Carbon dot reduced palladium nanoparticles as active ... · Carbon dot reduced palladium nanoparticles as active catalysts for carbon-carbon bond formation Deepa Dey*, Tamalika Bhattacharya,

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Supporting Information for

Carbon dot reduced palladium nanoparticles as active catalysts for carbon-carbon bond formation Deepa Dey*, Tamalika Bhattacharya, Biju Majumdar, Sonam Mandani, Bhagwati Sharma and Tridib K Sarma* Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore, IET Campus, DAVV, Khandwa Road, Indore 452017, India.

1. Experimental Section:

Materials

The cow milk from Sanchi (Indore, Madhya Pradesh) was the source of clotted cream. All the other chemicals were purchased from Sigma Aldrich or Alfa Aesar and were used without further purification. We used Millipore water (ultrapure level) throughout the experiments.

Synthetic Methods

Preparation of C-dots

Carbon dots (C-dots) were synthesised starting from clotted cream. The source of clotted cream was cow milk. The milk was first heated to about 80 oC for half an hour. On cooling to room temperature, a thick layer of fat and coagulated proteins was formed known as clotted cream or malai in India. Butter was obtained by blending the clotted cream and was washed three four times with cold water. The butter was then simmered on medium heat until a clear yellow liquid starts coming out. The yellow liquid (butter oil or Ghee in India) was drained off and the crude brown residue was collected in gram amount. The carbon dots could be easily extracted by dispersing the crude residue in hot water. Most of the crude residues could be dispersed in water with a small amount of undissolved residues remaining at the bottom of the beaker. Upon separation, the C-dot containing aqueous solution showed pale brown colour in daylight and blue fluorescence on irradiation with UV light at 365 nm. The lyophilized carbon dots exhibited yellow fluorescence in solid state while exposed to 365 nm UV light. The carbon dots showed excellent dispersibility in organic solvents also. As obtained aqueous C-dots were employed for the synthesis of Pd nanoparticles.

Synthesis of Pd@C-dots

In a typical synthesis, a mixture of 7.5 mL of 10 mM H2PdCl4 solution and 100 mL of aqueous solution of C-dots (100mg/100mL H2O, crude C-dots dispersed in hot water) were refluxed at 100oC with stirring in an oil bath. It is noteworthy to mention that we did not use any other stabilizing agent during the reaction. The colour of the solution turned from pale

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brown to black after 6 hours signifying the formation of Pd nanoparticles. The nanoparticles were centrifuged and washed for several times to remove the excess metal salts and unbound C-dots.

For synthesizing the Pd@C-dot-PVP composite, 50 mg of Pd@C-dot was dispersed in 50 ml of water and to it 10 mg of PVP was added (PVP mol. wt. 40000). The reaction was carried for 1 hour at room temperature, after which excess PVP was removed by centrifugation and repeated washing. The amount of Pd@C-dots in the composite was measured using thermo gravimetric analysis (TGA).

Suzuki Coupling

All reactions were run under air atmosphere. In a typical experiment, first, a quantitative amount of Pd@C-dot (1.6 mg, 0.5 mol% with respect to aryl boronic acids) or Pd@C-dot-PVP (0.5 mol% with respect to aryl boronic acids) was dispersed in 5 ml of water. To this 1.0 mmol of phenylboronic acid, 0.7 mmol of bromobenzene and 3 equivalent of 0.5 M KOH solution were added. The reaction was carried out at 60 °C with stirring. The extent of reaction was monitored by TLC (thin layer chromatography) and 1H NMR. After cooling to room temperature, the reaction mixture was extracted in ethyl acetate. Purification by column chromatography (silica gel/ethyl acetate/hexane) gave the desired products as confirmed by 1H and 13C NMR spectroscopy.

Heck Coupling

In a typical experiment, to a aqueous solution containing Pd@C-dot or Pd@C-dot-PVP (0.5 mol% with respect to styrene) was added aryl iodide (1.0 mmol), styrene or substituted styrene (1.2 mmol) and K2CO3 (2.0 equiv.). The reaction was carried out at 40 °C with stirring and the extent of the reaction was monitored by TLC and 1H NMR. After cooling to room temperature, the reaction mixture was extracted in ethyl acetate. Purification by column chromatography (silica gel/ethyl acetate/hexane) gave the desired products.

Catalyst recyclability studies

After extracting the reaction mixture by ethyl acetate several times, the aqueous solution containing Pd-C-dots-PVP were used further for another cycle for estimating the activity of the catalysts. For evaluating the structural morphology of the recycled catalysts, aqueous solution containing the catalyst was centrifuged and washed with water for several times. The structural characteristics of the recycled catalyst was evaluated by TEM and XPS studies.

Instrumentation and Characterisation

The powder XRD measurements were carried out using Bruker D8 Advance X-ray diffractometer with Cu K source (wavelength of X- rays was 0.154 nm). TEM images were obtained using a JEM-2100 microscope operated at 200 kV. Atomic force microscopy of C-dots (Tapping mode, SMART SPM 10000, AIST-NT) were analysed by spin coating the aqueous solution of C-dots on freshly cleaved mica surface. The Fourier transform infrared spectroscopy (FTIR) spectra were measured by Bruker Tensor-27 spectrometer with KBr


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pellet. UV-visible measurements were performed using a Varian Cary 100 Bio spectrophotometer. Emission spectra were taken in a fluoromax-4p fluorimeter from HoribaYovin (model: FM-100). The samples were excited at different excitation wavelength ranging from 310 to 520 nm. The time resolved fluorescence studies was performed on Horiba Yovin (model: Fluorocube-01-NL), a nanosecond time correlated single photon counting (TCSPC) system. 1H and 13C NMR spectra were recorded on a Bruker Advance (III) 400 MHz spectrometer. Data for 1H NMR are reported as a chemical shift (δ ppm), multiplicity (s = singlet, d = doublet, q = quartet, m = multiplet), coupling constant J (Hz), integration, and assignment, data for 13C are reported as a chemical shift. ICP-AES measurements were performed using instrument from M/s. Spectro, Germany (Model : Arcos). XPS spectra were recorded using an ESCA instrument: VSW of UK make.

2. Structural Characterization of C-dots and Pd@C-dots

Stability of C-dots at different solution pH:

The stability of the C-dots prepared by our method was studied by varying pH of the medium and studying their fluorescence emission properties. It was observed that at different pH the emission peak remained at nearly same position. (λex = 340 nm, λem = 432 nm). However the intensity of emission varied with pH. The C-dots showed maximum intensity in the pH range of 5-7, however the intensity decreased at lower or higher pH as shown in Figure S1.

Fig. S1. (a) Fluorescence spectra of C-dots in aqueous solution with pH 2 (black), 5 (yellow), 6.5 (red), 8 (green) and 10(blue). (b) Fluorescence Intensity versus pH of C-dots.

As observed from the Fig. S1, the pH value of the solution affected the fluorescence intensity of the C-dots. A declining trend in the fluorescence intensity of the C-dots was observed upon changing from neutral to either acidic (pH= 2, 59% ) or basic (pH = 10, 69 %) solution. However, there is no shift in the fluorescence peak with change in pH. Although the

70x103

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50

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012108642

pH

Fluo

resc

ence

Inte

nsity

(b)70x103

60

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650600550500450400350

Wavelenghth (nm)

Fluo

resc

ence

Inte

nsity (a)


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mechanism of this behaviour is not understood, this pH dependent property could be exploited for molecular sensing.

In different solvents:

Fig. S2. Digital images of C-dots dispersed in (1) acetonitrile (2) ethylacetate (3) N, N-dimethylformamide (4) hexane (5) ethanol and (6) chloroform illuminated under UV light (365 nm).

Chemical composition

The chemical composition of the purified C-dots obtained after dispersion in water (C, 31.35 %; H, 4.15 %; N, 1.915 % and O, 33.9 %) was vastly different from that of the crude C-dots (C, 53.53 %; H, 8.1267 %; N, 7.1086 % and O, 18.79 %), having higher content of oxygen. The decrease in the C/O ratio for purified C-dots was also justified from the FTIR (Fig. S3) with decrease in the intensity of the peaks in the 2900-2700 cm-1region.

Table S1. Elemental composition of crude and purified C-dots.

Element C H O N Adsorbed water C/O ratio

Wt % of crude C-dot 53.53 8.13 18.79 7.11 12.44 7.6 Atom ratio 4.46 8.1267 0.587 0.51 0.69 Wt % of pure C-dot 31.35 4.15 33.9 1.92 28.69 2.5 Atom ratio 2.61 4.15 1.06 0.14 1.59

Quantum Yield of C-dots

Quantum yield of C-dots at an excitation wavelength of 340 nm was calculated using the following equation

Φ = ΦR× I/IR × ODR/OD × ƞ2/ ƞR2

Where Φ and I are the quantum yield and measured integrated emission intensity, ƞ refractive index and OD the optical density. The subscript R refers to the reference fluorophore (Quinine sulphate, ΦR = 0.54) of known quantum yield. The quinine sulphate was dissolved in 0.1 M H2SO4 and C-dot was dissolved in Millipore water (ƞ = 1.33).


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Table S2:

FTIR Studies

Fig. S3. FTIR spectra of (a) solid crude C-dot synthesized by caramelization of clotted cream (b) C-dot (powder obtained by drying aqueous C-dot) (c) Pd@C-dot.

In general, C-dot samples consist of covalently attached oxygen-containing groups such as hydroxyl, carbonyl and carboxy groups. The FTIR spectrum of C-dots illustrates the characteristic features including stretching vibrational peak of O-H groups centred at 3430 cm-1, the C=O stretching vibrational peak in carboxyl and carbonyl at 1720 and 1770 cm-1 , deforming peaks of O-H groups at 1420 cm-1 and the C-O (alkoxy) stretching vibration at 1060 cm-1. The peak at 1625 cm-1 is assigned to C=C skeletal vibrations of un-oxidized graphitic domains. The peaks at 2850-2930 cm-1 corresponds to C-H stretching vibration. As observed from the FTIR spectra (Fig. S3), the crude C-dot solids as separated from butter oil showed strong peak in the region 2850-2930 cm-1 along with C=O stretching peak at 1720

Substance Absorbance at 340 m

Area Refractive Index Quantum Yield

Quinine sulphate 0.0897 5.5657 × 107 1.33 0.54(Ref.) C-dot 0.09748 1.6269 × 106 1.33 1.4 (calculated)

4000 3500 3000 2500 2000 1500 1000

Wavenumber (cm-1)

% T

rans

mitt

ance

(a. u

.)

a

b

c


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cm-1 showing high content of carbon (graph a, black). With the dispersion of the C-dots in water, the -OH vibrational peak at 3430 cm-1 becomes sharper and the vibrational peak in the region 2850-2930 cm-1 becomes weaker, signifying the presence of hydration layer around the C-dots (graph a, blue). In case of Pd@C-dot composites (graph c, red) the FTIR spectra showed some interesting illustrations: the C=O stretching peak of carboxyl and carbonyl at 1720 and 1770 cm-1 of C-dots decreased dramatically and almost entirely disappeared when they were involved in Pd2+ reduction. Further, the C-O (alkoxy) stretching vibration at 1060 cm-1 reduced to some extent, signifying the involvement of the carboxyl and carbonyl groups in the reduction process and subsequent action as a stabilizing agent where the metal surface is bound to the carboxylic moieties by coordination reactions.

Time-resolved Fluorescence Measurements:

For the time-resolved studies, we used a TCSPC system from Horiba Yovin (Model: Fluorocube-01-NL). The samples were excited at 375 nm using a picosecond diode laser (Model: Pico Brite-375L). The repetition rate was 5 MHz. The signals were collected at magic angle (54.70) polarization using a photomultiplier tube (TBX-07C) as detector, which has a dark counts less than 20 cps. The instrument response function is 150 ps. The data analysis was performed using IBH DAS (version 6, HORIBA Scientific, Edison, NJ) decay analysis software. The generated curve for intensity decay was fitted in the function

)exp()(ii

ittI

Where i is the initial intensity of the decay component i, having a life time of i . The mean lifetime of the excited state is given by:

i

n

iif

1

where if are defined by the equation:

jij

iiif

Table S3: Life-time data obtained using the bi-exponential model for the C-dots

Value χ2 τ1 1.97 x 10-9

1.08 τ2 7.18 x 10-9 α1 (%) 74 α2 (%) 26


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.Structural studies of C-dots and Pd@C-dots

Fig. S4. TEM image of C-dots in water and corresponding SAED pattern.

Fig. S5. HRTEM image of Pd@C-dot nanoparticles and corresponding SAED pattern.


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Structural studies of Pd@C-dot-PVP after first reaction cycle.

Fig. S6. (A) TEM image; scale bar 20 nm (B) HRTEM image, scale bar 10 nm and (C) particle size distribution of Pd@C-dot nanoparticles after 1st reaction cycle.

Fig. S7. (A) The XPS spectrum of (a) C-dots (b) Pd@C-dots nanoparticles. (B) High resolution XPS spectra of C 1s region of Pd@C-dot nanoparticles after 1st cycle of Suzuki coupling reaction.

292290288286284282

Binding energy (eV)

Cou

nts S

-1

C-C C-OHC=O

COOH

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) A B C

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nts S

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C 1sO 1s

a

b

A


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3. Pd catalysed Suzuki and Heck coupling reactions

Table S5. Suzuki-Miyaura coupling of aryl bromides with Pd@C-dot catalysta in water

aReaction conditions: aryl bromide (0.7 mmol), aryl boronic acid (1.0 mmol), Pd catalyst (mol% with respect to aryl boronic acid), base (3.0 equiv.), water (5 ml). bIsolated product, cproduct obtained after 4 hours, reaction did not proceed further and the catalyst was precipitated.

Entry Catalyst Catalyst Base Time (h) Temp. Yieldb (%) Loading (°C) (mol%)

1 Pd@C-dot 0.5 K2CO3 10 25 < 3

2 Pd@C-dot 1 K2CO3 10 25 < 3

3 Pd@C-dot 0.5 KOH 10 25 12

4 Pd@C-dot 1.0 KOH 10 25 25

5 Pd@C-dot 3 KOH 10 25 42

6 Pd@C-dot 0.5 KOH 10 40 22c

7 Pd@C-dot 0.3 KOH 10 60 30c

8 Pd@C-dot 0.5 KOH 10 60 45c

9 Pd@C-dot-PVP 0.3 KOH 6 25 24

10 Pd@C-dot-PVP 0.5 KOH 6 25 46

11 Pd@C-dot-PVP 0.3 KOH 6 40 36

12 Pd@C-dot-PVP 0.5 KOH 6 40 68

13 Pd@C-dot-PVP 0.3 KOH 6 60 58

14 Pd@C-dot-PVP 0.5 KOH 6 60 95


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Scheme S1. Suzuki-Miyaura coupling of benzyl bromide with thiophene boronic acid.

S

B(OH)2 Br Pd@C-dots-PVPH2O, KOH60 oC

S

Isolated Yield = 68%

Reaction conditions: aryl bromide (0.7 mmol), thiopheneboronic acid (1.0 mmol), Pd catalyst (0.5 mol%), base (3.0 equiv.), water (5 ml).

Table S6. Recyclability test of bromobenzene with phenylboronic acid at 60 °C; Pd catalyst (0.5 mol%).

Entry Time Conversion (%)

1st 6 95

2nd 6 86

3rd 8 84

4. Preliminary study of the reaction mechanism via Pd-leaching experiment:

Pd nanoparticles are usually considered as heterogeneous catalysts for organic transformations. However for Suzuki and Heck coupling reactions, this notion has been challenged by several groups in recent years.1 They have proposed that commonly used Pd catalysts such as Pd/C, Pd-PVP etc. are “quasi-heterogeneous” in nature where leached Pd catalyzes the reaction and re-adsorbs onto the support after the completion of the reaction. In order to study the reaction mechanism for the Pd@C-dot nanoparticle catalysis, we carried out the model reaction of 4-methyl phenylboronic acid (5 mmol) with bromobenzene (3.5 mmol) in presence of KOH (10 mmol) in water (30 ml). For this, two individual experiments were conducted (i) in presence of Pd@C-dot-PVP catalyst throughout the reaction, (ii) removing the catalyst after 1 hour by centrifugation. After the addition of the catalyst (0.5 mol%), the reaction temperature was raised to 60 C and the reaction was monitored with time using HPLC. As observed in case of (i), the reaction yield was 94% after 6 hours. In the case (ii), the reaction was stopped after 1 hour, when the conversion of the product was 30% and the Pd@C-dot-PVP catalyst was precipitated out by using a high speed centrifuge (centrifuged for 15 minutes at 18000 rpm, Kobuta Model 6500). The precipitated catalysts were separated from the reaction medium very carefully. This process was repeated for three times after which we assumed that all the solid catalysts were removed from the aqueous solution. When the reaction was carried out further in stirring conditions at 60 C in absence of the solid catalysts, it was observed that there was 82% conversion after 9 hours. As shown in Fig. S8, the Suzuki reaction continued even after the removal of the catalysts from the reaction medium. The results suggest that the coupling reaction may be catalysed largely by Pd species in the reaction solution (presumably homogeneous leached molecular species).


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Based on these findings, Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was employed on the reaction mixtures in order to further confirm the presence of Pd in the reaction solution. For this, the reaction mixtures, after removal of the Pd@C-dot-PVP catalyst and the product, were evaporated until completely dry, treated with aqua regia solution for 1 hour and diluted by water. The ICP-AES analyses (table S6) indicated that less than 1 ppm leached Pd existed in the reaction medium in both conditions (i) and (ii) after the removal of the Pd@C-dot-PVP catalyst by centrifugation. The results suggested that (a) Pd-leaching did occur and (b) the Suzuki reaction may be catalysed by the minute amount of soluble Pd active species as reported for other nanoparticle based systems.

However, there may be very small amount of Pd@C-dot-PVP catalyst remain in the solution, even after centrifugation for several times and interfere with these experiments. We confirmed the stability of the recycled nanoparticles by XPS measurements.

Table S6: Leached Pd amount determined by ICP

Experimental method Pd in reaction solution, μg/ml (ppm)

Case (i) Pd@C-dot-PVP catalyst throughout the reaction and removed by centrifugation after the completion of the reaction

0.09

Case (ii) Pd@C-dot-PVP catalyst was removed by centrifugation after 1 hour, after which the reaction continued for another 8 hours.

0.06

Fig. S8. Formation of p-methylbiphenyl as a function of time under standard conditions ( ) and removal of Pd@C-dot-PVP catalyst after 1 hour ( ).

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1086420

Removed Pd@C-dot-PVP

Reaction time, h

Prod

uct y

ield

, %

Regular Removed catalyst


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5. Comparison with the other Pd nanoparticle catalytic systems:

In order to have an idea about the efficiency of the Pd@C-dot nanoparticle catalytic system, we compared a few Suzuki and Heck coupling reaction with Pd-PVP and Pd/C, two commonly used nanoparticle based catalytic systems.

Synthesis of Pd-PVP nanoparticles: First, 0.10 ml of a 10.0 mM potassium tetrachloropalladate solution was added to 10.0 ml of deionized water with stirring. Next, 0.28 ml of a 1.0 mM PVP (M. W. 40,000) solution was added. This mixture was then stirred for 15 minutes at room temperature in air. Finally, 0.10 ml of a fresh 0.10 M sodium borohydride solution was added to give a brown solution which is typical of Pd nanoparticles. By TEM experiments, the particle size was found to be 3.1 ± 1.1 nm. Pd/C nanoparticles were purchased from Aldrich (5wt%, Degussa type, particle size 28~34 μm).

Table S9: Suzuki and Heck coupling reactions catalysed by Pd@C-dot-PVP, Pd-PVP and Pd/C catalysts in water.

Substrate Catalyst Catalyst loading (mol%)

Reaction conditionsa Yieldb (%)

Pd@C-dot-PVP

0.3 mol% KOH, 60 °C, water, 6 h 58%

Pd-PVP 0.3 mol% KOH, 60 °C, water, 6 h 95%

Pd/C 0.3 mol% KOH, 60 °C, water, 2 h 97%

B(OH)2 Br

+

OCH3

Pd@C-dot-PVP

0.3 mol% KOH, 60 °C, water, 6 h 49%

Pd-PVP 0.3 mol% KOH, 60 °C, water, 6 h 84%

Pd/C 0.3 mol% KOH, 60 °C, water, 2 h 91%

B(OH)2 I

+

Pd@C-dot-PVP

0.3 mol% K2CO3, 40 °C, water, 8 h 56%

Pd-PVP 0.3 mol% K2CO3, 40 °C, water, 8 h 90%

Pd/C 0.3 mol% K2CO3, 40 °C, water, 4 h 93%

aReaction conditions: aryl halide (0.7 mmol), aryl boronic acid (1.0 mmol), base (3.0 equiv.), water (5 ml). bIsolated product,

From the results, it is clearly evident that C-dot coating on the Pd nanoparticles have an inhibiting effect on the activity of the Pd nanoparticles. Although a detailed mechanistic study will be required to establish the effect of carbon dots, we believe that the following factors are also contributing to the lower catalytic activity of our catalytic system:

(i) The size of the Pd nanoparticles synthesized using C-dots had an average diameter of 12.4 ± 4.3 nm, which was higher compared to Pd-PVP or Pd/C nanoparticles. As studied extensively, the

B(OH)2 Br

+


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catalytic capability enhances with reduced diameter of the nanoparticles, due to enhanced surface area.

(ii) From the leaching experiments it was observed that Pd active species present in the solution (homogeneous) might play a major role in catalysis during the Suzuki and Heck coupling reactions. As C-dots can act as a reducing agent themselves under the present reaction conditions, they might influence the amount of Pd2+ ions released in the reaction medium.

Fig. S9 TEM image of Pd nanoparticles synthesized in presence of poly(N-vinyl-2-pyrrolidone) (PVP); scale bar 20 nm.


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6. Characterisation of the reaction products

1. Biphenyl: 1H NMR (CDCl3): 7.50-7.48 (dd, 4H, JHH = 8Hz), 7.36-7.31 (dd, 4H, J1 =4Hz), 7.26-7.24 (d, 2H, J2=8Hz) 13C NMR (CDCl3):141.25, 128.76, 127.26, 127.18.


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2. 4-Methyl biphenyl: 1H NMR (CDCl3: 7.56-7.54 (d, 2H, JHH = 8Hz), 7.47-7.45 (d, 2H, JHH

= 8Hz), 7.40-7.37 (t, 2H, JHH = 8Hz), 7.30-7.28 (d, 2H, JHH = 12Hz), 7.22-7.20 (d, 2H, JHH = 8Hz), 2.36 (s, 3H). 13C NMR (CDCl3): 140.86, 138.05, 136.67, 131.23, 129.71, 129.16, 128.39, 126.67, 20.77.


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3. 4-Ethyl biphenyl: 1H NMR (CDCl3): 7.71-7.69 (d, 2H, JHH = 8Hz), 7.59-7.57 (d, 2H, JHH = 8Hz), 7.53-7.5(d, 2H, JHH = 8Hz), 7.34-7.32(d, 2H, JHH = 8Hz), 2.73-2.67 (q, 2H, JHH = 8Hz)

13C NMR (CDCl3): 149.54, 143.71, 141.52, 136.14, 129.03, 128.55,127.93, 127.34, 28.85, 15.76.


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4. 4, 4'-Vinyl biphenyl: 1H NMR (CDCl3): 8.19-8.17 (d, 2H, JHH = 8Hz), 7.54-7.52 (d, 2H, JHH = 8Hz), 6.84-6.77 (q, 2H), 5.93-5.88 (d, 2H), 5.40-5.37 (d, 2H) 13C NMR (CDCl3):154.75, 129.03, 128.61, 127.41, 127.34, 113.93.


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5. 4-Biphenyl carboxaldehyde: 1H NMR (CDCl3) : 9.93 (s, 1H), 7.92 (d, 2H), 7.65 (d, 2H), 7.48-7.19 (m 5H) 13C NMR :197.13, 137.60, 137.60, 137.27, 137.59, 133.29, 132.24, 130.08, 127.8

CHO


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6. 4-Methoxy-(4’-methyl)-biphenyl: 7.42-7.34 (m, 4H), 7.14-7.12 (d, 1H), 6.85-6.88 (m, 2H), 6.68-6.66 (m, 2H), 3.74 (s, 3H), 2.28 (s, 3H) 13C NMR (CDCl3): 158.88, 136.33, 129.42, 127.93, 126.55, 116.01, 114.15, 55.31, 21.02

OMe


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7. 4-Methoxy biphenyl: 1H NMR (CDCl3) 7.57-752 (m, 4H), 7.49-7.40 (m, 2H), 7.32-7.30 (m, 2H), 6.99-6.97 (m, 2H), 3.66 (s, 3H) 13C NMR (CDCl3): 159.16, 134.23, 129.05, 128.50, 128.07, 127.08, 126.99, 55.69.

MeO


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8. 4-Methoxy-(4’-nitro)-biphenyl: 1H NMR (CDCl3) :7.47-7.44 (d, 2H), 7.34-7.32 (d, 2H), 7.23-7.16 (d, 2H), 6.92-6.80 (dd, 2H), 3.74 (s, 3H). : 13C NMR: 159.89, 140.57, 133.53, 128.42, 127.86, 127.45, 113.94, and 55.06.

MeO

NO2


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9. 2-Phenylthiophene: 1H NMR (CDCl3) 8.04-8.03 (d, 1H), 7.81-7.79 (d, 1H), 7.65-7.56 (dd, 2H), 7.32-7.30 (t, 1H), 7.21-7.19 (t, 1H)

S


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10. Stilbene: 1H NMR (CDCl3): 7.53-7.51 (d, 4H), 7.38-7.34 (t, 4H), 7.24 (t, 2H), 7.12 (s, 2H); 13C NMR (CDCl3): 137.45, 130.21, 128.66, 127.42, 126.50


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11. 4-Methylstilbene: 1H NMR (CDCl3): 7.43-7.41 (d, 2H), 7.34-7.32 (d, 2H), 7.16-7.15 (d, 1H), 7.16-7.15 (d, 1H), 7.09-7.07 (d, 2H), 6.99 (d, 2H). 13C NMR (CDCl3): 137.18, 137.13, 134.21, 129.87, 129.04, 128.29, 127.36, 127.04, 126.05, 126.08, 20.89.


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12. 4-Methoxystilbene: 1H NMR (CDCl3): 7.59-7.57 (dd, 2H), 7.39-7.33 (dd, 2H), 7.23-7.20 (m, 2H), 6.99-6.95 (t, 3H), 6.80-6.78 (d, 2H) 13C NMR (CDCl3): 158.91, 137.07, 131.59, 129.85, 128.25, 127.82, 127.34, 127.07, 126.82, 125.87, 113.75, 54.90

MeO


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13. 4 -Chlorostilbene: 1H NMR (CDCl3): 7.43-7.41 (d, 2H), 7.36-7.34 (d, 2H), 7.30-7.26 (t, 2H), 7.25-7.19 (m, 3H), 6.98 (d, 2H) 13C NMR (CDCl3): 136.65, 135.34, 130.59, 129.14, 128.99, 128.51, 128.51, 128.41, 127.34, 127.03, 126.23.

Cl


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References:

1. (a) D. A. Conlon, B. Pipik, S. Ferdinand, C. R. LeBlond, J. R Sowa, Jr., B. Izzo, P. Clooins, G. J. Ho, J. M. Williams, Y. J. Shi, and Y. K. Sun, Adv. Synth. Catal. 2003, 345, 931; (b) F. Zhao, B. M. Bhanage, M. Shirai and M. Arai, Chem. Eur. J. 2000, 6, 843; (c) N. T. S. Phan, M. Van Der Sluys and C. W. Jones, Adv. Synth. Catal. 2006, 348, 609; (d) C. Yang, A. K. Manocchi, B. Lee and H. Yi, J. Mater. Chem. 2011, 21, 187.


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Carbon dot reduced palladium nanoparticles as active ... · Carbon dot reduced palladium nanoparticles as active catalysts for carbon-carbon bond formation Deepa Dey*, Tamalika Bhattacharya,