S1

Electronic Supplementary Information

2-Positional pyrene end-capped oligothiophenes for high performance

organic field effect transistors

Kazuaki Oniwa,a Hiromasa Kikuchi,a Hidekazu Shimotani,b Susumu Ikeda,a Naoki Asao,a Yoshinori Yamamoto,a,c

Katsumi Tanigakia and Tienan Jin*a

a WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan. Fax:

+81-22-217-5979; Tel: +81-22-217-6177; E-mail: tjin@m.tohoku.ac.jp

b Graduate School of Science, Department of Physics, Sendai 980-8578, Tohoku University, Japan.

c State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China.

Electronic Supplementary Material (ESI) for ChemComm.This journal is © The Royal Society of Chemistry 2016

S2

General Information

The commercially available compounds and solvent were used as received. 1H NMR and 13C NMR spectra were

recorded on JEOL JNM AL 400 (400 MHz) spectrometers. 1H NMR spectra are reported as follows: chemical shift

in ppm δ relative to the chemical shift of CDCl3 at 7.26 ppm, integration, multiplicities (s = singlet, d = doublet, t =

triplet, q = quartet, m = multiplet and br = broadened), and coupling constants (Hz). 13C NMR spectra were recorded

on JEOL JNM AL 400 (100.5 MHz) spectrometers with complete proton decoupling, and chemical shift reported in

ppm δ relative to the central line of triplet for CDCl3 at 77 ppm. UV/Vis absorption spectra were recorded on a

JASCO V-650DS spectrometer. Fluorescence spectra were recorded on a HITACHI F-7000 spectrophotometer and

absolute fluorescence quantum yields were measured by a photon-counting method using an integration sphere on a

Hamamatsu Photonics C9920-02 spectrometer. Elemental analyses were measured on J-SCIENCE Lab JM-10 and

YANAKO YHS-11 in Central Analytical Facility, Institute of Multidisciplinary Research for Advanced Materials,

Tohoku University. DSC was measured by a RIGAKU DSC8230 using N2 atmosphere at a scan rate of 10 K/min.

TGA was measured by a RIGAKU TAG8120. X-Ray analysis was carried out at -173 °C with a Rigaku VariMax

with RAPID diffraction by using graphite monochromated Cu-Kα radiation. The structures were solved by direct

method. X-ray diffractions were measured by RIGAKU Smart Lab 9SW using Cu-Kα radiation and zero dimensional

mode Dte/X as high-speed detector. Column chromatography was carried out employing silica gel 60 N (spherical,

neutral, 40~100 μm, KANTO Chemical Co.). Analytical thin-layer chromatography (TLC) was performed on 0.2

mm precoated plate Kieselgel 60 F254 (Merck).

Materials

The commercially available compounds were used as received. Single crystals of BPy1T and BPy2T were grown by

a physical vapor transport (PVT) method under an argon gas flow using Separation Temperature Controller (AMF-

9P-III, ASAHI RIKA). The structures of BPy1T and BPy2T were determined by elemental analysis and X-ray

crystallography, and BPy3T was determined by elemental analysis.

Synthesis of 4,4,5,5-Tetramethyl-2-pyren-2-yl-[1, 3, 2]dioxaborolane (PyBpin)

To a hexane (15 mL) solution of Ir(μ-OMe)cod2 (180 mg, 0.27 mmol), dtbpy (144 mg, 0.54 mmol), and B2pin2 (300

mg, 1.07 mmol) were added pyrene (6.00 g, 29.7 mmol), B2pin2 (8.37 g, 33.0 mmol) and hexane (30 mL) in a sealed

tube under an Ar atmosphere. The reaction mixture was stirred at 80 °C for 16 h. The reaction mixture was passed

through a silica column chromatography (eluent: CH2Cl2) and the solvent was removed under reduced pressure.

Purification of the residue by a flush column chromatography (hexane/CH2Cl2= 1:1 as eluent) afforded PyBpin (5.09

g, 52%) as a white solid. 1H NMR (400 MHz, CDCl3): δ 8.64 (s, 2H), 8.17 (d, J = 8 Hz, 2H), 8.11 (d, J = 9 Hz, 2H),

8.06 (d, J = 9 Hz, 2H), 8.02 (t, J = 8 Hz, 1 H), 1.47 ppm (s, 12H); 13C NMR (100 MHz, CDCl3): δ 132.0, 131.6,

130.7, 128.1, 127.6, 126.8, 126.6, 125.3, 124.9, 84.6, 25.2 ppm (C-B not observed).

Synthesis of 2,5-di(pyren-2-yl)thiophene (BPy1T)

To a mixture of PyBpin (16.3 mmol, 5.36 g), Pd2(dba)3・CHCl3 (5 mol%, 280 mg), X-Phos (20 mol%, 524 mg),

K3PO4 (10 equiv, 11.5 g) was added the 2,5-dibromothiophene (5.40 mmol, 1.31 g) in DMF (50 mL) solution under

S3

N2 atmosphere. The reaction mixture was stirred for 24 h at 120 °C. The reaction mixture was filtered by washing

with THF, water and MeOH. The residue was further purified by sublimation at 370 °C (yellow solid; 2.20 g, 84%).

Anal. Calcd. for C36H20S: C, 89.22; H, 4.16; S, 6.62; Found: C 89.06, H 4.31, S 6.27%. HRMS (MALDI): [m/z]:

calcd for C36H20S, 484.12802; found, 484.12800.

Synthesis of 5,5'-di(pyren-2-yl)-2,2'-bithiophene (BPy2T)

BPy2T was prepared by coupling of PyBpin with 5,5'-dibromo-2,2'-bithiophene under the same conditions to BPy1T

and purified by sublimation at 380 °C (yellow solid; 1.34 g, 53%).

Anal. Calcd. for C40H22S2: C, 84.77; H, 3.91; S, 11.31; Found: C 84.71, H 3.98, S 11.22%. HRMS (MALDI): [m/z]:

calcd for C40H22S2, 566.11574; found, 566.11576.

Synthesis of 5,5''-di(pyren-2-yl)-2,2':5',2''-terthiophene (BPy3T)

BPy3T was prepared by coupling of PyBpin with 5,5''-dibromo-2,2':5',2''-terthiophene under the same procedures of

BPyT and purified by sublimation at 400 °C (red solid; 455 mg, 13%).

Anal. Calcd. for C44H24S3: C, 81.45; H, 3.73; S, 14.82; Found: C 81.45, H 3.88, S 14.76%. HRMS (MALDI): [m/z]:

calcd for C44H24S3, 648.10346; found, 648.10344.

Physical vapor transport (PVT) method for preparation of single crystals

BPy1T and BPy2T single crystals were grown by a PVT method in a stream of argon gas with a purity of 99.9999%.

The pure powders of BPy1T or BPy2T (1-5 mg) were placed in the aluminum foil at the end of the glass tube. After

being heated for 12 h with an Ar gas flow rate of 40 mL/min at 390 °C for BPy1T and 400 °C for BPy2T, the fine

film-like crystals of BPy1T and BPy2T were obtained. BPy3T was decomposed under the same PVT method at the

deposition temperature of 430 °C and partially recovered at the deposition temperature of 400 °C without observation

of sublimated materials.

Discussions concerning to the reviewers’ comments on the FET characterizations and performances [2]

(a) In output plots (Figure 3a and 3c), the drain currents remain almost zero until the drain voltage of -30 V. Can the

authors explain this phenomenon?

Response: We thought it might be due to the formation of non-ohmic contact resistances by the Schottky barrier. The

increase of Vd reduces the carrier injection barrier by Schottky effect, making the carrier injection possible.

(b) In single-crystal transistors, the threshold voltage is < 0 V, but for the same compound the value is > 0 V in thin

films for the same compound. Why?

Response: We ascribe the difference of threshold voltages to the thickness of single crystals and thin films. Generally,

in the bottom-gate/top-contact devices, the thickness of semiconductors influences the internal resistance from

electrode to channel and therefore affects the device performances such as threshold voltage (Vth). The

semiconducting layer with small thickness usually leads to a low Vth.

In addition, if the semiconductors are exposed to air before the measurement, the adsorbed oxygen on semiconductors

S4

may trap electrons, generating the doped holes. Particularly, oxygen may more easily access to the carrier

accumulation layer close to the semiconductor and insulator interface for the thin films having very small thickness

or low crystallinity, increasing the concentration of the doped holes, which probably results in Vth > 0.

(c) The HOMO level of BPy2T is closer to the Au work function than BPy1T. Is this another reason for the higher

mobility of BPy2T compared with BPy1T?

Response: We agree this comment that the correlation between HOMO of BPynT and Au work function should be

one of another reasons for the higher mobility of BPy2T compared with BPy1T.

Thermal analysis

Figure S1. DSC and TGA analysis. Melting points: BPy1T: 358 oC; BPy2T: 400 oC; BPy3T: 333 oC.

Decomposition temperatures (5% loss): BPy1T: 450 oC; BPy2T: 536 oC; BPy3T: 537 oC.

S5

Absorption and photoluminescence spectra in the solid state

Fig. S2 UV/vis absorption (solid line) and photoluminescence spectra of BPynT in the solid state.

S6

Theoretical calculation of HOMO and LUMO energy levels of BPynT

Computational Details

Calculations of monomer molecule were performed at the DFT level by means of the hybrid B3LYP functional as

implemented in Gaussian 09W. The 6-31G++(d, p) basis set was used for the all atoms.

Figure S3. Energy diagram of theoretical calculated HOMO and LUMO energy with work function of gold and

calcium.

Full Computational Details[1]

Cartesian Coordinates and Total Electron Energies

Table S1. BPy1T

SCF Done: E(RB3LYP) = -1782.24035451

-------------------------------------------------------------------------------------------------------------------

Center Atomic Atomic Coordinates(Angstroms)

Number Number Type X Y Z

-------------------------------------------------------------------------------------------------------------------

1 6 0 -9.54694 1.082561 0.000007

2 6 0 -8.57491 2.083987 -0.00086

3 6 0 -7.20782 1.758021 -0.00094

4 6 0 -6.82459 0.381204 -0.0001

5 6 0 -7.82556 -0.63886 0.000777

6 6 0 -9.17968 -0.26426 0.00081

7 6 0 -5.44441 0.02587 -0.00014

S7

8 6 0 -4.43893 1.038429 -0.00103

9 6 0 -3.08823 0.664932 -0.00105

10 6 0 -2.69007 -0.68356 -0.00015

11 6 0 -3.69039 -1.67379 0.000755

12 6 0 -5.05232 -1.34732 0.000728

13 6 0 -7.40337 -2.01509 0.001614

14 6 0 -6.08307 -2.35372 0.001603

15 6 0 -6.17361 2.758785 -0.00182

16 6 0 -4.8538 2.417172 -0.00188

17 6 0 -1.27098 -1.0625 -0.00009

18 16 0 0 0.14548 0.000139

19 6 0 1.270976 -1.0625 0.000115

20 6 0 0.709047 -2.32325 0.000022

21 6 0 -0.70905 -2.32325 -0.00013

22 6 0 2.690066 -0.68356 0.000169

23 6 0 3.08823 0.664932 0.001072

24 6 0 4.438932 1.038429 0.001038

25 6 0 5.444406 0.02587 0.000142

26 6 0 5.052322 -1.34732 -0.00072

27 6 0 3.69039 -1.67379 -0.00073

28 6 0 6.82459 0.381204 0.000082

29 6 0 7.207819 1.758021 0.000901

30 6 0 8.57491 2.083987 0.000801

31 6 0 9.546938 1.082561 -7.1E-05

32 6 0 9.179679 -0.26426 -0.00086

33 6 0 7.82556 -0.63886 -0.00081

34 6 0 6.083067 -2.35372 -0.0016

35 6 0 7.403371 -2.01509 -0.00163

36 6 0 4.853797 2.417172 0.001876

37 6 0 6.173607 2.758785 0.001798

38 1 0 -10.5987 1.353526 0.000051

39 1 0 -8.87104 3.129712 -0.00148

40 1 0 -9.94402 -1.03689 0.001476

41 1 0 -2.33917 1.451847 -0.00182

42 1 0 -3.41428 -2.72334 0.001566

43 1 0 -8.16677 -2.78877 0.002271

44 1 0 -5.78541 -3.39906 0.002254

45 1 0 -6.46787 3.805087 -0.00246

S8

46 1 0 -4.0876 3.187935 -0.00256

47 1 0 1.293382 -3.23553 0.000062

48 1 0 -1.29338 -3.23553 -0.00031

49 1 0 2.339168 1.451847 0.001837

50 1 0 3.414284 -2.72334 -0.00152

51 1 0 8.871039 3.129712 0.001415

52 1 0 10.5987 1.353527 -0.00013

53 1 0 9.944015 -1.03689 -0.00153

54 1 0 5.785411 -3.39906 -0.00224

55 1 0 8.16677 -2.78877 -0.00229

56 1 0 4.087596 3.187935 0.00256

57 1 0 6.467869 3.805087 0.002422

-------------------------------------------------------------------------------------------------------------------

Table S2. BPy2T

SCF Done: E(RB3LYP) = -2334.06379848

-----------------------------------------------------------------------------------------------------------

Center Atomic Atomic Coordinates (Angstroms)

Number Number Type X Y Z

-----------------------------------------------------------------------------------------------------------

1 6 0 -0.42453 11.66765 0

2 6 0 -1.54548 10.83639 0

3 6 0 -1.40263 9.438296 0

4 6 0 -0.08851 8.876413 0

5 6 0 1.054808 9.734015 0

6 6 0 0.862017 11.12561 0

7 6 0 -2.53107 8.545211 0

8 6 0 0.081559 7.461554 0

9 6 0 -1.05481 6.598329 0

10 6 0 -2.36673 7.191876 0

11 6 0 -0.86245 5.21018 0

12 1 0 -1.74138 4.571445 0

13 6 0 0.421942 4.637573 0

14 6 0 1.53555 5.498939 0

15 6 0 1.391132 6.891605 0

16 6 0 2.524814 7.780467 0

17 6 0 2.363355 9.133759 0

18 1 0 3.231075 9.788307 0

S9

19 1 0 3.521696 7.347454 0

20 1 0 -3.52938 8.974964 0

21 1 0 -0.55402 12.74598 0

22 1 0 -2.54314 11.26737 0

23 1 0 1.728783 11.78128 0

24 1 0 -3.23207 6.534347 0

25 1 0 2.539788 5.087738 0

26 6 0 0.611649 3.182116 0

27 6 0 1.788673 2.459933 0

28 16 0 -0.7569 2.080577 0

29 6 0 1.606761 1.054787 0

30 1 0 2.768714 2.921266 0

31 6 0 0.280525 0.666262 0

32 1 0 2.429169 0.348126 0

33 6 0 -0.28053 -0.66626 0

34 6 0 -1.60676 -1.05479 0

35 16 0 0.756902 -2.08058 0

36 6 0 -1.78867 -2.45993 0

37 1 0 -2.42917 -0.34813 0

38 6 0 -0.61165 -3.18212 0

39 1 0 -2.76871 -2.92127 0

40 6 0 -0.42194 -4.63757 0

41 6 0 0.862454 -5.21018 0

42 6 0 -1.53555 -5.49894 0

43 6 0 1.054808 -6.59833 0

44 1 0 1.741378 -4.57145 0

45 6 0 -1.39113 -6.89161 0

46 1 0 -2.53979 -5.08774 0

47 6 0 -0.08156 -7.46155 0

48 6 0 2.366727 -7.19188 0

49 6 0 -2.52481 -7.78047 0

50 6 0 0.088514 -8.87641 0

51 6 0 2.531068 -8.54521 0

52 1 0 3.232074 -6.53435 0

53 6 0 -2.36336 -9.13376 0

54 1 0 -3.5217 -7.34745 0

55 6 0 1.402627 -9.4383 0

56 6 0 -1.05481 -9.73402 0

S10

57 1 0 3.529384 -8.97496 0

58 1 0 -3.23108 -9.78831 0

59 6 0 1.545476 -10.8364 0

60 6 0 -0.86202 -11.1256 0

61 6 0 0.424525 -11.6677 0

62 1 0 2.543142 -11.2674 0

63 1 0 -1.72878 -11.7813 0

64 1 0 0.554017 -12.746 0

-----------------------------------------------------------------------------------------------------------

Table S3. BPy3T

SCF Done: E(RB3LYP) = -2885.88786277

----------------------------------------------------------------------------------------------------------

Center Atomic Atomic Coordinates (Angstroms)

Number Number Type X Y Z

----------------------------------------------------------------------------------------------------------

1 6 0 0 13.46618 -1.31799

2 6 0 0 12.49122 -2.31653

3 6 0 0 11.12509 -1.98652

4 6 0 0 10.74591 -0.60857

5 6 0 0 11.74992 0.408529

6 6 0 0 13.10288 0.029943

7 6 0 0 10.08798 -2.98423

8 6 0 0 9.366854 -0.24917

9 6 0 0 8.358404 -1.25883

10 6 0 0 8.769163 -2.63881

11 6 0 0 7.00887 -0.88134

12 1 0 0 6.257755 -1.6664

13 6 0 0 6.614702 0.468569

14 6 0 0 7.618238 1.456067

15 6 0 0 8.978911 1.125355

16 6 0 0 10.0127 2.128702

17 6 0 0 11.33191 1.786046

18 1 0 0 12.09763 2.557425

19 1 0 0 9.71821 3.174927

20 1 0 0 10.37913 -4.0314

21 1 0 0 14.51714 -1.59204

22 1 0 0 12.78425 -3.36312

S11

23 1 0 0 13.86949 0.800305

24 1 0 0 8.000744 -3.40736

25 1 0 0 7.345478 2.506456

26 6 0 0 5.19789 0.851283

27 6 0 0 4.639167 2.114335

28 16 0 0 3.923998 -0.35834

29 6 0 0 3.222512 2.121664

30 1 0 0 5.227595 3.023811

31 6 0 0 2.66031 0.858655

32 1 0 0 2.632267 3.031319

33 6 0 0 1.266519 0.479491

34 6 0 0 0.707651 -0.78536

35 16 0 0 0 1.697977

36 6 0 0 -0.70765 -0.78536

37 1 0 0 1.302208 -1.692

38 6 0 0 -1.26652 0.479491

39 1 0 0 -1.30221 -1.692

40 6 0 0 -2.66031 0.858655

41 6 0 0 -3.22251 2.121664

42 16 0 0 -3.924 -0.35834

43 6 0 0 -4.63917 2.114335

44 1 0 0 -2.63227 3.031319

45 6 0 0 -5.19789 0.851283

46 1 0 0 -5.2276 3.023811

47 6 0 0 -6.6147 0.468569

48 6 0 0 -7.00887 -0.88134

49 6 0 0 -7.61824 1.456067

50 6 0 0 -8.3584 -1.25883

51 1 0 0 -6.25776 -1.6664

52 6 0 0 -8.97891 1.125355

53 1 0 0 -7.34548 2.506456

54 6 0 0 -9.36685 -0.24917

55 6 0 0 -8.76916 -2.63881

56 6 0 0 -10.0127 2.128702

57 6 0 0 -10.7459 -0.60857

58 6 0 0 -10.088 -2.98423

59 1 0 0 -8.00074 -3.40736

60 6 0 0 -11.3319 1.786046

S12

61 1 0 0 -9.71821 3.174927

62 6 0 0 -11.1251 -1.98652

63 6 0 0 -11.7499 0.408529

64 1 0 0 -10.3791 -4.0314

65 1 0 0 -12.0976 2.557425

66 6 0 0 -12.4912 -2.31653

67 6 0 0 -13.1029 0.029943

68 6 0 0 -13.4662 -1.31799

69 1 0 0 -12.7842 -3.36312

70 1 0 0 -13.8695 0.800305

71 1 0 0 -14.5171 -1.59204

----------------------------------------------------------------------------------------------------------

S13

Crystal data of BPynT

Table S4. Crystallographic data for BPy1T and BPy2T

BPy1T BPy2T

Empirical Formula C36H20S C40H22S2

Formula Weight 484.58 566.73

T / K 90 90

Wavelength / Å 1.54187(Cu Kα) 1.54187(Cu Kα)

Crystal Color, Habit yellow, platelet yellow, block

Crystal Dimensions 0.800 x 0.200 x 0.005 mm 0.800 x 0.500 x 0.010 mm

Crystal System monoclinic monoclinic

Lattice Type Primitive Primitive

a / Å 23.8009(6) 22.725(7)

b / Å 3.84850(10) 3.8289(9)

c / Å 26.3591(8) 15.667(5)

α 90.000 90.000

β 113.9966(18) 109.48(2)

γ 90.000 90.000

V / Å 2205.75(10) 1285.2(7)

Space Group P21/c (#14) P21/c (#14)

Z value 4 2

Dcalc 1.459 g/cm3 1.464 g/cm3

F000 1008 588.00

Reflection collected 18601 10085

Unique reflections 3983 2319

Refined parameters 334 190

GOF on F2 1.102 1.077

R1 (I>2.00σ(I)) 0.0532 0.0716

wR2 (all data) 0.1465 0.2278

S14

Fabrication of single crystal OFET (OSCT) devices

A highly doped silicon wafer with a 300 nm thermally grown SiO2 layer was covered with OTS. The film-like crystal

having few micrometers thickness (estimated from the CCD camera to be in the range of 1~5 μm for BPy1T and

BPy2T) was laminated on the OTS-pretreated SiO2/Si substrate. The top contact symmetric and asymmetric

electrodes were deposited by evaporating of gold and calcium metals through a shadow mask on top of the crystal.

Electrical and optical characterizations were performed in the glove box under an inert Ar atmosphere by using a

semiconductor parameter analyzer (Agilent Technology B1500A) and a CCD camera through an optical microscope.

The observed light emission images were captured with a CCD camera.

Table S5. OSCT performances of BPy1T and BPy2T.

Compound (electrodes) μave (cm2/Vs) μmax (cm2/Vs) Vth on/off

BPy1T (Au-Au) 0.02 0.023 -23 104

BPy2T (Au-Au)

BPy2T (Au-Ca)

2.6

1.1

3.3

1.3

-39

-39

104

104

S15

Thin film OFET (OTFT) device fabrication and characterization

Device fabrication

A highly doped silicon wafer with a 300 nm thermally grown SiO2 layer was covered with OTS. These substrates

was used in the thin film deposition. Thin film transistors were fabricated by evaporating the highly pure molecules

under the high vacuum (10-6 Torr) with a thickness of 30 nm, as measured in situ by a quartz crystal microbalance.

The thin film deposition rate maintained at 0.1 Å/sec. The top contact symmetric electrodes were deposited by

evaporating gold metal through a shadow mask on the top of the thin film. The channel lengths (L) were in the range

of 0.05~0.15 mm and the widths (W) were in the range of 1~7.5 mm using the fixed W/L ratio of 20 and 50,

respectively. The electrical characterization of thin film transistors were analyzed similar to the single crystal devices.

Table S6. OTFT performances at various substrate temperatures (Tsub)

Compound Tsub (°C) μave (cm2/Vs) μmax (cm2/Vs) Vth On/off

BPy1T 40 7.3 × 10-6 8.8 × 10-6 -20 103

60 1.2 × 10-4 2.2 ×10-4 -19 103

80 2.5 × 10-4 2.7 × 10-4 6 104

100 8.4 × 10-5 1.1 × 10-4 -33 103

120 9.4 × 10-5 1.5 × 10-4 -66 103

140 1.0 × 10-4 1.2 × 10-4 -41 103

BPy2T 40 3.5 × 10-2 4.2 × 10-2 15 105

60 7.9 × 10-2 1.1 × 10-1 18 104

80 6.4 × 10-2 1.0 × 10-1 24 104

100 1.1 × 10-1 1.3 × 10-1 23 104

120 2.8 × 10-2 3.6 × 10-2 21 104

140 4.1 × 10-2 4.8 × 10-2 -8 105

BPy3T 40 9.4 × 10-3 1.2 × 10-2 -14 105

60 1.5 × 10-2 1.7 × 10-2 22 104

80 1.0 × 10-2 1.2 × 10-2 26 103

100 2.1 × 10-2 3.4 × 10-2 23 104

120 2.0 × 10-2 2.3 × 10-2 22 104

140 1.0 × 10-2 1.3 × 10-2 14 104

S16

Figure S4. X-ray diffraction (XRD) patters of the BPynT thin films at various Tsub: (a) BPy1T, (b) BPy2T, (c) BPy3T.

(a) (b)

(c)

S17

Scanning electron microscope (SEM) images of BPynT

Fig. S5 SEM images of BPy1T thin films at various substrate temperatures.

Fig. S6 SEM images of BPy2T thin films at various substrate temperatures.

S18

Fig. S7 SEM images of BPy3T thin films at various substrate temperatures.

References:

[1] Gaussian 09, Revision C.01, Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.;

Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.;

Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda,

R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A.; Peralta,

Jr., J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Keith, T.; Kobayashi,

R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam,

J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.;

Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V.

G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J.

V.; Cioslowski, J.; and Fox, D. J., Gaussian, Inc., Wallingford CT, 2010.

[2] H. Sirringhaus, Adv. Mater., 2014, 26, 1319.