Molecular paneling via coordination: Guest-controlled assembly of open cone and tetrahedron structures from eight metals and four ligands [19]

Full text of DOI:10.1021/ja001411i

7150
J. Am. Chem. Soc. 2000, 122, 7150-7151
(0.025 mmol) and guest 5 (0.25 mmol) were suspended in the
Molecular Paneling via Coordination:
Guest-Controlled Assembly of Open Cone and
Tetrahedron Structures from Eight Metals and Four
Ligands
aqueous solution (2.5 mL) of 2 (0.05 mmol). After the mixture
was stirred for 24 h at ambient temperature, excess 5 was filtered
off and the resulting solution was analyzed by NMR and ESI-
MS, which clearly evidenced the formation of open cone 3
accommodating one molecule of 5. In ESI-MS, some of the major
Kazuhiko Umemoto,† Kentaro Yamaguchi,‡ and
Makoto Fujita*,§
peaks were assigned as [3‚(5)m‚(NO3)16-n]
n+ m ) 0-2, n ) 3,4],8
The Graduate UniVersity for AdVanced Studies
Myodaiji, Okazaki 444-8585, Japan
Chemical Analysis Center, Chiba UniVersity
Yayoicho, Inageku, Chiba 263-8522, Japan
Department of Applied Chemistry
and no peaks could be found for other cone structures (e.g., M6L3
and M10L5 types, etc.). NMR displayed eight proton signals, which
stems from ligand 1 located on a C2-symmetric environment, in
good agreement with the structure of 3. The accommodation of
5 in the cone-shaped cavity of 3 was strongly suggested by the
outstanding upfield shifts of signals of 5 in D2O. The host-guest
ratio was estimated to be 1:1 by NMR integration ratio. After
the aqueous solution was allowed to stand at room temperature
for 1 week, a colorless precipitate was obtained, which was
washed with small portions of water and dried in vacuo to give
3‚5 complex in 78%.9 The same 1:1 complexes were also obtained
with other bulky guests such as 1,2-diphenyl-1,2-ethanediol and
1,1′-ferrocenedicarboxylic acid.
Graduate School of Engineering, Nagoya UniVersity, and
CREST, Japan Science and Technology Corporation (JST)
Chikusaku, Nagoya 464-8603, Japan
ReceiVed April 24, 2000
Triangular exo-polydentate ligands have been frequently em-
ployed for the metal-directed assembly of coordination polyhedra.1-4
By linking triangles at their corners or edges, a family of poly-
hedral structures can in principle be engaged at will. Here, we
design a triangular panel-like ligand with four donor sites on the
two edges of the triangle (two donor sites on each edge): namely,
compound 1 in Scheme 1. Having two-point binding sites on its
two edges, this triangular unit is expected to assemble into edge-
sharing polyhedral entity upon complexation with (en)Pd(NO3)2
(2), which is a versatile 90° coordination unit for metal-directed
assembly. Whereas previous triangular ligands all possess C3 sym-
metry,1-4 panel 1 is C2-symmetric and hence can be linked in
two different ways: parallel and antiparallel links. Interestingly,
these two options were perfectly controlled by the guests.5 We
show that some large guests induce the parallel link of the triangles
leading to open cone (tetragonal pyramidal) structure 3, whereas
antiparallel link is selected by some small tetrahedral guests giving
closed tetrahedron structure 4 (Scheme 1). Both assemblies have
the same M8L4 composition and, therefore, constitute a dynamic
receptor library6,7 from which each receptor is selected by its
optimal guests.
The combination of components 1 and 2 enjoys another way
of molecular paneling: the antiparallel link of adjacent ligands
leading to tetrahedral coordination assembly 4 (Scheme 1). This
was achieved in an efficient fashion by using small template mole-
cules such as CBr4 (6). Thus, the reaction of 1 (0.048 mmol) and
2 (0.106 mmol) in the presence of 6 (0.48 mmol, suspended) in
D2O (5.0 mL) resulted in the selective formation of 4‚6 complex.
Obviously, 6 templated the assembly of 4 and was efficiently
entrapped within the framework of 4. In fact, the entrapped 6
was observed at -26.9 ppm in 13C NMR when 13C-enriched 6
was employed. The antiparallel link of the ligands in 4 was
strongly supported by the observation of NOE between the adja-
cent ligands, which was not observed in 3. The complex was iso-
lated as a colorless precipitate in 93% yield by adding a large
amount of EtOH and the 4‚6 stoichiometry was confirmed by
elemental analysis.9 The selective formation of tetrahedron 4 was
also observed with similar small guests such as CHCl3 and CBrCl3.
The quantitative assembly of M8L4 open cone 3 was induced
by large guest molecules such as dibenzoyl (5). Thus, ligand 1
The structure of 4‚6 complex was finally determined by an
Scheme 1
10.1021/ja001411i CCC: $19.00 © 2000 American Chemical Society
Published on Web 07/11/2000

Communications to the Editor
J. Am. Chem. Soc., Vol. 122, No. 29, 2000 7151
Figure 2. The 1H NMR monitoring of reorganization process from 3‚5
to 4‚6 via guest exchange. (a) 3‚5 complex in D2O; (b-d) After the
addition of excess amount of 6 at 25 °C ((b) 3 h, (c) 8 h, (d) 24 h). Note
that free 5 is immiscible in water and, after guest exchange, becomes
invisible in the spectrum.
temperature for 3 days. As expected, the crystal structure of 4‚6
displayed the antiparallel junction of ligands. The whole tetra-
hedral structure is somewhat distorted in such a way that efficient
host-guest interaction and aromatic contact between the ligands
are gained. As a result, the 12-component assembly makes a
closed shell framework in which the guest molecule is completely
insulated (Figure 1, bottom).
In the absence of guests at 25 mM concentration, 1 and 2 were
assembled into a 3:2 mixture of two products, and the minor
product was identified as 3. The proportion of the major product
increased at lower concentrations, indicating that this product is
composed of fewer components than 3. Since its NMR is
qualitatively the same to that of 3, the major product was
tentatively assigned as an M6L3 trimeric open cone structure (7).11
Figure 1. Crystal structure of 4‚6. Top: ball and cylindrical representa-
tion; bottom: Space-filling representation.
X-ray crystallographic analysis (Figure 1).10 The single crystal
was obtained by standing the aqueous solution of 4‚6 at ambient
† The Graduate University for Advanced Studies.
‡ Chemical Analysis Center, Chiba University.
§ Department of Applied Chemistry, Graduate School of Engineering,
Nagoya University, and CREST, Japan Science and Technology Corporation.
(1) (a) Fujita, M.; Oguro, D.; Miyazawa, M.; Oka, H.; Yamaguchi, K.;
Ogura, K. Nature 1995, 278, 469-471. (b) Takeda, N.; Umemoto, K.;
Yamaguchi, K.; Fujita, M. Nature 1999, 398, 794. (c) Yu, S.-Y.; Kusukawa,
T.; Biradha, K.; Fujita, M. J. Am. Chem. Soc. 2000, 122, 2665-2666. (d)
Fujita, M. Chem. Soc. ReV. 1998, 27, 417-425.
(2) (a) Bru¨ckner, C.; Powers R. E.; Raymond, K. N. Angew. Chem., Int.
Ed. 1998, 37, 1837. (b) Johnson, D. W.; Xu, J.; Saalfrank, R. W.; Raymond,
K. N. Angew. Chem., Int. Ed. 1999, 38, 2882-2885. (c) Caulder, D. L.;
Raymond, K. N. Acc. Chem. Res. 1999, 32, 975.
(3) (a) Stang, P. J.; Olenyuk, B.; Muddiman, D. C.; Smith, R. D.
Organometallics 1997, 16, 3094. (b) Olenyuk, B.; Whiteford, J. A.; Fecht-
enko¨tter, A.; Stang, P. J. Nature 1999 398, 796-799. (c) Stang, P. J.; Olenyuk,
B. Acc. Chem. Res. 1997, 30, 502. (d) Leininger, S.; Olenyuk, B.; Stang, P.
J. Chem. ReV. 2000, 100, 853-908.
Being generated under thermodynamic control, three complexes
3, 4, and 7 are interconvertable with each other by guest addition
or exchange via remarkably effective reorganization processes.
Trimeric cone 7 (in the mixture of 3 and 7) was converted upon
the addition guest such as 5 to tetrameric cone 3 within 24 h.
The addition of 6 to the mixture of 3 and 7 resulted in the
disappearance of both complexes and reorganization into 4‚6
complex within a day. Once assembled open cone 3‚5 was
transformed into 4‚6 complex upon the addition of excess amount
of 6 within 24 h (Figure 2) via guest exchange.
(4) (a) Hartshorn, C. M.; Steel, P. J. J. Chem. Soc., Chem. Commun. 1997,
541. (b) Abrahams, B. F.; Egan, S. J.; Robson, R. J. Am. Chem. Soc. 1999,
121, 3535.
(5) Guest-controlled interconversion of helical and tetrahedral coordination
assemblies: Scherer, M.; Caulder, D. L.; Johnson, D. J.; Raymond, K. N.
Angew. Chem., Int. Ed. 1999, 38, 1588-1592.
(6) Dynamic libraries: (a) Hasenknopf, B.; Lehn, J.-M.; Baum G.; Fenske,
D. Proc. Natl. Acad. Sci. U.S.A. 1996, 93, 1397. (b) Hasenknopf, B.; Lehn,
J.-M.; Baum, G.; Kneisel, B. O.; Fenske, D. Angew. Chem., Int. Ed. Engl.
1996, 35, 1838. (c) Hasenknopf, B.; Lehn, J.-M.; Boumediene, N.; Dupont-
Gervais, A.; Dorsserlaer, A. V.; Kneisel, B.; Fenske, D. J. Am. Chem. Soc.
1997, 119, 10956. (d) Lehn, J.-M. Chem. Eur. J. 1999, 5, 2455. (e) Rowan,
S. J.; Sanders, J. K. M. J. Chem. Soc., Perkin Trans. 1 1997, 1407. (f) Brady,
P. A.; Sanders, J. K. M. J. Chem. Soc., Perkin Trans. 1 1997, 3237. (g) Calama,
M. C.; Timmerman, P.; Reinhoudt, D. N. Angew. Chem., Int. Ed. 2000, 39,
755. (h) Prins, L. J.; Jolliffe, K. A.; Hulst, R.; Timmerman, P.; Reinhoudt, D.
N. J. Am. Chem. Soc. 2000, 122, 3617. (i) Rivera, J. M.; Martin, T.; Rebek,
J., Jr. Science 1998, 279, 1021. (j) Rivera, J. M.; Martin, T.; Rebek, J., Jr. J.
Am. Chem. Soc. 1998, 120, 819. (k) Hof, F.; Nuckolls, C.; Rebek, J., Jr. J.
Am. Chem. Soc. 2000, 122, 4251.
Acknowledgment. We thank Dr. Kumar Biradha and Mr. Shigeru
Sakamoto for X-ray crystallographic analysis and ESI-MS measurement,
respectively.
Supporting Information Available: Preparation and physical proper-
ties of 1, 3‚5 and 4‚6, NMR spectra of 3‚5, 4‚6 complexes (1H, 13C, HH
COSY, NOESY, and CH COSY), and the mixture of complexes 3 and 7
(1H and HH COSY); detailed crystallographic data of 4‚6 complex (PDF).
This material is available free of charge via the Internet at http://pubs.
acs. org.
(7) Guest-controlled assembly of coordination cages: (a) Fujita. M.; Nagao,
S.; Ogura, K. J. Am. Chem. Soc. 1995, 117, 1649. (b) Hasenknopf, B.; Lehn,
J.-M.; Boumediene, N.; Dupont-Gervain, A.; Dorsselaer, A. V.; Keneisei, B.;
Fenske, D. J. Am. Chem. Soc. 1997, 119, 10956. (c) Lee, S. B.; Hwang, S.;
Chung, D. S.; Yun, H.; Hong, J.-I. Tetrahedron Lett. 1998, 39, 873. (d)
Hiraoka, S.; Fujita, M. J. Am. Chem. Soc. 1999, 121, 10239.
(8) Observation of [M‚(G)m‚(X)n]n+ peaks (G: guest or solvent, X:
counterion) is characteristics for the ESI-MS of a series of (en)Pd-linked metal
complexes. Sakamoto, S.; Fujita, M.; Kim, K.; Yamaguchi, K. Tetrahedron
2000, 56, 955.
JA001411I
(10) Crystal data of 4‚6: see Supporting Information.
(11) The equilibration 3‚3 / 4‚7 shifts toward 7 at low concentrations.
NMR data of 3 and 7 (from the mixture of 3 and 7): see Supporting
Information.
(9) Satisfactory NMR, ESI-MS, and elemental analysis data were obtained.
See Supporting Information.