• Journal of the Korean Chemical Society
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• v.53 no.6
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• pp.640-652
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• 2009

We have performed mPW1PW91 calculations to investigate the conformational characteristics and hydrogen bonds of p-tert-butylcalix[4]arene (1), p-tert-butylcalix[5]arene (2), calix[6]arene (3) and p-tertbutylcalix[6]arene (4). The structures of the different conformers of 1-3 were optimized by using mPW1PW91/6-31+G(d,p) method. The relative stability of the four conformers of 1 is in the following order: cone (most stable) > partial-cone > 1,2-alternate > 1,3-alternate. The relative stability of the conformers of 2 is in the following order: cone (most stable) > 1,2-alternate > partial-cone > 1,3-alternate. The relative stability of the various conformers of 3 is in the following order: cone (pinched: most stable) > partial-cone > cone (winged) - 1,2-alternate - 1,2,3-alternate > 1,4-alternate > 1,3-alternate > 1,3,5-alternate. The structures of the various conformers of 4 were optimized by using the mPW1PW91/6-31G(d,p) method followed by single point calculation of mPW1PW91/6-31+G(d,p). The relative stability of the conformers of 4 is in the following order: cone (pinched) > 1,2-alternate > cone (winged) > 1,4-alternate - partial-cone > 1,2,3-alternate > 1,3,5-alternate > 1,3-alternate. The primary factor affecting the relative stabilities of the various conformers of the 1-4 are the number and strength of the intramolecular hydrogen bonds. The hydrogen-bond distances are discussed based on two different calculation methods (B3LYP and mPW1PW91).

• Bulletin of the Korean Chemical Society
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• v.19 no.7
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• pp.770-776
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• 1998

Several ABCH type chiral calix[4]arenes were prepared from monoalkyl calix[4]arenes by treating with various acyl halide, followed by reacting with benzoyl chloride in pyridine. These asymmetrically substituted ABCH type calix[4]arenes are obtained as racemates mixture which are confirmed by the chiral shift reagent in 1H NMR spectra. The molecular and crystal structure of 5-nitro-26-allyloxy-25-benzoyloxy-28-isobutyryloxy-27-hydroxycalix[4]arene 8a has been determined by the X-ray diffraction method. Two independent enantiomeric molecules are crystallized in a 1: 1 racemate mixture. They are in the partial cone conformation in which the benzoyloxy phenyl group is down. There is a bifurcated intramolecular hydrogen bonding involving three functional groups in each molecule.

• Bulletin of the Korean Chemical Society
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• v.25 no.7
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• pp.957-958
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• 2004

• Journal of the Korean Chemical Society
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• v.44 no.3
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• pp.290-293
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• 2000

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.48-52
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• 2002

Using several molecular modeling programs we have performed computer simulations to investigate the complexation behaviors of an ester derivative of p-tert-butylcalix[5]arene (1e) toward a variety of butylammonium ions. Semi-empirical AM1 method was used for calculating the binding energies and the formation enthalpies. MM and CVFF forcefields for molecular mechanics calculations were adapted to express the complexation energies of the host. Molecular dynamics were performed to the calculated complex systems to simulate the ionophoric behavior of the host-guest complexes. The absolute Gibbs free energies of the host (1e) complexed with four kinds of butylammonium ions have been calculated using the Finite Difference Thermodynamic Integration (FDTI) method in Discover. Calculation results show that the trend in complex formation is n-$BuNH_3^+$ > iso-$BuNH_3^+$ >> sec-$BuNH_3^+$ > tert-$BuNH_3^+$, which is in good agreement with the experimental results.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1509-1516
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• 2012

Nano-assisted inclusion separation of alkali metals from basic solutions was reported by inclusion-facilitated emulsion liquid membrane process. The novelty of this study is application of nano-baskets of calixarene in the selective and efficient separation of alkali metals as both the carrier and the surfactant. For this aim, four derivatives of $p-tert-calix$[4]arene bearing different sulfonamide moieties were synthesized and their inclusion-extraction parameters were optimized including the calixarene scaffold $\mathbf{3}$ (4 wt %) as the carrier/demulsifier, the commercial kerosene as diluent in membrane, sulphonic acid (0.2 M) and ammonium carbonate (0.4 M) as the strip and the feed phases, the phase and the treat ratios of 0.8 and 0.3, mixing speed (300 rpm), and initial solute concentration (100 mg/L). The selectivity of membrane over more than ten interfering cations was examined and the results reveled that under the optimized operating condition, the degree of inclusion-extraction of alkali metals was as high as 98-99%.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1597-1605
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• 2022

A porous silica-based adsorbent was prepared by impregnating the pores of a silica support with the extractant 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]arene-R14) and an additive agent 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C₂mim ⁺ NTf^-₂) as the materials to remove cesium(I) (Cs⁺) ions from seawater. The as-prepared adsorbent showed excellent adsorption performance toward Cs⁺ ions, with adsorption equilibrium reached within 2 h and an adsorption amount of 0.196 mmol/g observed. The solution pH, temperature, and the presence of coexisting metal ions were found to have almost no effect on Cs⁺ adsorption. The adsorption mechanism was considered to proceed via ion exchange between Cs⁺ and C₂mim⁺. In addition, the particle-induced X-ray emission analysis results further clarified that the adsorbed Cs⁺ ion species on the adsorbent was in the form of both CsCl and CsBr.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.669-675
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• 2011

Fourier Transform Infrared Spectroscopy and in-situ Position Annihilation Lifetime Spectroscopy(PALS) analysis of hybrid film, which consist of silsesquioxane(SSQ) and 4-tert-butyl calix[4]arene-O,O',O",O'"-tetraacetic acid tetraethyl ester(CA[4]) have been investigated in order to understand initial formation of nanopore in the next generation porous low-k dielectrics(k < 2.0). SSQ/CA[4] can provide effective homogeneous thin film having porous structure. The porogen decomposition behavior were completely different in the two kinds of SSQ/CA[4] based hybrid film (i.e. SSQ/CA[4] 10 and SSQ/CA[4] 20%). Relatively small pores(1.5 nm) come from dispersion of uni-molecular CA[4] in the SSQ matrix have been generated at $300^{\circ}C$, while mesopores(2.5~3.0 nm) induced from self assembled CA[4] have been generated at $250^{\circ}C$. It might be due to highly interconnected structure of SSQ/CA[4] 20% hybrid thin film resulting in facile evacuating of decomposed fragment of CA[4] molecule.

• Bulletin of the Korean Chemical Society
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• v.28 no.5
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• pp.791-794
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• 2007

A new azocalix[4]arene, 5,14,17,23-tetra[(2-benzoic acid)(azo)phenyl] calix[4]arene (2), has been prepared by hydrolysis of its ester derivative and characterized by 1H NMR, IR, UV-Vis spectroscopy and elemental analysis. Based on UV spectral changes, we found that 2 exhibits Pb2+ ion selectivity. In basic media, Pb2+ forms a 1:1 complex with the ligand. Beer's law is obeyed in the range of 2.0 × 10?6 ? 2.4 × 10?5 mol L?1 of Pb2+. The molar absorptivity (ε ) of 2-Pb2+ complex is 1.89 × 104 L mol?1 cm?1 at 440 nm, and the detection limit is 1.6 × 10?6 mol L?1.

• Bulletin of the Korean Chemical Society
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• v.21 no.9
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• pp.867-874
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• 2000

Two new azobenzene crown ether calix[4]arenes, 10 and 11, were synthesized by two pathways. In the first pathway,two ethoxy nitrobenzene groups were attached to t-butylcalix[4]arenes in a 1,3 position. Subsequent reduction ofthe nitrobenzene group s by metallic zinc in an alkaline solution afforded 10 and 11 in8% and 12%,respectively. In the second pathway,an azobenzene containing two glycolic units was prepared prior connect-ing to t-butylcalix[4]arenes. The yields from the second approach (5%, 8% for 10 and 11, respectively) were lower than those from the former approach. Single crystals of 10 suitable for X-ray crystallography was ob-tained by recrystallization in methanol.Both the X-ray structure and the 1H-NMR spectrum of 10 indicated that the stereoisomer of the azobenzene moiety was trans and the calixarene platform was in cone conformation. 1H NMR spectroscopy suggested that 10 underwent an observable cis-trans isomerization in CDCl3 under room light and upon UV irradiation with cis:trans ratios of 33:67 and 36:64,respectively. Compound 6 which was the precursor of 11showed fluxional behavior and was found to have mixed conformations ofcone and partial cone with a ratio of 47:53 at -30 $^{\circ}C.$ 1H NMR spectrum of 11 suggested that 11 was initially isolated as cis azobenzene with calix[4]arene in cone conformation and underwent conformational interconversion through calix[4]arene annulas in a similar fashion to 6 upon exposing to light. The complexation studies of 10 with picrate salts of Na+ and K+ using 1H NMR spectroscopysuggested that Na+ preferred to bind the cis form of 10 while K+ preferred to bind the trans form. The stereoisomer of the azobenzene unit in 11 changed partially from cis to trans upon complexing with K+.