Green synthesis of carbon quantum dots from vanillin for modification of magnetite nanoparticles and formation of palladium nanoparticles: Efficient catalyst for Suzuki reaction

Article abstract of DOI:10.1016/j.tet.2016.11.014

In this report we prepared carbon quantum dots (CQD) from vanillin as an ecofriendly and naturally abundant compound for modification of magnetic nanoparticles (CQD@Fe₃O₄ NPs). This new magnetic solid has been used for complete reduction of PdCl₂ with formation of stabilized palladium nanoparticles (Pd@CQD@Fe₃O₄ NPs) and characterized by SEM, TEM, EDX, solid UV, VSM, XPS, XRD, and N₂ adsorption–desorption analyses. These magnetic supported Pd NPs have been used as an efficient catalyst for the Suzuki-Miyaura cross-coupling reactions of aryl bromides at room temperature in aqueous ethanol and of aryl chlorides at 120 °C in PEG200 under low catalyst loading in air. The heterogeneous catalyst can be easily recovered by an external magnet and reused for eight consecutive runs.

Full text of DOI:10.1016/j.tet.2016.11.014

Accepted Manuscript
Green synthesis of carbon quantum dots from vanillin for modification of magnetite
nanoparticles and formation of palladium nanoparticles: Efficient catalyst for Suzuki
reaction
Mohammad Gholinejad, Carmen Najera, Fatemeh Hamed, Mohammad
Seyedhamzeh, Maede Bahrami, Mohsen Kompany-Zareh
PII:
S0040-4020(16)31146-2
10.1016/j.tet.2016.11.014
TET 28228
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 30 June 2016
Revised Date: 25 October 2016
Accepted Date: 3 November 2016
Please cite this article as: Gholinejad M, Najera C, Hamed F, Seyedhamzeh M, Bahrami M, Kompany-
Zareh M, Green synthesis of carbon quantum dots from vanillin for modification of magnetite
nanoparticles and formation of palladium nanoparticles: Efficient catalyst for Suzuki reaction,
Tetrahedron (2016), doi: 10.1016/j.tet.2016.11.014.
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ACCEPTED MANUSCRIPT
Graphical Abstract
Green Synthesis of Carbon Quantum Dots
from Vanillin for Modification of Magnetite
Nanoparticles and Formation of Palladium
Nanoparticles: Efficient Catalyst for Suzuki
Reaction
Leave this area blank for abstract info.
Mohammad Gholinejad, Carmen Najera, Fatemeh Hamed, Mohammad Seyedhamzeh, Maede Bahrami, Mohsen
Kompany-Zareh
3 4
Fe O NPs
1
2
Ar1_ Ar2
5 examples
Ar X
Ar B(OH)
2
+
2
X= Cl, Br
Pd NPs
CQDs

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Green Synthesis of Carbon Quantum Dots from Vanillin for Modification of
Magnetite Nanoparticles and Formation of Palladium Nanoparticles: Efficient
Catalyst for Suzuki Reaction
a,
b,
a
a
Mohammad Gholinejad ∗ , Carmen Najera ∗ , Fatemeh Hamed , Mohammad Seyedhamzeh , Maede
a
a
Bahrami , and Mohsen Kompany-Zareh
a
Department of Chemistry, Institute for Advanced Studies in Basic Sciences, Gava Zang, Zanjan 45137-66731, Iran.
Departamento de Química Orgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA). Universidad de Alicante, Apdo. 99, E-03080-Alicante,
b
Spain.
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
In this report we prepare carbon quantum dots (CQD) from vanillin as an ecofriendly and
naturally abundant compound for modification of magnetic nanoparticles (CQD@Fe
This new magnetic solid are used for complete reduction of PdCl with formation of stabilized
palladium nanoparticles (Pd@CQD@Fe NPs), which are characterized by SEM, TEM, EDX,
solid UV, VSM, XPS, XRD, and N adsorption–desorption analyses. These magnetic supported
3 4
O NPs).
2
3
O
4
Available online
2
Pd NPs are efficient catalysts for the Suzuki-Miyaura cross-coupling reactions of aryl bromides
at room temperature in aqueous ethanol and of aryl chlorides at 120 °C in PEG200 under low
catalyst loading in air. The heterogeneous catalyst is recovered by an external magnet and reused
for eight consecutive runs.
Keywords:
Vanillin
Magnetite
Palladium
Quantum Dots
Suzuki
2
009 Elsevier Ltd. All rights reserved.
—
——
∗
∗
Corresponding author. Tel.: +98-024-3315-3231; fax: +98-024-3315-3232; e-mail: gholinejad@iasbs.ac.ir
Corresponding author. Tel.: +34-965903549; fax: +34-965903549; e-mail: cnajera@ua.es

2
Tetrahedron
1
. Introduction
vanillin as a cheap and naturally abundant compound for
ACCEPTED MANUSCRIPT
formation of CQD and its subsequent application for the
modification of Fe O NPs (CQD@Fe O ). We envisaged that
Palladium catalyzed cross-coupling reactions have become a
3
4
3
4
key and potent tool in organic synthesis for the formation of
carbon–carbon bonds. Among them, the Suzuki-Miyaura
reaction, which is the coupling between aryl, vinyl or alkyl
halides or pseudo-halides and organoboron reagents is one of the
advanced palladium catalyzed reactions for the formation of
CQD generated from vanillin bearing formyl groups would
facilitate the reduction of Pd(II) to Pd(0) and therefore the
formation of Pd NPs to be used in carbon-carbon bond forming
reactions. The CQD@Fe O would be further used not only for
1
3
4
the stabilization of Pd NPs but also for the easy recovery of this
2
different types of compounds. Traditionally, palladium pre-
catalysts in the presence of toxic phosphine or nitrogen ligands
heterogeneous catalyst, which is referred to as Pd@CQD@Fe O
3
4
3
4
throughout this manuscript.
are often employed for coupling reactions under homogeneous
conditions. However, when compared to heterogeneous catalysts,
homogeneous catalysts suffer from diminished catalytic activity
during the reaction, lack of catalyst reusability, and difficulty for
product purification. In the case of palladium, which is toxic and
costly, recycling is very important from both economic and
2
. Results and discussion
Preparations steps of Pd@CQD@Fe O are summarized in
3
4
scheme 1. Firstly, Fe O NPs were prepared using the Massart
procedure from the reaction of FeCl ·6H O and FeCl ·4H O
3
4
5,6
17
sustainable chemistry standpoints
3
2
2
2
salts (Scheme 1).
Nowadays, green chemistry objectives encourage chemists for
design and preparation of new methodologies that reduce or
eliminate the use or generation of hazardous substances. For this
purpose, in recent years designing of new recyclable and
heterogeneous catalysts with high efficiency and turnover
number, low cost, and minimal leaching of toxic metals has
7
received much attention. In the past few decades, a wide range of
efficient heterogeneous palladium catalysts using different solid
supports have been reported for various Pd catalyzed organic
reactions. However, usually separating of the heterogeneous
catalyst from the reaction mixture by conventional methods such
5,6
as simple filtration and centrifugation is not an easy task. To
address these challenges, many efforts have been made for using
magnetic nanoparticles with unique properties such as easy
isolation, high surface area and low toxicity as a promising
8
support for palladium catalysts. For this purpose, in recent years
different methods and ligands have been reported for
modification of magnetic nanoparticles and their relevant
applications as Pd supports for various carbon-carbon bond
Scheme 1. The preparation steps toward the catalyst.
8
formation reactions.
TEM image showed formation of magnetic nanoparticles in
5-20 nm average size (Fig. 1a). CQD were synthesized by
heating an ethanol solution of vanillin in a Teflon autoclave at
80 °C for 12 h. Photoluminescence (PL) emission study of
Fluorescent carbon quantum dots (CQD) are an emerging
class of carbon nanomaterials recently termed quasi-spherical
nano carbons with sizes below 10 nm. These CQD are comprised
of amorphous to nanocrystal line cores with predominantly
1
1
2
CQDs showed a broad emission centered at 413 nm in the
emission spectrum with an excitation wavelength at 350 nm
(Fig.1, ESI). Reaction of obtained CQD with magnetite NPs
afforded CQD coated Fe O NPs. Formation of CQD@Fe O was
graphitic or turbo static carbon (sp carbon) or graphene and
3
graphene oxide sheets fused by diamond-like sp hybridized
9
carbon insertions. CQD have unique properties such as high
3
4
3
4
solubility, photo-stability, fluorescence emission and they are
considered as green, non-toxic, abundant, and inexpensive
proved by TEM image showing carbon shells around the Fe O
3
4
9
nanoparticles (Fig. 1b). Finally, Pd@CQD@Fe O was obtained
3 4
materials. In recent years, different sources have been used for
by treating of aqueous solution of PdCl and CQD@Fe O at 80
2
3
4
the preparation of CQD. However, recent emerging efforts have
been paid for using inexpensive starting materials, such as
ºC for 24 h. Loading of Pd on the Pd@CQD@Fe O was
3
4
10
11
12
determined using atomic absorption spectroscopy (AAS) analysis
chitosan, orange peels and cabbage for the preparation of
CQD. Recently, CQD obtained from clotted cream have been
used for the synthesis of coated Pd nanoparticles (NPs) and used
-1
to be 0.14 mmolg . TEM images of Pd@CQD@Fe O showed
3
4
the presence of small Pd NPs attached on surface of
13
CQD@Fe O4 (Fig. 1c). Also SEM images of the catalyst
3
for Heck and Suzuki reactions. Also, very recently, we have
reported the preparation of CQD from citric acid and its using for
modification of magnetic Fe O nanoparticles and formation and
indicated the presence of dispersed and uniform particles (Fig.
d).
1
3
4
14
stabilization of Pd NPs.
Vanillin is a highly water soluble phenolic aldehyde, which
occurs widely in plants, usually as a glycoside bound to sugar or
as a precursor to vanillin bound to the large lignin molecule
abundant in wood. Vanillin is widely used to introduce flavors in
our food and free vanillin in the environment is not considered to
15
represent any biohazard.
In continuation of our interest in CQD and magnetic supported
16
palladium catalysts, now in this work we use for the first time

3
ACCEPTED MANUSCRIPT
3 4
Fig. 3. XPS spectrum of the Pd@CQD@Fe O NPs in Pd 3d region.
XPS analysis confirmed the presence of carbon in the
structure of Pd@CQD@Fe O NPs with related peaks to C1s at
3
4
2
84.8 eV corresponding to C=C, 286.4 eV for C-O, and 288.6 eV
20
for C=O forms of carbon (Fig. 4).
Fig. 1. TEM images of a) Fe NPs, c) Pd@CQD@
3
O
4
NPs, b) CQD@ Fe
3
O
4
Fe NPs, and d) SEM image of Pd@CQD@ Fe O NPs.
3
O
4
3 4
In order to find information about the oxidation state of
palladium in the catalyst, a solid UV spectrum of catalyst and
PdCl as a source of Pd(II) species was studied (Fig. 2). Results
2
indicated disappearing of a peak related to Pd(II) at 280 nm
18
which confirms the reduction of Pd(II) to Pd(0).
3 4
Fig. 4. XPS spectrum of the Pd@CQD@Fe O NPs in C 1s region.
The superparamagnetic performance of the catalyst was
confirmed using a magnetization curve showing Zero coercivity
and remanence on the magnetization loop and absence of
hysteresis loop (Fig. 5).
3 4
Fig. 2. Solid state UV-Vis spectra of the Pd@CQD@Fe O NPs.
Furthermore,
oxidation
state
of
palladium
in
Pd@CQD@Fe O was investigated using X-ray photoelectron
3
4
spectroscopy (XPS). Results showed two intensive doublet peaks
at 335.6 and 340.8 eV in Pd 3d region which are assigned to the
Pd(0) species (Figure 3). These results indicated that the
palladium is in reduced form, confirming the capability of
CQD@Fe O4 for efficient reduction of Pd(II) to Pd(0)
3
3
f, 16a, 19
nanoparticles.
This reduction only took place partially in
14
the case of citric acid derived CQD.
Fig. 5. Magnetization curves of Pd@CQD@Fe
3
O
4
NPs and reused catalyst
rd
after the 3 run.
The
nitrogen
adsorption–desorption
isotherms
for
Pd@CQD@Fe O NPs showed type-IV isotherms with a H3
3
4

4
Tetrahedron
hysteresis loop according to the IUPAC clas
A
sif
C
ica
C
tio
E
n
P
(Fig.
T
E
D
6). MAca
N
se
U
th
S
e
C
Pd
R
lo
I
ading was lower (0.1 mol% instead of 0.22 mol%)
P
T
Also, the Brunauer–Emmett–Teller (BET) surface areas for
Pd@CQD@Fe O NPS was determined to be 90 m g .
confirming the better efficiency of this new catalyst.
2
-1
3
4
Table 1. Optimization of the reaction conditions for the reaction of 4-
a
bromoanisol and phenylboronic acid catalyzed by Pd@CQD@Fe
3
O
4
NPs.
Br
+
Catalyst, 30 °C
B(OH)2
Base, Solvent
MeO
MeO
b
Entry Pd (mol%)
Base
Solvent
Yield(%)
1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.05
0.02
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
K
2
CO
NaOAc
Et
3
H
H
H
H
2
2
2
2
O
O
O
O
49
2
34
3
3
N
65
4
K
3
PO
4
57
Fig. 6. The nitrogen adsorption-desorption isotherm of the Pd@CQD@Fe
3
O
4
5
NaOAc
EtOH
EtOH
72
rd
NPs and reused catalyst after the 3 run.
6
K
2
CO
CO
CO
CO
3
3
3
3
83
7
K
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
O:EtOH
O:EtOH
O:EtOH
O:EtOH
O:EtOH
O:EtOH
O:EtOH
O:EtOH
100
70
X-ray powder diffraction (XRD) of sample showed diffracted
peaks observed at 2theta value of 30.1°, 35.5°, 43.1°, 53.4°,
8
K
2
9
K
2
18
5
7.0°and 62.6° correspond to (210), (311), (400), (422), (511),
and (440) plans of Fe O and also related diffraction peaks of
10
NaOAc
Et
DABCO
PO
NaOH
22
3
4
Pd(0) corresponding to (111), (200) and (220) plans are detected
at 40.2°, 46.7° and 68.2° (Fig. 7).
1
1
1
1
1
1
1
1
2
3
4
5
6
7
3
N
84
58
K
3
4
83
10
K
2
CO
CO
CO
3
3
3
CH
3
CN
11
K
2
THF
4
K
2
Toluene
2
a
Reaction conditions: 4-bromoanisol (0.5 mmol), base (0.75 mmol), solvent
(
2 mL).
GC yields.
b
With the optimized reaction conditions in hand, substrate
scope of the Suzuki-Miyaura cross-coupling reaction for
structurally different aryl halides and arylboronic acids was
examined (Table 2). Results of Table 2 indicated that for the aryl
bromides having electron-donating groups such as –OH, OMe as
well as bromobenzene and aryl bromides containing electron-
withdrawing groups such as –CHO, -Cl, -CN, and –NO2
reactions proceed efficiently and gave the corresponding
biphenyls in high isolated yields (Table 2, entries 1-8).
3 4
Fig. 7. XRD pattern of the Pd@CQD@Fe O .
The catalytic activity of the prepared Pd@CQD@Fe O NPs
3
4
was evaluated in the Suzuki–Miyaura cross-coupling reaction.
For this purpose, the reaction of 4-bromoanisol with
phenylboronic acid was select as the model reaction. Initially, the
reaction was studied in water and the effect of different bases
such as K CO , NaOAc, Et N and K PO at 30 °C was studied
2
3
3
3
4
Reactions of challenging heterocyclic aryl bromides such as 5-
bromopyrimidine and 5-bromoindole with phenylboronic acid
were also proceed very well and desired coupling products were
obtained in 84-93% yields at room temperature (Table 2, entries
(
Table 1, entries 1-4). Results indicated the formation of product
in low to moderate yields. However, using NaOAc and K CO in
2
3
EtOH as the solvent afforded 4-methoxybiphenyl in 72% and
3% yield, respectively (Table 1, entries 5 and 6). In continue,
8
9
and 10). We have also studied the scope of the reaction with
equal mixture of H O:EtOH was selected as solvent and effect of
2
different substituted arylboronic acids such as 3,5-
difluorophenyl, 3-nitrophenyl, 2-naphthyl, 4-methoxyphenyl and
different bases and catalyst loading were studied (Table 1, entries
7
-14). Results indicated that using K CO in aqueous ethanol
2 3
4
-chlorophenyl with aryl bromides, which proceeded efficiently
(1:1), the reaction took place almost quantitatively in 24 h using
and biphenyl products were obtained in high to excellent yields
0
.1 mol% of catalyst at 30 °C (Table 1, entry 7). By lowering the
(
Table 2, 11-20).
catalyst amount to 0.05 and 0.02 mol%, reactions yields
decreased to 70% and 18%, respectively (Table 1, entries 8 and
Reactions of less reactive aryl chlorides were studied under
9
). Using other bases such as DABCO, K PO , Et N, and NaOAc
3 4 3
optimized reaction conditions. However, reactions proceed
sluggish and very poor results were obtained. Therefore, we
examined different reaction conditions such as different
temperatures, solvents and bases for the reactions of aryl
chlorides (Table 1, SI). Results indicated that reactions of 4-
2
in aqueous ethanol (1:1) at 30 °C gave lower yields than K CO3
for this reaction (Table 1, entries 10-14). Other solvents such as
CH CN, THF and toluene gave very poor results (Table 1, entries
3
1
5-17). These reaction conditions (Table 1, entry 7) are similar to
14
the ones used with citric acid derived CQD. However, in this

5
chlorobenzaldehyde,
chloronitrobenzene in mixture of H O:EtOH using K CO , t-
BuOK and NaOH at 95 °C gave low to moderate yields (Table 1,
SI, entries 1-9). By changing solvent to xylene and increasing
reaction temperature to 120 °C, yields of reactions were
improved (Table 1, ESI, entries 10-18). However, best yields
4-chlorobenzonitrileACC
a
E
ndPTED4- MA
w
N
ere
U
ob
S
ta
C
in
R
edIPus
T
ing PEG200 as solvent and K CO as a base at
2 3
120 °C (Table 1, SI, entries 19, 22 and 25). Using these new
optimized reaction conditions, cross-couplings of activated aryl
chlorides with 4-methoxyphenyl- and phenylboronic acids were
also studied giving the corresponding products in good yields
2
2
3
(Table
2,
entries
21-23).
a
Table 2. The reactions of structurally different aryl chlorides and bromides with arylboronic acids in the presence of the catalyst Pd@CQD@Fe
3
O
4
NPs.
1
2
Catalyst, 30-120 °C
1_
2
Ar X Ar B(OH)
+
Ar Ar
2
K CO , H O:EtOH or PEG
2
3
2
X= Br, Cl
1
2
b
Entry
1
Ar X
Ar
Time
h)
Product
Yield (%)
(
Ph
Ph
10
94
1
a
2
10
93
1
b
1
3
4
Ph
Ph
2
7
93
83
c
1
d
5
6
7
Ph
Ph
Ph
1
0.5
2
94
91
94
1
e
1
f
1
g
8
9
Ph
Ph
24
17
90
84
1
h
1
i
1
0
Ph
24
93
1
j
1
1
1
2
3,5-difluorophenyl
3-nitrophenyl
4
92
95
1
k
36
NO2
NC
1
l

6
Tetrahedron
ACCEPTED MANUSCRIPT
1
3
2-naphthyl
24
70
1
m
1
1
4
5
3-nitrophenyl
36
3
92
88
1
n
4-metoxyphenyl
1
i
1
1
1
6
7
8
4-chlorophenyl
4-metoxyphenyl
4-chlorophenyl
3
4
3
94
92
83
1
o
1
p
1
e
1
2
2
2
2
9
0
1
2
3
4-chlorophenyl
4-metoxyphenyl
4-metoxyphenyl
Ph
3
93
94
91
80
81
1
q
3
1
r
b,c
b,c
b,c
15
15
15
Cl
Cl
Cl
NO2
1r
CN
1
f
Ph
CHO
1
c
a
Reaction conditions: ArBr (0.5 mmol), ArB(OH)
Isolated yields.
Reaction conditions: ArCl (0.5 mmol), ArB(OH)
2
(0.75 mmol), K
2
CO
3
(0.75 mmol), EtOH:H
2
O (2 mL, 1:1), catalyst (3.6 mg containing 0.1 mol% Pd).
b
c
°
2
(0.75 mmol), K
2
CO
3
(0.75 mmol), PEG200 (2 mL), catalyst (3.6 mg containing 0.1 mol% Pd) at 120 C.
Finally recycling of the Pd@CQD@Fe O NPs was studied
TEM and SEM (Fig. 9) images of reused catalyst confirmed
that catalyst preserves its structure during the reactions with
small increase in Pd NPs size.
3
4
using the reaction of 4-bromobenzonitrile and phenylboronic acid
under optimized reaction conditions. Results of this study by GC
indicated that the catalyst recycled for 8 consecutive runs with
1
(
2% decrease in activity until run 8 and 27% decrease until run 9
Fig. 8). It is worth mentioning that leaching of Pd after the 3 run
was determined to be 2.3%, slightly higher than in the case of
14
citric acid CQD.
Fig.9. a) TEM image and b) SEM image of reused catalyst after the 3rd
XPS analysis of the reused catalyst showed that Pd is
completely in its reduced form showing related doublet peaks at
3
35.6 and 340.8 eV (Fig. 10). Furthermore, VSM analysis of the
Fig. 8. Recycling of the catalyst for the reaction of 4-bromobenzonitrile with
phenylboronic acid at room temperature catalyzed by Pd@CQD@Fe NPs
yields were determined by GC).
reused catalyst showed a small decrease in magnetization value
and preserve of superparamagnetic property of material (Fig. 5).
These results are further confirmed by nitrogen adsorption–
desorption isotherm of reused catalyst which is similar to the
fresh catalyst (Fig. 6).
3
O
4
(

7
ACCEPTED MAso
N
lid
U
w
S
a
C
s
R
sep
I
arated magnetically, washed with water (3×20
P
T
mL) and ethanol (3×20 mL) and dried in an oven at 60 °C.
4
.3. General Procedure for calculating of loading of Pd
First, palladium solutions were prepared with known
concentrations of 2, 4, 6, 8 and 10 ppm. The calibration curve
was plotted according the absorption intensities of standard
solution which recorded by atomic absorption spectrometry.
Next, 5 mg of catalyst was dissolved in 5 mL of HCl and HNO3
(
ratio of HCl/HNO = 3:1 in volume) and was mechanically
3
stirred for 24 h. Finally, the solution diluted with distillated water
in volume of 25 mL and the absorption intensity of catalyst was
recorded. The amount of palladium was determined according
-
1
calibration plot to be 0.14 mmolg .
4
.4. General Procedure for the Suzuki-Miyaura coupling
reaction
Fig. 10. XPS spectrum of the reused catalyst Pd@CQD@Fe
rd run.
3
O
4
NPs after the
Aryl halide (0.5 mmol), arylboronic acid (0.75 mmol), K CO
(104 mg, 0.75 mmol), catalyst (3.6 mg, containing 0.1 mol% Pd)
2
3
3
and EtOH:H O (2 mL, 1:1), were added to a 5 mL flask, and the
2
mixture was stirred mechanically at 30 ºC. The progress of the
reaction was monitored by GC. After completion of the reaction,
the crude product was extracted using ethyl acetate. The pure
products were obtained by column chromatography on silica gel
using hexane and ethyl acetate as eluent.
3
. Conclusions
In conclusion, the prepared CQD using vanillin as a new
cheap and naturally abundant compound, used for modification
of Fe O NPs gave CQD@Fe O NPs, which was able to reduce
3
4
3
4
completely Pd(II) to Pd(0) in a greater extent than the previous
described citric acid derived CQD. This modified CQD@Fe O4
3
5
. Characterizations of products
NPs was used for stabilization of Pd NPs and the obtained solid
was applied as an efficient and magnetically separable
heterogeneous catalyst for the Suzuki-Miyaura reaction of aryl
and heteroaryl bromides at room temperature in aqueous ethanol
and aryl chlorides at 120 °C in PEG 200. The loading of Pd was
much lower than in the already described CQD composite Pd
Nps. This catalyst was recycled up to eight times with small
decrease in its activity and the fresh and recovered catalysts can
be characterized by spectroscopic and microscopic techniques.
21
5
.1. 1,1'-biphenyl (1a):
1
H NMR (400 MHz, CDCl ) δ (ppm): 7.65-7.67 (m, 4H), 7.48-
3
13
7.52 (m, 4H), 7.39-7.43 (m, 2H); C NMR (100 MHz, CDCl ) δ
(ppm): 141.28, 128.80, 127.30, 127.21.
3
21
5
.2. [1,1'-biphenyl]-4-ol (1b):
1
4
. Experimental section
H NMR (400 MHz, CDCl ) δ (ppm): 7.57-7.59 (m, 2H),
3
7
6
.51-7.55 (m, 2H), 7.43-7.47 (m, 2H), 7.33-7.37 (m, 1H), 6.93-
13
.97 (m, 2H), 4.79 (s, 1H); C NMR (100 MHz, CDCl ) δ
3
4
.1. Synthesis of CQD from vanillin as carbon source
(ppm): 155.06, 140.77, 134.08, 128.76, 128.44, 126.76, 126.75,
15.67.
1
Vanillin (0.9 g, 5.9 mmol) was dissolved in ethanol (90 mL)
and the mixture was transferred to an autoclave and heated at 180
C for 12 h. The autoclave was cooled to room temperature and
the obtained material was centrifuged at 10000 rpm for 10 min to
remove larger particles.
21
5
.3. [1,1'-biphenyl]-4-carbaldehyde (1c):
°
1
H NMR (400 MHz, CDCl ) δ (ppm): 10.10 (s, 1H), 7.98-8.01
3
(
2
m, 2H), 7.78-7.81 (m, 2H), 7.66-7.69 (m, 2H), 7.51-7.54 (m,
H), 7.44-7.50 (m, 2H); C NMR (100 MHz, CDCl ) δ
3
13
4
.2. Synthesis of CQD@Fe O4
(ppm):192.01, 147.24, 139.75, 135.20, 130.32, 129.05, 128.51,
27.73, 127.41.
3
1
1
7
Freshly prepared Fe O nanoparticles (0.5 g) were sonicated
3
4
21
5
.4. [1,1'-biphenyl]-3-carbaldehyde (1d):
in water (5 mL) for 15 min. Then, 7 mL of the CQD suspension
was added to the flask containing the magnetic nanoparticles.
The mixture was mechanically stirred for 24 h at 60 °C.
Resulting carbon quantum dots modified Fe O was subjected to
magnetic separation and the obtained material was washed with
deionized water (3×20 mL) and ethanol (3×20 mL) and dried
under vacuum.
1
H NMR (400 MHz, CDCl ) δ (ppm): 10.13 (s, 1H), 8.14-8.15
3
(
m, 1H), 7.89-7.92 (m, 2H), 7.63-7.73 (m, 3H), 7.50-7.54 (m,
3
4
13
2
1
1
H), 7.42-7.50 (m, 1H); C NMR (100 MHz, CDCl ) δ (ppm):
3
92.39, 142.20, 139.72, 136.93, 133.11, 129.53, 129.04, 128.67,
28.24, 128.05, 127.18.
21
5
.5. 4-chloro-1,1'-biphenyl (1e):
3
.3.3. Synthesis of Pd@CQD@Fe O NPs
3 4
1
H NMR (400 MHz, CDCl ) δ (ppm): 7.58-7.64 (m, 2H),
3
CQD@Fe O (500 mg) was sonicated in water (10 mL) for 30
min at room temperature. In another flask PdCl (60 mg, 0.33
mmol) dissolved in water (5 mL). The resulting solution was
added to the flask containing CQD@Fe O and the mixture was
mechanically stirred for 24 h at 60 °C under reflux. Then, the
3
4
13
7
.54-7.58 (m, 2H), 7.41-7.50 (m, 4H), 7.37-7.40 (m, 1H);
C
2
NMR (100 MHz, CDCl ) δ (ppm):140.02, 139.71, 133.80,
3
1
33.40, 128.92, 128.90, 128.42, 127.61, 127.01.
3
4
21
5
.6. [1,1'-biphenyl]-4-carbonitrile (1f):

8
Tetrahedron
1
H NMR (400 MHz, CDCl ) δ (ppm): 7
A
.75
C
-7
C
.7
E
8
P
(m
T
,
E
2H
D
), MA
N
N
MRUS(1
C
00
R
MHz, CDCl ) δ (ppm): 144.40, 137.60, 134.98,
3
IP
T
3
7
7
1
.71-7.74 (m, 2H), 7.61-7.71 (m, 2H), 7.50-7.55 (m, 2H), 7.44-
.50 (m, 1H); C NMR (100 MHz, CDCl ) δ (ppm): 145.70,
39.20, 132.64, 129.15, 128.70, 127.77, 127.27, 119.00, 110.93.
132.74, 129.36, 128.51, 127.61, 118.81, 111.29.
13
3
21
5
.16. 4,4'-dimethoxy-1,1'-biphenyl (1p):
1
21
H NMR (400 MHz, CDCl ) δ (ppm): 7.50-7.52 (m, 4H),
3
13
5
.7. [1,1'-biphenyl]-2-carbaldehyde (1g):
6
.98-7.01 (m, 4H), 3.88 (s, 3H); C NMR (100 MHz, CDCl ) δ
3
1
H NMR (400 MHz, CDCl ) δ (ppm): 10.02 (s, 1H), 8.06-8.08
(ppm):158.70, 133.50, 127.76, 114.17, 55.38.
3
(
m, 1H), 7.66-7.70 (m, 1H), 7.48-7.56 (m, 5H), 7.40-7.47 (m,
21
13
5.17. 4,4'-dichloro-1,1'-biphenyl (1q):
2
1
1
H); C NMR (100 MHz, CDCl ) δ (ppm):192.55, 146.02,
3
1
37.77, 133.73, 133.61, 130.81, 130.14, 128.46, 128.15, 127.81,
27.59.
H NMR (400 MHz, CDCl ) δ (ppm): 7.50-7.53 (m, 4H),
.43-7.46 (m, 4H); C NMR (100 MHz, CDCl ) δ (ppm):138.45,
3
13
7
3
21
133.77, 129.07, 128.24.
5
.8. 4-methoxy-1,1'-biphenyl (1h):
2
1
1
5.18. 4-methoxy-4'-nitro-1,1'-biphenyl (1r):
HNMR (400 MHz, CDCl ) δ(ppm): 7.56-7.62 (m, 4H), 7.45-
3
1
7
.49 (m, 2H), 7.33-7.37 (m, 1H), 7.01-7.05 (m, 2H), 3.90 (s, 3H);
H NMR (400 MHz, CDCl ) δ (ppm): 8.30 (d, J=8.4, 2H),
7.73 (d, J=8.8, 2H), 7.62 (d, J=8.8, 2H), 7.06 (d, J=8.8, 2H),
.91(s, 3H); C NMR (100 MHz, CDCl ) δ (ppm):160.45,
147.24, 131.10, 128.61, 128.60, 127.11, 124.18, 114.63, 55.46.
3
13
C NMR (100 MHz, CDCl ) δ (ppm):159.17, 140.86, 133.81,
3
13
1
28.76, 128.19, 126.77, 126.69, 114.23, 55.38.
3
3
21
5
.9. 5-phenylpyrimidine (1i):
1
HNMR (400 MHz, CDCl ) δ(ppm): 9.25 (s, 1H), 9.0 (s, 2H),
3
13
7
1
.63-7.51 (m, 5H); C NMR (100 MHz, CDCl ) δ 157.15,
3
Acknowledgments
54.92, 134.51, 134.11, 129.52, 129.17, 127.05.
2
1
5
.10. 5-phenyl-1H-indole (1j):
The authors are grateful to Institute for Advanced Studies in
Basic Sciences (IASBS) Research Council and Iran National
Science Foundation (INSF-Grant number of 94010666) for
support of this work. C. Nájera is also thankful to The Spanish
Ministerio de Economia y Competitividad (MINECO) (projects
CTQ2013-43446-P and CTQ2014-51912-REDC), FEDER, the
Generalitat Valenciana (PROMETEOII/2014/017) and the
University of Alicante for financial support.
1
H NMR (400 MHz, CDCl ) δ (ppm): 8.17 (s, 1H), 7.93 (s,
H), 7.71-7.73 (m, 2H), 7.49-7.54 (m, 4H), 7.38-7.40 (m, 1H),
.32-7.36 (m, 1H), 6.66-7.68 (m, 1H); C NMR (100 MHz,
CDCl ) δ (ppm):142.59, 135.34, 133.47, 128.70, 128.43, 127.45,
3
1
7
13
3
1
26.37, 124.90, 121.97, 119.31, 111.29, 103.07.
21
5
.11. 3',5'-difluoro-[1,1'-biphenyl]-4-carbonitrile (1k):
1
H NMR (400 MHz, CDCl ) δ (ppm): 7.78-7.80 (m, 2H),
3
References and notes
1
3
7
.67-7.70 (m, 2H), 7.11-7.17 (m, 2H), 6.88-6.93 (m, 1H);
C
NMR (100 MHz, CDCl ) δ (ppm):164.74, 164.62, 162.27,
1.
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3
1
1
1
62.14, 143.24, 143.21, 143.19, 142.48, 142.39, 142.29, 132.86,
27.75, 118.51, 112.25, 110.42, 110.35, 110.23, 110.16, 104.23,
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1
1
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.12. 3'-nitro-[1,1'-biphenyl]-4-carbonitrile (1l):
1
H NMR (400 MHz, CDCl ) δ (ppm): 8.49-8.50 (m, 1H),
3
2
.
8
7
(
.31-8.34 (m, 1H), 7.95-7.97 (m, 1H), 7.83-7.85 (m, 2H), 7.76-
.79 (m, 2H), 7.70-7.74 (m, 1H); C NMR (100 MHz, CDCl ) δ
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23.37, 122.18, 118.43, 112.43.
13
3
1
1
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5
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H NMR (400 MHz, CDCl ) δ (ppm): 8.09 (br, 1H), 7.98-8.00
3.
3
(
2
m, 1H), 7.91-7.97 (m, 2H), 7.84-7.86 (m, 2H), 7.79-7.81 (m,
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3
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2
23
5
.14. 3,4'-dinitro-1,1'-biphenyl (1n):
4
5
.
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H NMR (400 MHz, CDCl ) δ (ppm): 8.53-8.54 (m, 1H),
3
8
7
(
.39-8.42 (m, 2H), 8.33-8.34 (m, 1H), 7.98-8.02(m, 1H), 7.82-
.85 (m, 2H), 7.72-7.76 (m, 1H); C NMR (100 MHz, CDCl ) δ
ppm): 148.88, 147.93, 144.87, 140.47, 133.23, 130.29, 128.13,
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2
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.15. 4'-chloro-[1,1'-biphenyl]-4-carbonitrile (1o):
2
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3
1
3
7
.67-7.69 (m, 1H), 7.54-7.57(m, 1H), 7.46-7.50 (m, 1H);
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1
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