1
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Heck J, Kucenko A, Hoffmann A, Herres-Pawlis S. Position of substituents directs the electron transfer properties of entatic state complexes: new insights from guanidine-quinoline copper complexes. Dalton Trans 2024; 53:12527-12542. [PMID: 39016043 DOI: 10.1039/d4dt01539h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2024]
Abstract
In a previous study, we showed that the properties and the ability as an entatic state model of copper guanidine quinoline complexes are significantly influenced by a methyl or methyl ester substituent in the 2-position. To prove the importance of the 2-position of the substituent, two novel guanidine quinoline ligands with a methyl or methyl ester substituent in the 4-position and the corresponding copper complexes were synthesized and characterized in this study. The influence of the substituent position on the copper complexes was investigated with various experimental and theoretical methods. The molecular structures of the copper complexes were examined in the solid state by single-crystal X-ray diffraction (SCXRD) and by density functional theory (DFT) calculations indicating a strong dependency on the substituent position compared to the systems substituted in the 2-position from the previous study. Further, the significantly different influence on the donor properties in dependency on the substituent position was analyzed with natural bond orbital (NBO) calculations. By the determination of the redox potentials, the impact on the electrochemical stabilization was examined. With regard to further previously analyzed guanidine quinoline copper complexes, the electrochemical stabilization was correlated with the charge-transfer energies calculated by NBO analysis and ground state energies, revealing the substituent influence and enabling a comparatively easy and accurate possibility for the theoretical calculation of the relative redox potential. Finally, the electron transfer properties were quantified by determining the electron self-exchange rates via the Marcus theory and by theoretical calculation of the reorganization energies via Nelsen's four-point method. The results gave important insights into the dependency between the ability of the copper complexes as entatic state model and the type and position of the substituent.
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Affiliation(s)
- Joshua Heck
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany.
| | - Anastasia Kucenko
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany.
| | - Alexander Hoffmann
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany.
| | - Sonja Herres-Pawlis
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany.
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2
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Griffin PJ, Olshansky L. Rapid Electron Transfer Self-Exchange in Conformationally Dynamic Copper Coordination Complexes. J Am Chem Soc 2023; 145:20158-20162. [PMID: 37683290 DOI: 10.1021/jacs.3c05935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/10/2023]
Abstract
We report the electron transfer (ET) self-exchange rate constants (k11) for a pair of CuII/I complexes utilizing dpaR (dpa = dipicolylaniline, R = OMe, SMe) ligands assessed by NMR line broadening experiments. These ligands afford copper complexes that are conformationally dynamic in one oxidation state. With R = OMe, the CuI complex is dynamic, while with R = SMe, the CuII complex is dynamic. Both complexes exhibit unexpectedly large k11 values of 2.48(6) × 105 and 2.21(9) × 106 M-1 s-1 for [CuCl(dpaOMe)]+/0 and [CuCl(dpaSMe)]+/0, respectively. Among the fastest reported molecular copper coordination complexes to date, that of [CuCl(dpaSMe)]+/0 exceeds all others by an order of magnitude and compares only with those observed in type 1 blue copper proteins. The dynamicity of these complexes establishes pre-steady-state conformational equilibria that minimize the inner-sphere reorganization energies to 0.71 and 0.62 eV for R = OMe and SMe, respectively. In contrast to the emphasis on rigidity in the formulation of entatic states applied to blue copper proteins, the success of these two systems highlights the relevance of conformational dynamicity in mediating rapid ET.
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Affiliation(s)
- Paul J Griffin
- Department of Chemistry, Center for Biophysics and Quantitative Biology, and Materials Research Laboratory, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Lisa Olshansky
- Department of Chemistry, Center for Biophysics and Quantitative Biology, and Materials Research Laboratory, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
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3
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Liu Y, Resch SG, Chen H, Dechert S, Demeshko S, Bill E, Ye S, Meyer F. Fully Delocalized Mixed-Valent Cu 1.5 Cu 1.5 Complex: Strong Cu-Cu interaction and Fast Electron Self-Exchange Rate Despite Large Structural Changes. Angew Chem Int Ed Engl 2023; 62:e202215840. [PMID: 36504436 DOI: 10.1002/anie.202215840] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 12/07/2022] [Accepted: 12/08/2022] [Indexed: 12/14/2022]
Abstract
A flexible macrocyclic ligand with two tridentate {CNC} compartments can host two Cu ions in reversibly interconvertible states, CuI CuI (1) and mixed-valent Cu1.5 Cu1.5 (2). They were characterized by XRD and multiple spectroscopic methods, including EPR, UV/Vis absorption and MCD, in combination with TD-DFT and CASSCF calculations. 2 features a short Cu⋅⋅⋅Cu distance (≈2.5 Å; compared to ≈4.0 Å in 1) and a very high delocalization energy of 13 000 cm-1 , comparable to the mixed-valent state of the biological CuA site. Electron self-exchange between 1 and 2 is rapid despite large structural reorganization, and is proposed to proceed via a sequential mechanism involving an active conformer of 1, viz. 1'; the latter has been characterized by XRD. Such electron transfer (ET) process is reminiscent of the conformationally gated ET proposed for biological systems. This redox couple is a unique pair of flexible dicopper complexes, achieving fast electron self-exchange closely related to the function of the CuA site.
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Affiliation(s)
- Yang Liu
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, 37077, Göttingen, Germany
| | - Stefan G Resch
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, 37077, Göttingen, Germany
| | - Haowei Chen
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, P. R. China.,Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China
| | - Sebastian Dechert
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, 37077, Göttingen, Germany
| | - Serhiy Demeshko
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, 37077, Göttingen, Germany
| | - Eckhard Bill
- Department of Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Shengfa Ye
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, P. R. China
| | - Franc Meyer
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, 37077, Göttingen, Germany
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4
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Heck J, Metz F, Buchenau S, Teubner M, Grimm-Lebsanft B, Spaniol TP, Hoffmann A, Rübhausen MA, Herres-Pawlis S. Manipulating electron transfer - the influence of substituents on novel copper guanidine quinolinyl complexes. Chem Sci 2022; 13:8274-8288. [PMID: 35919707 PMCID: PMC9297705 DOI: 10.1039/d2sc02910c] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 06/11/2022] [Indexed: 11/21/2022] Open
Abstract
Copper guanidine quinolinyl complexes act as good entatic state models due to their distorted structures leading to a high similarity between Cu(i) and Cu(ii) complexes. For a better understanding of the entatic state principle regarding electron transfer a series of guanidine quinolinyl ligands with different substituents in the 2- and 4-position were synthesized to examine the influence on the electron transfer properties of the corresponding copper complexes. Substituents with different steric or electronic influences were chosen. The effects on the properties of the copper complexes were studied applying different experimental and theoretical methods. The molecular structures of the bis(chelate) copper complexes were examined in the solid state by single-crystal X-ray diffraction and in solution by X-ray absorption spectroscopy and density functional theory (DFT) calculations revealing a significant impact of the substituents on the complex structures. For a better insight natural bond orbital (NBO) calculations of the ligands and copper complexes were performed. The electron transfer was analysed by the determination of the electron self-exchange rates following Marcus theory. The obtained results were correlated with the results of the structural analysis of the complexes and of the NBO calculations. Nelsen's four-point method calculations give a deeper understanding of the thermodynamic properties of the electron transfer. These studies reveal a significant impact of the substituents on the properties of the copper complexes.
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Affiliation(s)
- Joshua Heck
- Institute of Inorganic Chemistry, RWTH Aachen University Landoltweg 1a 52074 Aachen Germany
| | - Fabian Metz
- Institute of Inorganic Chemistry, RWTH Aachen University Landoltweg 1a 52074 Aachen Germany
| | - Sören Buchenau
- Institute of Nanostructure and Solid State Physics, University of Hamburg Luruper Chaussee 149 22761 Hamburg Germany
| | - Melissa Teubner
- Institute of Inorganic Chemistry, RWTH Aachen University Landoltweg 1a 52074 Aachen Germany
- Institute of Nanostructure and Solid State Physics, University of Hamburg Luruper Chaussee 149 22761 Hamburg Germany
| | - Benjamin Grimm-Lebsanft
- Institute of Nanostructure and Solid State Physics, University of Hamburg Luruper Chaussee 149 22761 Hamburg Germany
| | - Thomas P Spaniol
- Institute of Inorganic Chemistry, RWTH Aachen University Landoltweg 1a 52074 Aachen Germany
| | - Alexander Hoffmann
- Institute of Inorganic Chemistry, RWTH Aachen University Landoltweg 1a 52074 Aachen Germany
| | - Michael A Rübhausen
- Institute of Nanostructure and Solid State Physics, University of Hamburg Luruper Chaussee 149 22761 Hamburg Germany
| | - Sonja Herres-Pawlis
- Institute of Inorganic Chemistry, RWTH Aachen University Landoltweg 1a 52074 Aachen Germany
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5
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Zhang W, Moore CE, Zhang S. Encapsulation of tricopper cluster in a synthetic cryptand enables facile redox processes from Cu ICu ICu I to Cu IICu IICu II states. Chem Sci 2020; 12:2986-2992. [PMID: 34164067 PMCID: PMC8179370 DOI: 10.1039/d0sc05441k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
One-pot reaction of tris(2-aminoethyl)amine (TREN), [CuI(MeCN)4]PF6, and paraformaldehyde affords a mixed-valent [TREN4CuIICuICuI(μ3-OH)](PF6)3 complex. The macrocyclic azacryptand TREN4 contains four TREN motifs, three of which provide a bowl-shape binding pocket for the [Cu3(μ3-OH)]3+ core. The fourth TREN caps on top of the tricopper cluster to form a cryptand, imposing conformational constraints and preventing solvent interaction. Contrasting the limited redox capability of synthetic tricopper complexes reported so far, [TREN4CuIICuICuI(μ3-OH)](PF6)3 exhibits several reversible single-electron redox events. The distinct electrochemical behaviors of [TREN4CuIICuICuI(μ3-OH)](PF6)3 and its solvent-exposed analog [TREN3CuIICuIICuII(μ3-O)](PF6)4 suggest that isolation of tricopper core in a cryptand enables facile electron transfer, allowing potential application of synthetic tricopper complexes as redox catalysts. Indeed, the fully reduced [TREN4CuICuICuI(μ3-OH)](PF6)2 can reduce O2 under acidic conditions. The geometric constraints provided by the cryptand are reminiscent of Nature's multicopper oxidases (MCOs). For the first time, a synthetic tricopper cluster was isolated and fully characterized at CuICuICuI (4a), CuIICuICuI (4b), and CuIICuIICuI (4c) states, providing structural and spectroscopic models for many intermediates in MCOs. Fast electron transfer rates (105 to 106 M-1 s-1) were observed for both CuICuICuI/CuIICuICuI and CuIICuICuI/CuIICuIICuI redox couples, approaching the rapid electron transfer rates of copper sites in MCO.
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Affiliation(s)
- Weiyao Zhang
- Department of Chemistry and Biochemistry, The Ohio State University 100 W. 18th Ave Columbus OH USA
| | - Curtis E Moore
- Department of Chemistry and Biochemistry, The Ohio State University 100 W. 18th Ave Columbus OH USA
| | - Shiyu Zhang
- Department of Chemistry and Biochemistry, The Ohio State University 100 W. 18th Ave Columbus OH USA
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6
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Llanos L, Vera C, Vega A, Aravena D, Lemus L. Reactivity of Cu IN 4 Flattened Complexes: Interplay between Coordination Geometry and Ligand Flexibility. Inorg Chem 2020; 59:15061-15073. [PMID: 33021785 DOI: 10.1021/acs.inorgchem.0c02037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The relation between redox activity and coordination geometry in CuIN4 complexes indicates that more flattened structures tend to be more reactive. Such a preorganization of the ligand confers to the complex geometries closer to a transition state, which has been termed the "entatic" state in metalloproteins, more recently extending this concept for copper complexes. However, many aspects of the redox chemistry of CuI complexes cannot be explained only by flattening. For instance, the role of ligand flexibility in this context is an open debate nowadays. To analyze this point, we studied oxidation properties of a series of five monometallic CuI Schiff-base complexes, [CuI(Ln)]+, which span a range of geometries from a distorted square planar (n = 3) to a distorted tetrahedron (n = 6, 7). This stepped control of the structure around the CuI atom allows us to explore the effect of the flattening distortion on both the electronic and redox properties through the series. Experimental studies were complemented by a theoretical analysis based on density functional theory calculations. As expected, oxidation was favored in the flattened structures, spanning a broad potential window of 370 mV for the complete series. This orderly behavior was tested in the reductive dehalogenation reaction of tetrachloroethane (TCE). Kinetic studies show that CuI oxidation by TCE is faster as the flattening distortion is higher and the oxidation potentials of the metal are lower. However, the most reactive complex was not the more planar, contradicting the trend expected from oxidation potentials. The origin of this irregularity is related to ligand flexibility and its connection with the atom/electron transfer reaction path, highlighting the need to consider effects beyond flattening distortion to better understand the reactivity of this important class of complexes.
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Affiliation(s)
- Leonel Llanos
- Departamento de Química de los Materiales, Facultad de Química y Biología, Universidad de Santiago de Chile, Av. Libertador Bernardo O'Higgins 3363, Estacio'n Central, Santiago, Chile
| | - Cristian Vera
- Departamento de Química de los Materiales, Facultad de Química y Biología, Universidad de Santiago de Chile, Av. Libertador Bernardo O'Higgins 3363, Estacio'n Central, Santiago, Chile
| | - Andrés Vega
- Facultad de Ciencias Exactas, Departamento de Ciencias Químicas, Universidad Andrés Bello, Quillota 980, Viña del Mar, Chile.,Centro para el Desarrollo de Nanociencias y Nanotecnología, CEDENNA, Santiago, Chile
| | - Daniel Aravena
- Departamento de Química de los Materiales, Facultad de Química y Biología, Universidad de Santiago de Chile, Av. Libertador Bernardo O'Higgins 3363, Estacio'n Central, Santiago, Chile
| | - Luis Lemus
- Departamento de Química de los Materiales, Facultad de Química y Biología, Universidad de Santiago de Chile, Av. Libertador Bernardo O'Higgins 3363, Estacio'n Central, Santiago, Chile
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7
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Jones SM, Heppner DE, Vu K, Kosman DJ, Solomon EI. Rapid Decay of the Native Intermediate in the Metallooxidase Fet3p Enables Controlled Fe II Oxidation for Efficient Metabolism. J Am Chem Soc 2020; 142:10087-10101. [PMID: 32379440 DOI: 10.1021/jacs.0c02384] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The multicopper oxidases (MCOs) couple four 1e- oxidations of substrate to the 4e- reduction of O2 to H2O. These divide into two groups: those that oxidize organic substrates with high turnover frequencies (TOFs) up to 560 s-1 and those that oxidize metal ions with low TOFs, ∼1 s-1 or less. The catalytic mechanism of the organic oxidases has been elucidated, and the high TOF is achieved through rapid intramolecular electron transfer (IET) to the native intermediate (NI), which only slowly decays to the resting form. Here, we uncover the factors that govern the low TOF in Fet3p, a prototypical metallooxidase, in the context of the MCO mechanism. We determine that the NI decays rapidly under optimal turnover conditions, and the mechanism thereby becomes rate-limited by slow IET to the resting enzyme. Development of a catalytic model leads to the important conclusions that proton delivery to the NI controls the mechanism and enables the slow turnover in Fet3p that is functionally significant in Fe metabolism enabling efficient ferroxidase activity while avoiding ROS generation.
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Affiliation(s)
- Stephen M Jones
- Department of Chemistry, Stanford University, 333 Campus Drive Stanford, California 94305, United States
| | - David E Heppner
- Department of Chemistry, Stanford University, 333 Campus Drive Stanford, California 94305, United States
| | - Kenny Vu
- Department of Biochemistry, The University at Buffalo, 140 Farber Hall, 3435 Main Street, Buffalo, New York 14214, United States
| | - Daniel J Kosman
- Department of Biochemistry, The University at Buffalo, 140 Farber Hall, 3435 Main Street, Buffalo, New York 14214, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University, 333 Campus Drive Stanford, California 94305, United States
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8
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Stroscio GD, Ribson RD, Hadt RG. Quantifying Entatic States in Photophysical Processes: Applications to Copper Photosensitizers. Inorg Chem 2019; 58:16800-16817. [DOI: 10.1021/acs.inorgchem.9b02976] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gautam D. Stroscio
- Division of Chemistry and Chemical Engineering, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Ryan D. Ribson
- Division of Chemistry and Chemical Engineering, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Ryan G. Hadt
- Division of Chemistry and Chemical Engineering, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, United States
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9
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Zerk TJ, Saouma CT, Mayer JM, Tolman WB. Low Reorganization Energy for Electron Self-Exchange by a Formally Copper(III,II) Redox Couple. Inorg Chem 2019; 58:14151-14158. [PMID: 31577145 DOI: 10.1021/acs.inorgchem.9b02185] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The rate constant for electron self-exchange (k11) between LCuOH and [LCuOH]- (L = bis-2,6-(2,6-diisopropylphenyl)carboximidopyridine) was determined using the Marcus cross relation. This work involved measurement of the rate of the cross-reaction between [Bu4N][LCuOH] and [Fc][BAr4F] (Fc+ = ferrocenium; BAr4F = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate)) by stopped-flow methods at -88 °C in CH2Cl2 and measurement of the equilibrium constant for the redox process by UV-vis titrations under the same conditions. A value of k11 = 3 × 104 M-1 s-1 (-88 °C) led to estimation of a value 9 × 106 M-1 s-1 at 25 °C, which is among the highest values known for copper redox couples. Further Marcus analysis enabled determination of a low reorganization energy, λ = 0.95 ± 0.17 eV, attributed to minimal structural variation between the redox partners. In addition, the reaction entropy (ΔS°) associated with the LCuOH/[LCuOH]- self-exchange was determined from the temperature dependence of the redox potentials, and found to be dependent upon ionic strength. Comparisons to other Cu redox systems and potential new applications for the formally CuIII,II system are discussed.
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Affiliation(s)
- Timothy J Zerk
- Department of Chemistry , Washington University in St. Louis , One Brookings Hall, Campus Box 1134 , St. Louis , Missouri 63130-4899 , United States
| | - Caroline T Saouma
- Department of Chemistry , University of Utah , 315 S 1400 E , Salt Lake City , Utah 84112 , United States
| | - James M Mayer
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520-8107 , United States
| | - William B Tolman
- Department of Chemistry , Washington University in St. Louis , One Brookings Hall, Campus Box 1134 , St. Louis , Missouri 63130-4899 , United States
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10
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Flexible vs. rigid bis(2-benzimidazolyl) ligands in Cu(II) complexes: Impact on redox chemistry and oxidative DNA cleavage activity. J Inorg Biochem 2019; 194:223-232. [DOI: 10.1016/j.jinorgbio.2019.01.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 01/27/2019] [Accepted: 01/27/2019] [Indexed: 11/21/2022]
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11
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Abstract
Biological metal sites are optimized for function by conformational properties of the protein macroligand.
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Affiliation(s)
- Wilfred R. Hagen
- Delft University of Technology
- Department of Biotechnology
- 2629HZ Delft
- The Netherlands
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12
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Stanek J, Konrad M, Mannsperger J, Hoffmann A, Herres-Pawlis S. Influence of Functionalized Substituents on the Electron-Transfer Abilities of Copper Guanidinoquinoline Complexes. Eur J Inorg Chem 2018. [DOI: 10.1002/ejic.201801078] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Julia Stanek
- Institute for Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Marc Konrad
- Institute for Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Johannes Mannsperger
- Institute for Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Alexander Hoffmann
- Institute for Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Sonja Herres-Pawlis
- Institute for Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
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13
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14
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Dicke B, Hoffmann A, Stanek J, Rampp MS, Grimm-Lebsanft B, Biebl F, Rukser D, Maerz B, Göries D, Naumova M, Biednov M, Neuber G, Wetzel A, Hofmann SM, Roedig P, Meents A, Bielecki J, Andreasson J, Beyerlein KR, Chapman HN, Bressler C, Zinth W, Rübhausen M, Herres-Pawlis S. Transferring the entatic-state principle to copper photochemistry. Nat Chem 2018; 10:355-362. [DOI: 10.1038/nchem.2916] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Accepted: 11/17/2017] [Indexed: 01/10/2023]
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15
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Stanek J, Sackers N, Fink F, Paul M, Peters L, Grunzke R, Hoffmann A, Herres-Pawlis S. Copper Guanidinoquinoline Complexes as Entatic State Models of Electron-Transfer Proteins. Chemistry 2017; 23:15738-15745. [DOI: 10.1002/chem.201703261] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Indexed: 12/17/2022]
Affiliation(s)
- Julia Stanek
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Nina Sackers
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Fabian Fink
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Melanie Paul
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Laurens Peters
- Department Chemie; Ludwig-Maximilians Universität München; Butenandtstraße 5-13 81377 München Germany
| | - Richard Grunzke
- Zentrum für Informationsdienste und Hochleistungsrechnen; Technische Universität Dresden; Zellescher Weg 12-14 01062 Dresden Germany
| | - Alexander Hoffmann
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Sonja Herres-Pawlis
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
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16
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Prosser KE, Chang SW, Saraci F, Le PH, Walsby CJ. Anticancer copper pyridine benzimidazole complexes: ROS generation, biomolecule interactions, and cytotoxicity. J Inorg Biochem 2017; 167:89-99. [DOI: 10.1016/j.jinorgbio.2016.11.006] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 10/12/2016] [Accepted: 11/03/2016] [Indexed: 12/19/2022]
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17
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Vollmers NJ, Müller P, Hoffmann A, Herres-Pawlis S, Rohrmüller M, Schmidt WG, Gerstmann U, Bauer M. Experimental and Theoretical High-Energy-Resolution X-ray Absorption Spectroscopy: Implications for the Investigation of the Entatic State. Inorg Chem 2016; 55:11694-11706. [DOI: 10.1021/acs.inorgchem.6b01704] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
| | | | - Alexander Hoffmann
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany
| | - Sonja Herres-Pawlis
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany
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18
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Hoffmann A, Stanek J, Dicke B, Peters L, Grimm-Lebsanft B, Wetzel A, Jesser A, Bauer M, Gnida M, Meyer-Klaucke W, Rübhausen M, Herres-Pawlis S. Implications of Guanidine Substitution on Copper Complexes as Entatic-State Models. Eur J Inorg Chem 2016. [DOI: 10.1002/ejic.201600655] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Alexander Hoffmann
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Julia Stanek
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
| | - Benjamin Dicke
- Universität Hamburg; Institut für Nanostruktur- und Festkörperphysik and Center for Free-Electron Laser Science; Notkestrasse 85 22607 Hamburg Germany
| | - Laurens Peters
- Department Chemie; Ludwig-Maximilians Universität München; Butenandtstraße 5-13 81377 München Germany
| | - Benjamin Grimm-Lebsanft
- Universität Hamburg; Institut für Nanostruktur- und Festkörperphysik and Center for Free-Electron Laser Science; Notkestrasse 85 22607 Hamburg Germany
| | - Alina Wetzel
- Universität Hamburg; Institut für Nanostruktur- und Festkörperphysik and Center for Free-Electron Laser Science; Notkestrasse 85 22607 Hamburg Germany
| | - Anton Jesser
- Department Chemie; Ludwig-Maximilians Universität München; Butenandtstraße 5-13 81377 München Germany
| | - Matthias Bauer
- Universität Paderborn; Department Chemie; Warburger Str. 100 33098 Paderborn Germany
| | - Manuel Gnida
- Universität Paderborn; Department Chemie; Warburger Str. 100 33098 Paderborn Germany
| | - Wolfram Meyer-Klaucke
- Universität Paderborn; Department Chemie; Warburger Str. 100 33098 Paderborn Germany
| | - Michael Rübhausen
- Universität Hamburg; Institut für Nanostruktur- und Festkörperphysik and Center for Free-Electron Laser Science; Notkestrasse 85 22607 Hamburg Germany
| | - Sonja Herres-Pawlis
- Institut für Anorganische Chemie; RWTH Aachen University; Landoltweg 1 52074 Aachen Germany
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Hoffmann A, Binder S, Jesser A, Haase R, Flörke U, Gnida M, Salomone Stagni M, Meyer-Klaucke W, Lebsanft B, Grünig LE, Schneider S, Hashemi M, Goos A, Wetzel A, Rübhausen M, Herres-Pawlis S. Den entatischen Zustand im Griff - ein Duo von Kupfer-Komplexen. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201306061] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Hoffmann A, Binder S, Jesser A, Haase R, Flörke U, Gnida M, Salomone Stagni M, Meyer-Klaucke W, Lebsanft B, Grünig LE, Schneider S, Hashemi M, Goos A, Wetzel A, Rübhausen M, Herres-Pawlis S. Catching an Entatic State-A Pair of Copper Complexes. Angew Chem Int Ed Engl 2013; 53:299-304. [DOI: 10.1002/anie.201306061] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 08/25/2013] [Indexed: 11/08/2022]
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21
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Gunderson WA, Hernández-Guzmán J, Karr JW, Sun L, Szalai VA, Warncke K. Local structure and global patterning of Cu2+ binding in fibrillar amyloid-β [Aβ(1-40)] protein. J Am Chem Soc 2012; 134:18330-7. [PMID: 23043377 PMCID: PMC3722434 DOI: 10.1021/ja306946q] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The amyloid-β (Aβ) protein forms fibrils and higher-order plaque aggegrates in Alzheimer's disease (AD) brain. The copper ion, Cu(2+), is found at high concentrations in plaques, but its role in AD etiology is unclear. We use high-resolution pulsed electron paramagnetic resonance spectroscopy to characterize the coordination structure of Cu(2+) in the fibrillar form of full-length Aβ(1-40). The results reveal a bis-cis-histidine (His) equatorial Cu(2+) coordination geometry and participation of all three N-terminal His residues in Cu(2+) binding. A model is proposed in which Cu(2+)-His6/His13 and Cu(2+)-His6/His14 sites alternate along the fibril axis on opposite sides of the β-sheet fibril structure. The local intra-β-strand coordination structure is not conducive to Cu(2+)/Cu(+) redox-linked coordination changes, and the global arrangement of Cu sites precludes facile multielectron and bridged-metal site reactivity. This indicates that the fibrillar form of Aβ suppresses Cu redox cycling and reactive oxygen species production. The configuration suggests application of Cu(2+)-Aβ fibrils as an amyloid architecture for switchable electron charge/spin coupling and redox reactivity.
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Affiliation(s)
| | | | - Jesse W. Karr
- Chemistry and Biochemistry Department, Siena College, Loudenville, New York, 12211 USA
| | - Li Sun
- Department of Physics, Emory University, Atlanta, GA 30322 USA
| | - Veronika A. Szalai
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899 USA
| | - Kurt Warncke
- Department of Physics, Emory University, Atlanta, GA 30322 USA
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Deng YY, Liu FQ, Jin YL. Synthesis, crystal structure, and electrocatalytic properties of a copper(II) complex of 1,2-bis(2-benzimidazolyl)benzene. TRANSIT METAL CHEM 2012. [DOI: 10.1007/s11243-012-9577-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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23
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Rodríguez A, Sousa-Pedrares A, García-Vázquez JA, Romero J, Sousa A. Synthesis and Structural Characterization of Copper(I), Silver(I) and Gold(I) Complexes with Pyrimidine-2-thionato Ligands and their Adducts with Phosphanes. Eur J Inorg Chem 2011. [DOI: 10.1002/ejic.201100156] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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24
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Electrochemical and homogeneous electron transfers to the Alzheimer amyloid-beta copper complex follow a preorganization mechanism. Proc Natl Acad Sci U S A 2010; 107:17113-8. [PMID: 20858730 DOI: 10.1073/pnas.1011315107] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Deciphering the electron transfer reactivity characteristics of amyloid β-peptide copper complexes is an important task in connection with the role they are assumed to play in Alzheimer's disease. A systematic analysis of this question with the example of the amyloid β-peptide copper complex by means of its electrochemical current-potential responses and of its homogenous reactions with electrogenerated fast electron exchanging osmium complexes revealed a quite peculiar mechanism: The reaction proceeds through a small fraction of the complex molecules in which the peptide complex is "preorganized" so as the distances and angles in the coordination sphere to vary minimally upon electron transfer, thus involving a remarkably small reorganization energy (0.3 eV). This preorganization mechanism and its consequences on the reactivity should be taken into account for reactions involving dioxygen and hydrogen peroxide that are considered to be important in Alzheimer's disease through the production of harmful reactive oxygen species.
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25
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Burg A, Meyerstein D. Is it always correct to use the Marcus cross relation for calculations of electron self-exchange rates? Inorganica Chim Acta 2010. [DOI: 10.1016/j.ica.2009.11.030] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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26
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Camargo A, Aguirre M, Cheuquepán W, Chen YY, Ramírez G. Electrooxidation of Nitrite Mediated by Cu-x-Tetraaminophenylporphyrin (x=2, 3, and 4) Glassy Carbon-Modified Electrodes: Effect of Substituent Position. ELECTROANAL 2008. [DOI: 10.1002/elan.200804369] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Grampp G, Großmann B, Heinze J, Landgraf S, Rasmussen K. Electron-Self-Exchange Kinetics of the Cyclooctatetraene/Cyclooctatetraene Radical-Anion Couple. Chemphyschem 2008; 9:854-60. [DOI: 10.1002/cphc.200700731] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Irangu J, Ferguson MJ, Jordan RB. Reaction of Copper(II) with Ferrocene and 1,1‘-Dimethylferrocene in Aqueous Acetonitrile: The Copper(II/I) Self-Exchange Rate. Inorg Chem 2005; 44:1619-25. [PMID: 15733005 DOI: 10.1021/ic048614i] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The kinetics of the reactions of copper(II) with ferrocene (Fc) and 1,1'-dimethylferrocene (Dmfc) have been studied at 25 degrees C in aqueous acetonitrile (AN) containing 50-97.5 vol % AN. With increasing % AN, the rate constant increases along with the driving-force for the reaction. The results are analyzed in terms of Marcus theory to estimate the Cu(II/I) electron self-exchange rate constant (k11) for the system. Over the solvent range studied, the calculated k11)changes from 1.1 x 10(-9) to 17 x 10(-9) M(-1) s(-1), with an average value of 5 x 10(-9). In addition, the structures of the trifluoromethanesulfonate salts of [Cu(AN)4]+, [Cu(OH2)2(AN)2]2+, and [Cu(AN)4]2+ are reported. It is found that the Cu-NCCH3 bond-length difference between the Cu(I) and Cu(II) oxidation states is only approximately 0.02 A.
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Affiliation(s)
- Japhet Irangu
- Department of Chemistry, and X-ray Crystallography Service Laboratory, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
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29
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Itoh S, Kishikawa N, Suzuki T, Takagi HD. Syntheses, structural analyses and redox kinetics of four-coordinate [CuL2]2+and five-coordinate [CuL2(solvent)]2+complexes (L = 6,6′-dimethyl-2,2′-bipyridine or 2,9-dimethyl-1,10-phenanthroline): completely gated reduction reaction of [Cu(dmp)2]2+in nitromethane. Dalton Trans 2005:1066-78. [PMID: 15739009 DOI: 10.1039/b415057k] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
[Cu(2,9-dimethyl-1,10-phenanthroline)(2)](2+) and [Cu(6,6'-dimethyl-2,2'-bipyridine)(2)](2+/+) complexes with no coordinated solvent molecule were synthesized and the crystal structures were analyzed: the coordination geometry around the Cu(i) center was in the D(2d) symmetry while a D(2) structure was observed for the four-coordinate Cu(ii) complexes. Coordination of a water or an acetonitrile molecule was found in the trigonal plane of the five-coordinate Cu(ii) complex in the Tbp(trigonal bipyramidal) structure. Spectrophotometric analyses revealed that the D(2) structure of the Cu(ii) complex was retained in nitromethane, although a five-coordinate Tbp species (green in color), was readily formed upon dissolution of the solid (reddish brown) in acetonitrile. The electron self-exchange reaction between D(2d)-Cu(I) and D(2)-Cu(II), observed by the NMR method, was very rapid with k(ex)=(1.1 +/- 0.2) x 10(5) kg mol(-1) s(-1) at 25 degrees C (DeltaH*= 15.6 +/- 1.3 kJ mol(-1) and DeltaS*=-96 +/- 4 J mol(-1) K(-1)), which was more than 10 times larger than that reported for the self-exchange reaction between D(2d)-Cu(I) and Tbp-Cu(II) in acetonitrile. The cross reduction reactions of D(2)-Cu(ii) by ferrocene and decamethylferrocene in nitromethane exhibited a completely gated behavior, while the oxidation reaction of D(2d)-Cu(i) by [Ni(1,4,7-triazacyclononane)(2)](3+) in nitromethane estimated an identically large self-exchange rate constant to that directly obtained by the NMR method. The electron self-exchange rate constant estimated from the oxidation cross reaction in 50% v/v acetonitrile-nitromethane mixture was 10 times smaller than that observed in pure nitromethane. On the basis of the Principle of the Least Motion (PLM) and the Symmetry Rules, it was concluded that gated behaviors observed for the reduction reactions of the five-coordinate Cu(ii)-polypyridine complexes are related to the high-energy C(2v)--> D(2d) conformational change around Cu(ii), and that the electron self-exchange reactions of the Cu(ii)/(i) couples are always adiabatic through the C(2v) structures for both Cu(ii) and Cu(i) since the conformational changes between D(2d), D(2) and C(2v) structures for Cu(i) as well as the conformational change between Tbp and C(2v) structures for Cu(ii) are symmetry-allowed. The completely gated behavior observed for the reduction reactions of D(2)-Cu(ii) species in nitromethane was attributed to the very slow conformational change from the ground-state D(2) to the entatic D(2d) structure that is symmetry-forbidden for d(9) metal complexes: the very slow back reaction, the forbidden conformational change from entatic D(2d) to the ground-state D(2) structure, ensures that the rate of the reduction reaction is independent of the concentration of the reducing reagent.
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Affiliation(s)
- Sumitaka Itoh
- Inorganic Chemistry Division, Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8602, Japan
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Comba P, Kerscher M, Roodt A. Slow Electron Self-Exchange in Spite of a Small Inner-Sphere Reorganisation Energy ? The Electron-Transfer Properties of a Copper Complex with a Tetradentate Bispidine Ligand. Eur J Inorg Chem 2004. [DOI: 10.1002/ejic.200400518] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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31
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Synthetic models for active sites of reduced blue copper proteins: minimal geometric change between two oxidation states for fast self-exchange rate constants. INORG CHEM COMMUN 2004. [DOI: 10.1016/j.inoche.2004.09.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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32
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Harkins SB, Peters JC. Amido-bridged Cu2N2 diamond cores that minimize structural reorganization and facilitate reversible redox behavior between a Cu1Cu1 and a class III delocalized Cu1.5Cu1.5 species. J Am Chem Soc 2004; 126:2885-93. [PMID: 14995206 DOI: 10.1021/ja037364m] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
A novel Cu(2)N(2) diamond core structure supported by an [SNS](-) ligand (1) ([SNS](-) = bis(2-tert-butylsulfanylphenyl)amido) has been prepared. This dicopper system exhibits a fully reversible one-electron redox process between a reduced Cu(1)Cu(1) complex, [[SNS][Cu]](2) (2), and a class III delocalized Cu(1.5)Cu(1.5) state, [[[SNS][Cu]](2)][B(3,5-(CF(3))(2)C(6)H(3))(4)] (3). Structural snapshots of both redox forms have been obtained to reveal remarkably little overall structural reorganization. The Cu...Cu bond distance nonetheless undergoes an appreciable compression (approximately 0.13 A) upon oxidation, providing a Cu...Cu distance of 2.4724(4) A in the mixed-valence state that is virtually identical to the Cu...Cu distance observed in the reduced form of the Cu(A) site of thiolate-bridged cytochrome c oxidase. Despite the low structural reorganization evident between 2 and 3, the [SNS](-) ligand is quite flexible. For example, square-planar geometries can prevail for divalent copper ions supported by [SNS](-) as evident from the crystal structure of [SNS]CuCl (4). Physical characterization for the mixed valence complex 3 includes electrochemical, magnetic (SQUID), EPR, and optical data. The complex has also been examined by density functional methods. An attempt was made to measure the rate of electron self-exchange k(s) between the Cu(1)Cu(1) and the Cu(1.5)Cu(1.5) complexes 2 and 3 by NMR line-broadening analysis in dichloromethane solution. While the system is certainly in the fast-exchange regime, the exchange process is too fast to be accurately measured by this technique. The value for k(s) can be bracketed with a conservative lower boundary of > or =10(7) M(-1) s(-1), a value that appears to be larger than other low molecular weight copper model complexes for which similar data is available. The unusually large magnitude of k(s) likely reflects the minimal structural reorganization that accompanies Cu(1)Cu(1) <--> Cu(1.5)Cu(1.5) interchange.
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Affiliation(s)
- Seth B Harkins
- Contribution from the Laboratories of Chemical Synthesis, California Institute of Technology, Pasadena, California 91125, USA
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33
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Affiliation(s)
- David B Rorabacher
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
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Börzel H, Comba P, Hagen KS, Kerscher M, Pritzkow H, Schatz M, Schindler S, Walter O. Copper-bispidine coordination chemistry: syntheses, structures, solution properties, and oxygenation reactivity. Inorg Chem 2002; 41:5440-52. [PMID: 12377039 DOI: 10.1021/ic011114u] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Copper(I) and copper(II) complexes of two mononucleating and four dinucleating tetradentate ligands with a bispidine backbone (2,4-substituted (2-pyridyl or 4-methyl-2-pyridyl) 3,7-diazabicyclo[3.3.1]nonanone) have been prepared and analyzed structurally, spectroscopically, and electrochemically. The structures of the copper chromophores are square pyramidal, except for two copper(I) compounds which are four-coordinate with one noncoordinated pyridine. The other copper(I) structures have the two pyridine donors, the co-ligand (NCCH(3)), and one of the tertiary amines (N3) in-plane with the copper center and the other amine (N7) coordinated axially (Cu-N3 > Cu-N7, approximately 2.25 A vs 2.20 A). The copper(II) compounds with pyridine donors have a similar structure, but the axial amine has a weaker bond to the copper(II) center (Cu-N3 < Cu-N7, approximately 2.03 A vs 2.30 A). The structures with methylated pyridine donors are also square pyramidal with the co-ligands (Cl(-) or NCCH(3)) in-plane. With NCCH(3) the same structural type as for the other copper(II) complexes is observed, and with the bulkier Cl(-) the co-ligand is trans to N7, leading to a square pyramidal structure with the pyridine donors rotated out of the basal plane and only a small difference between axial and in-plane amines (2.15, 2.12 A). These structural differences, enforced by the rigid bispidine backbone, lead to large variations in spectroscopic and electrochemical properties and reactivities. Oxygenation of the copper(I) complexes with pyridine-substituted bispidine ligands leads to relatively stable mu-peroxo-dicopper(II) complexes; with a preorganization of the dicopper chromophores, by linking the two donor sets, these peroxo compounds are stable at room temperature for up to 1 h. The stabilization of the peroxo complexes is to a large extent attributed to the square pyramidal coordination geometry with the substrate bound in the basal plane, a structural motif enforced by the rigid bispidine backbone. The stabilities and structural properties are also seen to correlate with the spectroscopic (UV-vis and Raman) and electrochemical properties.
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Affiliation(s)
- Heidi Börzel
- Anorganisch-Chemisches Institut der Universität Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
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Blackburn NJ, Rhames FC, Ralle M, Jaron S. Major changes in copper coordination accompany reduction of peptidylglycine monooxygenase: implications for electron transfer and the catalytic mechanism. J Biol Inorg Chem 2000; 5:341-53. [PMID: 10907745 DOI: 10.1007/pl00010663] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
X-ray absorption spectroscopy has been used to probe the local coordination of the copper centers in the oxidized and reduced states of the peptidylglycine monooxygenase catalytic core (PHMcc) in both the resting and substrate-bound forms of the enzyme. The results indicate that reduction causes significant changes in coordination number and geometry of both Cu centers (CuH and CuM). The CuH center changes from 4- or 5-coordinate tetragonal to a 2-coordinate configuration, with one of the three histidine ligands becoming undetectable by EXAFS (suggesting that it has moved away from the CuH by at least 0.3 A). The CuM center changes from 4- or 5-coordinate tetragonal to a trigonal or tetrahedral configuration, with an estimated 0.3-0.5 A movement of the M314 S ligand. Reduction also leads to loss of coordinated water from both of the coppers. Substrate binding has little or no effect on the local environment of the Cu centers in either oxidation state. These findings bring into question whether direct electron transfer between CuH and CuM via a tunneling mechanism can be fast enough to support the observed catalytic rate, and suggest that some other mechanism for electron transfer, such as superoxide channeling, should be considered.
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Affiliation(s)
- N J Blackburn
- Department of Biochemistry and Molecular Biology, Oregon Graduate Institute of Science and Technology, Beaverton 97006-8921, USA.
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Koshino N, Kuchiyama Y, Funahashi S, Takagi HD. Electron self-exchange, oxidation, and reduction reactions of bis(2,9-dimethyl-4,7-diphenyl- 1,10-phenanthroline)copper(II/I) and bis(6,6'-dimethyl-2,2'-bipyridine)copper(II/I) couples in acetonitrile: gated ET for the reduction, oxidation, and self-exchange processes. CAN J CHEM 1999. [DOI: 10.1139/v99-171] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The electron self-exchange rate constant for the Cu(dmbp)22+/+ couple (dmbp = 6,6'-dimethyl-2,2'-bipyridine) was measured in acetonitrile by the NMR method (kex = 5.5 × 103 kg mol-1 s-1, ΔH* = 35.0 ± 0.3 kJ mol-1 and ΔS* = -56 ± 1 J mol-1 K-1). Reduction reactions of Cu(bcp)22+ (bcp = 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) and Cu(dmbp)22+ with Co(bipy)32+ (bipy = 2,2'-bipyridine) and ferrocene (Fe(Cp)2 = bis(cyclopentadienyl)iron(II)), and oxidation reactions of Cu(bcp)2+ and Cu(dmbp)2+ by Ni(tacn)23+ (tacn = 1,4,7-triazacyclononane) and Mn(bipyO2)33+ (bipyO2 = N,N'-dioxo-2,2'-bipyridine) were also studied in acetonitrile. The electron self-exchange rate constants, kex, estimated for the Cu(bcp)22+/+ and Cu(dmbp)22+/+ couples from the oxidation reactions of Cu(bcp)2+ and Cu(dmbp)2+ by Ni(tacn)23+ and Mn(bipyO2)33+ were consistent with the directly measured values by NMR, while kex estimated from the reduction reactions of Cu(bcp)22+ and Cu(dmbp)22+ by Co(bipy)32+ ([Cu(bcp)22+]0, [Cu(dmbp)22+]0 >> [Co(bipy)32+]0) were 103 times smaller than those directly measured by the NMR method. The pseudo-first-order rate constant for the reduction reaction of Cu(bcp)22+ and Cu(dmbp)22+ by Fe(Cp)2 was not linear against the concentration of excess amounts of Fe(Cp)2. Analyses of the reactions revealed that the reductions of Cu(bcp)22+ and Cu(dmbp)22+ involve slow paths related to the deformation of Cu(II)N4 center from tetragonal to tetrahedral coordination. The energetic preference for the deformation of Cu(II) species rather than that of Cu(I) was discussed on the basis of the ligand field activation energy (LFAE).Key words: electron transfer, copper(II) and copper(I) complexes, gated behavior.
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Koshino N, Kuchiyama Y, Ozaki H, Funahashi S, Takagi HD. An Interpretation of Gated Behavior: Kinetic Studies of the Oxidation and Reduction Reactions of Bis(2,9-dimethyl-1,10-phenanthroline)copper(I/II) in Acetonitrile. Inorg Chem 1999; 38:3352-3360. [PMID: 11671071 DOI: 10.1021/ic9810687] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reduction reactions of Cu(dmp)(2)(2+) (dmp = 2,9-dimethyl-1,10-phenanthroline) by ferrocene (Fe(Cp)(2) = bis(cyclopentadienyl)iron(II)), decamethylferrocene (Fe(PMCp)(2) = bis(pentamethylcyclopentadienyl)iron(II)), and Co(bpy)(3)(2+) (bpy = 2,2'-bipyridine) and oxidation reactions of Cu(dmp)(2)(+) by Ni(tacn)(2)(3+) (tacn = 1,4,7-triazacyclononane) and Mn(bpyO(2))(3)(3+) (bpyO(2) = N,N'-dioxo-2,2'-bipyridine) were studied in acetonitrile for the purpose of interpreting the gated behavior involving copper(II) and -(I) species. It was shown that the electron self-exchange rate constants estimated for the Cu(dmp)(2)(2+/+) couple from the oxidation reaction of Cu(dmp)(2)(+) by Ni(tacn)(2)(3+) (5.9 x 10(2) kg mol(-)(1) s(-)(1)) and Mn(bpyO(2))(3)(3+) (2.9 x 10(4) kg mol(-)(1) s(-)(1)) were consistent with the directly measured value by NMR (5 x 10(3) kg mol(-)(1) s(-)(1)). In contrast, we obtained the electron self-exchange rate constant of Cu(dmp)(2)(2+/+) as 1.6 kg mol(-)(1) s(-)(1) from the reduction of Cu(dmp)(2)(2+) by Co(bpy)(3)(2+). The pseudo-first-order rate constant for the reduction reaction of Cu(dmp)(2)(2+) by Fe(Cp)(2) was not linear against the concentration of excess amounts of Fe(Cp)(2). A detailed analysis of the reaction revealed that the reduction of Cu(dmp)(2)(2+) involved the slow path related to the deformation of Cu(dmp)(2)(2+) (path B in Scheme 1). By using Fe(PMCp)(2) (the E degrees value is 500 mV more negative than that of Fe(Cp)(2)(+/0)) as the reductant, the mixing with another pathway involving deformation of Cu(dmp)(2)(+) (path A in Scheme 1) became more evident. The origin of the "Gated Behavior" is discussed by means of the energy differences between the "normal" and deformed Cu(II) and Cu(I) species: the difference in the crystal field activation energies corresponding to the formation of pseudo-tetrahedral Cu(II) from tetragonally distorted Cu(II) and the difference in the stabilization energies of the tetrahedral and tetragonal Cu(I) for the activation of Cu(I) species. The reduction reaction of Cu(dmp)(2)(2+) by Fe(PMCp)(2) confirmed that the mixing of the two pathways takes place by lowering the energy level corresponding to the less favorable conformational change of Cu(I) species.
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Affiliation(s)
- Nobuyoshi Koshino
- Inorganic and Analytical Chemistry Division, Department of Chemistry and Physics, Graduate School of Sciences, Nagoya University, Furocho, Chikusa, Nagoya, 464-8602 Japan
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