Unexpected Intrinsic Lability of Thiol-Functionalized Carboxylate Imidazolium Ionic Liquids
New thiol-functionalized carboxylate ionic liquids (ILs), varying both for the cation and for the anion structures, have been prepared as new potential redox switching systems by reacting either 3-mercapto propionic acid (3-MPA) or <i>N</i>-acetyl-cysteine (NAC) with commercially availab...
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doaj-534cc14e9060425bb28cf6fe59b9a1b02020-11-24T22:09:34ZengMDPI AGMolecules1420-30492019-10-012419357110.3390/molecules24193571molecules24193571Unexpected Intrinsic Lability of Thiol-Functionalized Carboxylate Imidazolium Ionic LiquidsAndrea Mezzetta0Lorenzo Poderelli1Felicia D’Andrea2Christian Silvio Pomelli3Cinzia Chiappe4Lorenzo Guazzelli5Department of Pharmacy, University of Pisa, Via Bonanno 33, 56126 Pisa, ItalyDepartment of Pharmacy, University of Pisa, Via Bonanno 33, 56126 Pisa, ItalyDepartment of Pharmacy, University of Pisa, Via Bonanno 33, 56126 Pisa, ItalyDepartment of Pharmacy, University of Pisa, Via Bonanno 33, 56126 Pisa, ItalyDepartment of Pharmacy, University of Pisa, Via Bonanno 33, 56126 Pisa, ItalyDepartment of Pharmacy, University of Pisa, Via Bonanno 33, 56126 Pisa, ItalyNew thiol-functionalized carboxylate ionic liquids (ILs), varying both for the cation and for the anion structures, have been prepared as new potential redox switching systems by reacting either 3-mercapto propionic acid (3-MPA) or <i>N</i>-acetyl-cysteine (NAC) with commercially available methyl carbonate ILs. Different ratios of thiol/disulfide ILs were obtained depending both on the acid employed in the neutralization reaction and on the reaction conditions used. Surprisingly, the imidazolium ILs displayed limited thermal stability which resulted in the formation of an imidazole 2-thione and a new sulfide ionic liquid. Conversely, the formation of the imidazole 2-thione was not observed when phosphonium disulfide ILs were heated, thus confirming the involvement of the imidazolium ring in an unexpected side reaction. An insight into the mechanism of the decomposition has been provided by means of DFT calculations.https://www.mdpi.com/1420-3049/24/19/3571thiol-functionalized ionic liquidsredox systemsthermal-promoted decompositionimidazole 2-thione |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Andrea Mezzetta Lorenzo Poderelli Felicia D’Andrea Christian Silvio Pomelli Cinzia Chiappe Lorenzo Guazzelli |
spellingShingle |
Andrea Mezzetta Lorenzo Poderelli Felicia D’Andrea Christian Silvio Pomelli Cinzia Chiappe Lorenzo Guazzelli Unexpected Intrinsic Lability of Thiol-Functionalized Carboxylate Imidazolium Ionic Liquids Molecules thiol-functionalized ionic liquids redox systems thermal-promoted decomposition imidazole 2-thione |
author_facet |
Andrea Mezzetta Lorenzo Poderelli Felicia D’Andrea Christian Silvio Pomelli Cinzia Chiappe Lorenzo Guazzelli |
author_sort |
Andrea Mezzetta |
title |
Unexpected Intrinsic Lability of Thiol-Functionalized Carboxylate Imidazolium Ionic Liquids |
title_short |
Unexpected Intrinsic Lability of Thiol-Functionalized Carboxylate Imidazolium Ionic Liquids |
title_full |
Unexpected Intrinsic Lability of Thiol-Functionalized Carboxylate Imidazolium Ionic Liquids |
title_fullStr |
Unexpected Intrinsic Lability of Thiol-Functionalized Carboxylate Imidazolium Ionic Liquids |
title_full_unstemmed |
Unexpected Intrinsic Lability of Thiol-Functionalized Carboxylate Imidazolium Ionic Liquids |
title_sort |
unexpected intrinsic lability of thiol-functionalized carboxylate imidazolium ionic liquids |
publisher |
MDPI AG |
series |
Molecules |
issn |
1420-3049 |
publishDate |
2019-10-01 |
description |
New thiol-functionalized carboxylate ionic liquids (ILs), varying both for the cation and for the anion structures, have been prepared as new potential redox switching systems by reacting either 3-mercapto propionic acid (3-MPA) or <i>N</i>-acetyl-cysteine (NAC) with commercially available methyl carbonate ILs. Different ratios of thiol/disulfide ILs were obtained depending both on the acid employed in the neutralization reaction and on the reaction conditions used. Surprisingly, the imidazolium ILs displayed limited thermal stability which resulted in the formation of an imidazole 2-thione and a new sulfide ionic liquid. Conversely, the formation of the imidazole 2-thione was not observed when phosphonium disulfide ILs were heated, thus confirming the involvement of the imidazolium ring in an unexpected side reaction. An insight into the mechanism of the decomposition has been provided by means of DFT calculations. |
topic |
thiol-functionalized ionic liquids redox systems thermal-promoted decomposition imidazole 2-thione |
url |
https://www.mdpi.com/1420-3049/24/19/3571 |
work_keys_str_mv |
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