Folding and anion-binding properties of an indolocarbazole dimer with urea appendages

Article abstract of DOI:10.1080/10610278.2012.713955

An indolocarbazole dimer with the urea functional group was prepared as an anion receptor which contained eight NH hydrogen bonds donors. Two indolocarbazole units were coupled through a butadiynyl linker to allow for helical folding of the resulting dime

Full text of DOI:10.1080/10610278.2012.713955

This article was downloaded by: [Fudan University]
On: 11 May 2015, At: 10:02
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,
37-41 Mortimer Street, London W1T 3JH, UK
Supramolecular Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/gsch20
Folding and anion-binding properties of an
indolocarbazole dimer with urea appendages
Hyun Joo Kim a , Jae-Min Suk a & Kyu-Sung Jeong a
a Department of Chemistry , Yonsei University , Seoul , 120-749 , South Korea
Published online: 31 Aug 2012.
To cite this article: Hyun Joo Kim , Jae-Min Suk & Kyu-Sung Jeong (2013) Folding and anion-binding properties of an
indolocarbazole dimer with urea appendages, Supramolecular Chemistry, 25:1, 46-53, DOI: 10.1080/10610278.2012.713955
To link to this article: http://dx.doi.org/10.1080/10610278.2012.713955
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the
Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and
should be independently verified with primary sources of information. Taylor and Francis shall not be liable for
any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever
or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of
the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

Supramolecular Chemistry
Vol. 25, No. 1, January 2013, 46–53
Folding and anion-binding properties of an indolocarbazole dimer with urea appendages
Hyun Joo Kim, Jae-Min Suk and Kyu-Sung Jeong*
Department of Chemistry, Yonsei University, Seoul 120-749, South Korea
(Received 20 June 2012; final version received 15 July 2012)
An indolocarbazole dimer with the urea functional group was prepared as an anion receptor which contained eight NH
hydrogen bonds donors. Two indolocarbazole units were coupled through a butadiynyl linker to allow for helical folding of
the resulting dimer by intramolecular hydrogen bonding and dipole–dipole attractions as proven in the 1H NMR
spectroscopy. The dimer was found to bind anions (Cl2, Br2, N23 , AcO2, H2PO24 and SO422) by multiple hydrogen bonds in
10% (v/v) MeOH–acetone, showing high selectivity for sulphate ion. The 1H NMR spectra clearly demonstrated that only
indolocarbazole NH protons were involved in the hydrogen bonding with small anions such as chloride, but all of the
existing indolocarbazole and urea NHs participated in the hydrogen bonding with sulphate ion. This difference in the
binding mode might be responsible for the high affinity and selectivity towards sulphate ion.
Keywords: anion receptor; hydrogen bond; indolocarbazole; urea; sulphate
Introduction
Results and discussion
Helical structures are a unique feature of biomacromo-
lecules such as DNA and proteins, which are closely
associated with the delicate functions such as recog-
nition, replication, transportation and catalysis. A variety
of molecules that are able to fold in ordered arrays have
been designed and prepared to understand the folding
principles of natural peptides and proteins as well as to
develop synthetic analogues mimicking their structures
and functions (1). Using an indolocarbazole with two
indole-type NHs (2), we prepared oligoindolocarbazole
trimers which strongly bound anions such as sulphate
and phosphate by multiple hydrogen bonds, and in turn
folded into helical conformations (3). More recently, we
prepared an indolocarbazole dimer that folded into a
helical conformation by intramolecular hydrogen bonds
in non-polar media. The helical sense of the molecule
could be completely inverted when complexed with
sulphate ion, thus functioning as a chiroptical molecular
switch (4).
The synthesis of dimer 7 is outlined in Scheme 1.
Compound 1 was prepared following the procedures
described previously (2 g, 2 h), and compound 3 was
prepared from 3-bromoaniline (2) by coupling with n-butyl
isocyanate. Sonogashira reaction (8) of 3 with ethynyl-
trimethylsilane followed by treatment with tetrabutylam-
monium fluoride afforded compound 4. Again,
Sonogashira reaction of 1 and 4 (1 equiv.) gave compound
5 (48%), which was converted to compound 6 (69% for two
steps). Finally, palladium-catalysed homo-coupling (9)
gave dimer 7 (43%) which was confirmed by elemental
analysis, NMR and mass spectroscopy.
According to computer modelling studies (MacroMo-
del 9.1)1 (10) in the gas phase, an energy-minimised
structure of 7 folds to generate a helical conformation
owing to intramolecular hydrogen bonds and dipole–
dipole attractions between the carbonyl groups and the
indolocarbazole NH units (Figure 1). It should be
mentioned that the angle and geometry of these
NZHꢀꢀꢀO hydrogen bonds are far from ideal, thus
exerting weak interactions. The 1H NMR spectrum and 2D-
ROESY experiment are consistent with the energy-
minimised structure. As shown in Figure 2, two
indolocarbazole NH signals of dimer 7 are downfield
shifted by Dd ¼ 0.34 and 0.10 ppm in 20% (v/v) CD3CN–
C2D2Cl4, compared with those of monomer 6 which has an
identical pattern of 1H NMR signals but no intramolecular
hydrogen bond. In addition, the CH signals of butyl units
are upfield shifted by Dd ¼ 0.2–0.3 ppm, suggesting that
Herein, we have prepared a new indolocarbazole dimer
7 with two urea groups at ends, which folds into a helical
conformation by intramolecular hydrogen bonds and
dipole–dipole interactions. Despite being acyclic, 7
possesses a rigid framework with eight hydrogen bond
donors, four indole-type NHs and four urea NHs, to be able
to bind anions strongly and selectively (5–7). In particular,
7 strongly binds sulphate ion more than any other anion
examined here by an order of magnitude in the association
constants in a polar medium, 10% (v/v) MeOH–acetone.
*Corresponding author. Email: ksjeong@yonsei.ac.kr
ISSN 1061-0278 print/ISSN 1029-0478 online
q 2013 Taylor & Francis
http://dx.doi.org/10.1080/10610278.2012.713955
http://www.tandfonline.com

Supramolecular Chemistry
47
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
N
N
H
H
I
I
N
N
H
(d)
N
H
(g)
(e),(f)
N
H
1
H
I
Br
Br
O
O
(a)
NH2
O
(b),(c)
C4H9
O
C4H9
C4H9
C4H9
N
H
N
H
N
H
N
H
N
N
N
N
H
H
H
H
2
3
4
5
6
t-Bu
t-Bu
t-Bu
t-Bu
H
N
H
H
N
H
N
N
H
C4H9
N
N
H
N
O H
O
folding
O
N
H
unfolding
H
H
C4H9
O
•
N
H
N
N
N
H
N
H
C4H9
N
H
t-Bu
7 (unfolded)
t-Bu
t-Bu
t-Bu
7 (folded)
Scheme 1. Reagents and conditions: (a) n-butyl isocyanate, THF, reflux, 10 h, 77%; (b) ethynyltrimethylsilane, CuI, PPh3, Pd(dba)2,
Et3N, THF, 858C, 12 h; (c) tetrabutylammonium fluoride (TBAF), THF, 08C to room temperature, 30 min, 82% for two steps; (d) CuI,
Pd(PPh3)2Cl2, Et3N, THF, 568C, 12 h, 48%; (e) ethynyltrimethylsilane, CuI, Pd(PPh3)2Cl2, Et3N, THF, 568C, 15 h; (f) TBAF, THF, 08C to
room temperature, 30 min, 69% for two steps; (g) Pd(OAc)2, CuI, DABCO, CH2Cl2, CH3CN, aerobic, room temperature, 2 h, 43%.
the butyl moiety should be located on the shielding zone of
the indolocarbazole ring current as a result of helical
folding. Next, 2D-ROESY experiment shows NOE
correlations between the NH and CH signals of the
indolocarbazole rings and CH signals of the butyl groups
(Figure 3). More specifically, the a-methylene proton (Hh)
of the butyl group shows NOE cross peaks with the CHq and
two NH signals of the indolocarbazole plane, and the other
butyl protons (He, Hf and Hg) exhibit NOE cross peaks with
the CHo and CHp protons in the indolocarbazole plane.
All of the NOE correlations observed here clearly support
the fact that 7 folds to give a helical structure as shown in
Figure 1.
Binding affinities of 7 with anions were determined by 1H
NMR titration experiments in 10% (v/v) CD3OH–acetone-d6
at 24 ^ 18C. The concentration of an anion gradually
increased as the tetrabutylammonium salt, while the
concentration (1.0 £ 1023 M) of 7 kept constant. The
association constant was determined by nonlinear squares
fitting (11) of the titration curves, plotted the downfield shift of
NH signals against the amount ofguest added. As summarised
in Table 1, dimer 7 has weak to moderate affinities
towards anions in a polar organic medium, 10% (v/v)
MeOH–acetone; azide (50 M21), chloride (1.7 £ 103 M21),
bromide (2.7 £ 102 M21), acetate (1.3 £ 104 M21) and
dihydrogen phosphate (1.0 £ 104 M21). Under the same
Figure 1. Top and side views of an energy-minimised structure of 7 (MacroModel 9.1, OPLS 2001 force field, gas phase). Weak
hydrogen-bonding interactions between NH protons and the urea oxygen atoms are marked as dotted lines.

48
H.J. Kim et al.
Figure 2. 1H NMR spectra (400 MHz, 20% (v/v) CD3CNZC2D2Cl4, 258C) of 6 (1 mM, bottom) and 7 (1 mM, top).
conditions, however, the binding constant between 7 and
sulphate ion could not be determined in the 1H NMR
spectroscopy because 1H NMR signals were broadened
out until addition of approximately 1 equiv. of bis(tetrabutyl-
ammonium) sulphate due to the intermediate rate of exchange
between compound 7 and its sulphate complex. The binding
affinity was therefore determined in the fluorescence
spectroscopy in which the hypo- and batho-chromic shifts of
7 were observed upon addition of sulphate ion (Figure 4).
Nonlinear squares fitting analysis gave the binding constant of
Ka ¼ 2.5 £ 105 M21 which is an order magnitude higher than
any other anion examined here.
Figure 3. Partial ROESY spectra (400 MHz, 258C, mixing time: 400 ms) of 7 (7 mM) in 15% (v/v) CD3CNZC2D2Cl4.

Supramolecular Chemistry
49
Table 1. Association constants (Ka ^ 15%, M21) of 7 with
anions in 10% (v/v) CD3OH–acetone-d6 at 24 ^ 18C.
˚
hydrogen bonds (2.43–2.70 A), but the urea NH protons are
˚
too far away (3.82–3.87 A) from the chloride ion to form
hydrogen bonds.
Aniona
Ka (M21
)
In conclusion, an indolocarbazole dimer with urea
functional groups has been prepared for the first time
which folds into a helical conformation and binds sulphate
ion strongly and selectively. This acylic dimer is able
to adopt a macrocycle-like conformation by weak
intramolecular interactions, which possibly reduces the
accompanying entropic penalty in the binding event of
acyclic receptors, thus enhancing the binding affinity
and selectivity towards a target guest. By extending the
approach shown here, it is possible to develop anion
receptors base on the foldable oligomers that are able to
strongly and selectively bind biologically important
polyatomic anions such as organic diphosphosphates and
triphosphates in the helical cavities.
Cl2
1700
270
50
Br2
N32
AcO2
H2PO24
SO242
13,000
10,000
25,0000b
a Anions were used as tetrabutylammonium salts.
b The association constant was determined by the fluorescence titration.
An evidence for the origin of high affinity and
selectivity of 7 towards sulphate ion could be seen in
1H NMR spectra (Figure 5). When complexedwith sulphate
ion, all of the four NH signals were largely downfield
shifted (Dd ¼ 2.67 and 1.89 ppm for two indolocarbazole
NH signals, and Dd ¼ 2.10 and 0.75 ppm for two urea NH
signals), implying that the NHs were all involved in the
hydrogen bonding with sulphate ion. In sharp contrast,
addition of chloride ion led to noticeable downfield shifts of
the signals only for the indolocarbazole NHs (Dd ¼ 1.80
and 1.48 ppm), whereas one (phenyl NH) of the two urea
NH signals was slightly shifted downfield (Dd ¼ 0.12 ppm)
and the other (butyl NH) was rather upfield shifted by
Dd ¼ 20.79 ppm, implying that the urea NH protons are
not directly involved in hydrogen bonding with chloride
ion. Here, the upfield shift of the butyl NH signal possibly
results from the conformational change upon the complex
formation which enforces the butyl NH proton to locate on
the indolocarbazole plane.
Experimental
General remarks
Thin layer chromatography was performed on silica gel 60
(F-254, 0.25 mm, Merck, Germany). Silica gel 60 (230–
240 mesh, Merck) was used for column chromatography.
Melting points were measured by using a Barnstead
Electrothermal (IA9100). FT-IR spectra were recorded on
a Jasco FT/IR-430 spectrometer (Japan). MALDI-TOF
mass spectra were conducted on a Bruker (LRF20).
Fluorescence emission spectra were recorded on a Jasco
(FP-6300). 1H NMR and 13C NMR spectra were obtained
on a Bruker Advance II 400 MHz spectrometer
(Germany). The chemical shifts of 1H NMR and 13C
NMR spectra are reported using the solvent signal as an
internal reference for 1H NMR spectra (DMSO-d6
2.48 ppm, acetonitrile-d3 1.94 ppm, 1,1,2,2-tetrachlor-
oethane-d2 6.00 ppm), for 13C NMR spectra (DMSO-d6
39.5 ppm). The elemental analysis data were obtained
from Research Institute for Basic Science at the Sogang
University. All reagents were used as received, and
Theoretical calculation (MacroModel 9.1) (10) also
shows apparent differences in the binding mode between
the sulphate and chloride complexes (Figure 6). In the
sulphate complex, all of the existing NH protons form
˚
hydrogen bonds with the distances of 1.76–2.11 A between
NH protons and sulphate oxygen atoms. In the chloride
complex, however, distances between four indolocarbazole
NH protons and chloride ion are in the range of normal
Figure 4. (a) Fluorescence spectral change of 7 upon addition of ðBu4NþÞ2SO422 in 10% (v/v) MeOH–acetone at 258C and (b) a
theoretical curve fitted to titration data (dots).

50
H.J. Kim et al.
Figure 5. Partial 1H NMR spectra (400 MHz, 20% (v/v) CD3CNZC2D2Cl4, 258C) of (a) 7 (1 mM), (b) 7 þ Bu4NþCl2 (1.2 equiv.) and
(c) 7 þ ðBu4NþÞ2SO242 (1.2 equiv.).
solvents were used either as purchased or purified by
standard methods.
d 8.59 (s, 1H; NH), 7.81 (dd, J ¼ 1.8, 2.0 Hz, 1H), 7.21 (m,
2H), 7.16 (t, J ¼ 7.7, 8.1 Hz, 1H), 6.19 (t, J ¼ 5.6 Hz, 1H;
NH), 3.06 (m, J ¼ 9.8 Hz, 2H), 1.41 (m, J ¼ 6.8 Hz, 2H),
1.29 (m, 2H), 0.89 (t, J ¼ 7.3 Hz, 3H); 13C NMR (100 MHz,
DMSO-d6) d 154.9, 142.3, 130.5, 123.4, 121.7, 119.7,
116.3, 38.7, 31.8, 19.5, 13.7; IR (KBr) y 3339 (NH), 1631
(CvO) cm21; MALDI-TOF m/z calcd for C11H15BrN2O
270.0 [M]þ, found 271.1 [M þ H]þ; Elemental analysis
calcd for C11H15BrN2O: C 48.72, H 5.58, N 10.33, found C
48.77, H 5.45, N 10.20.
Synthesis
1-(3-Bromophenyl)-3-butylurea (3)
3-Bromoaniline (2) (1.36 mL, 12.3 mmol) was dissolved in
anhydrous tetrahydrofuran (THF) (34 mL) and n-butyl
isocyanate (1.14 mL, 10.2 mmol) was added. The solution
was heated at reflux under nitrogen for 10 h. The reaction
mixture was concentrated, dissolved in CH2Cl2 and washed
with 1 M HCl, and distilled water sequentially. After
concentration, the residue was purified by flash column
chromatography (silica gel, CH2Cl2–EtOAc ¼ 3:1) to give
1-(3-bromophenyl)-3-butylurea (3) (2.14 g, 77%) as an
ivory solid. MP: 71–728C; 1H NMR (400 MHz, DMSO-d6)
1-Butyl-3-(3-ethynylphenyl)urea (4)
Compound 3 (2.14 g, 7.89mmol), CuI (30 mg, 0.16mmol),
PPh3 (207mg, 0.79mmol) and Pd(dba)2 (91 mg, 0.16mmol)
were added to a 50-mL Schlenk flask under N2 gas. The flask
Figure 6. Energy-minimised structures of (a) 7ꢀSO4 and (b) 7·Cl2 complexes (MacroModel 9.1, OPLS 2001 force field, gas phase).
22
Hydrogen bonds between NH protons and anion are marked as dotted lines.

Supramolecular Chemistry
51
was fitted with rubber septum, and then evacuated under
vacuum and back-filled with N2 gas three times. After
addition of dry THF (10 mL), Et3N (15 mL) and
ethynyltrimethylsilane (3.44 mL, 23.67 mmol), the septum
was changed into a screwed cock. After degassed three
times, the solution was stirred at 858C for 12h. The resulting
suspension was allowed to cool down to room temperature,
filtered through Celite and concentrated. The residue was
dissolved in CH2Cl2 and washed with distilled water. After
concentration, the mixture was dissolved in THF (24 mL).
The solution was treated with tetra-n-butylammonium
fluoride (1 M solution in THF, 7.11mL, 7.11mmol) at 08C,
and then stirred at room temperature for 30min. After
concentration, the crude mixture was purified by flash
column chromatography (silica gel, CH2Cl2 –
EtOAc ¼ 10:1) to give 1-butyl-3-(3-ethynylphenyl)urea
(4) (1.4g, 82% for two steps) as a white solid. MP: 100–
1028C; 1H NMR (400 MHz, DMSO-d6) d 8.53 (s, 1H; NH),
7.61 (dd, J ¼ 1.6 Hz, 1H), 7.30 (t, J ¼ 8.4 Hz, 1H), 7.21
(t, J ¼ 8.0 Hz, 1H), 6.98 (d, J ¼ 3.6 Hz, 1H), 6.19
(t, J ¼ 5.2, 5.6 Hz, 1H; NH), 4.11 (s, 1H), 3.07 (m,
J ¼ 9.6 Hz, 2H), 1.42 (m, J ¼ 6.8 Hz, 2H), 1.35 (m,
J ¼ 16 Hz, 2H), 0.89 (t, J ¼ 7.6 Hz, 3H); 13C NMR
(100MHz, DMSO-d6) d 155.1, 140.8, 129.0, 124.2, 121.9,
120.3, 118.2, 83.8, 80.0, 38.7, 31.8, 19.5, 13.7; IR (KBr) y
3299 (NH), 2117 (CuC), 1654 (CvO) cm21; MALDI-
TOF m/z calcd for C13H16N2O 216.1 [M]þ, found 217.1
[M þ H]þ; Elemental analysis calcd for C13H16N2O: C
72.19, H 7.46, N 12.95, found C 72.27, H 7.57, N 12.77.
125.8, 125.6, 125.5, 124.3, 123.9, 123.7, 122.8, 121.0,
120.6, 120.1, 118.8, 118.2, 117.5, 116.2 112.5, 112.4,
104.5, 93.2, 85.9, 76.7, 38.7, 34.5, 34.5, 31.9, 31.8, 19.5,
13.7; IR (KBr) y 3396 (NH), 1655 (CvO) cm21; MALDI-
TOF m/z calcd for C39H41IN4O 708.2 [M]þ, found 709.3
[M þ H]þ; Elemental analysis calcd for C39H41IN4O: C
66.10, H 5.83, N 7.91, found C 66.15, H 5.77, N 7.75.
1-Butyl-3-(3-((3,8-di-tert-butyl-10-ethynyl-11,12-
dihydroindolo[2,3-a]carbazol-1-yl)ethynyl)phenyl)urea
(6)
Compound 5 (1.01 g, 1.42 mmol), CuI (27 mg, 0.14 mmol)
and Pd(PPh3)2Cl2 (100 mg, 0.14 mmol) were added to a
50-mL Schlenk flask under nitrogen. The flask was fitted
with a rubber septum, and then evacuated under vacuum
and back-filled with N2 gas three times. After addition of
dry THF (7 mL), Et3N (13 mL) and ethynyltrimethylsilane
(0.62 mL, 4.26 mmol), the septum was changed into a
screwed cock. After degassed three times, the solution was
stirred at 568C for 15 h. The resulting suspension was
allowed to cool down to room temperature, filtered through
Celite and concentrated. The residue was dissolved in
CH2Cl2 and washed with distilled water. After concen-
tration under reduced pressure, the mixture was dissolved
in THF (10 mL). The solution was treated with tetra-n-
butylammonium fluoride (1 M solution in THF, 1.42 mL,
1.42 mmol) at 08C, and then stirred at room temperature for
30 min. After concentration, the crude product was purified
by flash column chromatography (silica gel, CH2Cl2) to
give 6 (0.59 g, 69% for two steps) as a pale yellow solid.
MP . 2008C (dec); 1H NMR (400 MHz, DMSO-d6) d
11.20 (s, 1H; NH), 11.14 (s, 1H; NH), 8.65 (s, 1H; NH),
8.28 (s, 2H), 8.03 (s, 2H), 7.88 (s, 1H), 7.66 (s, 1H), 7.58
(s, 1H), 7.43 (d, J ¼ 3.6, 4.6 Hz, 1H), 7.37 (t, J ¼ 7.3,
8.1 Hz, 1H), 7.29 (d, J ¼ 3.6 Hz, 1H), 6.24 (t, J ¼ 5.2,
5.3 Hz, 1H; NH), 4,76 (s, 1H), 3.12 (m, J ¼ 9.6 Hz, 2H)
1-Butyl-3-(3-((3,8-di-tert-butyl-10-iodo-11,12-
dihydroindolo[2,3-a]carbazol-1-yl)ethynyl)phenyl)urea
(5)
Compound 1 (2.15 g, 3.46 mmol), CuI (33 mg, 0.17 mmol)
and Pd(PPh3)2Cl2 (120 mg, 0.17 mmol) were added to a
50-mL Schlenk flask under nitrogen. The flask was fitted
with a rubber septum, evacuated under vacuum and back-
filled with nitrogen. After addition of dry THF (17 mL),
Et3N (15 mL) and compound 5, the rubber septum was
changed into a screwed cock. After degassed three times,
the solution was stirred at 568C for 12 h. The resulting
suspension was allowed to cool down to room temperature,
filtered through Celite and concentrated. The residue was
dissolved in CH2Cl2 and washed with distilled water. After
concentration, the residue was purified by flash column
chromatography (silica gel, hexane–EtOAc ¼ 3:1) to give
5 (1.22 g, 48%) as a pale yellow solid. MP . 2308C (dec);
1H NMR (400 MHz, DMSO-d6) d 11.23 (s, 1H; NH), 10.90
(s, 1H; NH), 8.64 (s, 1H; NH), 8.28 (s, 1H), 8.22 (s, 1H),
8.00 (m, 2H), 7.89 (s, 1H), 7.79 (s, 1H), 7.65 (s, 1H), 7.38
(m, 2H), 7.29 (d, J ¼ 3.6 Hz, 1H), 6.23 (t, 1H; NH), 3.11
(m, J ¼ 9.6 Hz, 2H), 1.43 (d, 18H), 1.33 (m, 4H), 0.89
(t, J ¼ 7.3 Hz, 3H); 13C NMR (100 MHz, DMSO-d6) d
155.2, 143.9, 142.0, 140.1, 139.0, 137.5, 130.7, 129.2,
1.44 (d, 20H), 1.34 (m, 2H), 0.88 (t, J ¼ 7.2 Hz, 3H); 13
C
NMR (100 MHz, DMSO-d6) d 155.2, 142.1, 141.9, 141.0,
138.2, 137.6, 129.3, 125.9, 125.8, 125.7, 125.5, 124.3,
123.8, 123.7, 122.8, 120.6, 120.5, 120.2, 118.3, 117.7,
117.5, 112.3, 104.5, 103.8, 93.3, 85.9, 84.8, 81.2, 38.8,
34.6, 34.5, 31.9, 31.8, 31.8, 19.6, 13.7; IR (KBr) y 3397
(NH), 2202 (CuC), 1655 (CvO) cm21; MALDI-TOF m/z
calcd for C41H42N4O 606.3 [M]þ, found 607.1 [M þ H]þ;
Elemental analysis calcd for C41H42N4O: C 81.15, H 6.98,
N 9.23, found C 81.12, H 7.12, N 8.83.
1,1(0-(3,30-(10,100-(Buta-1,3-diyne-1,4-diyl)bis(3,8-di-
tert-butyl-11,12-dihydroindolo[2,3-a]carbazole-10,1-
diyl)bis(ethyne-2,1-diyl))bis(3,1-phenylene))bis(3-
butylurea) (7)
Compound 6 (0.43 g, 0.71 mmol) was dissolved in
CH2Cl2 (3.5 mL) and acetonitrile (3.5 mL), and then

52
H.J. Kim et al.
(2011-0017945). H.J.K. acknowledges the fellowship of the BK
21 program from the Ministry of Education and Human
Resources Development.
Pd(OAc)2 (3.18 mg, 0.014 mmol), CuI (2.70 mg,
0.014 mmol) and DABCO (0.24 g, 2.13 mmol) were
added. The mixture was stirred in air at room temperature
for 2 h. The mixture was filtered through Celite and
concentrated under reduced pressure. The residue was
dissolved in CH2Cl2, washed with distilled water and
dried over anhydrous Na2SO4. After concentration, the
residue was purified by flash column chromatography
(silica gel, CH2Cl2) to give 7 (0.37 g, 43%) as a yellow
Note
1. The energy-minimised structures were obtained using OPLS
2001 force field via Monte Carlo conformational search
(5000 times, in the gas phase).
1
solid. MP . 2868C (dec); H NMR (400 MHz, DMSO-
d6) d 11.43 (s, 1H; NH), 11.17 (s, 1H; NH), 8.50 (s, 1H;
NH), 8.40 (s, 1H), 8.30 (s, 1H), 8.07 (s, 2H), 7.91 (s, 1H),
7.72 (s, 1H), 7.66 (s, 1H), 7.23 (m, 3H), 6.05 (t, J ¼ 6.0,
5.6 Hz, 1H; NH), 2.87 (m, J ¼ 9.6 Hz, 2H), 1.46 (d, 18H),
1.14 (m, 4H), 0.70 (t, J ¼ 7.2 Hz, 3H); 13C NMR
(100 MHz, DMSO-d6) d 155.0, 142.2, 142.1, 140.9,
138.6, 137.5, 129.1, 126.4, 125.9, 125.8, 125.7, 124.3,
124.1, 123.7, 122.7, 120.8, 120.4, 120.0, 119.2, 118.1,
117.5, 112.6, 112.3, 104.6, 102.2, 93.3, 85.7, 80.8, 77.6,
38.5, 34.6, 34.5, 31.8, 31.7, 31.6, 19.3, 13.5; IR (KBr) y
3397 (NH), 2134 (CuC), 1655 (CvO) cm21; MALDI-
TOF m/z calcd for C82H82N8O2 1210.7 [M]þ, found
1210.8 [M]þ; Elemental analysis calcd for C82H82N8O2:
C 81.29, H 6.82, N 9.25, found C 81.24, H 6.89, N 9.26.
References
(1) (a) Gellman, S.H. Acc. Chem. Res. 1998, 31, 173; (b) Hill,
D.J.; Mio, M.J.; Prince, R.B.; Hughes, T.S.; Moore, J.S.
Chem. Rev. 2001, 101, 3893; (c) Foldamers: Structure,
Properties, and Applications: Hecht, S., Huc, I., Eds.;
Wiley-VCH: Weinheim, Germany, 2007; (d) Juwarker, H.;
Suk, J.-m.; Jeong, K.-S. Chem. Soc. Rev. 2009, 38, 3316.
(2) For selected examples of anion receptors based on
indolocarbazoles, see: (a) Curiel, D.; Cowley, A.; Beer,
P.D. Chem. Commun. 2005, 236; (b) Chang, K.-J.; Moon,
D.; Lah, M.S.; Jeong, K.-S. Angew. Chem. Int. Ed. 2005, 44,
7926; (c) Kim, N.-K.; Chang, K.-J.; Moon, D.; Lah, M.S.;
Jeong, K.-S. Chem. Commun. 2007, 29, 3401; (d)
Chmielewski, M.J.; Zhao, L.; Brown, A.; Curiel, D.;
Sambrook, M.R.; Thompson, A.L.; Santos, S.M.; Felix, V.;
Davis, J.J.; Beer, P.D. Chem. Commun. 2008, 3154; (e) Ju,
J.; Park, M.; Suk, J.-m.; Lah, M.S.; Jeong, K.-S. Chem.
Commun. 2008, 3546; (f) Brown, A.; Mullen, K.M.; Ryu, J.;
Chmielewski, M.J.; Santos, S.M.; Felix, V.; Thompson,
A.L.; Warren, J.E.; Pascu, S.I.; Beer, P.D. J. Am. Chem. Soc.
2009, 131, 4937; (g) Zhao, Y.; Li, Y.; Li, Y.; Zheng, H.; Yin,
X.; Liu, H.; Chem. Commun. 2010, 46, 5698; (h) Lee, C.-H.;
Yoon, H.; Kim, P.; Cho, S.; Kim, D.; Jang, W.-D. Chem.
Commun. 2011, 47, 4246.
(3) (a) Suk, J.-m.; Jeong, K.-S. J. Am. Chem. Soc. 2008, 130,
11868; (b) Kim, J.-i.; Juwarker, H.; Liu, X.; Lah, M.S.;
Jeong, K.-S. Chem. Commun. 2010, 46, 764; (c) Suk, J.-m.;
Kim, J.-i.; Jeong, K.-S. Chem. Asian J. 2011, 6, 1992.
(4) Suk, J.-m.; Naidu, V.R.; Liu, X.; Lah, M.S.; Jeong, K.-S.
J. Am. Chem. Soc. 2011, 133, 13938.
(5) For a review of anion receptors based on indole-type NHs,
see: Gale, P.A. Chem. Commun. 2008, 4525; and also see: (a)
Chang, K.-J.; Kang, B.-N.; Lee, M.-H.; Jeong, K.-S. J. Am.
Chem. Soc. 2005, 127, 12214; (b) Yu, J.O.; Browning, S.;
Farrar, D.H. Chem. Commun. 2008, 1020; (c) Hiscock, J.R.;
Caltagirone, C.; Light, M.E.; Hursthouse, M.B.; Gale, P.A.
Titrations
The experiments were conducted using 1H NMR
spectroscopy and were all duplicated at 24 ^ 18C. A
solution of a receptor 7 (1.0 £ 1023 M) was prepared in
10% (v/v) CD3OH–acetone-d6. Using this solution, each
stock solution of tetra-n-butylammonium anion was
prepared and the concentrations ranged from 1.0 £ 1022
to 3.0 £ 1022 M, depending on the association constant. A
500 mL of 7 was transferred to an NMR tube, and an initial
spectrum was taken at 24 ^ 18C. Small portions of the
tetra-n-butylammonium anion solution (10 mL initially,
then 15–80 mL and finally 100–120 mL) were added, and
the spectrum was recorded after each addition and 12–15
data points were obtained.
In case of sulphate ion, titration was performed in the
fluorescence spectroscopy. A solution of 7 (2.0 £ 1026 M)
was prepared in 10% (v/v) CH3OH–acetone. Using this
solution, each stock solution of bis(tetrabutylammonium)
sulphate was prepared with the concentrations of
2.0 £ 1024 M. A 2.0 mL of 7 was transferred to a
fluorescence cuvette, and an initial spectrum was taken at
24 ^ 18C. Small portions of the anion solution (10 mL
initially, then 15–80 mL and finally 100 mL) were added,
and the spectrum was recorded after each addition and 11
data points were obtained.
´
Org. Biomol. Chem. 2009, 7, 1781; (d) Dydio, P.; Zielinski,
T.; Jurczak, J. Chem. Commun. 2009, 4560; (e) Caltagirone,
C.; Gale, P.A.; Hiscock, J.R.; Hursthouse, M.B.; Light, M.E.;
Tizzard, G.J. Supramol. Chem. 2009, 21, 125; (f) Gale, P.A.;
Hiscock, J.R.; Jie, C.Z.; Hursthouse, M.B.; Light, M.E.
Chem. Sci. 2010, 1, 215; (g) Wang, T.; Yan, X.-P.; Chem. Eur.
J. 2010, 16, 4639; (h) Wang, L.; He, X.; Guo, Y.; Wu, J.;
Shao, S. Org. Biomol. Chem. 2011, 9, 752.
(6) For recent reviews of urea-based anion receptors, see: (a)
Caltagirone, C.; Gale, P.A. Chem. Soc. Rev. 2009, 38, 520;
(b) Steed, J.W. Chem. Soc. Rev. 2010, 39, 3686; (c) Hay,
B.P. Chem. Soc. Rev. 2010, 39, 3700; (d) Li, A.-F.; Wang, J.-
H.; Wang, F.; Jiang, Y.-B. Chem. Soc. Rev. 2010, 39, 3729;
(e) Ballester, P. Chem. Soc. Rev. 2010, 39, 3810; (f)
Amendola, V.; Fabbrizzi, L.; Mosca, L. Chem. Soc. Rev.
2010, 39, 3889; (g) Dydio, P.; Lichosyt, D.; Jurczak, J.
Chem. Soc. Rev. 2011, 40, 2971.
Acknowledgements
This study was supported by the National Research Foundation
of Korea (NRF) grant funded by the Korea government (MEST)

Supramolecular Chemistry
53
(7) For selected recent examples of urea-based anion receptors,
see: (a) Hiscock, J.R.; Gale, P.A.; Caltagirone, C.;
Hursthouse, M.B.; Light, M.E. Supramol. Chem. 2010,
22, 647; (b) Bergamaschi, G.; Boiocchi, M.; Monzani, E.;
Amendola, V. Org. Biomol. Chem. 2011, 9, 8276; (c) Baggi,
G.; Boiocchi, M.; Fabbrizzi, L.; Mosca, L. Chem. Eur. J.
2011, 17, 9423; (d) Wenzel, M.; Light, M.E.; Davis, A.P.;
Gale, P.A. Chem. Commun. 2011, 47, 7641; (e) Custelcean,
R.; Bonnesen, P.V.; Duncan, N.C.; Zhang, X.; Watson, L.A.;
Berkel, G.V.; Parson, W.B.; Hay, B.P. J. Am. Chem. Soc.
2012, 134, 8525; (f) Wim, V.R.; Jef, C.; Koen, R.; Luc,
V.M.; Wouter, M.; Wim, D.J. Org. Chem. 2012, 77, 2791;
(g) Wu, B.; Jia, C.; Wang, X.; Li, S.; Huang, X.; Yang, X.-J.
Org. Lett. 2012, 14, 684; (h) Li, S.; Wei, M.; Huang, X.;
Yang, X.-J.; Wu, B. Chem. Commun. 2012, 48, 3097.
(8) Sonogashira, K. In Metal-Catalyzed Cross-Coupling Reac-
tions; Diederich, F., Stang, P.J., Eds; Wiley-VCH:
Weinheim, Germany; p. 203, 1998.
(9) Li, J.-H.; Liang, Y.; Xie, Y.-X. J. Org. Chem. 2005, 70, 4393.
(10) (a) Mohamadi, F.; Richards, N.G.J.; Guida, W.C.; Liskamp,
R.; Lipton, M.; Caufield, C.; Chang, G.; Hendrickson, T.;
Still, W.C. J. Comp. Chem. 1990, 11, 440; (b) Halgren, T.A.
J. Comp. Chem. 1996, 17, 490.
(11) (a) Long, J.R.; Drago, R.S. J. Chem. Educ. 1982, 59, 1037;
(b) Thordarson, P. Chem. Soc. Rev. 2011, 40, 1305.