CN106675577A - Biphenyl liquid crystal compound containing pyridine end group and preparation method and application thereof - Google Patents

Abstract

The invention discloses a biphenyl liquid crystal compound containing a pyridine end group and a preparation method and application thereof. The structure formula of the compound is as shown in the specification, wherein CnH2n+1 replaces C2-C5 linear alkyl. The liquid crystal compound is obtained through Suzuki coupled reaction of pyridyl boron ester and aromatic hydrocarbon iodide. The synthesis method is simple, the cost is relatively low, and the liquid crystal compound is suitable for industrial production. The liquid crystal compound has positive dielectric anisotropy and a certain nematic phase liquid crystal interval, is relatively high in clearing point, can be applied to an IPS display mode and a TN display mode, and can be applied to a dye-sensitized solar cell as a dye sensitizer molecule.

Description

A kind of biphenyl liquid crystal compound containing pyridine terminal group and its preparation method and application

technical field

The invention belongs to the technical field of liquid crystal compounds, and in particular relates to a biphenyl liquid crystal compound containing a pyridine terminal group, and a preparation method and application of the liquid crystal compound.

Background technique

Since the development of liquid crystal materials, they have been applied in many fields such as liquid crystal displays, liquid crystal optical devices, high-strength elastic materials, and organic solar cell materials. Therefore, liquid crystal materials, as an interdisciplinary research hotspot, have been extensively studied by researchers. Against the backdrop of the energy crisis and environmental pollution posing increasing challenges to global sustainable development, solar cells are increasingly being valued by the scientific and industrial circles. In the past two years, liquid crystal researchers have done a lot of experimental research, hoping to apply liquid crystal materials to the field of solar cell research. Today, some liquid crystal materials have been successfully used in the field of solar cells. For example, Agnieszka Iwan reported that doping a chiral photosensitive liquid crystal molecule (AZOX) into the active layer of an organic solar cell improved the photovoltaic performance of the device (Liquid Crystals, 2015, 42(7), 964-972).

Fan Li reported that the addition of an ionic liquid crystal (6CNBP-N) to the anode buffer layer of a bulk heterojunction polymer solar cell induced phase separation, crystallinity, and ordered structure of the active layer, increasing the Photovoltaic performance (RSC Adv.2015,5,52874-52881).

E.A.Soto-Bustamante reported that a liquid crystal (M6R8) nanoparticle doped into titanium dioxide nanoparticles can improve the photocurrent of organic-inorganic hybrid solar cells (J.Mater.Chem.C,2015,3,8566--8573) .

Kuan Sun reported that a nematic liquid crystal (BTR) is very suitable for printable organic solar cells, and doping into the active layer can improve the efficiency of solar cells (Nature Communications, 2015, 6, 6013).

Takashi Kato reported that a liquid crystal electrolyte (1/2-I ₂ ) is applied in dye-sensitized solar cells, which can make the cells operate normally at high temperatures (Chem. Mater. 2014, 26, 6496-6502).

However, there are no reports about the application of liquid crystal materials for display in solar cells.

Contents of the invention

The technical problem to be solved by the present invention is to provide a liquid crystal compound for display that only has a nematic phase and has relatively large positive dielectric anisotropy, and provides a preparation method and application of the liquid crystal compound for display.

The technical solution adopted to solve the above technical problems is: the liquid crystal compound for display is a biphenyl liquid crystal compound containing a pyridine terminal group, and its structural formula is as follows:

In the formula, C _n H _2n+1 represents a C ₂ -C ₅ linear alkyl group.

The preparation method of the above-mentioned biphenyl liquid crystal compound containing pyridine terminal groups is as follows: 4-pyridine acetylene and 4-bromophenylboronic acid pinacol ester are prepared by Heck coupling reaction to prepare pyridyl boron ester 1; and then N,N-dimethyl The mixture of methyl formamide and distilled water with a volume ratio of 5:1 is used as a solvent. Under the protection of an inert gas, pyridyl boronic ester 1 and aromatic hydrocarbon iodide nI, tetra-n-butylammonium bromide, tetrakis (triphenyl) phosphine Combine palladium and potassium carbonate in a molar ratio of 1:1~1.3:0.05~0.2:0.02~0.04:2~4, stir and react at 40~60°C for 12~24 hours, separate and purify the product, and obtain a pyridine-containing terminal group Benzene liquid crystal compound, its reaction equation is as follows:

In the preparation method of the above-mentioned biphenyl liquid crystal compound containing pyridine terminal group, the mol ratio of preferred pyridyl boron ester to aromatic hydrocarbon iodide nI, tetra-n-butylammonium bromide, tetrakis (triphenyl) phosphine palladium, potassium carbonate 1:1.2:0.1:0.03:3.

The aromatic hydrocarbon iodide of the present invention is synthesized according to the method disclosed in the Chinese invention patent application with the publication number CN 103805208A and the title of the invention "Biscyclohexylethylene substituted diphenylene liquid crystal compound and its preparation method".

The use of the biphenyl liquid crystal compound containing pyridine terminal groups in the preparation of dye-sensitized solar cells of the present invention, the specific use method is as follows:

1. Conductive glass pretreatment

Clean the conductive glass in detergent, ethanol, and deionized water with an ultrasonic wave at a frequency of 40 Hz and a power of 100 W for 30 minutes to 1 hour, and dry it at 110°C for later use.

2. Preparation of dye solution

Dissolve biphenyl liquid crystal compounds containing pyridine terminal groups in a mixed solvent with a volume ratio of acetonitrile and tert-butanol of 1:1 to prepare a dye solution with a concentration of 0.3 mmol/L.

3. Preparation of electrolyte solution

Add tetrabutylammonium iodide, lithium iodide, iodine, and p-tert-butylpyridine into acetonitrile to prepare an electrolyte solution. The concentrations are 0.6mol/L, 0.1mol/L, 0.05mol/L, and 0.5mol/L, respectively.

4. Preparation of photoanode

A nanoporous TiO ₂ film with an area of 0.25 cm ² and a thickness of 12-20 μm was prepared on the pretreated conductive glass by screen printing technology, sintered at 450°C for 30 minutes, and cooled to room temperature naturally to prepare a photoanode.

5. Preparation of working electrode

Immerse the photoanode in the dye solution for 12-24 hours to obtain a sensitized working electrode.

6. Prepare counter electrode

A platinum paste with an area of 0.25 cm ² and a thickness of 4-6 μm is prepared on the pretreated conductive glass by screen printing technology, and a pair of electrodes is prepared.

7. Sealing

At the peripheral position of the electrode, the sarin heat-sealing film is evenly placed at the set position by printing and spraying, the working electrode and the counter electrode are closed and sealed, and the electrolyte solution is poured and sealed by vacuum back suction, and the dye-sensitized solar cell is prepared.

The present invention has the following beneficial effects:

1. The liquid crystal compound of the present invention has a pyridine ring as the terminal group, and compared with the traditional liquid crystal compound with a flexible alkyl chain as the terminal group, it has a large positive dielectric anisotropy and a certain nematic liquid crystal interval , can be applied to TN display mode and IPS display mode.

2. For the first time in the present invention, biphenyl liquid crystal compounds containing pyridine terminal groups are used as dye sensitizers in dye-sensitized solar cells.

Description of drawings

FIG. 1 is a J-V curve diagram of a dye-sensitized solar cell prepared by a biphenyl liquid crystal compound containing a pyridine terminal group prepared in Example 1. FIG.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.

Example 1

Under nitrogen protection, 2.58g (8.46mmol) 4-bromophenylboronic acid pinacol ester, 0.73g (7.05mmol) 4-pyridylacetylene, 20mL triethylamine (TEA), 20mL DMF were added to a thermometer equipped with a condensing In a 100mL three-neck flask with a magnetic stirrer, stir at 40°C for 30 minutes and then heat up to 60°C, then add 0.16g (0.14mmol) tetrakis(triphenyl)phosphine palladium and 0.05g (0.28mmol) iodide Cuprous, continue to react at 100°C for 6 hours, cool the reaction solution to room temperature naturally, extract the reaction solution three times with dichloromethane, and finally combine the organic phases, wash the organic phases with brine three times, and dry over anhydrous magnesium sulfate for half an hour. The solvent was recovered after suction filtration, and the eluent with a volume ratio of petroleum ether and ethyl acetate of 5:1 was used for column chromatography separation and purification to obtain 0.65 g of white solid, i.e., pyridyl boroester 1, with a yield of 30%. .

Under the protection of nitrogen, 2.38g (7.8mmol) pyridylboronate 1, 0.25g (0.78mmol) tetra-n-butylammonium bromide, 3.23g (23.4mmol) potassium carbonate, 30mL N,N-dimethyl form Amide and 6mL of distilled water were added to a three-necked flask equipped with a thermometer, a magnetic stirrer, and a condenser, and the three-necked flask was placed in an oil bath and heated to 40°C. After the solid was completely dissolved, 3.33g (9.36mmol) 4-(trans-(4-n-propylcyclohexyl)ethyl)iodobenzene 3I and 0.27g (0.23mmol) tetrakis(triphenyl)phosphine palladium, heated to 60°C, stirred at constant temperature for 12 hours, and ended the reaction , the reaction solution was cooled to room temperature, and filtered with diatomaceous earth, the filtrate was extracted with ethyl acetate, and the organic phase obtained after liquid separation was washed to neutrality, then dried with anhydrous magnesium sulfate and concentrated, and the concentrated solution was subjected to column chromatography separation and purification ( Using silica gel as the stationary phase and a mixture of petroleum ether and ethyl acetate at a volume ratio of 5:1 as the eluent), the separated and purified liquid was concentrated and then recrystallized with ethanol to obtain white crystals—containing pyridine ends Base biphenyl liquid crystal compound 3N, its yield is 60%, chemical name is 1-{4-[2-(4-n-propyl cyclohexyl) ethyl] biphenyl}-2-[4-pyridyl ] Acetylene.

The structural characterization data of the obtained biphenyl liquid crystal compound containing pyridine terminal groups are as follows:

¹³ C-NMR (CDCl ₃ as solvent, TMS as internal standard, 101MHz, ppm): 149.85, 143.31, 142.02, 137.37, 132.43, 131.64, 129.03, 127.03, 127.00, 125.63, 120.61, 94.20, 87.29, 39.858, 39 37.62, 37.60, 33.34, 33.30, 33.13, 20.15, 14.55.

¹ H-NMR (CDCl ₃ as solvent, TMS as internal standard, 400MHz, ppm): 8.59(d, J=5.3Hz, 2H), 7.59(s,, 4H), 7.51(d, J=8.1Hz, 2H ), 7.41-7.35(m, 2H), 7.29-7.21(m, 2H), 2.80-2.51(m, 2H), 1.86-1.70(m, 4H), 1.58-1.47(m, 2H), 1.32-1.13 (m, 6H), 0.97-0.83 (m, 7H).

Combining the above analysis results, it was confirmed that the obtained white crystals were indeed the compound 1-{4-[2-(4-n-propylcyclohexyl)ethyl]biphenyl}-2-[4-pyridyl]acetylene.

The synthesized compound 1-{4-[2-(4-n-propylcyclohexyl)ethyl]biphenyl}-2-[ The thermal properties of 4-pyridyl]acetylene, the results show that the compound has a liquid crystal phase, the phase transition property is Cr 138.3°C N 245.1°C I, Cr means crystal, N means nematic phase, I means isotropic liquid, and the clearing point is 245.1°C. Through the polarizing microscope test, it was found that the compound had a typical nematic phase during the heating process.

Example 2

In Example 1, the 4-(trans-(4-n-propylcyclohexyl) ethyl) iodobenzene 3I used was used with equimolar 4-(trans-(4-n-pentylcyclohexyl) ethyl) iodine Benzene 5I was replaced, and other steps were the same as in Example 1 to obtain white crystals—biphenyl liquid crystal molecules 5N containing pyridine end groups, with a yield of 63%, and the chemical name was 1-{4-[2-(4-normal Pentylcyclohexyl) ethyl] biphenyl}-2-[4-pyridyl] acetylene, the specific reaction equation is as follows:

The structural characterization data of the obtained biphenyl liquid crystal compound containing pyridine terminal groups are as follows:

¹³ C-NMR (CDCl ₃ as solvent, TMS as internal standard, 101MHz, ppm): 149.85, 143.31, 142.02, 137.35, 132.40, 131.64, 129.04, 127.03, 126.99, 125.62, 120.61, 94.19, 87.28, 39.915, 37 37.61, 37.54, 33.34, 33.32, 33.12, 32.33, 26.79, 22.83, 14.24.

¹ H-NMR (CDCl ₃ as solvent, TMS as internal standard, 400MHz, ppm): 8.59(dd, J=4.5, 1.6Hz, 2H), 7.59(s, 4H), 7.51(d, J=8.2Hz, 2H), 7.41-7.35(m, 2H), 7.29-7.22(m, 2H), 2.69-2.60(m, 2H), 1.85-1.69(m, 4H), 1.57-1.47(m, 2H), 1.33- 1.11 (m, 10H), 0.97-0.82 (m, 7H).

Combining the above analysis results, it was confirmed that the obtained white crystals were indeed the compound 1-{4-[2-(4-n-pentylcyclohexyl)ethyl]biphenyl}-2-[4-pyridyl]acetylene.

The synthesized compound 1-{4-[2-(4-n-pentylcyclohexyl)ethyl]biphenyl}-2-[ The thermal properties of 4-pyridyl]acetylene, the results show that the compound has a liquid crystal phase, and the phase transition property is Cr 86.5°C N 163.5°C I, Cr means crystal, N means nematic phase, I means isotropic liquid, and the clearing point is 163.5°C. Observed by a polarizing microscope, the compound has a typical nematic phase during the heating process.

Example 3

The use of the biphenyl liquid crystal compound containing pyridine terminal groups prepared in Example 1 in the preparation of dye-sensitized solar cells, the specific use method is:

1. Conductive glass pretreatment

Clean the conductive glass in detergent, ethanol, and deionized water with an ultrasonic wave at a frequency of 40 Hz and a power of 100 W for 30 minutes to 1 hour, and dry it at 110°C for later use.

2. Preparation of dye solution

Dissolve biphenyl liquid crystal compounds containing pyridine terminal groups in a mixed solvent with a volume ratio of acetonitrile and tert-butanol of 1:1 to prepare a dye solution with a concentration of 0.3 mmol/L.

3. Preparation of electrolyte solution

Add tetrabutylammonium iodide, lithium iodide, iodine, and p-tert-butylpyridine into acetonitrile to prepare an electrolyte solution. The concentrations are 0.6mol/L, 0.1mol/L, 0.05mol/L, and 0.5mol/L, respectively.

4. Preparation of photoanode

A nanoporous TiO ₂ film with an area of 0.25 cm ² and a thickness of 15 μm was prepared on the pretreated conductive glass by screen printing technology, sintered at 450°C for 30 minutes, and cooled naturally to room temperature to prepare a photoanode.

5. Preparation of working electrode

The photoanode was immersed in the dye solution for 24 hours to obtain a sensitized working electrode.

6. Prepare counter electrode

A platinum paste with an area of 0.25 cm ² and a thickness of 6 μm was prepared on the pretreated conductive glass by screen printing technology, and a pair of electrodes was prepared.

7. Sealing

At the peripheral position of the electrode, the sarin heat-sealing film is evenly placed at the set position by printing and spraying, the working electrode and the counter electrode are closed and sealed, and the electrolyte solution is poured and sealed by vacuum back suction, and the dye-sensitized solar cell is prepared.

JV characteristic test system (model IV Test Station 2000, produced by CROWNTECH, USA) was used to test the prepared solar cells. The short-circuit current density of the cells was 0.22mA/cm ² , the open-circuit voltage was 459.91V, and the fill factor was 0.59. Conversion efficiency 0.06%.

Claims (4)

1. a kind of biphenyls liquid crystal compounds of base containing pyridyl end, it is characterised in that the structural formula of the compound is as follows：

C in formula_nH_2n+1Represent C₂~C₅Straight chained alkyl.

2. the preparation method of the biphenyls liquid crystal compounds of base containing pyridyl end described in a kind of claim 1, it is characterised in that：Will 4- pyridines acetylene prepares pyridine radicals boron ester 1 with 4- bromobenzeneboronic acids pinacol ester by Heck coupling reactions；Then with N, N- diformazans Base formamide is 5 with distilled water volume ratio:1 mixture is solvent, under inert gas shielding, by pyridine radicals boron ester 1 and virtue It is in molar ratio 1 that fragrant hydrocarbon iodo thing nI, tetra-n-butyl ammonium bromide, four (triphenyl) phosphines close palladium, potassium carbonate:1~1.3:0.05~ 0.2:0.02~0.04:2~4, stirring reaction 12~24 hours, isolate and purify product at 40~60 DEG C, obtain containing pyridine end End group biphenyls liquid crystal compounds；

3. the preparation method of the biphenyls liquid crystal compounds of base containing pyridyl end according to claim 2, it is characterised in that：Institute State pyridine radicals boron ester 1 and close palladium, the mol ratio of potassium carbonate with aromatic hydrocarbon iodo thing nI, tetra-n-butyl ammonium bromide, four (triphenyl) phosphines It is 1:1.2:0.1:0.03:3.

4. the biphenyls liquid crystal compounds of base containing pyridyl end described in claim 1 are in DSSC is prepared Purposes.