Sites of protonation and copper(II)-complexation in protic ionic liquids comprised of N-hexylethylenediaminium cation

Watanabe, Mayu; Takemura, Shinobu; Kawakami, Sayaka; Syouno, Emi; Kurosu, Hiromichi; Harada, Masafumi; Iida, Masayasu

doi:10.1016/j.molliq.2013.04.002

Cited by 17 publications

(4 citation statements)

References 36 publications

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“…There is some evidence to suggest alkaline earth cations can induce more pronounced solvent structure than alkali metals when dissolved in ILs, due to their divalent versus monovalent charge . In other studies, dissolved Mg 2+ , cations or transition metal ions (Cu 2+ , Ag + , or Zn 2+ ) − formed coordination complexes with IL anions, and thus changed the local ion self-assembly in the bulk. This is reminiscent of metal ion chelating behavior in aqueous electrolyte solution or that described previously for solvate ILs.…”

Section: The Bulk Structure Of Ionic Liquidsmentioning

confidence: 97%

Structure and Nanostructure in Ionic Liquids

Hayes

Warr

Atkin³

2015

Chem. Rev.

1,964

1,783

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Section: The Bulk Structure Of Ionic Liquidsmentioning

confidence: 97%

Structure and Nanostructure in Ionic Liquids

Hayes

Warr

Atkin³

2015

Chem. Rev.

1,964

1,783

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“…A related type of PIL is shown in Figure , where the protonation preferentially occurs at the secondary amine as shown; however, there is some protonation of the primary amine site. This PIL was able to form a chelate complex through coordination of copper(II) ions to the cation moiety …”

Section: New Subcategories Of Pilsmentioning

confidence: 99%

“…This PIL was able to form a chelate complex through coordination of copper(II) ions to the cation moiety. 107 The first phosphonium PILs consist of the cation tributylphosphonium, 103 trioctylphosphonium, 108 or triphenylphosphonium 108 with various anions. Tributylphosphonium Tf 2 N is shown in Figure 1b.…”

Section: New Subcategories Of Pilsmentioning

confidence: 99%

Protic Ionic Liquids: Evolving Structure–Property Relationships and Expanding Applications

2015

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“…From this point of view, protic ionic liquids (PILs) with chelating rings are prospective candidates that may universally accept transition-metal ions. In our previous studies, a series of PILs based on the alkylethylenediaminium cation was isolated and the physical properties of the PILs were evaluated. 15 N NMR chemical shift analysis revealed that the ionicities of the two PILs comprising HHexen(X) [HHexen = monoprotonated hexylethylenediamine; X = bis(trifluoromethanesulfonyl)amide (Tf 2 N); in previous papers abbreviated as “TFSA”) or trifluoroacetate (TFA)] were similar…”

Section: Introductionmentioning

confidence: 99%

Solvation Structure of a Copper(II) Ion in Protic Ionic Liquids Comprising N-Hexylethylenediamine

et al. 2014

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The fine and dynamic structure of the copper(II) ion solvated in a protic ionic liquid (PIL) comprising monoprotonated N-hexylethylenediaminium (HHexen(+)) and bis(trifluoromethanesulfonyl)amide (Tf2N(-)) [or trifluoroacetate (TFA(-))] was determined using NMR, visible electronic, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The chelate-diamine group in the cationic unit facilitates advantageous dissolution of transition-metal salts in the present PIL. The interaction of the copper(II) ion with the chelate-diamine PIL was explored by the addition of copper(II) salts to the PIL, demonstrating competitive complexation between the ligand of the added copper(II) salt and the components of the ionic liquid to the copper(II) ion. The favorable mode of interaction of the present chelating PIL with the copper(II) ion was clarified based on a comparison of the interactions with analogous liquids, including the monoprotonated hexylaminium HHexam(Tf2N)-PIL, neat N-hexylethylenediamine (Hexen), and neat ethylenediamine (En). The coordination modes of the bis-Hexen and tris-Hexen copper(II) complexes in molecular liquids and in solids were also studied for comparison of the coordination structures around the copper(II) ion with those in the present PILs. The paramagnetic-induced relaxations derived from (13)C (ΔT(1p)(-1)) and (15)N (ΔT(2p)(-1)) NMR, the visible electronic spectra, and EXAFS analysis showed that the copper(II) ion tends to form a bis-Hexen complex in the HHexen-PIL despite the electrostatic repulsion and the fact that the counteranions are located at the axial sites, whereas in the HHexam(Tf2N)-PIL, the copper(II) ion exhibits affinity for the Tf2N anion over the protonated amines. The lifetime of the copper(II) complex formed in the PIL was determined to be ≈10(-4) s based on (13)C (ΔT(1p)(-1)) and (14)N (ΔT(2p)(-1)) NMR, which is appreciably longer than that in conventional molecular solvents.

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Sites of protonation and copper(II)-complexation in protic ionic liquids comprised of N-hexylethylenediaminium cation

Cited by 17 publications

References 36 publications

Structure and Nanostructure in Ionic Liquids

Structure and Nanostructure in Ionic Liquids

Protic Ionic Liquids: Evolving Structure–Property Relationships and Expanding Applications

Solvation Structure of a Copper(II) Ion in Protic Ionic Liquids Comprising N-Hexylethylenediamine

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