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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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2
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Kafentzi MC, Papadakis R, Gennarini F, Kochem A, Iranzo O, Le Mest Y, Le Poul N, Tron T, Faure B, Simaan AJ, Réglier M. Electrochemical Water Oxidation and Stereoselective Oxygen Atom Transfer Mediated by a Copper Complex. Chemistry 2018; 24:5213-5224. [DOI: 10.1002/chem.201704613] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 12/19/2017] [Indexed: 11/06/2022]
Affiliation(s)
| | | | - Federica Gennarini
- Université de Bretagne Occidentale, CNRS UMR 6521; Laboratoire CEMCA; 6 Avenue Le Gorgeu, CS 93837 29238 Brest Cedex 3 France
| | - Amélie Kochem
- Aix Marseille Univ; CNRS, Centrale Marseille, iSm2; Marseille France
| | - Olga Iranzo
- Aix Marseille Univ; CNRS, Centrale Marseille, iSm2; Marseille France
| | - Yves Le Mest
- Université de Bretagne Occidentale, CNRS UMR 6521; Laboratoire CEMCA; 6 Avenue Le Gorgeu, CS 93837 29238 Brest Cedex 3 France
| | - Nicolas Le Poul
- Université de Bretagne Occidentale, CNRS UMR 6521; Laboratoire CEMCA; 6 Avenue Le Gorgeu, CS 93837 29238 Brest Cedex 3 France
| | - Thierry Tron
- Aix Marseille Univ; CNRS, Centrale Marseille, iSm2; Marseille France
| | - Bruno Faure
- Aix Marseille Univ; CNRS, Centrale Marseille, iSm2; Marseille France
| | - A. Jalila Simaan
- Aix Marseille Univ; CNRS, Centrale Marseille, iSm2; Marseille France
| | - Marius Réglier
- Aix Marseille Univ; CNRS, Centrale Marseille, iSm2; Marseille France
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3
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Chaparro D, Alí-Torres J. Assessment of the isodesmic method in the calculation of standard reduction potential of copper complexes. J Mol Model 2017; 23:283. [PMID: 28936691 DOI: 10.1007/s00894-017-3469-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 09/06/2017] [Indexed: 11/26/2022]
Abstract
Molecular phenomena involving electron transfer and reduction/oxidation processes are of the utmost importance in chemistry. However, accurate computational calculations of standard reduction potentials (SRPs) for transition metal complexes are still challenging. For this reason, some computational strategies have been proposed in order to overcome the main limitations in SRP calculations for copper complexes. However, these strategies are limited to particular coordination spheres and do not represent a general methodology. In this work, we present standard reduction potential calculations for copper complexes in aqueous solution covering a wide range of coordination spheres. These calculations were performed using the M06-2X density functional, and by employing the direct and isodesmic approaches. Result analysis reveals that values obtained with the use of the isodesmic method are in better agreement with experimental values than those obtained from the direct method (mean unsigned error 0.39 V with the direct and 0.08 V with the isodesmic method). This approach provides values with errors comparable to the experimental uncertainty due to the proper cancellation of computational errors. These results strongly suggest the isodesmic approach as an adequate methodology for the calculation of SRPs for copper complexes with diverse coordination spheres. Graphical Abstract Comparison between direct and isodesmic methods in the calculation of standard reduction potentials for copper complexes using DFT methods.
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Affiliation(s)
- Diego Chaparro
- Department of Chemistry, Universidad Nacional de Colombia, Av. Cra 30 # 45-03, Bogotá, Colombia
| | - Jorge Alí-Torres
- Department of Chemistry, Universidad Nacional de Colombia, Av. Cra 30 # 45-03, Bogotá, Colombia.
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Tsai YJ, Lee UH, Zhao Q. Synthesis and characterization of two polydentate pyridylamines, their acidified salts and late first-row transition metal complexes. Polyhedron 2017. [DOI: 10.1016/j.poly.2016.12.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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5
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Muthuramalingam S, Subramaniyan S, Khamrang T, Velusamy M, Mayilmurugan R. Copper(II)-Bioinspired Models for Copper Amine Oxidases: Oxidative Half-Reaction in Water. ChemistrySelect 2017. [DOI: 10.1002/slct.201601786] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Sethuraman Muthuramalingam
- Bioinorganic Chemistry Laboratory/Physical Chemistry; School of Chemistry; Madurai Kamaraj University; Madurai 625 021, Tamil Nadu India
| | - Shanmugam Subramaniyan
- Bioinorganic Chemistry Laboratory/Physical Chemistry; School of Chemistry; Madurai Kamaraj University; Madurai 625 021, Tamil Nadu India
| | - Themmila Khamrang
- Department of Chemistry; North Eastern Hill Universuty; Shillong- 793022 India
| | - Marappan Velusamy
- Department of Chemistry; North Eastern Hill Universuty; Shillong- 793022 India
| | - Ramasamy Mayilmurugan
- Bioinorganic Chemistry Laboratory/Physical Chemistry; School of Chemistry; Madurai Kamaraj University; Madurai 625 021, Tamil Nadu India
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6
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Ramos-Torres KM, Kolemen S, Chang CJ. Thioether Coordination Chemistry for Molecular Imaging of Copper in Biological Systems. Isr J Chem 2016; 56:724-737. [PMID: 31263315 DOI: 10.1002/ijch.201600023] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Copper is an essential element in biological systems. Its potent redox activity renders it necessary for life, but at the same time, misregulation of its cellular pools can lead to oxidative stress implicated in aging and various disease states. Copper is commonly thought of as a static cofactor buried in protein active sites; however, evidence of a more loosely bound, labile pool of copper has emerged. To help identify and understand new roles for dynamic copper pools in biology, we have developed selective molecular imaging agents for this metal, drawing inspiration from both biological binding motifs and synthetic model complexes that reveal thioether coordination as a general design strategy for selective and sensitive copper recognition. In this review, we summarize some contributions, primarily from our own laboratory, on fluorescence- and magnetic resonance-based molecular-imaging probes for studying copper in living systems using thioether coordination chemistry.
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Affiliation(s)
| | - Safacan Kolemen
- Department of Chemistry, University of California Berkeley, CA 94704 (USA)
| | - Christopher J Chang
- Department of Chemistry, University of California Berkeley, CA 94704 (USA).,Department of Molecular and Cell Biology, University of California Berkeley, CA 94704 (USA).,Howard Hughes Medical Institute, Tel.: (+1) 510-642-4704
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Maqsood SR, Bhat MA, Khan B. Electroanalytical, kinetic, and mechanistic investigations of coordination-inspired electron transfer between Fe(II)/Cu(II). J COORD CHEM 2013. [DOI: 10.1080/00958972.2013.778987] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
| | - Mohsin Ahmad Bhat
- a Department of Chemistry , University of Kashmir , Srinagar , India
| | - Badruddin Khan
- a Department of Chemistry , University of Kashmir , Srinagar , India
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Martínez-Alanis PR, Sánchez Eguía BN, Ugalde-Saldívar VM, Regla I, Demare P, Aullón G, Castillo I. Copper versus thioether-centered oxidation: mechanistic insights into the non-innocent redox behavior of tripodal benzimidazolylaminothioether ligands. Chemistry 2013; 19:6067-79. [PMID: 23495176 DOI: 10.1002/chem.201203498] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Indexed: 11/11/2022]
Abstract
A series of Cu(+) complexes with ligands that feature varying numbers of benzimidazole/thioether donors and methylene or ethylene linkers between the central nitrogen atom and the thioether sulfur atoms have been spectroscopically and electrochemically characterized. Cyclic voltammetry measurements indicated that the highest Cu(2+)/Cu(+) redox potentials correspond to sulfur-rich coordination environments, with values decreasing as the thioether donors are replaced by nitrogen-donating benzimidazoles. Both Cu(2+) and Cu(+) complexes were studied by DFT. Their electronic properties were determined by analyzing their frontier orbitals, relative energies, and the contributions to the orbitals involved in redox processes, which revealed that the HOMOs of the more sulfur-rich copper complexes, particularly those with methylene linkers (-N-CH2-S-), show significant aromatic thioether character. Thus, the theoretically predicted initial oxidation at the sulfur atom of the methylene-bridged ligands agrees with the experimentally determined oxidation waves in the voltammograms of the NS3- and N2S2-type ligands as being ligand-based, as opposed to the copper-based processes of the ethylene-bridged Cu(+) complexes. The electrochemical and theoretical results are consistent with our previously reported mechanistic proposal for Cu(2+)-promoted oxidative C-S bond cleavage, which in this work resulted in the isolation and complete characterization (including by X-ray crystallography) of the decomposition products of two ligands employed, further supporting the novel reactivity pathway invoked. The combined results raise the possibility that the reactions of copper-thioether complexes in chemical and biochemical systems occur with redox participation of the sulfur atom.
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Affiliation(s)
- Paulina R Martínez-Alanis
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, CU, México DF, 04510, México
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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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10
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Schnödt J, Sieger M, Sarkar B, Fiedler J, Manzur J, Su CY, Kaim W. Copper(I) Chelation by Tetradentate NSSN Donor Ligands: Reversible Oxidation but no Oxygenation. Z Anorg Allg Chem 2011. [DOI: 10.1002/zaac.201100026] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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11
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Schnödt J, Manzur J, García AM, Hartenbach I, Su CY, Fiedler J, Kaim W. Coordination of a Hemilabile N,N,S Donor Ligand in the Redox System [CuL2]+/2+, L = 2-Pyridyl-N-(2′-alkylthiophenyl)methyleneimine. Eur J Inorg Chem 2011. [DOI: 10.1002/ejic.201001183] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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12
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Lee Y, Lee DH, Park GY, Lucas HR, Narducci Sarjeant AA, Kieber-Emmons MT, Vance MA, Milligan AE, Solomon EI, Karlin KD. Sulfur donor atom effects on copper(I)/O(2) chemistry with thioanisole containing tetradentate N(3)S ligand leading to μ-1,2-peroxo-dicopper(II) species. Inorg Chem 2011; 49:8873-85. [PMID: 20822156 DOI: 10.1021/ic101041m] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To better understand the effect of thioether coordination in copper-O(2) chemistry, the tetradentate N(3)S ligand L(ASM) (2-(methylthio)-N,N-bis((pyridin-2-yl)methyl)benzenamine) and related alkylether ligand L(EOE) (2-ethoxy-N,N-bis((pyridin-2-yl)methyl)ethanamine) have been studied. The corresponding copper(I) complexes, [(L(ASM))Cu(I)](+) (1a) and [(L(EOE))Cu(I)](+) (3a), were studied as were the related compound [(L(ESE))Cu(I)](+) (2a, L(ESE) = (2-ethylthio-N,N-bis((pyridin-2-yl)methyl)ethanamine). The X-ray structure of 1a and its solution conductivity reveal a monomeric molecular structure possessing thioether coordination which persists in solution. In contrast, the C-O stretching frequencies of the derivative Cu(I)-CO complexes reveal that for these complexes, the modulated ligand arms, whether arylthioether, alkylthioether, or ether, are not coordinated to the cuprous ion. Electrochemical data for 1a and 2a in CH(3)CN and N,N-dimethylformamide (DMF) show the thioanisole moiety to be a poor electron donor compared to alkylthioether (1a is ∼200 mV more positive than 2a). The structures of [(L(ASM))Cu(II)(CH(3)OH)](2+) (1c) and [(L(ESE))Cu(II)(CH(3)OH)](2+) (2c) have also been obtained and indicate nearly identical copper coordination environments. Oxygenation of 1a at reduced temperature gives a characteristic deep blue intermediate [{(L(ASM))Cu(II)}(2)(O(2)(2-))](2+) (1b(P)) with absorption features at 442 (1,500 M(-1) cm(-1)), 530 (8,600 M(-1) cm(-1)), and 605 nm (10,400 M(-1) cm(-1)); these values compare well to the ligand-to-metal charge-transfer (LMCT) transitions previously reported for [{(L(ESE))Cu(II)}(2)(O(2)(2-))](2+) (2b(P)). Resonance Raman data for [{(L(ASM))Cu(II)}(2)(O(2)(2-))](2+) (1b(P)) support the formation of μ-1,2-peroxo species ν(O-O) = 828 cm(-1)(Δ((18)O(2)) = 48), ν(sym)(Cu-O) = 547 cm(-1) (Δ((18)O(2)) = 23), and ν(asym)(Cu-O) = 497 cm(-1) (Δ((18)O(2)) = 22) and suggest the L(ASM) ligand is a poorer electron donor to copper than is L(ESE). In contrast, the oxygenation of [(L(EOE))Cu(I)](+) (3a), possessing an ether donor as an analogue of the thioether in L(ESE), led to the formation of a bis(μ-oxo) species [{(L(EOE))Cu(III)}(2)(O(2-))(2)](2+) (3b(O); 380 nm, ε ∼ 10,000 M(-1) cm(-1)). This result provides further support for the sulfur influence in 1b(P) and 2b(P), in particular coordination of the sulfur to the Cu. Thermal decomposition of 1b(P) is accompanied by ligand sulfoxidation. The structure of [{(L(EOE))Cu(II)(Cl)}(2)](+) (3c) generated from the reductive dehalogenation of organic chlorides suggests that the ether moiety is weakly bound to the cupric ion. A detailed discussion of the spectroscopic and structural characteristics of 1b(P), 2b(P), and 3b(O) is presented.
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Affiliation(s)
- Yunho Lee
- Department of Chemistry, the Johns Hopkins University, Baltimore, Maryland 21218, USA
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13
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Martínez-Alanis PR, Ugalde-Saldívar VM, Castillo I. Electrochemical and Structural Characterization of Tri- and Dithioether Copper Complexes. Eur J Inorg Chem 2010. [DOI: 10.1002/ejic.201000960] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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14
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Horak J, Hofer S, Lindner W. Optimization of a ligand immobilization and azide group endcapping concept via “Click-Chemistry” for the preparation of adsorbents for antibody purification. J Chromatogr B Analyt Technol Biomed Life Sci 2010; 878:3382-94. [DOI: 10.1016/j.jchromb.2010.10.025] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Revised: 10/13/2010] [Accepted: 10/23/2010] [Indexed: 11/15/2022]
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15
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Qi ZP, Yuan Q, Cai K, Okamura TA, Sun WY, Ueyama N. Zinc(II) Complexes with 1H-Imidazol-4-yl-Containing Polyamine Ligand. Z Anorg Allg Chem 2010. [DOI: 10.1002/zaac.201000051] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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16
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Mankad NP, Harkins SB, Antholine WE, Peters JC. Multifrequency EPR studies of [Cu(1.5)Cu(1.5)](+) for Cu2(mu-NR2)2 and Cu2(mu-PR2)2 diamond cores. Inorg Chem 2009; 48:7026-32. [PMID: 19572723 DOI: 10.1021/ic801864z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Multifrequency electron paramagnetic resonance (EPR) spectroscopy is used to explore the electronic structures of a series of dicopper complexes of the type {(LXL)Cu}(2)(+). These complexes contain two four-coordinate copper centers of highly distorted tetrahedral geometries linked by two [LXL](-) ligands featuring bridging amido or phosphido ligands and associated thioether or phosphine chelate donors. Specific chelating [LXL](-) ligands examined in this study include bis(2-tert-butylsulfanylphenyl)amide (SNS), bis(2-di-iso-butylphosphinophenyl)amide (PNP), and bis(2-di-iso-propylphosphinophenyl)phosphide (PPP). To better map the electronic coupling to copper, nitrogen, and phosphorus in these complexes, X-, S-, and Q-band EPR spectra have been obtained for each complex. The resulting EPR parameters implied by computer simulation are unusual for typical dicopper complexes and are largely consistent with previously published X-ray absorption spectroscopy and density functional theory data, where a highly covalent {Cu(2)(mu-XR(2))(2)}(+) diamond core has been assigned in which removal of an electron from the neutral {Cu(2)(mu-XR(2))(2)} can be viewed as ligand-centered to a substantial degree. To our knowledge, this is the first family of dicopper diamond core model complexes for which the compendium of X-, S-, and Q-band EPR spectra have been collected for comparison to Cu(A).
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Affiliation(s)
- Neal P Mankad
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge Massachusetts 02139, USA
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Huerta R, Flores-Figueroa A, Ugalde-Saldívar VM, Castillo I. Electrochemical Behavior of an Aminotrithioether Ligand: Copper(II)-Mediated Oxidative C−C Bond Formation. Inorg Chem 2007; 46:9510-2. [DOI: 10.1021/ic7009429] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Raúl Huerta
- Instituto de Química and Facultad de Química, División de Estudios de Posgrado, Universidad Nacional Autónoma de México, Ciudad Universitaria, México D.F., 04510 México
| | - Aarón Flores-Figueroa
- Instituto de Química and Facultad de Química, División de Estudios de Posgrado, Universidad Nacional Autónoma de México, Ciudad Universitaria, México D.F., 04510 México
| | - Víctor M. Ugalde-Saldívar
- Instituto de Química and Facultad de Química, División de Estudios de Posgrado, Universidad Nacional Autónoma de México, Ciudad Universitaria, México D.F., 04510 México
| | - Ivan Castillo
- Instituto de Química and Facultad de Química, División de Estudios de Posgrado, Universidad Nacional Autónoma de México, Ciudad Universitaria, México D.F., 04510 México
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Poul NL, Campion M, Douziech B, Rondelez Y, Clainche LL, Reinaud O, Mest YL. Monocopper center embedded in a biomimetic cavity: from supramolecular control of copper coordination to redox regulation. J Am Chem Soc 2007; 129:8801-10. [PMID: 17580945 DOI: 10.1021/ja071219h] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The electrochemical behavior of diversely substituted Cu-N3-calix[6]arene, enzyme-like, "funnel" complexes is analyzed. The Cu(II)/Cu(I) redox process is regulated by the supramolecular organization of the Cu coordination. The presence of a "shoetree" alkyl nitrile guest molecule inside the host cavity is a prerequisite for a dynamic redox behavior. Combination of supramolecular CH-pi weak interactions with the calixarene cavity and electronic/steric effects from the N3 substituting groups (pyridine, imidazole, pyrrolidine) enforces the preferential geometrical pattern adopted by Cu. This dictates the pathway of the electron-transfer process and, thus, the thermodynamics and kinetics of the redox reaction in the framework of a square-scheme mechanism. The present observations recall strongly the redox control exerted by the protein matrix on copper proteins through biological concepts such as induced fit mechanism, protein foldings, and entatic and allosteric effects.
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Affiliation(s)
- Nicolas Le Poul
- Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, CS 93837, 6 avenue Le Gorgeu, 29238 Brest cedex 3, France
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19
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Chaka G, Sonnenberg JL, Schlegel HB, Heeg MJ, Jaeger G, Nelson TJ, Ochrymowycz LA, Rorabacher DB. A definitive example of a geometric "entatic state" effect: electron-transfer kinetics for a copper(II/I) complex involving A quinquedentate macrocyclic trithiaether-bipyridine ligand. J Am Chem Soc 2007; 129:5217-27. [PMID: 17391036 DOI: 10.1021/ja068960u] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The quinquedentate macrocyclic ligand cyclo-6,6'-[1,9-(2,5,8-trithianonane)]-2,2'-bipyridine ([15]aneS3bpy = L), containing two pyridyl nitrogens and three thiaether sulfurs as donor atoms, has been synthesized and complexed with copper. The CuII/IL redox potential, the stabilities of the oxidized and reduced complex, and the oxidation and reduction electron-transfer kinetics of the complex reacting with a series of six counter reagents have been studied in acetonitrile at 25 degrees C, mu = 0.10 M (NaClO4). The Marcus cross relationship has been applied to the rate constants obtained for the reactions with each of the six counter reagents to permit the evaluation of the electron self-exchange rate constant, k11. The latter value has also been determined independently from NMR line-broadening experiments. The cumulative data are consistent with a value of k11 = 1 x 10(5) M(-1) s(-1), ranking this among the fastest-reacting CuII/I systems, on a par with the blue copper proteins known as cupredoxins. The resolved crystal structures show that the geometry of the CuIIL and CuIL complexes are nearly identical, both exhibiting a five-coordinate square pyramidal geometry with the central sulfur donor atom occupying the apical site. The most notable geometric difference is a puckering of an ethylene bridge between two sulfur donor atoms in the CuIL complex. Theoretical calculations suggest that the reorganizational energy is relatively small, with the transition-state geometry more closely approximating the geometry of the CuIIL ground state. The combination of a nearly constant geometry and a large self-exchange rate constant implies that this CuII/I redox system represents a true geometric "entatic state."
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Affiliation(s)
- Gezahegn Chaka
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
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Le Poul N, Campion M, Izzet G, Douziech B, Reinaud O, Le Mest Y. Electrochemical behavior of the tris(pyridine)-Cu funnel complexes: an overall induced-fit process involving an entatic state through a supramolecular stress. J Am Chem Soc 2005; 127:5280-1. [PMID: 15826140 DOI: 10.1021/ja043073h] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The electrochemical behavior of the tris(pyridine) calix[6]arene Cu adducts is unique as compared to that of most classical Cu complexes in a strain-free environment. The presence of MeCN buried inside the cavity is a prerequisite for a quasi-reversible behavior in a dynamic mode. The CV behavior assisted by simulation outlines that the coordination adaptability of the Cu(II)/Cu(I) redox states is completely reversed, with a Td geometry enforced at either redox states. Hence, the supramolecular control of the Cu coordination by a protein-like pocket determines the dynamics of the electron transfer process, its thermodynamics, and the kinetics of the reorganizational barrier and generates a preorganized state for oxidation. This redox behavior corresponds to an overall induced-fit process generating a truly entatic highly oxidizing Cu(II) state through a protein-like strain by involvement of the secondary coordination sphere.
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Affiliation(s)
- Nicolas Le Poul
- Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, 6 av. Le Gorgeu, 29238 Brest Cedex 3, France
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Izzet G, Douziech B, Prangé T, Tomas A, Jabin I, Le Mest Y, Reinaud O. Calix[6]tren and copper(II): a third generation of funnel complexes on the way to redox calix-zymes. Proc Natl Acad Sci U S A 2005; 102:6831-6. [PMID: 15867151 PMCID: PMC1100775 DOI: 10.1073/pnas.0500240102] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mono-copper enzymes play an important role in biology and their functionality is based on Cu(II)/Cu(I) redox processes. Modeling a mono-nuclear site remains a challenge for a better understanding of its intrinsic reactivity. The first member of a third generation of calixarene-based mono-copper "funnel" complexes is described. The ligand is a calix[6]arene capped by a tren unit, hence presenting a N(4) coordination site confined in a cavity. Its Cu(II) complexes were characterized by electronic and EPR spectroscopies. The x-ray structure of one of them shows a five-coordinated metal ion in a slightly distorted trigonal bipyramidal geometry thanks to its coordination to a guest ligand L (ethanol). The latter sits in the heart of the hydrophobic calixarene cone that mimics the active site chamber and the hydrophobic access channel of enzymes. Competitive binding experiments showed a preference order dimethylformamide > ethanol > MeCN for L binding at the single exchangeable metal site. Cyclic voltammetry studies showed irreversible redox processes in CH(2)Cl(2) when L is an oxygen donor caused by the redox-driven ejection of the guest at the Cu(I) level. In the presence of MeCN, a pseudoreversible process was obtained, owing to a fast equilibrium between a four and a five-coordinate Cu(I) species. Finally, a redox-driven ligand interchange of dimethylformamide for MeCN at the Cu(I) state allowed the trapping of the thermodynamically less stable Cu(II)-MeCN adduct. Hence, this work represents an important step toward the elaboration of a functional supramolecular model for redox mono-copper enzymes, named redox calix-zymes.
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Affiliation(s)
- Guillaume Izzet
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, Unité Mixte de Recherche Centre National de la Recherche Scientifique 8601, Université René Descartes, 45 Rue des Saints-Pères, 75270 Paris Cedex 06, France
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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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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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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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Affiliation(s)
- David B Rorabacher
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
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