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Yeboah J, Metott ZJ, Butch CM, Hillesheim PC, Mirjafari A. Are nature's strategies the solutions to the rational design of low-melting, lipophilic ionic liquids? Chem Commun (Camb) 2024; 60:3891-3909. [PMID: 38420843 PMCID: PMC10994746 DOI: 10.1039/d3cc06066g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2024]
Abstract
Ionic liquids (ILs) have emerged as a new class of materials, displaying a unique capability to self-assemble into micelles, liposomes, liquid crystals, and microemulsions. Despite evident interest, advancements in the controlled formation of amphiphilic ILs remain in the early stages. Taking inspiration from nature, we introduced the concept of lipid-like (or lipid-inspired) ILs more than a decade ago, aiming to create very low-melting, highly lipophilic ILs that are potentially bio-innocuous - a combination of attributes that is frequently antithetical but highly desirable from several application-specific standpoints. Lipid-like ILs are a subclass of functional organic liquid salts that include a range of lipidic side chains such as saturated, unsaturated, linear, branched, and thioether while retaining melting points below room temperature. It was observed in several homologous series of [Cnmim] ILs that elongation of N-appended alkyl chains to greater than seven carbons leads to a substantial increase in melting point (Tm) - which is the most characteristic feature of ILs. Accordingly, it is challenging to develop ILs with low Tm values while preserving their hydrophobicity and self-organizing properties. We found that two alternative Tm depressive approaches are useful. One of these is the replacement of the double bonds with thioether moieties in the alkyl chains, as detailed in several published papers detailing the chemistry of these ILs. Employing thiol-ene and thiol-yne click reactions is a facile, robust, and orthogonal method to overcome the challenges associated with the synthesis of alkyl thioether-functionalized ILs. The second approach involves replacing the double bonds with the cisoid cyclopropyl motif, mimicking the strategy used by certain organisms to modulate cell membrane fluidity. This discovery has the potential to greatly impact the utilization of lipid-like ILs in various applications, including gene delivery, lubricants, heat transfer fluids, and haloalkane separations, among others. This feature article presents a concise, historical overview, highlighting key findings from our work while offering speculation about the future trajectory of this de novo class of soft organic-ion materials.
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Affiliation(s)
- John Yeboah
- Department of Chemistry, State University of New York at Oswego, Oswego, New York 13126, USA.
| | - Zachary J Metott
- Department of Chemistry, State University of New York at Oswego, Oswego, New York 13126, USA.
| | - Christopher M Butch
- Department of Chemistry, State University of New York at Oswego, Oswego, New York 13126, USA.
| | - Patrick C Hillesheim
- Department of Chemistry and Physics, Ave Maria University, Ave Maria, Florida, 34142, USA.
| | - Arsalan Mirjafari
- Department of Chemistry, State University of New York at Oswego, Oswego, New York 13126, USA.
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O'Brien RA, Hillesheim PC, Soltani M, Badilla-Nunez KJ, Siu B, Musozoda M, West KN, Davis JH, Mirjafari A. Cyclopropane as an Unsaturation "Effect Isostere": Lowering the Melting Points in Lipid-like Ionic Liquids. J Phys Chem B 2023; 127:1429-1442. [PMID: 36745872 DOI: 10.1021/acs.jpcb.2c07872] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The replacement of unsaturation with a cyclopropane motif as a (bio)isostere is a widespread strategy in bacteria to tune the fluidity of lipid bilayers and protect membranes when exposed to adverse environmental conditions, e.g., high temperature, low pH, etc. Inspired by this phenomenon, we herein address the relative effect of the cyclopropanation, both cis and trans configurations, on melting points, packing efficiency, and order of a series of lipid-like ionic liquids via a combination of thermophysical analysis, X-ray crystallography, and computational modeling. The data indicate there is considerable structural latitude possible when designing highly lipophilic ionic liquids that exhibit low melting points. While cyclopropanation of the lipid-like ionic liquids provides more resistance to aerobic degradation than their olefin analogs, the impact on the melting point decrease is not as pronounced. Our results demonstrate that incorporating one or more cyclopropyl moieties in long aliphatic chains of imidazolium-based ionic liquids is highly effective in lowering the melting points of such materials relative to their counterparts bearing linear, saturated, or thioether side chains. It is shown that the cyclopropane moiety effectively disrupts packing, favoring formation of gauche conformer in the side chains, resulting in enhancement of fluidity. This was irrespective of the configuration of the methylene bridge, although marked differences in the effect of cis- and trans-monocyclopropanated ILs on the melting points were observed.
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Affiliation(s)
- Richard A O'Brien
- Department of Chemistry, The University of South Alabama, Mobile, Alabama 36688, United States
| | - Patrick C Hillesheim
- Department of Chemistry and Physics, Ave Maria University, Ave Maria, Florida 34142, United States
| | - Mohammad Soltani
- Department of Chemistry, The University of South Alabama, Mobile, Alabama 36688, United States
| | - Kelly J Badilla-Nunez
- Department of Chemical and Biomolecular Engineering, The University of South Alabama, Mobile, Alabama 36688, United States
| | - Ben Siu
- Department of Chemical and Biomolecular Engineering, The University of South Alabama, Mobile, Alabama 36688, United States
| | - Muhammadiqboli Musozoda
- Department of Chemistry, State University of New York at Oswego, Oswego, New York 13126, United States
| | - Kevin N West
- Department of Chemical and Biomolecular Engineering, The University of South Alabama, Mobile, Alabama 36688, United States
| | - James H Davis
- Department of Chemistry, The University of South Alabama, Mobile, Alabama 36688, United States
| | - Arsalan Mirjafari
- Department of Chemistry, State University of New York at Oswego, Oswego, New York 13126, United States
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Mirjafari A. Ionic liquid syntheses via click chemistry: expeditious routes toward versatile functional materials. Chem Commun (Camb) 2018; 54:2944-2961. [DOI: 10.1039/c8cc00372f] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The application of click reaction (e.g. CuAAC, thiol–X, oxime formation and nucleophilic ring opening) has recently begun to draw attention for efficient and robust synthesis of new functional ionic liquids, requiring minimal purification.
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Affiliation(s)
- Arsalan Mirjafari
- Department of Chemistry and Physics
- Florida Gulf Coast University
- Fort Myers
- USA
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Thigpen AS, Nestor ST, O'Brien RA, Minkowicz S, Sheng Y, Davis JH, West KN, Mirjafari A. Thioether-functionalized picolinium ionic liquids: synthesis, physical properties and computational studies. NEW J CHEM 2017. [DOI: 10.1039/c6nj02451c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Facile and robust construction of picolinium ionic liquids via thiol–ene reaction bestows materials with low Tg/Tm values along with high hydrophobicity and heat capacity.
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Affiliation(s)
- A. Shay Thigpen
- Department of Chemical and Biomolecular Engineering
- University of South Alabama
- Mobile
- USA
| | - Stephen T. Nestor
- Department of Chemistry and Physics
- Florida Gulf Coast University
- Fort Myers
- USA
| | | | - Samuel Minkowicz
- Department of Chemistry and Physics
- Florida Gulf Coast University
- Fort Myers
- USA
| | - Yinghong Sheng
- Department of Chemistry and Physics
- Florida Gulf Coast University
- Fort Myers
- USA
| | - James H. Davis
- Department of Chemistry
- University of South Alabama
- Mobile
- USA
| | - Kevin N. West
- Department of Chemical and Biomolecular Engineering
- University of South Alabama
- Mobile
- USA
| | - Arsalan Mirjafari
- Department of Chemistry and Physics
- Florida Gulf Coast University
- Fort Myers
- USA
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Huynh TLY, Poiroux K, O'Brien RA, West KN, Davis JH, West CW. Fusion and Thermal Degradation Behavior of Symmetric Sulfur-Containing Quaternary Ammonium Bromides. J Phys Chem B 2016; 120:1330-5. [PMID: 26849572 DOI: 10.1021/acs.jpcb.6b00747] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Quaternary ammonium salts are widely used in consumer products and industrial processes, where their instability at elevated temperatures limits their range of applications. In this work, the thermal behavior of a new class of quaternary ammonium salts was investigated using differential scanning calorimetry. These salts contain a sulfur atom in each chain at the fourth position from the central nitrogen and are thus termed thiaquats. The temperatures at which these salts melt and thermally degrade were determined, and enthalpies and entropies of fusion were evaluated. Their melting points increase with chain lengths, in contrast to the behavior of traditional quaternary ammonium salts. Furthermore, they exhibit enthalpies and entropies of fusion significantly lower than corresponding tetraalkyl analogues. These trends provide physical insight into the molecular-level behavior of these salts, suggesting that they do not fully dissociate upon melting. The thiaquats also exhibit thermal stability to markedly higher temperatures than traditional quaternary ammonium bromides, a phenomenon that can be explained in by strong pairing between the quaternary cation and bromide anion, which inhibits possible decomposition mechanisms. This enhanced thermal stability may enable applications of these salts in processes where traditional salts are not viable, such as phase-transfer-catalyzed systems performed at elevated temperatures.
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Affiliation(s)
- Thai L Y Huynh
- Department of Chemical and Biomolecular Engineering, University of South Alabama , Mobile, Alabama 36688, United States
| | - Kaitlyn Poiroux
- Department of Chemical and Biomolecular Engineering, University of South Alabama , Mobile, Alabama 36688, United States
| | - Richard A O'Brien
- Department of Chemistry, University of South Alabama , Mobile, Alabama 36688, United States
| | - Kevin N West
- Department of Chemical and Biomolecular Engineering, University of South Alabama , Mobile, Alabama 36688, United States
| | - James H Davis
- Department of Chemistry, University of South Alabama , Mobile, Alabama 36688, United States
| | - Christy Wheeler West
- Department of Chemical and Biomolecular Engineering, University of South Alabama , Mobile, Alabama 36688, United States
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O’Brien RA, Mirjafari A, Mattson KM, Murray SM, Mobarrez N, Salter EA, Wierzbicki A, Davis JH, West KN. The Effect of the Sulfur Position on the Melting Points of Lipidic 1-Methyl-3-Thiaalkylimidazolium Ionic Liquids. J Phys Chem B 2014; 118:10232-9. [DOI: 10.1021/jp5058513] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Arsalan Mirjafari
- Department
of Chemistry and Physics, Florida Gulf Coast University, Fort Myers, Florida 33965, United States
| | | | | | - Niloufar Mobarrez
- Department
of Chemistry and Physics, Florida Gulf Coast University, Fort Myers, Florida 33965, United States
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Mirjafari A, O'Brien RA, West KN, Davis JH. Synthesis of New Lipid‐Inspired Ionic Liquids by Thiol‐ene Chemistry: Profound Solvent Effect on Reaction Pathway. Chemistry 2014; 20:7576-80. [DOI: 10.1002/chem.201402863] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Indexed: 12/22/2022]
Affiliation(s)
- Arsalan Mirjafari
- Department of Chemistry and Physics, Florida Gulf Coast University, 10501 FGCU Blvd. S., Fort Myers, FL 33965 (USA)
| | - Richard A. O'Brien
- Departments of Chemistry/Chemical and Biomolecular Engineering, University of South Alabama, 307 N. University Blvd., Mobile, AL 36688 (USA)
| | - Kevin N. West
- Departments of Chemistry/Chemical and Biomolecular Engineering, University of South Alabama, 307 N. University Blvd., Mobile, AL 36688 (USA)
| | - James H. Davis
- Departments of Chemistry/Chemical and Biomolecular Engineering, University of South Alabama, 307 N. University Blvd., Mobile, AL 36688 (USA)
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