The synthesis and spectroscopic properties of macrocyclic polyethers containing two different aromatic moieties and their [2] catenanes incorporating cyclobis(paraquat-p-phenylene)

Article abstract of DOI:10.1002/(SICI)1521-3765(19980310)4:3<449::AID-CHEM449>3.0.CO;2-8

The synthesis of six derivatives of bis-p-phenylene-34-crown-10 (BPP34C10) in which one or both of the p-phenylene rings are replaced by other η-electron-rich aromatic ring systems, and their subsequent use as templates for the self-assembly of the tetrac

Full text of DOI:10.1002/(SICI)1521-3765(19980310)4:3<449::AID-CHEM449>3.0.CO;2-8

FULL PAPER
The Synthesis and Spectroscopic Properties of Macrocyclic Polyethers
Containing Two Different Aromatic Moieties and Their [2]Catenanes
Incorporating Cyclobis(paraquat-p-phenylene)**
Roberto Ballardini,* Vincenzo Balzani,* Maria Teresa Gandolfi, Richard E. Gillard,
J. Fraser Stoddart,* and Elena Tabellini
Abstract: The synthesis of six deriva-
tives of bis-p-phenylene-34-crown-10
(BPP34C10) in which one or both of
the p-phenylene rings are replaced by
other p-electron-rich aromatic ring sys-
tems, and their subsequent use as tem-
plates for the self-assembly of the tetra-
cationic cyclophane cyclobis(paraquat-
p-phenylene) and thus the construction
of [2]catenanes, are described. The p-
phenylene rings in BPP34C10 have been
replaced variously by p-xylyl units, 1,5-,
1,6-, 2,6- and 2,7-naphtho units, and a
naphthalene-2,6-dimethylyl ring system
in the six new crown ether derivatives.
Five of the [2]catenanes have the poten-
tial to exist in solution as equilibrating
mixtures of two translational isomers,
the proportions of which have been
spectra and luminescence properties
(fluorescence, phosphorescence, and ex-
citation spectra, excitation state life-
times, and fluorescence quantum yields)
of the BPP34C10 derivatives (in which
one of the p-phenylene rings has been
replaced by either a p-xylyl unit or a
naphthalene-2,6-dimethylyl unit or
where both of the p-phenylene rings
have been replaced, one by a p-xylyl unit
and the other by a 1,5-naphtho unit) and
their derived [2]catenanes, with cyclo-
bis(paraquat-p-phenylene) as the inter-
locking cyclophane component, have
been investigated. Comparison with the
properties of simple model compounds
shows the presence of intra- and inter-
molecular electronic interactions be-
tween the component units of the crown
ethers and catenanes. The main conse-
quences of these interactions in the
crown ethers are small perturbations in
the absorption spectra of the two chro-
mophoric units, and strong changes in
the luminescence properties due to the
occurrence of intercomponent energy-
transfer processes and charge-transfer
(CT) interactions. In the [2]catenanes,
perturbations in the absorption spectra
of the component units of the crown
ether and tetracationic cyclophane, ac-
companied by the appearance of CT
absorption bands in the visible region,
and complete luminescence quenching
caused by the presence of low-energy
CT levels are observed.
Keywords: catenanes
´
charge
transfer ´ luminescence ´ self-assem-
bly ´ translational isomerism
1
determined in solution by dynamic H
NMR spectroscopy. The absorption
Introduction
[*] Prof. J. F. Stoddart,[‡] Dr. R. E. Gillard
School of Chemistry, University of Birmingham
Edgbaston, Birmingham B15 2TT (UK)
Self-assembly processes,[1] which are widespread in biological
systems, are currently being employed by synthetic chemists
for the construction of nanometer-scale compounds and
complexes.[2] Conventional organic synthesis can be used to
synthesize subunits that can recognize[3] one another through
noncovalent bonding interactions to afford stable, well-
defined molecular assemblies and supramolecular[4] arrays.
The interactions between p-electron acceptors (e.g., the
paraquat dication[5]) and p-electron donors (e.g., the hydro-
quinone unit[6]) have provided the inspiration for the synthesis
of a wide range of mechanically interlocked structures.[7] It
may be recalled that the [2]catenane 44‡, comprised of bis-p-
phenylene-34-crown-10 (BPP34C10) and cyclobis(paraquat-
p-phenylene), is formed in a remarkable 70% yield[8] at
ambient pressure in MeCN (Scheme 1), where 3 acts as a
template for the reaction of 2 with 14‡. The efficiency of this
catenation is, in part, a result of the high level of preorganiza-
Dr. R. Ballardini
Istituto FRAE-CNR, via Gobetti 101
I-40129 Bologna (Italy)
Fax : (‡ 39)51-6399-844
Prof. V. Balzani, Prof. M. T. Gandolfi, Dr. E. Tabellini
Dipartimento di Chimica G. Ciamician, Universita di Bologna
Á
Via Selmi 2, I-40126 Bologna (Italy)
Fax : (‡ 39)51-259456
‡
[ ] Current address
Department of Chemistry and Biochemistry
University of California at Los Angeles
405 Hilgard Avenue, Los Angeles, CA90095 (USA)
Fax : (‡ 1)310-206-1843
E-mail: stoddart@chem.ucla.edu
[**] Molecular Meccano, Part 31. For Part 30, see D. B. Amabilino, P. R.
Ashton, V. Balzani, S. E. Boyd, A. Credi, J. Y. Lee, S. Menzer, J. F.
Stoddart, M. Venturi, D. J. Williams, J. Am. Chem. Soc., submitted.
Chem. Eur. J. 1998, 4, No. 3
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449

R. Ballardini, V. Balzani, J. F. Stoddart et al.
FULL PAPER
This paper records results that relate to changing the nature
of the neutral macrocyclic polyether component of the
[2]catenane. Translational isomerism in [2]catenanes that
incorporate two different aromatic p-electron-rich units in
the macrocyclic polyether component is determined by the
balance between p ± p stacking interactions and solvation.
Here, the incorporation of p-xylyl units and 1,5-, 1,6-, 2,6-, and
2,7-naphtho ring systems into the macrocyclic polyether
component will be discussed.
1·2PF6
4·4PF6
O
O
O
O
3
O
O
O
O
O
O
O
O
O
+
+
N
N
+
+
N
N
N
2PF6
O
O
N
N
+
+
N
i, MeCN RT
+
Br
Br
ii, NH4PF6 H2O
70%
O
O
O
O
O
2
4PF6
Electronic interactions between subunits play an important
role in determining the structure and reactivity of multi-
component species.[4, 16] For the design of more efficient
chemical,[17] photochemical,[18] and electrochemical[17a, 18d, 19]
molecular devices based on rotaxanes and catenanes it is
necessary to investigate the behavior of these interlocked
molecules containing the new components and to extend our
knowledge of the intercomponent interactions. Each one of
the crown ethers 5, 19, and 26 illustrated in Scheme 3 contains
two distinct chromophoric and luminescent units. It is
interesting to compare their absorption and luminescence
properties with those of simple model compounds in order to
elucidate the degree of intercomponent interaction and the
occurrence of energy-transfer processes. In the [2]catenanes
64‡, 204‡, and 304‡ illustrated in Scheme 4, the electron-donor
units of the crown ethers are expected to undergo charge-
transfer (CT) interactions with the electron-acceptor bipyr-
idinium units of the tetracationic cyclophane with profound
changes in the absorption and luminescence properties.
Scheme 1. The self-assembly of the [2]catenane 4 ´ 4PF6.
tion present in the macrocyclic polyether. The [2]catenane is
stabilized by p ± p stacking,[9] as well as by [C ± H ´´´ O]
hydrogen bonding[10] and T-type[11] interactions. Dynamic H
1
NMR spectroscopy reveals that the [2]catenane is, not
surprisingly, highly ordered in solution. At 258C each of the
macrocyclic rings is circumrotating through the cavity of the
other macrocyclic ring. The two dynamic processes are
distinct and observable by 1H NMR spectroscopy
(Scheme 2).[12] [2]Catenanes in which one of the ring compo-
nents incorporates two different aromatic units can poten-
tially exist as two translational isomers.[13] In principle, control
over the thermodynamic equilibrium associated with transla-
tional isomerism can be achieved by either steric or electronic
means.
O
O
O
O
O
O
O
O
O
O
Results and Discussion
+
+
+
+
+
+
+
+
1
B
2
D
1
2
D
B
Incorporation of p-xylyl units into the macrocyclic polyether
component: The hydroquinone rings contained in macrocyclic
polyethers are p-electron rich. It seemed logical, therefore,
that replacing the phenolic oxygen atoms with benzylic
methylene groups would decrease the p-electron-donating
nature of the p-phenylene ring(s) in the macrocyclic polyether
component. p-Phenylene-p-xylyl-36-crown-10 (5) has been
synthesized (Scheme 3) in 23% yield. The catenation of 5 with
cyclobis(paraquat-p-phenylene) gave the [2]catenane 6 ´ 4PF6
in 47% yield (Scheme 4). In CD3COCD3 solution at 233 K,
the ratio of translational isomers was 88:12 in favor of the
hydroquinone ring residing inside the tetracationic cyclo-
phane. In the more polar solvent CD3CN at the same
temperature, this ratio decreased to 61:39.
Process I
O
O
O
O
O
O
O
O
O
O
Process II
Process II
O
O
O
O
O
O
O
O
O
O
+
+
+
+
+
+
+
+
Process I
B
D
D
2
1
2
1
B
Clearly, the tetracationic cyclophane is able to accept the p-
xylyl unit into its cavity. In fact, the acyclic polyether a,a'-
bis[2-(2-hydroxyethoxy)ethoxy]-p-xylene (7) is bound by
cyclobis(paraquat-p-phenylene) (8 ´ 4PF6) with an association
O
O
O
O
O
O
O
O
O
O
1
constant of 1900m 1 (cf. 2200m for the binding of the acyclic
Scheme 2. The two dynamic processes (I and II) that are distinct and
1
observable by H NMR spectroscopy.
polyether 1,4-bis[2-(2-hydroxyethoxy)ethoxy]benzene (9)
with 8 ´ 4PF6).[20] The propensity of the p-xylyl unit to be
included inside the cavity of the tetracationic cyclophane 8 ´
4PF6 is probably a consequence of the electrostatic inter-
actions between the oxygen atoms adjacent to the p-xylyl unit
and the dicationic bipyridinium units of the tetracationic
cyclophane, as well as of p ± p stacking. Thus, it should be
Considerable effort has been devoted to changing the
nature of the p-electron acceptor and donor units in the ring
components of the [2]catenane 44‡. The bipyridinium units of
the tetracationic cyclophane have been replaced by trans-1,2-
bis(pyridinium)ethylene[14] and 2,7-diazapyrenium units.[15]
450
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[2]Catenanes
449±459
aromatic protons that corresponds to the averaged resonance
O
O
O
OH
OH
O
O
O
O
O
O
O
O
OTs
OTs
for the inside and alongside p-xylyl units, indicating that
Macrocycle
1
Process I (Scheme 2) is fast on the H NMR timescale. On
+
cooling a CD3COCD3 solution of the [2]catenane down to
233 K, two signals can be observed corresponding to aromatic
protons on the p-xylyl units located inside (d ˆ 4.02) and
alongside (d ˆ 7.00) the cavity of the tetracationic cyclophane.
The energy barrier associated with this process was calculated
from the line broadening[21] of the signal at d ˆ 7.00 to be
O
O
O
5
O
O
O
O
∆
19
Cs2CO3
DMF
O
O
O
O
O
O
O
1
1
5 d
11.9 kcalmol , that is, 3.7 kcalmol less than for the same
process in the [2]catenane 4 ´ 4PF6. This decrease in the
energy barrier for Process I is a consequence of the weaker
interactions between the macrocyclic polyether component
and the tetracationic cyclophane in 12 ´ 4PF6 compared with
4 ´ 4PF6.
26
27
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
28
29
O
O
Since the p-xylyl unit of the macrocyclic polyethers 5 and 11
has the propensity to be included inside the cavity of the
tetracationic cyclophane, it was decided to remove the oxygen
atoms adjacent to the p-xylyl unit completely in order to
influence further the ratio of the translational isomers. To this
end, the 34-crown-8 derivative 15 was synthesized in 34%
yield from 1,4-bis[2-[2-(2-p-toluenesulfonylethoxy)ethoxy]-
ethoxy]benzene (13) and 1,4-phe-
O
O
Scheme 3. Synthesis of the macrocyclic polyethers 5, 19, and 26 ± 29.
1·2PF6
Macrocycle
O
O
O
O
O
O
O
O
O
O
5
+
11
15
19
26
27
28
29
+
N
N
nylene dipropanol (14) in the pres-
O
O
O
O
OCH2
2PF6
+
ence of NaH under high dilution
conditions. The catenation of 15
with 8 ´ 4PF6 gave the [2]catenane
16 ´ 4PF6 in 11% yield (Scheme 3).
In both CD3COCD3 and CD3CN
solutions over the range of acces-
N
N
+
O
O
O
O
CH
O
2
Br
Br
15
2
sible temperatures, only one translational isomer could be
observed for 16 ´ 4PF6 by H NMR spectroscopy, that is, the
i, MeCN rt
ii, NH4PF6 H2O
1
one with the hydroquinone ring located inside (d ˆ 3.90,
CD3COCD3) and the p-xylyl unit located alongside (d ˆ 6.59,
CD3COCD3) the tetracationic cyclophane. Process I could not
be observed for this [2]catenane although we anticipate that
circumrotation does occur. However, the coalescence of two
signals corresponding to the a-CH protons of the bipyrid-
inium units located inside and alongside the cavity of the
macrocyclic polyether at 205 K is consistent with Process II
O
O
O
O
O
[2]Catenane
%Yield
+
+
6·4PF6
12·4PF6
16·4PF6
20·4PF6
30·4PF6
31·4PF6
32·4PF6
33·4PF6
47
38
11
45
52
41
42
28
N
N
N
+
N
+
1
(Scheme 2) becoming fast on the H NMR timescale. The
energy barrier for this process was calculated, by means of the
O
O
O
O
O
4PF6
1
coalescence approach,[22] to be 9.2 kcalmol , that is,
3.0 kcalmol 1 lower than the same process in the [2]catenane
4 ´ 4PF6. The lower energy barrier for this process, compared
with that for 4 ´ 4PF6, is almost certainly a consequence of the
poor recognition displayed between the p-xylyl unit and the
tetracationic cyclophane in the [2]catenane 16 ´ 4PF6; an
observation supported by the decrease in the efficiency of
the self-assembly process (11% yield of 16 ´ 4PF6 compared
with 70% yield for 4 ´ 4PF6).
Scheme 4. The self-assembly of the [2]catenanes, 6 ´ 4PF6, 12 ´ 4PF6, 16 ´
4PF6, 20 ´ 4PF6, and 30 ´ 4PF6 ± 33 ´ 4PF6. Note that the constitutions of
these [2]catenanes can be deduced from the key in Scheme 3.
possible to assemble a [2]catenane that incorporates a macro-
cyclic polyether containing two p-xylyl units and 8 ´ 4PF6.
Bis-p-xylyl-38-crown-10 (11) was synthesized by the reac-
tion of tetraethylene glycol (10) with 1,4-bis(bromomethyl)-
benzene (2) in the presence of
NaH under high dilution condi-
tions. The catenation of 11 with 8 ´
Incorporation of naphthalene-2,6-dimethylyl in the macro-
cyclic polyether component: The macrocyclic polyether
H2CO
O
O
O
OCH2
4PF6 gave the [2]catenane 12 ´
4PF6 in 38% yield (Scheme 4).
At 333 K in CD3CN, 1H NMR
spectroscopy of 12 ´ 4PF6 showed
a signal at d ˆ 5.12 for eight
naphthalene-2,6-dimethylyl-p-phenylene-38-crown-10
(19)
was synthesized from 17 and hydroquinone (18) in 18% yield
(Scheme 3). The catenation of 19 with 8 ´ 4PF6 gave the
H2C O
O
O
O
CH
O
2
1
[2]catenane 20 ´ 4PF6 in 45% yield (Scheme 4). Dynamic H
11
NMR spectroscopy of this [2]catenane in CD3COCD3 solu-
Chem. Eur. J. 1998, 4, No. 3
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R. Ballardini, V. Balzani, J. F. Stoddart et al.
FULL PAPER
tion revealed the presence of only one translational isomerÐ
that with the hydroquinone ring located inside the cavity of
the tetracationic cyclophane. In CD3CN solution, a small
amount (5%) of the other translational isomer could be
observed. These observations are in accordance with the low
sponding to the a protons on the bipyridinium units located
inside and alongside the tetracationic cyclophane at 267 K is a
consequence of Process II becoming fast on the 1H NMR
timescale. An energy barrier of 13.4 kcalmol 1 was calculated
for this process. For the [2]catenanes 32 ´ 4PF6 and 33 ´ 4PF6,
although some broadening of the 1H NMR spectrum could be
observed on cooling down the samples (an indication that
Process II was happening), the temperature could not be
reduced sufficiently for energy barriers for this process to be
obtained.
1
binding constant (Ka ˆ 796m in MeCN at 298 K) of the
acyclic naphthalene-2,6-dimethylyl-containing polyether,
compared with that of the hydroquinone-containing poly-
ether.
Incorporation of p-xylyl and dioxynaphthalene units in the
macrocyclic polyether component: A series of macrocyclic
polyethers, incorporating dioxynaphthalene units with differ-
ent substitution patterns and a p-xylyl unit, have been
synthesized. The bistosylate 21 was reacted with either 1,5-,
1,6-, 2,6-, or 2,7-dihydroxynaphthalene (22, 23, 24, and 25,
respectively) in the presence of Cs2CO3 under high dilution
conditions to give the macrocyclic polyethers in yields of 12 to
53% (Scheme 3). The catenations of the macrocyclic poly-
ethers 26, 27, 28, and 29 with 8 ´ 4PF6 gave the [2]catenanes
30 ´ 4PF6, 31 ´ 4PF6, 32 ´ 4PF6, and 33 ´ 4PF6 in 52, 41, 42, and
28% yields, respectively (Scheme 4).
Dynamic 1H NMR spectroscopy revealed both solvent and
temperature dependences upon the equilibrium position of
the translational isomerism in [2]catenane 30 ´ 4PF6. In
CD3COCD3, and also in CD3CN solution, the 1,5-dioxynaph-
thalene unit resides preferentially inside the cavity of the
tetracationic cyclophane. In CD3COCD3, the ratio is 60:40 at
282 K, increasing to 81:19 on cooling to 193 K. In CD3CN, the
ratio is 54:46 at 281 K, increasing to 73:27 on cooling to 228 K.
In the case of the [2]catenanes 31 ´ 4PF6 ± 33 ´ 4PF6, in
CD3COCD3 and CD3CN, only one translational isomer can be
observedÐthat in which the p-xylyl unit is located inside the
cavity of the tetracationic cyclophane. This result is presum-
ably a consequence of the better steric match between the p-
xylyl unit and the bipyridinium units of the tetracationic
cyclophane when compared with that between the 1,6-, 2,6-, or
2,7-dioxynaphthalene units and the bipyridinium units of the
tetracationic cyclophane. Although Process I is without doubt
happening, it could not be observed in the [2]catenanes 31 ´
4PF6 ± 33 ´ 4PF6 because only one translational isomer in each
case could be detected by dynamic 1H NMR spectroscopy. For
[2]catenane 31 ´ 4PF6, the coalescence of the signals corre-
Absorption spectra, luminescence properties, and intercom-
ponent electronic interactions: These studies have been
focused on the macrocyclic polyethers 5, 19, and 26 and their
[2]catenanes 64‡, 204‡, and 304‡. In order to elucidate the
occurrence of intercomponent electronic interactions, it is
necessary to compare the absorption and luminescence
behavior of the macrocyclic polyethers and of their [2]cate-
nanes with those of suitable model compounds. Therefore, we
have investigated the absorption and luminescence properties
of 1,4-dimethoxybenzene (1,4-DMB), 1,4-xylyl (1,4-Xyl), 2,6-
dimethylnaphthalene (2,6-DMeN), and 1,5-dimethoxynaph-
thalene (1,5-DMN), which are good models for the aromatic
units incorporated in the macrocyclic polyethers and corre-
sponding catenanes. The absorption and luminescence prop-
erties of the model compounds, the macrocyclic polyethers,
and the derived [2]catenanes are given in Table 1. The
cyclophane 84‡, which is a common component of the
[2]catenanes examined in this paper, shows an absorption
band with a maximum at 261 nm in MeCN solution, but no
luminescence.[20]
Macrocyclic polyether 5 and [2]catenane 64‡: The absorption
and fluorescence spectra in MeCN solution at room temper-
ature of the chromophoric and luminescent moieties of the
macrocyclic polyether 5 and of the model compounds 1,4-
DMB and 1,4-Xyl are shown in Figure 1. The absorption
spectrum of the macrocyclic polyether is different from the
sum of the absorption spectra of its two components: the
vibrational structure of the 1,4-Xyl around 270 nm is missing
and the intensity in the band maximum is noticeably smaller.
As shown in Figure 1 and Table 1, 1,4-DMB and 1,4-Xyl
exhibit a strong fluorescence band in MeCN solution at room
Table 1. Table 1 Absorption and emission data.[a]
Absorption
lmax (nm) e (m 1 cm
Fluorescence RT
Fluorescence, 77 K
Phosphorescence 77 K
1
)
lmax (nm)
t (ns)
f[b]
lmax (nm)
t (ns)
lmax (nm)
t (s)
1,4-DMB
1,4-Xyl
1,5-DMN
2,6-DMeN
5
290
2900
410
8500
4500
2200
320
293
330[d]
343[d]
325
2.0
9.3
7
11.5
2.2
0.11
0.08
0.38
0.14
0.09
317[c]
288[c]
3.27[d]
340[c, d]
317[c]
3.8[c]
32[c]
11
408[c]
396[c]
514[d]
458[c, d]
412[c]
2.1[c]
7.2[c]
ꢀ 2
267[d]
294[d]
237[d]
290
50[c]
4.1[c]
0.5[c]
2.2[c]
64‡
263, 465 40000, 430
295[d]
9000
265, 520 37000, 520
275 5700
263, 440 35000, 770
26
304‡
345[d]
8
0.30
327[d]
14
483[d]
1.8
19
340[d], 435[e]
0.38, 10
0.004, 0.036[f]
337[c, d]
80[c]
477[c, d]
2.1[c]
204‡
[a] Air-equilibrated MeCN solution, unless otherwise noted; for errors, see experimental. [b] The standard used was naphthalene in degassed cyclohexane,
f ˆ 0.23 (see ref. [28]) unless otherwise noted. [c] Butyronitrile solution. [d] Structured band. [e] Exciplex-type emission, see text. [f] The standard used was
quinine sulfate in H2SO4 1n, f ˆ 0.55 (see ref. [29]).
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[2]Catenanes
449±459
Figure 3. Absorption spectrum in MeCN solution of the [2]catenane 64‡
compared with the sum of the spectra of its 5 and 84‡ components. The
dotted line shows the band in the visible region exhibited by the
[2]rotaxane 344‡, comprised of a 1,4-dimethoxybenzene-type unit sur-
rounded by the tetracationic cyclophane.[20]
Figure 1. Absorption (unbroken lines) and emission (dashed lines) spectra
of the macrocyclic polyether 5 and of the model compounds 1,4-DMB and
1,4-Xyl in MeCN solution at room temperature. For more details, see the
text.
temperature. In the macrocyclic polyether 5, the fluorescence
band of the 1,4-dimethoxybenzene-type unit is present with
almost the same lifetime and quantum yield as in the 1,4-
DMB model compound, whereas there is no trace of the
fluorescence band of the 1,4-xylyl-type component. The same
is true for the fluorescence and phosphorescence spectra in a
rigid butyronitrile matrix at 77 K (Table 1): the macrocyclic
polyether 5 shows only the fluorescence and phosphorescence
bands of its 1,4-dimethoxybenzene-type unit, regardless of the
excitation wavelength. These results show that in the macro-
cyclic polyether the S1 (and, if populated, T1) level of the 1,4-
xylyl-type unit is quenched by the lower-lying S1 (and T1) level
of the 1,4-dimethoxybenzene-type unit, as schematized in
Figure 2. Since the excitation spectrum of 5 (lem ˆ 330 nm)
coincides with the absorption spectrum throughout the entire
spectral region, the quenching takes place by energy trans-
fer[16] from the 1,4-xylyl- to the 1,4-dimethoxybenzene-type
unit.
and a new, broad absorption band in the visible region, with a
maximum at 465 nm. Bands of this kind are found in the
absorption spectra of all the catenanes and rotaxanes
containing
electron-donor
and
electron-acceptor
units.[14c, 20, 23] In particular, the [2]rotaxane 344‡, containing a
O
O
O
OSi(i-Pr)3
+
+
N
N
N
+
N
+
(i-Pr)3SiO
O
O
O
344+
1,4-dimethoxybenzene-type unit surrounded by the tetracat-
ionic cyclophane, shows a CT band of comparable intensity
with lmax ˆ 470 nm (Figure 3).[20] Therefore, this visible band
of 64‡ can be assigned to a CT transition from the 1,4-
dimethoxybenzene-type unit present in the macrocyclic poly-
ether to the electron-acceptor bipyridinium units of the
tetracationic cyclophane. The difference between the spec-
trum of 64‡ and the sum of the spectra of its two components
shows the presence of another band at shorter wavelength
(lmax ꢀ 330 nm in Figure 3). This new band can be attributed
to a CT transition from the 1,4-xylyl-type unit of the macro-
cyclic polyether, which is a worse electron donor than the 1,4-
dimethoxybenzene-type unit, to the bipyridinium units of the
tetracationic cyclophane.
The absorption spectrum (Figure 3) of the [2]catenane 64‡ is
similar to the sum of the spectra of its 5 and 84‡ components in
the UV region, but it shows a tail in the 310 ± 400 nm region
As far as emission is concerned, it should be noted that in
the spectrum of 64‡ the strong fluorescence bands of the 1,4-
xylyl and 1,4-dimethoxybenzene-type units (the latter one still
present in the emission spectrum of the macrocyclic poly-
ether) are no longer observed (Table 1). This result can be
accounted for by the presence, clearly shown by the absorp-
tion spectra (vide supra), of CT excited states lying below the
potentially fluorescent levels of the two units, which offer a
route to fast radiationless decay (Figure 4).
Figure 2. Schematic energy-level diagram for the macrocyclic polyether 5.
The energy levels of the S1 and T1 excited states have been evaluated from
the onset of the emission spectra of the model compounds. Only the most
relevant processes are shown.
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453

R. Ballardini, V. Balzani, J. F. Stoddart et al.
FULL PAPER
indicate that in the macrocyclic polyether 26 the S1 (and
presumably the T1) level of the 1,4-xylyl-type unit are
quenched by energy transfer to the lower-lying S1 (T1) level
of the 1,5-dimethoxynaphthalene-type unit (cf., macrocyclic
polyether 5, vide supra).
As in the case of the [2]catenane 64‡, the absorption
spectrum (Figure 6) of 304‡ shows an intense absorption tail in
Figure 4. Schematic energy-level diagram for the [2]catenane 64‡. Only the
most relevant processes are shown.
Macrocyclic polyether 26 and [2]catenane 304‡: The absorp-
tion and fluorescence spectra in MeCN solution at room
temperature of the chromophoric and luminescent moieties of
the macrocyclic polyether 26 and of the model compounds
1,4-Xyl and 1,5-DMN are shown in Figure 5. The absorption
Figure 6. Absorption spectrum in MeCN solution of the [2]catenane 304‡
compared with the sum of the spectra of its 26 and 84‡ components. The
dotted line shows the band in the visible region exhibited by tethered
pseudorotaxane 354‡
, where a 1,5-dimethoxynaphthalene-type unit is
enclosed in a tetracationic cyclophane.[18d]
the 300 ± 400 nm spectral region and a new absorption band in
the visible region (lmax ˆ 520 nm), which are not present in the
spectra of its macrocyclic polyether and tetracationic cyclo-
phane components. The band with lmax ˆ 520 nm is very
similar to that shown by the teth-
ered pseudorotaxane 354‡ (Fig-
O
O
O
O
ure 6) in which a 1,5-dimethoxy-
naphthalene-type unit is enclosed
within the tetracationic cyclo-
phane.[18d] Therefore, this band
can be assigned to a CT transition
from the 1,5-dimethoxynaphtha-
lene-type unit present in the mac-
rocyclic polyether to the electron-
acceptor bipyridinium units of the
tetracationic cyclophane. The dif-
ference between the spectrum of 304‡ and the sum of the
spectra of its two components in the 300 ± 400 nm region
(Figure 6) shows the presence of another CT band with lmax
around 330 nm, as in the case of the [2]catenane 64‡. Once
again, this band can be attributed to a CT transition from the
1,4-xylyl-type unit of the macrocyclic polyether to the
bipyridinium unit of the tetracationic cyclophane. The [2]cat-
enane 304‡ does not exhibit any luminescence bands for the
same reasons, previously discussed for 64‡, that are related to
the presence of low-energy, non-emitting CT levels.
+
+
N
N
N
+
N
+
Figure 5. Absorption (unbroken lines) and emission (dashed lines) spectra
of the macrocyclic polyether 26 and of the model compounds 1,4-Xyl and
1,5-DMN in MeCN solution at room temperature. For more details, see the
text.
354+
MeO
O
O
spectrum of the macrocyclic polyether is very similar to the
sum of the absorption spectra of its two components. Both 1,4-
Xyl and 1,5-DMN exhibit a strong fluorescence band in
MeCN solution at room temperature (Figure 5 and Table 1).
The macrocyclic polyether 26 shows an intense band with a
maximum at 345 nm, which is very similar (also in structure,
intensity, and lifetime) to the band exhibited by the 1,5-DMN
model compound. No trace can be found of the fluorescence
band of the p-xylyl component. The same is true for the
fluorescence and phosphorescence spectra in a rigid butyr-
onitrile matrix at 77 K (Table 1): the macrocyclic polyether 26
shows only the fluorescence and phosphorescence bands of its
1,5-dimethoxynaphthalene-type unit, regardless of the exci-
Macrocyclic polyether 19 and [2]catenane 204‡: The absorp-
tion and fluorescence spectra in MeCN solution at room
temperature of the chromophoric and luminescent moieties of
the macrocyclic polyether 19 and of the model compounds
1,4-DMB and 2,6-DMeN are shown in Figure 7. The absorp-
tation wavelength. The excitation spectrum of 26 (lem
345 nm) at room temperature coincides with the absorption
spectrum throughout the entire spectral region. These results
ˆ
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[2]Catenanes
449±459
molecular movements and/or the lack of solvent reorganiza-
tion.
The presence of interchromophoric interactions in 19 has
been investigated in more detail. On going from MeCN to
CH2Cl2 solution, the emission maximum at 435 nm undergoes
a blue shift, as expected on account of the destabilization of
CT-type excited states on decreasing the dielectric constant of
the solvent. In MeCN solution, addition of CF3COOH or
NH4PF6 causes a decrease in the intensity of the 435 nm band;
this indicates that when the oxygen atoms of the macrocyclic
polyether are engaged in hydrogen bonding the intercompo-
nent electronic interaction is, at least in part, prevented. The
metal complex [Pt(bpy)2(NH3)2]2‡ (bpy ˆ 2,2'-bipyridine),
which is known to give adducts with aromatic macrocyclic
polyethers,[25, 26] can be dissolved in CH2Cl2 only in the
presence of 19. Figure 8 shows the absorption spectrum of
Figure 7. Absorption (unbroken lines) and emission (dashed lines) spectra
in MeCN solution at room temperature of the macrocyclic polyether 19 and
of the model compounds 1,4-DMB and 2,6-DMeN. The emission spectra of
the two model compounds are given in an inset for clarity. For more details,
see the text.
tion spectrum of the macrocyclic polyether is different from
the sum of the absorption spectra of its two components since
1
the structure of the Lb (p ± p*) band of 2,6-DMeN in the
310 ± 330 nm region[24] is missing. This difference could arise
from electronic intercomponent interactions or physical
constraints imposed upon the chromophoric group by the
macrocyclic structure. As shown in the right-hand part of
Figure 7 (see also Table 1), in MeCN solution at room
temperature, the macrocyclic polyether 19 has two emission
bands: a weak, short-lived, and structured band with a
maximum at 340 nm, and a more intense, relatively long-
lived, broad band with a maximum at 435 nm. Comparison
with the emission spectra of the 1,4-DMB and 2,6-DMeN
model compounds (Figure 7, inset) shows that the fluores-
cence band of the 1,4-dimethoxybenzene-type unit is almost
completely missing (its intensity is <0.1% of that shown by
1,4-DMB), and that of the 2,6-dimethylnaphthalene-type unit
is about 40 times weaker than in the 2,6-DMeN model
compound (a parallel decrease in the fluorescence lifetime
is also observed, Table 1) regardless of the excitation wave-
length. The broad band with maximum at 435 nm, which is not
present in the spectra of the components, must result from an
intercomponent interaction between the two chromophoric
units. The most likely hypothesis is the presence of a CT (or
exciplex-type) excited state involving the 1,4-dimethoxyben-
zene-type unit as an electron donor and the naphthalene
moiety as an electron acceptor. The excitation spectrum
matches the absorption spectrum in the entire spectral region
both at lem ˆ 330 nm (emission of the 2,6-dimethylnaphtha-
lene-type unit) and at lem ˆ 440 nm (new emission band). This
result indicates that excitation of the 1,4-dimethoxybenzene-
type unit is followed by a very efficient energy transfer to the
fluorescent level of the 2,6-dimethylnaphthalene-type unit,
which then partially deactivates to the lower-lying interchro-
mophoric CT level. In a rigid butyronitrile matrix at 77 K, the
macrocyclic polyether 19 shows only the fluorescence and
phosphorescence bands of its 2,6-dimethylnaphthalene-type
unit, an indication that, under such conditions, there is no
low-energy interchromophoric CT level, presumably because
of constraints imposed by the rigid matrix on the intra-
Figure 8. Absorption spectrum in CH2Cl2 solution of the adduct between
the macrocyclic polyether 19 and [Pt(bpy)2(NH3)2]2‡ (a) compared with the
sum of the spectra of the two components (b).
the adduct, which exhibits an intense tail above 330 nm,
indicative of a CT transition from the electron-donor units of
the macrocyclic polyether to the electron deficient 2,2'-
bipyridine ligand of the complex.[25] In the adduct, neither
the residual fluorescence of the S1 excited state of the 2,6-
dimethylnaphthalene-type moiety (lmax ˆ 340 nm), nor the
CT-type emission (lmax ˆ 435 nm) of free macrocyclic poly-
ether 19 (Figure 7) are observed. As in the case of
[Pt(bpy)2(NH3)2]2‡ adducts with other macrocyclic hosts, it is
likely that the flat metal complex intercalates between the two
aromatic moieties of the macrocyclic polyether. This p ± p
stacking interaction would i) prevent intercomponent elec-
tronic interactions between the two chromophoric moieties
and ii) result in the presence of low-energy CT excited
states[25, 26] capable of deactivating the upper-lying lumines-
cent levels.
As in the case of the [2]catenanes 64‡ and 304‡, the
absorption spectrum of the [2]catenane 204‡ shows a tail in the
310 ± 400 nm region (Figure 9) and a new, broad absorption
band in the visible region with a maximum at 440 nm not
present in the spectra of its macrocyclic polyether and
tetracationic components. This band can be assigned to CT
transitions from the electron-donor units present in the
macrocyclic polyether to the electron-acceptor bipyridinium
Chem. Eur. J. 1998, 4, No. 3
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455

R. Ballardini, V. Balzani, J. F. Stoddart et al.
FULL PAPER
properties. Comparison with the behavior of simple model
compounds has shown the presence of electronic inter-
actions causing energy-transfer processes between the
aromatic units of the macrocyclic polyethers and CT
processes in the [2]catenanes.
This investigation has demonstrated how subtle changes in
the stereoelectronic information imprinted within the molec-
ular components of a series of [2]catenanes can dramatically
affect the efficiency of the self-assembly process, as well as
influencing the molecular recognition and electronic inter-
actions within the resulting structures.
Experimental Section
Figure 9. Absorption spectrum in MeCN solution of the [2]catenane 204‡
compared with the sum of the spectra of its 19 and 84‡ components. The
dotted line shows the band in the visible region exhibited by the
[2]rotaxane 344‡. The dashed line shows the difference between the spectra
General methods: Solvents were dried where necessary by literature
methods.[27] NaH was used as a 60% dispersion in mineral oil, which was
not removed before use. Thin-layer chromatography was performed on
aluminum plates pre-coated with Merck 5735 silica gel 60 F254. Plates were
air-dried and scrutinized under a UV lamp. Column chromatography was
performed with silica gel 60 (particle size 0.040 ± 0.063 mm, Merck 9385).
Melting points were determined with an Electrothermal 9200 melting point
apparatus and are uncorrected. Mass spectra were obtained from Kratos
MS25 or Profile instruments, the latter being equipped with a FAB facility
(with a krypton or xenon primary atom beam in conjunction with a 3-
nitrobenzyl alcohol matrix). Positive-ion electrospray mass spectra were
recorded on either a VG Quattro triple quadrupole mass spectrometer, or a
VG Platform single quadrupole instrument. 1H NMR spectra were
recorded on Bruker AC250 (250 MHz), AC300 (300 MHz), AMX360
(360 MHz), AMX400 (400 MHz), or AMX500 (500 MHz) (with the
deuterated solvent as the lock and residual solvent or TMS as the internal
reference) spectrometers. 13C NMR spectra were recorded on Bruker
AC300 (75 MHz), or AC360 (90 MHz) spectrometers. Microanalyses were
performed by the University of Birmingham and by the University of North
London Microanalytical Services.
of 204‡ and 344‡
.
units of the tetracationic cyclophane. The broad CT band can
be deconvoluted into two components, one (lmax ˆ 470 nm)[20]
corresponding to that previously found in the rotaxane 344‡
and the other one with lmax ˆ 430 nm. The latter band can be
attributed to a CT transition involving the 2,6-dimethylnaph-
thalene-type unit of the macrocyclic polyether, which is a
worse electron donor than the 1,4-dimethoxybenzene-type
unit. Considering the intense tail of the UV band, the intensity
of the 470 nm band appears to be larger than that of the
430 nm band.
As in the case of 64‡ and 304‡, 204‡ does not exhibit any
luminescence bands. This result is expected because of the
previously discussed presence of low-energy CTexcited states
below the fluorescent levels of the component units. It should
also be noted that interactions between the two chromophoric
moieties of the macrocyclic polyether are impossible in the
[2]catenane, because of the interposed bipyridinium unit of
the tetracationic cyclophane.
a,a'-Bis[2-[2-[2-(2-hydroxyethoxy)ethoxy]ethoxy]ethoxy]-p-xylene (10):
1,4-Bis(bromomethyl)benzene (10.0 g, 37.9 mmol) was added to a suspen-
sion of NaH (6.06 g, 151.5 mmol) in tetraethylene glycol (200 mL) under N2
and stirred for 48 h at 408C. After this had cooled down to room
temperature, H2O (500 mL) was added, and the solution extracted with
Et2O (100 mL) and CH2Cl2 (3 Â 150 mL). The CH2Cl2 layers were
combined, washed with H20 (3 Â 30 mL),and dried (MgSO4), and the
solvent removed. The residue was purified by column chromatography
(SiO2, CH2Cl2/MeOH 20:1) to yield 10 as a colorless oil (13.10 g, 71%). 1H
NMR (300 MHz, CDCl3): d ˆ 7.33 (s, 4H), 4.56 (s, 4H), 3.58 ± 3.74 (m,
32H), 2.72 (brs, 2H); 13C NMR (CDCl3, 75 MHz): d ˆ 137.6, 127.8, 73.0,
70.6, 70.6, 70.6, 70.6, 70.6, 70.3, 69.4, 61.7; MS (FAB): m/z (%) ˆ 491 (36)
Conclusions
The nature of the aromatic units in the macrocyclic polyether
has been shown to have a dramatic effect on i) the efficiency
of the catenation with 8 ´ 4PF6, ii) ratios of translational
isomers, and iii) the dynamic processes occurring in the
[2]catenanes.
‡
[M ‡H].
a,a'-Bis[2-[2-[2-(2-p-toluenesulfonylethoxy)ethoxy]ethoxy]ethoxy]-p-xy-
lene (21): The diol 10 (17.5 g, 35.6 mmol) was dissolved in CH2Cl2 (250 mL)
along with Et3N (7.2 g, 71.3 mmol) and 4-(dimethylamino)pyridine (cat.)
and cooled to 08C. A solution of p-toluenesulfonyl chloride (13.6 g,
71.3 mmol) in CH2Cl2 (150 mL) was added during 1 h and the reaction
stirred overnight. The solution was washed with 5% aqueous HCl (2 Â
200 mL) and H2O (200 mL), and dried (MgSO4). The solution was
concentrated and the residue purified by column chromatography (SiO2,
CH2Cl2/MeOH 50:1) to yield 21 as a colorless oil (26.00 g, 91%). 1H NMR
(CDCl3, 30O MHz): d ˆ 7.78 (d, J ˆ 8.0 Hz, 4H), 7.32 (d, J ˆ 8.0 Hz, 4H),
7.28 (s, 4H), 4.53 (s, 4H), 3.54 ± 3.69 (m, 32H), 2.42 (s, 6H); 13C NMR
(CDCl3, 75 MHz): d ˆ 144.9, 137.7, 133.0, 129.9, 127.9, 127.8, 72.9, 70.6, 70.6,
70.6, 70.5, 70.5, 69.4, 69.4, 68.6, 21.6; MS (FAB): m/z (%) ˆ 799 (13)
*
Replacement of the phenolic oxygen atoms by methylene
groups in the hydroquinone ring greatly reduces the
recognition between the aromatic ring and the tetra-
cationic cyclophane.
*
The p-xylyl and 1,5-dioxynaphthalene units compete for
inclusion within the cavity of the tetracationic cyclophane.
In each of the three [2]catenanes incorporating a macro-
cyclic polyether containing a p-xylyl unit and either the
1,6-, 2,6-, or 2,7-dioxynaphthalene units, only the p-xylyl
unit is located inside the tetracationic cyclophane.
‡
[M ‡H]; C38H54O14S2 (798): calcd C 57.13, H 6.81; found C 57.50, H 6.96.
p-Phenylene-p-xylyl-36-crown-10 (5): Hydroquinone (0.97 g, 8.81 mmol) in
dry DMF (100 mL) and 21 (7.00 g, 8.77 mmol) in dry DMF (100 mL) were
added to a stirred slurry of Cs2CO3 (55.3 g, 0.170 mol) in dry DMF
(600 mL) under N2. The reaction was stirred at 708C for 5 d and then
cooled down to room temperature and filtered. The solvent was removed to
give a brown solid, which was dissolved in PhMe (200 mL) and washed with
*
The macrocyclic polyethers 5, 19, and 26, which contain
two different aromatic moieties, and their [2]catenanes 64‡,
204‡, and 304‡ exhibit interesting UV/Vis and luminescence
456
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Chem. Eur. J. 1998, 4, No. 3

[2]Catenanes
449±459
H2O (200 mL). The aqueous layer was extracted with PhMe (3 Â 100 mL)
and the combined organic extracts were dried (MgSO4).The solution was
concentrated to give a brown oil which was purified by column chroma-
tography (SiO2, acetone/hexane 7:5) to yield 5 as a clear colorless oil
(1.12 g, 23%). 1H NMR (300 MHz, CDCl3, 298 K): d ˆ 7.27 (s, 4H), 6.80 (s,
4H), 4.51 (s, 4H), 4.02 ± 4.06 (m, 4H), 3.80 ± 3.84 (m, 4H), 3.63 ± 3.73 (m,
20H), 3.55 ± 3.65 (m, 4H); 13C NMR (75 MHz, CDCl3): d ˆ 153.2, 137.7,
127.7, 115.7, 73.0, 70.9, 70.8. 70.8, 70.7, 70.7, 69.8, 69.6, 68.3; MS (FAB): m/z
1,6-Naphtho-p-xylyl-37-crown-10 (27): The procedure described for the
preparation of 26, with 1,6-dihydroxynaphthalene, was followed to give 27
as a white crystalline solid (0.69 g, 33%). M.p.: 96.0 ± 97.08C; 1H NMR
(CDCl3, 300 MHz): d ˆ 8.18 (d, J ˆ 11.3 Hz, 1H), 7.99 (s, 1H), 7.25 (m, 6H),
7.07 (d, J ˆ 4.0 Hz, 1H), 6.65 (dd, J ˆ 2.5, 9.0 Hz, 1H), 4.45 (s, 2H), 4.40 (s,
2H), 4.25 (t, 2H), 4.19 (t, 2H), 3.95 (t, 2H), 3.88 (t, 2H), 3.44 ± 3.80 (m,
24H); 13C NMR (75 MHz, CDCl3): d ˆ 157.5, 154.9, 137.8, 136.0, 127.9,
127.9, 127.9, 126.7, 124.1, 121.2, 119.6, 118.0, 106.8, 103.2, 73.0, 71.3, 71.1,
‡
‡
(%) ˆ 564 (46) [M ]; C30H44O10 (564): calcd C 63.81, H 7.85; found C 63.8 1,
70.9, 70.9, 70.0, 69.9, 69.5, 68.1, 67.7; MS (FAB): m/z (%) ˆ 614 (100) [M ];
H 7.68.
C34H46O10 (614): calcd C 66.43, H 7.54; found C 66.61, H 7.51.
2,6-Naphtho-p-xylyl-38-crown-10 (28): The procedure described for the
preparation of 26, with 2,6-dihydroxynaphthalene, was followed to give 28
as a white crystalline solid (1.62 g, 53%). M.p.: 98.0 ± 98.58C; 1H NMR
(300 MHz, CDCl3): d ˆ 7.56 (d, J ˆ 15.0 Hz, 2H), 7.17 (s, 4H), 7.13 (dd, J ˆ
2.5, 9.0 Hz, 2H), 7.08 (d, J ˆ 2.5 Hz, 2H), 4.37 (s, 4H), 4.20 (t, 4H), 3.92 (t,
4H), 3.73 (t, 4H), 3.54 ± 3.70 (m, 16H), 3.45 (t, 4H); 13C NMR (75 MHz,
CDCl3): d ˆ 155.4, 137.6, 129.8, 128.2, 127.6, 119.3, 107.5, 72.9, 71.0, 70.9,
Bis-p-xylyl-38-crown-10 (11): A solution of 1,4-bis(bromomethyl)benzene
(6.00 g, 22.7 mmol) and tetraethylene glycol (4.40 g, 22.7 mmol) in dry THF
(300 mL) was added over 48 h to a refluxing suspension of NaH (2.3 g,
56.8 mmol) in dry THF (300 mL) under N2 with stirring, and heated under
reflux for 24 h. After cooling down to room temperature, H2O (20 mL) was
added and the solvent removed to yield an oily residue which was dissolved
in PhMe (200 mL) and washed with aqueous 0.1m HCl (200 mL). The
aqueous solution was extracted with PhMe (2 Â 100 mL), the combined
organic layers were dried (MgSO4), and the solution concentrated. The
resulting pale oil was purified by column chromatography (SiO2,
CH3COCH3/hexane 5:7) to yield 11 as a colorless oil (500 mg, 4%). 1H
NMR (300 MHz, CD3COCD3): d ˆ 7.32 (s, 8H), 4.51 (s, 8H), 3.58 (m,
32H); 13C NMR (75 MHz, CD3COCD3): d ˆ 139.4, 128.1, 73.1, 71.3, 71.2,
‡
70.8, 70.7, 70.6, 69.8, 69.5. 67.8; MS (FAB): m/z (%) ˆ 614 (100) [M ];
C34H46O10 (614): calcd C 66.43, H 7.54; found C 66.56, H 7.41.
2,7-Naphtho-p-xylyl-37-crown-10 (29): The procedure described for the
preparation of 26, with 2,7-dihydroxynaphthalene, was followed to give 29
1
as a white crystalline solid (0.28 g, 12%). M.p.: 102.0 ± 102.58C; H NMR
(300 MHz, CDCl3): d ˆ 7.62 (d, J ˆ 9.0 Hz, 2H), 7.29 (s, 4H), 7.01 (m, 4H),
4.53 (s, 4H), 4.23 (t, 4H), 3.90 (t, 4H), 3.50 ± 3.80 (m, 24H); 13C NMR
(CDCl3, 75 MHz): d ˆ 157.4, 137.7, 135.8, 129.1, 127.6, 124.5, 116.4, 106.4,
72.9, 70.9, 70.9, 70.8, 70.7, 70.7, 69.7, 69.5, 67.4; MS (FAB): m/z (%) ˆ 637
‡
70.3; MS (FAB): m/z (%) ˆ 591 (6) [M ‡H]; C32H48O10 (592): calcd C
64.84, H 8.16; found: C 64.60, H 8.40.
34-Crown-8 derivative (15): A solution of 13 (4.50 g, 6.60 mmol) in dry
THF (200 mL) was added over 15 min to a refluxing suspension of 1,4-
phenylene dipropanol (14) (1.28 g, 6.60 mmol) and NaH (0.79 g,
19.79 mmol) in dry THF (400 mL) under N2, and the solution was heated
under reflux for 4 d. The reaction was cooled down to room temperature
and quenched with H2O, and the solution was concentrated. The residue
was dissolved in CH2Cl2 (150 mL), washed with H2O (3 Â 100 mL), and
dried (MgSO4). The solvent was removed and the residue purified by
column chromatography (SiO2, CH2Cl2/MeOH 100:1) to yield 15 as a white
crystalline solid (1.20 g, 34%). M.p.: 42.0 ± 42.58C; 1H NMR (300 MHz,
CDCl3): d ˆ 7.06 (s, 4H), 6.78 (s, 4H), 4.03 (t, 4H), 3.83 (t, 4H), 3.62 ± 3.76
(m, 12H), 3.59 (t, 4H), 3.47 (t, 4H), 2.64 (t, 4H), 1.85 (m, 4H); 13C NMR
(CD3COCD3, 75 MHz): d ˆ 153.3, 139.5, 128.6, 115.8, 71.0, 71.0, 70.9, 70.5,
‡
‡
(100) [M ‡Na], 614 (24) [M ]; C34H46O100 (614): calcd C 66.42, H 7.54;
found C 66.26, H 7.48.
[2]Catenane 6 ´ 4PF6:
A solution of 5 (0.20 g, 0.355 mmol), 1 ´ 2PF6
(125 mg, 0.177 mmol) and 2 (52 mg, 0. 195 mmol) in dry MeCN (7 mL)
was stirred for 6 d in a sealed flask. The solvent was removed and the
residue purified by column chromatography (SiO2, MeOH/2m NH4Cl/
MeNO2 7:2:1). Counterion exchange (NH4PF6/H2O) afforded 6 ´ 4PF6 as a
red solid (139 mg, 47%). M.p.: >2508C; 1H NMR (300 MHz, CD3CN,
233 K): d ˆ 8.85 (m, 8H), 7.79 (m, 8H), 7.61 (m, 8H), 6.62 (s, 2.48H), 6.22 (s,
1.52H), 5.68 (s, 1.52H), 5.66 (s, 2.48H), 4.02 (s, 4H), 3.41 (s, 2.48H), 3.58 (s,
1.52H), 3.50 ± 3.99 (m, 32H); 13C NMR (75 MHz, CD3CN): d ˆ 155.3, 150.7,
149.5, 141.9, 141.6, 137.0, 136.1, 133.0, 130.8, 130.5, 129.8, 118.1, 77.0, 76.2,
76.1, 75.8, 75.2, 75.1, 74.9, 71.9, 70.0, 66.4; MS (FAB): m/z (%) ˆ 1664 (1)
‡
70.3, 70.0, 68.4, 32.0, 31.6; MS (FAB): m/z (%) ˆ 532 (100) [M ]; HRMS
‡
calcd for [M ] C30H44O8 532.3036, found 532.3038.
‡
‡
‡
‡
[M ], 1519 (17) [M
PF6], 1374 (21) [M
2PF6], 1229 (4) [M
3PF6];
C66H76F24N4O10P4 (1664): calcd C 47.60, H 4.60, N 3.36; found: C 47.36, H
4.40, N 3.11.
Naphthalene-2,6-dimethylyl-p-phenylene-38-crown-10 (19): The proce-
dure for the preparation of 5 was followed, with 17 (6.00 g, 7.07 mmol),
hydroquinone (0.78 g, 7.10 mmol), and Cs2CO3 (44.6 g, 0.137 mol) to yield
colorless crystals of 19 (0.77 g, 18%). M.p.: 61.5 ± 62.08C; 1H NMR
(300 MHz, CDCl3, 298 K): d ˆ 7.77 (d, J ˆ 8.0 Hz, 2H), 7.73 (brs, 2H), 7.44
(dd, J ˆ 1.5, 8.0 Hz, J ˆ 1.5 Hz, 2H), 6.69 (s, 4H), 4.71 (s, 4H), 3.92 ± 3.96
(m, 4H), 3.76 ± 3.82 (m, 4H), 3.64 ± 3.74 (m, 24H); 13C NMR (CDCl3,
75 MHz): d ˆ 153.2, 135.9, 128.1, 132.8, 126.1, 126.0, 115.5, 73.3, 70.8, 70.8,
[2]Catenane 12 ´ 4PF6: A solution of 11 (360 mg, 0.61 mmol), l ´ 2PF6
(210 mg, 0.31 mmol) and 2 (90 mg, 0.34 mmol) in dry MeCN (7 mL) was
stirred for 5 d. The reaction was worked up as described for 6 ´ 4PF6 to yield
11 ´ 4PF6 as a pale yellow solid (200 mg, 38%). M.p.: >2508C; 1H NMR
(400 MHz, CD3CN, 333 K): d ˆ 8.86 (d, 8H), 7.79 (d, J ˆ 7.0 Hz, 8H), 7.73 (s,
8H), 5.71 (s, 8H), 5.51 (brs, 8H), 3.97 (s, 8H), 3.76 ± 3.90 (m, 32H); 13C
‡
70.8, 70.8, 70.8, 69.7, 69.6, 68.1; MS (FAB): m/z (%) ˆ 614 (100) [M ];
NMR (75 MHz, CD3CN): d ˆ 147.3, 145.6, 138.1, 137.9, 131.7, 128.0, 127.7,
‡
C34H46O10 (614): calcd C 66.43, H 7.54; found C 66.73, H 7.51.
72.8, 71.2, 65.7; MS (FAB): m/z (%) ˆ 1547 (11) [M
PF6], 1403 (5)
‡
[M ‡H 2PF6]; C68H80F24N4O10P4 (1692): calcd C 48.23, H 4.76, N 3.31;
1,5-Naphtho-p-xylyl-38-crown-10 (26): 1,5-Dihydroxynaphthalene (0.80 g,
5.01 mmol) was added to a previously degassed suspension of Cs2CO3
(32.7 g, 100 mmol) and CsOTs (1.53 g, 5.01 mmol) in dry DMF (400 mL)
under N2. After stirring for 1 h at 808C, a solution of 20 (4.00 g, 5.01 mmol)
and CsOTs (1.53 g, 5.01 mmol) in dry, degassed DMF (200 mL) was added
over 1 h and the heating was maintained for 5 d. After cooling down to
room temperature, the reaction mixture was filtered. The filtrate was
collected and the solvent removed to leave a solid residue, which was
dissolved in PhMe (200 mL) and washed with H2O (250 mL). The aqueous
layer was washed with PhMe (3 Â 100 mL). The organic layers were
combined and dried (MgSO4), and the solution was concentrated. The
resulting brown oil was purified by column chromatography (SiO2, CH2Cl2/
MeOH 100:2), followed by recrystallization (CHCl3/hexane) to yield 26 as
a white crystalline solid (1.50 g, 52%). M.p.: 104.0 ± 104.58C; 1H NMR
(300 MHz, CDCl3): d ˆ 7.86 (d, J ˆ 8.0 Hz, 2H), 7.30 (d, J ˆ 8.0 Hz, 2H),
7.18 (s, 4H), 6.79 (d, J ˆ 8.0 Hz, 2H), 4.39 (s, 4H), 4.26 (t, 4H), 3.79 (t, 4H),
3.56 ± 3.73 (m, 16H), 3.46 (t, 4H); 13C NMR (CDCl3, 75 MHz): d ˆ 154.4,
137.6, 127.6, 126.9, 125.1, 114.7, 105.8, 72.9, 71.1, 70.9, 70.9, 70.7, 70.6, 69.8,
found: C 47.93, H 4.77, N 3.50.
[2]Catenane 16 ´ 4PF6: A solution of 15 (250 mg, 0.47 mmol), 1 ´ 2PF6
(133 mg, 0.19 mmol) and 2 (55 mg, 0.21 mmol) in dry MeCN (7 mL) was
stirred for 5 d. The reaction was worked up as described for 6 ´ 4PF6 to yield
16 ´ 4PF6 as an orange/red solid (34 mg, 11%). M.p.: >2508C; 1H NMR
(400 MHz, CD3COCD3, 298 K): d ˆ 9.35 (d, 8H), 8.26 (d, 8H), 8.08 (s, 8H),
6.59 (s, 4H), 6.04 (s, 8H), 3.70 ± 4.03 (m, 32H), 3.27 (t, 4H); 13C NMR
(100 MHz, CD3COCD3): d ˆ 151.1, 147.6, 146.1, 139.6, 137.8, 131.9, 128.6,
126.8, 114.0, 71.7, 71.5, 71.0, 70.9, 70.8, 69.3, 67.4, 65.7, 31.6, 31.5; MS (FAB):
‡
‡
‡
m/z (%) ˆ 1487 (13) [M
PF6], 1342 (27) [M
2PF6], 1197 (6) [M
‡
3PF6]; HRMS calcd for [M
PF6] C68H80F18N4O10P3 1487.4589, found
1487.4624.
[2]Catenane 20 ´ 4PF6: A solution of 19 (230 mg, 0.38 mmol), 1 ´ 2PF6
(115 mg, 0.16 mmol) and 2 (48 mg, 0. 18 mmol) in dry MeCN (7 mL) was
stirred for 5 d. The reaction was worked up as described for 6 ´ 4PF6 to yield
1
20 ´ 4PF6 as an orange/red solid (125 mg, 45%). M.p.: >2508C; H NMR
(300 MHz, CD3CN, 343 K): d ˆ 8.77 (d, J ˆ 7.0 Hz, 8H), 7.79 (s, 8H), 7.44 (d,
J ˆ 7.0 Hz, 8H), 7.20 (d, J ˆ 7.9 Hz, 2H), 7.11(d, J ˆ 8.0 Hz, 2H), 7.07 (brs,
2H), 5.70 (s, 8H), 4.37 (s, 4H), 3.72 ± 3.99 (m, 28H), 3.70 (s, 4H), 3.47 (m,
‡
69.5, 68.1; MS (FAB): m/z (%) ˆ 614 (100) [M ]; C34H46O10 (608): calcd C
66.42, H 7.54; found C 66.12, H 7.76.
Chem. Eur. J. 1998, 4, No. 3
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457

R. Ballardini, V. Balzani, J. F. Stoddart et al.
FULL PAPER
4H); 13C NMR (CD3CN, 75 MHz): d ˆ 155.3, 150.7, 149.5, 141.9, 141.6,
Research Topics), MURST, and CNR (Progetto Strategico Tecnologie
Chimiche Innovative) in Italy. We thank Dr. Lucia Flamigni (FRAE-CNR)
for the picosecond measurements.
137.0, 136.1, 133.0, 130.8, 130.5, 129.8, 118.1, 77.0, 76.2, 76.1, 75.8, 75.2, 75.1,
‡
74.9, 71.9, 70.0, 66.4; MS (FAB): m/z (%) ˆ 1569 (13) [M
PF6], 1424 (28)
‡
‡
[M
2PF6], 1279 (8) [M
3PF6]; C70H78F24N4O10P4 (1714): calcd C 49.01,
H 4.58, N 3.27; found: C 48.71, H 4.70, N 3.44.
Received: June 30, 1997 [F741]
[2]Catenane 30 ´ 4PF6: A solution of 26 (225 mg, 0.38 mmol), 1 ´ 2PF6
(104 mg, 0. 15 mmol) and 2 (43 mg, 0. 16 mmol) in dry MeCN (7 mL)
was stirred for 5 d. The reaction was worked up as described for 6 ´ 4PF6 to
[1] D. Philp, J. F. Stoddart, Angew. Chem. 1996, 108, 1242 ± 1286; Angew.
Chem. Int. Ed. Engl. 1996, 35, 1154 ± 1196.
1
yield 30 ´ 4PF6 as a purple solid (130 mg, 52%). M.p.: >2508C; H NMR
(400 MHz, CD3CN, 278 K): d ˆ 8.51 ± 8.89 (m, 8H), 7.75 ± 8.03 (m, 8H),
7.08 ± 7.38 (m, 8H), 5.61 ± 5.91 (m, 8H), 6.62 (s), 6.48 (d), 6.19 (d), 3.63 (brs),
3.36 ± 4.24 (m, 40H); 13C NMR (CD3CN, 75 MHz) broad at room temper-
Â
Â
[2] M. Gomez-Lopez, J. A. Preece, J. F. Stoddart, Nanotechnology 1996, 7,
183 ± 192.
[3] For articles dealing with molecular recognition see: a) J. Rebek, Jr.,
Angew. Chem. 1990, 102, 261 ± 272; Angew. Chem. Int. Ed. Engl. 1990,
29, 245 ± 255; b) H.-J. Schneider, Angew. Chem. 1991, 103, 1419 ± 1439;
Angew. Chem. Int. Ed. Engl. 1991, 30, 1417 ± 1436; c) F. Diederich,
D. B. Smithrud, E. M. Sanford, T. B. Wyman, S. B. Ferguson, D. R.
Carcanague, I. Chao, K. N. Houk, Acta Chem. Scand. 1992, 46, 205 ±
215; d) M. Mascal, Contemp. Org. Synth. 1994, 1, 31 ± 46; e) F. W.
Lichtenthaler, Angew. Chem. 1994, 106, 2456 ± 2467; Angew. Chem.
Int. Ed. Engl. 1994, 33, 2364 ± 2374.
[4] J.-M. Lehn, Supramolecular ChemistryÐConcepts and Perspectives,
VCH, Weinheim, 1995.
[5] For examples of paraquat receptors, see: a) P. R. Ashton, E. J. T.
Chrystal, J. P. Mathias, K. P. Parry, A. M. Z. Slawin, N. Spencer, J. F.
Stoddart, D. J. Williams, Tetrahedron Lett. 1987, 28, 6367 ± 6370;
‡
‡
ature; MS (FAB): m/z (%) ˆ 1714 (2) [M ], 1570 (20) [M ‡H PF6], 1425
‡
‡
(16) [M ‡H 2PF6], 1297 (6) [M ‡NH4 3PF6]; C70H78F24N4O10P4
(1714): calcd C 49.01, H 4.58, N 3.27; found: C 48.71, H 4.28, N 3.53.
[2]Catenane 31 ´ 4PF6: A solution of 27 (262 mg, 0.43 mmol), 1 ´ 2PF6
(121 mg, 0. 17 mmol) and 2 (50 mg, 0. 19 mmol) in dry MeCN (7 mL)
was stirred for 5 d. The reaction was worked up as described for 6 ´ 4PF6 to
yield 31 ´ 4PF6 as a red solid (121 mg, 41%). M.p.: >2508C; 1H NMR
(400 MHz, CD3COCD3, 203 K): d ˆ 9.26 (m, 8H), 8.04 (m, 8H), 7.73 (s,
8H), 8.03 (s, 8H), 7.38 (d, J ˆ 9.3 Hz, 1H), 7.36 (t, J ˆ 7.9 Hz, 1H), 7.11 (d,
J ˆ 8.4 Hz, 1H), 6.85 (d, J ˆ 7.7 Hz, 1H), 6.71 (d, J ˆ 1.7 Hz, 1H), 6.52 (dd,
3J ˆ 9.2 Hz, 1H), 6.02 (s, 8H), 3.48 ± 4.06 (m, 36H); 13C NMR (75 MHz,
CD3CN): d ˆ 155.6, 146.6, 145.2, 138.2, 135.7, 131.5, 130.0, 129.1, 126.8,
119.7, 107.4, 72.1, 71.8, 71.4, 71.4, 71.0, 70.7, 70.6, 69.9, 68.3; MS (FAB): m/z
‡
‡
‡
(%) ˆ 1715 (2) [M ‡H], 1570 (18) [M ‡H 2PF6], 1425 (23) [M ‡H
Â
b) A. R. Bernado, T. Lu, E. Cordova, L. Zhang, G. W. Gokel, A. E.
‡
3PF6], 1280 (5) [M ‡H 4PF6]; C70H78F24N4O10P4 (1714): calcd C 49.01, H
Kaifer, J. Chem. Soc. Chem. Commun. 1994, 529 ± 530; c) M. J.
Gunter, M. R. Johnston, B. W. Skelton, A. H. White, J. Chem. Soc.
Perkin Trans. 1 1994, 116, 1009 ± 1018; d) A. P. H. J. Schenning, B.
de Bruin, A. E. Rowan, H. Kooijman, A. L. Spek, R. J. M. Nolte,
Angew. Chem. 1995, 107, 2288 ± 2289; Angew. Chem. Int. Ed. Engl.
1995, 34, 2132 ± 2134.
4.58, N 3.27; found: C 49.08, H 4.66, N 3.26.
[2]Catenane 32 ´ 4PF6: A solution of 28 (300 mg, 0.49 mmol), 1 ´ 2PF6
(140 mg, 0.20 mmol) and 2 (60 mg, 0.21 mmol) in dry MeCN (7 mL) was
stirred for 5 d. The reaction was worked up as described for 6 ´ 4PF6 to yield
32 ´ 4PF6 as a purple solid (145 mg, 42%). M.p.: >2508C; 1H NMR
(CD3CN, 400 MHz, 343 K): d ˆ 8.73 (d, 8H), 7.80 (s, 8H), 7.53 (d, 8H), 7.14
(d, J ˆ 8.4 Hz, 2H), 6.82 (d, J ˆ 8.4 Hz, 2H), 6.41 (s, 2H), 5.71 (s, 8H), 4.05
(s, 4H), 3.62 ± 3.90 (m, 36H); 13C NMR (CD3CN, 75 MHz): d ˆ 155.9, 146.3,
145.2, 137.8, 136.2, 131.5, 129.9, 129.1, 126.8, 119.7, 107.6, 72.1, 71.8, 71.4,
[6] J. F. Stoddart, Pure Appl. Chem. 1988, 60, 467 ± 472.
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1989, 28, 1396 ± 1399.
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‡
71.4, 71.1, 70.8, 70.6, 70.0, 68.4, 65.4; MS (FAB): m/z (%) ˆ 1714 (2) [M ],
‡
‡
‡
1569 (10) [M
PF6], 1424 (11) [M
2PF6], 1279 (2) [M
3PF6];
C70H78F24N4O10P4 (1714): calcd C 49.01, H 4.58, N 3.27; found: C 48.81, H
4.53, N 3.31.
[2]Catenane 33 ´ 4PF6: A solution of 29 (148 mg, 0.24 mmol), 1 ´ 2PF6
(68 mg, 0.10 mmol) and 2 (28 mg, 0. 11 mmol) in dry MeCN (7 mL) was
stirred for 5 d. The reaction was worked up as described for 6 ´ 4PF6 to yield
33 ´ 4PF6 as an orange solid (46 mg, 28%). M.p.: >2508C; 1H NMR
(400 MHz, CD3CN, 313 K): d ˆ 8.86 (d, 8H), 7.82 (s, 8H), 7.66 (d, 8H), 7.04
(d, J ˆ 8.5 Hz, 2H), 6.74 (dd, J ˆ 1.8, 8.5 Hz, 2H), 6.59 (d, J ˆ 2.0 Hz, 2H),
5.73 (s, 8H), 4.10 (s, 4H), 3.54 ± 4.12 (m, 36H); 13C NMR (75 MHz,
CD3CN): d ˆ 158.1, 146.6, 145.3, 136.6, 131.7, 131.7, 130.3, 127.5, 127.1, 118.6,
117.0, 107.1, 72.9, 71.1, 71.1, 71.1, 70.9, 70.9, 70.9, 70.1, 68.4, 65.5; MS (FAB):
‡
‡
‡
m/z (%) ˆ 1714 (2) [M ], 1569 (16) [M
PF6], 1424 (22) [M
2PF6],
‡
1279 (6) [M
3PF6]; C70H78F24N4O10P4 (1714): calcd C 49.01, H 4.58, N
3.27; found: C 48.83, H 4.47, N 3.17.
Absorption and luminescence measurements: Unless otherwise stated,
room temperature experiments were carried out in air-equilibrated MeCN
(spectrofluorimeter grade) solutions. Electronic absorption spectra were
recorded with a Perkin ± Elmer l6 spectrophotometer. Emission spectra
and phosphorescence lifetimes were obtained with a Perkin ± Elmer LS50
spectrofluorimeter. Emission spectra in a butyronitrile rigid matrix at 77 K
were recorded with quartz tubes immersed in a quartz Dewar flask filled
with liquid nitrogen. Fluorescence quantum yields were determined with
either naphthalene in degassed cyclohexane (f ˆ 0.23)[28] or quinine sulfate
in 1n H2SO4 (f ˆ 0.55)[29] as standards. Nanosecond and picosecond lifetime
measurements were performed with an Edinburgh single-photon counter
and a picosecond spectrometer based on a Nd YAG (PY62-10 Continuum)
laser and a Hamamatsu C1587 streak camera.[30] Experimental errors:
absorption maxima, Æ 2 nm; emission maxima, Æ 2 nm; excited state
lifetimes, Æ 10%; and fluorescence quantum yields, Æ 20%.
Acknowledgements: This research was supported by the Engineering and
Physical Sciences Research Council (EPSRC) as well as by Merck Sharp &
Dohme in the UK, and by the University of Bologna (Funds for Selected
[12] Process I is defined as the circumrotation of the macrocyclic polyether
through the cavity of the tetracationic cyclophane. Process II is
458
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0947-6539/98/0403-0458 $ 17.50+.50/0
Chem. Eur. J. 1998, 4, No. 3

[2]Catenanes
449±459
defined as the circumrotation of the tetracationic cyclophane through
Chem. Soc. 1995, 117, 5275 ± 5291; d) P. R. Ashton, R. Ballardini, V.
Â
Â
the cavity of the macrocyclic polyether.
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Balzani, S. E. Boyd, A. Credi, M. T. Gandolfi, M. Gomez-Lopez, S.
Iqbal, D. Philp, J. A. Preece, L. Prodi, H. G. Ricketts, J. F. Stoddart,
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Â
Gandolfi, L. Perez-García, L. Prodi, C. H. McLean, D. Philp, N.
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Â
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Â
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[14] a) P. R. Ashton, R. Ballardini, V. Balzani, M. T. Gandolfi, D. J.-F.
Â
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Â
571 ± 574; c) P. R. Ashton, R. Ballardini, V. Balzani, A. Credi, M. T.
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