Chain-Growth Polymerization of Unusual Anion-Radical Monomers Based on Naphthalene Diimide: A New Route to well-defined n-type Conjugated Copolymers

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1 upporting Information Chain-Growth Polymerization of Unusual Anion-adical Monomers Based on aphthalene Diimide: A ew oute to well-defined n-type Conjugated Copolymers Volodymyr enkovskyy 1 *, oman Tkachov 1, Hartmut Komber 1, Michael ommer 2, Maria Heuken 1, igitte Voit 1, Wilhelm T.. Huck 2, Vladislav Kataev 3, Andreas Petr 3 and Anton Kiriy 1 * Instrumentation and materials ynthesis of TDIT ynthesis of -TDIT- General procedure for polymerization pectroscopic data Discussion of the polymerization mechanism Instrumentation H ( MHz), C ( MHz) and P ( MHz) M spectra were recorded on a uker Avance III spectrometer using a 5 mm H/ C/ F/ P gradient probe at 303 K. The H 13 and C M spectra were referenced to the solvent peak (CDCl : δ( H) = 7.26 ppm, δ( C) = 77.0 ppm; THF-d : δ( H) = 1.72 ppm). The P M spectra were recorded using THF-d as solvent and referenced to external H P (δ = 0 ppm). The samples for in-situ experiments 3 4 were prepared in a glovebox under argon atmosphere GPC measurements were carried out on an Agilent 1100 eries (Agilent, UA) normaltemperature size exclusion chromatograph, equipped with refractive index detector and one column PL Gel MIXED-B (Polymer Laboratories, UK). Chloroform was used as eluent and the flow rate was 1 ml/min. umber average molecular weights (M n ) and polydispersity indexes (PDI) of obtained polymers were determined based on calibration with polystyrene standards obtained from Polymer tandards ervice (P, Germany). The E measurements were conducted in the X-band using a uker EMX spectrometer and a rectangular cavity (E4104). The modulation frequency was 100 khz. 1

2 Materials. 1 2,6-Dibromonaphthalene-1,4,5,8-tetracarboxylic-, -bis(2-octyldodecyl) diimide DI- 2 and Ph-idppe- 2 were synthesized as described elsewhere. ieke zinc was prepared by the reduction of ZnCl 2 with sodium naphthalenide. 3 Tetrahydrofuran (THF) was distilled over sodium benzophenone ketyl. All other chemicals were purchased from Aldrich and used as received. ynthesis. 2,6-Bis(2-thienyl)naphthalene-1,4,5,8-tetracarboxylic-, -bis(2-octyldodecyl) diimide TDIT. TDIT was prepared by tille coupling according to a standard protocol. DI- 2 (4.4 g, 4.46 mmol), Pd(PPh 3 ) 2 Cl 2 (72 mg, 0.1 mmol) and 2-(tributylstannyl)thiophene (4.01 g, 10.7 mmol) were placed into a double-neck round bottom flack, equipped with a magnet stirrer bar and a reflux condenser. The atmosphere was replaced by argon and the freshly distillated anhydrous THF (100 ml) was added by syringe. The mixture was stirred under reflux overnight, evaporated to dryness and dissolved in boiling isopropanol. An orange solid, precipitated upon cooling, was separated by filtration, washed with cold isopropanol, methanol and dried in vacuo at 40 C. Yield 4.0 g (91%). M data (comp. Figure 1): 1 H M (500 MHz, CDCl 3 ) δ = 8.76 (s, 2H; H 6 ), 7.56 (dd, 3 J(H,H) = 5.1 Hz, 4 J(H,H) = 1.1 Hz, 2H; H 1 ), 7.31 (dd, 3 J(H,H) = 3.6 Hz, 4 J(H,H) = 1.1 Hz, 2H; H 3 ), 7.19 (dd, 3 J(H,H) = 5.1 Hz, 3 J(H,H) = 3.6 Hz, 2H; H 2 ), 4.07 (d, 3 J(H,H) = 7.3 Hz, 4H; H a ), 1.96 (m, 2H; H b ), (64H; H c-g, H c -g ), 0.87 and 0.86 ppm (2 t, 3 J(H,H) = 7.0 Hz, 12H; H h, H h ). 13 C M (126 MHz, CDCl 3 ) δ = (C 11 ), (C 10 ), (C 4 ), (C 5 ), (C 6 ), (C 3 ), (C 1 ), (C 8 ), (C 2 ), (C 7 ), (C 9 ), (C a ), (C b ), (C f,f ), (C c,c ), (C e,e ), (C d,d ), (C g,g ), ppm (C h,h ). 2,6-Bis(2-bromothien-5-yl)naphthalene-1,4,5,8-tetracarboxylic-, -bis(2-octyldodecyl) diimide -TDIT-. TDIT (4.0 g, 4.03 mmol) was dissolved in 240 ml of a 1:1 (v/v) mixture of chloroform and acetic acid. -omosuccinimide (2.15 g, 12.1 mmol) was added 1 Guo, X.; Watson, M. D. rg. Lett. 2008, 10, V. enkovskyy,. Tkachov, T. Beryozkina, H. Komber, U. ertel, M. Horecha, V. Bocharova, M. tamm,. A. Gevorgyan, F. C. Krebs, A. Kiriy, J. Am. Chem. oc. 2009, 131, odium naphthalenide was prepared according to the protocol published in the work of ieke with the only difference that sodium was used instead of lithium: Chen, T.; Wu, X.; ieke,. D. J. Am. Chem. oc. 1995,117,

3 in one portion and the mixture was stirred at 60 C until reaction was completed (TLC control). The chloroform was evaporated under reduced preassure precipitated dark red solid was collected by filtration, washed with MeH and recrystalized from boiling EtH (~100 ml/g). Yield 4.2 g (90%). M data (comp. Figure 2): 1 H M (500 MHz, CDCl 3 ) δ = 8.72 (s, 2H; H 6 ), 7.14 (d, 3 J(H,H) = 3.9 Hz, 2H; H 2 ), 7.08 (d, 3 J(H,H) = 3.9 Hz, 2H; H 3 ), 4.08 (d, 3 J(H,H) = 7.3 Hz, 4H; H a ), 1.94 (m, 2H; H b ), (64H; H c-g, H c -g ), 0.87 and 0.85 ppm (2 t, 3 J(H,H) = 7.0 Hz, 12H; H h, H h ). 13 C M (126 MHz, CDCl 3 ) δ = (C 11 ), (C 10 ), (C 4 ), (C 5 ), (C 6 ), (C 2 ), (C 3 ), (C 8 ), (C 7 ), (C 9 ), (C 1 ), (C a ), (C b ), (C f,f ), (C c,c ), (C e,e ), (C d,d ), (C g,g ), ppm (C h,h ). General procedure for polymerization. All operations were done under an inert gas atmosphere. The charge-transfer monomer was prepared as follows: -TDIT- (0.1 mmol) was placed in a round-bottomed flask equipped with a magnetic stirrer and a septum, and the atmosphere was replaced with argon. Dry THF (20 ml) and active Zn (1.05 mmol) were added via a syringe and the mixture was stirred at room temperature for 1 h. Afterwards, a catalytic amount of i(dppe)cl 2, i(dppp)cl 2, or Ph-i(dppe) ( mmol) was added. Polymerization times ranged between 1 to 24 hours at temperatures from 0 C to 50 C. The mixtures were quenched with 5 M HCl and extracted with CHCl 3. The organic layers were washed with water, dried over anhydrous Mg 4 and concentrated under reduced pressure to give the crude polymers. Acetone was added and the precipitates were washed with warm acetone, collected by filtration and dried in vacuo at 40 C to give pure P(TDIT) samples. 3

4 (a) c' d' e' f ' g' h' = a b c d e f g h (b) Figure 1. (a) 1 H and (b) 13 C M spectrum of TDIT (solvent: CDCl 3 ). 4

5 (a) c' d' e' f ' g' h' = a b c d e f g h (b) Figure 2. (a) 1 H and (b) 13 C M spectrum of -TDIT- (solvent: CDCl 3 ). 5

6 [G] Figure 3. The electron paramagnetic resonance spectrum of the radical anion of -TDIT- /Zn in THF solution. 1 [T-473]=0.1 mg/ml in Chloroform 2 mm, eferenz Chloroform 0.75 Absorbance Wavelength (nm) Figure 4. UV-vis spectra of PTDIT in chloroform. 6

7 c' d' e' f ' g' h' n = a b c d e f g h Figure C M spectrum of P(TDIT) (solvent: C 2 D 2 Cl 4, 353K). P(TDIT) was measured in 1,1,2,2-tetrachloroethane-d 2 at 353 K. The spectra were referenced on the solvent signal (δ( 1 H) = 5.98 ppm, δ( 13 C) = 73.7 ppm). M data: 1 H M (500 MHz, C 2 D 2 Cl 4, 353 K) δ = 8.87 (2H; H 6 ), 7.40 (4H; H 2, H 3 ), 4.17 (4H; H a ), 2.08 (2H; H b ), (64H; H c-g, H c -g ), 0.90 ppm (12H; H h, h ). 13 C M (126 MHz, C 2 D 2 Cl 4, 353 K) δ = (C 10, C 11 ), (C 4 ), and (C 1,C 5 ), (C 6 ), (C 2 ), (C 9 ), (C 7 ), (C 3 ), (C 8 ), 45.0 (C a ), 36.5 (C b ), 31.8 (C c,c ), 31.6 (C f,f ), (C e,e ), 26.3 (C d,d ), 22.3 (C g,g ), 13.7 ppm (C h,h ). 7

8 c' d' e' f ' g' h' n = a b c d e f g h Figure 6. 1 H M spectrum of P(TDIT) (solvent: C 2 D 2 Cl 4, 353K). ignals of the H-T end group are marked by # and signals of the B-T end group by symbol *. 8

9 p m o n f X b a e d X= X= c Figure 7. 1 H M spectrum of Ph/(H) terminated P(TDIT) (aromatic/thiophene protons region), solvent: CDCl 3, # 13 C satellites, assignment of H p and H e by CY. 9

10 c a b Ph Ph e f P 1 i P Ph 2 d Ph (a) (b) Figure 8. (a) 1 H CY spectrum of -TDIT-i(dppe)- complex (aromatic/thiophene protons region) showing the 3 J HH correlations between H a and H b of the brominated T-moiety (red square) and between H c and H d of the T-moiety bonded to the i center (blue square) and (b) 31 P- 1 H-correlated spectrum showing a J-coupling between H f and P 1 of the i(dppe) moiety (green lines). x = naphthalene from Zn monomer synthesis. (solvent: THF-d 8 ). 10

11 Figure P M spectra of (a) the reaction mixture after addition of several equivalents of -TDIT-/Zn to i(dppe)cl 2 and (b) after 10 minutes reaction time (solvent: THF-d 8, 303 K). 11

12 Discussion of the polymerization mechanism. i-catalyzed polymerization of -TDIT- /Zn monomer reported herein is highly unusual process. Although to date we have no clearcut understanding of its mechanism, some proposals can be made as described below. A catalytic cycle most of transition metal-catalyzed couplings and coupling polymerizations consists of oxidative addition (A), reductive elimination (E) and transmetallation (TM) elementary steps. The closest analogue of the polymerization studied herein, i-catalyzed egishi-coupling, which involves Zn-organic monomers -Ar-Zn, also involves these three steps. General mechanism of this polymerization is depicted below (Figure 10): Initiation: TM E 2 -Ar-Zn + i(dppe) 2 -Ar-i(dppe)-Ar- -Ar-Ar- + i(dppe) Chain propagation: A TM (+-Ar-Zn; -Zn 2 ) -Ar-Ar- + i(dppe) -Ar-Ar-i(dppe) -Ar-Ar-i(dppe)-Ar- E A Figure 10. Mechanism of egishi-coupling polycondensation based on generally accepted mechanism of egishi coupling of small molecules. We tentatively hypothesize that i-catalyzed polymerization of -TDIT-/Zn studied herein may involve E and A elementary steps which are operative in usual egishi coupling. This is supported by the fact that the structure of at least one intermediate of the polymerization, P(TDT)-i(dppe), formed after A step, was identified in this work. Furthermore, since the polymerization shows the chain-growth behaviour, we propose that most of the i(0) species formed after E undergo intramolecular A (i.e. the intramolecular catalyst-transfer process observed earlier in polycondensations of electron-rich monomers). The TM is the most poorly understood step here because of highly unconventional structure of the monomer. In catalyst-transfer polycondensations, TM is an important elementary step of the catalytic cycle that is responsible for the addition of monomers to the growing polymer 12

13 chain. ormally, TM occurs as a result of a nucleophilic attack of the monomer by its metalorganic centre onto electrophilic i centre of P(TDT)-i(dppe)- concomitant with Zn 2 elimination (equation 1). However, there is no insertion of Zn between C and atoms in the monomer -TDIT-/Zn, therefore there is no well-defined carbanionic centre in this monomer, such as existing in -Ar-Zn. For the coupling reaction of the polymer chain end -Ar-i(dppe)- with the monomer -TDIT-/Zn to occur, the following elementary transformations should be involved (they are listed in an arbitrary order): 1) the formation of a bond between i of the propagating chain end P(TDT)-i(dppe)- and carbon atom from the monomer (one of two which in the monomer are bound to atoms): 2) transfer of two electrons from the monomer (one of which is delocalized on the TDIT core, another one still sitting on Zn) onto i and C atoms those involved into i-c bound formation according to 1): 3) elimination of two anions, one of which from P(TDT)-i(dppe)- and another one from the monomer. In general, there are several variations of the mechanism depending on the order of the three steps listed above. ne of the most probable mechanism is presented in cheme 2 of the main text (see also the main text for discussion of this mechanism). Alternatively, the mechanism of quasi-tm step can be proposed having a different sequence of the elementary transformations. In the first step, -TDIT-/Zn in its mesomeric structure with the anion localized on oxygen and the radical localized on thiophene ring nearby the bromine atom reacts with P(TDT)-i(dppe)- as shown in Figure 11. Here the radical attacks the nickel atom leading to the formation of i(iii) species. elaxation of this intermediate to more stable compounds requires reduction of i(iii) top i(ii) via ET from Zn + and recovering of the aromatisity of the core concomitant with the elimination of two bromine anions (again, Zn 2 is eliminated in overall). 13

14 Zn Zn -TDT-i- Zn TDIT- i Zn - e TDIT- i -Zn 2 i-tdit- Figure 11. Possible mechanism of quasi-transmetalation step occurring via i(iii) intermediates (dppe ligand is omitted). To monitor possible electron transfer processes and possible paramagnetic radial species, the polymerization was conducted while measuring EP spectra. o new paramagnetic species (other then signals from starting monomer) were found in this experiment. uch result might be due to 1) paramagnetic intermediates are not involved in the polymerization or 2) paramagnetic intermediates are too short-lived intermediates to be detected. In a conclusion, more research are necessary to verify mechanism of the polymerization discovered herein. 14