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Cobalt complexes with redox-active anthraquinone-type ligands

Shiga, Takuya; Kumamaru, Rina; Newton, Graham N.; Oshio, Hiroki


Takuya Shiga

Rina Kumamaru

Hiroki Oshio


Three anthraquinone-type multidentate ligands, HL1-3 (HL = 2-R-1H-anthra[1,2-d]imidazole6,11-dione, HL1; R = (2-pyridyl), HL2; R = (4,6-dimethyl-2-pyridyl), HL3; R = (6-methoxy-2pyridyl)), were prepared, and their complexation behaviour were investigated. Three bis-chelate cobalt complexes with the formula [CoII(L1-3)2].n(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. Further 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 have 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.


Shiga, T., Kumamaru, R., Newton, G. N., & Oshio, H. (2018). Cobalt complexes with redox-active anthraquinone-type ligands. Dalton Transactions, 47(23),

Journal Article Type Article
Acceptance Date May 14, 2018
Online Publication Date May 31, 2018
Publication Date Jun 21, 2018
Deposit Date Jun 8, 2018
Publicly Available Date Jun 1, 2019
Journal Dalton Transactions
Print ISSN 1477-9226
Electronic ISSN 1477-9234
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 47
Issue 23
Public URL
Publisher URL!divAbstract
Copyright Statement Copyright information regarding this work can be found at the following address:


Graham Newton Cobalt complexes with redox-active.pdf (1.2 Mb)

Copyright Statement
Copyright information regarding this work can be found at the following address:

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