New Journal of Chemistry Supporting Information Facile ... · Sonal Guptaab and Asit Patra*ab...
Transcript of New Journal of Chemistry Supporting Information Facile ... · Sonal Guptaab and Asit Patra*ab...
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New Journal of Chemistry
Supporting Information
Facile polymerization method for poly(3,4-ethylenedioxythiophene)
and related polymers using iodine vapour
Sonal Guptaab and Asit Patra*ab
aPhotovoltaic Metrology Section, Advanced Materials & Device Metrology Division, CSIR-National Physical
Laboratory, Dr. K. S. Krishnan Marg, New Delhi-110012, India bAcademy of Scientific and Innovative Research (AcSIR), Ghaziabad- 201002, India
Note added after first publication
This supporting information replaces the version published on 18th September 2019, which contained errors in Fig. S1(a).
Table of content
1. Synthesis of monomers………………………………………..S2
2. General procedure for dedoping of polymers………………..S5
3. Preparation of polymer films for UV-vis measurement……..S5
4. Sample preparation procedure for GPC……………………..S6
5. Proposed mechanism of the polymerization………………….S6
6. NMR, GPC, UV-vis, FT-IR and CV data……………… …...S7
7. References………………………………………………… …S16
Electronic Supplementary Material (ESI) for New Journal of Chemistry.This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2020
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1. Synthesis of monomers
Monomers 2,5-dichloro-3,4-ethylenedioxythiophene (DCEDOT)1, 2,5-dibromo-3,4-
ethylenedioxythiophene (DBEDOT)1, 2,5-diiodo-3,4-ethylenedioxythiophene (DIEDOT)1, 2,5-
dibromo-3,4-propylenedioxythiophene (DBProDOT)2, DBEDOT-C63, and DBEDOT-C8
3 were
prepared by previously reported method.
Synthesis of 2,5-dibromo-3,4-propylenedioxythiophene (DBProDOT; M3)
OO
S
ProDOT
S
MeO OMe OH OH
PTSA
Toluene
NBS
CHCl3
OO
S
DBProDOT
BrBr
56% 91%
Synthesis of ProDOT. To a well stirred solution of 3,4-dimethoxythiophene (1.0 g, 6.9 mmol) in dry
toluene (50 mL) was added 4 equivalents of propane-1,3-diol and followed by p-toluenesulphonic
acid (PTSA) (80 mg). The resulting reaction mixture was allowed to stir for 48 hours at 100 °C with
under N2 atmosphere. The resulting mixture was diluted with 100 mL H2O and extracted with ether
(3× 50 mL). The combined organic extracts were washed with brine, dried over Na2SO4. After that,
solvent was evaporated and purified by the column chromatography to produce ProDOT in 56%
yield (600 mg). UV-vis (hexane) 𝜆max at 250 nm, 1H NMR (600 MHz, CDCl3) δ 6.51 (s, 2H), 4.06 (t,
J=5.4 Hz, 4H), 2.18 (t, J=5.4 Hz, 2H), 13C NMR (150 MHz, CDCl3) δ 150.8, 106.5, 71.3 and 33.9.
Synthesis of DBProDOT (M3). To a well stirred solution of ProDOT (300 mg, 1.92 mmol) in 20
mL dry CHCl3 at 0 °C, was added 2 equivalents of n-bromosuccinimide (NBS) in small portions. The
resulting reaction mixture was allowed to stir for 1.0 hour at room temperature. The reaction mixture
was diluted with 30 mL H2O and extracted with chloroform (3× 25 mL) and dried over Na2SO4. The
solvent was evaporated under reduce pressure and purification was carried out by column
chromatography. The compound DBProDOT was obtained in 91% yield (550 mg) as a white solid.
UV-vis (hexane) 𝜆max at 253 nm; 1H NMR (500 MHz, CDCl3) δ 4.16 (t, J=5.0 Hz, 4H), 2.28-2.22 (m,
2H).
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Synthesis of 2,5-diiodo-3,4-propylenedioxythiophene (DIProDOT; M4)
OO
S
CH3COOH, Hg(OAc)2
20°C
I2
CH3CNAcOHg HgOAc
ProDOT 1 DIProDOT
OO
SII
OO
S
75% 48%
Synthesis of 2,5-diacetoxymercuri-ProDOT (1). To a well stirred solution of ProDOT (1.0 g, 6.4
mmol) in acetic acid (60 mL) at 20 °C, was added drop-wise a solution of mercury (II) acetate
[Hg(OAc)2] (4.085 g, 12.8 mmol) in acetic acid (100 mL) over 2 hours. The resulting reaction
mixture was allowed to stir for 12 hours. A white precipitate was appeared and resulting precipitate
was filtered and washed with methanol followed by diethyl ether. The filtered product was dried
under vacuum to give 1 as a white solid (3.25 g, 75%). Without further characterization, the
compound was used for next step.
Synthesis of DIProDOT (M4). To the stirred solution of 1 (3.25 g, 4.7 mmol) in acetonitrile (250
mL), was added drop-wise a solution of iodine (2.43 g, 9.6 mmol) in acetonitrile (200 mL). A
yellow-orange colored solution was obtained. After concentration of the resulting solution, saturated
solution of potassium iodide was added. The combined resulting mixture was diluted with 100 mL
H2O, extracted with chloroform (3×50 mL) and finally dried over Na2SO4. The organic solvent was
evaporated and purification was carried out by column chromatography. The compound DIProDOT
was obtained in 48% yield (90 mg) as a light brown colored solid. UV-vis (hexane) 𝜆max at 328 nm;
1H NMR (500 MHz, CDCl3) δ 4.09 (t, J=5.0 Hz, 4H), 2.20-2.16 (m, 2H).
Synthesis of hexyl-2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT-C6; M5)
OO
S
C6H13
S
MeO OMe
PTSA
Toluene
NBS
CHCl3
HO OH
C6H13
OO
S
C6H13
BrBr
EDOT-C6 DBEDOT-C668% 89%
Synthesis of EDOT-C6. To a well stirred solution of 3,4-dimethoxythiophene (420 mg, 2.92 mmol)
in dry toluene (20 mL) was added 4 equivalents of 1,2-octanediol and followed by p-
toluenesulphonic acid (PTSA) (50 mg). The resulting reaction mixture was allowed to stir for 30
hours at 100 °C with under N2 atmosphere. The resulting mixture was diluted with 100 mL H2O and
extracted with ether (3× 50 mL). The combined organic extracts were washed with brine, dried over
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Na2SO4. After that, solvent was evaporated under reduce pressure and purified by the column
chromatography. The pale yellow oily liquid EDOT-C6 was obtained in 68% yield (448 mg). UV-vis
(hexane) 𝜆max at 257 nm; 1H NMR (500 MHz, CDCl3) δ 6.32 (s, 2H), 4.19-4.10 (m, 2H), 3.89 (dd,
J=11.5 and 8.0 Hz, 1H), 1.72-1.50 (m, 4H), 1.40-1.21 (m, 6H), 0.91 (t, J = 7.0 Hz, 3H).
Synthesis of DBEDOT-C6 (M5). To a well stirred solution of EDOT-C6 (300 mg, 1.32 mmol) in 20
mL dry CHCl3 at 0 °C, was added 2 equivalents (470 mg, 2.64 mmol) of n-bromosuccinimide (NBS)
in small portions. The resulting reaction mixture was allowed to stir for 1.0 hour at room
temperature. The resulting mixture was then diluted with 30 mL H2O and extracted with chloroform
(3× 25 mL) and dried over Na2SO4. After that, solvent was evaporated and purification was carried
out by column chromatography. The compound DBEDOT-C6 was obtained in 89% yield (454 mg)
as a pale yellow oily liquid. 1H NMR (500 MHz, CDCl3) δ 4.17 (dd, J=3.0 and 11.5 Hz, 1H), 4.14-
4.04 (m, 1H), 3.85 (dd, J=11.5 and 3.0 Hz, 1H), 1.72-1.62 (m, 2H), 1.56-1.17 (m, 8H), 0.83 (t, J =
7.0 Hz, 3H).
Synthesis of octyl-2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT-C8; M6)
OO
S
C8H17
S
MeO OMe
PTSA
Toluene
NBS
CHCl3
HO OH
C8H17
OO
S
C8H17
BrBr
EDOT-C8 DBEDOT-C864% 92%
Synthesis of EDOT-C8. To a well stirred solution of 3,4-dimethoxythiophene (400 mg, 2.77 mmol)
in dry toluene (20 mL) was added 4 equivalents of 1,2-decanediol and followed by p-
toluenesulphonic acid (PTSA) (50 mg). The resulting reaction mixture was allowed to stir for 30
hours at 100 °C with under N2 atmosphere. The resulting mixture was diluted with 100 mL H2O and
extracted with ether (3× 50 mL). The combined organic extracts were washed with brine, dried over
Na2SO4. After that, solvent was evaporated and purified by the column chromatography. The pale
yellow oily liquid EDOT-C8 was obtained in 64% yield (450 mg) and was characterized by UV-vis-
NIR absorption and NMR spectroscopy. UV-vis (hexane) 𝜆max at 256 nm; 1H NMR (500 MHz,
CDCl3) δ 6.30 (s, 2H), 4.16-4.08 (m, 2H), 3.86 (dd, J=11.5 and 8.0 Hz, 1H), 1.71-1.50 (m, 4H), 1.40-
1.20 (m, 10H), 0.88 (t, J = 7.0 Hz, 3H).
Synthesis of DBEDOT-C8 (M6). To a well stirred solution of EDOT-C8 (300 mg, 1.18 mmol) in 20
mL dry CHCl3 at 0 °C, was added 2 equivalents of n-bromosuccinimide (NBS) (420 mg, 2.36 mmol)
in small portions. The resulting reaction mixture was allowed to stir for around 1.0 hour at room
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temperature. The resulting solution was then diluted with 30 mL H2O and extracted with chloroform
(3× 25 mL) and dried over Na2SO4. After that, solvent was evaporated and purification was carried
out by column chromatography. The compound DBEDOT-C8 was obtained in 92% yield (448 mg)
as a yellow oily liquid. The compound was characterized by NMR spectroscopy. 1H NMR (500
MHz, CDCl3) δ, 4.23 (dd, J=2.0 and 11.5 Hz, 1H), 4.17-4.12 (m, 1H), 3.92 (dd, J=11.5 and 7.0 Hz,
1H), 1.72-1.50 (m, 4H), 1.46-1.23 (m, 10H), 0.91 (t, J = 7.0 Hz, 3H).
2. General procedure for dedoping of polymers.
To a stirred mixture of as prepared polymer (100 mg) in deoxygenated CHCl3 (10 mL) at
room temperature was added hydrazine hydrate (50 mg in 2 mL acetonitrile). (Solvents CHCl3,
MeOH and hexane were purged with dry N2 for 30 minutes for deoxygenation). The resulting
mixture was stirred overnight at room temperature. CHCl3 was removed under reduced pressure and
the resulting residue was collected in to a Whatman extraction thimble under N2 atmosphere. The
resulting dedoped black residue was purified by repeated Soxhlet extraction with deoxygenated
MeOH (6 cycles) and hexane (6 cycles). For insoluble polymers (br-PEDOT, i-PEDOT, br-
PProDOT and i-PProDOT), after Soxhlet extraction, the resulting polymer was dried under reduced
pressure and the polymers were kept under N2 atmosphere. For soluble polymers (PEDOT-C6 and
PEDOT-C8), after Soxhlet extraction, the resulting polymer in Whatman extraction thimble was
further Soxhlet extraction with deoxygenated CHCl3. After few cycles the soluble portion of the
polymer in CHCl3 was collected in to round bottom flask and finally CHCl3 was removed under
reduced pressure yielded deep black blue polymers.
Further doping of the dedoped polymers
About 50 mg of elemental iodine was placed in the bottom of a vial (10 mL). Then a well-ground
powder of dedoped polymer (100 mg) in a Whatman paper was hung in the vial (10 mL). The iodine
vapour was slowly diffused to polymer at room temperature and continued for 6 hours for further
doping.
3. Preparation of polymer films for UV-vis measurement.
For insoluble polymers (br-PEDOT, i-PEDOT, br-PProDOT and i-PProDOT). Neutral polymer
(dedoped) was crushed into very fine powder. The fine powder (10 mg) was put into deoxygenated
CHCl3 (2 mL) and make a suspension mixture under N2 atmosphere. The resulting suspension
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mixture was drop-cast on the glass slide and spread over the slide and dried under N2 atmosphere.
This slide was used for UV-vis measurements.
For soluble polymers (PEDOT-C6 and PEDOT-C8). Neutral polymer (dedoped) (10 mg) was
dissolved into deoxygenated CHCl3 (2 mL) and make a solution under N2 atmosphere. The resulting
solution was drop-casted on the glass slide and spread over the slide and dried under N2 atmosphere.
This slide was used for UV-vis measurements.
4. Sample preparation procedure for GPC
The polymer was dissolved initially in CHCl3 (2 mg/mL), and allowed to solubilize for 3 hours
period at 50 °C. Then at room temperature the solution was filtered through a Millipore 0.5 µm filter.
Injections of ~200 µL were performed and retention times were calibrated against narrow molecular
weight polystyrene standards.
5. Proposed mechanism of the polymerization
The polymerization occurs by an oxidation of DBEDOT promoted by I2 to produce radical cation.
The radical cation reacts with another monomer unit to form radical cation dimer followed by the
release of bromine (Scheme 1) or iodine (Scheme 2). During the polymerization process, bromine
and iodine generated in bromo and iodo derivative respectively act as dopant for the resulting
polymers. It is significant to mention that Br2 is a strong oxidizing agent so oxidizes I- to I2 and itself
reduces to Br-. Following the same procedure leads to the formation of polymers.4
S
OO
BrBrS
OO
BrBr
S
OO
BrBr
S
OO
BrS
OO
Br
Br
Br
I2I
Br
S
O
BrS
OO
Br
-Br2
S
OO
BrS
OO
BrS
OOn
Br2 + 2I - I2 + Br -
S
OO
BrBr
Scheme S1. Proposed mechanism for the iodine vapour polymerization of br-PEDOT
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S
OO
IIS
OO
II
S
OO
II
S
OO
IS
OO
I
I
I
I2I
I
S
O
IS
OO
I
-I2
S
OO
IS
OO
IS
OOn
S
OO
II
Scheme S2. Proposed mechanism for the iodine vapour polymerization of i-PEDOT.
6. NMR, GPC, UV-vis, FT-IR and CV data
OO
S
C6H13
n
(a)
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0 10 20 30 40
0
5
10
Inte
nsity
Retention time (minute)
(c)
0 10 20 30 40
0
5
10
15
20
Inte
nsity
Retention time (minute)
(d)
Fig. S1. 1H NMR of neutral (a) PEDOT-C6 in CDCl3, (b) PEDOT-C8 in CDCl3 and GPC curve of (c)
PEDOT-C6 and (d) PEDOT-C8 in CHCl3. GPC measurements were performed in CHCl3 at 40 °C and
molecular weight of polymer is calculated from the retention time using polystyrene standard
reference kit.
OO
S
C8H17
n
(b)
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400 600 800 10000.0
0.1
0.2
0.3
0.4
Ab
so
rptio
n
Wavelength (nm)
PEDOT
Fig. S2. UV-vis spectrum of electrochemically polymerized PEDOT on ITO coated glass in
monomer free 0.1 M TBAPF6 in acetonitrile at applied potential of -0.8 V (neutral state or undoped).
Polymer film on ITO was prepared by electropolymerization of EDOT monomer at 0.1 M TBAPF6
in acetonitrile at scan rate 50 mV/s between -1.0 V to 1.6 V.
400 600 800 10000.00
0.02
0.04
0.06
0.08
0.10
Ab
so
rptio
n
Wavelength (nm)
P3 (br-PProDOT)
P4 (i-PProDOT)
473 nm
512 nm
442 nm
Fig. S3. UV-vis spectra of PProDOT polymers films on glass slide prepared by iodine vapour
polymerization.
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400 500 600 700 800
0.0
0.1
0.2
0.3
Abso
rptio
n
Wavelength (nm)
PEDOT-C6
643 nm
590 nm555 nm
Fig. S4. UV-vis spectrum of PEDOT-C6 polymer in CHCl3 prepared by iodine vapour
polymerization.
400 600 800 1000
0.0
0.2
0.4
0.6
0.8
Absorp
tion
Wavelength (nm)
PEDOT-C8
639 nm
589 nm550 nm
Fig. S5. UV-vis-NIR spectrum of PEDOT-C8 polymer film prepared by iodine vapour
polymerization.
3000 2500 2000 1500 1000 500
Tra
nsm
itta
nce
(%
)
Wavenumber (cm-1)
PEDOT by SSP
P1 (br-PEDOT)
P2 (i-PEDOT)
(A)
(B)
(C)
Fig. S6. FT-IR spectra of the (A) PEDOT by SSP, (B) br-PEDOT and (C) i-PEDOT in KBr pellet.
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3000 2500 2000 1500 1000 500
Tra
nsm
itta
nce
(%)
Wavenumber (cm-1)
P3 (br-PProDOT)
P4 (i-PProDOT)
(A)
(B)
Fig. S7. FT-IR spectra of the (A) br-PProDOT and (B) i-PProDOT in KBr pellet.
-0.8 -0.4 0.0 0.4-2
-1
0
1
2
Curr
ent
den
sity
(m
A/c
m2)
Potential (V)
50 mV/s
75 mV/s
100 mV/s
125 mV/s
150 mV/s
200 mV/s
Fig. S8. CV of PEDOT synthesized by SSP on glassy carbon electrode with Ag/Ag+ as the reference
electrode in 0.1 M TBAPF6 in acetonitrile at different scan rates.
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6 8 10 12 14 16-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Pe
ak C
urr
en
t D
en
sity
(mA
/cm
2)
(scan rate)1/2(mV/s)
Anodic current
Cathodic current
a)
6 8 10 12 14 16-9
-6
-3
0
3
6
9
(scan rate)1/2(mV/s)
Pe
ak C
urr
en
t D
en
sity
(mA
/cm
2)
Anodic Current
Cathodic Current
b)
6 8 10 12 14
-1
0
1
2
Pe
ak C
urr
en
t D
en
sity (
mA
/cm
2)
(scan rate)1/2 (mV/s)
Anodic Current
Cathodic Current
c)
Fig. S9. Plot of redox peak currents vs SQRT of scan rates derived from CV data of a) br-PEDOT at
50-225 mV/s scan rates; b) i-PEDOT at 50-225 mV/s scan rates and c) PEDOT synthesized by SSP
at 50-200 mV/s scan rates on a glassy carbon electrode in 0.1 M TBAPF6 in acetonitrile.
-0.8 -0.4 0.0 0.4 0.8 1.2
-8
-4
0
4
8
Curr
ent
Den
sity
(m
A/c
m2)
Potential (V)
25 mV/s
50 mV/s
75 mV/s
100 mV/s
125 mV/s
150 mV/s
175 mV/s
200 mV/s
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Fig. S10. CV of br-PPrODOT synthesized by iodine vapour polymerization on glassy carbon
electrode with Ag/Ag+ as the reference electrode in 0.1 M TBAPF6 in acetonitrile at different scan
rates.
-0.5 0.0 0.5 1.0-8.0
-4.0
0.0
4.0
8.0
Curr
ent
Den
sity
(mA
/cm
2)
Potential(V)
25 mV/s
50 mV/s
75 mV/s
100 mV/s
125 mV/s
150 mV/s
175 mV/s
200 mV/s
Fig. S11. CV of i-PPrODOT synthesized by iodine vapour polymerization on glassy carbon electrode
with Ag/Ag+ as the reference electrode in 0.1 M TBAPF6 in acetonitrile at different scan rates.
4 6 8 10 12 14-9
-6
-3
0
3
6
Pe
ak C
ure
nt D
en
sity
(mA
/cm
2)
(Scan rate)1/2(mV/s)
Anodic current
Cathodic Current
a)
4 6 8 10 12 14-8
-6
-4
-2
0
2
4
6
8
Peak C
urr
ent
Density
(mA
/cm
2)
(Scan Rate)1/2 (mV/s)
Anodic current
Cathodic current
b)
Fig. S12. Plot of redox peak currents vs SQRT of scan rates derived from CV data of (a) br-
PPrODOT at 25-200 mV/s scan rates and (b) i-PPrODOT at 25-200 mV/s scan rates on a glassy
carbon electrode in 0.1 M TBAPF6 in acetonitrile.
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250 300 350 400 4500.0
0.1
0.2
0.3
0.4
Abso
rba
nce
(a
.u)
Wavelength (nm)
(a)
250 300 350 400 450 5000.0
0.2
0.4
0.6
Abso
rba
nce
(a
.u)
Wavelength (nm)
(b)
Fig. S13.UV-vis absorption spectra of (a) EDOT-C6 and (b) EDOT-C8 in hexane.
300 350 400 450
0.1
0.2
0.3
0.4
0.5
Absorp
tion
Wavelength(nm)
(a)
225 250 275 300 325 3500.0
0.1
0.2
0.3
0.4
Ab
so
rptio
n
Wavelength(nm)
(b)
220 240 260 280 300 3200.0
0.1
0.2
0.3
Absorp
tion
Wavelength (nm)
(c)
Fig. S14. UV-vis absorption spectra of (a) DIProDOT, (b) DBrProDOT, and (c) ProDOT in hexane.
Fig. S15. 1H NMR spectrum of ProDOT at 600 MHz in CDCl3.
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Fig. S16. 13C NMR spectrum of ProDOT at 150 MHz in CDCl3.
Fig. S17. 1H NMR spectrum of DBProDOT at 500 MHz in CDCl3.
S16
Fig. S18. 1H NMR spectrum of DIProDOT at 500 MHz in CDCl3.
References
1. H. Meng, D. F. Perepichka, M. Bendikov, F. Wudl, G. Z. Pan, W. Yu, W. Dong, S. Brown, J. Am.
Chem. Soc., 2003, 125, 15151-15162.
2. B. Kim, J. K. Koh, J. Kim,W. S.Chi, J. H. Kim, E. Kim, ChemSusChem, 2012, 5, 2173-2180.
3. D. Bhardwaj, Shahjad, S. Gupta, P. Yadav, R. Bhargav, A. Patra, Chemistry Select, 2017, 2, 9570-
9562. DBEDOT-C8 was preapred according to the procedure adopted for the compound DBEDOT-
C6.
4. R. M. Walczak, J. K. Leonard, J. R. Reynolds, Macromolecules, 2008, 41, 691-700.