Characterization of the first Peacock-Weakley polyoxometalate containing a transplutonium element: curium bis-pentatungstate [Cm(W 5 O 18 ) 2 ] 9 .

Leveraging microgram-level techniques, we here present the first transplutonium bis-pentatungstate complex: NaCs 8 Cm(W 5 O 18 ) 2 ·14H 2 O (CmW 5 ). Single crystal XRD, Raman, and fluorescence characterization show significant differences relative to analogous lanthanide compounds. The study reveals the unsuspected impact of counterions on fluorescence and vibrational modes of the curium complex and its lanthanide counterparts.