Molecular structure, proton affinity and hydrogen bonds of (2-hydroxyethyl)amine- N -oxides: DFT, MP2 and FTIR study

2018

The results of structural analysis and cation–anion interactions of 10 ion pairs and their relevance for the physicochemical properties of triethylammonium-based protic ionic liquids are reported. The calculations were mainly performed by dispersion corrected density functional theory method (B3LYP-GD3). It is shown that the dispersion correction is important in the evaluation of the interaction energies of these compounds. The role of anions in the formation of ion pairs and hydrogen-bonded structure are analyzed. To obtain a quantitative measure of the strength of H-bonds, the Bader’s theory of atoms in molecule (AIM) was applied. The correlations between hydrogen bond lengths, their energies, and electron-topological parameters at the H···O bond critical point are presented.

Section: Methodsmentioning

confidence: 99%

Ab Initio Investigation of the Interionic Interactions in Triethylammonium-Based Protic Ionic Liquids: The Role of Anions in the Formation of Ion Pair and Hydrogen Bonded Structure

2018

“…Quantum chemistry has recently become one of the most effective instruments for studying the structure and predicting the properties of new types of ILs. − Quantum-chemical simulation allows us to significantly decrease both time and material costs by reducing the number of compounds that should be synthesized and tested experimentally for creating PILs with the required properties. Density functional theory (DFT) methods are most often used in computational studies of these systems as they allow us to obtain reasonable evaluations of the structural parameters and cation–anion interaction strengths. − The accuracy of the calculations for this functional can be increased by introducing empirical corrections for dispersion interactions (DFT-D). − The hybrid meta functionals of the M06 family , with a correction for dispersion interactions are also widely used.…”

Section: Introductionmentioning

confidence: 99%

Influence of Cation Size on the Structural Features and Interactions in Tertiary Alkylammonium Trifluoroacetates: A Density Functional Theory Investigation

2018

We present the results of electronic structure calculations based on density functional theory (DFT) in order to investigate the reactions of the interaction of tertiary alkylamines with alkyl groups of different sizes (triethyl, tributyl, dimethylethyl, and diisopropylethyl) with trifluoroacetic acid. We have obtained data on the affinity of the studied amines with a proton. It has been shown that amine interaction with the acid leads to proton transfer from the acid to the amine and formation of ions held together in the ion pair by electrostatic interaction and a very strong hydrogen bond. We have also investigated the energy profiles of the proton transfer from the tertiary alkylammonium cation to the trifluoroacetate anion within the ion pair and found different correlations between the geometric characteristics of the H-bond and the parameters obtained by the natural bond orbitals and quantum theory of atoms in molecules analyses. It has been established that the interionic interactions in these systems weaken as the length and the degree of cation alkyl chain branching increase. A good qualitative agreement between the theoretical results and the experimental data on physicochemical properties has been obtained.

“…These calculations employed the hybrid B3LYP density functional , corrected for dispersion interactions using the Grimme GD3 empirical term . The B3LYP functional has been used successfully and extensively to study the structure and interionic interactions in the ion pairs of ionic liquids. ,,,− The 6-31++G(d,p) basis set was employed to find the optimal geometries. Our previous calculations indicated that the effect of a basis set on the magnitude of the interaction energy of the ion pairs with TEOA cation and inorganic anion is insignificant if much more computationally expensive basis sets, such as cc-pvtz and aug-cc-pvtz, are used and all of these give the same qualitative trends for these compounds.…”

Section: Theoretical Methodsmentioning

confidence: 99%

Quantum Chemical Modeling of the Structure and H Bonding in Triethanolammonium-Based Protic Ionic Liquids with Sulfonic Acids

2019

The results of electronic structure calculations based on density functional theory (DFT) for protic ionic liquids (PILs) consisting of triethanolammonium cation paired with anion of different sulfonic acids are reported. The influence of the anion nature on the structure and interactions in the ion pairs that are formed in these PILs is discussed in detail. Multiple H-bonding interactions exist between the protons in the NH/OH groups of the cation and different oxygen atoms of the acid anion in the ion pairs. The quantum theory of “atoms in molecules” has been used to estimate the individual contributions of each hydrogen bond to the stability of the ion pair. The hydrogen-bonding interactions in the ion pairs vary in their strength ranging from weak to moderately strong. In addition to these hydrogen bonds, there are other dispersion and electrostatic-dominant interactions that play an important role in the overall stability of PILs and their physicochemical properties. Aided by results from our previous DFT studies of triethanolammonium class of PILs with inorganic anions, these new data allow us to gain an improved understanding of the structure–property relationships in the studied ionic liquids. Close to linear correlation, in particular, has been found between the melting points and the binding energies of the cation and anion in the ion pairs.