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ChemComm
The visual photo-responsive behavior of metallo-gel [1 + apy]– the Shanghai Shuguang Program and Pujiang Program, the
H2O was further confirmed by SEM and UV studies (see ESI†). Shanghai Leading Academic Discipline Project (B108), and
Instead of the MNPs morphologies observed in Fig. 4a, the the Department of Chemistry, Fudan University is gratefully
images of [1 + apy]–H2O revealed dense long nanofibers, which acknowledged.
were ca. 50 nm wide and several mm long (Fig. 4b). Among these
long and thin nanofibers, a small number of crystal-like rods
were found (inset view in Fig. 4b). The coordination of trans-2,20-
apy with the Cu center of complex 1 to form a new adduct may be
responsible for the difference in morphologies between the
metallogels 1–H2O and [1 + apy]–H2O. After irradiation under
UV light at 320 nm for 2 hours the gel collapsed and bulky and
long crystalline rods were also found in the SEM image (Fig. 4c).
In accordance with the HR-MS experiments, the substitution
Notes and references
1 F. Wang, Y. Yang and T. M. Swager, Angew. Chem., Int. Ed., 2008,
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2 J. de Jong, B. L. Feringa and J. van Esch, in Responsive molecular gels
in Molecular Switches, ed. B. L. Feringa and W. R. Browne, Wiley-
VCH, 2nd edn, 2011, p. 517.
3 (a) X. Yang, G. Zhang and D. Zhang, J. Mater. Chem., 2012, 22, 38;
(b) M.-O. M. Piepenbrock, G. O. Lloyd, N. Clarke and J. W. Steed,
Chem. Rev., 2010, 110, 1960; (c) T. Miyata, N. Asami and T. Uragami,
Nature, 1999, 399, 766.
4 (a) T. Tu, W. Fang and Z. Sun, Adv. Mater., 2013, 25, 5304;
(b) X. Chen, Z. Huang, S.-Y. Chen, K. Li, X.-Q. Yu and L. Pu, J. Am.
Chem. Soc., 2010, 132, 7297.
5 (a) Y. Zheng, A. Hashidzume, Y. Takashima, H. Yamaguchi and
A. Harada, Langmuir, 2011, 27, 13790; (b) A. Hashidzume, Y. Zheng,
Y. Takashima, H. Yamaguchi and A. Harada, Macromolecules, 2013,
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of two chloro ligands in complex 1 by cis-2,20-apy in situ resulted
+
in an adduct signal of [M(1+apyꢀ2Cl)
]
(m/z found: 546.1124;
calculated: 546.1104), which indicated that apy coordinated to
complex 1 in a 1 : 1 ratio. The results further proved that the
small number of crystal-like rods in Fig. 4b belonged to the
adduct of complex 1 and cis-2,20-apy, and also revealed that there
were even small amounts of the cis-form in the newly prepared
trans-apy. After resting under visible light (440 nm) for a quarter
of an hour, a dark-brown gel reformed and a similar SEM
morphology to Fig. 4b was observed (see ESI†) with more crystal-
line rods, indicating that there was a photostationary state
between trans- and cis-apys, and that not all of the cis-isomer
could be switched back to its trans form by irradiation with
6 P. Mukhopadhyay, Y. Iwashita, M. Shirakawa, S. Kawano, N. Fujita
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´
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¨
visible light. This was also consistent with the observation from a 10 (a) M. Hapke, L. Brandt and A. Lu¨tzen, Chem. Soc. Rev., 2008,
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(1: 1) in five irradiation cycles where except in the first cycle
11 (a) P. J. Lusby, P. Mu¨ller, S. J. Pike and A. M. Z. Slawin, J. Am. Chem.
when the intensity of absorption decreased ca. 10% between the
original and reformed state, no obvious intensity decrease was
observed during the rest of the cycles (Fig. 4d).
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13 (a) T. Tu, X. Bao, W. Assenmacher, H. Peterlik, J. Daniels and
Based on visual discrimination of 2,20-bipyridine from its
positional isomers via selective thixotropic metallo-hydrogel
collapse, a novel photo-switchable two-component metallo-
hydrogel system was fabricated with pincer type Cu(II) complex
1 and photo-responsive 2,20-azopyridine. With the assistance of
SEM, HR-MS, UV and crystal analysis, the mechanism of gel
collapse by addition of 1,10-phenanthroline, 2,20-bipyridine
and cis-azopyridine was explained, which not only further
demonstrated that p-stacking and metal–metal interactions
between molecules of 1 are responsible for the gel formation,
but also indicated that the molecular assembly blocking strategy
is a good approach to fabricate a new platform for visual
discrimination and photo-responsive soft materials.
K. H. Dotz, Chem.–Eur. J., 2009, 15, 1853; (b) T. Tu,
¨
¨
W. Assenmacher, H. Peterlik, G. Schnakenburg and K. H. Dotz,
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H. Peterlik, R. Weisbarth, M. Nieger and K. H. Dotz, Angew. Chem.,
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¨
14 (a) W. Fang, Q. Deng, M. Xu and T. Tu, Org. Lett., 2013, 15, 3678;
(b) Z. Liu, N. Dong, M. Xu, Z. Sun and T. Tu, J. Org. Chem., 2013,
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¨
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¨
K. H. Dotz, Adv. Synth. Catal., 2009, 351, 1029; (e) T. Tu,
¨
J. Malineni and K. H. Dotz, Adv. Synth. Catal., 2008, 350, 1791.
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Financial support from the National Natural Science Founda-
tion of China (No. 21172045 and 91127041), the Changjiang
Scholars and Innovative Research Team in University (IRT1117),
3316 | Chem. Commun., 2014, 50, 3313--3316
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