Flipping of the coordinated triazine moiety in Cu(i)-L<inf>2</inf> and the small electronic factor, κ<inf>el</inf>, for direct outer-sphere cross reactions

Syntheses, crystal structures and redox behaviour of copper(II)/(i)-L<inf>2</inf> complexes (L = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine)

Atsutoshi Yamada, Takuya Mabe, Ryohei Yamane, Kyoko Noda, Yuko Wasada, Masahiko Inamo, Koji Ishihara, Takayoshi Suzuki, Hideo D. Takagi

    Research output: Contribution to journalArticle

    3 Citations (Scopus)

    Abstract

    Six-coordinate [Cu(pdt)<inf>2</inf>(H<inf>2</inf>O)<inf>2</inf>]<sup>2+</sup> and four-coordinate [Cu(pdt)<inf>2</inf>]<sup>+</sup> complexes were synthesized and the cross redox reactions were studied in acetonitrile (pdt = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine). Single crystal analyses revealed that [Cu(pdt)<inf>2</inf>(H<inf>2</inf>O)<inf>2</inf>](BF<inf>4</inf>)<inf>2</inf> was of pseudo-D<inf>2h</inf> symmetry with two axial water molecules and two symmetrically coordinated equatorial pdt ligands, while the coordination structure of [Cu(pdt)<inf>2</inf>]BF<inf>4</inf> was a squashed tetrahedron (dihedral angle = 54.87°) with an asymmetric coordination by two pdt ligands: one pdt ligand was coordinated to Cu(i) through pyridine-N and triazine-N2 while another pdt ligand was coordinated through pyridine-N and triazine-N4, and a stacking interaction between the phenyl ring on one pdt ligand and the triazine ring on another pdt ligand caused the squashed structure and non-equivalent Cu-N bond lengths. The cyclic voltammograms for [Cu(pdt)<inf>2</inf>(H<inf>2</inf>O)<inf>2</inf>]<sup>2+</sup> and [Cu(pdt)<inf>2</inf>]<sup>+</sup> in acetonitrile were identical to each other and quasi-reversible. The reduction of [Cu(pdt)<inf>2</inf>(H<inf>2</inf>O)<inf>2</inf>]<sup>2+</sup> by decamethylferrocene and the oxidation of [Cu(pdt)<inf>2</inf>]<sup>+</sup> by [Co(2,2′-bipyridine)<inf>3</inf>]<sup>3+</sup> in acetonitrile revealed that both cross reactions were sluggish through a gated process (the structural change took place prior to the electron transfer) accompanied by slow direct electron transfer processes. It was found that the triazine ring of the coordinated pdt ligand rotates around the C-C bond between the triazine and pyridine rings with the kinetic parameters k = 51 ± 5 s<sup>-1</sup> (297.8 K), ΔH<sup>‡</sup> = 6.2 ± 1.1 kJ mol<sup>-1</sup> and ΔS<sup>‡</sup> = -192 ± 4 J mol<sup>-1</sup> K<sup>-1</sup>. The electron self-exchange process was directly measured using the line-broadening method: k<inf>ex</inf> = (9.9 ± 0.5) × 10<sup>4</sup> kg mol<sup>-1</sup> s<sup>-1</sup> (297.8 K) with ΔH<sup>‡</sup> = 44 ± 7 kJ mol<sup>-1</sup> and ΔS<sup>‡</sup> = 0.2 ± 2.6 J mol<sup>-1</sup> K<sup>-1</sup>. By comparing this rate constant with the self-exchange rate constants estimated from the cross reactions using the Marcus cross relation, the non-adiabaticity (electronic) factors, κ<inf>el</inf>, for the direct electron transfer processes between [Cu(pdt)<inf>2</inf>]<sup>+/2+</sup> and non-copper metal (Fe<sup>2+</sup> and Co<sup>3+</sup>) complexes were estimated as ca. 10<sup>-7</sup>, indicating that the electronic coupling between the d orbitals of copper and of non-copper metals is very small.

    Original languageEnglish
    Pages (from-to)13979-13990
    Number of pages12
    JournalDalton Transactions
    Volume44
    Issue number31
    DOIs
    Publication statusPublished - 2015 Jun 19

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    Triazines
    Copper
    Crystal structure
    Ligands
    Electrons
    Rate constants
    Metals
    Redox reactions
    Bond length
    Dihedral angle
    Oxidation-Reduction
    3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine
    Kinetic parameters
    Single crystals
    Oxidation
    Molecules
    Water

    ASJC Scopus subject areas

    • Inorganic Chemistry

    Cite this

    Flipping of the coordinated triazine moiety in Cu(i)-L<inf>2</inf> and the small electronic factor, κ<inf>el</inf>, for direct outer-sphere cross reactions : Syntheses, crystal structures and redox behaviour of copper(II)/(i)-L<inf>2</inf> complexes (L = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine). / Yamada, Atsutoshi; Mabe, Takuya; Yamane, Ryohei; Noda, Kyoko; Wasada, Yuko; Inamo, Masahiko; Ishihara, Koji; Suzuki, Takayoshi; Takagi, Hideo D.

    In: Dalton Transactions, Vol. 44, No. 31, 19.06.2015, p. 13979-13990.

    Research output: Contribution to journalArticle

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    title = "Flipping of the coordinated triazine moiety in Cu(i)-L2 and the small electronic factor, κel, for direct outer-sphere cross reactions: Syntheses, crystal structures and redox behaviour of copper(II)/(i)-L2 complexes (L = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine)",
    abstract = "Six-coordinate [Cu(pdt)2(H2O)2]2+ and four-coordinate [Cu(pdt)2]+ complexes were synthesized and the cross redox reactions were studied in acetonitrile (pdt = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine). Single crystal analyses revealed that [Cu(pdt)2(H2O)2](BF4)2 was of pseudo-D2h symmetry with two axial water molecules and two symmetrically coordinated equatorial pdt ligands, while the coordination structure of [Cu(pdt)2]BF4 was a squashed tetrahedron (dihedral angle = 54.87°) with an asymmetric coordination by two pdt ligands: one pdt ligand was coordinated to Cu(i) through pyridine-N and triazine-N2 while another pdt ligand was coordinated through pyridine-N and triazine-N4, and a stacking interaction between the phenyl ring on one pdt ligand and the triazine ring on another pdt ligand caused the squashed structure and non-equivalent Cu-N bond lengths. The cyclic voltammograms for [Cu(pdt)2(H2O)2]2+ and [Cu(pdt)2]+ in acetonitrile were identical to each other and quasi-reversible. The reduction of [Cu(pdt)2(H2O)2]2+ by decamethylferrocene and the oxidation of [Cu(pdt)2]+ by [Co(2,2′-bipyridine)3]3+ in acetonitrile revealed that both cross reactions were sluggish through a gated process (the structural change took place prior to the electron transfer) accompanied by slow direct electron transfer processes. It was found that the triazine ring of the coordinated pdt ligand rotates around the C-C bond between the triazine and pyridine rings with the kinetic parameters k = 51 ± 5 s-1 (297.8 K), ΔH‡ = 6.2 ± 1.1 kJ mol-1 and ΔS‡ = -192 ± 4 J mol-1 K-1. The electron self-exchange process was directly measured using the line-broadening method: kex = (9.9 ± 0.5) × 104 kg mol-1 s-1 (297.8 K) with ΔH‡ = 44 ± 7 kJ mol-1 and ΔS‡ = 0.2 ± 2.6 J mol-1 K-1. By comparing this rate constant with the self-exchange rate constants estimated from the cross reactions using the Marcus cross relation, the non-adiabaticity (electronic) factors, κel, for the direct electron transfer processes between [Cu(pdt)2]+/2+ and non-copper metal (Fe2+ and Co3+) complexes were estimated as ca. 10-7, indicating that the electronic coupling between the d orbitals of copper and of non-copper metals is very small.",
    author = "Atsutoshi Yamada and Takuya Mabe and Ryohei Yamane and Kyoko Noda and Yuko Wasada and Masahiko Inamo and Koji Ishihara and Takayoshi Suzuki and Takagi, {Hideo D.}",
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    T1 - Flipping of the coordinated triazine moiety in Cu(i)-L2 and the small electronic factor, κel, for direct outer-sphere cross reactions

    T2 - Syntheses, crystal structures and redox behaviour of copper(II)/(i)-L2 complexes (L = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine)

    AU - Yamada, Atsutoshi

    AU - Mabe, Takuya

    AU - Yamane, Ryohei

    AU - Noda, Kyoko

    AU - Wasada, Yuko

    AU - Inamo, Masahiko

    AU - Ishihara, Koji

    AU - Suzuki, Takayoshi

    AU - Takagi, Hideo D.

    PY - 2015/6/19

    Y1 - 2015/6/19

    N2 - Six-coordinate [Cu(pdt)2(H2O)2]2+ and four-coordinate [Cu(pdt)2]+ complexes were synthesized and the cross redox reactions were studied in acetonitrile (pdt = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine). Single crystal analyses revealed that [Cu(pdt)2(H2O)2](BF4)2 was of pseudo-D2h symmetry with two axial water molecules and two symmetrically coordinated equatorial pdt ligands, while the coordination structure of [Cu(pdt)2]BF4 was a squashed tetrahedron (dihedral angle = 54.87°) with an asymmetric coordination by two pdt ligands: one pdt ligand was coordinated to Cu(i) through pyridine-N and triazine-N2 while another pdt ligand was coordinated through pyridine-N and triazine-N4, and a stacking interaction between the phenyl ring on one pdt ligand and the triazine ring on another pdt ligand caused the squashed structure and non-equivalent Cu-N bond lengths. The cyclic voltammograms for [Cu(pdt)2(H2O)2]2+ and [Cu(pdt)2]+ in acetonitrile were identical to each other and quasi-reversible. The reduction of [Cu(pdt)2(H2O)2]2+ by decamethylferrocene and the oxidation of [Cu(pdt)2]+ by [Co(2,2′-bipyridine)3]3+ in acetonitrile revealed that both cross reactions were sluggish through a gated process (the structural change took place prior to the electron transfer) accompanied by slow direct electron transfer processes. It was found that the triazine ring of the coordinated pdt ligand rotates around the C-C bond between the triazine and pyridine rings with the kinetic parameters k = 51 ± 5 s-1 (297.8 K), ΔH‡ = 6.2 ± 1.1 kJ mol-1 and ΔS‡ = -192 ± 4 J mol-1 K-1. The electron self-exchange process was directly measured using the line-broadening method: kex = (9.9 ± 0.5) × 104 kg mol-1 s-1 (297.8 K) with ΔH‡ = 44 ± 7 kJ mol-1 and ΔS‡ = 0.2 ± 2.6 J mol-1 K-1. By comparing this rate constant with the self-exchange rate constants estimated from the cross reactions using the Marcus cross relation, the non-adiabaticity (electronic) factors, κel, for the direct electron transfer processes between [Cu(pdt)2]+/2+ and non-copper metal (Fe2+ and Co3+) complexes were estimated as ca. 10-7, indicating that the electronic coupling between the d orbitals of copper and of non-copper metals is very small.

    AB - Six-coordinate [Cu(pdt)2(H2O)2]2+ and four-coordinate [Cu(pdt)2]+ complexes were synthesized and the cross redox reactions were studied in acetonitrile (pdt = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine). Single crystal analyses revealed that [Cu(pdt)2(H2O)2](BF4)2 was of pseudo-D2h symmetry with two axial water molecules and two symmetrically coordinated equatorial pdt ligands, while the coordination structure of [Cu(pdt)2]BF4 was a squashed tetrahedron (dihedral angle = 54.87°) with an asymmetric coordination by two pdt ligands: one pdt ligand was coordinated to Cu(i) through pyridine-N and triazine-N2 while another pdt ligand was coordinated through pyridine-N and triazine-N4, and a stacking interaction between the phenyl ring on one pdt ligand and the triazine ring on another pdt ligand caused the squashed structure and non-equivalent Cu-N bond lengths. The cyclic voltammograms for [Cu(pdt)2(H2O)2]2+ and [Cu(pdt)2]+ in acetonitrile were identical to each other and quasi-reversible. The reduction of [Cu(pdt)2(H2O)2]2+ by decamethylferrocene and the oxidation of [Cu(pdt)2]+ by [Co(2,2′-bipyridine)3]3+ in acetonitrile revealed that both cross reactions were sluggish through a gated process (the structural change took place prior to the electron transfer) accompanied by slow direct electron transfer processes. It was found that the triazine ring of the coordinated pdt ligand rotates around the C-C bond between the triazine and pyridine rings with the kinetic parameters k = 51 ± 5 s-1 (297.8 K), ΔH‡ = 6.2 ± 1.1 kJ mol-1 and ΔS‡ = -192 ± 4 J mol-1 K-1. The electron self-exchange process was directly measured using the line-broadening method: kex = (9.9 ± 0.5) × 104 kg mol-1 s-1 (297.8 K) with ΔH‡ = 44 ± 7 kJ mol-1 and ΔS‡ = 0.2 ± 2.6 J mol-1 K-1. By comparing this rate constant with the self-exchange rate constants estimated from the cross reactions using the Marcus cross relation, the non-adiabaticity (electronic) factors, κel, for the direct electron transfer processes between [Cu(pdt)2]+/2+ and non-copper metal (Fe2+ and Co3+) complexes were estimated as ca. 10-7, indicating that the electronic coupling between the d orbitals of copper and of non-copper metals is very small.

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