Synthesis and mesomorphism of asymmetric triphenylene discotic liquid crystals bearing with mono-amido-based alkyl soft chains

Article abstract of DOI:10.1080/15421406.2011.569516

A series of triphenylene discotic liquid crystals with amido-based alkyl chains in different lengths were synthesized and characterized. The liquid crystal properties were studied with differential scanning calorimetry and polarizing optical microscopy. The influences of amide alkyl chain lengths on the mesomorphism were discussed. Based on the results, we concluded that the triphenylene discogens with an amido-based alkyl chain could form intermolecular hydrogen bonds inside their columnar stacks, and hence, exhibit higher melting and clearing points, and wider mesophase ranges. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15421406.2011.569516

This article was downloaded by: [Moskow State Univ Bibliote]
On: 04 September 2013, At: 05:59
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Molecular Crystals and Liquid Crystals
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/gmcl20
Synthesis and Mesomorphism of
Asymmetric Triphenylene Discotic Liquid
Crystals Bearing with Mono-Amido-Based
Alkyl Soft Chains
K. Q. Zhao a , J. Z. Guo a , W. H. Yu a , L. Wang a , P. Hu a , B. Q.
Wang a , H. Monobe b & Y. Shimizu b
a School of Chemistry and Materials Sciences, Sichuan Normal
University, Chengdu, China
b National Institute of Advanced Industrial Science and Technology,
Kansai Center, Midorigaoka, Ikeda, Osaka, Japan
Published online: 14 Jun 2011.
To cite this article: K. Q. Zhao , J. Z. Guo , W. H. Yu , L. Wang , P. Hu , B. Q. Wang , H. Monobe &
Y. Shimizu (2011) Synthesis and Mesomorphism of Asymmetric Triphenylene Discotic Liquid Crystals
Bearing with Mono-Amido-Based Alkyl Soft Chains, Molecular Crystals and Liquid Crystals, 542:1, 37/
[559]-47/[569], DOI: 10.1080/15421406.2011.569516
To link to this article: http://dx.doi.org/10.1080/15421406.2011.569516
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or
howsoever caused arising directly or indirectly in connection with, in relation to or arising
out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &

Conditions of access and use can be found at http://www.tandfonline.com/page/terms-
and-conditions

Mol. Cryst. Liq. Cryst., Vol. 542: pp. 37=[559]–47=[569], 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421406.2011.569516
Synthesis and Mesomorphism of Asymmetric
Triphenylene Discotic Liquid Crystals Bearing
with Mono-Amido-Based Alkyl Soft Chains
K. Q. ZHAO,1 J. Z. GUO,1 W. H. YU,1 L. WANG,1
P. HU,1 B. Q. WANG,1 H. MONOBE,2 AND
Y. SHIMIZU2
1School of Chemistry and Materials Sciences, Sichuan Normal
University, Chengdu, China
2National Institute of Advanced Industrial Science and Technology,
Kansai Center, Midorigaoka, Ikeda, Osaka, Japan
A series of triphenylene discotic liquid crystals with amido-based alkyl chains in
different lengths were synthesized and characterized. The liquid crystal properties
were studied with differential scanning calorimetry and polarizing optical
microscopy. The influences of amide alkyl chain lengths on the mesomorphism were
discussed. Based on the results, we concluded that the triphenylene discogens with
an amido-based alkyl chain could form intermolecular hydrogen bonds inside their
columnar stacks, and hence, exhibit higher melting and clearing points, and wider
mesophase ranges.
Keywords Columnar phase; discotic liquid crystal; intermolecular hydrogen
bonds; mesophase anchoring; supramolecular; triphenylene
1. Introduction
A discotic liquid crystal (DLC) molecule is normally composed of a polycyclic
aromatic core, which is a big conjugated p-electron system, and six to eight periph-
eral soft alkyl chains [1]. Triphenylene discotic liquid crystal (TPDLC) is one of the
most widely investigated DLCs [2,3].
TPDLCs, through the p-p interactions among triphenylene cores, can sponta-
neously assemble to highly ordered helical phase and hexagonal columnar meso-
phase, and therefore, demonstrate high charge carrier mobility [4–6]. These
properties have attracted much attentions on TPDLCs, especially on their great
potential applications as molecular conducting wires, organic light emitting diodes
(OLED), solar cells, high-speed copy machines, scanner’s photo-conducting toners,
and so on [1,4,6].
Address correspondence to K. Q. Zhao, School of Chemistry and Materials Sciences,
Sichuan Normal University, Chengdu 610066, China. Tel.: þ86-28-84764743; Fax:
þ86-28-84764743; E-mail: kqzhao@sicnu.edu.cn
37=[559]

38=[560]
K. Q. Zhao et al.
The fast charged carrier mobility of TPDLCs’ has been proved to be associated
with their highly ordered columnar phases [7–9]. As a result, most research on
TPDLCs, up to date, is focused on stabilizing their columnar phases or the mole-
cules’ ordered stackings by means of molecular designs. Introducing intermolecular
hydrogen bonds in TPDLCs for controlling the ordered columnar stacks and
molecular dynamics is one of those very effective methods.
Intermolecular hydrogen-bonds are dynamically reversible and are responsive to
external stimulations. The utilization of intermolecular hydrogen bonds to build
dynamically functionalized, environmentally friendly, low cost and processing mate-
rials is an attractive direction of material research [10–13]. In addition, liquid crystals
with hydrogen bond interactions are featured with a variety of properties, such as
charge conductivity, information storage, molecular sensing and dynamic behaviors.
These liquid crystals are also able to respond to external stimulations and change
their self-assembled structures through hydrogen-bonding associations and dissocia-
tions. Stabilizing columnar phases through intermolecular hydrogen bonds among
amido-groups has been studied by several research groups [14–17] and shown
improved semi-conducting properties [7–9,18–22].
Besides, we [23–25] synthesized various triphenylene discogens C18H6(OR)6-n
-
(OCH2CONHC4H9)n (n ¼ 1, 2, 3). Our experimental results, combined with semi-
quantitative calculation studies [26,27], showed that the intermolecular hydrogen
Figure 1. Synthesis of mono-amido-triphenylene discotic liquid crystals. (Figure appears in
color online.)

Hydrogen Bonds Stabilized Columnar Mesophase
39=[561]
bondings could cooperatively contribute to the stability of the hexagonal columnar
phases (Colh).
In this article, we are focusing on the mesomorphism of TPDLCs. The
mesomorphism, as we expected, could be affected by both intermolecular hydrogen
bondings and the molecular symmetry of discogens; and the latter is associated
with the length of amide alkyl soft chains. As a result of this, we designed, synthe-
sized and studied a series of triphenylene discotic compounds C18H6(OC6H13)5-
(OCH2CONHCnH2nþ1), n ¼ 1–8, 10, 11, 12, 16, in which five peripheral hexyloxy
chains remain unchanged, only one amide-based alkyl chain was varied in its length.
We also compared our TPDLCs with the previously reported hexaalkoxytripheny-
lene discogens C18H6(OC6H13)5(OCmH2mþ1) [28]; and found that the amide group
could improve the mesomorphism of discogens.
Our target TPDLCs were synthesized as described in Figure 1.
2. Experimental
Instruments and Methods
NMR was recorded on a Bruker-Advance-600 MHz instrument using TMS as the
internal standard, CDCl3 as the solvent. Mesomorphic textures were observed and
recorded using XP-201 Polarized Optical Microscope (POM) installed with a
XP-201 hotplate and a XPR-201 temperature controller. Phase transition tempera-
tures and enthalpies of discogens were investigated using a TA-DSC Q100 instru-
ment under N2 atmosphere with heating and cooling rates as 10ꢀC=min. Unless
otherwise noted, the reagents and solvents were commercially available and used
without further purifications. The commercial unavailable primary amines were
prepared according to the Gabriel synthesis method [29].
2-Hydroxyl-3-methoxy-6,7,10,11-tetra(hexyloxy)triphenylene (2). It was synthe-
sized according to a reported method [30].
2-Methoxy-3,6,7,10,11-penta(hexyloxy)triphenylene (3). A mixture of 2 (4.7 g,
6.97 mmol), C6H13Br (1.73 g, 10.46 mmol) and K2CO3 (3.85 g, 27.88 mmol) in
EtOH (100 ml) was heated refluxed. The reaction was monitored by TLC (40%
chloroform in petroleum ether). After 24 hours, the reaction was poured into
hydrochloride acid (3% as an aqueous solution), extracted with CH2Cl2 (3 ꢁ 50 ml).
The combined organic layers were dried through MgSO4, concentrated. Resulting
blue solid was purified by column chromatography (28% chloroform in petroleum
ether). Recrystallization from ethanol followed by drying under high vacuum give
a light blue crystal as the title compound 3 (5.14 g, 97% yield.)
2-Hydroxyl-3,6,7,10,11-penta(hexyloxy)triphenylene (4). Li (0.23 g, 32.55 mmol)
was added to a solution of Ph3P (3.56 g, 13.56 mmol) in freshly distilled THF
(30 mL). The reaction was carried out under N2 atmosphere. After refluxing for 3
hours, t-BuCl (1.25 g, 13.56 mmol) was added and the reaction was refluxed for
additional 1 hour when 3 (5.14 g, 6.78 mmol) was added. The reaction was then
monitored by TLC (33% CH2Cl2 in petroleum ether). After refluxing for another
5 hours, the reaction was cooled to room temperature, and was poured into
hydrochloride acid (3% as an aqueous solution), extracted with CH2Cl2 (3 ꢁ 50 ml).
The combined organic layers were dried through MgSO4, concentrated under

40=[562]
K. Q. Zhao et al.
reduced pressure. The resulting white solid was purified by column chromatography
(17% CH2Cl2 in petroleum ether). Recrystallization from ethanol followed by drying
under high vacuum give a white crystal as the title compound 3 (4.04 g, 80% yield.)
2-(Ethoxycarbonylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene, C18H6(OC6H13)5
(OCH2COOC2H5), 5. The reaction of 4 (1.5 g, 2 mmol), BrCH2COOC2H5 (0.41 g,
2.5 mmol) and K2CO3 (1.10 g, 8 mmol) in DMF (15 ml) was carried out under
room temperature. The reaction was monitored by thin-layer chromatography (75%
CH2Cl2 in petroleum ether). After 24 hours, the reaction was poured into
hydrochloride acid (3% as an aqueous solution), extracted with CH2Cl2 (3 ꢁ 50ml).
The combined organic layers were dried through MgSO4, concentrated under
reduced pressure. The resulting white solid was purified by column chromatogarphy
(67% CH2Cl2 in petroleum ether). Recrystallization from ethanol followed by drying
under high vacuum gave a white crystal as the title compound 3 (1.54 g, 92% yield.)
General procedure for the synthesis of TPDLCs 6-n. The mixture of
C18H6(OC6H13)5(OCH2COOC2H5) (5) (1.0 equiv.) and a primary amine (3 mL)
was heated to reflux under 80ꢀC. The reaction was monitored by thin-layer chroma-
tography. After completion, the reaction was concentrated under reduced pressure,
and purified by column chromatography. TPDLCs 6-n were then recrystallized from
ethanol, and dried under high vacuum.
6–1: 2-(Methylcarbamoylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene. TPDLC
6–1 was synthesized by the reaction of 5 (150mg, 0.18mmol) with methylamine
(3 mL, 21mmol) following the general procedure, afforded the compound as a
1
white solid in yield 98%. H NMR (CDCl3, TMS, 600 MHz) d: 0.92–0.96 (m, 15H),
1.37–1.45 (m, 20H), 1.55–1.60 (m, 10H), 1.91–1.97 (m, 10H), 2.97 (d, J ¼ 2.7 Hz),
4.22–4.27 (m, 10H), 4.76 (s, 2H), 7.26 (s, 1H), 7.77 (s, 1H), 7.85 (b, 5H). IR (KBr)
v: 3422, 1691, 1659, 1618cmꢂ1. Anal. calcd for C51H77NO7: C 75.05, H 9.51, N
1.72; found C 74.68, H 9.53, N 1.62.
6–2: 2-(Ethylcarbamoylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene. TPDLC
6–2 was synthesized by the reaction of 5 (120 mg, 0.15 mmol) with ethylamine
(3 mL, 36 mmol) following the general procedure, afforded the compound as a
white solid in yield 89%. 1H NMR (CDCl3, TMS, 600 MHz) d: 0.93–0.96 (m,
15H), 1.24 (t, J ¼ 7.2 Hz, 3H), 1.38–1.42 (m, 20H), 1.54–1.61 (m, 10H), 1.93–1.97
(m, 10H), 3.42–3.46 (m, 2H), 4.22–4.27 (m, 10H), 4.74 (s, 2H), 7.26 (s, 1H), 7.77
(s, 1H), 7.84 (b, 5H). IR(KBr) v: 3408, 1688, 1618 cmꢂ1. Anal. calcd for
C52H79NO7: C 75.23, H 9.59, N 1.69; found C 75.30, H 9.46, N 1.65.
6–3: 2-(Propylcarbamoylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene. TPDLC
6–3 was synthesized by the reaction of 5 (120 mg, 0.15mmol) with n-propylamine
(3 mL, 36.5 mmol) following the general procedure, afforded the compound as a
1
white solid in yield 91.5%. H NMR (CDCl3, TMS, 600 MHz) d: 0.95–0.99 (m,
18H), 1.37–1.44 (m, 20H), 1.55–1.64 (m, 12H), 1.91–1.97 (m, 10H), 3.35–3.39 (m,
2H), 4.22–4.27 (m, 10H), 4.75 (s, 2H), 7.26 (s, 1H), 7.77 (s, 1H), 7.84 (b, 5H).
IR(KBr) v: 3416, 1690, 1618 cmꢂ1. Anal. calcd for C53H81NO7: C 75.40, H 9.67, N
1.66; found C 75.40, H 9.52, N 1.64.
6–4: 2-(Butylcarbamoylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene. TPDLC
6–4 was synthesized by reaction of 5 (120 mg, 0.15 mmol) with n-butylamine

Hydrogen Bonds Stabilized Columnar Mesophase
41=[563]
1
(3 mL, 30.4 mmol) in yield 93.2%. H NMR (CDCl3, TMS, 600 MHz) d: 0.93–0.96
(m, 18H), 1.36–1.44 (m, 22H), 1.56–1.62 (m, 12H), 1.91–1.98 (m, 10H), 3.35–3.39
(m, 2H), 4.21–4.26 (m, 10H), 4.75 (s, 2H), 7.26 (s, 1H), 7.77 (s, 1H), 7.84 (b, 5H).
IR(KBr) v: 3416, 1689, 1618 cmꢂ1. Anal. calcd for C54H83NO7: C 75.57, H 9.75,
N 1.63; found C 75.57, H 9.53, N 1.60.
6–5: 2-(Pentylcarbamoylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene. TPDLC
6–5 was synthesized in yield 80.5%. 1H NMR (CDCl3, TMS, 600 MHz) d:
0.88–0.90 (m, 3H), 0.92–0.96 (m, 15H), 1.33–1.44 (m, 24H), 1.55–1.60 (m, 12H),
1.91–1.98 (m, 10H), 3.37–3.41 (m, 2H), 4.22–4.27 (m, 10H), 4.75 (s, 2H), 7.26 (s,
1H), 7.77 (s, 1H), 7.84 (b, 5H). IR(KBr) v: 3414, 1689, 1619 cmꢂ1. Anal. calcd for
C55H85NO7: C 75.73, H 9.82, N 1.61; found C 75.64, H 9.70, N 1.58.
6–6: 2-(Hexylcarbamoylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene. TPDLC
1
6–6 was synthesized in yield 88%. H NMR (CDCl3, TMS, 600 MHz) d: 0.86 (t,
J ¼ 6.9 Hz, 3H), 0.92–0.96 (m, 15H), 1.28–1.30 (m, 4H), 1.36–1.44 (m, 22H),
1.56–1.60 (m, 12H), 1.93–1.97 (m, 10H), 3.39 (d, J ¼ 3.3 Hz, 2H), 4.22–4.27 (m,
10H), 4.75 (s, 2H), 7.26 (s, 1H), 7.77 (s, 1H), 7.84 (b, 5H). IR(KBr) v: 3414, 1689,
1619cmꢂ1. Anal. calcd for C56H87NO7: C 75.89, H 9.89, N 1.58; found C 75.96, H
9.85, N 1.58.
6–7: 2-(Heptylcarbamoylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene. TPDLC
1
6–7 was synthesized in yield 78%. H NMR (CDCl3, TMS, 600 MHz) d: 0.86 (t,
J ¼ 6.9 Hz, 3H), 0.92–0.96 (m, 15H), 1.23–1.30 (m, 6H), 1.36–1.44 (m, 22H),
1.55–1.60 (m, 12H), 1.93–1.97 (m, 10H), 3.39 (d, J ¼ 3.3 Hz), 4.22–4.27 (m, 10H),
4.75 (s, 2H), 7.26 (s, 1H), 7.77 (s, 1H), 7.84 (b, 5H). IR(KBr) v: 3412, 1689,
1619cmꢂ1. Anal. calcd for C57H89NO7: C 76.04, H 9.96, N 1.56; found C 75.77, H
9.91, N 1.51.
6–8: 2-(Octylcarbamoylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene. TPDLC
1
6–8 was synthesized in yield 86%. H NMR (CDCl3, TMS, 600 MHz) d: 0.86 (t,
J ¼ 6.9 Hz, 3H), 0.92–0.96 (m, 15H), 1.23–1.29 (m, 8H), 1.33–1.44 (m, 22H),
1.55–1.61 (m, 12H), 1.93–1.97 (m, 10H), 3.38 (d, J ¼ 3.3 Hz, 2H), 4.22–4.27 (m,
10H), 4.75 (s, 2H), 7.26 (s, 1H), 7.77 (s, 1H), 7.84 (b, 5H). IR(KBr) v: 3407, 1688,
1619 cmꢂ1. Anal. calcd for C58H91NO7: C 76.19, H 10.03, N 1.53; found C 75.92,
H 10.09, N 1.54.
6–10: 2-(Decylcarbamoylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene. TPDLC
1
6–10 was synthesized in yield 88%. H NMR (CDCl3, TMS, 600 MHz) d: 0.87 (t,
J ¼ 6.9 Hz, 3H), 0.92–0.96 (m, 15H), 1.23–1.29 (m, 12H), 1.33–1.44 (m, 22H),
1.55–1.60 (m, 12H), 1.93–1.97 (m, 10H), 3.38 (d, J ¼ 3.3 Hz, 2H), 4.22–4.27 (m,
10H), 4.75 (s, 2H), 7.26 (s, 1H), 7.77 (s, 1H), 7.84 (b, 5H). IR(KBr) v: 3411, 1690,
1618cmꢂ1. Anal. calcd for C60H95NO7: C 76.47, H 10.16, N 1.49; found C 76.38,
H 10.27, N 1.49.
6–11: 2-(Undecylcarbamoylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene. TPDLC
1
6–11 was synthesized in yield 84%. H NMR (CDCl3, TMS, 600 MHz) d: 0.87 (t,
J ¼ 6.9 Hz, 3H), 0.92–0.96 (m, 15H), 1.23–1.29 (m, 14H), 1.33–1.44 (m, 22H),
1.55–1.61 (m, 12H), 1.93–1.97 (m, 10H), 3.38 (d, J ¼ 3.3 Hz, 2H), 4.22–4.27 (m, 10H),
4.75 (s, 2H), 7.26 (s, 1H), 7.77 (s, 1H), 7.84 (b, 5H). IR(KBr) v: 3417, 1689, 1619 cmꢂ1
Anal. calcd for C61H97NO7: C 76.60, H 10.22, N 1.46; found C 76.67, H 10.15, N 1.47.
.

42=[564]
K. Q. Zhao et al.
6–12: 2-(Dodecylcarbamoylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene. TPDLC
1
6–12 was synthesized in yield 87%. H NMR (CDCl3, TMS, 600MHz) d: 0.88 (s,
3H), 0.92–0.96 (m, 15H), 1.23–1.33 (m, 16H), 1.38–1.43 (m, 22H), 1.56–1.60 (m, 12H),
1.93–1.97 (m, 10H), 3.37–3.4 (m, 2H), 4.22–4.27 (m, 10H), 4.75 (s, 2H), 7.26 (s, 1H),
7.77 (s, 1H), 7.84 (b, 5H). IR(KBr) v: 3415, 1689, 1619 cmꢂ1. Anal. calcd for
C62H99NO7: C 76.73, H 10.28, N 1.44; found C 76.46, H 10.32, N 1.43.
6–16: 2-(Hexadecylcarbamoylmethoxy)-3,6,7,10,11-penta(hexyloxy)triphenylene. TPDLC
1
6–16 was synthesized in yield 88%. H NMR (CDCl3, TMS, 600 MHz) d: 0.93–0.96 (m,
18H), 1.23–1.33 (m, 24H), 1.37–1.44 (m, 22H), 1.54–1.60 (m, 12H), 1.93–1.97 (m, 10H),
3.37–3.40 (m, 2H), 4.22–4.27 (m, 10H), 4.75 (s, 2H), 7.26 (s, 1H), 7.77 (s, 1H), 7.84 (b,
5H). IR(KBr) v: 3412, 1689, 1618 cmꢂ1. Anal. calcd for C66H107NO7: C 77.22, H 10.51,
N 1.36; found C 76.76, H 10.35, N 1.34.
3. Results and Discussion
3.1. Synthesis and Characterizations
Hydroxytriphenylenes are key intermediates for the synthesis of functional or poly-
meric TPDLCs [30–37], and 2-Hydroxyl-3,6,7,10,11-pentahexyloxytriphenylene 4 is
an important intermediate for the synthesis of mono-amido-functionalized TPDLCs.
It has been prepared by reacting FeCl3 with 1,2-dihexyloxybenzene 1 and 2-methox-
yphenol. After the reaction, 2-hydroxyl-3-methoxy-6,7,10,11-tetrahexyloxytripheny-
lene 2 [34] and the by-product 2,3,6,7,10,11-hexahexyloxytriphenylene were
obtained, which were then easily separated using flash chromatography 2 was then
treated with 1-bromohexane to form 2-methoxy-3,6,7,10,11-pentahexyloxytripheny-
lene 3, followed by demethylation with Ph2Li to obtain 2-hydroxy-3,6,7,10,11-
pentahexyloxy triphenylene 4 [35].
Comparing with other reported synthetic methods for hydroxytriphenylenes,
this route has the advantage of readily available starting materials, less synthetic
steps, easy experimental operations, isomer separations and product purifications.
Besides, this route also provides moderate yields, and can be easily scaled up to
multi-grams synthesis.
The alkylation of hydroxytriphenylene 4 with ethyl bromoacetate produced 5, it
further reacted with alkylamine yielding the target compounds 6-n. In addition, sev-
eral primary amines we used in the last step were prepared via Gabriel synthesis [29].
3.2. Mesomorphism of Compounds 6-n
We then studied the liquid crystal properties of compounds 6-n using POM installed
with a hot plate as well as using DSC. Except for 6–16 (no mesophase was observed),
all other 6-n compounds were found to possess one columnar mesophase. The phase
transition temperatures and the corresponding enthalpy changes were included in
Table 1. Besides, these TPDLCs were found to have fan-shaped textures (Fig. 2) that
are typically shown by columnar mesophases. The DSC traces of heating and cooling
runs were shown in Figure 3.
Furthermore, most compounds among 6-n only exhibited transition peaks cor-
responding to changes from crystal to liquid crystal then to liquid phases in the DSC
curves. However, interestingly, compounds 6–1, 6–11 and 6–12 showed an extra
transition peak representing a change from crystal to crystal phase during the second

Hydrogen Bonds Stabilized Columnar Mesophase
43=[565]
Table 1. Thermotropic properties of triphenylene discogens, TP(OC6H13)5
(OCH2CONHCnH2nþ1), [n ¼ 1–8, 10, 11, 12, 16]
Mesophases, transition temperature and enthalpy changes
Second heating=ꢀC
(DH, KJ=mol)
First cooling=ꢀC
(DH, KJ=mol)
Compd.
n ¼ 1
Cry271 (3.94) Cry1 79 (38.70)
Colh 133 (5.12) I
I 133 (5.49) Colh 46 (34.78) Cry
n ¼ 2
n ¼ 3
n ¼ 4
Cry 69 (39.45) Colh 138 (6.57) I
Cry 74 (34.63) Colh 141 (6.48) I
Cry 69 (39.97) Colh 143 (7.32) I
I 138 (6.33) Colh 51 (39.00) Cry
I 140 (6.41) Colh 57 (36.23) Cry
I 142 (7.14) Colh 52 (6.85) Cry1 47
(1.02) Cry2
n ¼ 5
n ¼ 6
n ¼ 7
n ¼ 8
n ¼ 10
n ¼ 11
Cry 65 (36.28) Colh 138 (7.05) I
Cry 57 (35.78) Colh 135 (7.24) I
Cry 65 (40.85) Colh 127 (6.13) I
Cry 64 (44.87) Colh 117 (5.37) I
Cry 64 (59.19) Colh 96 (3.99) I
Cry2 62 (26.15) Cry1 67 (10.11)
Colh 88 (3.85) I
I 138 (6.93) Colh 51 (36.22) Cry
I 134 (6.67) Colh 39 (34.59) Cry
I 127 (6.26) Colh 42 (37.67) Cry
I 118 (5.49) Colh 41 (39.94) Cry
I 98 (4.51) Colh 36 (48.38) Cry
I 88 (3.67) Colh 39 (45.09) Cry
n ¼ 12
n ¼ 16
Cry2 54 (2.82) Cry1 58 (21.56)
Colh 77 (2.76) I
Cry 55 (41.35) I
I 75 (2.69) Colh 37 (34.15) Cry
I 40 (38.23) Cry
heating run; and 6–4 also gave an extra transition peak indicating a crystal to crystal
phase change during a second cooling run.
Phase diagrams of compounds 6-n were shown in Figure 4. From the pictures,
the clearing points of compounds 6-n were increasing and arrived at the highest when
n ¼ 4. Then the clearing points started to decrease with the alkyl chain lengthening.
Importantly, the compound 6–12 still demonstrated liquid crystal properties.
Figure 2. Polarising optical photomicrograph of triphenylene discogen. (Figure appears in
color online.)

44=[566]
K. Q. Zhao et al.
Figure 3. DSC traces of triphenylene derivatives, C18H6(OC6H13)5(OCH2CONHCnH2nþ1
)
(n ¼ 1 ꢃ 8, 10, 11, 12, 16): (A) is obtained at 2nd heating, and (B) at 1st cooling, with heating
and cooling rate of 10ꢀC=min.
&
Figure 4. Phase diagram of triphenylene discogens, ( ) C18H6(OC6H13)5(OCH2CONHCn
~
H2nþ1) (m ¼ n þ 3); ( ), C18H6(OC6H13)5(OCmH2mþ1) [28]. (Figure appears in color online.)

Hydrogen Bonds Stabilized Columnar Mesophase
45=[567]
Besides, compound 6–1 had the highest melting point, and compound 6–3, which
possesses the highest molecular symmetry, had the second highest melting point.
Through the formation of intermolecular hydrogen bonds and the lengths varia-
tions of the amide alkyl chains, molecular dipoles of TPDLCs 6-n could be changed.
The mesomorphic ranges of compounds 6–1 to 6–6 tended to change in an odd-even
fashion; and compound 6–6 showed the widest mesomorphic scope, which could be
explained as a result of the equilibrium among intermolecular forces and the molecu-
lar symmetry. Such equilibrium could also be mirrored when an excessive alkyl chain
length was given. When alkyl chains were too long, though molecular flexibility was
increased, its rigidity was dropping down and molecular symmetry was lowered. This
could lower down intermolecular forces and disturb the columnar ordered stackings
of discotic molecules. Hence, mesomorphic ranges got narrowed.
By comparing 6-n with previously reported six-alkyl-chain TPDLCs C18H6(OC6
H13)5(OCmH2mþ1), m ¼ 2 ꢃ 14, 16, 18 [28] that bear the same length of periphery,
though both serieses have similar trends of phase transition temperature changes,
but clearing points and melting points of 6-n are around 30ꢀC, and 5ꢃ10ꢀC higher
than those of the six-alkyl-chain TPDLCs, respectively. Furthermore, 6-n exhibited
wider mesomorphic temperature ranges, which are important for the measurements
of charge carrier mobilities and practical applications of materials as organic
semiconductors.
Besides, 6–12 still possesses liquid crystal property (K 58ꢀC Colh 77ꢀC Iso), but
the six-alkyl-chain triphenylene C18H6(OC6H13)5(OR), as previously reported, began
to lose the mesomorphism from tridecyloxy (C13) [28]. This difference might be
explained by that the amido-TPDLCs, through the formation of intermolecular
hydrogen bonds, had high tendency to form columnar mesophase and can tolerate
with low molecular symmetry caused by lengthening of one peripheral chain. In more
details, in addition to intermolecular p-p interactions and van der Waals forces, intro-
ducing amido functionalities into the alkyl soft chains of triphenylene molecules
could increase dipole interactions and intermolecular hydrogen bonds. These effects
would improve the columnar stackings of discotic molecules, and consequently, the
stability of columnar phases. As a result, it is true that length changes of one alkyl
chains on the triphenylene core could affect the molecular symmetry, which has
adverse effects on mesomorphism; but intermolecular hydrogen bondings could
counteract such adverse effect and stabilize the columnar phases of discogens.
4. Conclusions
In summary, we have synthesized a series of asymmetric TPDLCs bearing amido
functional groups C18H6(OC6H13)5(OCH2CONHCnH2nþ1) and have investigated
their thermotropic liquid crystal properties. We also found that with the increase
of the amido alkyl chain length, clearing points of our TPDLCs were first increased
and then decreased till the loss of mesomorphism when n ¼ 16. By comparing our
TPDLCs with previously reported six-alkoxy-chain TPDLCs [C18H6(OC6H13)5
(OCmH2mþ1)], the introduction of amido group has made our TPDLCs with higher
clearing points and wider mesomorphic temperature ranges. As a result, the one
amido-alkyl-chain TPDLCs, through p-p interaction and van der Waals interaction,
as well as intermolecular hydrogen bonds, could anchor columnar phases and
counteract the adverse effects on discotic mesomorphism brought by the low
molecular symmetry.

46=[568]
K. Q. Zhao et al.
Acknowledgment
This work was supported by the National Natural Science Foundation of China
(Contract No. 50973076).
References
[1] Laschat, S., Baro, A., Steinke, N., Giesselmann, F., Hagele, C., Scalia, G., Judele, R.,
Kapatsina, E., Sauer, S., Schreivogel, A., & Tosoni, M. (2007). Angew. Chem. Int. Ed.,
46, 4832.
[2] Kumar, S. (2004). Liq. Cryst., 31, 1037.
[3] Kumar, S. (2005). Liq. Cryst., 32, 1089.
[4] Sergeyev, S., Pisula, W., & Geerts, Y. H. (2007). Chem. Soc. Rev., 36, 1902.
[5] Wu, J. S., Pisula, W., & Mullen, K. (2007). Chem. Rev., 107, 718.
¨
[6] Shimizu, Y., Oikawa, K., Nakayama, K., & Guillon, D. (2007). J. Mater. Chem., 17,
4223.
[7] Paraschiv, I., Giesbers, M., van Lagen, B., Grozema, F. C., Abellon, R. D., Siebbeles,
L. D. A., Marcelis, A. T. M., Zuilhof, H., & Sudholter, E. J. R. (2006). Chem. Mater.,
18, 968.
[8] Paraschiv, I., de Lange, K., Giesbers, M., van Lagen, B., Grozema, F. C., Abellon, R. D.,
Siebbeles, L. D. A., Sudholter, E. J. R., Zuilhof, H., & Marcelis, A. T. M. (2008).
J. Mater. Chem., 18, 5475.
[9] Paraschiv, I., Tomkinson, A., Giesbers, M., Sudhoter, E. J. R., Zuilhof, H., & Marcelis,
A. T. M. (2007). Liq. Cryst., 34, 1029.
[10] Lehn, J.-M. (2002). Science, 295, 2400.
[11] Kato, T., Mizoshita, N., & Kishimoto, K. (2006). Angew. Chem. Int. Ed., 45, 38.
[12] Kato, T. (2002). Science, 295, 2414.
[13] Li, M., Yang, Y.-L., Zhao, K.-Q., Zeng, Q.-D., & Wang, C. (2008). J. Phy. Chem. C, 112,
10141.
[14] van Gorp, J. J., Vekemans, J. A. J. M., & Meijer, E. W. (2002). J. Am. Chem. Soc., 124,
14759.
[15] van Gestel, J., Palmans, A. R. A., Titulaer, B., Vekemans, J. A. J. M., & Meijer, E. W.
(2005). J. Am. Chem. Soc., 127, 5490.
[16] Martin-Rapun, R., Byelov, D., Palmans, A. R. A., de Jeu, W. H., & Meijer, E. W. (2009).
Langmuir, 25, 8794.
[17] Bushey, M. L., Nguyen, T. Q., Zhang, W., Horoszewski, D., & Nuckolls, C. (2004).
Angew. Chem. Int. Ed., 43, 5446.
[18] Ishi-I, T., Kuwahara, R., Takata, A., Jeong, Y., Sakurai, K., & Mataka, S. (2006). Chem.
Eur. J., 12, 763.
[19] Gearba, R. I., Lehmann, M., Levin, J., Ivanov, D. A., Koch, M. H. J., Barbera, J.,
Debije, M. G., Piris, J., & Greerts, Y. H. (2003). Adv. Mater., 15, 1614.
[20] Dou, X., Pisula, W., Wu, J., Bodwell, G. J., & Mullen, K. (2008). Chem. Eur. J., 14, 240.
¨
[21] Mizoshita, N., Monobe, H., Inoue, M., Ukon, M., Watanabe, T., Shimizu, Y.,
Hanabusa, K., & Kato, T. (2002). Chem. Commun., 428.
[22] Hirai, Y., Monobe, H., Mizoshita, N., Moriyama, M., Hanabusa, K., Shimizu, Y., &
Kato, T. (2008). Adv. Funct. Mater., 18, 1668.
[23] Zhao, K. Q., Gao, C. Y., Hu, P., Wang, B. Q., & Li, Q. (2006). Acta Chimica Sinica, 64,
1051.
[24] Wang, B. Q., Zhao, K. Q., Hu, P., Yu, W. H., Gao, C. Y., & Shimizu, Y. (2007). Mol.
Cryst. Liq. Cryst., 479, 135.
[25] Yu, W. H., Zhao, K. Q., Wang, B. Q., & Hu, P. (2007). Acta Chimica Sinica, 65, 1140.
[26] Wang, B. Q., Ding, F. J., & Zhao, K. Q. (2008). Acta Chimica Sinica, 66, 627.
[27] Sun, D. G., Ding, F. J., & Zhao, K. Q. (2008). Acta Chimica Sinica, 66, 738.

Hydrogen Bonds Stabilized Columnar Mesophase
47=[569]
[28] Paraschiv, I., Delforterie, P., Giesbers, M., Posthumus, M. A., Marcelis, A. T. M.,
Zuilhof, H., & Sudholter, E. J. R. (2005). Liq. Cryst., 32, 977.
[29] Furniss, B. S., Hannaford, A. J., Smith, P. W. G., & Tatchell, A. R. (1987). Vogel’s Text-
book of practical organic chemistry – 5th ed., John Wiley & Sons: New York, p. 779.
[30] Schulte, J. L., Laschat, S., Vill, V., Nishikawa, E., Finkelmann, H., & Nimtz, M. (1998).
Eur. J. Org. Chem., 2499.
[31] Boden, N., Bushby, R. J., Cammidge, A. N., Mansoury, A. E., Martin, P. S., & Lu, Z. B.
(1999). J. Mater. Chem., 9, 1391.
[32] Closs, F., Haussling, L., Henderson, P., Ringsdorf, H., & Schuhmacher, P. (1995).
J. Chem. Soc. Perkin Trans. 1, 829.
[33] Wright, P. T., Gillies, I., & Kilburn, J. D. (1997). Synthesis, 1007.
[34] Kumar, S., & Manickam, M. (1998). Synthesis, 1119.
[35] Zhao, K., Yang, G., Yu, W., Wang, B., & Hu, P. (2009). Chin. J. Org. Chem., 29, 2017.
[36] Xing, C., Lam, J. W. Y., Zhao, K., & Tang, B. Z. (2008). J. Polym. Sci. A Polym. Chem.,
46, 2960.
[37] Wan, W., Monobe, H., Tanaka, Y., & Shimizu, Y. (2003). Liq. Cryst., 30, 571.