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Silva R, Montes-Campos H, Lobo Ferreira AI, Bakis E, Santos LM. Thermodynamic Study of Alkylsilane and Alkylsiloxane-Based Ionic Liquids. J Phys Chem B 2024; 128:3742-3754. [PMID: 38573787 PMCID: PMC11033869 DOI: 10.1021/acs.jpcb.3c08333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 02/23/2024] [Accepted: 03/20/2024] [Indexed: 04/06/2024]
Abstract
The thermodynamic properties of ionic liquids (ILs) bearing alkylsilane and alkylsiloxane chains, as well as their carbon-based analogs, were investigated. Effects such as the replacement of carbon atoms by silicon atoms, the introduction of a siloxane linkage, and the length of the alkylsilane chain were explored. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the thermal and phase behavior (glass transition temperature, melting point, enthalpy and entropy of fusion, and thermal stability). Heat capacity was obtained by high-precision drop calorimetry and differential scanning microcalorimetry. The volatility and cohesive energy of these ILs were investigated via the Knudsen effusion method coupled with a quartz crystal microbalance (KEQCM). Gas phase energetics and structure were also studied to obtain the gas phase heat capacity as well as the energy profile associated with the rotation of the IL side chain. The computational study suggested the existence of an intramolecular interaction in the alkylsiloxane-based IL. The obtained glass transition temperatures seem to follow the trend of chain flexibility. An increase of the alkylsilane chain leads to a seemingly linear increase in molar heat capacity. A regular increment of 30 J·K-1·mol-1 in the molar heat capacity was found for the replacement of carbon by silicon in the IL alkyl chain. The alkylsilane series was revealed to be slightly more volatile than its carbon-based analogs. A further increase in volatility was found for the alkylsiloxane-based IL, which is likely related to the decrease of the cohesive energy due to the existence of an intramolecular interaction between the siloxane linkage and the imidazolium headgroup. The use of Si in the IL structure is a suitable way to significantly reduce the IL's viscosity while preserving its large liquid range (low melting point and high thermal stability) and low volatilities.
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Affiliation(s)
- Rodrigo
M.A. Silva
- CIQUP,
Institute of Molecular Sciences (IMS), Department of Chemistry and
Biochemistry, Faculty of Science, University
of Porto, Rua do Campo Alegre, Porto 4169-007, Portugal
| | - Hadrián Montes-Campos
- CIQUP,
Institute of Molecular Sciences (IMS), Department of Chemistry and
Biochemistry, Faculty of Science, University
of Porto, Rua do Campo Alegre, Porto 4169-007, Portugal
| | - Ana I.M.C. Lobo Ferreira
- CIQUP,
Institute of Molecular Sciences (IMS), Department of Chemistry and
Biochemistry, Faculty of Science, University
of Porto, Rua do Campo Alegre, Porto 4169-007, Portugal
| | - Eduards Bakis
- Faculty
of Chemistry, University of Latvia, Jelgavas 1, Riga LV-1004, Latvia
| | - Luís M.N.B.F. Santos
- CIQUP,
Institute of Molecular Sciences (IMS), Department of Chemistry and
Biochemistry, Faculty of Science, University
of Porto, Rua do Campo Alegre, Porto 4169-007, Portugal
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R de Moraes B, Paschoal VH, Keppeler N, El Seoud OA, Ando RA. The Coiling Effect in Ether Ionic Liquids: Exploiting Acetate as a Probe for Transport Properties and Microenvironment Analysis. J Phys Chem B 2024. [PMID: 38608137 DOI: 10.1021/acs.jpcb.3c08162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2024]
Abstract
The inherently high viscosity of ionic liquids (ILs) can limit their potential applications. One approach to address this drawback is to modify the cation side chain with ether groups. Herein, we assessed the structure-property relationship by focusing on acetate (OAc), a strongly coordinating anion, with 1,3-dialkylimidazolium cations with different side chains, including alkyl, ether, and hydroxyl functionalized, as well as their combinations. We evaluated their viscosity, thermal stabilities, and microstructure using Raman and infrared (IR) spectroscopies, allied to density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. The viscosity data showed that the ether insertion significantly enhances the fluidity of the ILs, consistent with the coiling effect of the cation chain. Through a combined experimental and theoretical approach, we analyzed how the OAc anion interacts with ether ILs, revealing a characteristic bidentate coordination, particularly in hydroxyl functionalized ILs due to specific hydrogen bonding with the OH group. IR spectroscopy showed subtle shifts in the acidic hydrogens of imidazolium ring C(2)-H and C(4,5)-H, suggesting weaker interactions between OAc and the imidazolium ring in ether-functionalized ILs. Additionally, spatial distribution functions (SDF) and dihedral angle distribution obtained via AIMD confirmed the intramolecular hydrogen bonding due to the coiling effect of the ether side chain.
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Affiliation(s)
- Beatriz R de Moraes
- Laboratório de Espectroscopia Molecular, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo 05508-900, Brazil
| | - Vitor H Paschoal
- Laboratório de Espectroscopia Molecular, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo 05508-900, Brazil
| | - Nicolas Keppeler
- Grupo de polímero e surfactantes, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo 05508-900, Brazil
| | - Omar A El Seoud
- Grupo de polímero e surfactantes, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo 05508-900, Brazil
| | - Rômulo A Ando
- Laboratório de Espectroscopia Molecular, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo 05508-900, Brazil
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3
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Goloviznina K, Bakis E, Philippi F, Scaglione N, Rekis T, Laimina L, Costa Gomes M, Padua A. Attraction between Like Charged Ions in Ionic Liquids: Unveiling the Enigma of Tetracyanoborate Anions. J Phys Chem Lett 2024; 15:248-253. [PMID: 38165169 DOI: 10.1021/acs.jpclett.3c02983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
Intermolecular interactions in ionic liquids are mainly governed by Coulombic forces. Attraction between cations has been previously observed and was attributed to dispersion interactions between nonpolar moieties, hydrogen bonding, or π stacking. In this study, we present the intriguing behavior of tetracyanoborate anions in ionic liquids that, unlike their dicyanamide and tricyanomethanide counterparts, form dimers in both solid and liquid phases. A joint simulation and experimental study uncovers the origin of such anion-anion attraction: stabilization by induction and dispersion forces between several cyano groups, which is strong enough to overcome electrostatic repulsion. These findings open up new opportunities in the rational design of ionic liquids, where interactions between ions of the same charge can be controlled and fine-tuned by the presence of cyano groups.
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Affiliation(s)
- Kateryna Goloviznina
- Physicochimie des Électrolytes et Nanosystèmes Interfaciaux (PHENIX), Sorbonne Université and CNRS, F-75005 Paris, France
| | - Eduards Bakis
- Faculty of Chemistry, University of Latvia, Jelgavas 1, Riga LV-1001, Latvia
| | - Frederik Philippi
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 0BZ, United Kingdom
| | - Nicolas Scaglione
- Laboratoire de Chimie, Ecole Normale Superieure de Lyon and CNRS, F-69364 Lyon, France
| | - Toms Rekis
- Faculty of Chemistry, University of Latvia, Jelgavas 1, Riga LV-1001, Latvia
| | - Laura Laimina
- Faculty of Chemistry, University of Latvia, Jelgavas 1, Riga LV-1001, Latvia
| | - Margarida Costa Gomes
- Laboratoire de Chimie, Ecole Normale Superieure de Lyon and CNRS, F-69364 Lyon, France
| | - Agilio Padua
- Laboratoire de Chimie, Ecole Normale Superieure de Lyon and CNRS, F-69364 Lyon, France
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4
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Sloboda D, Weber CC, Bakis E. A kinetics study of copper-catalysed click reactions in ionic liquids. Org Biomol Chem 2023; 21:7984-7993. [PMID: 37755136 DOI: 10.1039/d3ob00237c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/28/2023]
Abstract
Copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions are of extensive interest in chemical synthesis. While the use of ionic liquids (ILs) as solvents for synthesis has been widely explored in recent years, the understanding of their influence on the mechanism and reactivity of CuAAC reactions remains poorly understood. Here, we investigate the kinetics of a phenylacetylene-benzylazide and acetylene-benzylazide CuAAC reaction to probe the influence of IL structure, including the role of the base used to promote the reaction and the importance of water content. The use of 'wet' ILs led to remarkable changes in the kinetic profile of the reaction by eliminating the initial induction period. The reaction rate was found to be dependent on the copper(I) source. The effect of an added base was also studied, with the use of a tertiary amine-bearing IL leading to high conversions in under 5 min at ambient temperature. The results of this study highlight the nature and complexity of CuAAC reactions in ILs. As more ILs are getting involved in industrial processes, the data obtained from this study are valuable for better understanding processes that affect the CuAAC reaction in IL media and for creating customized systems for organic synthesis, thus improving the efficiency and sustainability of such processes.
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Affiliation(s)
- Diana Sloboda
- Faculty of Chemistry, University of Latvia, Jelgavas 1, Riga, LV-1004, Latvia.
| | - Cameron C Weber
- School of Chemical Sciences, University of Auckland, 23 Symonds St, Auckland, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand
| | - Eduards Bakis
- Faculty of Chemistry, University of Latvia, Jelgavas 1, Riga, LV-1004, Latvia.
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