Electrochemical synthesis and crystal structure studies of defective dicubane tetranuclear hydroxo and carboxamide ligand bridged cobalt(II)–cobalt(III) complexes with carboxamides produced from unprotected hydroxyaromatic carboxylic acids

Meghdadi, Soraia; Mirkhani, Valiollah; Mereiter, Kurt

doi:10.1016/j.crci.2014.11.001

Cited by 4 publications

(1 citation statement)

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“…We hypothesized that the asymmetric species could correspond to a complex in which one of the amide groups is deprotonated and likely coordinated to the metal ion through the N atom, as Ncoordination of deprotonated amide groups to Co(III) was reported previously. 71,72 We therefore carried out the synthesis using the same conditions in the absence of a base. This afforded a blue solid that corresponds to the [Co(CB-TE2AM)]Cl 3 complex, as confirmed by the mass spectrum and 1 H and 13 C NMR studies (see below).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Endeavor toward Redox-Responsive Transition Metal Contrast Agents Based on the Cross-Bridge Cyclam Platform

Uzal-Varela,

Rodríguez-Rodríguez,

Lalli

et al. 2024

Inorg. Chem.

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We present the synthesis and characterization of a series of Mn(III), Co(III), and Ni(II) complexes with cross-bridge cyclam derivatives 4,8,]hexadecane) containing acetamide or acetic acid pendant arms. The X-ray structures of [Ni(CB-TE2AM)]Cl 2 •2H 2 O and [Mn(CB-TE1AM)(OH)](PF 6 ) 2 evidence the octahedral coordination of the ligands around the Ni(II) and Mn(III) metal ions, with a terminal hydroxide ligand being coordinated to Mn(III). Cyclic voltammetry studies on solutions of the [Mn(CB-TE1AM)(OH)] 2+ and [Mn(CB-TE1A)(OH)] + complexes (0.15 M NaCl) show an intricate redox behavior with waves due to the Mn III /Mn IV and Mn II /Mn III pairs. The Co(III) and Ni(II) complexes with CB-TE2A and CB-TE2AM show quasireversible features due to the Co III /Co II or Ni II /Ni III pairs. The [Co(CB-TE2AM)] 3+ complex is readily reduced by dithionite in aqueous solution, as evidenced by 1 H NMR studies, but does not react with ascorbate. The [Mn(CB-TE1A)(OH)] + complex is however reduced very quickly by ascorbate following a simple kinetic scheme (k 0 = k 1 [AH − ], where [AH − ] is the ascorbate concentration and k 1 = 628 ± 7 M −1 s −1 ). The reduction of the Mn(III) complex to Mn(II) by ascorbate provokes complex dissociation, as demonstrated by 1 H nuclear magnetic relaxation dispersion studies. The [Ni(CB-TE2AM)] 2+ complex shows significant chemical exchange saturation transfer effects upon saturation of the amide proton signals at 71 and 3 ppm with respect to the bulk water signal.

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Section: ■ Results and Discussionmentioning

confidence: 99%