Properties of aqueous CeIVDOTA prepared radiolytically and electrochemically in the presence of halide and azide anions

Guy Yardeni, Inna Popivker, Dan Meyerstein, Dalia Gitin, Eric Maimon, Tomer Zidki, Michael Khorosh, Haim Cohen, Philippe Moisy, Svetlana Pevzner, Israel Zilbermann

Research output: Contribution to journalArticlepeer-review

Abstract

CeIV(DOTA) (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) was produced both radiolytically and electrochemically in the presence of halides and azide anions. Only fluoride, the hardest Lewis base studied, ligates to both [CeIII(DOTA)(H2O)] and CeIV(DOTA), stabilizing the high oxidation state by two orders of magnitude versus [CeIV/III(DOTA)]0/− in its absence. The CeIV(DOTA) complexes are long-lived in the dark (decompose photochemically). The tetravalent complexes decompose mainly via kinetics which obeys a first order rate law. The first step is de-carboxylation of the DOTA ligand followed by the formation of CH2O. The kinetics of oxidation of [CeIII(DOTA)(H2O)] by Cl2[rad]−, Br2[rad]− and N3[rad] were studied. Cl2[rad]−, the strongest oxidizing agent studied, reacts mainly via H atom abstraction from the DOTA ligand. Br2[rad]− at both acidic and neutral pH oxidizes [CeIII(DOTA)(H2O)] with rate constants of <3 × 106 M−1s−1, as measured by pulse radiolysis, via an inner sphere mechanism. N3[rad] oxidizes [CeIII(DOTA)(H2O)] to its tetravalent analogue as well, as proved by UV–vis data after steady-state radiolysis. The presence of F increased the yield of the CeIV(DOTA) formed. The oxidation rate by N3[rad] is probably lower than that measured for Br2[rad]−.

Original languageEnglish
Article number122521
JournalInorganica Chimica Acta
Volume578
DOIs
StatePublished - 1 Apr 2025

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