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최종인 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.11
Molecular structures of the various conformers for the four stereoisomers of tetra-t-butyl-tetra-O-methylsulfinylcalix[4]arene (1) were optimized using DFT BLYP and mPW1PW91/6-31G(d,p) (hybrid HF-DF) calculation methods. We have analyzed the total electronic and Gibbs free energies and normal vibrational frequencies of 16 different structures from four major conformations (cone (CONE), partial cone (PC), 1,2-alternate (1,2-A), 1,3-alternate (1,3-A)) of the four stereoisomers [1(rccc), 1(rcct), 1(rctt), 1(rtct)]. The mPW1PW91/6-31G(d,p) calculations suggested that the 1(rccc)CONE, 1(rcct)PC, 1(rctt)PC, and 1(rtct)1,3-A were the most stable conformations of the respective stereoisomers. These outcomes are in accordance with the experimental structures obtained from X-ray crystallography. The electrostatic repulsion between the sulfinyl and methoxy groups is a primary factor for the relative stabilities of the four different conformations. The IR spectra of the most stable conformers [1(rccc)CONE, 1(rcct)PC, 1(rctt)PC, 1(rtct)1,3-A]of each stereoisomer were compared to each other.
DFT Study for Cage-annulated p-tert-Butylcalix[4]crown-ether Complexed with Potassium Ion
최종인,김광호,Seong Jun Park 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.7
Using DFT B3LYP/6-31+G(d,p)//B3LYP/6-31G(d,p) calculation method, stable molecular structures were optimized for the p-tert-butylcalix[4]arene functionalized at lower rim by cage-annulated crown ether (1) in two different conformers and their potassium-ion complexes. Cone conformer of free host 1 was slightly more stable than partial-cone conformer. For two different kinds of complexation mode, the potassium ion in benzene-rings (bz) pocket showed comparable complexation efficiency with the cation in cage-annulated crown-ether (cr) for the cone and partial-cone conformers of 1. The complex (1•K+) in the cr-binding mode for the partial-cone conformer was more stable than the cone conformer for B3LYP/6-31G(d,p) geometry optimization. However, 1(cone)•K+(cr) showed lower single-point energy than the 1(pc)•K+(cr) for B3LYP/6- 31+G(d,p) calculation method.
DFT Conformational Study of Calix[5]arene and Calix[4]arene: Hydrogen Bond
최종인,김광호,Seong Jun Park 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.10
We have performed DFT calculations to investigate the conformational characteristics and hydrogen bonds of the p-tert-butylcalix[5]arene (1) and p-tert-butylcalix[4]arene (2). The structures of different conformers of 1 were optimized by using B3LYP/6-31+G(d,p) method. The relative stability of the various conformers of 1 is in the following order: cone (most stable) > 1,2-alternate > partial-cone > 1,3-alternate. The relative stability of four conformers of 2 is in the following order: cone (most stable) > partial-cone > 1,2-alternate > 1,3-alternate. The primary factor affecting the relative stabilities of the various conformers of the 1 and 2 are the number and strength of the intramolecular hydrogen bonds. The hydrogen-bond distances are discussed based on different calculation methods.
최종인 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.12
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.
DFT Conformational Study of the Monomethoxycalix[5]arene
최종인,김광호,Sang Hyun Lee 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.11
In this study, we have performed DFT calculations to investigate the conformational characteristics and the hydrogen bonds of the monomethyl ether of p-tert-butylcalix[5]arene (1: 5,11,17,23,29-Penta-tert-butyl-31- methoxy-32,33,34,35-tetrahydroxycalix[5]arene). The structures of different conformers of 1 were optimized by using B3LYP/6-31+G(d,p) method. The relative stability of the various conformers of 1 is in the following order: 2,3-alternate (most stable) > 1-partial-cone ~ 1,2-alternate > cone > 2-partial-cone > 3-partial-cone ~ 2,4- alternate ~ 1,3-alternate. The primary factor affecting the relative stabilities of the various conformers of the monomethoxy-t-butylcalix[5]arene (1) are the number of the intramolecular hydrogen bonds.
최종인 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.2
Molecular structures were optimized for the 1,3-diethoxycalix[4]crown-5-ether (2) in the various isomers and their potassium-ion complexes by using B3LYP/6-31+G(d,p)//B1LYP/6-31G(d,p) method after ab initio RHF/6-31G calculation. The cone-shaped isomer of 2 with cr-binding mode has shown the strongest binding efficiency among the six different complexes attributed to seven electrostatic interactions between the potassium cation and the oxygen atoms of crown-5-ether and ethoxy groups of the host (2). The vibrational spectra of 2 and its K+-complexes were obtained by restricted Hartree-Fock (RHF) calculations with the 6-31G basis set. The characteristic vibrational frequencies of various C-O-C stretching and bending motions are analyzed.