About: Redox-induced spin-state switching and mixed valency in quinonoid-bridged dicobalt complexes     Goto   Sponge   NotDistinct   Permalink

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  • The complexes [{(tmpa)Co(II) }2 (mu-L(1) )(2-) ](2+) (1(2+) ) and [{(tmpa)Co(II) }2 (mu-L(2) )(2-) ](2+) (2(2+) ), with tmpa=tris(2-pyridylmethyl)amine, H2 L(1) =2,5-di-[2-(methoxy)-anilino]-1,4-benzoquinone, and H2 L(2) =2,5-di-[2-(trifluoromethyl)-anilino]-1,4-benzoquinone, were synthesized and characterized. Structural analysis of 2(2+) revealed a distorted octahedral coordination around the cobalt centers, and cobalt-ligand bond lengths that match with high-spin Co(II) centers. Superconducting quantum interference device (SQUID) magnetometric studies on 1(2+) and 2(2+) are consistent with the presence of two weakly exchange-coupled high-spin cobalt(II) ions, for which the nature of the coupling appears to depend on the substituents on the bridging ligand, being antiferromagnetic for 1(2+) and ferromagnetic for 2(2+) . Both complexes exhibit several one-electron redox steps, and these were investigated with cyclic voltammetry and UV/Vis/near-IR spectroelectrochemistry. For 1(2+) , it was possible to chemically isolate the pure forms of both the one-electron oxidized mixed-valent 1(3+) and the two-electron oxidized isovalent 1(4+) forms, and characterize them structurally as well as magnetically. This series thus provided an opportunity to investigate the effect of reversible electron transfers on the total spin-state of the molecule. In contrast to 2(2+) , for 1(4+) the metal-ligand distances and the distances within the quinonoid ligand point to the existence of two low-spin Co(III) centers, thus showing the innocence of the quintessential non-innocent ligands L. Magnetic data corroborate these observations by showing the decrease of the magnetic moment by roughly half (neglecting spin exchange effects) on oxidizing the molecules with one electron, and the disappearance of a paramagnetic response upon two-electron oxidation, which confirms the change in spin state associated with the electron-transfer steps.
  • The complexes [{(tmpa)Co(II) }2 (mu-L(1) )(2-) ](2+) (1(2+) ) and [{(tmpa)Co(II) }2 (mu-L(2) )(2-) ](2+) (2(2+) ), with tmpa=tris(2-pyridylmethyl)amine, H2 L(1) =2,5-di-[2-(methoxy)-anilino]-1,4-benzoquinone, and H2 L(2) =2,5-di-[2-(trifluoromethyl)-anilino]-1,4-benzoquinone, were synthesized and characterized. Structural analysis of 2(2+) revealed a distorted octahedral coordination around the cobalt centers, and cobalt-ligand bond lengths that match with high-spin Co(II) centers. Superconducting quantum interference device (SQUID) magnetometric studies on 1(2+) and 2(2+) are consistent with the presence of two weakly exchange-coupled high-spin cobalt(II) ions, for which the nature of the coupling appears to depend on the substituents on the bridging ligand, being antiferromagnetic for 1(2+) and ferromagnetic for 2(2+) . Both complexes exhibit several one-electron redox steps, and these were investigated with cyclic voltammetry and UV/Vis/near-IR spectroelectrochemistry. For 1(2+) , it was possible to chemically isolate the pure forms of both the one-electron oxidized mixed-valent 1(3+) and the two-electron oxidized isovalent 1(4+) forms, and characterize them structurally as well as magnetically. This series thus provided an opportunity to investigate the effect of reversible electron transfers on the total spin-state of the molecule. In contrast to 2(2+) , for 1(4+) the metal-ligand distances and the distances within the quinonoid ligand point to the existence of two low-spin Co(III) centers, thus showing the innocence of the quintessential non-innocent ligands L. Magnetic data corroborate these observations by showing the decrease of the magnetic moment by roughly half (neglecting spin exchange effects) on oxidizing the molecules with one electron, and the disappearance of a paramagnetic response upon two-electron oxidation, which confirms the change in spin state associated with the electron-transfer steps. (en)
Title
  • Redox-induced spin-state switching and mixed valency in quinonoid-bridged dicobalt complexes
  • Redox-induced spin-state switching and mixed valency in quinonoid-bridged dicobalt complexes (en)
skos:prefLabel
  • Redox-induced spin-state switching and mixed valency in quinonoid-bridged dicobalt complexes
  • Redox-induced spin-state switching and mixed valency in quinonoid-bridged dicobalt complexes (en)
skos:notation
  • RIV/61388955:_____/14:00428492!RIV15-GA0-61388955
http://linked.open...avai/riv/aktivita
http://linked.open...avai/riv/aktivity
  • I, P(GA203/09/0705)
http://linked.open...iv/cisloPeriodika
  • 12
http://linked.open...vai/riv/dodaniDat
http://linked.open...aciTvurceVysledku
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http://linked.open...iv/duvernostUdaju
http://linked.open...titaPredkladatele
http://linked.open...dnocenehoVysledku
  • 41695
http://linked.open...ai/riv/idVysledku
  • RIV/61388955:_____/14:00428492
http://linked.open...riv/jazykVysledku
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  • bridging ligands; mixed-valent compounds; non-innocent ligands (en)
http://linked.open.../riv/klicoveSlovo
http://linked.open...odStatuVydavatele
  • DE - Spolková republika Německo
http://linked.open...ontrolniKodProRIV
  • [0104ED4B56A4]
http://linked.open...i/riv/nazevZdroje
  • Chemistry - A European Journal
http://linked.open...in/vavai/riv/obor
http://linked.open...ichTvurcuVysledku
http://linked.open...cetTvurcuVysledku
http://linked.open...vavai/riv/projekt
http://linked.open...UplatneniVysledku
http://linked.open...v/svazekPeriodika
  • 20
http://linked.open...iv/tvurceVysledku
  • Fiedler, Jan
  • Sarkar, B.
  • Deibel, N.
  • Schweinfurth, D.
  • Neugebauer, P.
  • Hohloch, S.
  • Marx, R.
  • Peremykin, I.
  • Rechkemmer, Y.
  • van Slageren, J.
http://linked.open...ain/vavai/riv/wos
  • 000332747400030
issn
  • 0947-6539
number of pages
http://bibframe.org/vocab/doi
  • 10.1002/chem.201302858
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