Oligocatenanes made to order

Article abstract of DOI:10.1021/ja9720873

The construction of catenanes, comprised of between two and seven interlocked rings, has been achieved. Two tris-1,5-naphtho-57-crown-15 macrocycles template the formation of cyclobis(paraquat-4,4'-biphenylene) to give a [3]catenane, which acts as a templ

Full text of DOI:10.1021/ja9720873

J. Am. Chem. Soc. 1998, 120, 4295-4307
4295
Oligocatenanes Made to Order1
David B. Amabilino,† Peter R. Ashton, Vincenzo Balzani,* Sue E. Boyd, Alberto Credi,
,§
†
,#
†
#
†
‡
,†
#
Ju Young Lee, Stephan Menzer, J. Fraser Stoddart,* Margherita Venturi, and
David J. Williams*,‡
Contribution from The School of Chemistry, The UniVersity of Birmingham, Edgbaston,
Birmingham B15 2TT, UK, The Chemical Crystallography Laboratory, Department of Chemistry,
Imperial College, South Kensington, London SW7 2AY, UK,
and Dipartimento di Chimica “G. Ciamician” dell’UniVersit a` , Via Selmi 2, 40126 Bologna, Italy
ReceiVed June 24, 1997. ReVised Manuscript ReceiVed March 15, 1998
Abstract: The construction of catenanes, comprised of between two and seven interlocked rings, has been
achieved. Two tris-1,5-naphtho-57-crown-15 macrocycles template the formation of cyclobis(paraquat-4,4′-
biphenylene) to give a [3]catenane, which acts as a template for the construction of one and then another
cyclobis(paraquat-p-phenylene) to give a [4]- and [5]catenane (Olympiadane). When high pressure was used
in these templated syntheses, a [6]- and [7]catenane, as well as a [5]catenane that is topologically isomeric
with Olympiadane, were also obtained. X-ray analyses of the [3]-, [5]-, and [7]catenanes reveal an optimum
use of electrostatic, π-π stacking, [C-H‚‚‚π] interactions, and [C-H‚‚‚O] hydrogen bonds in the organization
of the component rings within the molecules. Noteworthy in the [7]catenane structure is the location of four
-
+
1
of the PF6 anions within voids present in the 20 ion. Temperature-dependent H NMR spectroscopic studies
and electrochemical investigations have revealed the dynamic and redox behavior of these catenanes in solution.
Introduction
copper(I) as a template has spawned catenates containing up to
seven interlocked rings as illustrated by 1 in Figure 1, where n
) 3. Furthermore, polycatenanes of type 2 in Figure 1 have
been formed by polymerization of preformed bifunctional [2]-
Catenanes2,3 are becoming commonplace molecular com-
4
5
pounds. Recently, template-direction and self-assembly, as-
sisted by supramolecular interactions,6 have allowed many
1
1
7
catenane monomers.
However, the controlled creation of
topologically fascinating molecules to be constructed. Higher
catenanes have proven to be more elusive sso much so that
8
polycatenanes of types 3 or 4 in Figure 1 has yet to be
12
addressed. Indeed, high molecular weight linear polycatenanes
might be regarded as a “holy grail” in unnatural product
the construction of multiply interlocked chainlike molecules
remains a challenge.9 The preparation of [3]catenates with
10
1
3
synthesis. One of the attractions of these exotic molecules is
the potential materials properties that they may possess on
account of their mechanically interlocked components.14 Con-
*
Correspondence should be addressed to Dr. J. F. Stoddart, Department
of Chemistry and Biochemistry, University of California at Los Angeles,
4
2
05 Hilgard Avenue, Los Angeles CA90095. Tel: 310-206-7078. Fax: 310-
06-1843. E-mail: stoddart@chem.ucla.edu.
†
University of Birmingham.
Imperial College.
Universit a´ di Bologna.
(9) Amabilino, D. B.; Stoddart, J. F. Pure Appl. Chem. 1993, 65, 2351-
2359.
‡
#
(10) Bitsch, F.; Hegy, G.; Dietrich-Buchecker, C. O.; Leize, E.; Sauvage,
J.-P.; van Dorsselaer, A. New J. Chem. 1994, 18, 801-807.
(11) (a) Geerts, Y.; Muscat, D.; M u¨ llen, K. Macromol. Chem. Phys. 1995,
196, 3425-3435. (b) Menzer, S.; White, A. J. P.; Williams, D. J.;
Belohradsky, M.; Hamers, C.; Raymo, F. M.; Shipway, A. N.; Stoddart, J.
F. Macromolecules 1998, 31, 295-307.
(12) Some not so convincing reports on linear polycatenanes have
appeared in the literature at a time when the analytical techniques available
for characterizing these compounds were not so sophisticated. For a lead
article, see: Karagounis, G.; Pandi-Agathokli, I.; Kontaraki, E. IUPAC
Colloid & Interface Sci. International Conf. 1975, 1, 671-678.
(13) Stoddart, J. F. Nature 1988, 334, 10-11.
(14) Relatively poorly defined macromolecular systems that can be
regarded as polycatenanes have been prepared. They show interesting
properties when compared with their noninterlocked components. See, for
example: (a) Millar, J. R. J. Chem. Soc. 1960, 1311-1317. (b) Garrido,
L.; Mark, J. E.; Clarson, S. J.; Semlyen, J. A. Polym. Commun. 1985, 26,
55-57. A number of crystalline solids contain interlocked rings which are
formed in the process of crystallization. However, their superstructures do
not persist in solution. For pertinent articles on related solids with references
therein, see: (c) Ermer, O. J. Am. Chem. Soc. 1988, 110, 3747-3754. (d)
Stumpf, H. O.; Ouahab, L.; Pei, Y.; Grandjean, D.; Kahn, O. Science 1993,
261, 447-449. (e) Fujita, M.; Ibukuro, F.; Yamaguchi, K.; Ogura, K. J.
Am. Chem. Soc. 1995, 117, 7287-7288. (f) Abrahams, B. F.; Batten, S.
R.; Hamit, H.; Hoskins, B. F.; Robson, R. Chem. Commun. 1996, 1313-
1314. (g) Hirsch, K. A.; Wilson, S. R.; Moore, J. S. Chem. Eur. J. 1997, 3,
765-771.
§
Current Address: Institut de Ci e` ncia de Materials de Barcelona (CSIC),
Campus Universitari, 08193-Bellaterra, Spain.
1) Molecular Meccano 30. For part 29, see; Ballardini, R.; Balzani, V.;
(
Credi, A.; Gandolfi, M. T.; Marquis, D. J. F.; P e´ rez-Garc ´ı a, L.; Stoddart, J.
F. Eur. J. Org. Chem. 1998, 81, 1-89.
(
2) For comprehensive reviews on catenanes, see: (a) Dietrich-
Buchecker, C. O.; Sauvage, J.-P. Chem. ReV. 1987, 87, 795-810. (b)
Amabilino, D. B.; Stoddart, J. F. Chem. ReV. 1995, 95, 2725-2828. (c)
J a¨ ger, R.; V o¨ gtle, F. Angew. Chem., Int. Ed. Engl. 1997, 36, 930-944.
(3) For a recent communication on catenanes, see: Hamilton, D. G.;
Feeder, N.; Prodi, L.; Teat, S. J.; Clegg, W.; Sanders, J. K. M. J. Am. Chem.
Soc. 1998, 120, 1096-1097.
(4) (a) Anderson, S.; Anderson, H. L.; Sanders, J. K. M. Acc. Chem.
Res. 1993, 26, 469-475. (b) Hoss, R.; V o¨ gtle, F. Angew. Chem., Int. Ed.
Engl. 1994, 33, 375-384.
(
5) (a) Lawrence, D. S.; Jiang, T.; Levett, M. Chem. ReV. 1995, 95,
2
229-2260. (b) Gillard, R. E.; Raymo, F. M.; Stoddart, J. F. Chem. Eur.
J. 1997, 3, 1933-1940.
(
(
6) Fyfe, M. C. T.; Stoddart, J. F. Acc. Chem. Res. 1997, 30, 393-401.
7) See, for example: (a) Walba, D. M.; Zheng, Q. Y.; Schilling, K. J.
Am. Chem. Soc. 1992, 114, 6259-6260. (b) Nierengarten, J.-F.; Dietrich-
Buchecker, C. O.; Sauvage, J.-P. New J. Chem. 1996, 20, 685-693.
(8) For an example of higher catenanes based on metal-ion templated
synthesis, see: Dietrich-Buchecker, C. O.; Frommberger, B.; L u¨ er, I.;
Sauvage, J.-P.; V o¨ gtle, F. Angew. Chem., Int. Ed. Engl. 1993, 32, 1434-
1
437.
S0002-7863(97)02087-8 CCC: $15.00 © 1998 American Chemical Society
Published on Web 04/28/1998

4296 J. Am. Chem. Soc., Vol. 120, No. 18, 1998
Amabilino et al.
Figure 2. The [4]catenane 5‚8PF
6
which was formed from the
macrocyclic polyether TPP51C15 via the intermediate [3]catenane
incorporating two macrocyclic polyethers and one cyclobis(paraquat-
4
,4′-biphenylene) tetracation.
Figure 1. Cartoon representations of four types (1-4) of polycatenane.
sequently, we have embarked upon a “crusade” to fashion
molecular chains. Our methodology exploits the cooperativity
of weak noncovalent interactionsse.g. aromatic π-π stack-
1
5
16
ing, [C-H‚‚‚π] interactions, and [C-H‚‚‚O] hydrogen
17
bonds sbetween complementary components to construct
interlocked molecules. This approach has led to the self-
Figure 3. Cartoon representations of the two topologically stereoiso-
meric [5]catenanes, a [6]- and a [7]catenane.
18
5
19-21
assembly of [2]-, [3]-, and bis[2]catenanes
and also to the
linear [4]catenane,22 5‚8PF6 in Figure 2. The subsequent
progression to a compound believed to be a [5]catenane was
highly inefficient, even under high-pressure reaction condi-
TN57C15, as well as its ability to template the formation of
2
5
cyclobis(paraquat-p-phenylene) and cyclobis(paraquat-4,4′-
2
6
biphenylene) as integral components of catenanes. In par-
2
3
27
tions.
ticular, we describe the synthesis of the linear pentacatenane,
2
8
which we have named Olympiadane. In addition, we have
To improve the templating abilities of the previously em-
ployed macrocyclic polyether, tris-p-phenylene-51-crown-15
2
9
identified a topological stereoisomer of Olympiadane, along
with the intermediate [6]catenane, formed en route to a branched
[7]catenane (Figure 3). The catenanes have been characterized
by NMR spectroscopy, electrochemistry, and mass spectrometry.
(
1
5
TPP51C15), we replaced the three hydroquinone rings with
,5-dioxynaphthalene ring systems24 to give tris-1,5-naphtho-
7-crown-15 (TN57C15). Here, we report the preparation of
30
Highlights are the X-ray crystal structure of the heptacatenane
3
1
(15) For reviews discussing π-π stacking, see, along with references
and of Olympiadane.
therein: (a) Dahl, T. Acta Chem. Scand. 1994, 48, 95-106. (b) Hunter, C.
A. Chem. Soc. ReV. 1994, 101-109. In the case of the types of compounds
we are concerned with in this paper, the π-π stacking leads to charge-
transfer bands in the visible region of the electronic absorption spectrum.
For a review concerning interactions between neutral donors and charged
acceptors, see: Kamper, V. E. Russ. Chem. ReV. 1982, 51, 107-118. For
a review on charge-transfer interactions in cyclophanes, see: Schwartz, M.
H. J. Inclusion Phenom. 1990, 9, 1-35.
(23) Amabilino, D. B.; Ashton, P. R.; Brown, C. L.; C o´ rdova, E.;
God ´ı nez, L.; Goodnow, T. T.; Kaifer, A. E.; Newton, S. P.; Pietraszkiewicz,
M.; Philp, D.; Raymo, F. M.; Reder, A. S.; Rutland, M. T.; Slawin, A. M.
Z.; Spencer, N.; Stoddart, J. F.; Williams, D. J. J. Am. Chem. Soc. 1995,
117, 1271-1293.
(24) The binding constants for substrates containing 1,5-dioxynaphthalene
ring systems withsand consequently their templating actions in the
formation ofscyclobis(paraquat-p-phenylene) are known to be greater than
those for those substrates containing hydroquinone rings. See: Ashton, P.
R.; Blower, M.; Philp, D.; Spencer, N.; Stoddart, J. F.; Tolley, M. S.;
Ballardini, R.; Ciano, M.; Balzani, V.; Gandolfi, M. T.; Prodi, L.; McLean,
C. H. New J. Chem. 1993, 17, 689.
(25) Asakawa, M.; Dehaen, W.; L’abb e´ , G.; Menzer, S.; Nouwen, J.;
Raymo, F. M.; Stoddart, J. F.; Williams, D. J. J. Org. Chem. 1996, 61,
9591-9595.
(26) Asakawa, M.; Ashton, P. R.; Menzer, S.; Raymo, F. M.; Stoddart,
J. F.; White, A. J. P.; Williams, D. J. Chem. Eur. J. 1996, 2, 877-893.
(27) Amabilino, D. B.; Ashton, P. R.; Reder, A. S.; Spencer, N.; Stoddart,
J. F. Angew. Chem., Int. Ed. Engl. 1994, 33, 1286-1290.
(
16) Nishio, M.; Umezawa, Y.; Hirota, M.; Takeuchi, Y. Tetrahedron
995, 51, 8665-8701.
17) (a) Aeker o¨ y, C. B.; Seddon, K. R. Chem. Soc. ReV. 1993, 22, 397-
07. (b) Desiraju, G. R. Chem. Commun. 1997, 1475-1482.
18) Amabilino, D. B.; Stoddart, J. F.; Williams, D. J. Chem. Mater.
994, 6, 1159-1167.
19) Ashton, P. R.; Ballardini, R.; Balzani, V.; Credi, A.; Gandolfi, M.
1
4
1
(
(
(
T.; Menzer, S.; P e´ rez-Garc ´ı a, L.; Prodi, L.; Stoddart, J. F.; Venturi, M.;
White, A. J. P.; Williams, D. J. J. Am. Chem. Soc. 1995, 117, 11171-
1
1197.
(20) Ashton, P. R.; Brown, C. L.; Chrystal, E. J. T.; Goodnow, T. T.;
Kaifer, A. E.; Parry, K. P.; Slawin, A. M. Z.; Spencer, N.; Stoddart, J. F.;
Williams, D. J. Angew. Chem., Int. Ed. Engl. 1991, 30, 1039-1042.
(28) (a) Walba, D. M. New J. Chem. 1993, 17, 618. (b) van Gulick, N.
New J. Chem. 1993, 17, 619-625..
(29) (a) Frisch, H. L.; Wasserman, E. J. Am. Chem. Soc. 1961, 83, 3789-
3795. (b) Sokolov, V. I. Russ. Chem. ReV. 1973, 42, 452-463. (c) Walba,
D. M. Tetrahedron 1985, 41, 3161-3212. (d) Chambron, J.-C.; Dietrich-
Buchecker, C. O.; Sauvage, J.-P. Top. Curr. Chem. 1993, 165, 131-162.
(21) Ashton, P. R.; Huff, J.; Menzer, S.; Parsons, I. W.; Preece, J. A.;
Stoddart, J. F.; Tolley, M. S.; White, A. J. P.; Williams, D. J. Chem. Eur.
J. 1996, 2, 31-44.
(22) Amabilino, D. B.; Ashton, P. R.; Reder, A. S.; Spencer, N.; Stoddart,
J. F. Angew. Chem., Int. Ed. Engl. 1994, 33, 433-437.

Oligocatenanes Made to Order
J. Am. Chem. Soc., Vol. 120, No. 18, 1998 4297
Scheme 1
Results and Discussion
12 kbar, the [4]catenane, in which the TN57C15 ring is
interlocked by three cyclobis(paraquat-p-phenylene) tetracations,
has also been characterized. The efficiency of these template-
directed processes compares favorably with the equivalent
reactions involving TPP51C15 as the template where only
the corresponding [2]catenane could be isolated.
I. Synthesis of the Macrocyclic Polyethers. See Scheme
1
. Reaction of 6 with 1,5-dihydroxynaphthalene, using Cs2-
3
2
CO3 as base, afforded TN57C15 along with 1,5-naphtho-19-
22
33
crown-5 (N19C5) and di-1,5-naphtho-38-crown-10 (DN38C10).
On account of the low yield (6%) of TN57C15, an alternative
preparation via the diols 7 and 8 was employed. Along with
DN38C10 (3%) and the diol 9, 7, and 8 were isolated when
The self-assembly of the [3]catenane 18‚4PF6, incorporating
cyclobis(paraquat-4,4′-biphenylene), was achieved by reaction
(
Scheme 3) of 15‚2PF6 with 16 in MeCN/DMF (10:1) in the
1
,5-dihydroxynaphthalene was treated with 1.0 mol equiv of
presence of an excess of TN57C15, followed by the “usual”
workup procedure. A small amount of the [2]catenane 17‚-
4
NaH and 0.5 mol equiv of 6. TN57C15 was obtained by
reacting 7 with 10 or 8 with 6. The bistosylate 10 was prepared
by reacting an excess of 6 with 1,5-dihydroxynaphthalene in
DMF with K2CO3 as base. Finally, tetra-1,5-naphtho-76-crown-
36
PF6 was also isolated. All attempts to increase the efficiency
37
of this template-directed reaction were unsuccessful. When
8‚4PF6 was stirred with 11‚2PF6 and 12 in DMF for 4 days,
the [4]catenane 19‚8PF6 and Olympiadanesthe [5]catenane 20‚-
1
3
4
2
0 (TN76C20) was obtained from reaction of 9 with 6.
II. Self-Assembly of Catenanes Incorporating TN57C15.
27
1
2PF6swere obtained in 31% and 5% yields, respectively,
Reaction (Scheme 2) of 11‚2PF6 with 12 in DMF in the presence
of 0.5 mol equiv of TN57C15 afforded, after chromatography
and counterion exchange, the [2]- and [3]catenanes 13‚4PF6 and
after the usual workup procedure. When the reaction time was
extended to 14 days, these percentages rose to 51 and 18,
respectively. Aside from unreacted [3]catenane, the reaction
mixture also contained traces of higher catenanes.
1
4‚8PF6, respectively.35 When the reaction was carried out at
The use of ultrahigh pressure38 proved to be beneficial in
promoting the cascade of self-assembly steps summarized in
(
30) For a preview of the X-ray crystal structure of the heptacatenane,
see: Amabilino, D. B.; Ashton, P. R.; Boyd, S. E.; Lee, J. Y.; Menzer, S.;
Stoddart, J. F.; Williams, D. J. Angew. Chem., Int. Ed. Engl. 1997, 36,
2
070-2072.
31) For a preliminary glimpse of the X-ray crystal structure of
Olympiadane, see: Dagani, R. Chem. Eng. News 1996, Sept. 2, 31.
32) For a review discussing the “cesium effect” upon cyclizations, see:
Ostrowicki, A.; Koepp, E.; V o¨ gtle, F. Top. Curr. Chem. 1991, 161, 37-
7.
(36) In principle, this [2]catenane can act as a ditopic receptor for
molecules incorporating π-electron rich and deficient moieties. See:
Amabilino, D. B.; Stoddart, J. F. Supramolecular Stereochemistry; Siegel,
J. S., Ed.; Kluwer: Boston, 1995; pp 33-40. Preliminary experiments
indicate that the [2]catenane 17‚4PF6 does indeed act as a host for 1,5-
dioxynaphthalene derivatives: Amabilino, D. B.; Stoddart, J. F. Unpublished
results.
(37) The highest yield achieved for a catenation involving this tetraca-
tionic cyclophane is 31%. It has been attained by using the macrocyclic
polyether DN38C10 as a the template. The selectivity displayed for the
formation of the [3]catenane in preference to the [2]catenane in the self-
assembly process is less for TN57C15 than for DN38C10. A similar
phenomenon was observed for the hydroquinone ring-containing macro-
cyclic polyether templates.
(
(
6
(
33) Ashton, P. R.; Chrystal, E. J. T.; Mathias, J. P.; Parry, K. P.; Slawin,
A. M. Z.; Spencer, N.; Stoddart, J. F.; Williams, D. J. Tetrahedron Lett.
987, 28, 6367-6370.
34) This macrocyclic polyether (TN76C20) can be used as a template
1
(
for the formation of cyclobis(paraquat-p-phenylene), leading to a variety
of catenanes, which will be described elsewhere by: Amabilino, D. B.;
Lee, J. Y.; Stoddart, J. F. Unpublished results.
(35) Amabilino, D. B.; Ashton, P. R.; Stoddart, J. F.; Menzer, S.;
Williams, D. J. J. Chem. Soc., Chem. Commun. 1994, 2475-2478.
(38) Isaacs, N. S. Tetrahedron 1991, 47, 8463-8497.

4298 J. Am. Chem. Soc., Vol. 120, No. 18, 1998
Amabilino et al.
Scheme 2
Scheme 3. After 6 days at 12 kbar of pressure, none of the
(ii) two [C-H‚‚‚O] hydrogen bonds (see the caption for Figure
4). The [3]catenanes are packed to form extended two-
dimensional mosaic-like sheets (Figure 6) cemented by further
π-π and [C-H‚‚‚π] interactions.
[
3]catenane 18‚4PF6 was present in the reaction mixture, from
which the [5]-, [6]-, and [7]catenanes 20‚12PF6, 22‚16PF6, and
3‚20PF6 were isolated as the major products. In addition,
2
29
traces of the topological stereoisomer of 20‚12PF6, namely
the branched [5]catenane 21‚12PF6, were present in the chro-
matography fractions containing Olympiadane. The two iso-
meric [5]catenanes can be separated by fractional crystallization
The solid-state structure of 20‚12PF6 shows (Figures 7 and
) the molecule to have maximized its potential for π-π
8
stacking between the components. These interactions are
accompanied by the series of [C-H‚‚‚π] interactions illustrated
in Figure 7 and also [C-H‚‚‚O] hydrogen bonds (see the caption
for Figure 7). Despite the absence of any intermolecular π-π
stacking interactions involving the smaller tetracationic cyclo-
phanes, the [5]catenane molecules aggregate to form sheets that
are essentially coplanar with the mean planes of these smaller
cyclophanes. There are intersheet π-π stacking interactions
between one of the rings of each biphenylene unit (of the large
tetracationic cyclophane) of lattice-translated molecules.
(vapor diffusion of i-Pr2O into EtOAc/MeCN solution) since
2
0‚12PF6 forms deep purple needlelike crystals, whereas 21‚-
12PF6 precipitates from solution subsequently as an amorphous
powder. The self-assembly process favors greatly the forma-
tion of the linear pentacatenane in preference to its branched
isomer. The [7]catenane 23‚20PF6 results from the templated
formation of cyclobis(paraquat-p-phenylene) tetracations around
all four 1,5-dioxynaphthalene ring systems that are “free” in
the [3]catenane 18‚4PF6. When hydroquinone rings are present
in the macrocyclic polyether components of the [3]catenane
instead of 1,5-dioxynaphthalene ring systems, the major product
One of the tantalizing questions posed by the structure of
the [5]catenane was the following: How can additional cyclobis-
(paraquat-p-phenylene) tetracations be clipped on to the “non-
encircled” 1,5-dioxynaphthalene ring systems in 201 ? The
answer is provided by the X-ray structure (Figure 9) of the
branched [7]catenane. Both TN57C15 macrocycles are “opened
2
2
isolated from an analogous reaction is a [4]catenane. This
observation reaffirms the fact that 1,5-dioxynaphthalene ring
systems template the formation of cyclobis(paraquat-p-phe-
2+
nylene) tetracations far more efficiently than do hydroquinone
rings.39
3
out” to form pseudo-C symmetric arrangements of their three
1
,5-dioxynaphthalene ring systems. These “dilations” are
III. X-ray Crystal Structures. The X-ray of 18‚4PF6 shows
Figures 4 and 5) the molecule to have Ci symmetry with four
sufficient to permit the accommodation of an additional
encircling cyclobis(paraquat-p-phenylene) tetracation onto each
macrocyclic polyether. We now have the optimum scenario in
that all the π-electron rich and deficient moieties have been
utilized in the self-assembly of the interlocked molecular
compound 23‚20PF6. The process of “dilating” each of the
TN57C15 macrocycles creates small voids at the centers of these
(
of the six 1,5-dioxynaphthalene ring systems (D) forming a
DADDAD stack with two bipyridinium units (A). The extended
π-π stacking interactions within the [3]catenane are augmented
by (i) [C-H‚‚‚π] interactions as illustrated in Figure 4b and
(39) Although the ring-closure reaction in this catenation is controlled
by kinetics, the thermodynamics of binding clearly must play an initial role
in the self-assembly process. See: Amabilino, D. B.; Ashton, P. R.; P e´ rez-
Garc ´ı a, L.; Stoddart, J. F. Angew. Chem., Int. Ed. Engl. 1995, 34, 2378-
-
rings, permitting the docking of pairs of PF6 anions (Figure
1
0) into both their upper and lower surfaces. The [C‚‚‚F]
2
380.
contacts between both pyridinium and phenylene carbon atoms

Oligocatenanes Made to Order
J. Am. Chem. Soc., Vol. 120, No. 18, 1998 4299
Scheme 3
and the embedded anions indicate40 that they are being held in
position via a series of [C-H‚‚‚F] hydrogen bonds. The [C‚‚‚F]
contacts are less than 3.2 Å and the orientations of the aryl rings
provide favorable directionalities of their peripheral C-H bonds.
Further support for the above conclusions comes from the fact
that all four of these anions are orderedsa comparatively rare
component macrocycles. Both “fragmentation” patterns are
42
1
9
typical of these kinds of interlocked compounds. The LSI
mass spectrum (Figure 11) of the [7]catenane (molecular
formula, C300H300N20O30P20F120) reveals a clutch of peaks for
-
the molecular ion with loss of between two and six PF6 anions.
All of the observed peaks are based on the centroid of that
expected for an unresolved isotopic distribution of atoms.
Similar groups of signals are observed for the loss of cyclo-
phanes from the heptacatenane, leading to signals corresponding
to the [6]catenane 22‚16PF6 and the [5]catenanes 20‚12PF6 and
-
41
situation for PF6 anions.
IV. Mass Spectrometry. FAB and LSI mass spectrometries
were employed in the characterization of all the new catenanes.
The general features of the spectra reveal signals resulting (i)
-
21‚12PF , and so on.
from the loss of PF6 anions and then (ii) from the loss of the
6
1
1
V. H NMR Spectroscopy. The relevant H NMR chemical
shift data for the catenanes and their componentssTN57C15,
cyclobis(paraquat-p-phenylene) 24 , and cyclobis(paraquat-
(40) In view of the limited resolution of the data, we have not carried
out a detailed analysis of potential [CsH‚‚‚O] and [CsH‚‚‚F] interactions,
though these undoubtedly will be playing a supporting role in the cooperative
forces that constitute the “adhesive” within this complex multicomponent
molecule.
4+
4+
4
,4′-biphenylene) 25 sare summarized in Table 1. The kinetic
4
3
and thermodynamic data associated with the relative move-
ments of the catenane components are listed in Table 2.
In the catenanes 13‚4PF6 and 14‚8PF6, incorporating TN57C15
and respectively one and two cyclobis(paraquat-p-phenylene)
(
41) Recently, however, we have uncovered, in a series of solid state
-
structures, a significant number of highly ordered PF6 anions trapped within
crystalline supermolecules made up of crown ethers as receptors for organic
cations containing one or two secondary dialkylammonium centers. See
for example: Fyfe, M. C. T.; Glink, P. T.; Menzer, S.; Stoddart, J. F.; White,
A. J. P.; Williams, D. J. Angew. Chem., Int. Ed. Engl. 1997, 36, 2068-
(42) The characteristics of the mass spectra of catenanes were first
described by: Vetter, W.; Schill, G. Tetrahedron 1967, 23, 3079-3093.
2
070.

4300 J. Am. Chem. Soc., Vol. 120, No. 18, 1998
Amabilino et al.
Figure 5. Space-filling representation of the [3]catenane 184+.
Figure 4. (a) Ball-and-stick representation of the [3]catenane 184+
shaded circle ) N, part shaded circle ) O, open circle ) C) and (b)
(
a related cartoon version showing the aromatic π-π stacking and edge-
to-face [C-H‚‚‚π] interactions: mean interplanar separation (Å)
associated with π-π stacking (a 3.39; b 3.35; c 3.55 Å) and [H‚‚‚π
centroid] distance, [C-H‚‚‚π] angle (d 2.74 Å, 142°). The molecular
structure is stabilized further by [C-H‚‚‚O] hydrogen bonds involving
R-bipyridinium protons at two centrosymmetrically related corners of
the tetracationic cyclophane and the central crown ether oxygen atoms
in the nearby polyether loops of the macrocyclic polyether compo-
nent: [C‚‚‚O] and [H‚‚‚O] distances and [C-H‚‚‚O] angle 3.16 Å, 2.26
Å, 157°.
Figure 6. Space-filling representation of the crystal packing in [3]-
catenane 184
+
.
protons on the phenylene ring in the cyclophanes, appear at
increasingly lower fields as the number of cyclophanes is
increased from one to two to three on the TN57C15 macrocycle,
an observation that is a result of the decreased “alongside”
interaction of the 1,5-dioxynaphthalene ring systems with the
bipyridinium units. The solid-state structure of 13‚4PF6 reveals
π-π stacking interactions of the “outside” 1,5-dioxynaphthalene
ring systems with both a bipyridinium unit and one of the
phenylene spacers in the cyclophane componentsa situation that
tetracations, equilibration between the included and free 1,5-
1
dioxynaphthalene residues is slow on the H NMR time scale
(400 MHz) at room temperature. This picture is supported by
the fact that the hydrogen atomssH-2/6, H-3/7, and H-4/8son
the naphthalene ring system included “inside” the tetracationic
cyclophane resonate at approximately δ 6.1, 5.7, and 2.1,
respectively. The signals from the H-4/8 hydrogen atoms appear
at very high field because they are directed toward the π-face
of the p-xylyl spacer of the cyclophane components in solution
as in the solid state. The corresponding signals for the “outside”
naphthalene ring systems resonate in the region of δ 6.5, 7.2,
and 7.4, respectively. The mean chemical shifts (Table 1) for
the R-CH and â-CH bipyridinium protons, as well as for the
35
seems to be sustained, at least to some extent, in solution. At
1
44
just below 273 K, the H NMR spectrum of the [3]catenane
4‚8PF6 reveals a total of four resonances for the eight R-CH
1
and eight â-CH protons associated with the bipyridinium units
of the two cyclophanes. First, two R-CH proton environments
are created by the local C2h symmetry imposed on the cyclo-
phanes by the included 1,5-dioxynaphthalene ring systems.
Second, one side of each of the cyclophanes is directed toward
each other whereas the other side, in each case, is pointing in
the direction of the one unoccupied or “outside” 1,5-dioxynaph-
(43) The kinetic and thermodynamic data were calculated by using the
coalescence method, where values for the rate constant kc at the coalescence
temperature (Tc) were calculated (Sutherland, I. O. Annu. Rep. NMR
Spectrosc. 1971, 4, 71-235) from the approximate expression kc ) π(∆ν)/
1
/2
(
2) , where ∆ν is the chemical shift difference (in Hz) between the
1
coalescing signals in the absence of exchange. The Eyring equation was
subsequently employed to calculate ∆G c values from kc at Tc.
(44) The H NMR spectra of the [3]catenane 14‚8PF6 were too complex
‡
to afford kinetic data.

Oligocatenanes Made to Order
J. Am. Chem. Soc., Vol. 120, No. 18, 1998 4301
Figure 9. Ball-and-stick representation of the branched [7]catenane
20+
2
3
(shaded circle ) N, part shaded circle ) O, open circle ) C)
showing the alignment of each π-electron rich 1,5-dioxynaphthalene
ring system with associated π-electron deficient bipyridinium units.
Figure 7. (a) Ball-and-stick representation of olympiadane 2012+
(shaded circle ) N, part shaded circle ) O, open circle ) C) and (b)
a related cartoon version showing the aromatic π-π stacking and
edge-to-face [C-H‚‚‚π] interactions: mean interplanar separation (Å)
associated with π-π stacking (a 3.3; b 3.4; c 3.4; d 3.5; e 3.7; f 3.6 Å)
and [H‚‚‚π centroid] distance, [C-H‚‚‚π] angle (g 2.52 Å; 147°; h
2
.63 Å, 147°; i 2.91 Å, 144°; k 2.88 Å, 160°). The twist angle of the
large cyclophane with reference to the small one is 74°. The tilt angle
of the large cyclophane with respect to the small one is ca. 25°. The
molecular structure is stabilized further by [C-H‚‚‚O] hydrogen bonds
involving R-bipyridinium protons in the tetracationic cyclophanes and
crown ether oxygen atoms in the two macrocyclic polyether compo-
nents: [C‚‚‚O] and [H‚‚‚O] distances and [C-H‚‚‚O] angle 3.18, 2.32
Å, 149° and 3.30, 2.41 Å, 153° involving the larger tetracation and
Figure 10. Space-filling representation of the branched [7]catenane
20+
-
6
2
3
showing the docked PF
anions within the voids at the centers
of each macrocyclic polyether ring. The front and back [P‚‚‚P]
separations are each 6.1 Å, and the associated side-to-side distances
are 14.6 and 15.4 Å.
3
.16, 2.29 Å, 152° and 3.25, 2.43 Å, 144° involving the smaller
tetracation.
respectively). As the numbers of smaller tetracationic cyclo-
phanes is increased on each of the macrocyclic polyether
components, the resonances attributable to the R-CH and â-CH
bipyridinium hydrogen atoms of the larger, central, tetracationic
cyclophanes appear at increasingly low field. In the case of
the less symmetrical [4]- and [6]catenanes, distinct resonances
are observable for R-CH and â-CH protons of bipyridinium units
residing in the nonequivalent polyether macrocycles.46 Simi-
larly, and perhaps more strikingly, the corresponding resonances
of the smaller cyclophanes are influenced mainly by their
immediate local environments, rather than by gross molecular
structures. Two distinct sets of resonances are observed for
the R-CH and â-CH bipyridinium hydrogen atoms of the
smaller, peripheral, tetracationic cyclophanes, i.e., first, those
whose immediate environment includes a TN57C15 macrocycle
with a single unoccupied recognition site (denoted by the symbol
Figure 8. Space-filling representation of olympiadane 2012+
.
thalene residue. This sidedness is also evident and is expressed
in the two signals observed for each of the constitutionally
identical hydrogen atoms on the “inside” 1,5-dioxynaphthalene
residues. The energy barrier for the coalescence behavior of
the R-CH bipyridinium proton resonances in the [2]catenane
.
in Figure 12), and second, tetracations located on macrocyclic
1
3‚4PF6 is recorded in Table 2. The exchange of the R-CH
(45) (a) A similar process has been observed previously in a related [2]-
catenane in which the same cyclophane and DN38C10 are the two
components. See: Ashton, P. R.; Brown, C. L.; Chrystal, E. J. T.; Goodnow,
T. T.; Kaifer, A. E.; Parry, K. P.; Philp, D.; Slawin, A. M. Z.; Spencer, N.;
Stoddart, J. F.; Williams, D. J. J. Chem. Soc., Chem. Commun. 1991, 634-
bipyridinium hydrogen atoms may result from one of two
dynamic processessby the 1,5-dioxynaphthalene residue depart-
ing from the cavity of the tetracationic cyclophane and then
re-entering the cavity with a changed geometry or alternatively
6
39. For a detailed kinetic analysis of the dynamic processes occurring in
4
5
a related [3]catenane, see: (b) Ashton, P. R.; Boyd, S. E.; Claessens, C.
G.; Gillard, R. E.; Menzer, S.; Stoddart, J. F.; Tolley, M. S.; White, A. J.
P.; Williams, D. J. Chem. Eur. J. 1997, 3, 788-798.
by the rotation of the bipyridinium unit about its long axis.
1
The H NMR chemical shift data for the catenanes 19‚8PF6,
0‚12PF6, 22‚16PF6, and 23‚20PF6 containing between four and
2
(46) At 273 K, the resonances attributable to one set of R-CH and â-CH
bipyridinium hydrogen atoms in the [4]catenane 19‚8PF6 are broadened by
additional, unidentified, exchange processes. Resonances assignable to these
nuclei are, however, resolved above room temperature as these processes
enter the fast exchange regime (400 MHz).
seven rings, along with their “parent” [3]catenane 18‚4PF6, are
1
listed in Table 1. Their partial H NMR spectra at both 273 K
and 343 K are compared in Figures 12 (parts a and b,

4302 J. Am. Chem. Soc., Vol. 120, No. 18, 1998
Amabilino et al.
Figure 11. LSI mass spectrum of the [7]catenane 23‚20PF
6
. Cartoons denote the groups of peaks attributable to the “fragment catenanes” arising
-
from the successive loss of various component macrocycles. Within each group we see the sets of peaks attributable to the successive loss of PF
6
anions from each of the “fragment catenanes”.
1
Table 1. Selected H NMR Data [δ Values in Ppm] in CD
3
CN for the [n]Catenanes and Their Components
naphthalene
small tetracationic cyclophane
large tetracationic cyclophane
“outside”
“inside”
compound T/K RCH
âCH
C
6
H
4
CH
2
N+ RCH âCH (C N+ H-2/6 H-3/7 H-4/8 H-2/6 H-3/7 H-4/8
6 4
H
)
2
CH
2
TNP57C15 300
6.79
7.29
7.73
a
2
4‚4PF
5‚4PF
6
300 8.86
300
8.16
7.52
5.74
a
2
6
8.95 8.25
7.54
.66
5.82
7
1
3‚4PF
6
6
6.79
6.86
7.86
7.10
7.10
7.11
7.59
7.61
7.65
7.83
7.90
7.98
5.48
5.63
5.39
5.56
5.66
5.72
6.56
6.80
6.38
7.18
7.33
7.00
7.44
7.52
7.00
5.97
5.68
2.11
1
4‚8PF
6.10
6.15
5.77
5.89
2.05
2.27
17‚4PF
18‚4PF
19‚8PF
6
6
6
7.56
.64
7.70
.93
7.75
7.90
5.69
5.57
6.78b 6.51b 6.46b
6.50b 6.63b 6.33b
6.3-5.8a
7
7
7.21
7.98
5.73
5.58
5.76
8
.00
2
0‚12PF
6
6
273 8.42
6.97
7.07
8.81
8.85
7.84
7.88
7.94
8.02
7.85
7.98
5.52
5.59
5.55
5.69
8.59 6.75
7.71
7.95
7.77
7.81
8.06
5.58
6.25-5.85b
6.4-5.7b
6.10c
5.44e
5.82c
2.10c
2.20c
8.84
c
d
c
d
c
c
c
d
d
c
e
2
2‚16PF
273 8.44
6.99
7.10
7.13
7.31
8.70 6.84
6.96
5.53
5.59
5.40
5.83
c
d
c
c
d
8
8
8
.64
.86
.91
6.13
2.30
3.83
d
6.17d 5.92
d
e
d
5.37d 5.37
d
d
2.28e
2
3‚20PF
6
283 8.53
.87
7.08
7.26
5.59
8.60 6.89
7.74
8.03
5.43
6.17e
5.88
3.92
d
8
a
For the homologous [4]catenane, in which the TN57C15 ring is interlocked by three cyclobis(paraquat-p-phenylene) tetracations, signals were
+
observed at δ 8.56, 8.90 (RCH), δ 7.10, 7.29 (âCH), δ 7.89, 8.01 (C
6
H
4
), and δ 5.64 (CH
2
N ) for the tetracationic cyclophanes and at δ 6.17
(
H-2/6), δ 5.91 (H-2/7), and δ 2.29 (H-4/8) for the “inside” naphthalene rings in a spectrum recorded in CD
3
CN at 273 K. b Rings rotate through
one another at such a rate that some of their associated resonances are broadened into the baseline of the NMR spectrum at this temperature.
c
Related to the small tetracation denoted by the symbol . in Figure 12. d Related to the small tetracations denoted by the symbol b in Figure 12.
e
Related to the large tetracation.
polyethers in which all the recognition sites are occupied
denoted by the symbol b in Figure 12). In the latter case, the
absence of “alongside” interactions between free 1,5-dioxynaph-
thalene residues and the bipyridinium units of the small
tetracations accounts most likely for the low field shift observed
for these resonances relative to those of the former case.
(

Oligocatenanes Made to Order
J. Am. Chem. Soc., Vol. 120, No. 18, 1998 4303
Table 2. Kinetic and Thermodynamic Parameters Obtained from
also clear that the site-exchange rates involving 1,5-dioxynaph-
thalene protons decrease dramatically as the size of the catenanes
increases. In the [7]catenane, an extremely highly ordered
molecule in solution, the rate of movement of included 1,5-
dioxynaphthalene residues between different recognition sites
1
the Temperature-Dependent H NMR Data Recorded for the
a
[n]Catenanes
probe protons
undergoing
site-exchange ∆ν (Hz) k T
q
∆G
c
compd
c c
(s-1) (K) (kcal mol-1)
1
is slow on the H NMR time scale, even at 343 K (Figure 13).
b
d
1
1
1
3‚4PF
8‚4PF
9‚8PF
6
6
6
R-CH {.}
R-CH {1}
179
210
44
23
166
41
43
71
48
136
74
398
467
98
51
369
92
326
204
297
362
310
296
295
328
327
337
327
310
15.2
9.3
The reason for the high activation energy of this process is
clearly associated with the fact that it must involve the
synchronous disruption of five π-π stacking interactions
between π-electron rich moieties and π-electron deficient
groups, in addition to numerous [C-H‚‚‚O] hydrogen bonds,
c
e
b
d
e
â-CH {.}
14.7
18.5
14.5
14.7
14.6
16.0
16.2
16.0
15.9
15.3
R-CH {1}
R-CH {.}
â-CH {.}
b
b
d
2
2
0‚12PF
6
6
d
d
2‚16PF
â-CH {.}f
96
[
C-H‚‚‚π] T-type interactions, and other Coulombic interac-
â-CH {b}
â-CH {1}
106
158
302
165
108
tions.
e
b
f
VI. Absorption Spectra. All the examined catenanes
2
3‚20PF
6
R-CH {b}f
19
â-CH {b}
exhibit the well-known charge-transfer bands in the visible
f
C H
6 4
{b}
48
region, which are not present in their isolated components. Since
the energy and the intensity of a charge-transfer band depend
on the precise nature of the interacting partners and on their
distance in the present, very complicated systems specific
a
Determined by the coalescence method (see ref 43 (v/v) CD
3
CN/
d
CD
3
COCD
3
). Related to the small tetracation denoted by the symbol
e
.
1
in Figure 12. Related to the large tetracation denoted by the symbol
f
in Figure 12. Related to the small tetracations denoted by the symbol
47
assignments, such as those proposed for simpler catenanes,
b in Figure 12.
cannot be made.
VII. Electrochemistry. A. Catenane Components. The
three basic components of the oligocatenanes, namely the
The energy barriers obtained from the coalescence of the
resonances for the R-CH and â-CH bipyridinium hydrogen
atoms in the catenanes 18‚4PF6, 19‚8PF6, 20‚12PF6, 22‚16PF6,
and 23‚20PF6 are summarized in Table 2. The site-exchange
rates, exhibited by the nuclei of the small tetracations, like their
resonance frequencies, are influenced predominantly by their
respective local environments. The site-exchange rates exhibited
by the â-CH bipyridinium hydrogen atoms of tetracations, whose
immediate environment includes a TN57C15 macrocycle with
a single unoccupied recognition site, are approximately 95 times
per second at room temperature, whereas those, whose immedi-
ate environment includes a TN57C15 macrocycle with no
unoccupied recognition sites, approximate to 160 times per
second at 328 K. The coalescence of the pairs of resonances
observed for each of the R-CH and â-CH bipyridinium hydrogen
atoms of the large tetracationic cyclophanes of the [4]- and [6]-
catenanes provides a measure of the rate of circumrotation of
the large tetracation through the cavities of the two macrocyclic
polyether components, a dynamic process not observable in the
more symmetrical systems. The rate of exchange of the â-CH
protons in the [6]catenane is 106 times per second at 327 K,
while for the R-CH protons of the linear [4]catenane, it is only
some 50 times per second at 362 K. This large difference in
the observed rate of the circumrotation of the large tetracation
is attributed to “alongside” interactions of bipyridinium units
with the unoccupied 1,5-dioxynaphthalene units of the two
macrocyclic polyether components in 19‚8PF6 (as witnessed in
the crystal structure of the [3]catenane 18‚4PF6) which are absent
in 22‚16PF6.
4
+
4+
tetracationic cyclophanes 24 and 25 and the TN57C15
macrocycle, contain electroactive units. The electrochemical
data for all the examined compounds are gathered in Table 3.
4
+
The two bipyridinium units of 24 undergo a first simulta-
neous one-electron reduction at -0.28 V and a second one at
1
9
4+
-
0.72 V. The behavior of 25 , where the two bipyridinium
units are connected by biphenylene spacers, is very similar.
The TN57C15 macrocycle contains three equivalent 1,5-
dimethoxynaphthalene (DMN)-type electroactive units which
4
8
undergo distinct oxidation processes.
Such a contrasting
behavior between the tetracationic cyclophanes and TN57C15
can be interpreted considering that, in the cyclophanes, the
rigidity of the structure prevents interaction between the two
bipyridinium units, whereas the flexible structure of the mac-
rocycle allows the three DMN-type units to approach one
another. The first oxidation process of TN57C15 occurs at a
potential (+0.98 V) much less positive than that of DMN. This
result can be accounted for by the formation of a stabilized
structure where the oxidized DMN-type unit is sandwiched
between the two non-oxidized units. Upon further one-electron
oxidation, the most stable structure could be one where the two
oxidized units sandwich the non-oxidized one. After the third
oxidation process, the three positively charged DMN-type units
most likely separate.
On going from the separated cyclophane or macrocycle
components to their catenanes, it can be expected that (i)
electronic interactions between the donor units of macrocycle
TN57C15 and the acceptor units of cyclophanes 244 and 25
+
4+
The quantification of the rates of circumrotation of the
macrocyclic polyether components through the various tetra-
cationic cyclophane components of the catenanes, 19‚4PF6 to
displace the reduction processes to more negative potentials and
the oxidation processes to more positive potentials and (ii) the
two bipyridinium units of each cyclophane and the three DMN-
type units of the TN57C15 macrocycle may maintain or lose
their spatial equivalence; in the latter case, splitting of degenerate
23‚20PF6, could not be achieved because of either the complex-
ity of the spectra or the magnitudes of the energy barriers
involved. Qualitative analysis of the spectra provided in Figures
1
2 and 13 shows that the site-exchange rates between the 1,5-
(47) Ballardini, R.; Balzani, V.; Brown, C. L.; Credi, A.; Gillard, R. E.;
Montalti, M.; Philp, D.; Stoddart, J. F.; Venturi, M.; White, A. J. P.;
Williams, B. J.; Williams, D. J. J. Am. Chem. Soc. 1997, 119, 12503-
dioxynaphthalene units vary markedly with the extent of the
catenation of the molecules. In the [3]catenane 18‚4PF6, the
proton resonances of the π-electron rich units appear as well-
resolved, averaged signals at 343 K, i.e., the exchange between
free and included 1,5-dioxynaphthalene units is fast on the H
NMR time scale (400 MHz), while at 273 K they are broadened
as a result of a slower exchange process being operative. It is
12513.
(48) Two distinct oxidation processes have also been observed for the
1/5DN38C10 macrocyclic polyether, which contains two DMN-type units,
see: Asakawa, M.; Ashton, P. R.; Balzani, V.; Credi, A.; Hamers, C.;
Mattersteig, G.; Montalti, M.; Shipway, A. N.; Spencer, N.; Stoddart, J. F.;
Tolley, M. S.; Venturi, M.; White, A. J. P.; Williams, D. J. Angew. Chem.,
Int. Ed. Engl. 1998, 37, 333-337.
1

4304 J. Am. Chem. Soc., Vol. 120, No. 18, 1998
Amabilino et al.
1
Figure 12. The partial H NMR spectra of the catenanes, based on the parent [3]catenane 18‚4PF
6
, containing between three and seven rings
3
recorded at 400 MHz in CD CN at (a) 273 K and (b) 343 K.
1
Figure 13. Partial H NMR spectra of the [7]catenane 23‚20PF
6
at 285 and 343 K (400 MHz, CD
3
CN).
4
+
4+
12+
processes should be observed. We have examined the electro-
chemical behavior of [2]catenane 13 , [3]catenane 14 , [2]-
catenane 17 , [3]catenane 18 , [5]catenane 20
(Olympi-
4+
8+
20+
adane), and [7]catenane 23
.

Oligocatenanes Made to Order
J. Am. Chem. Soc., Vol. 120, No. 18, 1998 4305
Table 3. Electrochemical Properties of the Examined Catenanes and Their Componentsa
b,c
compd
E
red [n] (∆E)
E
ox
TN57C15
+0.98; +1.15; +1.25
4
4
4
8
4
4
1
2
+
24
25
13
14
17
18
20
23
-0.28 [2.0] (62); -0.72 [2.0] (65)
+
-0.31 [1.9] (67); -0.72 [1.9] (66)
+
-0.36 [1.1] (68); -0.47 [0.9] (63); -0.81 [1.6] (81)
-0.33 [1.9] (72); -0.41 [1.9] (68); -0.79 [1.8] (64); -0.85 [1.8] (60)
-0.30 [0.9] (82); -0.39 [1.0] (83); -0.73 [1.8] (65)
-0.45 [1.9] (92); -0.82 [2.0] (65)
+1.19; +1.26; +1.57
+1.31; +1.60
+1.16; +1.26; +1.52
+1.07; +1.12; +1.23; +1.51
+1.14; +1.34; +1.41; +1.56
f
+
+
+
2+
0+
c,d
c,d
-0.34 [2.0]; -0.39 [3.7]; -0.84 [5.9] (80)
c,e
c,e
c,e
-0.29 [5.4]; -0.37 [4.6]; -0.87 [9.5]
a
Argon-purged MeCN solution, 298 K; halfwave potential values in V vs SCE; reversible processes, unless otherwise noted; for reversible
b
processes, [n] ) number of exchanged electrons, (∆E) ) separation in mV between cathodic and anodic peaks in cyclic voltammograms. All
oxidation processes are not fully reversible. Potential values estimated from DPV peaks. Not resolved with CV technique. e The anodic part of
c
d
f
the cyclic voltammogram is affected by adsorption phenomena. No oxidation process has been observed.
Figure 14. Correlation diagrams for the electrochemical behavior: (a) [2]catenane 13 +, [3]catenane 148+, and their 244+ and TN57C15 components;
4
4
+
4+
4+
(
b) [2]catenane 17 , [3]catenane 18 , and their 25 and TN57C15 components.
B. [2]Catenane 134 and [3]Catenane 14 . The correla-
+
8+
flexibility of the TN57C15 macrocycle which (i) allows one of
the DMN-type units to interact with the “alongside” bipyri-
dinium unit of the cyclophane and, at the same time, (ii) does
not force two DMN-type units to sandwich the “inside”
bipyridinium unit. After the first reduction, the electron donor-
acceptor interaction becomes weaker and the flexible nature of
the TN57C15 macrocycle could facilitate a fast interchange
between monoreduced “inside” and “alongside” units, with a
consequent lack of splitting of the second process. For
4+
8+
tion diagram for [2]catenane 13 , [3]catenane 14 , and their
components 24 and TN57C15 is shown in Figure 14a. In
the catenanes, the two electroactive units of 24 are engaged
in donor-acceptor interactions and occupy spatially different
sites. Therefore, it can be expected that their reduction takes
place in separated processes at more negative potentials
4
+
4
+
4+
compared to free 24 . This is clearly the case for the first
4+
reduction of the two bipyridinium units in 13 : the “alongside”
unit is reduced at -0.36 V, and the “inside” one at -0.47 V.
Comparison with the previously investigated [2]catenane,
composed of 24 and DN38C10, shows that in 13 the first
reduction process occurs at a slightly more negative potential,
whereas the second one is considerably displaced toward less
negative potentials. This difference could result from the great
8
+
[3]catenane 14 scomposed of TN57C15 and two equivalent
1
9
4+
24 cyclophaness(Figure 15), simultaneous reduction of the
4
+
4+
“alongside” units of the two cyclophanes is followed by
simultaneous reduction of the “inside” units. Both processes
are displaced to less negative potentials compared with 134
because the ratio between electron-donor and electron-
+

4306 J. Am. Chem. Soc., Vol. 120, No. 18, 1998
Amabilino et al.
4+
process, already observed for 13 , and its very small displace-
ment toward more negative potentials clearly indicate that, once
the two bipyridinium units have been monoreduced, the large
size of the two components prevents any further charge-transfer
4
+
interaction. The oxidation pattern of 17 is fully consistent
4
+
with that observed for 13 .
4
+
The [3]catenane 18 shows two bielectronic reduction
processes, because the two bipyridinium units of 254 occupy
equivalent positions. Figure 15 shows the cyclic voltammogram
+
4+
for the reduction of 18 . The strong displacement toward more
4
+
negative potentials, compared with 25 , is obviously due to
the charge-transfer interaction with the electron-donor units of
the encircling macrocyclic polyether. The further displacement,
compared to that observed for the first reduction of the “inside”
4
+
unit of 17 , can be attributed to the presence of two DMN-
type units inside the cyclophane. This feature could favor a
geometry where a close approach between the electron-donor
and -acceptor units is sterically enforced, thereby optimizing
the charge-transfer interaction. As indicated by the noticeable
displacement of the second reduction to more negative poten-
tials, such a structure seems to be essentially maintained, even
after one-electron reduction of the two bipyridinium units. In
4
+
conclusion, the reduction pattern of 18 is consistent with a
structure like that shown in Figure 4. The oxidation pattern
(Figure 14b), although very complicated, is consistent, at least
from a qualitative viewpoint, with a structure of the type shown
in Figure 4. The first process is assigned to the oxidation of
the two DMN-type units not involved in stacking interactions,
the second one to the two “alongside” units, and the subsequent
ones to oxidation of the two (interacting) DMN-type units
contained inside the cyclophane.
8
+
Figure 15. Cyclic voltammograms for reduction of [3]catenanes 14
1
2+
and 18 (MeCN solution, 298 K, scan rate 200 mV s-1, glassy carbon
as working electrode). The wave with E1/2 ) +0.40 V is that of
4
+
D. [5]Catenane 20
(Olympiadane) and [7]Catenane
2
32 . These multiply interlocked catenanes contain a large
0+
number of electroactive units: six DMN-type units and six
bipyridinium units in Olympiadane, and six DMN-type units
ferrocene used as a standard.
acceptor units decreases from 3/2 to 3/4. The splitting of the
second reduction process of the bipyridinium units is consistent
with the crowded structure of the catenane, which presumably
prevents fast interchange between “inside” and “alongside” units.
In 13 , the three DMN-type units of the TN57C15 macro-
cycle undergo distinct oxidation processes. As a consequence
of the charge-transfer interaction, all these processes move to
more positive potential values with respect to the free macro-
cycle. A detailed comparison between the two oxidation
patterns is made difficult because, in the catenane structure, the
donor-acceptor interactions between non-oxidized and oxidized
DMN-type units are partially or completely prevented. In the
20+
and 10 bipyridinium units in 23 . It is worth noting that no
20+
oxidation process has been observed for 23 . Oxidation of
12+
2
0
shows a pattern consistent with its structure: a process
attributed to the two DMN-type units not encircled by cyclo-
phanes is followed by a second process assigned to oxidation
of the two DMN-type units encircled by smaller cyclophanes.
The two subsequent processes can be assigned to oxidation of
the interacting DMN-type units inside the larger cyclophane.
4+
For Olympiadane (2012+), the first two-electron reduction
process can be assigned to simultaneous one-electron reduction
of two “alongside” bipyridinium units of the smaller cyclo-
phanes. The subsequent four-electron process can be attributed
to the simultaneous reduction of two “inside” bipyridinium units
of the smaller cyclophanes, which overlaps with the reduction
process of the two equivalent bipyridinium units of the larger
cyclophane. These results are consistent with the structure
shown in Figure 7, where two bipyridinium units of the 244
cyclophanes are at least partially engaged with two nonencircled
DMN-type units of the two TN57C15 macrocycles. The second
reductions of all six bipyridinium units overlap, giving rise to
a broad DPV peak at -0.84 V.
8+
[
3]catenane 14 , only two oxidation processes are observed, a
feature that is consistent with the presence of an “outside” and
two equivalent “inside” DMN-type units.
4+
4+
C. [2]Catenane 17 and [3]Catenane 18 . The correla-
tion diagram for 17 , 18 , and their components, 25 and
TN57C15, is shown in Figure 14b. On reduction, a general
4+
4+
4+
+
displacement toward more negative potentials is observed on
going from the free cyclophane 254+ to its catenanes. In 174+,
the first reduction of the two bipyridinium units of the
cyclophane component occurs, as expected, in two distinct
processes. It is worth noting that the first process is not at all
diplaced, indicating that the “alongside” unit is practically
unperturbed by the macrocyclic polyether. This situation is
presumably related to the large size and rigidity of the
cyclophane, which, in the most stable catenane geometry, leaves
one of the two bipyridinium units far away from the electron-
donor units of TN57C15. The lack of splitting of the second
2
0+
On reduction, 23
yields two processes characterized by
two large DPV peaks. Each process corresponds to the
exchange of 10 electrons, as expected for the first and second
reduction of the ten bipyridinium units of the five cyclophanes.
The first DPV peak shows a shoulder and can be analyzed as
made of two overlapping peaks whose areas are in a ratio close
to 6:4. The first component peak is much larger than the second

Oligocatenanes Made to Order
J. Am. Chem. Soc., Vol. 120, No. 18, 1998 4307
1
one, suggesting that in its turn it results from overlapping
processes. Second reductions of all the bipyridinium units
merge into a broad DPV peak at -0.87 V.
(e) Dynamic H NMR spectroscopy of the catenanes in
solution reveals that the rates of circumrotation of the rings with
respect to each other varies markedly on going from the lower
to higher order catenanes. One thing is sure in systems where
the changes in co-conformations are extremely complexsthe
circumrotation of the crown ether rings through the tetracationic
cyclophane becomes more and more difficult on progressing
from the lower to the higher order catenanes.
Concluding Remarks
The results that we have presented and discussed in this paper
lead us to draw the following conclusions:
(a) The best synthetic approach so far to higher catenanes,
based on ring components with matching π-electron donating
and π-electron accepting units, involves a two-stage procedure
whereby a [3]catenane is self-assembled first of all in one step,
and then, subsequently, in further successive stepssnamely one
through foursit is converted into one [4]catenane, two isomeric
(
f) In the lower order catenanes, the electrochemical processes
can be assigned to specific units. In the higher order catenanes,
where a large number of electrons are exchanged, overlap of
processes makes difficult specific assignments, but the overall
picture is consistent with their molecular structures.
[
5]catenanes, one linear and one branched, and one [6]catenane
and one [7]catenane, both branched.
b) In the self-assembly of higher order catenanes, i.e., those
In summary, our research has demonstrated that a synthetic
methodology, which affords [2]catenanes in excellent yields,
can be extended, in principle at least, as far as a branched [7]-
catenane. The question is the following: Where do we go from
here? Of many possible approaches to polycatenanes, two that
appeal to us currently involve (1) the linking together of
oligocatenanes (two [6]catenanes to give, for example, a [13]-
catenane) and (2) the use of a more traditional synthetic
approach to fuse together covalently some [2]catenane “mono-
mers”, followed by subsequent rearrangements or chemical
modifications to afford oligocatenanes and ultimately polyca-
tenanes. One thing is certain: it is only a matter of time now
until the making of polycatenanes will be a routine activity in
the research laboratory.
(
involving more than three interlocked rings, which result from
the template-directed formation of tetracationic cyclophanes
containing two π-accepting bipyridinium units on a repetitive
basis around suitably sized crown ethers comprised of two or
more π-donating recognition sites, the 1,5-dioxynaphthalene ring
system provides a much better template than does the hydro-
quinone ring.
(c) Although ultrahigh pressure reaction conditions proved
beneficial subsequently in driving the kinetically controlled self-
assembly process involving the template-directed formation in
a stepwise manner of cyclobis(paraquat-p-phenylene) tetraca-
tions around the remaining four “free” 1,5-dioxynaphthalene
recognition sites in the intermediate [3]catenane to afford
catenanes with four through seven rings, it was not helpful in
the process of self-assembling this key intermediate in the first
place.
Acknowledgment. This research was supported by the
British Council, the Biotechnology and Biological Sciences
Research Council, and the Engineering and Physical Sciences
Research Council in the UK. Financial support from the Italian
MURST and University of Bologna (Funds for Special Projects)
is also acknowledged. This work has been carried out within
the framework of the EU TMR Project FMRX-CT96-0076.
(d) In the solid state, both the [3]- and the [5]catenane exist
as centrosymmetric molecules that manage to maximize the use
of many different kinds of noncovalent bonding interactions
between matching donor and acceptor units in the components.
Although the [7]catenane does not feature a center of symmetry,
a total of four highly ordered hexafluorophosphate counterions
are located symmetrically in pairs in two different voids in the
molecular structure of this polycation carrying 20 positive
charges. Perhaps the anions actually assist in the self-assembly
process, leading first to the [6]catenane and then to the
Supporting Information Available: Experimental proce-
dures and tables of cystallographic data (44 pages, print/PDF).
See any current masthead page for ordering information and
Web access instructions.
[7]catenane.
JA9720873