A liquid crystal compound based on a 4,5,6,7-tetrahydrobenzo[b]thiophene skeleton, a related liquid crystal composition and applications

Abstract

This invention discloses a liquid crystal compound based on a 4,5,6,7-tetrahydrobenzene[b]thiophene skeleton, related liquid crystal compositions, and their applications. The disclosed liquid crystal compound has the structure shown in general formula (1), and the disclosed liquid crystal composition comprises a liquid crystal compound as shown in general formula (1). The liquid crystal compound of this invention has advantages such as a wide nematic phase temperature range, large dielectric anisotropy, and high birefringence. The liquid crystal composition containing the liquid crystal compound of this invention has advantages such as a wide operating temperature range, good photostability, and high birefringence, and can be used in various displays with different display modes, as well as in microwave liquid crystal communication devices, liquid crystal optical devices, and liquid crystal phase shifters. (1)

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal material technology, specifically relating to a liquid crystal compound based on a 4,5,6,7-tetrahydrobenzyl[b]thiophene skeleton, related liquid crystal compositions and their applications, mainly used in liquid crystal displays, microwave liquid crystal communication devices, liquid crystal optical devices and other fields. Background Technology

[0002] The development of fluorine-substituted liquid crystal materials has significantly improved the performance of liquid crystal displays (LCDs) over the past two decades, greatly facilitating people's work and lives. Although LCD technology has faced strong challenges from organic light-emitting diode (OLED) display technology in recent years, LCDs still dominate the field of large-size displays. With the rapid development of small LED (mLED) and micro LED (μLED) backlighting technologies, the contrast ratio of traditional LCDs is expected to be greatly improved, making them a strong contender for the next generation of high-performance display technologies. This new backlighting also places higher demands on the liquid crystal materials used in conjunction with LCDs, especially requiring improved dielectric anisotropy to reduce energy consumption. At the same time, applications of liquid crystal materials in non-display fields such as microwave communication, smart windows and soft robots, and optical devices are also emerging. Traditional display liquid crystal materials have low birefringence and cannot be directly used in these emerging fields. Therefore, there is an urgent need to develop new liquid crystal materials to meet the increasingly diverse new application requirements.

[0003] Based on the molecular structure characteristics of liquid crystal materials, molecular structure innovation can be achieved by changing their lateral substituents, nucleus units, connecting bridges, and terminal groups. Among these, the nucleus unit directly affects the intermolecular interactions and molecular packing of liquid crystal molecules, and is the most important structural unit determining the properties of liquid crystal molecules. Chem. Soc. Rev. (2007, 36, 2070–2095). Traditional crystal nucleation units, such as 1,4-disubstituted benzene and trans-1,4-disubstituted cyclohexane, have been widely used in display liquid crystal materials, and their research is relatively complete. Simple permutations and combinations can no longer achieve significant changes in the properties of liquid crystal molecules.

[0004] In recent years, researchers have obtained novel liquid crystal molecules by introducing heterocyclic crystal nuclei into liquid crystal molecules. J. Mater. Chem. C , 2017, 5, 12308–12337; RSC Adv. September 2019, 23161–23228; J Mol. Liquid. , 2020, 297, 111909; J Mol. Liq. , 2020, 297, 111686). Currently, a series of liquid crystal molecules based on different heterocyclic skeletons have been developed, such as benzoxazoles ( J Mol. Liq. , 2024, 394, 123677), benzimidazoles ( Liquid Crystal. , 2020, 47, 1281–1290), flavonoids ( Liquid Crystal. , 2008, 35, 157–162), coumarins ( Liquid Cryst. , 2010, 37, 1549–1557), benzothiazoles ( Liquid Crystal ., 2010, 37, 547–554), triazoles ( Liquid Cryst. (e.g., 2012, 39, 1099–1111). These heterocyclic crystal nuclei containing nitrogen, sulfur, or oxygen atoms not only greatly enrich the types of liquid crystal materials, but also allow for the regulation of the thermal properties, phase transition behavior, and physical properties of liquid crystal molecules, making them a current research hotspot.

[0005] However, the introduction of heterocyclic crystal nuclei can also enhance the interaction between liquid crystal molecules, leading to an increase in the melting point and viscosity of the compound, which affects its practical application. Summary of the Invention

[0006] Based on the urgent need for novel heterocyclic crystal nuclei to construct high-performance liquid crystal materials, this invention provides a liquid crystal compound based on a 4,5,6,7-tetrahydrobenzyl[b]thiophene skeleton, related liquid crystal compositions, and their applications.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A liquid crystal compound based on the 4,5,6,7-tetrahydrobenz[b]thiophene skeleton, characterized in that the compound structure is as shown in general formula (1): (1) Wherein, R1 is a saturated alkyl group with 1 to 9 carbon atoms, an unsaturated alkyl group with 1 to 9 carbon atoms, a fluorine atom (F), a chlorine atom (Cl), a cyano group (CN), or an isothiocyano group (NCS); the ring H is a benzene ring or trans-cyclohexane; the L1 and L2 bridging bonds are a single bond, an ethylene bridging bond (-C=C-), and an acetylene bridging bond (-C≡C-), respectively; A1, A2, A3, and A4 are hydrogen atoms or fluorine atoms; n = 0, 1, 2; R2 and R3 are independently hydrogen atoms, saturated alkyl groups with 1 to 9 carbon atoms, or unsaturated alkyl groups.

[0009] The novel 4,5,6,7-tetrahydrobenzyl[b]thiophene liquid crystal molecules of this invention can increase the birefringence, dielectric anisotropy, and phase transition temperature range of liquid crystal molecules without causing a significant increase in melting point and viscosity. The preferred structure is shown in the following general formula: .

[0010] The present invention also provides a method for synthesizing the liquid crystal compound based on the 4,5,6,7-tetrahydrobenz[b]thiophene skeleton, as follows:

[0011] This synthetic method uses substituted cyclohexanone thiophene as a starting material. First, a substituted 4,5,6,7-tetrahydrobenzo[b]thiophene intermediate is obtained by reduction with hydrazine hydrate. This intermediate then reacts with NBS to yield a 2-brominated thiophene intermediate. Finally, this 2-brominated intermediate undergoes a palladium-catalyzed coupling reaction with a fluorinated arylboronic acid derivative to prepare the aforementioned liquid crystal compound. This synthetic method has advantages such as simple route, readily available starting materials, ease of operation, high yield, and controllable synthesis cost.

[0012] The present invention also provides a liquid crystal composition, characterized in that it comprises one or more 4,5,6,7-tetrahydrobenz[b]thiophene liquid crystal compounds of preferred structural formula (1). Optionally, the mass fraction of the compound of formula (1) in the liquid crystal composition of the present invention is 1% to 100%.

[0013] The liquid crystal composition provided by the present invention further includes one or more liquid crystal compounds of general formula (2) as a second component. Optionally, the mass fraction of the second component is 0-97%.

[0014] (2) Wherein, R4 and R5 are independently saturated alkyl groups with 1 to 9 carbon atoms, unsaturated alkyl groups with 1 to 9 carbon atoms, saturated alkoxy groups with 1 to 9 carbon atoms, unsaturated alkoxy groups with 1 to 9 carbon atoms, fluorine atoms (F), chlorine atoms (Cl), cyano (CN), isothiocyano (NCS), trifluoromethyl (CF3), or trifluoromethoxy (OCF3); L3 and L4 bridging bonds are independently single bonds, ethylene bridging bonds (-C=C-), ethane bridging bonds (-CC-), acetylene bridging bonds (-C≡C-), difluoromethyl ether bridging bonds (-CF2O-), or difluoroethylene bridging bonds (-FC=CF-); ring O, ring P, and ring Q are independently benzene rings, trans-cyclohexane, cyclohexene, or benzene rings substituted with fluorine (F), chlorine (Cl), trifluoromethyl (CF3), methyl (CH3), or ethyl (CH3CH2); m = 0, 1, 2. The preferred structure of general formula (2) is as follows:

[0015] Where X is a fluorine atom.

[0016] The liquid crystal composition of the present invention may further contain one or more chiral additives, the amount of which is 0.01%-1% by mass of the liquid crystal composition; preferably 0.1%-0.5%. The chiral additive is preferably derived from the following structures:

[0017] Wherein, R is an alkyl group or an alkoxy group with 1 to 9 carbon atoms, each having an independent number of carbon atoms from 1 to 9.

[0018] The liquid crystal composition of the present invention further comprises a plurality of hindered phenols as an antioxidant stabilizer, wherein the content in the liquid crystal composition is 1 ppm-10000 ppm; preferably 10 ppm-1000 ppm. The antioxidant stabilizer is preferably derived from the following structures:

[0019] Wherein, R' is an alkyl group with 1 to 9 independent carbon atoms.

[0020] The liquid crystal composition of the present invention further comprises one or more ultraviolet light stabilizers in an amount of 1 ppm to 10,000 ppm; preferably 10 ppm to 1,000 ppm. The ultraviolet light stabilizer is preferably derived from the following structure:

[0021] The liquid crystal compounds and their compositions obtained by this invention have large dielectric anisotropy, high birefringence, wide operating temperature range, and low material cost, making them suitable for high-performance liquid crystal display elements and non-display liquid crystal elements, such as liquid crystal optical devices. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, and are not intended to limit the scope of the present invention.

[0023] Liquid crystal formulation preparation method: A thermal dissolution method is adopted. First, monomer liquid crystals of different weight ratios are weighed using a precision balance, heated to 60℃~100℃, and stirred for 1~2 hours to ensure uniform dissolution of all components. After cooling, the mixture is filtered, and the resulting liquid is degassed under high vacuum (≤100Pa). Finally, it is encapsulated with high-purity nitrogen to obtain the target mixed liquid crystal.

[0024] Unless otherwise specified, all liquid crystal compositions involved in this invention are prepared according to this method.

[0025] The detailed test method for testing the physical and photoelectric properties of the mixed liquid crystal involved in this invention is as follows: (1) Liquid crystal phase transition temperature and liquid crystal phase state: Differential scanning calorimetry (DSC): Under nitrogen atmosphere, the heating rate was set to 2℃ / min.

[0026] Polarizing hot stage method (POM): The liquid crystal sample is coated on a glass slide and placed in an orthogonal polarizing microscopic hot stage, with a heating rate of 2℃ / min. The changes in the texture of the liquid crystal sample are observed under a polarizing microscope to determine the liquid crystal phase.

[0027] (2) Birefringence (Δn): Using an Abbe refractometer, under constant temperature conditions of 25℃, the birefringence (Δn) of the ordinary ray was measured separately. o ) and unusual light (n e The refractive index of ) and the birefringence Δn = n e -n o .

[0028] (3) Dielectric constant (Δε): Tested using an LCR meter under constant temperature conditions of 25℃. Δε = ε ∥ -ε ⊥ That is, the dielectric constant along the long axis of the molecule (ε) ∥ ) and the dielectric constant along the short axis of the molecule (ε) ⊥ The difference between ).

[0029] (4) Elastic constant (K) 11 K 33 Under constant temperature conditions of 25℃, K was obtained by fitting the capacitance-voltage (CV) curve of the liquid crystal. 11 and K 33 .

[0030] (5) Rotational viscosity (γ1): Under constant temperature of 25℃, the transient current value I of liquid crystal molecules deflected by electric field was measured by applying voltage to the liquid crystal test cell. p The rotational viscosity γ1 was calculated.

[0031] (2) Low Temperature Storage (LTS): Pour approximately 1 mL of the mixed liquid crystal into a transparent glass bottle and place it in a low-temperature freezer. Set the temperature to -20℃, -30℃, and -40℃, and store for 10 days respectively, observing whether crystals precipitate or smectic phases appear. If no crystals precipitate at -30℃, the LTS is ≤ -30℃.

[0032] The basic formulation HOST in the following examples is obtained by mixing the following three fluorinated liquid crystal monomers in a mass ratio of 1:1:1.

[0033] .

[0034] The codes and descriptions involved in this invention are shown in Tables 1-3: Table 1 Physical parameters

[0035] Table 2 Structural Abbreviations

[0036] Table 3 Examples of structural abbreviations

[0037] Example 1: This example is 2-(4-(4-propylcyclohexyl)phenyl)-4,5,6,7-tetrahydrobenzo[ b The synthesis of thiophene, with the following structural formula:

[0038] The synthetic route is shown below:

[0039] The specific method is as follows: Step 1: Remove 6,7-dihydrobenzo[ b The reaction mixture of thiophene-4(5H)-one (10.0 g), hydrazine hydrate (13.5 g), potassium hydroxide (12.9 g), and diethylene glycol (100 mL) was heated at 200 °C for 6 hours, cooled to room temperature, diluted with water, and extracted three times with toluene. The organic phases were combined, washed once with water, dried over anhydrous magnesium sulfate, and filtered to obtain the filtrate. The solvent was removed under reduced pressure, and the residue was purified by silica gel column chromatography (eluent: n-heptane / toluene = 10 / 1, V / V) to give the intermediate 4,5,6,7-tetrahydrobenzo[ b Thiophene was a light yellow oily substance (8.8 g, yield 80%).

[0040] The compound characterization data are as follows: 1 H NMR (500 MHz, CDCl3): δ = 7.07 (d, J = 5.00 Hz, 1H), 6.78 (d, J = 5.00 Hz, 1H), 2.81 (t, J = 6.00 Hz, 2H), 2.66 (t, J = 6.00 Hz, 2H),1.90–1.82 (m, 4H) ppm. 13 C NMR (125 MHz, CDCl3): δ = 135.6, 135.3, 127.8,121.6, 25.7, 25.1, 23.9, 23.1 ppm. MS m / z (RI, %): 138.2 (M +, 68.1), 110.2(100.0), 137.1 (25.9), 97.1 (16.4), 111.1 (13.8), 139.1 (9.3). Step 2: Remove 4,5,6,7-tetrahydrobenzo[ b The mixture of thiophene (8.8 g) and dichloromethane (100 mL) was cooled to -15 °C, and then added... N - Bromosuccinimide (10.8 g), followed by continued reaction at the same temperature for 2 hours; after the reaction was complete, 100 mL of water was added to quench the reaction, followed by extraction with dichloromethane, washing the organic phase with water, drying with anhydrous magnesium sulfate, filtering to obtain the filtrate, and removing the solvent under reduced pressure to obtain 2-bromo-4,5,6,7-tetrahydrobenzo[ b Thiophene was a pale yellow oil (13.8 g). The crude compound could be used directly in the next coupling reaction without further purification.

[0041] The compound characterization data are as follows: MS m / z (RI, %): 137.1 (M + , 100.0), 190.0 (67.6), 188.0 (66.9), 218.1 (54.2), 216.1 (53.6), 109.1 (29.3). Step 3: Under nitrogen protection, 4-(4-ethylcyclohexyl)phenyl)boronic acid (1.19 g), 2-bromo-4,5,6,7-tetrahydrobenzo[ b A mixture of thiophene (1.00 g), potassium carbonate (1.27 g), Pd(PPh3)2Cl2 (0.03 g), tetrabutylammonium bromide (0.1 g), and solvent (toluene / ethanol / water, 100 mL, V / V / V = 1 / 1 / 1) was heated at 100 °C for 6 hours and then cooled to room temperature. The reaction mixture was extracted with toluene to obtain the organic phase. After washing the organic phase with water, the solvent was removed under reduced pressure. The residue was purified by silica gel column chromatography (eluent: n-heptane / toluene = 8 / 1, V / V) to give compound 2-(4-(4-propylcyclohexyl)phenyl)-4,5,6,7-tetrahydrobenzo[ b Thiophene is a white solid (1.4 g, 87% yield).

[0042] The compound characterization data are as follows: 1 H NMR (500 MHz, CDCl3): δ = 7.47 (d, J = 8.50 Hz, 2H), 7.19 (d, J = 8.50 Hz, 2H), 6.93 (s, 1H), 2.78 (t,J = 6.00 Hz, 2H), 2.63 (t, J =6.00 Hz, 2H), 2.50–2.44 (m, 1H), 1.94–1.80 (m, 8H), 1.51–1.21 (m, 7H), 1.11–1.03 (m, 2H), 0.93 (t, J = 7.00 Hz, 3H) ppm. 13 C NMR (125 MHz, CDCl3): δ = 146.9,140.7, 136.3, 135.1, 132.7, 127.3, 125.6, 123.4, 44.5, 39.9, 37.2, 34.4,33.7, 25.8, 25.2, 23.8, 23.1, 20.2, 14.55 ppm. MS m / z (RI, %): 338.1 (M + ,100.0), 339.2 (24.6), 253.0 (17.9), 227.0 (14.1), 212.1 (13.8), 310.1 (10.3). DSC and POM tests revealed that the phase transition temperature and phase transition type of the compound are: Cr 113.7 N 138.3 I.

[0043] When the compound was added to the base formulation HOST at a mass fraction of 10%, the compound dissolved well and showed no obvious crystallization at room temperature.

[0044] Further testing of its physical properties yields the birefringence Δ of this compound. n = 0.2147, dielectric anisotropy Δ ε = 2.15.

[0045] Example 2: This example is 2-(2-fluoro-4-(4-propylcyclohexyl)phenyl)-4,5,6,7-tetrahydrobenzo[ b Thiophene, with the following structural formula:

[0046] Using the same preparation method as in Example 1, but replacing 4-(4-ethylcyclohexyl)phenylboronic acid with 2-fluoro-4-(4-propylcyclohexyl)phenylboronic acid, 2-(2-fluoro-4-(4-propylcyclohexyl)phenyl)-4,5,6,7-tetrahydrobenzo[ b Thiophene is a white solid.

[0047] The compound characterization data are as follows:1 H NMR (500 MHz, CDCl3): δ = 7.45 (t, J = 8.50 Hz, 1H),7.08 (s, 1H), 6.98–6.95 (m, 2H), 2.79 (t, J = 6.50 Hz, 2H), 2.64 (t, J = 6.00 Hz,2H), 2.49–2.43 (m, 1H), 1.92–1.79 (m, 8H), 1.47–1.20 (m, 7H), 1.09–1.01 (m,2H), 0.91 (t, J = 7.50 Hz, 3H) ppm. 13 C NMR (125 MHz, CDCl3): δ = 159.1 (d, J =247.50 Hz), 148.9 (d, J = 6.25 Hz), 136.1, 135.9 (d, J = 2.50 Hz), 133.6 (d, J =2.50 Hz), 128.3 (d, J = 3.75 Hz), 126.8 (d, J = 6.25 Hz), 122.9 (d, J = 3.75 Hz), 120.2 (d, J = 12.50 Hz), 114.5 (d, J = 22.50 Hz), 44.2, 39.8, 37.1, 34.2, 33.5,25.7, 25.1, 23.7, 23.1, 20.2, 14.6 ppm. MS m / z (RI, %): 356.2 (M + , 100.0), 357.2 (34.4), 328.1 (28.0), 230.0 (12.4), 245.0 (12.3), 271.0 (12.0). DSC and POM tests revealed that the phase transition temperature and phase transition type of the compound are: Cr 109.7 N 114.6I.

[0048] When the compound was added to the base formulation HOST at a mass fraction of 10%, the compound dissolved well and showed no obvious crystallization at room temperature.

[0049] Further testing of its physical properties yields the birefringence Δ of this compound. n = 0.2057, dielectric anisotropy Δ ε = 2.33.

[0050] Example 3: This example is 2-(3-fluoro-4'-propyl-[1,1'-biphenyl]-4-yl)-4,5,6,7-tetrahydrobenzo[ b Thiophene, with the following structural formula:

[0051] Using the same preparation method as in Example 1, but replacing 4-(4-ethylcyclohexyl)phenyl)boronic acid with (3-fluoro-4'-propyl-[1,1'-biphenyl]-4-yl)boronic acid, 2-(3-fluoro-4'-propyl-[1,1'-biphenyl]-4-yl)-4,5,6,7-tetrahydrobenzo[ b Thiophene is a white solid.

[0052] The compound characterization data are as follows: 1 H NMR (500 MHz, CDCl3): δ = 7.58 (t, J = 8.00 Hz, 1H), 7.50 (d, J = 7.50 Hz, 2H), 7.36–7.33 (m, 2H), 7.25 (d, J = 8.50 Hz, 2H), 7.16 (s,1H), 2.79 (t, J = 6.00 Hz, 2H), 2.66–2.61 (m,4H), 1.89–1.79 (m, 4H), 1.71–1.64(m, 2H), 0.97 (t, J = 7.00 Hz, 3H) ppm. 13 C NMR (125 MHz, CDCl3): δ = 159.4 (d, J =248.75 Hz), 142.7, 141.3 (d, J = 7.50 Hz), 136.9 (d, J = 2.50 Hz), 136.5 (d, J =3.75 Hz), 136.4, 133.2 (d, J = 3.75 Hz), 129.2, 128.7 (d, J= 3.75 Hz), 127.3 (d, J = 7.50 Hz), 126.7, 122.7 (d, J = 2.50 Hz), 121.3 (d, J = 13.75 Hz), 114.5 (d, J =22.50 Hz), 37.8, 25.7, 25.1, 24.7, 23.7, 23.1, 14.0 ppm. MS m / z (RI, %):350.2 (M + , 100.0), 322.1 (52.4), 351.2 (39.5), 293.1 (34.3), 321.1 (29.4), 146.5 (25.1). DSC and POM tests revealed that the phase transition temperature and phase transition type of the compound are: Cr 99.2 N 117.6I.

[0053] When the compound was added to the base formulation HOST at a mass fraction of 5%, the compound dissolved well and showed no obvious crystallization at room temperature.

[0054] Further testing of its physical properties yields the birefringence Δ of this compound. n = 0.3617, dielectric anisotropy Δ ε = 2.44.

[0055] Example 4: This embodiment is 2-(3,5-difluoro-4'-propyl-[1,1'-biphenyl]-4-yl)-4,5,6,7-tetrahydrobenzo[ b Thiophene, with the following structural formula:

[0056] Using the same preparation method as in Example 1, but replacing 4-(4-ethylcyclohexyl)phenyl)boronic acid with (3,5-difluoro-4'-propyl-[1,1'-biphenyl]-4-yl)boronic acid, 2-(3,5-difluoro-4'-propyl-[1,1'-biphenyl]-4-yl)-4,5,6,7-tetrahydrobenzo[ b Thiophene is a white solid.

[0057] The compound characterization data are as follows: 1 H NMR (500 MHz, CDCl3): δ = 7.50 (d, J = 8.00 Hz, 2H), 7.27 (d, J= 8.00 Hz, 2H), 7.24 (s, 1H), 7.23–7.19 (m, 2H), 2.83 (t, J = 6.50 Hz,2H), 2.69–2.63 (m, 4H), 1.92–1.82 (m, 4H), 1.73–1.65 (m, 2H), 0.98 (t, J = 7.00Hz, 3H) ppm. 13 C NMR (125 MHz, CDCl3): δ = 159.9 (dd, J = 247.50 Hz, J = 7.50 Hz), 143.4, 141.0 (t, J = 10.00 Hz), 137.8 (t, J = 5.00 Hz), 135.9 (t, J = 2.50 Hz), 135.5, 130.1 (t, J = 5.00 Hz), 129.3, 126.7, 125.6 (t, J = 3.75 Hz), 111.1 (t, J =16.25 Hz), 110.0 (dd, J = 20.00 Hz, J = 5.00 Hz), 37.8, 25.6, 25.0, 24.6, 23.7,23.1, 14.0 ppm. MS m / z (RI, %): 368.4 (M + , 100.0), 340.3 (59.2), 369.4 (34.4), 311.2 (29.6), 155.7 (24.8), 339.3 (16.6). DSC and POM tests revealed that the compound has a melting point of 97.6°C. o C, no liquid crystal phase transition behavior.

[0058] When the compound was added to the base formulation HOST at a mass fraction of 10%, the compound dissolved well and showed no obvious crystallization at room temperature.

[0059] Further testing of its physical properties yields the birefringence Δ of this compound. n = 0.3287, dielectric anisotropy Δ ε = 2.84.

[0060] Example 5: This embodiment is 2-(2',3,5-trifluoro-4'-propyl-[1,1'-biphenyl]-4-yl)-4,5,6,7-tetrahydrobenzo[ b Thiophene, with the following structural formula:

[0061] Using the same preparation method as in Example 1, but replacing 4-(4-ethylcyclohexyl)phenyl)boronic acid with (2',3,5-trifluoro-4'-propyl-[1,1'-biphenyl]-4-yl)boronic acid, 2-(2',3,5-trifluoro-4'-propyl-[1,1'-biphenyl]-4-yl)-4,5,6,7-tetrahydrobenzo[ b Thiophene is a white solid.

[0062] The compound characterization data are as follows: 1 H NMR (500 MHz, CDCl3): δ = 7.36 (t, J = 8.00 Hz, 1H),7.25 (s, 1H), 7.20 (d, J = 9.00 Hz, 2H), 7.05 (dd, J = 8.00 Hz, J = 1.50 Hz, 1H), 7.00 (dd, J = 12.00 Hz, J = 1.50 Hz, 1H), 2.83 (t, J = 6.50 Hz, 2H), 2.68 (t, J =6.50 Hz, 2H), 2.63 (t, J = 7.50 Hz, 2H), 1.92–1.82 (m, 4H), 1.72–1.65 (m, 2H), 0.98 (t, J = 7.00 Hz, 3H) ppm. 13 C NMR (125 MHz, CDCl3): δ = 159.8 (d, J = 247.50Hz), 159.5(dd, J = 247.50 Hz, J = 7.50 Hz), 145.8 (d, J = 7.50 Hz), 138.0 (t, J =3.75 Hz), 135.6 (t, J= 11.25 Hz), 130.3 (t, J = 6.25 Hz), 129.8 (d, J = 2.50 Hz), 125.5 (t, J = 3.75 Hz), 124.9 (d, J = 2.50 Hz), 123.7 (dt, J = 12.50 Hz, J = 2.50Hz), 116.4 (d, J = 22.50 Hz), 112.2 (dd, J = 27.50 Hz, J = 3.75 Hz), 112.2 (dd, J =16.25 Hz, J = 3.75 Hz), 111.7 (t, J = 17.50 Hz), 37.6, 25.6, 25.0, 24.3, 23.7,23.1, 13.9 ppm. MS m / z (RI, %): 386.2 (M + , 100.0), 358.2 (64.7), 387.3 (26.3), 329.1 (24.5), 164.6 (17.1), 359.2 (15.3). DSC and POM tests revealed that the phase transition temperature and phase transition type of the compound are: Cr 90.4 SmA 100.8I.

[0063] When the compound was added to the base formulation HOST at a mass fraction of 10%, the compound dissolved well and showed no obvious crystallization at room temperature.

[0064] Further testing of its physical properties yields the birefringence Δ of this compound. n = 0.3067, dielectric anisotropy Δ ε = 3.01.

[0065] Example 6: This example is 2-((4-propylphenyl)ynyl)-4,5,6,7-tetrahydrobenzo[ b Thiophene, with the following structural formula:

[0066] The synthetic route is shown below:

[0067] The specific method is as follows: Under nitrogen protection, 2-bromo-4,5,6,7-tetrahydrobenzo[] was added to a three-necked flask. b Thiophene (1.00 g), Pd(PPh3)2Cl2 (0.07 g), CuI (0.03 g), and triethylamine (100 mL) were reacted. The reaction system was heated to 100 °C, and a triethylamine solution of 1-ethynyl-4-pentylbenzene (0.70 g / 10 mL) was slowly added dropwise. After the addition was complete, the reaction was continued for 6 hours and then cooled to room temperature. The organic phases were extracted with toluene, washed with water, and combined. The solvent was removed under reduced pressure, and the residue was purified by silica gel column chromatography (eluent: n-heptane / toluene = 5 / 1, V / V) to give compound 2-((4-propylphenyl)ynyl)-4,5,6,7-tetrahydrobenzo[ b Thiophene is a white solid (0.9 g, 70% yield).

[0068] The compound characterization data are as follows: 1 H NMR (500 MHz, CDCl3): δ = 7.40 (d, J = 8.00 Hz, 2H), 7.14 (d, J = 8.50 Hz, 2H), 6.92 (s, 1H), 2.74 (t, J = 5.50 Hz, 2H), 2.61–2.57 (m,4H), 1.88–1.77 (m, 4H), 1.68–1.61 (m, 2H), 0.94 (t, J = 7.50 Hz, 3H) ppm. 13 C NMR (125 MHz, CDCl3): δ = 143.2, 138.2, 135.5, 132.6, 131.4, 128.6, 120.6, 119.6,92.7, 82.9, 38.1, 25.5, 25.3, 24.5, 23.6, 22.9, 13.9 ppm. MS m / z (RI, %):280.4 (M + , 100.0), 251.3 (68.7), 252.3 (42.8), 281.4 (28.4), 223.2 (26.8),253.3 (10.8). DSC and POM tests revealed that the melting point of this compound is 81.2°C. o C, no liquid crystal phase transition behavior.

[0069] When the compound was added to the base formulation HOST at a mass fraction of 10%, the compound dissolved well and showed no obvious crystallization at room temperature.

[0070] Further testing of its physical properties yields the birefringence Δ of this compound. n = 0.2907, dielectric anisotropy Δ ε = 2.67.

[0071] Example 7: This embodiment is 2-((4'-propyl-[1,1'-biphenyl]-4-yl)ethynyl)-4,5,6,7-tetrahydrobenzo[ b Thiophene, with the following structural formula:

[0072] Using the same preparation method as in Example 6, but replacing 1-ethynyl-4-pentylbenzene with 4-ethynyl-4'-propyl-biphenyl, 2-((4'-propyl-[1,1'-biphenyl]-4-yl)ethynyl)-4,5,6,7-tetrahydrobenzo[ b Thiophene is a white solid.

[0073] The compound characterization data are as follows: 1 H NMR (500 MHz, CDCl3): δ = 7.59–7.52 (m, 6H), 7.26(d, J = 8.00 Hz, 2H), 6.95 (s, 1H), 2.76 (t, J = 6.00 Hz, 2H), 2.65–2.59 (m, 4H), 1.89–1.78 (m, 4H), 1.73–1.65 (m, 2H), 0.98 (t, J = 7.00 Hz, 3H) ppm. 13 C NMR (125MHz, CDCl3): δ = 142.4, 140.9, 138.5, 137.8, 135.6, 132.8, 131.8, 129.1,126.9, 126.9, 122.0, 119.4, 92.6, 84.2, 37.8, 25.5, 25.3, 24.7, 23.6, 22.9,14.0 ppm. MS m / z (RI, %): 356.2 (M +, 100.0), 149.5 (28.1), 357.2 (27.9), 327.1 (22.7), 328.1 (21.3), 299.1 (19.3). DSC and POM tests revealed that the phase transition temperature and phase transition type of this compound are: Cr 204.67 I.

[0074] When the compound was added to the base formulation HOST at a mass fraction of 10%, the compound dissolved well and showed no obvious crystallization at room temperature.

[0075] Further testing of its physical properties yields the birefringence Δ of this compound. n = 0.4015, dielectric anisotropy Δ ε = 2.78.

[0076] Example 8: The liquid crystal composition, its mass ratio and performance parameters are shown in Table 5 below.

[0077] Table 5

[0078] The liquid crystal composition exhibits good low-temperature performance, retaining the nematic phase at -20 °C.

[0079] Example 9: The liquid crystal composition, its mass ratio and performance parameters are shown in Table 6 below.

[0080] Table 6

[0081] The liquid crystal composition has a high birefringence of 0.5010 and can retain the nematic phase at room temperature.

[0082] Example 10: The liquid crystal composition that can be used for microwave communication has the following mass ratio and performance parameters as shown in Table 7.

[0083] Table 7

[0084] This liquid crystal composition exhibits low dielectric loss and high quality factor at a high frequency of 19 GHz.

[0085] Comparative Example 1: The compound of Comparative Example 1 is 2',6'-difluoro-4''-propyl-1,1':4',1''-triphenyl, and its structural formula is shown below.

[0086]

[0087] Using the same preparation method as in Example 1, but replacing 4-(4-ethylcyclohexyl)phenyl)boronic acid with phenylboronic acid, 2',6'-difluoro-4''-propyl-1,1':4',1''-triphenyl is obtained as a white solid.

[0088] The compound characterization data are as follows: 1 H NMR (500 MHz, CDCl3): δ = 7.54–7.47 (m, 6H), 7.43–7.40 (m, 1H), 7.29 (d, J = 8.00 Hz, 2H), 7.25–7.21 (m, 2H), 2.66 (t, J = 8.00 Hz,2H), 1.74–1.67 (m, 2H), 0.99 (t, J = 7.00 Hz, 3H) ppm. 13 C NMR (125 MHz, CDCl3): δ = 160.4 (dd, J = 246.25 Hz, J = 8.75 Hz), 143.4, 142.7 (t, J = 10.00 Hz), 136.2(t, J = 2.50 Hz), 130.5, 129.34, 129.32, 128.4, 128.3, 126.8, 116.8 (t, J = 18.75Hz), 110.0 (dd, J = 21.25 Hz, J = 7.50 Hz), 37.9, 24.6, 14.0 ppm. MS m / z (RI, %):76.9 (M + , 100.0), 278.8 (66.5), 307.8 (32.0), 51.0 (29.9), 52.0 (22.1), 200.7 (20.9). DSC and POM tests revealed that the phase transition temperature and phase transition type of this compound are: Cr 116.85 I.

[0089] When the compound was added to the base formulation HOST at a mass fraction of 10%, the compound dissolved well and showed no obvious crystallization at room temperature.

[0090] Further testing of its physical properties yields the birefringence Δ of this compound. n =0.1750, dielectric anisotropy Δ ε = 2.54.

[0091] Compared to the compound of Example 4, the compound of Comparative Example 1 uses a conventional 1,4-substituted benzene ring as the crystal core structure. As shown in Table 8 below, its birefringence and dielectric anisotropy are both lower than those of the compound of Example 4, but its melting point is higher than that of the compound of Example 4. This highlights the technical advantage of the novel 4,5,6,7-tetrahydrobenz[b]thiophene liquid crystal core, which can increase the birefringence and dielectric anisotropy of liquid crystal molecules without causing a significant increase in the molecular melting point.

[0092] Table 8

[0093] Comparative Example 2: Comparative Example 2 compound is 2-(3,5-difluoro-4'-propyl-[1,1'-biphenyl]-4-yl)benzo[ b Thiophene, with the following structural formula:

[0094] Using the same preparation method as in Example 1, 2-(3,5-difluoro-4'-propyl-[1,1'-biphenyl]-4-yl)benzo[ b Thiophene is a white solid.

[0095] The compound characterization data are as follows: 1 H NMR (500 MHz, CDCl3): δ = 7.89–7.85 (m, 2H), 7.81(s, 1H), 7.53 (d, J = 8.00 Hz, 2H), 7.41–7.35 (m, 2H), 7.30–7.27 (m, 4H), 2.65(t, J = 7.50 Hz, 2H), 1.73–1.66 (m, 2H), 0.99 (t, J = 7.00 Hz, 3H) ppm. 13 C NMR (125 MHz, CDCl3): δ = 160.4 (dd, J = 250.00 Hz, J = 7.50 Hz), 143.7, 142.8 (t, J =11.25 Hz), 140.4, 139.5, 135.7, 130.1, 129.4, 126.8, 126.1 (t, J= 5.00 Hz),124.9, 124.5, 124.0, 122.0, 110.6 (t, J = 16.25 Hz), 110.3 (dd, J = 21.25 Hz, J =5.00 Hz), 37.9, 24.6, 14.0 ppm. DSC and POM tests revealed that the phase transition temperature and phase transition type of this compound are: Cr 183.9 I.

[0096] Whether the compound was added to the base formulation HOST at a mass fraction of 10% or 5%, significant crystallization occurred, indicating poor solubility of the compound in the base formulation. Compared to the compound in Example 4, which uses benzothiophene as the crystal nucleus structure, this structure leads to a sharp increase in the compound's melting point, affecting its solubility in the parent liquid crystal and limiting its application. This highlights the advantages of the novel 4,5,6,7-tetrahydrobenzo[b]thiophene liquid crystal nucleus technology of this invention.

Claims

1. A liquid crystal compound based on a 4,5,6,7-tetrahydrobenzene[b]thiophene skeleton, characterized in that, The structure of the compound is shown in general formula (1): （1） Wherein, R1 is a saturated alkyl group with 1 to 9 carbon atoms, an unsaturated alkyl group with 1 to 9 carbon atoms, a fluorine atom, a chlorine atom, a cyano group, or an isothiocyano group; the ring H is a benzene ring or trans-cyclohexane; the L1 and L2 bridging bonds are each independently a single bond, an ethylene bridging bond, or an acetylene bridging bond; A1, A2, A3, and A4 are each independently a hydrogen atom or a fluorine atom; n = 0, 1, 2; R2 and R3 are each independently a hydrogen atom, a saturated alkyl group with 1 to 9 carbon atoms, or an unsaturated alkyl group with 1 to 9 carbon atoms.

2. The liquid crystal compound based on the 4,5,6,7-tetrahydrobenzene[b]thiophene skeleton according to claim 1, characterized in that, The liquid crystal compound is selected from one of formulas (1)-1 to (1)-10: 。 3. The method for synthesizing liquid crystal compounds based on the 4,5,6,7-tetrahydrobenzene[b]thiophene skeleton as described in claim 1, characterized in that, The synthesis method includes: Step 1: Using substituted cyclohexanone thiophene as a raw material, the intermediate substituted 4,5,6,7-tetrahydrobenz[b]thiophene was obtained by reduction with hydrazine hydrate; Step 2: The substituted 4,5,6,7-tetrahydrobenzene[b]thiophene intermediate is reacted with NBS to give the 2-brominated thiophene intermediate; Step 3: Finally, the thiophene 2-brominated intermediate undergoes a palladium-catalyzed coupling reaction with a fluorinated arylboronic acid derivative to prepare the liquid crystal compound of claim 1.

4. A liquid crystal composition, characterized in that, The composition comprises one or more of the liquid crystal compounds of claim 1.

5. The liquid crystal composition according to claim 4, characterized in that, The composition further includes a second component selected from one or more liquid crystal compounds of general formula (2), and the mass fraction of the second component is 0 to 97%. （2） Among them, R4 and R5 are independently saturated alkyl groups with 1 to 9 carbon atoms, unsaturated alkyl groups with 1 to 9 carbon atoms, saturated alkoxy groups with 1 to 9 carbon atoms, unsaturated alkoxy groups with 1 to 9 carbon atoms, fluorine atoms, chlorine atoms, cyano groups, isothiocyano groups, trifluoromethyl groups, or trifluoromethoxy groups. The L3 and L4 bridging bonds can be independently single bonds, ethylene bridging bonds, ethane bridging bonds, acetylene bridging bonds, difluoromethyl ether bridging bonds, or difluoroethylene bridging bonds, respectively. Ring O, ring P, and ring Q are each independently a benzene ring, trans-cyclohexane, cyclohexene, or a benzene ring substituted with fluorine, chlorine, trifluoromethyl, methyl, or ethyl. m=0、1、2。 6. The liquid crystal composition according to claim 4, characterized in that, The mass fraction of the liquid crystal compound according to claim 1 is 0~100%, excluding the value of 0 at the end.

7. The liquid crystal composition according to claim 4, characterized in that, The mass fraction of the second component is 0-97%.

8. A liquid crystal display element, characterized in that, The raw materials for preparing the liquid crystal display element include the liquid crystal composition according to any one of claims 4 to 7.

9. A non-display liquid crystal element, characterized in that, The raw materials for preparing the non-display liquid crystal element include the liquid crystal composition according to any one of claims 4 to 7.

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