Investigation of Properties of Protic Ionic Liquids by Quantum Mechanical Calculations and Ab initio Molecular Dynamics Simulations

 

CONTENT……………………………………………………………..……PAGE

Chapter One: Introduction

1.1 Ionic liquids…………………………………………………………………………2

1.2 Protic ionic liquids and aprotic ionic liquids…………………………..…………………..….2

1.3 Historical view on ionic liquid………………………………..…………………..……………..4

1.4 Properties of Ionic liquids………………………………………………………………………………………….5

1.4.1  Factors influencing physicochemical properties of ILs………………………………………………5

1.5  Structure of  ionic liquids …………………………………………………………………………………………7

1.6  Different type of protic ionic liquids……………………………………….………9

1.7 Applications of ionic liquids ……………………….…………………………………………..10

1.8  Advantage of Morpholinium PILs….…………..…………………………….………………11

1.9  Theoretical studies and simulations of ILs  …..………………………..…………………..12

1.10 The objective of thesis ………………………………………………..……………………….…13

Chapter Two:  Literature Review

2.1 Literature Review…………………………..…………………………………………………16

Chapter Three: Theoretical Methods

         3.1 Quantum Mechanics……………………………………………………..…………….20

3.2 TheSchrödinger Equation …………………………………………………….……………..21

3.3 Ab initio Methods………………………….……………………………….……………….22

         3.4 Hartree-Fock approximation……….…………………..…………..…………………..22

       3.5  Moller-Plessent Perturbation Theory …………………………….……………………23

      3.6  Density Functional Theory………………………………………………………..….…23

     3.7  Methods of Becke-Lee-Yang-Parr……………………………………………..………….27

    3.8  Basis set……………………………………………………..……………………………28

      3.9   Molecular Mechanics…………………………………………………………….….….29

        3.10  Simulations………………………………………………………………………..…..31

  3.10.1 Molecular Dynamics Simulations……..………………….…………………………32

        3.10.2 Car- Parrinello Molecular Dynamics  simuations…………….. ……………………33

Chapter Four: Results and Discussion

 4.1 Introduction…………………………………………………………………………………36

 4.2 Method of calculations……………………….…………………………………….….…..38

 4.3 Relative structure of anions and cations…………………………………………..……….40

4.4  Physical and thermo-physical properties……………………………………………………52

4.4.1 Interaction Energy………….……………………………………………………….………52

4.4.3 Bond length (N-H), (H-O^–), (H-O*)…………………………………………….…………58

4.4.4 Angles and Dihedrals……………………………………………………………….…….71

4.4.5 Polarizability(α)…………………………………………………………………………..81

4.4.6  Dipole moment (µ)……………………………………………………..……………….84

4.4.7 Thermal energy (E_th)…………………………………………………..…………………90

4.4.8  Highest occupied (HOMO) and lowest unoccupied (LUMO) molecular orbitals………………..92

 

Chapter Four: Part II

4.5 Car-Parrinello Molecular Dynamics (CPMD)Simulation Results…………………..………106

4.5.1  Structuralproperties: Correlation function………………………..…………….………..108

4.5.2 Spatial distribution function……………………………………………………..……….120

 

Chapter Five

Conclusion…………………………………………………………….….

References

 

 

 

 

 

 

 

TABLE OF FIGURES

 

Figure………………………………………………..…………………………Page

Figure 4.1 Optimized structure of morpholinium formate [Morph][For] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd) …………..…………………………………………………………41

Figure 4.2  Optimized structure of methylmorpholinium formate [MeMorph][For] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd) …………………………………..……..………….…41

Figure 4.3  Optimized structure of ethylmorpholinium formate [EtMorph][For] Ionic liquid, calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b …………………..42

Figure 4.4  Optimized structure of propylmorpholinium formate [ProMorph][For] Ionic Liquid calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b ………..…………43

Figure 4.5  Optimized structure of butylmorpholinium formate [ButMorph][For] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b…………………………43

Figure 4.6 Optimized structure of pantylmorpholinium formate [PanMorph][For] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b…………………….44

Figure 4.7  Optimized structure of morpholinium acetate [Morph][Ace] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b……………………….……..….44

Figure 4.8  Optimized structure of methylmorpholinium acetate[MeMorph][Ace] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b…………………….45

Figure 4.9  Optimized structure of methylmorpholinium propionate [MeMorph][Pro] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd):(a) conformer a, (b) conformer b……………………….45

Figure 4.10  Optimized structure of methylmorpholinium butanoate [MeMorph][But] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b………………………………………………………………………………………..…………46

Figure 4.11 Optimized structure of methylmorpholinium pentanoate [MeMorph] [Pent] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd):(a) conformer a, (b) conformer b…………………46

Figure 4.12  Optimized structure of methylmorpholinium hexanoate [MeMorph] [Hex] Ionic Liquid calculated at B3LYP/6-311++g (3df,3pd): (a) conformer a, (b) conformer b…………….47

Figure 4.13  Optimized structure of methylmorpholinium decanoate [MeMorph] [Deca] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b……………48

Figure 4.14 Optimized structure of ethylmorpholonium acetate [EtMorph] [Ace] Ionic liquid calculated atB3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b……………………..…49

Figure 4.15 Optimized structure of ethylmorpholonium propionate [EtMorph][Pro] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b…………………..50

Figure 4.16  Optimized structure of ethylmorpholinium butanoate [EtMorph][But] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b…………………..50

Figure 4.17  Optimized structure of ethylmorpholinium pentanoaten [EtMorph] [Pent] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b……………..51

Figure 4.18  Optimized structure of ethylmorpholonium hexanoate [EtMorph] [Hex] Ionic liquid calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b…………………..51

Figure 4.19  Optimized structure of ethyl morpholonium decanoate [EtMorph] [Deca] Ionic Liquid calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b…………..52

Figure 4. 20 Variation of Interaction Energies of N-alkyl-Morpholonium Formate ILwith Alkyl Chain Length of  Cation calculated at B3LYP/6-311++g(3df,3pd)………………………….….54

Figure 4.21 Variation of Interaction Energies of Methylmorpholonium Carboxylate ILwith Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd) ……………………………..55

Figure 4.22   Variation of Interaction Energies of  Ethylmorpholinium carboxylateIL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd)………………………………56

Figure 4.23 Bond Length Variation of N-Alkyl-MorpholiniumFormate ILwith Alkyl Chain Length of Cation calculated at B3LYP/6-311++g(3df,3pd)…………………………………….62

Figure 4.24   Variation of Bond Length of Ethylmorpholinium Carboxylate IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd) …………………………………….63

Figure 4.25 Variation of Bond Length of Ethylmorpholinium Carboxylate IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd)……………………..……….………64

Figure 4.26 Optimized geometries of [Morph][For] and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd) :(a) conformer a, (b) conformer b………………………………………………………………………………………………….65

Figure 4.27  Optimized geometries of [MeMorph][For]  and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b……………………66

Figure 4.28  Optimized geometries of [EtMorph][For] and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b…………………….67

Figure 4.29  Optimized geometries of [PropMorph][For] and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b…………………..68

Figure 4.30 Optimized geometries of [ButylMorph][For] and Hydrogen bonds and bond angle calculatedatB3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b……………………68

Figure 4.31  Optimized geometries of [PantylMorph][For] and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b………………..….69

Figure 4.32  Optimized geometries of [Morph][Ace]  and Hydrogen bonds and bond angle calculatedatB3LYP/6-311++g (3df,3pd): (a) conformera ,(b) conformer b………………..……70

Figure 4.33  Optimized geometries of [MeMorph][Ace]  and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b……………………71

Figure 4.34 Optimized geometries of [MeMorph][Pro] and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b……………………71

Figure 4.35 Optimized geometries of [MeMorph][Butylate] and Hydrogen bonds and bond angle. calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a,  (b) conformer b……………………………………………………………………………………………………72

Figure 4.36. Optimized geometries of [MeMorph][Pent] and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a,  (b) conformer b.………………….72

Figure 4.37 Optimized geometries of [MeMorph][Hexa] and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b………………………………………………………………………………………….…….…73

Figure 4.38  Optimized geometries of [MeMorph][Deca] and Hydrogen bonds and bonds angle. calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b……………………………………………………………………………………….………..….73

Figure 4. 39  Optimized geometries of [EtMorph][Ace] and Hydrogen bonds and bond angle calculatedatB3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer  b…………………………………………………………………………………………………74

Figure 4. 40 Optimized geometries of [EtMorph][Pro] and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b………………………………………………………………………………………….……..74

Figure 4.41  Optimized geometries of [EtMorph][Butanoate]  and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd):(a) conformer a,  (b) conformer b………………………………………………………………………………………………….75

Figure 4.42  Optimized geometries of [EtMorph][Pentanoate]  and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b…………………………………………………………………………………………………..75

Figure 4.43 Optimized geometries of [EtMorph][Hexanoate] and Hydrogen bonds and bond angle, calculated at B3LYP/6-311++g(3df,3pd): (a) conformer a, (b) conformer b……………………………………………………………………………………………….….76

Figure 4.44  Optimized geometries of [EtMorph][Decanoate]  and Hydrogen bonds and bond angle calculated at B3LYP/6-311++g(3df,3pd):(a) conformer a, (b) conformer b…………………………………………………………………………………………………77

Figure  4.45  Dihedral Angle Variation of Methyl-morpholinium Carboxylate(N-H-C-O^–) IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd). All conformer b…………………………………………………………………………………………….……80

Figure 4. 46  Dihedral Angle Variation of Ethyl-Morpholinium Carboxylates(N-H-C-O^–) IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd).All conformer b…………………………..……………………………………………………………………..81

Figure 4. 47   Variation of Polarizability (α) of N-alkyl-Morpholonium Formate IL with Alkyl Chain Length of Cation calculated at B3LYP/6-311++g(3df,3pd)…………………………..…82

Figure 4. 48  Variation of Polarizability of Methyl-Morpholonium Carboxylate IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd)……………………..……….83

Figure 4.49   Variation of Polarizability of Ethyl-Morpholonium Carboxylate IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd)………………..……………84

Figure 4. 50  Variation of Dipole Moment of N-alkyl-Morpholinium Formate IL with Alkyl Chain Length of Cation calculated at B3LYP/6-311++g(3df,3pd)………………………….…..85

Figure 4. 51  Variation of Dipole Moment of Methyl-Morpholinium Carboxylate IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd)………………………………86

Figure 4. 52  Variation of Dipole Moment of Ethyl-Morpholinium Carboxylate IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd)………………………..…..…87

Figure 4. 53 Variation of Thermal  Energies of N-alkyl-Morpholinium Formate IL with Alkyl Chain Length of Cation calculated at B3LYP/6-311++g(3df,3pd). …………………………….91

Figure 4. 54 Variation of Thermal  Energies of Methyl-Morpholinium Carboxylate IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd). ……………………………91

Figure 4. 55   Variation of Thermal Energies of  Ethyl-Morpholinium Carboxylate IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd)………………………………92

Figure 4.56 HOMO-LUMO energy gap Variation of N-Alkyl-Morpholinium Formate IL with Alkyl Chain Length of Cation calculated at B3LYP/6-311++g(3df,3pd)……………………….97

Figure 4.57  Electronegativity Variation of N-Alkyl-Morpholinium Formate IL with Alkyl Chain Length of Cation calculated at B3LYP/6-311++g(3df,3pd)…………………………………….98

Figure 4.58  Hardness Variation of N-Alkyl-Morpholinium Formate IL with Alkyl Chain Length of Cation calculated at B3LYP/6-311++g(3df,3pd)……………………………………………..99

Figure 4.59  Variation of HUMO- LUMO energy gap of  Methyl-Morpholinium Carboxylate ILs with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g (3df,3pd)…………..…99

Figure 4. 60  Variation of Electronegativity of  Methyl-Morpholinium Carboxylate ILs with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd)………………………100

Figure 4. 61  Hardness variation of  Methyl-Morpholinium Carboxylate ILs with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd)……………………………………..100

Figure 4. 62   Variation of HOMO- LUMO energy gap of  Ethyl-Morpholinium Carboxylate IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd)…………………101

Figure 4. 63  Variation of Electronegativity of  Ethyl-Morpholinium Carboxylate IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd)………………..……………102

Figure 4. 64  Hardness variation of Ethyl-Morpholinium Carboxylate IL with Alkyl Chain Length of Anion calculated at B3LYP/6-311++g(3df,3pd)……………………………………………103

Figure 4.65  Geometry of 5 [Morph][For] ion pairs simulated in NVT ensemble by CPMD…………………………………………………………………………………………107

Figure 4.66. Geometry of 5 [MeMorph][For] ion pairs simulated in NVT ensemble by CPMD……………………………………………………………………………………………108

Figure 4.68. The schematic representation of atom site used for structural relation by MD simulation.  ……………………………………………………………………………………110

Figure 4.69. Radial distribution function simulated by CPMD for H13 and  N in [MeMorph][For] at 298 K……………………………………………………………….……………………….110

Figure 4.70  Radial distribution function simulated by CPMD for H13 and  N18 in [MeMoroh][Ace] at 298 K……………………………………………………………………..111

Figure 4.71 Radial distribution function simulated by CPMD for H10 and  N in [EtMorph][For] at  298K………………………………….……………………………………………………..112

Figure 4.73   Radial distribution function simulated by CPMD for Oˉ and  H13 in [MeMorph][For] at 298K………………………………………………………………………115

Figure 4.74  Radial distribution function simulated by CPMD for H13 and  Oˉ in [MeMoroh][Ace] at 298 K………………………………………………………………………115

Figure 4.75 Radial distribution function simulated by CPMD for H10 and  Oˉ in [EtMoroh][For] at 298K……………..………………….………………………………………………………116

Figure 4.76  Radial distribution function simulated by CPMD for H22 and  Oˉ in [EtMoroh][Ace] ………………………………………………………………………………..117

Figure 4.77  Radial distribution function simulated by CPMD for H13 and  O* in [MeMoroh][For] at 298 K…………………………………..…………………………….……118

Figure 4.78 Radial distribution function simulated by CPMD for H13 and  O* in [MeMoroh][For] at 298 K………………………………………………………………………118

Figure 4.79 Radial distribution function simulated by CPMD for H10 and  O* in [EtMoroh][For] at 298 K…………………………………………………………………………………………119

Figure 4.80  Radial distribution function simulated by CPMD for H22 and  O* in [EtMoroh][Ace] at 298 K…………………………………………………………………….120

Figure 4.81 Spatial distribution function of [For]ˉ anion around [Morph]⁺cation…………………………………………………………………………….……122

Figure 4.82 Spatial distribution function of [For]ˉ anion around [MeMorph]⁺cation…………..122

Figure 4.83  Spatial distribution function of [Ace]ˉ anion around [MeMorph]⁺cation………..123

Figure 4.85 Spatial distribution function of [Ace]ˉanion around [EtMorph]⁺cation………….124

Figure 4.86 Spatial distribution function of [Propionate]ˉanion around [EtMorph]⁺cation…………………………………………………………………………………………..124

Figure 4.87  Spatial distribution function of anion around [MeMorph]⁺cation with cation chain length………………………….……………………………………………………..………..125

Figure 4.88  Spatial distribution function of anion around [EtMorph] ⁺cation with anion chain length…………………………………………………………………………………….……126

 

 

LIST OF TABLE

 

Table………………………………………………………………….…….Page

 

Table 4.1 Values of interaction and thermal energies (kJmol^-1) for N-AlkylmorpholiniumFormate ILs calculated at B3LYP/6-311++g(3df,3pd)……………………………………………………………….55

Table 4.2 Values of Interaction and Thermal Energies (kJmol^-1) for Methylmorpholinium Carboxylate ILs calculated at B3LYP/6-311++g(3df,3pd)……………….…………………….56

Table 4.3  Values of Interaction and Thermal Energies (kJmol^-1) for Ethylmorpholinium Carboxylate ILs calculated at B3LYP/6-311++g(3df,3pd)………………….…………………..57

Table 4.4  Bond Length Values of N-Alkylmorpholinium Formate ILs calculated at

B3LYP/6-311++g(3df,3pd)……………………………………………………….……………59

Table 4.5 Bond Length Values of Methylmorpholinium Carboxylate ILs calculated at B3LYP/6-311++g(3df,3pd)………………………………………………………………………….……59

Table 4.6  Bond Length Values of Ethylmorpholinium Carboxylate ILs calculated atB3LYP/6-311++g(3df,3pd)……………………………………………………………………………….60

Table 4.7 Bond Angle and Dihedral Angle Values of Methylmorpholinium Carboxylates ILs calculated at B3LYP/6-311++g(3df,3pd)……………………………………………………..78

Table 4.8  Bond Angle and Dihedral Angle Values of Ethylmorpholinium Carboxylates ILs calculated at B3LYP/6-311++g(3df,3pd) ………………………………………………………..78

Table 4.9 Values of Dipole Moment and Polarizabilityfor N-Alkylmorpholinium Formate ILs calculated at B3LYP/6-311++g(3df,3pd)……………………………………………………………87

Table 4.10 Values of Dipole Moment and Polarizability for Methylmorpholinium Carboxylate IL calculated at B3LYP/6311++g(3df,3pd)…………………………………… ….…….………..88

Table 4.11 Values of Dipole Moment and Polarizability for Ethylmorpholinium Carboxylate ILs calculated at B3LYP/6-311++g(3df,3pd)……………………………………………….……….89

Table 4.12 HOMO-LUMO and the energy gaps, Electronegativity and Hardness Values of N-Alkylmorpholinium Formate ILs calculated at B3LYP/6-311++g(3df,3pd)……………………..94

Table 4.13  HOMO-LUMO and the energy gaps, Electronegativity and Hardness Values of Methylmorpholinium Carboxylate ILs calculated at B3LYP/6-311++g(3df,3pd)……………….95

Table 4.14 HOMO-LUMO and the energy gaps, Electronegativity and Hardness Values of Ethylmorpholinium Carboxylate ILs calculated at B3LYP/6-311++g(3df,3pd)……………….96

Table 4.15 Characteristics of the Ensembles Simulated with  CPMD………………………….108

Table 4.16  Comparison of distance between  in gas phase and liquid bulk obtained from DFT and CPMD results……………………………………………………………………………….113

Table 4.17  Comparison the distance between Oˉ…H in gas phase and liquid bulk obtained from DFT calculation and RDF CPMD……………………