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Updated: Jul 31, 2025
06:44
From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
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Keggin-Type Anions as Halogen Bond Acceptors
Luka Fotović1, Nikola Bedeković1, Vladimir Stilinović1
1Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia.
Crystal Growth & Design
|May 9, 2023
Summary
Keggin-type polyoxometalate anions can accept halogen bonds, primarily at terminal M=O oxygen atoms. Reduced phosphomolybdic acid anions show shorter halogen bond lengths, indicating steric availability drives acceptance.
Area of Science:
- Inorganic Chemistry
- Supramolecular Chemistry
- Crystallography
Background:
- Polyoxometalates (POMs) are versatile anionic clusters with diverse applications.
- Halogen bonding is a significant non-covalent interaction crucial in crystal engineering and molecular recognition.
- Understanding anion behavior as halogen bond acceptors is key to designing novel functional materials.
Purpose of the Study:
- To investigate the potential of Keggin-type polyoxometalate anions as halogen bond acceptors.
- To explore the influence of anion structure and oxidation state on halogen bonding interactions.
- To elucidate the role of electrostatic potential and steric factors in directing halogen bond acceptance.
Main Methods:
- Synthesis and crystallographic analysis of ten novel halogen-bonded compounds.
- Utilizing phosphomolybdic and phosphotungstic acids with halogenopyridinium cations.
- Computational calculation of electrostatic potentials on anion surfaces.
Main Results:
- Keggin-type anions successfully formed halogen bonds with halogenopyridinium cations.
- Halogen bonds preferentially formed with terminal M=O oxygen atoms over bridging oxygen atoms.
- Reduced phosphomolybdic anions ([Mo12PO40]4-) exhibited shorter halogen bond lengths compared to oxidized forms.
- Electrostatic potential calculations indicated terminal M=O sites are least negative, suggesting steric availability is the primary driver for acceptance.
Conclusions:
- Keggin-type polyoxometalate anions are effective halogen bond acceptors.
- Terminal M=O oxygen atoms are preferred sites for halogen bonding due to steric accessibility.
- Anion reduction can influence halogen bond strength and length.
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