Electron-Transfer Kinetics and Thermodynamic Characterization of Copper(II/I) Complexes with Acyclic Tetrathiaethers in Aqueous Solution

Dunn, Brian C.; Wijetunge, Prabodha; Vyvyan, James R.; Howard, Turner; Grall, Andrew J.; Ochrymowycz, L. A.; Rorabacher, D. B.

doi:10.1021/ic970441s

Cited by 18 publications

(17 citation statements)

References 35 publications

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“…In all three systems, the k 11(A) and k 11(B) values were similar to those observed with the Cu(II/I) systems involving the singly derivatized trans-cyclohexane and trans-cyclopentane derivatives. In a separate study, Dunn et al 141 also studied the electron-transfer kinetics of four comparable noncyclic tetrathiaether complexes with Cu(II/I) in which the central bridging moiety was ethylene, propylene, cis-cyclohexane, or trans-cyclohexane (listed at the beginning of Table 7). The k 11 values were surprisingly small (within the range of 10 -2 to 10 2 M -1 s -1 ) compared to the corresponding Cu II/I ( [14]aneS 4 ) values.…”

Section: Table 8 Electron Self-exchange Rate Constants For Pathways mentioning

confidence: 99%

“…Many blue copper sites exhibit redox potentials within the relatively narrow range of 0.2-0.4 V (vs SHE); 182 however, potentials as high as 1.0 V have been recorded. 183 The Cu(II/I) potentials of inorganic complexes in which the copper is coordinated to unsaturated nitrogen donors, to thiaether sulfur donor atoms, or to both are generally comparable to, and often exceed, these potentials, the highest value reported being 0.83 V. 141 Comparisons of the electron-transfer kinetic behavior of the cupredoxins to inorganic copper systems are somewhat problematic. The proteins normally function by having the substrate bind to a specific surface patch through electrostatic or hydrogenbonding interactions.…”

Section: Comparative Copper(ii/i) Blue Copper Protein Propertiesmentioning

confidence: 99%

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Electron Transfer by Copper Centers

2004

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Section: Table 8 Electron Self-exchange Rate Constants For Pathways mentioning

confidence: 99%

Section: Comparative Copper(ii/i) Blue Copper Protein Propertiesmentioning

confidence: 99%

Electron Transfer by Copper Centers

2004

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“…[The ligand numbering scheme adopted is contiguous with numbers assigned to recently studied macrocyclic 14 and acyclic 61 tetrathiaether ligands. ]…”

Section: Introductionmentioning

confidence: 99%

Influence of Coordination Geometry upon Copper(II/I) Redox Potentials. Physical Parameters for Twelve Copper Tripodal Ligand Complexes

et al. 1999

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Twelve related tripodal ligands have been synthesized in which the three legs linked to a bridgehead nitrogen are 2-methyl- or 2-ethylthioethyl and/or 2-pyridylethyl or -methyl. Utilization of both terminal methyl and ethyl groups on the thiaether legs was designed to determine whether slight differences in solvation or steric effects might cause detectable changes in properties. Inclusion of both methyl and ethyl linkages of the pyridines to the bridgehead nitrogen provides a comparison of the effect of five- versus six-membered chelate rings, respectively. For each of the tripodal ligands included in this work, the protonation constants and Cu(II) complex stability constants were carefully determined in aqueous solution at 25 °C, μ = 0.10 M (ClO4 -). The CuII/IL redox potentials were also determined using slow-scan cyclic voltammetry, thereby permitting the stability of the Cu(I) complexes to be calculated. The stability constants for the twelve Cu(II) complexes range from 106 to 1017, increasing by 104−105 as the first and second alkylthioethyl substituents are replaced by 2-pyridylmethyl groupswith only a slight increase upon the introduction of a third pyridyl leg. When 2-pyridylethyl groups are introduced, much smaller trends are noted. For the corresponding Cu(I) complexes, the calculated stability constants are relatively constant (at ∼1015) regardless of the donor set or the length of the pyridyl linkages to the bridgehead. Combination of these data with previous measurements on related macrocyclic and acyclic ligands containing both thiaether sulfur and amine nitrogen donor atoms reveals that, for 35 different uncharged terdentate, quadridentate and quinquedentate ligands, the stabilities of the CuIL complexes lie within the narrow range of about 1012−1016, with few exceptions, regardless of large differences in coordination geometry and donor strength. For these same 35 ligands, the CuIIL stability constants span 26 orders of magnitude. Thus, the Cu(II/I) potentials, which cover a range of 1.5 V, are shown to be inversely related to the logarithmic values of the CuIIL stability constants for a wide range of ligand types. Future strategies for manipulating the redox behavior of Cu(II/I) systems should recognize that alteration of the ligand coordination geometry primarily impacts the properties of the Cu(II) complex with almost no effect upon the Cu(I) properties.

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“…For Cu II ([14]aneNS 3 -b), the measurements were carried out at pH 3.77 using a total ligand concentration of 28 µM while the total Cu() concentration was varied from 93 to 280 µM to yield a conditional stability constant value of K Cu II L Ј = (8.25 ± 0.09) × 10 3 M Ϫ1 . Our past studies with acyclic polythiaethers49 have amply demonstrated that the Cu()-polythiaether complexes are exceptionally weak in aqueous solution in the absence of complete coordination by a quadridentate macrocycle. Based on these prior observations, it is presumed that the protonated complex with[14]aneNS 3 , Cu II HL, is not a stable species under the conditions used in the current work.…”

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confidence: 99%