An aggregation-induced emissive chromophore as a ratiometric fluorescent sensor for cyanide in aqueous media

Article abstract of DOI:10.1016/j.tet.2012.12.034

A para-terphenyl derivative containing a lateral diphenylamino group and two terminal dicyanovinyl groups has been designed and synthesized. This compound displays aggregation-induced emission characteristics and thus shows intense intramolecular charge transfer fluorescence even in the condensed state, including in the aggregates formed in an aqueous solvent system consisting of greater than 99% water and in the solid state. The addition of cyanide to its aggregates in aqueous media induces a large blue shift in fluorescence, enabling ratiometric fluorescence sensing of cyanide anions. In addition, its prompt fluorescence responses to cyanide anions were also observed even in the solid state.

Full text of DOI:10.1016/j.tet.2012.12.034

Tetrahedron 69 (2013) 1700e1704
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
An aggregation-induced emissive chromophore as a ratiometric
fluorescent sensor for cyanide in aqueous media
*
Guang-Liang Fu, Cui-Hua Zhao
School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 27 October 2012
Received in revised form 5 December 2012
Accepted 14 December 2012
Available online 22 December 2012
A para-terphenyl derivative containing a lateral diphenylamino group and two terminal dicyanovinyl
groups has been designed and synthesized. This compound displays aggregation-induced emission
characteristics and thus shows intense intramolecular charge transfer fluorescence even in the con-
densed state, including in the aggregates formed in an aqueous solvent system consisting of greater than
99% water and in the solid state. The addition of cyanide to its aggregates in aqueous media induces
a large blue shift in fluorescence, enabling ratiometric fluorescence sensing of cyanide anions. In addi-
tion, its prompt fluorescence responses to cyanide anions were also observed even in the solid state.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Intramolecular charge transfer
Aggregation-induced emission
Ratiometric fluorescent sensor
Aqueous media
Cyanide
1. Introduction
solvent, significantly rare in aqueous media.7 In this regard, it is still
very challenging to obtain ratiometric fluorescent sensor for cya-
The sensitive and selective recognition of anions has attracted
significant consideration because of their indispensable roles in
biological, environmental, and industrial processes.1 Among vari-
ous anions, cyanide detection is particularly important due to its
extreme toxicity in physiological systems2 and the increasing en-
vironmental concern caused by its widespread industrial uses in
petrochemical, gold mining, photographic, and steel manufactur-
ing.3 To detect cyanide anions, fluorescence sensing is one of the
most powerful methods owing to its simplicity and high sensitivity.
The conventional fluorescence methodology, which monitors the
fluorescence intensity at a single wavelength, is easily interfered by
sensor concentration, photobleaching, and illumination intensity.
To eliminate these effects, it is desirable to develop a ratiometric
fluorescent measurement, which uses the ratio of the fluorescent
intensities at two different wavelengths, allowing precise and
quantitative analysis and imaging even in complicated systems.
Although a variety of fluorescent cyanide sensors have been de-
veloped based on reversible binding and reaction-based ap-
proaches,4,5 the ratiometric fluorescent ones are still quite limited.6
Another problem encountered in the fluorescent sensing of cyanide
is that most of the fluorescent sensors only function in either pure
organic solvents or solutions containing a large amount of organic
nide, which can be used in aqueous media.
To realize the ratiometric fluorescent sensing of cyanide in
aqueous media, one major obstacle is that most organic fluo-
rophores suffer from the aggregation-induced fluorescence
quenching phenomenon and are weakly emissive or even non-
emissive in water as a result of the aggregates formation. So it is
desirable to design the cyanide active fluorophores, which exhibit
the aggregation-induced emission characteristics and are highly
emissive in aqueous phase despite the formation of aggregates.8e10
Herein we designed a new cyanide sensor 1, a lateral diphenyla-
mino substituted para-terphenyl derivative with two dicyanovinyl
groups attached at the terminal positions (Fig. 1). In this molecular
design, we chose the lateral diphenylamino-substituted para-ter-
phenyl system since it has been proved to be an effective strategy to
attain intense fluorescence in the condensed state by introduction
* Corresponding author. Tel.: þ86 531 88363756; fax: þ86 531 88564464; e-mail
address: chzhao@sdu.edu.cn (C.-H. Zhao).
Fig. 1. Molecular design concept of 1.
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.12.034

G.-L. Fu, C.-H. Zhao / Tetrahedron 69 (2013) 1700e1704
1701
Table 1
of the bulky electron-donating diphenylamino group at the side
position of an electron-accepting para-terphenyl framework.11 The
dicyanovinyl group was introduced because it can act not only as
a strong electron-accepting group to induce an intramolecular
charge transfer (ICT) transition but also as a cyanide reactive unit.12
We envisioned that this molecule would display intense ICT fluo-
rescence even in the aggregates formed in an aqueous media. The
UV/vis absorption and fluorescence data of 1 in various solvents
labs (nm)a
ε (Me1 cmꢀ1
)
lem (nm)
FF
b
Solvent
Cyclohexane
Benzene
CHCl3
THF
MeCN
448
446
458
442
442
2273
407
304
402
1462
543
568
585
589
n.d.c
0.56
0.18
0.0047
0.0015
n.d.c
nucleophilic attack of cyanide to the a-position of the dicyanovinyl
a
Only the longest maxima are shown.
Calculated using Rhodamine B as standard.
Not detected.
group would disrupt the ICT transition and lead to significant
changes in fluorescence, enabling the ratiometric fluorescent
sensing of cyanide. We indeed found that compound 1 displays
intense fluorescence and prompt ratiometric fluorescent responses
to cyanide in an aqueous solvent system consisting of greater than
99% water. Moreover, its intense fluorescence and prompt fluo-
rescence responses to cyanide were also observed even in the solid
state.
b
c
568 nm in benzene; 585 nm in CHCl3; 589 nm in THF) while the
absorption spectra display trivial solvent dependence. In addition,
the large bathochromism in emission is accompanied by a signifi-
cant decrease of the fluorescence efficiency with the increasing
solvent polarity. And thus the fluorescence in THF (FF¼0.0015) is
almost invisible to the naked eyes and in MeCN is not detectable
even by the spectrometer. These facts clearly suggest a higher po-
larity in excited state than in the ground state.
2. Results and discussion
2.1. Synthesis
To elucidate the influence of the geometric and electronic
structure of 1 on photophysical properties, we conducted theoret-
ical calculations. The optimizations of the molecular geometry
were carried out using density-functional theory (DFT) at the
B3LYP/6-31G(d) level of theory. We also performed time-
dependent density-functional theory (TD-DFT) calculations at the
B3LYP/6-31G(d) theory. The optimized molecular structure and the
pictorial drawing of the molecular orbitals are shown in Fig. 3 and
Fig 4, respectively.
Compound 1 was easily synthesized via a one-step reaction as
depicted in Scheme 1. In the presence of basic aluminum oxide, the
condensation of malononitrile with compound 2, which was pre-
viously prepared through Pd(0)-catalyzed SuzukieMiyaura cou-
pling of 2,5-dibromo-N,N-diphenylaminobenzene with para-
formylphenylboronic acid,11 provided 1 as yellowish orange solids
in 56% yield. Its structure was fully characterized by 1H NMR, 13
NMR spectroscopy, and high-resolution mass spectrometry.
C
Fig. 3. Optimized structure of 1 calculated at B3LYP(6-31G(d)) theory.
Scheme 1. Synthesis of 1.
2.2. Photophysical properties
The UV/vis absorption and emission spectra of 1 are shown in
Fig. 2 and the related data are summarized in Table 1. In cyclo-
hexane, the absorption of 1 features a much weaker band at the
longer wavelength (labs¼448 nm, ε¼2273 Mꢀ1 cmꢀ1) relative to the
intense band at 355 nm (ε¼32,350 Mꢀ1 cmꢀ1). In the fluorescence
spectra, 1 exhibits an intense emission at 543 nm with a high
quantum yield (FF¼0.56). It is notable that a large solvatochromism
was observed in fluorescence (lem¼543 nm in cyclohexane;
Fig. 4. Pictorial drawings of (a) HOMO and (b) LUMO of 1 calculated at B3LYP/6-31G(d)
theory.
As shown in Fig. 3, the terphenylene moiety of 1 shows a non-
planar main chain structure, similar to that of the single crystal X-
ray structure of other lateral diphenylamino-substituted terphenyl
derivatives.11 The dihedral angles between the two terminal ben-
zene rings and the central benzene ring are 34.9ꢁ and 47.6ꢁ, re-
spectively. Apparently, the difference in the dihedral angles arises
from the difference in the steric congestion between the two ter-
minal benzene rings and the central benzene ring. Owing to the
twisted main chain structure and the steric hindrance of the lateral
diphenylamino group, it is presumed that the molecules of 1 in the
condensed state would be far apart from each other, suppressing
intermolecular interactions. Another notable feature for the opti-
mized structure of 1 is that the terminal dicyanovinyl groups are
almost completely coplanar with the attached benzene rings, sug-
gesting the possible effective conjugation between the
cyclohexane
benzene
chloroform
THF
300
400
500
600
700
Wavelength / nm
Fig. 2. UV/vis absorption and fluorescence spectra of 1.

1702
G.-L. Fu, C.-H. Zhao / Tetrahedron 69 (2013) 1700e1704
dicyanovinyl groups with the terphenyl main chain framework. As
for the electronic structure, compound 1 has a HOMO localized on
the central diphenylaminophenylene moiety. It is noteworthy that
the LUMO is delocalized over the entire terphenyl framework in-
cluding the dicyanovinyl unit, indicating the efficient extension of
conjugation through the terminal dicyanovinyl groups. The TD-DFT
calculations indicate that the weak absorption at the longest
wavelength is assignable to an ICT transition from the HOMO to the
LUMO. The oscillator strength for the lowest ICT transition is very
low (f¼0.0449), which is consistent with the particularly low in-
tensity of the ICT absorption band. The possible reason is due to the
twisted terphenylene framework, which would prevent the oc-
currence of the ICT transition.
It is intriguing to note that the powder of 1 shows very bright
yellowish orange fluorescence despite that it is almost non-
emissive in polar solvents (Fig. 5). The quantum yield for the
powder of 1 is 0.11, as determined by the calibrated integrating
sphere system. The fluorescence efficiency of the powder is al-
most 100 times higher than that in THF solution, suggesting its
high fluorescence efficiency in the condensed state. This obser-
vation prompted us to investigate its photophysical properties in
aggregates in aqueous media, the intense fluorescence of which
would make it possible to realize the ratiometric fluorescence
sensing of cyanide in aqueous media. To apply compound 1 effi-
ciently in an aqueous environment, cetyltrimethylammonium
bromide (CTAB) was introduced into the aqueous phase due to the
insolubility of 1 in water.13 The aqueous dispersions were pre-
2.3. Sensing properties
Considering the intense ICT fluorescence of 1 in aqueous media,
we next explored its potential utility as a fluorescent sensor of
anions. The fluorescence spectra changes were first examined in
the presence of cyanide anions using tetrabutylammonium cyanide
(TBACN) as the cyanide source based on the reported fluorescence
sensing ability of several dicyanovinyl-containing compounds for
cyanide detection.12 The addition of cyanide to the dispersion of 1
in CTAB micellar solution resulted in a significant blue shift of
emission from 590 nm to 450 nm (Dl¼140 nm) immediately. The
prompt response of 1 to cyanide in CTAB micelles is possibly as-
cribed to the electrostatic interactions between anionic cyanide and
cationic CTAB, which would attract the cyanide to the micellar
surface and thus facilitate the attack of cyanide to 1.13 In addition to
the large blue shift, another notable feature in the fluorescence
spectral change of 1 in CTAB micellar solution upon addition of
cyanide is the significant increase in the fluorescence intensity. The
remarkable blue shift and high fluorescence intensity of 1 irre-
spective of the binding mode suggest its potential ratiometric
fluorescence sensing ability for cyanide anions. The titration ex-
periment of 1 with cyanide was carried out and the fluorescence
spectral change is shown in Fig. 6. As the concentration of cyanide
increased, the emission band at 590 nm decreased and the blue-
shifted band at 450 nm increased gradually. This change became
saturated when the concentration of cyanide amounted to 196 mM.
The presence of a clear isobestic point might suggest that only one
new species was formed during the titration process. Fig. 7 shows
a correlation between intensity ratios of fluorescence intensity at
450 nm with those at 590 nm versus cyanide concentration. It is
noteworthy that the ratios of emission intensities at 450 and
590 nm (I450/I590) exhibit a dramatic change from 0.19:1 to 23.8:1,
demonstrating the ratiometric fluorescent sensing ability of 1 for
cyanide detection in CTAB micellar solution, a solvent system
consisting of greater than 99% water. Moreover, a dramatic color
change of emission was observed from orangish red to blue, thus
enabling colorimetric cyanide ion sensing by the naked eyes. De-
spite the utilization of several dicyanovinyl-based fluorescent
pared via the rapid injection of a solution of 1 in THF (100
mL,
4.18 mM) into micellar aqueous solution of cetyl-
a
trimethylammonium bromide (CTAB) (10 mL, 2.0 mM) under
vigorous stirring for 30 s. The formation of nanoaggregates was
evidenced by the transmission electron microscopy (TEM) images
(see Supplementary data), illustrating the morphology of spheri-
cal micelles of CTAB, in which compound 1 is presumed to be very
concentrated to form aggregates. Notably, the fluorescence in-
tensity increases by more than 10 times once it forms aggregates
in CTAB micellar solution relative to that in THF solution, dem-
onstrating the aggregate-induced emission characteristics of 1.
Such fluorescence behavior may be ascribed to the easily ex-
changeable multiple conformations of the nonplanar structure of
the main chain, which facilitate the nonradiative decay of the
excited state. In the aggregates, the exchanges between multiple
conformations are greatly suppressed due to the spatial conges-
tion of the molecular stacking in the condensed state.8e10 The
intense emission of 1 in aggregates is also probably ascribed to
the efficient ICT transition with large Stokes shift as well as the
absence of strong intermolecular interactions, which facilitating
the fluorescence quenching in the condensed state.11 In addition,
the absence of strong intermolecular interactions was further
evidenced by the similarity in the absorption and emission
spectra in water compared with those in THF solution.
Fig. 6. Fluorescence spectra change of 1 (2.80 mM) in 2 mM CTAB micellar solution
upon addition of TBACN (lex¼370 nm). Inset: emission color change upon addition of
TBACN.
25
20
15
10
5
0
0
50
100
150
200
CN
/ µM
Fig. 5. Absorption and fluorescence spectra of 1 in THF (dotted line), 2 mM CTAB
micellar solution (solid line). Inset: photographs of 1 under irradiation of 365 nm,
arranged in the following order: in THF, powder and CTAB micellar solution.
Fig. 7. Plot of fluorescence intensity ratios between 450 and 590 (I450/I590) versus
concentration of CNe in 2 mM CTAB micelles.

G.-L. Fu, C.-H. Zhao / Tetrahedron 69 (2013) 1700e1704
1703
sensors for cyanide detection,12 their ratiometric fluorescent
sensing of cyanide in an aqueous media consisting of greater than
99% water has been unprecedented so far.
In the design of cyanide sensor, the interference by other anions,
such as fluoride and acetate is a serious challenge. To evaluate the
sensing selectivity of 1, fluorescence changes upon addition of
various anions including fluoride (Fꢀ), chloride (Clꢀ), bromide
(Brꢀ), iodide (Iꢀ), dihydrogenphosphate (H2PO4ꢀ), nitrite (NOꢀ2 ),
nitrate ðNO3ꢀÞ, hydrocarbonate ðHCO3ꢀÞ, bisulfate ðHSO4ꢀÞ, per-
ꢀ
chlorate ðClO4 Þ, acetate (AcOꢀ) were evaluated. In contrast to the
remarkable fluorescence change with the reaction of 1 with cya-
nide anion, no obvious fluorescence changes were observed for
these anions. In addition, the fluorescence ratio data (I450/I590) is in
good consistence with results of the emission spectra (Fig. 8), in-
dicating the high sensing selectivity of 1 toward cyanide over other
anions. This is reasonable considering the stronger nucleophilicity
of cyanide compared with other anions.
Fig. 8. The fluorescence intensity ratio (I450/I590) response profiles of 1 (2.80 mM) upon
addition of various anions (0.30 mM) in 2 mM CTAB micellar solution (lex¼370 nm).
Fig. 10. Partial 1H NMR spectra (300 MHz, CDCl3) of 1 (4.54 mM) with CNe (as TBA
salt).
The realization of solid state detection is quite meaningful for
the sensor in its practical application in portable sensing devices. To
facilitate the use of 1 for the detection of cyanide, we prepared test
papers of 1 by dipping a filter paper into the solution of 1 in THF
upon addition of 1 equiv cyanide and disappeared completely when
2 equiv cyanide anions were added while two new signals at 4.28
and 4.21 ppm arose at the same time. Interestingly, no signals as-
signable to the
These observations clearly suggest that two cyanide anions are
added simultaneously to the -position of the dicyanovinyl groups
(2.8 m
M) following by exposing it to air to dry it.13a,14 The fluores-
b-protons of the malonitrile groups developed.
cence color didn’t show any change if the test paper was immersed
in an aqueous solution of cyanide (0.3 mM) in water. Intriguingly,
the emission color changed immediately from red to blue once the
test paper was immersed into an aqueous solution (0.3 mM) of
cyanide in CTAB micelles (Fig. 9), suggesting important role of CTAB
to promote the interactions between the cyanide and compound 1.
Thereby compound 1 exhibits excellent fluorescence sensing per-
formance even in the solid state, which will be very useful for the
fabrication of sensing devices with fast and convenient detection
for cyanide and ions.
a
via a nucleophilic conjugate addition and that only one stable an-
2ꢀ
ionic species 1 ꢂ CN2
was formed during the titration. The for-
2ꢀ
mation of the sole species 1 ꢂ CN2 and the absence of 1ꢂCNꢀ are
consistent with the presence of only one clear isobestic point in the
fluorescence spectra titration. Due to the conjugate nucleophilic
addition of cyanide to the terminal dicyanovinyl groups, the con-
jugation between the dicyanovinyl groups and terphenyl frame-
work is interrupted, which would disrupt the ICT transition and
thus induce significant hypsochromic shift in fluorescence.
3. Conclusion
In summary, we have disclosed a novel lateral diphenylamino
group substituted para-terphenyl
1 containing anion-reactive
dicyanovinyl groups at terminal positions. This compound dis-
played intense ICT fluorescence in the condensed state, including in
the aggregates formed in aqueous CTAB micelles and in the solid
state. The nucleophilic attack of cyanide to the dicyanovinyl group
induces the remarkable fluorescence spectra and color changes,
enabling ratiometric and colorimetric fluorescent sensingof cyanide
anions in an aqueous solvent system consisting of greater than 99%
water. Moreover, this compound also shows prompt fluorescence
responses to cyanide anions even in the solid state, allowing the uses
of the easy-to-prepare test paper for the convenient detection of
cyanide anions in daily applications. Our results have not only pro-
vided a successful example of the ratiometric fluorescent sensor for
Fig. 9. Photographs of 1 on test papers (a) before and after (b) immersion into aqueous
solutions with CNe (0.3 mM) under irradiation at 365 nm.
To investigate the mechanism of 1 in sensing of cyanide, its 1H
NMR spectral changes induced by the addition of cyanide anions
were measured in CDCl3 at room temperature. As shown in Fig 10,
all of the aromatic proton signals assigned to the terminal phenyl
rings are up-field shifted after addition of cyanide. In addition, the
olefinic protons at 7.96 and 7.99 ppm are weakened simultaneously

1704
G.-L. Fu, C.-H. Zhao / Tetrahedron 69 (2013) 1700e1704
343e353; (d) Gale, P. A.; García-Garrido, S. E.; Garric, J. Chem. Soc. Rev. 2008, 37,
151e190; (e) Gaunnlaugsson, T.; Glynn, M.; Tocci (nee Hussey), G. M.; Kruger, P.
E.; Pfeffer, F. M. Coord. Chem. Rev. 2006, 250, 3094e3117.
cyanide in aqueous media, but also demonstrated a successful ex-
ample for the application of our -conjugated molecules, which
ꢀ
p
exhibit intense fluorescence even in the condensed state by in-
troduction of bulky electron-donating groups at the side positions of
electron-accepting framework. Further design of functional emis-
sive materials utilizing this molecular design concept to explore
their potential applications in other fields is underway in our group.
2. (a) Kulig, K. W. Cyanide Toxity; U. S. Department of Health and Human Services:
Atlanta, GA, 1991; (b) Baskin, S. I.; Brewer, T. G. In Medical Aspects of Chemical
and Biological Warfare; Sidell, F., Takafuji, E. T., Franz, D. R., Eds.; TMM: Wash-
ington, DC, 1997; Chapter 10, pp 271e286.
3. (a) Koenig, R. Science 2000, 287, 1737e1738; (b) Miller, G. C.; Pritsos, C. A.
Cyanide: Soc., Ind. Econ. Aspects, Proc. Symp. Annu. Meet. TMS 2001, 73e81;
(c) Young, C.; Tidwell, L.; Anderson, C. Cyanide: Social, Industrial and
Economic Aspects; Mineral, Metals, and Materials Society: Warrendale, 2001.
4. (a) Xu, Z.; Chen, X.; Kim, H. N.; Yoon, J. Chem. Soc. Rev. 2010, 39, 127e137.
5. (a) Shiraishi, Y.; Sumiya, S.; Hirai, T. Chem. Commun. 2011, 4953e4955; (b)
Ekmekci, Z.; Yilmaz, M. D.; Akkaya, E. U. Org. Lett. 2008, 10, 461e464; (c) Kim,
H. J.; Ko, K. C.; Lee, J. H.; Lee, J. Y.; Kim, J. S. Chem. Commun. 2011, 2886e2888;
(d) Park, S.; Kim, H.-J. Sens. Actuators, B 2012, 161, 317e321.
6. (a) Saha, S.; Ghosh, A.; Mahato, P.; Mishra, S.; Mishra, S. K.; Suresh, E.; Das, S.;
Das, A. Org. Lett. 2010, 12, 3406e3409; (b) Yuan, L.; Lin, W.; Yang, Y.; Song, J.;
Wang, J. Org. Lett. 2011, 13, 3730e3733; (c) Yu, H.; Zhao, Q.; Jiang, Z.; Qin, J.; Li, Z.
Sens. Actuators, B 2010, 148, 110e116; (d) Chen, C.-L.; Chen, Y.-H.; Chen, C.-Y.;
Sun, S.-S. Org. Lett. 2006, 8, 5053e5056; (e) Divya, K. P.; Sreejith, S.; Balakrishna,
B.; Jayamurthy, P.; Anees, P.; Ajayaghosh, A. Chem. Commun. 2010, 6069e6071;
(f) Lv, X.; Liu, J.; Liu, Y.; Zhao, Y.; Sun, Y.-Q.; Wang, P.; Guo, W. Chem. Commun.
2011, 12843e12845.
7. (a) Kim, Y.; Huh, H.-S.; Lee, M. H.; Lenov, I. L.; Zhao, H.; Gabbaï, F. P. Chem.dEur.
J. 2011, 17, 2057e2062; (b) Jung, H. S.; Han, J. H.; Kim, Z. H.; Kang, C.; Kim, J. S.
Org. Lett. 2011, 13, 5056e5059; (c) Chen, X.; Nam, S.-W.; Kim, G.-H.; Song, N.;
Jeong, Y.; Shin, I.; Kim, S. K.; Kim, J.; Park, S.; Joon, J. Chem. Commun. 2010,
8953e8955; (d) Jo, J.; Lee, D. J. Am. Chem. Soc. 2009, 131, 16283e16291; (e) Lee,
K. S.; Kim, H.-J.; Kim, G.-H.; Shin, I.; Hong, J. I. Org. Lett. 2008, 10, 49e51; (f)
Peng, L.; Wang, M.; Zhang, G.; Zhang, D.; Zhu, D. Org. Lett. 2009, 11, 1943e1946.
8. (a) Hong, Y.; Lam, J. W. Y.; Tang, B. Z. Chem. Soc. Rev. 2011, 40, 5361e5388; (b)
Hong, Y.; Lam, J. W. Y.; Tang, B. Z. Chem. Commun. 2009, 4332e4353.
9. (a) Chen, J.; Law, C. C. W.; Lam, J. W. Y.; Dong, Y.; Lo, S. M. F.; Williams, I. D.; Zhu,
D.; Tang, B. Z. Chem. Mater. 2003, 15, 1535e1546; (b) Mei, J.; Wang, J.; Sun, J. Z.;
Zhao, H.; Yuan, W.; Deng, C.; Chen, S.; Sung, H. H. Y.; Lu, P.; Qin, A.; Kwok, H. S.;
Ma, Y.; Williams, I. D.; Tang, B. Z. Chem. Sci. 2012, 3, 549e558; (c) Liu, Y.; Deng,
C.; Tang, L.; Qin, A.; Hu, R.; Sun, J. Z.; Tang, B. Z. J. Am. Chem. Soc. 2011, 133,
660e663; (d) Yuan, W. Z.; Chen, S.; Lam, J. W. Y.; Deng, C.; Lu, P.; Sung, H. H.-Y.;
Williams, I. D.; Kwok, H. S.; Zhang, Y.; Tang, B. Z. Chem. Commun. 2011,
11216e11218; (e) Zhao, Z.; Wang, Z.; Lu, P.; Chan, C. Y. K.; Liu, D.; Lam, J. W. Y.;
Sung, H. H. Y.; Williams, I. D.; Ma, Y.; Tang, B. Z. Angew. Chem., Int. Ed. 2009, 48,
7608e7611; (f) Yu, G.; Yin, S.; Liu, Y.; Chen, J.; Xu, X.; Sun, X.; Ma, D.; Zhan, X.;
Peng, Q.; Shuai, Z.; Tang, B.; Zhu, D.; Luo, Y. J. Am. Chem. Soc. 2005, 127,
6335e6346; (g) Luo, J.; Xie, Z.; Lam, J. W. Y.; Cheng, L.; Chen, H.; Qiu, C.; Kwok,
H. S.; Zhan, X.; Liu, Y.; Zhu, D.; Tang, B. Z. Chem. Commun. 2001, 1740e1741.
10. (a) Zhang, Z.; Xu, B.; Su, J.; Shen, L.; Xie, Y.; Tian, H. Angew. Chem., Int. Ed. 2011,
50, 11654e11657; (b) Wang, B.; Wang, Y.; Hua, J.; Jiang, Y.; Huang, J.; Qian, S.;
Tian, H. Chem.dEur. J. 2011, 17, 2647e2655; (c) Kim, S.; Zheng, Q.; He, G. S.;
Bharali, D. J.; Pudavar, H. E.; Baev, A.; Prasad, P. N. Adv. Funct. Mater. 2006, 16,
2317e2323; (d) An, B.-K.; Kwon, S.-K.; Jung, S. D.; Park, S. Y. J. Am. Chem. Soc.
2002, 124, 14410e14415.
11. Zhao, C.-H.; Zhao, Y.-H.; Pan, H.; Fu, G.-L. Chem. Commun. 2011, 5518e5520.
12. (a) Lee, C.-H.; Yoon, H.-J.; Shim, J.-S.; Jang, W.-D. Chem.dEur. J. 2012, 18,
4513e4516; (b) Liu, Z.; Wang, X.; Yang, Z.; He, W. J. Org. Chem. 2011, 76,
10286e10290; (c) Cheng, X.; Zhou, Y.; Qin, J.; Li, Z. ACS Appl. Mater. Interfaces
2012, 4, 2133e2138; (d) Hong, S.-J.; Yoo, J.; Kim, S.-H.; Kim, J. S.; Yoon, J.; Lee, C.-
H. Chem. Commun. 2009, 189e191; (e) Lin, Y.-D.; Peng, Y.-S.; Su, W.; Tu, C.-H.;
Sun, C.-H.; Chou, T. J. Tetrahedron 2012, 68, 2523e2526; (f) Cheng, X.; Tang, R.;
Jia, H.; Feng, J.; Qin, J.; Li, Z. ACS Appl. Mater. Interfaces 2012, 4, 4387e4392.
13. (a) Hu, R.; Feng, J.; Hu, D.; Wang, S.; Li, S.; Li, Y.; Yang, G. Angew. Chem., Int. Ed.
2010, 49, 4915e4918; (b) Zhao, Y.; Zhong, Z. Org. Lett. 2006, 8, 4715e4717; (c)
Zhang, X.; Zhang, X.; Wang, S.; Liu, M.; Tao, L.; Wei, Y. Nanoscale, http://dx.doi.
org/10.1039/c2nr32698a.
4. Experimental section
4.1. General
1H and 13C NMR spectra were recorded with a Bruker 300 spec-
trometer. The ESI mass spectra were measured on a Agilent Q-
TOF6510 spectrometer. Melting points (mp) were measured on
a TECH XT-4 instrument. UVevis absorption spectra and fluores-
cence spectra measurement were performed with a Hitachi UV-4100
spectrophotometer and a Perkin Elmer LS-55 Luminescence spec-
trometer, respectively. The TEM measurement was carried out using
a JEM-1400 transmissionelectronmicroscope at120 kV. The reaction
for the preparation of 1 was carried out under nitrogen atmosphere.
Compound 2 was synthesized according to the literature.11
4.2. Computational methods
All calculations were conducted by using Gaussian 09
program.15
4.3. Synthesis of compound 1
To a mixture of 2 (140 mg, 0.31 mmol), malonitrile (122 mg,
1.86 mmol), and basic aluminum oxide (316 mg, 3.1 mmol) was
added dehydrated toluene 15 mL. The resulting mixturewas refluxed
under N2 overnight. After filtration to remove basic aluminum oxide,
the mixture was concentrated under reduced pressure. The resulting
crude product was subjected to a silica gel column chromatography
(1/2 petroleum ether/CH2Cl2), (Rf¼0.31) to afford 96 mg (0.41 mmol)
of 1 in 56% yield as orange solids: mp 304e307 ꢁC; 1H NMR (CDCl3,
300 MHz):
7.54e7.77(m, 8H), 7.95 (d, J¼8.4Hz,2 H);13CNMR (CDCl3, 400 MHz):
82.2, 82.6,112.61,112.63,113.6,113.7,122.3,122.4,124.2,127.8,127.9,
d 6.84e6.90 (m, 6H), 7.07e7.12 (m, 4H), 7.38e7.44 (m, 3H),
d
129.0,129.5,129.6,130.2,130.4,131.3,132.3,138.1,140.7,145.6,145.8,
146.2, 147.0, 158.8, 159.1; HRMS (EI): 550.2032 ([MþH]þ); calcd for
C38H24N5: 550.2059.
Acknowledgements
We are grateful for the financial support from the National
Natural Science Foundation of China (grant nos. 21072117,
21272141) and 973 program (grant no. 2010CB933504).
14. (a) Wang, J.; Mei, J.; Yuan, W.; Lu, P.; Qin, A.; Sun, J.; Ma, Y.; Tang, B. Z. J. Mater.
Chem. 2011, 21, 4056e4059; (b) Qin, A.; Lam, J. W. Y.; Tang, L.; Jim, C. K. W.;
Zhao, H.; Sun, J.; Tang, B. Z. Macromolecules 2009, 42, 1421e1424.
Supplementary data
15. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.;
Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Na-
katsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng,
G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;
Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery,
J. A.; Peralta, J. E., Jr.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K.
N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.;
Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene,
M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.;
Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.;
Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dan-
nenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.;
Cioslowski, J.; Fox, D. J. Gaussian 09, Revision A.02; Gaussian: Wallingford CT,
2009.
Supplementary data associated with this article can be found in
the online version, at http://dx.doi.org/10.1016/j.tet.2012.12.034.
These data include MOL files and InChiKeys of the most important
compounds described in this article.
References and notes
1. (a) Beer, P. D.; Gale, P. A. Angew. Chem., Int. Ed. 2001, 40, 486e516; (b) Martínez-
ꢀ~
ꢀ
Manez, R.; Sancenon, F. Chem. Rev. 2003, 103, 4419e4476; (c) Amendola, V.;
ꢀ
Esteban-Gomez, D.; Fabbrizzi, L.; Licchelli, M. Acc. Chem. Res. 2006, 39,