  The chemical properties of actinide materials are often predefined and
described based on the data available for isostructural species. This is the
case for potassium plutonyl (PuVI) carbonate, K4PuVIO2(CO3)3(cr), a complex
relevant for nuclear technology and the environment, of which the
crystallographic and thermodynamic properties of which are still lacking. We
report here the synthesis and characterization of PuVI achieved by
single-crystal X-ray diffraction analysis and high-energy-resolution
fluorescence-detected X-ray absorption near-edge structure at the Pu M4-edge
coupled with electronic structure calculations. The crystallographic properties
of PuVI are compared with isostructural uranium (U) and neptunium (Np)
compounds. Actinyl (AnVI) axial bond lengths, [O-AnVI-O]2+, are correlated
between solid, K4AnVIO2(CO3)3(cr), and aqueous, [AnVIO2(CO3)3]4-(aq) species
for the UVI-NpVI-PuVI series. The spectroscopic data are compared to
KPuVO2CO3(cr) and PuIVO2(cr) to tackle the trend in the electronic structure of
PuVI regarding the oxidation state changes and local structural modifications
around the Pu atom
