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Structure and bonding of a radium coordination compound in the solid state
Frankie D White1, Nikki A Thiele2, Megan E Simms3
1Radioisotope Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA. whitefd@ornl.gov.
Nature Chemistry
|November 9, 2023
Summary
Researchers synthesized a radium (Ra) complex, revealing unique coordination and water bonding. This challenges the use of barium (Ba) as a predictive surrogate for radium chemistry due to differing structural properties.
Area of Science:
- Inorganic Chemistry
- Radiochemistry
- Crystallography
Background:
- The chemical structure and bonding of radium (Ra) are poorly understood due to its scarcity and radioactivity.
- Barium (Ba) is often used as a non-radioactive surrogate for studying radium chemistry.
Purpose of the Study:
- To synthesize and characterize a molecular radium (Ra2+) complex.
- To investigate the coordination environment and bonding of radium compared to barium (Ba2+).
- To assess the validity of using barium as a predictive surrogate for radium chemistry.
Main Methods:
- Synthesis of a radium (226Ra) complex with dibenzo-30-crown-10 ligand.
- Solid-state characterization using single-crystal X-ray diffraction.
- Comparative analysis with barium (Ba2+) complexes synthesized under identical conditions.
Main Results:
- The radium complex exhibits an 11-coordinate structure with a bound water molecule.
- The Ra-O bond to water is significantly longer than predicted, indicating higher water lability.
- Barium yielded a 10-coordinate structure lacking water, differing from the radium complex.
Conclusions:
- Radium (Ra2+) exhibits distinct coordination chemistry compared to barium (Ba2+).
- The assumption that barium can always predict radium chemistry is invalid.
- This study provides crucial insights into radium's unique structural and bonding properties.
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