Molecular recognition abilities of a new class of water-soluble cyclophanes capable of encompassing a neutral cavity

Article abstract of DOI:10.1021/ja9725256

We developed a new class of water-soluble cyclophanes, pyrenophanes, capable of encompassing a neutral cavity, in which the hydrophobic area is constructed by aligning two flat polynuclear aromatic rings parallel at an appropriate space that could interpo

Full text of DOI:10.1021/ja9725256

1452
J. Am. Chem. Soc. 1999, 121, 1452-1458
Molecular Recognition Abilities of a New Class of Water-Soluble
Cyclophanes Capable of Encompassing a Neutral Cavity
Masahiko Inouye,*,†,‡ Kazuhisa Fujimoto,‡ Masaru Furusyo,# and Hiroyuki Nakazumi‡
Contribution from PRESTO, Japan Science and Technology Corporation (JST), Department of Applied
Materials Science, Osaka Prefecture UniVersity, Sakai, Osaka 599-8531, Japan
ReceiVed July 25, 1997
Abstract: We developed a new class of water-soluble cyclophanes, pyrenophanes, capable of encompassing
a neutral cavity, in which the hydrophobic area is constructed by aligning two flat polynuclear aromatic rings
parallel at an appropriate space that could interpose just one layer of aromatic plane. The height, depth, and
width of the cavity in an open conformation of the pyrenophane are 0.46, 0.95, and 1.31 nm, respectively, i.e.,
the area of this cavity is so large that even porphirin compounds might be incorporated. In the fluorescence
spectra, the pyrenophanes showed only excimer-emission, reflecting the existence of two proximal pyrene
rings. Treatment of the pyrenophanes with anionic and cationic aromatic compounds revealed the formation
of complexes in the UV and fluorescence spectra, suggesting that the binding affinities of the pyrenophanes
for aromatic compounds were mainly governed by hydrophobic and/or π-stacking interactions. The macrocyclic
structures of the pyrenophanes were found to be indispensable for the complexation.
Introduction
the so-called “induced-fit” mechanism.4 Water solubility of the
cyclophanes is often given by introducing positive charges near
the cavity of the cyclophanes, so anionic substrates are
preferentially accommodated into the cavity.3,4 Thus, designing
a new class of water-soluble cyclophanes possessing a well-
defined neutral cavity may be a worthwhile subject for further
construction of sophisticated artificial models.
In our successive model studies on molecular recognition,5
our initial goal in this area described above is to create artificial
receptors that recognize specific substrates via hydrogen bonds
in water. With this in mind, we focused our attention on
continuous stackings of nucleobase pairs seen in double-helical
DNA, in which negatively charged phosphate is located on the
periphery of the helix and the neutral hydrophobic areas are in
the inside, so that specific hydrogen bondings between comple-
mentary nucleobases can be formed in water.6 The hydrophobic
areas of DNA are well-defined in shape and size but still have
substantial flexibility, so plane aromatic compounds can inter-
calate into this area.7 In this article, we present the synthesis
and molecular recognition abilities of a new class of water-
soluble cyclophanes, pyrenophanes, capable of encompassing
a neutral cavity resembling the hydrophobic inside of DNA.
All of vital functions are based on molecular recognition in
water at an initial process. To draw out chemical answers
concerning the intermolecular interactions at a molecular level
as seen in such processes, various artificial models have been
developed.1 Among them, cyclodextrins2 and cyclophanes3 are
representative. Although naturally occurring cyclodextrins have
been widely used as a building block of artificial models for
enzymes and receptors because of their ready-made availability
and well-defined cavity, the limitation for the synthetic versatili-
ties of them may offset the advantages. On the other hand, a
number of cyclophanes have been designed and synthesized in
their own right, and most cyclophanes employ the recognition
strategy of substrate-induced organization of the conformation,
* To whom correspondence should be addressed. E-mail: inouye@
chem.osakafu-u.ac.jp.
† PRESTO.
‡ Osaka Prefecture University.
# CAE Research Center, Sumitomo Electric Industries, Hikaridai, Seika,
Soraku, Kyoto 619-0237, Japan.
(1) Recent reviews: Dugas, H. Bioorganic Chemistry, 2nd ed.; Springer-
Verlag: New York, 1989; Chapter 4. Vo¨gtle, F. Supramolecular Chemistry;
Wiley: Chichester, 1991. van Doorn, A. R.; Verboom, W.; Reinhoudt D.
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5517-5518. Inouye, M.; Noguchi, Y.; Isagawa, K. Angew. Chem., Int. Ed.
Engl. 1994, 33, 1163-1166. Inouye, M.; Miyake, T.; Furusyo, M.;
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(6) Saenger, W. Principles of Nucleic Acid Structure; Springer-Verlag:
New York, 1984.
10.1021/ja9725256 CCC: $18.00 © 1999 American Chemical Society
Published on Web 02/04/1999

A New Class of Water-Soluble Cyclophanes
J. Am. Chem. Soc., Vol. 121, No. 7, 1999 1453
Figure 1. Candidates of water-soluble cyclophanes capable of en-
compassing a neutral cavity.
Molecular Design and Synthesis
As a starting point for the design of new cyclophanes, we
thought that such DNA-like hydrophobic area would be
constructed by aligning two flat polynuclear aromatic rings
parallel at an appropriate space that could interpose just one
layer of aromatic plane. Turning the idea into the water-soluble
cyclophanes, accumulation of the following key-structural motifs
is necessary: (i) moderately rigid three-dimensional hydrophobic
frames, (ii) π-plane arrangement inducing changes of optical
properties of the cyclophanes upon complexation with aromatic
compounds for the detection, and (iii) hydrophilic parts making
the pyrenophanes soluble in water.8 Figure 1 showed candidates
of such cyclophanes based on the considerations described
above. The main characteristics of the candidates are the
following: (1) sp and sp2 carbons were mainly used for the
basic skeleton to reduce the flexibility of the cyclophanes, (2)
pyrenes were selected as a basic unit for hydrophobic walls,
(3) the π-stacking force of pyrene rings which occupy the up
and down faces of the cyclophane frame is expected to serve
as a main intermolecular interaction, (4) meta-substituted
benzenes perpendicular to the pyrenes regulate the height of
the cavity exactly when planer aromatic guests are inserted, and
(5) quaternary ammonium groups extending to the outside of
the cyclophane frame will make the cyclophanes soluble in water
and leave the cavity uncharged.
Figure 2. An open conformation for the pyrenophane 2: (a) top view,
(b) side view, and (c) the cavity size of the pyrenophanes.
layer of aromatic compounds (the thickness of a π-plane is 0.34
nm) in the cavity. The depth and width are 0.95 and 1.31 nm,
respectively, i.e., the area of this cavity is so large that even
porphirin compounds might be incorporated.7,10 The pyrenophane,
however, still has flexibility, so a number of closed (collapsed)
conformations can exist, and some of the closed forms may be
stable than the open form because hydrophobic forces will
operate to keep the pyrene surfaces together.11 This does not
mean that the pyrenophane 2 cannot adopt a conformation
capable of accepting an aromatic guest as illustrated in Figure
2. In the presence of an aromatic guest molecule, the loss in
energy resulting from the parting of the pyrene surfaces may
be compensated for by newly developed host-guest interactions.
The pyrenophane 1 was prepared from two components, the
bis(alkynylstannane) derivative 13 and the bis(bromopyrene)
derivative 14, by macrocyclization of Stille-type coupling in
the final step (Scheme 1).12 Quaternarization at the external
nitrogen of 1 produced the water-soluble pyrenophane 2.
Reduction of the acetylenic bonds of 1 followed by quaternari-
zation yielded the saturated counterpart 4. Both 13 and 14 were
derived from 12 by stannylation and Sonogashira reaction13 with
1,6-dibromopyrene, respectively. The key intermediate 12 was
prepared from di-n-butyl 5-hydroxyisophthalate (15) in five steps
by standard synthetic methods (Scheme 2). Other compounds
were commercially available or easily synthesized. Pyrene
derivatives 5-7 for comparison, aromatic guest compounds
8-10, and nucleotides (11) were shown in Scheme 3.
To realize the appropriateness of the molecular design of the
new cyclophanes, pyrenophanes, CPK model examination and
computer modeling were performed.9 Geometry optimization
of the pyrenophane 2 was carried with hydrophilic groups
omitted from the pyrenophanes for simplification of the calcula-
tion. In an open conformation (Figure 2), the height of the cavity
is ca. 0.46 nm (the distance between the π-plane centers of two
pyrenes is 0.80 nm), so the pyrenophane can accommodate one
(7) Recent reviews: Dugas, H. Bioorganic Chemistry, 2nd ed.; Springer-
Verlag: New York, 1989; pp 140-153. Johnson, D. S.; Boger, D. L. In
ComprehensiVe Supramolecular Chemistry; Atwood, J. L., Davies, J. E.,
MacNicol, D., Vo¨gtle, F., Eds.; Elsevier: Oxford, 1996; Vol. 4, pp 73-
176. Representative papers: Wang, A. J.; Nathans, J.; van der Marel, G.;
van Boom, J. H.; Rich, A. Nature 1978, 276, 471-474. Sun, J.-S.; Francois,
J. C.; Montaney-Garestier, T.; Saison-Behmoaras, T.; Roig, V.; Thuong,
N. T.; He´le`ne, C. Proc. Natl. Acad. Sci. U.S.A. 1989, 88, 5602-5606.
Thuong, N. T.; He´le`ne, C. Angew. Chem., Int. Ed. Engl. 1993, 32, 666-
690. Fox, K. R.; Polucci, P.; Jenkins, T. C.; Neidle, S. Proc. Natl. Acad.
Sci. U.S.A. 1995, 92, 7887-7891. Slama-Schwok, A.; Teulade-Fichou, M.-
P.; Vignerson, J.-P.; Taillandier, E.; Lehn, J.-M. J. Am. Chem. Soc. 1995,
117, 6822-6830.
(10) Allwood, B. L.; Shahrivari-Zavareh, H.; Stoddart, J. F.; Williams,
D. J. J. Chem. Soc., Chem. Commun. 1987, 1058-1061. Odell, B.;
Reddington, M. V.; Slawin, A. M. Z.; Spencer, N.; Stoddart, J. F.; Williams,
D. J. Angew. Chem., Int. Ed. Engl. 1988, 27, 1547-1550. Ashton, P. R.;
Odell, B.; Reddington, M. V.; Slawin, A. M. Z.; Stoddart, J. F.; Williams,
D. J. Angew. Chem., Int. Ed. Engl. 1988, 27, 1550-1556.
(11) One of the reviewers of this paper kindly investigated the Macro-
Model calculations using the Monte Carlo Molecular Mechanics search
routine involving 1000 separate minimizations for the pyrenophane 2. The
reviewer informed us that all the accessible conformations were closed,
and that the closed conformation is 74 kJ mol-1 lower in energy than the
open one. We are grateful to the reviewer for these calculations.
(12) Ito, Y.; Inouye, M.; Yokota, H.; Murakami, M. J. Org. Chem. 1990,
55, 2567-2568.
(8) Diederich, F.; Dick, K. Tetrahedron Lett. 1982, 23, 3167-3170.
Diederich, F.; Dick, K. Angew. Chem., Int. Ed. Engl. 1983, 22, 715-716.
Diederich, F.; Grieble, D. J. Am. Chem. Soc. 1984, 106, 8037-8046.
Peterson, B. R.; Diederich, F. Angew. Chem., Int. Ed. Engl. 1994, 33, 1625-
1628. Mattei, P.; Diederich, F. Angew. Chem., Int. Ed. Engl. 1996, 35,
1341-1344.
(9) Fujitu, Ltd.; Stewart, J. J. P. Quantum Chem. Prog. Exch. 1993, 13,
40-42.
(13) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N.
Synthesis 1980, 627-630.

1454 J. Am. Chem. Soc., Vol. 121, No. 7, 1999
Inouye et al.
Scheme 1a
a (a) Tributyltin(IV) chloride, n-BuLi, THF; (b) 1,6-dibromopyrene,
PdCl2(PPh3)2, CuI, morpholine; (c) PdCl2(PPh3)2, toluene; (d) H2 (1
atm), PtO2, THF; (e) methyl trifluoromethanesulfonate, CH2Cl2.
Figure 3. 1H NMR chemical shifts (ppm) for pyrene protons in CDCl3
(1, 5, 21, and 22; black number), CD3OD (2; red number), and CD3-
OD-D2O-ethylene glycol-d6 (4:3:1) (2; blue number).
Scheme 2a
a (a) LiAlH4, THF; (b) ClCH2OCH3, NaH, DMF; (c) propargyl
bromide, NaH, DMF, THF; (d) concentrated HCl, MeOH; (e) MsO-
(CH2)3NMe2‚HCl (20), NaH, DMF.
Figure 4. (a) Electronic absorption spectra of 2 (2.0 × 10-5 M) and
7 (4.0 × 10-5 M) in water-ethylene glycol (3:1). (b) Fluorescence
emission spectra of 2 (8.2 × 10-5 M) and 5 (4.3 × 10-3 M) in MeOH.
The excitation wavelength was 403 nm.
Scheme 3
protons as a function of solvent polarity reflect that the
hydrophobic interaction between the two pyrene rings became
stronger, so that the pyrene-pyrene distance shortened.
UV and Fluorescence Spectra of the Pyrenophanes. The
optical properties of the pyrenophanes are expected to be
different from those of the parent pyrene, because of the
presence of two proximal pyrene rings.14,15 The electronic
absorption spectrum of pyrenophane 2 showed a small red shift
of the longest wavelength bands and significant hypochromism,
compared with that of the referential monomer 7 in H2O-
ethylene glycol (3:1) (Figure 4a). These phenomena resemble
the absorbance decrease of nucleobases during the change from
single-stranded to double-helical DNA that results from the
stacking of the aromatic bases.
Fluorescence spectra were much affected by their structures
(Figure 4b). Thus, the fluorescence emission spectrum of the
pyrenophane 2 in CH3OH (λmax ) 500 nm) showed a red shift
compared with that of the reference monomer 5 (λmax ) 433,
460 nm). The wavelength of the emission maximum of 2 was
independent of its concentration, while that of 5 revealed
dependence on the concentration: at g4.0 × 10-4 M, a new
emission (λmax ) 500 nm) that was thought to be for an excimer
appeared. These results indicated that the pyrenophane 2 showed
only excimer emission, owing to the proximity of the two pyrene
rings.
Results and Discussion
1H NMR Chemical Shifts of the Pyrenophanes. The
resonances were observed at 7.51-8.21 ppm for the pyrene
protons of 1 in CDCl3 and at 8.09-8.55 ppm for the nonmac-
rocyclic analogue 5 (Figure 3). The upfield shifts for the pyrene
protons of 1 were due to the proximity of the two pyrene rings.
The shifts were lower than that predicted in the case where the
complete stacking of the two pyrene rings occurred such as in
21 and 22 developed by Misumi (7.20-7.47 and 7.22-7.51
ppm in CDCl3, respectively).14 These results indicated that the
pyrene rings of 1 are close to each other but do not come into
contact, so there will be some cavity between the two pyrene
walls, and/or that in structures of 1 and 2 the opposite pyrene
moiety is tilted.
1
Solvent polarity affected the H NMR chemical shifts for
pyrene protons of the pyrenophanes (Figure 3). Thus, the pyrene
protons of 2 appeared at 7.53-8.03 and 7.28-7.85 ppm in CD3-
OD and CD3OD-D2O-ethylene glycol-d6 (4:3:1) mixed sol-
vent, respectively. The increasing upfield shifts of the pyrene
Fluorescence lifetimes for 1 and 5 were measured to reinforce
the above conclusions. The fluorescence decay curve of 1 was
(15) Diederich, F.; Dick, K.; Grieble, D. J. Am. Chem. Soc. 1984, 106,
8037-8046. De Schryver, F. C.; Collart, P.; Vandendriessche, J.; Goedeweeck,
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1975, 15, 3159-3162. Kawashima, T.; Otsubo, T.; Sakata, Y.; Misumi, S.
Tetrahedron Lett. 1978, 19, 5115-5118.

A New Class of Water-Soluble Cyclophanes
J. Am. Chem. Soc., Vol. 121, No. 7, 1999 1455
Table 1. Association Constants Determined for the Binding of 2 to
the Guests in Water-Ethylene Glycol (3:1) at 25 °C
guest
Ka (M-1
)
guest
Ka (M-1
)
8
9
10
11A
g1.0 × 106
g5.0 × 105
g5.0 × 105
11U
11G
11C
(1.8 ( 0.1) × 104
(3.5 ( 0.5) × 104
(9.0 ( 0.5) × 103
(1.2 ( 0.1) × 104
Figure 5. Electronic absorption spectra of 2 (2.0 × 10-5 M) in water-
ethylene glycol mixed solvent (3:1) in the presence of (a) 8 (0.25-
1.25 equiv) and (b) 9 (2.0 equiv). In part b, the spectra were recorded
at 10 min intervals.
due to a one-component system, and that of 5 to a binary system.
In CH2Cl2, the lifetime for 1 (τ1) was 19.3 ns and those for 5
(τ1 and τ2) were 3.77 and 24.5 ns, respectively, i.e., the
pyrenophane 1 showed only one emission that is attributed to
pyrene-excimer fluorescence.16 This behavior is irresponsible
for the presence of the acetylene linkages. Indeed, in the case
of the reduced pyrenophane 3, similar results (λmax ) 480 nm,
τ1 ) 35.3 ns) were obtained in CH2Cl2. According to the above
points, two pyrene rings in 1-4 were located in the positions
giving only excimer emissions. These results will be receiving
attention from not only molecular recognition but also investiga-
tion of transannular π-electron interaction between spatially
arranged chromophores.14,17,18
Spectroscopic Detection of the Complexation. Under the
conditions for detecting the complexation between the pyreno-
phanes and various aromatic compounds, the solubility of 2 and
4 is poor in pure water, so that the water-ethylene glycol (3:1)
mixed solvent was used.8 Aromatic compounds of 8-11 were
chosen as a guest molecule. The aromatic guests thus selected
showed no absorption bands above 350 nm in the mixed solvent,
so the changes for absorption or fluorescence spectra of the
pyrenophanes in such a region can be used directly to obtain
the information for the guest binding. Intermolecular stacking
(aggregation) of 2 can be ruled out since 2 obeyed the Lambert-
Beer law at e8.2 × 10-5 M, so that all binding assays were
carried out below that concentration.
Figure 6. Fluorescence quenching of 2 in the presence of (a) 8 and
(b) 9 in water-ethylene glycol mixed solvent (3:1): (a) [2] ) 1.0 ×
10-6 M, (b) [2] ) 1.0 × 10-5 M. The excitation wavelength was 380
nm.
that the even cationic aromatic guest 9 displayed Ka g 5.0 ×
105 M-1 for the cationic pyrenophane 2, suggesting that the
binding affinities of the pyrenophanes for aromatic compounds
were mainly governed by hydrophobic and/or π-stacking not
by electrostatic interactions because of the neutral cavity. Unique
and time-dependent complexation behavior was observed for 2
and 9. When a solution of 9 (4.0 × 10-5 M) was added into a
solution of 2 (2.0 × 10-5 M), the decrease of the absorbance
of 2 was observed. Further decrease of the absorbance then
gradually occurred over the course of time, and after about 2 h,
equilibrium was reached (Figure 5b). Such a slow interaction
might result from the absence of the long-reaching electrostatic
interaction that will be initially important for the approach of
an anionic guest molecule to the cationic pyrenophane 2, and
from the difficulty of insertion of nonplaner 9 into the narrow
hydrophobic cavity of 2. The counteranion of 9 is not important.
Indeed, similar slow changes for spectra of 2 were obtained in
the case of 10, but never with 8 and 11. The absorption spectra
of 7 and the corresponding acyclic analogue of 2 showed only
negligible changes upon addition of any of the aromatic
compounds under identical experimental conditions. As ex-
pected, the change for the absorption spectra of 2 in CH3OH
was too small to obtain any information for the complexation.
The complexation for nucleobases is particularly interesting,
because the further introduction of nucleobase recognition motif
in the cavity of the pyrenophane might be expected to produce
artificial nucleobase receptors in water. The decrease of the
absorbance 2 was observed by the addition of various nucleo-
tides, AMP (11A), UMP (11U), GMP (11G), and CMP (11C).
The association constants were summarized in Table 1, in which
different values for each nucleotide were obtained, and selective
binding of GMP was shown. These results also indicated the
importance of the π-stacking interactions.
The absorption spectra of 2 changed upon the addition of
various aromatic guests in the solvent. When the anionic guest
8 was added incrementally to the solution of 2, the decrease of
the absorbance at 370 and 390 nm of 2 was observed with
several isosbestic points (Figure 5a). From these changes, 1:1
stoichiometry was confirmed, and the association constant (Ka)
was estimated to be at least 1.0 × 106 M-1 19
. It is noteworthy
(16) Birks, J. B. Photophysics of Aromatic Molecules; Elsevier: New
York, 1968. Fo¨rster, Th. Angew. Chem., Int. Ed. Engl. 1969, 8, 333-343.
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1991.
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A. P. B.; Leznoff, C. C.; Cerny, R. L. Can. J. Chem. 1989, 67, 1087-
1097. Harriman, A.; Heitz, V.; Sauvage, J.-P. J. Phys. Chem. 1993, 97,
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Fluorescence spectra of the pyrenophane 2 were influenced
by the presence of aromatic compounds (Figure 6). In the mixed
solvent, additions of 1 and 2 equiv of 8 induced a 60% and an
80% quenching of the fluorescence emission of 2 (1.0 × 10-6
M).20 This type of quenching was also observed for 9. Similar
(20) Jazwinski, J.; Blacker, A. J.; Lehn, J.-M.; Cesario, M.; Guilhem,
J.; Pascard, C. Tetrahedron Lett. 1978, 19, 5115-5118.
(19) Deranleau, D. A. J. Am. Chem. Soc. 1969, 91, 4044-4049.

1456 J. Am. Chem. Soc., Vol. 121, No. 7, 1999
Inouye et al.
equiv). The concentration of 2 was 2.0 × 10-5 M. The stoichiometry
and association constants were estimated by using an iterative least-
squares curve-fitting to the absorbance changes at 370-390 nm with
weighting of data points according to the error analysis of Deranleau.19
Di-n-butyl 5-Hydroxyisophthalate (15). An n-BuOH (250 mL)
suspension of 5-hydroxyisophthalic acid (25.0 g, 137 mmol) and
concentrated H2SO4 (a few drops) was refluxed with a Dean-Stark
apparatus for 24 h. To the reaction mixture was added a saturated
NaHCO3 aqueous solution until no more CO2 evolved. After removal
of the solvent, the residue was recrystallized from hexane to give 15:
yield 99% (40.0 g); mp 58-59 °C; IR (KBr) 3438, 2956, 1722, 1612,
1463, 1396, 1295, 1236, 1106 cm-1; 1H NMR (CDCl3) δ 0.97 (t, J )
6.3 Hz, 6 H), 1.47 (m, 4H), 1.76 (m, 4H), 4.35 (t, J ) 6.7 Hz, 4 H),
7.32 (br s, 1 H), 7.84 (d, J ) 1.2 Hz, 2 H), 8.22 (t, J ) 1.2 Hz, 1 H);
13C NMR (CDCl3) δ 13.66, 19.19, 30.58, 65.57, 121.00, 122.43, 131.89,
156.76, 166.40; MS m/e (rel intensity) 294 (M+, 5.4%).
phenomena were obtained for nucleotides. In these cases, only
negligible or no changes of the fluorescence emission of the
acyclic analogue 7 were observed under identical conditions in
agreement with the UV spectra. The UV and fluorescence
experiments revealed the importance of the macrocyclic structure
of the pyrenophane for the binding to aromatic compounds.
1H NMR spectroscopy was used to try to detect the com-
plexation. Unfortunately, in the D2O-ethylene glycol-d6 (3:1)
1
mixed solvent, H NMR signals of 2 (2.5 × 10-3 M) were
considerably broadened up to 70 °C, indicating that 2 exists as
an aggregate at such high concentration in contrast to the UV
experiments (vide supra). Furthermore, precipitation occurred
upon addition of the aromatic compounds. The precipitate was
1
analyzed to be 1:1 complex by H NMR after dissolving it in
DMSO-d6.
3,5-Bis(hydroxymethyl)phenol (16). To a THF (300 mL) suspension
of LiAlH4 (6.85 g, 180 mmol) was added a THF (100 mL) solution of
15 (12.5 g, 42.5 mmol) dropwise at 0 °C. The reaction mixture was
refluxed for 12 h. H2SO4 aqueous solution (10%) was carefully added
dropwise at 0 °C to the mixture until no more hydrogen evolved. The
reaction mixture was filtered, and the filtrate was evaporated and
chromatographed (silica gel; eluent, CH2Cl2:MeOH ) 10:1) to give
16: yield 85% (5.58 g); mp 71-73 °C; IR (KBr) 3110, 2947, 1601,
1529, 1456, 1309, 1225, 1159, 1039 cm-1; 1H NMR (CD3OD) δ 4.57
(s, 4 H), 6.75 (s, 2 H), 6.85 (s, 1H); 13C NMR (CD3OD) δ 65.11, 113.65,
117.59, 144.31, 158.68; FABMS (in 3-nitrobenzyl alcohol) m/e (rel
intensity) 154 (M+, 66%). Anal. Calcd for C8H10O3‚1/8H2O: C, 61.43;
H, 6.61. Found: C, 61.46; H, 6.61.
Conclusion
We developed novel water-soluble cyclophanes, pyrenophanes.
The well-defined neutral hydrophobic area of the pyrenophanes
was constructed by mimicking the π-plane arrangement seen
in double-helical DNA. The fluorescence emission spectra of
the pyrenophanes gave only excimer-emission in any concentra-
tion. The two pyrenes of the pyrenophanes were found to be
situated in positions where electronic perturbations could occur.
Complexation of the pyrenophanes was observed with cationic
aromatic guests as well as anionic ones. The driving force for
the binding was found to be governed by hydrophobic and/or
aromatic π-stacking interactions. We are currently modifying
the hydrophilic site of the pyrenophanes in order to dissolve it
in pure water. In the future, the introduction of the nucleobase
recognition site in the cavity of the pyrenophane might be
expected to produce artificial nucleobese receptors in water.
1,3-Bis(hydroxymethyl)-5-(methoxymethoxy)benzene (17). To a
DMF (75 mL) suspension of NaH (1.40 g, 35.0 mmol; commercial
60% dispersion was washed thoroughly with hexane prior to use) was
added a DMF (100 mL) solution of 16 (5.22 g, 34.0 mmol) dropwise
at 0 °C. After the solution was stirred 1 h at that temperature, ClCH2-
OCH3 (2.86 g, 35.5 mmol) was added dropwise at 0 °C. The reaction
mixture was stirred at room temperature for an additional 12 h. After
removal of the solvent, CH2Cl2 was added to the residue. The mixture
was stirred for 1 h and filtered. The filtrate was evaporated and
chromatographed (silica gel; eluent, CH2Cl2:MeOH ) 25:1) to give
17: yield 85% (5.70 g); mp 76-77 °C; IR (KBr) 3257, 3184, 2929,
Experimental Section
Instrumentation. H and 13C NMR spectra were recorded at 270
1
1
1599, 1456, 1290, 1155, 1028 cm-1; H NMR (CDCl3) δ 3.39 (s, 3
and 67.8 MHz, respectively, unless otherwise noted. EI mass spectra
were measured at 70 eV. For FAB mass experiments, Xe was used as
the atom beam accelerated to 8 keV. Melting points are uncorrected.
Materials. The starting materials were all commercially available,
and 1,6-dibromopyrene21 and the cationic guest 922 were prepared
according to literature procedures.
H), 4.29 (br s, 2 H), 4.45 (d, J ) 3.1 Hz, 4 H), 5.07 (s, 2 H), 6.82 (s,
2 H), 6.85 (s, 1 H); 13C NMR (CDCl3) δ 55.80, 64.19, 94.07, 113.42,
118.63, 142.75, 157.04; FABMS (in 3-nitrobenzyl alcohol) m/e (rel
intensity) 198 (M+, 44%). Anal. Calcd for C10H14O4: C, 60.60; H, 7.12.
Found: C, 60.97; H, 7.33.
Computational Method. Molecular modeling was performed with
Chem 3D. Geometry optimization for the pyrenophane was carried out
by using the PM3 level approximation on MOPAC 93 with EF
PRECISE key words.9 Molecular dynamics calculation was performed
on Chem 3D by using the MM2 force field with a time step of 2 ×
10-15 and a target temperature of 300 K.
1,3-Bis(propargyloxymethyl)-5-(methoxymethoxy)benzene (18).
To a THF (15 mL) suspension of NaH (1.10 g, 27.5 mmol; commercial
60% dispersion was washed thoroughly with hexane prior to use) was
added a DMF (50 mL) solution of 17 (2.28 g, 11.5 mmol) dropwise at
0 °C. After the solution was stirred 1 h at that temperature, propargyl
bromide (5.47 g, 46.0 mmol) was added dropwise at -78 °C. The
reaction mixture was warmed to room temperature gradually and stirred
at that temperature for an additional 12 h. After removal of the solvent,
the residue was dissolved in water and extracted with Et2O. The Et2O
extract was evaporated and chromatographed (silica gel; eluent, CH2-
Cl2) to give 18: yield 79% (2.49 g); oil; IR (KBr) 3290, 2902, 2360,
1599, 1458, 1352, 1149, 1084 cm-1; 1H NMR (CDCl3) δ 2.48 (t, J )
2.4 Hz, 2 H), 3.47 (s, 3 H), 4.18 (d, J ) 2.4 Hz, 4 H), 4.57 (s, 4 H),
5.18 (s, 2 H), 6.98 (s, 2 H), 7.00 (s, 1 H); 13C NMR (CDCl3) δ 56.01,
57.24, 71.21, 74.75, 79.54, 94.35, 115.18, 120.90, 139.13, 157.52; MS
m/e (rel intensity) 274 (M+, 4%).
3,5-Bis(propargyloxymethyl)phenol (19). A MeOH (12 mL) solu-
tion of 18 (2.22 g, 8.12 mmol) containing a small amount of
concentrated HCl aqueous solution (a few drops) was stirred at room
temperature for 1 day. After removal of the solvent, the residue was
dissolved in water and extracted with CH2Cl2. The CH2Cl2 extract was
evaporated and chromatographed (silica gel; eluent, CH2Cl2:AcOEt )
20:1) to give 19: yield 95% (1.80 g); oil; IR (KBr) 3290, 2858, 2117,
1603, 1458, 1302, 1157, 1082 cm-1; 1H NMR (CDCl3) δ 2.50 (t, J )
2.4 Hz, 2 H), 4.16 (d, J ) 2.4 Hz, 4 H), 4.54 (s, 2 H), 6.76 (br s, 2 H),
Fluorescence Spectra. The fluorescence spectra of the pyrenophanes
were obtained below the concentration without quenching of the
emission: [2] e 8.2 × 10-5 M and [5] ) 4.3 × 10-3 M.
Measurement of Fluorescence Lifetime. Fluorescence lifetimes
were measured by time correlation, a single-photon counting methodol-
ogy using a nanosecond fluorometer. The excitation wavelengths were
excitation maximum of the pyrenophanes and the acyclic analogues
(370-400 nm). Emissions were detected in the range 460-520 nm.
These measurements were performed at concentrations of ca. 10-5
-
10-6 M in open air. Fluorescence decay profiles were analyzed on the
basis of the following equation: If(t) ) A1exp(-t/τ1) + A2exp(-t/τ2).
Methods for the Evaluation of Stoichiometry and Association
Constants. These measurements were performed by UV titration at
25 °C. The absorbances of pyrenophane 2 (370 nm) were measured as
a function of the concentration of aromatic compounds (0.25-2.0
(21) Grimshaw, J.; Trocha-Grimshaw, J. J. Chem. Soc., Perkin Trans. 1
1972, 1622-1623.
(22) Summers, L. A. The Bipyridinium Herbicides; Academic Press:
London, 1980.

A New Class of Water-Soluble Cyclophanes
J. Am. Chem. Soc., Vol. 121, No. 7, 1999 1457
6.87 (s, 1 H); 13C NMR (CDCl3) δ 57.00, 71.05, 75.03, 79.31, 114.65,
119.60, 138.79, 156.23; MS m/e (rel intensity) 230 (M+, 7%).
3-(N,N′-Dimethylamino)propyl Methanesulfonate Hydrochloride
(20). To a CH2Cl2 (100 mL) solution of 3-(N,N′-dimethylamino)-1-
propanol (5.00 g, 48.5 mmol) was added methanesulfonyl chloride (13.9
g, 120 mmol) dropwise at 0 °C. After the solution was stirred 6 h at
room temperature, the resulting precipitate was filtered to afford 20:
yield 100% (10.6 g); IR (KBr) 3585, 2921, 2670, 2474, 2360, 1481,
reaction mixture was stirred at that temperature for 2 days. After
removal of the solvent, the residue was dissolved in water and extracted
with CHCl3. The CHCl3 extract was evaporated and chromatographed
(silica gel; eluent, CH2Cl2:Et3N ) 40:1). The eluent was corrected and
evaporated. The residue was washed with MeOH to give 1: yield 8%
(88 mg); IR (KBr) 3170, 2854, 2684, 1743, 1596, 1456, 1351, 1297,
1
1166, 1062 cm-1; H NMR (CDCl3) δ 2.05 (m, 4 H), 2.30 (s, 12 H),
4.12 (t, J ) 6.7 Hz, 4 H), 4.62 (s, 8 H), 4.93 (s, 8 H), 7.05 (s, 4 H),
7.44 (s, 2 H), 7.51 (d, J ) 7.9 Hz, 4 H), 7.60 (d, J ) 9.2 Hz, 4 H),
7.78 (d, J ) 7.9 Hz, 4 H), 8.21 (d, J ) 9.2 Hz, 2 H); 13C NMR (CDCl3)
δ 45.58, 56.47, 57.48, 66.44, 71.03, 85.82, 90.61, 114.35, 117.16,
124.78, 125.54, 127.61, 129.55, 130.13, 130.50, 131.65, 134.64, 138.95,
157.14; FABMS (in 3-nitrobenzyl alcohol) m/e (rel intensity) 1028
(MH+, 54%).
1
1336, 1267, 1174, 1014 cm-1; H NMR (DMSO-d6) δ 2.12 (m, 2 H),
2.73 (d, J ) 4.9 Hz, 6 H), 3.10 (m, 2 H), 3.22 (s, 3 H), 4.30 (t, J ) 6.1
Hz, 2 H), 10.92 (br s, 1 H); 13C NMR (DMSO-d6) δ 23.89, 36.87,
42.15, 53.26, 67.82; FABMS (in 3-nitrobenzyl alcohol) m/e (rel
intensity) 182 (M+ - Cl, 100%).
1,3-Bis(propargyloxymethyl)-5-[3-(N,N′-dimethylamino)propoxy]-
benzene (12). To a DMF (25 mL) suspension of NaH (0.63 g, 15.7
mmol; commercial 60% dispersion was washed thoroughly with hexane
prior to use) was added a DMF (10 mL) solution of 19 (1.76 g, 7.50
mmol) dropwise at 0 °C. After the solution was stirred 1 h at that
temperature, 20 (1.71 g, 7.85 mmol) was added by portions at 0 °C.
The reaction mixture was warmed to room temperature gradually and
stirred at that temperature for an additional 12 h. After removal of the
solvent, the residue was dissolved in water and extracted with CHCl3.
The CHCl3 extract was evaporated and chromatographed (silica gel;
eluent, CH2Cl2:MeOH ) 8:1) to give 12: yield 90% (2.13 g); oil; IR
(KBr) 3291, 2945, 2860, 2767, 1599, 1458, 1167, 1086 cm-1; 1H NMR
(CDCl3) δ 1.95 (m, 2H), 2.26 (s, 6 H), 2.46 (t, J ) 7.9 Hz, 2 H), 2.50
(t, J ) 2.4 Hz, 2 H), 4.04 (t, J ) 8.5 Hz, 2 H), 4.17 (d, J ) 2.4 Hz,
4 H), 4.56 (s, 4 H), 6.85 (s, 2 H), 6.91 (s, 1 H); 13C NMR (CDCl3) δ
27.26, 45.25, 56.21, 57.00, 66.03, 71.13, 74.06, 79.44, 113.34, 119.56,
138.83, 159.20; MS m/e (rel intensity) 316 (MH+, 100%).
Bis(alkynylstannane) Derivative 13. To a THF (25 mL) solution
of 12 (1.13 g, 3.58 mmol) was added a n-hexane solution of n-BuLi
(7.15 mmol) dropwise at 0 °C. After the solution was stirred 1 h at
that temperature, tributyltin(IV) chloride (2.46 g, 7.54 mmol) was added.
The reaction mixture was warmed to room temperature gradually and
stirred at that temperature for an additional 12 h. After removal of the
solvent, the residue was dissolved in saturated potassium fluoride
aqueous solution and extracted with Et2O. The Et2O extract was filtered
and evaporated to give crude 13. This compound was used in the next
reaction without further purification: yield 100% (3.20 g); oil; IR (KBr)
2956, 2927, 2854, 1598, 1521, 1457, 1375, 1294, 1164, 1082 cm-1;1H
NMR (CDCl3) δ 0.90 (t, J ) 7.3 Hz 18 H), 1.01 (m, 12 H), 1.34 (m,
12 H), 1.94 (m, 2 H), 2.25 (s, 6 H), 2.44 (t, J ) 6.7 Hz 2 H), 4.01 (t,
J ) 6.7 Hz 2 H), 4.18 (t, J ) 4.3 Hz 4 H), 4.57 (s, 4 H), 6.85 (s, 2 H),
6.90 (s, 1 H); 13C NMR (CDCl3) δ 10.93, 13.55, 26.86, 27.54, 28.76,
45.41, 56.33, 58.05, 66.04, 70.79, 89.87, 105.59, 113.29, 119.60, 139.23,
159.24; FABMS (in 3-nitrobenzyl alcohol) m/e (rel intensity) 892
(MH+, 100%).
Pyrenophane 2. To a CH2Cl2 (2 mL) solution of 1 (41 mg, 0.040
mmol) was added methyl trifluoromethanesulfonate (66 mg, 0.40 mmol)
dropwise at 0 °C. The reaction mixture was stirred at that temperature
for 1 h. After removal of the solvent at 0 °C, the residue was washed
sequentially with hexane, Et2O, and CH2Cl2 to afford 2: yield 92%
(50 mg); IR (KBr) 2854, 1601, 1487, 1259, 1165, 1029 cm-1; 1H NMR
(CD3OD) δ 2.35 (br m, 4 H), 3.23 (s, 18 H), 3.65 (m, 4 H), 4.27 (t, J
) 5.5 Hz, 4 H), 4.69 (s, 8 H), 5.01 (s, 8 H), 7.16 (s, 4 H), 7.53 (d, J
) 9.2 Hz, 4 H), 7.58 (d, J ) 7.9 Hz, 4 H), 7.62 (s, 2 H), 7.77 (d, J )
7.9 Hz, 2 H), 8.03 (d, J ) 9.2 Hz, 2 H); 13C NMR (CD3OD) δ 26.34,
30.02, 53.49, 53.71, 58.42, 72.06, 77.91, 86.58, 91.96, 115.25, 118.28,
123.92, 125.96, 126.22, 128.59, 130.47, 131.66, 132.53, 140.88, 144.60,
151.31; FABMS (in 3-nitrobenzyl alcohol) m/e (rel intensity) 1205 (M+
- OTf, 100%).
Pyrenophane 3. A THF (5 mL) suspension of 1 (26 mg, 0.025
mmol) and PtO2 (3 mg) was stirred at room temperature for 12 h under
hydrogen at a pressure of 1 atm. The reaction mixture was filtered
through Celite. The filtrate was evaporated and washed with MeOH to
give 3: yield 95% (25 mg); IR (KBr) 2940, 2864, 1597, 1456, 1362,
1
1294, 1103, 1063 cm-1; H NMR (CDCl3) δ 2.09 (m, 12 H), 2.37 (s,
12 H), 2.61 (t, J ) 7.3 Hz, 4 H), 3.36 (t, J ) 7.9 Hz, 8 H), 3.59 (t, J
) 6.1 Hz, 8 H), 4.08 (t, J ) 6.1 Hz, 4 H), 4.56 (s, 8 H), 6.84 (s, 4 H),
7.29 (s, 2 H), 7.52-7.67 (m, 12 H), 8.01 (d, J ) 9.2 Hz, 4 H); 13C
NMR (CDCl3) δ 27.42, 30.17, 31.87, 45.35, 53.86, 56.43, 69.61, 72.84,
112.87, 119.02, 122.25, 124.25, 125.04, 126.88, 127.06, 128.72, 129.28,
135.77, 140.58, 159.14; FABMS (in 3-nitrobenzyl alcohol) m/e (rel
intensity) 1043 (MH+, 100%).
Pyrenophane 4. This compound was synthesized from 3 (35 mg,
0.034 mmol) in a manner similar to that described for 2. 4: yield 97%
(45 mg); IR (KBr) 2939, 2862, 1601, 1487, 1259, 1163, 1032 cm-1
;
1H NMR (DMSO-d6) δ 2.08 (m, 8 H), 2.24 (m, 4 H), 2.84 (m, 4 H),
3.11(s, 18 H), 3.52 (m, 12 H), 4.12 (t, J ) 6.1 Hz, 8 H), 4.55 (s, 8 H),
6.87 (s, 4 H), 7.26 (s, 2 H), 7.58 (d, J ) 7.9 Hz, 12 H), 7.68 (d, J )
7.9 Hz, 12 H), 7.74 (d, J ) 9.2 Hz, 4 H), 8.05 (d, J ) 9.2 Hz, 4 H);
13C NMR (DMSO-d6) δ 22.81, 29.61, 31.80, 52.47, 63.23, 64.93, 69.14,
71.87, 112.61, 119.57, 122.14, 124.49, 127.13, 128.26, 128.88, 136.08,
140.77, 158.29; FABMS (in 3-nitrobenzyl alcohol) m/e (rel intensity)
1221 (M+ - OTf, 100%).
Bis(bromopyrene) Derivative 14. A morpholine (270 mL) suspen-
sion of 1,6-dibromopyrene21 (4.39 g, 12.1 mmol), (PPh3)2PdCl2 (143
mg, 0.20 mmol), and CuI (18.9 mg, 0.10 mmol) was stirred at 80 °C
until the reaction mixture became homogeneous. To the solution was
added 12 (0.96 g, 3.06 mmol). The reaction mixture was stirred at that
temperature for an additional 12 h. After removal of the solvent, the
residue was dissolved in water and extracted with CHCl3. The CHCl3
extract was evaporated and chromatographed (silica gel; eluent, CHCl3:
EtOH ) 8:1) to give 14: yield 40% (1.07 g); IR (KBr) 3291, 2945,
Acyclic Analogue 5. The THP-protected intermediate of 5 was
derived from 1,6-dibromopyrene21 (180 mg, 0.50 mmol) and 2-(1,4-
dioxahept-6-ynyl)tetrahydropyran23 (230 mg, 1.25 mmol) in a manner
similar to that described for 14. Deprotection of the intermediate was
carried out in a manner similar to that described for 19 to give 5: yield
(from 1,6-dibromopyrene in two steps) 35% (70 mg); IR (KBr) 3750,
1
2860, 2767, 1599, 1458, 1167, 1086 cm-1; H NMR (CDCl3) δ 1.98
3290, 2888, 1706, 1598, 1436, 1351, 1261, 1112, 1074, 1024 cm-1
;
(m, 2 H), 2.25 (s, 6 H), 2.46 (t, J ) 6.7 Hz, 2 H), 4.08 (t, J ) 6.1 Hz,
2 H), 4.64 (s, 4 H), 4.83 (s, 4 H), 7.01 (s, 2 H), 7.22 (s, 1 H), 7.77 (d,
J ) 8.5 Hz, 2 H), 7.84 (d, J ) 9.2 Hz, 2 H), 7.87 (d, J ) 8.5 Hz, 2 H),
7.90 (d, J ) 7.9 Hz, 2 H), 8.00 (d, J ) 7.9 Hz, 2 H), 8.06 (d, J ) 7.9
Hz, 2 H), 8.22 (d, J ) 9.2 Hz, 2 H), 8.36 (d, J ) 8.5 Hz, 2 H); 13C
NMR (CDCl3) δ 27.42, 45.35, 56.35, 58.25, 66.27, 71.61, 85.50, 91.06,
113.82, 117.70, 120.31, 120.45, 123.40, 124.72, 125.04, 125.42, 125.87,
126.52, 127.83, 128.44, 129.41, 130.15, 130.21, 130.86, 131.83, 139.31,
159.61; FABMS (in 3-nitrobenzyl alcohol) m/e (rel intensity) 877 (M+
+ 2, 42%).
1H NMR (CDCl3) δ 3.87 (s, 8 H), 4.68 (s, 4 H), 8.11 (m, 6 H), 8.55
(d, J ) 9.2 Hz, 2 H); 13C NMR (CDCl3) δ 59.62, 61.95, 71.43, 85.44,
90.84, 117.70, 120.45, 125.12, 126.23, 128.23, 130.27, 131.27, 132.17;
FABMS (in 3-nitrobenzyl alcohol) m/e (rel intensity) 398 (M+, 13%).
Acyclic Analogue 6. This compound was synthesized from 1,6-
dibromopyrene21 (500 mg, 1.39 mmol) and 1-(N,N′-dimethylamino)-
2-propyne (289 mg, 3.47 mmol) in a manner similar to that described
for 14. 6: yield 36% (183 mg); mp 152-153 °C; IR (KBr) 2939, 2863,
1
1603, 1462, 1321, 1157, 1038 cm-1; H NMR (CDCl3) δ 2.52 (s, 12
Pyrenophane 1. To a toluene (450 mL) solution of 14 (938 mg,
1.07 mmol) and (PPh3)2PdCl2 (50 mg, 0.0712 mmol) was added a
toluene (50 mL) solution of 13 (1054 mg, 1.18 mmol) at 50 °C. The
(23) Inouye, M.; Akamatsu, K.; Nakazumi, H. J. Am. Chem. Soc. 1997,
119, 9160-9165.

1458 J. Am. Chem. Soc., Vol. 121, No. 7, 1999
Inouye et al.
H), 3.73 (s, 4 H), 8.10-8.13 (m, 6 H), 8.60 (d, J ) 9.2 Hz, 2 H); 13C
NMR (DMSO-d6) δ 44.48, 49.07, 84.23, 90.73, 118.43, 124.11, 124.94,
126.13, 129.09, 128.01, 131.09, 130.15, 130.92, 132.01; MS m/e (rel
intensity) 365 (MH+, 48%).
that temperature for 1 h. After removal of the solvent at 0 °C, the residue
was washed sequentially with hexane, Et2O, and CH2Cl2 to afford 10:
yield 97% (300 mg); IR (KBr) 3112, 3066, 1648, 1573, 1515, 1450,
1276, 1141, 1031 cm-1; 1H NMR (DMSO-d6) δ 4.45 (s, 6 H), 8.75 (d,
J ) 7.3 Hz, 4 H), 9.26 (d, J ) 6.7 Hz, 4 H); 13C NMR (DMSO-d6) δ
48.23, 118.48, 123.23, 126.32, 146.86, 148.54; FABMS (in 3-nitroben-
zyl alcohol) m/e (rel intensity) 335 (M+ - OTf, 100%).
Acyclic Analogue 7. This compound was synthesized from 6 (94
mg, 0.26 mmol) in a manner similar to that described for 2. 7: yield
98% (174 mg); mp 263-265 °C; IR (KBr) 2976, 1502, 1431, 1201,
1
1140, 893, 600 cm-1; H NMR (D2O) δ 3.45 (s, 18 H), 4.79 (s, 4 H),
8.06 (d, J ) 9.8 Hz, 2 H), 8.15-8.17 (m, 4 H), 8.29 (d, J ) 9.2 Hz,
2 H); 13C NMR (DMSO-d6) δ 52.54, 56.46, 84.18, 88.90, 115.95,
123.02, 126.02, 129.09, 131.09, 131.43, 131.76; FABMS (in 3-nitro-
benzyl alcohol) m/e (rel intensity) 543 (M+ - OTf, 100%).
Methyl Viologen 10. To a CH2Cl2 (2 mL) solution of 4,4′-bipyridyl
(100 mg, 0.64 mmol) was added methyl trifluoromethanesulfonate (630
mg, 3.84 mmol) dropwise at 0 °C. The reaction mixture was stirred at
Acknowledgment. We are grateful to Professor Kazuhiko
Mizuno and Yohtaro Inoue (Osaka Prefecture University) for
measurement of fluorescence lifetime. The preliminary work
in this paper was supported by Sumitomo Foundation.
JA9725256