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Updated: Aug 5, 2026

Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate
Published on: April 24, 2018
[O─I─O]+ Halogen-Bonded Complexes of Pyridine N-Oxides
Rakesh Puttreddy1, Sergi Burguera2, Antonio Frontera2
1University of Jyvaskyla, Jyvaskyla, Finland.
Researchers characterized novel [O─I─O]+ halogen-bonded complexes using X-ray diffraction. These complexes exhibit the shortest halogen bonds (XBs) for N-oxide systems and unique electronic properties, paving the way for new materials.
Area of Science:
- Supramolecular Chemistry
- Crystallography
- Computational Chemistry
Background:
- Halogen bonding (XB) is a crucial non-covalent interaction.
- Three-center-four-electron (3c4e) halogen-bonded systems are of significant interest.
- The [O─I─O]+ motif has been elusive until now.
Purpose of the Study:
- To characterize novel [O─I─O]+ halogen-bonded complexes.
- To investigate the electronic and bonding characteristics of [O─I─O]+ systems.
- To compare [O─I─O]+ complexes with related [N─I─N]+ and [S─I─S]+ systems.
Main Methods:
- Single-crystal X-ray diffraction analysis.
- Solution complexation studies using 1H, 15N HMBC NMR spectroscopy.
- Density Functional Theory (DFT) calculations.
Main Results:
- Eight [O─I─O]+ halogen-bonded complexes were characterized.
- The shortest halogen bonds (XBs) for N-oxide systems were reported (I+–O bond lengths of 2.172(17)-2.227(6) Å).
- DFT calculations revealed that the N-oxide O-atom in [O─I─O]+ complexes retains a second lone pair, enabling secondary interactions like hydrogen bonds, unlike N and S analogs.
Conclusions:
- The [O─I─O]+ complexes represent a unique class within 3c4e halogen-bonded systems.
- The retained electron density on the oxygen atom offers potential for secondary interactions.
- These findings highlight the utility of [O─I─O]+ complexes in designing organic reactions and supramolecular materials.
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