Synthesis and characterization of triphenylene derivatives containing two terminal functional groups at the periphery

Article abstract of DOI:10.1080/15421400801915084

Three novel series of triphenylene-based derivatives possessing functional group (ester, carboxylic acid, or hydroxy) at the ends of two aliphatic chains on the opposite position of triphenylene core have been synthesized and studied on mesomorphic proper

Full text of DOI:10.1080/15421400801915084

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Synthesis and Characterization
of Triphenylene Derivatives
Containing Two Terminal
Functional Groups at the
Periphery
a
a
a
a
W. Wan , P. Y. Wang , H. Zh. Jiang & J. Hao
a
Department of Chemistry , Shanghai University ,
Shanghai, China
Published online: 22 Sep 2010.
To cite this article: W. Wan , P. Y. Wang , H. Zh. Jiang & J. Hao (2008) Synthesis and
Characterization of Triphenylene Derivatives Containing Two Terminal Functional
Groups at the Periphery, Molecular Crystals and Liquid Crystals, 482:1, 42-56, DOI:
10.1080/15421400801915084
To link to this article: http://dx.doi.org/10.1080/15421400801915084
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Mol. Cryst. Liq. Cryst., Vol. 482, pp. 42–56, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400801915084
Synthesis and Characterization of Triphenylene
Derivatives Containing Two Terminal Functional
Groups at the Periphery
W. Wan, P. Y. Wang, H. Zh. Jiang, and J. Hao
Department of Chemistry, Shanghai University, Shanghai, China
Three novel series of triphenylene-based derivatives possessing functional group
(ester, carboxylic acid, or hydroxy) at the ends of two aliphatic chains on the
opposite position of triphenylene core have been synthesized and studied on meso-
morphic properties. Their chemical structures were characterized by FT-IR,
1
13
H-NMR, C-NMR, MS, and the thermotropic liquid crystalline properties were
also investigated by polarizing optical microscopy, differential scanning calor-
imetry, and X-ray diffraction. It is found that the triphenylene derivatives contain-
ing terminal carboxylic acid or hydroxyl chains in the series of 9 or 10 show
themortropic columnar mesophase, while the corresponding derivatives possessing
terminal esters don’t show any mesomorphism.
Keywords: columnar mesophase; discotic; liquid crystal; triphenylene
INTRODUCTION
Discotic liquid crystals are usually composed of disk-shaped molecules
with aliphatic tails. A variety of mesophase, such as discotic nematic
phase, ordered hexagonal phases, tilted columnar phases, rectangular
disordered columnar phases, plastic columnar phases, and highly
ordered helical phases have been observed in discotic liquid crystals
[
1]. Such columnar structures are characteristic for rapid one-
dimensional transport of excitons or charge carriers, which makes
discotic liquid crystal materials potentially applicable in the areas of
one-dimensional conductors, light-emitting diodes, phototconductors,
information storage, field effect transistors, and high-resolution
Received September 4, 2007; accepted December 5, 2007.
Address correspondence to Dr. W. Wan, Department of Chemistry, Shanghai
University, Shangda Road 99, Shanghai 200444, China. E-mail: wanwen@staff.shu.edu.cn
4
2

Synthesis of Triphenylene Derivatives
43
xerography, photovoltaic solar cells etc. [2–6]. Conductivity along
the columns in columnar mesophases has been reported to be several
orders of magnitude greater than that in the perpendicular
direction [7].
Triphenylene derivatives are one of the best and longest studied
families of discotic liquid crystals, due to their high tendency to form
the required columnar phases and the presence of large conjugated
aromatic molecular core with a large delocalized p-electron system
[
8–10]. Triphenylene-based discotic liquid crystals have also been
extensively studied for various physical properties, such as one-dimen-
sional charge and energy migration, electroluminescence, ferroelectric
switching, alignment, and self-assembling behavior on surfaces and
other properties [11–13].
But many of those potential applications require thin films of poly-
meric discotic liquid crystals. The prerequisite to study the properties
of polymers is to synthesize asymmetrically-substituted discotic mono-
mers as precursor molecules for polymeric discotics [14,15]. So far, the
asymmetrical functionalization of triphenylene can be achieved either
by sophisticated synthetic routes or by statistical methods involving
partial alkylation of the hexaacetoxy-triphenylene or partial ether
cleavage of hexaalkoxytriphenylene [16,17]. These methods would
definitely result in a mixture of inseparable isomers of ill-defined
structure. However, an efficient way to the synthesis of unsymmetri-
cally substituted ethers of triphenylene derivatives has been
developed and reported by Boden [18,19], to obtain highly-pure func-
tionalized triphenylene derivatives using the iron (III) chloride
mediated coupling of a dialkyloxybene to a tetraalkoxybiphenyl, fol-
lowed by a reductive work-up.
In our previous work, triphenylene derivatives containing ter-
minal ester or carboxylic acid groups at neighboring position on tri-
phenylene core have been reported [20,21], which shows that the
mesomorphic phase can be stabilized by strong intermolecular
hydrogen-bonding interaction. Here, Boden’s strategy for the syn-
thesis of unsymmetrically substituted triphenylene derivatives was
adopted in this work. Novel triphenylene derivatives possessing
opposite terminal functional chains are designed and synthesized
with an improved synthetic process of the required dialkoxy-
biphenyl. Application of tosylate group, not acetate group, in the
synthesis of biphenyl in this work results in large-scale and a con-
venient process for preparation of alkoxybiphenyl and pure func-
tional triphenylene derivative, which overcame the difficulties of
poor yield, limited scale and a mixture of inseparable isomers of
ill-defined structure.

4
4
W. Wan et al.
EXPERIMENTAL PROCEDURES
The synthetic route to the triphenylene derivatives 9 containing
unsymmetrically substituted carboxylic acid chains and 10 containing
hydroxyl group is outlined in Scheme I. Compound 1 was prepared by
tosylation of anisole, instead of acetylation [21], which shows high
orienting effect on the iodation at the metaposition of tosylate. Thus,
satisfactory yield and convenient purification process of compound 3
were obtained by iodination and hydrolysis of 1. An unsymmetrical
ꢀ
SCHEME I (a). TosCl, Et N, 15 C, 6 h, 96%; (b) ICl, HAc, ZnCl , 92%;
3
2
(
(
c) KOH, Ethanol reflux, 87%; (d) C
5
H
11Br, K
, 74%; (g) Ph
, EtOH, reflux; (i) KOH, EtOH; (j) LiAlH
4
2
CO
3
, Ethanol, reflux, 86%;
ꢀ
e) Cu powder, 270 C, 54%; (f) FeCl
3
2
PH, n-BuLi, THF, 77%; (h)
, THF.
Br (CH
2
)
n
COOEt, K
2
CO
3

Synthesis of Triphenylene Derivatives
45
triphenylene derivative 6 was synthesized using an iron (III) chloride
0
0
mediated oxidative coupling of 4,4 -dimethoxy-3,3 -bis (pentyloxy)-
biphenyl and 1,2-dipentyloxy benzene, followed by a reductive meth-
anol work-up procedure. Subsequent demethylation with lithium
diphenylphosphide gave the diphenol. Thus, hydrolysis or reduction
of 8 containing ester chain gave 9 and 10, respectively.
General Information
1
13
H-NMR, C-NMR spectra were recorded in CDCl3 on a Bruker
l
AV-500 spectrometer. Chemical shifts for H-NMR spectra are
reported in ppm downfield from TMS (Trimethyl Chlorosilane), chemi-
1
3
cal shifts for C-NMR spectra are reported in ppm relative to internal
1
3
chloroform (d 77.0 ppm for C). Low-resolution mass spectra (MS)
were recorded on a HP5989 mass spectrometer. Infrared (IR) spectra
were recorded on AVATAR 370 FT-IR spectrometer. The transition
temperatures and thermal behavior were determined by differential
scanning calorimetry (DSC) (Net2stch STA409PC, Germany) operated
ꢀ
at a scanning rate of 5 C=min. The mesophases were identified accord-
ing to the textures observed under an Orthlux-II POLBK polarizing
microscope. X-ray diffraction (XRD) studies were conducted with
XRD (Rigaku D=max 2550, CuKa) with a custom-built hot stage, per-
ꢀ
formed over angular ranges of 2h ¼ 4–30 , scanned at a speed of
ꢀ ꢀ
.01 =s and a step of 0.01 .
0
2-Methoxyphenyl 4-Methylbenzenesulfonate (1)
4
-Methylbenzene-1-sulfonyl chloride was added dropwise to the mix-
ture of anisole (37.4 g, 0.34 mol) and triethylamine (300 ml) with stir-
ring over 1 hr and the mixture stirred for a further 5 hrs
ꢀ
maintaining the reaction temperature under 15 C. The solid was fil-
tered and washed by triethylamine and water, afforded 1 (78.3 g,
ꢀ
ꢁ1
9
4%), mp 84.0–85.4 C. IR (KBr), nmax cm : 1597, 1499 s (C=C, in
1
plane, str), 1185s (CꢁO, str), 781,758 (ArꢁH, w). H-NMR (CDCl )
3
d=ppm: 7.52 (dd, 4H, ArꢁH), 7.17 (m, 2H, ArꢁH), 6.88 (m, 2H, ArꢁH),
3
.55 (s, 3H, OCH ), 2.44 (s, 3H, ArꢁCH ).
3
3
2-(Methyloxy)-5-iodophenol (3)
Compound 1 (33 g, 0.12 mol) and anhydrous zinc chloride were dis-
ꢀ
solved in acetic acid (150 mL) and cooled to 10 C. Iodine monochloride
(
25 g, 0.154 mol) in acetic acid (50 mL) was added dropwise, maintain-
ꢀ
ing the reaction temperature between 8 to 13 C. The mixture was

4
6
W. Wan et al.
stirred at room temperature overnight and washed with sodium meta-
bisulfite until the iodine color disappeared, and then washed with
water. The white solid was filtrated in vacuo to give white solid
5
-iodo-2-methoxyphenyl-4-methylbenzenesulfonate 2 (42.5 g, 90%),
ꢀ
ꢁ1
mp 147.5 C. IR (KBr), n
1
cm : 1595, 1493s (C=C, in plane, str),
max
1
184 s (CꢁO, str), 781,758 (ArꢁH, w). H-NMR (CDCl ) d=ppm: 7.62
3
(
d, 2H, ArꢁH), 7.32 (d, 2H, ArꢁH), 7.45 (d, 1H, ArꢁH), 7.41 (s, 1H,
ArꢁH), 6.60 (d, 1H, ArꢁH), 3.55 (s, 3H, OCH ), 2.46 (s, 3H, ArꢁCH ).
3
3
The white solid 2 (30 g) was further dissolved in ethanol (100 mL)
and a solution of sodium hydroxide (20 g) in ethanol (50 mL) and water
(
50 mL) was added. The solution was refluxed for 24 h, allowed to cool,
and carefully acidified with 40% sulfuric acid. The mixture was
extracted with dichloromethane and the organic solutions were dried
(
MgSO ). Removal of solvent in vacuo followed by recrystallization of
4
the residue from ethanol gave a white crystal 3 (15.8 g, 87%), mp
ꢀ
ꢁ1
ꢁ1
1
8
7.3 C. IR (KBr), nmax cm : 3471, 857, 798 cm . H-NMR (CDCl )
3
d=ppm: 7.23 (s, lH, ArꢁH), 7.15 (d, lH, J ¼ 8 Hz, ArꢁH), 6.59 (d, lH,
J ¼ 8 Hz, ArꢁH), 5.58 (s, lH, OꢁH), 3.85 (s, 3H, OCH ).
3
2-(Pentyloxy)-5-iodoanisole (4)
Compound 3 (15.1 g, 0.06 mol) and potassium carbonate (50 g) were
stirred in ethanol (100 mL) for 10 min. n-Bromopentane (10 g, 0.066 mol)
was added and the solution was stirred at room temperature for
3
days. The mixture was acidified with dilute sulfuric acid and
extracted with dichloromethane. The solvents were removed in vacuo
and the residue was recrystallized from ethanol to give white solid 4
ꢀ
ꢁ1
(
14.6 g, 76%), mp 59.4 C. IR (KBr), nmax cm : 1604, 1502 (C=C, in
1
plane, str), 1251s (CꢁO, str), 857, 796, 747 (ArꢁH, w). H-NMR
(
CDCl ) d=ppm: 7.09 (d, lH, ArꢁH), 7.04 (s, lH, ArꢁH), 6.43 (d, lH,
3
ArꢁH) 3.94 (t, 2H, ArꢁH), 3.83 (s, 3H, OCH ), 1.71 (m, 2H,
3
OCH CH ), 1.31 (m, 4H, CH CH ), 0.90 (t, 3H, CH ).
2
2
2
2
3
0 0
,4 -Dimethoxy-3,3 -bis(pentyloxy)biphenyl (5)
4
Compound 4 (12 g, 37.5 mmol) was mixed intimately with copper pow-
ꢀ
der (24 g). The mixture was heated rapidly to 250 C and carefully to
ꢀ
2
70 C, where an exothermic reaction took place causing the tempera-
ꢀ
ture to rise to 320 C. After cooling the mixture was extracted repeat-
edly with dichloromethane (350 mL). The solvent was removed in
vacuo and the residue was recrystallized from methanol to give 5
3.9 g, 54%), mp 69.8 C. IR (KBr), nmax cm : 1610, 1509s (C=C, in
plane, str), 1256s (CꢁO, str), 841, 798 (ArꢁH, w). H-NMR (CDCl )
ꢀ
ꢁ1
(
1
3

Synthesis of Triphenylene Derivatives
47
d=ppm: 7.08 (m, 4H, ArꢁH), 6.90 (d, 2H, ArꢁH), 4.07 (t, 4H, OCH ),
2
3
0
.90 (s, 6H, OCH ), 1.85 (m, 4H, OCH CH ), 1.45 (m, 8H, CH CH ),
3 2 2 2 2
.92 (t, 6H, CH3).
2
,7-Dimethoxy-3,6,10,11-tetra-pentyloxy)triphenylene (6)
Compound 5 (3 g, 7.77 mmol) and 1,2-bis(pentyloxy)benzene (5.83 g,
3.3 mmol) were stirred in dichloromethane (50 mL) and iron (II1)
2
chloride (18.9 g) was added. After stirring for 1 h, the mixture was
poured onto methanol (100 mL) and the resulting solid immediately
filtered off and dried in a desiccator. Purification by column chromato-
graphy (silica gel, petroleum:dichloromethane 4:l) afforded 6 (3.6 g,
ꢀ
þ
ꢁ1
7
3%), mp 102.4 C. MS (ESI, m=z): M 632.7. IR (KBr), nmax cm
:
1
619, 1518s (C=C, in plane, str), 1263s (CꢁO, str), 840 (ArꢁH, w).
1
H-NMR (CDCl ) d=ppm: 7.91 (t, 6H, ArꢁH), 4.21 (dd, 8H, OCH ),
3
2
4
1
.1 (s, 6H, OCH ), 1.95 (m, 8H, OCH CH ), 1.55 (m, 16H, CH CH ),
.0 (t, 12H, CH3).
3
2
2
2
2
2
,7-Dihydroxy-3,6,10,11-tetra(pentyloxy)triphenylene (7)
Diphenylphosphine (2 mL, 11.8 mmol), was dissolved in dry THF
Tetrahydrofuran) (20 mL) and cooled in an ice bath under argon.
Butyllithium (1.6 M in hexanes, 12 mL, 30.7 mmol) was added over
(
1
0 min. Compound 6 (3.0 g, 4.75 mmol) was added and the solution
ꢀ
magnetically stirred at 50–60 C for 4 h and at room temperature over-
night. The mixture was poured onto dilute sulfuric acid and extracted
with ethyl acetate. The solvent was removed in vacuo and the residue
precipitated from dichloromethane with methanol. The precipitate
was filtered off, dried, and purified by column chromatography (silica
gel, petroleum: dichloromethane 1:2) to give 7 (2.2 g, 77%), mp
ꢀ
þ
ꢁ1
1
05.0 C. MS (ESI, m=z): M 604.8. IR (KBr), nmax cm : 3529, 3393
(
(
OꢁH, str), 1615, 1512s (C=C, in plane, str), 1266s (CꢁO, str), 849
1
ArꢁH, w). H-NMR (CDCl ) d=ppm: 7.95 (s, 2H, ArꢁH), 7.8 (s, 2H,
3
ArꢁH), 7.7 (s, 2H, ArꢁH), 5.9 (s, 2H, OꢁH), 4.3 (t, 4H, OCH ), 4.2
2
(
(
t, 4H, OCH ), 1.95 (m, 8H, OCH CH ), 1.55 (m, 16H, CH CH ), 1.0
m, 12H, CH3).
2
2
2
2
2
0
Representative Procedure for the Synthesis of Diethyl-5,5 -
3,6,10,11-Tetrakis(pentyloxy)triphenylene-2,7-diyl)bis(oxy)-
dipentanoate (8b)
(
Compound 7 (0.5 g, 0.83 mmol) was dissolved in ethanol (20 mL),
potassium carbonate (0.165 g, 1.2 mmol) was added and ethyl

4
8
W. Wan et al.
5
-bromopentanoate (0.21 g, 1.0 mmol) was added in drops. The sol-
ꢀ
ution was magnetically stirred at 78 C for 2 days. The mixture was
poured into dilute sulfuric acid and extracted with ethyl acetate.
The solvent was removed in vacuo and the precipitate was purified
by column chromatography (silica, dichloromethane) to give 8 (0.6 g,
7
1
8
ꢀ
þ
ꢁ1
4%), mp 63.7 C. MS (ESI, m=z): M 860.5. IR (KBr), nmax cm
:
734 (C=O, str), 1616, 1514s (C=C, in plane, str), 1262s (CꢁO, str),
1
37 (ArꢁH, w). H-NMR (500 MHz, CDCl ) d=ppm): 7.83 (s, 6H,
3
ArꢁH), 4.28 (m, 12H, J ¼ 6 Hz, OCH ), 4.13 (q, 4H, OCH ), 2.49 (t,
2
2
4
H, CH CO), 2.00–1.93 (m, 16H, OCH CH ), 1.60–1.53 (m, 8H,
2 2 2
CH ), 1.50–1.41 (m, 8H, CH ), 1.24 (t, 6H, J ¼ 6 Hz, CH CH ), 0.98
2
2
2
3
1
3
(
t, 12H, CH CH ). C-NMR (126 MHz, CDCl , d=ppm): 174.1, 149.2,
2 3 3
1
2
49.1, 148.9, 123.7, 107.5, 107.4, 107.3, 51.7, 33.9, 29.3, 29.2, 29.0,
8.6, 28.5, 22.8, 22.7, 21.9, 14.3, 14.2.
0
pentyloxy)triphenylene-2,7-diyl)bis(oxy)-dibutanoate (8a)
Analytical Data for Diethyl-5,5 -(3,6,10,11-Tetrakis
(
ꢀ
þ .
ꢁ1
Mp 63.7 C. MS (ESI, m=z): M 832.9. IR (KBr), nmax cm : 1734s
(
8
C=O, str), 1616, 1514s (C=C, in plane, str), 1262, 1174 (CꢁO, str),
1
37 (ArꢁH, w). H-NMR (500 MHz, CDCl , d=ppm): 7.90 (s, 2H,
3
ArH), 7.88 (s, 2H, ArH), 7.85 (s, 2H, ArH), 4.32 (t, 4H, J ¼ 6 Hz,
OCH ), 4.29–4.24 (m, 8H, J ¼ 6.5 Hz, OCH ), 4.19 (q, 4H, J ¼ 7 Hz,
2
2
OCH ), 2.67 (t, 4H, J ¼ 7 Hz, COCH ), 2.28 (m, 4H, OCH CH ),
2
2
2
2
2
.00–1.95 (m, 8H, OCH CH ), 1.62–1.46 (m, 8H, CH ), 1.30 (t, 6H,
2 2 2
1
3
J ¼ 7 Hz, CH ), 1.02–0.99 (m, 12H, CH ). C-NMR (126 MHz, CDCl
3
3
3,
d=ppm): 173.4, 149.1, 148.9, 148.7, 123.7, 123.6, 107.5, 107.4, 107.2,
6
0.4, 30.7, 29.2, 29.1, 28.5, 28.4, 24.7, 22.6, 22.5, 14.3, 14.1.
0
pentyloxy)triphenylene-2,7-diyl)bis(oxy)-dihexanoate (8c)
Analytical Data for Diethyl-5,5 -(3,6,10,11-Tetrakis
(
ꢁ
1
Liquid 81%. IR (KBr), nmax cm : 1736 s (C=O, str), 1616, 1519s (C=C,
1
in plane, str), 1262, 1172 (CꢁO, str), 840 (ArꢁH, w). H-NMR
(
500 MHz, CDCl , d=ppm): 7.83 (s, 6H, ArH), 4.23 (m, 12H, OCH ),
3 2
4
.13 (q, 4H, J ¼ 7 Hz, OCH ), 2.38 (t, 4H, J ¼ 7 Hz, COCH ), 2.28
2
2
(
m, 4H, OCH CH ), 1.90 (m, 16H, CH ), 1.62–1.46 (m, 20H, CH ),
2 2 2 2
1
.30 (t, 6H, J ¼ 7 Hz, OCH CH ), 0.98 (t, 12H, J ¼ 7 Hz, CH ).
2
3
3
1
3
C-NMR (126 MHz, CDCl d=ppm): 173.6, 149.0, 148.9, 148.8,
3
,
1
2
23.7, 123.6, 123.5, 107.4, 107.3, 107.2, 60.3, 34.3, 32.2, 29.2, 28.4,
6.4, 24.8, 22.6, 14.3, 14.1.

Synthesis of Triphenylene Derivatives
49
Representative Procedure for the Synthesis
of 5,5 -(3,6,10,11-Tetrakis(pentyloxy)triphenylene-
0
,7-diyl)bis(oxy)-dipentanoic acid (9b)
2
Compound 8b (1.5 g, 1.74 mmol) was dissolved in ethanol (20 mL) and
a solution of potassium hydroxide (1.5 g, 26.8 mmol) in ethanol (20 mL)
and water (10 mL) was added. The solution was refluxed for 24 h,
allowed to cool, and carefully acidified with 20% sulfuric acid. The
mixture was extracted with dichloromethane and the organic solu-
tions were dried (MgSO ). The solvent was removed in vacuo and
4
the precipitate was further purified by column chromatography (silica
gel, petroleum:ethyl acetate 5:2) to give 9b (1.0 g, 71%). MS (ESI,
þ
ꢁ1
m=z): M 804.7. IR (KBr), nmax cm : 3448–2500 (COOH, str), 1706
(
C=O, str), 1619, 1517s (C=C, in plane, str), 1262s (CꢁO, str), 836
1
(
ArꢁH, w). H-NMR (500 MHz, CDCl , d=ppm): 11.45 (s, 2H, COOH),
3
7
2
1
.82 (s, 6H, ArꢁH), 4.26–4.21 (m, 12H, OCH ), 2.53 (t, 4H, CH CO),
2
2
.02–1.92 (m, 16H, OCH CH ), 1.60–1.53 (m, 8H, CH CH ), 1.59–
2
2
2
2
1
3
.41 (m, 8H, CH ), 1.00 (t, 12H, CH ). C-NMR (126 MHz, CDCl3,
2
3
d=ppm): 179.4, 149.0, 148.9, 148.7, 123.7, 123.6, 123.5, 107.3, 107.2,
1
07.0, 33.8, 29.2, 29.1, 28.7, 28.4, 22.6, 22.5, 21.7, 14.1.
0
Analytical Data for 5,5 -(3,6,10,11-Tetrakis(pentyloxy)
triphenylene-2,7-diyl)bis(oxy)-dibutaonic acid (9a)
þ .
ꢁ1
Yield 65%. MS (ESI, m=z): M 776 IR (KBr), nmax cm : 3442–2500br
(
1
COOꢁH, str), 1708 (C=O, str), 1618, 1517s (ArC=C, in plane, str),
1
173 (CꢁO), 837 (ArCꢁH, w). H-NMR (500 MHz, CDCl , d=ppm):
3
1
0.53 (s, 2H, COOH), 7.93 (s, 2H, ArH), 7.90 (s, 2H, ArH), 7.87 (s, 2H,
ArH), 4.17 (t, 4H, OCH ), 4.11 (t, 4H, OCH CH ), 2.52 (t, 4H, CH CO),
2
2
2
2
2
1
.06–2.01 (m, 4H, OCH CH ), 1.79–1.72 (m, 8H, CH ), 1.47–1.29 (m,
2 2 2
1
3
6H, CH ), 0.85–0.82 (m, 12H, CH ). C-NMR (126 MHz, CDCl3,
2
3
d=ppm): 173.7, 149.2, 149.1, 148.9, 123.7, 123.6, 123.5, 107.4, 107.1,
1
07.0, 29.8, 28.4, 24.8, 22.4, 13.6, 13.5.
0
Analytical Data for 5,5 -(3,6,10,11-Tetrakis(pentyloxy)-
triphenylene-2,7-diyl)bis(oxy)-dihexanoic acid (9c)
þ .
ꢁ1
Yield 69%. MS (ESI, m=z): M
2
832. IR (KBr), nmax cm : 3450–
500br (COOH, str), 1707 (C=O, str), 1617, 1518s (ArC=C, in plane,
1
str), 1261, 1172s (CꢁO, str), 837 (ArꢁH, w). H-NMR (500 MHz,
1
CDCl , d=ppm): H-NMR (500 MHz, CDCl , d=ppm): 7.81 (s, 6H,
3
3
ArH), 4.21 (m, 12H, OCH ), 2.43 (t, 4H, COCH ), 1.97–1.90 (m, 12H,
2
2
OCH CH ), 1.78 (m, 4H, CH ), 1.64 (m, 4H, CH ), 1.54 (m, 4H,
2
2
2
2

5
0
W. Wan et al.
13
CH ), 1.46 (m, 4H, CH ), 0.97 (t, 12H, CH ). C-NMR (126 MHz,
2
2
3
CDCl3, d=ppm): 177.8, 149.3, 149.2, 149.0, 123.9, 123.8, 123.7, 107.8,
1
07.7, 107.5, 33.8, 33.1, 29.3, 29.2, 28.5, 25.9, 24.7, 22.7, 22.6, 14.3.
0
Representative Procedure for the Synthesis of 5,5 -
(3,6,10,11-Tetrakis(pentyloxy)triphenylene-2,7-
diyl)bis(oxy)dipentan-1-ol (10b)
A solution of compound 8b (1.5 g, 1.74 mmol) in dry THF (10 mL) was
added dropwisely to a mixture of LiAlH (0.5 g, 0.85 mmol) and THF
4
(
(
10 mL) under ice bath. After refluxed for 2 hrs, Na SO ꢂ 10H O
2
4
2
10 g, 32 mmol) was added to the mixture. The crude product was
obtained by extracted by CHCl and further purified by column chro-
3
matography (silica gel, CHCl :EtOAc 1:1) to give 10b (0.8 g, 59%). MS
3
þ .
ꢁ1
ꢁ1
(
ESI, m=z): M 776. IR (KBr), nmax cm : IR (KBr, cm ) nmax: 3421
(
1
OꢁH), 2952, 2929, 2859 (CꢁH), 1618, 1517 (C=C, in plane, str), 1262,
1
173 (CꢁO), 836 (w, ArꢁH, out of plane). H-NMR (500 MHz, CDCl ,
3
d=ppm): 7. 82 (s, 6H, ArH), 4.26–4.22 (m, 12H, OCH ), 3.72 (t, 4H,
2
J ¼ 6 Hz, OCH ), 2.00–1.96 (t, 12H, OCH CH ), 1.74–1.66 (m, 10H,
2
2
2
CH ), 1.60–1.42 (m, 8H, CH ), 0.98 (t, 12H, J ¼ 8.5 Hz, CH ).
2
2
3
13
C-NMR (126 MHz, CDCl d=ppm): 149.0, 148.7, 148.8, 123.7,
3
,
1
2
23.5, 107.3, 107.2, 107.1, 69.7, 69.4, 69.5, 62.8, 32.5, 29.2, 29.1,
8.4, 28.3, 22.6, 22.5, 14.2.
0
,7-diyl)bis(oxy)dibutan-1-ol (10a)
Analytical Data for 4,4 -(3,6,10,11-Tetrakis(pentyloxytriphenylene-
2
þ
ꢁ1
Yield 59%. MS (ESI, m=z): M 748. IR (KBr), nmax cm : 3445 (OꢁH),
2
8
952, 2928, 2862 (CꢁH), 1618, 1517 (C=C, in plane, str), 1262 (CꢁO),
1
36 (w, ArꢁH, out of plane). H-NMR (500 MHz, CDCl , d=ppm):
3
&
7.83 (s, 2H, ArH), 7.82 (s, 2H, ArH), 7.80 (s, 2H, ArH), 4.29 (t, 4H,
J ¼ 6 Hz, OCH ), 4.23 (t, 8H, J ¼ 6.5 Hz, OCH ), 3.80 (t, 4H, J ¼ 6 Hz,
2
2
Hz, OCH ), 2.10–2.06 (m, 4H, OCH CH ), 1.99–1.85 (m, 12H, CH ),
2
2
2
2
13
1
(
.60–1.42 (m, 16H, CH ), 0.98 (t, 12H, J ¼ 8.5 Hz, CH ). C-NMR
2
3
126 MHz, CDCl , d=ppm): 149.1, 148.7, 148.4, 123.6, 123.5, 123.4,
3
1
2
07.3, 106.6, 106.4, 69.7, 69.4, 69.3, 62.4, 30.1, 29.2, 29.0, 28.4, 25.9,
2.6, 22.5, 14.2, 14.1.
0
,7-diyl)bis(oxy)dihexan-1-ol (10c)
Analytical Data for 6,6 -(3,6,10,11-Tetrakis(pentyloxy)triphenylene-
2
þ
ꢁ1
Yield 64%. MS (ESI, m=z): M 804.9. IR (KBr), nmax cm : 3510
(
OꢁH), 2955, 2934, 2860 (CꢁH), 1614, 1511 (C=C, in plane, str),

Synthesis of Triphenylene Derivatives
51
1
1
264, 1170 (CꢁO), 837 (w, ArꢁH, out of plane). H-NMR (500 MHz,
CDCl , d=ppm): 7.83 (s, 6H, ArH), 4.24–4.22 (m, 12H, OCH ), 3.69 (t,
3
2
4
2
H, J ¼ 6.5 Hz, OCH ), 1.98–1.92 (m, 12H, OCH CH ), 1.66–1.42 (m,
2
2
2
13
8H, CH ), 0.98 (t, 12H, J ¼ 8.5 Hz, CH ). C-NMR (126 MHz, CDCl ,
2
3
3
d=ppm): 149.0, 148.9, 148.4, 123.7, 123.6, 107.4, 107.3, 69.7, 69.5, 69.4,
2.9, 32.8, 29.4, 29.2, 29.1, 28.4, 28.3, 26.0, 25.6, 22.6, 22.5, 14.2.
6
RESULTS AND DISCUSSION
Thermal behaviors of three triphenylene-based series of 8a–c, 9a–c,
and 10a–c were studied by DSC and the phase texture is investigated
under crossed polarizing optical microscope (POM) with custom hot-
stage. Results show that none of 8a, 8b, 8c, which contain two
terminal ester chains at periphery, can exhibit thermotropic liquid
crystalline behavior on heating and cooling run. However, columnar
mesophase was observed in the series of 9a, 9b, 9c, in which terminal
carboxylic acid chains substitute terminal ester chains in the corre-
sponding series of 8a, 8b, 8c. It is found that mesophase can’t be
observed in compounds 9a and 9c on heating under polarizing
microscopy, which was also confirmed by DSC measurements that
only one endothermic peak was found on heating process. However,
fine fan-shape texture for 9a and 9c was seen under POM on cooling
from isotropic phase. And also, it is found that this monotropic colum-
nar phase was so unstable that crystallization behaviors began while
the columnar mesophase appeared on slow cooling from isotropic
ꢀ
phase. The columnar texture for 9c taken under POM at 104 C was
given in Figure 1. Crystallization behavior could be clearly observed
from Figure 1 while the fan-shape domains appeared on cooling from
isotropic phase.
As for compound 9b, the DSC measurements show two endothermic
ꢀ
ꢀ
peaks at around 107.3 C and 116.3 C, respectively, on first heating
ꢀ
run. On cooling, only one exothermic peak was observed at 113.6 C
(
Fig. 2).
The study of liquid crystalline properties on 9b was further determ-
ined by POM. It is found that compound 9b exhibits two phase transi-
tions of solid state-mesophase and mesophase-isotropic phase on
ꢀ
heating, which correspond to the result of DSC at 107.3 C and
ꢀ
1
1
16.3 C, respectively. On cooling the isotropic phase at around
00 C, a well-defined texture of columnar mesophase appeared
Fig. 3), which corresponds to the exothermic peak at 113.6 C by
ꢀ
ꢀ
(
DSC. No crystallization peak down to room temperature was found
in DSC, which was also confirmed by the observation of the stable
mesomorphic texture at room temperature for a few hours on cooling.

5
2
W. Wan et al.
FIGURE 1 Texture of 9c obtained with a polarizing microscope on cooling at
ꢀ
1
04 C (ꢃ200).
The exact nature for the columnar mesophase was deduced by
detailed powder XRD studies for 9b. Figure 4 shows XRD patterns
ꢀ
for 9b at 90 C. It is typical for a hexagonal columnar (Col ) mesophase,
h
which is often obtained for the untreated low molecular mass discotic
liquid crystals in the Col mesophase [22,23], and this pattern for 9b is
h
comparable with those. The lattice constant ahex for 9b was calculated
ꢀ
FIGURE 2 The DSC traces of 9b on heating and cooling (scan rate 5 C
ꢁ
1
min ).

Synthesis of Triphenylene Derivatives
53
FIGURE 3 Texture of 9b obtained with a polarizing microscope on cooling at
ꢀ
1
00 C (ꢃ200)
˚
to be 20.4 A, which is much smaller than the estimated diameter of a
˚
fully extended 9b (28.5 A). Two additional reflections were also
˚
˚
observed at c.4.4 A (broad halo) and c.3.6 A (weak peak), which are
assigned to the average distance of the molten alkyl chains and the
intracolumnar order, respectively. These results strongly indicate
the existence of an ordered hexagonal columnar mesophase (Colho)
of compound 9b.
Meanwhile, TG (Thermogravimetry analysis) results showed that
ꢀ
the synthesized compound 9b had a high thermal stability until 340 C.
ꢀ
FIGURE 4 X-RD of 9b at 90 C on cooling.

5
4
W. Wan et al.
For the series 10a–c, which possessing two terminal hydroxy chains
at the periphery of the triphenylene core, only monotropic columnar
mesophases could be observed for the compounds 10a and 10c. Typical
fan-shape texture was observed under polarizing microscopy. How-
ever, 10b didn’t show any mesomorphism by studying its DSC curve
and observation under POM.
The phase transition and enthalpy of the three series of 8, 9, and 10
are summarized in Table 1.
As only the two series of 9 and 10 show thermotropic columnar
mesophase, it can be inferred from Table 1 that the strong intermole-
cular hydrogen bonding interaction of functional group of carboxylic
acids, or the intermolecular hydrogen bonding interaction between
hydroxyl groups, which are at the end of the aliphatic chain of the tri-
phenylene core, would contribute to the formation of columnar meso-
phase. As the hydroxyl bonding interaction between carboxylic acids
is stronger than that between hydroxyl group, thus, the series 9,
which have terminal carboxylic acid chains, exhibit more stable meo-
sphase than the series 10, which contain terminal hydroxyl chains.
The effect of hydrogen bonding interaction on the mesomorphism is
under study.
In conclusion, we have synthesized a new kind of triphenylene
derivatives containing two terminal ester, carboxylic acid and
hydroxyl chains on the opposite position of discotic triphenylene core.
None of the compounds 8a, 8b, 8c, possessing ester chains, shows
TABLE 1 Transition Temperatures and Enthalpies of 8, 9 and 10
ꢀ
DH=kJ ꢂ molꢁ1
Compounds
Phase transition
Temperatures ( C)
8
8
8
9
a
b
c
a
Cr—Iso
Cr—Iso
—
Cr—Iso
63.1
70.0
—
48.93
40.33
—
a
147.7
135.5
107.3
116.3
115.5
107.8
100.4
95.0
43.15
3.05
53.06
2.28
60.73
2.84
41.25
3.42
(
Col
Cr—Col
Col —Iso
Cr—Iso
Col -Iso)
Cr—Iso
h
-Iso)
9
b
c
h
h
9
(
h
1
0a
(
Col-Iso)
Cr—Iso
Cr—Iso
1
1
0b
0c
91.7
80.3
75.5
37.99
45.62
2.89
(
Col-Iso)
a
Liquid at room temperature.

Synthesis of Triphenylene Derivatives
55
mesomorphism, while most of the corresponding triphenylene deriva-
tives containing carboxylic acid chains or hydroxyl chains exhibit col-
umnar mesophase. In addition, the suitable length of carboxylic acid
chain on the triphenylene core, for example 9b, is found to show stable
Colho mesophase and exhibits high thermal stability. The three series
of 8, 9, and 10 are also good monomer candidates for the synthesis of
discotic liquid crystals polymers.
ACKNOWLEDGMENTS
This work was supported by the Scientific Research Foundation for
the Returned Overseas Chinese Scholars, State Education Ministry
of China, and Shanghai Municipal Education Commission.
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