Hydrogen-bonded host–guest systems are stable in ionic liquids

Abstract

We show that H-bonded host–guest systems associate in ionic liquids (ILs), pure salts with melting point below room temperature, in which dipole–dipole electrostatic interactions should be negligible in comparison with dipole-charge interactions. Binding constants (Ka) obtained from titrations of four H-bonded host–guest systems in two organic solvents and two ionic liquids yield smaller yet comparable Ka values in ionic liquids than in organic solvents. We also detect the association event using force spectroscopy, which confirms that the binding is not solely due to (de)solvation processes. Our results indicate that classic H-bonded host–guest supramolecular chemistry takes place in ILs. This implies that strong H-bonds are only moderately affected by surroundings composed entirely of charges, which can be interpreted as an indication that the balance of Coulombic to covalent forces in strong H-bonds is not tipped towards the former.

Stability of Quadruple Hydrogen Bonds in an Ionic Liquid Environment

“…When embedded in a polymer matrix, it becomes difficult to directly measure changes in the association strength of these H-bond moieties, and only a few studies of changes in bonding strength in bulk polymers have been reported, [13,[19][20][21][22][23] mainly focusing on the impact of organic solvents. [24] We here report a systematic study on the influence of ionic liquids (ILs) on the association of the quadruple H-bonding motif UPy, by systematically embedding them into a microenvironment of increasing IL content. As the behavior of such UPy-system is crucial in the design of self-healing electrolytes or 3D-printing, [25] knowledge of their stability in ILs is important.…”

“…When embedded in a polymer matrix, it becomes difficult to directly measure changes in the association strength of these H‐bond moieties, and only a few studies of changes in bonding strength in bulk polymers have been reported, [ 13,19‐23 ] mainly focusing on the impact of organic solvents. [ 24 ]…”

The effect of anion architecture on the lubrication chemistry of phosphonium orthoborate ionic liquids

“…It was not until the second half of the twentieth century that interest in the subject area increased, catalysed by the potential use of ionic liquid as solvents in electrochemical applications 5 . The areas to which ionic liquid have been directed have expanded, particularly since the development of air stable ionic liquids 5 , to include rather diverse fields from chemistry (including cellulose processing 6 , gas capture 7 , synthesis 8 and understanding the nature of hydrogen bonding 9 ) to more machine industry targeted applications, such as tribology 10 .…”

The Effect of Anion Architecture on the Lubrication Chemistry of Phosphonium Orthoborate Ionic Liquid

“…It was not until the second half of the 20th century that interest in the subject area increased, catalyzed by the potential use of ionic liquid as solvents in electrochemical applications. 5 The areas to which ionic liquid have been directed have expanded, particularly since the development of air stable ionic liquids, 5 to include rather diverse elds from chemistry (including cellulose processing, 6 gas capture, 7 synthesis 8 and understanding the nature of hydrogen bonding 9 ) to more machine industry targeted applications, such as tribology. 10 The changing technological landscape, with the rapid shift towards vehicle electri cation and green energy production being the obvious examples, along with environmental concerns, has resulted in a need for lubricants with enhanced functionality such as electrical responsivity.…”