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Synthesis of Information-bearing Peptoids and their Sequence-directed Dynamic Covalent Self-assembly
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Synthesis, solid-state, solution, and theoretical characterization of an "in-cage" scandium-NOTA complex
Kelly E Aldrich1, Ivan A Popov1,2, Harrison D Root1
1Los Alamos National Laboratory, Los Alamos, NM, USA. erb@lanl.gov.
Dalton Transactions (Cambridge, England : 2003)
|June 23, 2022
Summary
This study challenges assumptions about scandium(III) (Sc3+) complexation with the 1,4,7-triazacyclononane-1,4,7-triacetic acid (H3NOTA) chelator. New methods demonstrate full Sc3+ encapsulation, crucial for rare-earth element applications.
Area of Science:
- Inorganic Chemistry
- Coordination Chemistry
- Materials Science
Background:
- Rare-earth elements (Sc, Y, La, lanthanides) are vital in modern technologies.
- Developing selective chelators for rare-earth elements is a significant challenge.
- The 1,4,7-triazacyclononane-1,4,7-triacetic acid (H3NOTA) chelator is thought to underperform for scandium(III) (Sc3+) complexation.
Purpose of the Study:
- To investigate the complexation chemistry of Sc3+ with the H3NOTA chelator.
- To challenge the assumption that Sc3+ is not fully encapsulated by the NOTA3- macrocycle.
- To develop a synthetic approach that ensures Sc3+ encapsulation.
Main Methods:
- Single crystal X-ray diffraction to determine the Na[Sc(NOTA)(OOCCH3)] structure.
- Density functional theory (DFT) calculations.
- 45Sc nuclear magnetic resonance (NMR) spectroscopy.
Main Results:
- A novel synthetic approach successfully encapsulated Sc3+ within the NOTA3- binding pocket.
- Sc3+ encapsulation was confirmed in solution via DFT and 45Sc NMR.
- The [Sc(NOTA)(OOCCH3)]1- complex can accommodate a water capping ligand.
- Sc-OOCCH3 and Sc-H2O interactions stabilize the Sc-NOTA complex.
Conclusions:
- The study refutes the notion that H3NOTA is an underperformer for Sc3+ complexation.
- Full Sc3+ encapsulation is achievable and stable.
- Capping ligands play a critical role in stabilizing rare-earth element chelates.
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