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Theoretical Chemistry Accounts

Current research reports and chronological list of recent articles..




TCA publishes papers in all fields of theoretical chemistry, computational chemistry, and modeling. Fundamental studies as well as applications are included in the scope.

The publisher is Springer. The copyright and publishing rights of specialized products listed below are in this publishing house. This is also responsible for the content shown.

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Additional research articles see Current Chemistry Research Articles. Magazines with similar content (theoretical chemistry):

 - International Journal of Quantum Chemistry,

 - Journal of Mathematical Chemistry.



Theoretical Chemistry Accounts - Abstracts



CO 2 induced swing effect at imidazolate of zeolitic imidazolate framework-90 using molecular simulations

Abstract

The influence of adsorbed CO2 molecules on the lattice structure of ZIF-90 has been examined. Parameters verified by adsorption simulations have been used. Two lattice structures corresponding to so-called gate opening can be observed depending upon the amount of adsorbed guest molecules and the temperature. A transition region has been found in which both of the structures appear temporarily leading to broad statistical distributions of window diameters. Diameters up to 4.43 Å are found. An increased window diameter is observed at high temperature even for the empty lattice.


Datum: 16.09.2019


Automatic routing of Goldstone diagrams using genetic algorithms

Abstract

This paper presents an algorithm for an automatic transformation (= routing) of time-ordered topologies of Goldstone diagrams (i.e., Wick contractions) into graphical representations of these topologies. Since there is no hard criterion for an optimal routing, the proposed algorithm minimizes an empirically chosen cost function over a set of parameters. Some of the latter are naturally of discrete type (e.g., interchange of particle/hole lines due to antisymmetry) while others (e.g., xy-position of nodes) are naturally continuous. In order to arrive at a manageable optimization problem, the position space is artificially discretized. In terms of the (1) cost function, (2) the discrete vertex placement, (3) the interchange of particle/hole lines the routing problem is now well defined and fully discrete. However, it shows an exponential complexity with the number of vertices suggesting to apply a genetic algorithm for its solution. The presented algorithm is capable of routing non-trivial (several loops and crossings) Goldstone diagrams from given topologies. The resulting diagrams are qualitatively fully equivalent to manually routed ones. The proposed algorithm is successfully applied to several coupled cluster approaches and a perturbative (fixpoint iterative) CCSD expansion with repeated diagram substitution.


Datum: 13.09.2019


QCT study of the vibrational and translational role in the H + C 2 H 6 ( ν 1 , ν 2 , ν 5 , ν 7 , ν 9 and ν 10 ) reactions

Abstract

Two important issues were analysed in the title reaction: the effects of vibrational excitation, associated with mode selectivity, and the role of translational energy, associated with Polanyi’s rules. Based on a global analytical potential energy surface, PES-2018, recently developed in our group, quasi-classical trajectory (QCT) calculations were performed at total energy of 35 kcal mol−1, either as translation or as a combination of translation and vibration energy. Independent vibrational excitation by one quantum of any of the CH3 stretching modes in ethane leads to similar dynamics pictures of reaction cross sections and H2(v′, j′) rotovibrational and scattering distributions, ruling out mode selectivity. Normal mode analysis showed a cold, non-inverted, H2(v′) product vibrational distribution, while the C2H5(v′) co-product presented many vibrational states, all of them with a low population, practically simulating a classical behaviour. An equivalent amount of energy as translation raises reactivity somewhat less effective than vibrational energy, contrary to that found for the O(3P) + CH4 reaction. Both reactions present “central” barriers, so this opposite behaviour shows the difficulties for a straightforward application of the Polanyi′s rules. The role of vibrational and translational energy on dynamics has been rationalized by the coupling between vibrational modes, which makes analysis of vibrational excitation difficult in polyatomic systems. Finally, the role of the total energy on reactivity and mode selectivity was analysed, concluding that at lower energy, 15 kcal mol−1, translational energy is much more effective than vibrational energy to enhance reactivity, while at intermediate energy, 20 kcal mol−1, the situation is more confusing and strongly dependent on the counting methods used in the QCT calculations. Therefore, very small mode selectivity is found, and translation seems to be more effective in enhancing reactivity than vibration at low collision energies, while this behaviour is reversed as we increase the collision energy, being the turning point around 20 kcal mol−1.


Datum: 10.09.2019


Enthalpies of formation of the benzyloxyl, benzylperoxyl, hydroxyphenyl radicals and related species on the potential energy surface for the reaction of toluene with the hydroxyl radical

Abstract

The reaction of toluene (T) with ·OH produces addition products as well as the benzyl radical (TR). TR can react with ·OH or O2 to produce oxygenated species, for many of which there is no experimental information available. We present here theoretically determined heats of formation (HFs) of 17 such species using the non-isodesmic reactions on the potential energy surface of TR + O2 and T + ·OH +O2. For those species the experimental HFs of which are known, we obtained a good correlation between experimental and theoretical values at the G4 (r2 = 0.999) and M06/cc-pVQZ (r2 = 0.997) levels, thus showing the goodness of the methods used. Experimentally unknown HFs of other radicals (benzyloxyl, spiro [1,2-dioxetane benzyl], hydroxyphenyl and benzylperoxyl) and closed-shell species (salicylic alcohol, benzo[b]oxetane and p-hydroxy cyclohexa-2,5-dienone) were later determined using those methods.


Datum: 05.09.2019


Computational investigation on the reaction of dimethyl ether with nitric dioxide. I. Underlying mechanism and accurate energetics

Abstract

The reaction of dimethyl ether (DME) with nitrogen dioxide (NO2), which plays a critical role in the low-temperature oxidation behavior of DME, is employed as prototype for reactions of heavier clean ether fuels to assess different hybrid density functionals and “double-hybrid” density functionals. The reaction energies and barrier heights for the reaction system were computed with CCSD(T) theory extrapolated to the complete basis set limit using augmented cc-pVDZ and cc-pVTZ basis sets. The involved energetics were also improved by the CCSD(T)/6-311+G(2df,2p), QCISD(T)/6-311+G(2df,2p), G3B3, G3MP2B3, CBS-QB3, G4, and G4MP2 calculations. It is shown that “double-hybrid” density functionals with the TZVP basis set can give accurate geometries and principal moments of inertia of reactants and products and the B2PLYP/TZVP level can achieve results for barrier heights comparable in accuracy to the high-level ab initio results, which is identified as an important potential theoretical level for direct kinetics studies on the rates of these and homologous reaction systems. The calculated results indicate that NO2 preferentially captures an out-of-plane hydrogen atom from the DME molecule by the O or the N end via three distinct channels to produce trans-HONO, cis-HONO, and HNO2, respectively, and each channel involves the formation of a van der Waals post-reaction adducts lying lower in energy than their separate products.


Datum: 05.09.2019


A density functional theory study on complexation processes and intermolecular interactions of triptycene-derived oxacalixarenes

Abstract

Triptycene-derived oxacalixarenes (TP) exhibit two different conformations: cis-isomer (TPA) and trans-isomer (TPB). The geometries structures were optimized by the density functional theory (DFT) based on ωB97XD and B3LYP-D3 functionals. The oxacalixarenes favor the inclusion complex through noncovalent interactions, such as hydrogen bonding, π···π stacking, and C–H···π interactions. The formation of a inclusion complex is spontaneous and thermodynamically favorable. The calculated 1H nuclear magnetic resonance (1HNMR) spectrum of MV2+@TPA (MV2+: methyl viologen cation) showed the chemical shifts of its protons have changed upon complexation. The frontier molecular orbitals and the energy of band gap were constructed and analyzed. The interaction between host and guest was investigated and characterized by the molecular electrostatic potential (MESP), vibration frequency, the natural bond orbital (NBO), and quantum theory of atoms in molecules (AIM) methods. And also the reduced density gradient (RDG) isosurface map and scatter diagram reflected the location and intensity of the noncovalent interactions.


Datum: 03.09.2019


On the impact of a phosphoryl group in the recognition capabilities of 2-aminopyridines toward carboxylic acids

Abstract

Inspired by natural molecular recognition processes, many research efforts have been routed in recent years toward the design of new host–guest molecular systems based on non-covalent interactions. Within this field, 2-aminopyridines (2APs) have been widely studied due to their tunable spectroscopic response in the presence of carboxylic acids. Herein, we present and analyze a novel family of 2AP core compounds based on 2-phosphorylamidopyridine (2PAP). Linear response time-dependent density functional theory (TD-DFT) has been used to characterize and model several spectroscopic properties of 2PAP. Our results, validated through experiments, show that TD-DFT can provide a reliable description of the electronic excited states of these aromatic systems. In addition, we have also studied the amino–imino tautomerization of 2AP and 2PAP in light of TD-DFT tools. We show that the presence of a carboxylic acid has a catalytic effect on the tautomerization reaction, which otherwise does not occur spontaneously at room temperature. These results suggest that this low-cost computational approach can be applied to more complex organic systems derived from 2-aminopyridine, paving the way for the development of potentially useful sensing materials and organic species for molecular recognition.


Datum: 03.09.2019


Size effects in charge migration in alkyne chains

Abstract

The charge migration dynamics initiated by an outer-valence ionization of alkyne chains containing between 4 and 12 carbon atoms is studied using ab initio methods only. It is shown that the removal of a \(\hbox {HOMO}\) –1 electron from each of the molecules in the series leads to the population of the same structure of a main state and correlation satellites in their ionization spectra. The resulting pure electron dynamics manifest as an ultrafast charge migration oscillations between the center of the molecule and its extremities. The charge migration follows the same pattern in all studied cases with a slight monotonic increase of the time scale with the system size. This shows that the correlation-driven charge migration can exhibit scaling properties and constitutes a proof of concept for the possibility of molecular design for charge migration. As alkynes are used as molecular wires, it is argued that the present results may open the door for ultrafast molecular electronics.


Datum: 30.08.2019


Thermal rate coefficients and kinetic isotope effects of the reaction HO + H 2 O → H 2 O + OH

Abstract

Hydrogen-transfer reactions take place in a wide range of chemically active environments. In this work, thermal rate coefficients of the prototypical hydrogen-transfer reaction HO + H2O → H2O + OH and its various isotopologues are computed using both tunneling-corrected transition state and quasi-classical trajectory methods on a recently developed global potential energy surface. On the one hand, the calculated rate coefficients and kinetic isotope effects agree well with available experimental results, indicating the high fidelity of the potential energy surface. On the other hand, the observed normal primary and inverse secondary kinetic isotope effects appear to be prevalent in hydrogen abstraction reactions, which are rationalized by the change of classical and adiabatic minimum energy paths. In addition, there exists strong non-Arrhenius behavior at low temperatures due to the significant quantum tunneling effect.


Datum: 30.08.2019


Theoretical investigations of structural, thermal properties and stability of the group 12 metal M(XH) isomers in atmosphere: M = (Zn, Cd, Hg) and XH = (OH, SH)

Abstract

Electronic structure calculations have been performed of the group 12 metal (Zn, Cd, Hg) reaction between hydroxyl OH and hydrosulfide SH to understand the processes of transformation in the atmosphere. DFT/B3LYP methods are employed to calculate the structure of reactants, intermediates, transition states and products as well as their equilibrium geometries, electronic properties, dissociation energy. The scalar relativistic effects have been accurately included by making use of the relativistic effective potentials. The computing results obtained at B3LYP/MWB level of M(OH) and M(SH) for doublet and quartet (2,4+, 2A′, 4A″ and 2,4∏) state suggest that the doublet states are most stable than the quartet. The computed potential hypersurface 2A′ indicates four stationary points; two of them correspond to the stable structures with symmetries: MOH/MSH(2A′) and OMH/SMH(2∏), and two points correspond to transition states with the symmetries: MOH/MSH(2+) and MOH/MSH(2A′). The isomerization process MXH(2A′) → XMH(2∏) via the transition state and the atmospheric stability of M(XH) are also discussed. Examination of dissociation energy, enthalpy of reaction and wavelength from linear form OMH/SMH(2∏) estimate that the molecule has appreciable stability. As for the angled form MOH/MSH(2A′), the values obtained suggest that it is easily dissociable in the presence of solar radiation. Our results are compared with previous work, when available.


Datum: 28.08.2019


Equidensity orbitals in resultant -information description of electronic states

Abstract

The equidensity orbitals (EO) are used in the resultant entropic description of molecular states which combines the probability and current contributions in the overall information content. Continuities of the modulus and phase components of electronic wavefunctions are examined, and the Harriman–Zumbach–Maschke (HZM) construction of Slater determinants yielding the prescribed electron density is explored. The conditional probability interpretation of (complex) HZM wavefunctions is formulated, the entropy/information contributions due to the state phase component are summarized, and a nonclassical origin of quantum dynamics of the resultant gradient information, related to average kinetic energy of electrons, is emphasized. The phase equilibria maximizing the resultant-entropy measures are explored, and “thermodynamic” phase minimizing the overall gradient information is determined. It generates finite orbital currents giving rise to the vanishing resultant flow of electrons in the system as a whole. Potential use of atomic and molecular EO bases in electronic structure calculations and interpretations in chemistry is discussed, and illustrative example of Gaussian probability distribution is examined in some detail.


Datum: 27.08.2019


Methane functionalization by an Ir(III) catalyst supported on a metal–organic framework: an alternative explanation of steric confinement effects

Abstract

A highly selective Ir catalyst supported on the metal–organic framework (MOF) UiO-67 for the catalytic borylation of methane has recently been synthesized. The high chemoselectivity of the catalyst toward monoborylated methane (CH3Bpin, Bpin = pinacolborane) instead of diborylated methane (CH2Bpin2) was speculated to be caused by the steric confinement of MOF UiO-67. In this study, we applied quantum mechanical methods to determine: (1) the steric effect of the UiO-67 framework in promoting the chemoselectivity of the Ir catalyst toward CH3Bpin and (2) the borylation mechanisms over the Ir catalyst supported on UiO-67. Our results show that UiO-67 framework sterically obstructs the diffusion of the larger CH2Bpin2 molecule within the MOF while allowing the smaller CH3Bpin molecule to pass through with little energy penalty. The diffusion of CH2Bpin2 from the tetrahedral pore to the tetragonal pyramidal pore within modified UiO-67 with coordinated Ir(Bpin)3 complex has an estimated barrier of 24.7 kcal/mol and is 14.2 kcal/mol higher than the diffusion of CH3Bpin. The electronic and steric effects of the support at the Ir catalytic center are much smaller than this confinement effect on diffusion, and the catalytic center behaves similarly to the homogeneous Ir catalyst. We determined an overall free energy of activation of 34.6 kcal/mol for the CH4 borylation reaction using the Ir(III) catalyst. We also determined that the turnover-determining step for the catalytic methane borylation is the isomerization of seven-coordinated Ir(V) complex instead of the commonly assumed C–H bond activation by oxidative addition.


Datum: 24.08.2019


Bonding and Diels–Alder reactions of substituted 2-borabicyclo(1.1.0)but-1(3)-enes: a theoretical study

Abstract

Substituted 2-borabicyclo(1.1.0)but-1(3)-enes (2BB’s) are a kind of novel molecules with inverted carbon–carbon bonds whose orders range between one and two. Considering the significant interest in the Diels–Alder (D–A) reactions of substituted cyclopropenes, here we studied the bonding and D–A reactions of 24 substituted 2BB molecules at the B3LYP-D3/6-311G** theoretical level. Computations showed that the inverted C=C bond lengths fall in the range of 1.46–1.50 Å and 2BB is of significant characteristic of a singlet biradical with two σ single electrons and π aromatic conjugation over the three-membered rings. Yet ab initio valence bond computations showed that the inverted bonds are charge-shifted, and the ionic resonance structures arising from charge-shifting are of carbene characteristics as well. Thus, substituted 2BB’s can also be considered as B-heterocyclic carbenes. Since the LUMOs of the 2BB derivatives are similar to those of ethene and cyclopropene, we studied their D–A reactions with butadiene. All cycloaddition reactions kinetically and thermodynamically favor the formation of the derivatives of 7-bora-oct-3-ene[4.1.1]propellane undergoing endo transition states. Notably, there is a good correlation between the reaction barriers and the hyperconjugative aromatic and antiaromatic stabilization enthalpies for all substituted 2BB’s. In other words, the differences in their reactivity result from the difference in their aromatic stability.


Datum: 24.08.2019


DFT study of two-photon absorption of octupolar molecules

Abstract

The two-photon absorption (TPA) properties of octupolar molecules based on a triphenyl-isocyanurate cyclotrimer, a 1,3,5-triphenyl-benzene or a triphenyl-triazine core were theoretically investigated using DFT and TD-DFT computations. These compounds are very promising regarding their potential application, especially for optical limitation. These systems, which exhibit a threefold axis, contain three arms with a terminal electron-donating group linked in 1, 3 and 5 positions to the central C3N3O3 isocyanurate, benzene or triazine ring. The SAOP functional and a DZP basis set were selected for the TPA computations. The so-computed TPA energies and cross sections are in good agreement with the observed data. Increasing the strength of the donor terminal group enhances the TPA cross section values. The compound with triazine core presents the highest two-photon cross section value compared to the values found for the isocyanurate or the 1,3,5-phenyl core as central ring. Furthermore, this study brings to light a cooperative enhancement of the TPA property between the three arms attached to the isocyanurate ring.


Datum: 13.08.2019


Comparative study of 1:1 Lewis acid–base adducts between Cp 2 M(L)H (M = V, Nb, Ta; L = CO, C 2 H 4 , P(CH 3 ) 3 ) and BF 3 /AlF 3

Abstract

Transition metal hydrides play important roles in organometallic catalysis and synthetic reactions. Metallocenes niobium or tantalum hydride derivatives show high reactivities with variety of main group 13 Lewis acids. In this work, the nature of MH···B/Al interaction between Cp2M(L)H(M = V, Nb, and Ta) and BF3/AlF3 in 1:1 Lewis acid–base adducts as well as the influences of different types of ligands on the interactions is investigated. The results show that in Cp2M(L)H···BF3/AlF3, the MH···B interaction belongs to covalent interaction, and MH···Al shows partly covalent character. The covalent character of MH···B/Al bonds decreases with the increasing period of metal atom. The strength of MH···B/Al interaction is related to the type of metal atom (M) and ligand (L) in Cp2M(L)H, and the influences of L are larger than those of M. For the same M, the strength of MH···B/Al bonds is mainly influenced by the type of ligand, and they increase in the sequence of L = CO, C2H4, and P(CH3)3. The formation of Cp2M(L)H···BF3/AlF3 increases the polarity of M–H bond of Cp2M(L)H.


Datum: 12.08.2019


On the effect of charge and spin in He (q) @X n Z 12−n H 12 ( n−2) molecules, with X = {C, Si}, Z = {B, Al} and q  = {0, + 1, + 2}, n  = {0, 1}

Abstract

We study the effect of introducing He(q)q = {0, + 1, + 2}, into icosahedral molecules—XnZ12−nH 12( n−2), with X = {C, Si}, Z = {B, Al} and n = {0, 1}—to see the effect of charge and spin on the stability and potential existence for these endohedral complexes. For q = 0 and q = +1, all endohedral systems correspond to energy minima with the He atom/ion remaining inside the cage. However, when the charge of the He ion is q = +2, the He atom/ion is ejected from the He(2+)@B12H 12(2−) and He(2+)@CB11H 12(−) cages, but this is not the case for the Al12H 12(2−) and SiAl11H 12(−) cages, which retain what is nominally the He(2+) ion inside. These results could be helpful for designing quantum bits with atoms encapsulated inside heteroatomic molecular icosahedral cages since the s, p and d atomic levels do not split under an icosahedral field.


Datum: 09.08.2019


Effects of complexation with a metal ion on the intramolecular hydrogen bonds in acylphloroglucinols

Abstract

Complexation with a metal ion of an organic molecule containing one or more intramolecular hydrogen bonds (IHBs) influences the characteristics of the IHBs. These influences are here investigated computationally for the complexes of selected antioxidant acylphloroglucinols with a Cu2+ ion, and also the complexes of a number of structurally-related molecules meant to highlight the influence of specific molecular features. All the low energy conformers of acylphloroglucinols (compounds structurally derived from 1,3,5-trihydroxybenzene and characterised by the presence of a CRO group) contain an IHB between the sp2 O of CRO and a neighbouring phenol OH. Additional O–H···O or O–H···π IHB are present when the molecule contains substituents with groups that can form IHBs. The results show various effects that can be ascribed to complexation, such as changes in the IHB parameters and in the red shift of the vibrational frequency of the donor OH caused by the IHB. For O–H···O IHBs, complexation may cause the transfer of the proton from the donor to the acceptor O atom, more frequently when the acceptor is an sp2 O (i.e. for stronger IHBs). In some cases, IHBs that are not present in the uncomplexed conformers appear in the complex. The type and extent of the changes depend mainly on the site/s to which the Cu2+ ion binds and, to a less extent, also on the geometry features of the conformer. Some changes offer clear indications of weakening or strengthening of specific IHBs for specific binding sites of the ion.


Datum: 09.08.2019


Molecular structure, QTAIM and bonding character of cation–π interactions of mono- and divalent metal cations (Li + , Na + , K + , Be 2+ , Mg 2+ and Ca 2+ ) with drug of acetaminophen

Abstract

The molecular modeling analysis via density functional theory (DFT) calculations is performed on all the formed complexes from interaction between mono- and divalent metal cations (Li+, Na+, K+, Be2+, Mg2+ and Ca2+) with acetaminophen. The interaction energies are calculated by M06-2X method in the gas phase and the solution. The obtained structures are analyzed by topological parameters in terms of electron density (ρ) and its Laplacian (∇2ρ) at the bond critical point (BCP) using the atoms in molecules (AIM) methodology. The evaluated results from calculations suggest that the strongest interaction and the highest electron density at BCP are related to the Be2+ complex. In addition, the natural bond orbital (NBO) analysis is performed to investigate the charge distribution in the related complexes. The MEP (molecular electrostatic potential) is given the visual representation of the chemically active sites and comparative reactivity of atoms. Finally, the quantum molecular descriptors such as energy gap, electronic chemical potential, global hardness and electrophilicity index are calculated to evaluate the electronic properties, stability and reactivity of the analyzed complexes.


Datum: 08.08.2019


A DFT and TD-DFT study of ESIPT-mediated NLO switching and UV absorption by 2-(2′-hydroxy-5′-methylphenyl)benzotriazole

Abstract

Solvent effects on the excited-state intramolecular proton transfer (ESIPT) mechanism of 2-(2′-hydroxy-5′-methylphenyl)benzotriazole (HMPBT) on the one hand and ESIPT-switchable nonlinear optical (NLO) properties of HMPBT on the other hand, are theoretically investigated herein. The density functional theory and its time-dependent extension via global hybrid (PBE0) and range-separated (CAM-B3LYP and ωB97XD) functionals have been used along with the Karlsruhe basis sets: KTZVP and def2-TZVP. Results obtained from the quantum theory of atoms in molecules, geometric and infrared vibrational spectral analyses showed significant strengthening of HMPBT’s intramolecular hydrogen bond upon photo-induced excitation to the first excited state, which is indicative of the feasibility of ESIPT in the molecule. The results also revealed that HMPBT can undergo ESIPT in gas and solvent media, and that the process is apparently more favorable in the gas phase. Furthermore, HMPBT is found to exhibit large and reversible NLO contrasts due to remarkable and reversible changes in its first and second hyperpolarizabilities (static and dynamic). The hyperpolarizability changes are found to be related to keto–enol ESIPT-mediated interconversions. Interestingly, reversible changes in HMPBT’s NLO properties including: second-harmonic generation, electro-optical pockels effect and third-harmonic generation, are also observed. HMPBT is equally found to be a strong absorber of ultraviolet (UV) radiation in both the UVA and UVB regions of the electromagnetic spectrum, and to safely dissipate the absorbed energy in the visible and near-infrared regions via fluorescence. From our findings, HMPBT is a potent UV-absorber and a potential ESIPT-mediated NLO molecular switch.


Datum: 06.08.2019


The possibility of cadmium extraction to the ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate in the presence of hydrochloric acid: a molecular dynamics study of the water–IL interface

Abstract

Hydrophobic ionic liquids (ILs) can form biphasic systems with aqueous media and are appropriate candidates for liquid–liquid extraction (LLE). In this study, a biphasic system composed of water and the hydrophobic IL, 1-hexyl-3-methylimidazolium hexafluorophosphate, [HMIM][PF6] was studied using molecular dynamics (MD) simulation to understand the molecular-level distribution of the heavy metal cadmium ions, Cd2+, in the water–IL biphasic system in the presence of hydrochloric acid. The experimentally observed positive effect of adding chloride to the aqueous phase on the metal extraction was studied at the molecular scale. Particularly, the effect of hydrochloric acid addition on the solubility of the IL cations and anions in the water was investigated. It was found that with adding hydrochloric acid (1 M) to the water phase, the IL cation solubility in water decreased; however, the IL anion solubility almost did not change. This can affect the extraction process of the metal ions. Moreover, it was found that during the [CdCl4]2− migration to the IL phase, a gradual breaking of the hydrogen bonds occurs between the complex and the water molecules at the interface. Therefore, quantum mechanics (QM) calculations were performed to explain the interaction energies of the cadmium complex with water and the IL. The calculated interaction energy of the ternary complex of IL–[CdCl4]2−–H2O was found to be greater than that of the binary complexes of IL–[CdCl4]2− and H2O–[CdCl4]2−. The results obtained in this work give some insights into the behaviour of the IL-based extraction systems in contact with aqueous solutions containing salts or mineral acids.


Datum: 05.08.2019


 


Category: Current Chemistry Research

Last update: 11.04.2018.






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