Eight‐Coordination Chemistry

Lippard, Stephen J.

doi:10.1002/9780470166093.ch3

Cited by 97 publications

(9 citation statements)

References 221 publications

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“…These values are fairly close to the expected values of 15/4 ( S = 3/2) and 35/4 ( S = 5/2) for two noninteracting ions when g = 2.0. The magnetic susceptibility data were analyzed using eqs – and derived using the Heisenberg intra cluster magnetic exchange for a binuclear complex H = − JS 1 · S 2 where for 1 , S = 3/2 and and for 2 and 6 , S = 5/2 and Here, N is the Avogadro number, k is the Boltzmann constant, T is the temperature in Kelvin, g is the Landé g factor, β is the Bohr magneton, ρ is the paramagnetic contribution, θ is the Weiss constant for paramagnetic impurities, J is the intra dimer coupling constant, and S is the spin. A satisfying description of the experimental data over the whole temperature range was obtained with the following set of parameters:…”

Section: Resultsmentioning

confidence: 99%

Arsenic(III)-Capped 12-Tungsto-2-Arsenates(III) [M₂(As^IIIW₆O₂₅)₂(As^IIIOH)_x]ⁿ⁻ (M = Cr^III, Fe^III, Sc^III, In^III, Ti^IV, Mn^II) and Their Magnetic Properties

et al. 2021

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Six arsenic(III)-capped 12-tungsto-2-arsenates(III) of the type [M2(AsIIIW6O25)2(AsIIIOH) x ] n− (M = CrIII, 1; FeIII, 2; ScIII, 3; InIII, 4; TiIV, 5; MnII, 6) have been synthesized in aqueous medium by direct reaction of the elements using a one-pot strategy and structurally characterized by FT-IR spectroscopy, single-crystal XRD, and elemental analysis. Polyanions 1–6 are comprised of two octahedrally coordinated guest metal ions M sandwiched between two {AsW6} units, resulting in a structure with C 2h point-group symmetry. Polyanions 1–5 contain tri- and tetravalent metal ion guests M (M = CrIII, FeIII, ScIII, InIII, and TiIV, respectively), and they have one {AsIIIOH} group grafted on each {AsW6} unit, whereas the divalent MnII-containing derivative 6 has two such {AsIIIOH} groups grafted on each {AsW6} unit. Magnetic studies on polyanions 3–5 over the temperature range 1.8–295 K and magnetic fields of 0–7 T confirmed that they are diamagnetic. On the other hand, polyanions 1, 2, and 6 are strongly magnetic and follow the Curie–Weiss law above 30 K. The susceptibility plots of 1 and 6 exhibit broad peaks suggesting short-range antiferromagnetic ordering, while the very weak antiferromagnetic ordering of 2 is overshadowed by traces of a paramagnetic impurity. The magnetization data of 1, 2, and 6 at 1.8 K over 0–7 T were analyzed by using the Heisenberg exchange procedure. Small (negative) values of the obtained J values help in understanding the absence of long-range antiferromagnetic ordering.

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Section: Resultsmentioning

confidence: 99%

Arsenic(III)-Capped 12-Tungsto-2-Arsenates(III) [M₂(As^IIIW₆O₂₅)₂(As^IIIOH)_x]ⁿ⁻ (M = Cr^III, Fe^III, Sc^III, In^III, Ti^IV, Mn^II) and Their Magnetic Properties

et al. 2021

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“…Nature has developed highly specialized molecular building blocks capable of transporting charge with unprecedented efficiency, i.e. fast and at long distances 2,3 . Understanding the mechanisms behind biological ET is key to elucidate the changes in the charge transport regime caused by specific structural variations of the associated molecular machinery, which ultimately lead to, for instance, malfunctioning of the mitochondria.…”

Section: Introductionmentioning

confidence: 99%

Bioengineering a Single-Protein Junction

et al. 2017

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Bioelectronics moves toward designing nanoscale electronic platforms that allow in vivo determinations. Such devices require interfacing complex biomolecular moieties as the sensing units to an electronic platform for signal transduction. Inevitably, a systematic design goes through a bottom-up understanding of the structurally related electrical signatures of the biomolecular circuit, which will ultimately lead us to tailor its electrical properties. Toward this aim, we show here the first example of bioengineered charge transport in a single-protein electrical contact. The results reveal that a single point-site mutation at the docking hydrophobic patch of a Cu-azurin causes minor structural distortion of the protein blue Cu site and a dramatic change in the charge transport regime of the single-protein contact, which goes from the classical Cu-mediated two-step transport in this system to a direct coherent tunneling. Our extensive spectroscopic studies and molecular-dynamics simulations show that the proteins' folding structures are preserved in the single-protein junction. The DFT-computed frontier orbital of the relevant protein segments suggests that the Cu center participation in each protein variant accounts for the different observed charge transport behavior. This work is a direct evidence of charge transport control in a protein backbone through external mutagenesis and a unique nanoscale platform to study structurally related biological electron transfer.

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“…The square-planar coordination geometry in [Th(OAr′) 4 ] 1– was surprising given that tetrahedral geometry is sterically favored and the electron configuration of the new complex is not one of the d 7 –d 9 electron configurations that electronically favor square-planar geometries. − It is possible that the arrangement of the eight tert -butyl groups is optimized with the OAr′ ligands in a square-planar array, although most eight-coordinate structures are similar in energy. , The eight tert -butyl tertiary carbon atoms define a square antiprism, which is one of the several common geometries for ML 8 compounds and M 8 L x clusters.…”

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confidence: 99%

“…30−32 It is possible that the arrangement of the eight tert-butyl groups is optimized with the OAr′ ligands in a square-planar array, although most eightcoordinate structures are similar in energy. 33,34 The eight tertbutyl tertiary carbon atoms define a square antiprism, which is one of the several common geometries for ML 8 compounds and M 8 L x clusters.…”

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Isolation of a Square-Planar Th(III) Complex: Synthesis and Structure of [Th(OC₆H₂^tBu₂-2,6-Me-4)₄]^1–

et al. 2019

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Reduction of Th(OC6H2 tBu2-2,6-Me-4)4 using either KC8 or Li in THF forms a new example of a crystallographically characterizable Th(III) complex in the salts [K(THF)5(Et2O)][Th(OC6H2 tBu2-2,6-Me-4)4] and [Li(THF)4][Th(OC6H2 tBu2-2,6-Me-4)4]. Surprisingly, in each structure the four aryloxide ligands are arranged in a square-planar geometry, the first example of this coordination mode for an f element complex. The Th(III) ion and four oxygen donor atoms are coplanar to within 0.05 Å with O–Th–O angles of 89.27(8) to 92.02(8)° between cis ligands. The ligands have Th–O–C(ipso) angles of 173.9(2) to 178.6(4)°, and the aryl rings make angles of 58.5 to 65.1° with the ThO4 plane. The effect of the eight tert-butyl substituents in generating the unusual structure through packing and/or dispersion forces is discussed. EPR spectroscopy reveals an axial signal consistent with a metal-based radical in a planar complex. DFT calculations yield a C 4-symmetric structure that accommodates a low-lying SOMO of 6d z 2 character with 7s Rydberg admixture.

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Eight‐Coordination Chemistry

Cited by 97 publications

References 221 publications

Arsenic(III)-Capped 12-Tungsto-2-Arsenates(III) [M₂(As^IIIW₆O₂₅)₂(As^IIIOH)_x]ⁿ⁻ (M = Cr^III, Fe^III, Sc^III, In^III, Ti^IV, Mn^II) and Their Magnetic Properties

Arsenic(III)-Capped 12-Tungsto-2-Arsenates(III) [M₂(As^IIIW₆O₂₅)₂(As^IIIOH)_x]ⁿ⁻ (M = Cr^III, Fe^III, Sc^III, In^III, Ti^IV, Mn^II) and Their Magnetic Properties

Bioengineering a Single-Protein Junction

Isolation of a Square-Planar Th(III) Complex: Synthesis and Structure of [Th(OC₆H₂^tBu₂-2,6-Me-4)₄]^1–

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Eight‐Coordination Chemistry

Cited by 97 publications

References 221 publications

Arsenic(III)-Capped 12-Tungsto-2-Arsenates(III) [M2(AsIIIW6O25)2(AsIIIOH)x]n− (M = CrIII, FeIII, ScIII, InIII, TiIV, MnII) and Their Magnetic Properties

Arsenic(III)-Capped 12-Tungsto-2-Arsenates(III) [M2(AsIIIW6O25)2(AsIIIOH)x]n− (M = CrIII, FeIII, ScIII, InIII, TiIV, MnII) and Their Magnetic Properties

Bioengineering a Single-Protein Junction

Isolation of a Square-Planar Th(III) Complex: Synthesis and Structure of [Th(OC6H2tBu2-2,6-Me-4)4]1–

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About

Arsenic(III)-Capped 12-Tungsto-2-Arsenates(III) [M₂(As^IIIW₆O₂₅)₂(As^IIIOH)_x]ⁿ⁻ (M = Cr^III, Fe^III, Sc^III, In^III, Ti^IV, Mn^II) and Their Magnetic Properties

Arsenic(III)-Capped 12-Tungsto-2-Arsenates(III) [M₂(As^IIIW₆O₂₅)₂(As^IIIOH)_x]ⁿ⁻ (M = Cr^III, Fe^III, Sc^III, In^III, Ti^IV, Mn^II) and Their Magnetic Properties

Isolation of a Square-Planar Th(III) Complex: Synthesis and Structure of [Th(OC₆H₂^tBu₂-2,6-Me-4)₄]^1–