Covalently Copper(II) Porphyrin Cross-Linked Graphene Oxide: Preparation and Catalytic Activity

Article abstract of DOI:10.1007/s10562-019-02665-2

Abstract: In this study, copper(II)-coordinated 5,10,15,20-tetrakis(aminophenyl)porphyrin (CuPPh) as a macrocyclic copper complex was covalently linked to the surface of graphene oxide (GO–CuPPh). This covalently cross-linked catalyst was characterized with various analysis such as FT-IR, SEM, TEM, EDS, ICP, TGA and UV–Vis. All analysis confirm the successful covalently immobilization of CuPPh on the GO. Then, the activity of catalyst has been tested for the preparation of propargylamine derivatives by the reaction of different aldehydes/ketones various amines and phenylacetylene via A³ and KA² coupling reactions. The catalytic system indicated great catalytic activity in this reaction and the yields of the products were good to marvelous. The results of this work are hoped to aid the establishment of new class of heterogeneous catalysts as the high performance and low-cost candidates for industrial applications. Graphical Abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s10562-019-02665-2

Catalysis Letters
https://doi.org/10.1007/s10562-019-02665-2
Covalently Copper(II) Porphyrin Cross-Linked Graphene Oxide:
Preparation and Catalytic Activity
Amir Khojastehnezhad1 · Mehdi Bakavoli1 · Ali Javid2 · Mohammad Mehdi Khakzad Siuki1 · Farid Moeinpour3
Received: 8 September 2018 / Accepted: 12 January 2019
© Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract
In this study, copper(II)-coordinated 5,10,15,20-tetrakis(aminophenyl)porphyrin (CuPPh) as a macrocyclic copper complex
was covalently linked to the surface of graphene oxide (GO–CuPPh). This covalently cross-linked catalyst was characterized
with various analysis such as FT-IR, SEM, TEM, EDS, ICP, TGA and UV–Vis. All analysis confirm the successful covalently
immobilization of CuPPh on the GO. Then, the activity of catalyst has been tested for the preparation of propargylamine
derivatives by the reaction of different aldehydes/ketones various amines and phenylacetylene via A3 and KA2 coupling
reactions. The catalytic system indicated great catalytic activity in this reaction and the yields of the products were good to
marvelous. The results of this work are hoped to aid the establishment of new class of heterogeneous catalysts as the high
performance and low-cost candidates for industrial applications.
Graphical Abstract
X
N
H
O
+
R1
R2
NH2
Ph
O
O
N
N
N
N
N
H
N
H
OH
O
HO
HO
R1
HO
O
NH2
R2
DCE, Reflux
N
NH2
Ph
X
O
O
N
N
N
N
N
H
N
H
NH2
Cross-linked GO-Cu(II)-Porphyrin
Keywords Heterogeneous catalysis · Porphyrin · Graphene oxide · Propargylamine
1 Introduction
* Amir Khojastehnezhad
akhojastehnezhad@yahoo.com
Graphene nano sheet (GNS) is first described in 2004 [1].
Recently, due to its extraordinary electronic [2], thermal [3]
and mechanical properties [4] it has attracted much atten-
tion. With heterogeneous properties and large specific sur-
face area, GNS has been greatly used as a catalyst for the
organic reactions [5–7]. The oxide form of GNS is graphene
oxide (GO) that has plentiful functional groups on its surface
1
2
3
Department of Chemistry, Faculty of Science, Ferdowsi
University of Mashhad, 91775-1436 Mashhad, Iran
Department of Chemistry, Mashhad Branch, Islamic Azad
University, Mashhad, Iran
Department of Chemistry, Bandar Abbas Branch, Islamic
Azad University, 7915893144 Bandar Abbas, Iran
Vol.:(0123456789)
1 3

A. Khojastehnezhad et al.
including hydroxyls, epoxides, diols and carboxyls and pro-
vides the reactive site for covalent functionalization and
preparation of nano heterogeneous catalysts [8]. Also, its
two-dimensional structure with a huge surface area makes
it a promising support for different nanoparticles (NPs) and
complexes [9, 10]. In particular, the two-dimensional struc-
ture and nano sheet features of GO may allow the reactants
to increase in the local concentration and promote the reac-
tion effectively. Another advantage of GO is its easy dispers-
ibility in water and other organic solvents to better carry out
the reaction [11].
dioxide adsorption. Their analysis showed that the prepared
solid complex possesses high specific surface area regarding
to gas adsorption [17].
Propargylamines are main frameworks [18] or syntheti-
cally versatile and key intermediates [19] for the preparation
of many nitrogen-including biological active compounds,
such as β-lactams, peptides, and important structural ele-
ments of natural products and therapeutics drug molecules
[20]. Propargylamines were prepared by three component
one-pot coupling reaction (A3 coupling) of aldehydes,
alkynes and amines. Different transition metal catalysts able
to perform three component A3 coupling reactions of alde-
hyde, terminal alkynes and amines via C–H activation such
as Ag salt [21], Au salt [22], Cu salt [23], iridium complexes
[24] and Hg2Cl2 [25] system under homogenous conditions.
Many of the synthetic methods for propargylamines suffer
from one or more disadvantages such as low yields, harsh
reaction conditions, difficult work-up and separation of cata-
lyst, lengthened time period and the application of danger-
ous and costly catalysts and solvents. Hence the establish-
ment of clean, high yielding, and environmentally harmless
approaches is still attractive and much in demand.
Substituted tetraphenylporphyrins are aromatic macrocy-
clic compounds which composes of four pyrrole rings bound
through methine (=CH) bridges to form a planar and highly
conjugated macrocycle [12]. The metalloporphyrins espe-
cially copper-porphrines (Cu-PPh) present high catalytic
activities and high selectivities in organic synthesis without
co-reducing reagents. So the catalytic effect of metallopor-
phyrins (MPPhs) on the activity of inactive C–H bonds has
been given considerable attention [13–15].
Anchoring of MPPhs onto the GO has been extensively
employed, since immobilized MPPhs have the fewer of the
drawbacks of homogeneous ones, such as the difficulties in
recovery and regeneration. In 2018, Zeng and co-workers
immobilized zincporphyrin onto the basal plane on GO and
photoelectrochemical activity of their functionalized GO
nanocomposites was evaluated under visible-light irradia-
tion, and enhancement of the photoelectrocatalytic reduction
of CO2 was achieved [16]. Zhou and co-workers prepared
graphene–terpyridine complex hybrid material for carbon
In continuation of our success in preparation of nano
catalysts [26–30] in this study, at first, the GO has been
synthesized by Hummer method and hydroxyl groups on
the its edges were converted to acyl chloride and Cu(II)-
tetrakis(aminophenyl)porphyrin (Cu-PPh) was covalently
linked on edges of GO by nucleophilic reaction between acyl
groups of GO and amine group of porphyrin and GO cross-
linked Cu-PPh (GO–Cu-PPh) was prepared (Scheme 1).
NH2
NH2
H
N
1) Propionic acid
Acetic Anhydride
reflux, 180 min
O
O
NH
N
N
N CuN
N
H
+
O
NH2
N
H
H2N
N
N
2) HCl
HN
H
SnCl2·2H2O
NH3
O2N
NH2
1. Et3N
NH2 PPh
DMF, 80 o
C
2. Cu(OAc)2
DMF, reflux
NH2
OH
HO
OH
O
O
O
O
N CuN
N
H
1) Hummer
Method
Cl
N
H
O
N
N
Graphite
Cl
2) SOCl2
OH
Cl
DMF, 70 o
C
O
O
O
NH2
Cl
GO-CuPPh
GO-Cl
Scheme 1 Preparation of catalyst (GO–CuPPh)
1 3

Covalently Copper(II) Porphyrin Cross-Linked Graphene Oxide: Preparation and Catalytic…
After full characterization of catalyst, the activity of catalyst
has been studied for the preparation of propargylamine via
three component one-pot coupling reaction (A3 coupling)
of different aldehydes/ketones, terminal alkynes and amines
(Scheme 2).
2 Results and Discussion
The catalyst (GO–CuPPh) was prepared according to the
method explained in scheme 1. The GO and porphyrin
ligand was synthesized in accord with the literature [31, 32],
Fig. 1 FT-IR spectra of a NO2–PPh and b PPh (NH2–PPh)
The synthesized porphyrin was grafted covalently on the
synthesized GO and in the following, metalation step was
accomplished and GO–CuPPh was successfully prepared
(see scheme 2 for details). The structure of catalyst was well
characterized using various techniques including FT-IR, UV,
SEM, EDS, TEM, ICP and TGA.
(Fig. 2d). This analysis confirms the successful covalently
immobilization of porphyrin on the edges of GO [34].
Scanning electron microscope (SEM), transition electron
microscope (TEM) and energy dispersive spectrum (EDS)
was applied for the characterization of GO–CuPPh from
viewpoint of morphology, structure and elemental analysis,
respectively (Fig. 3). In SEM image of GO (Fig. 3a), it is
clearly seen from the top-view image that the GO layers have
a uniform surface, composed of sheet-like structures from
1 µm to few microns in the lateral dimension [35]. The SEM
and TEM images of final catalyst (GO–CuPPh) are shown
in Fig. 3b, c respectively. These photographs show the suc-
cessful covalently linkage of CuPPh on the edge of GO [34].
Although, they display that some CuPPh are non-covalently
attached on the surface of GO by π–π stacking of aromatic
moieties of PPh with SP2 carbons of GO [16, 36, 37]. Also
TEM image displays relatively transparent sheets with large
monolayer structures. The EDS analysis of catalyst proves
the elemental analysis of desired materials in the construc-
tion of the nano-catalyst such as copper, chlorine, oxygen,
At first, FT-IR analysis was studied. In Fig. 1, the FT-IR
measurement have been showed the successful synthesis of
NO2 and NH2-porphyrine. As illustrated in Fig. 1a, the weak
band at 3313 cm−1 is attributed to the N–H stretching bands
of pyrrole moiety. The bands appeared at 1595, 1519 and
1346 cm−1 correspond to the N=O of nitro group in phenyl
section. After converting NO2 to NH2 in phenyl section by
reduction reaction, the new broad band reveals at 3359 cm−1
ascribed to the stretching vibrations of N–H bonds of NH2
group.
The FT-IR analysis for preparation of catalyst was stud-
ied to investigate the bonding interactions in GO after the
functionalization processes. The existence of various types
of functionalities in GO cause the appearance of broad
absorption band at 3407 cm−1, which is attributed to the
O–H stretching bands of hydroxy and carboxylic acid moie-
ties [33]. The bands appeared at 1716, 1587, 1222 cm−1 cor-
respond to the C=O of carboxyl group, C=C aromatic rings
and C–O epoxy group respectively. (Fig. 2a). The FT-IR
spectrum of PPh (Fig. 2b), has been explained in previ-
ous figure. After covalent functionalization with porphy-
rins (Fig. 2c), the sharp band appears at around 3388 cm−1
ascribed to the stretching vibrations of N–H of porphyrin
molecule. Moreover, C=O stretching vibration shifts to
1600 cm−1. After insertion of copper ion into the porphy-
rin ring, there are not any differences in FT-IR spectrum
R2
R1
O
X
Ph
GO-CuPPh
DCE, reflux
+
+
Ph
N
R1
R2
N
H
X
1a-h
2a-b
4a-n
3
Scheme 2 Synthesis of propargylamine in presence of GO–CuPPh
Fig. 2 FT-IR spectra of a GO, b PPh, c GO–PPh and d GO–CuPPh
1 3

A. Khojastehnezhad et al.
Fig. 3 a SEM image of GO, b
SEM image of GO–CuPPh, c
TEM image of GO–CuPPh and
d EDS pattern of GO–CuPPh
and carbon (Fig. 3d). This analysis confirms successful cova-
lently linkage of CuPPh on GO.
Thermal gravimetric analysis (TGA) was used to confirm
the high thermal stability of the GO and GO–CuPPh cata-
lyst. TGA plot of GO is shown in Fig. 4a. In the GO sample,
the first weight lost was between 150 and 300 °C, indicating
decomposition of water and oxygenic functional groups like
OH, CO2 and CO2H on the basal plane and edges of GO.
At temperatures below 600 °C, the second weight lost was
observed which is related to decomposition of GO structure
[38, 39]. In the TGA of final catalyst (GO–CuPPh), there
are two main weight losses. Firstly, the weight loss starts at
50 °C with gentle slope and continues to about 300 °C (15%)
is allocated to physically and hydrogen bonded water and
decomposition of oxygenic functional groups on GO. The
second weight loss (30%) in the range 300–700 °C is related
to the organic parts which are covalently anchored to the GO
surface. Based on the TGA analysis results, ligand grafting
had been successfully performed [40].
UV–Vis analysis was also conducted and the spectra is
shown in Fig. 5. According to literature, the spectrum of GO
shows a strong UV absorption at 239 nm and the shoulder
peak at lower energy (277 nm) [41]. Porphyrin has two char-
acteristic bands namely soret (one band) and Q (three bands)
bands related to the π–π* electron transfer [42]. The UV–Vis
spectrum of GO–CuPPh has a peak at 239 and 439 nm which
is attributed to the GO and soret band of porphyrin ring.
Fig. 4 TGA of a GO and b GO–CuPPh catalyst
1 3

Covalently Copper(II) Porphyrin Cross-Linked Graphene Oxide: Preparation and Catalytic…
the molar ratios of starting materials based on mechanistic
investigations and previously reported literatures, the other
reaction conditions such as solvent, amount of catalyst and
temperature were optimized. At first, in order to optimize the
catalyst dosage and temperature, the synthesis of compound
4a was carried out as a pattern reaction. Therefore, a mixture
of benzaldehyde (1.0 mmol), morpholine (1.1 mmol) and
phenylacetylene (1.0 mmol) in the presence of GO–CuPPh
was stirred at room temperature (Table 1). No product was
achieved in the lack of the catalyst (entry 1). This indicates
that the catalyst is vital for the reaction. The yield of product
4a increased with increasing amount of catalyst and temper-
ature (entries 2–5). The reaction in the presence of 5.0 mg
of the GO–ZrPPh under reflux conditions was performed
in different solvents (acetonitrile, ethanol, water, toluene,
dichloromethane and dichloroethane) to assess the effect
of solvent on the reaction yield (entries 6–11). Yields of
the reaction in chlorosolvents was better compared to other
solvents (entries 10,11). The best outcome was obtained in
dichloroethane as a solvent, 5.0 mg of catalyst at reflux con-
dition (entry 11); further rising the catalyst dosage up to
20 mg did not noticeably increase the yield (entries 12, 13).
Also, the model reaction was studied in the presence of GO,
GO–PPh and bare CuPPh. In presence of GO and GO–PPh,
trace product was achieved (entries 14, 15), while, the reac-
tion was carried out with lower yield (84%) in presence of
bare CuPPh as a catalyst (entry 16). These results showed
that the existence of copper is necessary for proceed the
Fig. 5 UV–vis of GO–CuPPh catalyst
Although the Q bands are very week and are not observed.
The existence of soret band can be valid evidence for the
presence of porphyrin in the structure of catalyst.
According to inductively coupled plasma (ICP) tech-
nique, the content of copper in the sample was confirmed.
The weight percentage of Cu in fresh and recovered catalyst
(after six times) was 6.012 wt% and 5.74 wt% respectively.
On these results, we can conclude that there is no substantial
difference in weight percentage of copper in recovered and
fresh catalyst that was used the first time in the reaction.
Also this evidence showed that Cu linked with PPh ring and
these linkages are stable. In addition, no leaching occurs in
reaction medium.
The catalytic application of the GO–CuPPh as nano-
catalyst was studied for the synthesis of propargylamine
derivatives via A3 and KA2 coupling reactions. After finding
Table 1 Screening of the
amount of the catalyst and
temperature for the formation
of 4a
Entry
Condition
Catalyst (mg)
Temperature (°C)
Time (h)
Yielda (%)
1
2
3
4
5
6
7
8
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
CH3CN
C2H5OH
H2O
Toluene
–
3
5
5
5
5
5
5
5
5
5
10
20
5b
5c
5d
rt
rt
rt
50
5
3
3
2
1
2
2
2
Trace
18
29
45
64
Trace
Trace
Trace
10
70
96
95
96
Trace
Trace
84
60
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
9
2
1
10
11
12
13
14
15
16
CH2Cl2
C2H4Cl2
C2H4Cl2
C2H4Cl2
C2H4Cl2
C2H4Cl2
C2H4Cl2
0.5
0.5
0.5
0.5
0.5
0.5
Reaction conditions: benzaldehyde (1.0 mmol), morpholine (1.1 mmol), phenylacetylene (1.0 mmol)
aIsolated yiel
bIn presence of GO
cIn presence of GO-PPh
dIn presence of bare CuPPh
1 3

A. Khojastehnezhad et al.
reaction. We believe when we used CuPPh linked to GO,
due to the nano features of GO sheets and adsorption of the
reactants on the surface of the catalyst, there was an increase
in the local concentration of reactants around the active sites
of the GO–CuPPh which promoted the reaction effectively.
After investigation of several conditions on the reaction
proceed, we studied other kinds of reactants under the opti-
mum conditions. Among electron donor and electron defi-
cient groups, no significant difference was monitored. All
the derivatives were in good to superb yields. The reason for
this may be higher activity of the catalyst which balances the
reaction progress of each derivative (Table 2).
of the recovered catalyst is the same as the amount of the
fresh catalyst that was used the first time in the reaction.
3 Conclusion
In conclusion, the new cross-linked catalytic system has
been prepared via the covalently immobilization of Cu(II)-
coordinated 5,10,15,20-tetrakis(aminophenyl)porphyrin
on the GO. The catalyst has been characterized with vari-
ous methods like: FT-IR, UV–Vis, TEM, SEM, EDX, ICP
and TGA analysis. According to TEM and SEM images,
addition to the edges, CuPPh grafted onto the basal plan of
GO by π–π stacking of aromatic moieties of PPh with SP2
carbons of GO. The prepared catalyst has been carried out
the synthesis of propargylamine derivatives via A3 and KA2
coupling reactions quickly with high yields.
The merit of the present work has been compared with
other heterogeneous catalysts for the synthesis of propar-
gylamine 4a (benzaldehyde, morpholine, phenylacetylene)
(Table 3). According to the obtained results, our catalyst
shows a more satisfied catalytic activity in shorter reaction
time and higher yield.
In order to study the heterogeneous nature of GO–CuPPh
nanocatalyst, the hot filtration test has been carried out on
model reaction under the optimized condition. In this test, a
mixture of GO–CuPPh (5.0 mg), phenylacetylene (1 mmol),
morpholine (1 mmol) and benzaldehyde (1 mmol) was
refluxed in DCE for 15 min. After 50% conversion, the
catalyst was separated from the reaction mixture and then
the reaction was continued for an additional time (15 min).
No further product formation was observed which was
monitored by TLC. This result clearly demonstrates that no
leaching of Cu or CuPPh took place during the reaction, and
GO–CuPPh is truly heterogeneous in nature.
4 Experimental
Melting points of products were recorded with an electro-
thermal type 9200 melting point apparatus. FT-IR spectra
were recorded with a Nicolet Avatar 370 FT-IR spectrom-
eter. NMR spectra were obtained with a Bruker Avance
instrument at 300 MHz in CDCl3. Mass spectra were
obtained with a Varian Mat CH-7 at 70 eV. Transmission
electron microscopy (TEM) was performed with a Leo
912AB (120 kV) microscope) Zeiss, Germany). Inductively
coupled plasma optical emission spectroscopy (ICP-OES)
analysis was carried out with a Varian VISTA-PRO, CCD
(Australia). Elemental compositions were determined with
EDX analysis (model 7353, Oxford Instruments, UK), with
133 eV resolution. TGA was performed with a Shimadzu
thermogravimetric analyzer (TG-50) under air atmosphere
at a heating rate of 10 °C min−1.
As illustrated in Scheme 3, the proposed mechanism was
described [47]. Beginning with alkyne activation in which
the alkyne terminus is acidified by binding to copper. As
a result, the corresponding copper–acetylide complex is
formed on the surface of the catalyst. Then, an addition
of the copper–acetylide complex to the imine ion gener-
ated in situ from the reaction between the aldehyde and the
amine occurs to give the desired product, and the catalyst
is regenerated.
4.1 Synthesis of GO–COCl
To investigation the reusability of the catalyst
(GO–CuPPh,) the pattern reaction was investigated. After
completing of each run, the reused catalyst was isolated
using simple centrifuging and washed completely using
acetone and water to eliminate the remained product, dried
at 100 °C under vacuum and reutilized in a following reac-
tion in very good yields. It exhibited the same activity as
the new catalyst without any considerable failure in its per-
formance (Fig. 6).
According to literature reports, GO was prepared using a
modification of Hummers method [31]. For conversion of
hydroxyl groups on the edges of GO to acylchloride, to the
mixture of GO (0.5 g) in DMF (5 mL), SOCl2 (30 mL) was
added at room temperature and the stirred at 70 °C for 24 h
under nitrogen atmosphere. The resulted solution was fil-
tered and washed with anhydrous tetrahydrofuran (THF)
and dried under vacuum, yielding acylated graphene oxide
(GO–COCl).
The FT-IR spectra of GO–CuPPh catalyst before use
(fresh) and after reuse six times (recovered) were studied.
As shown in Fig. 7, the FT-IR spectrum of the recovered
GO–CuPPh showed that the structure of catalysts remained
almost the same aftrer six-run reuse. In addition, the weight
4.2 Synthesis of PPh
This compound was prepared by the method explained
in the literature as follows [32]. A mixture of
1 3

Covalently Copper(II) Porphyrin Cross-Linked Graphene Oxide: Preparation and Catalytic…
Productb
Time (min)
30
Yield (%)c
96
Table 2 Synthesis of
Entry
1
R1 , R2
Ph, H
X
O
propargylamine derivatives in
presence of catalyst
H
Ph
N
O
MeO
Me2N
Cl
H
Ph
Ph
2
3
4
4-OMeC6H4, H
4-(NMe2)C6H4 ,H
4-Cl C6H4 , H
O
O
O
60
45
60
88
86
92
N
O
H
N
O
H
Ph
N
O
Me
H
Ph
5
6
7
4-MeC6H4 , H
O
C
C
50
30
60
90
95
89
N
O
H
Ph
Ph , H
N
Me
MeO
Cl
H
N
Ph
4-Me C6H4, H
H
N
Ph
8
4-OMe C6H4, H
C
60
92
H
N
Ph
9
4-Cl C6H4, H
C
O
45
50
93
96
Ph
Ph
10
Cyclohexanone
N
N
O
11
12
13
14
Cyclopentanone
Cyclohexanone
Cyclopentanone
2-Furyl, H
O
C
C
O
60
45
60
50
96
98
94
85
O
Ph
Ph
N
N
H
N
Ph
O
O
1 3

A. Khojastehnezhad et al.
Table 2 (continued)
Different aldehyde/ketones 1a-h (1.0 mmol), amines 2a-b (1.1 mmol), phenylacetylene 3 (1.0 mmol), cata-
lyst (5.0 mg) in dichloro ethane reflux
aThe known products were identified by comparing of their melting points and some selected compounds
were characterized with 1H NMR, 13C-NMR, mass and CHN analysis
bIsolated yields
Table 3 The comparison of
GO–CuPPh catalyst with other
heterogeneous catalysts in
Entry
Catalyst
Solvent
Temp. (°C)
Time (h)
Yield (%)a
Ref.
1
2
3
4
5
6
Au-MCM-41
GO–Cu
Au-Mont
ZnII/HAP/Fe3O4
CuI
GO–CuPPh
H2O
H2O
Toluene
Solvent-free
H2O
80
24
15
3
3
0.33
0.5
80
83
91
95
90
96
[43]
[44]
[45]
[46]
[23]
This study
synthesis of propargylamine 4a
100
100
110
rt
DCE
40
aBased on isolated yield
Scheme 3 The proposed
X
mechanism for the synthesis of
propargylamine derivatives in
the presence of GO–CuPPh
N
Ph
R2
[CuPPh]
R1
Ph
H
Alkyne activation
Copper elimination
X
Ph
H
[PhPCu]
Ph
N
R2
[CuPPh]
R1
H
Copper acetylide
R2
R1
N
X
Ph
R1
[CuPPh]
X
R2
Ph
[CuPPh]
O
+
N
X
R1
R2
N
H
Imine coordination
Condensation to imine
4-nitrobenzaldehyde (22.0 g, 145 mmol) and acetic anhy-
dride (24.0 mL, 254 mmol) in propionic acid (600 mL) was
refluxed, to which pyrrole (10.0 ml, 144 mmol) was slowly
added. After 30 min, the resulting mixture was cooled to
obtain a precipitate which was collected by filtration,
washed with H2O and methanol, and dried under vacuum.
This prepared powder was dissolved in pyridine (160 mL)
which was refluxed for 1 h. After cooling, the precipitate
was collected by filtration and washed with acetone to give
5,10,15,20-tetrakis(4-nitrophenyl)porphyrin as a purple
crystal. The product (4.13 g, 0.005 mmol) was dissolved
in hot HCl (500 mL) at 70 °C and SnCl2·2H2O (18.0 g,
Fig. 6 Reusability of catalyst for model reaction
1 3

Covalently Copper(II) Porphyrin Cross-Linked Graphene Oxide: Preparation and Catalytic…
Fig. 7 FT-IR spectrum of a
fresh and b reused ctalyst after
six times
0.08 mmol) was added to the mixture which was stirred at
70 °C for 30 min and then cooled to 0 °C. Afterwards, the
mixture was neutralized with aqueous NH3, the obtained
product was collected by filtration followed by drying under
vacuum yielded purple crystals.
(1.0 mmole) in 1,2-dichloroethane, (2.0 mL), GO–CuPPh
catalyst (5.0 mg) was added and refluxed for 0.5–2 h. The
progress of reaction was monitored by TLC and after com-
pletion the catalyst was separated by centrifuging. The sol-
vent was evaporated and product (propargylamine) was iso-
lated by column chromatography or plate chromatography
by using hexane–ethyl acetate (5:1) as eluent to obtain the
pure compound. The product was identified by CHN, Mass
spectrometry, 1HNMR, and 13CNMR spectroscopy.
4.3 Synthesis of GO–PPh
GO–COCl (30 mg) and synthesized porphyrin (60 mg) in
DMF (15 mL) were taken in a 100 mL round bottom flask
and triethylamine (3.0 mL) were added and heated to 80 °C
for 72 h under a nitrogen atmosphere and an additional 1 h
with intermittent sonication to give a homogeneous black
dispersion. Afterwards, the resulting black mixture was per-
mitted to cool to room temperature and then poured into
diethyl ether (300 mL) to precipitate the product. The black
precipitate was collected by centrifuging at 8000 rpm for
30 min. The supernatant was discarded contained unreacted
ligand. Finally, another diethyl ether (100 mL) was added
and the mixture was centrifuged at 8000 rpm for 30 min and
the immobilized ligand on the GO was collected.
4.5.1 4-(1,3-Diphenylprop-2-yn-1-yl)morpholine (Entry 1)
1HNMR (300 MHz, CDCl3): δ = 2.69 (4H, t, J = 4.35),
3.77–3.81 (4H, m), 4.85(1H, s), 7.38–7.70(10H, m); 13C
NMR (CDCl3, 75 Hz): δ=50, 62.07, 67.20, 85.09, 88.54,
123.01, 127.83, 128.28, 128.31, 128.36, 128.64, 131.85,
137.84. Anal.calc. for C19H19NO: C, 82,31; H, 6.86; N, 5.08;
O, 5.72; Found: C, 82.28; H, 6.90; N, 5.05; M.S. (70 ev) m/z
(%): 277 (M+, 100).
4.5.2 4-(1-(4-Methoxyphenyl)-3-phenylprop-2-yn-1-l)
morpholine (Entry2)
4.4 Synthesis of GO–CuPPh
1HNMR (300 MHz, CDCL3): δ = 2.66–2.70 (4H, m),
3.78–3.79 (4H, m), 4.79 (1H, s), 6.94–6.97 (d, 2H, J=8.7,
Ar), 7.36–7.39 (2H, m, J = 6.3, Ar), 7.59–7.62 (d, 2H,
J = 8.2, Ar); 13C NMR (CDCl3, 75 Hz): δ = 49.87, 55.30,
61.49, 67.20, 85.48, 88.33, 113.62, 123.08, 128.29, 128.38,
129.78, 129.92, 131.85, 159.27. Anal.calc. for C20H21NO2:
C, 78.20; H, 6.87; N, 4.55; Found: C, 78.15; H, 6.89; N,
4.56; O, 10.41; M.S. (70 ev) m/z (%): 307 (M+, 100).
The complex was prepared by adding Cu(OAc)2 (3.0 g) in to
the solution of GO–PPh (1.0 g) and DMF (80 mL). For the
complete metallation, the reaction mixture was refluxed for
6 h. The obtained GO–CuPPh was collected by centrifuging
at 8000 rpm for 30 min. Finally, 20 ml of water was added
and the mixture was centrifuged at 8000 rpm for 30 min and
the obtained Cu-complex on the GO was collected.
4.5 General procedure for synthesis
of propargylamines
4.5.3 1-(1,3-Diphenylprop-2-yn-1-yl) piperidine (Entry 6)
1HNMR (300 MHz, CDCL3): δ = 1.58–1.60 (2H, m),
1.63–1.79 (4H, m), 2.70 (4H, t, J = 5.25), 4.94 (1H, s),
7.39–7.45 (6H, m, 2×Ar), 7.62–7.65 (2H, m, Ar), 7.76–7.78
To a solution of aldehyde and ketone derivatives, (1.0
mmole), secondary amines (1.1 mmole), and phenylacetylene
1 3

A. Khojastehnezhad et al.
(2H, m, Ar); 13CNMR (CDCl3, 75 Hz): δ = 24.55, 26.26,
50.78, 62.46, 6.13, 88.03, 123.44,127.60, 128.18, 128.39,
128.66, 131.92, 138.61.
15. Jiang Y-X, Su T-M, Qin Z-Z, Huang G (2015) RSC Adv
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4.5.4 1-(3-Phenyl-1-(p-tolyl)prop-2-yn-1-yl) piperidine
(Entry7)
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1HNMR (300 MHz, CDCL3): δ = 1.58–1.63 (2H, m),
1.66–1.75 (4H, m), 2.46 (3H, s), 2.67 (4H, t, J=4.9), 7.27
(2H, d, J=8.1), 7.39–7.43 (3H, m), 7.6–7.62 (2H, m), 7.63
(2H, d, J=8.1); 13C NMR (CDCl3, 75 Hz): δ=21.24, 24.58,
29.28, 50.70, 62.22, 86.46, 87.73, 123.50, 128.10, 128.36,
128.58, 128.86, 131.90, 135.64, 137.16.
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4.5.5 4-(1-(Phenylethynyl)cyclohexyl) morpholine (Entry
12)
1HNMR (300 MHz, CDCL3): δ = 1.28–1.77 (8H, m),
2.05–2.09 (3H, m), 2.76 (4H, t, J = 4.8 Hz), 3.80 (4H, t,
J=4.8 Hz), 7.30–7.48 (5H, m); 13C NMR (CDCl3, 75 Hz):
δ=22.78, 25.71, 29.34, 35.46, 46.67, 58.95, 67.50, 86.53,
89.78, 123.44, 128.23, 131.74; Anal.calc. for C18H23NO: C,
80.29; H, 8.59; N, 5.18; Found: C, 80.26; H, 8.61; N, 5.20;
O, 5.94; M.S. (70 ev) m/z (%): 269 (M+, 100).
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Acknowledgements The authors are thankful to the Iran National Sci-
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