Exploring Solvation Properties of Protic Ionic Liquids by Employing Solvatochromic Dyes and Molecular Dynamics Simulation Analysis
Solvation properties are key for understanding the interactions between solvents and solutes, making them critical for optimizing chemical synthesis and biochemical applications. Designable solvents for targeted optimization of these end-uses could, therefore, play a big role in the future of the re...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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MDPI AG
2024-03-01
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| Series: | Liquids |
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| Online Access: | https://www.mdpi.com/2673-8015/4/1/14 |
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| author | Stuart J. Brown Andrew J. Christofferson Calum J. Drummond Qi Han Tamar L. Greaves |
| author_facet | Stuart J. Brown Andrew J. Christofferson Calum J. Drummond Qi Han Tamar L. Greaves |
| author_sort | Stuart J. Brown |
| collection | DOAJ |
| description | Solvation properties are key for understanding the interactions between solvents and solutes, making them critical for optimizing chemical synthesis and biochemical applications. Designable solvents for targeted optimization of these end-uses could, therefore, play a big role in the future of the relevant industries. The tailorable nature of protic ionic liquids (PILs) as designable solvents makes them ideal candidates. By alteration of their constituent structural groups, their solvation properties can be tuned as required. The solvation properties are determined by the polar and non-polar interactions of the PIL, but they remain relatively unknown for PILs as compared to aprotic ILs and their characterization is non-trivial. Here, we use solvatochromic dyes as probe molecules to investigate the solvation properties of nine previously uncharacterized alkyl- and dialkylammonium PILs. These properties include the Kamlet–Aboud–Taft (KAT) parameters: π* (dipolarity/polarizability), α (H-bond acidity) and β (H-bond basicity), along with the E<sub>T</sub>(30) scale (electrophilicity/polarizability). We then used molecular dynamics simulations to calculate the radial distribution functions (RDF) of 21 PILs, which were correlated to their solvation properties and liquid nanostructure. It was identified that the hydroxyl groups on the PIL cation increase α, π* and E<sub>T</sub>(30), and correspondingly increase the cation–anion distance in their RDF plots. The hydroxyl group, therefore, reduces the strength of the ionic interaction but increases the polarizability of the ions. An increase in the alkyl chain length on the cation led to a decrease in the distances between cations, while also increasing the β value. The effect of the anion on the PIL solvation properties was found to be variable, with the nitrate anion greatly increasing π*, α and anion–anion distances. The research presented herein advances the understanding of PIL structure–property relationships while also showcasing the complimentary use of molecular dynamics simulations and solvatochromic analysis together. |
| first_indexed | 2024-04-24T18:04:54Z |
| format | Article |
| id | doaj.art-7d7aa90746154e98b78adc18d5c21b06 |
| institution | Directory Open Access Journal |
| issn | 2673-8015 |
| language | English |
| last_indexed | 2024-04-24T18:04:54Z |
| publishDate | 2024-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Liquids |
| spelling | doaj.art-7d7aa90746154e98b78adc18d5c21b062024-03-27T13:51:29ZengMDPI AGLiquids2673-80152024-03-014128830410.3390/liquids4010014Exploring Solvation Properties of Protic Ionic Liquids by Employing Solvatochromic Dyes and Molecular Dynamics Simulation AnalysisStuart J. Brown0Andrew J. Christofferson1Calum J. Drummond2Qi Han3Tamar L. Greaves4School of Science, STEM College, RMIT University, Melbourne, VIC 3000, AustraliaSchool of Science, STEM College, RMIT University, Melbourne, VIC 3000, AustraliaSchool of Science, STEM College, RMIT University, Melbourne, VIC 3000, AustraliaSchool of Science, STEM College, RMIT University, Melbourne, VIC 3000, AustraliaSchool of Science, STEM College, RMIT University, Melbourne, VIC 3000, AustraliaSolvation properties are key for understanding the interactions between solvents and solutes, making them critical for optimizing chemical synthesis and biochemical applications. Designable solvents for targeted optimization of these end-uses could, therefore, play a big role in the future of the relevant industries. The tailorable nature of protic ionic liquids (PILs) as designable solvents makes them ideal candidates. By alteration of their constituent structural groups, their solvation properties can be tuned as required. The solvation properties are determined by the polar and non-polar interactions of the PIL, but they remain relatively unknown for PILs as compared to aprotic ILs and their characterization is non-trivial. Here, we use solvatochromic dyes as probe molecules to investigate the solvation properties of nine previously uncharacterized alkyl- and dialkylammonium PILs. These properties include the Kamlet–Aboud–Taft (KAT) parameters: π* (dipolarity/polarizability), α (H-bond acidity) and β (H-bond basicity), along with the E<sub>T</sub>(30) scale (electrophilicity/polarizability). We then used molecular dynamics simulations to calculate the radial distribution functions (RDF) of 21 PILs, which were correlated to their solvation properties and liquid nanostructure. It was identified that the hydroxyl groups on the PIL cation increase α, π* and E<sub>T</sub>(30), and correspondingly increase the cation–anion distance in their RDF plots. The hydroxyl group, therefore, reduces the strength of the ionic interaction but increases the polarizability of the ions. An increase in the alkyl chain length on the cation led to a decrease in the distances between cations, while also increasing the β value. The effect of the anion on the PIL solvation properties was found to be variable, with the nitrate anion greatly increasing π*, α and anion–anion distances. The research presented herein advances the understanding of PIL structure–property relationships while also showcasing the complimentary use of molecular dynamics simulations and solvatochromic analysis together.https://www.mdpi.com/2673-8015/4/1/14ionic liquidsprotic ionic liquidsKATmolecular dynamicssolvation |
| spellingShingle | Stuart J. Brown Andrew J. Christofferson Calum J. Drummond Qi Han Tamar L. Greaves Exploring Solvation Properties of Protic Ionic Liquids by Employing Solvatochromic Dyes and Molecular Dynamics Simulation Analysis Liquids ionic liquids protic ionic liquids KAT molecular dynamics solvation |
| title | Exploring Solvation Properties of Protic Ionic Liquids by Employing Solvatochromic Dyes and Molecular Dynamics Simulation Analysis |
| title_full | Exploring Solvation Properties of Protic Ionic Liquids by Employing Solvatochromic Dyes and Molecular Dynamics Simulation Analysis |
| title_fullStr | Exploring Solvation Properties of Protic Ionic Liquids by Employing Solvatochromic Dyes and Molecular Dynamics Simulation Analysis |
| title_full_unstemmed | Exploring Solvation Properties of Protic Ionic Liquids by Employing Solvatochromic Dyes and Molecular Dynamics Simulation Analysis |
| title_short | Exploring Solvation Properties of Protic Ionic Liquids by Employing Solvatochromic Dyes and Molecular Dynamics Simulation Analysis |
| title_sort | exploring solvation properties of protic ionic liquids by employing solvatochromic dyes and molecular dynamics simulation analysis |
| topic | ionic liquids protic ionic liquids KAT molecular dynamics solvation |
| url | https://www.mdpi.com/2673-8015/4/1/14 |
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