Probing the nature of the Co(III) ion in corrins: The reactions of aquacyano-5-seco-cobyrinic acid heptamethyl ester with anionic ligands

Nowakowska, Monika; Chemaly, Susan M.; Rousseau, Amanda L.; Govender, Penny Poomani; Varadwaj, Pradeep R.; Yamashita, Koichi; Marques, Helder M.

doi:10.1016/j.ica.2018.09.073

Cited by 2 publications

(1 citation statement)

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“…Probably, the binding of HSO 5 − via the Co(III) ion of dioxo-secocobalamins facilitates its deprotonation and labilization of the O-O bond ( Scheme 2 ). It is well known that the Co(III) ion in Cbls exhibits a relatively soft metal center [ 26 , 44 ], whereas corrin ring cleavage to give the dioxo-seco species makes the Co(III) ion harder [ 45 ]. Therefore, the coordination of HSO 5 − , a hard base, is more plausible on the Co(III) ion in dioxo-seco-Cbl than in unmodified Cbl.…”

Section: Resultsmentioning

confidence: 99%

Aquacobalamin Accelerates Orange II Destruction by Peroxymonosulfate via the Transient Formation of Secocorrinoid: A Mechanistic Study

Dereven’kov

Sakharova

Osokin

et al. 2022

IJMS

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Besides its use in medicine, vitamin B12 (cobalamin) and its derivatives have found in numerous applications as catalysts. However, studies related to the activation of oxidants via cobalamin are scant. In this work, we showed how the addition of aquacobalamin (H2OCbl) accelerates the destruction of azo-dye Orange II by peroxymonosulfate (HSO5−) in aqueous solutions. In neutral and weakly alkaline media, the process is initiated by the modification of the corrin macrocycle with HSO5−, which requires the preliminary deprotonation of the aqua-ligand in H2OCbl to give hydroxocobalamin, producing 5,6-dioxo-5,6-secocobalamin or its isomer (14,15-dioxo-14,15-secocobalamin). In acidic solutions, where the concentration of hydroxocobalamin is negligible, the formation of dioxo-seco-species is not observed, and the reaction between H2OCbl and HSO5− results in slow chromophore bleaching. Using terephthalic acid, we demonstrated the formation of hydroxyl radicals in the mixture of H2OCbl with HSO5-, whereas the generation of sulfate radicals was proved by comparing the effects of ethanol and nitrobenzene on Orange II destruction using the H2OCbl/HSO5− system. The reaction mechanism includes the binding of HSO5− to the Co(III) ion of dioxo-secocobalamin, which results in its deprotonation and the labilization of the O-O bond, leading to the formation of sulfate and hydroxyl radicals which further react with Orange II.

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Section: Resultsmentioning

confidence: 99%