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GHABDIAN ET AL.
washed using ethanol and dichloromethane, and used
in repeated Sonogashira coupling. No copper was
detected in the filtrates by AAS in each run, as illustrated
in Figure 5, so it is clear that the catalyst worked well for
up to several cycles with no remarkable decrease in
reactivity.
4.3 | Synthesis of Cu (II) salen complex (3)
Functionalized salen ligand (2; 1.0 mmol) was dissolved
in ethanol (20 ml), and then NaOH (1.67 mmol) along
with copper (II) acetate one hydrate (1 mmol) in H2O
(3 ml) were added and the mixture was refluxed for
1 hr (Scheme 2). The resulting mixture was filtered and
washed with methanol, water and diethyl ether three
times, respectively. The solvents were evaporated off
and the residue was recrystallized from EtOH to give a
green solid (98% yield). This was followed by drying at
80°C in an oven under vacuum.
ACKNOWLEDGMENTS
The authors are grateful to the University of Birjand for
financial support.
ORCID
4.4 | General procedure for the
preparation of Cu (II) salen@GO
Graphene oxide was prepared and purified by the Hum-
mers method.[39] GO was dispersed in 75 ml dry toluene
for 20 min. Later, 0.5 g of homogeneous Cu (II) salen
complex (3) was added into the suspension (Scheme 3).
After refluxing for 20 hr, the immobilized catalyst was
washed with dry toluene, EtOH and dichloromethane,
respectively. The solid was dried at 70°C under vacuum
conditions for 6 hr to give Cu (II) salen@GO catalyst with
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3105
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