Fluorine-containing benzyne liquid crystal compound, preparation method and composition thereof

Abstract

The invention discloses a fluorobenzyne liquid crystal compound, a preparation method and a composition thereof. The structure of the fluorobenzyne liquid crystal compound is shown as a general formula I; the liquid crystal composition disclosed by the invention comprises one or more liquid crystal compounds as shown in a general formula I. The liquid crystal compound has the advantages of low dielectric loss, good light stability, wide nematic liquid crystal phase, high birefringence, low viscosity, good low-temperature intermiscibility and the like. The composition based on the liquid crystal compound provided by the invention obtains relatively high dielectric tuning rate, extremely low dielectric loss and low rotary viscosity under high frequency; and the material has the advantages of good light stability, large birefringence, wide working temperature range and the like. The liquid crystal composition disclosed by the invention is suitable for manufacturing liquid crystal optical elements and high-frequency components, including phase modulators, gratings, wavelength selective switches and the like. # imgabs0 #

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid crystal materials, and particularly relates to a fluorinated phenylacetylene-based liquid crystal compound, a liquid crystal composition, a liquid crystal high-frequency component, a liquid crystal optical element, and a synthesis method thereof. Background Art

[0002] Liquid crystal materials have been widely used in optoelectronic display devices, such as various liquid crystal TVs, desktop liquid crystal displays, mobile display terminals, etc. In recent years, with the continuous development of technologies such as microwave and terahertz communication, optical communication, and laser phased array, there is an urgent need for liquid crystal materials with high birefringence. The higher the birefringence (Δn) of the liquid crystal, the greater the dielectric anisotropy value in the microwave (1 - 100G) band. In addition, in liquid crystal devices such as optical communication and laser phased array, by using a liquid crystal with a high birefringence (Δn), the response time can be significantly shortened while ensuring the optical phase modulation amount.

[0003] To improve the birefringence of liquid crystal materials, a structure with a long conjugated chain needs to be adopted in the liquid crystal molecules. For example, the molecular skeleton adopts a long conjugated structure of biphenyl, terphenyl, quaterphenyl, or diphenylacetylene. Among them, liquid crystal molecules containing an alkyne bond (-C≡C-) have a high polarizability anisotropy, so the birefringence is relatively high. Further, by introducing an isothiocyanate group (NCS) at the end of the liquid crystal molecule, the conjugation degree of the liquid crystal is greatly increased, and the dielectric constant in the microwave frequency band is greatly increased. Patents CN107955630A, CN105368465A, CN110499163A, US2019292458A1, and CN113528154A disclose a composition of a liquid crystal compound containing a diphenylacetylene molecular skeleton and an NCS group at the end group, which has the advantage of large dielectric constant tunability in the microwave frequency band. However, liquid crystal compounds and their compositions containing an NCS group have poor photo-stability. When irradiated with ultraviolet light and visible light, they are prone to photochemical reactions, resulting in a rapid deterioration of performance. Due to the poor photo-stability of NCS liquid crystals, many problems are brought to the production process and application process. Especially for antenna devices that are transparent to visible light or optical devices in application scenarios such as visible light, NCS liquid crystals are not applicable. In addition, liquid crystals containing an NCS group also have a relatively low resistivity.

[0004] Patents CN 104011175 A and CN108865179A disclose a composition containing a fluorine-substituted diphenylacetylene-based liquid crystal compound. Such liquid crystal compounds do not contain an NCS group and have relatively good photo-stability, but there are still problems such as large dielectric loss and small dielectric tunability.

[0005] To further meet the working performance requirements such as light stability for microwave, optical and other components, it is urgent to research and develop new liquid crystal structures and compositions with good light stability, low dielectric loss, wide nematic phase temperature range, low viscosity, high birefringence and high resistivity. Summary of the Invention

[0006] In order to overcome the defects or deficiencies in the background technology, the present invention provides a new type of fluorinated phenylacetylene-based liquid crystal compound and...

[0007] To achieve the above tasks, the present invention adopts the following technical solutions:

[0008] The structure of the fluorinated phenylacetylene-based liquid crystal compound described in the present invention is shown in general formula Ⅰ:

[0009]

[0010] Wherein:

[0011] R1 is an alkyl group with 1 to 10 carbon atoms, an alkyl group with 1 to 10 carbon atoms in which hydrogen is substituted by fluorine, an alkoxy group with 1 to 10 carbon atoms, an alkoxy group with 1 to 10 carbon atoms in which hydrogen is substituted by fluorine, an alkenyl group with 2 to 10 carbon atoms, an alkenyl group with 2 to 10 carbon atoms in which hydrogen is substituted by fluorine, an alkenyloxy group with 2 to 10 carbon atoms, an alkenyloxy group with 2 to 10 carbon atoms in which hydrogen is substituted by fluorine, a cycloalkyl group with 3 to 8 carbon atoms or a cycloalkyl group with 3 to 8 carbon atoms in which hydrogen is substituted by fluorine;

[0012] R2 is F, Cl, CN, CF3, OCF3 or SF6;

[0013] Z1 and Z2 are each independently a single bond or -C≡C-, and Z1 and Z2 are not simultaneously -C≡C-;

[0014] Ring A and ring C are each independently a benzene ring, a cyclohexane, a cyclohexene or a benzene ring in which hydrogen is substituted by fluorine, chlorine, methyl or / and ethyl;

[0015] Ring B is:

[0016]

[0017] n = 0, 1, 2.

[0018] Preferably, n = 1. Or n = 1, and ring A and ring C are each independently a benzene ring or a cyclohexane. Or n = 2, and R2 is F.

[0019] Preferably, the structural formula of the fluorinated phenylacetylene-based liquid crystal compound is shown in any one of the structural formulas of Ⅰ-1 to Ⅰ-6;

[0020]

[0021] The liquid crystal compound of the present invention, after introducing a fluorine substituent at a specific position of the benzene ring, compared with similar liquid crystal compounds disclosed in the prior art, obtains surprising results, with a significant reduction in dielectric loss at high frequencies, a significant improvement in the quality factor, and high light stability. The above advantages are very beneficial for microwave antennas, liquid crystal optical devices, etc.

[0022] The present invention also provides a method for synthesizing the above-mentioned fluorinated phenylacetylene liquid crystal compound, and the preparation method includes:

[0023] (1) 4-bromo-2,5-difluoroiodobenzene and a phenylacetylene derivative are subjected to a selective coupling reaction in the presence of a transition metal catalyst A and a copper salt catalyst to obtain a bromo-substituted diphenylacetylene derivative intermediate;

[0024] (2) The bromo-substituted diphenylacetylene derivative intermediate and an arylboronic acid derivative are subjected to a coupling reaction under the catalysis of a transition metal catalyst B to obtain a fluorinated phenylacetylene liquid crystal compound.

[0025] An optional solution is that the transition metal catalyst A and the transition metal catalyst B are each independently selected from palladium- or nickel-containing complexes. The copper salt is cuprous halide.

[0026] The present invention also provides a liquid crystal composition, which contains one or more liquid crystal compounds selected from those shown in the general structural formula I. An optional solution is that the mass percentage of the liquid crystal compound shown in the general structural formula I contained in the liquid crystal composition is 10% - 100%. A further optional solution is that the liquid crystal composition further contains one or more liquid crystal compounds selected from those shown in the general structural formula II as a second component, and the mass ratio of the second component is 0 - 95%;

[0027]

[0028] Wherein:

[0029] R3 and R4 are each independently an alkyl group having 1 - 10 carbon atoms, an alkoxy group having 1 - 10 carbon atoms, an alkenyl group having 2 - 10 carbon atoms, an alkenyloxy group having 2 - 10 carbon atoms, fluorine, chlorine, a cyano group (-C≡N), an isothiocyanate group (-N=C=S), a trifluoromethyl group (-CF3) or a trifluoromethoxy group (-OCF3);

[0030] Z3 and Z4 are each independently a single bond, -C≡C-, -CH=CH-, -CF=CF-, -CF2O- or -CH2CH2;

[0031] Ring C, ring D, and ring E are each independently a benzene ring, a cyclohexane, a cyclohexene, or a benzene ring in which hydrogen is substituted by fluorine, chlorine, methyl, or / and ethyl;

[0032] m = 0, 1, 2.

[0033] Preferably, the liquid crystal composition further contains one or more liquid crystal compounds selected from those represented by Structural Formulas II-1 to II-8:

[0034]

[0035] Wherein:

[0036] R5 in Formulas II-1 to II-8 are each independently an alkyl group having 1 to 7 carbon atoms or an alkoxy group having 1 to 7 carbon atoms; R6 in Formulas II-1 and II-6 are each independently an alkyl group having 1 to 7 carbon atoms or an alkoxy group having 1 to 7 carbon atoms; R7 in Formulas II-6 to II-8 are each independently fluorine, chlorine, methyl or ethyl;

[0037] Ring C in Formulas II-1 and II-2 are each independently a benzene ring or a cyclohexane ring;

[0038] m in Formulas II-1, II-2 and II-4 each independently takes 0, 1 or 2.

[0039] The liquid crystal compounds of the present invention have the advantages of low dielectric loss, good light stability, a relatively wide nematic liquid crystal phase, high birefringence, low viscosity, and good low-temperature compatibility. Compositions based on the liquid crystal compounds of the present invention obtain a large dielectric tuning rate, extremely low dielectric loss, and low rotational viscosity at high frequencies; and have the advantages of good light stability, large birefringence, and a wide operating temperature range.

[0040] The liquid crystal composition of the present invention, due to its characteristics such as large birefringence and low viscosity, is suitable for manufacturing liquid crystal optical elements and high-frequency components, including phase modulation devices, gratings, wavelength selective switches (WSS), etc. The liquid crystal compounds and compositions of the present invention have high light stability and are particularly suitable for manufacturing transparent antennas. Detailed Embodiments

[0041] Unless otherwise specified, scientific and technical terms and methods in this article are understood or implemented according to the knowledge of those of ordinary skill in the relevant fields or using existing relevant methods.

[0042] According to the disclosure of the present invention, those skilled in the art can select appropriate components and ratios to achieve the effects of the present invention. In a preferred embodiment of the present invention, the liquid crystal composition comprises one or more compounds of structural formula I. In another preferred embodiment of the present invention, the liquid crystal composition comprises one or more compounds of structural formula I and one or more compounds of structural formula II. The liquid crystal composition according to the present invention preferably comprises 5% to 100%, preferably 10% to 90%, more preferably 15% to 80% of the compound of formula I based on the total amount of the mixture; and 0 to 90%, preferably 5% to 80%, particularly preferably 10% to 70% of the compound of structural formula II based on the total amount of the mixture. In specific embodiments, those skilled in the art can make optimized selections based on the disclosure of the present invention.

[0043] The liquid crystal composition according to the present invention is composed of a variety of compounds, preferably 3 to 20 compounds, more preferably 5 to 18 and even more preferably 7 to 15 compounds. These compounds can be mixed in a conventional manner: weigh various compounds according to a predetermined mass ratio, then heat up, and at the same time use magnetic stirring or ultrasonic stirring and other stirring methods for homogeneous mixing until all components are completely dissolved; and then obtain it after filtration. The liquid crystal composition can also be prepared by other conventional methods, such as using a so-called premix, or using a so-called "multi-bottle" system, in which the components themselves are ready-to-use mixtures.

[0044] The preferred liquid crystal composition of the present invention has a dielectric tuning rate τ≥0.24 at high frequencies, such as 19 to 30 GHz, and more preferably τ≥0.25; the vertical dielectric loss tangent tanδ of the preferred liquid crystal material ⊥ ≤0.008, and more preferably tanδ ⊥ ≤0.007; the material figure of merit η≥30, preferably η≥35.

[0045] The nematic phase temperature range of the preferred liquid crystal composition of the present invention is 0 to 70 °C or above, and more preferably the nematic phase temperature range is -10 to 90 °C or above.

[0046] The rotational viscosity γ1 of the preferred liquid crystal composition is ≤500 mPa·s, and more preferably ≤400 mPa·s.

[0047] The liquid crystal composition of the present invention has a relatively high birefringence (Δn). The preferred liquid crystal composition of the present invention has Δn≥0.30 at 25 °C and 589 nm, and more preferably Δn≥0.32.

[0048] In specific embodiments, the liquid crystal composition of the present invention may further comprise 0.001% to 1% of additives, such as hindered phenol antioxidants, hindered amine light stabilizers, etc. Among them, the hindered phenol antioxidants are preferably selected from the following structures:

[0049]

[0050] In the above three structural formulas, each R' is independently an alkyl or alkoxy group having 1 to 9 carbon atoms.

[0051] The hindered amine light stabilizer described is preferably selected from the following structures:

[0052]

[0053] The addition amounts of the preferred hindered phenol antioxidants and hindered amine light stabilizers are 0.01% to 0.5%, more preferably 0.02% to 0.2%.

[0054] In some other embodiments, the liquid crystal composition of the present invention may further comprise one or more chiral additives, with a content of 0.01% to 1%; preferably 0.1% to 0.5%. The chiral additives are preferably selected from the following structures:

[0055]

[0056] Each R″ in the above formula is independently an alkyl group having 1 to 9 carbon atoms or an alkoxy group having 1 to 9 carbon atoms.

[0057] The performance of the liquid crystals described herein at high frequencies is measured using the test method reported in the literature: Penirschke, A. (2004). Cavity perturbation method for characterization of liquid crystals up to 35 GHz. Microwave Conference,2004.34th European .

[0058] The liquid crystal is introduced into a polytetrafluoroethylene (PTFE) or fused silica capillary, and the filled capillary is introduced into the middle of a chamber having a resonance frequency of 19 GHz. Then, an input signal source is applied, and a vector network analyzer is used to record the results of the output signal. The changes in the resonance frequency and Q factor between the capillary filled with the liquid crystal and the blank capillary are measured, and the dielectric constant and loss tangent value are calculated. The dielectric constant components perpendicular and parallel to the liquid crystal director are obtained by the alignment of the liquid crystal in a magnetic field, and the direction of the magnetic field is set accordingly and then rotated by 90° accordingly.

[0059] The liquid crystal composition of the present invention is very suitable for preparing microwave components, such as phase shifters that can be tuned by applying an external magnetic field or electric field. These phase shifters can operate in the UHF-band (0.3 - 1 GHz), L-band (1 - 2 GHz), S-band (2 - 4 GHz), C-band (4 - 8 GHz), X-band (8 - 12 GHz), Ku-band (12 - 18 GHz), K-band (18 - 27 GHz), Ka-band (27 - 40 GHz), V-band (50 - 75 GHz), W-band (75 - 110 GHz) and up to 1 THz. The construction of the phase shifter according to the present application is known to those skilled in the art. Typically, loaded line phase shifters, inverted microstrip lines, finline phase shifters, preferably antipodal finline phase shifters, slotted phase shifters, microstrip line phase shifters or coplanar waveguide (CPW) phase shifters are used. These components can achieve reconfigurable antenna arrays.

[0060] The present invention will be further described in detail below with reference to specific embodiments.

[0061] It should be noted that the detailed test methods for the physical properties and optoelectronic properties involved in the present invention are as follows:

[0062] (1) Liquid crystal phase transition temperature:

[0063] Differential scanning calorimetry (DSC) is used: under a nitrogen atmosphere, the heating (cooling) rate is set to 5 °C / min.

[0064] Polarizing hot stage method: The liquid crystal sample is placed in an orthogonal polarizing microscope hot stage, and the heating rate is set to 2 °C / min. Observe the texture image of the liquid crystal phase transition in the polarizing microscope to determine the liquid crystal phase state.

[0065] (2) Birefringence (Δn): The liquid crystal monomer is added to the basic formulation HOST in a mass ratio of 15:85%, and heated and mixed evenly. Using an Abbe refractometer, at a constant temperature of 25 °C and a light source of 589 nm, measure the refractive indices of the ordinary light (n o ) and extraordinary light (n e ) respectively, and extrapolate to obtain the birefringence.

[0066] (3) Dielectric constant (Δε, 1 KHz): The liquid crystal monomer is added to the basic formulation HOST in a mass ratio of 15:85%, and heated and mixed evenly. At a constant temperature of 25 °C, use an LCR meter to test. Δε = ε ∥ -ε ⊥ , that is, the difference between the dielectric constant in the direction of the long axis of the molecule (ε ∥ ) and the dielectric constant in the direction of the short axis of the molecule (ε ⊥ ), and extrapolate to obtain the dielectric anisotropy value Δε.

[0067] (4) Rotational viscosity (γ1): The liquid crystal monomer was added to the basic formulation HOST in a mass ratio of 15:85%, and heated and mixed evenly. Under the condition of constant temperature at 25°C, by applying a voltage to the liquid crystal test cell, the transient current value Ip of the liquid crystal molecules deflecting with the electric field was measured, and the rotational viscosity γ1 was calculated and extrapolated.

[0068] (5) Dielectric constant and dielectric loss (Δε, tanδ, 19 GHz): The liquid crystal monomer was added to the basic formulation M0 in a mass ratio of 15:85%, and heated and mixed evenly; under the condition of constant temperature at 25°C, the liquid crystal was poured into a polytetrafluoroethylene (PTFE) or fused silica capillary tube, and the capillary tube filled with the liquid crystal was inserted into the middle of the resonant cavity. Then, an input signal source was applied, and a vector network analyzer was used to record the results of the output signal. The changes in the resonance frequency and Q factor between the capillary tube filled with the liquid crystal and the blank capillary tube were measured, and the dielectric constant and loss tangent value were calculated; the dielectric constant components perpendicular and parallel to the liquid crystal director were obtained by the orientation of the liquid crystal in the magnetic field, and the direction of the magnetic field was set accordingly, and then rotated by 90° accordingly.

[0069] The basic formulation HOST described in the following examples was obtained by evenly mixing the following three monomer liquid crystals in a mass ratio of 1:1:1.

[0070]

[0071] The relevant explanations of the codes involved in this article are as follows:

[0072] Table 1 Physical parameters

[0073] Code name Description Unit <![CDATA[ε ⊥ > Dielectric constant perpendicular to the director <![CDATA[ε ∥ > Dielectric constant parallel to the director Δε Dielectric anisotropy <![CDATA[tanδ ⊥ > Dielectric loss tangent perpendicular to the director <![CDATA[tanδ ∥ > Dielectric loss tangent parallel to the director Δn Birefringence <![CDATA[γ1]]> Rotational viscosity mPa·s τ <![CDATA[Dielectric tuning rate; τ = Δε / ε ∥ > η <![CDATA[Microwave quality factor; η = Δε / (ε ∥ *tanδ ⊥ )]]>

[0074] Liquid crystal phase transition temperature: C represents the melting point, S represents the smectic phase, N represents the nematic phase, and I represents the liquid phase.

[0075] Table 2 Structure abbreviations

[0076]

[0077]

[0078] Table 3 Abbreviation examples

[0079]

[0080] Example 1:

[0081] This example is 2,4',5-trifluoro-4-((4-n-propylphenyl)ethynyl)-1,1'-biphenyl, and the structural formula is as follows:

[0082]

[0083] The synthetic route is as follows:

[0084]

[0085] The specific method is as follows:

[0086] (1) Under nitrogen protection, add 15.9 g of 2,5-difluoro-4-bromoiodobenzene, 100 mL of triethylamine, 0.35 g of dichlorobis(triphenylphosphine)palladium(II), 0.29 g of copper(I) iodide, and 0.39 g of triphenylphosphine to the reaction flask. At room temperature, slowly add a 30 mL triethylamine solution containing 7.2 g of 4-propylphenylacetylene dropwise. After the addition, stir at room temperature for 4 h. Filter the reaction mixture, concentrate the filtrate to dryness under reduced pressure, add 100 mL of toluene, wash with water, dry, remove toluene under reduced pressure, and recrystallize with ethanol to obtain 13.7 g of white solid 1-bromo-2,5-difluoro-4-((4-propylphenyl)ethynyl)benzene;

[0087] (2) Under nitrogen protection, add 13.4 g of 1-bromo-2,5-difluoro-4-((4-propylphenyl)ethynyl)benzene, 5.9 g of 4-fluorophenylboronic acid, 0.28 g of dichlorobis(triphenylphosphine)palladium(II), 11.1 g of potassium carbonate, 60 mL of toluene, 60 mL of ethanol, and 60 mL of water to the reaction flask. Heat the reaction mixture under reflux for 8 h. After cooling, add 100 mL of toluene, wash with water, dry, and remove toluene under reduced pressure. Dissolve the product in n-heptane and pass it through a silica gel column, eluting with n-heptane. Concentrate the eluate to dryness under reduced pressure and recrystallize with n-heptane to obtain 10.9 g of white solid 2,4',5-trifluoro-4-((4-n-propylphenyl)ethynyl)-1,1'-biphenyl;

[0088] The structure identification data of the product are as follows:

[0089] 1 H NMR(500MHz,CDCl3)δ(ppm): 0.985(t,3H,J = 7Hz),1.655~1.729(m,2H),2.649(t,2H,J = 8Hz),7.162~7.226(m,5H),7.285~7.324(m,1H),7.524~7.570(m,4H).

[0090] 13 C NMR(125MHz,CDCl3)δ(ppm): 13.7,24.3,38.0,81.0,96.1,112.3,115.6,115.8,116.6,119.6,120.0,120.2,128.6(2C),129.3,130.3,130.6,131.7(2C),144.0,155(J C-F = 250Hz),158.8(JC-F = 250 Hz), 162.8 (J C-F = 250 Hz).

[0091] MS m / z (RI, %): 350.2 (M + , 66), 321.2 (100).

[0092] DSC: C 82.92 N 132.7 I.

[0093] The compound was mixed with the above basic formulation at a mass percentage of 15%, and further tests were carried out to obtain the physical property parameters of the compound: Δn = 0.339, Δε = 5.2, γ1 = 199 mPa·s.

[0094] Example 2:

[0095] This example is 2,4',5-trifluoro-4-((4-n-pentylphenyl)ethynyl)-1,1'-biphenyl, and the structural formula is as follows:

[0096]

[0097] 4-Pentylphenylacetylene was used to replace 4-propylphenylacetylene in Example 1, and the same synthesis method as in Example 1 was used for other operations to obtain 2,4',5-trifluoro-4-((4-n-pentylphenyl)ethynyl)-1,1'-biphenyl.

[0098] The structure identification data are as follows:

[0099] 1 H NMR (500 MHz, CDCl3) δ (ppm): 0.944 (t, 3H, J = 7 Hz), 1.325 - 1.424 (m, 4H), 1.638 - 1.698 (m, 2H), 2.666 (t, 2H, J = 8 Hz), 7.165 - 7.232 (m, 5H), 7.288 - 7.327 (m, 1H), 7.510 - 7.574 (m, 4H).

[0100] 13 C NMR (125 MHz, CDCl3) δ (ppm): 14.0, 22.5, 30.9, 31.5, 35.9, 81.0, 96.1, 112.2, 115.6, 115.8, 116.7, 119.6, 120.0, 120.2, 128.6 (2C), 129.3, 130.6, 131.7 (2C), 144.3, 155.0 (J C-F = 250 Hz), 158.5 (J C-F = 250 Hz), 162.9 (J C-F= 250 Hz).

[0101] MS m / z(RI,%): 378.2(M + , 68), 321.1(100).

[0102] DSC: C63.4 N 124.7I.

[0103] The compound was mixed with the above basic formulation at a mass percentage of 15%, and further tests were carried out to obtain the physical property parameters of the compound: Δn = 0.322, Δε = 4.3, γ1 = 221 mPa·s.

[0104] Example 3:

[0105] This example is 4'-chloro-2,5-difluoro-4-((4-n-pentylphenyl)ethynyl)-1,1'-biphenyl, and the structural formula is as follows:

[0106]

[0107] 4-Pentylphenylacetylene was used to replace 4-propylphenylacetylene in Example 1, and 4-chlorophenylboronic acid was used to replace 4-fluorophenylboronic acid in Example 1. Other operations were carried out using the same synthesis method as in Example 1 to obtain 4'-chloro-2,5-difluoro-4-((4-n-pentylphenyl)ethynyl)-1,1'-biphenyl.

[0108] The structure identification data are as follows:

[0109] 1 H NMR(500 MHz, CDCl3) δ(ppm): 0.942(t, 3H, J = 7 Hz), 1.322~1.422(m, 4H), 1.640~1.672(m, 2H), 2.669(t, 2H, J = 8 Hz), 7.186~7.230(m, 5H), 7.280~7.321(m, 1H), 7.512~7.578(m, 4H).

[0110] 13 C NMR(125 MHz, CDCl3) δ(ppm): 14.0, 22.5, 30.9, 31.5, 36.0, 81.0, 96.3, 112.5, 116.6, 119.5, 120.1, 120.3, 128.6(2C), 129.0(2C), 129.1, 130.1, 131.7(2C), 132.7, 134.6, 144.3, 154(J C-F = 250 Hz), 158.8(J C-F = 250 Hz).

[0111] MS m / z (RI, %): 394.1 (M + , 77), 396.1 (28), 337.1 (100), 339.1 (36).

[0112] DSC: C 89.4 N 160.0 I.

[0113] The compound was mixed with the above basic formulation at a mass percentage of 15%, and further tests were carried out to obtain the physical property parameters of the compound: Δn = 0.352, Δε = 5.7, γ1 = 335 mPa·s.

[0114] Example 4:

[0115] This example is 4'-trifluoromethoxy-2,5-difluoro-4-((4-n-propylphenyl)ethynyl)-1,1'-biphenyl, and the structural formula is as follows:

[0116]

[0117] 4-Trifluoromethoxyphenylboronic acid was used to replace 4-fluorophenylboronic acid in Example 1, and the same synthesis method as in Example 1 was adopted for other operations to obtain 4'-trifluoromethoxy-2,5-difluoro-4-((4-n-propylphenyl)ethynyl)-1,1'-biphenyl.

[0118] The structure identification data are as follows:

[0119] 1 H NMR (500 MHz, CDCl3) δ (ppm): 0.989 (t, 3H, J = 7 Hz), 1.659~1.733 (m, 2H), 2.653 (t, 2H, J = 8 Hz), 7.177~7.232 (m, 3H), 7.309~7.348 (m, 3H), 7.520 (d, 2H, J = 8 Hz), 7.612 (d, 2H, J = 8 Hz).

[0120] 13 C NMR (125 MHz, CDCl3) δ (ppm): 13.7, 24.3, 38.0, 81.0, 96.4, 112.7, 116.6, 116.7, 119.5, 120.1, 120.3, 121.0, 121.5, 128.6 (2C), 128.8, 130.3, 131.7 (2C), 132.9, 144.1, 155.0 (J C-F = 250 Hz), 158.8 (J C-F = 250 Hz).

[0121] MS m / z (RI, %): 416.3 (M +,66),387.2(100).

[0122] DSC: C 51.3S100.4N 141.0I.

[0123] The compound was mixed with the above basic formulation at a mass percentage of 15%, and further tests were carried out to obtain the physical property parameters of the compound: Δn = 0.309, Δε = 7.9, γ1 = 216 mPa·s.

[0124] Example 5:

[0125] This example is 4'-trifluoromethyl-2,5-difluoro-4-((4-n-propylphenyl)ethynyl)-1,1'-biphenyl, and the structural formula is as follows:

[0126]

[0127] 4-Trifluoromethylphenylboronic acid was used to replace 4-fluorophenylboronic acid in Example 1, and the same synthesis method as in Example 1 was adopted for other operations to obtain 4'-trifluoromethyl-2,5-difluoro-4-((4-n-pentylphenyl)ethynyl)-1,1'-biphenyl.

[0128] 1 H NMR(500MHz,CDCl3)δ(ppm): 0.992(t,3H,J = 7Hz),1.661~1.735(m,2H),2.655(t,2H,J = 8Hz),7.202~7.234(m,3H),7.323~7.343(m,1H),7.522(d,2H,J = 8Hz),7.723(dd,4H,J1 = 27Hz J1 = 8Hz).

[0129] 13 C NMR(125MHz,CDCl3)δ(ppm): 13.7,24.3,38.0,80.9,96.7,113.2,116.7,119.5,120.2,120.4,123.0,125.1,125.6,128.7(2C),129.2,130.3,130.6,131.8(2C),137.9,144.2,155.0(J C-F = 250Hz),158.8(J C-F = 250Hz).

[0130] MS m / z(RI,%): 400.2(M + ,67),371.2(100).

[0131] DSC: C 132.5I.

[0132] The compound was mixed with the above basic formulation at a mass percentage of 5%, and further tests were conducted to obtain the physical property parameters of the compound: Δn = 0.309, Δε = 10.8, γ1 = 325 mPa·s.

[0133] Example 6:

[0134] This example is 2,5-difluoro-4-((4-fluorophenyl)ethynyl)-4'-n-pentyl-1,1'-biphenyl, and the structural formula is as follows:

[0135]

[0136] 4-Fluorophenylethyne was used to replace 4-propylphenylethyne in Example 1, and 4-n-pentylphenylboronic acid was used to replace 4-fluorophenylboronic acid in Example 1. Other operations were carried out using the same synthesis method as in Example 1 to obtain 2,5-difluoro-4-((4-fluorophenyl)ethynyl)-4'-n-pentyl-1,1'-biphenyl.

[0137] 1 H NMR(500MHz,CDCl3)δ(ppm): 0.954(t,3H,J = 7Hz),1.394~1.407(m,4H),1.685~1.727(m,2H),2.694(t,2H,J = 8Hz),7.085~7.119(m,2H),7.209~7.319(m,4H),7.510~7.599(m,4H).

[0138] 13 C NMR(125MHz,CDCl3)δ(ppm): 14.0,22.6,31.1,31.6,35.7,81.6,94.4,111.2,115.7,115.9,116.7,118.7,119.9,120.1,128.7(2C),128.8,130.8,131.5,133.7,133.8,143.6,155.2(J C-F = 250Hz),158.5(J C-F = 250Hz),162.9(J C-F = 250Hz).

[0139] MS m / z(RI,%): 378.2(M + ,69),321.1(100).

[0140] DSC: C 71.3N 114.7I.

[0141] The compound was mixed with the above basic formulation at a mass percentage of 15%, and further tests were conducted to obtain the physical property parameters of the compound: Δn = 0.313, Δε = 3.3, γ1 = 201 mPa·s.

[0142] Example 7:

[0143] This example is 2,4',5-trifluoro-4-((4-(trans-4-propylcyclohexyl)phenyl)ethynyl)-1,1'-biphenyl, and the structural formula is as follows:

[0144]

[0145] 4-(trans-4-Propylcyclohexyl)phenylacetylene was used to replace 4-propylphenylacetylene in Example 1, and the same synthesis method as in Example 1 was adopted for other operations to obtain 2,4',5-trifluoro-4-((4-(trans-4-propylcyclohexyl)phenyl)ethynyl)-1,1'-biphenyl.

[0146] DSC: C 94.7 N 308.4 I.

[0147] The compound was mixed with the above basic formulation at a mass percentage of 15%, and further tests were conducted to obtain the physical property parameters of the compound: Δn = 0.322, Δε = 4.5, γ1 = 513 mPa·s.

[0148] Example 8:

[0149] The liquid crystal composition of this example has the following mass ratio and performance parameters in Table 4:

[0150] Table 4

[0151]

[0152] This liquid crystal composition has very low dielectric loss and a large quality factor at a high frequency of 19 GHz.

[0153] Example 9:

[0154] The liquid crystal composition of this example has the following mass ratio and performance parameters in Table 5:

[0155] Table 5

[0156]

[0157]

[0158] This liquid crystal composition has very low dielectric loss and a large quality factor at a high frequency of 19 GHz.

[0159] Example 10:

[0160] The liquid crystal composition of this embodiment has the following mass ratios and performance parameters as shown in Table 6 below:

[0161] Table 6

[0162]

[0163]

[0164] This liquid crystal composition has a very low dielectric loss and a large quality factor at a high frequency of 19 GHz.

[0165] Comparative Example 1:

[0166] This comparative example is a liquid crystal composition containing a fluorinated diphenylacetylene structure disclosed in Patent CN104087309A. The dielectric properties at 19 GHz were tested, and the data are shown in Table 7 below:

[0167] Table 7

[0168]

[0169]

[0170] Compared with Comparative Example 1, although Example 8 has a similar molecular skeleton, when the substitution position of the lateral fluorine atoms is adjusted, the dielectric loss at 19 GHz is significantly reduced; the dielectric loss in the vertical direction is reduced by 79%; at the same time, the dielectric anisotropy Δε and the dielectric tuning rate τ at 19 GHz are also significantly increased; the corresponding quality factor η is doubled. In addition, Example 8 also has a higher birefringence and a higher clearing point. It can be seen that the liquid crystal compounds and their compositions of the present invention have unexpected technical effects.

Claims

1. A 2,5-difluorophenylacetylene-based liquid crystal compound, characterized in that, The structure of the said compound is shown in General Formula I: Wherein: R1 is an alkyl group with 1 to 10 carbon atoms, an alkyl group with 1 to 10 carbon atoms in which hydrogen is substituted by fluorine, an alkoxy group with 1 to 10 carbon atoms, an alkoxy group with 1 to 10 carbon atoms in which hydrogen is substituted by fluorine, an alkenyl group with 2 - 10 carbon atoms, an alkenyl group with 2 - 10 carbon atoms in which hydrogen is substituted by fluorine, an alkenyloxy group with 2 - 10 carbon atoms, an alkenyloxy group with 2 - 10 carbon atoms in which hydrogen is substituted by fluorine, a cycloalkyl group with 3 - 8 carbon atoms or a cycloalkyl group with 3 - 8 carbon atoms in which hydrogen is substituted by fluorine; R2 is F, Cl, CN, CF3, OCF3 or SF6; Z1 and Z2 are each independently a single bond or -C≡C-, and Z1 and Z2 are not simultaneously -C≡C-; Ring A and Ring C are each independently a benzene ring, cyclohexane, cyclohexene or a benzene ring in which hydrogen is substituted by fluorine, chlorine, methyl or / and ethyl; Ring B is: n＝0，1，2。 2. The liquid crystal compound according to claim 1, characterized in that, n＝1。 3. The liquid crystal compound according to claim 1, wherein n = 1, Ring A and Ring C are each independently a benzene ring or cyclohexane.

4. The liquid crystal compound according to claim 1, characterized in that, n = 2, R2 is F.

5. The liquid crystal compound according to claim 1, wherein The structural formula of the said compound is shown as any one of the structural formulas of I-1 to I-6; 6. A method for synthesizing the fluorinated phenylacetylene liquid crystal compound according to claim 1, characterized in that the method Including: (1) 4-bromo-2,5-difluoroiodobenzene and a phenylacetylene derivative undergo a selective coupling reaction in the presence of a transition metal catalyst A and a copper salt catalyst to obtain a bromo-substituted diphenylacetylene derivative intermediate; (2) The bromo-substituted diphenylacetylene derivative intermediate and an arylboronic acid derivative undergo a coupling reaction under the catalysis of a transition metal catalyst B to obtain a fluorinated phenylacetylene liquid crystal compound.

7. The synthesis method according to claim 6, characterized in that, The said transition metal catalyst A and transition metal catalyst B are each independently selected from palladium- or nickel-containing complexes.

8. The synthesis method according to claim 6, characterized in that, The said copper salt is cuprous halide.

9. A liquid crystal composition, characterized in that, The said liquid crystal composition contains one or more liquid crystal compounds selected from those shown in General Formula I.

10. The liquid crystal composition according to claim 9, characterized in that, The mass percentage of the liquid crystal compound shown in General Formula I contained in the said liquid crystal composition is 10% - 100%.

11. The liquid crystal composition according to claim 9, characterized in that, The said liquid crystal composition further contains one or more liquid crystal compounds selected from those shown in General Formula II as the second component, and the mass ratio of the second component is 0 - 95%; Wherein: R3 and R4 are each independently an alkyl group with 1 to 10 carbon atoms, an alkoxy group with 1 to 10 carbon atoms, an alkenyl group with 2 - 10 carbon atoms, an alkenyloxy group with 2 - 10 carbon atoms, fluorine, chlorine, cyano group, isothiocyanate group, trifluoromethyl group or trifluoromethoxy group; Z3 and Z4 are each independently a single bond, -C≡C-, -CH=CH-, -CF=CF-, -CF2O- or -CH2CH2; Ring C, Ring D, Ring E are each independently a benzene ring, cyclohexane, cyclohexene or a benzene ring in which hydrogen is substituted by fluorine, chlorine, methyl or / and ethyl; m＝0，1，2。 12. The liquid crystal composition according to claim 9, wherein The said liquid crystal composition further contains one or more liquid crystal compounds selected from those shown in Formulas II-1 to II-8: Wherein: R5 in Formulas II-1 to II-8 are each independently an alkyl group with 1 to 7 carbon atoms or an alkoxy group with 1 to 7 carbon atoms; R6 in Formulas II-1 and II-6 are each independently an alkyl group with 1 to 7 carbon atoms or an alkoxy group with 1 to 7 carbon atoms; R7 in Formulas II-6 to II-8 are each independently fluorine, chlorine, methyl or ethyl; The ring C in Formulae II-1 and II-2 is each independently a benzene ring or a cyclohexane; In Formulae II-1, II-2 and II-4, m is each independently 0, 1 or 2.

13. A liquid crystal high-frequency component, characterized in that, The liquid crystal high-frequency component is prepared by using the liquid crystal compound according to any one of claims 1-5 or a liquid crystal composition comprising the liquid crystal compound according to any one of claims 9-12.

14. A liquid crystal optical element, characterized in that, Wherein the liquid crystal optical element is prepared by using the liquid crystal compound according to any one of claims 1-5 or a liquid crystal composition comprising the liquid crystal compound according to any one of claims 9-12.

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