NO2 Solvation Structure in Choline Chloride Deep Eutectic Solvents

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B: Liquids; Chemical and Dynamical Processes in Solution 2

NO Solvation Structure in Choline Chloride Deep Eutectic Solvents – the Role of the Hydrogen Bond Donor Simone L Waite, Hua Li, and Alister J. Page J. Phys. Chem. B, Just Accepted Manuscript • DOI: 10.1021/acs.jpcb.8b01508 • Publication Date (Web): 22 Mar 2018 Downloaded from http://pubs.acs.org on March 23, 2018

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The Journal of Physical Chemistry

NO2 Solvation Structure in Choline Chloride Deep Eutectic Solvents – the Role of the Hydrogen Bond Donor Simone L. Waite,1 Hua Li, 1,† Alister J. Page1,* 1

School of Environmental & Life Sciences, The University of Newcastle, Callaghan NSW 2308, Australia

†

Current address: School of Molecular Sciences, The University of Western Australia, Crawley WA 6009, Australia

ACS Paragon Plus Environment

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Abstract

Deep eutectic solvents (DESs) are promising candidates as alternate media for industrial gas sequestration processes, such as denitrification via NO2 adsorption. Here, quantum chemical methods are employed to characterise NO2 solvation structure and the adsorption mechanism in choline chloride DES with urea, methylurea and thiourea hydrogen bond donors. Our results show that the solvation structure of NO2 in bulk choline chloride DES is determined by the type of hydrogen bond donor present. Changing the structure of the hydrogen bond donor not only changes its NO2 coordination mechanism, but also the coordination mechanism between NO2 and the choline and chloride ions in the DES as well. By using an energy decomposition analysis scheme, we show that the principle forces stabilizing NO2 in these DES are dispersion and polarization interactions and, consequently, that NO2 adsorption is most favourable in the choline chloride – thiourea DES. These results highlight a potential route for optimization of choline chloride DES for denitrification, by modulating the hydrogen bond donor structure.


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1. Introduction Atmospheric concentrations of greenhouse gases, including CO2, CH4, SOx and NOx due to anthropogenic emissions remain an acute global concern. Stricter regulation on emissions and the desire to improve air quality has driven development of efficient combustion capture technologies, and in particular carbon (i.e. CO2) capture technologies. However, the removal of nitrogen oxides (NOx) remains a compelling issue due to its environmental impacts, as they contribute to photochemical smog, acid rain, ozone depletion, and greenhouse effects.1,2 Reversible adsorption of NOx through temperature or pressure changes would also lead to valueadded industrial applications, including the development of hypergolic fuel,3 organic synthesis applications (such as oxidation, nitration and nitrosation),4-6 and NOx sensing.7 Current NOx capture technologies (e.g. selective catalytic reduction8) require high operating temperatures, suffer from solvent/catalyst contamination,9 and often employ toxic catalytic materials (e.g. V2O510). A promising alternative is NOx adsorption/storage, however an appropriate sorbent material is needed. To remove NOx in typical applications the sorbent must additionally be able to selectively adsorb NO2 from oxygen-rich combustion gases that contain multiple nitrogenous compounds (e.g. NO2, NO, N2), as well as O2, H2O, SO2 and CO2. Ionic Liquids (ILs) are ionic compounds that melt below 100 °C.11 They have been proposed as a novel alternative for the reversible and selective adsorption for a range of gases including CO2, SO2 and nitrogen oxides (NO, NO2, N2O), their excellent physiochemical properties, and their stability and tunable nature.12-14 However, ILs have not yet been proven to be alternative materials for large-scale industrial gas capture applications for several reasons, notably such as low capacity and high synthesis cost.15,16 Deep eutectic solvents (DES) have been recognised as a potential low cost alternative to overcome the associated problems with ILs, while still


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exhibiting similar favourable properties.17 So-called "type-III" DESs are a class of liquids analogous to ILs, formed by combining two molecular compounds - one a solid inorganic salt, and the other a hydrogen-bond donor (HBD).18 This mixture leads to a eutectic with a lowered melting point compared to the two parent compounds. In some cases this deep eutectic point can be dramatic; for instance, a 1:2 molar ratio mixture of choline chloride (mp = 302 °C) and urea (mp = 133 °C) melts at 12 ºC.19 Molecular dynamics,20 quantum chemical21-23 and neutron diffraction24 investigations have aimed at elucidating the structure within such choline chloride DES, and hence the origin of their melting point depressions. Recent quantum chemical molecular dynamics simulations23 have shown the drop in melting point to correlate with the degree of anion – HBD association within the bulk liquid. This drives the spontaneous intercalation of the HBD into the choline chloride salt lattice, which in turn disrupts long-range electrostatic interactions and results in an entropy increase (hence melting). DESs have several advantages over traditional ILs as solvents for gas adsorption, such as simple synthesis, lower component cost and biodegradable nature. Current gas adsorption studies in DESs have focused on CO2 adsorption,25-30 with studies of other pertinent atmospheric gases (e.g. SO2,31-34 methane35) being limited. To the best of our knowledge, NO2 adsorption has only been investigated in the type-III DES formed between choline chloride and caprolactam.36 Further systematic investigation into the solvation structure and adsorption mechanism of NO2 in type-III DES is therefore warranted. To address this issue, we present a quantum chemical investigation of NO2 adsorption in three archetypal type-III DESs based on choline chloride (ChCl), with urea, methylurea and thiourea HBDs. Using density functional tight binding molecular dynamics, we report here the solvation structure of NO2 in these bulk DESs. The nature of the NO2-DES adsorption mechanism is then


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further elucidated quantum chemically via reduced density gradient (RDG) and energy decomposition analyses (EDA). We show that modulating the hydrogen bond donor structure not only changes its NO2 coordination mechanism, it also changes the coordination mechanism between NO2 and the choline and chloride ions in the DES as well. This coordination is principally driven by dispersion and polarization interactions. Consequently, we show here that NO2 adsorption is most favourable in the choline chloride – thiourea DES.

2. Computational Methods 2.1. Quantum Chemical Molecular Dynamics Adsorption of NO2 in DESs formed between 1:2 molar ratio mixtures of choline chloride and urea (ChCl:urea), methylurea (ChCl:meth) and thiourea (ChCl:thio) has been investigated here using classical molecular dynamics based on the quantum chemical density functional tight binding (DFTB) potential. DFTB is an extended Hückel-like approximation to Kohn-Sham density functional theory (DFT),37 based on the Foulkes-Haydock ansatz. The Kohn-Sham electron density (ρ) is approximated as a small perturbation to a known reference density, i.e. ρ ∼ ρο+∆ρ. With this assumption, the Kohn-Sham DFT energy can be expanded as a Taylor series around the reference density ρ, ௩௔௟௘௡௖௘

‫ = )ߩ(ܧ‬෍ ݊௜ ߝ௜ + ௜

௔௧௢௠௦

௔௧௢௠௦

௔௧௢௠௦

1 1 1 ௥௘௣ ෍ ‫ܧ‬஺஻ + ෍ ߛ஺஻ ∆‫ݍ‬஺ ∆‫ݍ‬஻ + ෍ Γ஺஻ Δ‫ݍ‬஺ ଶ Δ‫ݍ‬஻ +. . . 2 2 3 ஺,஻

஺,஻

(1)

஺,஻

The first term in equation (1) is the electronic energy contribution to the total energy (ni and ɛi are the occupation and energy of the ith molecular orbital respectively) and the second term is the


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pairwise repulsive potential between atoms A and B. Together, these terms constitute 1st order DFTB (also known as non-self-consistent-charge DFTB, NCC-DFTB). Inclusion of the third term in the expansion, which describes the density fluctuations between atoms A and B using a monopole approximation, via charge fluctuations ∆‫ݍ‬஺ and the chemical hardness (Hubbard parameter), ߛ஺஻ , gives the 2nd order variant of DFTB (DFTB2, or self-consistent charge (SCC) DFTB). Inclusion of the fourth term describes the fluctuation of the Hubbard derivative due to the local densities of atoms A and B via the Hubbard derivate, Γ஺஻ , and constitutes 3rd order DFTB (DFTB3).38 DFTB3 has previously been shown to be particularly effective for describing structure of DES and related ILs, in the bulk,23,39,40 at interfaces41,42 and in the presence of dissolved salts and molecular solutes.43 All MD simulations reported here employ DFTB3 in conjunction with the 3ob-3-1 parameter set44,45 and Grimme D3 dispersion.46,47 The DFTB+ package48 was used to perform all simulations reported in this work.

2.2. NO2 Adsorption in Choline Chloride DES Adsorption of NO2 in ChCl:urea, ChCl:meth and ChCl:thio has been simulated here with model systems consisting of a single NO2 molecule solvated in 10 formula units (i.e. 10 ChCl ion pairs, 20 hydrogen bond donors) of each respective DES. Packmol49 was used to generate starting structures for all systems using distinct choline, Cl-, hydrogen bond donor and NO2 molecules to ensure no aggregration in the unit cell prior to MD relaxation. Each Packmol structure was initially optimised at 0 K using DFTB3-D3/3ob-3-1 before MD simulations were performed in an NVT ensemble at 298 K. Three-dimensional periodic boundary conditions were employed for each system and were also relaxed during the 0 K optimisation. Partial radial


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distribution functions (RDF) were then calculated using TRAVIS50 on the basis of equilibrated 100 ps DFTB3-D3/MD trajectories. Snapshots from the DFTB3-3D/3ob-3-1 MD trajectories for the three DES considered here are shown in Figure 1. (a)

(b)

(c)

Figure 1. Snapshots of periodic unit cells during DFTB3-D3/MD simulations of NO2 adsorbed in (a) ChCl:urea, (b) ChCl:meth and (c) ChCl:thio DES. Grey, white, blue, red, yellow and green spheres represent C, H, N, O, S and Cl.

2.3. Analysis of NO2-DES Interactions The solvation structure of NO2 in the DES considered here has been elucidated further with quantum chemical energy decomposition analysis (EDA) and reduced density gradient (RDG) analysis based on NO2-DES clusters consisting of a single NO2 molecule and a single DES formula unit (i.e. 1 ChCl ion pair and 2 HBD molecules). For each DES, 2,000 random trial clusters were generated using Addicoat's Kick3 stochastic algorithm51 and optimised at 0 K using DFTB3-D3/3ob-3-1. This gave 68, 74 and 80 unique structures for ChCl:urea-NO2, ChCl:methNO2 and ChCl:thio-NO2 complexes, respectively. The 20 most stable structures for each DESNO2 complex were then re-optimised using the M06-2X Minnesota density functional52 in conjunction with a 6-31++G(d,p) Pople basis set. Harmonic vibrational frequencies were also calculated at the M06-2X/6-31++G(d,p) level of theory, to ensure that all stationary points


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corresponded to local minima on the potential energy surface. All M06-2X/6-31G++G(d,p) geometry optimisations and frequency calculations were performed using Gaussian09.53 The interaction between NO2 and individual DES components in the 20 lowest M06-2X/631G++G(d,p) ChCl:urea, ChCl:meth and ChCl:thio clusters has been analysed via the RDG method of Johnson et al.54 and Su et al.’s localised molecular orbital energy decomposition analysis (LMOEDA),55 as implemented in GAMESS.56,57 The latter is based on KitauraMorokuma EDA.58 Li et al.33 similarly employed RDG to elucidate the adsorption of SO2 in the DES formed between ChCl and glycerol. The RDG and EDA analyses afford, respectively, a qualitative and quantitative understanding of the forces driving NO2 adsorption in DES. RDG analysis is ideally suited to domains within molecular complexes with small electron density (ρ) and low reduced density gradients s(ρ), which are typical of van der Waals interactions, hydrogen bonds, dipole-dipole, and steric repulsions. It is based on the sign of the λ2 eigenvalue of the electron-density Hessian (second derivative) matrix, which differentiates bonding interactions (λ2 < 0) from non-bonding (λ2 >0) interactions. The magnitude of the density itself indicates the strength of the interaction. Thus, at each point of the calculated electron density, the magnitude of ρ is combined with sign(λ2) to afford a spatial representation of the weak interactions present in the complex. Within LMOEDA, the total interaction energy (∆E) between specified monomers within a complex is decomposed such that, ∆E = Ees + Eex + Erep + Epol + Edisp

(2)

where Ees is the electrostatic interaction energy, Eex and Erep are the Pauli exchange and repulsion energies, Epol is the intramolecular polarization and Edisp is the dispersion energy between all interacting monomers. Here, ∆E is calculated at the M06-2X/6-31G(d,p) level of theory at M06-


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2X/6-31G++G(d,p) – optimized structures and include basis set superposition errors. We have removed the diffuse functions from the 6-31G++G(d,p) basis set for the LMOEDA analysis to assist with persistent numerical instabilities in the MO localization procedure due to the presence of diffuse basis functions.

3. Results and discussion 3.1. NO2 Solvation Structure in Choline Chloride DES Solvation structure of NO2 in bulk ChCl:urea, ChCl:meth and ChCl:thio DES (Figure 1) is examined via RDFs of the principle interactions (see atom labels given in Figure 2), which are provided in Figure 3. These interactions are those between the NO2 nitrogen/oxygen and the Ch+ hydroxyl H atom (HCh), the Cl- anion, the HBD amide hydrogen atoms (HU, HM1,M2, HT) and the amide C=O oxygen (OU, OM for the urea and methylurea HBDs) and C=S sulfur (ST for the thiourea HBD). Coordination numbers corresponding to the principle peaks in these RDFs, integrated between 0 – 4 Å, are provided in Table 1.

N O

OU

OM

O HU

S

HU

HM2

HT

HT

NU

NU

NM

NM

NT

NT

HU

HU

HM1

HM2

HT

HT

OChHCh N+

Cl-

ChCl

urea

methylurea

thiourea

Figure 2. Atom labels used for molecular components of ChCl:urea, ChCl:meth and ChCl:thio DES, and NO2.


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3.1.1. NO2 – HBD Interactions in ChCl DES Figure 3 and Table 1 show that nature of coordination between NO2 and the DES components is a function of the HBD structure. Of the three DES considered here, the NO2 – HBD interaction is strongest in the case of urea. In ChCl:urea, this HBD – NO2 interaction occurs predominantly via the urea -NH2 hydrogen atoms. This is evidenced by Figure 3(a), which shows strong peaks in both the O-HU and N-HU RDFs for the ChCl:urea DES. As anticipated, the O-HU interaction is shorter in range (RDF peak at ~2 Å) because of the stronger H-bonding interaction, compared to the N-HU interaction (RDF peak at ~2.7 Å). The relatively high symmetry and planar structure of urea enables both NO2 nitrogen and oxygen to intercalate between the two proximal NH2 hydrogen atoms, as evident by a formal coordination exceeding 2.0 in both cases (Table 1). NO2 interaction with the HBD C=O oxygen is also significant in the ChCl:urea DES. However, the C=O oxygen exhibits coordination numbers of 0.99 and 0.55 around the NO2 nitrogen and oxygen, respectively, which correspond to relatively diffuse interactions between ~3.0 – 3.5 Å in both cases (Figure 3(b)). Table 1. DFTB3-D3/3ob-3-1 coordination numbers (0-4 Å) corresponding to the primary peaks in partial radial distribution functions shown in Figure 3. ChCl:urea

N-HCh 0.63

N-Cl0.99

ChCl:meth

0.11

1.15

ChCl:thio ChCl:urea

1.26 O-HCh 0.66

1.45 O-Cl0.92

ChCl:meth

0.08

1.20

ChCl:thio

0.74

1.95

N-HU/HM1,M2/HT 2.30 1.05 (N-HM1) 0.46 (N-HM2) 0.88 O-HU/HM1,M2/HT 2.59 0.67 (O-HM1) 0.60 (O-HM2) 1.00

N-OU/OM/S 0.99 0.60 0.02 O-OU/OM/S 0.55 0.57 0.00


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Figure 3. DFTB3-D3/3ob-3-1 partial radial distribution functions (RDFs) for principal interactions between NO2 and (a) HBD amide hydrogens, (b) HBD O/S atoms, (c) Ch+ hydroxyl hydrogen and (d) Cl- anion, for the ChCl:urea, ChCl:meth and ChCl:thio DES model systems shown in Figure 1. Atom labels as per Figure 2. Black, grey and yellow lines correspond to ChCl:urea, ChCl:meth and ChCl:thio DES, respectively.


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By contrast, NO2 coordination with the methylurea HBD is relatively weak in ChCl:meth. Comparison of the N-HM1/HM2 and O-HM1/HM2 RDFs (Figure 3(a)) with the N-OM and O-OM RDFs (Figure 3(b)) shows that direct, short range interactions (e.g. < 3 Å) between the NO2 moiety and the methylurea HBD in ChCl:meth are only observed in the N-HM1/HM2 and OHM1/HM2 RDFs. This means that NO2 coordinates predominantly with methylurea via the amide hydrogens, rather than through the C=O oxygen, which is consistent with the coordination numbers reported in Table 1. The length scale of this N–HM1 interaction in ChCl:meth is comparable to the analogous N-HU interaction in ChCl:urea (Figure 3(b)). However, the peak height in the N–HM1 RDF is markedly reduced and it decays more rapidly with distance, compared to the N-HU RDF. Combined, these two factors yield a markedly reduced coordination number between the NO2 nitrogen and the methylurea amide hydrogens (1.05). The N–HM2 interaction, i.e. between the NO2 nitrogen and the methylamide hydrogen on the HBD is even weaker by comparison, corresponding to a coordination number of 0.46. Figure 3(a) shows that there is little short-range character to the N–HM2 interaction, with the only appreciable (albeit diffuse) peak in the N–HM2 RDF observed between ~ 4 -5 Å. This suggests that methylation of the urea amide moiety reduces the capacity for NO2-HBD hydrogen bonding in the ChCl:meth DES. However, the O-HM1 and O-HM2 coordination numbers in Table 1 are effectively the same (0.67, 0.60, respectively) and thus do not support this hypothesis. This means that the reduced coordination of HM2 around the NO2 in ChCl:meth is likely due to the steric hindrance of the bulky methyl group. Indeed, this is consistent with the reduction in the coordination between the NO2 nitrogen and the C=O oxygen in ChCl:meth (0.60), compared to ChCl:urea (0.99). We now consider the effect thiation of the urea HBD may have on the solvation structure of NO2. Comparison of the ChCl:urea and ChCl:thio RDFs in Figure 3 and Table 1 reveal some


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marked differences in the NO2 – HBD interactions. Most notably, there is little, if any, formal coordination between NO2 nitrogen/oxygens with the thiourea sulfur. Both the N-ST and O-ST RDFs (Figure 3(b)) remain essentially negligible at distances shorter than 4 Å, and this means that the corresponding coordination numbers in Table 1 are effectively zero. Consequently, the thiourea HBD in ChCl:thio coordinates with the NO2 molecule exclusively via hydrogen bonding of the NH2 hydrogens. Figure 3(a) shows that the range and height of the primary peak in the NHT RDF (at ~2.6 Å) is comparable to that in the N-HU for the ChCl:urea DES. However, the decay of this peak in the N-HT RDF is dramatically more abrupt compared to that of the primary peak in the N-HU RDF. Consequently, the coordination number of the thiourea HT around the NO2 nitrogen is reduced to 0.88 (compared to 2.30 for the N-HU interaction). We note here that several RDFs for the ChCl:thio DES shown in Figure 3 exhibit relatively sharp peaks compared to the other DES considered here. This is consistent with an overall increase in the NO2 – DES interaction strength, which yields lower diffusivity of NO2 in the bulk liquid; we return to a more detailed discussion of these points below. Interestingly, the apparent strengths of the N-HT and O-HT hydrogen bonding interactions in ChCl:thio are more consistent compared to the N-HU and O-HU interactions in ChCl:urea. This is inferred from comparison of the N-HT and O-HT RDFs in Figure 3(a), which shows that these two interactions occur at effectively the same distance (~2.5 Å). Although the primary peak in the O-HT RDF peak is substantially smaller than that in the N-HT RDF, ultimately the coordination numbers are comparable (1.00 and 0.88, respectively). 3.1.2. NO2 – Ch+ / Cl- Interactions in ChCl DES Naturally, the interaction between NO2 and the HBD in ChCl DES can be expected to vary with the HBD structure, as established in the preceding discussion. However, the identity of the HBD


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also influences the interaction between NO2 and the Ch+ and Cl- ions in these bulk DES. This is evident from the N/O-HCh and N/O-Cl- interactions. For instance, compared to ChCl:urea, the coordination numbers of HCh around the NO2 nitrogen and oxygen in the ChCl:meth DES are both reduced by ~0.5 to 0.11 (N-HCh) and 0.08 (O-HCh). The corresponding RDFs, shown in Figure 3(c), are consistent with such a weak coordination; the N-HCh and O-HCh pair correlation functions are both essentially featureless up to 7 Å. Instead, the presence of the methylurea HBD increases the NO2–Cl- interaction. For instance, coordination numbers of Cl- anions around the NO2 nitrogen and oxygen in ChCl:meth (1.15 and 1.20 for N-Cl- and O-Cl-, respectively) are consistently larger than observed in ChCl:urea (0.99 and 0.92 for N-Cl- and O-Cl-, respectively). This is expected from the corresponding RDFs for ChCl:urea and ChCl:meth in Figure 3(d): while the primary peak in the N-Cl- for ChCl:urea is stronger than that observed for ChCl:meth, it decays much more abruptly and therefore yields a smaller coordination number. The O-ClRDF in ChCl:meth and ChCl:urea both exhibit principle peaks at ~3 Å, however the peak is stronger for ChCl:meth. The presence of the thiourea HBD leads to notable differences in the solvation structure of NO2, compared to that observed in both the ChCl:urea and ChCl:meth DES. For instance, the NHCh interaction is markedly stronger in ChCl:thio. This is evidenced by the much larger N-HCh coordination number in ChCl:thio (1.26) compared to that observed in ChCl:urea (0.63) and ChCl:meth (0.11). The corresponding N-HCh RDFs shown in Figure 3(c) are consistent with these differences. The coordination of the HCh atom around the NO2 oxygen is also stronger in the ChCl:thio DES, albeit not to such a dramatic extent. For ChCl:thio the O-HCh coordination number is 0.74, while for ChCl:urea and ChCl:meth it is 0.66 and 0.08, respectively. Interestingly, the coordination of the Cl- anion around the NO2 nitrogen/oxygen in the ChCl:thio


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DES is significantly larger than that observed in the ChCl:urea and ChCl:meth DES. This is evident from the N-Cl- and O-Cl- RDFs shown in Figure 3(d), as well as the corresponding coordination numbers in Table 1. 3.2. Analysis of NO2 - DES Interactions Comparison of the solvation structure of NO2 in the ChCl:urea, ChCl:meth and ChCl:thio DES indicates how the HBD dictates the association between the NO2 and the Ch+, Cl- and HBD components in each DES. Changes in these associations – as gauged via differences in the NO2 solvation structure and coordination with the Ch+, Cl- and HBD components – consistently indicate that NO2 may interact more strongly with the ChCl:thio DES, compared to the ChCl:urea and ChCl:meth DES. To test this hypothesis quantitatively and qualitatively, we elucidate the NO2-DES interaction here via quantum chemical LMOEDA and an analysis of the non-covalent interactions present between the NO2 and the three DES considered here. 3.2.1. NO2 - DES Interaction Strength: Energy Decomposition Analysis LMOEDA decomposes the total interaction energy (∆E) of two fragments in a complex into electrostatic (∆Ees), exchange (∆Eex), repulsion (∆Erep), polarization (∆Epol), and dispersion (∆Edisp) energy contributions. Our aims here are not only to compare quantitatively the interaction energies between the adsorbed NO2 and the ChCl:urea, ChCl:meth and ChCl:thio DES, we also seek to establish trends in the components of these interaction energies. This requires the contributions to ∆E within DES components themselves to be subtracted from those in the DES-NO2 complex. This is achieved via two successive LMOEDA calculations (as depicted in Figure 4(a)). Firstly, the total interaction energy in the DES-NO2 complex (∆ENO2DES)

is calculated with the Ch+, Cl- and HBD components of the DES and the NO2 molecule each


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defined as a unique fragment in the EDA calculation. ∆ENO2-DES is the result of all DES-DES and DES-NO2 interactions present in the complex. To remove the portion of this interaction energy arising solely from interactions between the DES components, the NO2 moiety is removed from the DES-NO2 complex and the total interaction energy is recalculated (at the same geometry), again with the Ch+, Cl- and HBD components each defined as unique fragments in the EDA (∆EDES). The difference between ∆ENO2-DES and ∆EDES yields the total energy of interaction (∆E) between the NO2 molecule and the DES components.

Figure 4. (a) Fragmentation scheme applied for LMOEDA analysis of NO2 binding in ChCl:urea, ChCl:meth and ChCl:thio clusters (shown for ChCl:urea-NO2 complex). The NO2DES interaction is calculated by the removal of the interactions between individual DES components. (b) M06-2X/6-31G(d,p) LMOEDA interaction energies (∆E, kcal mol-1) and (c) the corresponding ∆Ees, ∆Eex, ∆Erep, ∆Epol and ∆Edisp components of these interaction energies (kcal mol-1), calculated for the 20 lowest energy M06-2X/6-31++G(d,p) – optimised structures of ChCl:urea-NO2, ChCl:meth-NO2 and ChCl:thio-NO2 complexes. Data points in (b, c) show individual energy values, green lines indicate mean energy values, colored boxes indicate ±1 standard deviation from the mean in each case. Blue, black and brown data refer to ChCl:urea, ChCl:meth and ChCl:thio DES, respectively.

Figure 4(b) shows M06-2X/6-31G(d,p) LMOEDA ∆E values for the 20 lowest M06-2X/631++G(d,p) – optimised structures of ChCl:urea-NO2, ChCl:meth-NO2 and ChCl:thio-NO2


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complexes. It is clear from this figure that the NO2-DES interaction is strongest in the case of ChCl:thio. For this DES monomer, ∆E is -16.9 kcal mol-1, whereas ∆E for the ChCl:urea and ChCl:meth are -7.7 and -6.6 kcal mol-1, respectively. Figure 4(b) also shows appreciable standard deviations in these overall interaction energies (1σ = 3.3, 3.3, 3.7 kcal mol-1 for ChCl:urea, ChCl:meth and ChCl:thio, respectively), and this is because of the stochastic approach of the Kick3 search algorithm used to generate the structures. Nevertheless, the difference between ∆E for ChCl:thio and those for ChCl:urea and ChCl:meth is beyond the magnitude of this statistical error. These results therefore support the hypothesis posed in the preceding discussion, i.e. that the NO2 adsorbate interacts more strongly with the ChCl:thio DES, compared to the ChCl:urea and ChCl:meth DES. Figure 4(c) presents the contributions to ∆E from electrostatic (∆Ees), exchange (∆Eex), repulsion (∆Erep), polarization (∆Epol), and dispersion (∆Edisp) interactions between the NO2 and DES components. In general terms, Figure 4(c) indicates that the principle interaction stabilizing the NO2 molecule in these DES is dispersion, followed by polarization interactions. For instance, the mean ∆Edisp for the ChCl:urea – NO2 complexes is -11.9 kcal mol-1, which is notably stronger than the mean ∆Ees, and ∆Eex values (-4.7 and -3.3 kcal mol-1, respectively). Polarisation interactions are also stronger than electrostatic and exchange effects in this case although not the same extent, the mean ∆Epol value being -5.74 kcal mol-1. Similarly, for the ChCl:meth – NO2 complexes, dispersion is the principle stablising effect (∆Edisp = -11.0 kcal mol-1), compared to electrostatic interactions (∆Ees = -3.2 kcal mol-1) and exchange effects (∆Eex = -1.6 kcal mol-1). Polarisation interactions in the ChCl:meth – NO2 complexes (∆Epol = -3.9 kcal mol-1) are, on average, comparable to those observed in the ChCl:urea – NO2 complexes, likely due to the


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similarity in the individual polarizabilities in the urea and methylurea HBDs. Figure 4(c) shows that, in general, the stabilising components of ∆E for the ChCl:thio – NO2 complexes are exaggerated compared to those for the ChCl:urea and ChCl:meth DES, while the repulsive contribution (∆Erep) does not significantly increase; this is consistent with the stronger overall interaction between the ChCl:thio components and the NO2 moiety. Nevertheless, dispersion remains the key stabilizing interaction between the NO2 molecule and the ChCl:thio DES components, with ∆Edisp (-13.4 kcal mol-1) being larger than ∆Eex (-4.7 kcal mol-1) and ∆Epol (9.1 kcal mol-1). Electrostatic interactions between the NO2 moiety and the ChCl:thio DES components are notably larger compared to the ChCl:urea and ChCl:meth DES, with ∆Ees being -13.2 kcal mol-1, which is comparable to the strength of ChCl:thio – NO2 dispersion interactions. 3.2.1. Non-Covalent NO2-DES Interactions The significance of dispersion interactions in these DES – NO2 complexes is somewhat unsurprising - NO2 is a neutral species and therefore purely non-covalent interactions and polarizability will likely dominate over electrostatic effects. We note however that Izgorodina et al.59,60 have recently established that, for ionic liquids, dispersive interactions even between cations and anions (i.e. charged species) are responsible for an appreciable fraction of the overall binding energy and hence the bulk properties of these liquids. To elucidate the origins of the non-covalent interactions quantified with LMOEDA in the preceding discussion, we utilize RDG analysis on representative DES – NO2 complex structures. Non-covalent interactions in the lowest energy M06-2X/6-31++G(d,p) - optimised ChCl:urea-NO2, ChCl:meth-NO2 and ChCl:thio-NO2 DES are shown in Figure 5.


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Figure 5 shows that the NO2 - DES interaction consists of both weak/diffuse and strong/directional interactions between the DES and the NO2 moiety. For each DES considered here, the dominant attractive interaction between NO2 and the DES is a charge-dipole interaction. This is characterised by blue, strongly directional regions on the RDG isosurface in Figure 5. For the ChCl:urea and ChCl:methylurea DES, this charge dipole interaction exists between the NO2 nitrogen and Cl- anion, while for the ChCl:thiourea DES, the charge dipole interaction exists between the NO2 nitrogen and the HBD sulfur. This difference is attributed to the increased polarizability of thiourea,61 compared to urea and methylurea, which enables more extensive electrostatic (i.e. charge-dipole) interactions between the NO2 and the DES components.

(a)

(b)

(c)

0.02 a.u.

-0.02 a.u.

Figure 5. Reduced density gradient isosurfaces (σ = 0.35 a.u.) for the highest NO2 binding energy structures for the (a) ChCl:urea, (b) ChCl:meth and (c) ChCl:thio DES. The surfaces are coloured according to the values of sign(λ2)ρ; Blue regions on the isosurface indicate strong electrostatic/charge dipole interactions interactions, green indicates van der Waals/hydrogen


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bonding interactions and red indicates strong repulsive interactions. Lower inserts are zoomed and rotated to highlight DES-NO2 hydrogen bond interactions more clearly.

Hydrogen bonding is characterised by green regions on the RDG isosurface with clear directionality, while van der Waals interactions correspond to green regions that are more diffuse in structure and non-directional. For each of the DES considered here, extensive van der Waals interactions between the NO2 moiety and the methyl groups on the ammonium charge centre are present. van der Waals interactions are also evident between the choline cation and HBD in each DES, which is consistent with the current understanding of the ChCl:urea DES bulk structure. 2022,24

However, Figure 5 indicates that hydrogen bonding between NO2 and the DES components

is more limited for the ChCl:urea and ChCl:methylurea DES, and is only observed between NO2 and the choline hydroxyl moiety, or between the DES components themselves. For example, in the ChCl:urea - NO2 complex, hydrogen bonding is evident (1) between the oxygen atoms of the NO2 and the choline hydroxyl moiety, (2) between the Cl- anion and the HBD amide hydrogen atoms, (3) between the Cl- anion and the choline hydrogen atoms in the ethyl backbone, (4) between the HBD oxygen atom and the hydrogens on the ammonium charge centre methyl groups, and (5) between the HBD oxygen and amide hydrogen atoms. A similar DES hydrogen bonding structure is evident for the ChCl:methylurea - NO2 complex in Figure 5(b). However, the NO2 no longer forms hydrogen bonds with the choline hydroxyl moiety, thus the NO2 is limited to only van der Waals interactions with the DES components. The ChCl:thiourea DES exhibits a different NO2 interaction mechanism; Figure 5 shows that for the ChCl:thiourea - NO2 complex, hydrogen bonds exist (1) between the HBD amide hydrogens and the NO2 oxygen atoms, and (2) between the NO2 moiety and the methyl groups on the ammonium charge centre. This is a direct consequence of the S-N charge dipole interaction, which draws the NO2 moiety


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close enough to facilitate hydrogen bond formation. DES hydrogen bonding and the S-N charge dipole interaction are therefore synergistic in nature, and are consistent with a greater total NO2DES interaction energy as discussed in the preceding section. We note briefly at this point that steric repulsions, characterised by orange/red regions on the RDG isosurface in Figure 5, are limited for the DES - NO2 complexes considered here. Further, these steric interactions correspond almost exclusively to intra-molecular interactions in the choline cation, viz. methylmethyl steric repulsions. 4. Conclusions We have presented a quantum chemical investigation study that establishes the solvation structure and adsorption mechanism of NO2 adsorption in ChCl-based DESs. We have shown that the hydrogen bond donor structure not only changes its NO2 coordination mechanism, it also changes the coordination mechanism between NO2 and the choline and chloride ions in the DES as well. This coordination is principally driven by dispersion and polarization interactions for each DES considered here, and our results indicate that NO2 adsorption is most favourable in the ChCl:thio DES. These results suggest that the polarisability of the HBD can be exploited as a novel design parameter for optimising DESs for use in not only denitrification technologies, but also the capture of other industrially/environmentally relevant gaseous species, such as NO2, NO, O2, H2O, SO2 and CO2.

Corresponding Author *[email protected] Author Contributions


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The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Acknowledgement AJP acknowledges support from the Australian Research Council (INTERSECT, LE170100032). SLW3 acknowledges a University of Newcastle Postgraduate Scholarship award. This research was undertaken with th1e assistance of resources provided at the NCI National Facility systems at the Australian National University and INTERSECT systems, through the National Computational Merit Allocation Scheme supported by the Australian Government. References (1) Richter, A.; Burrows, J. P.; Nüß, H.; Granier, C.; Niemeier, U. Increase in Tropospheric Nitrogen Dioxide Over China Observed From Space. Nature 2005, 437, 129-132. (2) Lamsal, L. N.; Martin, R. V.; Parrish, D. D.; Krotkov, N. A. Scaling Relationship for NO2 Pollution and Urban Population Size: a Satellite Perspective. Env. Sci. Tech. 2013, 47, 78557861. (3) Tani, H.; Terashima, H.; Daimon, Y.; Koshi, M. Hypergolic Ignition Mechanism of Hydrazine/Nitrogen Tetroxide Co-Flowing Jets At Low Temperatures. Int. J. Ener. Mater. Chem. Propul. 2015, 14, 71-84. (4) Commeyras, A.; Collet, H.; Boiteau, L.; Taillades, J.; Vandenabeele-Trambouze, O.; Cottet, H.; Biron, J.-P.; Plasson, R.; Mion, L.; Lagrille, O.; Martin, H.; Selsis, F.; Dobrijevic, M. Prebiotic Synthesis of Sequential Peptides on the Hadean Beach By a Molecular Engine Working with Nitrogen Oxides as Energy Sources. Polym. Int. 2002, 51, 661-665. (5) Nonnenberg, C.; Frank, I.; Klapötke, T. M. Ultrafast Cold Reactions in the Bipropellant Monomethylhydrazine/Nitrogen Tetroxide: CPMD Simulations. Angew. Chem., Int. Ed. 2004, 43, 4586-4589. (6) Pierce, R. A.; Campbell-Kelly, R. P.; Visser, A. E.; Laurinat, J. E. Removal of Chloride From Acidic Solutions Using NO2. Ind. Eng. Chem. Res. 2007, 46, 2372-2376. (7) Toniolo, R.; Dossi, N.; Pizzariello, A.; Doherty, A. P.; Bontempelli, G. a Membrane Free Amperometric Gas Sensor Based on Room Temperature Ionic Liquids for the Selective Monitoring of NOx. Electroanalysis 2012, 24, 865-871. (8) Busca, G.; Lietti, L.; Ramis, G.; Berti, F. Chemical and Mechanistic Aspects of the Selective Catalytic Reduction of NOx by Ammonia Over Oxide Catalysts: a Review. Appl. Catal. B 1998, 18, 1-36. (9) Goo, J. H.; Irfan, M. F.; Kim, S. D.; Hong, S. C. Effects of NO2 and SO2 on Selective Catalytic Reduction of Nitrogen Oxides By Ammonia. Chemosphere 2007, 67, 718-723.


22

Page 23 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(10) Wang, J.; Dong, X.; Wang, Y.; Li, Y. Effect of the Calcination Temperature on the Performance of a CeMoOx Catalyst in the Selective Catalytic Reduction of NOx With Ammonia. Catal. Today 2015, 245, 10-15. (11) Greaves, T. L.; Drummond, C. J. Protic Ionic Liquids: Properties and Applications. Chem. Rev. 2008, 108, 206-237. (12) Anderson, J. L.; Dixon, J. K.; Maginn, E. J.; Brennecke, J. F. Measurement of SO2 Solubility in Ionic Liquids. J. Phys. Chem. B 2006, 110, 15059-15062. (13) Yuan, X. L.; Zhang, S. J.; Lu, X. M. Hydroxyl Ammonium Ionic Liquids: Synthesis, Properties, and Solubility of SO2. [Erratum To Document Cited in CA146:366408]. J. Chem. Eng. Data 2007, 52, 1150. (14) Zhai, L.; Zhong, Q.; He, C.; Wang, J. Hydroxyl Ammonium Ionic Liquids Synthesized By Water-Bath Microwave: Synthesis and Desulfurization. J. Hazard. Mater. 2010, 177, 807-813. (15) García, G.; Aparicio, S.; Ullah, R.; Atilhan, M. Deep Eutectic Solvents: Physicochemical Properties and Gas Separation Applications. Energy & Fuels 2015, 29, 2616-2644. (16) Ali, E.; Hadj-Kali, M. K.; Mulyono, S.; Alnashef, I.; Fakeeha, A.; Mjalli, F.; Hayyan, A. Solubility of CO2 in Deep Eutectic Solvents: Experiments and Modelling Using the PengRobinson Equation of State. Chem. Eng. Res. Des. 2014, 92, 1898-1906. (17) Zhang, Q.; De Oliveira Vigier, K.; Royer, S.; Jerome, F. Deep Eutectic Solvents: Syntheses, Properties and Applications. Chem. Soc. Rev. 2012, 41, 7108-7146. (18) Smith, E. L.; Abbott, A. P.; Ryder, K. S. Deep Eutectic Solvents (DESs) and their Applications. Chem. Rev. 2014, 114, 11060-11082. (19) Abbott, A. P.; Capper, G.; Davies, D. L.; Rasheed, R. K.; Tambyrajah, V. Novel Solvent Properties of Choline Chloride/Urea Mixtures. Chem. Commun. 2003, 70-71. (20) Sun, H.; Li, Y.; Wu, X.; Li, G. Theoretical Study on the Structures and Properties of Mixtures of Urea and Choline Chloride. J. Mol. Model. 2013, 19, 2433-2441. (21) Zahn, S.; Kirchner, B.; Mollenhauer, D. Charge Spreading in Deep Eutectic Solvents. Chemphyschem 2016, 17, 3354-3358. (22) Ashworth, C. R.; Matthews, R. P.; Welton, T.; Hunt, P. A. Doubly Ionic Hydrogen Bond Interactions Within the Choline Chloride-Urea Deep Eutectic Solvent. Phys. Chem. Chem. Phys. 2016, 18, 18145-18160. (23) Stefanovic, R.; Ludwig, M.; Webber, G. B.; Atkin, R.; Page, A. J. Nanostructure, Hydrogen Bonding and Rheology in Choline Chloride Deep Eutectic Solvents as a Function of the Hydrogen Bond Donor. Phys. Chem. Chem. Phys. 2017, 19, 3297--3306. (24) Hammond, O. S.; Bowron, D. T.; Edler, K. J. Liquid Structure of the Choline ChlorideUrea Deep Eutectic Solvent (Reline) From Neutron Diffraction and Atomistic Modelling. Green Chem. 2016, 18, 2736-2744. (25) Li, X.; Hou, M.; Han, B.; Wang, X.; Zou, L. Solubility of CO2 in a Choline Chloride + Urea Eutectic Mixture. J. Chem. Eng. Data 2008, 53, 548-550. (26) Chen, Y.; Mutelet, F.; Jaubert, J.-N. Solubility of Carbon Dioxide, Nitrous Oxide and Methane in Ionic Liquids At Pressures Close To Atmospheric. Fluid Phase Equilib. 2014, 372, 26-33. (27) Francisco, M.; Van Den Bruinhorst, A.; Zubeir, L. F.; Peters, C. J.; Kroon, M. C. a New Low Transition Temperature Mixture (LTTM) Formed by Choline Chloride + Lactic Acid: Characterization as Solvent for CO2 Capture. Fluid Phase Equilib. 2013, 340, 77-84. (28) Leron, R. B.; Li, M.-H. Solubility of Carbon Dioxide in a Eutectic Mixture of Choline Chloride and Glycerol at Moderate Pressures. J. Chem. thermo. 2013, 57, 131-136.


23


Page 24 of 27

(29) Su, W. C.; Wong, D. S. H.; Li, M. H. Effect of Water on Solubility of Carbon Dioxide in (Aminomethanamide + 2-Hydroxy-N,N,N-Trimethylethanaminium Chloride). J. Chem. Eng. Data 2009, 54, 1951-1955. (30) Trivedi, T. J.; Lee, J. H.; Lee, H. J.; Jeong, Y. K.; Choi, J. W. Deep Eutectic Solvents as Attractive Media for CO2 Capture. Green Chem. 2016, 18, 2834-2842. (31) Sun, S. Y.; Niu, Y. X.; Xu, Q.; Sun, Z. C.; Wei, X. H. Efficient SO2 Absorptions by Four Kinds of Deep Eutectic Solvents Based on Choline Chloride. Ind. Eng. Chem. Res. 2015, 54, 8019-8024. (32) Yang, D. Z.; Hou, M. Q.; Ning, H.; Zhang, J. L.; Ma, J.; Yang, G. Y.; Han, B. X. Efficient SO2 Absorption by Renewable Choline Chloride-Glycerol Deep Eutectic Solvents. Green Chem. 2013, 15, 2261-2265. (33) Li, H. P.; Chang, Y. H.; Zhu, W. S.; Wang, C. W.; Wang, C.; Yin, S.; Zhang, M.; Li, H. M. theoretical Evidence of Charge Transfer Interaction Between SO2 and Deep Eutectic Solvents formed By Choline Chloride and Glycerol. Phys. Chem. Chem. Phys. 2015, 17, 28729-28742. (34) Korotkevich, A.; Firaha, D. S.; Padua, A. A. H.; Kirchner, B. Ab Initio Molecular Dynamics Simulations of SO2 Solvation in Choline Chloride/Glycerol Deep Eutectic Solvent. Fluid Phase Equilib. 2017, 448, 59-68. (35) Patiño, J.; Gutiérrez, M. C.; Carriazo, D.; Ania, C. O.; Parra, J. B.; Ferrer, M. L.; del Monte, F. Deep Eutectic Assisted Synthesis of Carbon Adsorbents Highly Suitable for LowPressure Separation of CO2–CH4 Gas Mixtures. Energy & Environmental Science 2012, 5, 86998707. (36) Duan, E.; Guo, B.; Zhang, D.; Shi, L.; Sun, H.; Wang, Y. Absorption of NO and NO2 in Caprolactam Tetrabutyl Ammonium Halide Ionic Liquids. J. Air Waste Man. Assoc. 2011, 61, 1393-1897. (37) Elstner, M.; Porezag, D.; Jungnickel, G.; Elsner, J.; Haugk, M.; Frauenheim, T.; Suhai, S.; Seifert, G. Self-Consistent-Charge Density-Functional Tight-Binding Method for Simulations of Complex Materials Properties. Phys. Rev. B 1998, 58, 7260-7268. (38) Gaus, M.; Cui, Q.; Elstner, M. DFTB3: Extension of the Self-Consistent-Charge DensityFunctional Tight-Binding Method (SCC-DFTB). J. Chem. Theory Comput. 2011, 7, 931-948. (39) Addicoat, M. A.; Stefanovic, R.; Webber, G. B.; Atkin, R.; Page, A. J. Assessment of the Density Functional Tight Binding Method for Protic Ionic Liquids. J. Chem. Theory Comput. 2014, 10, 4633-4643. (40) Zentel, T.; Kuhn, O. Hydrogen Bonding in the Protic Ionic Liquid Triethylammonium Nitrate Explored By Density Functional Tight Binding Simulations. J. Chem. Phys. 2016, 145, 234504. (41) Li, H.; Atkin, R.; Page, A. J. Combined Friction force Microscopy and Quantum Chemical Investigation of the Tribotronic Response at the Propylammonium Nitrate-Graphite Interface. Phys. Chem. Chem. Phys. 2015, 17, 16047-16052. (42) Page, A. J.; Elbourne, A.; Stefanovic, R.; Addicoat, M. A.; Warr, G. G.; Voitchovsky, K.; Atkin, R. 3-Dimensional Atomic Scale Structure of the Ionic Liquid-Graphite Interface Elucidated by AM-AFM and Quantum Chemical Simulations. Nanoscale 2014, 6, 8100-8106. (43) Stefanovic, R.; Webber, G. B.; Page, A. J. Nanostructure of Propylammonium Nitrate in the Presence of Poly(Ethylene Oxide) and Halide Salts. J. Chem. Phys. 2018, 148, 193826. (44) Gaus, M.; Goez, A.; Elstner, M. Parametrization and Benchmark of DFTB3 for Organic Molecules. J. Chem. theory Comput. 2013, 9, 338-354.


24

Page 25 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(45) Kubillus, M.; Kubař, T.; Gaus, M.; Řezáč, J.; Elstner, M. Parameterization of the DFTB3 Method for Br, Ca, Cl, F, I, K, and Na in Organic and Biological Systems. J. Chem. theory Comput. 2015, 11, 332-342. (46) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. a Consistent and Accurate Ab initio Parametrization of Density Functional Dispersion Correction (DFT-D) for the 94 Elements H-Pu. J. Chem. Phys. 2010, 132, 154104. (47) Grimme, S.; Ehrlich, S.; Goerigk, L. Effect of the Damping Function in Dispersion Corrected Density Functional Theory. J. Comput. Chem. 2011, 32, 1456-1465. (48) Aradi, B.; Hourahine, B.; Frauenheim, T. DFTB+, a Sparse Matrix-Based Implementation of the DFTB Method. J. Phys. Chem. A 2007, 111, 5678-5684. (49) Martinez, L.; Andrade, R.; Birgin, E. G.; Martinez, J. M. PACKMOL: A Package for Building Initial Configurations for Molecular Dynamics Simulations. J. Comput. Chem. 2009, 30, 2157-2164. (50) Brehm, M.; Kirchner, B. TRAVIS - A Free Analyzer and Visualizer for Monte Carlo and Molecular Dynamics Trajectories. J. Chem. Inf. Model. 2011, 51, 2007-2023. (51) Addicoat, M. A.; Fukuoka, S.; Page, A. J.; Irle, S. Stochastic Structure Determination for Conformationally Flexible Heterogenous Molecular Clusters: Application To Ionic Liquids. J. Comput. Chem. 2013, 34, 2591-2600. (52) Zhao, Y.; Lynch, B. J.; Truhlar, D. G. Development and assessment of a New Hybrid Density Functional Model for thermochemical Kinetics. J. Phys. Chem. A 2004, 108, 2715-2719. (53) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Et Al. Gaussian09 Revision A.1 Ed.; Gaussian, inc., Wallingford CT: 2009. (54) Johnson, E. R.; Keinan, S.; Mori-Sanchez, P.; Contreras-Garcia, J.; Cohen, A. J.; Yang, W. T. Revealing Noncovalent Interactions. J. Am. Chem. Soc. 2010, 132, 6498-6506. (55) Su, P. F.; Li, H. Energy Decomposition Analysis of Covalent Bonds and Intermolecular Interactions. J. Chem. Phys. 2009, 131, 014102. (56) Schmidt, M. W.; Baldridge, K. K.; Boatz, J. A.; Elbert, S. T.; Gordon, M. S.; Jensen, J. H.; Koseki, S.; Matsunaga, N.; Nguyen, K. A.; Su, S. J.; Windus, T. L.; Dupuis, M.; Montgomery, J. A. General Atomic and Molecular Electronic-Structure System. J. Comput. Chem. 1993, 14, 1347-1363. (57) Gordon, M. S.; Schmidt, M. W. in Theory and Applications of Computational Chemistry: The First forty Years; Dykstra, C. E., Frenking, G., Kim, K. S., Scuseria, G. E., Eds.; Elsevier: 2005. (58) Kitaura, K.; Morokuma, K. New Energy Decomposition Scheme for Molecular-Interactions within Hartree-Fock Approximation. Int. J. Quantum Chem. 1976, 10, 325-340. (59) Izgorodina, E. I.; Golze, D.; Maganti, R.; Armel, V.; Taige, M.; Schubert, T. J. S.; Macfarlane, D. R. Importance of Dispersion Forces for Prediction of Thermodynamic and Transport Properties of some Common Ionic Liquids. Phys. Chem. Chem. Phys. 2014, 16, 72097221. (60) Izgorodina, E. I.; Seeger, Z. L.; Scarborough, D. L. A.; Tan, S. Y. S. Quantum Chemical Methods for the Prediction of Energetic, Physical, and Spectroscopic Properties of Ionic Liquids. Chem. Rev. 2017, 117, 6696-6754. (61) Santos, O. L.; Fonseca, T. L.; Sabino, J. R.; Georg, H. C.; Castro, M. A. Polarization Effects on the Electric Properties of Urea and Thiourea Molecules in Solid Phase. J. Chem. Phys. 2015, 143, 234503.


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NO2 Solvation Structure in Choline Chloride Deep Eutectic Solvents

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