Hydrogen bonding investigation in 1-ethyl-3-methylimidazolium based ionic liquids from density functional theory and atoms-in-molecules methods

Housaindokht, Mohammad Reza; Eshtiagh‐Hosseini, Hossein; Googheri, Mohammad Sadegh Sadeghi; Monhemi, Hassan; Najafabadi, R.; Ashraf, Narjes; Gholizadeh, Mostafa

doi:10.1016/j.molliq.2012.10.006

Cited by 40 publications

(21 citation statements)

References 42 publications

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“…Bond critical point density has been identified for a range of [C 2 C 1 im]X X = [NTf 2 ] À , [EtSO 4 ] À , [lactate] À , [NO 3 ] À and [PF 6 ] À , values ranged from 0.018 to 0.057 a.u. 152 We are able to reproduce similar r BCP , but not the negative Laplacian values reported.…”

Section: Qtaim Analysis Of the Doubly Ionic H-bondmentioning

confidence: 58%

Hydrogen bonding in ionic liquids

2015

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Ionic liquids (IL) and hydrogen bonding (H-bonding) are two diverse fields for which there is a developing recognition of significant overlap. Doubly ionic H-bonds occur when a H-bond forms between a cation and anion, and are a key feature of ILs. Doubly ionic H-bonds represent a wide area of H-bonding which has yet to be fully recognised, characterised or explored. H-bonds in ILs (both protic and aprotic) are bifurcated and chelating, and unlike many molecular liquids a significant variety of distinct H-bonds are formed between different types and numbers of donor and acceptor sites within a given IL. Traditional more neutral H-bonds can also be formed in functionalised ILs, adding a further level of complexity. Ab initio computed parameters; association energies, partial charges, density descriptors as encompassed by the QTAIM methodology (ρBCP), qualitative molecular orbital theory and NBO analysis provide established and robust mechanisms for understanding and interpreting traditional neutral and ionic H-bonds. In this review the applicability and extension of these parameters to describe and quantify the doubly ionic H-bond has been explored. Estimating the H-bonding energy is difficult because at a fundamental level the H-bond and ionic interaction are coupled. The NBO and QTAIM methodologies, unlike the total energy, are local descriptors and therefore can be used to directly compare neutral, ionic and doubly ionic H-bonds. The charged nature of the ions influences the ionic characteristics of the H-bond and vice versa, in addition the close association of the ions leads to enhanced orbital overlap and covalent contributions. The charge on the ions raises the energy of the Ylp and lowers the energy of the X-H σ* NBOs resulting in greater charge transfer, strengthening the H-bond. Using this range of parameters and comparing doubly ionic H-bonds to more traditional neutral and ionic H-bonds it is clear that doubly ionic H-bonds cover the full range of weak through to very strong H-bonds.

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Section: Qtaim Analysis Of the Doubly Ionic H-bondmentioning

confidence: 58%

Hydrogen bonding in ionic liquids

2015

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“…62,63 Calculations on the TFSI À containing imidazolium ILs reveal two kinds of structures. B3LYP and Hartree-Fock based studies employing rather moderate basis sets 48,[64][65][66] predict the anion to be in front of the C 2 -H 2 fragment in the plane of the imidazolium ring. In these structures the anion was found in the trans-conformation with respect to its C-S-N-S-C fragment and strong directional hydrogen bonds were observed between the C 2 -H 2 hydrogen and anion's nitrogen and/or oxygen atoms.…”

Section: Main Structural Features Of the Ion Pairsmentioning

confidence: 99%

Non-covalent interactions in ionic liquid ion pairs and ion pair dimers: a quantum chemical calculation analysis

Marekha

Kalugin

Idriss

2015

Phys. Chem. Chem. Phys.

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Ionic liquids (ILs) being composed of bulky multiatomic ions reveal a plethora of non-covalent interactions which determine their microscopic structure. In order to establish the main peculiarities of these interactions in an IL-environment, we have performed quantum chemical calculations for a set of representative model molecular clusters. These calculations were coupled with advanced methods of analysis of the electron density distribution, namely, the quantum theory of atoms in molecules (QTAIM) and the non-covalent interaction (NCI; J. Am. Chem. Soc., 2010, 132, 6499) approaches. The former allows for profound quantitative characterization of non-covalent interactions between atoms while the latter gives an overview of spatial extent, delocalization, and relative strength of such interactions. The studied systems consist of 1-butyl-3-methylimidazolium (Bmim(+)) cations and different perfluorinated anions: tetrafluoroborate (BF4(-)), hexafluorophosphate (PF6(-)), trifluoromethanesulfonate (TfO(-)), and bis(trifluoromethanesulfonyl)imide (TFSI(-)). IL ion pairs and ion pair dimers were considered as model structures for the neat ILs and large aggregates. Weak electrostatic hydrogen bonding was found between the anions and the imidazolium ring hydrogen atoms of cations. Weaker but still appreciable hydrogen bonding was also noted for hydrogen atoms adjacent to the imidazolium ring alkyl groups of Bmim(+). The relative strength of the hydrogen bonding is higher in BmimTfO and BmimBF4 ILs than in BmimPF6 and BmimTFSI, whereas BmimTfO and BmimTFSI reveal higher sensitivity of hydrogen bonding at the different hydrogen atoms of the imidazolium ring.

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“…The structures studied in this work were firstly optimized without symmetry restrictions at B3LYP/6-311++G ⁄⁄ level using Gaussian 03 program [24][25][26][27], and then the geometries were refined at B3LYP-D3/6-311++G ⁄⁄ level by Orca 3.0.3 version [28][29][30]. All energies of obtained structures were calculated both at B3LYP/6-311++G ⁄⁄ and B3LYP-D3/6-311++G ⁄⁄ level through Orca program.…”

Section: Methodsmentioning

confidence: 99%