Two guest complexation modes in a cyclotriveratrylene-based molecular container

Article abstract of DOI:10.1039/b906075h

We report the synthesis of a cyclotriveratrylene-based molecular container and its distinctly different modes of complexation with dimethyldiazapyrenium and 4,4′-biphenylbisdiazonium ions.

Full text of DOI:10.1039/b906075h

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FEATURE ARTICLE
Mikiko Sodeoka and
Yoshitaka Hamashima
COMMUNICATION
Sheng-Hsien Chiu et al.
Two guest complexation modes in a Chiral Pd aqua complex-catalyzed
cyclotriveratrylene-based molecular asymmetric C–C bond-forming reactions:
1359-7345(2009)39;1-S
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Two guest complexation modes in a cyclotriveratrylene-based molecular
containerw
a
b
a
a
a
Ming-Jhe Li, Chien-Chen Lai, Yi-Hung Liu, Shie-Ming Peng and Sheng-Hsien Chiu*
Received (in Cambridge, UK) 26th March 2009, Accepted 12th June 2009
First published as an Advance Article on the web 29th June 2009
DOI: 10.1039/b906075h
We report the synthesis of a cyclotriveratrylene-based molecular
container and its distinctly different modes of complexation with
into the field of molecular switches and functional inter-
locked molecules—we sought to functionalize the linkers
between a pair of CTV units with specific guest-complexing
moieties. In particular, we suspected that the significant
complexation properties of crown ethers would make
oligoethylene glycol chains attractive linkers within CTV-based
container-like hosts for a variety of guest species. Herein,
we report the synthesis of the CTV-based molecular
container 1 and its dual modes of complexation with dimethyl-
0
dimethyldiazapyrenium and 4,4 -biphenylbisdiazonium ions.
Trapping guests in container-like host molecules is a relatively
unexplored means of catalyzing reactions, delivering potent
molecules, and isolating or protecting reactive chemical
1
species. Cyclotriveratrylene (CTV), which was discovered
almost a century ago, has a fascinating concave molecular
structure that makes it a unique building block for the
2
construction of host molecules. Although most simple CTV
0
diazapyrenium (DMDAP) and 4,4 -biphenylbisdiazonium
(
BPBD) ions.
derivatives display poor guest complexation abilities in
solution, linking two of them together in a face-to-face manner
with spacers connecting the aromatic rings produces
cryptophane-type hosts (Fig. 1) that can bind alkylammonium
We synthesized the molecular container 1 in three steps
6
from the dialdehyde 2 (Scheme 1). NaBH -mediated reduction
4
of the dialdehyde 2, followed by oxidation of the resulting diol
with pyridinium chlorochromate (PCC), afforded the aldol 3.
3
4
5
cations, haloalkane units, and xenon atoms as guests. To
allow CTV-based container-like molecules to recognize other
possible guest molecules—so that they can also be extended
Condensation of the benzyl alcohol functionalities of three
units of 3, catalyzed by Sc(OTf) , provided the CTV-based
3
7
trisaldehyde 4. Reduction of the three formyl groups of 4
3
followed by Sc(OTf) (8 mol%)-catalyzed macrocyclization/CTV
formation gave the desired molecular container 1.
Previously, we reported that the molecular cage 5 forms an
extremely stable complex with DMDAP through the cooperative
8
effect of many weak [C–HꢀꢀꢀO] hydrogen bonds (Fig. 2). Thus,
we anticipated that the ethylene glycol chains in the molecular
container 1 would similarly assist in stabilizing the positioning of
a DMDAP unit within its internal cavity. Because the molecular
container 1 has two types of openings (i.e., 24- and 34-membered
rings), pairs of which are positioned adjacent and opposite to one
another (Fig. 1), we suspected that threading of the termini of the
rigid DMDAP guest in solution would mainly occur through
either two 24-membered-ring openings or two oppositely located,
9
unequally sized openings.
Fig. 1
a
Department of Chemistry, National Taiwan University, Taipei,
Taiwan, 10617, R.O.C. E-mail: shchiu@ntu.edu.tw;
Fax: þ886 2 33661677; Tel: þ886 2 33661675
b
Institute of Molecular Biology, National Chung Hsing University and
Department of Medical Genetics, China Medical University Hospital,
Taichung, Taiwan, R.O.C.
w Electronic supplementary information (ESI) available: Experimental
procedures for the preparation of all new compounds and their
characterization data. CCDC 722771 and 722772. For ESI and
crystallographic data in CIF or other electronic format see DOI:
1
0.1039/b906075h
Scheme 1 Synthesis of the CTV-based molecular container 1.
This journal is ꢁc The Royal Society of Chemistry 2009
5
814 | Chem. Commun., 2009, 5814–5816

supported by the observation of a significant downfield shift
in the signal of the methyl protons of the complexed DMDAP
1
unit. No signals for the free species appeared in the H NMR
spectra upon diluting an equimolar mixture of the molecular
container 1 and DMDAPꢀ2PF from 1 mM to 10 mM (see the
6
Supporting Informationw), suggesting that the binding affinity
5
ꢂ1
of the two units is very strong (K
a
410 M ).
Only one set of aromatic signals appeared for the
2
1
1
unit in the H NMR spectra recorded after
DMDAP
Fig. 2
cooling an equimolar (2 mM) solution of the molecular container
1
and DMDAPꢀ2PF
6 3 3
in CDCl –CD CN (1 : 1) from 298 to
253 K, suggesting that the chemical environments of the two
cationic pyridinium motifs were identical in the complex under
these conditions. This behavior, in conjunction with the slow
exchange characteristics, led us to suspect that the structure of
the complex [1*DMDAP][2PF ] in CDCl –CD CN (1 : 1)
6
3
3
21
featured the cationic termini of DMDAP positioned within
two different DB24C8-like openings (Fig. 2).
We grew single crystals suitable for X-ray crystallography
through liquid diffusion of isopropyl ether into an equimolar
CH
3
CN solution of the molecular container 1 and DMDAPꢀ
10,11
.
2PF
6
The solid state structure confirms our proposed
21
binding geometry for the complex [1*DMDAP] (Fig. 4):
21
the two N-methylpyridinium units of DMDAP are threaded
through two DB24C8-like openings and 12 [C–Hꢀ ꢀ ꢀO] hydrogen
bonds are formed between the methyl and a-pyridinium C–H
11
units and the oxygen atoms on the ethylene glycol chains.
It has been reported that small crown ethers, such as 18C6
and 21C7, can form such stable complexes with diazonium
1
2
ions that their further reactions are inhibited. Although the
complexation of larger crown ethers with diazonium ions is
relatively weak, we suspected that the collaborative effect of
the six triethylene glycol chains in the molecular container 1
1
Fig. 3 Partial H NMR spectra [400 MHz, CDCl
98 K] of (a) the molecular container 1, (b) an equimolar (2 mM)
, and (d) a mixture
3 3
–CD CN (1 : 1),
2
mixture of 1 and DMDAPꢀ2PF
6
, (c) DMDAPꢀ2PF
6
of 1 (2 mM) and DMDAPꢀ2PF
6
(4 mM).
0
would allow its complexation to the 4,4 -biphenylbisdiazonium
1
The H NMR spectrum of an equimolar (2 mM) mixture
(BPBD) ion with reasonable affinity. Single crystals suitable
for X-ray crystallography were grown through diffusion of
of the molecular container
1
and DMDAPꢀ2PF in
6
CDCl –CD CN (1 : 1) at ambient temperature displays
3
isopropyl ether into an equimolar CH CN solution of the
3
3
significant changes in the chemical shifts of the protons of
the complex relative to those of its free components
molecular container 1 and BPBDꢀ2PF ; the solid state structure
6
1
revealed a binding mode for the 1 : 1 complex in which one of
3
21
(
Fig. 3). We observe no signals of the free species in the
the diazonium moieties of BPBD is located within the cavity
of the DB24C8-like unit and the other is positioned within the
oppositely located 34-membered ring (Fig. 5).
spectrum, suggesting that either the rates of complexation
and decomplexation are fast under these conditions
1
(
i.e., time-averaged signals) or that the rates of complexation
Upon titration with BPBDꢀ2PF , the H NMR spectra of a
6
1
and decomplexation are slow on the H NMR spectroscopic
solution of the molecular cage 1 in CDCl –CD CN (1 : 1) at
3
3
timescale and the complex forms with a high association
1
constant. The H NMR spectrum of a nonstoichiometric
mixture of the molecular container
1 (2 mM) and
DMDAPꢀ2PF6 (4 mM) in CDCl –CD CN (1 : 1) reveals
3
3
two sets of signals, present in a 1 : 1 ratio, where one set
corresponds to the signals of the free DMDAP ions (Fig. 3d)
and the other to the signals of a 1 : 1 complex. Thus, the
binding stoichiometry of the molecular container 1 to
DMDAP is 1 : 1 and the rates of exchange for the complexa-
1
tion and decomplexation processes are slow on the H NMR
spectroscopic timescale under these conditions. The significant
d c
upfield shifts of the aromatic protons H of DMDAP and H
of the molecular container 1 are consistent with the formation
of an inclusion complex between the two species. The existence of
Fig. 4 Ball-and-stick representation of the solid state structure of the
21
[
C–Hꢀ ꢀ ꢀO] hydrogen bonds between the two species is
complex [1*DMDAP]
.
This journal is ꢁc The Royal Society of Chemistry 2009
Chem. Commun., 2009, 5814–5816 | 5815

the construction of novel interlocked molecules and molecular
machines. Currently, we are synthesizing molecular containers
of different sizes and are investigating the possibility of
incarcerating guest units within them.
This study was supported by the National Science Council,
Taiwan (NSC-95-2113-M-002-016-MY3).
Notes and references
1
(a) D. J. Cram and J. M. Cram, Container Molecules and
Their Guests, Royal Society of Chemistry, Cambridge, 1994;
(
(
b) A. Jasat and J. C. Sherman, Chem. Rev., 1999, 99, 931;
c) L. R. Macgillivray and J. L. Atwood, Angew. Chem., Int. Ed.,
1
2
999, 38, 1019; (d) M. Yoshizawa and M. Fujita, Pure Appl. Chem.,
005, 77, 1107; (e) G. Seeber, B. E. F. Tiedemann and
Fig. 5 Ball-and-stick representation of the solid state structure of the
2
1
.
K. N. Raymond, Top. Curr. Chem., 2006, 265, 147; (f) S. Biros
and J. Rebek, Jr, Chem. Rev., 2007, 36, 93; (g) O. Ugono,
J. P. Moran and K. T. Holman, Chem. Commun., 2008, 1404;
complex [1*BPBD]
room temperature display (see the Supporting Informationw)
an increase in the intensities of the signals of the complex
together with a decrease in those of the free molecular
container 1. The spectra suggest that the binding stoichiometry
(
h) S. Liu and B. C. Gibb, Chem. Commun., 2008, 3709.
2 (a) A. Collet, Tetrahedron, 1987, 43, 5725; (b) J. W. Steed and
J. L. Atwood, Supramolecular Chemistry, Wiley, Chichester, 2000;
(
c) J. M. Knaust, C. Inman and S. W. Keller, Chem. Commun.,
004, 492; (d) K. T. Holman, in Encyclopedia of Supramolecular
2
of the molecular container 1 to BPBDꢀ2PF
6
is 1 : 1 and
Chemistry, ed. J. Atwood, Marcel Dekker, New York, 2004,
p. 340; (e) T. Brotin and J.-P. Datasta, Chem. Rev., 2009, 109, 88.
(a) L. Garel, B. Lozach, J.-P. Dutasta and A. Collet, J. Am. Chem.
Soc., 1993, 115, 11652; (b) M. Miura, S. Yuzawa, M. Takeda,
M. Takeda, Y. Habata, T. Tanase and S. Akabori, Supramol.
Chem., 1996, 8, 53; (c) P. D. Kirchhoff, J. P. Dutasta, A. Collet and
J. A. Mccammon, J. Am. Chem. Soc., 1997, 119, 8015.
that the rates of exchange during the complexation and
decomplexation processes are slow under these conditions.
Unlike the complexation between the molecular container 1
3
and DMDAPꢀ2PF , which displayed only one set of signals for
6
21
the complexed DMDAP units, the complexation between
4
5
(a) J. Canceill, L. Lacombe and A. Collet, J. Am. Chem. Soc., 1986,
1
molecular container 1 and BPBDꢀ2PF
6
gave two sets of
08, 4230; (b) L. Garel, J.-P. Dutasta and A. Collet, Angew. Chem.,
Int. Ed. Engl., 1993, 32, 1169; (c) M. R. Caira, A. Jacobs and
L. R. Nassimbeni, Supramol. Chem., 2004, 16, 337.
21
signals for the protons of the complexed BPBD moieties.
Theoretically, threading this bisdiazonium ion through
oppositely located 24- and 34-membered-ring openings would
(a) T. Brotin, A. Lesage, L. Emsley and A. Collet, J. Am. Chem.
Soc., 2000, 122, 1171; (b) C. Hilty, T. J. Lowery, D. E. Wemmer
and A. Pines, Angew. Chem., Int. Ed., 2006, 45, 70;
1
result in a H NMR spectrum displaying two sets of signals
with equal intensity for the desymmetrized a and b protons of
(
c) H. A. Fogarty, P. Berthault, T. Brotin, G. Huber,
H. Desvaux and J.-P. Dutasta, J. Am. Chem. Soc., 2007, 119,
0332.
2
1
the complexed BPBD
unit. We find, however, that the
1
integration ratios of the signals in the various spectra were
not close to 1 : 1, suggesting that two or more complexation
modes are possible in solution; e.g., the two diazonium units of
6
A. M. Elizarov, T. Chang, S.-H. Chiu and J. F. Stoddart, Org.
Lett., 2002, 4, 3565.
7 T. Brotin, V. Roy and J.-P. Dutasta, J. Org. Chem., 2005, 70, 6187.
C.-F. Lin, Y.-H. Liu, C.-C. Lai, S.-M. Peng and S.-H. Chiu,
Chem.–Eur. J., 2006, 12, 4594.
For examples of the binding bipyridinium guests with crown ether-
based cryptand hosts, see: (a) F. Huang, H. W. Gibson,
W. S. Bryant, D. S. Nagvekar and F. R. Fronczek, J. Am. Chem.
Soc., 2003, 125, 9367; (b) A. M.-P. Pederson, R. C. Vetor,
M. A. Rouser, F. Huang, C. Slebodnick, D. V. Schoonover and
H. W. Gibson, J. Org. Chem., 2008, 73, 5570.
21
8
BPBD are located within two DB24C8-like openings, as we
observed for the complexation of the molecular container 1
21
and DMDAP , or within oppositely located 24- and
9
3
4-membered rings.
When we cooled an equimolar (2 mM) mixture of the
molecular container 1 and BPBDꢀ2PF
6 3 3
in CDCl –CD CN
(
1 : 1) to 253 K, signals representative of the desymmetrized
1
1
0 Crystallographic data (excluding structure factors) for
have been deposited
complexed structure disappeared while the other remained
as a sharp AB pattern. This result suggested that the two
[1*DMDAP]ꢀ2PF
6
and [1*BPBD]ꢀ2PF
6
with the Cambridge Crystallographic Data Centre as
supplementary publications CCDC 722771 and 722772.
diazonium moieties of BPBDꢀ2PF were positioned within the
6
1 Crystal
CH CN][2PF
Fdd2; a ¼ 22.4430(6), b ¼ 110.268(3), c ¼ 15.7305(4) A; V ¼
data
for
[1*DMDAP]ꢀ2PF
6
:
[C94
H
110
O
24
N
2
ꢀ
cavities of identically sized macrocyclic rings of the molecular
container 1. Because the smaller DB24C8-like units in the
molecular container 1 presumably interact with the diazonium
ions more strongly than do the larger 34-membered-ring units,
we suspect that threading of both diazonium moieties through
two DB24C8-like cavities is most likely the predominant
structure at low temperature.
4
3
6
];
M
r
¼
2106.00; orthorhombic; space group
˚
3
ꢂ3
ꢂ1
;
˚
4
2 398.0(19) A ; rcalcd ¼ 1.320 g cm ; m(MoKa) ¼ 1.182 mm
T ¼ 200(2) K; colorless cubes; 16 751 independent measured reflec-
2
tions; Rint ¼ 0.1129; F refinement; R
12 (a) G. W. Gokel and D. J. Cram, J. Chem. Soc., Chem. Commun.,
973, 481; (b) R. A. Bartsch, H. Chen, N. F. Haddock and
1
¼ 0.1105; wR
2
¼ 0.2540.
1
P. N. Juri, J. Am. Chem. Soc., 1976, 98, 6753; (c) R. M. Izatt,
J. D. Lamb, C. S. Swain, J. J. Christensen and B. L. Haymore,
J. Am. Chem. Soc., 1980, 102, 3032.
The linking of two CTV units with six triethylene glycol
chains provides a molecular container 1 that is capable of
13 Crystal
data
CN][2PF ]; M
for
[1*BPBD]ꢀ2PF :
6
[C90H104O24N ꢀ
4
2
1
21
ꢀ
5
1
r
CH
3
6
r
¼ 2120.98; triclinic; space group P1; a ¼
complexing DMDAP and BPBD ions in solution. We
have identified two possible binding modes for molecular
container 1 to complex with these linear cationic species. This
unique molecular container has the potential to be applied to
3
˚
˚
5.2574(6), b ¼ 15.6396(6), c ¼ 24.9315(9) A; V ¼ 5192.4(3) A ;
ꢂ3
ꢂ1
calcd ¼ 1.357 g cm ; m(MoKa) ¼ 1.219 mm ; T ¼ 250(2) K; red
2
cubes; 18 667 independent measured reflections; Rint ¼ 0.0189; F
refinement; R
1
¼ 0.0734; wR
2
¼ 0.2072.
5
816 | Chem. Commun., 2009, 5814–5816
This journal is ꢁc The Royal Society of Chemistry 2009