RSC Advances
Paper
With the purpose of testing the applicability of our catalytic group.21 As displayed in Fig. 6C, Z-bridged azobenzene showed a
system, we investigated its potential for generation of asym- distinctive absorption band at l z 400 nm, while E-bridged
metric azobenzene from corresponding aromatic amines, and azobenzene displayed a absorption peak at l z 500 nm.
the results were summarized in Fig. 5 (Table S4†). These results
In conclusion, we have successfully developed a facile and
demonstrated that asymmetric substituted azobenzenes con- efficient approach for synthesis of symmetric and asymmetric
taining various electro-withdrawing or donating groups can be aromatic azo compounds and a bridged azobenzene by using
constructed efficiently by this simple catalytic system in common red copper as catalyst under mild reaction conditions.
accepted yields.
Easy availability of red copper as catalyst, low reaction
In addition, we surprisingly found that our catalytic system temperature and high catalytic efficiency render this system as
was also suitable for the synthesis of bridged azobenzene (yield: attractive candidates for industrial and synthetic applications.
50%) from its corresponding precursor (Scheme 1). This data Further study of this efficient catalytic system is ongoing in our
has a signicant improvement compared with the results from laboratory to investigate wider applications.
previous reports.21
The bridged azobenzene can exhibit highly efficient revers-
ible Z–E photoisomerization with visible light through ultravi-
Acknowledgements
olet absorption. From Fig. 6, the solution of Z-bridged
H. W. G. acknowledges the nancial support from NSFC (no.
azobenzene was light yellow before irradiation (Fig. 6A).
21003092, no. 21373006), the Key Project of Chinese Ministry of
However, the solution turned to bright red colour (Fig. 6B) upon
Education (no. 211064), and the Priority Academic Program
UV irradiation at l ¼ 365 nm, due to the photoisomerization of
Development of Jiangsu Higher Education Institutions.
molecules from Z-bridged azobenzene to E-bridged azobenzene.
This result was consistent with the data reported from Temps
Notes and references
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B. Sahraoui, J. Luc, A. Meghea, R. Czaplicki, J. L. Fillaut
16610 | RSC Adv., 2014, 4, 16607–16611
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