Jump to main content
Jump to site search

Issue 23, 2018
Previous Article Next Article

Cobalt complexes with redox-active anthraquinone-type ligands

Author affiliations


Three anthraquinone-type multidentate ligands, HL1–3 (HL = 2-R-1H-anthra[1,2-d]imidazole-6,11-dione; HL1: R = (2-pyridyl), HL2; R = (4,6-dimethyl-2-pyridyl), HL3; R = (6-methoxy-2-pyridyl)), were prepared, and their complexation behaviour was investigated. Three bis-chelate cobalt complexes with the formula [CoII(L1–3)2n(solv.) (1, 2, and 3 for HL1, HL2, and HL3, respectively), in which the ligands adopted tridentate binding modes, were synthesized and structurally characterized by single-crystal X-ray analyses. Electrochemical studies of 1–3 in CH2Cl2 reveal three reversible redox waves, assigned to ligand and cobalt-centred processes. Additional complexes were obtained in which HL1 adopted a bidentate binding mode, stabilising the mono-chelate [CoII(HL1)(NO3)2(DMF)2] (4) species and tris-chelate [CoIII(L1)3] (5) complex in which the cobalt ion was in its 3+ state. The electrochemical properties of complex 5 were investigated in DMF, and the Co(II)/Co(III) redox couple was found to be negatively shifted compared to that of complex 1, while the ligand-based processes became irreversible. Tridentate chelation is found to stabilise the anthraquinone ligands and unlocks their redox multi-stability.

Graphical abstract: Cobalt complexes with redox-active anthraquinone-type ligands

Back to tab navigation

Supplementary files

Publication details

The article was received on 12 Feb 2018, accepted on 14 May 2018 and first published on 31 May 2018

Article type: Paper
DOI: 10.1039/C8DT00586A
Citation: Dalton Trans., 2018,47, 7804-7811
  •   Request permissions

    Cobalt complexes with redox-active anthraquinone-type ligands

    T. Shiga, R. Kumamaru, G. N. Newton and H. Oshio, Dalton Trans., 2018, 47, 7804
    DOI: 10.1039/C8DT00586A

Search articles by author