CN101353352A - Hexathiophene and its derivatives and their preparation method and application - Google Patents

Abstract

The invention discloses hexathiophene and its derivatives as well as their preparation method and application. Hexathiophene derivatives, the structural formula is shown in formula (I), wherein, R is H, alkyl or aryl. The present invention also provides the preparation method of the compound of formula (I). The synthesis route of the present invention is simple and effective; the OFET prepared with the hexathiophene of the present invention as the organic semiconductor layer has high mobility and high on-off ratio (μ up to 0.06cm ² /V·s, and on-off ratio is 10 ⁵ ) , have a good application prospect in OFET.

Description

Hexathiophene and its derivatives and their preparation method and application

technical field

The present invention relates to hexathiophene and its derivatives, their preparation method and application.

Background technique

Since the first organic field effect transistor (OFET) was reported in 1986 (Tsumura, A.; Koezuka, H.; Ando, T. Appl. Phys. Lett, 1986, 49, 1210), OFET has made great progress . The advantages of organic field-effect transistors are: simple preparation process, low cost, light weight and good flexibility. They can be used in smart cards, electronic trademarks, electronic paper, memory, sensors and active matrix displays. They are ideal for organic optoelectronic devices and circuits. key components.

Thiophene compounds are an important class of organic semiconductor materials. α-thiophene (α-nT) and its derivatives have been widely used in organic field effect transistors (Katz, HE; Laquindanum, JG; Lovinger, AJ Chem. Mater.1998, 10, 633. Ong, BS; Wu, Y .; Liu P.; Gardner, S.Adv.Mater.2005, 17, 1141), however, because the thiophene molecule is easy to bend, it is not easy to form a plane, thereby affecting the band gap of the molecule (Videlot-Ackermann, C.; Ackermann, J.; Brisset, H.; Kawamura, K.; Yoshimoto, N.; Raynal, P.; .; Gilat, SLAcc. Chem. Res. 2001, 34, 359). Increasing the overlapping of π-orbitals is beneficial to the electronic coupling between adjacent molecules, thus enhancing the carrier mobility. Compared with thiophene, fused-ring thiophene has better orbital overlap, and it is easier to adopt the face-to-face π-π stacking method, which is conducive to obtaining high carrier mobility. In recent years, derivatives of condensed dithiophene and dithiophene have been widely used in organic field effect transistors (Murphy AR; Fréchet, JMJ Chem. Rev. 2007, 107, 1066). Pentacene molecules are herringbone stacking in the single crystal structure, and the intermolecular CH-π interaction contributes a lot to charge transport (Mattheus, CC; de Wijs, GA; de Groot, RA; Palstra, TTMJAm.Chem .Soc.2003,125,6323), yet pentacene is very unstable in the air, which seriously restricts its preparation process and practical application. Pentathiophene has a molecular structure similar to pentacene, but has higher stability. The thin film field effect transistor prepared with pentathiophene has a mobility of 0.045cm ² /V·s and an on/off ratio of 10 ³ , ( Xiao, K.; Liu, Y.; Qi, T.; Zhang, W.; Wang, F.; Gao, J.; Qiu, W.; Ma, Y.; Cui, G.; Chen, S.; Zhan, X.; Yu, G.; Qin, J.; Hu, W.; Zhu, DJ Am. Chem. Soc. 2005, 127, 13281).

Contents of the invention

The object of the present invention is to provide hexathiophene and its derivatives and their preparation methods.

The hexathiophene and its derivatives provided by the present invention have structures as shown in formula (1):

Formula (I)

Wherein, R is hydrogen, alkyl or aryl.

The method for the compound shown in the preparation formula (I) provided by the present invention, comprises the following steps:

1) Cool the anhydrous ether solution of 3,6-dibromodithiophene to -10～-20°C, add n-butyllithium in n-hexane, and react for 1-1.5 hours to obtain the mixed system a;

2) Add the anhydrous diethyl ether solution of compound II into the mixed system a at -10 to -20°C, react for 1-1.5 hours, and then react at room temperature for 12 to 15 hours to obtain compound III;

3) Prepare an anhydrous ether solution of compound III, cool it to 0～-10°C, add n-butyllithium in n-hexane, react for 2-3 hours, and then react at room temperature for 2-5 hours to obtain white precipitate. solution b;

4) Cool the anhydrous ether solution of anhydrous copper chloride to 0～-10°C to obtain a brown solution c, add the solution b to the solution c, carry out an oxidation coupling reaction, and obtain hexathiophene as the nucleus A compound of formula (I);

Wherein, the structural formulas of compound II and compound III are as follows:

Formula (II) Formula (III)

Wherein, R is hydrogen, alkyl or aryl.

The method also includes the steps of washing the compound obtained in step 4) with methanol and acetone in sequence, and sublimating and purifying in a gradient sublimation furnace.

Wherein, the concentration of 3,6-dibromodithiophene in the anhydrous ether solution of 3,6-dibromodithiophene is 0.03-0.1 mmol/ml. The n-butyl lithium concentration in the n-butyl lithium n-hexane solution is 1.6-2.5 mol/L. The concentration of the anhydrous copper chloride in the anhydrous ether solution of the anhydrous copper chloride is 0.3-0.5 mmol/ml.

The molar ratio of 3,6-dibromodithiophene to n-butyl lithium in the step 1) is 1:(2-2.5).

The molar ratio of compound III to n-butyllithium in step 3) is 1:(4-5).

Another object of the present invention is to provide the use of hexathiophene represented by formula (I) and its derivatives.

The use of the compound represented by the formula (I) provided by the present invention is the application of the compound in the preparation of organic field effect transistors.

The advantages of the present invention are:

1. The synthetic route is simple and effective, and the synthetic cost is low;

2. HTA is a linear large π-conjugated molecule with a rigid planar structure, which can be used to prepare OFET devices with high mobility;

3. High thermal stability (decomposition temperature greater than 320°C);

4. It has a lower HOMO energy level (about -5.06eV), and has high stability to oxygen, which is beneficial to obtain OFET devices with stable high switching ratio in air.

5. The OFET prepared with the hexathiophene of the present invention as the organic semiconductor layer has very high mobility and on-off ratio (μ is up to 0.06cm ² /V·s, and the on-off ratio is 10 ⁵ ), and has a good switching ratio in OFET. Application prospects.

Description of drawings

Figure 1 is a synthetic route diagram of hexathiophene.

Fig. 2 is the thermogravimetric analysis curve of hexathiophene in Example 1.

Fig. 3 is the ultraviolet absorption spectrum and fluorescence spectrum of embodiment 1 hexathiophene solution.

Fig. 4 is the ultraviolet absorption spectrum of the hexathiophene film of Example 1.

Fig. 5 is the cyclic voltammetry curve of Example 1 hexathiophene.

Fig. 6 is a schematic structural view of an organic field effect transistor using hexathiophene as an organic layer in Example 1.

Fig. 7 is the output curve of the organic field effect transistor with hexathiophene as the organic layer in Example 1.

Fig. 8 is a transfer curve diagram of an organic field effect transistor with hexathiophene as an organic layer in Example 1.

Detailed ways

Embodiment 1, the synthesis of hexathiophene (in the formula (I), R is the compound of H)

3,6-dibromodithiophene and two (3-thiothiophene) (R in the formula (II) are the compounds of hydrogen) synthetic methods see references (Fuller, L.S.; Iddon, B.; Smith.K.A.J.Chem. Soc., Perkin Trans. 11997, 3465. Lumbroso, H.; Catel, J.M.; Le Coustumer, G.; Andrieu, C.G.J. Mol. Struct.1999, 513, 201.)

Synthesis of bis(3-thiothiophene):

Cool the 0.5~1mmol/ml 3-bromothiophene anhydrous ether solution to -55~-78℃, add 1.6~2.5mol L ^-1 n-butyllithium n-hexane solution, react for 1~1.5 hours, add Elemental sulfur is reacted for another 1 to 1.5 hours, and potassium ferricyanide hexahydrate is added for oxidative coupling to obtain bis(3-thiothiophene).

The synthesis of bis(2-alkyl-4-thiothiophene) refers to the synthesis method of bis(3-thiothiophene), only need to replace 3-bromothiophene with 2-alkyl-4-bromothiophene.

The synthesis of bis(2-aryl-4-thiothiophene) refers to the synthesis method of bis(3-thiothiophene), only need to replace 3-bromothiophene with 2-aryl-4-bromothiophene.

1) Synthesis of 3,6-bis-(3-thiothiophene) and dithiophene (R is a compound of hydrogen in formula (III))

Under the protection of nitrogen, add 2.98g (10.0mmol) of 3,6-dibromodithiophene to a 250ml three-necked flask, and add 100mL of anhydrous ether solution, cool to -10～-20°C, add dropwise 2.5mol L ^-1 8 mL (20 mmol) of n-hexane solution of butyllithium was reacted for 1 hour to obtain the mixed system a with white precipitate. Under nitrogen protection, add 4.60 g (20 mmol) of bis(3-thiothiophene) and 50 mL of anhydrous ether to another 250 ml three-necked flask to obtain an anhydrous ether solution of bis(3-thiothiophene), and cool to -10～- 20°C, slowly added dropwise to the mixed system a, reacted for 1.5 hours, the reaction liquid was brought to room temperature, and reacted for another 12 hours, then the solvent was evaporated to dryness, and the mixture was mixed with 2.0mol L ^-1 hydrochloric acid aqueous solution/dichloromethane (volume ratio 1:1) Extract (300ml×2); combine the organic phases and dry over anhydrous magnesium sulfate. The organic solvent was removed by vacuum rotary evaporation, and the crude product was purified by silica gel chromatography (eluent-petroleum ether), and the component with R _f of 0.2 was collected to obtain a white solid 3,6-bis-(3-thiothiophene) di Thiophene (3.12 mg, 82% yield).

The structural characterization data of 3,6-bis-(3-thiothiophene)dithiophene are as follows:

Mass spectrum: MS m/z 368 (M ⁺ , 100).

Elemental analysis: molecular formula: C ₁₄ H ₈ S ₆ ; theoretical value: C, 45.62; H, 2.19. measured value: C, 45.66; H, 2.26.

Proton nuclear magnetic spectrum: ¹ H NMR (CDCl ₃ , 400MHz): δ=7.01-7.02ppm (d, 2H, J=4.0Hz), 7.30-7.31ppm (d, 6H, J=4.0Hz).

Carbon NMR: ¹³ CNMR(CDCl ₃ )δ _C 123.9(s), 126.5(s), 126.6(s), 127.9(s), 128.6(s), 130.3(s), 140.5(s).

2) Synthesis of hexathiophene (HTA)

Under the protection of nitrogen, add 2 g (5.5 mmol) of 3,6-bis-(3-thiothiophene)-dithiophene prepared in step 1) and 100 mL of anhydrous ether into a 250 ml three-necked flask, cool to -10°C, and add dropwise 2.5 10 mL (25 mmol) of n-hexane solution of n-butyllithium in mol L ^-1 was reacted for 2 hours. The reaction solution was brought to room temperature, and then reacted for 2 hours to obtain solution b with white precipitate.

Under the protection of nitrogen, add 3.38g (25mmol) of anhydrous copper chloride and 50mL of anhydrous ether to another 250ml three-necked flask, cool to -10°C, and react for 1 hour to obtain a brown solution c, and a solution with white precipitate b was slowly added dropwise into the brown solution c, and reacted for 1 hour. The reaction solution was raised to room temperature and reacted for another 12 hours. Then the solvent was evaporated to dryness by rotary evaporation, and washed with 2.0 mol L ^-1 hydrochloric acid aqueous solution (60ml×3); a brown-yellow solid was obtained. The crude product was washed successively with methanol and acetone, and then sublimated and purified three times in a gradient sublimation furnace. Finally, light yellow hexathiophene (HTA) (120 mg, yield 6.0%) was obtained.

The structural characterization data of hexathiophene are as follows:

Mass spectrum: HRMS (MALDI) m/z [C ₁₄ H ₄ S ₆ ] Theoretical value: 363.8637, found value: 363.8639.

Elemental analysis: molecular formula: C ₁₄ H ₄ S ₆ ; theoretical value: C, 46.12; H, 1.11. measured value: C, 46.04; H, 1.39.

Proton nuclear magnetic spectrum: ¹ H NMR (p-Cl ₂ Ph, 300MHz, 380k), δ _H = 7.16-7.18 (2H, d, J = 6.0); 7.11-1.13 (2H, d, J = 6.0).

Using the same synthesis process, 2-alkyl-4-bromothiophene or 2-aryl-4-bromothiophene is lithiated with butyl, and then oxidized and coupled with potassium ferricyanide to obtain di(2-alkyl-4 -thiothiophene) or two (2-aryl-4-thiothiophene), respectively react with 3,6-dibromodithiophene to obtain the corresponding alkyl-substituted or aryl group based on hexathiophene as the nucleus Alternative organic field effect materials.

Example 2, thermodynamic properties, spectral properties, electrochemical properties and field effect transistor properties of hexathiophene

1) Thermodynamic properties

Figure 2 is the TGA-DTA curve of hexathiophene. It can be seen from the figure that hexathiophene shows good thermal stability, and the decomposition temperature is about 320°C.

2) UV absorption spectrum and fluorescence spectrum of tetrahydrofuran solution and thin film of hexathiophene

The thin film of hexathiophene is a thin film (thickness: 50 nm) prepared by vapor-depositing hexathiophene on a quartz plate under a vacuum close to 10 ^-4 Pa.

As can be seen from Figure 3, the position of the maximum ultraviolet absorption peak of hexathiophene in solution is about 312nm, and the position of the maximum emission peak of fluorescence is around 415nm; it can be seen from Figure 4 that the position of the maximum ultraviolet absorption peak of hexathiophene in the solution is 353nm, and the optical band The gap is 2.82eV.

3) Electrochemical properties of hexathiophene

Figure 5 is the cyclic voltammetry curve of hexathiophene. The electrolytic cell adopts a three-electrode test system. Under a vacuum close to 10 ^-4 Pa, hexathiophene is evaporated onto an indium tin oxide (ITO) modified glass sheet to make a thin film (thickness 10nm) as the working electrode, and Ag/AgCl as the working electrode. Reference electrode, platinum wire as counter electrode, Bu ₄ NPF ₆ (0.1M) as supporting electrolyte. The conditions of cyclic voltammetry are: the scanning range is 0-1.8V (vs. Ag/AgCl), and the scanning rate is 50mV/s.

Electrochemical tests show that its initial oxidation potential is about 0.86, and the calculated HOMO (highest occupied orbital level) is -5.06eV, indicating that hexathiophene has high oxidation stability.

4) Field-effect transistor properties of hexathiophene

The preparation of organic field effect transistors: using highly doped silicon (Si) as the substrate, 470nm thick silicon dioxide as the insulating layer, and gold (Au) as the source electrode (S) and drain electrode (D) , and hexathiophene was vapor-deposited on an octadecyltrichlorosilane-modified (OTS) silicon dioxide wafer at a vacuum close to 10 ^-4 Pa, with a thickness of about 50 nm. A schematic diagram of the structure of an organic field effect transistor is shown in Figure 6.

The electrical properties of the as-prepared organic field-effect transistors (OFETs) were measured with a Hewlett-Packard (HP) 4140B semiconductor tester at room temperature. Two key parameters that determine the performance of OFETs are: carrier mobility (μ) and device on/off ratio (I _on /I _off ). Mobility refers to the average carrier drift velocity (unit: cm ² /V·s) under a unit electric field, which reflects the mobility of holes or electrons in a semiconductor under an electric field. The switching ratio is defined as: under a certain gate voltage, the ratio of the current of the transistor in the "on" state and the "off" state, which reflects the switching performance of the device. For a high performance field effect transistor, its mobility and switching ratio should be as high as possible.

Fig. 7 shows the output curves of the fabricated field effect transistors under different gate voltages V _G (0V, -20V, -40V, -60V, -80V, -100V). It shows a very good linear region and saturation region, indicating that the OFET device of hexathiophene has a good field effect control performance.

Fig. 8 is the transfer curve of the prepared field effect transistor. The mobility and switching ratio of field effect transistors can be obtained from the figure.

The carrier mobility can be calculated from the equation:

I _DS ＝(W/2L)C _i μ(V _G -V _T ) ² (saturation region, V _DS ＝V _G -V _T )

Among them, I _DS is the drain current, μ is the carrier mobility, V _G is the gate voltage, V _T is the threshold voltage, W is the channel width (W=3mm), L is the channel length (L=0.05 mm), C _i is the insulator capacitance (C _i =7.5×10 ^-9 F/cm ² ). Use (ID _DS , sat) ^1/2 to plot V _G and perform linear regression. The carrier mobility (μ) can be calculated from the slope of the regression line, and V _T can be obtained from the intercept point of the regression line and the X-axis. Mobility can be calculated from the slope of the transfer curve according to the formula. I _DS =(W/2L)C _i μ(V _G −V _T ) ² .

The on-off ratio can be obtained from the ratio of the maximum value to the minimum value of the source-drain current on the right side of the figure.

We used the new compound synthesized in the present invention as the organic layer to make many organic field effect transistor devices. Among these devices, the highest mobility can reach 0.06cm ² /V·s, and the on-off ratio is 10 ⁵ .

The experimental results show that hexathiophene is an excellent organic field effect transistor material. The good performance of the device is attributed to the original design idea of the present invention. Six monothiophene rings are condensed together, so that the conjugated system of the molecule can be expanded, and a high-performance OFET material is obtained. The present invention is not limited to the reported material, there are many kinds of substitution compounds with hexathiophene as the central core, and the synthesis method provided by the present invention is simple and effective. This will make a great contribution to the screening of field effect materials based on hexathiophene and its derivatives.

Claims (10)

1, the compound shown in the formula (I):

Formula (I)

Wherein, R is H, alkyl or aryl.

2 ,-and kind prepare the method for the described compound of claim 1, may further comprise the steps:

1) with 3, the anhydrous ether solution of 6-dibromo and two thiophene is cooled to-10～-20 ℃, adds the hexane solution of n-Butyl Lithium, and reaction 1～1.5h forms mixed system a;

2) under-10～-20 ℃, the anhydrous ether solution of Compound I I is added among the described mixed system a, reaction 1-1.5h at room temperature reaction 12～15h hour, obtains compound III then;

3) anhydrous ether solution of preparation compound III is cooled to 0～-10 ℃, adds the hexane solution of n-Butyl Lithium, and reaction 2～3h then at room temperature reaction 2～5h hour, obtains the solution b that the adularescent precipitation generates;

4) anhydrous ether solution with anhydrous cupric chloride is cooled to 0～-10 ℃, obtains brown solution c, and described solution b is added among the described solution c, carries out the oxidation coupling reaction, obtains the compound shown in the formula (I);

Wherein, the structural formula of Compound I I, compound III is as follows:

Formula (II) formula (III)

Wherein, R is H, alkyl or aryl.

3, method according to claim 2 is characterized in that: described method comprises that also the compound that step 4) is obtained uses methyl alcohol successively, washing with acetone, the step of purifying with the distillation of gradient subliming furnace again.

4, according to claim 2 or 3 described methods, it is characterized in that: described 3, in the anhydrous ether solution of 6-dibromo and two thiophene 3, the concentration of 6-dibromo and two thiophene is 0.03～0.1mmol/ml.

5, according to claim 2 or 3 described methods, it is characterized in that: the concentration of n-Butyl Lithium is 1.6～2.5mol/L in the hexane solution of described n-Butyl Lithium.

6, according to claim 2 or 3 described methods, it is characterized in that: in the described step 1) 3, the mol ratio of 6-dibromo and two thiophene and n-Butyl Lithium is 1: (2-2.5).

7, according to claim 2 or 3 described methods, it is characterized in that: the mol ratio of compound III and n-Butyl Lithium is 1 in the described step 3): (4-5).

8, according to claim 2 or 3 described methods, it is characterized in that: the concentration of anhydrous cupric chloride is 0.3～0.5mmol/ml in the anhydrous ether solution of described anhydrous cupric chloride.

9, the application of the described compound of claim 1 in the preparation organic field effect tube.

10, a kind of organic field effect tube is characterized in that: described organic field effect tube is with the organic field effect tube of the described compound of claim 1 as organic semiconductor layer.

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