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Free-Standing Supramolecular Pyridine N-Oxide-Silver(I) Metallogels.
Rakesh Puttreddy1, Boonya Thongrom2, J Mikko Rautiainen1
1University of Jyvaskyla, Department of chemistry, University of Jyvaskyla, P.O. BOX 35, Jyvaskyla, FI-40014, Finland.
Advanced Materials (Deerfield Beach, Fla.)
|July 1, 2025
Summary
Pyridine N-oxide silver(I) trifluoroacetate (PyNO-AgTFA) complexes form gels, especially with electron-donating groups. These robust gels can be shaped and exhibit predictable structural motifs, highlighting the N-O group
Area of Science:
- Supramolecular Chemistry
- Coordination Chemistry
- Materials Science
Background:
- Pyridine N-oxides (PyNOs) are versatile ligands in coordination chemistry.
- The gelation properties of metal-organic complexes are of significant interest for materials development.
- Understanding the structure-property relationships in PyNO-metal complexes is crucial for designing novel functional materials.
Purpose of the Study:
- To investigate the gelation behavior of silver(I) trifluoroacetate (AgTFA) complexes with various pyridine N-oxides (PyNOs).
- To explore the influence of electronic properties of PyNO substituents on gel formation.
- To characterize the structural features and mechanical properties of the resulting gels.
Main Methods:
- Synthesis and characterization of 27 PyNO-AgTFA complexes.
- Solvent-dependent gelation studies across eight different solvents.
- X-ray crystallography and powder X-ray diffraction for structural analysis.
- Mechanical testing of gel materials.
- Density functional theory (DFT) calculations for non-covalent interactions.
Main Results:
- Selective gelation observed with PyNOs containing electron-donating groups; electron-withdrawing or mixed groups did not form gels.
- Co-gelation of PyNOs with opposing electronic properties demonstrated.
- PyNO-AgTFA gels exhibited significant mechanical strength, allowing fabrication of load-bearing structures.
- Four distinct structural motifs were identified in 65 X-ray crystal structures, indicating ligand-metal coordination preference.
- DFT calculations revealed interaction energies ranging from -1 to -92 kJ mol⁻¹ for non-covalent interactions.
Conclusions:
- The N-O functionality in PyNOs is essential for coordinating with silver(I) and facilitating gelation.
- The electronic nature of substituents on the pyridine ring significantly impacts gel-forming ability.
- PyNO-AgTFA complexes form predictable structural motifs, leading to robust and shapeable supramolecular gels.
- These findings provide a foundation for designing novel supramolecular materials with tunable properties.
