CN111285842A - Trifluoromethyl thiophene ethylene thiophene donor, polymer and application thereof - Google Patents

Abstract

The invention discloses a trifluoromethyl thiophene ethylene thiophene donor, a polymer thereof and application thereof. The structural formula of the trifluoromethyl thiophene ethylene thiophene donor is shown as a formula II, and the structural formula of the polymer containing the trifluoromethyl thiophene ethylene thiophene donor is shown as a formula I. The invention provides a CF₃The TVT polymer has lower FMO energy level, is beneficial to the injection and transmission of single electrons, and can be used for preparing a high-performance pure n-type field effect transistor device; with the present invention CF₃The organic field effect transistor prepared by taking the TVT polymer as the semiconductor layer has higher mobility (mu) and on-off ratio (the electron mobility is up to 1.37 cm)²V^‑1s^‑1) In a single n-type OFETs has good application prospect.

Description

Trifluoromethyl thiophene ethylene thiophene donor, polymer and application thereof

Technical Field

The invention relates to a trifluoromethyl thiophene ethylene thiophene donor, a polymer thereof and application thereof, belonging to the field of materials.

Background

Organic field-effect transistors (OFETs) are a class of Organic electronic devices. One of the cores is an organic semiconductor layer, which can be an organic small molecule material or an organic polymer material. Among them, organic polymer materials have received more and more attention due to their characteristics of low cost, large-area preparation, and preparation of fully flexible electronic devices, and have become a hot point of research. In recent years, Donor-Acceptor (Donor-Acceptor) type polymer semiconductor materials have become an effective means for synthesizing materials having high mobility. Organic semiconductor materials can be classified into p-type, n-type, and bipolar materials according to carrier transport characteristics, and carriers thereof are holes, electrons, holes, and electrons, respectively. Most of the current high-performance polymer organic semiconductor materials are p-type materials and bipolar materials, and the development of high-performance n-type materials is delayed.

Disclosure of Invention

The invention aims to provide a polymer of thiophene ethylene thiophene ((E) -1,2-di (thiophenyl-2-yl) ethane, TVT for short) donor with trifluoromethyl, which can be used for preparing an organic semiconductor layer in an organic field effect transistor.

The polymer provided by the invention has a lower Lowest Unoccupied Molecular Orbital (LUMO) energy level, is beneficial to the injection of electrons, and also has a very low Highest Occupied Molecular Orbital (HOMO) energy level, so that the transmission of holes is effectively prevented, and test results show that the polymer shows an excellent single n-type transmission characteristic. The trifluoromethyl TVT donor expands the variety of n-type materials and has good application prospect.

The invention provides, first, a compound of formula II, i.e., CF₃TVT donor:

CF₃the TVT donor can be prepared as follows:

a) taking ruthenium terpyridyl hexahydrate and cuprous acetate as catalysts, taking potassium carbonate as alkali, and reacting 2-formaldehyde thiophene-3-boric acid with iodotrifluoromethane in a DMF (N, N-dimethylformamide) solvent under the excitation of blue visible light to obtain 2-formaldehyde thiophene-3-trifluoromethyl shown in a formula II-a;

b) adding the 2-formaldehyde thiophene-3-trifluoromethyl shown in the formula II-a obtained in the step a) and zinc powder into a tetrahydrofuran solvent, and obtaining trifluoromethyl thiophene ethylene thiophene (namely CF) shown in the formula II under the catalysis of titanium tetrachloride or tetrahydrofuran titanium chloride₃TVT)。

In the step a) of the method, the feeding molar ratio of the 2-formaldehyde thiophene-3-boric acid to the trifluoroiodomethane is 1: 2-10, specifically 1: 5; calculated by taking boric acid as one molar equivalent, the using amount of the alkali is 1-3 equivalents, the using amount of ruthenium terpyridyl hexahydrate is 0.01-0.1 equivalent, and the using amount of cuprous acetate is 0.05-0.5 equivalent; in the reaction step, the temperature is 60-80 ℃, the time is 12-24 hours, for example, the reaction is carried out for 12 hours at 60 ℃;

in the step b) of the method, the feeding molar ratio of the 2-formaldehyde thiophene-3-trifluoromethyl, the tetrahydrofuran titanium chloride and the zinc powder is 1: 2.5-5: 5-10; in the reaction step, the temperature is 70-100 ℃ and the time is 2-4 hours.

The invention provides a method for preparing a fluorine-containing polymer with CF₃TVT-Donor CF₃The structural formula of the TVT polymer is shown as the formula I:

in formula I, Acceptor represents an electron Acceptor group;

n represents a polymerization degree, is a natural number between 5 and 100, and specifically can be 10 to 40, more specifically 13 to 40, 13 to 20, or 18 to 40.

The structural formula of the electron acceptor group is shown as follows:

in the following formulas, the first and second groups,

represents a substitution site, and R is a linear or branched alkyl group having 1 to 40 carbon atoms, preferably a linear or branched alkyl group having 16 to 37 or 24 carbon atoms.

The polymers provided by the present invention are preferably of the formula I-1 (IID-CF)₃TVT) or formula I-2 (F-IID-CF)₃TVT) polymer:

in the formula I-1, R is preferably a straight chain or branched chain alkyl of 1-40, preferably a straight chain or branched chain alkyl with 16-37 carbon atoms, and more preferably 4-decyl tetradecyl;

in the formula I-2, R is preferably a straight chain or branched alkyl group of 1-40, preferably a straight chain or branched alkyl group of 16-37 carbon atoms, and more preferably a 4-decyl tetradecyl group.

The invention also provides a preparation method of the polymer, which comprises the following steps:

carrying out polymerization reaction on the compound shown in the formula II and receptor monomers under the action of a catalyst and a ligand to obtain a polymer shown in the formula I;

the acceptor monomer is selected from any one of the following compounds:

in the above production method, the catalyst is at least one selected from the group consisting of Herrmann catalyst, tetrakis (triphenylphosphine) palladium, bis (triphenylphosphine) palladium dichloride and tris (dibenzylideneacetone) dipalladium;

the ligand is selected from at least one of triphenylphosphine, tri (o-tolyl) phosphine and triphenylarsine.

In the preparation method, the molar ratio of the compound shown in the formula II, the receptor monomer, the catalyst and the ligand is 1: 1: 0.01-0.10: 0.04 to 0.80;

the temperature of the polymerization reaction is 90-140 ℃, and the time is 1 minute-24 hours.

The solvent for the polymerization reaction is at least one selected from the group consisting of toluene, chlorobenzene, and xylene.

The method may further comprise the following purification steps:

in the preparation method, after the polymerization reaction is finished, the obtained reaction system is cooled, then a mixed solvent of concentrated hydrochloric acid and methanol is added, the mixture is stirred for more than two hours at room temperature, then the mixture is filtered, the obtained precipitate is sequentially extracted by methanol, acetone, ethyl acetate and n-hexane by a Soxhlet extractor until the precipitate is colorless, micromolecules and a catalyst are removed, and the precipitate is extracted by trichloromethane to obtain the product; wherein, the volume ratio of the methanol to the hydrochloric acid can be specifically 20: 1, the concentration of hydrochloric acid may be 12M.

The polymer provided by the invention can be used for preparing an organic semiconductor layer in an organic field effect transistor, has higher mobility (mu) and on-off ratio, and has good application prospect in single n-type OFETs.

The invention has the following beneficial effects:

1. the polymerization method is C-H activated polymerization, the atom economy is high, and meanwhile, the device preparation process adopts non-chlorine solvents (toluene, xylene, tetralin and the like) for processing, so that the method has strong commercial application prospect;

2. the raw materials are commercial products, the synthetic route is simple, and compared with other synthetic methods, the synthetic route is green and efficient, and does not use and generate products polluting the environment. Meanwhile, the monomer and the polymer are new molecules, and can be popularized to the synthesis of polymers of various other receptors;

3、CF₃the TVT polymer has lower FMO energy level, is favorable for single electron injection and transmission, and can be used for preparing high-performanceA pure n-type field effect transistor device of (1);

4. with the present invention CF₃The organic field effect transistor prepared by taking the TVT polymer as the semiconductor layer has higher mobility (mu) and on-off ratio (the electron mobility is up to 1.37 cm)²V^-1s^-1) And has good application prospect in single n-type OFETs.

Drawings

FIG. 1 shows a polymer IID-CF₃TVT (FIG. 1(a)) and F-IID-CF₃UV-VIS absorption spectrum of TVT (FIG. 1 (b)).

FIG. 2 is a drawing of polymer IID-CF₃TVT (FIG. 2(a)) and F-IID-CF₃Cyclic voltammogram of TVT (fig. 2 (b)).

FIG. 3 is a CF of the present invention₃The TVT polymer is a structural schematic diagram of an organic field effect transistor with a semiconductor layer.

FIG. 4 shows the polymer IID-CF according to the present invention₃TVT (FIGS. 4(a) and 4(b)) and F-IID-CF₃TVT (fig. 4(c) and 4(d)) is a graph of output characteristics and a graph of transfer characteristics of the polymer field effect transistor of the semiconductor layer.

Detailed Description

The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

Example 1 Compound (CF) of formula II₃TVT) preparation

The synthetic route is as follows:

1) preparation of 2-Methylolthiophene-3-trifluoromethyl

In a glove box, 936 mg of 2-formaldehyde thiophene-3-boronic acid, 36.8 mg of cuprous acetate, 45 mg of ruthenium terpyridyl hexahydrate and 830 mg of potassium carbonate were added to a 100ml reaction tube. Then, an N, N-dimethylformamide solvent having 30 mmol of iodotrifluoromethane was added thereto. The reaction was carried out at 60 ℃ for 12 hours under the irradiation of a 30-watt blue LED lamp. Washing with water, extracting organic phase with ether, and separating by column chromatography to obtain the product. Pale yellow liquid (yield 36.8%).

In the reaction process, the molar ratio of the 2-formaldehyde thiophene-3-boric acid to the trifluoroiodomethane is 1: 5; calculated by taking boric acid as one molar equivalent, the dosage of the alkali is 1 equivalent, the dosage of the ruthenium terpyridyl hexahydrate is 0.01 equivalent, and the dosage of the cuprous acetate is 0.05 equivalent.

The structural characterization data is as follows:

¹H NMR(400MHz,CDCl3)δppm 10.16(s,1H),7.78(d,J＝4.0Hz,1H),7.38(d,J＝8.0Hz,1H)；¹³C NMR(100MHz,CDCl3)δppm 181.3(m),143.2(m),135.7(q,J＝72 Hz),134.2,127.3(q,J＝7.5Hz),121.7(q,J＝541Hz)；¹⁹F NMR(376MHz,CDCl3)δ ppm-54.9；HRMS(EI-TOF)m/z:[M+H]⁺Calculated for C₆H₃F₃OS:179.9857；Found: 178.9854.

2) preparation of trifluoromethylthiopheneethylthiophene (i.e. CF of formula II)₃TVT donor)

In a 100ml reaction flask, 1.66 g of tetrahydrofuran titanium chloride and 654 mg of activated zinc powder were added, and 10 ml of tetrahydrofuran solvent was further added, and heated under reflux at 70 ℃ for one hour. 360 mg of 2-formylthiophene-3-trifluoromethyl was dissolved in 2 ml of tetrahydrofuran, and the solution was added to the above reaction system while maintaining 70 degrees, followed by heating and refluxing for one hour. After the reaction is finished, cooling, pouring into silica gel, washing an organic phase by ethyl acetate, washing by water, extracting, and finally separating by column chromatography to obtain white solid CF₃TVT (42.7% yield).

In the reaction process, the feeding molar ratio of the 2-formaldehyde thiophene-3-trifluoromethyl, the tetrahydrofuran titanium chloride and the zinc powder is 1: 2.5: 5.

the structural characterization data is as follows:

¹H NMR(400MHz,CDCl₃)δppm 7.35(s,2H),7.27(d,2H,J＝3.6Hz),7.20(d,2H, J＝3.6Hz)；¹³C NMR(100MHz,CDCl3)δppm 142.2,128.5(q,J＝67Hz),126.5,124.9, 122.5(q,J＝540Hz),121.6；¹⁹F NMR(376MHz,CDCl3)δppm-56.3；HRMS(EI-TOF) m/z:[M+H]⁺Calculated for C₁₂H₆F₆S₂:327.9815；Found:327.9810.

example 2 Polymer IID-CF of formula I-1₃Preparation of TVT

Cyclized indigo-dibromo (as shown in formula III-1, R is 4-decyl tetradecyl) (110mg,0.1mmol), 3-trifluoromethyl-2 (2- (3-trifluoromethyl-2-thienylethylene) vinylthiophene) (32.8mg,0.1mmol), Herrmann's catalyst (2.4mg,0.002mmol), the ligand tri (o-tolyl) phosphine (1.4mg,0.004mmol), pivalic acid (10.2 mg,0.1mmol), cesium carbonate (98mg,0.3mmol), and toluene (5mL) were added to a pressure-resistant reaction flask, oxygen was removed by three freeze-pump-thaw cycles under nitrogen, and the reaction mixture was heated to 120 ℃ for polymerization for 18 hours. After cooling, the mixture was poured into 100mL of methanol, stirred at room temperature for 3 hours, and filtered. The obtained precipitate is loaded into a Soxhlet extractor for extraction. Firstly, methanol, acetone and normal hexane are used for extraction until the mixture is colorless, micromolecules and catalysts are removed, and then chloroform is used for extraction to obtain a final product 113.2mg with the yield of 81%.

The structural characterization data is as follows:

molecular weight: GPC M_n＝20.0kDa,M_w＝42.3kDa,PDI＝2.1。

Elemental analysis: anal, calcd, for C₇₈H₉₆F₂N₂O₂S₄:C 72.34,H 8.79；found:C 72.16,H8.65.

As can be seen from the above, the polymer has a correct structure and is a polymer IID-CF represented by the formula I-1₃TVT, wherein R is 4-decyl tetradecyl, and n is a natural number of 18-40.

Example 3, formula I-2The polymer F-IID-CF₃Preparation of TVT

Difluorocycloindigo-dibromo (as shown in formula III-2, R is 4-decyltetradecyl) (113mg,0.1mmol), 3-trifluoromethyl-2 (2- (3-trifluoromethyl-2-thienylethylene) vinylthiophene) (32.8mg,0.1mmol), Herrmann's catalyst (2.4mg,0.002mmol), the ligand tris (o-tolyl) phosphine (1.4mg,0.004mmol), pivalic acid (10.2 mg,0.1mmol), cesium carbonate (98mg,0.3mmol), and toluene (5mL) were added to a pressure-resistant reaction flask, deoxygenated under nitrogen for three freeze-pump-thaw cycles, and the reaction mixture was heated to 120 ℃ for polymerization for 18 hours. After cooling, the mixture was poured into 100mL of methanol, stirred at room temperature for 3 hours, and filtered. The obtained precipitate is loaded into a Soxhlet extractor for extraction. Firstly, methanol, acetone and normal hexane are used for extraction until the mixture is colorless, micromolecules and catalysts are removed, and then chloroform is used for extraction to obtain a final product of 110.5mg, wherein the yield is 76%.

The structural characterization data is as follows:

molecular weight: GPC M_n＝15.7kDa,M_w＝20.5kDa,PDI＝1.3。

Elemental analysis: anal, calcd, for C₇₈H₉₆F₂N₂O₂S₄:C,70.34；H,8.39.Found(％):C,70.22；H, 8.41.

As can be seen from the above, the polymer has a correct structure and is a polymer F-IID-CF represented by the formula I-2₃TVT, wherein R is 4-decyl tetradecyl, and n is a natural number of 13-20.

Following the procedures of examples 2 and 3, using as the acceptor a compound of formula III-3-III-6, respectively, with CF of formula II₃And polymerizing the TVT donor to obtain the polymer containing the trifluoromethyl thiophene ethylene thiophene donor.

Example 4 Polymer IID-CF₃TVT and F-IID-CF₃Spectral, electrochemical and field effect transistor performance of TVT

1) Polymer IID-CF₃TVT and F-IID-CF₃Spectral and electrochemical Properties of TVT

FIG. 1 shows a polymer IID-CF₃TVT and F-IID-CF₃Uv-vis absorption spectra of TVT in solution and thin films.

As can be seen from FIG. 1, the polymer IID-CF₃TVT and F-IID-CF₃The optical bandgaps of TVT are 1.67eV and 1.61eV, respectively (optical bandgaps according to equation E)_g1240/λ calculation, where E_gIs the optical band gap, and λ is the boundary value of the ultraviolet absorption curve). As can be seen from FIG. 1, both polymers have a relatively strong intramolecular charge transfer peak, indicating that the polymer has a strong intermolecular force.

The spectra of the polymers prepared from the compounds of the formulae III-3 to III-6 as acceptors were also determined, and the results showed that each polymer also had a relatively strong intramolecular charge transfer peak.

FIG. 2 is a drawing of polymer IID-CF₃TVT and F-IID-CF₃Cyclic voltammogram of TVT films.

The measurements were performed at the electrochemical workstation CHI660c and tested using a conventional three-electrode configuration with platinum as the working electrode, platinum wire as the counter electrode, silver/silver chloride as the reference electrode, and tetrabutylammonium hexafluorophosphate as the supporting electrolyte. The test was performed in acetonitrile solution. The cyclic voltammetry conditions were: the scan range is-1.8 to 1.8 volts (vs. Ag/AgCl) and the scan rate is 50 millivolts per second. Both polymers have oxidation peaks and reduction peaks and can be used as organic semiconductor materials. According to cyclic voltammograms, polymers IID-CF₃TVT and F-IID-CF₃The HOMO levels of the TVT are-6.02 eV and-6.11 eV, respectively, and the LUMO levels are-3.88 eV and-4.08 eV, respectively. The above indicates that the polymer has a lower HOMO level and a suitable LUMO level and is therefore a single n-type material.

And the cyclic voltammetry curves of the polymers prepared by using the compounds shown in the formulas III-3-III-6 as acceptors are simultaneously measured, and the results show that each polymer has a lower HOMO energy level and a proper LUMO energy level, so that the polymer is a single n-type material.

2) Polymer IID-CF₃TVT and F-IID-CF₃Field effect transistor performance of TVT

Fig. 3 is a schematic structural diagram of an organic field effect transistor, and as shown in the figure, a silicon wafer with a 300nm silicon dioxide layer is used as a substrate, silicon is used as a gate electrode, gold is used as a source and drain anode electrode, OTS (octadecyltrichlorosilane) modified silicon dioxide is used as an insulating layer, the polymers obtained in examples 1 to 2 are used as a semiconductor layer, a xylene solution with the concentration of 5mg/ml is used as a charge transport layer on the silicon wafer substrate by a glue spreading method, annealing is carried out on a hot stage at 200 ℃ for 10 minutes, and then 30 nm-thick gold is thermally evaporated by a vacuum evaporation method and used as a source and drain electrode, so that the preparation of the organic field effect transistor device is completed.

The electrical properties of the field effect devices prepared were measured at room temperature with a Keithley 4200SCS semiconductor tester. Two key parameters that determine the performance of OFETs are: carrier mobility (μ) and on-off ratio (I) of the device_on/I_off). The mobility refers to the average drift velocity of a carrier (unit is cm) under the action of a unit electric field²V^-1s^-1) Which reflects the mobility of holes or electrons in a semiconductor under an electric field. The on-off ratio is defined as: the ratio of the current in the "on" state and the "off" state of the transistor reflects the performance of the device switch. For a high performance field effect transistor, the mobility and switching ratio should be as high as possible.

FIG. 4 is a graph based on IID-CF₃TVT and F-IID-CF₃Transfer characteristic curve and output characteristic curve of field effect transistor prepared from TVT polymer. Two polymer field effect transistors exhibit a single n-type transfer characteristic.

The carrier mobility can be calculated from the equation:

I_DS＝(W/2L)C_iμ(V_G–V_T)²(saturation region)

Wherein, I_DSIs the drain current, μ is the carrier mobility, V_GIs the gate voltage, V_TIs the threshold voltage, W is the channel width, L is the channel length, C_iIs an insulator capacitor. Utilizing (I)_DS，sat)^1/2To V_GPlotting, and performing linear regression to obtain carrier mobility (μ) from the slope of the regression line, and determining V from the intercept of the regression line and the X-axis_T。

The mobility can be calculated from the slope of the transfer curve according to the formula, and the device properties of the polymer field effect transistor prepared in each of the above examples are shown in table 1. The switching ratio can be derived from the ratio of the maximum value to the minimum value of the side source-drain current in fig. 4.

Experimental results show that the trifluoromethyl substituted thiophene ethylene thiophene donor polymer is an excellent novel single n-type material.

The transfer characteristic curve and the output characteristic curve of the field effect transistor prepared based on the polymer prepared from the compound represented by the formula III-3-formula III-6 as an acceptor were simultaneously measured, and the results showed that each of the polymer field effect transistors exhibited a single n-type transmission characteristic.

The invention is not limited to the recorded materials, a series of polymers can be obtained by changing different acceptor units, and the synthesis method provided by the invention is simple and effective, and has great guiding significance for synthesizing new single n-type materials.

TABLE 1 device Performance of the Polymer field Effect transistor

Claims (9)

1. A compound of the formula II,

2. a preparation method of a compound shown as a formula II comprises the following steps:

1) taking ruthenium terpyridyl hexahydrate and cuprous acetate as catalysts, taking potassium carbonate as alkali, and reacting 2-formaldehyde thiophene-3-boric acid with trifluoroiodomethane under the excitation of blue visible light to obtain 2-formaldehyde thiophene-3-trifluoromethyl shown in a formula II-a;

2) under the catalysis of titanium tetrachloride or tetrahydrofuran titanium chloride and in the presence of zinc powder, 2-formaldehyde thiophene-3-trifluoromethyl shown in a formula II-a is reacted to obtain trifluoromethyl thiophene ethylene thiophene shown in a formula II in claim 1.

3. A polymer of the formula I,

in formula I, Acceptor represents an electron Acceptor group;

n represents a polymerization degree and is a natural number between 5 and 100.

4. The polymer of claim 3, wherein: the structural formula of the electron acceptor group is shown as follows:

in the following formulas, the first and second groups,

represents a substitution site, and R is a linear or branched alkyl group having 1 to 40 carbon atoms.

5. A process for the preparation of a polymer as claimed in claim 3 or 4, comprising the steps of:

carrying out polymerization reaction on a compound shown in a formula II and receptor monomers under the action of a catalyst and a ligand to obtain a polymer shown in a formula I according to claim 3 or 4;

the acceptor monomer is selected from any one of the following compounds:

6. the method of claim 5, wherein: the catalyst is selected from at least one of Herrmann's catalyst, tetrakis (triphenylphosphine) palladium, bis (triphenylphosphine) palladium dichloride, and tris (dibenzylideneacetone) dipalladium;

the ligand is selected from at least one of triphenylphosphine, tri (o-tolyl) phosphine and triphenylarsine.

7. The production method according to claim 5 or 6, characterized in that: the molar ratio of the compound shown in the formula II, the receptor monomer, the catalyst and the ligand is 1: 1: 0.01-0.10: 0.04 to 0.80;

the temperature of the polymerization reaction is 90-140 ℃, and the time is 1 minute-24 hours.

The solvent for the polymerization reaction is at least one selected from the group consisting of toluene, chlorobenzene, and xylene.

8. Use of a polymer according to claim 3 or 4 for the preparation of an organic effect transistor.

9. An organic field effect transistor, characterized by: the material of the semiconductor layer of the organic field effect transistor is the polymer according to claim 3 or 4.

Images