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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 31, Number 11
BKCSDE 31(11)
November 20, 2010 

BLYP and mPW1PW91 Calculated Structures and IR Spectra of the Stereoisomers of Tetra-O-methylsulfinylcalix[4]arene
Jong In Choe
mPW1PW91, Conformer, Stereoisomer, Infrared, Sulfinylcalix[4]arene
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.
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