Tuning mechanism in helical columnar thiophene host system with 2-thienylacetic acid by using (1R, 2S)-2-amino-1, 2-diphenylethanol

Article abstract of DOI:10.1016/j.tet.2010.05.098

A tunable supramolecular thiophene host system with a chiral channel-like cavity is developed using (1R, 2S)-2-amino-1, 2-diphenylethanol. This thiophene host system possesses a chiral helical columnar structure. The chiral cavities are formed by the self-assembly of the helical column, and guest molecules are included by varying the helical structure and packing arrangement of this column.

Full text of DOI:10.1016/j.tet.2010.05.098

Tetrahedron 66 (2010) 5589e5593
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Tetrahedron
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Tuning mechanism in helical columnar thiophene host system with
2-thienylacetic acid by using (1R,2S)-2-amino-1,2-diphenylethanol
,
,
*
Naoki Shiota a, Takafumi Kinuta a, Tomohiro Sato b, Reiko Kuroda b c, Yoshio Matsubara a
,
,
Yoshitane Imai a
*
a Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
b JST ERATO-SORST Kuroda Chiromorphology Team, 4-7-6, Komaba, Meguro-ku, Tokyo 153-0041, Japan
c Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A tunable supramolecular thiophene host system with a chiral channel-like cavity is developed using
(1R,2S)-2-amino-1,2-diphenylethanol. This thiophene host system possesses a chiral helical columnar
structure. The chiral cavities are formed by the self-assembly of the helical column, and guest molecules
are included by varying the helical structure and packing arrangement of this column.
Ó 2010 Elsevier Ltd. All rights reserved.
Received 23 April 2010
Received in revised form
22 May 2010
Accepted 24 May 2010
Available online 31 May 2010
Keywords:
2-Amino-1,2-diphenylethanol
Crystal-engineering
Helical column
Hosteguest
Thiophene
1. Introduction
thiophene acid derivatives as the fluorescence unit.4 Characteris-
tically, this host system is formed by the self-assembly of a 1D
In the field of hosteguest chemistry, the use of solid-state
fluorescence host systems and, in particular, supramolecular or-
ganic fluorescence host systems comprising two or more organic
molecules, as molecular host systems has attracted considerable
attention;1 this is because the physical and chemical properties of
these supramolecular host systems can be easily controlled by
simply changing their component molecules.2 However, it is diffi-
cult to predict the structure of solid-state supramolecular organic
complexes with new component molecules. Moreover, there have
been few reports of solid-state supramolecular fluorescence host
systems with chiral cavities.3 Therefore, basic fluorescence supra-
molecular building blocks have been increasingly used to de-
termine the structural information of chiral supramolecular organic
complexes as a bottom-up approach to the study of solid-state
supramolecular fluorescence hosteguest chemistry. We have re-
cently developed a solid-state fluorescence host system using
a chiral supramolecular organic fluorophore composed of (1R,2S)-
2-amino-1,2-diphenylethanol [(1R,2S)-1] as the chiral unit and
columnar hydrogen- and ionic-bonded network structure that
lacks strong interactions between individual columns. Guest mol-
ecules are included into a channel-like cavity, that is, formed by the
self-assembly of this 1D columnar structure. Hence, guest mole-
cules can be expected to be included in the host system by altering
the packing arrangement of the 1D columns. However, the tuning
mechanism in a 1D columnar thiophene host system has not been
studied.
In this paper, we report the formation and structural in-
formation of a chiral helical columnar thiophene host system by
employing a combination of supramolecular building blocksd
(1R,2S)-1 and 2-thienylacetic acid (2). Recently, numerous organic
functional materials having various electrochemical and photo-
chemical properties have been prepared using a polythiophene
backbone.5 Therefore, 2, which is one of the most basic units of the
polythiophene backbone, is used as a supramolecular building
block although it hardly exhibits fluorescence. Four types of n-alkyl
alcoholsdmethanol (MeOH), ethanol (EtOH), n-propanol (n-PrOH),
and n-butanol (n-BuOH)dpossessing different alkyl chain lengths
are used as guest molecules in order to study the influence of the
size of the constituent guest molecule on the host system. This
study is expected to provide useful information on the construction
* Corresponding authors. Tel.: þ81 06 6730 5880x5241; fax: þ81 06 6727 2024;
e-mail addresses: y-matsu@apch.kindai.ac.jp (Y. Matsubara), y-imai@apch.kindai.
ac.jp (Y. Imai).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.05.098

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N. Shiota et al. / Tetrahedron 66 (2010) 5589e5593
of novel solid-state supramolecular fluorescence host systems with
thiophene units.
2. Results and discussion
We attempted to prepare the supramolecular thiophene host
system by crystallization using guest solutions. First, a MeOH
molecule was used as a guest. A mixture of (1R,2S)-1 and 2 was
dissolved in MeOH, and left to stand at room temperature. After
3e5 days, a colorless complex I was obtained. On the basis of X-ray
crystal structure analysis, this complex was observed to comprise
(1R,2S)-1 and 2 and include MeOH as guest molecules, as shown in
Figure 1.
The stoichiometry of complex I is (1R,2S)-1/2/MeOH¼1:1:1, and
its space group is C2. This complex has a characteristic pseudo-21-
helical columnar network structure along the b-axis (Fig. 1a and b).
This structure is mainly formed because of two types of bonds: (1)
the hydrogen and ionic bonds between the ammonium hydrogen
atom of the protonated amine (shown in Fig. 1 in green) and the
carboxylate oxygen atom of the carboxylic acid anion (shown in
Fig. 1 in blue) and (2) a thiopheneebenzene edge-to-face in-
teraction (2.81 Å; indicated in Fig. 1a by the red arrow A) between
the hydrogen atom of the thiophene ring of 2 and the benzene ring
of (1R,2S)-1.6 As is expected, complex I is formed by the self-
assembly of the helical column, resulting in the formation of two
types of chiral channel-like cavities (indicated in Fig. 1c by red and
blue circles). Characteristically, these channel-like cavities are
maintained by two thiopheneebenzene edge-to-face interactions
(2.77 and 2.71 Å; indicated in Fig.1c by the red arrow B and the blue
arrow C, respectively) between the hydrogen atom of the thiophene
ring in 2 and the benzene ring of (1R,2S)-1.6 The guest MeOH
molecules (shown in Fig. 1 in red) are trapped one-dimensionally
along the direction of the cavity. Each MeOH molecule is connected
to the column by two types of interactions. The first type of in-
teraction is because of the hydrogen bonds between the hydroxyl
group of the MeOH molecule and the carboxyl group of 2, and
between the hydroxyl group of the MeOH molecule and the hy-
droxyl group of (1R,2S)-1. The other type of interaction is the CHe
interaction (2.77 Å; indicated in Fig. 1c by the purple arrow D)
between the
-proton of MeOH and the thiophene ring of 2.6
p
a
In complex I, the channel-like cavities are formed by the packing
arrangement of the helical columns without strong interactions.
Therefore, the size and shape of these cavities may vary depending
on the guest molecules, and a variety of guest molecules may be
included into the thiophene host complex. In order to study this
process, three other types of n-alkyl alcohol with longer alkyl
chains (EtOH, n-PrOH, and n-BuOH) were used as guest molecules
and their inclusion mechanism was investigated. Good-quality
colorless complexes, II, III, and IV, were obtained from the EtOH, n-
PrOH, and n-BuOH solutions, respectively, and their crystal struc-
tures were analyzed. The crystal structure of complex II containing
guest EtOH molecules is shown in Figure 2.4
Figure 1. Crystal structure of complex I. (1R,2S)-1, 2, and MeOH molecules are in-
dicated in green, blue, and red, respectively. (a) Pseudo-21-helical columnar hydrogen-
and ionic-bonded network observed along the b-axis. The red arrow (A) indicates
a thiopheneebenzene edge-to-face interaction. (b) View along the a-axis. (c) Packing
structure observed along the b-axis. The red arrow (B) and blue arrow (C) indicate
thiopheneebenzene edge-to-face interactions. The purple arrow (D) indicates a CHe
p
The X-ray analysis of complex II revealed that its stoichiometry
is the same as that of complex I, i.e., (1R,2S)-1/2/EtOH¼1:1:1.
However, its space group is P212121. Although the component
molecule of 2 is disordered, this complex has a 21-helical columnar
network structure (Fig. 2a). Further, the helical columnar structure
in complex II is formed by the hydrogen and ionic bonds between
the ammonium hydrogen atoms of the protonated amine (shown in
Fig. 2 in green) and the carboxylate oxygen atom of the carboxylic
interaction. The red and blue circles indicate the two types of channel-like cavities.
acid anion (shown in Fig. 2 in blue) and by the thiopheneebenzene
edge-to-face interactions (2.94 Å; indicated in Fig. 2b by the red
arrows A) between the hydrogen atom of the thiophene ring of 2
and the benzene ring of (1R,2S)-1.6 Complex II also has channel-like
cavities formed by the assembly of the helical columns. These
cavities are maintained by the thiopheneebenzene edge-to-face

N. Shiota et al. / Tetrahedron 66 (2010) 5589e5593
5591
Figure 3. Crystal structure of complex III. (1R,2S)-1, 2, and n-PrOH molecules are in-
dicated in green, blue, and red, respectively. (a) 21-Helical columnar hydrogen- and
ionic-bonded network observed along the a-axis. (b) Packing structure observed along
Figure 2. Crystal structure of complex II. (1R,2S)-1, 2, and EtOH molecules are in-
dicated in green, blue, and red, respectively. (a) 21-Helical columnar hydrogen- and
ionic-bonded network observed along the b-axis. (b) Packing structure observed along
the a-axis. The red arrow (A) and blue arrow (B) indicate thiopheneebenzene edge-to-
face interactions.
the b-axis. The red arrow (A) indicates CHep interaction.
component molecule of 2 is disordered in complex III, complexes
III and IV have the same 21-helical columnar hydrogen- and ionic-
bonded network structure (shown in Figs. 3a and 4a, respectively).
In contrast to the helical columns in complexes I and II, the helical
intercolumnar interactions (2.75 Å; indicated in Fig. 2b by the blue
arrows B) between the 2 and (1R,2S)-1 molecules.6 The guest EtOH
molecules are included into the channel-like cavities by hydrogen
bonds in the same manner as that observed in complex I (Fig. 2b). In
column in these complexes is maintained by the CHe
p intra-
columnar interactions (2.80 and 2.69 Å; indicated in Figs. 3b and 4b,
respectively, by red arrows A) between the hydrogen atom of the
acetic acid group of 2 and the benzene ring of (1R,2S)-1.6 The chiral
channel-like cavities of these complexes are formed by the as-
sembly of this helical column (shown in Figs. 3b and 4b, re-
spectively). Guest n-PrOH and n-BuOH molecules (indicated in Figs.
3 and 4, respectively, in red) are inserted into the cavities because of
the same hydrogen bonds as those in the cases of complexes I and
complex II, the CHep interaction between the EtOH molecules and
the thiophene ring of 2 is not observed.6 Interestingly, in this
complex, the packing arrangement of the helical column is quite
different from that observed in complex I. In complex I, two guest
MeOH molecules are included into one channel-like cavity along
the column. Moreover, the MeOH molecules are arranged in two
manners in two types of cavities (indicated in Fig. 1c by red and
blue circles, respectively). In contrast, in complex II, one guest EtOH
molecule is included into one channel-like cavity along the column.
In addition, the arrangement of the helical column in complex II is
different from that in complex I. In complex I, the two thiophene
rings of 2 along one helical column are in opposite directions
(Fig. 1b). In contrast, in complex II, the two thiophene rings of 2 are
in the same direction (Fig. 2a). These results suggest that guest
molecules are included in this thiophene host system by varying
the style and packing arrangement of the helical columns
accordingly.
II. The CHep interaction (2.76 Å; indicated in Fig. 4b by blue arrows
B) between the a-proton of n-BuOH and the thiophene ring of 2 is
observed only in complex IV.6
As is expected, the packing arrangement of the helical columns
in complexes III and IV is quite different from that in complexes I
and II (as observed in Figs. 1c, 2b, 3b, and 4b). Moreover, in complex
II, although sulfur atoms in the thiophene ring of 2 are in the di-
rection of the guest molecule along the helical column (Fig. 2b), in
complexes III and IV, these sulfur atoms are in the direction of the
benzene ring of (1R,2S)-1 (Figs. 3b and 4b, respectively). A com-
parison between the sizes of the channel-like cavities of III and IV
reveals that the sizes depend on the type of the guest molecule.
When the guest molecule is changed from n-PrOH to n-BuOH, the
distance between the shared helical columns along the c-axis (in-
dicated in Figs. 3b and 4b by C) increases from 16.21 to 16.41 Å. In
contrast, the distance between the shared helical columns along
the a-axis (indicated in Figs. 3b and 4b by D) reduces from 12.66 to
Furthermore, the crystal structures of complexes III and IV,
which contain n-PrOH and n-BuOH, respectively, are studied; these
structures are shown in Figures 3 and 4, respectively.
X-ray analyses revealed that these host complexes have the
same stoichiometry as that of complexes I and II, i.e., (1R,2S)-1/2/n-
PrOH (or n-BuOH)¼1:1:1, and their space group is P21. Although the

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N. Shiota et al. / Tetrahedron 66 (2010) 5589e5593
4.2. Formation of complex by crystallization from guest
solution
(1R,2S)-1 (10 mg, 0.047 mmol) and 2 (8 mg, 0.056 mmol) were
dissolved in each guest solution (3 mL) under heat and left to stand
at room temperature. After 3e5 days, a large number of crystals
[crystals of complex I including MeOH (9 mg), crystals of complex II
including EtOH (8 mg), crystals of complex III including n-PrOH
(8 mg), and crystals of complex IV including n-BuOH (7 mg)] were
obtained. The weight of crystal is the total weight of obtained
crystals in one batch.
4.3. X-ray crystallographic study of crystal I
The X-ray diffraction data for single crystals were collected using
Bruker Apex. The crystal structures were solved by the direct
method8 and refined by full-matrix least-squares using SHELXL97.8
The diagrams were drawn using PLATON.9 The absorption correc-
tions were performed using SADABS.10 The nonhydrogen atoms
were refined with anisotropic displacement parameters, and the
hydrogen atoms were included in the models at their calculated
positions in the riding-model approximation. Crystallographic data
of I: 2C14H15NO$2C6H6O2S$2CH4O, M¼774.96, Monoclinic, space
group C2, a¼35.488(3), b¼5.7117(4), c¼24.8421(19) Å,
b
¼128.7950
(10)ꢀ, V¼3924.6(5) Å3, Z¼4, Dc¼1.312 g cmꢁ3
,
m
(Mo
K
a)¼
0.191 mmꢁ1, 12,296 reflections measured, 7373 unique, final R(F2)¼
0.0567 using 6163 reflections with I>2.0
s
(I), R(all data)¼0.0703,
T¼115(2) K. CCDC 764089. Crystallographic data of II4: C14H15NO$-
C6H6O2S$C2H6O, M¼401.51, Orthorhombic, space group P212121,
a¼5.6782(5), b¼14.9054(12), c¼24.921(2) Å, V¼2109.3(3) Å3, Z¼4,
Figure 4. Crystal structure of complex IV. (1R,2S)-1, 2, and n-BuOH molecules are
indicated in green, blue, and red, respectively. (a) 21-Helical columnar hydrogen- and
ionic-bonded network observed along the a-axis. (b) Packing structure observed along
Dc¼1.264 g cmꢁ3
,
m
(Mo K
a
)¼0.180 mmꢁ1, 129,612 reflections mea-
sured, 4822 unique, final R(F2)¼0.0708 using 4158 reflections with
the b-axis. The red arrow (A) and blue arrow (B) indicate CHe
p interactions.
I>2.0
s
(I), R(all data)¼0.0845, T¼115(2) K. CCDC 746697. Crystallo-
graphic data of III: C14H15NO$C6H6O2S$C3H8O, M¼415.53, Mono-
12.51 Å. From these results, it is inferred that guest molecules can
be included in the thiophene host system by changing the style and
helical structure and packing arrangement of the helical columns
accordingly.
clinic, space group P21, a¼12.6628(13), b¼5.5068(6), c¼16.2066(16)
Å,
b
¼104.606(2)ꢀ, V¼1093.6(2) Å3, Z¼2, Dc¼1.262 g cmꢁ3
, m(Mo
K
a
)¼0.176 mmꢁ1, 6653 reflections measured, 4466 unique, final R
(F2)¼0.0750 using 3580 reflections with I>2.0
(I), R(all data)¼
s
0.0948, T¼115(2) K. CCDC 764090. Crystallographic data of IV:
C14H15NO$C6H6O2S$C4H10O, M¼429.56, Monoclinic, space group
3. Conclusion
P21, a¼12.5130(13), b¼5.5796(6), c¼16.4093(18) Å,
b
¼100.127(2)ꢀ,
On the basis of the X-ray crystallographic analyses, this two-
component supramolecular thiophene host system was observed
to comprise (1R,2S)-2-amino-1,2-diphenylethanol [(1R,2S)-1] and
2-thienylacetic acid (2). Suitable channel-like cavities are formed
via recognition of the guest molecule in two tuning processes. In
one process, a helical columnar network structure suitable for the
guest molecule is formed by tuning the direction of the thiophene
ring of 2. In the other process, channel-like cavities suitable for the
guest molecule are formed by varying the packing arrangement of
the helical column. The effect of the solvent on the hydrogen-
bonded network structure has not been widely studied thus far.7
Our study is expected to be useful in analyzing the inclusion
mechanisms of multicomponent host systems and in designing
new types of molecular host systems, especially novel chiral su-
pramolecular fluorescence host systems possessing a thiophene
unit.
V¼1127.8(2) Å3, Z¼2, Dc¼1.265 g cmꢁ3
,
m
(Mo
K
a
)¼0.173 mmꢁ1
,
7049 reflections measured, 4804 unique, final R(F2)¼0.0651 using
3894 reflections with I>2.0
s
(I), R(all data)¼0.0841, T¼115(2) K.
CCDC 764091. Crystallographic data can be obtained free of charge
via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cam-
bridge Crystallographic Data Center, 12, Union Road, Cambridge
CB21EZ, UK; fax: þ44 1223 336 033; deposit@ccdc.cam.ac.uk).
Acknowledgements
This study was supported by a Grant-in-Aid for Scientific Re-
search (No. 22750133) from the Ministry of Education, Culture,
Sports, Science and Technology, Japan, and the Shorai Foundation
For Science And Technology.
Supplementary data
4. Experimental
Supplementary data for this article can be found in the online
version, at doi:10.1016/j.tet.2010.05.098.
4.1. General methods
References and notes
All reagents were used directly as obtained commercially.
Component molecule (1R,2S)-1 was purchased from TOKYO
CHEMICAL INDUSTRY Co., Ltd. Component molecule 2 and four
guest solvents were purchased from Wako Pure Chemical Industry.
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