Interaction of Calix[4]arene and Aliphatic Amines: A Combined NMR, Spectrophotometric and Conductimetric Investigation

Nachtigall, Francine Furtado; Lazzarotto, Márcio; Nome, Faruk

doi:10.1590/s0103-50532002000300002

Cited by 22 publications

(6 citation statements)

References 8 publications

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“…[23,38] This can be attributed to a reduction in host symmetry, leading to poor packing, and which is a consequence of proton transfer from one phenolic hydroxyl to one of the amines, in accord with calixarene pK a values. [39][40][41] The X-ray data supports this, as only three of the phenolic oxygens are proton bearing, and excess electron density is found around one of the amino groups. The highly symmetrical and efficient packing schemes observed in 1:1 and 2:1 inclusion compounds are therefore not available in basic media.…”

Section: Resultsmentioning

confidence: 64%

Pseudopolymorphism of Aliphatic Amine/4‐tert‐Butylcalix[4]arene Inclusion Compounds: Supramolecular Stabilization as a Route to Polar Clusters and Layers

Brown

Udachin

Enright

et al. 2006

Chemistry A European J

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4-tert-Butylcalix[4]arene (4tBC4A) is a versatile host capable of forming a variety of 1:1 and 2:1 inclusion compounds typically stabilized through van der Waals interactions. Preliminary studies in our group have demonstrated that inclusion of n-butylamine in 4tBC4A results in a series of pseudopolymorphic inclusion compounds, including a new 3:1 inclusion motif. Using a combination of SCXRD, TGA, solid state NMR, and PXRD, we now elaborate upon the relationship between these pseudopolymorphs. We also demonstrate that larger amines demonstrate a similar degree of pseudopolymorphism, allowing for the production of customized materials using self-assembly guided by competing weak forces. Finally, we comment on the structural implications of the relative dominance such forces in the formation of calixarene-based supramolecular frameworks.

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Section: Resultsmentioning

confidence: 64%

Pseudopolymorphism of Aliphatic Amine/4‐tert‐Butylcalix[4]arene Inclusion Compounds: Supramolecular Stabilization as a Route to Polar Clusters and Layers

Brown

Udachin

Enright

et al. 2006

Chemistry A European J

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“…This strong intramolecular H-bonding leads to pK a values for CAs being different from the monomeric units, 4,5 and the balance of the interaction between the guest molecule and either the benzene or the hydroxyl group sites is very subtle. For example, recent studies reported that the ''calix [4]arene(C4A)-aliphatic amine'' complex exists as the exo-complex in which a protonated amine is bound to C4A outside the cavity via the N + -HÁ Á ÁO À form, 6,7 though the complex was initially suggested to be the endo-complex.…”

Section: Introductionmentioning

confidence: 99%

Encapsulation of Arn complexes by calix[4]arene: endo- vs. exo-complexes

Ebata

Hontama

Inokuchi

et al. 2010

Phys. Chem. Chem. Phys.

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The structure of the calix[4]arene(C4A)-Ar(n) complexes has been investigated by laser induced fluorescence spectroscopy, mass-selected resonant two-color two-photon ionization (2C-R2PI) spectroscopy, fragment detected IR photodissociation (FDIRPD) spectroscopy, and high level first principles electronic structure calculations at the MP2 and CCSD(T) levels of theory. C4A has a very high ability to form van der Waals complexes with rare gas atoms. For the C4A-Ar dimer two isomers are observed. A major species shows a 45 cm(-1) red-shift of its band origin with respect to the monomer, while that of a minor species is 60 cm(-1). The binding energy of the major species is determined to be in the range of 350-2250 cm(-1) from 2C-R2PI spectroscopy and FDIRPD spectroscopy. Two isomers are also identified in the quantum chemical calculations, depending on whether the Ar atom resides inside (endo) or outside (exo) the C4A. We propose a scheme to derive CCSD(T)/Complete Basis Set (CBS) quality binding energies for the C4A-Ar complex based on CCSD(T) calculations with smaller basis sets and the ratio of CCSD(T)/MP2 energies for the smaller model systems benzene-Ar and phenol-Ar, for which the CCSD(T) level of theory converges to the experimentally determined binding energies. Our best computed estimates for the binding energies of the C4A-Ar endo- and endo-complexes at the CCSD(T)/CBS level of theory are 1560 cm(-1) and 510 cm(-1), respectively. For the C4A-Ar(2) trimer the calculations support the existence of two nearly isoenergetic isomers: one is the {2 : 0} endo-complex, in which the Ar(2) dimer is encapsulated inside the C4A cavity, and the other is the {1 : 1} endo-exo-complex, in which one Ar resides inside and the other outside the C4A cavity. However, the experimental evidence strongly suggests that the observed species is the {2 : 0} endo-complex. The endo structural motif is also suggested for the larger C4A-Ar(n) complexes because of the observed systematic red-shifts of the complexes with the number of bound Ar atoms suggesting that the Ar(n) complex is encapsulated inside the C4A cavity. The formation of the endo-complex structures is attributed to the anisotropy of the interaction with C4A during the complex formation in the expansion region.

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“…Early values of pK a of calix [4]arene were obtained by Nachtigall using an indirect approach from titrations with amines as 16.6 in acetonitrile [15], that agrees with the high acidity of these compounds, when compared with the analogous phenols [16]. Machado showed that the values of pK a of phenols in acetonitrile and water displayed a linear relationship [17] (pK a (CH 3 CN) = 1.68 pK a (water) ?…”

Section: Calix[4]arene In Acetonitrilementioning

confidence: 63%

Counter-ion and solvent effects on the acidity of calix[4]arene and para-tert-butylcalix[6]arene

Miñambres

Jaques

Veglia

et al. 2014

J Incl Phenom Macrocycl Chem

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Spectrophotometric titrations of calix[4]arene and p-tert-butylcalix[6]arene with LiOH, NaOH, KOH, tetramethylmmonium and tetrabutylammonium hydroxides as bases were carried in ethanol 95 % and acetonitrile. The dependence of pK a of the first deprotonation of calix[4]-arene with the nature of the cation was only modest in ethanol 95 %, spanning from 8.53 pK a unit for NaOH until 9.00 for LiOH, whereas in acetonitrile the proton transfer is quantitative. The first deprotonation of p-t-butylcalix[6]arene in both solvents is quantitative and the extension of the second deprotonation is very dependent of the nature of the cation in ethanol and acetonitrile. Tetramethylammonium hydroxide was the strongest base for both solvents, and both deprotonations proceed quantitatively and concomitantly in ethanol, followed by potassium hydroxide, and the weakest base was tetrabutylammonium hydroxide. This behavior indicates that the ability to form N ? -C-H-p and K ? -p interactions plays an important role to stabilize the mono and dianion calixarene. Lithium and sodium exhibit non-usual acid-base behavior in acetonitrile, attributed to aggregation of the species.

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Interaction of Calix[4]arene and Aliphatic Amines: A Combined NMR, Spectrophotometric and Conductimetric Investigation

Cited by 22 publications

References 8 publications

Pseudopolymorphism of Aliphatic Amine/4‐tert‐Butylcalix[4]arene Inclusion Compounds: Supramolecular Stabilization as a Route to Polar Clusters and Layers

Pseudopolymorphism of Aliphatic Amine/4‐tert‐Butylcalix[4]arene Inclusion Compounds: Supramolecular Stabilization as a Route to Polar Clusters and Layers

Encapsulation of Arn complexes by calix[4]arene: endo- vs. exo-complexes

Counter-ion and solvent effects on the acidity of calix[4]arene and para-tert-butylcalix[6]arene

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