title: Complexation of NpO(2)(+) with N-methyl-iminodiacetic acid: a comparison with iminodiacetic and dipicolinic acids.
abstract: Complexation of Np(v) with N-methyl-iminodiacetic acid (MIDA) in 1 M NaClO(4) solution was studied with multiple techniques including potentiometry, spectrophotometry, and microcalorimetry. The 1 : 2 complex, NpO(2)(MIDA)(2)(3-) was identified for the first time in aqueous solution. The correlation between its optical absorption properties and symmetry was discussed, in comparison with Np(v) complexes with two structurally related nitrilo-dicarboxylic acids, iminodiacetic acid (IDA) and dipicolinic acid (DPA). The order of the binding strength (DPA > MIDA > IDA) is explained by the difference in the structural and electronic properties of the ligands. In general, the nitrilo-dicarboxylates form stronger complexes with Np(v) than oxy-dicarboxylates due to a much more favorable enthalpy of complexation.
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: Guoxin
authors.initials: G
authors.lastname: Tian
authors.forename: Linfeng
authors.initials: L
authors.lastname: Rao