Alkyl side-chain branching point effects in thieno[3,4-c]pyrrole-4,6-dione copolymers
Supplementary Information
2013
Alkyl side-chain branching point effects in
thieno[3,4-c]pyrrole-4,6-dione copolymers
Joseph W. Rumer,†,* Christine K. L. Hor,† Iain Meager,† Chin P. Yau,† Zhenggang
Huang,† Christian B. Nielsen,† Scott E. Watkins,θ Hugo Bronstein,‡ and Iain
McCulloch†
†
Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London SW7
2AZ, UK
θ
CSIRO Materials Science and Engineering, VIC 3169, Australia
‡
Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK
*E-mail: jwrumer@imperial.ac.uk
Supporting Information
General Experimental
Additional Schemes & Figures
Experimental Procedures
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Alkyl side-chain branching point effects in thieno[3,4-c]pyrrole-4,6-dione copolymers
Supplementary Information
2013
General experimental
Instrumental
Microwave chemistry was performed in a Biotage initiator v.2.3. NMR spectra were
recorded on a Bruker DPX0 400 MHz spectrometer using an internal deuterium lock at
ambient probe temperatures unless stated otherwise. Chemical shifts (δ) are quoted in ppm
relative to the solvent residual peak, with peak multiplicity (bs, broad singlet; s, singlet; d,
doublet; t, triplet; q, quartet; m, multiplet), integration and coupling constants (J) quoted in
Hz (uncorrected) as appropriate. CDCl3 was used as the solvent for all spectra unless stated
otherwise. Proton solvent residual peaks are taken as: 7.26 for CDCl3, 7.15 for C6D6, 3.34 for
methanol-d4, 2.52 for DMSO-d6; and carbon solvent residual peaks as: 77.16 for CDCl3,
128.6 for C6D6, 49.9 for methanol-d4, 39.7 for DMSO-d6. Mass spectra: low resolution and
high resolution mass spectra (HRMS) were obtained using positive or negative electrospray
(ES) or chemical (CI) ionisation unless otherwise stated. Infrared spectra were recorded
using an FTIR spectrometer as evaporated films or neat using sodium chloride windows.
Melting points are uncorrected. UV-Vis detection was performed using a UV-1601 Shimadzu
UV-Vis spectrometer; solutions are dilute in chlorobenzene and thin-films prepared by spincoating from 1 mg/mL hot chlorobenzene solutions on glass substrates. Molecular weights
(Number-average [Mn] and weight-average [Mw]) were recorded on an Agilent Technologies
1200 series GPC in chlorobenzene at 80°C, using two PL mixed B columns in series,
calibrated against narrow polydispersity polystyrene standards. Ionisation potentials were
evaluated by Photo-electron Spectroscopy in Air (PESA) on a Riken Keiki AC-2 PESA
spectrometer. PESA samples were prepared by spin-coating polymer thin-films on glass
substrates from 5 mg/mL solutions in hot chlorobenzene and were run with a light intensity
of 5 nW and data processed with a power number of 0.5. Differential scanning calorimetry
(DSC) experiments were carried out on a TA Instruments DSC Tzero Q20 instrument. X-ray
diffraction (XRD) measurements were carried out with a PANALYTICAL X’PERT-PRO
MRD diffractometer equipped with a nickel-filtered Cu K α 1 beam and a X’ CELERATOR
detector, using a current of 40 mA and an accelerating voltage of 40 kV; films were drop-cast
from polymer solution (10 mg/mL in hot chlorobenzene) onto an Si substrate and allowed to
dry in air for 24 h.
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Alkyl side-chain branching point effects in thieno[3,4-c]pyrrole-4,6-dione copolymers
Supplementary Information
2013
Reagents & procedures
Detailed experimental procedures are described below. All solvents, reagents and other
chemicals were used as received from commercial sources, or purified using standard
procedures unless stated otherwise. The use of anhydrous chemicals, intuitive from the
reaction, infers anhydrous conditions under an argon or nitrogen atmosphere. Glassware for
inert atmosphere reactions was oven dried and cooled under a flow of nitrogen. All
temperatures – other than room temperature – are recorded as bath temperatures of the
reaction, unless stated otherwise. Merck aluminium backed precoated silica gel (50 F254)
plates were used for thin-layer chromatography (TLC). Visualisation was by ultraviolet light
(254 nm) and/or either potassium permanganate(VII), vanillin, iodine or Molybdate staining
with heating as appropriate. Column chromatography was performed on Merck silia gel
(Merck 9385 Kieselgel 60, 230-400 mesh) under a positive air pressure using reagent or GR
(guaranteed reagent) grade solvent as received.
PE refers to petroleum spirit 60-80 °C; Hex refers to hexane; DMSO refers to dimethyl
sulfoxide; NBS refers to N-bromosuccinimide;; EtOAc refers to ethyl acetate; CB refers to
chlorobenzene.
(Left) Scheme S1. Synthesis of the TPD-2T copolymers.
(Right) Scheme S2. Synthesis of 3-ethyl-iodoheptane.
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Alkyl side-chain branching point effects in thieno[3,4-c]pyrrole-4,6-dione copolymers
Supplementary Information
2013
Figure S1. A structurally optimized computational model of the TPD-2T polymer (modeled
at the B3LYP/6-31G* level, for an N-methyl substituted tetramer) showing the calculated
HOMO and LUMO densities.
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Alkyl side-chain branching point effects in thieno[3,4-c]pyrrole-4,6-dione copolymers
Supplementary Information
2013
Experimental procedures
Thieno[3,4-c]pyrrole-4,6-dione (2)
A mixture of thiophene-3,4-dicarboxylic anhydride (4.00 g, 26.0 mmol, 1 eq) and formamide
(10 mL, 77.9 mmol, 3 eq) was refluxed at 210 °C overnight in the dark. The reaction mixture
was allowed to cool to room temperature and the brown residue suspended in hot water (25
mL). Filtration and recrystallization from ethanol afforded the title compound as colourless
needles (2.87 g, 72%, m.p. 292-295 °C, lit.1 293-294 °C). 1H NMR (400 MHz, DMSO-d6):
11.26 (s, 1H, NH), 8.27 (s, 2H, -S-CH-);
13
C NMR (400 MHz, CDCl3): 127.79, 132.55,
137.62, 163.76.
1,3-Dibromo-thieno[3,4-c]pyrrole-4,6-dione (3)
To a solution of 2 (150 mg, 0.98 mmol, 1 eq) in dry DMF (2 mL) was added Nbromosuccinimide (1.05g, 5.88 mmol, 6 eq) and the mixture heated at 100 °C overnight in
the dark. The reaction was allowed to cool to room temperature, hot water added and the
precipitate filtered off and washed with acetone to give afford the title compound as a
crystalline white solid (0.13 g, 42%).2
1,3-dibromo-5-(3-ethylheptyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (4a)
To a solution of 3 (300 mg, 0.97 mmol, 1 eq) in dry DMF (2 mL) was added sodium hydride
(50 mg, 1.25 mmol, 1.3 eq) and the mixture stirred at room temperature for 1 hour. The
mixture was then added dropwise to a solution of 2-ethyl-iodoheptane (736 mg, 2.89 mmol, 3
eq) in dry DMF (3 mL) at 50 °C. This mixture was stirred for 12 hours at room temperature
and the crude product then extracted with petroleum ether, washed with water, dried
(MgSO4), filtered and concentrated in vacuo. The crude product was purified via column
chromatography on silica gel eluting in 8:2 chloroform/hexane. The colourless residue was
further purified by recrystallisation from methanol/chloroform to afford the title compound as
a white crystalline solid (85 mg, 20%). 1H NMR (400 MHz, CDCl3): 3.85 (t, J = 7.6 Hz, 2H,
N-CH2-), 1.62-1.52 (m, 2H, -N-CH2-CH2-), 1.40-1.15 (m, 9H), 0.93-0.80 (m, 6H, -CH3); 13C
NMR (400 MHz, CDCl3): 10.73, 14.26, 23.19, 25.74, 28.80, 31.64, 32.66, 36.86, 37.08,
113.02, 134.98, 160.48; HRMS (CI+): [M+NH4]+ requires 452.9839, found 452.9847.
1,3-dibromo-5-(1-ethylpentyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (4b)
To a solution of 3 (300 mg, 0.97 mmol, 1 eq) in dry DMF (2 mL) was added sodium hydride
(50 mg, 1.25 mmol, 1.3 eq) and the mixture stirred at room temperature for 1 hour. The
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Alkyl side-chain branching point effects in thieno[3,4-c]pyrrole-4,6-dione copolymers
Supplementary Information
2013
mixture was then added dropwise to a solution of 3-bromoheptane (518 mg, 2.89 mmol, 3 eq)
in dry DMF (3 mL) at 50 °C. This mixture was stirred for 12 hours at room temperature and
the crude product then extracted with petroleum ether, washed with water, dried (MgSO4),
filtered and concentrated in vacuo. The crude product was purified via column
chromatography on silica gel eluting in 8:2 chloroform/hexane. The colourless residue was
further purified by recrystallisation from methanol/chloroform to afford the title compound as
a white crystalline solid (88 mg, 24%). 1H NMR (400 MHz, CDCl3): 4.01 (tt, J = 8.0, 8.0 Hz,
1H, N-CH-), 2.06-1.93 (m, 2H, -N-CH-CH2-), 1.79-1.61 (m, 2H, -N-CH-CH2-), 1.39-1.16 (m,
4H, -CH2-), 0.91 (t, J = 7.3 Hz, 6H, -CH3);
13
C NMR (400 MHz, CDCl3): 11.31, 14.12,
22.52, 25.38, 28.97, 31.78, 55.07 (-N-CH-), 112.97, 134.59, 160.98; HRMS (CI+):
[M+NH4]+ requires 424.9519, found 424.9534.
P1
A microwave vial was charged with 4a (85 mg, 0.19 mmol, 1eq), 4,4’-didecyl-5,5’bis(trimethylstannyl)-2,2’-bithiophene
(150
mg,
0.19
mmol,
1eq),
2.2
mol%
of
tris(dibenzylideneacetone)dipalladium and 8.8 mol% of tri(o-tolyl)phosphine. The vial was
then sealed, chlorobenzene added (2 mL), the mixture degassed for approximately 40 minutes
and submitted to the microwave reactor for: 3 minutes at each of 100 °C, 120 °C, 140 °C, 160
°C and finally 50 minutes at 180 °C. The crude polymer was precipitated in methanol and
then purified by Soxhlet extraction with acetone, hexane and chloroform. Remaining
palladium residues were removed by vigorously stirring the latter fraction with aqueous
sodium diethyldithiocarbamate for 3 hours at 55 °C. The organic phase was then separated,
washed (water), concentrated in vacuo and again precipitated in methanol, filtered off and
dried under high vacuum to afford the title compound as a black solid (141 mg, 64%). Mn = 7
kDa, Mw = 9 kDa, PDI = 1.3.
P2
A microwave vial was charged with 1,3-dibromo-5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole4,6(5H)-dione (219 mg, 0.52 mmol, 1eq), 4,4’-didecyl-5,5’-bis(trimethylstannyl)-2,2’bithiophene (254 mg, 0.52 mmol, 1eq), 2.2 mol% of tris(dibenzylideneacetone)dipalladium
and 8.8 mol% of tri(o-tolyl)phosphine. The vial was then sealed, chlorobenzene added (2 mL),
the mixture degassed for approximately 40 minutes and submitted to the microwave reactor
for: 3 minutes at each of 100 °C, 120 °C, 140 °C, 160 °C and finally 50 minutes at 180 °C.
The crude polymer was precipitated in methanol and then purified by Soxhlet extraction with
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Alkyl side-chain branching point effects in thieno[3,4-c]pyrrole-4,6-dione copolymers
Supplementary Information
2013
acetone, hexane and chloroform. Remaining palladium residues were removed by vigorously
stirring the latter fraction with aqueous sodium diethyldithiocarbamate for 3 hours at 55 °C.
The organic phase was then separated, washed (water), concentrated in vacuo and again
precipitated in methanol, filtered off and dried under high vacuum to afford the title
compound as a black solid (141 mg, 27%). Mn = 6 kDa, Mw = 9 kDa, PDI = 1.4.
P3
A microwave vial was charged with 4b (36 mg, 0.09 mmol, 1eq), 4,4’-didecyl-5,5’bis(trimethylstannyl)-2,2’-bithiophene
(68
mg,
0.09
mmol,
1eq),
2.2
mol%
of
tris(dibenzylideneacetone)dipalladium and 8.8 mol% of tri(o-tolyl)phosphine. The vial was
then sealed, chlorobenzene added (2 mL), the mixture degassed for approximately 40 minutes
and submitted to the microwave reactor for: 3 minutes at each of 100 °C, 120 °C, 140 °C, 160
°C and finally 50 minutes at 180 °C. The crude polymer was precipitated in methanol and
then purified by Soxhlet extraction with acetone, hexane and chloroform. Remaining
palladium residues were removed by vigorously stirring the latter fraction with aqueous
sodium diethyldithiocarbamate for 3 hours at 55 °C. The organic phase was then separated,
washed (water), concentrated in vacuo and again precipitated in methanol, filtered off and
dried under high vacuum to afford the title compound as a black solid (40 mg, 64%). Mn = 8
kDa, Mw = 11 kDa, PDI = 1.4.
P4
A microwave vial was charged with 1,3-dibromo-5-(octyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)dione (219 mg, 0.52 mmol, 1eq), 4,4’-didecyl-5,5’-bis(trimethylstannyl)-2,2’-bithiophene
(254 mg, 0.52 mmol, 1eq), 2.2 mol% of tris(dibenzylideneacetone)dipalladium and 8.8 mol%
of tri(o-tolyl)phosphine. The vial was then sealed, chlorobenzene added (2 mL), the mixture
degassed for approximately 40 minutes and submitted to the microwave reactor for: 3
minutes at each of 100 °C, 120 °C, 140 °C, 160 °C and finally 50 minutes at 180 °C. The
crude polymer was precipitated in methanol and then purified by Soxhlet extraction with
acetone, hexane and chloroform. Remaining palladium residues were removed by vigorously
stirring the latter fraction with aqueous sodium diethyldithiocarbamate for 3 hours at 55 °C.
The organic phase was then separated, washed (water), concentrated in vacuo and again
precipitated in methanol, filtered off and dried under high vacuum to afford the title
compound as a black solid (116 mg, 25%). Mn = 5 kDa, Mw = 7 kDa, PDI = 1.4.
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Alkyl side-chain branching point effects in thieno[3,4-c]pyrrole-4,6-dione copolymers
Supplementary Information
2013
3-Ethyl-1-iodoheptane (6)
To a solution of 2-ethylhexylbromide (10.86 g, 56.2 mmol) in dry THF (~50 mL) at rt was
added finely ground magnesium (1.78 g, 73.1 mmol) and the mixture heated to ~50 °C. A
spatula of iodine was added and the mixture spontaneously refluxed until the magnesium
solids had been fully consumed, indicating formation of the Grignard reagent.
Paraformaldehyde (2.40 g, 78.7 mmol) was added in one portion and the mixture heated at
reflux overnight. The mixture was allowed to cool to rt, diluted with EtOAc, quenched with
dilute HCl, separated and extracted with further EtOAc, the combined organic extracts being
subsequently washed with dilute HCl then brine; dried (MgSO4), filtered and concentrated in
vacuo. The residue was purified by dry flash chromatography on silica eluting in 1:1
PE/chloroform to afford 3-ethyl-1-heptanol 5 as a clear pale yellow oil (4.78 g, 59%) which
was used without further purification. 1H NMR (400 MHz, CDCl3): 3.66 (t, J = 7.1 Hz, 2H,
HO-CH2-), 1.52 (td, J = 6.8, 6.8 Hz, 2H, HO-CH2-CH2-), 1.40-1.20 (m, 9H, CH & CH2),
0.93-0.79 (m, 6H, CH3).
To a solution of 3-ethyl-1-heptanol 5 (4.78 g, 33.1 mmol) in DCM (~100 mL) at 0 °C was
added triphenyl phosphine (7.27 g, 27.7 mmol) and imidazole (2.36 g, 34.6 mmol) followed
by portion-wise iodine (7.70 g, 30.0 mmol) and the mixture allowed to warm to rt stirring
over 3 h to give an opaque dark red-brown suspension. The mixture was quenched with
Na2SO3 sat. aq. (100 mL), separated, washed with brine (2 x 100 mL), dried (MgSO4),
filtered and evaporated. The residue was taken up in hexane and purified by dry flash
chromatography on silica to afford the title compound as a clear, colourless oil (4.44 g, 53%).
1
H NMR (400 MHz, CDCl3): 3.19 (t, J = 7.6 Hz, 2H, I-CH2-), 1.80 (td, J = 7.6, 6.1 Hz, 2H,
I-CH2-CH2-), 1.40-1.15 (m, 9H, CH & CH2), 0.93-0.79 (m, 6H, CH3); 13C NMR (400 MHz,
CDCl3): 5.49, 10.71, 14.24, 23.18, 25.25, 28.78, 32.14, 37.9, 40.1; LRMS (EI+): [M-H]+
calculated 253, found 253.
1
2
Sice, J. J. Org. Chem. 1954, 19, 70.
Griffini, G.; Douglas, J. D.; Piliego, C.; Holcombe, T. W.; Turri, S.; Fréchet, J. M. J.; Mynar, J. L. Adv. Mater.
2011, 23, 1660-1664.
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