KR20230020824A - Circularly Polarized Light-Emitting Compounds with Cholesteric Liquid Crystal and Method for Preparing the same - Google Patents

Abstract

The present invention relates to circularly polarized light-emitting liquid crystalline compounds with a cholesteric liquid crystal and a manufacturing method thereof and, specifically, to circularly polarized light-emitting liquid crystalline compounds with a cholesteric liquid crystal by introducing an alkyl group of a racemic mixture and an alkyl group having a chiral center at the ninth substitution position of fluorene, and introducing a mesogen group having flexible chains at both ends around the fluorene, and a manufacturing method thereof.

Description

Circularly Polarized Light-Emitting Compounds with Cholesteric Liquid Crystal and Method for Preparing the same}

The present invention relates to a circularly polarized light emitting liquid crystal compound having a cholesteric liquid crystal phase and a method for preparing the same.

Organic Light Emitting Diode (OLED) is a display that emits light by itself using the electro luminescence (EL) phenomenon that emits light when current flows through a light emitting organic material. Unlike LCD), it does not require a backlight unit, so it can be manufactured with a lightweight thin film and has high quality characteristics such as high brightness and low power consumption, so the range of application is expanding as a next-generation display device for portable electronic devices.

The basic structure of an OLED device is a structure in which an organic thin film is laminated between an anode and a cathode, and when electricity is applied to the device, holes formed at the anode and cathode are formed in the hole injection layer. HIL), electrons are injected into the Electron Injection Layer (EIL) and then move to the Emisson Layer (EML) to form excited state excitons, and as the excitons fall to the ground state, they emit light. will emit

Among the structures of OLED, TFT (Thin Film Transistor) and electrodes are metal materials and have a very high light reflectance, making it difficult to recognize the screen as external light is reflected. Therefore, a polarizing plate is used to secure outdoor visibility. The polarizer used in OLED is a circular polarizer and is composed of a linear polarizer and a retardation film (45°). As unpolarized natural light from the outside passes through the vertical linear polarizer, it becomes linearly polarized light that oscillates vertically, and a phase difference of 45° occurs as it passes through the retardation film, resulting in circular polarization. The light is reflected by the electrode of the OLED and passes through the retardation film again, resulting in a retardation of 45° and consequently a retardation of 90°, resulting in horizontally vibrating linearly polarized light. Does not reach the eyes. When the light emitted from the light emitting layer of the OLED passes through the polarizer and comes out, the efficiency of the light is reduced by the linear polarizer.

However, if the organic light-emitting material emits polarized light, the efficiency of light passing through the polarizer can be improved. If the organic light emitting material has liquid crystallinity, it can emit highly linearly polarized light. In particular, when organic light emitting materials emit light with high circular polarization, the decrease in light efficiency when passing through the polarizer of OLED can be improved, so that bright OLED can be realized with low power, so the need for development is emerging.

In this regard, Korean Patent Publication No. 10-2019-0089021 discloses a diffraction device based on a cholesteric liquid crystal (CLC) liquid crystal including a plurality of chiral structures.

As part of the research to develop a liquid crystalline organic compound capable of emitting circularly polarized light, the present inventor introduced an alkyl group of a racemic mixture and an alkyl group having a chiral center at the 9-substituted position of fluorene, and the fluorene as the center As a result, a chiral mesogenic compound was synthesized by introducing an achiral flexible chain group at both ends and a mesogenic group having a chain containing a chiral center, leading to the present invention.

Domestic Patent Publication No. 10-2019-0089021 (2019.07.29.)

An object of the present invention to solve the above problems is to introduce an alkyl group of a racemic mixture and an alkyl group having a chiral center at the 9th substitution position of fluorene, and meso having flexible chains at both ends centered on the fluorene. It is to provide a circularly polarized light-emitting liquid crystal compound having a cholesteric liquid crystal phase by introducing a gen group and a method for preparing the same.

The compound for circularly polarized light emitting liquid crystals of the present invention for solving the above problems is characterized by having a structure represented by Chemical Formula 1 below.

[Formula 1]

(Wherein R ₁ , R ₂ and R ₄ are each independently an alkyl group or alkoxy having 1 to 20 carbon atoms, n is an integer of 1 to 5, and R ₃ is biphenyl, naphthalene, bisphenol A or a combination thereof one of them.)

Preferably, R ₁ and R ₂ are alkyl groups having 1 to 20 carbon atoms, specifically, a racemic mixture and an alkyl group having a chiral center, and a specific example is 1-Bromo-2 having an ethylhexyl group as a racemic mixture. -Ethylhexane, an alkyl group having a chiral center, may include (S)-(+)-Citronellyl bromide.

The R ₃ is a mesogen group of any one of biphenyl, naphthalene, bisphenol A, or a combination thereof, and preferably, biphenyl is used.

R ₄ is an alkyl group or an alkoxy group having 1 to 20 carbon atoms, and preferably, may be an achiral flexible chain, an alkyl chain containing a chiral center, or any combination thereof. As a specific example, the achiral flexible chain may be pentyloxy, the alkyl chain containing a chiral center may be (S)-1-bromo-3,7-dimethyl octane, or any combination thereof.

Preferably, R ₃ of the compound for circularly polarized light emitting liquid crystals of the present invention is biphenyl, and is represented by Chemical Formula 2 below.

[Formula 2]

The method for preparing a compound for circularly polarized light emitting liquid crystal of the present invention to solve the above problems is a first step of preparing a fluorene derivative compound by introducing R ₁ and R ₂ to the 9th carbon substitution position of fluorene; and R ₃ terminal Step 2 of preparing an R ₃ derivative compound by introducing R ₄ into the R 3 derivative compound; Step 3 _of preparing an R ₃ derivative compound into which boron is introduced by introducing boron into the R 3 derivative compound; and Step 3 of preparing an R ₃ derivative compound into which boron is introduced. It includes; 4 steps of polymerizing the compound and the fluorene derivative compound.

In step 1, R ₁ and R ₂ are introduced at the 9th carbon substitution position of fluorene through an alkylation reaction to prepare a fluorene derivative compound of the following [Formula 3].

[Formula 3]

(The R ₁ and R ₂ are each independently selected from hydrogen or an alkyl group having 1 to 20 carbon atoms, and the X ₁ is selected from Br, Cl, and I.)

In step 2, R ₄ is introduced to the R ₃ terminal to prepare an R ₃ derivative compound, and R ₄ is introduced to the R ₃ terminal through a Williamson ether synthesis reaction.

In step 3, boron is introduced into the R ₃ derivative compound to prepare a compound through the suzuki-Miyaura coupling reaction in step 4 to prepare an R ₃ derivative compound into which boron is introduced.

In step 4, the boron-introduced R ₃ derivative compound and the fluorene derivative compound are polymerized, and at this time, a palladium (Pd) supported catalyst is used to polymerize through a suzuki-Miyaura coupling reaction .

As described above, according to the circularly polarized light emitting liquid crystal compound having a cholesteric liquid crystal phase and a method for producing the same according to the present invention, it has cholesteric liquid crystal and circularly polarized light emitting property to improve the light efficiency decrease when passing through the polarizing plate of OLED. It has the effect of realizing bright OLED with low power.

1 is a synthesis route of Compound I among compounds for circularly polarized light emitting liquid crystals according to an embodiment of the present invention.
2 is a synthesis route of Compound II among compounds for circularly polarized light emitting liquid crystals according to another embodiment of the present invention.
3(A) is a ¹ H-NMR spectrum of synthesized 4-bromo-4'-(pentyloxy)-1,1'-biphenyl, (B) is a synthesized (4'-(pentyloxy)-[1,1 ¹ H-NMR spectrum of '-biphenyl]-4-yl)boronic acid.
Figure 4 (A) is the ¹ H-NMR spectrum of the synthesized 2,7-dibromo-9,9-bis (2-ethylhexyl) -9H-fluorene, (B) is the synthesized (S) -1-bromo-3 ¹ H-NMR spectrum of 7-dimethyloctane.
Figure 5 (A) is the ¹ H-NMR spectrum of the synthesized 2,7-dibromo-9,9-bis ((S) -3,7-dimethyloctyl) -9H-fluorene, (B) is the synthesized (S) ¹ H-NMR spectrum of -4-bromo-4'-((3,7-dimethyloctyl)oxy)-1,1'-biphenyl.
6 is a ¹ H-NMR spectrum of synthesized (S)-(4'-((3,7-dimethyloctyl)oxy)-[1,1'-biphenyl]-4-yl) boronic acid.
7 (A) is an FT-IR spectrum of Compound Ia, and (B) is a ¹ H-NMR spectrum of Compound Ia.
8(A) is an FT-IR spectrum of Compound Ib, and (B) is a ¹ H-NMR spectrum of Compound Ib.
9 (A) is an FT-IR spectrum of Compound IIa, and (B) is a ¹ H-NMR spectrum of Compound IIa.
Figure 10 (A) is an FT-IR spectrum of compound IIb, Figure 10 (B) is ^{a 1} H-NMR spectrum of compound IIb.
11 (A) is a DSC thermogram of Compound Ia, and (B) is a DSC thermogram of Compound Ib.
12 (A) is a DSC thermogram of compound IIa, and (B) is a DSC thermogram of compound IIb.
Figure 13 shows a POM image (X100) of Compound Ia, (a) to (c) show changes upon heating at 92 ° C, 101 ° C, and 108 ° C, respectively, (d) shows secondary cooling at 68 ° C, Changes in (e) during secondary cooling at 72°C and (f) during secondary heating at 223°C.
Figure 14 shows the POM image of Compound Ib, (a) when heated to 82 ℃, (b) and (c) the change when secondary heating to 120 ℃, 128 ℃, respectively, (d) and (e ) is the change when cooling to 76 ℃ and 54 ℃, respectively, (f) is the change when the secondary heating to 193 ℃.
Figure 15 shows the POM image (X100) of compound IIa, (a) to (d) change upon heating at 41 ℃, 76 ℃, 95 ℃, 119 ℃, respectively, (e), (f) is 95 ℃, changes upon cooling to 30 ℃.
Figure 16 shows the POM image of compound Ⅱb, (a) to (c) change when heated to 106 ℃, 108 ℃, 109 ℃, respectively, (d) when cooled to 40 ℃, (e) 106 When the second heating to ℃, (f) changes when the second heating to 142 ℃.
Figure 17 (A) is a UV-vis absorption spectrum showing the absorption characteristics of the four compounds synthesized, Figure 17 (B) is the emission spectrum through PL spectroscopy.
Figure 18 is a CV diagram of the four compounds synthesized, (A) is Compound Ia, (B) is Compound Ib, (C) is Compound IIa, and (D) is Compound IIb.

Hereinafter, the present invention will be described in detail in the following with reference to a preferred embodiment. However, the following examples are intended to specifically illustrate the present invention, but are not limited thereto, and if it is determined that the detailed description of functions and configurations related to the present invention may unnecessarily obscure the gist of the present invention. will omit the detailed description.

Using a fluorene-based chromophore, which is a blue light-emitting organic material, the effect of structural change on light absorption and emission characteristics was studied. In order to emit light with high circular polarization, an alkyl group having chirality is introduced at the 9th substituted position of fluorene to induce a helical structure to represent cholesteric liquid crystal, and biphenyl groups, which are mesogenic groups, are present on both sides of fluorene. was introduced to increase liquid crystallinity. In addition, by introducing an alkyl group having chirality at both ends, the change in the degree of circularly polarized light emission was investigated.

Specifically, a racemic mixture of an alkyl group, 1-Bromo-2-ethylhexane, and a levorotatory alkyl group, (S)-(+)-Citronellyl bromide, are introduced at the 9th substituted position of fluorene, and biphenyl having pentyloxy flexible chains at both ends. Compound I was synthesized by substituting the structure, and Compound II was synthesized by introducing a biphenyl group having a chiral alkyl group at both ends of the same fluorene structure as Compound I.

1 is a synthesis route of Compound I among compounds for circularly polarized light emitting liquid crystals according to an embodiment of the present invention, and FIG. 2 shows a synthesis route of Compound II among compounds for circularly polarized light emitting liquid crystals according to another embodiment of the present invention. .

The structure and composition of the obtained compound were investigated by ¹ H-NMR and FT-IR spectroscopy. Thermal characteristics and liquid crystal phase were confirmed by DSC and POM, and absorption and emission characteristics were investigated by UV-vis and PL spectrophotometers. The energy level of the compound was measured by cyclic voltammetry and the optical activity was measured using a polarimeter.

1. Synthesis of Compound for Circularly Polarized Light Emitting Liquid Crystal

reagents and instruments

The reagents, solvents and catalysts used in the experiment were 4-bromo-4'-hydroxybiphenyl, 1-bromopentane, trimethyl borate, dimethyl sulfoxide (DMSO), 2,7-dibromofluorene, 1-bromo-2-ehtylhexane, and potassium iodide from TCI. (KI), 2.5M n-butyllithium solution (n-buLi) from Sigma aldrich, tetrakis(triphenylphosphine)palladium(0) (Pd(PPH ₃ ) ₄ ), 10 wt% palladium on carbon (10% Pd/C), (S)-(+)-citronellyl bromide, Daejung ethyl acetate (EA), N,N-dimethylformamide (DMF), dichlorometane (DCM), ethanol, acetone, 35% hydrochloric acid (HCl), tetrahydrofuran (THF), Hexane, potassium hydroxide (KOH), potassium carbonate anhydrous (K ₂ CO ₃ ), sodium chloride (NaCl), and magenesium sulfate (MgSO ₄ ) were purchased and used. Tetrahydrofuran (THF) was dried using sodium and benzophenone and used as a solvent, and other reaction reagents and catalysts were used without a separate purification process. The silica gel used for column chromatography was 0.040-0.063 mm in size from Merck.

The structure of the compound synthesized in each reaction was confirmed using Bruker's Biospine 400 Mhz NMR spectrometer, and the structure of the final compound was determined using Bruker's Vertex 80v FT-IR spectrometer, Thermo Fisher's Flash 2000, and Elementar Americas' Vario Max CN elemental analyzer. confirmed through The thermal properties of the synthesized compound were measured at a heating rate of 5°C/min until the second heating under a nitrogen atmosphere using a DSC 200 F3 from NETZSCH, and the liquid crystal phase was confirmed using a Carl Zeiss Axioskop 40 polarizing microscope.

Absorption and emission characteristics of the compound were confirmed by measuring a Mecasys Optizen 3220UV spectrophotometer and RF-5301PC fluorescence spectrophotometer, and the HOMO and LUMO levels of the compound were measured using a WizECM-1200 Premium potentiometer. In addition, optical activity was measured using a Perkin Elmer Polarimeter 341 polarimeter manufactured by Perkin Elmer (U.S.A).

1-1. Synthesis of Compound I

Chiral fluorene derivatives were synthesized by introducing two types of chiral alkyl groups at position 9 of fluorene and biphenyl groups having pentyloxy groups at both ends.

Synthesis of 4-bromo-4'-(pentyloxy)-1,1'-biphenyl

After completely dissolving 4-bromo-4'-hydroxybiphenyl (5.02 g, 20.15 mmol) in DMF, add Potassium carbontae (5.56 g, 40.23 mmol) and 1-bromopentane (3.90 g, 25.83 mmol) at 80℃ for 12 hours. It was stirred under reflux. The reactant was precipitated in an excess of distilled water, extracted with ethyl acetate to collect only the organic layer, dried with MgSO ₄ , filtered under reduced pressure, and distilled under reduced pressure to remove the solvent.

Column chromatography was performed using dichloromethane as a solvent, and recrystallization was performed with ethanol to obtain a white solid product. Yield: 92.09%; ¹ H-NMR (acetone-d6 δH in ppm): 0.91-0.95 (3H, t, J = 7.2 Hz), 1.35-1.51 (4H, m), 1.76-1.83 (2H, quint, J = 8.1 Hz), 4.02–4.05 (2H, t, J = 6.5 Hz), 7.01–7.03 (2H, d, J = 8.8 Hz), 7.57–7.60 (6H, m).

3(A) shows the ¹ H-NMR spectrum of synthesized 4-bromo-4'-(pentyloxy)-1,1'-biphenyl .

Synthesis of (4'-(pentyloxy)-[1,1'-biphenyl]-4-yl)boronic acid

After completely dissolving 4-bromo-4'-(pentyloxy)-1,1'-biphenyl (5.147 g, 16.12 mmol) in dry THF under a nitrogen atmosphere, n-buthyllityium (1.239 g, 19.35 mmol) was prepared at -78℃. was added slowly. After reacting while maintaining -78℃ for 2 hours, trimethyl borate (2.513 g, 24.19 mmol) was added dropwise, and the temperature was raised to room temperature and stirred for 8 hours. Thereafter, an aqueous solution of hydrochloric acid was added to the reaction mixture to lower the pH to 2, and the mixture was stirred for 3 hours. After completion of the reaction, only the organic layer was obtained after extraction using diethyl ether and distilled water. The resulting organic layer was dried with MgSO ₄ , filtered under reduced pressure, and the solvent was removed using a rotary vacuum evaporator. Then, the dried product was washed with hexane to remove impurities, and the precipitate was filtered under reduced pressure to obtain a white solid product. Yield: 89.08%; ^1H -NMR (DMSO-d6δH in ppm): 0.88-0.91 (3H, t, J = 7.0 Hz), 1.32-1.43 (4H, m), 1.69-1.76 (2H, quint, J = 6.7 Hz), 3.98 -4.01 (2H, t, J = 6.5 Hz), 6.99-7.02 (2H, d, J = 8.8 Hz), 7.57-7.62 (4H, q, J = 8.8 Hz), 7.83-7.85 (2H, d, J = 8.8 Hz) = 8.3 Hz), 8.04 (2H, s).

3(B) shows the ¹ H-NMR spectrum of synthesized (4'-(pentyloxy)-[1,1'-biphenyl]-4-yl)boronic acid.

Synthesis of 2,7-dibromo-9,9-bis(2-ethylhexyl)-9H-fluorene

After completely dissolving 2,7-dibromofluorene (3.03 g, 9.351 mmol) in DMSO while heating, add potassium hydroxide (5.32 g, 94.83 mmol) and potassium iodide (0.174 g, 1.048 mmol) in powder form and bring the temperature to room temperature. put it down After slowly adding 1-bromo-2-ethylhexane (3.87 g, 20.04 mmol) dropwise, the mixture was stirred at room temperature for 8 hours. After the reaction was terminated, the mixture was precipitated by pouring in an excess of distilled water, and extracted with ethyl acetate to obtain an organic layer. The resulting organic layer was dried with MgSO ₄ and filtered under reduced pressure, and then the solvent was removed using a rotary vacuum evaporator. Column chromatography was performed using hexane as a solvent to obtain a yellow viscous liquid product. : Yield: 54.611%; ¹ H-NMR (chloroform-d δH in ppm): 0.44-0.50 (2H, quint, J = 5.8 Hz), 0.52-0.56 (6H,td, J = 7.4, 2.8 Hz), 0.64-0.83 (6H, m ), 0.86–0.93 (6H, m), 1.92–1.94 (4H, d,J = 5.8 Hz), 7.43–7.53 (6H, m).

4(A) shows the ¹ H-NMR spectrum of synthesized 2,7-dibromo-9,9-bis(2-ethylhexyl)-9H-fluorene.

Synthesis of Compound Ia

(4'-(pentyloxy)-[1,1'-biphenyl]-4-yl)boronic acid (1.06 g, 3.73 mmol) and 2,7-dibromo-9,9-bis(2-ethylhexyl)-9H- After completely dissolving fluorene (0.96 g, 1.75 mmol) in THF, an aqueous solution of K ₂ CO ₃ and tetrakis(triphenylphosphine)palladium(0) (0.12 g, 0.104 mmol) were added and refluxed for 24 hours. After the reaction was completed, the reactants were precipitated in an excess of distilled water and extracted with diethyl ether to obtain only the organic layer. The obtained organic layer was dried with MgSO ₄ , then MgSO ₄ was removed using a vacuum filter, and the solvent was removed by distillation under reduced pressure. Column chromatography was performed using a DCM:hexane (1:2 v/v) mixed developing solvent, and recrystallization with acetone was performed to obtain a white solid product. Yield: 65.55%; IR (KBr pellet, cm ^-1 ): 3029 (aromatic CH stretch), 2955, 2920, 2857 (aliphatic CH strtch), 1650, 1605, 1529, 1499 (aromatic C=C stretch), 1460 (aliphatic CH ₂ and CH ₃ ), 1382 (CH bend), 1283, 1247, 1174, 1049 (CO stretch), 988, 813 (aromatic CH out of plane bend); ¹ H-NMR (chloroform-d δH in ppm): 0.53-0.57 (6H, td, J = 7.3, 2.8 Hz), 0.62-0.65 (8H, t, J = 6.5 Hz), 0.71-0.91 (16H, m ), 0.94–0.98 (6H, t, J = 7.1 Hz), 1.38–1.52 (8H, m), 1.80–1.87 (4H, quint, J = 7.9 Hz), 2.05–2.15 (4H, m), 4.01– 4.04 (4H, t, J = 6.7 Hz), 6.99-7.02 (4H, d J = 8.6 Hz), 7.58-7.63 (6H, m), 7.65-7.67 (6H, d, J = 8.7 Hz), 7.69- 7.73 (4H, m), 7.77–7.79 (2H, d, J = 7.2 Hz).

Synthesis of (S)-1-bromo-3,7-dimethyloctane

(S)-(+)-citronellyl bromide (5.02 g, 22.90 mmol) was completely dissolved in THF under a nitrogen atmosphere, and Pd/C (10 wt%) (0.86 g, 8.081 mmol) was added thereto. The needle of the hydrogen balloon was put into the solution and stirred at room temperature for 24 hours. After completion of the reaction, Pd/C was removed by filtering under reduced pressure using a filter agent, and the solvent was evaporated through distillation under reduced pressure. Purification was performed by column chromatography using DCM as a solvent, and the solvent was removed by distillation under reduced pressure to obtain a clear liquid product. Yield: 96.33%; ^1H -NMR (chloroform-d δH in ppm): 0.86-0.89 (9H, t, J = 7.0 Hz), 1.10-1.32 (6H, m), 1.49-1.54 (1H, m), 1.57-1.75 (3H , m), 1.80–2.06 (2H, m), 3.37–3.50 (2H, m).

4(B) shows the ¹ H-NMR spectrum of synthesized (S)-1-bromo-3,7-dimethyloctane.

Synthesis of 2,7-dibromo-9,9-bis((S)-3,7-dimethyloctyl)-9H-fluorene

After completely dissolving 2,7-dibromofluorene (2.8 g, 8.641 mmol) in DMSO while heating, add potassium hydroxide (2.61 g, 46.52 mmol) and potassium iodide (0.17 g, 0.602 mmol) in powder form and bring the temperature to room temperature. put it down (S) -1-bromo-3,7-dimethyloctane (4.55 g, 20.57 mmol) was slowly added dropwise thereto, followed by stirring at room temperature for 8 hours. After the reaction was completed, the mixture was precipitated in an excess of distilled water and extracted with ethyl acetate to obtain an organic layer. The resulting organic layer was dried with MgSO ₄ , filtered under reduced pressure, and distilled under reduced pressure to remove the solvent. Column chromatography was performed using hexane as a solvent to obtain a transparent viscous liquid product. Yield: 59.76%; ¹ H-NMR (Chloroform-d δH in ppm): 0.38-0.60 (4H, m), 0.68-0.70 (6H, d, J = 6.6 Hz), 0.81-0.92 (14H, m), 1.02-1.15 (12H , m), 1.40–1.50 (2H, m, J = 6.5 Hz), 1.85–2.00 (4H, quintd, J = 13.1, 6.1 Hz), 70.43–7.46 (4H, m), 7.51–7.53 (2H, d , J = 8.1 Hz).

5(A) shows the ¹ H-NMR spectrum of synthesized 2,7-dibromo-9,9-bis((S)-3,7-dimethyloctyl)-9H-fluorene.

Synthesis of Compound Ib

(4'-(pentyloxy)-[1,1'-biphenyl]-4-yl)boronic acid (0.95 g, 3.34 mmol) and 2,7-dibromo-9,9-bis((S)-3,7 After completely dissolving -dimethyloctyl)-9H-fluorene (1.01 g, 1.67 mmol) in THF, K ₂ CO ₃ aqueous solution and tetrakis(triphenylphosphine)palladium(0) (0.11 g, 0.097 mmol) were added thereto and refluxed for 24 hours. After the reaction was completed, the reactants were precipitated in an excess of distilled water and extracted with diethyl ether to obtain only the organic layer. The obtained organic layer was dried with MgSO ₄ , then MgSO ₄ was removed using a vacuum filter, and the solvent was removed by distillation under reduced pressure. Column chromatography was performed using a DCM:hexane (1:2 v/v) mixed developing solvent, and recrystallization with acetone was performed to obtain a white solid product. Yield: 65.20%; IR (KBr pellet, cm ^-1 ): 3030 (aromatic CH stretch), 2953, 2924, 2860 (aliphatic CH strtch), 1605, 1530, 1500 (aromatic C=C stretch), 1463 (aliphatic CH ₂ and CH ₃ ) , 1384 (CH bend), 1288, 1247, 1204, 1177, 1051 (CO stretch), 992, 912, 814, 732 (aromatic out of plane CH bend); ¹ H-NMR (chloroform-d δH in ppm): 0.55-0.88 (24H, m), 0.94-1.10 (16H, m), 1.14-1.16 (2H, m), 1.36-1.50 (10H, m), 1.80 −1.87 (4H, quint, JC 7.0 Hz), 2.01–2.14 (quintd, J = 12.7, 5.1 Hz), 4.01–4.04 (4H, t, J = 6.0 Hz), 6.99–7.02 (4H, d, J = 6.0 Hz) 8.8 Hz), 7.58–7.67 (12H, m), 7.71–7.74 (4H, d, J = 8.3 Hz), and 7.78–7.80 (2H, d, J = 7.9 Hz).

1-2. Synthesis of Compound II

A chiral fluorene derivative was synthesized by introducing two types of chiral alkyl groups at position 9 of fluorene and a biphenyl group having two other types of chiral alkyl groups at both ends of fluorene.

Synthesis of (S)-4-bromo-4'-((3,7-dimethyloctyl)oxy)-1,1'-biphenyl

After completely dissolving 4-bromo-4'-hydroxybiphenyl (4.99 g, 20.03 mmol) in DMF, potassium carbontae (5.55 g, 40.12 mmol) and (S) -1-bromo-3,7-dimethyl octane (5.50 g, 24.87 mmol) was added and refluxed at 80 °C for 12 hours. The reactants were precipitated in an excess of distilled water, extracted with EA and washed to obtain only the organic layer. The obtained organic layer was dried with MgSO ₄ and filtered under reduced pressure, and then distilled under reduced pressure to remove the solvent. Column chromatography was performed using DCM as a solvent, and the product was recrystallized with ethanol to obtain a white solid product. Yield: 55.5%; ¹ H-NMR (acetone-d6 δH in ppm): 0.87-0.88 (6H, d, J = 6.6 Hz), 0.96-0.98 (3H, d, J = 6.6 Hz), 1.17-1.40 (6H, m), 1.52–1.75 (3H, m), 1.80–1.89 (1H, m), 4.05–4.14 (2H, m), 7.02–7.04 (2H, d, J = 8.9 Hz), 7.55–7.61 (6H, m).

5(B) shows the ¹ H-NMR spectrum of synthesized (S)-4-bromo-4'-((3,7-dimethyloctyl)oxy)-1,1'-biphenyl.

Synthesis of (S)-(4'-((3,7-dimethyloctyl)oxy)-[1,1'-biphenyl]-4-yl) boronic acid

After completely dissolving (S)-4-bromo-4'-((3,7-dimethyloctyl)oxy)-1,1'-biphenyl (4.06 g, 10.43 mmol) in dry THF under a nitrogen atmosphere, a temperature of -78℃ n-buthyllityium (1.057 g, 16.50 mmol) was slowly added dropwise thereto. After reacting while maintaining -78 ℃ for 2 hours, trimethyl borate (2.423 g, 23.32 mmol) was added dropwise and the temperature was raised to room temperature and stirred for 8 hours. After extracting the reactants using diethyl ether and distilled water, only the organic layer was obtained. The collected organic layer was dried with MgSO ₄ , filtered under reduced pressure, and the solvent was removed using a rotary vacuum evaporator. Thereafter, the dried product was washed with hexane, and the precipitate was filtered under reduced pressure to obtain a white solid product. Yield: 59.83%; ¹ H-NMR (acetone-d6 δH in ppm): 0.98-0.99 (6H, d, J = 6.6 Hz), 1.08-1.09 (3H, d, J = 6.6 Hz), 1.31-1.50 (6H, m), 1.61-1.76 (2H, m), 1.80-1.99 (2H, m), 4.18-4.25 (2H, m), 7.13-7.15 (2H, d, J = 8.8 Hz), 7.26 (2H, s), 7.70- 7.74 (4H, td, J = 6.6, 1.5 Hz),8.03–8.05 (2H, d, J = 8.2 Hz).

6 shows the ¹ H-NMR spectrum of synthesized (S)-(4'-((3,7-dimethyloctyl)oxy)-[1,1'-biphenyl]-4-yl) boronic acid.

Synthesis of Compound IIa

(4'-((2-ethylhexyl)oxy)-[1,1'-biphenyl]-4-yl)boronic acid (1.62 g, 4.57 mmol) and 2,7-Dibromo-9,9-bis(2- After completely dissolving ethylhexyl)-9H-fluorene (1.12 g, 2.04 mmol) in THF, an aqueous solution of K ₂ CO ₃ and tetrakis(triphenylphosphine)palladium(0) (0.22 g, 0.19 mmol) were added and refluxed for 24 hours.

After the reaction was completed, the reactants were precipitated in an excess of distilled water and extracted with diethyl ether to obtain only the organic layer. The obtained organic layer was dried with MgSO ₄ , then MgSO ₄ was removed using a vacuum filter, and the solvent was removed by distillation under reduced pressure. Column chromatography was performed with a DCM: hexane (1:2 v/v) mixed eluent and recrystallized with acetone to obtain a bluish white viscous product. Yield: 47.33%; IR (solvent : chloroform): 2954, 2923, 2869 (aliphatic CH strtch), 1607, 1501 (aromatic C=C stretch), 1463 (aliphatic CH ₂ and CH ₃ ), 1380 (CH bend), 1284, 1245, 1198 , 1176, 1029 (CO stretch), 999, 813, 756, 740 (aromatic CH out of plane bend); ¹ H-NMR (chloroform-d δH in ppm): 0.53-0.57 (6H, td, J = 7.3, 2.8 Hz), 0.62-0.65 (8H, t, J = 6.4 Hz), 0.74-0.83 (6H, m ), 0.88-0.90 (18H, d, J = 6.6 Hz), 0.96-0.98 (6H, d, J = 6.4 Hz), 1.17-1.387 (16H, m), 1.50-1.72 (8H, m), 1.83- 2.91 (2H, m, J = 7.7 Hz), 2.05-2.15 (4H, m), 4.01-4.11 (4H, m), 7.00-7.02 (4H, d, J = 8.9 Hz), 7.59-7.72 (16H, m),7.77–7.79 (2H, d, J = 8.0 Hz).

Synthesis of Compound IIb

(S)-(4'-((3,7-dimethyloctyl)oxy)-[1,1'-biphenyl]-4-yl)boronic acid (2.58g, 7.28 mmol) and 2,7-dibromo-9, After completely dissolving 9-bis((S)-3,7-dimethyloctyl)-9H-fluorene (2.00 g, 3.31 mmol) in THF, 2 M K ₂ CO ₃ aqueous solution and tetrakis (triphenylphosphine) palladium(0) ( 0.38 g, 0.33 mmol) was added and refluxed for 24 hours. After the reaction was completed, the reactants were precipitated in an excess of distilled water and extracted with diethyl ether to obtain only the organic layer. The obtained organic layer was dried with MgSO ₄ , then MgSO ₄ was removed using a vacuum filter, and the solvent was removed by distillation under reduced pressure. Column chromatography was performed with a DCM: hexane (1:2 v/v) mixed developing solvent, and recrystallization with acetone was performed to obtain a white solid product. Yield: 44.6%; IR (solvent : chloroform): 3031 (aromatic CH stretch), 2953, 2923, 2861 (aliphatic CH strtch), 1609, 1501 (aromatic C=C stretch), 1464 (aliphatic CH ₂ and CH ₃ ), 1383 (CH bend) ), 1289, 1246, 1178, 1035 (CO stretch), 815, 737 (aromatic CH out of plane bend); ¹ H-NMR (chloroform-d δH in ppm): 0.54-0.63 (2H, m), 0.70-0.77 (20H, dd, J = 22.6, 6.5 Hz), 0.88-0.98 (20H, dd, J = 33.7, 6.6 Hz), 0.99-1.20 (18H, m), 1.26-1.43 (9H, m), 1.60-1.75 (5H, m), 1.83-1.91 (12H, m, J = 5.5Hz), 2.01-2.15 (4H , quintd, J = 12.5, 5.0 Hz), 4.01–4.11 (4H, m), 7.00–7.02 (4H, d, J = 8.8 Hz), 7.58–7.67 (12H, m), 7.72–7.74 (4H, d , J = 8.4 Hz), 7.78–7.80 (2H, d, J = 7.0 Hz).

Four types of chiral mesogenic compounds were synthesized by introducing an achiral flexible chain group and a biphenyl group having a chiral center-containing chain group at both ends of a fluorene center structure having an alkyl group with a chiral center. Experimental methods used in the synthesis include an alkylation reaction to introduce an alkyl chain containing a chiral center at the substituted position of carbon number 9 of fluorene, a Williamson ether synthesis reaction to introduce an alkyl chain to the biphenyl structure at both ends, and bromine and It was synthesized through the Suzuki-Miyaura coupling reaction, which synthesizes compounds by reacting boronic acid of biphenyl. The synthesis of the synthesized compound was confirmed by structural analysis using ¹ H-NMR and FT-IR spectroscopy. Acetone-d6, chloroform-d, and DMSO-d6 solvents were used for ¹ H-NMR measurement, and FT-IR was measured with a KBr pellet and a solution dissolved in chloroform. In addition, the final product was subjected to elemental analysis and is shown in Table 1 below. Table 1 shows the results of elemental analysis according to the synthesized compounds.

In the FT-IR spectrum of Compund Ⅰa, the peak due to stretching vibration of aromatic CH is 3029 cm ^-1 , the peak due to stretching vibration of aliphatic CH is 2955, 2920, 2857 cm ^-1 , and the peak due to stretching vibration of aromatic C=C is 1650 , 1605, 1529, 1499 cm ^-1 , aliphatic CH ₂ and CH ₃ peaks at 1460 cm ^-1 , CH bending vibration peaks at 1382 cm ^-1 , CO stretching vibration peaks at 1283, 1247, 1174, 1047 cm ^-1 , peaks due to aromatic CH oop bending vibration appeared at 988, 913 cm ^-1 . In ^{the 1} H-NMR spectrum, the proton resonance peak of biphenyl group and fluorene is 6.99-7.79 ppm, the resonance peak of the chain located next to the oxygen atom is 4.01-4.04 ppm, and the carbon chain of fluorene and the flexible chain at both ends A resonance peak appeared at 0.53-2.15 ppm.

7(A) is an FT-IR spectrum of Compound Ia, and FIG. 7(B) shows ^{a 1} H-NMR spectrum of Compound Ia.

In the FT-IR spectrum of Compound Ib, the peak due to stretching vibration of aromatic CH is 3030 cm ^-1 , the peak due to stretching vibration of aliphatic CH is 2953, 2924, 2860 cm ^-1 , and the peak due to stretching vibration of aromatic C=C is 1605 , 1530, 1500 cm ^-1 , aliphatic CH ₂ and CH ₃ peaks at 1463 cm ^-1 , CH bending vibration peaks at 1384 cm ^-1 , CO stretching vibration peaks at 1288, 1247, 1204, 1177, 1051 cm ^-1 , peaks due to aromatic CH oop bending vibration appeared at 992, 912, 812, and 732 cm ^-1 . In ^{the 1} H-NMR spectrum, the biphenyl group and fluorene proton resonance peaks are 6.99-7.80 ppm, the resonance peaks of the chains located next to the oxygen atom are 4.01-4.04 ppm, and the carbon chain of fluorene and the flexible chain at both ends A resonance peak appeared at 0.55-2.14 ppm.

8(A) is an FT-IR spectrum of Compound Ib, and FIG. 8(B) shows ^{a 1} H-NMR spectrum of Compound Ib.

In the FT-IR spectrum of Compund IIa, peaks due to aliphatic CH stretching vibrations are 2954, 2923, and 2869 cm ^-1 , peaks due to aromatic C=C stretching vibrations are 1607, 1501 cm ^-1 , and peaks due to aliphatic CH ₂ and CH ₃ is 1463 cm ^-1 , peaks due to CH bending vibration are 1380 cm ^-1 , peaks due to CO stretching vibration are 1284, 1245, 1198, 1176, 1029 cm ^-1 , peaks due to aromatic CH oop bending vibration are 999, 813 , 756 and 740 cm ^-1 . In ^{the 1} H-NMR spectrum, the proton resonance peaks of biphenyl group and fluorene are 7.00-7.79 ppm, the resonance peaks of chains located next to oxygen atoms are 4.01-4.11 ppm, and the carbon chain of fluorene and the flexible chain at both ends A resonance peak appeared at 0.53-2.15 ppm.

9(A) is an FT-IR spectrum of compound IIa, and FIG. 9(B) shows ^{a 1} H-NMR spectrum of compound IIa.

In the FT-IR spectrum of Compund IIb, the peak due to the stretching vibration of aromatic CH is 3031 cm ^-1 , the peak due to stretching vibration of aliphatic CH is 2953, 2923, 2861 cm ^-1 , and the peak due to stretching vibration of aromatic C=C is 1609 , 1501 cm ^-1 , aliphatic CH ₂ and CH ₃ peaks at 1464 cm ^-1 , CH bending vibration peaks at 1383 cm ^-1 , CO stretching vibration peaks at 1289, 1246, 1178, 1035 cm ^-1 , peaks due to aromatic CH oop bending vibrations appeared at 815, 737 cm ^-1 . In ^{the 1} H-NMR spectrum, the proton resonance peaks of biphenyl group and fluorene are 7.00-7.80 ppm, and the resonance peaks of chains located next to oxygen atoms are 4.01-4.11 ppm. A resonance peak appeared at 0.54-2.15 ppm. The final product was subjected to elemental analysis to determine the molecular formula and purity of the organic compound by measuring the content of carbon, hydrogen and oxygen. Table 1 compares the analysis results and calculated values of the elemental ratio. The carbon and hydrogen abundances of the four compounds were found to be within ± 0.3% of the allowable error range, except for the hydrogen content of Compound IIa, but the oxygen abundances showed an error of -0.966 to -0.401%.

FIG. 10(A) is an FT-IR spectrum of compound IIb, and FIG. 10(B) shows ^{a 1} H-NMR spectrum of compound IIb.

2. Thermal Transition Behavior of Circularly Polarized Light-emitting Liquid Crystal Compounds

Changes in thermal transition temperature and enthalpy (ΔH) of the four final compounds synthesized were measured using DSC, and the values are shown in Table 2.

DSC measurement was conducted under a nitrogen atmosphere and measured by heating and cooling at a heating rate of 5 °C/min.

11(A) is a DSC thermogram of Compound Ia, and FIG. 11(B) shows a DSC thermogram of Compound Ib.

The DSC graph of Compound Ia having an ethylhexyl group at the fluorene 9-carbon substitution position and a flexible chain with 5 carbon chains at both ends is shown in FIG. 11(A). During the first heating, a solid-solid transition (T _kk ) appeared at 84.5 ° C, and an isotropic liquefaction transition (T _i ) appeared at 226.6 ° C. In the case of the first cooling and the second heating, only T _i appeared at 226.0 ℃ and 226.4 ℃, respectively.

The DSC graph of Compound Ib having an alkyl group having a chiral center at the fluorene number 9 carbon substitution position and having 5 carbon chains at both ends is shown in FIG. 11(B). During the first heating, T _kk did not appear, the melting point (T _m ) appeared at 120.1 ° C, and T _i appeared at 193.8 ° C. During the first cooling, T _i was shown at 193.3 ° C, and crystallization behavior (T _c ) was shown at 86.9 ° C. During the secondary heating, T _m at 119.4 ° C and T _i at 193.3 ° C appeared.

Figure 12 (A) is a DSC thermogram of Compound IIa, and Figure 12 (B) shows a DSC thermogram of Compound IIb.

A DSC graph of Compound IIa having an ethylhexyl group at the fluorene 9-carbon substitution position and an alkyl chain having chiral centers at both ends is shown in FIG. 12(A). Compound IIa is a viscous liquid compound, and T _kk and T _m do not appear, and T _i appears at 136.5 ℃ during the first heating, 136.5 ℃ during the first cooling, and 138.4 ℃ during the second heating. Compound IIa was additionally measured by DSC at a low temperature of -80 ° C or lower, and it was confirmed that T _m appeared at -32.9 ° C.

A DSC graph of Compound IIb having an alkyl group having a chiral center at the fluorene number 9 carbon substitution position and having an alkyl chain having a chiral center at both ends is shown in FIG. 12(B). During the first heating, T _m appeared at 105.9 ° C and T _i appeared at 143 ° C. During the first cooling, T _i was shown at 142.7 °C and crystallization behavior was shown at 58.2 °C. During the second heating, T _m appeared at 102.2 ° C and T _i appeared at 143 ° C. It was confirmed that all of the isotropic liquefaction transitions (T _i ) appeared in the DSC graphs of the four final compounds, and that they were all liquid crystal compounds.

3. Optical organization of circularly polarized light-emitting liquid crystalline compounds

Based on the change in thermal transition behavior confirmed through DSC, the change in optical structure of each compound at a specific temperature according to the change in temperature was observed with a polarizing microscope. The measured heating rate and cooling rate were measured at 5°C/min as in the DSC measurement.

Figure 13 shows a POM image (X100) of Compound Ia, (a) to (c) show changes upon heating at 92 ° C, 101 ° C, and 108 ° C, respectively, (d) shows secondary cooling at 68 ° C, (e) shows the change during secondary cooling at 72 ° C, and (f) during secondary heating at 223 ° C.

In (a), melting began at 92 °C after T _kk and a liquid crystal phase was formed at 101 °C after T _m passed. The formed liquid crystal phase showed oily streaks, a typical cholesteric liquid crystal phase. In (d) and (e), a cholesteric liquid crystal fingerprint texture was observed at around 68℃ during cooling. (f) It was confirmed that the liquid crystal phase changed to an isotropic liquid state from 223 ° C.

Figure 14 shows the POM image of Compound Ib, (a) when heated to 82 ℃, (b) and (c) the change when secondary heating to 120 ℃, 128 ℃, respectively, (d) and (e ) shows the change upon cooling to 76 ° C and 54 ° C, respectively, and (f) shows the change upon secondary heating to 193 ° C.

In (b), a cholesteric liquid crystal phase with oily streaks was formed at 120 °C after T _m , and then (f) the liquid crystal phase disappeared at 193 °C, resulting in an isotropic liquid state. Upon cooling, (d) crystallization behavior was observed around 76°C.

Figure 15 shows the POM image (X100) of compound IIa, (a) to (d) change upon heating at 41 ℃, 76 ℃, 95 ℃, 119 ℃, respectively, (e), (f) is 95 ℃, shows the change upon cooling to 30 ℃. When heated, (b) showed oily streaks of cholesteric liquid crystal at around 76°C. In (d), it can be observed that the liquid crystal phase decreases and the isotropic liquid phase increases around 119 ° C.

Figure 16 shows the POM image of compound Ⅱb, (a) to (c) change when heated to 106 ℃, 108 ℃, 109 ℃, respectively, (d) when cooled to 40 ℃, (e) 106 Upon secondary heating to °C, (f) shows the change upon secondary heating to 142 °C.

Upon heating, (a) solid crystals began to melt at around 106 °C, (b) oily streaks of a cholesteric liquid crystal phase appeared at 108 °C, and (f) an isotropic liquid phase appeared as the liquid crystal phase decreased at 141 °C. After passing T _i during cooling, a cholesteric liquid crystal phase was formed and (d) crystallization behavior was observed at 76 °C. All four compounds showed a cholesteric liquid crystal phase, which is because the alkyl chain introduced into the light-emitting liquid crystal compound contains a chiral center.

4. Light Absorption and Emission Characteristics of Circularly Polarized Light-emitting Liquid Crystal Compounds

The absorption and emission characteristics of the four synthesized compounds were measured respectively in a chloroform solution. Absorption characteristics were measured through UV-vis and the absorption spectrum is shown in FIG. 17(A). Table 3 summarizes the calculated values of the optical band gap calculated through the wavelength and the onset wavelength in the absorption band.

The maximum absorption peaks were 341.5 nm for Compound Ia, 343 nm for Compound Ib, 342 nm for Compound IIa, and 342.5 nm for Compound IIb, all of which exhibited absorption peaks around 340 nm and were measured in a similar manner.

There was no difference in absorbance according to the fluorene 9 carbon substitution position and the alkyl chains at both ends. The emission characteristics were measured by PL spectroscopy, and the emission spectrum is shown in FIG. 17(B), and the maximum emission peak is shown in Table 3.

The maximum emission peaks are 391 and 413 nm for Compound Ia, 393 and 413 nm for Compound Ib, 389 and 412 nm for Compound IIa, and 391 and 414 nm for Compound IIb. was

In the luminescent properties, the fluorene 9 carbon substitution position and the alkyl chains at both ends did not have a significant effect on the luminescence wavelength, and only the luminescence intensity by concentration showed a difference.

5. Energy Levels of Circularly Polarized Light Emitting Liquid Crystalline Compounds

In organic electronic materials, HOMO and LUMO energy levels are one of the important characteristics, and a band gap value, which is a difference between HOMO and LUMO energy levels, can be known. The bandgap is a factor that determines the color of OLED, and is related to the emission wavelength, energy transfer, and luminous efficiency. In order to measure the energy levels of HOMO and LUMO of the synthesized compound, they were measured by cyclic voltammetry, and the results are shown in Table 4.

18, (A) is compound Ia, (B) is compound Ib, (C) is compound IIa, and (D) is a CV diagram of compound IIb.

The experiment was measured with a 0.1 M tetrabutylammonium hexafluorophosphate electrolyte solution in THF as a solvent, and Ag/AgCl was used as a reference electrode. Oxidation and reduction potentials measured by cyclic voltammetry can be obtained by converting them into HOMO and LUMO energy levels as an energy standard (0 eV) in vacuum. For this purpose, the HOMO energy level value of -4.8 eV in vacuum of ferrocene was used and calculated through the formula below. The value of the oxidation potential onset of ferrocene measured using the same solvent and supporting electrolyte was measured to be 0.55 V.

Compound Ia, b showed a similar HOMO level value of about -5.8, Compound IIa, b showed a HOMO level value of about -5.9, and the LUMO level value was -2.61, -3.41, -3.6, - respectively It turned out to be 2.35. As a result of comparing the band gap calculated through the HOMO and LUMO values with the band gap value measured by UV-vis, it was calculated as a lower value than the optical band gap calculated from the UV-vis measurement value.

6. Optical activity and specific rotation of circularly polarized light-emitting liquid crystalline compounds

Optical rotation measurement was used to evaluate the properties of the optically active material. The property of rotating the plane of polarization when the vibration of light occurs in one plane is passed through the specimen is called optical rotation, which is a characteristic of chiral compounds. Optical rotation is the angle at which a material rotates the plane of polarized light and is measured using a polarimeter. The experiment used a 1 cm cell with chloroform as a solvent, and was conducted at 22°C and 589 nm. Specific rotation, which is a measure of the rotational ability of the polarization plane of the optically active material through the measured optical activity, was calculated through Equation 2 below and shown in Table 5.

As a result of the measurement, Compound Ia had an optical activity value of 0.0093 and a specific rotation value of +9.38. The optical activity value of Compound Ib was measured as 0.0084 and the value of specific rotation was calculated as +9.10. The optical activity value of Compound IIa was measured as 0.0018 and the value of specific rotation was calculated as +3.57. In the case of Compound IIb, the optical activity value was measured as 0.0047 and the specific rotation value was calculated as +8.83. As a result, it can be confirmed that all of them rotate the polarization plane to the right.

In the present invention, by setting the alkyl group of the racemic mixture and the alkyl group having a chiral center as variables, biphenyl having flexible chains at both ends centered on fluorene was introduced to synthesize a circularly polarized light emitting liquid crystalline compound and characterize it. A total of four compounds were synthesized, and the synthesis of the products of each reaction step was confirmed through ¹ H-NMR. In the case of the final product, ¹ H-NMR, FT-IR, and elemental analysis were performed. As a result of the measurement, when the resonance peak of ¹ H-NMR and the absorption peak of FT-IR were compared with the expected values, it was found that the synthesis was made. It was confirmed that the titration error was close.

The thermal properties of the compounds were investigated through DSC measurements. The melting points (T _m ) of Compounds Ia and Ib were approximately 92.5°C and 120°C, and the isotropic liquefaction transition temperatures (T _i ) were approximately 226°C and 193°C. In the case of Compound IIa, a viscous non-solid compound, T _i was measured at 136.5 ° C and T _m was shown at a low temperature of -32.9 ° C. Compound IIb had T _m at 105.9 °C and T _i at 143 °C.

As all four compounds exhibited isotropic liquefaction transition temperatures, it was confirmed that they were liquid crystalline materials. Based on the DSC measurement results, the liquid crystal phase change according to temperature was measured using a polarizing microscope. All synthesized final products showed a cholesteric liquid crystal phase with oily streaks, and a fingerprint structure was observed in Compound Ia.

The absorption and emission characteristics of the compounds were investigated by UV-vis and PL spectroscopy in a chloroform solution. All four compounds showed similar measurement results, and it was confirmed that there was no effect by the alkyl chain. The maximum absorption wavelength appeared around 340 nm, and the maximum emission peaks were measured around 390 and 410 nm. The optical band gap due to the UV-vis absorption wavelength was calculated to be 3.62 and 3.63 eV.

The HOMO and LUMO energy levels of the compounds were measured by cyclic voltammetry, and the HOMO levels showed similar values from -5.80 to -5.94 eV, but the LUMO levels showed deviations of -2.62, -3.41, -3.6, and -1.49. occurred. Therefore, the values of the energy band gaps calculated by the CV method were calculated to be 2.58, 2.39, 2.32, and 3.59 eV, which were lower than the values of the optical band gaps calculated by the UV-vis spectroscopy method.

The optical activity of the compound was measured with a polarimeter, and the specific rotation was obtained by calculating the resulting value. All of the specific optical rotations are + values, and have the property of rotating the polarization plane to the right. Contrary to the expectation that Compound Ib and IIb with chiral groups will show high values, Compound Ia has the highest value and Compound IIa has the lowest value. It was calculated.

As described above, the present invention has been described with reference to the accompanying drawings, but within the scope that those skilled in the art do not deviate from the technical spirit and scope described in the claims of the present invention. In the present invention can be carried out by various modifications or variations. Accordingly, the scope of the present invention should be construed by the claims which are written to include examples of these many variations.

Claims (5)

A compound for circularly polarized light emitting liquid crystals represented by Formula 1 below.
[Formula 1]

In the above formula, R ₁ , R ₂ and R ₄ are each independently hydrogen or an alkyl group having 1 to 20 carbon atoms or an alkoxy group, n is an integer of 1 to 5, and R ₃ is biphenyl, naphthalene, bisphenol A or any of these any of the combinations.
According to claim 1,
Wherein R ₃ is biphenyl, a compound for circularly polarized light emitting liquid crystals, characterized in that represented by the following formula (2).
[Formula 2]

In the method for producing a compound for a circularly polarized light emitting liquid crystal represented by Formula 1 below,
[Formula 1]

(In the above formula, R ₁ , R ₂ and R ₄ are each independently hydrogen or an alkyl group having 1 to 20 carbon atoms or an alkoxy group, wherein n is an integer of 1 to 5, and R ₃ is biphenyl, naphthalene, bisphenol A or these Any one of the combinations of.)
Step 1 of preparing a fluorene derivative compound by introducing R ₁ and R ₂ at the 9th carbon substitution position of fluorene; and
Step 2 of preparing an R ₃ derivative compound by introducing R ₄ at the end of R ₃ ; and
a third step of introducing boron into the R ₃ derivative compound to prepare a boron-introduced R ₃ derivative compound;
4 steps of polymerizing the boron-introduced R ₃ derivative compound and the fluorene derivative compound; characterized in that it comprises
A method for preparing a compound for circularly polarized light emitting liquid crystals.
According to claim 3,
The fourth step is
Characterized in that polymerization is performed through a suzuki-Miyaura coupling reaction using a palladium (Pd) supported catalyst
A method for preparing a compound for circularly polarized light emitting liquid crystals.
An organic light emitting diode comprising the compound for circularly polarized light emitting liquid crystals according to claim 1 or 2.

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