A chemical-responsive bis(m-phenylene)-32-crown-10/2,7-diazapyrenium salt [2]pseudorotaxane

Article abstract of DOI:10.1039/c2cc33783e

A chemical-responsive bis(m-phenylene)-32-crown-10/2,7-diazapyrenium salt [2]pseudorotaxane was prepared. It was found to form a supramolecular poly[2]pseudorotaxane in the solid state driven by π-π stacking interactions.

Full text of DOI:10.1039/c2cc33783e

View Online / Journal Homepage / Table of Contents for this issue
Dynamic Article Links
ChemComm
Cite this: Chem. Commun., 2012, 48, 8201–8203
www.rsc.org/chemcomm
COMMUNICATION
A chemical-responsive bis(m-phenylene)-32-crown-10/2,7-diazapyrenium
salt [2]pseudorotaxanew
Xuzhou Yan, Xiujuan Wu, Peifa Wei, Mingming Zhang and Feihe Huang*
Received 26th May 2012, Accepted 25th June 2012
DOI: 10.1039/c2cc33783e
A chemical-responsive bis(m-phenylene)-32-crown-10/2,7-diaza-
pyrenium salt [2]pseudorotaxane was prepared. It was found to
form a supramolecular poly[2]pseudorotaxane in the solid state
driven by p–p stacking interactions.
and self-assembled structures from bis(m-phenylene)-32-crown-10
and 2,7-diazapyrenium derivatives have not been exploited
yet, possibly because of the preconception that the cavity of
bis(m-phenylene)-32-crown-10 was not large enough to allow
the DAP derivatives to thread.
Of continuing interest in the field of supramolecular chemistry,
in particular, in the design of molecular machines,1 supra-
molecular polymers,2 and functional supramolecular materials,3
is the bottom-up construction of externally addressable supra-
molecular structures.4 As a result, host–guest chemistry based
on macrocyclic compounds (such as crown ethers, cyclodextrins,
pillararenes etc.) has seen mighty progress in various aspects of
supramolecular chemistry due to its good selectivity, high efficiency,
and stimuli-responsiveness.5 In host–guest chemistry, pseudo-
rotaxanes,6 the fundamental building blocks for the preparation of
advanced mechanically interlocked supramolecular architectures
with fascinating properties, are host–guest complexes in which
linear molecular components (guests) are encircled by macrocyclic
components (hosts). Therefore, the fabrication and preparation of
pseudorotaxanes, especially with novel topologies and using new
host–guest recognition motifs which can exhibit response to
external stimuli, have been a topic of great interest and challenge.
2,7-Diazapyrenium (DAP) derivatives, which integrate the
features of pyrene, viologens, and nucleic acid intercalators, have
been proved to be versatile building blocks in supramolecular
chemistry.7 The p-electron-deficient character and extended
p-surface ensure efficient supramolecular associations with
various p-electron-rich counterparts, thereby facilitating the
construction of advanced supramolecular architectures. For
example, Stoddart and coworkers prepared functional molecular
machines based on the recognition of crown ether derivatives to
DAP derivatives.8 Kaifer et al. designed and prepared DAP-based
fluorescence probes for the detection of ions and neurotransmitters
due to their good host–guest association and luminescence
properties.9 However, up to now, the host–guest complexation
Herein, a novel bis(m-phenylene)-32-crown-10 (BMP32C10)
derivative bearing two electron-rich pyrogallol trimethyl ether
groups (3) was synthesized. By the self-assembly of 3 with
dimethyldiazapyrenium (DMDAP) dication 6, a threaded
[2]pseudorotaxane was obtained, and then a supramolecular
poly[2]pseudorotaxane was formed in the solid state driven by
p–p stacking interactions. More interestingly, the assembly
and disassembly of this [2]pseudorotaxane can be reversibly
controlled by the sequential addition of basic and acidic
chemicals (Et2NH and TFA, respectively). For comparison,
the host–guest chemistry between host 3 and guests 4, 5, and 7
was also addressed.
Department of Chemistry, Zhejiang University, 310027 Hangzhou,
P. R. China. E-mail: fhuang@zju.edu.cn; Fax: +86-571-8795-3189;
Tel: +86-571-8795-3189
w Electronic supplementary information (ESI) available: Compound
characterization, synthetic details, determination of association constants,
ESIMS, X-ray crystallographic files (CIF) for 3*6 and 3*7, X-ray
analysis data on 3*6 and 3*7, and other materials. CCDC 879994. For
ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c2cc33783e
Equimolar acetone solutions of host 3 with guests 4–7 are
yellow because of charge transfer interactions between electron-
rich aromatic rings of the host and electron-poor pyridinium
rings of the guests, which is direct evidence for complexation.
Job’s plots10 (Fig. S4, ESIw) based on UV–vis spectroscopy
absorbance data in acetone demonstrated that all these
host–guest complexes were of 1 : 1 stoichiometry in solution.
c
This journal is The Royal Society of Chemistry 2012
Chem. Commun., 2012, 48, 8201–8203 8201

View Online
This was further confirmed by electrospray ionization mass
spectrometry (ESIMS): m/z 1315.6 for [3*4 À PF6]+, m/z
585.5 for [3*4 À 2PF6]2+, m/z 1313.7 for [3*5 À PF6]+,
m/z 584.6 for [3*5 À 2PF6]2+, m/z 1364.1 for [3*6 À PF6]+,
m/z 1337.6 for [3*7 À PF6]+, and m/z 596.6 for [3*7 À 2PF6]2+
(Fig. S5–S8, ESIw). No peaks with other complexation
stoichiometries were found. The association constants (Ka)
were determined in acetone by using a UV–vis titration
method to be 1.67 Â 102 MÀ1 for 3*4, 63.6 MÀ1 for 3*5,
2.17 Â 103 MÀ1 for 3*6, 3.91 Â 102 MÀ1 for 3*7. It is worth
noting that the Ka values of 3*6 (or 7) are about 13 (or 6)
times higher than that of 3*4 (or 5), indicating that the
p-electron-deficient character and extended p-surface of 6 and 7
can enhance the binding affinity of the crown ether portion for
their heterocyclic cores.
The proton NMR spectra of equimolar (1.00 mM) acetone
solutions of 3 and 6 (Fig. 1d) showed that the complexation is
fast exchange. In the spectrum of the complex 3*6, pronounced
upfield shifts in the signals of the aromatic protons of 3
(H3a, H3b) and 6 (H6a, H6b) suggest that stacking occurs
between these electronically complementary aromatic rings.
The proton NMR spectrum of an equimolar (1.00 mM)
acetone solution of 3 and 4 (Fig. 1a–c) was also investigated
for comparison and only slight chemical shift changes were
observed for the protons of both 3 and 4, indicating that the
binding ability of complex 3*6 was stronger than that of
3*4. Similar chemical shift changes were also observed in the
cases of 3*5 and 3*7 (Fig. S13, ESIw). These results are
consistent with the association constant difference between
these complexes.
Fig. 2 Ball–stick views of the X-ray structures of 3*6 (a) and 3*7
(b). Host 3 is red, guests 6 and 7 are blue, hydrogeÀns are purple,
oxygens are green, and nitrogens are sky blue. PF6 counterions,
solvent molecules, and hydrogens except the ones involved in hydrogen
bonding between 3 and 6 (or 7) are omitted for clarity. Hydrogen bond
parameters are as follows: CÁ Á ÁO distance (A), HÁ Á ÁO distance (A),
C–HÁ Á ÁO angles (1): a, 3.05, 2.36, 130.8; b, 3,35, 2.57, 134.0; c, 3.32, 2.53,
143.4; d, 3.27, 2.34, 162.3; e, 3.19, 2.31, 154.4; f, 3.48, 2.62, 145.5; g, 3.25,
2.48, 134.1; h, 3.37, 2.60, 138.5; i, 3.12, 2.24, 154.1; j, 3.45, 2.62, 146.0.
Face to face p-stacking parameters: centroid–centroid distance (A) k,
3.78; ring plane–ring plane inclination (1): 0. (c) Supramolecular
poly[2]pseudorotaxane structure of 3*6 in the solid state driven by
p–p stacking interactions.
To further study the host–guest complexation and self-
assembled structures, a yellow crystal of 3*6 with 1 : 1
stoichiometry was grown by a vapor diffusion method. The
X-ray crystal structure of complex 3*6 demonstrated that
host 3 and guest 6 form a [2]pseudorotaxane-type threaded
structure in the solid state (Fig. 2a) instead of the common
taco complex structures observed in the BMP32C10–paraquat
complexation, possibly because the two big pyrogallol trimethyl
ether groups make the complex 3*6 assume a ‘‘zig–zig’’ geometry
(Fig. 2a), as observed by Gibson et al.6a The complex 3*6 is
stabilized by hydrogen bonding and face-to-face p-stacking
interactions. The crystal structure shows that eight hydrogen
bonds are formed between six hydrogen atoms of guest 6 and
six oxygen atoms of host 3. Four a-pyridinium hydrogen
atoms (a, b, and c) and two N-methyl hydrogen atoms (d) are
involved in these hydrogen bonding interactions (Fig. 2a). What is
more interesting is that a supramolecular poly[2]pseudorotaxane
structure forms driven by p–p stacking interactions between
the electron-rich pyrogallol trimethyl ether groups on host 3
molecules in different 3*6 complexes in the solid state
(Fig. 2c). The dihedral angle between two neighbouring phenyl
rings is 01, which maximizes the p–p stacking interactions in
this supramolecular poly[2]pseudorotaxane structure. From a
control experiment, the single crystal structure of the complex 3*7
was also obtained and the supramolecular poly[2]pseudorotaxane
structure was not observed in the solid state, indicating that
the formation of supramolecular polypseudorotaxane structure
is guest-dependent (Fig. 2b).
Moreover, the assembly and disassembly of the [2]pseudo-
rotaxane between 3 and 6 can be reversibly controlled by the
sequential addition of diethylamine (DEA) and trifluoroacetic
acid (TFA). When DEA was added into the yellow solutions
of 3 and 6, they became dark green because the more stable
Fig. 1 Partial 1H NMR spectra (acetone-d6, 293 K, 400 MHz):
(a) 1.00 mM 4; (b) 1.00 mM 3 and 4; (c) 1.00 mM 3; (d) 1.00 mM
3 and 6; (e) 1.00 mM 6.
c
8202 Chem. Commun., 2012, 48, 8201–8203
This journal is The Royal Society of Chemistry 2012

View Online
(2012QNA3013), Program for New Century Excellent Talents
in University, and Zhejiang Provincial Natural Science Foun-
dation of China (R4100009).
Notes and references
1 (a) J. D. Badjic, V. Balzani, A. Credi, S. Silvi and J. F. Stoddart,
´
Science, 2004, 303, 1845; (b) F. Huang, K. A. Switek and
H. W. Gibson, Chem. Commun., 2005, 3655; (c) W. Wang and
A. E. Kaifer, Angew. Chem., Int. Ed., 2006, 45, 7042; (d) E. R. Kay,
D. A. Leigh and F. Zerbetto, Angew. Chem., Int. Ed., 2007, 46, 72;
(e) X. Ma and H. Tian, Chem. Soc. Rev., 2010, 39, 70; (f) K. Zhu,
V. N. Vukotic and S. J. Loeb, Angew. Chem., Int. Ed., 2012,
51, 2168.
2 (a) F. Huang, D. S. Nagvekar, C. Slebodnick and H. W. Gibson,
J. Am. Chem. Soc., 2005, 127, 484; (b) F. Huang and
H. W. Gibson, Prog. Polym. Sci., 2005, 30, 982; (c) Y. Jiang,
J.-B. Guo and C.-F. Chen, Chem. Commun., 2010, 46, 5536;
(d) Z. Niu, F. Huang and H. W. Gibson, J. Am. Chem. Soc.,
2011, 133, 2836; (e) L. Zhu, M. Lu, Q. Zhang, D. Qu and H. Tian,
Macromolecules, 2011, 44, 4092; (f) X. Yan, M. Zhou, J. Chen,
X. Chi, S. Dong, M. Zhang, X. Ding, Y. Yu, S. Shao and
F. Huang, Chem. Commun., 2011, 47, 7086; (g) Y.-S. Su,
J.-W. Liu, Y. Jiang and C.-F. Chen, Chem.–Eur. J., 2011,
17, 2435; (h) X. Yan, D. Xu, X. Chi, J. Chen, S. Dong, X. Ding,
Y. Yu and F. Huang, Adv. Mater., 2012, 24, 362.
3 (a) W. Zhang, W. Jin, T. Fukushima, A. Saeki and T. Aida,
Science, 2011, 334, 340; (b) E. Krieg, H. Weissman, E. Shirman,
E. Shimoni and B. Rybtchinski, Nat. Nanotechnol., 2011, 6, 141.
4 (a) R. J. Wojtecki, M. A. Meador and S. J. Rowan, Nat. Mater.,
2011, 10, 14; (b) L. Lafferentz, V. Eberhardt, C. Dri, C. Africh,
G. Comelli, F. Esch, S. Hecht and L. Grill, Nat. Chem., 2012,
4, 215; (c) X. Yan, F. Wang, B. Zheng and F. Huang, Chem. Soc.
Rev., 2012, DOI: 10.1039/c2cs35091b.
Fig. 3 Partial 1H NMR spectra (acetone-d6, 293 K, 400 MHz):
(a) 1.00 mM 3; (b) 1.00 mM 3 and 6; (c) after addition of DEA to b;
(d) after addition of TFA to c; (e) 1.00 mM 3.
adduct between 6 and DEA was formed while the complex
3*6 was dissociated. Subsequently, the complex 3*6 can
form again when enough TFA was added to neutralize DEA.
Meanwhile, the dark green solution gradually reverted to
yellow. This reversible process was confirmed by proton
NMR experiments (Fig. 3) and UV–vis spectroscopy
(Fig. S14, ESIw). When DEA (10.0 equiv.) was added to a
solution of 3 (1.00 mM) and 6 (1.00 mM) in acetone-d6
(0.5 mL), the intensity of the arene signals of 6 disappeared
substantially and the protons of 3 returned to almost their
uncomplexed values (Fig. 3c). However, after addition of TFA
(10.0 equiv.) to this solution, the complexation between 3 and
6 was recovered; large chemical shift changes corresponding to
the protons of 3 and 6 were observed again (Fig. 3d). This
reversible complexation process provides a simple on–off
switch which can be used in the construction of controllable
molecular switches.
5 (a) G. Koshkakaryan, L. M. Klivansky, D. Cao, M. Snauko,
S. J. Teat, J. O. Struppe and Y. Liu, J. Am. Chem. Soc., 2009,
131, 2078; (b) L. M. Klivansky, G. Koshkakaryan, D. Cao and
Y. Liu, Angew. Chem., Int. Ed., 2009, 48, 4185; (c) Z. Niu,
C. Slebodnick and H. W. Gibson, Org. Lett., 2011, 13, 4616;
(d) C.-F. Chen, Chem. Commun., 2011, 47, 1674; (e) N. Noujeim,
K. Zhu, V. N. Vukotic and S. J. Loeb, Org. Lett., 2012, 14, 2484;
(f) W. Jiang, K. Nowosinski, N. L. Low, E. V. Dzyuba,
¨
F. Klautzsch, A. Schafer, J. Huuskonen, K. Rissaner and
¨
C. A. Schalley, J. Am. Chem. Soc., 2012, 134, 1860; (g) M. Xue,
Y. Yang, X. Chi, Z. Zhang and F. Huang, Acc. Chem. Res., 2012,
DOI: 10.1021/ar2003418; (h) X. Shu, S. Chen, J. Li, Z. Chen,
L. Weng, X. Jia and C. Li, Chem. Commun., 2012, 48, 2967.
6 (a) Z. Niu, C. Slebodnick, K. Bonrad, F. Huang and
H. W. Gibson, Org. Lett., 2011, 13, 2872; (b) X. Yan, M. Zhang,
P. Wei, B. Zheng, X. Chi, X. Ji and F. Huang, Chem. Commun.,
2011, 47, 9840; (c) M. Zhang, B. Zheng and F. Huang, Chem.
Commun., 2011, 47, 10103; (d) X. Yan, P. Wei, M. Zhang, X. Chi,
J. Liu and F. Huang, Org. Lett., 2011, 13, 6370; (e) X. Yan, P. Wei,
B. Xia, F. Huang and Q. Zhou, Chem. Commun., 2012, 48, 4968;
(f) A. E. Kaifer, W. Li, S. Silvi and V. Sindelar, Chem. Commun.,
2012, 48, 6693.
7 (a) M. A. Cejas and F. M. Raymo, Langmuir, 2005, 21, 5795;
(b) M. Liu, X. Yan, M. Hu, X. Chen, M. Zhang, B. Zheng, X. Hu,
S. Shao and F. Huang, Org. Lett., 2010, 12, 2558.
8 (a) R. Ballardini, V. Balzani, A. Credi, M. T. Gandolfi,
S. J. Langford, S. Menzer, L. Prodi, J. F. Stoddart, M. Venturi
and D. J. Williams, Angew. Chem., Int. Ed., 1996, 35, 978;
(b) L. Fang, C. Wang, A. C. Fahrenbach, A. Trabolsi,
Y. Y. Botros and J. F. Stoddart, Angew. Chem., Int. Ed., 2011,
50, 1805.
In summary, we have synthesized a novel bis(m-phenylene)-
32-crown-10 derivative bearing two electron-rich pyrogallol
trimethyl ether groups and studied its binding abilities to
guests 4–7. We found that the p-electron-deficient character
and extended p-surfaces of 6 and 7 can enhance the binding
affinity of the crown ether portion for their heterocyclic cores
compared to the cases of 3*4 (or 5). By the self-assembly of 3
with 6, a threaded [2]pseudorotaxane was obtained instead of
a folded taco complex, and then a supramolecular poly[2]-
pseudorotaxane was formed in the solid state driven by p–p
stacking interactions. More interestingly, we demonstrated
that the assembly and disassembly of this [2]pseudorotaxane
can be reversibly controlled by the sequential addition of
diethylamine and trifluoroacetic acid. Our current efforts are
focused on extending this chemical-responsive recognition
motif to fabricate molecular switches and mechanically inter-
locked molecular machines.
9 (a) V. Sindelar, M. A. Cejas, F. M. Raymo, W. Chen, S. E. Parker
and A. E. Kaifer, Chem.–Eur. J., 2005, 11, 7054; (b) C.-F. Lin,
Y.-H. Liu, C.-C. Lai, S.-M. Peng and S.-H. Chiu, Chem.–Eur. J.,
2006, 12, 4594.
This work was supported by the National Natural Science
Foundation of China (20834004, 91027006, and 21125417),
the Fundamental Research Funds for the Central Universities
10 P. Job, Ann. Chim. (Paris), 1928, 9, 113.
c
This journal is The Royal Society of Chemistry 2012
Chem. Commun., 2012, 48, 8201–8203 8203