Abstract
The kinetics of oxidation of adrenaline by μ-dioxytetrakis(histidinato)dicobalt(II) complex has been investigated. Adrenaline is oxidized into leucoadrenochrome and adrenochrome. The rate of formation of leucoadrenochrome and adrenochrome is linearly dependent upon [NaOH]. The rate of oxidation of adrenaline increases with the increase in [adrenaline]. [Display omitted]
•The mechanism of oxidation of adrenaline by an oxygen carrier is investigated.•μ-Dioxytetrakis(histidinato)dicobalt(II) oxidizes adrenaline at neutral pH also.•At high temperature and in alkaline medium adrenochrome is formed.•The rate of oxidation of adrenaline is linearly dependent upon [NaOH].
The cobalt(II)histidine complex binds molecular oxygen reversibly to form an oxygen adduct complex, μ-dioxytetrakis-(histidinato)dicobalt(II). The molecular oxygen can be released from the oxygenated complex by heating it or by passing N2, He or Ar gas through its solution. μ-Dioxytetrakis-(histidinato)dicobalt(II) complex oxidizes adrenaline into leucoadrenochrome at 25°C while at higher temperature (>40°C) adrenochrome with λmax at 490nm is formed. The rate of formation of leucoadrenochrome was found to be independent of [bis(histidinato)cobalt(II)]. The rate of reaction for the formation of leucoadrenochrome and adrenochrome increased with the increase in [adrenaline] at its lower concentration but become independent at higher concentration. Similarly, the rate of formation of both leucoadrenochrome and adrenochrome was linearly dependent upon [NaOH]. The values of activation parameters i.e. ΔEa, ΔH‡ and ΔS‡ for the formation of leucoadrenochrome are reported.