Controlling the Interface between Salts, Solvates, Co-crystals, and Ionic Liquids with Non-stoichiometric Protic Azolium Azolates

Max E. Easton; Kai Li; Hatem M. Titi; Steven P. Kelley; Robin D. Rogers

doi:10.1021/acs.cgd.9b01733

Controlling the Interface between Salts, Solvates, Co-crystals, and Ionic Liquids with Non-stoichiometric Protic Azolium Azolates

Max E. Easton
, Kai Li
, Hatem M. Titi
, Steven P. Kelley
, Robin D. Rogers

Research output: Contribution to journal › Article › peer-review

6 Scopus citations

Abstract

A non-stoichiometric approach to control the solid-state behavior of protic ionic liquids (PILs) was demonstrated by direct mixing of 4,5-dicyanoimidazole (HDCNim) with either 1-ethylimidazole (C₂im) or 1-butylimidazole (C₄im) in different mole fractions. Isolation and characterization of three crystalline materials (all having melting points < 100 °C, thus fitting the PIL definition) revealed three different but closely related systems. The structure of [HC₂im][DCNim] consists of a confused proton system, which is so named for the fast proton exchange between basic and acidic fragments and the formation of hydrogen-bonded anionic oligomers. The compound [HC₂im][DCNim]·HDCNim consists of an oligomeric delocalized anion (a confused proton located between two azole fragments, in which one acts as a neutral moiety while the other as an ionic fragment, DCNim-H-DCNim) and [HC₄im][DCNim]·HDCNim can be classified as a salt co-crystal. We believe that these observations will allow a deeper understanding of the behavior of "confused protons" and provide additional strategies for controlling the properties of important classes of materials such as active pharmaceutical ingredients.

Original language	English
Pages (from-to)	2608-2616
Number of pages	9
Journal	Crystal Growth and Design
Volume	20
Issue number	4
DOIs	https://doi.org/10.1021/acs.cgd.9b01733
State	Published - Apr 1 2020
Externally published	Yes

Funding

We thank the National Sciences and Engineering Research Council of Canada (NSERC) for financial support (NSERC Discovery Grant RGPIN-2016-04944). This research was undertaken, in part, thanks to funding from the Canada Excellence Research Chairs Program. R.D.R. thanks the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Heavy Elements program under Award No. DE-SC0019220.

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10.1021/acs.cgd.9b01733

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title = "Controlling the Interface between Salts, Solvates, Co-crystals, and Ionic Liquids with Non-stoichiometric Protic Azolium Azolates",

abstract = "A non-stoichiometric approach to control the solid-state behavior of protic ionic liquids (PILs) was demonstrated by direct mixing of 4,5-dicyanoimidazole (HDCNim) with either 1-ethylimidazole (C2im) or 1-butylimidazole (C4im) in different mole fractions. Isolation and characterization of three crystalline materials (all having melting points < 100 °C, thus fitting the PIL definition) revealed three different but closely related systems. The structure of [HC2im][DCNim] consists of a confused proton system, which is so named for the fast proton exchange between basic and acidic fragments and the formation of hydrogen-bonded anionic oligomers. The compound [HC2im][DCNim]·HDCNim consists of an oligomeric delocalized anion (a confused proton located between two azole fragments, in which one acts as a neutral moiety while the other as an ionic fragment, DCNim-H-DCNim) and [HC4im][DCNim]·HDCNim can be classified as a salt co-crystal. We believe that these observations will allow a deeper understanding of the behavior of {"}confused protons{"} and provide additional strategies for controlling the properties of important classes of materials such as active pharmaceutical ingredients.",

author = "Easton, \{Max E.\} and Kai Li and Titi, \{Hatem M.\} and Kelley, \{Steven P.\} and Rogers, \{Robin D.\}",

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AU - Li, Kai

AU - Titi, Hatem M.

AU - Kelley, Steven P.

AU - Rogers, Robin D.

PY - 2020/4/1

Y1 - 2020/4/1

N2 - A non-stoichiometric approach to control the solid-state behavior of protic ionic liquids (PILs) was demonstrated by direct mixing of 4,5-dicyanoimidazole (HDCNim) with either 1-ethylimidazole (C2im) or 1-butylimidazole (C4im) in different mole fractions. Isolation and characterization of three crystalline materials (all having melting points < 100 °C, thus fitting the PIL definition) revealed three different but closely related systems. The structure of [HC2im][DCNim] consists of a confused proton system, which is so named for the fast proton exchange between basic and acidic fragments and the formation of hydrogen-bonded anionic oligomers. The compound [HC2im][DCNim]·HDCNim consists of an oligomeric delocalized anion (a confused proton located between two azole fragments, in which one acts as a neutral moiety while the other as an ionic fragment, DCNim-H-DCNim) and [HC4im][DCNim]·HDCNim can be classified as a salt co-crystal. We believe that these observations will allow a deeper understanding of the behavior of "confused protons" and provide additional strategies for controlling the properties of important classes of materials such as active pharmaceutical ingredients.

AB - A non-stoichiometric approach to control the solid-state behavior of protic ionic liquids (PILs) was demonstrated by direct mixing of 4,5-dicyanoimidazole (HDCNim) with either 1-ethylimidazole (C2im) or 1-butylimidazole (C4im) in different mole fractions. Isolation and characterization of three crystalline materials (all having melting points < 100 °C, thus fitting the PIL definition) revealed three different but closely related systems. The structure of [HC2im][DCNim] consists of a confused proton system, which is so named for the fast proton exchange between basic and acidic fragments and the formation of hydrogen-bonded anionic oligomers. The compound [HC2im][DCNim]·HDCNim consists of an oligomeric delocalized anion (a confused proton located between two azole fragments, in which one acts as a neutral moiety while the other as an ionic fragment, DCNim-H-DCNim) and [HC4im][DCNim]·HDCNim can be classified as a salt co-crystal. We believe that these observations will allow a deeper understanding of the behavior of "confused protons" and provide additional strategies for controlling the properties of important classes of materials such as active pharmaceutical ingredients.

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ER -

Controlling the Interface between Salts, Solvates, Co-crystals, and Ionic Liquids with Non-stoichiometric Protic Azolium Azolates

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