| 1. |
- Rusanova, Daniela, et al.
(author)
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Copper(I) O,O '-dialkyldithiophosphate clusters : EXAFS, NMR and X-ray diffraction studies
- 2007
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In: Journal of coordination chemistry (Print). - : Informa UK Limited. - 0095-8972 .- 1029-0389. ; 60:5, s. 517-525
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Journal article (peer-reviewed)abstract
- Copper K- edge EXAFS data for six polycrystalline cubic cluster compounds, {Cu-8[ S2P(OR)(2)](6)(mu(8)- S)} with R= Et, Pr-n, Pr-i, Bu-n, Bu-i and Am-i, show that the architecture of their Cu-8(S2P)(2)S cores is fairly rigid and independent of both length and branching of the alkyl chain, and that the structure of the cluster is maintained in acetone solution. Solid- state P-31 CP-MAS and static Cu-65 NMR data for {Cu-8[S2P(O-n Pr)(2)] 6(mu(8)- S)} and {Cu-8[S2P(OEt)(2)](6) mu(8)- S)} show similarities in the icosahedral O,O'- dialkyldithiophosphate shells and in the `cubic' copper cores in these cluster compounds. The crystal structure of {Cu-8[S2P(O-n Pr)(2)](6) (mu(8)- S)} was resolved using single- crystal X- ray diffraction.
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| 2. |
- Golets, M., et al.
(author)
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Understanding the thermal decomposition mechanism of a halogen-free chelated orthoborate-based ionic liquid : a combined computational and experimental study
- 2016
-
In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 18, s. 22458-22466
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Journal article (peer-reviewed)abstract
- In the last few decades, ionic liquids (ILs) have gained significant attention as lubricants and lubricant additives due to their polar nature, low vapour pressure and tunable physicochemical properties. In this work, quantum chemistry calculations and atomistic Molecular Dynamics (MD) simulations were employed to predict thermal degradation mechanisms of a potential lubricating agent - the tributyloctylphosphonium bis(oxalato)borate ([P4,4,4,8][BOB]) IL. It was found that the onset of decomposition of the studied IL coincides with a cleavage of the B-O bonds in the [BOB](-) anion. Consequently, a series of chemical reactions of the [P4,4,4,8](+) cation with the [BOB](-) anion was triggered yielding alkylboranes, alkenes, trialkylphosphines, CO and CO2. Another ionic system, consisting of [P4,4,4,8][Cl], was also tested for a comparison. Thermogravimetric measurements have shown a higher thermal stability of [P4,4,4,8][BOB] compared to that of [P4,4,4,8][Cl] at least at the initial stage of decomposition, in accord with the presented calculations. Quantum chemical frequency calculations also agreed with the experimental Fourier Transform Infrared (FTIR) spectroscopy results.
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| 3. |
- Wang, Yonglei, et al.
(author)
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Atomistic insight into tetraalkylphosphonium-bis(oxalato)borate ionic liquid/water mixtures : 2. Volumetric and Dynamic Properties
- 2016
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In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 120:30, s. 7446-7455
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Journal article (peer-reviewed)abstract
- Atomistic simulations have been performed to investigate the microscopic structural organization of aqueous solutions of trihexyltetradecylphosphonium bis(oxalato)borate ([P6,6,6,14][BOB]) ionic liquid (IL). The evolution of the microscopic liquid structure and the local ionic organization of IL/water mixtures as a function of the water concentration is visualized and systematically analyzed via radial and spatial distribution functions, coordination numbers, hydrogen bond network, and water clustering analysis. The microscopic liquid structure in neat IL is characterized by a connected apolar network composed of the alkyl chains of [P6,6,6,14] cations and isolated polar domains consisting of the central segments of [P6,6,6,14] cations and [BOB] anions, and the corresponding local ionic environment is described by direct contact ion pairs. In IL/water mixtures with lower water mole fractions, the added water molecules are dispersed and embedded in cavities between neighboring ionic species and the local ionic structure is characterized by solvent-shared ion pairs through cation-water-anion triple complexes. With a gradual increase in the water concentration in IL/water mixtures, the added water molecules tend to aggregate and form small clusters, intermediate chain-like structures, large aggregates, and eventually a water network in water concentrated simulation systems. A further progressive dilution of IL/water mixtures leads to the formation of self-organized micelle-like aggregates characterized by a hydrophobic core and hydrophilic shell consisting of the central polar segments in [P6,6,6,14] cations and [BOB] anions in a highly branched water network. The striking structural evolution of the [P6,6,6,14][BOB] IL/water mixtures is rationalized by the competition between favorable hydrogen bonded interactions and strong electrostatic interactions between the polar segments in ionic species and the dispersion interactions between the hydrophobic alkyl chains in [P6,6,6,14] cations
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| 4. |
- Wang, Yong-Lei, et al.
(author)
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Solvation structures of water in trihexyltetradecylphosphonium-orthoborate ionic liquids
- 2016
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In: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 145:6
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Journal article (peer-reviewed)abstract
- Atomistic molecular dynamics simulations have been performed to investigate effective interactions of isolated water molecules dispersed in trihexyltetradecylphosphonium-orthoborate ionic liquids (ILs). The intrinsic free energy changes in solvating one water molecule from gas phase into bulk IL matrices were estimated as a function of temperature, and thereafter, the calculations of potential of mean force between two dispersed water molecules within different IL matrices were performed using umbrella sampling simulations. The systematic analyses of local ionic microstructures, orientational preferences, probability and spatial distributions of dispersed water molecules around neighboring ionic species indicate their preferential coordinations to central polar segments in orthoborate anions. The effective interactions between two dispersed water molecules are partially or totally screened as their separation distance increases due to interference of ionic species in between. These computational results connect microscopic anionic structures with macroscopically and experimentally observed difficulty in completely removing water from synthesized IL samples and suggest that the introduction of hydrophobic groups to central polar segments and the formation of conjugated ionic structures in orthoborate anions can effectively reduce residual water content in the corresponding IL samples
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| 5. |
- Wang, Yong-Lei, et al.
(author)
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Atomistic insight into tetraalkylphosphonium-bis(oxalato)borate ionic liquid/water mixtures. I. Local microscopic structure
- 2015
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In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 119:16, s. 5251-5264
-
Journal article (peer-reviewed)abstract
- Atomistic simulations have been performed to investigate the microscopic structural organization of aqueous solutions of trihexyltetradecylphosphonium bis(oxalato)borate ([P6,6,6,14][BOB]) ionic liquid (IL). The evolution of the microscopic liquid structure and the local ionic organization of IL/water mixtures as a function of the water concentration is visualized and systematically analyzed via radial and spatial distribution functions, coordination numbers, hydrogen bond network, and water clustering analysis. The microscopic liquid structure in neat IL is characterized by a connected apolar network composed of the alkyl chains of [P6,6,6,14] cations and isolated polar domains consisting of the central segments of [P6,6,6,14] cations and [BOB] anions, and the corresponding local ionic environment is described by direct contact ion pairs. In IL/water mixtures with lower water mole fractions, the added water molecules are dispersed and embedded in cavities between neighboring ionic species and the local ionic structure is characterized by solvent-shared ion pairs through cation-water-anion triple complexes. With a gradual increase in the water concentration in IL/water mixtures, the added water molecules tend to aggregate and form small clusters, intermediate chain-like structures, large aggregates, and eventually a water network in water concentrated simulation systems. A further progressive dilution of IL/water mixtures leads to the formation of self-organized micelle-like aggregates characterized by a hydrophobic core and hydrophilic shell consisting of the central polar segments in [P6,6,6,14] cations and [BOB] anions in a highly branched water network. The striking structural evolution of the [P6,6,6,14][BOB] IL/water mixtures is rationalized by the competition between favorable hydrogen bonded interactions and strong electrostatic interactions between the polar segments in ionic species and the dispersion interactions between the hydrophobic alkyl chains in [P6,6,6,14] cations.
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| 6. |
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| 7. |
- Farzaneh, Amirfarrokh, et al.
(author)
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Adsorption of Butanol and Water Vapors in Silicalite‑1 Films with a Low Defect Density
- 2016
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 32, s. 11789-11798
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Journal article (peer-reviewed)abstract
- Pure silica zeolites are potentially hydrophobic and have therefore been considered to be interesting candidates for separating alcohols, e.g., 1-butanol, from water. Zeolites are traditionally synthesized at high pH, leading to the formation of intracrystalline defects in the form of silanol defects in the framework. These silanol groups introduce polar adsorption sites into the framework, potentially reducing the adsorption selectivity toward alcohols in alcohol/water mixtures. In contrast, zeolites prepared at neutral pH using the fluoride route contain significantly fewer defects. Such crystals should show a much higher butanol/water selectivity than crystals prepared in traditional hydroxide (OH−) media. Moreover, silanol groups are present at the external surface of the zeolite crystals; therefore, minimizing the external surface of the studied adsorbent is important. In this work, we determine adsorption isotherms of 1-butanol and water in silicalite-1 films prepared in a fluoride (F−) medium using in situ attenuated total reflectance−Fourier transform infrared (ATR−FTIR) spectroscopy. This film was composed of well intergrown, plate-shaped b-oriented crystals, resulting in a low external area. Single-component adsorption isotherms of 1-butanol and water were determined in the temperature range of 35− 80 °C. The 1-butanol isotherms were typical for an adsorbate showing a high affinity for a microporous material and a large increase in the amount adsorbed at low partial pressures of 1-butanol. The Langmuir−Freundlich model was successfully fitted to the 1-butanol isotherms, and the heat of adsorption was determined. Water showed a very low affinity for the adsorbent, and the amounts adsorbed were very similar to previous reports for large silicalite-1 crystals prepared in a fluoride medium. The sample also adsorbed much less water than did a reference silicalite-1(OH−) film containing a high density of internal defects.The results show that silicalite-1 films prepared in a F− medium with a low density of defects and external area are very promising for the selective recovery of 1-butanol from aqueous solutions.
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| 8. |
- Hammond, Oliver S., et al.
(author)
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Molecular Architecture Effects on Bulk Nanostructure in Bis(Orthoborate) Ionic Liquids
- 2023
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In: Small. - : John Wiley and Sons Inc. - 1613-6810 .- 1613-6829.
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Journal article (peer-reviewed)abstract
- A series of 19 ionic liquids (ILs) based on phosphonium and imidazolium cations of varying alkyl-chain lengths with the orthoborate anions bis(oxalato)borate [BOB]−, bis(mandelato)borate, [BMB]− and bis(salicylato)borate, [BScB]−, are synthesized and studied using small-angle neutron scattering (SANS). All measured systems display nanostructuring, with 1-methyl-3-n-alkyl imidazolium-orthoborates forming clearly bicontinuous L3 spongelike phases when the alkyl chains are longer than C6 (hexyl). L3 phases are fitted using the Teubner and Strey model, and diffusely-nanostructured systems are primarily fitted using the Ornstein-Zernicke correlation length model. Strongly-nanostructured systems have a strong dependence on the cation, with molecular architecture variation explored to determine the driving forces for self-assembly. The ability to form well-defined complex phases is effectively extinguished in several ways: methylation of the most acidic imidazolium ring proton, replacing the imidazolium 3-methyl group with a longer hydrocarbon chain, substitution of [BOB]− by [BMB]−, or exchanging the imidazolium for phosphonium systems, irrespective of phosphonium architecture. The results suggest there is only a small window of opportunity, in terms of molecular amphiphilicity and cation:anion volume matching, for the formation of stable extensive bicontinuous domains in pure bulk orthoborate-based ILs. Particularly important for self-assembly processes appear to be the ability to form H-bonding networks, which offer additional versatility in imidazolium systems. © 2023 The Authors.
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| 9. |
- Wang, Yong-Lei, et al.
(author)
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Atomistic Insight into Orthoborate-Based Ionic Liquids : Force Field Development and Evaluation
- 2014
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In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 118:29, s. 8711-8723
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Journal article (peer-reviewed)abstract
- We have developed an all-atomistic force field for a new class of halogen-free chelated orthoborate-phosphonium ionic liquids. The force field is based on an AMBER framework with determination of force field parameters for phosphorus and boron atoms, as well as refinement of several available parameters. The bond and angle force constants were adjusted to fit vibration frequency data derived from both experimental measurements and ab initio calculations. The force field parameters for several dihedral angles were obtained by fitting torsion energy profiles deduced from ab initio calculations. To validate the proposed force field parameters, atomistic simulations were performed for 12 ionic liquids consisting of tetraalkylphosphonium cations and chelated orthoborate anions. The predicted densities for neat ionic liquids and the [P-6,P-6,P-6,P-14][BOB] sample, with a water content of approximately 2.3-2.5 wt %, are in excellent agreement with available experimental data. The potential energy components of 12 ionic liquids were discussed in detail. The radial distribution functions and spatial distribution functions were analyzed and visualized to probe the microscopic ionic structures of these ionic liquids. There are mainly four high-probability regions of chelated orthoborate anions distributed around tetraalkylphosphonium cations in the first solvation shell, and such probability distribution functions are strongly influenced by the size of anions.
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