Synthesis and characterization of mesogenic triphenylene-perylene dyads with phenoxy-alkoxy linkers

Article abstract of DOI:10.1080/15421406.2017.1328218

Three novel triphenylene-perylene dyads with phenoxy-alkoxy linkers (PDI-OPhO-C_n-O- TP₆, n = 6, 8, 10) have been synthesized and characterized by FT-IR, MS, ¹³C, and ¹H NMR. The mesomorphic properties of these compounds were investigated by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). It was found that the dyads (PDI-OPhO-C_n-O-TP₆, n = 6, 8) only showed thermotropic columnar mesophase in the heating process, while the dyad (PDI-OPhO-C₁₀-O-TP₆) showed enantiotropic columnar mesophase in both heating and cooling processes.

Full text of DOI:10.1080/15421406.2017.1328218

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: http://www.tandfonline.com/loi/gmcl20
Synthesis and characterization of mesogenic
triphenylene-perylene dyads with phenoxy-alkoxy
linkers
Xiangfei Kong, Shengping Dai, Guixia Wang, Zhouyang Zhang, Laiqi Zhang,
Peihai Liao & Wenting Liu
To cite this article: Xiangfei Kong, Shengping Dai, Guixia Wang, Zhouyang Zhang, Laiqi Zhang,
Peihai Liao & Wenting Liu (2017) Synthesis and characterization of mesogenic triphenylene-
perylene dyads with phenoxy-alkoxy linkers, Molecular Crystals and Liquid Crystals, 650:1, 56-64,
DOI: 10.1080/15421406.2017.1328218
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Date: 25 August 2017, At: 21:14

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
, VOL. , –
https://doi.org/./..
Synthesis and characterization of mesogenic
triphenylene-perylene dyads with phenoxy-alkoxy linkers
Xiangfei Konga, Shengping Daia, Guixia Wanga, Zhouyang Zhanga, Laiqi Zhanga,
Peihai Liaoa, and Wenting Liub
aGuangxi Key Laboratory of Electrochemical and Magnetochemical Functional Materials, Guilin University of
Technology, Guilin, China; bJiangsu Hecheng Display Technology Co., Ltd., NanJing, China
ABSTRACT
KEYWORDS
Columnar phase; discotic
liquid crystal; dyad; perylene
diimide; triphenylene
Three novel triphenylene-perylene dyads with phenoxy-alkoxy linkers
(PDI-OPhO-Cn-O- TP6, n = 6, 8, 10) have been synthesized and charac-
terized by FT-IR, MS, 13C, and 1H NMR. The mesomorphic properties of
these compounds were investigated by polarizing optical microscopy
(POM) and differential scanning calorimetry (DSC). It was found that the
dyads (PDI-OPhO-Cn-O-TP6, n = 6, 8) only showed thermotropic colum-
nar mesophase in the heating process, while the dyad (PDI-OPhO-C10-
O-TP6) showed enantiotropic columnar mesophase in both heating and
cooling processes.
Introduction
Since the discovery of mesogenic benzene-hexa-n-alkanoate by Chandrasekhar in 1977 [1],
discotic liquid crystals (DLCs) have received increasing attention due to their attractive poten-
tials in the field of organic electronics. The molecule of DLCs usually features a planar core
and several flexible side chains. These molecules tend to self-organize into columns due to
π–π interactions between the neighboring cores, as well the van der Waals forces of the side
chains. This behavior offers DLCs good electron and/or hole transporting properties along the
columnar axes [2], which make them potential application in the areas of one-dimensional
conductors, organic light emitting diodes (OLEDs), photoconductors, information storage,
and organic photovoltaic devices, etc. [3].
Triphenylene-based discogens have been the most widely investigated discotic liquid
crystal materials so far. They have a large conjugated aromatic core with delocalized
π-electron system and strong electron donating ability, and show a strong tendency for colum-
nar mesophase formation. Furthermore, mesogenic triphenylenes readily forming columnar
phase can spontaneously form face-on alignment as thin films on solid substrates for device
fabrication [4]. Due to the symmetry forbidden S0–S1 transitions [5], thriphenylenes have
longer excited-state lifetimes and used in energy- and charge-transfer systems [6].
Perylene is another important organic material and several columnar mesophases have
been observed in its suitably functionalized structures [7]. Perylene diimides (PDI) have
attracted much attention as organic n-type semiconductors due to their strong electron
CONTACT GuixiaWang
China.
@glut.edu.cn
GuilinUniversityofTechnology,JianganRoad,Guilin,Guangxi,,
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gmcl.
©  Taylor & Francis Group, LLC

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
57
Scheme . Synthesis of PDI intermediates. Reagents and conditions: (a) i. Mg, THF, refluxing, ii. HCOOCH;
(b) DEAD, PPh, THF, RT,  hr; (c) Hydrazine hydrate, Ethanol, °C,  hr; (d) PTCDA, Imidazole, °C,  hr; (e)
Ceric ammonium nitrate, DCE, °C,  hr; (f) Hydroquinone, KCO, DMF, °C,  hr.
accepting ability [8]. Besides, PDI reveal a strong absorption in the visible region and has
high photochemical stability which are very important for device applications [9].
Recently discotic liquid crystal dyads, triads and oligomers having electron donor units
and electron acceptor units connected by covalent bond bridges, have been synthesized [10].
Efficient light-induced electron and energy transfer processes also occurred in these systems
when excited in the visible region [10e]. In these materials, the intermingling of light-induced
intramolecular electron transfer and one dimensional hole and electron transport pathways
can be used for fabricating ideal structure of OPVs, although which has never been realized
so far [11].
In this paper, the novel dyads composing of hexaalkoxy triphenylene and perylene diimide,
used as electron donor units and electron acceptor units respectively, covalently linked by
phenoxy-alkoxy were synthesized (Schemes 1–3). Liquid crystal phase transitions of which
were also investigated.
Experimental
Materials and physical measurements
The synthetic route can be divided into three parts: in the Scheme 1, the 1-bromoheptane
(1) was converted into pentadecan-8-ol (2) by nucleophilic substitution and then nucle-
ophilic addition reaction. Pentadecan-8-amine (4) was prepared by Gabriel reaction from
pentadecan-8-ol (2) [13]. Perylene diimide (5) was obtained by usual established method

58
X. KONG ET AL.
Scheme . Synthesis of triphenylene intermediates. Reagents and conditions: (g) CHBr, KCO, Ethanol,
refluxing,  hr; (h) Nitro methane, DCM, FeCl, °C,  hr; (i) -Bromo--hexanol, DMF, °C,  hr; (j) ,-
Octanediol, DEAD, P(Ph), THF, RT,  hr; (k) ,-Dibromodecane, TBAB, KOH, DCM/HO, RT,  hr.
Scheme . Synthesis of dyads PDI-OPhO-Cn-TP (n = , , ). Reagents and conditions: (l) For compound
15/16: 12/13, DIAD, P(Ph), THF, RT,  hr; For compound 17: 14, KCO, KI, DMF, °C,  hr.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
59
from pentadecan-8-amine (4) and perylene-3, 4, 9, 10-tetracarboxylic dianhydride [13]; pery-
lene diimide (5) was nitrated by ceric ammonium nitrate as an effective nitrification reagent
at its bay to give 1-nitro perylene diimide (6) [14]. 1-(4-Hydroxylphenoxy) perylene diimide
(7) was prepared by nucleophilic substitution reaction with hydroquinone in the presence
of potassium carbonate [15]; in the Scheme 2, in the presence of potassium carbonate, cat-
echol (8) and 1-bromohexane refluxed in ethanol to give 1,2-dihexyloxybeneze (9) and 2-
hexyloxy phenol (10) by Williamson reaction [16]; monohydroxypentahexyloxytriphenylene
(TP6-OH, 11) was synthesized by Scholl Reaction [17]. Then, 11 reacted respectively with
6-bromo-1-hexanol and 1,10-dibromodecane by Williamson reaction to give compound 12
and 14 [18], and reacted with 1,8-octanediol by Mitsunobu reaction to prepare compound
13; at last, 7 reacting with compound 12, 13, and 14 by Mitsunobu reaction or Williamson
reaction to afford the target compounds 15, 16, and 17, respectively, were presented in the
Scheme 3 [19].
Reagents and solvents were commercially available and used without further purification if
not specified. DMF was dried over CaH2 under N2 and freshly distilled prior to use. Tetrahy-
drofuran (THF) was refluxed over a mixture of Na and benzophenone under N2 and distilled
before use. Column chromatography was performed using a silica gel (200–300 mesh). Thin
layer chromatography (TLC) was performed using glass sheets previously coated with silica
gel (GF254).
1H and 13C NMR spectra were recorded in CDCl3 on a Bruker 500 MHz, 400 MHz or
300 MHz spectrometer, TMS (trimethyl chlorosilane) as the internal standard for 1H-NMR
spectra, chloroform (77.0 ppm) for 13C-NMR spectra. Mass spectra were obtained on Agi-
lent ESI 6400 mass spectrometer. Infrared spectra were obtained on VECTOR 22 (KBr pel-
let) spectrometer. Elemental analyses were carried out with Thermo Finngan Flash EA 1112
analyzer; Melting points were obtain on XT5 melting-point apparatus with microscope and
uncorrected. The transition temperatures and thermal behavior were determined by differen-
tial scanning calorimetry (DSC) (Thermal Analysis Q100, USA), operated at a scanning rate
of 10°C/min under N2 atmosphere. The mesophases were identified according to the texture
observed under an Olympus THMS600 polarizing microscope.
Synthesis of N, Nꢀ -di(1-heptyloctyl)perylene-3, 4, 9, 10-tetracarboxylic diimide (5)
Compound 4 (2.00 g, 8.81 mmol), 3,4,9,10-perylenetetracarboxylic dianhydride (1.57 g,
4.00 mmol), and imidazole(7.13 g) were added into a three-necked flask with stirring and
the mixture was stirred at 130°C and refluxing for 3 hr. The mixture was cooled to room
temperature and water (70 mL) was added, and then extracted with DCM (20 mL) three
times. The organic layer was washed by brine, dried over MgSO4, and then the solvent was
removed in vacuo. The residue was purified by column chromatography eluting with ethyl
acet−at1e/petroleum ether (1/25) to give compound 5 as a red solid (2.66 g, 82%). IR (KBr) νmax
1
=
(cm ): 3430, 2920, 2850, 1700 (C O), 1660, 1460, 1340, 1250, 1170, 1110, 961. H-NMR
(400 MHz, CDCl3) δ/ppm: 8.70–8.63 (m, 8 H), 5.26–5.12 (m, 2 H), 2.22–2.30 (m, 4 H), 1.84–
1.90 (m, 4 H), 1.39–1.20 (m, 40 H), 0.84 (t, J = 6.8 Hz, 12 H).
Synthesis of N, Nꢀ -di(1-heptyloctyl)perylene-1-nitro-3, 4, 9, 10-tetracarboxylic
diimide (6)
Compound 5 (0.66 g, 0.82 mmol), 98% sulfuric acid (0.40 g, 4.07 mmol), and ceric ammonium
nitrate (2.23 g, 4.07 mmol) were added into 1, 2-dichloroethane (30 mL). After refluxing for

60
X. KONG ET AL.
2 hr, the reaction mixture was cooled to room temperature, and water (30 mL) was added,
extracted with DCM (20 mL) three times. The organic layer was washed by saturated salt
water, dried over MgSO4, and the solvent was removed in vacuo. The residue was purified by
column chromatography eluting with DCM/petroleum ether (3/10) to give compound 6 as
−1
=
a red solid (0.54 g, 77%). IR (KBr) νmax (cm ): 3420, 3130, 2930, 2850, 1700 (C O), 1600,
1540 (-NO2), 1400, 1260, 1110. 1HNMR (500 MHz, CDCl3) δ/ppm: 8.79–8.57 (m, 6 H), 8.24
(d, J = 8.0 Hz, 1 H), 5.20–5.08 (m, 2 H), 2.25–2.19 (m, 4 H), 1.84 (m, 4 H), 1.32–1.19 (m,
40 H), 0.82 (t, J = 6.0 Hz, 12 H).
Synthesis of N, Nꢀ-di(1-heptyloctyl)perylene-1-(4-hydroxyphenoxy)-3, 4, 9,
10-tetracarboxylic diimide (7)
Under nitrogen atmosphere, compound 6 (0.70 g, 0.82 mmol), hydroquinone (0.45 g,
4.10 mmol), K2CO3 (1.13 g, 8.20 mmol) and KI (0.32 g, 0.08 mmol) were added into dry
DMF (30 mL), the resulting mixture was stirred at 70°C for 3 hr. Then methanol (10 mL) and
10% HCl (5 mL) were added, the mixture was cooled to room temperature. The precipitate
was filtered off, and purified by column chromatography eluting with DCM/petroleum ether
(3/2) to give compound 7 as a red solid (0.47 g, 61%). IR(KBr) νmax (cm−1): 3430(OH), 2920,
1
=
2850, 1710(C O), 1640, 1690, 1500, 1450, 1410, 1330, 1260, 1200, 927, 800, 745. H NMR
(400 MHz, CDCl3) δ/ppm: 9.60 (d, J = 8.4 Hz, 1 H), 8.67–8.28 (m, 6 H), 7.10 (d, J = 8.4 Hz,
2 H), 6.98 (d, J = 8.4 Hz, 2 H), 6.07 (s, 1 H), 5.29–5.01 (m, 2 H), 2.33–2.09 (m, 4 H), 1.86 (m,
4 H), 1.34–1.15 (m, 40 H), 0.80 (t, J = 6.0 Hz, 12 H).
Synthesis of 2-(6-hydroxyhexyloxy)-3, 6, 7, 10, 11-pentahexyloxytriphenylene (12)
Under nitrogen atmosphere, compound 11 (0.94 g, 1.26 mmol), 6-chlorohexan-1-ol (0.32 g,
2.34 mmol) and anhydrous potassim carbonate (0.30 g, 2.17 mmol) were added into dry DMF
(15 mL); the resulting mixture was stirred at 80°C for 72 hr. When cooled to room tempera-
ture, water (100 mL) was added, the mixture was extracted with ethyl acetate (20 mL) three
times. The organic layer was washed by saturated salt water, dried over MgSO4, and the solvent
was removed in vacuo. Finally, the residue was purified by column chromatography eluting
with DCM to give compound 12 as a colorless solid (0.64 g, 60%). mp: 55–56°C; IR (KBr)
−1
1
–
νmax (cm ): 3430 (O H), 2920, 2850, 1620, 1520, 1440, 1390, 1260, 1170, 1050, 836. HNMR
(500 MHz, CDCl3) δ/ppm: 7.85 (s, 6 H), 4.24–4.28 (m, 12 H), 3.71 (t, J = 6.5 Hz, 2 H), 2.01–
1.92 (m, 11 H), 1.70–1.49 (m, 18 H), 1.46–1.37 (m, 20 H), 0.95 (t, J = 6.5 Hz, 15 H).
Synthesis of 2-(8-hydroxyoctyloxy)-3, 6, 7, 10, 11-pentahexyloxytriphenylene (13)
Under nitrogen atmosphere, compound 11 (0.95 g, 1.25 mmol), diethyl azodicarboxy-
late (0.24 g, 1.38 mmol), 1,8-octanediol (0.94 g, 6.25 mmol) and triphenyl phosphine
(0.36 g,1.38 mmol) were added to dry THF solution (15 mL), which was stirred at room tem-
perature for 48 hr in the darkness. At this time, the reaction was quenched by water (75 mL)
and extracted with DCM (30 mL) three times. Then, the organic layer was washed by sat-
urated salt water, dried over MgSO4, and filtered. The solvent was removed under reduced
pressure and the crude product was purified by column chromatography eluting with ethyl
acetate/petroleum ether (1/10) to provide compound 13 as a colorless solid (0.58 g, 53%).mp:
63–64°C, IR (KBr) νmax (cm−1): 3440 (OH), 2930, 2850, 1620, 1520, 1440, 1390, 1260, 1170,
1070, 1050, 925, 837. 1H NMR (500 MHz, CDCl3) δ/ppm: 7.86 (s, 6 H), 4.25 (t, J = 6.5 Hz,

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
61
12 H), 3.67 (t, J = 6.5 Hz, 2 H), 1.99–1.93 (m, 12 H), 1.66–1.55 (m, 17 H), 1.45–1.39 (m, 24 H),
0.95 (d, J = 6.5 Hz, 15 H).
Synthesis of PDI-OPhO-Cn-O-TP6 (n = 6, 8) (15, or 16)
Under nitrogen atmosphere, compound 7 (0.58 g, 0.69 mmol), diisopropyl azodicarboxy-
late (0.11 g, 0.52 mmol) compound 12 or 13 (0.44 mmol) and triphenyl phosphine (0.13 g,
0.48 mmol) were added to dry THF (10 mL), which was stirred at room temperature for 72 hr
in the darkness. Then, the reaction was quenched by water (50 mL) and extracted with DCM
(20 mL) three times. The organic layer was washed by saturated salt water, dried over MgSO4,
and filtered. The solvent was removed under reduced pressure and the crude product was
purified by column chromatography, eluting with ethyl acetate/petroleum ether (1/10) to give
a red solid.
PDI-OPhO-C6-O-TP6 (15): yield 39%. IR (KBr) νmax (cm−1): 3430, 2930, 2850, 1700
1
=
=
(C O), 1650 (C O), 1590, 1500, 1430, 1410, 1330, 1260, 1170, 1040, 807, 748. HNMR
(400 MHz, CDCl3) δ/ppm: 9.61 (d, J = 8.4 Hz, 1 H), 8.75–8.56 (m, 5 H), 8.24 (d, J = 8.4 Hz,
1 H), 7.82 (m, 6 H), 7.14 (d, J = 8.8 Hz, 2 H), 7.01 (d, J = 8.8 Hz, 2 H), 5.15 (m, 2 H), 4.28–4.21
(m, 12 H), 4.04 (t, J = 6.4 Hz, 2 H), 2.29–2.16 (m, 4 H), 2.07–1.77 (m, 18 H), 1.74–1.55 (m,
14 H), 1.44–1.22 (m, 60 H), 0.95–0.92 (m, 15 H), 0.85–0.77 (m, 12 H). 13C NMR (75 MHz,
CDCl3) δ/ppm: 164.51, 157.21, 156.41, 148.50, 128.78, 128.07, 123.12, 115.79, 106.83, 69.24,
68.02, 54.20, 31.93, 31.5, 31.13, 28.92, 26.58, 25.55, 22.20, 13.61. Elemental analysis calcd for
C
114H156N2O12 (1746): C, 78.40, H, 9.00, N, 1.60, found: C, 78.32, H, 8.94, N, 1.54.
PDI-OPhO-C8-O-TP6 (16): yield 65%. IR (KBr)νmax(cm−1): 3430, 2930, 2850,
1
=
=
1690(C O), 1650 (C O), 1590, 1500, 1400, 1250, 1170, 1040, 807. HNMR (400 MHz,
CDCl3) δ/ppm: 9.60 (d, J = 8.4 Hz, 1 H), 8.74–8.57 (m, 5 H), 8.24 (d, J = 8.4 Hz, 1 H), 7.81
(m, 6 H), 7.14 (d, J = 8.4 Hz, 2 H), 7.00 (d, J = 8.4 Hz, 2 H), 5.23–5.06 (m, 2 H), 4.25–4.21
(m, 12 H), 4.01 (t, J = 6.4 Hz, 2 H), 2.29–2.23 (m, 4 H), 2.01–1.76 (m, 18 H), 1.60–1.20 (m,
78 H), 0.95–0.92 (m, 15 H), 0.85–0.77 (m, 12 H). 13CNMR (75 MHz, CDCl3) δ/ppm: 163.63,
158.95, 157.36, 157.11, 148.93, 147.59, 134.33, 133.91, 131.74, 129.25, 128.50, 126.98, 125.46,
123.53, 123.20, 121.85, 116.23, 107.19, 69.65, 68.52, 54.65, 32.38, 32.02, 31.58, 29.88, 29.00,
27.03, 26.53, 25.74, 22.66, 14.09. Elemental analysis calcd for C116H160N2O12 (1774): C, 78.51,
H, 9.09, N, 1.58, found: C, 78.49, H, 9.09, N, 1.48.
PDI-OPhO-C-O-TP ()
Under nitrogen atmosphere, compound 7 (0.30 g, 0.33 mmol), compound 14 (0.45 g,
0.49 mmol), anhydrous K2CO3 (0.09 g, 0.64 mmol) and KI (0.01 g, 0.06 mmol) were added
into dry DMF (15 mL), which was stirred at 80°C for 24 hr. Then the reaction was quenched
by water (150 mL) and extracted with DCM (30 mL) three times. The organic layer was
washed by saturated salt water, dried over MgSO4, and filtered. The solvent was removed
under reduced pressure and the crude product was purified by column chromatography, elut-
ing with ethyl acetate/petroleum ether (1/10) to give compound 17 as a red solid (0.30 g, 49%).
−1
=
=
IR(KBr) νmax (cm ): 3420, 3130, 2930,1690 (C O), 1650 (C O), 1500, 1400, 1340, 1260,
1060, 807.1H NMR (400 MHz, CDCl3) δ/ppm: 9.60 (d, J = 8.4 Hz, 1 H), 8.62 (m, 5 H), 8.26
(d, J = 7.2 Hz, 1 H), 7.81 (s, 6 H),7.16 (d, J = 8.4 Hz, 2 H),7.02 (d, J = 8.4 Hz, 2 H), 5.25–5.17
(m, 2 H), 4.24 (t, J = 6.4 Hz, 12 H), 4.03 (t, J = 6.4 Hz, 2 H), 2.31–2.23 (m, 4 H), 2.02–1.84 (m,
18 H), 1.61–1.24 (m, 82 H), 0.96 (m, 15 H), 0.88–0.81 (m,12 H). 13CNMR (CDCl3) δ/ppm:
164.71, 157.31, 156.91, 148.93, 147.58, 134.34, 133.9,3 131.79, 130.28, 131.79, 127.74, 126.98,
124.49, 122.95, 122.92, 120.38, 116.24, 107.17, 69.65, 68.53, 54.64, 32.38, 32.01, 31.58, 31.07,

62
X. KONG ET AL.
Figure . The DSC traces of dyads of 15, 16, and 17 (peak values marked).
28.95, 27.03, 26.87, 25.70, 22.66, 14.09. Elemental analysis calcd for C118H164N2O12 (1802): C,
78.62, H, 9.17, N, 1.55, found: C, 78.52, H, 9.01, N, 1.43.
Results and discussions
Thermal behaviors of compound 15, 16, and 17 were investigated by using differential scan-
ning calorimetry (DSC, Fig. 1) and the phase texture was studied by polarizing optical
microscopy (POM, Fig. 2). The phase transition and enthalpy of compounds (15, 16, and
17) are summarized in Table 1.
DSC curves showed two endothermic peaks at 82°C and 148°C, respectively on heating
circle for compound 15, and only one exothermic peak at 142°C. Under microscopic obser-
vation, it melted and flowed at 81°C, but the birefringent remained; keeping heating, the
birefringent disappeared at 153°C. When cooled, the isotropic liquid recovered birefringent
phenomenon at 151°C, and then solidified immediately.
Figure . Optical textures of Compound 17 at °C (cooling from the isotropic liquid, crossed polarizers,
scale bar is  µm).

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
63
Table . Phase transition temperatures (peak,°C) and associated enthalpy changes (KJ·mol− in parenthe-
ses) of Compounds 15, 16, and 17. Cr: crystal state, LC: Liquid crystal, I: isotropic liquid.
Compounds
Phase transition temperature(°C) and enthalpy (KJ/mol)
17
16
15
DSC curves showed compound 16 had the similar behaviors of phase transition as that
of compound 15, two endothermic peaks at 80°C and 159°C in the heating circle, and one
exothermic peak at 155°C. Under microscopic observation, when heated the crystal melted
at 80 °C, the birefringent phenomenon remained till 164°C. When cooled the isotropic liquid
showed birefringent again at 163°C, and solidified immediately.
DSC curves showed two endothermic peaks at 63°C and 151°C, respectively on heating
circle for compound 17, and two exothermic peaks at 29°C and 143°C, respectively on the
cooling circle. Under microscopic observation, when heated the crystal melted at 48 °C, the
birefringent phenomenon remained till 156°C. The birefringent fluid resorted at 154°C dur-
ing cooling, the fluid solidified at 35°C, and the birefringent remained.
These results showed that compound 15 and 16 have thermotropic mesophase only in the
heating process, while compound 17 have enantiotropic mesophase both in heating and cool-
ing processes. The phenomena proved that the length of soft linker showed a subtle influence
on the properties of these dyads. With the increase of the length of bridges, the melting point
of the dyads (Compound 15, 16, and 17) decreased successively, and the temperature range of
liquid crystal phase increased. This behavior is typical for systems that combine two different
discotic units covalently. Compound 17 is unique in the series and particularly interesting; its
texture (Fig. 2) is similar to the straight linear defects for hexagonal columnar phase [10e].
Conclusions
In conclusion, three novel triphenylene-perylene dyads with phenoxy-alkoxy linkers of
varying length have been synthesized, and characterized by FT-IR, 13C- and 1H-NMR, and
MS. Their mesomorphic properties were investigaed by polarizing optical microscopy and
differential scanning calorimetry. It was found that the dyad bearing the longest bridge
(-OC6H4O(CH2)10O-) showed enantiotropic columnar mesophase in both heating and
cooling circles; the other two dyads having shorter bridges ((-OC6H4O(CH2)nO-), n = 6
and 8) showed thermotropic mesophase only in the heating cricles. As such these are rare
examples of columnar mesogens comprising significantly different units.
Acknowledgment
We thank Guangxi key laboratory of hidden metallic ore deposits exploration for providing support
with the POM measurements.
Funding
This work was supported by the Natural Science Foundation of China (No.11364013), the Education
Department of Guangxi Province (No. KY2015YB129), Opening fund of Guangxi Key Laboratory of

64
X. KONG ET AL.
Electrochemical and Magnetochemical Functional Materials (EMFM20162202) and the startup Foun-
dation for Doctor of Guilin University of Technology.
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