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

[Display omitted] •CeIV(DOTA) was obtained both, radiolytically and electrochemically in presence of halides and azide.•Halides (except F−) do not ligate to neither [CeIII(DOTA)(H2O)]− nor CeIV(DOTA).•Cl2.−; Br2.− and N3. oxidize [CeIII(DOTA)(H2O)]− by different mechanisms.•F− stabilizes CeIV(DOTA) by two orders of magnitude.•CeIV(DOTA) is relatively long-lived and decomposes mainly by decarboxylation, yielding formaldehyde as a major product. 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−, Br2− and N3 were studied. Cl2−, the strongest oxidizing agent studied, reacts mainly via H atom abstraction from the DOTA ligand. Br2− at both acidic and neutral pH oxidizes [CeIII(DOTA)(H2O)]− with rate constants of