Radiation chemistry of cobalt(II) nitrilotriacetate in aqueous solutions

Abstract

The radiolysis of cobalt(II) nitrilotriacetate (CO^IINTA) was studied in neutral aqueous solutions by both γ-radiolysis and pulse radiolysis methods. The OH radicals were found to abstract a hydrogen atom from the ligand with k=(1.0 ± 0.1)× 10⁹ dm³ mol^–1 s^–1 and the ligand radicals decayed by disproportionation with 2k=(9.3 ± 0.9)× 10⁴ dm³ mol^–1 s^–1. Ligand oxidation products were identified as iminodiacetic acid (IDA) and glyoxalic acid in equal amounts. However, O^–₂ oxidized the complex to Co^IIINTA, probably through an intermediate binuclear species. e^–_aq reduces the Co^IINTA to Co^INTA, k=(9.6 ± 0.9)× 10⁸ dm³ mol^–1 s^–1, which is an order of magnitude slower than that for the free metal ion Co²⁺_aq. Formyl and t-butyl radicals react with Co^IINTA with rate constants of (7.3 ± 0.7)× 10⁷ and (1.1 ± 0.2)× 10⁷ dm³ mol^–1 s^–1, respectively, to form transient metal–carbon bonds.