Cooperative interaction of <i>n</i>‐butylammonium ion with 1,3‐alternate tetrapropoxycalix [4]arene: NMR and theoretical study

Křı́ž, Jaroslav; Dybal, Jiřı́; Budka, Jan; Makrlík, Emanuel

doi:10.1002/mrc.2188

Cited by 6 publications

(4 citation statements)

References 33 publications

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“…Both effects must be operative as the shifts of the signals of carbons and the attached protons differ both in relative magnitude and in sign: the largest relative shift in 1 H NMR spectrum is that of signal www.interscience.wiley.com/journal/mrc 5 whereas the largest negative shift in 13 C NMR spectrum (except signal 1) is that of signal 6 + 7.…”

Section: Nmr Spectramentioning

confidence: 97%

“…The dynamics of the system thus deserves some scrutiny. From the largest value of δ max in 13 C NMR spectra which is −2.1 ppm, we can estimate the upper bound of the correlation time of exchange τ ex to be about 1 ms. However, if we try more exact, direct methods of measurement of τ ex , we meet interesting complications.…”

Section: Proton Hydration State In the Complexmentioning

confidence: 99%

“…1 H and 13 C NMR spectra were measured at 300.13 and 75.45 MHz, respectively, with an upgraded Bruker Avance DPX300 spectrometer. 32 and 64 k points were measured for 1 H and 13 C NMR, respectively.…”

Section: Nmr Spectramentioning

confidence: 99%

“…32 and 64 k points were measured for 1 H and 13 C NMR, respectively. In order to improve the sensitivity as well as to avoid obscuring the strong signals of nitrobenzene, 13 C NMR measurements were performed using 1 H-13 C polarization transfer, namely combining DEPT sequences [14] (using a π /8 read pulse and collecting 8000 scans) optimized for J CH 145 and 12 Hz. Exponential weighting (lb = 1 Hz) was used before Fourier transform.…”

Section: Nmr Spectramentioning

confidence: 99%

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NMR and theoretical study of the cooperative interaction of hydrated proton with dibenzo‐24‐crown‐8

Křı́ž¹,

Dybal²,

Budka³

et al. 2008

Magnetic Reson in Chemistry

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Interaction of hydrated protons (HPs) with dibenzo-24-crown-8 (DBC in nitrobenzene-d(5) was studied by (1)H and (13)C NMR under assistance of ab initio-density functional theory (DFT) quantum calculations. HPs were afforded by hydrogen bis(1,2-dicarbollyl) cobaltate (HDCC) with 3.5 M excess of H(2)O. The forming of a complex between HP and DBC leads to marked and additive relative shifts of both (1)H and (13)C signals. This was utilized for the estimation of the stabilization constant K of the complex. Its value is at least 10(6) l/mol, which agrees with the result of independent extraction method (log K = 6.3). Using absolute integral intensities of the HP signal in a water-saturated system, it was shown that the form of HP present in the complex must be H(5)O(2)(+), in accord with formerly published structure of the complex in crystalline form. The investigation of the dynamics of exchange between bound and free DBC by transverse relaxation using variably spaced pulses in the Carr-Purcell-Meiboom-Gill (CPMG) sequence or on-resonance rotating-frame relaxation with variable spin-lock field intensity was partly hampered by the fast relaxation of some signals in the complex because of relative immobilization of its internal motions. In order to remove these effects, a pulse sequence dipolar interaction-free transverse relaxation (DIFTRE) for static DIFTRE was devised and the MLEV17 pulse sequence with high intensity of electromagnetic field was used in a separate series of experiments. Using the results of these latter experiments, the correlation time of exchange was established to be about 0.8 ms, which complied with the shape of the spectra. The accompanying ab initio DFT calculations showed that the apparent symmetry of the molecules of both DBC and its complex with H(5)O(2)(+) was probably the result of averaging of energetically close conformations (five for DBC and four for the complex). Both NMR and the calculations show that the basic mode of binding of the ion in the complex is analogous to that found in crystal but the most pronounced conformation is slightly different.

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Section: Nmr Spectramentioning

confidence: 97%

Section: Proton Hydration State In the Complexmentioning

confidence: 99%

Section: Nmr Spectramentioning

confidence: 99%

Section: Nmr Spectramentioning

confidence: 99%

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NMR and theoretical study of the cooperative interaction of hydrated proton with dibenzo‐24‐crown‐8

Křı́ž¹,

Dybal²,

Budka³

et al. 2008

Magnetic Reson in Chemistry

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Threading the Calix[5]arene Annulus

Gattuso

Notti

Parisi

et al. 2010

Chemistry A European J

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Among the fast-expanding collection of molecular systems available for nanoscale applications, mechanically interlocked molecules, [1] such as rotaxanes and catenanes, have already moved towards becoming technological realities. [2] Rotaxanes (and their pseudorotaxane precursors), in particular, have been constructed by using the most diverse macrocyclic receptors as wheel components. Crown ethers, [1,3] cyclodextrins, [4] cyclic amides, [5] and more recently cucurbiturils [6] have all been threaded onto suitable complementary linear axle components. Calix[n]arenes, [7] on the other hand, have received much less attention as building blocks for the construction of interlocked supermolecules, [8] despite their tunable size, their versatility of derivatization (both at the wide and narrow rims), and their ready availability. The only notable exceptions are the findings of Arduini, Pochini, and co-workers, who have extensively investigated pseudorotaxanes and rotaxanes based on heterotopic calix[6]arene receptors adorned with ureido groups and viologen-derived linear components. [9] Leaving aside calix[4]arenes, [10] the cavity of which is too small to be threaded by a linear guest, the slightly larger calix [5]arenes are the next potential candidates for pseudorotaxane formation. Although calix [5]arenes have previously been shown to efficiently perform a number of tasks, which range from the complexation of alkyl(di)ammonium ions [11] and ion pairs [12] to the self-assembly of supramolecular polymers, [13] to the best of our knowledge, no studies have so far Inspection of this structure revealed that the spatial arrangement of the oxygen atoms around the nitrogen atom of the included guest is reminiscent of the oxygen array present in crown ether/secondary ammonium ion complexes.[15] Even though the cavity size of a calix [5]arene (at its narrow rim) appears to be slightly smaller than that found in the solidstate structure of the dibenzo[24]crown-8 encircling the dibutylammonium ion (ca. 5 vs. 6 , [16] respectively), calix[5]-arenes were judged to be sufficiently flexible to allow for the inclusion of secondary alkylammonium cations. After a preliminary screening, penta-tert-butylpentakis(tert-butoxycarbonylmethoxy)calix [5]arene [17] (1) was selected as the prototype wheel component, whereas di-n-butylammonium (2·H + ) and di-n-hexylammonium (3·H + ) were chosen as axle components. The axle components were all tested as chloride, picrate (Pic À ), and hexafluorophosphate salts to evaluate the influence of ion pairing [18] on the pseudorotaxane assembly process.

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Cooperative Interaction of Hydronium Ion with an Ethereally Fenced Hexaarylbenzene-Based Receptor: An NMR and Theoretical Study

et al. 2010

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Using (1)H and (13)C NMR and DFT calculations, the structure and interactions of the symmetric ethereally fenced hexaarylbenzene receptor 1 with hydronium ions were studied. Both 1 and its equimolecular complex 1.H(3)O(+) exhibit C(3v) symmetry. According to DFT, two similar optimal structures of the complex exist, the more stable one being 15.4 kJ/mol lower in energy. The equilibrium between 1 and 1.H(3)O(+) complexes is characterized by the stabilization constant K = 1.97 x 10(6) (i.e., the binding constant eta = 6.3) according to both proton and carbon NMR spectra. The exchange dynamics between 1 and the complex measured by the delay-varied CPMG sequence had to be corrected for the internal exchange processes in both 1 (conformation change) and the complex (vacillation between the two minima). After this correction, the correlation time of exchange was found to be 4.76 x 10(-5) s. Such relatively fast exchange can be explained only by it being mediated by the excess water molecules present in the system.

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Cooperative interaction of n‐butylammonium ion with 1,3‐alternate tetrapropoxycalix [4]arene: NMR and theoretical study

Cited by 6 publications

References 33 publications

NMR and theoretical study of the cooperative interaction of hydrated proton with dibenzo‐24‐crown‐8

NMR and theoretical study of the cooperative interaction of hydrated proton with dibenzo‐24‐crown‐8

Threading the Calix[5]arene Annulus

Cooperative Interaction of Hydronium Ion with an Ethereally Fenced Hexaarylbenzene-Based Receptor: An NMR and Theoretical Study

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