| 1. |
- Rusanova, Daniela, et al.
(författare)
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Copper(I) O,O '-dialkyldithiophosphate clusters : EXAFS, NMR and X-ray diffraction studies
- 2007
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Ingår i: Journal of coordination chemistry (Print). - : Informa UK Limited. - 0095-8972 .- 1029-0389. ; 60:5, s. 517-525
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Tidskriftsartikel (refereegranskat)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. |
- Filippov, Andrei, et al.
(författare)
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Dynamics and Structure of a Bitumen Emulsion as Studied by 1H NMR Diffusometry
- 2023
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Ingår i: ACS Omega. - : Amer Chemical Soc. - 2470-1343. ; 8:39, s. 36534-36542
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Tidskriftsartikel (refereegranskat)abstract
- Self-diffusion in a bitumen emulsion was studied by H-1 NMR. The emulsion forms two phases: continuous and dispersed. The continuous aqueous phase contains mainly water, with the energy of activation of the diffusion process equal to that of bulk water, while its diffusivity is smaller than that of bulk water by a factor of 2. The dispersed phase consists of bitumen droplets containing confined water, whose dynamics is characterized by a fully restricted diffusion regime in cavities with sizes of similar to 0.11 mu m. Therefore, the studied bitumen emulsion can be described by a model of a complex multiple emulsion of the water/oil/water (WOW) type. The suggested model does agree well with data from H-1 NMR spectroscopy and diffusometry of the bitumen emulsion doped with paramagnetic MnSO4(aq) as well as with an additional H-1 NMR study of the emulsion structure, in which emulsion stability was compromised by freezing at 253 K.
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| 3. |
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| 4. |
- Filippov, Andrei, et al.
(författare)
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Dynamic Properties of Imidazolium Orthoborate Ionic Liquids Mixed with Polyethylene Glycol Studied by NMR Diffusometry and Impedance Spectroscopy
- 2018
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Ingår i: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X. ; 56:2, s. 113-119
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Tidskriftsartikel (refereegranskat)abstract
- We used 1H pulsed field gradient (PFG) NMR to study the self-diffusion of polyethylene glycol (PEG) with average molecular mass of 200 and ions in mixtures of PEG with imidazolium bis(mandelato)borate (BMB) and imidazolium bis(oxalato)borate (BOB) ionic liquids (ILs). The ionic liquid was mixed with PEG in the concentration range of 0–100 wt%. Within the temperature range of 295 to 353 K, the diffusion coefficient of BMB is slower than that of the imidazolium cation. The diffusion coefficients of PEG, as well as the imidazolium cation and BMB anions, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state. Generally, increasing the concentration of PEG leads to an increase in the diffusion coefficients of PEG and both the ions, and decreases their activation energy for diffusion. NMR chemical shift alteration analysis showed that the presence of PEG changes the chemical shifts of both ions but in different directions. Impedance spectroscopy was used to measure the ionic conductivity of the ionic liquids mixed with PEG.
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| 5. |
- Filippov, Andrei, PhD, 1957-, et al.
(författare)
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Rapid carbene formation increasing ion diffusivity in an imidazolium acetate ionic liquid confined between polar glass plates
- 2019
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 21:40, s. 22531-22538
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Tidskriftsartikel (refereegranskat)abstract
- 1-Ethyl-3-methyl-imidazolium acetate ([EMIM][OAc]) is one of the most widely used ionic liquids for various applications. This study is focussed on the chemical stability of [EMIM][OAc] on the surfaces of polar glass plates. 1H and 13C NMR spectroscopy and NMR diffusometry of [EMIM][OAc] IL confined between glass plates with a specific surface area 105–106 m−1 are thoroughly investigated. A rapid and spontaneous reaction took place on the surfaces of glass plates leading to the formation of neutral chemical moieties as evident by the appearance of new signals in the 1H NMR spectra. These new products are assigned as N-heterocyclic carbene (NHC) and acetic acid. These neutral chemical moieties have significantly increased the ion diffusivity by dissociation of the cation and the anion in [EMIM][OAc] IL. The yield and rate of formation of NHC and acetic acid are found to increase with the increasing surface area of polar glass plates and the time of contact between the IL and glass surfaces. Based on NMR spectroscopy, a dissociative reaction mechanism is proposed for the formation of free NHC in the neat [EMIM][OAc] IL.
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| 6. |
- Golets, M., et al.
(författare)
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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
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 18, s. 22458-22466
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Tidskriftsartikel (refereegranskat)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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| 7. |
- Trublet, Mylene
(författare)
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Titanium(IV) Phosphates : The Next Generation of Wastewater Sorbents
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Treatment of industrial waters containing heavy metal ions is essential before being discharged into the environment. Consequently, European regulations have been established to control and limit the amount of heavy metals released. There is a need to develop efficient water treatment techniques that can remove contaminants with respect to these EU regulations.Ion-exchange is one of the processes that is being investigated due to fast kinetics, high treatment capacity and its ability to remove heavy metal ions present in trace amounts. Titanium phosphates (TiP) are a group of inorganic ion-exchangers that have demonstrated to be particularly selective towards transition metal ions in aqueous solutions. Two types of ion-exchange units are present in TiP material, which are –HPO4 and –H2PO4 groups. Their structural characteristic is highly dependent on the synthesis conditions, which include the source of titanium, temperature, reaction time and P2O5:TiO2 ratio. Most of the studies have been performed on amorphous TiP containing a mixture of both exchange units, with –HPO4 groups being predominant; as crystalline TiP and –H2PO4 based TiP are often obtained in difficult conditions, high temperature (up to 250 °C) and/or long reaction time (up to 30 days) and/or using autoclave. Despite promising properties depicted in batch conditions, very few data in continuous flow systems (fixed-bed columns) have been reported.In this work, amorphous TiP composed of entirely –H2PO4 ion-exchange units (TiP1) was synthesized at mild conditions using a TiOSO4 solution and HCl/deionized water as post-synthesis treatments. The sorbent was characterized using a range of techniques (solid-state 31P MAS NMR, Raman, XRD, TGA, BET, Elemental analysis, EXAFS and XANES,) and tested in batch and column set-ups towards single and multi-component waters. The chemical formula of TiP1 was established as TiO(OH)(H2PO4)·H2O and it was found that the synthesis of TiP1 was also dependent on the TiO2/H2SO4 content in the primary titanium solution.The material displayed a high maximum exchange capacity of ca. 6.4 meq.g-1, expressed as the sodium uptake. The actual ion-exchange capacity towards divalent metal ions was calculated to be ca. 3.4 meq.g-1 in batch condition and up to 4.1 meq.g-1 in fixed-bed column, which is to date the highest recorded for TiP materials. Kinetics of the exchange processes have been studied and the equilibrium was reached within 5-20 minutes. Modeling of the breakthrough curves was achieved using the Thomas model, indicating that the rate driving forces of the processes follow second-order reversible kinetics. The TiP1 sorbent has shown to maintain a high selectivity towards heavy metal ions in multi-component systems (including closed-mine waters) when column studies were performed. The sorption behavior of TiP1 in batch experiments correlates very well with data obtained in fixed-bed column conditions, confirming that prediction of the sorption behavior on the basis of batch data is conceivable.Another important aspect of this work also involves the mild syntheses of crystalline α-TiP, Ti(HPO4)·H2O, and LTP (Linked Titanium Phosphate) composed of α-TiP and TiP1, where the structural characteristics of these materials were investigated using solid-state NMR, XRD, TGA, EXAFS and XANES.
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| 8. |
- Wang, Yonglei, et al.
(författare)
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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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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 120:30, s. 7446-7455
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Wang, Yong-Lei, et al.
(författare)
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Solvation structures of water in trihexyltetradecylphosphonium-orthoborate ionic liquids
- 2016
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 145:6
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Tidskriftsartikel (refereegranskat)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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| 10. |
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