Analysis of ion association reactions in aqueous solutions between alkali metal–crown ether complexes and pairing anions by capillary zone electrophoresis

Manege, Ludovick C.; Takayanagi, Toshio; Oshima, Mitsuko; Motomizu, Shoji

doi:10.1039/a909525j

Cited by 12 publications

(10 citation statements)

References 18 publications

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“…Such bridging properties of thiocyanates are well known in supramolecular chemistry [29] and have been studied by X-ray crystallography [29] and capillary zone electrophoresis. [30] The DSC curves of complexes NH 4 PF 6 ·1 b-g revealed monotropic mesophases for all derivatives between 48 and 138 8C. Complexes NH 4 PF 6 ·1 e,g showed a glass to mesophase transition at 63 and 52 8C, respectively, upon second heating.…”

Section: Resultsmentioning

confidence: 88%

Columnar Mesophases Controlled by Counterions in Potassium Complexes of Dibenzo[18]crown‐6 Derivatives

Kaller

Tussetschläger

Fischer

et al. 2009

Chemistry A European J

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Dibenzo[18]crown-6 derivatives 1 with two lateral tetraalkyloxy o-terphenyl units were prepared and converted to the corresponding complexes KX1 (X = halide, BF(4), PF(6), SCN) and NH(4)PF(6)1. Complexation was probed by MALDI-TOF spectrometry and NMR spectroscopy. Downfield shifts of (1)H NMR signals for complexes with soft anions Br, I, SCN, and PF(6) indicated the presence of tight ion pairs, whereas complexes with hard anions F, Cl, or BF(4) showed no or little shifts. In (13)C NMR spectra, upfield shifts were detected for soft anions. The character of the anion also influenced the mesomorphic properties of complexes MX1 (M = K, NH(4)), which were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and XRD in comparison to neat 1. Hard anions slightly stabilize or even destabilize the mesophase. Soft anions, however, improve the mesomorphic properties yielding mesophases with up to 70 degrees C phase widths in the case of KI1, KPF(6)1, and NH(4)PF(6)1. For complexes KSCN1 with a soft and bridging anion, the balance between mesophase stabilization and high order is shifted in favor of the plastic crystal phase.

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Section: Resultsmentioning

confidence: 88%

Columnar Mesophases Controlled by Counterions in Potassium Complexes of Dibenzo[18]crown‐6 Derivatives

Kaller

Tussetschläger

Fischer

et al. 2009

Chemistry A European J

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“…However, these interactions are weak, limiting practical use. Motomizu and coworkers achieved complexation of the hydrophobic inorganic anions perchlorate and thiocyanate, as well as some organic anions, by using alkali metal‐crown ether complexes in the BGE 29, 30. Masár et al utilized cyclodextrins to improve inorganic anion separations 31, but this approach has not been exploited further.…”

Section: Introductionmentioning

confidence: 99%

Protonated diamines as anion‐binding agents and their utility in capillary electrophoresis separations

2011

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Capillary zone electrophoresis is a proven method for separating small ions because of the inherent charge and differences in mobility of these analytes. Despite its resolving power, CZE can be insufficient for separating ions with similar mobilities. One remedy is to modify mobilities via the addition of background electrolyte complexation agents. However, this approach is not straightforward for inorganic anions, which lack complexation options. To address this shortfall, the diprotonated diamine moiety was investigated for complexation of dianions. Dicationic diamines significantly complexed dianions, and this interaction was not purely electrostatic in nature because affinities varied with dianion identity. Aqueous association constants were measured with affinity capillary electrophoresis (ACE) and found to be similar in magnitude but different in selectivity to those of dianions with magnesium ion. Binding was also investigated for zwitterionic buffers containing the protonated diamine moiety. Zwitterions exhibited binding constants as high as 18 M(-1) (30-mM ionic strength). This work discusses the observed binding constants and their potential usefulness in CZE separations of inorganic anions. Also covered are improvements to ACE methodology and an evaluation of some of the assumptions employed.

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“…The π–π stacking between the aryl moieties would further increase the intracolumnar order. Such bridging properties of thiocyanates are well known in supramolecular chemistry29 and have been studied by X‐ray crystallography29 and capillary zone electrophoresis 30…”

Section: Resultsmentioning

confidence: 99%

Double Activation of an N‐Alkylimidazole

Huertos

Pérez

Riera

2012

Chemistry A European J

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Analysis of ion association reactions in aqueous solutions between alkali metal–crown ether complexes and pairing anions by capillary zone electrophoresis

Cited by 12 publications

References 18 publications

Columnar Mesophases Controlled by Counterions in Potassium Complexes of Dibenzo[18]crown‐6 Derivatives

Columnar Mesophases Controlled by Counterions in Potassium Complexes of Dibenzo[18]crown‐6 Derivatives

Protonated diamines as anion‐binding agents and their utility in capillary electrophoresis separations

Double Activation of an N‐Alkylimidazole

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