solutions of organic radicals and nonmetal electrolytes, it is often difficult to distinguish between these states. In the first part of this work, we report evidence for the formation of SSIPs in low-polarity solvents and distinct measurements of CIP, SSIP, and FI, by using the ν(C≡N) infrared (IR) band of a nitrile-substituted fluorene radical anion. Use of time-resolved IR detection following pulse radiolysis allowed us to unambiguously assign the peak of the FI. In the presence of nonmetal electrolytes, two distinct red-shifted peaks were observed and assigned to the CIP and SSIP. The assignments are interpreted in the framework of the vibrational Stark effect (VSE) and are supported by (1) the solvent dependence of ion-pair populations, (2) the observation of a cryptand-separated sodium ion pair that mimics the formation of SSIPs, and (3) electronic structure calculations. In the second part of this work, we show that a blue-shift of the ν(C≡N) IR band due to the VSE can be induced in a nitrile-substituted fluorene radical anion by covalently tethering it to a metal-chelating ligand that forms an intramolecular ion pair upon reduction and complexation with sodium ion. This adds support to the conclusion that the shift in IR absorptions by ion pairing originates from the VSE. These results combined show that we can identify ion-pair structures by using the VSE, including the existence of SSIPs in a low-polarity solvent.
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Affiliation(s)
- John Hack
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973-5000, United States.,Chemical Engineering Department, University of Virginia , 102 Engineers' Way, PO Box 400741, Charlottesville, Virginia 22904-4741, United States
| | - David C Grills
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973-5000, United States
| | - John R Miller
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973-5000, United States
| | - Tomoyasu Mani
- Chemistry Department, Brookhaven National Laboratory , Upton, New York 11973-5000, United States
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12
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Iwahara J, Esadze A, Zandarashvili L. Physicochemical Properties of Ion Pairs of Biological Macromolecules. Biomolecules 2015; 5:2435-63. [PMID: 26437440 PMCID: PMC4693242 DOI: 10.3390/biom5042435] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 09/09/2015] [Accepted: 09/11/2015] [Indexed: 11/23/2022] Open
Abstract
Ion pairs (also known as salt bridges) of electrostatically interacting cationic and anionic moieties are important for proteins and nucleic acids to perform their function. Although numerous three-dimensional structures show ion pairs at functionally important sites of biological macromolecules and their complexes, the physicochemical properties of the ion pairs are not well understood. Crystal structures typically show a single state for each ion pair. However, recent studies have revealed the dynamic nature of the ion pairs of the biological macromolecules. Biomolecular ion pairs undergo dynamic transitions between distinct states in which the charged moieties are either in direct contact or separated by water. This dynamic behavior is reasonable in light of the fundamental concepts that were established for small ions over the last century. In this review, we introduce the physicochemical concepts relevant to the ion pairs and provide an overview of the recent advancement in biophysical research on the ion pairs of biological macromolecules.
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Affiliation(s)
- Junji Iwahara
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA.
| | - Alexandre Esadze
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Levani Zandarashvili
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
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13
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Nie HJ, Yang WW, Zheng RH, Shi Q, Chen H, Yao J, Zhong YW. Metal Chelation-Assisted Amine–Amine Electronic Coupling through the 4,4′-Positions of 2,2′-Bipyridine. Inorg Chem 2015; 54:1272-82. [DOI: 10.1021/ic5024967] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hai-Jing Nie
- Beijing National Laboratory
for Molecular Sciences, CAS Key Laboratory of Photochemistry, State
Key Laboratory for Structural Chemistry of Unstable and Stable Species,
Institute of Chemistry, Chinese Academy of Sciences, 2 Bei Yi
Jie, Zhong Guan Cun, Beijing 100190, People’s Republic of China
| | - Wen-Wen Yang
- Beijing National Laboratory
for Molecular Sciences, CAS Key Laboratory of Photochemistry, State
Key Laboratory for Structural Chemistry of Unstable and Stable Species,
Institute of Chemistry, Chinese Academy of Sciences, 2 Bei Yi
Jie, Zhong Guan Cun, Beijing 100190, People’s Republic of China
| | - Ren-Hui Zheng
- Beijing National Laboratory
for Molecular Sciences, CAS Key Laboratory of Photochemistry, State
Key Laboratory for Structural Chemistry of Unstable and Stable Species,
Institute of Chemistry, Chinese Academy of Sciences, 2 Bei Yi
Jie, Zhong Guan Cun, Beijing 100190, People’s Republic of China
| | - Qiang Shi
- Beijing National Laboratory
for Molecular Sciences, CAS Key Laboratory of Photochemistry, State
Key Laboratory for Structural Chemistry of Unstable and Stable Species,
Institute of Chemistry, Chinese Academy of Sciences, 2 Bei Yi
Jie, Zhong Guan Cun, Beijing 100190, People’s Republic of China
| | - Hui Chen
- Beijing National Laboratory
for Molecular Sciences, CAS Key Laboratory of Photochemistry, State
Key Laboratory for Structural Chemistry of Unstable and Stable Species,
Institute of Chemistry, Chinese Academy of Sciences, 2 Bei Yi
Jie, Zhong Guan Cun, Beijing 100190, People’s Republic of China
| | - Jiannian Yao
- Beijing National Laboratory
for Molecular Sciences, CAS Key Laboratory of Photochemistry, State
Key Laboratory for Structural Chemistry of Unstable and Stable Species,
Institute of Chemistry, Chinese Academy of Sciences, 2 Bei Yi
Jie, Zhong Guan Cun, Beijing 100190, People’s Republic of China
| | - Yu-Wu Zhong
- Beijing National Laboratory
for Molecular Sciences, CAS Key Laboratory of Photochemistry, State
Key Laboratory for Structural Chemistry of Unstable and Stable Species,
Institute of Chemistry, Chinese Academy of Sciences, 2 Bei Yi
Jie, Zhong Guan Cun, Beijing 100190, People’s Republic of China
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14
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Zandarashvili L, Iwahara J. Temperature dependence of internal motions of protein side-chain NH3(+) groups: insight into energy barriers for transient breakage of hydrogen bonds. Biochemistry 2014; 54:538-45. [PMID: 25489884 DOI: 10.1021/bi5012749] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Although charged side chains play important roles in protein function, their dynamic properties are not well understood. Nuclear magnetic resonance methods for investigating the dynamics of lysine side-chain NH3(+) groups were established recently. Using this methodology, we have studied the temperature dependence of the internal motions of the lysine side-chain NH3(+) groups that form ion pairs with DNA phosphate groups in the HoxD9 homeodomain-DNA complex. For these NH3(+) groups, we determined order parameters and correlation times for bond rotations and reorientations at 15, 22, 28, and 35 °C. The order parameters were found to be virtually constant in this temperature range. In contrast, the bond-rotation correlation times of the NH3(+) groups were found to depend strongly on temperature. On the basis of transition state theory, the energy barriers for NH3(+) rotations were analyzed and compared to those for CH3 rotations. Enthalpies of activation for NH3(+) rotations were found to be significantly higher than those for CH3 rotations, which can be attributed to the requirement of hydrogen bond breakage. However, entropies of activation substantially reduce the overall free energies of activation for NH3(+) rotations to a level comparable to those for CH3 rotations. This entropic reduction in energy barriers may accelerate molecular processes requiring hydrogen bond breakage and play a kinetically important role in protein function.
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Affiliation(s)
- Levani Zandarashvili
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch , Galveston, Texas 77555-1068, United States
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15
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Falceto A, Casanova D, Alemany P, Alvarez S. Distortions of π-coordinated arenes with anionic character. Chemistry 2014; 20:14674-89. [PMID: 25236369 DOI: 10.1002/chem.201403889] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Indexed: 11/10/2022]
Abstract
A qualitative analysis of the distortions that operate on the π system of bridging arenes with anionic character is presented and substantiated by computational studies at the density functional B3LYP and CASSCF levels. The observed effects of bonding to two metal atoms and of the negative charge are an expansion of the arene ring due to the partial occupation of π* orbitals, an elongation or compression distortion accompanied by a loss of the equivalence of carbon-carbon bonds due to a Jahn-Teller distortion of the arene dianions, and a ring puckering due to a second-order Jahn-Teller distortion that may appear independently of the existence of the first-order effect. The workings of the orbital mixing produced by these distortions have been revealed in a straightforward way by a pseudosymmetry analysis of the HOMOs of the distorted conformations. The systems studied include Li(I) and Y(III) adducts of benzene, as well as trimethylsilyl-substituted derivatives in the former case. An analysis of the structural data of a variety of purported di- and tetraanionic arene ligands coordinated to transition metals in several bridging modes has reproduced the main geometrical trends found in the computational study for the benzene and trimethylsilyl-substituted benzene dianions, allowing a classification of the variety of structural motifs found in the literature.
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Affiliation(s)
- Andrés Falceto
- Departament de Química Inorgànica and Institut de Química, Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona (Spain)
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16
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Anderson KM, Esadze A, Manoharan M, Brüschweiler R, Gorenstein DG, Iwahara J. Direct observation of the ion-pair dynamics at a protein-DNA interface by NMR spectroscopy. J Am Chem Soc 2013; 135:3613-9. [PMID: 23406569 PMCID: PMC3721336 DOI: 10.1021/ja312314b] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Ion pairing is one of the most fundamental chemical interactions and is essential for molecular recognition by biological macromolecules. From an experimental standpoint, very little is known to date about ion-pair dynamics in biological macromolecular systems. Absorption, infrared, and Raman spectroscopic methods were previously used to characterize dynamic properties of ion pairs, but these methods can be applied only to small compounds. Here, using NMR (15)N relaxation and hydrogen-bond scalar (15)N-(31)P J-couplings ((h3)J(NP)), we have investigated the dynamics of the ion pairs between lysine side-chain NH3(+) amino groups and DNA phosphate groups at the molecular interface of the HoxD9 homeodomain-DNA complex. We have determined the order parameters and the correlation times for C-N bond rotation and reorientation of the lysine NH3(+) groups. Our data indicate that the NH3(+) groups in the intermolecular ion pairs are highly dynamic at the protein-DNA interface, which should lower the entropic costs for protein-DNA association. Judging from the C-N bond-rotation correlation times along with experimental and quantum-chemically derived (h3)J(NP) hydrogen-bond scalar couplings, it seems that breakage of hydrogen bonds in the ion pairs occurs on a sub-nanosecond time scale. Interestingly, the oxygen-to-sulfur substitution in a DNA phosphate group was found to enhance the mobility of the NH3(+) group in the intermolecular ion pair. This can partially account for the affinity enhancement of the protein-DNA association by the oxygen-to-sulfur substitution, which is a previously observed but poorly understood phenomenon.
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Affiliation(s)
- Kurtis M. Anderson
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555
- Department of NanoMedicine and Biomedical Engineering, Institute of Molecular Medicine, University of Texas Health Science Center at Houston, Houston, TX 77225
| | - Alexandre Esadze
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555
| | - Mariappan Manoharan
- Chemical Sciences Laboratory, Department of Chemistry and Biochemistry, and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306
| | - Rafael Brüschweiler
- Chemical Sciences Laboratory, Department of Chemistry and Biochemistry, and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306
| | - David G. Gorenstein
- Department of NanoMedicine and Biomedical Engineering, Institute of Molecular Medicine, University of Texas Health Science Center at Houston, Houston, TX 77225
| | - Junji Iwahara
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555
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Hernán-Gómez A, Martín A, Mena M, Santamaría C. Contact and solvent-separated ion pair aluminium “ate” complexes on a titanium oxide molecular model. Dalton Trans 2013; 42:5076-84. [DOI: 10.1039/c3dt32725f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Renz M, Kess M, Diedenhofen M, Klamt A, Kaupp M. Reliable Quantum Chemical Prediction of the Localized/Delocalized Character of Organic Mixed-Valence Radical Anions. From Continuum Solvent Models to Direct-COSMO-RS. J Chem Theory Comput 2012; 8:4189-203. [DOI: 10.1021/ct300545x] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Manuel Renz
- Technische Universität Berlin, Institut für Chemie, Theoretische Chemie,
Sekr. C7, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Martin Kess
- Technische Universität Berlin, Institut für Chemie, Theoretische Chemie,
Sekr. C7, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Michael Diedenhofen
- COSMOlogic GmbH & Co. KG, Burscheider Strasse 515, D-51381 Leverkusen, Germany
| | - Andreas Klamt
- COSMOlogic GmbH & Co. KG, Burscheider Strasse 515, D-51381 Leverkusen, Germany
| | - Martin Kaupp
- Technische Universität Berlin, Institut für Chemie, Theoretische Chemie,
Sekr. C7, Strasse des 17. Juni 135, 10623 Berlin, Germany
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Gómez-Pantoja M, Gómez-Sal P, Hernán-Gómez A, Martín A, Mena M, Santamaría C. Co-complexation of lithium gallates on the titanium molecular oxide {[Ti(η5-C5Me5)(μ-O)}3(μ3-CH)]. Inorg Chem 2012; 51:8964-72. [PMID: 22845551 DOI: 10.1021/ic301057u] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Amide and lithium aryloxide gallates [Li(+){RGaPh(3)}(-)] (R = NMe(2), O-2,6-Me(2)C(6)H(3)) react with the μ(3)-alkylidyne oxoderivative ligand [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CH)] (1) to afford the gallium-lithium-titanium cubane complexes [{Ph(3)Ga(μ-R)Li}{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CH)] [R = NMe(2) (3), O-2,6-Me(2)C(6)H(3) (4)]. The same complexes can be obtained by treatment of the [Ph(3)Ga(μ(3)-O)(3){Ti(η(5)-C(5)Me(5))}(3)(μ(3)-CH)] (2) adduct with the corresponding lithium amide or aryloxide, respectively. Complex 3 evolves with formation of 5 as a solvent-separated ion pair constituted by the lithium dicubane cationic species [Li{(μ(3)-O)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-CH)}(2)](+) together with the anionic [(GaPh(3))(2)(μ-NMe(2))](-) unit. On the other hand, the reaction of 1 with Li(p-MeC(6)H(4)) and GaPh(3) leads to the complex [Li{(μ(3)-O)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-CH)}(2)][GaLi(p-MeC(6)H(4))(2)Ph(3)] (6). X-ray diffraction studies were performed on 1, 2, 4, and 5, while trials to obtain crystals of 6 led to characterization of [Li{(μ(3)-O)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-CH)}(2)][PhLi(μ-C(6)H(5))(2)Ga(p-MeC(6)H(4))Ph] 6a.
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Affiliation(s)
- María Gómez-Pantoja
- Departamento de Química Inorgánica, Universidad de Alcalá, Campus Universitario, 28871 Alcalá de Henares, Madrid, Spain
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Leeland JW, Finn C, Escuyer B, Kawaguchi H, Nichol GS, Slawin AMZ, Love JB. Synthesis and structures of transition metal pacman complexes of heteroditopic Schiff-base pyrrole macrocycles. Dalton Trans 2012; 41:13815-31. [DOI: 10.1039/c2dt31850d] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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21
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Bozkaya U, Schaefer HF. The ten chemically transparent dinitronaphthalene isomers and their radical anions. Mol Phys 2010. [DOI: 10.1080/00268976.2010.507225] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Uğur Bozkaya
- a Department of Chemistry , Middle East Technical University , Ankara 06531 , Turkey
- b Department of Chemistry , Atatürk University , Erzurum 25240 , Turkey
- c Center for Computational Quantum Chemistry , University of Georgia , Athens , GA 30602 , USA
| | - Henry F. Schaefer
- c Center for Computational Quantum Chemistry , University of Georgia , Athens , GA 30602 , USA
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22
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Affiliation(s)
- Zai-Qun Liu
- Department of Organic Chemistry, College of Chemistry, Jilin University, Changchun 130021, China
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23
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Bodineau N, Mattalia JM, Hazimeh H, Handoo KL, Timokhin V, Négrel JC, Chanon M. About the Inhibition of Grignard Reagent Formation byp-Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the SRN1 Mechanism. European J Org Chem 2010. [DOI: 10.1002/ejoc.200901469] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Na SJ, S S, Cyriac A, Kim BE, Yoo J, Kang YK, Han SJ, Lee C, Lee BY. Elucidation of the structure of a highly active catalytic system for CO2/epoxide copolymerization: a salen-cobaltate complex of an unusual binding mode. Inorg Chem 2010; 48:10455-65. [PMID: 19780527 DOI: 10.1021/ic901584u] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Salen-type ligands comprised of ethylenediamine or 1,2-cyclohexenediamine, along with an salicylaldehyde bearing a methyl substituent on its 3-position and a -[CR(CH(2)CH(2)CH(2)N(+)Bu(3))(2)] (R = H or Me) on its 5-position, unexpectedly afford cobalt(III) complexes with uncoordinated imines. In these complexes, two salen-phenoxys and two 2,4-dinitrophenolates (DNPs), which counter the quaternary ammonium cations, coordinate persistently with cobalt, while two other DNPs are fluxional between a coordinated and an uncoordinated state in THF at room temperature. The complexes of this binding mode show excellent activities in carbon dioxide/propylene oxide copolymerization (TOF, 8300-13,000 h(-1)) but with some fluctuation in induction times (1-10 h), depending on how dry the system is. The induction time is shortened (<1.0 h) and activity is increased approximately 1.5 times upon the replacement of the two fluxional DNPs with 2,4-dinitrophenol-2,4-dinitrophenolate homoconjugation ([DNP...H...DNP](-)). Imposing steric congestion either by replacing the methyl substituent on the salicylaldehyde with tert-butyl or by employing H(2)NCMe(2)CMe(2)NH(2) instead of ethylenediamine or 1,2-cyclohexenediamine results in conventional imine-coordinating complexes, which show lower activities than uncoordinated imine complexes.
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Affiliation(s)
- Sung Jae Na
- Department of Molecular Science and Technology, Ajou University, Suwon 443-749 Korea
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26
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Rosokha SV, Lorenz B, Rosokha TY, Kochi JK. One- and two-dimensional coordination networks of the tetracyanoethylene anion-radicals with potassium counter-ions. Polyhedron 2009. [DOI: 10.1016/j.poly.2009.10.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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27
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Rosokha SV, Lu J, Han B, Kochi JK. Unusual structural effects of intermolecular π-bonding in the tetracyanopyrazine (ion-radical) dimer. NEW J CHEM 2009. [DOI: 10.1039/b812829d] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Rosokha SV, Lu J, Rosokha TY, Kochi JK. Counter-ion modulation of long-distance π-bonding of the open-shell p-benzoquinone anions. Phys Chem Chem Phys 2009; 11:324-32. [DOI: 10.1039/b811816g] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Yuasa J, Yamada S, Fukuzumi S. Accelerating and Decelerating Effects of Metal Ions on Electron-Transfer Reduction of Quinones as a Function of Temperature and Binding Modes of Metal Ions to Semiquinone Radical Anions. Chemistry 2008; 14:1866-74. [DOI: 10.1002/chem.200701420] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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30
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Rosokha SV, Newton MD, Jalilov AS, Kochi JK. The Spectral Elucidation versus the X-ray Structure of the Critical Precursor Complex in Bimolecular Electron Transfers: Application of Experimental/Theoretical Solvent Probes to Ion-Radical (Redox) Dyads. J Am Chem Soc 2008; 130:1944-52. [DOI: 10.1021/ja076591b] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sergiy V. Rosokha
- Department of Chemistry, University of Houston, Houston, Texas 77204, and Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973
| | - Marshall D. Newton
- Department of Chemistry, University of Houston, Houston, Texas 77204, and Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973
| | - Almaz S. Jalilov
- Department of Chemistry, University of Houston, Houston, Texas 77204, and Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973
| | - Jay K. Kochi
- Department of Chemistry, University of Houston, Houston, Texas 77204, and Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973
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31
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Yuasa J, Fukuzumi S. OFF−OFF−ON Switching of Fluorescence and Electron Transfer Depending on Stepwise Complex Formation of a Host Ligand with Guest Metal Ions. J Am Chem Soc 2007; 130:566-75. [DOI: 10.1021/ja0748480] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Junpei Yuasa
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
| | - Shunichi Fukuzumi
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
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32
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Rosokha SV, Kochi JK. The question of aromaticity in open-shell cations and anions as ion-radical offsprings of polycyclic aromatic and antiaromatic hydrocarbons. J Org Chem 2007; 71:9357-65. [PMID: 17137362 DOI: 10.1021/jo061695a] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Arene cation-radicals and anion-radicals result directly from the one-electron oxidation and reduction of many aromatic hydrocarbons, yet virtually nothing is known of their intrinsic (thermodynamic) stability and hence "aromatic character". Since such paramagnetic ion radicals lie intermediate between aromatic (Hückel) hydrocarbons with 4n + 2-electrons and antiaromatic analogues with 4n-electrons, we can now address the question of pi-delocalization in these odd-electron counterparts. Application of the structure-based "harmonic oscillator model of aromaticity" or the HOMA method leads to the surprising conclusion that the aromaticity of these rather reactive, kinetically unstable arene cation and anion radicals (as measured by the HOMA index) is actually higher than that of their (diamagnetic) parent-contrary to conventional expectations.
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Affiliation(s)
- Sergiy V Rosokha
- Department of Chemistry, University of Houston, Houston, Texas 77204, USA
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Yuasa J, Yamada S, Fukuzumi S. A mechanistic dichotomy in scandium ion-promoted hydride transfer of an NADH analogue: delicate balance between one-step hydride-transfer and electron-transfer pathways. J Am Chem Soc 2007; 128:14938-48. [PMID: 17105305 DOI: 10.1021/ja064708a] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The rate constant (kH) of hydride transfer from an NADH analogue, 9,10-dihydro-10-methylacridine (AcrH2), to 1-(p-tolylsulfinyl)-2,5-benzoquinone (TolSQ) increases with increasing Sc(3+) concentration ([Sc(3+)]) to reach a constant value, when all TolSQ molecules form the TolSQ-Sc(3+) complex. When AcrH2 is replaced by the dideuterated compound (AcrD2), however, the rate constant (kD) increases linearly with an increase in ([Sc(3+)]) without exhibiting a saturation behavior. In such a case, the primary kinetic deuterium isotope effect (kH/kD) decreases with increasing ([Sc(3+)]). On the other hand, the rate constant of Sc(3+)-promoted electron transfer from tris(2-phenylpyridine)iridium [Ir(ppy)3]to TolSQ also increases linearly with increasing ([Sc(3+)]) at high concentrations of Sc(3+) due to formation of a 1:2 complex between TolSQ*- and Sc(3+), [TolSQ*--(Sc(3+)2], which was detected by ESR. The significant difference with regard to dependence of the rate constant of hydride transfer on ([Sc(3+)]) between AcrH2 and AcrD2 in comparison with that of Sc3+-promoted electron transfer indicates that the reaction pathway is changed from one-step hydride transfer from AcrH2 to the TolSQ-Sc3+ complex to Sc3+-promoted electron transfer from AcrD2 to the TolSQ-Sc3+ complex, followed by proton and electron transfer. Such a change between two reaction pathways, which are employed simultaneously, is also observed by simple changes of temperature and concentration of Sc3+.
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Affiliation(s)
- Junpei Yuasa
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
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Yuasa J, Suenobu T, Fukuzumi S. Binding modes in metal ion complexes of quinones and semiquinone radical anions: electron-transfer reactivity. Chemphyschem 2007; 7:942-54. [PMID: 16521156 DOI: 10.1002/cphc.200500640] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
9,10-Phenanthrenequinone (PQ) and 1,10-phenanthroline-5,6-dione (PTQ) form 1:1 and 2:1 complexes with metal ions (M (n+)=Sc (3+), Y (3+), Mg (2+), and Ca (2+)) in acetonitrile (MeCN), respectively. The binding constants of PQ--M (n+) complexes vary depending on either the Lewis acidity or ion radius of metal ions. The one-electron reduced species (PTQ(-)) forms 1:1 complexes with M (n+), and PQ(-) also forms 1:1 complexes with Sc(3+), Mg(2+), and Ca(2+), whereas PQ(-) forms 1:2 complexes with Y(3+) and La(3+), as indicated by electron spin resonance (ESR) measurements. On the other hand, semiquinone radical anions (Q(-) and NQ(-)) derived from p-benzoquinone (Q) and 1,4-naphthoquinone (NQ) form Sc(3+)-bridged pi-dimer radical anion complexes, Q(-)--(Sc(3+))(n)--Q and NQ(-)--(Sc(3+))(n)-NQ (n=2 and 3), respectively. The one-electron reduction potentials of quinones (PQ, PTQ, and Q) are largely positively shifted in the presence of M (n+). The rate constant of electron transfer from CoTPP (TPP(2-)=dianion of tetraphenylporphyrin) to PQ increases with increasing the concentration of Sc(3+) to reach a constant value, when all PQ molecules form the 1:1 complex with Sc(3+). Rates of electron transfer from 10,10'-dimethyl-9,9'-biacridine [(AcrH)(2)] to PTQ are also accelerated significantly by the presence of Sc(3+), Y(3+), and Mg(2+), exhibiting a first-order dependence with respect to concentrations of metal ions. In contrast to the case of o-quinones, unusually high kinetic orders are observed for rates of Sc(3+)-promoted electron transfer from tris(2-phenylpyridine)iridium(III) [Ir(ppy)(3)] to p-quinones (Q): second-order dependence on concentration of Q, and second- and third-order dependence on concentration of Sc(3+) due to formation of highly ordered radical anion complexes, Q()--(Sc(3+))(n)--Q (n=2 and 3).
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Affiliation(s)
- Junpei Yuasa
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, SORST, Japan
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Sun D, Rosokha SV, Kochi JK. Reversible Interchange of Charge-Transfer versus Electron-Transfer States in Organic Electron Transfer via Cross-Exchanges between Diamagnetic (Donor/Acceptor) Dyads. J Phys Chem B 2007; 111:6655-66. [PMID: 17388558 DOI: 10.1021/jp068994o] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The choice of appropriate electron donors (D) and acceptors (A) allows for the first time the simultaneous observation of Mulliken charge-transfer states, [D,A], that can coexist in reversible equilibrium with electron-transfer states, {D+*,A-*}, for various diamagnetic organic redox dyads. The theoretical analysis based on the (two-state) Mulliken-Hush analysis of the intervalence optical transition, together with the spectral identification of the transient ion-radical pairs of D+* and A-*, leads to the construction of the unusual potential-energy surface consisting of a single minimum without any reorganizational barrier for electron-transfer cross-exchanges with driving forces close to the isergonic limit. The mechanistic implications of this direct demonstration of the facile charge-transfer/electron-transfer interchange are discussed.
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Affiliation(s)
- Duoli Sun
- Department of Chemistry, University of Houston, Houston, Texas 77204, USA
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36
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Rosokha SV, Kochi JK. Continuum of outer- and inner-sphere mechanisms for organic electron transfer. Steric modulation of the precursor complex in paramagnetic (ion-radical) self-exchanges. J Am Chem Soc 2007; 129:3683-97. [PMID: 17338527 DOI: 10.1021/ja069149m] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Transient 1:1 precursor complexes for intermolecular self-exchange between various organic electron donors (D) and their paramagnetic cation radicals (D+*), as well as between different electron acceptors (A) paired with their anion radicals (A-*), are spectrally (UV-NIR) observed and structurally (X-ray) identified as the cofacial (pi-stacked) associates [D, D+*] and [A-*, A], respectively. Mulliken-Hush (two-state) analysis of their diagnostic intervalence bands affords the electronic coupling elements (HDA), which together with the Marcus reorganization energies (lambda) from the NIR spectral data are confirmed by molecular-orbital computations. The HDA values are found to be a sensitive function of the bulky substituents surrounding the redox centers. As a result, the steric modulation of the donor/acceptor separation (rDA) leads to distinctive electron-transfer rates between sterically hindered donors/acceptors and their more open (unsubstituted) parents. The latter is discussed in the context of a continuous series of outer- and inner-sphere mechanisms for organic electron-transfer processes in a manner originally formulated by Taube and co-workers for inorganic (coordination) donor/acceptor dyads-with conciliatory attention paid to traditional organic versus inorganic concepts.
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Affiliation(s)
- Sergiy V Rosokha
- Department of Chemistry, University of Houston, Houston, Texas 77204, USA
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Rosokha SV, Kochi JK. Molecular and Electronic Structures of the Long-Bonded π-Dimers of Tetrathiafulvalene Cation-Radical in Intermolecular Electron Transfer and in (Solid-State) Conductivity. J Am Chem Soc 2007; 129:828-38. [PMID: 17243819 DOI: 10.1021/ja064166x] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Tetrathiafulvalene (TTF) as the prototypical electron donor for solid-state (electronics) applications is converted to the unusual cation-radical salt, TTF+* CB- (where CB- is the non-coordinating closo-dodecamethylcarboranate), for crystallographic and spectral analyses. Near-IR studies establish the spontaneous self-association of TTF+* to form the diamagnetic [TTF+,TTF+] dication and to also undergo the equally rapid cross-association with its parent donor to form the mixed-valence [TTF+*,TTF] cation-radical. The latter, most importantly, represents the first (dyad) member of a series of p-doped tetrathiafulvalene (stacked) arrays, and the thorough scrutiny of its electronic structure with the aid of Mulliken-Hush (two-state) analysis of the diagnostic (intervalence) NIR band reveals Robin-Day Class II behavior. The theoretical consequences of the unique structure of the mixed-valence [TTF+*,TTF] dyad on (a) the electron-transfer mechanism for self-exchange, (b) the molecular-orbital analysis of the Marcus reorganization energy, and (c) the ab initio computation of the coupling element or transfer integral in p-doped (solid-state) arrays are discussed.
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Affiliation(s)
- Sergiy V Rosokha
- Department of Chemistry, University of Houston, Houston, Texas 77204, USA
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Lü JM, Rosokha SV, Neretin IS, Kochi JK. Quinones as Electron Acceptors. X-Ray Structures, Spectral (EPR, UV−vis) Characteristics and Electron-Transfer Reactivities of Their Reduced Anion Radicals as Separated vs Contact Ion Pairs. J Am Chem Soc 2006; 128:16708-19. [PMID: 17177421 DOI: 10.1021/ja066471o] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Successful isolation of a series of pure (crystalline) salts of labile quinone anion radicals suitable for X-ray crystallographic analysis allows for the first time their rigorous structural distinction as "separated" ion pairs (SIPs) vs "contact" ion pairs (CIPs). The quantitative evaluation of the precise changes in the geometries of these quinones (Q) upon one-electron reduction to afford the anion radical (Q-*) is viewed relative to the corresponding (two-electron) reduction to the hydroquinone (H2Q) via the Pauling bond-length/bond-order paradigm. Structural consequences between such separated and contact ion pairs as defined in the solid state with those extant in solution are explored in the context of their spectral (EPR, UV-vis) properties and isomerization of tightly bound CIPs. Moreover, the SIP/CIP dichotomy is also examined in intermolecular interactions for rapid (self-exchange) electron transfer between Q-* and Q with second-order rate constants of kET approximately equal to 10(8) M-1 s-1, together with the spectral observation of the paramagnetic intermediates [Q,Q-*]leading to 1:1 adducts, as established by X-ray crystallography.
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Affiliation(s)
- Jian-Ming Lü
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
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Mulliken–Hush elucidation of the encounter (precursor) complex in intermolecular electron transfer via self-exchange of tetracyanoethylene anion-radical. Chem Phys 2006. [DOI: 10.1016/j.chemphys.2005.10.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Rosokha SV, Dibrov SM, Rosokha TY, Kochi JK. Electronic structures of intermolecular charge-transfer states in fast electron transfers with tetrathiafulvalene donor. Thermal and photoactivation of [2 + 4] cycloaddition to o-chloranil acceptor. Photochem Photobiol Sci 2006; 5:914-24. [PMID: 17019469 DOI: 10.1039/b607431f] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Tetrathiafulvalene (TTF) spontaneously forms a series of unusual charge-transfer complexes with various quinonoid acceptors such as o-chloranil (CA) that show pronounced near-IR absorption (lambda(CT) = 1100 nm). The successful isolation of the corresponding [1 : 1] donor-acceptor complex from solution and X-ray crystallographic analysis at low temperatures reveal the polarized charge-transfer state: [TTF(q+),CA(q-)] with high degree of charge-transfer (q = 0.6), which is spectrally and crystallographically distinguished from the separate redox (ion-pair) state: [TTF(+*) + CA(-*) ]. The unique interconversion of charge-transfer and electron-transfer states is theoretically well-accommodated by Mulliken theory using semi-empirical valence-bond and molecular-orbital methodologies. Mechanistic implications are discussed of both the thermally activated and the photochemically promoted processes via fast (intracomplex) electron transfer followed by collapse of the adiabatic and the non-adiabatic (vibrationally-excited) ion-pairs, respectively, to the [2 + 4] cycloadduct of tetrathiafulvalene and o-chloranil.
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Affiliation(s)
- S V Rosokha
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
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41
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Yuasa J, Suenobu T, Fukuzumi S. Thermochromism of Metal Ion Complexes of Semiquinone Radical Anions. Control of Equilibria between Diamagnetic and Paramagnetic Species by Lewis Acids. J Phys Chem A 2005; 109:9356-62. [PMID: 16833278 DOI: 10.1021/jp053616p] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Metal ion complexes of semiquinone radical anions exhibit different types of thermochromism depending on metal ions and quinones. Metal ion complexes of 1,10-phenanthroline-5,6-dione radical anion (PTQ(.-)) produced by the electron-transfer reduction of PTQ by 1,1'-dimethylferrocene (Me(2)Fc) in the presence of metal ions (Mg(2+) and Sc(3+)) exhibit the color change depending on temperature, accompanied by the concomitant change in the ESR signal intensity. In the case of Mg(2+), electron transfer from Me(2)Fc to PTQ is in equilibrium, when the concentration of the PTQ(.-)-Mg(2+) complex (lambda(max) = 486 nm) increases with increasing temperature because of the positive enthalpy for the electron-transfer equilibrium. In contrast to the case of Mg(2+), electron transfer from Me(2)Fc to PTQ is complete in the presence of Sc(3+), which is a much stronger Lewis acid than Mg(2+), to produce the PTQ(.-)-Sc(3+) complex (lambda(max) = 631 nm). This complex is in disproportionation equilibrium and the concentration of the PTQ(.-)-Sc(3+) complex increases with decreasing temperature because of the negative enthalpy for the proportionation direction, resulting in the remarkable color change in the visible region. On the other hand, the p-benzosemiquinone radical anion (Q(.-)) forms a 2:2 pi-dimer radical anion complex [Q(.-)-(Sc(3+))(2)-Q] with Q and Sc(3+) ions at 298 K (yellow color), which is converted to a 2:3 pi-dimer radical anion complex [Q(.-)-(Sc(3+))(3)-Q] with a strong absorption band at lambda(max) = 604 nm (blue color) when the temperature is lowered to 203 K. The change in the number of binding Sc(3+) ions depending on temperature also results in the remarkable color change, associated with the change in the ESR spectra.
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Affiliation(s)
- Junpei Yuasa
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
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Rosokha SV, Lü JM, Newton MD, Kochi JK. Intermolecular Electron-Transfer Mechanisms via Quantitative Structures and Ion-Pair Equilibria for Self-Exchange of Anionic (Dinitrobenzenide) Donors. J Am Chem Soc 2005; 127:7411-20. [PMID: 15898790 DOI: 10.1021/ja051063q] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Definitive X-ray structures of "separated" versus "contact" ion pairs, together with their spectral (UV-NIR, ESR) characterizations, provide the quantitative basis for evaluating the complex equilibria and intrinsic (self-exchange) electron-transfer rates for the potassium salts of p-dinitrobenzene radical anion (DNB(-)). Three principal types of ion pairs, K(L)(+)DNB(-), are designated as Classes S, M, and C via the specific ligation of K(+) with different macrocyclic polyether ligands (L). For Class S, the self-exchange rate constant for the separated ion pair (SIP) is essentially the same as that of the "free" anion, and we conclude that dinitrobenzenide reactivity is unaffected when the interionic distance in the separated ion pair is r(SIP) > or =6 Angstroms. For Class M, the dynamic equilibrium between the contact ion pair (with r(CIP) = 2.7 Angstroms) and its separated ion pair is quantitatively evaluated, and the rather minor fraction of SIP is nonetheless the principal contributor to the overall electron-transfer kinetics. For Class C, the SIP rate is limited by the slow rate of CIP right arrow over left arrow SIP interconversion, and the self-exchange proceeds via the contact ion pair by default. Theoretically, the electron-transfer rate constant for the separated ion pair is well-accommodated by the Marcus/Sutin two-state formulation when the precursor in Scheme 2 is identified as the "separated" inner-sphere complex (IS(SIP)) of cofacial DNB(-)/DNB dyads. By contrast, the significantly slower rate of self-exchange via the contact ion pair requires an associative mechanism (Scheme 3) in which the electron-transfer rate is strongly governed by cationic mobility of K(L)(+) within the "contact" precursor complex (IS(CIP)) according to the kinetics in Scheme 4.
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Affiliation(s)
- Sergiy V Rosokha
- Department of Chemistry, University of Houston, Texas, 77204, USA
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Hazimeh H, Mattalia JM, Marchi-Delapierre C, Barone R, Nudelman NS, Chanon M. Radical clocks and electron transfer. Comparison of crown ether effects on the reactivity of potassium and magnesium towards 1-bromo-2-(3-butenyl)benzene. The incidence of homogeneous versus heterogeneous electron transfer on selectivity. J PHYS ORG CHEM 2005. [DOI: 10.1002/poc.986] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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