• Bulletin of the Korean Chemical Society
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• 제28권10호
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• pp.1871-1873
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• 2007

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2310-2314
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• 2007

Stable molecular conformations were calculated for the p-tert-butylcalix[4]arene crown ether bridged at the lower rim with pyridyl unit (1) in the various conformers and their potassium-ion complexes. The structures of three distinct conformations have been optimized using DFT B3LYP/6-31G(d,p) method. Relative stability of free host 1 is in following order: cone (most stable) > partial-cone > 1,3-alternate conformer. For two different kinds of complexation mode, the potassium cation in the crown-ether moiety (cr) has much better complexation efficiency than in the benzene-rings (bz) pocket for all three kinds of conformation of host molecule 1. The relative stability of complex (1+K+) in the cr-binding mode is in following order: partial-cone (most stable) ~ cone > 1,3-alternate conformer.

• 한국결정학회지
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• 제7권2호
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• pp.105-112
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• 1996

Tetra-tert-butyl-dipropionyloxy-dihydroxycalis[4]arene (C50H64O6)의 구조를 X-선 회절법으로 연구하였다. 결정의 공간군은 C2/c이다. 단위세포 상수는 a=16.067(2), b=26.391(17), c=10.335(1)Å, β=94.26(1)°, Z=4, V=4370.2(29)Å3, Dc=1.16, Dm=1.2 gcm-3이다. 회절반점들의 세기는 Enraf-Nonius CAD-4 Diffractometer로 얻었으며, Cu-Kα radiation (λ=1.5418Å)을 사용하였다. 분자구조는 직접법으로 풀었으며 최소 자승법으로 정밀화하였다. 최종 신뢰도 R값은 2354개의 회절반점에 대하여 0.07이였다. 이 Calix[4]arene은 1, 3-alternate conformation을 가진 분자로 2개의 propionyloxy groups이 위쪽에 있고, 마주보는 두 개의 hydroxy groups이 아래로 향해 있으며, 분자 한 가운데에 결정학적 symmetry axis와 일치하는 2-fold symmetry axis가 있는 분자이다.

• 한국결정학회지
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• 제13권3_4호
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• pp.158-164
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• 2002

Tetrahomodioxa p-phenylcalix(4)arene dihexylether (C/sub 66/H/sub 68/O/sub 6/)를 합성하여 분자 및 결정 구조를 X-선 회절법으로 연구하였다. p-Phenylphenol의 탈수, 고리화 반응으로 만든 tetrahomodioxa p-phenylcalix(4)arene을 DMF에서 NaH와 hexyl iodide를 환류시켜 합성하였다. 결정은 사방정계이고 공간군은 P2₁2₁2₁, a =9.764(2), b = 16.167(2), c = 32.994(3) Å, V=5208(1) ų, Z= 4, Dc=1.221 gcm/sup -3/이다. 직접법으로 구조를 해석하였으며, 최소자승법으로 정밀화하여 최종 신뢰도 R 값은 2009개의 회절 반점에 대해 0.070 이었다. 이 분자는 마주 보고 있는 phenyl group 두 쌍이 거의 평행을 이루며, C-1,2-alternate conformation이고, lower rim의 1,3 위치에 hexyl 기가 치환된 비대칭 homooxacalixarene이다.

• Bulletin of the Korean Chemical Society
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• 제23권11호
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• pp.1585-1589
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• 2002

Two novel calixarene-based fluoroionophores were synthesized. Their conformations were confirmed to 1,3-alternate by X-ray crystal structures. From CHEF by blocking the PET mechanism in fluorescence spectra, we observed $In^{3+}$ and $Pb^{2+}$ selectivity over other metal ions. For $In^{3+}$ion, calix[4]-bis-azacrown-5 showed about 20 times more sensitive than calix[4]-mono-azacrown-5 because the source of the binding selectivity comes from the calixarene framework and azacrown ligand by controlling the fluorescence and PET mechanisms as-sociated with the amine moiety.

• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.961-965
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• 1997

1H NMR spectra of 3,3-dimethylpiperidine (1) at -70 to 30 ℃ exhibit gradual change from slow to rapid exchange between two alternate chair forms. The exchange rate constant was determined as a function of temperature by simulating the line shape of the signal from the two methyl groups using the modified Bloch equations. The resulting free energy of activation is ΔG* = 44.4±1.9 kJ mol-1 at 298 K. The 1H NMR spectrum of a D2O or dimethylsulfoxide-d6 (DMSO-d6) solution containing 1 and [SiW11CoⅡO39]6- exhibits separate signals for the free ligand and the complex, indicating that the ligand exchange is slow on the NMR time scale. In D2O the piperidine ring is frozen as a chair form even at room temperature with the cobalt ion bonded to the axial position of the nitrogen atom. When DMSO-d6 is added to the D2O solution, the NMR spectral change suggests that a rapid exchange occurs between the chair form and another conformer. It is proposed that the conformation of ^b1^b coordinated to [SiW11CoⅡO39]6- in DMSO-d6 is close to a twist form.

• Bulletin of the Korean Chemical Society
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• 제33권2호
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• pp.583-588
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• 2012

Functional interaction between Drosophila orphan receptor FTZ-F1 (NR5A3) and a segmentation gene product fushi tarazu (FTZ) is crucial for regulating genes related to define the identities of alternate segmental regions in the Drosophila embryo. FTZ binding to the ligand-binding domain (LBD) of FTZ-F1 is of essence in activating its transcription process. We determined solution structures of the cofactor peptide ($FTZ^{PEP}$) derived from FTZ by NMR spectroscopy. The cofactor peptide showed a nascent helical conformation in aqueous solution, however, the helicity was increased in the presence of TFE. Furthermore, $FTZ^{PEP}$ formed ${\alpha}$-helical conformation upon FTZ-F1 binding, which provides a receptor bound structure of $FTZ^{PEP}$. The solution structure of $FTZ^{PEP}$ in the presence of FTZ-F1 displays a long stretch of the ${\alpha}$-helix with a bend in the middle of helix.

• 한국결정학회지
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• 제10권1호
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• pp.66-70
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• 1999

The calix[4]arene molecule adopting the 1,3-alternate conformation forms a square cavity, and two pair phenyl rings lying above and below a least-square plane defined by the four bridging methylene groups in the calix[4]arene are widened upwards and downwards, respectively, from central axis, which leads to O1-O4=4.064 and O2-O3=3.864 . Two propyloxy groups are stabilized with all trans conformations, but the rather short azacrown ether chain with two oxygen atoms includes cis/trans conformations with O1-C35=2.906 . Therefore the cavity does not seem to be big enough to form a host-guest complex.

• Bulletin of the Korean Chemical Society
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• 제21권5호
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• pp.465-470
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• 2000

The conformations and energies of p-tert-butylcalix[4] crown-6-ether (1) and its alkyl ammonium complexes have been simulated by AM1 semi-empirical quantum mechanics and molecular mechanics calculations using a variety of forcefields (MM2, MM+, CVFF). We performed molecular dynamics calculations to simulate the behavior of these coplexes primartily focusing on the three representative conformations (cone, partial cone, 1,3-alternate) of host molecule 1. When we performed AM1 semi-empirical and molecular mechanics calculations, the one conformation was generally found to be most stable for all the employed calculation methods. The primary binding site of host 1 for the recognition of alkyl ammonium guests was confirmed to be the central part of the crown moiety. The complexation enthalpy calculations revealed that the alkyl amonium cations having smaller and linear alkyl group showed the better complexation efficiencies when combined with p-tert-butylcalix[4]crown-6-ether, that is in satisfactory agreement with the experimental results.

• 대한화학회지
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• 제37권3호
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• pp.344-350
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• 1993

25,26,27,28-테트라아세트오키시[4]에렌·일수화물은 사방정계의 Pbca의 공간군을 갖고 있으며 a = 14.979(4), b = 15.154(4), c = 27.890(3) ${\AA}$, Z = 8, V = 6330.6 ${\AA}^{-3}$, D$_c$ = 1.28 $g{\cdot}cm^{-3}$, ${\lambda}$(Mo K${\alpha}$) = 0.71069 ${\AA}$, ${\mu}$ = 0.86 cm$^{-1}$, F(000) = 2600이고, 1.0 ${\sigma}$(I)보다 큰 강도를 가진 3376갱의 관측된 회절반점에 대하여 최종 R값은 0.069이다. 직접적에 의하여 구조를 풀었으며, 계단식 대각최소자승법에 의하여 정밀화하여, 모든 C-H 결합길이 (=0.96 ${\AA}$) 및 메칠기와 메칠렌기는 이상적인 기하학적 구조에 맞추어 계산하였다. 큰 고리는 1,3 alternate conformation을 하고 있으며 메칠렌기의 평균 평면으로부터 벤젠고리는 각각 110.7, 68.4, 113.7 및 60.8$^{\circ}$를 이루고 있으며, 4개의 각 아세트오키시기는 그들 자신의 벤젠고리와 각각 68.2, 97.6, 78.9 및 71.3$^{\circ}$의 각을 만들고 있다. 반대편에 마주 위치한 벤젠고리 (1)과 (3)은 135.6$^{\circ}$, (2)과 (4)는 135.2$^{\circ}$의 상대적 각을 이루고 있다. 물분자는 메칠렌기를 포한하고 잇는 큰고리의 평면의 z-좌표와 거의 같은 높이에 있으며, 분자내의 O(8)부터 2.942(5) ${\AA}$, 타분자의 O(2)(1/2-x, -1/2＋y, z)부터는 2.901 ${\AA}$의 거리에 있으며, 가장 짧은 분자간 거리는 O(4) 와 C(3)(1/2＋x, 1/2-y,-z)의 3.193 ${\AA}$이다.