Investigation of neptunium(VI) complexation by SiW11O398− by visible/near infrared spectrophotometry and factor analysis

Abstract

Neptunium(VI) complexation by a lacunary heteropolyanion (SiW₁₁O₃₉⁸⁻) in an aqueous medium at pH 1 was investigated by spectrophotometry in two regions of the spectrum: in visible light (540–670 nm) and in the near infrared (1120–1260 nm). Principal components analysis (PCA) revealed the formation of two species depending on the additive ligand in solution: a NpO₂(SiW₁₁O₃₉)⁶⁻ complex and the free species NpO₂²⁺ that was initially present at pH 1. Modeling factor analysis (MFA) was used to calculate a similar absolute constant for both wavelength regions: log β₁=11.6±0.1. This technique was also used to determine the spectrum of the NpO₂(SiW₁₁O₃₉)⁶⁻ complex formed in aqueous solution.