Résumé
Understanding the structure of polynuclear plutonium ions in aqueous solution is crucial to de-velop separations technologies, predict the long-term behavior of actinide materials in wet sys-tems and model accurately solution to solid precipitation mechanisms. It is an euphemism to say that plutonium chemistry in aqueous solution is complex. Diverse and multifaceted species has been identified and, most often, several of which coexist with each other. In this context, the structural information provided by EXAFS measurements can be a lighthouse for the chemist and the rich visible/near infrared plutonium absorption properties is an excellent asset too. Nev-ertheless none of which are easy to interpret because few structural models are available for plu-tonium. This presentation aims to recall how multiple spectroscopic approaches can benefit from reference structures (crystallographic and/or theoretical) to identify plutonium compounds in so-lution focusing on plutonium hydrolysis compounds and polycondensation in aqueous solu-tions. Single crystal X-ray diffraction and spectroscopies has been applied to describe small plutonium clusters in solution.[1-3] Apart from the structural description, this plutonium hexanuclear core resulted in a peculiar absorption spectrum in the visible range that is a valuable footprint to de-tect it in several systems. The other actinide cluster geometries known [4-7] are also useful to support spectroscopic analysis in complex plutonium solution including nanomaterials. EXAFS spectra derived from crystal structures and ab-initio calculations how the cluster geometry and nuclearity translates into EXAFS scattering paths and may help to identify the plutonium clusters in solution.[8] This approach is one among others that is used to study larger plutonium assem-blies. Overall, several structural and electronic properties of the nanosized plutonium oxides and colloids may be compared and analyzed on the basis of molecular bonds from plutonium clus-ters.[9-10] And ultimately, in the plutonium ions route to from colloidal suspensions or PuO2 nanoparticles, polynuclear plutonium clusters are found to be an intermediate species, that the appropriate spectroscopic tools may help to capture.