Int. J. Mol. Sci. 2013, 14(12), 23257-23273; doi:10.3390/ijms141223257

Article
Synthesis of 1,4-Bis(phenylethynyl)benzenes and Their Application as Blue Phase Liquid Crystal Composition
Ning Li 2,3, Zhengqiang Li 2,3, Xing Zhang 2,3 and Ruimao Hua 1,2,3,*
1
Department of Chemistry, Tsinghua University, Beijing 100084, China
2
Beijing R&D Center, Shijiazhuang Chengzhi Yonghua Display Materials Co. Ltd., Beijing 100083, China; E-Mails: nnl3875@163.com (N.L.); zhengqiang9527@gmail.com (Z.L.); zx@slichem.com (X.Z.)
3
Hebei Engineering & Technology Center for FPD Materials, Shijiazhuang 050091, China
*
Author to whom correspondence should be addressed; E-Mail: ruimao@mail.tsinghua.edu.cn; Tel.: +86-10-6279-2596; Fax: +86-10-6277-1149.
Received: 14 September 2013; in revised form: 16 October 2013 / Accepted: 11 November 2013 /
Published: 25 November 2013

Abstract

: A number of 1,4-bis(phenylethynyl)benzene derivatives (BPEBs) and their analogues with different numbers of side-substitute fluorine atoms on benzene rings, and alkyl chains, ethoxyl groups, fluorine atoms and trifluoromethyl groups as the end groups have been synthesized. The effects of the different substituents on their properties such as thermal behavior of melting point and clearing point, the temperature of nematic phase, optical anisotropy and dielectric anisotropy have been well investigated, and it has been found that some BPEBs have a wide range of the nematic phase temperature with high optical anisotropy (Δn) and acceptable dielectric anisotropy (Δɛ), which have been applied as the crucial compositions to constitute a liquid crystal mixture having the properties of Δɛ = 29.0 and Δn = 0.283 at 25 °C. With the addition of the chiral dopant to the obtained liquid crystal mixture, blue phase liquid crystal with a blue phase temperature range of 8 °C has been achieved.
Keywords:
1,4-bis(phenylethynyl)benzene derivatives; blue phase; liquid crystal

1. Introduction

Liquid crystals (LCs) have had a multitude of applications in the past few decades [1,2]. One of the important and unique applications is their use as the key fundamental materials to develop LC displays [3], which have actually changed people’s lifestyle due to the use of mobiles, notebook computers, flat panel desktop monitors, and LCD televisions, etc. The development of excellent LC displays, which have the advantages of fast response, high contrast ratio, and low driving voltage, depends greatly on the development of new types and properties of LCs. The demand for LCDs with a fast response is one of the crucial factors to improve the quality of the displays, and blue phase liquid crystal (BPLC) is commonly considered to be one of the strongest candidates [47].

On the other hand, the molecular and electronic structures of 1,4-bis(phenylethynyl)-benzene derivatives (BPEBs), as well as their applications have attracted much attention recently [812]. In particular, BPEBs have been applied as the important components in LCs with the characters of high melting point (mp), clearing point (cp), and large optical anisotropy values (Δn) [1322]. It is important and interesting to investigate the substituent effect on the properties of BPEBs. Therefore, in this paper, we describe the synthesis of a number of BPEBs with different alkyl chains, the numbers of fluorine atoms and other substituents in benzene rings as shown in Scheme 1, and the study on the substituent effects on their properties, as well as their application as blue phase liquid crystal composition.

2. Results and Discussion

2.1. Synthesis of BPEBs and Analogues (125)

The synthetic routes of 125 are outlined in Scheme 2, including the key steps of the formation of terminal and internal alkynes via Sonogashira cross-coupling reactions of aryl iodides/bromides catalyzed by palladium(0) complexes in good to high yields, and a typical synthetic procedure for the formation of 12 is described in the Experimental Section (vide infra).

2.2. Thermal Properties

The thermal properties of the melting point (mp) and clearing point (cp) are critical in the practical utilization of the synthesized BPEBs as the composition of LCs, thus the mp and cp were determined by DSC (Differential Scanning Calorimetry), and their thermal data as well as enthalpic data (ΔH) are concluded in Table 1. It was found that mp and cp greatly depended upon the molecular and electronic structures of BPEBs. BPEBs 14 clearly show the effect of alkyl chain length on mp and cp, and when n-C3H7 and C2H5 groups are used as the end groups, BPEBs 1 and 2 give the similar mp and cp (1vs.2). However, when the longer alkyl chains of C4 and C5 were employed, BPEBs 3 and 4 showed similar thermal properties, but both mp and cp decreased greatly (1 & 2vs.3 & 4) [23]. It can be concluded that BPEBs 3 and 4 bearing the longer alkyl chains have a wider range of nematic phase temperature than those of BPEBs 1 and 2, possibly due to the longer alkyl chains being more flexible than short alkyl chains. Both 3 and 4 show a nematic phase temperature range of about 140 °C, and the wide nematic phase temperature are very important to make a practical LC mixture.

By comparison of 2 and 5, it was found that decreasing the number of fluorine atoms in the end benzene ring leads to the increase of both mp and cp in a range of about 10 °C, and a similar trend of mp was also found between 4,4′-bis(phenylethynyl)biphenyls 6 and 7, which are the analogues of BPEBs 2 or 5.

The thermal properties of other BPEBs are also compared to each other, as shown in Figure 1, and two notable features of the relationship between mps and their chemical structure could be concluded as follows: (1) The introduction of the fluorine atom on the middle benzene ring shows a great effect on the change of mp. In general, one or two fluorine atom-substituted benzene result in the increase of mp, and the introduction of the second fluorine atom leads to much more significant increase of mp relative to the first fluorine atom introduction (e.g., 81012; 91113). (2) When the end group of OCF3 is replaced by a fluorine atom, the mps decreased (e.g., 10vs.11; 12vs.13; 14vs.15), and only one exception (8vs.9) was observed.

2.3. Nematic Phase

Among the synthesis of BPEBs and analogues, only BPEBs 15, 8, 2021 (Figure 2, on heating run) and 9, 1415 (on cooling run) show nematic phases under polarizing microscope with the structural character without side-substituted fluorine atoms bonded to the middle benzene ring, and the analogues of BPEBs 6 and 7 have no nematic phase either. It was found that the nematic phase temperature is quite different depending on the end groups and the numbers of fluorine atoms. As shown in Figure 3 and Table 1, BPEBs 15 with OC2H5 as the end group possess wide nematic phase temperatures from 121.6 to 147.0 °C, and have apparently disclosed that longer alkyl chains generally result in a wider temperature of nematic phase. BPEBs 3 and 4 bearing the longer alkyl chain of n-C4H9 or n-C5H11 give the maximum nematic phase temperatures, while BPEBs 8, 20 and 21 with OCF3 or F as the end groups show the relatively narrow nematic phase temperature range.

2.4. Optical Anisotropy (Δn)

The optical anisotropy or birefringence (Δn) of the BPEBs showing nematic phase in host LC was determined, and the obtained results were concluded in Table 2. As expected, a large π-conjugated structure leads to relatively high Δn value, and therefore BPEBs 15 have higher Δn values than 89, 1415, and 2021. It is reasonable to understand that much more side-substituted fluorine atoms in different benzene rings will decrease the integrity of π-conjugated structures to result in a decrease of optical anisotropy.

2.5. Dielectric Anisotropy (Δɛ)

Table 3 shows the values of dielectric anisotropy (Δɛ) of the BPEBs having nematic phase in host LC. It was found that with the number increase of side-substituted fluorine atoms, BPEBs 89, 1415, and 2021 have higher dielectric anisotropy values than BPEBs 15. In addition, comparison of BPEBs with the end groups of OCF3 (8, 14, 20) and F (9, 15, 21), BPEBs 8, 14 and 20 have relatively higher dielectric anisotropy values, possibly due to the stronger electronegativity of the OCF3 group relative to the fluorine atom.

2.6. Applications of BPEBs as Blue Phase Liquid Crystal Composition

Because the synthesized some of BPEBs have high Δn and acceptable Δɛ as described above, we are interested in investigation of the application of them as the compositions in blue phase liquid crystals (BPLC) to possibly increase the Kerr constant, which is key parameter for practical BPLC. After detailed screening the composition and contents, we got a LC mixture containing BPEBs 1, 34, 89, 14, 15, 21 (5 wt % each) and other liquid crystal mixture (cp: 83.0 °C; Δn = 0.230, and Δɛ = 29.6, at 25 °C), which shows the properties of Δn = 0.283, and Δɛ = 29.0 at 25 °C, which is expected to have high potential applications as BPLC [24]. After adding chiral dopants (R811: 10 wt % and BDH1281: 7 wt %), we obtained a BPLC with a blue phase temperature range of 8 K (from 41 to 33 °C, on the second cooling run). Figure 4 shows a typical BP texture of the obtained BPLC at 36 °C.

3. Experimental Section

3.1. General Method

All organic starting materials and catalysts are analytically pure and used without further purification. Nuclear magnetic resonance (NMR) spectra were recorded on a JEOL ECA-300 spectrometer (Tokyo, Japan) using CDCl3 as solvent at 298 K. 1H-NMR (300 MHz) chemical shifts (δ) were referenced to internal standard TMS (for 1H, δ = 0.00 ppm). 13C-NMR (75 MHz) chemical shifts were referenced to internal solvent CDCl3 (for 13C, δ = 77.16 ppm). Mass spectra (MS) were obtained on a Shimadzu GCMS-QP2010S (Kyoto, Japan). Element analyses were obtained with a Flash EA 1112 Element Analyzer (Thermo Fisher Scientific, Waltham, MA, USA). Polarizing microscope LWT300LPT (CEWEI photoelectric technology Co. Ltd., Shanghai, China) equipped with a Weitu WT-3000 hot stage and a TCA 5.0 MP camera was used to observe and record the optical textures of liquid crystal samples. The calorimetric studies were performed on a TA Instruments DSC 2010 (TA Instruments, New Castle, DE, USA) with a heating temperature rate of 10 °C/min. A NAR-4T Abbe refractometer (ATAGO Co. Ltd., Tokyo, Japan) was used to measure optical anisotropy (Δn), and a 3522-50 LCR Hitester (HIOKI E.E. Co., Ueda, Japan) for dielectric anisotropy (Δɛ). All the samples for measuring the Δn and Δɛ were composed of BPEB and nematic host LC at a ratio of 5–10/95–90 (wt %/wt %). The nematic host LC (SLC960524) was prepared by our laboratory, which has the values of Δn = 0.1202 (589 nm) and Δɛ = 3.121 (1000 Hz) at 25 °C.

3.2. A Typical Experimental Procedure for Synthesis of BPEB 12 and the Characterization Data of All the BPEBs

As shown in Scheme 2, BPEBs and analogues (125) were synthesized by the similar synthetic route, and their structures were characterized by 1H-NMR, 13C-NMR (for BPEBs 6 and 7, the 13C-NMR could not be obtained due to their very low solubility in CDCl3, DMSO-d6 or DMF-d7), and elemental analyses. In this section, the synthetic procedure of BPEB 12 was only described in details, and the characterization data of all the other BPEBs are given.

Preparation of 2,6-difluoro-4-n-propylphenyl acetylene (12c) (See Scheme S1).

2-Methyl-3-butyn-2-ol (21.8 g, 0.3 mol) was added to a mixture of 2,6-difluoro-4-n-propyl-1- iodobenzene (56.4 g, 0.2 mol), tetrakis(triphenylphosphine) palladium(0) (1.0 g, 0.87 mmol), CuBr (0.5 g) and LiBr (2.0 g) in triethylamine (50 mL) with stirring at room temperature. After the mixture was heated at 60 °C for 5 h, it was then cooled to room temperature and the saturated NH4Cl aqueous solution (100 mL) and ethyl acetate (200 mL) were added. After separation of the organic phase, the aqueous phase was extracted by ethyl acetate (3 × 150 mL), and the combined organic extracts are dried by K2CO3 and concentrated on a rotary evaporator, the intermediate 12b was obtained by column chromatographic separation (40.5 g, 0.17 mol, 85.0%) for the next reaction.

Sodium hydroxide (20.0 g, 0.5 mol) was added to a solution of 12b (40.0 g) in toluene (150 mL), and then the obtained mixture was heated under reflux for 5 h. After removal of the insoluble excess of Sodium hydroxide by filtration and the solvent under reduced pressure, 12c was isolated by column chromatography as light yellow oil (17.2 g, 0.095 mol, 55.9%). Characterization data for 12c: 1H-NMR (300 MHz, CDCl3) δ 6.70 (d, 2H, 3JF–C–C–H = 8.4 Hz), 6.67 (s, 1H), 3.44 (s, 1H), 2.52 (t, 2H, J = 7.5 Hz), 1.61–1.54 (m, 2H), 0.89 (t, 3H, J = 7.5 Hz); 13C-NMR (75 MHz, CDCl3) δ 163.5 (dd, 1JC–F = 253.6 Hz, 5JC–F = 6.0 Hz), 147.1 (t, 3JC–F = 9.0 Hz), 111.1 (dd, 2JC–F = 17.1 Hz, 4JC–F = 6.0 Hz), 98.2 (t, 2JC–F = 19.8 Hz), 86.5, 70.9, 37.8, 23.7, 13.4; MS m/z (% rel. intensity) 180 (M+, 44), 151 (100); Anal. calcd for C11H10F2: C, 73.33; H, 5.56. Found: C, 73.62; H, 5.59.

Preparation of [2,6-difluoro-4-(2′,6′-difluoro-4′-n-propylphenyl)ethynyl]phenyl acetylene (12g) (See Scheme S2).

A mixture of 2-bromo-1,3-difluoro-5-iodobenzene (11.16 g, 0.035 mol), ethynyl trimethylsilane (3.8 g, 0.039 mol), tetrakis(triphenylphosphine) palladium(0) (0.5 g, 0.44 mmol) and CuI (1.0 g) in triethylamine (40.0 mL) was stirred in under argon at room temperature for 16 h. After work-up as described for 12b, 12e was obtained in 85.7% (10.0 g, 0.03 mol).

A mixture of 12e (5.6 g), 12c (3.0 g, 0.017 mol), tetrakis(triphenylphosphine)palladium(0) (0.2 g, 0.17 mmol) and CuI (0.4 g) in triethylamine (40.0 mL) was heated with strring at 60 °C for 5 h, After work-up as described for 12b, the intermediated 12f was obtained as colorless solid in 76.4% (4.8 g, 0.013 mol). And then stirring a mixture of 12f (4.8 g, 0.013 mol) and K2CO3 (0.1 g, 0.7 mmol) in methanol (150 mL) at room temperature for 5 h, after work up as described for the isolation of 12c, 12g was isolated as colorless solid in 84.6% (3.47 g, 0.011 mol). Characterization data for 12g: 1H-NMR (300 MHz, CDCl3) δ 7.11 (d, 2H, 3JF–C–C–H = 7.5 Hz), 6.77 (d, 2H, 3JF–C–C–H = 8.1 Hz), 3.59 (s, 1H), 2.59 (t, 2H, J = 7.5 Hz), 1.68–1.60 (m, 2H), 0.94 (t, 3H, J = 7.4 Hz); 13C-NMR (300 MHz, CDCl3) δ 163.3 (dd, 1JC–F = 255.0 Hz, 5JC–F = 6.6 Hz), 162.8 (dd, 1JC–F = 254.2 Hz, 5JC–F = 5.8 Hz), 147.6 (t, 3JC–F = 9.1 Hz), 125.1 (t, 3JC–F = 11.9 Hz), 114.5 (dd, 2JC–F = 18.2 Hz, 4JC–F = 6.8.Hz), 111.4 (dd, 2JC–F = 17.3 Hz, 4JC–F = 6.3.Hz), 102.1 (t, 2JC–F = 19.6 Hz), 98.4 (t, 2JC–F = 19.6 Hz), 88.8, 88.9, 80.7, 70.5, 38.0, 23.8, 13.6; MS m/z (% rel. intensity) 316 (M+, 56); 287 (100); Anal. calcd for C19H12F4: C, 72.15; H, 3.80. Found: C, 72.52; H, 3.98.

Preparation of 1-[(2′,6′-difluoro-4′-n-propylphenyl)ethynyl]-4-[(3″,5″-difluoro-4″-trifluoro-methoxy-phenyl) ethynyl]-3,5-difluorobenzene (BPEB 12) (See Scheme S3).

A solution of 4-bromo-2,6-difluoro(trifluoromethoxy)benzene (2.2 g, 8.04 mmol) in toluene (10.0 mL) was added into a solution of 12g (1.69 g, 5.36 mmol), tetrakis(triphenylphosphine)palladium(0) (0.1 g, 0.09 mmol), and CuI (0.2 g) in triethylamine (20.0 mL) under argon at 60 °C, and then the obtained mixture was stirred at 60 °C for 5 h. After work-up as described for 12c, the desired BPEB 12 was isolated as colorless solid in 79.1% (2.17 g, 4.24 mmol). Characterization data for BPEB 12: 1H-NMR (300 MHz, CDCl3) δ 7.24 (d, 2H, 3JF–C–C–H = 7.5), 7.15 (d, 2H, 3JF–C–C–H = 7.5 Hz), 6.78 (d, 2H, 3JF–C–C–H = 8.4 Hz), 2.60 (t, 2H, J = 7.5 Hz), 1.69–1.61 (m, 2H), 0.95 (t, 3H, J = 7.4 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.9 (dd, 1JC–F = 254.3 Hz, 5JC–F = 5.7 Hz), 162.6 (dd, 1JC–F = 254.8 Hz, 5JC–F = 6.0 Hz), 155.9 (dd, 1JC–F = 253.9 Hz, 5JC–F = 3.6 Hz ), 147.7 (t, 3JC–F = 9.0 Hz), 126.3 (t, 3JC–F = 15.6 Hz), 125.6 (t, 3JC–F = 12.1 Hz), 123.0 (t, 3JC–F = 10.6 Hz), 120.5 (q, 1JC–F = 260.3 Hz), 116.0 (dd, 2JC–F = 16.2 Hz, 4JC–F = 5.0 Hz), 114.6 (dd, 2JC–F = 18.2 Hz, 4JC–F = 7.0 Hz), 111.4 (dd, 2JC–F = 17.2 Hz, 4JC–F = 5.7 Hz), 102.0 (t, 2JC–F = 18.7 Hz), 98.5 (t, 2JC–F = 19.7 Hz), 96.8, 95.5, 81.1, 79.2, 38.0, 23.8, 13.6; Anal. calcd for C26H13F9O: C, 60.93; H, 2.54. Found: C, 61.33; H, 2.50.

Characterization data for BPEB 1: 1H-NMR (300 MHz, CDCl3) δ 7.56–7.45 (m, 6H), 6.87 (d, 2H, J = 8.8 Hz), 6.78 (d, 2H, J = 8.2 Hz), 4.04 (q, 2H, J = 7.0 Hz), 2.65 (q, 2H, J = 7.6 Hz), 1.42 (t, 3H, J = 7.0 Hz), 1.24 (t, 3H, J = 7.6 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.1 Hz, J = 6.0 Hz), 159.3, 147.9 (t, J = 8.9 Hz), 133.2, 131.7, 131.4, 124.1, 122.2, 115.0, 114.7, 110.7 (dd, J = 16.9 Hz, J = 6.3 Hz), 99.4 (t, J = 19.9 Hz), 98.1, 91.8, 87.9, 78.9, 63.6, 28.9, 14.9, 14.8; Anal. calcd for C26H20F2O: C, 80.83; H, 5.18. Found: C, 81.03; H, 4.90.

Characterization data for BPEB 2: 1H-NMR (300 MHz, CDCl3) δ 7.56–7.45 (m, 6H), 6.87 (d, 2H, J = 8.7 Hz), 6.76 (d, 2H, J = 8.0 Hz), 4.04 (q, 2H, J = 7.0 Hz), 2.58 (t, 2H, J = 7.4 Hz), 1.70–1.58 (m, 2H), 1.42 (t, 3H, J = 7.0 Hz), 0.95 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.0 Hz, J = 6.0 Hz), 159.3, 146.4 (t, J = 9.0 Hz), 133.2, 131.7, 131.4, 124.1, 122.2, 115.0, 114.7, 111.3 (dd, J = 16.6 Hz, J = 6.0 Hz), 99.4 (t, J = 20.1 Hz), 98.1, 91.8, 87.9, 78.3, 63.6, 38.0, 23.9, 14.8, 13.7; Anal. calcd for C27H22F2O: C, 81.00; H, 5.50. Found: C, 81.43; H, 5.74.

Characterization data for BPEB 3: 1H-NMR (300 MHz, CDCl3) δ 7.56–7.45 (m, 6H), 6.87 (d, 2H, J = 8.7 Hz), 6.76 (d, 2H, J = 8.1 Hz), 4.04 (q, 2H, J = 7.0 Hz), 2.60 (t, 2H, J = 7.5 Hz), 1.61–1.54 (m, 2H), 1.45–1.30 (m, 5H), 0.94 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.0 Hz, J = 6.1 Hz), 159.3, 146.7 (t, J = 9.0 Hz), 133.2, 131.7, 131.4, 124.1, 122.2, 115.0, 114.7, 111.2 (dd, J = 16.8 Hz, J = 6.0 Hz), 99.4 (t, J = 20.0 Hz), 98.1, 91.8, 87.9, 78.3, 63.6, 35.7, 32.8, 22.2, 14.8, 13.9; Anal. calcd for C28H24F2O: C, 81.16; H, 5.80. Found: C, 81.53; H, 5.84.

Characterization data for BPEB 4: 1H-NMR (300 MHz, CDCl3) δ 7.55–7.45 (m, 6H), 6.87 (d, 2H, J = 8.7 Hz), 6.76 (d, 2H, J = 8.1 Hz), 4.04 (q, 2H, J = 7.0 Hz), 2.60 (t, 2H, J = 7.5 Hz), 1.66–1.57 (m, 2H), 1.43 (t, 3H, J = 7.0 Hz), 1.36–1.25 (m, 4H), 0.91 (t, 3H, J = 6.9 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.2 Hz, J = 6.1 Hz), 159.3, 146.7 (t, J = 9.0 Hz), 133.2, 131.7, 131.4, 124.1, 122.2, 115.0, 114.6, 111.2 (dd, J = 17.0 Hz, J = 6.1 Hz), 99.4 (t, J = 19.5 Hz), 98.1, 91.8, 87.9, 78.3, 63.6, 35.9, 31.4, 30.4, 22.5, 14.8, 14.1; Anal. calcd for C29H26F2O: C, 81.31; H, 6.07. Found: C, 81.26; H, 6.34.

Characterization data for BPEB 5: 1H-NMR (300 MHz, CDCl3) δ 7.54–7.39 (m, 7H), 6.94 (d, 2H, J = 8.4 Hz), 6.87 (d, 2H, J = 8.3 Hz), 4.04 (q, 2H, J = 6.7 Hz), 2.60 (t, 3H, J = 7.3 Hz), 1.72–1.59 (m, 2H), 1.43 (t, 3H, J = 6.8 Hz), 0.96 (t, 3H, J = 7.2 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.7 (d, J = 251.6 Hz), 159.3, 146.1 (d, J = 7.2 Hz), 133.2, 133.1, 131.6, 131.4, 124.3, 123.8, 122.6, 115.5 (d, J = 20.3 Hz), 114.9 (d, J = 27.2 Hz), 114.7, 108.9 (d, J = 16.0 Hz), 93.6, 91.6, 88.0, 84.8, 63.6, 37.9, 24.1, 14.9, 13.8; Anal. calcd for C27H23FO: C, 84.82; H, 6.02. Found: C, 84.88; H, 6.13.

Characterization data for BPEB 6: 1H-NMR (300 MHz, CDCl3) δ 7.64–7.53 (m, 8H), 7.49–7.45 (m, 2H), 7.41 (d, 1H, J = 7.5 Hz), 6.96–6.92 (m, 2H), 6.88 (d, 2H, J = 8.7 Hz), 4.06 (q, 2H, J = 7.0 Hz), 2.61 (t, 2H, J = 7.3 Hz), 1.72–1.60 (m, 2H), 1.43 (t, 3H, J = 7.0 Hz), 0.95 (t, 3H, J = 7.3 Hz); Anal. calcd for C33H27FO: C, 86.46; H, 5.90. Found: C, 86.98; H, 5.93.

Characterization data for BPEB 7: 1H-NMR (300 MHz, CDCl3) δ 7.66–7.55 (m, 8H), 7.48 (d, 2H, J = 8.8 Hz), 6.88 (d, 2H, J = 8.8 Hz), 6.77 (d, 2H, J = 8.1 Hz), 4.06 (q, 2H, J = 7.0 Hz), 2.59 (t, 2H, J = 7.4 Hz), 1.71–1.59 (m, 2H), 1.43 (t, 3H, J = 7.0 Hz), 0.95 (t, 3H, J = 7.4 Hz); Anal. calcd for C33H26F2O: C, 83.19; H, 5.46. Found: C, 83.26; H, 5.72.

Characterization data for BPEB 8: 1H-NMR (300 MHz, CDCl3) δ 7.58–7.48 (m, 4H), 7.17 (d, 2H, J = 7.8 Hz), 6.77 (d, 2H, J = 8.1 Hz), 2.59 (t, 2H, J = 7.4 Hz),1.71–1.59 (m, 2H), 0.95 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.3 Hz, J = 5.8 Hz), 155.8 (dd, J = 255.8 Hz, J = 3.6 Hz), 146.8 (t, J =8.9 Hz), 131.8, 131.7, 125.6 (t, J = 17.2 Hz), 123.8 (t, J = 9.1 Hz), 122.1, 120.6 (q, J = 259.6 Hz), 115.8 (d, J = 17.5 Hz, J = 6.2 Hz), 111.3 (dd, J = 16.9 Hz, J = 6.1 Hz), 99.2 (t, J = 19.9 Hz), 97.6, 92.0, 87.9, 79.1, 38.0, 23.8, 13.6; Anal. calcd for C26H15F7O: C, 65.55; H, 3.15. Found: C, 64.98; H, 3.13.

Characterization data for BPEB 9: 1H-NMR (300 MHz, CDCl3) δ 7.57–7.47 (m, 4H), 7.16–7.11 (m, 2H), 6.76 (d, 2H, J = 8.1 Hz), 2.59 (t, 2H, J = 7.4 Hz), 1.71–1.58 (m, 2H), 0.95 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.1 Hz, J = 5.8 Hz), 151.1 (ddd, J = 251.1 Hz, J = 10.4 Hz, J = 4.9 Hz), 146.7 (t, J = 9.0 Hz), 140.5 (dt, J = 255.7 Hz, J = 15.3 Hz), 131.8, 131.7, 123.5, 122.4, 119.0 9 (td), 116.0 (ddd, J = 15.2 Hz, J = 7.3 Hz), 111.3 (dd, J =17.0 Hz, J = 5.9 Hz), 99.2 (t, J = 20.0 Hz), 97.7, 90.6, 88.2, 78.9, 38.0, 23.9, 13.6; Anal. calcd for C25H15F5: C, 73.17; H, 3.66. Found: C, 73.02; H, 3.51.

Characterization data for BPEB 10: 1H-NMR (300 MHz, CDCl3) δ 7.47 (t, 1H, J = 7.6 Hz), 7.35–7.30 (m, 2H), 7.20 (d, 2H, J = 7.8 Hz), 6.77 (d, 2H, J = 8.2 Hz), 2.59 (t, 2H, J = 7.4 Hz), 1.71–1.59 (m, 2H), 0.95 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.9 Hz, J = 6.0 Hz), 162.3 (d, J = 253.5 Hz), 155.8 (dd, J = 255.4 Hz, J = 3.8 Hz), 147.2 (t, J = 9.1 Hz), 133.3, 127.6 (d, J = 3.2 Hz), 126.1 (t, J = 15.8 Hz), 125.6 (d, J = 9.3 Hz), 123.3 (t, J = 11.0 Hz), 120.5 (q, J = 261.0 Hz), 118.7 (d, J = 22.7 Hz), 115.9 (dd, J = 15.5 Hz, J = 4.3 Hz), 111.4 (dd, J = 17.5 Hz, J = 5.6 Hz), 111.1, 98.8 (t, J = 19.6 Hz), 96.4, 92.6, 85.5, 80.0, 40.0, 23.8, 13.6; Anal. calcd for C26H14F8O: C, 63.16; H, 2.83. Found: C, 63.03; H, 2.56.

Characterization data for BPEB 11: 1H-NMR (300 MHz, CDCl3) δ 7.45 (t, 1H, J = 7.4 Hz), 7.36–7.26 (m, 2H), 7.21–7.14 (m, 2H), 6.77 (d, 2H, J = 8.2 Hz), 2.59 (t, 2H, J = 7.3 Hz), 1.71–1.58 (m, 2H), 0.95 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.6 Hz, J = 5.6 Hz), 162.3 (d, J = 253.2 Hz), 151.1 (ddd, J = 251.0 Hz, J = 10.5 Hz, J = 4.8 Hz), 147.2 (t, J = 8.9 Hz), 140.6 (dt, J = 250.7 Hz, J = 10.9 Hz), 133.3, 127.6 (d, J = 3.3 Hz), 125.3 (d, J = 9.3 Hz), 118.6 (dd, J = 12.4 Hz, J = 6.9 Hz), 116.1 (dd, J = 15.5 Hz, J = 7.4 Hz), 111.4, 111.4 (dd, J = 17.8 Hz, J = 6.3 Hz), 98.9 (t, J = 19.4 Hz), 96.5 (d, J = 3.2 Hz), 92.9, 84.1, 79.9, 38.0, 23.8, 13.6; Anal. calcd for C25H14F6: C, 70.09; H, 3.27. Found: C, 70.33; H, 3.46.

Characterization data for BPEB 13: 1H-NMR (300 MHz, CDCl3) δ 7.22–7.12 (m, 4H), 6.78 (d, 2H, J = 8.2 Hz), 2.60 (t, 2H, J = 7.4 Hz), 1.71–1.59 (m, 2H), 0.95 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 254.0 Hz, J = 5.4 Hz), 162.6 (dd, J = 255.1 Hz, J = 6.4 Hz), 151.2 (ddd, J = 252.3 Hz, J = 10.7 Hz, J = 4.4 Hz), 147.6 (t, J = 6.4 Hz), 140.9 (dt, J = 256.0 Hz, J = 15.4 Hz), 125.3 (t, J = 12.2 Hz), 118.4, 116.2 (dd, J = 15.5 Hz, J = 7.6 Hz), 114.5 (dd, J =17.7 Hz, J = 7.1 Hz), 111.4 (dd, J = 16.4 Hz, J = 5.1 Hz), 102.3 (t, J = 21.5 Hz), 98.6 (t, J = 20.2 Hz), 97.3, 95.6, 80.9, 77.8, 38.0, 23.7, 13.5; Anal. calcd for C25H13F7: C, 67.26; H, 2.91. Found: C, 69.52; H, 2.66.

Characterization data for BPEB 14: 1H-NMR (300 MHz, CDCl3) δ 7.57–7.48 (m, 4H), 7.17 (d, 2H, J = 7.9 Hz), 6.77 (d, 2H, J = 8.1 Hz), 2.61 (t, 2H, J = 7.5 Hz), 1.65–1.55 (m, 2H), 1.42–1.30 (m, 2H), 0.94 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.4 Hz, J = 6.2 Hz), 155.8 (dd, J = 255.3 Hz, J = 3.7 Hz), 147.0 (t, J = 9.1 Hz), 131.8, 131.7, 125.8 (t, J = 16.3 Hz), 123.8 (t, J = 8.8 Hz), 122.1, 120.4 (q, J = 258.9 Hz), 115.8 (dd, J = 17.5 Hz, J = 6.2 Hz), 111.3 (dd, J = 16.7 Hz, J = 5.7 Hz), 99.2 (t, J = 20.1 Hz), 97.6, 92.0, 87.9, 79.0, 35.7, 32.8, 22.3, 13.9; Anal. calcd for C27H17F7O: C, 66.12; H, 3.47. Found: C, 66.01; H, 3.36.

Characterization data for BPEB 15: 1H-NMR (300 MHz, CDCl3) δ 7.56–7.46 (m, 4H), 7.13 (t, 2H, J = 6.9 Hz), 6.76 (d, 2H, J = 8.1 Hz), 2.60 (t, 2H, J = 7.4 Hz), 1.64–1.54 (m, 2H), 1.42–1.30 (m, 2H), 0.94 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.4 Hz, J = 6.0 Hz), 151.1 (ddd, J = 250.6 Hz, J = 10.1 Hz, J = 4.2 Hz), 146.9 (t, J = 9.0 Hz), 140.4 (dt, J = 254.7 Hz, J = 14.9 Hz), 131.8, 131.7, 123.5, 122.4, 119.1 (td), 116.0 (ddd, J = 15.4 Hz, J = 7.3 Hz, J = 4.8 Hz), 111.2 (dd, J =17.1 Hz, J = 5.9 Hz), 99.2 (t, J = 19.8 Hz), 97.7, 90.6, 88.2, 78.9, 35.7, 32.8, 22.3, 13.9; Anal. calcd for C26H17F5: C, 73.58; H, 4.01. Found: C, 73.51; H, 3.96.

Characterization data for BPEB 16: 1H-NMR (300 MHz, CDCl3) δ 7.47 (t, 1H, J = 7.5 Hz), 7.39–7.29 (m, 2H), 7.20 (d, 2H, J = 7.7 Hz), 6.77 (d, 2H, J = 8.2 Hz), 2.61 (t, 2H, J = 7.6 Hz), 1.65–1.55 (m, 2H), 1.42–1.30 (m, 2H), 0.94 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.8 Hz, J = 5.8 Hz), 162.3 (d, J = 253.7 Hz), 155.8 (dd, J = 255.5 Hz, J = 3.7 Hz), 147.5 (t, J = 8.9 Hz), 133.3, 127.6 (d, J = 3.4 Hz), 126.1 (t, J = 15.8 Hz), 125.6 (d, J = 9.4 Hz), 123.3 (t, J = 11.2 Hz), 120.5 (q, J = 261.0 Hz), 118.7 (d, J = 22.8 Hz), 115.9 (dd, J = 16.2 Hz, J = 6.4 Hz), 111.3 (dd, J = 16.1 Hz, J = 5.8 Hz), 111.1, 98.8 (t, J = 19.5 Hz), 96.4, 92.5, 85.5, 80.0, 35.7, 32.8, 22.3, 13.9; Anal. calcd for C27H16F8O: C, 63.78; H, 3.15. Found: C, 63.61; H, 3.26.

Characterization data for BPEB 17: 1H-NMR (300 MHz, CDCl3) δ 7.44 (t, 1H, J = 7.4 Hz), 7.33–7.27 (m, 2H), 7.16 (t, 2H, J = 6.6 Hz), 6.76 (d, 2H, J = 8.2 Hz), 2.60 (t, 2H, J = 7.5 Hz), 1.64–1.54 (m, 2H), 1.42–1.29 (m, 2H), 0.94 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.7 Hz, J = 5.8 Hz), 162.3 (d, J = 253.4 Hz), 151.1 (ddd, J = 250.9 Hz, J = 10.4 Hz, J = 4.3 Hz), 147.4 (t, J = 9.0 Hz), 140.7 (dt, J = 255.1 Hz, J = 14.7 Hz), 133.3, 127.6 (d, J = 3.3 Hz), 125.3 (d, J = 9.5 Hz), 118.6 (dd, J = 14.2 Hz, J = 9.1 Hz), 116.1 (dd, J = 15.4 Hz, J = 7.3 Hz), 111.5, 111.3 (dd, J = 17.0 Hz, J = 5.9 Hz), 98.8 (t, J = 19.6 Hz), 96.5 (d, J = 3.1 Hz), 92.9, 84.1, 79.9, 35.7, 32.8, 22.3, 13.9; Anal. calcd for C26H16F6: C, 70.59; H, 3.62. Found: C, 70.68; H, 3.36.

Characterization data for BPEB 18: 1H-NMR (300 MHz, CDCl3) δ 7.23 (d, 2H, J = 7.7 Hz), 7.14 (d, 2H, J = 7.3 Hz), 6.78 (d, 2H, J = 8.2 Hz), 2.62 (t, 2H, J = 7.6 Hz), 1.65–1.55 (m, 2H), 1.41–1.30 (m, 2H), 0.94 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.9 (dd, J = 254.1 Hz, J = 5.8 Hz), 162.7 (dd, J = 255.4 Hz, J = 6.2 Hz), 155.9 (dd, J = 255.8 Hz, J = 3.6 Hz), 147.9 (t, J = 9.0 Hz), 126.3 (t, J = 15.8 Hz), 125.6 (t, J = 12.0 Hz), 123.0 (t, J = 10.1 Hz), 120.5 (q, J = 260.8 Hz), 116.0 (dd, J = 17.0 Hz, J = 6.6 Hz), 114.6 (dd, J = 17.8 Hz, J = 7.9 Hz), 111.3 (dd, J = 17.0 Hz, J = 5.6 Hz), 102.0 (t, J = 18.5 Hz), 98.2 (t, J = 19.9 Hz), 96.9, 95.5, 81.1, 79.2, 35.7, 32.7, 22.2, 13.8; Anal. calcd for C27H15F9O: C, 61.60; H, 2.85. Found: C, 60.99; H, 2.64.

Characterization data for BPEB 19: 1H-NMR (300 MHz, CDCl3) δ 7.20 (t, 2H, J = 6.7 Hz), 7.12 (d, 2H, J = 7.1 Hz), 6.77 (d, 2H, J = 8.2 Hz), 2.62 (t, 2H, J = 7.5 Hz), 1.65–1.55 (m, 2H), 1.42–1.30 (m, 2H), 0.94 (t, 3H, J = 7.3 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 254.1 Hz, J = 5.7 Hz), 162.6 (dd, J = 254.7 Hz, J = 6.2 Hz), 151.1 (ddd, J = 251.3 Hz, J = 10.4 Hz, J = 4.4 Hz), 147.9 (t, J = 9.2 Hz), 140.9 (dt, J = 256.0 Hz, J = 15.6 Hz), 125.2 (t, J = 12.0 Hz), 118.4 (td), 116.3 (ddd, J = 15.4 Hz, J = 7.3 Hz), 114.6 (dd, J =18.2 Hz, J = 7.6 Hz), 111.4 (dd, J = 17.2 Hz, J = 5.7 Hz), 102.2 (t, J = 19.8 Hz), 98.4 (t, J = 20.1 Hz), 97.3, 95.6, 80.9, 77.8, 35.7, 32.8, 22.3, 13.9; Anal. calcd for C26H15F7: C, 67.83; H, 3.26. Found: C, 67.77; H, 3.44.

Characterization data for BPEB 20: 1H-NMR (300 MHz, CDCl3) δ 7.57–7.48 (m, 4H), 7.16 (d, 2H, J = 7.7 Hz), 6.77 (d, 2H, J = 8.2 Hz), 2.60 (t, 2H, J = 7.5 Hz), 1.65–1.56 (m, 2H), 1.38–1.28 (m, 4H), 0.91 (t, 3H, J = 6.7 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.4 Hz, J = 6.0 Hz), 155.8 (dd, J = 255.4 Hz, J = 3.7 Hz), 147.0 (t, J = 9.1 Hz), 131.8, 131.7, 125.8 (t, J = 16.5 Hz), 123.8 (t, J = 8.7 Hz), 122.2, 120.6 (q, J = 259.6 Hz), 115.8 (dd, J = 17.6 Hz, J = 6.4 Hz), 111.2 (dd, J = 17.1 Hz, J = 6.1 Hz), 99.1 (t, J = 19.9 Hz), 97.6, 92.0, 87.9, 79.1, 35.9, 31.3, 30.3, 22.5, 14.0; Anal. calcd for C28H19F7O: C, 66.67; H, 3.77. Found: C, 66.35; H, 3.46.

Characterization data for BPEB 21: 1H-NMR (300 MHz, CDCl3) δ 7.56–7.46 (m, 4H), 7.16–7.11 (m, 2H), 6.76 (d, 2H, J = 8.2 Hz), 2.60 (t, 2H, J = 7.6 Hz), 1.66–1.56 (m, 2H), 1.38–1.29 (m, 4H), 0.91 (t, 3H, J = 6.6 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.2 Hz, J = 6.0 Hz), 151.1 (ddd, J = 250.7 Hz, J = 10.3 Hz, J = 4.5 Hz), 147.0 (t, J = 8.9 Hz), 140.5 (dt, J = 256.0 Hz, J = 15.6 Hz), 131.8, 131.7, 123.5, 122.4, 119.1 (td), 116.0 (ddd, J = 15.2 Hz, J = 7.2 Hz, J = 4.3 Hz), 111.2 (dd, J = 16.6 Hz, J = 5.6 Hz), 99.2 (t, J = 19.7 Hz), 97.7, 90.6, 88.2, 78.9, 35.9, 31.3, 30.4, 22.5, 14.0; Anal. calcd for C27H19F5: C, 73.97; H, 4.34. Found: C, 73.49; H, 4.44.

Characterization data for BPEB 22: 1H-NMR (300 MHz, CDCl3) δ 7.46 (t, 1H, J = 7.5 Hz), 7.34–7.29 (m, 2H), 7.19 (d, 2H, J = 7.1 Hz), 6.77 (d, 2H, J = 8.2 Hz), 2.60 (t, 2H, J = 7.5 Hz), 1.61 (m, 2H), 1.36–1.30 (m, 4H), 0.91 (t, 3H, J = 6.6 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.9 Hz, J = 5.8 Hz), 162.3 (d, J = 253.6 Hz), 155.8 (dd, J = 255.5 Hz, J = 3.5 Hz), 147.5 (t, J = 9.0 Hz), 133.3, 127.6 (d, J = 3.4 Hz), 126.1 (t, J = 15.8 Hz), 125.6 (d, J = 9.5 Hz), 123.3 (t, J = 10.9 Hz), 120.5 (q, J = 261.0 Hz), 118.7 (d, J = 22.7 Hz), 115.9 (dd, J = 16.0 Hz, J = 6.5 Hz), 111.3 (dd, J = 14.6 Hz, J = 6.1 Hz), 111.1, 98.8 (t, J = 19.9 Hz), 96.4, 92.6, 85.5, 80.0, 36.0, 31.3, 30.3, 22.5, 14.0; Anal. calcd for C28H18F8O: C, 64.37; H, 3.45. Found: C, 63.89; H, 3.26.

Characterization data for BPEB 23: 1H-NMR (300 MHz, CDCl3) δ 7.44 (t, 1H, J = 7.6 Hz), 7.32–7.27 (m, 2H), 7.16 (d, 2H, J = 6.8 Hz), 6.77 (d, 2H, J = 8.1 Hz), 2.60 (t, 2H, J = 7.9 Hz), 1.61 (m, 2H), 1.36–1.29 (m, 4H), 0.91 (t, 3H, J = 6.6 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.8 (dd, J = 253.8 Hz, J = 5.8 Hz), 162.3 (d, J = 253.4 Hz), 151.1 (ddd, J = 251.1 Hz, J = 10.4 Hz, J = 4.4 Hz), 147.4 (t, J = 9.1 Hz), 140.7 (dt, J = 256.0Hz, J = 15.5 Hz), 133.2, 127.6 (d, J = 3.2 Hz), 125.3 (d, J = 9.5 Hz), 118.6 (dd, J = 15.6 Hz, J = 6.9 Hz), 116.1 (dd, J = 15.3 Hz, J = 7.3 Hz), 111.5, 111.3 (dd, J = 17.1 Hz, J = 6.9 Hz), 98.9 (t, J = 19.9 Hz), 96.5, 92.9, 84.1, 79.9, 36.0, 31.4, 30.3, 22.5, 14.0; Anal. calcd for C27H18F6: C, 71.05; H, 3.95. Found: C, 71.17; H, 4.11.

Characterization data for BPEB 24: 1H-NMR (300 MHz, CDCl3) δ 7.23 (d, 2H, J = 7.7 Hz), 7.14 (d, 2H, J = 7.2 Hz), 6.78 (d, 2H, J = 8.2 Hz), 2.61 (t, 2H, J = 7.5 Hz), 1.61 (m, 2H), 1.38–1.27 (m, 4H), 0.90 (t, 3H, J = 6.9 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.9 (dd, J = 254.7 Hz, J = 6.4 Hz), 162.6 (dd, J = 254.8 Hz, J = 6.1 Hz), 155.8 (dd, J = 255.7 Hz, J = 3.6 Hz), 148.0 (t, J = 9.4 Hz), 126.3 (t, J = 15.8 Hz), 125.5 (t, J = 12.6 Hz), 123.0 (t, J = 10.6 Hz), 120.5 (q, J = 260.4 Hz), 116.0 (dd, J = 17.5 Hz, J = 6.2 Hz), 114.6 (dd, J = 18.1 Hz, J = 7.3 Hz), 111.4 (dd, J = 17.2 Hz, J = 5.5 Hz), 102.0 (t, J = 17.6 Hz), 98.4 (t, J = 19.9 Hz), 96.9, 95.5, 81.1, 79.2, 36.0, 31.3, 30.3, 22.5, 14.0; Anal. calcd for C28H17F9O: C, 62.22; H, 3.15. Found: C, 62.18; H, 3.12.

Characterization data for BPEB 25: 1H-NMR (300 MHz, CDCl3) δ 7.19 (t, 2H, J = 6.8 Hz), 7.12 (d, 2H, J = 7.2 Hz), 6.77 (d, 2H, J = 8.2 Hz), 2.61 (t, 2H, J = 7.5 Hz), 1.61 (m, 2H), 1.34–1.32 (m, 4H), 0.90 (t, 3H, J = 6.6 Hz); 13C-NMR (75 MHz, CDCl3) δ 162.9 (dd, J = 254.1 Hz, J = 5.6 Hz), 162.6 (dd, J = 255.0 Hz, J = 6.4 Hz), 151.2 (ddd, J = 251.5 Hz, J = 10.6 Hz, J = 4.9 Hz), 147.9 (t, J = 9.6 Hz), 140.9 (dt, J = 256.8 Hz, J = 15.5 Hz), 125.2 (t, J = 11.6 Hz), 118.4 (td), 116.2 (ddd, J = 15.4 Hz, J = 7.6 Hz), 114.5 (dd, J = 18.5 Hz, J = 7.6 Hz), 111.3 (dd, J = 17.9 Hz, J = 5.2 Hz), 102.2 (t, J = 19.6 Hz), 98.5 (t, J = 20.1 Hz), 97.2, 95.6, 80.9, 77.8, 36.0, 31.3, 30.3, 22.5, 13.9; Anal. calcd for C27H17F7: C, 68.35; H, 3.59. Found: C, 68.38; H, 3.76.

4. Conclusions

In summary, we have designed and synthesized BPEBs by convenient Sonogashira cross-coupling reactions, which have different numbers of side-substitute fluorine atoms on benzene rings, and alkyl chains, ethoxyl groups, fluorine atoms and trifluoromethyl groups as the end groups. The detailed investigation of the synthesized BPEBs properties have disclosed that the melting points, clearing points, nematic phase, optical anisotropy (Δn) and dielectric anisotropy (Δɛ) greatly depend on both the numbers of side-substitute fluorine atoms and structures of the end groups. On the basis of the obtained properties of the synthesized BPEBs, some of them have been expected to have high potential application as the compositions in blue phase liquid crystals. Therefore, a mixture of blue phase liquid crystal has been prepared with a relative wide blue phase temperature range of 8 °C. The obtained results have implied that the synthesized BPEBs will certainly be important in the development of new types and properties of LCs. Further study on the application of BPEBs in making other new types of LCs is underway in our laboratory.

Supplementary Information

Acknowledgments

Financial support from the National High Technology Research and Development Program, China (No. 2011AA02A209) is gratefully acknowledged.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Carlton, R.J.; Hunter, J.T.; Miller, D.S.; Abbasi, R.; Mushenheim, P.C.; Tan, L.N.; Nicholas, L.; Abbott, N.L. Chemical and biological sensing using liquid crystals. Liq. Cryst. Rev 2013, 1, 29–51.
  2. Tadwee, I.; Shahi, S.; Ramteke, V.; Syed, I. Liquid crystals pharmaceutical application: A review. Int. J. Pharm. Res. Allied Sci 2012, 1, 6–11.
  3. Goodby, J.W. The nanoscale engineering of nematic liquid crystals for displays. Liq. Cryst 2011, 38, 1363–1387.
  4. Kitzerow, H.-S. Blue phases come of age: A review. Proc. SPIE 2009, doi:10.1117/12.813372.
  5. Hong, H. Analysis of focal length of blue-phase liquid crystal (BPLC) cylindrical lens for the light of the various incident angles and polarizations. Liq. Cryst 2013, 40, 450–457.
  6. Yamamoto, S.-I.; Haseba, Y.; Higuchi, H.; Okumura, Y.; Kikuchi, H. Lattice plane control of liquid crystal blue phase. Liq. Cryst 2013, 40, 639–645.
  7. Li, P.; Sun, Y.; Wang, Q. A transflective and viewing angle controllable bluephase liquid crystal display. Liq. Cryst 2013, 40, 1024–1027.
  8. Tour, J.M. Molecular electronics. Synthesis and testing of components. Acc. Chem. Res 2000, 33, 791–804.
  9. Bunz, U.H.F. Poly (aryleneethynylene)s: Syntheses, properties, structures, and applications. Chem. Rev 2000, 100, 1605–1644.
  10. Levitus, M.; Schmieder, K.; Ricks, H.; Shimizu, K.D.; Bunz, U.H.F.; Garcia-Garibay, M.A. Steps to demarcate the effects of chromophore aggregation and planarization in poly(phenyleneethynylene)s. 1. Rotationally interrupted conjugation in the excited states of 1,4-bis(phenylethynyl)benzene. J. Am. Chem. Soc 2001, 123, 4259–4265.
  11. Beeby, A.; Findlay, K.; Low, P.J.; Marder, T.B. A re-evaluation of the photophysical properties of 1,4-bis(phenylethynyl)benzene: A model for poly(phenyleneethynylene). J. Am. Chem. Soc 2002, 124, 8280–8284.
  12. Schwab, P.F.H.; Smith, J.R.; Michl, J. Synthesis and properties of molecular rods. 2. Zig-zag rods. Chem. Rev 2005, 105, 1197–1279.
  13. Wu, S.-T.; Hsu, C.-S.; Shyu, K.-F. High birefringence and wide nematic range bis-tolane liquid crystals. Appl. Phys. Lett 1999, 74, 344–346.
  14. Tanaka, T.; Sekine, C.; Ashida, T.; Ishitobi, M.; Konya, N.; Minai, M.; Fujisawa, K. Highly anisotropic molecular materials for LCD. Mol. Cryst. Liq. Cryst 2000, 346, 209–216.
  15. Long, T.M.; Swager, T.M. Triptycene-containing bis(phenylethynyl)benzene nematic liquid crystals. J. Mater. Chem 2002, 12, 3407–3412.
  16. Liao, Y.-M.; Chen, H.-L.; Hsu, C.-S.; Gauza, S.; Wu, S.-T. Synthesis and mesomorphic properties of super high birefringence isothiocyanato bistolane liquid crystals. Liq. Cryst 2007, 34, 507–517.
  17. Lydon, D.P.; Albesa-Jové, D.; Shearman, G.C.; Seddon, J.M.; Howard, J.A.K.; Marder, T.B.; Low, P.J. The synthesis and liquid crystalline behaviour of alkoxy-substituted derivatives of 1,4-bis(phenylethynyl)benzene. Liq. Cryst 2008, 35, 119–132.
  18. Dziaduszek, J.; Kula, P.; Dąbrowski, R.; Drzewiński, W.; Garbat, K.; Urban, S.; Gauza, S. General synthesis method of alkyl-alkoxy multifluorotolanes for negative high birefringence nematic mixtures. Liq. Cryst 2012, 39, 239–247.
  19. Miao, Z.-C.; Wang, D.; Zhang, Y.-M.; Jin, Z.-K.; Liu, F.; Wang, F.; Yang, H. Asymmetrical phenyldiacetylenes liquid crystalline compounds with high birefringence and characteristics of selective reflection. Liq. Cryst 2012, 39, 1291–1296.
  20. Zhang, Y.-M.; Wang, D.; Miao, Z.-C.; Jin, S.-K.; Yang, H. Novel high birefringence bistolane liquid crystals with lateral fluorosubstituent. Liq. Cryst 2012, 39, 1330–1339.
  21. Herman, J.; Dziaduszek, J.; Dąbrowski, R.; Kędzierski, J.; Kowiorski, K.; Dasari, V.S.; Dhara, S.; Kula, P. Novel high birefringent isothiocyanates based on quaterphenyl and phenylethynyltolane molecular cores. Liq. Cryst 2013, 40, 1174–1182.
  22. Yatabe, T.; Okumoto, H.; Kawanishi, Y.; Inoue, T. Charge-carrier transport in 1,4-bis(phenylethynyl)benzene derivatives exhibiting crystal mesophases. Chem. Lett 2013, 42, 764–766.
  23. Imrie, C.T.; Taylor, L. The preparation and properties of low molar mass liquid crystals possessing lateral alkyl chains. Liq. Cryst 1989, 6, 1–10.
  24. Iwata, T.; Suzuki, K.; Higuchi, H.; Kikuchi, H. A method for enlarging the Kerr constant of polymer-stabilised blue phases. Liq. Cryst 2009, 36, 947–951.
Ijms 14 23257f1 200
Figure 1. Effect of side-substituted fluorine atoms and end groups on melting points.

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Figure 1. Effect of side-substituted fluorine atoms and end groups on melting points.
Ijms 14 23257f1 1024
Ijms 14 23257f2 200
Figure 2. Polarizing optical micrographs photos of BPEBs 15, 8, 9, 14, 15, 20 and 21.

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Figure 2. Polarizing optical micrographs photos of BPEBs 15, 8, 9, 14, 15, 20 and 21.
Ijms 14 23257f2 1024
Ijms 14 23257f3 200
Figure 3. Nematic phase temperature range.

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Figure 3. Nematic phase temperature range.
Ijms 14 23257f3 1024
Ijms 14 23257f4 200
Figure 4. The typical blue phase texture.

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Figure 4. The typical blue phase texture.
Ijms 14 23257f4 1024
Ijms 14 23257f5 200
Scheme 1. The structures of 1,4-bis(phenylethynyl)benzene derivatives and analogues (125).

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Scheme 1. The structures of 1,4-bis(phenylethynyl)benzene derivatives and analogues (125).
Ijms 14 23257f5 1024
Ijms 14 23257f6 200
Scheme 2. Synthesis of 1,4-bis(phenylethynyl)benzene derivatives and analogues.

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Scheme 2. Synthesis of 1,4-bis(phenylethynyl)benzene derivatives and analogues.
Ijms 14 23257f6 1024
Table 1. Melting points and clearing points of 1,4-bis(phenylethynyl)benzene derivatives (BPEBs) and analogues by DSC.

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Table 1. Melting points and clearing points of 1,4-bis(phenylethynyl)benzene derivatives (BPEBs) and analogues by DSC.
BPEBStructureMp (°C)ΔH (J/g)Cp (°C)ΔH (J/g)
1 Ijms 14 23257f7129.562.9251.23.0
2 Ijms 14 23257f8130.267.8254.23.8
3 Ijms 14 23257f991.063.7238.03.8
4 Ijms 14 23257f1088.755.7232.43.8
5 Ijms 14 23257f11140.446.0262.03.0
6 Ijms 14 23257f12213.241.2
7 Ijms 14 23257f13190.457.3
8 Ijms 14 23257f14131.159.8152.95.8
9 Ijms 14 23257f15141.488.5a
10 Ijms 14 23257f16150.768.7
11 Ijms 14 23257f17142.877.4
12 Ijms 14 23257f18178.254.0
13 Ijms 14 23257f19176.466.5
14 Ijms 14 23257f20142.669.3b
15 Ijms 14 23257f21125.273.6c
16 Ijms 14 23257f22147.845.7
17 Ijms 14 23257f23136.255.4
18 Ijms 14 23257f24178.364.6
19 Ijms 14 23257f25170.855.3
20 Ijms 14 23257f26131.359.7144.30.81
21 Ijms 14 23257f27107.762.5122.30.29
22 Ijms 14 23257f28131.341.2
23 Ijms 14 23257f29126.051.7
24 Ijms 14 23257f30171.166.8
25 Ijms 14 23257f31158.766.0

aThe nematic phase was only observed during cooling in the temperature range 118.3 to 89.3 °C, and iso-N 118.3 °C (ΔH = 0.25 J/g), N-Cr 89.3 °C (ΔH = 60.4 J/g);bThe nematic phase was only observed during cooling in the temperature range 139.6 to 121.4 °C, and iso-N 139.6 °C (ΔH = 0.71 J/g), N-Sm 121.4 °C (ΔH = 0.61 J/g), Sm-Cr 113.8 °C (ΔH = 60.27 J/g);cThe nematic phase was only observed during cooling in the temperature range 107.0 to 71.4 °C, and iso-N 107.0 °C (ΔH = 0.16 J/g), N-Cr 71.4 °C (ΔH = 59.1 J/g).

Table 2. Δn values of BPEBs.

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Table 2. Δn values of BPEBs.
BPEBnenoΔn
12.0271.5310.496
21.9871.5110.476
31.9471.5110.436
42.0071.5110.496
52.1031.5210.582
81.8371.4910.346
91.8671.5210.346
141.7971.4680.329
151.8671.5210.346
201.8071.4910.316
211.8671.5110.356

ne: Extraordinary refraction index; no: Ordinary refraction index.

Table 3. Δɛ values of BPEBs.

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Table 3. Δɛ values of BPEBs.
BPEBɛ//ɛΔɛ
18.93.45.5
28.03.05.0
37.23.04.2
48.13.05.1
57.33.24.1
829.55.524.0
926.15.320.8
1429.56.023.5
1526.45.421.0
2026.15.220.9
2125.05.020.0

ɛ//: Parallel dielectric constant; ɛ: Vertical dielectric constant.

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