ISMSC 2007 - Università degli Studi di Pavia

PSB 65
Switching of Self to non-Self Supramolecular Structures by Isomerization
Yoshinori Takashima, Naoki Tomimasu, Hiroyasu Yamaguchi and Akira Harada*
Department of Macromolecular Science, Graduate School of Science, Osaka University,
Toyonaka, Osaka 560-0043, Japan; e-mail: takasima@chem.sci.osaka-u.ac.jp
In recent years, supramolecular chemistry
has been expanding to supramolecular
polymer chemistry. More recently,
construction of sophisticated
supramolecular polymeric structures has
been reported, such as columnar, helices,
and rotaxane polymers. Previously, we
reported alternating supramolecular
polymers of α-CD derivative and β-CD
derivatives. Here we report new
supramolecular structures formed by 2-(O)cinnamoyl
α-CD (2-CiO-α-CD) and 3-(O)cinnamoyl
α-CD (3-CiO-α-CD), and
switching of supramolecular structures by
isomerization.
We have obtained a single crystal of
2-CiO-α-CD suitable for X-ray
crystallographic analysis. The X-ray
crystallographic analysis showed formation
of a cyclic dimer. However, although the
PFG NMR spectra of 2-CiO-α-CD show a
definite diffusion coefficient (D) over 10
mM, that of 3-CiO-α-CD shows that
diffusion coefficient decreases
monotonously with its concentrations.
These results indicate that although 2-CiOα-CD
formed a cyclic dimer, 3-CiO-α-CD
formed weak supramolecular oligomers in
aqueous solutions.
Figure 1. Schematic illustration of the formation of
supramolecular complexes using CiO-α-CDs.
Although 2-CiO-α-CD and 3-CiO-α-CD did not isomerize at high concentrations, each
isomer was found to isomerize in dilute aqueous solutions to give a 1:1 mixture. Interestingly,
the mixture of 2-CiO-α-CD and 3-CiO-α-CD forms an alternative supramolecular complex, and
not self-supramolecular complex.
2-CiO-α-CD and 3-CiO-α-CD organized by itself to give a supramolecular cyclic dimer
and a weak supramolecular oligomer, respectively, at high concentrations. In contrast, at low
concentrations, CiO-α-CD isomerizes to its isomer to give stable alternating supramolecular
polymers. These results are interesting because each isomer switches from self recognition to
non-self recognition by isomerization. We are now studying the mechanism in detail.
Sulfides peroxide oxidation in the presence of crown ethers
A.V.Anisimov, A.V.Tarakanova, Pham Vinh Thai, A.A.Seleznev, N.S.Kulikov
Moscow State University, Department of Chemistry, 119992, Moscow, RUSSIA
E-mail: anis@petrol.chem.msu.ru
Sulfides oxidation is very important route for purification of hydrocarbon raw materials and
oil fractions from sulfur compounds. Among the different catalysts proposed in literature for this
process transition metal peroxocomplexes are the most frequently studied. There are many
difficulties to carry out benzothiophene derivatives oxidation in the presence of homogeneous
and heterogeneous conditions. In the present work, we dedicated particular attention to crown
ethers as possible catalysts of peroxide oxidation of alkyl aryl sulfides and and
benzothiophenes. As model reaction oxidation of methylphenylsulfide and benzothiophene was
selected at 20-40 O C temperature by hydrogen peroxide. In most cases oxidation of
methylphenyl sulfide proceed with the formation of the mixture of corresponding sulfoxide and
sulfone. The kinetic studies of the process showed that sulfide oxidation is two step reaction.
The first step is the formation of sulfoxide and the second one their oxidation to sulfone. The
practically quantitative yield of methylphenyl sulfone was obtained by 40 O C when reaction
proceeded for 4 hrs. The only product of benzothiophene oxidation was corresponding sulfone.
The highest yield of benzothiophene sulfone (80%) was achieved at 40 o C by reaction time
about 6 hrs. The structure of crown ethers complexes with sulfides and hydrogen peroxide and
oxidation products were confirmed by NMR spestroscopy, and mass-spectromertry..
We thank RFBR to financial support, grant N 06-03-32367.
PSB 66