Solution-processible n-type organic semiconductors based on. angular-shaped 2-(12H-dibenzofluoren-12-ylidene)malononitrile

Transcription

1 Solution-processible n-type organic semiconductors based on angular-shaped 2-(12H-dibenzofluoren-12-ylidene)malononitrile diimide Debin Xia, Tomasz Marszalek, Mengmeng Li, Xin Guo, Martin Baumgarten, *, Wojciech Pisula,, and Klaus Müllen*, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, Germany Department of Molecular Physics, Lodz University of Technology, Zeromskiego 116, Lodz, Poland Table of Contents Materials and Methods..S2 Experimental Section. S3 TGA and DSC curves.... S7 XRD of zone-cast films of 2a and 2b.... S8 POM images for 2a and 2b zone-cast layers S9 Crystal orientation of 2b in the zone-cast films.. S9 POM images of powder S10 Photophysical and electrochemical properties.....s10 DFT calculations for model compounds s11 1 H NMR and 13 C NMR Spectra S12 Appendix: HRMS spectra of 2a and 2b.....S19 Appendix: EI mass spectrum of S20 References S20 1

2 Materials and Methods 1 H NMR and 13 C NMR spectra were recorded in deuterated solvents such as CD 2 Cl 2, using a Bruker DPX 250 spectrometer, with the solvent proton or carbon signal as an internal standard. FD mass spectra were performed with a VG-Instrument ZAB 2-SE-FDP. Elemental analysis was carried out using a Foss Heraeus Vario EL in the Institute of Organic Chemistry at the Johannes Gutenberg-University. UV vis absorption spectra were recorded at room temperature using Perkin Elmer Lambda 900 spectrophotometer. Fluorescence spectra were recorded on a SPEX-Fluorolog II(212) spectrometer. CV measurements were carried out on a computer-controlled GSTAT12 in a three-electrode cell in a DCM solution of Bu 4 NPF 6 (0.1 M) with a scan rate of 100 mv/s at room temperature, using glassy carbon discs as the working electrode, Pt wire as the counter electrode, Ag/AgCl electrode as the reference electrode. Thermogravimetric analysis (TGA) was carried out on a Mettler 500 at a heating rate of 10 ºC /min under nitrogen flow, differential scanning calorimetry (DSC) was performed on a Mettler DSC 30 at a heating/cooling rate of 10 ºC/min under nitrogen flow. All reagents and starting materials were obtained from commercial suppliers and used without further purification. Column chromatography was performed on silica gel 60 (Macherey-Nagel, Si60) with dichloromethane, hexane, ethyl acetate or tetrahydrofuran (Sigma-Aldrich). All reported yields are isolated yields. Zone-cast layer of 2b were deposited on hexamethyldisilazane (HMDS) treated silicon dioxide (SiO 2 ). The zone-casting setup is custom built and has been described elsewhere [add: W. Pisula, Ž. Tomović, C. Simpson, M. Kastler, T. Pakula, K. Müllen, Chemistry of Materials 17, 4296, 2005]. For the zone-cast procedure, 2b compound was dissolved in 1,2-dichlorobenzene (o-dcb) at a concentration of 2.0 mg ml -1. The fabrication took place in ambient atmosphere. The solvent temperature was 78 C and the substrate temperature was 83 C. The substrate velocity was 3 mm s -1. XRD measurements were performed on a Siemens D-500 powder diffractometer (Cu-Ka: nm) with a scan rate of 0.1/20 s. Polarized optical images of the films were taken using a Hitachi KP-D50 Color Digital charge-coupled device (CCD) camera on a Zeiss microscope equipped with polarizing filters. 2

3 Experimental Section Scheme 1. Synthetic route of 1a-b and 2a-b. Reagents and conditions: (i) (a) n-buli, THF, -78 o C, 3,4-dimethylbenzaldehyde, Ar; (b) I 2, K 2 CO 3, t-bu-oh, 90 o C, 95%; (ii) Pd(OAc) 2, K 2 CO 3, Ag 2 O, TFA, 140 o C, Ar, 75%; (iii) Br 2, CCl 4, hv, 80 o C, Ar, 81%; (iv) NaI, DMF, 90 o C, Ar, 67~72%; (v) Malononitrile, CHCl 3, TiCl 4, pyridine, 80 o C, Ar, 74~80%. n-butyllithium (1.60 M solution in hexane, ml, mmol) was added dropwise to a solution of 4-bromo-1,2-dimethylbenzene (5.00 g mmol) in THF (100 ml) at -78 o C for 40 min. Then, 3,4-dimethylbenzaldehyde (3.76 ml, mmol) was added to the mixture at -78 o C and the obtained mixture was stirred at room temperature overnight. After removal of the solvent, I 2 (6.85 g, mmol), K 2 CO 3 (11.18 g, mmol) and t-buoh (70 ml) were added and the obtained mixture was stirred for 8 hrs at refluxing conditions. The reaction mixture was quenched with 100 ml Na 2 SO 3 solution and was extracted with 200 ml dichloromethane three times. The organic layer was washed with brine three times and dried over Na 2 SO 4 for 6 hours. After the solvent had been completely removed by rotary evaporator, affording 6.10 g product white powder in a yield of 95%. 3

4 FD-Mass: calc.: found: H NMR (250 MHz, C 2 D 2 Cl 2 ): δ 7.60 (s, 2H), 7.52 (dd, J = 7.8, 1.9 Hz, 2H), 7.28 (d, J = 7.7 Hz, 2H), 2.39 (s, 6H), 2.37 (s, 6H). 13 C NMR (250 MHz, C 2 D 2 Cl 2 ): δ / ppm: , , , , , , , 20.12, HR-MS (MALDI) m/z calcd. for C17H19O [M + ]: , found Melting point: o C. Under air atmosphere, palladium acetate (100 mg, mmol), Ag 2 CO 3 (3.06 g, mmol), K 2 CO 3 (3.04 g, mmol) and 3 (2.10 g, 8.82 mmol) were added into a Schlenktube dried by a hot-gun. The tube was stopped and degassed with argon for three times. Then, trifluoroacetic acid (20.00 ml, 262 mmol) was added by syringe. The mixture was stirred under argon atmosphere at 140 C for 24 h. Then the mixture was cooled down to room temperature and 500 ml water was added and extracted by 200 ml dichloromethane three times, further purified by flash chromatography on silica gel with dichloromethane as eluent to give the product (1.56 g, 75%) as yellow solid. FD-Mass: calc.: found: H (250 MHz, C 2 D 2 Cl 2 ): δ 7.25 (s, 2H), 7.17 (s, 2H), 2.24 (s, 6H), 2.19 (s, 6H). 13 C NMR (250 MHz, C 2 D 2 Cl 2 ): δ / ppm: , , , , , , , 20.83, HR-MS (MALDI) m/z calcd. for C17H16O [M + ]: , found Melting point: o C. The compound 4 (0.36 g, 1.56 mmol) was added into a flask filled with Ar. Then, CCl 4 (25 ml) was injected. The mixture was heated to reflux and irradiated with a 250 W light bulb. Bromine (3.22 ml, 62.3 mmol) was slowly added dropwise to the solution. After 2 days, the mixture was cooled down to room temperature and the yellow product was collected by filtration and washed with chloroform to give the product g with 81% yield. 1 H NMR (250 MHz, THF-d 8 ): δ 8.49 (s, 1H), 8.11 (s, 1H), 7.64 (s, 1H), 7.59 (s, 1H). 13 C NMR (250 MHz, THF-d 8 ): δ / ppm: , 4

5 143.87, , , , , , HR-MS (MALDI) m/z calcd. for C17H9Br8O [M + ]: , found Melting point: o C. To a solution of 5 (0.46 g, 0.53 mmol) in dry DMAc (15 ml), NaI (0.79 g, 5.30 mmol) and maleimide (R= 2-ethylhexyl) (0.28 g, 1.32 mmol) were added. Then the mixture was heated at 80 C under Ar for 20h. After cooling, 20 ml water was added into the mixture. The product was collected by filtration, and washed with 30 ml water four times. The compound 1a was purified by short column chromatography with THF as eluent to give the product 1a in 67% yield. FD-Mass: calc.: found: H NMR (500 MHz, C 2 D 2 Cl 2 ): δ 8.47 (s, 2H), 8.40 (s, 2H), 8.38 (s, 2H), 8.37 (s, 2H), 3.68 (d, J = 7.0 Hz, 4H), (m, 2H), (m, 16H), 0.98 (t, J = 7.4 Hz, 6H), 0.92 (t, J = 6.6 Hz, 6H). 13 C NMR (500 MHz, C 2 D 2 Cl 2 ): δ / ppm: , , , , , , , , , , , , , 42.72, 38.64, 31.06, 28.73, 24.43, 22.88, 13.84, HR-MS (MALDI) m/z calcd. for C41H43N2O5 [M + ]: , found Melting point: o C. To a stirred mixture of 1a (90 mg, 140 mmol) and malononitrile (28 mg, 420 mmol) in 60 ml CHCl 3 was slowly added 1mol/L TiCl 4 (0.42 ml, 420 mmol) followed by dried pyridine (66 mg, 840 mmol). The mixture was refluxed for 36 hrs under Ar. Every 5 hrs, identical amounts of malononitrile, TiCl 4 and pyridine were added. After cooling down, the mixture was poured on ice/water and extracted with DCM. The combined organic layers were dried with Na 2 SO 4 for five hrs. The solvent was removed under vacuum and the residue was purified by column chromatography (using eluent: DCM: methanol = 200:1) to give 2a as orange solid. Finally the solid was washed with 300 ml acetone to give the pure product in 74% yield. FD-Mass: calc.: found:

6 1 H NMR (250 MHz, CD 2 Cl 2 ): δ 9.17 (s, 2H), 8.39 (s, 4H), 8.32 (s, 2H), 3.57 (d, J = 7.5 Hz, 4H), (m, 2H), (m, 16H), (m, 12H). 13 C NMR (250 MHz, C 2 D 2 Cl 2 ): δ / ppm: , , , , , , , , , , , , , 77.29, 42.70, 38.77, 30.95, 28.92, 24.28, 23.41, 14.24, HRMS (TOF MS ES+): m/z calcd for C 44 H 43 N 4 O , found Melting point: o C. Compound 1b was synthesized according to the previously method used to synthesize 1a. Yield: 72%. FD-Mass: calc.: found: H NMR (250 MHz, C 2 D 2 Cl 4 ): δ 8.45 (s, 2H), 8.37 (s, 4H), 8.36 (s, 2H), 3.60 (d, J = 7.2 Hz, 4H), (m, 2H), (m, 48H), (m, 12H). ). 13 C NMR (250 MHz, C 2 D 2 Cl 2 ): δ / ppm: , , , , , , , , , , , , , 43.05, 37.47, 32.30, 32.23, 31.91, 30.37, 30.06, 29.96, 29.71, 26.68, 26.65, 23.07, 23.06, 23.06, 14.27, HR-MS (MALDI) m/z calcd. for C 57 H 75 N 2 O 5 [M + ]: , found Melting point: o C. Compound 2b was synthesized according to the previously method used to synthesize 2a. Yield: 80%. FD-Mass: calc.: found: H NMR (250 MHz, C 2 D 2 Cl 4 ): δ 9.19 (s, 2H), 8.43 (s, 2H), 8.41 (s, 2H), 8.36 (s, 2H), 3.62 (d, J = 7.2 Hz, 4H), (m, 2H), (m, 48H), (m, 12H). 13 C NMR (250 MHz, C 2 D 2 Cl 2 ): δ / ppm: , , , , , , , , , , , , , 77.23, 32.30, 32.23, 31.90, 30.37, 30.05, 29.96, 29.71, 26.67, 23.08, 23.06, 14.28, HRMS (TOF MS ES+): m/z calcd. for C 60 H 75 N 4 O 4 [M + ]: , found Melting point: o C. 6

7 O N R: C 2 H 5 R C 4 H 9 C 6 H 13 C8H17 6 O Pyrrole-2,5-dione derivatives were synthesized according to the described procedure in the literature.[1, 2] TGA and DSC curves Figure S1. TGA curves of 1a-b and 2a-b. All of them showed good thermal stability with the temperatures of 5% weight loss at 442, 441, 411 and 404 C for 1a, 2a, 1b and 2b, respectively. 7

8 Figure S2. DSC thermograms of the 1a-b and 2a-b on heating and cooling cycles, heating/cooling rate = 10 C/min. XRD of zone-cast films of 2a and 2b Figure S3. XRD of zone-cast films of (A) 2a and (B) 2b (reflections are assigned by Miller s indexes). The additional peak (*) at 1.39 Å -1 is assigned to minor misalignment of the molecules. 8

9 POM images for 2a and 2b zone-cast layers Figure S4. Polarized optical microscopy images for 2a (A and B) and 2b (D and E) zone-cast layers. The red arrow indicates the zone-casting direction. Figure (C) and (F) illustrates schematically the organization of the 2a and 2b molecules on the surface. Red color suggests that the molecule is rotated by 180º with respect to the orange molecule (face-to-face organization). Crystal orientation of 2b in the zone-cast films Figure S5. Schematic illustration of the crystal orientation of 2b in the zone-cast films. 9

10 POM images of powder Figure S6. Optical microphotographs: 1a-2a and 1b-2b were heated to 270 C and 375 C, respectively, and then slowly cooled down to r.t. The images were taken at 25 C Photophysical and electrochemical properties of 1a-b and 2a-b Table S1. Summary of photophysical and electrochemical properties of 1a-b and 2a-b. E red1/2 vs absorption LUMO HOMO Eg Fc + /Fc(V) [a] edge (nm) (ev) [b] (ev) [c] (ev) [d] 1a b a b [a] In CH 2 Cl 2, Bu 4 NPF 6 (0.1 M), 295 K, scan rate = 100 mv/s, versus Fc+/Fc. [b] Determined from E LUMO = - [E red1/2 - E (Fc+/Fc) + 4.8] ev. [c] Calculated from E HOMO = E LUMO - E gap. [d] Determined from the onset of absorption ( M). 10

11 DFT calculations Figure S7. HOMO and LUMO energy levels for model compounds according to DFT calculations at the B3LYP/6-31G(d) level. Table S2. Calculated HOMO and LUMO energy levels for M1 and M2 with the DFT method at the B3LYP/6-311 G (d) level. HOMO(eV) LUMO(eV) M M

12 1 H NMR and 13 C NMR Spectra 1H NMR spectrum of Compound 3 in CD2Cl2 13C NMR spectrum of Compound 3 in CD2Cl2 12

13 1H NMR spectrum of Compound 4 in CD2Cl2 13C NMR spectrum of Compound 4 in CD2Cl2 13

14 1H NMR spectrum of Compound 5 in THF-d8 13C NMR spectrum of Compound 5 in THF-d8 14

15 1H NMR spectrum of Compound 1a in CD2Cl2 13C NMR spectrum of Compound 1a in CD2Cl2 15

16 1H NMR spectrum of Compound 2a in CD2Cl2 13C NMR spectrum of Compound 2a in CD2Cl2 16

17 1H NMR spectrum of Compound 1b in C2D2Cl4 13C NMR spectrum of Compound 1b in CD2Cl2 17

18 1H NMR spectrum of Compound 2b in C2D2Cl4 13C NMR spectrum of Compound 2b in CD2Cl2 18

19 HRMS spectra 19

20 EI mass spectrum References 1. Guo, X., et al., Thieno[3,4-c]pyrrole-4,6-dione-Based Polymer Semiconductors: Toward High-Performance, Air-Stable Organic Thin-Film Transistors. Journal of the American Chemical Society, (34): p Usta, H., et al., Anthracenedicarboximide-based semiconductors for air-stable, n-channel organic thin-film transistors: materials design, synthesis, and structural characterization. Journal of Materials Chemistry, (10): p