Trivalent Actinide Ions Showing Tenfold Coordination in Solution.

Area of Science:

• Coordination Chemistry
• Solution Chemistry
• Actinide Chemistry

Background:

• Trivalent actinides typically form ninefold coordinated complexes in solution.
• The ligand 2,6-Bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (nPr-BTP) forms ninefold coordinated [An(nPr-BTP)3]3+ complexes.

Purpose of the Study:

• To investigate the coordination chemistry of curium(III) with the nPr-BTP ligand.
• To identify and characterize novel coordination complexes of curium(III) in solution.
• To explore the influence of anions on the coordination environment of curium(III).

Main Methods:

• Time-resolved laser fluorescence spectroscopy (TRLFS)
• Vibronic side band spectroscopy (VSBS)
• X-ray photoelectron spectroscopy (XPS)
• Density functional theory (DFT) calculations

Main Results:

• A tenfold coordinated Cm(III) complex, [Cm(nPr-BTP)3(NO3)]2+, was identified in solution.
• The formation of this complex is specific to nitrate ions and exhibits slow kinetics.
• Spectroscopic and computational data confirm the coordination of nitrate and the increased coordination number.

Conclusions:

• The study reports a unique tenfold coordinated Cm(III) complex, a significant deviation from typical actinide coordination chemistry.
• The findings provide new fundamental understanding of actinide complexation in solution.
• This discovery opens avenues for exploring novel coordination environments in actinide chemistry.