Anions Stabilize Each Other inside Macrocyclic Hosts

Fatila, Elisabeth M.; Twum, Eric B.; Sengupta, Arkajyoti; Pink, Maren; Karty, Jonathan A.; Raghavachari, Krishnan; Flood, Amar H.

doi:10.1002/anie.201608118

Cited by 126 publications

(148 citation statements)

References 47 publications

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“…[27] They are supported by the layered structure (see Figure 2) and the stacking clearly compensates for the anionic repulsive forces.T he situation is similar to that in ILs in which H-bonds can overcome the repulsion between like-charged ions. [28][29][30][31][32][33] TheX -ray structural features are strongly supported by B3LYP/6-311G** and B3LYP-D3/6-311G** calculations on dimers and tetramers of ion-pairs. [34][35][36] Cut-outs of the X-ray structures are used as starting geometry.Only if the dispersion correction is taken into account do the optimized structures resemble the X-ray structures,which are mainly characterized by the stacking between the rings of N-methyl-6-hydroxyquinolinium cations and the hydrogen bond between the hydroxy proton and the sulfonyl oxygen atom (see SI7).…”

Section: Introductionmentioning

confidence: 94%

Large Stokes Shift Ionic‐Liquid Dye

et al. 2017

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Abstract:We have incorporated the dye N-methyl-6-oxyquinolone [6MQz] in its protonated form as acation into an ionic liquid (IL) and thus to synthesize an IL dye.T he IL dye N-methyl-6-hydroxyquinolinium bis(trifluoromethylsulfonyl) imide [6MQc][NTf 2 ]w as characterized by NMR, ATRI R spectroscopya nd X-ray crystallography.T he fluorescence of the IL dye has al arge Stokes shift of Dl = 116 nm and aq uantum yield of f F = 0.56 in acetonitrile.C haracteristic solvent dependent shifts can be detected in the emission spectra. In other ILs,acetonitrile and THF we observe abathochromic shift of up to 28 nm compared to the pure IL dye at 467 nm. Forstronger polar solvents the fluorescence signals are strongly red-shifted to 650 nm indicating proton transfer to the solvent molecules in the excited state.T his underlines the importance of the IL building block [ MQc] + as photo acid.Fluorescent dyes are important tools in many branches of chemistry related sciences,s uch as biological chemistry, [1][2][3][4][5][6][7][8] materials science, [9][10][11] or solar-energy conversion. [12,13] Attractive fluorescent dyes are characterized by their extended spectral range,h igh emission quantum yields,p hotostability and good solubility in the solvent. Thef luorescent dye N-methyl-6-oxyquinolone [6MQz] was used for studying solvation phenomena. Thec olor of this solvatochromatic dye molecule depends strongly on the polarity of the surrounding,a st he permanent dipole moments strongly change upon excitation from the ground to the excited state.T hus [6MQz] has been used as dye for understanding solvation processes and proton transfer to solvents. [14][15][16][17][18][19][20][21][22] In some cases the polarity probe was incorporated into biomolecules such as sugars or enzymes for probing the chemical environment and providing biocompatibility. [10,11,18,19] Whereas other dyes have been extensively applied to probe the polarity of ionic liquids,t he protonated form of [6MQz] has never been used as moiety of an ionic liquid itself. [23,24] Thus,t he goal of our work was to incorporate the dye N-methyl-6-oxyquinolone [6MQz] in its protonated form as acation into an ionic liquid (IL) and thus to synthesize an IL dye.T he resulting ionic liquid dye N-methyl-6-hydroxyquinolinium bis(trifluoromethylsulfonyl) imide ]involves anion metathesis reaction and is shown in Scheme 1. Initial N-methyl-6-hydroxyquinolinium iodide was prepared using ak nown procedure which is also described in the Supporting Information (SI0). [25,26] Then, equimolar amounts of N-methyl-6-hydroxyquinolinium iodide (287 mg, 1mmol) and silver bis(trifluoromethylsulfonyl)imide (388 mg, 1mmol) were dissolved in 15 mL water each. Thet wo solutions were combined and the reaction mixture was stirred for 15 min. Silver iodide,which precipitates instantly,was filtered off and discarded. Them other liquor was removed on ar otary evaporator and the residue was dissolved in 25 mL ethanol to carry out ah ot-filtration with activated charcoal. After filtration, the solvent wa...

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Section: Introductionmentioning

confidence: 94%

Large Stokes Shift Ionic‐Liquid Dye

et al. 2017

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“…10d In 2015, the Das group published a polyammonium-functionalized tripodal receptor capable of encapsulating a hydrogen sulfate dimer. 11 Very recently, Flood 12 reported that their macrocyclic hosts could stabilize a bisulfate dimer via borderline-strong hydrogen bonds, albeit in a 2:2 (receptor-bisulfate) binding stoichiometry. These reports notwithstanding, the rational capture of two sulfate anions (as opposed to hydrogen sulfate) within the same synthetic framework remains an unmet challenge.…”

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confidence: 99%

A Bis-calix[4]pyrrole Enzyme Mimic That Constrains Two Oxoanions in Close Proximity

Kelliher

Bähring

et al. 2017

J. Am. Chem. Soc.

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Herein we describe a large capsule-like bis-calix[4]pyrrole 1, which is able to host concurrently two dihydrogen phosphate anions within a relatively large internal cavity. Evidence for the concurrent, dual recognition of the encapsulated anions came from 1H NMR and UV–vis spectroscopies and ITC titrations carried out in CD2Cl2/CD3OD (9/1, v/v) or dichloroethane (DCE), as well as single crystal X-ray diffraction analyses. Receptor 1 was also found to bind two dianionic sulfate anions bridged by two water molecules in the solid state. The resulting sulfate dimer was retained in DCE solution, as evidenced by spectroscopic analyses. Finally, receptor 1 was found capable of accommodating two trianionic pyrophosphate anions in the cavity. The present experimental findings are supported by DFT calculations along with 1H NMR and UV–vis spectroscopies, ITC studies, and single crystal X-ray diffraction analyses.

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“…[6][7][8] Furthermore, ditopic ionophoresh ave the ability to drive ionextractionp rocesses in liquid-liquid biphasic solvents or promote transport across organic membranes. [5,10,[12][13][14][15][16][17][18][19][20] The design of ditopic ionophores typically involves predictions about appropriate combinationso f chemicalg roups capable of acting as electron and/orh ydrogen-bond donors to drive processes of molecular recognition involving cationic and anionic guest species. Anion binding is typically more elusivet han that of cationsa nd constitutes am ore challenging field from the viewpoints of both experimentsa nd computation.…”

Section: Introductionmentioning

confidence: 99%

“…Anion binding is typically more elusivet han that of cationsa nd constitutes am ore challenging field from the viewpoints of both experimentsa nd computation. [5,10,[12][13][14][15][16][17][18][19][20] The design of ditopic ionophores typically involves predictions about appropriate combinationso f chemicalg roups capable of acting as electron and/orh ydrogen-bond donors to drive processes of molecular recognition involving cationic and anionic guest species. [16] Modeling of these materials is acomplext ask that demands ap rofoundu nderstanding of the relevant intra-and intermolecular interactions, steric and conformational effects, and solvent interactions.…”

Section: Introductionmentioning

confidence: 99%

Benchmark Ditopic Binding of Cl⁻ and Cs⁺ by the Macrocycle Hexacyclen

2017

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The ditopic binding of organic and inorganic anions and cations constitutes a distinct feature of polyazamacrocycles that underlies their action as intermediate docking and exchange ionophoric sites for tailored supramolecular synthesis and sensors. This work investigates the Cl and Cs complexes formed by hexacyclen (1,4,7,10,13,16-hexaazacyclooctadecane, ha18c6), a benchmark building block of ion-pair polyamine receptors. IR action spectroscopy is employed to characterize the anionic and cationic complexes under controlled environmental conditions in an ion trap. This allows for accurate modeling of the isolated complexes with quantum chemical computations. A comparison of the experimental and computational spectra serves to assess the low-energy conformers dominantly populated at room temperature, which comprise, in both cases, three structures of C , C , and C symmetry with relative energies within about 5 kJ mol . The ion-pair complex Cl -ha18c6-Cs is predicted to host the cation and anion on opposite sides of the macrocycle in a C conformation that does not correlate with the lowest energy structures of the binary complexes. This indicates that the formation of the ion-pair complex in its most stable conformation demands a rearrangement of the hexacyclen ring structure upon the incorporation of the counterion.

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Anions Stabilize Each Other inside Macrocyclic Hosts

Cited by 126 publications

References 47 publications

Large Stokes Shift Ionic‐Liquid Dye

Large Stokes Shift Ionic‐Liquid Dye

A Bis-calix[4]pyrrole Enzyme Mimic That Constrains Two Oxoanions in Close Proximity

Benchmark Ditopic Binding of Cl⁻ and Cs⁺ by the Macrocycle Hexacyclen

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Anions Stabilize Each Other inside Macrocyclic Hosts

Cited by 126 publications

References 47 publications

Large Stokes Shift Ionic‐Liquid Dye

Large Stokes Shift Ionic‐Liquid Dye

A Bis-calix[4]pyrrole Enzyme Mimic That Constrains Two Oxoanions in Close Proximity

Benchmark Ditopic Binding of Cl− and Cs+ by the Macrocycle Hexacyclen

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Benchmark Ditopic Binding of Cl⁻ and Cs⁺ by the Macrocycle Hexacyclen