Investigation of the role of hydrogen bonding in ionic liquid-like salts with both N- and S-soft donors

In search of ionic liquids (ILs) with multiple types of soft donor atoms capable of preferentially complexing a range of soft metal ions over harder ions, we investigated structural clues to the role of hydrogen bonding in IL behavior through a series of salts with anions containing both N- and S-do...

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Bibliographic Details
Published in:CrystEngComm 2023-01, Vol.25 (4), p.53-54
Main Authors: Renier, Olivier, Bousrez, Guillaume, Smetana, Volodymyr, Mudring, Anja-Verena, Rogers, Robin D
Format: Article
Language:English
Subjects:
Bonding strength
Chemical bonds
Chemistry
Crystallography
Hydrogen bonding
Hydrogen bonds
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Ionic liquids
Ions
Melting points
Single crystals
Structural analysis
Tetrazoles
Thermal analysis
Thermodynamic properties
Triethylamine
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Summary:In search of ionic liquids (ILs) with multiple types of soft donor atoms capable of preferentially complexing a range of soft metal ions over harder ions, we investigated structural clues to the role of hydrogen bonding in IL behavior through a series of salts with anions containing both N- and S-donor atoms based on azole thiolates. Reaction of equimolar amounts of triethylamine (Et 3 N) or diisobutylamine (DBA) with 1-phenyl-1 H -tetrazole-5-thiol (PhTzSH), 1-methyl-1 H -tetrazole-5-thiol (MeTzSH), or 5-methyl-1,3,4-dithiazole-2-thiol (MeDiTSH) yielded [Et 3 NH][MeTzS] ( 1 ), a yellow liquid, and the low melting yellow solids [DBAH][MeTzS] ( 2 ), [Et 3 NH][PhTzS] ( 3 ), [DBAH][PhTzS] ( 4 ), [Et 3 NH][MeDiTS] ( 5 ), and [DBAH][MeDiTS] ( 6 ). Thermal analysis revealed that all of them qualify as ILs with melting points below 100 °C. Single crystal X-ray structure analysis of 2-6 revealed the presence of an extensive H-bonding network that includes the rare N-H S hydrogen bonds in 3 , 4 , and 6 . These weaker interactions appear to significantly influence thermal behavior, where strong bonding leads to higher melting temperatures and lower decomposition points. Ionic liquid or not: hydrogen bonds such as the relatively rare N-H S hydrogen bond lead in ionic liquid forming ion combinations to higher melting temperatures and lower decomposition points.
ISSN:1466-8033
1466-8033
DOI:10.1039/d2ce00961g