The effect of ether-functionalisation in ionic liquids analysed by DFT calculation, infrared spectra, and Kamlet-Taft
A Tsurumaki1, F Trequattrini2, O Palumbo3
1Department of Chemistry, University of Rome "La Sapienza", Piazzale Aldo Moro 5, 00185 Rome, Italy. mariassunta.navarra@uniroma1.it.
Abstract:
The effect of ether-functionalisation on ionic liquids (ILs) is discussed based on Kamlet-Taft parameters and the infrared (IR) spectra of N-ethoxyethyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide ([P1,2O2][TFSI]) and N-ethoxyethyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide ([M1,2O2][TFSI]). The results are analysed taking into consideration their ion conformers, electronegativity and hardness, and the IR active vibrations obtained by means of DFT calculations. From the evaluation of Kamlet-Taft parameters, the ether-functionalisation in the cationic ring is found to improve the polarity and hydrogen bond acidity of the ILs. This correlates with the computational result which designates that the oxygen atom in the cationic ring increases the electronegativity of the cation. The comparison with the IR spectra, which were obtained experimentally and computationally, revealed that trans-[TFSI] was preferably formed in [M1,2O2][TFSI] compared to [P1,2O2][TFSI]. Although the Kamlet-Taft parameters indicate that [M1,2O2][TFSI] has a higher polarity, this IL preferably adopts trans-[TFSI], which is normally stabilised with the cations having a lower polarity. This may be due to the presence of the oxygen in the cationic ring which delocalises the electron density of the lowest unoccupied molecular orbitals (LUMO) and increases the conformational freedom of the hydrogen bonds between cations and anions. Moreover, the mixtures of pure ILs with a suitable Li-salt were also investigated to analyze the effect of the Li salt on the polarity and the ion conformers.
Related Concept Videos
02:39Emission Spectra
03:10Ionic Radii
00:42Ionic Bonds
When atoms gain or lose electrons to achieve a more stable electron configuration they form ions. Ionic bonds are electrostatic attractions between ions with opposite charges. Ionic compounds are rigid and brittle when solid and may dissociate into their constituent ions in water. Covalent compounds, by contrast, remain intact unless a chemical reaction breaks them.
Opposing Charges Hold Ions Together in Ionic Compounds
Ionic bonds are reversible electrostatic interactions between ions...
02:54Molecular and Ionic Solids
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
01:20Relation of DFT to z-Transform
To understand how the DFT works, it's helpful to consider the z-transform, which is a method for representing discrete sequences in the complex frequency domain. The z-transform involves summing the...
02:55Solubility of Ionic Compounds