A solution- and gas-phase study of uranyl hydroxamato complexes

This study compares the binding properties towards the uranyl cation of three hydroxamates derived from benzohydroxamic acid (BHAH), N-methylacetohydroxamic acid (NMAH) and 1-hydroxypiperidine-2-one (PIPOH), as models of the binding sites found in natural chelators that could be involved in the mobilization of uranyl in the vicinity of abandoned mines. Solution speciation studies of the UO 2 2+ /BHAH system by affinity capillary electrophoresis allowed to estimate stability constants for both ML [log K110 = 7.4(1)] and ML2 [log K120 = 7.0(1)] species in aqueous media [0.1 M (H,Na)ClO4, 25 °C], which lie in-between those reported by us elsewhere for NMA− and PIPO−. By contrast, gas phase studies demonstrate that one of the U=O bonds can be activated in the NMA− and PIPO− complexes, whereas this is not the case for the BHA− complex.