DOI: 10.1039/C4CC04869E
Page 3 of 3
ChemComm
a State Key Laboratory of Supramolecular Structure and Materials,
gelation.15 Further studies are needed to confirm if asymmetric
conformation is a common and effective strategy of identifying
linear π-conjugated gelators without auxiliary groups.
College of Chemistry, Jilin University, Changchun, P. R. China, E-mail:
60 xuepengchong@jlu.edu.cn; luran@mail.jlu.edu.cn
b State Key Laboratory of Theoretical and Computational Chemistry,
Institute of Theoretical Chemistry, Jilin University, Changchun, P. R.
China
The solutions were found to have very weak emission, and the
gel emitted very strong blue fluorescence (Fig. 1d). The dilute
cyclohexane solution emitted weak blue fluorescence with a
maximum of 420 nm (Fig. S6). The fluorescence quantum yield
(Φ) in cyclohexane solution was as low as 0.027. Such low Φ can
be attributed to the intramolecular rotation of single bonds and
5
† Electronic Supplementary Information (ESI) available: [NMR, MS,
65 XRD, UV-vis, fluorescence, and time-resolved fluorescence spectra of
C1CVB, molecular packing with dipole-dipole interaction of C1CVB and
packing of PVB, BVDP and BVDA in crystals]. See
DOI: 10.1039/b000000x/
10 the cis-trans isomerisation of double bond.16
1 a) P. Terech and R. G. Weiss, Chem. Rev., 1997, 97, 3133-3159; b) S.
70
75
80
85
90
S. Babu, V. K. Praveen and A. Ajayaghosh, Chem. Rev., 2014, 114,
1973–2129.
In a hot cyclohexane solution, the maximal absorption peak of
C1CVB was located at 356 nm, which gradually decreased and
red shifted to 368 nm (Fig. S7a), indicating a head-to-tail
arrangement,17 in accordance with the crystal structure.
15 Concentration-dependent NMR spectra also confirm π-π
interaction between C1CVB (Fig. S8). A weak emissive band
with a maximum of 420 nm similar to that of dilute solution was
observed for the hot cyclohexane solution. During gelation, the
intensity of the emissive band was gradually enhanced,
20 accompanied by a red shift of 25 nm (Fig. S7b). The emissive
intensity of gel increased 16-fold, indicating that C1CVB was an
aggregation-induced emission enhancement (AIEE) gelator.18
Moreover, the absolute fluorescence quantum yield of xerogel
was obtained using an integrating sphere and reached as high as
25 0.71, which was an increase of more than 26 times relative to that
in solution. In gel, the molecules stacked together in a J-aggregate
model, and multiple C-H∙∙∙π interactions were found between 1D
aggregates (Fig. 2b). This molecular packing prevented the single
bond from freely rotating and suppressed cis-trans isomerisation.
30 Therefore, the restriction of intramolecular rotation and J-
aggregate formation induced AIEE phenomenon.19 To further
understand AIEE mechanism, the time-resolved emission spectra
of solution and gel were measured and compared (Fig. S9). In
toluene, the average lifetime was 0.95 ns, and the radiative (Kr)
35 and nonradiative (Knr) rates were found to be 0.012 and 1.4 ns–1,
respectively. After gelating cyclohexane, C1CVB had a longer
life time of 2.2 ns, Kr increased to 0.32 ns–1, and Knr decreased by
more than 10-fold (ultimately reaching 0.13 ns–1). This result
clearly revealed that the J-aggregate formation in gel accelerated
40 the radiative relaxation because such transition from excited state
to ground state was allowed, suppressing nonradiative transition.
In summary, a linear coplanar C1CVB was a gelator for some
solvents. The crystal structures suggested that 1D arrangement
was important for molecules to gelate a solvent. Furthermore,
45 asymmetric conformation may play an important role in
promoting gelation. π-Conjugated C1CVB is also an AIEE
gelator with minimal molecular weight. This work tells us a
design strategy of introducing asymmetric moiety to obtain
simple and functional π-conjugated gelator.
2
a) N. Yan, Z. Xu, K. K. Diehn, S. R. Raghavan, Y. Fang and R. G.
Weiss, J. Am. Chem. Soc., 2013, 135, 8989−8999; b) S. S. Babu, S.
Prasanthkumar and A. Ajayaghosh, Angew. Chem. Int. Ed., 2012, 51,
1766–1776; c) Z. Zhao, J. W. Y. Lam and B. Z. Tang, Soft Matter,
2013, 9, 4564–4579; d) S. K. Samanta and S. Bhattacharya, Chem.
Commun., 2013, 49, 1425–1427.
3
4
a) b) L. E. Buerklea and S. J. Rowan, Chem. Soc. Rev., 2012, 41,
6089–6102; b) S. Bhattacharya and S. K. Samanta, Langmuir, 2009,
25, 8378–8381; c) H. Jintoku, M. Takafuji, R. Oda and H. Ihara,
Chem. Comm., 2012, 48, 4881-4883.
a) X. Yang, R. Lu, T. Xu, P. Xue, X. Liu and Y. Zhao, Chem.
Commun., 2008, 453–455; b) X. Zhang, R. Lu, J. Jia, X. Liu, P. Xue,
D. Xu and H, Zhou, Chem. Commun., 2010, 46, 8419–8421; c) Z.
Ding, Q. Zhao, R. Xing, X. Wang, J. Ding, L. Wang and Y. Han, J.
Mater. Chem. C, 2013, 1, 786–792.
5
6
Z. Xie, V. Stepanenko, B. Fimmel and F. Würthner, Mater. Horiz.,
2014, 1, 355–359.
a) L. Sambri, F. Cucinotta, G. D. Paoli, S. Stagnic and L. De Cola,
New J. Chem., 2010, 34, 2093–2096; b) A. Griffith , T. J. Bandy , M.
Light and E. Stulz, Chem. Commun., 2013, 49, 731–733.
a) J. Seo, J. W. Chung, I. Cho and S. Y. Park, Soft Matter, 2012, 8,
7617-7622; c) J. Lee, J. E. Kwon, Y. You and S. Y. Park, Langmuir,
2014, 30, 2842–2851.
7
95 8 a) S. J. Langford, M. J. Latter, V. Lau, L. L. Martin and A. Mechler,
Org. Lett., 2006, 8, 1371-1373; b) K. Tanaka, S.t Hayashi and M. R.
Caira, Org. Lett., 2008, 10, 2119-2122; c) T. Naota and H. Koori, J.
Am. Chem. Soc., 2005, 127, 9324–9325.
9
H. Shigemitsu, I. Hisaki, E. Kometani, D. Yasumiya, Y. Sakamoto, K.
Osaka, T. S. Thakur, A. Saeki, S. Seki, F. Kimura, T. Kimura, N.
Tohnai and M. Miyata, Chem. Eur. J., 2013, 19, 15366–15377.
100
105
110
10 a) P. Xue, P. Chen, J. Jia, Q. Xu, J. Sun, B. Yao, Z. Zhang and Ran Lu,
Chem. Commun., 2014, 50, 2569–5671; b) P. Xue, B. Yao, J. Sun, Q.
Xu, P. Chen, Z. Zhang and Ran Lu, J. Mater. Chem. C, 2014, 2,
3942–3950.
11 a) X. Yu, L. Chen, M. Zhang and T. Yi, Chem. Soc. Rev., 2014, 43,
5346-5371; b) G. Cravotto and P. Cintas, Chem. Soc. Rev., 2009, 38,
2684–2697.
12 S. Yoon, S. Varghese, S. K. Park, R. Wannemacher, J. Gierschner
and S. Y. Park, Adv. Opt. Mater., 2013, 1, 232-237.
13 S. Yoon, J. W. Chung, J. Gierschner, K. S. Kim, M. Choi, D. Kim
and S. Y. Park, J. Am Chem. Soc., 2010, 132, 13675-13683.
14 K. Kishikawa, S. Furusawa, T. Yamaki, S. Kohmoto, M. Yamamoto
and K. Yamaguchi, J. Am. Chem. Soc., 2002, 124, 1597-1605.
115 15 A. P. Sivada, N. S. S. Kumar, D. D. Prabhu, S. Varghese, S. K. Prasad,
D. S. S. Rao and S. Das, J. Am. Chem. Soc., 2014, 136, 5417-5423.
16 Y. Hong, J. W. Y. Lama and B. Z. Tang, Chem. Soc. Rev., 2011, 40,
5361-5388.
50
This work was financially supported by the National Natural
Science Foundation of China (21103067, and 21374041), the
Youth Science Foundation of Jilin Province (20130522134JH),
the Open Project of the State Key Laboratory of Supramolecular
Structure and Materials (SKLSSM201407), the Open Project of
17 a) F. Würthner, T. E. Kaiser and C. R. Saha-Möller, Angew. Chem. Int.
120
Ed., 2011, 50, 3376–3410; b) H. Jintoku, M. Yamaguchi, M. Takafuji
and H. Ihara, Adv. Funct. Mater., 2014, 24, 410-4112; c) H. Jintokua
and Hirotaka Ihara, Chem. Commun., 2012, 48, 1144-1146.
18 a) Z. Zhao, J. W. Y. Lam and B. Z. Tang, Soft Matter, 2013, 9, 4564-
4579; b) P. Xue, Ran Lu, G. Chen, Y. Zhang, H. Nomoto, M.
Takafuji and H. Ihara, Chem. Eur. J., 2007, 13, 8231-8239.
19 A. Qin, B. Z. Tang, Aggregation-induced emission: fundamentals,
Wiley, 2013.
55 State Laboratory of Theoretical and Computational Chemistry
(K2013-02).
125
Notes and references
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