Browsing by Author "Fiedler, Jan"

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    Homodinuclear complexes of [Cu(dppf)]+ or [Ru(bpy)2]2+ with 1,4‐Bis(camphorquinoneimino)benzene (bcqb) as a redox‐active bridging ligand
    (2021) Filippou, Vasileios; Bubrin, Martina; Fiedler, Jan; Kaim, Wolfgang
    The product μ‐bcqb from the reaction between p‐phenylenediamine and two equivalents of camphorquinone has been used as a potentially conjugated molecular bridge between two complex fragments [Cu(dppf)]+, dppf=1,1‘‐bis(diphenylphosphino)ferrocene, to yield 12+, and between two [Ru(bpy)2]2+ moieties, resulting in 24+. The molecular structure of 1(BF4)2 shows an intramolecular Cu-Cu distance of 8.04 Å and a torsionally twisted conformation of the bridge, while cyclic voltammetry, EPR, IR and UV‐vis‐NIR spectroelectrochemistry reveal two closely spaced one‐electron reductions and a ferrocene‐based two‐electron oxidation. Compound 2(PF6)4 exhibits at least three one‐electron reduction waves and one 2e‐oxidation, the former attributed to μ‐bcqb and the latter assigned to metal‐based processes showing no evidence for a Ru-Ru mixed‐valent intermediate. However, intra‐ligand based mixed valency with intense LLIVCT absorptions in the near infrared was observed for the metal coordinated μ‐bcqb.- and μ‐bcqb.3- bridges. The two examples 1n+ and 2n+ illustrate that a combination of physical methods is advantageous to analyze and define the correct electronic structures in complexes involving several metal centers and noninnocent ligand components.
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    Tetrazine chelate ligands bridging two [Ru(acac)2] fragments : mixed valency and radical complex formation
    (2022) Kaim, Wolfgang; Löw, Isabell; Ringenberg, Mark R.; Schwederski, Brigitte; Filippou, Vasileios; Fiedler, Jan
    Using bis(3‐methyl‐2‐pyridyl)‐1,2,4,5‐tetrazine 1, 3‐(2‐pyrimidyl)‐6‐methyl‐1,2,4,5‐tetrazine 2 and bis(2‐pyrimidyl)‐1,2,4,5‐tetrazine=bmtz as ligands, the complexes 3=[Ru(acac)2(1)], 4={[Ru(acac)2]2(1)], 5={[Ru(acac)2]2(bmtz)], and 6={[Ru(acac)2]2(2)] were prepared and identified by structure analysis of crystallized material. The one‐electron oxidized form 6(PF6) was also studied structurally, suggesting a Class II mixed‐valent situation. The neutral dinuclear systems exhibit two reversible oxidation processes with comproportionation constants 109.2