Supramolecular assemblies and redox modulation of pyromellitic diimide-based cyclophane via noncovalent interactions with naphthol

Article abstract of DOI:10.1021/jo0600196

This paper reports the electroscopic and electrochemical properties of [2 + 2] pyromellitic diimide-based cyclophane 1 as well as acyclic N,N′-bis(2-methoxybenzyl)pyromellitic diimide 2 and the clathrate compounds formed by 1. Compound 1 was synthesized b

Full text of DOI:10.1021/jo0600196

Supramolecular Assemblies and Redox Modulation of Pyromellitic
Diimide-Based Cyclophane via Noncovalent Interactions with
Naphthol1
Shin-ichiro Kato,†,‡ Taisuke Matsumoto,§ Keiko Ideta,§ Toshiaki Shimasaki,†,‡
Kenta Goto,† and Teruo Shinmyozu*,†
Institute for Materials Chemistry and Engineering (IMCE) and Department of Molecular Chemistry,
Graduate School of Sciences, Kyushu UniVersity, 6-10-1 Higashi-ku, Fukuoka 812-8581, Japan, and
Institute for Materials Chemistry and Engineering (IMCE), 6-1 Kasuga-koh-en, Kasuga 816-8580, Japan
shinmyo@ms.ifoc.kyushu-u.ac.jp
ReceiVed December 30, 2005
This paper reports the electroscopic and electrochemical properties of [2 + 2] pyromellitic diimide-
based cyclophane 1 as well as acyclic N,N′-bis(2-methoxybenzyl)pyromellitic diimide 2 and the clathrate
compounds formed by 1. Compound 1 was synthesized by direct cyclocondensation. Its structure was
determined by an X-ray crystallographic analysis of a single crystal obtained by recrystallization from
DMF. The intramolecular charge-transfer interactions of 1 and 2 were characterized by UV/vis spectroscopy
and MO calculations. The UV/vis spectra showed that the tail of a longer wavelength absorption of both
1 and 2 reached the visible region. MO calculations (B3LYP/6-31G*) showed that the HOMO and LUMO
orbitals of 1 and 2 substantially localize in the xylyl and pyromellitic diimide moieties across the methylene
linker, respectively. The X-ray crystallographic analyses demonstrated that single crystals grown from a
mixture of 1 and R-naphthol and a mixture of 1 and â-naphthol were the clathrate compounds with 1D
and 2D supramolecular assemblies, respectively, which are formed by a combination of hydrogen-bonding
and charge-transfer interactions. From the cyclic voltammetry measurements, both 1 and 2 showed
reversible reduction processes, and the reduction potential observed at -1.09 V vs Ag/Ag+ for 2 split
into two potentials at -1.01 and -1.14 V for 1. The addition of R- and â-naphthol induced a decrease
in the potentials due to the diradical anion of 1 and radical anion of 2 by about 80 mV, and their reduction
processes were reversible.
1. Introduction
In the field of supramolecular chemistry, there has been much
interest over the past two decades in the design of molecular
receptors and mechanically interlocked molecules. For example,
catenanes and rotaxanes, and nanoscale supramolecular as-
semblies, have led to the exploitation of many types of
intermolecular interactions, including hydrogen bonding,2 the
solvophovic effect,3 metal-ligand coordination,4 and charge-
* To whom correspondence should be addressed. Tel: +81 92 642 2716.
Fax: +81 92 642 2735.
† Institute for Materials Chemistry and Engineering (IMCE), Kyushu Uni-
versity.
(1) Molecular Tubes and Capsules. 2. For part 1, see: Iwanaga, T.;
Nakamoto, R.; Yasutake, M.; Takemura, H.; Sako, K.; Shinmyozu, T.
Angew. Chem., Int. Ed. 2006, 45, 3643-3647.
‡ Department of Molecular Chemistry, Kyushu University.
§ Institute for Materials Chemistry and Engineering (IMCE).
10.1021/jo0600196 CCC: $33.50 © 2006 American Chemical Society
Published on Web 05/27/2006
J. Org. Chem. 2006, 71, 4723-4733
4723

Kato et al.
transfer (CT) interaction.5 In the CT interaction, aromatic
diimide-based macrocycles with a strong electron-withdrawing
properties have been widely used for the creation of the above
supramolecular structures1,6-9 and investigation of transannular
interactions.10-12 For example, the construction of aromatic-
diimide based macrocycles is a key synthetic procedure for
various neutral [2]catenanes by taking advantage of the CT
interaction between the electron-rich aromatic host and an
included electron-deficient aromatic diimide derivatives as a
guest.7,8 New supramolecular assemblies such as [3]pseudo-
rotaxane13 and macrocycle-tweezer complexes14 have been
successfully synthesized by using this methodology. The
aromatic diimide-based macrocycles with a planar chirality have
recently been reported.15 Lately, we have reported the first
FIGURE 1. Structures of [2 + 2] pyromellitic diimide-based cyclo-
phane 1 and acyclic pyromellitic dimide derivative 2.
(2) For reviews of hydrogen-bonded assemblies, see: (a) Conn, M. M.;
Rebek, J., Jr. Chem. ReV. 1997, 97, 1647-1668. (b) Rebek, J., Jr. Acc.
Chem. Res. 1999, 32, 278-286. (c) Rebek, J., Jr. Chem. Commun. 2000,
637-643. (d) Greig, L. M.; Philp, D. Chem. Soc. ReV. 2001, 30, 287-302.
(e) Prins, L. J.; Reinhoudt, D. N.; Timmerman, P. Angew. Chem., Int. Ed.
2001, 40, 2382-2426.
example of “cyclophanes within cyclophanes” that has been
confirmed by X-ray crystallography and whose driving force
is a CT interaction between an aromatic diimide and a benzene
ring.1 The created supramolecular structures would be consid-
ered as attractive functional materials due to the presence of
photophysically and electrochemically active aromatic diim-
ides.16,17 Therefore, it is important to understand the nature of
the relationship between the activities and molecular structures
of aromatic diimide-based macrocycles as structural components
for supramolecular structures. Furthermore, aromatic diimides,
whose conformation is controlled by 2-tert-butylphenyl groups
at the nitrogen atoms, have been reported to form sandwich-
like clathrate compounds and a 2D network by a combination
of CT interactions, CH-π interactions, and hydrogen bonding.18
In this context, our interest in the electroscopic and electro-
chemical properties of the aromatic diimide-based macrocycles
and their formation of new-type supramolecular assemblies via
noncovalent interactions led us to design and synthesize the
simple [2 + 2] pyromellitic diimide-based cyclophane 1 (Figure
1). The high solubility in common organic solvents due to the
attachment of butoxy groups to the benzene unit should allow
the investigation of the electroscopic and electrochemical
properties under various solution conditions, and the introduction
of a methylene linker between the pyromellitic diimide moiety
and the benzene unit should leave the sufficient electron-
withdrawing property to the pyromellitic diimide moiety for the
formation of supramolecular assemblies. We now report here
the synthesis and structural properties of 1 and its electroscopic
and electrochemical properties with the acyclic N,N′-bis(2-
methoxybenzyl)pyromellitic diimide 2 as a reference. We will
then describe the formation of clathrate compounds formed of
1 with naphthols and their electroscopic and electrochemical
properties based on the UV/vis spectra, MO calculations, cyclic
voltammograms, and X-ray crystallographic analyses. Finally,
the redox modulation of 1 and 2 via noncovalent interactions
with naphthols will be demonstrated in cyclic voltammetry
measurements.
(3) Cubberley, M. S.; Iverson, B. L. J. Am. Chem. Soc. 2001, 123, 7560-
7563 and references therein.
(4) For reviews of metal-coordinative assemblies, see: (a) Fujita, M.
Chem. Soc. ReV. 1998, 27, 417-425. (b) Caulder, D. L.; Raymond, K. N.
Acc. Chem. Res. 1999, 32, 975-982. (c) Caulder, D. L.; Raymond, K. N.
J. Chem. Soc., Dalton Trans. 1999, 1185-1200. (d) Seidel, S. R.; Stang,
P. J. Acc. Chem. Rec. 2002, 35, 972-983. (e) Vilar, R. Angew. Chem., Int.
Ed. 2003, 42, 1460-1477. (f) Fujita, M.; Tominaga, M.; Hori, A.; Therrien,
B. Acc. Chem. Res. 2005, 38, 371-380.
(5) For reviews of aromatic interactions, see: (a) Hunter, C. A.; Lawson,
K. R.; Perkins, J.; Urch, C. J. J. Chem Soc., Perkin Trans. 2 2001, 651-
669. (b) Meyer, E. A.; Castellano, R. K.; Diederich, F. Angew. Chem., Int.
Ed. 2003, 42, 1210-1250. (c) Kla¨rner, F.-G.; Kahlert, B. Acc, Chem. Res.
2003, 36, 919-932. (d) Zhao, D.; Moore, J. S. Chem. Commun. 2003, 807-
818.
(6) For molecular receptors, see: (a) Jazwinski, J.; Blacker, A. J.; Lehn,
J.-M.; Cesario, M.; Guilhem, J.; Pascard, C. Tetrahedron Lett. 1987, 28,
6057-6060. (b) Anderson, H. L.; Hunter, C. A.; Meah, M. N.; Sanders, J.
K. M. J. Am. Chem. Soc. 1990, 112, 5780-5789. (c) Bilyk, A.; Harding,
M. M. Chem. Commun. 1995, 1697-1698. (d) Houghton, M. A.; Bilyk,
A.; Harding, M. M.; Turner, P.; Hambley, T. W. J. Chem. Soc., Dalton.
Trans. 1997, 2725-2733. (e) Chen, G.; Lean, J. T.; Alcala´, M.; Mallouk,
T. E. J. Org. Chem. 2001, 66, 3027-3034.
(7) For review of catenanes and oligocatenanes, see: Raehm, L.;
Hamilton, D. G.; Sanders, J. K. M. Synlett 2002, 1743-1761.
(8) For neutral [2]catenanes, see: (a) Hamilton, D. G.; Sanders, J. K.
M.; Davies, J. E.; Clegg, W.; Teat, S. J. Chem. Commun. 1997, 897-898.
(b) Hamilton, D. G.; Davies, J. E.; Prodi, L.; Sanders, J. K. M. Chem. Eur.
J. 1998, 4, 608-620. (c) Zhang, Q.; Hamilton, D. G.; Feeder, N.; Teat, S.
J.; Goodman, J. M.; Sanders, J. K. M. New. J. Chem. 1999, 23, 897-903.
(d) Hamilton, D. G.; Prodi, L.; Feeder, N.; Sanders, J. K. M. J. Chem.
Soc., Perkin Trans. 1 1999, 1057-1065. (e) Hamilton, D. G.; Montalti,
M.; Prodi, L.; Fontani, M.; Zanello, P.; Sanders, J. K. M. Chem. Eur. J.
2000, 6, 608-617. (f) Hansen, J. G.; Feeder, N.; Hamilton, D. G.; Gunter,
M. J.; Becher, J.; Sanders, J. K. M. Org. Lett. 2000, 2, 449-452. (g) Gunter,
M. J.; Farquhar, S. M. Org. Biomol. Chem. 2003, 1, 3450-3457. (h) Fallon,
G. D.; Lee, M. A.-P.; Langford, S. J.; Nichols, P. J. Org. Lett. 2004, 6,
655-658.
(9) For [2]rotaxanes, see: (a) Nakamura, Y.; Minami, S.; Iizuka, K.;
Nishimura, J. Angew. Chem., Int. Ed. 2003, 42, 3158-3162. (b) Wang,
X.-Z.; Li, X.-Q.; Shao, X.-B.; Zhao, X.; Deng, P.; Jiang, X.-K.; Li, Z.-T.;
Chen, Y.-Q. Chem. Eur. J. 2003, 9, 2904-2913. (c) Iijima, T.; Vignon, S.
A.; Tseng, H.-R.; Jarrosson, T.; Sanders, J. K. M.; Marchioni, F.; Venturi,
M.; Apostoli, E.; Balzani, V.; Stoddart, J. F. Chem. Eur. J. 2004, 10, 6375-
6392.
(15) Degenhardt, C. F., III; Smith, M. D.; Shimizu, K. D. Org. Lett.
2002, 4, 723-726.
(16) For review of perylene bisimide dyes, see: Wu¨rthner, F. Chem.
Commun. 2004, 1564-1579.
(17) (a) Wu¨rthner, F.; Sautter, A.; Schmid, D.; Weber, P. J. A. Chem.
Eur. J. 2001, 7, 894-902. (b) You, C.-C.; Wu¨rthner, F. J. Am. Chem. Soc.
2003, 125, 9716-9725. (c) Wu¨rthner, F.; Sautter, A. Org. Biomol. Chem.
2003, 1, 240-243.
(18) (a) Kishikawa, K.; Tsubokura, S.; Kohmoto, S.; Yamamoto, M.;
Yamaguchi, K. J. Org. Chem. 1999, 64, 7568-7578. (b) Kishikawa, K.;
Iwashima, C.; Kohmoto, S.; Yamaguchi, K.; Yamamoto, M. J. Chem. Soc.,
Perkin Trans. 1 2000, 2217-2221.
(10) Borkent, J. H.; Verhoeven, J. W.; de Boer, Th. J. Chem. Phys. Lett.
1976, 42, 50-53.
(11) Staab, H. A.; Nikolic, S.; Krieger, C. Eur. J. Org. Chem. 1999,
1459-1470.
(12) Hansen, J. G.; Bang, K. S.; Thorup, N.; Becher, J. Eur. J. Org.
Chem. 2000, 2135-2144.
(13) Colquhoun, H. M.; Williams, D. J.; Zhu, Z. J. Am. Chem. Soc. 2002,
124, 13346-13347.
(14) (a) Colquhoun, H. M.; Zhu, Z.; Williams, D. J. Org. Lett. 2003, 5,
4353-4356. (b) Colquhoun, H. M.; Zhu, Z. Angew. Chem., Int. Ed. 2004,
43, 5040-5045.
4724 J. Org. Chem., Vol. 71, No. 13, 2006

Supramolecular Assemblies of Pyromellitic Diimide-Based Cyclophane
SCHEME 1. Synthesis of [2 + 2] Pyromellitic Diimide-Based
Cyclophane 1 and Acyclic Pyromellitic Dimide Derivative 2
as a Reference
FIGURE 2. ORTEP drawings of the clathrate compound between the
pyromellitic diimide-based cyclophane 1 and DMF (1:2): (a) side view;
(b) bird’s-eye view. Selected bond lengths (Å) and angles (deg): C1-
C3 1.499(2), C2-C4 1.496(2), C3-C4 1.391(2), C4-C5 1.384(2), C5-
C6 1.388(2), C6-C7 1.394(2), C6-C10 1.495(2), C7-C8 1.383(2),
C7-C9 1.496(2), C11-C12 1.515(2), C16-C18 1.511(2), O1-C1
1.204(2), O2-C2 1.206(2), O3-C9 1.206(2), O4-C10 1.203(2), N1-
C1 1.391(2), N1-C2 1.390(2), N1*-C18 1.462(2), N2-C9 1.394(2),
N2-C10 1.392(2), N2-C11 1.454(2), N2-C11-C12 113.4(1), N1*-
C18-C16 114.2(1).
2. Results and Discussion
Synthesis. The synthesis of [2 + 2] pyromellitic diimide-
based cyclophane 1 was achieved by means of the direct
cyclocondensation of 1,3-bis(aminomethyl)-4,6-di-n-butoxy-
benzene 7 with pyromellitic dianhydride 8 (Scheme 1). The key
synthetic intermediate 7 was prepared from resorcinol 3 via four
steps (Williamson ether synthesis, iodination, cyanation, and
reduction) in about 40% overall yield by optimization of the
synthetic procedures reported by Tobe et al.19 The reduction of
1,3-di-n-butoxy-4,6-dicyanobenzene 6 was accomplished by the
treatment of diisobutylaluminum hydride at 110 °C in 81% yield
to afford the diamine 7. The direct cyclocondensation of the
diamine 7 with the dianhydride 8 in dry THF at 60 °C gave an
amic acid,18a which was dehydrated to give 1 by treatment with
Ac2O and NaOAc in 24% yield. The formation of the
intermediary amic acids were supported by the presence of the
broad signals due to the carboxylic acid protons at ca. 13-14
clathrate with DMF having the 1:2 stoichiometry. Figure 2
shows the molecular structure of 1 with the selected bond lengths
and angles. Transannular pyromellitic diimide π-faces of 1 set
in parallel across the xylyl moiety (Figure 2a) with the average
transannular distance between the central six-membered rings
being 5.06 Å, suggesting very weak transannular π-electronic
interactions between them. The distance between C17 and C17*
was 9.67 Å. Two xylyl π-faces were almost coplanar but slanted
with the distance of only 1.17 Å across the pyromellitic diimide
moiety (Figure 2b). The dihedral angle between the pyromellitic
diimide π-face and the xylyl π-face was almost perpendicular
(85.4°). In 1‚(DMF)2, the DMF molecules served as an adhesive
that bound the diimide molecules to form the 1D network
aligning the a-axis (Figure 3). The DMF molecule not only
interacted with the one imide ring of the diimide 1 but also
with the carbonyl oxygen of the diimide moiety of the
neighboring cyclophane via noncovalent multipoint interactions.
In addition to the parallel-conformer observed in the solid
state as described above (Figure 2), the syn- and anti-conformers
in 1 may be considered as stable conformational isomers (Figure
4). The temperature-dependent 1H NMR spectrum of 1 in CD2-
Cl2 displayed slight shifts and a broadening of some signals,
but no coalescence of the signals due to the stable conformers
was observed down to 173 K (Figure S1, Supporting Informa-
tion), indicating that the cyclophane 1 was quite flexible. To
estimate the relative stability of the possible three conformers
of 1, we examined the MO calculations for the cyclophane 1′,
in which the butoxy groups were replaced with methoxy groups
in 1 (Figure 5). The B3LYP/6-31G* level of MO calculations
predicted that syn-1′ was the most stable and the parallel-1′
and anti-1′ were less stable by 0.5 and 1.1 kcal/mol, respec-
tively.20 In the solid state, crystal packing forces may contribute
to the further stability of the parallel-conformers.
1
ppm in the H NMR spectrum in DMSO-d6. This coupling
reaction exclusively gave the [2 + 2] product 1 and the higher
oligomers such as [3 + 3] and [4 + 4] type macrocycles were
not isolated. In consequence, 1 was easily purified by conven-
tional column chromatography on silica gel with CHCl3. To
estimate the effect of the cyclophane moiety on electroscopic
and electrochemical properties, acyclic model compound N,N′-
bis(2-methoxybenzyl)pyromellitic diimide 2 as a reference was
prepared from 8 and 2-methoxybenzylamine 9 in 72% yield
according to similar procedures for the synthesis of 1. Com-
pounds 1 and 2 have been fully characterized by spectroscopy
and elemental analysis. The molecular structure of 1 has been
finally determined by an X-ray crystallographic analysis as
described below.
Compound 1 is soluble in CHCl3 and DMF. When it was
recrystallized from CHCl3 by vapor diffusion with hexane, pale
green needles were obtained, but they gradually effloresced.
Single crystals suitable for an X-ray crystallographic analysis
were obtained by recrystallization from DMF over 1 week as a
(19) Sasaki, S.; Mizuno, M.; Naemura, K.; Tobe, Y. J. Org. Chem. 2000,
65, 275-283.
J. Org. Chem, Vol. 71, No. 13, 2006 4725

Kato et al.
FIGURE 3. 1D molecular arrangement aligning a-axis formed in 1‚(DMF)2. Dashed lines are within the sum of the van der Waals radius. Hydrogen
atoms are omitted for clarify.
FIGURE 4. Stable conformers of the cyclophane 1.
UV/vis Spectra. Figure 6a shows the UV/vis spectra of 1
and 2 in CHCl3. The cyclophanes 1 [285 (ꢀ 10600), 305 (ꢀ
5400), and 317 nm (ꢀ 4500)] and 2 [274 (ꢀ 7300), 310 (ꢀ 2300),
and 320 nm (ꢀ 2500)] exhibited similar spectra with three
absorption maxima (λmax) over 250 nm due to the pyromellitic
FIGURE 5. Optimized structures of 1′ by MO calculations (Gaussian
03, B3LYP/6-31G*).
diimide and alkoxy-substituted benzene chromophores. The
Similarly, in the UV/vis spectrum of 2, the longer absorption
bands of 1 and 2 at around 305-310 nm and 317-320 nm were
band was broad and its tail reached near the visible region
assigned to the short and long axis polarized π-π* transitions
analogous to 1. These probably involved a weak intramolecular
at the pyromellitic diimide moiety, respectively.21 The relative
CT character from the electron-donating alkoxy-substituted
intensities of these two bands of 2 were changed when compared
benzene to the electron-withdrawing pyromellitic diimide
with the corresponding bands of 1. The absorption coefficients
moiety. The intramolecular CT character was supported by MO
(ꢀ) (2500) ascribed to a long axis polarized π-π* transition
calculations (B3LYP/6-31G*) which showed the HOMO and
was slightly higher than that (2300) of the short axis polarized
LUMO orbitals of 1 and 2 to be substantially localized in the
π-π* transition in 2, whereas the intensity (ꢀ 4500) ascribed
benzene and pyromellitic diimide moieties, respectively, across
to a long axis polarized π-π* transition was lower than that of
the methylene linker (Figure 7). Furthermore, the longer
the short axis polarized π-π* transition (ꢀ 5400) in 1. The
intramolecular CT band of 1 compared to that of 2 was predicted
magnified figure of the UV/vis spectra over 350 nm of 1 and 2
by the calculations (∆ HOMO-LUMO). As a result, the CHCl3
showed that the tail of the longer absorption band in 1 (Figure
solution of both 1 and 2 as well as in the solid state showed a
6b), which included an out-of-plane polarized n-π* transition
slight green-yellow color.
(340-360 nm),21 reached the visible region (>400 nm).
Complexation Studies. The finding that the clathrate 1‚
(DMF)2 formed a 1D network led us to construct a new
(20) Optimization of the structures of syn-1′, anti-1′, and parallel-1′
supramolecular assembly based on 1 as the clathrate host. We
conformers was performed by the MO calculations of B3LYP/6-31G* level
considered that the pyromellitic diimide moiety of 1 should serve
as an electron acceptor because the intramolecular CT character
was quite weak. To investigate the CT complexation of the
electron-poor host 1 and donor guests, the UV/vis spectra of 1
in the presence of various electron-rich aromatic guests were
of theory, and the sum of electronic and zero-point energies was calculated
to be -1670584.863 (syn-1′), -1670583.752 (anti-1′), and -1670584.247
(parallel-1′) kcal/mol (Tables S1-S3, Supporting Information).
(21) Gawron´ski, J.; Brzostowska, M.; Gawron´ska, K.; Koput, J.; Ry-
chlewska, U.; Skowronek, P.; Norde´n. B. Chem. Eur. J. 2002, 8, 2484-
2494.
4726 J. Org. Chem., Vol. 71, No. 13, 2006

Supramolecular Assemblies of Pyromellitic Diimide-Based Cyclophane
FIGURE 6. (a) UV/vis absorption spectra of 1 (solid line) and 2 (dashed line) in CHCl3 at 1 × 10-4 and 2 × 10-4 M, respectively. (b) Magnified
figure around 350-450 nm.
FIGURE 7. (a) HOMO and (b) LUMO orbitals of 1 and (c) HOMO and (d) LUMO orbitals of 2 calculated using the B3LYP/6-31G* level of
theory.
FIGURE 8. (a) Absorption spectra of 1 in CHCl3 at 1 × 10-3 M in the presence of 0-500 equiv of R-naphthol. (b) Benesi-Hildebrand plot.
measured in the concentrated CHCl3 solution (1: 1.0 × 10-3
M). As electron-rich aromatic guests, R-naphthol, â-naphthol,
indole, p-dimethoxybenzene, and p-xylene were used. Additional
CT bands should appear in the intermolecular CT complex
between 1 as an acceptor and a donor guest. In the case of
R-naphthol, â-naphthol, indole, and p-dimethoxybenzene, the
addition of an excessive amount of the guest to 1 provided the
new absorption band in the visible region, which was assigned
to the CT band from electron-rich aromatic guests to 1. For
example, the UV/vis spectral changes in Figure 8a typically
showed the monotonic growth of the diagnostic CT absorbance
upon the incremental addition of R-naphthol to a solution of 1
at 25 °C. The appearance of new CT bands indicated the CT
complex formation between 1 and R-naphthol, â-naphthol,
J. Org. Chem, Vol. 71, No. 13, 2006 4727

Kato et al.
TABLE 1. Charge-Transfer Association and HOMO/LUMO
Energy Levels of 1 and Guestsa
b
compd
KCT
HOMO (eV)
LUMO (eV)
1
-5.629
-5.464
-5.543
-5.398
-5.230
-6.139
-3.004
-0.653
-0.789
-0.653
+0.086
+0.195
R-naphthol
â-naphthol
indole
p-dimethoxybenzene
p-xylene
1.0
0.4
1.0
0.3
a HOMO and LUMO energy levels were calculated using the B3LYP/
6-31G* level of theory. b In CHCl3 containing 1 mM 1 and 20-3000 mM
aromatic guests at 25 °C.
indole, or p-dimethoxybenzene in CHCl3 solution (Figures S2-
S4, Supporting Information). For the quantitative analysis of
the host-guest association in solution via CT interaction, the
spectrophotometric changes were treated by the Benesi-
Hildebrand procedure22 as shown in Figure 8b, which extracted
the association constants (KCT) of 1 with donor guests: KCT
)
1.0 for R-naphthol, 0.4 for â-naphthol, 1.0 for indole, and 0.3
for p-dimethoxybenzene (Table 1). These KCT values were
significantly smaller than those of pyromellitic diimide-based
molecular duplexes23 and macrocycle-tweezer complexes,14a
which suggested the CT complexes formation of an 1:1 molar
ratio in the outside of the cavity of 1. The addition of p-xylene
to 1 in CHCl3 could not provide a clear spectral change (Figure
S5, Supporting Information). The HOMO and LUMO energies
of 1 and electron-rich aromatic guests are also summarized in
Table 1 (B3LYP/6-31G*). The observed tendency of the CT
complex formation was related to the finding that the calculated
HOMO energy levels of R-naphthol, â-naphthol, indole, and
p-dimethoxybenezene are higher than that of 1, whereas the
HOMO energy level of p-xylene are lower than that of 1.
In the case of R-naphthol, â-naphthol, and indole, the CT
FIGURE 9. 1H NMR observation of 1 recorded in CDCl3 at 5 × 10-3
M (300 MHz, 25 °C, TMS as an external standard) in the presence of
(a) 0, (b) 2, (c) 5, or (d) 10 equiv of R-naphthol.
type complexes with 1 and the R- and â-naphthols, we examined
their solid-state structures. Recrystallization of 1 from CH2Cl2
in the presence of R- or â-naphthol as a guest by vapor diffusion
with hexane at room temperature gave yellow crystals suitable
for an X-ray crystallographic analysis. The stoichiometric ratios
of the 1/R-naphthol and 1/â-naphthol complexes were 1:2 and
1:1, respectively. We presumed that a coprecipitation effect
along with the CT interaction served as driving force for the
formation of the 1:2 1/R-naphthol complex in crystals because
the 1:1 stoichiometric ratio was expected in CHCl3 solution by
the UV/vis spectral titration study. On the other hand, the
stoichiometric ratio of the 1/â-naphthol (1:1) in crystals cor-
responded to that in solution. To investigate the effect of the
association ability of the guest on cocrystallization phenomena,
a competitive cocrystallization experiment of 1 with R- and
â-naphthol was examined in CHCl3 solution. The composition
of the clathrate was 1/R-naphthol/â-naphthol (1.0:1.5:0.5) based
1
complex formation could be also monitored in the H NMR
spectral change upon the incremental addition of donor guests
to the CHCl3 solution of 1 (5.0 × 10-3 M). As shown in Figure
9, the addition of R-naphthol provided the subtle but distinctive
upfield shifts of the signals of the pyromellitic diimide protons
(Ha) and inner benzene protons (Hc) (δ∆ ) ca. 0.02 ppm, for
1:10 stoichiometry), whereas the shift of the benzylic (Hb) and
outer benzene protons (Hd) were scarcely observed. This ring-
current-induced complexation shifts confirmed that the pyro-
mellitic diimide π-face should be in the proximity of R-naphthol
π-face in the complexation process. Analogous complexation
shifts were observed for 1 with â-naphthol and 1 with indole
(Figure S6, Supporting Information).
In the IR spectra, the addition of 10 equiv of â-naphthol to
the CHCl3 solution of 1 (1.0 × 10-2 M) showed almost no shifts
to the shorter wavenumber of the stretching vibration of the
both imidecarbonyl groups of 1 and OH groups of â-naphthol
(Figure S7, Supporting Information).24 The results indicated that
the hydrogen bonding between 1 and donor guests scarcely
occurs in CHCl3 even under concentrated conditions.
1
on the H NMR spectrum,25 and this suggested that the guest
with stronger association ability was preferentially included in
the clathrate [R-naphthol (KCT 1.0) and â-naphthol (KCT 0.4)].
The hydroxyl groups of both R- and â-naphthols were respon-
sible for the hydrogen bonding with the carbonyl oxygens of 1
as described below, which resulted in a 50% static disorder in
the crystal.
Figure 10 shows the relative arrangement of the donor (R-
naphthol) and acceptor (pyromellitic diimide moiety) of the 1‚
(R-naphthol)2 complex. The R-naphthol and pyromellitic diimide
π-face are almost completely stacked, and this complete D
(donor)-A (acceptor) overlap is interpreted by the efficient
orbital interactions of the LUMO of the imide and the HOMO
X-ray Crystal Structures. Since the UV/vis spectral experi-
ments strongly suggested the formation of intermolecular CT-
(22) (a) Benesi, H. A.; Hildebrand, J. H. J. Am. Chem. Soc. 1949, 71,
2703-2707. (b) Person, W. B. J. Am. Chem. Soc. 1965, 87, 167-170.
(23) (a) Zhou, Q.-Z.; Jiang, X.-K.; Shao, X.-B.; Chen, G.-J.; Jia, M.-X.;
Li, Z.-T. Org. Lett. 2003, 5, 1955-1958. (b) Zhou, Q.-Z.; Jia, M.-X.; Shao,
X.-B.; Wu, L.-Z.; Jiang, X.-K.; Li, Z.-T.; Chen, G.-J. Tetrahedron 2005,
61, 7117-7124.
(25) The stoichiometric 1/R-naphthol/â-naphthol ratio in the crystal was
1
(24) In CHCl3 solution, the OH stretching vibrations of R- and â-naphthol
determined to be 1:1.5:0.5 by the H NMR spectra (see the Experimental
were observed at 3600 and 3324 and 3600 and 3316 cm-1, respectively.18a
Section and Figure S8, Supporting Information).
4728 J. Org. Chem., Vol. 71, No. 13, 2006

Supramolecular Assemblies of Pyromellitic Diimide-Based Cyclophane
molecular arrangement of the R-naphthol‚1‚R-naphthol provided
the D-A-A-D type stacking. The hydrogen bonding was also
supported by the IR spectra. The cyclophane 1 exhibited
asymmetric and symmetric stretching vibrations of the imide-
carbonyl groups at 1777 and 1730 cm-1, respectively. In 1‚(R-
naphthol)2, the corresponding asymmetric stretching vibration
slightly shifted to 1774 cm-1 and the symmetric vibration was
split at 1725 and 1714 cm-1 (Table 2). Additionally, the OH
peaks of R-naphthol observed at 3324 and 3600 cm-1 in CHCl3
but they were converged to the peak at 3443 cm-1 in crystals
(Table 2).
FIGURE 10. Top (left) and side (right) view of packing arrangement
between 1 and R-naphthol.
Figure 13 shows the overlapping mode of â-naphthol (donor)
and the pyromellitic diimide moiety (acceptor). They were
stacked with the D-A distance of 3.47 Å, which was slightly
longer than that of 1‚(R-naphthol)2. In contrast to the complete
D-A overlap in 1‚(R-naphthol)2, a partial D-A overlap was
observed and the overlapping mode deviated from the ideal
efficient HOMO-LUMO interactions (Figure 11a,c). The
incline of the â-naphthol π-plane and the pyromellitic diimide
π-plane was only 7.8°. Figure 14 shows the supramolecular
arrangement of the 1‚â-naphthol. Analogous to 1‚(R-naphthol)2,
hydrogen bonding was formed between the hydroxyl proton and
the carbonyl oxygen at the imide group, with an O‚‚‚O distance
being 2.898(2) Å as summarized in Table 2. The hydrogen
bonding was also supported by the IR spectra, which exhibited
slight shifts to a shorter wavenumber of the imidecarbonyl
absorptions. Similar to 1‚(R-naphthol)2, the OH peaks of
â-naphthol at 3316 and 3600 cm-1 in CHCl3 converged 3462
cm-1 in crystals (Table 2). The hydrogen bonding in 1‚â-
naphthol was almost linear with an O-H‚‚‚O angle of 176°,
whereas that in 1‚(R-naphthol)2 was significantly bent with an
O-H‚‚‚O angle of 148° and 151°. It is well-known that a shorter
hydrogen-bonding distance and larger O-H‚‚‚O angle close to
180° are required for stronger hydrogen bonding. It is considered
that the strong hydrogen bonding in the 1‚â-naphthol would
induce the partial D-A overlap, and the overlapping mode was
quite different from that of 1‚(R-naphthol)2. The alternate
arrangement of 1 and â-naphthol formed the A-A-D stacking,
and repetition of this stacking mode formed a columnar
arrangement aligning the b-axis. In addition, the hydrogen
bonding between the stacked aromatic columns aligning the
a-axis resulted in the 2D supramolecular network. These
observations indicated that the cyclophane 1 could form different
supramolecular assemblies depending on the positions of the
hydroxyl groups of the naphthol. Thus, the pyromellitic diimide
moiety included in the cyclophane framework interacted quite
differently with the naphthol compared to the acyclic diimide
such as N,N′-bis(2-tert-butylphenyl)pyromellitic diimide reported
by Kishikawa and co-workers.18a,26
FIGURE 11. (a) LUMO orbital of 1, (b) HOMO orbital of R-naphthol,
and (c) HOMO orbital of â-naphthol calculated using B3LYP/6-31G*
level of theory.
FIGURE 12. 1D molecular arrangement aligning a-axis via charge-
transfer interaction and hydrogen bonding in 1‚(R-naphthol)2. Dashed
lines show hydrogen bonding. Hydrogen atoms are omitted for clarify.
of R-naphthol (Figure 11a,b). The incline of the R-naphthol
π-plane and the pyromellitic diimide π-plane was only 6.0°,
which revealed that the two π-planes were almost parallel. The
distance between the center of the R-naphthol π-face and the
pyromellitic diimide π-face, which represented the D-A
distance, was 3.39 Å, supporting the presence of CT interactions
between 1 and R-naphthol. Figure 12 shows the molecular
packing of 1‚(R-naphthol)2. In sharp contrast to the CHCl3
solution, the hydrogen bonding between the carbonyl oxygens
of the imide moiety of 1 and the hydroxyl groups of R-naphthol
was observed with an O‚‚‚O distance of 2.834(3) and 2.837(3)
Å as summarized in Table 2. Clearly, the combination of the
hydrogen bonding and CT interactions afforded the 1D su-
pramolecular network aligning the a-axis and the 1D arrange-
ment to form a herringbone geometry. The sandwich-like
In the clathrate complexes of 1‚(R-naphthol)2 and 1‚â-
naphthol, slight structural changes in 1 were observed. In both
1‚(R-naphthol)2 and 1‚â-naphthol, the dihedral angles between
the pyromellitic diimide π-face and xylyl π-face were signifi-
cantly decreased (69.0° in 1‚(R-naphthol)2 and 72.5° in 1‚â-
naphthol) compared to that of 1‚(DMF)2 (85.4°). Furthermore,
the distance of the two xylyl π-faces was 0.70 Å in 1‚â-naphthol,
while the two xylyl π-faces were completely coplanar in 1‚(R-
naphthol)2. These observations complement the previously noted
structural flexibility of 1.
(26) It was reported that the clathrate compounds formed by N,N′-bis-
(2-tert-butylphenyl)pyromellitic diimide and phenols or indoles construct
a piled sandwich-like structures in all cases.
J. Org. Chem, Vol. 71, No. 13, 2006 4729

Kato et al.
TABLE 2. Lengths and Angles of Hydrogen Bonds and IR Peaks of the Carbonyls and OH in 1 and Clathrare Compounds
length (Å)
angle (deg)
νa (cm-1
)
compd
O‚‚‚O
O-H
H‚‚‚O
O-H‚‚‚O
CdO (1)
CdO (2)
O-H
1
1777
1774
1730
1725, 1714
1‚(R-naphthol)2
2.834(3)
2.837(3)
2.898(2)
0.95(3)
0.95(3)
0.96(2)
1.98(4)
1.97(4)
1.94(2)
148
151
176
3443
3462
1‚â-naphthol
1775
1725
a The IR spectra were measured by the KBr method.
FIGURE 13. Top (left) and side (right) view of packing arrangement
between 1 and â-naphthol.
FIGURE 15. CV traces for (a) 1 (blue line) and (b) 2 (black line).
TABLE 3. Potentials (V vs Ag/Ag+) for the Reduction Processes
Associated with 1 and 2a
compd
1E1/2
2E1/2
1
-1.01
-0.94
+0.07
-0.94
+0.07
-1.09
-1.01
+0.08
-1.01
+0.08
-1.14
-1.06
+0.08
-1.05
+0.09
-1.76
1 + excess R-naphtholb
∆E
1 + excess â-naphtholb
∆E
2
-1.60
2 + excess R-naphtholb
∆E
2 + excess â-naphtholb
∆E
FIGURE 14. 2D molecular arrangement via charge-transfer interac-
tions (b-axis) and hydrogen bonding (a-axis) in 1‚â-naphthol. Dashed
lines show hydrogen bonding. Hydrogen atoms are omitted for clarify.
a All electrochemical measurements were performed in CH2Cl2 solution
(5 × 10-4 M) containing 0.10 M tetra-n-butylammonium hexafluorophos-
phate at scan rate of 200 mV s-1 b The potential was switched immediately
.
after the first cathodic peak in the presence of 200 equiv.
Electrochemistry. Cyclic voltammetric (CV) traces of 1 and
2 were recorded in CH2Cl2 solution with tetra-n-butylammonium
hexafluorophosphate as the supporting electrolyte (Figure 15).
The referential compound 2 exhibited two reversible one-
electron reductions at -1.09 and -1.60 V vs Ag/Ag+, and the
first and second waves were ascribed to the radical anion and
dianion species, respectively, based on the previously reported
pyromellitic diimide derivatives (Table 3).8e,27 Reversible redox
processes were observed in both 1 and 2. The cyclophane 1
showed the first two-electron reduction process followed by the
second two-electron reduction (Figure 15). Interestingly, the first
two-electron reduction wave of 1 was split into two waves at
-1.01 and -1.14 V, and these waves might be ascribed to the
radical anion and diradical anion species (Figure 16). Although
the distance of the two pyromellitic diimide π-faces of 1 is too
long to expect π-electronic interactions in the neutral species,
this suggested the presence of a weak interaction between the
radical anion and the neutral diimide moiety. Thus, the first
radical anion of the one pyromellitic diimide moiety may
increase the electron-density of the other diimide moiety. As a
result, further one-electron reduction of the radical anion species
may become harder than the first one-electron reduction. This
may be one of the reasons for the observation of two distinct
single-electron reduction processes for each pyromellitic diimide
moiety. The second reduction processes for both pyromellitic
diimide moieties were observed at the same potential (-1.76
V), which indicated that the interaction between the radical anion
and the dianion hardly occurred.
Redox-dependent binding is conveniently detected by looking
at the CV of the redox-active component (receptor) with and
without its binding partner (substrate) present.28 If the binding
partner binds more strongly to the oxidized form of the receptor,
it makes it more difficult to reduce the receptor, and half-wave
potential (E1/2) of the receptor shifts toward more negative
(27) Carroll, J. B.; Gray, M.; McMenimen, K. A.; Hamilton, D. G.;
Rotello, V. M. Org. Lett. 2003, 5, 3177-3180.
4730 J. Org. Chem., Vol. 71, No. 13, 2006

Supramolecular Assemblies of Pyromellitic Diimide-Based Cyclophane
FIGURE 17. CV traces for the diradical anion of 1 in the presence of
(a) 0, (b) 50, (c) 100, (d) 150, or (e) 200 equiv of R-naphthol.
FIGURE 16. Reversible sequential reduction processes for 1 and 2.
potentials in the presence of the substrate.29 In contrast, if the
substrate binds more strongly to the reduced form of the
receptor, it will be easier to reduce the receptor in the presence
of the substrate, and the E1/2 shifts toward more positive
potentials.30
Figure 17 shows the CV traces of 1 (diradical anion species)
by itself and in the presence of R-naphthol (0.025-0.1 M). The
addition of 200 equiv of R-naphthol caused the reduction to
shift toward more positive potentials by ca. 80 mV with no
significant change in wave height. This indicated that the
diradical anion species of 1 were stabilized via noncovalent
interactions between the pyromellitic diimide moiety and
R-naphthol. If the potential was switched immediately after the
reduction, the height of the return peak in the presence of
R-naphthol remained the same as the forward peak, indicating
that the diradical anion species was stable under these conditions.
As summarized in Table 3, analogous positive shifts were
observed for all four possible combinations of 1 and 2 with R-
and â-naphthol. Hamilton and Rotello’s group has recently
reported that the dianion of the N,N′-di-n-butylpyromellitic
diimide was stabilized in the presence of dialkylthiourea because
the hydrogen bonding became strong with the increasing
acceptor charge density,27 and it was pointed out that the
FIGURE 18. CV traces for the tetranion of 1 in the presence of (a) 0,
(b) 0.5, (c) 1, (d) 2, (e) 5, (f) 10, (g) 20, or (h) 50 equiv of R-naphthol.
bifurcated hydrogen-bonding interactions was necessary for its
effective stabilization according to no detectable shift in its
reduction potential in the presence of excessive amounts of the
trialkyl thiourea. Consequently, it is necessary to consider the
pKa value of the hydrogen bonding donor (naphthol and
thiourea) in order to interpret the observations that naphthol,
which is not a bifurcated hydrogen bonding donor, provided a
decrease in the reduction potentials of 1 and 2. The pKa value
(ca. 9.5) of naphthol is quite higher than that (ca. 14.5) of the
thiourea derivatives, indicating that the hydroxyl group of
naphthol is a strong hydrogen-bonding donor compared to the
amino group of the thiourea derivatives. Considering this insight,
these results indicated a reversible interaction between the di-
radical anion of 1 or radical anion of 2 and naphthol. From the
structural considerations, it is considered to be the reversible
hydrogen bonding between the imide CdO’s and the naphthol
O-H’s leading to the efficient stabilization of their reduced
species via charge delocalization.
If the potential was scanned more negative (tetraanion in 1
and dianion in 2) in the presence of naphthol, larger positive
shifts in potential were observed for the second reduction in all
four possible combinations of 1 and 2 with R- and â-naphthol.
For example, the addition of 50 equiv of R-naphthol provided
even larger positive shift in potential by ca. 360 mV for the
second reduction as shown in Figure 18. Contrary to the case
of the di-radical anion of 1 and radical anion of 2, these shifts
accompanied a large increase in reduction current and the lack
of a return peak for the second reduction, which indicated that
the irreversible multielectron processes have occurred. These
(28) For recent reviews containing aspects of supramolecular electro-
chemistry, see: (a) Boulas, P. L.; Go´mez-Kaifer, M.; Echegoyen, L. Angew.
Chem., Int. Ed. 1998, 37, 216-247. (b) Niemz, A.; Rotello, V. M. Acc.
Chem. Res. 1999, 32, 44-52. (c) Kaifer, A. E. Acc. Chem. Res. 1999, 32,
62-71. (d) Tucker, J. H. R.; Collinson, S. R. Chem. Soc. ReV. 2002, 31,
147-156. (e) Cooke, G.; Rotello, V. M. Chem. Soc. ReV. 2002, 31, 275-
286.
(29) For hydrogen-bonded host-guest complexes with binding efficien-
cies that increase upon electrochemical oxidation, see: (a) Carr, J. D.;
Lambert, L.; Hibbs, D. E.; Hursthouse, M. B.; Malik, K. M. A.; Tucker, J.
H. R. Chem. Commun. 1997, 1649-1650. (b) Carr, J. D.; Coles, S. J.;
Hursthouse, M. B.; Light, M. E.; Tucker, J. H. R.; Westwood, J. Angew.
Chem., Int. Ed. 2000, 39, 3296-3299. (c) Collinson, S. R.; Gelbrich, T.;
Hursthouse, M. B.; Tucker, J. H. R. Chem. Commun. 2001, 555-556. (d)
Bourgel, C.; Boyd, A. S. F.; Cooke, G.; de Cremiers, H. A.; Duclairoir, F.
M. A.; Rottello, V. M. Chem. Commun. 2001, 1954-1955.
(30) For hydrogen-bonded host-guest complexes with binding efficien-
cies that increase upon electrochemical reduction, see: (a) Ge, Y.; Lilienthal,
R. R.; Smith, D. K. J. Am. Chem. Soc. 1996, 118, 3976-3977. (b) Ge, Y.;
Miller, L.; Ouimet, T.; Smith, D. K. J. Org. Chem. 2000, 65, 8831-8838.
(c) Bu, J.; Lilienthal, N. D.; Woods, J. E.; Nohrden, C. E.; Hoang, K.-P.
T.; Truong, D.; Smith, D. K. J. Am. Chem. Soc. 2005, 127, 6423-6429.
(d) Chan-Leonor, C.; Martin, S. L.; Smith, D. K. J. Org. Chem. 2005, 70,
10817-10822.
J. Org. Chem, Vol. 71, No. 13, 2006 4731

Kato et al.
dianhydride 8 (1.15 g, 5.26 mmol) in dry THF (200 mL) were
simultaneously added to dry THF (100 mL) at 60 °C over a period
of 7 h with stirring under an argon atmosphere. After the addition,
the reaction mixture was stirred at 60 °C for 12 h, and the reaction
mixture was evaporated in vacuo to dryness to give the amic acid.
In the 1H NMR spectra, the broad COOH signals of the intermediate
amic acid derivatives were observed at around 13-14 ppm in
DMSO-d6 solution. A solution of the amic acid and NaOAc (431
mg, 5.26 mmol) in Ac2O (60 mL) was heated at 110 °C for 4 h.
The reaction mixture was poured into water (400 mL), and the
precipitate was collected by filtration. The precipitate was dissolved
in CHCl3 (500 mL), insoluble material was removed by filtration,
and the filtrate was evaporated in vacuo to dryness. The residue
was purified by silica gel column chromatography eluting with
CHCl3 to give 1 in 24% yield (583 mg, 0.63 mmol) as a pale green
powder: mp > 300 °C; IR (KBr) νmax 2957, 1777, 1730 (νCdO),
1621, 1510, 1383, 1307, 1187 cm-1; 1H NMR (300 MHz, CDCl3)
δ 1.01 (t, J ) 7.3 Hz, 12 H, CH3), 1.52-1.62 (m, 8 H, CH2), 1.84
(tt, J ) 6.2 Hz, 8 H, CH2), 4.04 (t, J ) 6.2 Hz, 8 H, OCH2), 4.87
(s, 8 H, benzyl H), 6.30 (s, 2 H, ArH), 6.48 (s, 2 H, ArH) 8.15 (s,
4 H, ArH); FAB-MS (NBA, positive) 925 [(M + H)+]. Anal. Calcd
for C52H52N4O12: C, 67.52; H, 5.67; N, 6.06. Found: C, 67.27; H,
5.69; N, 6.09.
phenomena may be responsible for proton transfer from naphthol
to the more basic tetraanion of 1 or dianion of 2, quite possibly
facilitated by the hydrogen bonding as is the case with the
diarylurea/dinitrobenzene2- (2:1) system.30d
3. Conclusions
In conclusion, we have demonstrated that the newly synthe-
sized [2 + 2] pyromellitic diimide-based cyclophane 1 con-
structed 1D and 2D supramolecular assemblies and exhibited
redox modulation via noncovalent interactions with naphthols.
A combination of the CT interactions and hydrogen bonding
led to the formation of clathrate compounds with the regio-
selectivity of the hydroxyl group of naphthol, which resulted
in the 1D network in the clathrate of 1 and R-naphthol in an
1:2 ratio, and the 2D network in the clathrate of 1 and â-naphthol
in an 1:1 ratio. Our approach is an example of creating a
supramolecular assembly in the solid state using both the CT
interaction and hydrogen bonding in the outside of the cavity
of the cyclophane host 1. Upon the addition with naphthol, the
first two-electron reduction potential ascribed to the di-radical
anion of 1 and the radical anion of 2 are moderately decreased
due to the formation of reversible hydrogen bonding with an
increasing charge density of the acceptor.
In UV/vis spectroscopy, a very weak intramolecular CT
interaction was observed between the pyromellitic diimide
moiety and the alkoxy-substituted benzene moiety of 1 and 2.
This is attributed to the introduction of a methylene linker
between them, which could not decrease the electron-withdraw-
ing property of the pyromellitic diimide moiety to form the
observed supramolecular assemblies in the solid states. In the
cyclic voltammetry measurements, two different reduction
potentials in 1 were observed for the first two-electron reduction,
and this may be ascribed to the stepwise reduction of the neutral
species to the radical anion, followed by a further reduction to
the dianion species.
N,N′-Bis(2-methoxybenzyl)pyromellitic Diimide (2). To a
solution of the anhydride 8 (1.00 g, 4.59 mmol) in dry THF (20
mL) was added a dry THF solution (10 mL) of 2-methoxybenzyl-
amine 9 (1.38 g, 10.1 mmol) with stirring at room temperature under
an argon atmosphere. After the mixture was stirred at 60 °C for 12
h, the reaction mixture was evaporated in vacuo to dryness to give
the amic acid. A solution of the amic acid and NaOAc (346 mg,
4.59 mmol) in Ac2O was heated at 110 °C for 4 h, the reaction
mixture was poured into water (300 mL), and the precipitate was
collected by filtration. The precipitate was dissolved in CHCl3 (300
mL), and insoluble material was removed by filtration. The residue
was purified by silica gel column chromatography eluting with
CHCl3/AcOEt (20:1, v/v) and recrystallized from CHCl3 to give 2
in 72% yield (1.51 g, 3.30 mmol) as a pale green powder: mp
283-284 °C; IR (KBr) νmax 1773, 1710 (νCdO), 1495, 1464, 1444,
1
1393, 1343, 1273, 1250, 1107, 1032 cm-1; H NMR (300 MHz,
We expect that the cyclophane 1, which has not only a fully
structural flexibility but also parallel arrangement of the
transannular pyromellitic diimide π-faces, is a candidate as a
structural component for the construction of a new covalent
organic nanotube31 with an extended 1D π-system because an
additional structural modification of 1 may be possible at the
3- and 6-positions of its pyromellitic diimide moieties. Our
synthetic study of the covalent organic nanotubes utilizing a
pyromellitic diimide-based cyclophane structure is now in
progress, and the results will be reported elsewhere. We believe
that the present study provides valuable information for the
creation of new pyromellitic diimide-based supramolecular
structures.
CD2Cl2) δ 3.82 (s, 6 H, OCH3), 4.10 (s, 4 H, benzyl H), 6.89 (td,
J ) 1.2, 7.2 Hz, 2 H, ArH), 6.90 (dd, J ) 1.2, 7.2 Hz, 2 H, ArH),
7.19 (dd, J ) 1.7, 7.6 Hz, 2 H, ArH), 7.28 (dd, J ) 1.7, 7.6 Hz, 2
H, ArH); FAB-MS (NBA, positive) 457 [(M + H)+]. Anal. Calcd
for C26H20N2O6: C, 68.42; H, 4.42; N, 6.14. Found: C, 68.17; H,
4.39; N, 6.11.
1,3-Bis(aminomethyl)-4,6-di-n-butoxybenzene (7). Preparation
of this compound has been already reported,19 but we describe a
modified high-yield procedure here. To a solution of the dinitrile
6 (817 mg, 3.00 mmol) in dry toluene (5 mL) was added 1.5 M
diisobutylaluminum hydride solution (20.0 mL, 30.0 mmol) at room
temperature under an argon atmosphere. After the mixture was
heated at 110 °C for 4 h, the reaction mixture was poured into
ice-water (50 mL). Aqueous NaOH solution (1 N, 10 mL) was
added, and the mixture was extracted with Et2O (30 mL × 3). The
combined organic layers were washed with brine, dried with Na2-
SO4, and evaporated in vacuo to dryness to give 1,3-bis(amino-
methyl)-4,6-di-n-butoxybenzene 7 in 81% yield (667 mg, 2.42
mmol) as colorless oil whose 1H NMR data are in complete
agreement with those in the literature:19 1H NMR (300 MHz, CDCl3)
δ 0.99 (t, J ) 7.3 Hz, 6 H, CH3), 1.44-1.58 (m, 4 H, CH2), 1.74-
1.84 (m, 4 H, CH2), 3.74 (s, 4 H, benzyl H), 3.98 (t, J ) 6.3 Hz,
4 H, OCH2), 6.42 (s, 1 H, ArH), 7.05 (s, 1 H, ArH).
Determination of Association Constants (KCT). In the presence
of a large excess of electron-rich aromatic guests, KCT values of
the CT complexes were determined in CHCl3 by a spectrophoto-
metric procedure based on the Benesi-Hildebrand relationship22
at 25 °C. In all cases, linear correlations were observed, indicating
an 1:1 molar ratio for the CT complexes. From the linear plot of
∆absorbance-1 against [guest]-1, consisting of at least eight data
4. Experimental Section
[2 + 2] Pyromellitic Diimide-Based Cyclophane (1). A solution
of 1,3-bis(aminomethyl)-4,6-di-n-butoxybenzene 7 (1.45 g, 5.26
mmol) in dry THF (200 mL) and a solution of pyromellitic
(31) For covalent organic nanotubes, see: (a) Harada, A.; Li, J.; Kamachi,
M. Nature 1993, 364, 516-518. (b) Ikeda, A.; Shinkai, S. Chem. Commun.
1994, 2375-2376. (c) Pe´rez-Adelmar, J.-A.; Abraham, H.; Sa´nchez, C.;
Rissanen, K.; Prados, P.; de Mendoza, J. Angew. Chem., Int. Ed. Engl. 1996,
35, 1009-1011. (d) Kim, S. K.; Sim, W.; Vicens, J.; Kim, J. S. Tetrahedron
Lett. 2003, 44, 805-809. (e) Kim, S. K.; Vicens, J.; Park, K.-M.; Lee, S.
S.; Kim, J. S. Tetrahedron Lett. 2003, 44, 993-997. (f) Kim, Y.; Mayer,
M. F.; Zimmerman, S. C. Angew. Chem., Int. Ed. 2003, 42, 1121-1126.
(g) Organo, V. G.; Leontiev, A. V.; Sgarlata, V.; Dias, H. V. R.; Rudkevich,
D. M. Angew. Chem., Int. Ed. 2005, 44, 3043-3047. (h) Jin, W.; Fukushima,
T.; Kosaka, A.; Niki, M.; Ishii, N.; Aida, T. J. Am. Chem. Soc. 2005, 127,
8284-8285.
4732 J. Org. Chem., Vol. 71, No. 13, 2006

Supramolecular Assemblies of Pyromellitic Diimide-Based Cyclophane
-1
points, the slope was estimated as (KCTꢀCT
(ꢀCT
correlation coefficient of > 0.999.
)
and the intercept as
using the Becke’s three-parameter hybrid functional (B3)33 with
the correlation functional of Lee, Yang, and Parr (LYP),34,35 and
the basis sets 6-31G*. Restricted calculations were performed, as
all relevant species were closed shell molecules. All reported
energies include zero-point energy.
)
-1. Linear fits obtained by the least-squares method had a
Preparation of the Charge-Transfer Complexes. General
procedure for the preparation of 1‚(R-naphthol)2 and 1‚â-
naphthol: Recrystallization of 1 (7.0 mg, 7.6 × 10-3 µmol) from
the CH2Cl2 solution (2 mL) in the presence of R-naphthol (3.3 mg,
2.3 × 10-2 µmol) by vapor diffusion with hexane (6 mL) at room
temperature gave yellow crystals on standing for 1 d. The resultant
crystals were collected by decantation from the solvent.
Competitive cocrystallization experiment: Recrystallization of
1 (7.0 mg, 7.6 × 10-3 µmol) from the CH2Cl2 solution (2 mL) in
the presence of R-naphthol (2.2 mg, 1.5 × 10-2 µmol) and
â-naphthol (2.2 mg, 1.5 × 10-2 µmol) by vapor diffusion with
hexane (6 mL) at room temperature gave yellow crystals on standing
for 1 d. The resultant crystals were collected by decantation from
the solvent and determined to be 1/R-naphthol/â-naphthol (1:1.5:
0.5) complex based on the comparison between the integral intensity
Acknowledgment. S.K. is grateful for the partial financial
support by the Sasakawa Scientific Research Grant from The
Japan Science Society. We gratefully acknowledge the financial
support by the Theme Project of Molecular Architecture of
Organic Compounds for Functional Design (Professor Tahsin
J. Chow), Institute of Chemistry, Academia Sinica, Taiwan,
R.O.C. We are also grateful for partial financial support by the
Joint Project of Chemical Synthesis Core Research Institutions,
Research and Education for Inter-University Research Project,
MEXT, Japan. We thank Professor Shuntaro Mataka and Dr.
Tsutomu Ishi-i (Kyushu University) for the cyclic voltammetry
measurements and Professor Masaaki Mishima (Kyushu Uni-
versity) for the MO calculations.
Supporting Information Available: Temperature-dependent 1H
NMR spectra of 1 (Figure S1), UV/vis spectra of 1 and 1 plus
â-naphthol (Figure S2), UV/vis spectra of 1 and 1 plus indole
(Figure S3), UV/vis spectra of 1 and 1 plus p-dimethoxybenzene
(Figure S4), UV/vis spectra of 1 and 1 plus p-xylene (Figure S5),
1H NMR observations of 1 recorded in CDCl3 in the presence of
â-naphthol and indole (Figure S6), IR spectra of 1 plus â-naphthol
in CHCl3 (Figure S7), ORTEP drawings for 1 and R-naphthol
(Figure S8), ORTEP drawings for 1 and â-naphthol (Figure S9),
CV traces for 1 in the presence of â-naphthol (Figure S10), CV
traces for 2 in the presence of R-naphthol (Figure S11), CV traces
for 2 in the presence of â-naphthol (Figure S12), calculated
coordinates and/or total energies of optimized syn-1′ (Table S1),
anti-1′ (Table S2), parallel-1′ (Table S3), 1 (Table S4), and 2 (Table
S5), and structural data for the X-ray analyses (positional and
thermal parameters, bond distances and angles in CIF format) of
1‚(DMF)2, 1‚(R-naphthol)2, and 1‚â-naphthol. This material is
available free of charge via the Internet at http://pubs.acs.org.
1
in the H NMR spectrum of 1/R-naphthol/â-naphthol complex, 1
(1 × 10-2 M) in the presence of R-naphthol (2 × 10-2 M), and 1
(1 × 10-2 M) in the presence of â-naphthol (2 × 10-2 M) (Figure
S8, Supporting Information).
X-ray Crystallographic Structural Analysis. Data are sum-
marized in the Supporting Information.
Theoretical Methods. All calculations were performed using
the Gaussian 0332 suite of programs. Optimized structure, frequency
calculations, and single-point energy calculations were performed
(32) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K.
N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.;
Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;
Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li,
X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.;
Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.;
Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich,
S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A.
D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A.
G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.;
Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham,
M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.;
Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian
03, revision C.02; Gaussian, Inc.: Wallingford, CT, 2004.
JO0600196
(33) Becke, A. D. J. Chem. Phys. 1993, 98, 5648-5652.
(34) Lee, C.; Yang, W.; Parr, R. G. Phys. ReV. B 1988, 37, 785-789.
(35) Miehlich, B.; Savin, A.; Stoll, H.; Preuss, H. Chem. Phys. Lett. 1989,
157, 200-206.
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