Flying-seed-like liquid crystals 5: Liquid crystals based on octakisphenylthiophthalocyanine and their optical properties

Article abstract of DOI:10.1142/S1088424615500479

We have synthesized three novel flying-seed-like liquid crystals based on phthalocyaninato copper(II) (abbreviated as PcCu) substituted by bulky groups {(o-C₁)PhS (i), (m-C₁)PhS (j), [m, p-(C₁)₂]PhS (k)} instead

Full text of DOI:10.1142/S1088424615500479

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2015; 19: 1–12
DOI: 10.1142/S1088424615500479
Published at http://www.worldscinet.com/jpp/
Flying-seed-like liquid crystals 5†: Liquid crystals based
on octakisphenylthiophthalocyanine and their optical
properties
Aya Ishikawaa, Kazuchika Ohta*a◊ and MikioYasutakeb
a Smart Material Science and Technology, Interdisciplinary Graduate School of Science and Technology,
Shinshu University, 1-15-1 Tokida, Ueda, 386-8567, Japan
b Comprehensive Analysis Center for Science, Saitama University, 255 Shimo-okubo, Sakura-ku,
Saitama 338-8570, Japan
Received 15 December 2014
Accepted 11 February 2015
ABSTRACT:We have synthesized three novel flying-seed-like liquid crystals based on phthalocyaninato
copper(II) (abbreviated as PcCu) substituted by bulky groups {(o-C1)PhS (i), (m-C1)PhS (j), [m,p-
(C1)2]PhS (k)} instead of using long alkyl chains, in order to investigate their mesomorphism. Their
phase transition behavior and the mesophase structures have been established by using a polarizing
optical microscope, a differential scanning calorimeter, and a temperature-dependent small angle
X-ray diffractometer. As the results, [(o-C1)PhS]8PcCu (8i), [(m-C1)PhS]8PcCu (8j) and {[m,p-(C1)2]
PhS}8PcCu (8k) show a Coltet.o mesophase at 314.9~362.9°C, a Colro(P2m) mesophase at 287.4~334.2°C
and a Colro(P2m) mesophase at 331.8~386.8°C, respectively. Very interestingly, each of the derivatives
thus exhibits a columnar mesophase at very high temperatures. The mesomorphism is apparently
originated from the novel bulky groups (i~k). It is also noteworthy that the Q-bands of the present PhS-
containing Pc derivatives 8i~8k in THF significantly red-shift by about 35 nm in comparison with those
of the corresponding PhO-containing derivatives in THF.
KEYWORDS: flying-seed-like liquid crystals, metallomesogen, phthalocyanine, columnar mesophase.
broadly categorized into two groups of calamitic liquid
INTRODUCTION
crystals and discotic liquid crystals. The first group of
Liquid crystals are intermediate phases between
calamitic liquid crystals has a rod-like molecular shape,
liquid and crystal as the name suggests, and they have
whereas the second group of discotic liquid crystals
both flexibility of liquid and molecular orientational
found by Chandrasekhar et al. in 1977 [3] has a disk-
order of crystal. From this unique fascinating nature,
like molecular shape. Both groups of the liquid crystals
many liquid crystals have been synthesized since the first
commonly have long alkyl chains in periphery and a flat
liquid crystals were discovered by Reinitzer in 1888 [1,
central core. Accordingly, people have long believed that
2]. Liquid crystals may be originated from orientational
liquid crystals should have both a rigid central core and
order of the rigid central core parts and fluidity of the
flexible peripheral alkyl chains. However, a very few
molten peripheral long alkyl chains. Therefore, they can
liquid crystals being out of this common sense have been
show both characteristics of liquid and crystal. Almost
reported [4–12].
all the liquid-crystalline materials know up to date can be
In 1910 Vorländer reported that potassium dime-
thylacetate ((CH3)2CHCOOK: 1 in Fig. 1a), potassium
diethylacetate ((C2H5)2CHCOOK: 2) and sodium diphe-
◊ꢀSPP full member in good standing
nylacetate (Ph2CHCOONa: 3) show liquid crystalline
property (= mesomorphism) [4]. These alkali metal
carboxylates have neither a rigid central core nor flexible
*Correspondence to: Kazuchika Ohta, email: ko52517@
shinshu-u.ac.jp, tel: +81 268-21-5492, fax: +81 268-21-5492
†Part 4: Ref. 17 in this paper.
Copyright © 2015 World Scientific Publishing Company

2
A. ISHIKAWA ET AL.
(a)
X
(b)
a: X =
b: X =
c: X =
H
H
CH3
O-
C2H5
H3C
O
C2H5
C
C
C
C
O
CH3
CH3
1
2
X
Colh
O
O-
N
N
N
N
K+
K+
O
Cu N
N
O
X
SmA
SmA
N
N
CH3
H
O
CH3
CH3
CH3
C
C
Colrh
X =
d:
X
3
O
O-
4
Na+
Colh
H3C
H3C
H3C
CH3
CH3
CH3
CH3
CH3
CH3
O
O
H
H
O
(c)
HOOC
O
O
O
N
O
5d
X
(d)
X
O
O
CH3
b:
X =
X =
O
O
O
O
CH3
Tb
O
O
Colr
CH3
d:
CH3
CH3
O
X
6
H3CO
(e)
monotoropi
c Colro
e:
f:
X =
X =
[(o-C1)PhO]8PcCu
[(m-C1)PhO]8PcCu
X
O
X
OCH3
O
Colro
N
N
N
N
X
X
X
X
N
M
N
N
g:
X =
O
OCH3
[(p-C1)PhO]8PcCu
K
N
M = Cu
OCH3
OCH3
X
X
h:
X =
{[m,p-(C1)2]PhO}8PcCu
O
Colro
7
Fig. 1. Flying-seed-like liquid crystals synthesized to date
Copyright © 2015 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2015; 19: 2–12

FLYING-SEED-LIKE LIQUID CRYSTALS 5†
3
peripheral long alkyl chains, but each of them shows
mesomorphism. They are very far from general concept
of liquid crystals and show mesophases only at very high
temperatures. Accordingly, these liquid crystals have
seldom been investigated in detail for about 100 years.
In 2006, we revealed by using temperature-dependent
X-ray diffraction technique that both (CH3)2CHCOOK
(1) and (C2H5)2CHCOOK (2) show a smectic A (SmA)
mesophase and Ph2CHCOONa (3) shows a hexagonal
columnar (Colh) mesophase [9]. Since these liquid
crystalline materials resemble flying-seeds like as a maple
seed, this type of liquid crystals is named as “flying-seed-
like liquid crystals.” They are the third type of liquid
crystals different from calamitic and discotic liquid
crystals. These flying-seed-like liquid crystals may show
mesomorphism by free rotation of the bulky substituents
to form soft parts instead of long alkyl chains [9]. As far
as we know, the other alkali metal carboxylates having no
long alkyl chains have been studied until now by a very
few researchers: Demus et al. in 1970 [5], Sanesi et al. in
1978 [6, 7] and Binnemans et al. in 2005 [8].
In 2009, Usol’tseva and her co-workers found from
polarizing optical microscopic observations that a
phthalocyanine (Pc) derivative substituted by four
triphenylmethyl groups, (3Ph-PhO)4PcCu (4a), depicted
in Fig. 1b shows a mesophase [13, 14]. The substituent of
triphenylmethyl group in this compound very resembles
the molecular structure of Ph2CHCOONa (3) in Fig. 1a.
Therefore, we thought that this Pc derivative might be
one of the flying-seed-like liquid crystals induced by free
rotation of the peripheral bulky substituents. In 2012,
we carried out temperature-dependent X-ray diffraction
studies on these Pc derivatives 4a~4d and revealed
that they show columnar mesophases [15]. Recently,
we reported that introduction of the bulky substituents
to the other cores also induce a nematic mesophase for
Compound 5d in Fig. 1c and a rectangular columnar
mesophase for compounds 6b and 6d in Fig. 1d [16].
Furthermore, we have revealed for novel flying-
seed-like Pc compounds 7e~7h in Fig. 1e that their
mesomorphism is originated from flip-flop of bulky
substituents and greatly depend on the substitution
position of methoxy group [17]. In these compounds, two
adjacent phenoxy groups cannot freely rotate but flip-flop
within the restricted angles. However, when this phenoxy
group is further substituted by (a) methoxy group(s) at
the o, m, p positions, the resulting bulkier phenoxy group
originates bigger excluded volume for the derivatives by
the flip-flop. Accordingly, mesomorphism may be also
induced not only by free rotation but also by flip-flop of
bulky substituents. As the results, [(o-C1)PhO]8PcCu
(7e) shows a monotropic Colro(P2m) mesophase; [(m-C1)
PhO]8PcCu (7f) and {[m,p-(C1)2]PhO}8PcCu (7h) show
enantiotropic columnar mesophases of Colro(P21/a),
whereas [(p-C1)PhO]8PcCu (7g) show no mesophase.
Thus, the derivative (7g) substituted by a methoxy group
at a para position does not show mesomorphism, because
the excluded volume originated by the flip-flopping
substituent is small. On the other hand, the derivatives
substituted by (a) methoxy group(s) at (a) meta position(s)
(7f and 7h) show enantiotropic mesomorphism, because
the excluded volume is big enough. The derivative (7e)
substituted by a methoxy group at an ortho position
shows monotropic mesomorphism, because the excluded
volume is big enough but the steric hindrance may
block the stacking the central Pc cores. Thus, we could
successfully induce their mesomorphism by using a novel
series of bulky substituents. These novel mesophase-
inducing groups (e, f and h) are more advantageous
in synthesis of flying-seed-like liquid crystals than the
previous mesophase-inducing groups (a~d), because the
synthesis becomes much easier. The target compounds
7e~7g could be prepared in only two steps from the
starting material.
If this new type of flying-seed-like liquid crystals may
additionally exhibit fast charge mobility, we can easily
obtain donor semiconductor liquid crystals at very high
temperatures. They may extremely improve thermal
stability of organic thin film solar cells. Phenylthio
group may possess a band gap of the HOMO–LUMO
narrower than that of phenoxy group, so that the charge
carrier mobility may be improved. It can be deduced
from the analogy between the Pc derivatives substituted
by alkylthio group and/or alkoxy group [18]. The charge
carrier mobility of the alkylthio-substituted liquid crystal,
(C12S)8PcH2, is 5 times higher than that of the alkoxy-
substituted liquid crystal, (C12O)8PcH2 [19]. Therefore
we can expect that if novel phenylthio-substituted Pc
liquid crystals could be synthesized, they would show
very fast charge carrier mobilities.
In this study, we have synthesized three novel
flying-seed-like liquid crystals based on octaphenythio-
phthalocyaninato copper(II) (abbreviated as (PhS)8PcCu)
inwhicheachofthephenylthiogroupisfurthersubstituted
by (a) methoxy group(s) at the o, m, p positions, in order
to investigate the mesomorphism and electronic spectral
properties. Up to date, a few derivatives based on
(PhS)8PcCu have been reported [20, 21], and there have
never been reports of the mesomorphism. We believe that
this study may contribute to further develop the field of
flying-seed-like liquid crystals which is still in infancy.
EXPERIMENTAL
Synthesis
In Scheme 1 is shown synthetic route for novel
flying-seed-like liquid crystals based on (PhS)8PcCu.
The starting materials of 4,5-dichlorophthalonitrile,
o-methoxythiophenol (9i), m-methoxythiophenol (9j)
and m,p-dimethoxythiophenol (9k) were purchased from
Tokyo Kasei. The phthalonitrile derivatives (10i~10k)
were prepared by the method of Wöhrle et al. [22]. Each of
Copyright © 2015 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2015; 19: 3–12

4
A. ISHIKAWA ET AL.
Y
Y
Xm
Cl
CN
CN
Xp
Xo
S
Xm
N
N
N
Xp
Xo
Cl
(ii)
CN
CN
Y
Y
Y
Y
N
Cu
N
N
(i)
S
SH
N
N
9
Xo
Xp
Xm
Y
Y
i
j
k
10
8
Xo
Xm
Xp
MeO
H
H
H
MeO
H
H
MeO
MeO
=
H3CO
S
,
,
Y =
Y =
[(o-C1)PhS]8PcCu
[(m-C1)PhS]8PcCu
i:
j:
OCH3
OCH3
S
S
k:
OCH3
{[m,p-(C1)2]PhS}8PcCu
Y =
Scheme 1. Synthetic route for the flying-seed-like compounds, 8i~8k: (i) K2CO3, DMSO, (ii) CuCl2, DBU, 1-hexanol. DMSO =
dimethylsulfoxide and DBU = 1,8-diazabicyclo[5,4,0]-undec-7-ene
the final (PhS)8PcCu derivatives (8i~8k) was synthesized
by cyclic tetramerization of the phthalonitrile derivatives
(10i~10k). The detailed synthetic procedures are described
belowonlyfortherepresentativephthalocyaninederivative,
[(m-C1)PhS]8PcCu (8j). For the other phthalocyanine
derivatives (8i and 8k) and the precursors (10i and 10k),
only their physical properties are described.
J2 = 1.8 Hz, Ar-S-Ar-H), 7.26 (dd, 2H, J1 = 8.3 Hz, J2 =
1.0 Hz, Ar-S-Ar-H), 7.13~7.11 (m, 4H, Ar-S-Ar-H), 3.83
(s, 6H, -CH3).
4,5-Bis(3,4-dimethoxyphenylthio)phthalonitrile
(10k). It was purified by column chromatography (silica
gel, dichloromethane, Rf = 0.13). Yield 61.9%, mp
232.7°C. IR (KBr) n, cm-1 2842.58 (-OCH3), 2227.20
1
4,5-Bis(3-methoxyphenylthio)phthalonitrile
(10j). A mixture of o-methoxythiophenol (9j: 0.372 g,
2.65 mmol), dry DMSO (8 mL) and K2CO3 (3.02 g,
21.9 mmol) was heated at 90°C for 15 min with stirring
under nitrogen atmosphere. Then, to this reaction mixture
was added 4,5-dichlorophthalonitrile (0.245 g, 1.24 mmol)
and it was heated at 90°C for more 1.5 h with stirring under
nitrogenatmosphere.Aftercoolingtort,thereactionmixture
was extracted with chloroform and washed with water. The
organic layer was dried over Na2SO4 and then evaporated
in vacuo. The residue was recrystallized from methanol at
-20°C. The methanolic layer was removed by filtration. The
residue was purified by column chromatography (silica gel,
dichloromethane, Rf = 0.65). After removal of the solvent,
0.307 g of pale yellow solid was obtained. Yield 61.1%,
mp 142.7°C. IR (KBr) n, cm-1 2834.62 (-OCH3), 2226.68
(-CN), 1583.99 (C=C). H NMR ((D3C)2S=O, TMS):
d, ppm 7.21 (dd, 2H, J1 = 8.3 Hz, J2 = 2.0 Hz, Ar-H),
7.17~7.15 (m, 4H, Ar-S-Ar-H), 7.11 (s, 2H, Ar-S-Ar-H),
3.85 (s, 6H, -CH3), 3.80 (s, 6H, -CH3).
[(m-C1)PhS]8PcCu (8j). A mixture of 4,5-bis(3-metho-
xyphenylthio)phthalonitrile (10j) (0.100 g, 0.247mmol),
1-hexanol (5 mL) and CuCl2 (0.0454 g, 0.338 mmol) was
refluxed under nitrogen atmosphere for 0.5 h. Then, DBU
(5 drops) was added to the reaction mixture and it was
refluxed under nitrogen atmosphere for 14 h. After cooling
to rt, methanol was poured into the reaction mixture to
precipitate the target compound. The methanolic layer
was removed by filtration. The residue was washed with
methanol, ethanol and acetone successively to afford
0.0604 g of dark green solid was obtained. Yield 58.2%.
[(o-C1)PhS]8PcCu (8i). Yield 36.0%.
1
(-CN), 1590.62 (C=C). H NMR ((D3C)2S=O, TMS): d,
{[m,p-(C1)2]PhS}8PcCu (8k). Yield 19.7%. MALDI-
TOF mass data for 8i~8k: see Table 1. Elemental analysis
data for 8h: see Table 1. UV-vis spectral data 8i~8k: see
Table 2.
ppm 7.45~7.50 (m, 2H, Ar-H), 7.39 (s, 2H, Ar-S-Ar-H),
7.10 (m, 6H, Ar-S-Ar-H), 3.80 (s, 6H, -CH3).
4,5-Bis(2-methoxyphenylthio)phthalonitrile (10i).
It was purified by column chromatography (silica gel,
chloroform : n-hexane = 4:1, Rf = 0.50). Yield 44.0%,
mp 192.7°C. IR (KBr) n, cm-1 2836.67 (-OCH3), 2225.93
Measurements
1
(-CN), 1583.07 (C=C). H NMR ((D3C)2S=O, TMS): d,
The infrared absorption spectra were recorded by using
a Nicolet NEXUS670 FT-IR. The 1H NMR measurements
ppm 7.61~7.56 (m, 2H, Ar-H), 7.47 (dd, 2H, J1 = 7.8 Hz,
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FLYING-SEED-LIKE LIQUID CRYSTALS 5†
5
Copyright © 2015 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2015; 19: 5–12

6
A. ISHIKAWA ET AL.
were carried out by using aBruker Ultrashield 400 MHz.
TheelementalanalyseswereperformedbyusingaPerkin-
Elmer Elemental Analyzer 2400. The MALDI-TOF
mass spectral measurements were carried out by using
a Bruker Daltonics Autoflex III spectrometer (matrix:
dithranol). Electronic absorption (UV-vis) spectra were
recorded by using a Hitachi U-4100 spectrophotometer.
Phase transition behavior of the present compounds was
observed with a polarizing optical microscope (Nikon
ECLIPSE E600 POL) equipped with a Mettler FP82HT
hot stage and a Mettler FP-90 Central Processor, and a
Shimadzu DSC-50 differential scanning calorimeter.
The mesophases were identified by using a small angle
X-ray diffractometer (Bruker Mac SAXS System)
equipped with a temperature-variable sample holder
adopted a Mettler FP82HT hot stage. Figures S1 and S2
illustrate the setup of the SAXS system and the setup of
the temperature-variable sample holder, respectively. As
can be seen from Fig. S1, the generated X-ray is bent
by two convergence monochrometers to produce point
X-ray beam (diameter = 1.0 mm). The point beam runs
through holes of the temperature-variable sample holder.
As illustrated in Fig. S2, into the temperature-variable
sample holder of Mettler FP82HT hot stage, a glass plate
(76 mm × 19 mm × 1.0 mm) having a hole (diameter =
1.5 mm) is inserted. The hole can be charged with a
powder sample (ca. 1 mg). The measurable range is from
3.0 Å to 100 Å and the temperature range is from rt to
375°C. This SAXS system is available for all condensed
phases including fluid nematic phase and isotropic liquid.
{[m,p-(C1)2]PhS}8PcCu (8k), showed poor solubility
in many solvents. They did not dissolve at all in
chloroform, DMF and DMSO. The electronic absorption
spectra could not be measured in these solvents. THF
gave comparatively better solubility among the other
solvents, so that THF was selected as the measurement
solvent. Although the solutions were prepared in a very
lower concentration at 1.0 × 10-5 M, a small amount
of precipitates were seen in the THF solutions. Hence,
the real concentrations were slightly lower than this
concentration. In spite of the precipitation, the Q-band
peak could be clearly detected independently from the
small aggregation peak. If strong aggregation would
occur, the Q-band peak would be covered by the big
aggregation band. Thus, the Q-band peak could be
observed independently from the aggregation band.
In order to investigate the effect of S and O atoms on
electronicabsorptionwavelength,thespectraofourprevious
PhO-containing derivatives, [(o-C1)PhO]8PcCu (7e), [(m-
C1)PhO]8PcCu (7f) and {[m,p-(C1)2]PhO}8PcCu (7g)
[16],werealsomeasuredinthesamesolventTHF.InTable2
are listed these spectral data as well. As can be seen from
this table, the Q-bands of the PhS-containing derivatives
are located in 709.7~714.2 nm, which were significantly
red-shifted by 34.1~37.5 nm from the Q-bands of the PhO-
containing derivatives located in 675.5~678.0 nm. Q-band
in Pc derivatives corresponds to the band gap between
HOMO and LUMO. Therefore, the PhS group induced
a band gap of the HOMO–LUMO narrower than that of
PhO group, so that we can expect faster charge carrier
mobility for the PhS-substituted PcCu derivatives than that
of the PhO-substituted PcCu derivatives. It can be deduced
from the analogy between the Pc derivatives substituted
by alkylthio group and/or alkoxy group [18]. The charge
carrier mobility of the alkylthio-substituted liquid crystal,
(C12S)8PcH2, is five times higher than that of the alkoxy-
substituted liquid crystal, (C12O)8PcH2 [19].
RESULTS AND DISCUSSION
Synthesis
The compounds synthesized here were characterized
1
by using H NMR, FT-IR, MALDI-TOF mass spectra
(Table 1), elemental analysis (Table 1) and electronic
absorption spectra (Table 2). In the elemental analysis,
all the present (PhS)8PcCu derivatives were much
less flammable than the long alkyl-chain-substituted
(PhO)8PcCu derivatives. Especially, [(o-C1)PhS]8PcCu
(8i) and [(m-C1)PhS]8PcCu (8j) were not completely
burnt out so that the observed carbon content showed
lower percentage than the calculated value by several
percent as the same case of our previous Pc derivatives
[17, 23]. Therefore, these data are omitted in this table.
This is a well-known characteristic of less flammable
phthalocyanine derivatives [24]. However, it could be
confirmedfromtheirMALDI-TOFmassspectrainTable1
and the electronic absorption spectra in Table 2 that the
target derivatives 8i~8k were surely synthesized.
Phase transition behavior
Phase transitions of the present flying-seed-like
(PhS)8PcCu derivatives 8i~8k are summarized in Table 3.
As can be seen from this table, when the freshly
prepared sample of [(o-C1)PhS]8PcCu (8i) was heated
from rt, K1 crystals relaxed into K2 crystals at about
180°C. On further heating, the K2 crystals transformed
into K3 crystals at 301.7°C, and then the K3 crystals
melted into a tetragonal ordered columnar mesophase
(Coltet.o) at 314.9°C. The Coltet.o mesophase cleared
into isotropic liquid at 362.9°C, accompanied by rapid
decomposition.
When the freshly prepared sample of [(m-C1)
PhS]8PcCu (8j) was heated from rt, K1 crystals relaxed
into K2 crystals at about 180°C. On further heating, the
K2 crystals melted into a rectangular ordered columnar
mesophase having a P2m symmetry (Colro(P2m)) at
287.4°C. The Colro(P2m) mesophase cleared into
Electronic absorption spectra
Each of the present PhS-containing derivatives,
[(o-C1)PhS]8PcCu (8i), [(m-C1)PhS]8PcCu (8j) and
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FLYING-SEED-LIKE LIQUID CRYSTALS 5†
7
Table 3. Phase transition temperatures and enthalpy changes of 8i–8k
T, °C [∆H(kJ.mol-1)]
Compound
Phase
Phase
K1
362.9 [2.90]
301.7 [50.1]
314.9 [7.77]
K3
I.L.
(decomp.)
8i: [(o-C1)PhS]8PcCu
8j: [(m-C1)PhS]8PcCu
8k: {[m,p-(C1)2]PhS}8PcCu
ca. 180
Coltet.o
K2
K1
334.2 [6.72]
386.8 [3.23]
287.4 [3.78]
K2
I.L.
ca. 180
Colro(P2m)
Colro(P2m)
(decomp.)
267.7 [1.84]
331.8 [34.0]
K2
I.L.
(decomp.)
K1
Fig. 2. Photomicrographs of K1, K2 and Colho mesophase and DSC thermogram of [(m-C1)PhS]8PcCu (8j) for the 1st heating run at
10°C/min
isotropic liquid at 334.2°C with rapid decomposition.
Figure 2 shows photomicrographs of K1, K2 and
Colro(P2m) mesophase together with a DSC thermogram
of [(m-C1)PhS]8PcCu (8j) for the 1st heating run at
10°C/min. As can be seen from the photomicrographs
in this figure, the freshly prepared (virgin) K1 crystals
were needle-like and the needle-like crystalline shape
maintained in the rigid higher temperature K2 crystals;
on the other hand, the Colro(P2m) mesophase showed
stickiness with birefringence when the cover glass plate
was pressed. As can be seen from the DSC thermogram
in this figure, a big exothermic peak could be observed
at ca. 180°C as the onset temperature. Since it was
not accompanied by a glass transition, the exothermic
peak could be assigned as a relaxation directly from K1
crystals to K2 crystals. The relaxation and the other phase
transitions could be rationally explained by a schematic
free energy vs. temperature (G-T) diagram illustrated in
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8
A. ISHIKAWA ET AL.
Fig. 3. A schematic G-T diagram of [(m-C1)PhS]8PcCu (8j)
Fig. 3. When the freshly prepared virgin sample of K1
crystals is heated from rt to ca. 180°C, the relaxation
from line K1 to line K2 occurs at an uncertain temperature
due to molecular rearrangement which is much easier
at the higher temperatures than at rt; on further heating,
the resulted K2 crystals run along the line K2 to an
intersection at 287.4°C, which is the melting point from
K2 to Colro(P2m). Then, the Colro(P2m) mesophase runs
along the line Colro(P2m) till another intersection at
334.2°C, which is the clearing point of the Colro(P2m)
mesophase. Thus, the thermal behavior can be rationally
explained by using the G-T diagram.
As can be seen from Table 3, when the freshly prepared
sample of {[m,p-(C1)2]PhS}8PcCu (8k) was heated from
rt, it showed not relaxation but a solid-solid (K1-K2) phase
transition at 267.7°C. On further heating, the K2 crystals
melted into a Colro(P2m) mesophase at 331.8°C, and the
Colro(P2m) mesophase cleared into isotropic liquid at
386.8°C with rapid decomposition.
Very interestingly, each of the derivatives thus exhibits
a columnar mesophase at very high temperatures. The
mesomorphism is apparently originated from the novel
bulky groups (i~k).
Fig. 4. Photomicrographs of the mesophases of 8i–8k: (a) 8i: [(o-
C1)PhS]8PcCu at 330°C, (b) 8j: [(m-C1)PhS]8PcCu at 300°C, and
(c) 8k: {[m,p-(C1)2]PhS}8PcCu at 350°C
Polarizing optical microscopic observation
Figure 4 shows photomicrographs of the (PhS)8PcCu
derivatives, 8i~8k. Each of the (PhS)8PcCu derivatives
rapidly decomposed just after clearing into isotropic
liquid, so that it could not give a natural texture which
would be obtained by slow cooling from isotropic liquid.
However, as can be seen from the photomicrographs
in Fig. 4, each of the derivatives was spread to show
stickiness together with birefringence when the cover
glass was pressed at the temperature denoted in this figure
caption. Stickiness with birefringence is characteristic to
mesomorphism. Hence, these states could be identified
as mesophases.
These mesophases were fairly stable under nitrogen
atmosphere during the DSC measurements, but they were
unstable in the air during the POM observations. Figure 5
shows photomicrographs of the Colro(P2m) mesophase
of {[m,p-(C1)2]PhS}8PcCu (8k) at 350°C. As can be
seen from these photomicrographs, rapid decomposition
occurred depending the annealing time. Holding the hot
stage at 350°C in advance, the sample between two glass
plates was put on the hot stage and pressed to spread. The
thin film was immediately observed under a polarizing
optical microscope. Figure 5(a) was a photomicrograph
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J. Porphyrins Phthalocyanines 2015; 19: 8–12

FLYING-SEED-LIKE LIQUID CRYSTALS 5†
9
lost by decomposition. Hence, the present mesophases
of (PhS)8PcCu (8i~8k) are very unstable in the air at
the high temperatures. We should pay attention on this
instability in the air for the temperature-dependent X-ray
diffraction measurements.
Temperature-dependent X-ray diffraction
measurements
Temperature-dependent small angle X-ray diffraction
measurements were carried out by using our originally
developed apparatuses illustrated in Figs S1 and S2. As
illustrated in Fig. S2, a liquid crystalline material was
filled into a hole of glass plate. As already mentioned
above, rapid decomposition of the {[m,p-(C1)2]PhS}8PcCu
(8k) derivative occurred within 5 min at 350°C.
Therefore, holding the hot stage at 350°C in advance,
the glass plate filled the liquid crystalline material 8k in
the hole was put on the hot stage. Immediately after the
hot stage was set on the hot stage holder illustrated in
Fig. S1, the X-ray diffraction measurement was carried
out in 5 min, in order to prevent the decomposition in
the air as possible as we could. In this case, we could
successfully obtain the X-ray diffraction pattern as shown
in Fig. 6(c). Therefore, each of the X-ray measurements
for the (PhS)8PcCu (8i~8k) derivatives was carried out
in 5 min immediately after the sample insertion. The
diffraction patterns of liquid crystal phase and X-ray data
were summarized in Fig. 6 and Table 4, respectively.
Figure 6(a) shows a diffraction pattern of [(o-C1)
PhS]8PcCu (8i) at 340°C. As can be seen from this X-ray
diffraction (XRD) pattern, two reflection peaks were
observed in the region from 2Q = 3° to 7°. The spacings
of these peaks are exactly in a ratio of 1: 1/√2 (Table 4),
which is characteristic of 2D tetragonal symmetry. Broad
halos at 2Q = ca.13 and ca.24 may correspond to thermal
fluctuations of the phenylthio groups and stacking
distance of intracolumnar disks, respectively. Therefore,
this mesophase was identified as a Coltet.o mesophase
(a = 20.0 Å, h 3.76 Å). However, when the number (Z)
of molecules in a lattice was calculated from Z Value
Calculation[25]byusinganassumeddensityr=1.0gcm-3,
the Z value was obtained as 0.54. The Z value should
be 1.0 for a Coltet.o mesophase. Hereupon, we referred
to our previous work on the very similar flying-seed-
like mesogen [(o-C1)PhO]8PcCu [17] for the stacking
distance (h). The previous [(o-C1)PhO]8PcCu derivative
shows a Colro(P2m) mesohase having lattice constants,
a = 20.7 Å, b = 19.2 Å and h = 7.00 Å. This Colro(P2m)
mesohase of [(o-C1)PhO]8PcCu is very close to the
present Coltet mesophase of [(o-C1)PhS]8PcCu, because
it has a ≈ b. Therefore, we thought the stacking distance
of the present [(o-C1)PhS]8PcCu homolog might be also
7.00 Å, although this reflection peak was covered by a
big halo due to thermal fluctuations of the phenylthio
groups (Fig. 6(a)). The stacking distance of 7.00Å is very
long in comparison with the stacking distances usually
Fig. 5. Annealing-time-dependent birefringence of {[m,p-(C1)2]
PhS}8PcCu (8k) at 350°C: (a) for 0 min, (b) for 3 min, and (c) for
5 min
taken immediately after setting on the hot stage. It
clearly shows birefringence. After holding it for 3 min,
the birefringence was losing (Fig. 5(b)), and after 5 min,
the birefringence completely disappeared (Fig. 5(c)). The
birefringence only disappeared without clearing into the
isotropic liquid. This means that the birefringence was
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J. Porphyrins Phthalocyanines 2015; 19: 9–12

10
A. ISHIKAWA ET AL.
unite lattice, Avogadro’s number and molecular weight,
respectively, Z value can be obtained from following
equation:
Z = (rVN)/M = [r(a2 × h)N]/M
= [1.0(g.cm-3) × (20.0 × 10-8 cm)2
ꢀꢀꢀꢀꢀꢀ× (7.00 × 10-8cm) × 6.02 × 1023(mol-1)]/
1681.57(g.mol-1)
= 1.00
(1)
The calculated value Z = 1.0 is the same as the theore-
tical number of molecules in a 2D tetragonal lattice: Z =
1.0. Therefore, this big stacking distance h = 7.00 Å is a
rationally proper value.
However, a very big peak denoted as X appeared in
the very small angle region (d = 77.3 Å) could not be
assigned as a reflection from any 2D lattices for columnar
mesophases known up to date. It may be originated from
helicity of columns [26, 27]. At present time, it is not
clear and we need further study for this peak.
Figure 6(b) shows a diffraction pattern of [(m-C1)
PhS]8PcCu (8j) at 300°C. As can be seen from this
pattern, the mesophase also gave a very big peak X in the
very small angle region (d = 98.5 Å). In the region from
2Q = 3° to 15°, six peaks could be observed. From these
peaks, we could identify this mesophase as a Colro(P2m)
mesophase (Table 4). The lattice constants are a = 20.7 Å,
b = 18.1 Å and h = 6.82 Å. The number (Z) of molecules
in a lattice can be obtained from following equation:
Z = (rVN)/M = [r × (a × b × h) × N}/M
= [1.1(g.cm-3) × (20.7 × 10-8 cm)
× (18.1 × 10-8 cm) × (6.82 × 10-8cm)
× 6.02 × 1023(mol-1)]/1681.57(g.mol-1)
= 1.01
(2)
The calculated value Z = 1.0 is the same as the
theoretical number of molecules in a 2D rectangular
lattice having a P2m symmetry: Z = 1.0. Therefore, this
stacking distance h = 6.82 Å is a rationally proper value.
Fig. 6(c) shows an XRD pattern of {[m,p-(C1)2]
PhS}8PcCu (8k) at 350°C. As can be seen from this
pattern, Peak X did not appear in the very small angle
region. It differs from two previous derivatives, 8i and
8j. This point may be very helpful to clarify the origin
of Peak X in further study. As can be seen also from this
XRD pattern, two big peaks appeared closely at around
2Q = 4~5°. This diffraction pattern is often observed
for rectangular columnar (Colr) mesophases. According
to our expectation, five peaks were well fitted to a 2D
reciprocal rectangular lattice calculated from the lattice
constants of a = 37.1 Å and b = 20.8 Å, as can be seen
from Table 4. Using the stacking distance h = 3.95 Å
and an assumed density r = 1.05(g.cm-3), the calculated
Z value is 1.0. This value indicates that this mesophase
should have a P2m symmetry [25].
Fig. 6. Small angle X-ray diffraction patterns: (a) 8i at 340°C,
(b) 8j at 300°C and (c) 8k at 350°C
observed at 3.5 Å for conventional tetragonal columnar
mesophases, but this stacking distance can be proven as a
proper value from Z Value Calculation [25]. The number
(Z) of molecules in a lattice can be calculated from this
stacking distance (h = 7.00 Å) and the lattice constant of
2D tetragonal lattice (a = 20.0 Å) listed in Table 4. When
r, V, N and M are density of mesophase, volume of
The stacking distances of [(o-C1)PhS]8PcCu (8i)
and [(m-C1)PhS]8PcCu (8j) are 7.00 Å and 6.82 Å,
Copyright © 2015 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2015; 19: 10–12

FLYING-SEED-LIKE LIQUID CRYSTALS 5†
11
Table 4. X-ray data of 8i~8k
Compound [mesophase]
Lattice constant, Å
Spacing, Å
Miller indices (h k l)
Obserevd
Calculated
8i: [(o-C1)PhS]8PcCu [Coltet.o at 340°C]
77.3
20.0
14.1
ca. 7.00
3.76
—
X
(1 0 0)
(1 1 0)
(2 2 0) + h + #
(5 2 0)
a = 20.0
20.0
14.1
7.04
3.71
h = 7.00
Z = 1.0 for r = 1.0
8j: [(m-C1)PhS]8PcCu [Colro(P2m) at 300°C]
98.5
18.1
13.6
10.1
9.16
6.82
ca. 5.91
3.98
—
X
a = 20.7 b = 18.1
h = 6.82
Z = 1.0 for r = 1.1
18.1
13.6
10.3
9.05
6.81
5.79
4.03
(0 1 0)
(1 1 0)
(2 0 0)
(0 2 0)
(2 2 0) + h
(1 3 0) +ꢀ#
(5 2 0)
8k: {[m,p-(C1)2]PhS}8PcCu [Colro(P2m) at 350°C]
21.0
18.4
9.04
7.83
7.43
21.0
18.4
9.07
7.83
7.43
—
(0 1 0)
(2 0 0)
(2 2 0)
(3 2 0)
(5 0 0)
#
a = 37.1 b = 20.8
h = 3.95
Z = 1.0 for r = 1.05
ca. 5.94
3.95
—
h
h: Stacking distance = (0 0 1). #: Broad halo due to thermal fluctuation of the phenylthio groups. X: Reflection unable to be assigned.
r: Assumed density (g/cm3)
respectively, whereasthestackingdistanceof{[m,p-(C1)2]
PhS}8PcCu (8k) is 3.95 Å. In our previous work [17], the
(PhO)8PcCu derivatives substituted by mono-methoxy
groupstendtoshowalongstackingdistance, 6.09~7.00Å,
whereas the (PhO)8PcCu derivatives substituted by multi-
methoxy groups tend to show a short stacking distance,
3.87~4.80 Å. Interestingly, this tendency can be also seen
in the present (PhS)8PcCu derivatives.
Thus, each of the present (PhS)8PcCu derivatives,
8i~8k, exhibits a columnar mesophase at a very high
temperature region. It is very noteworthy that the
mesomorphism with a very high temperature region is
apparently originated from the novel bulky groups (i~k).
corresponding PhO-containing derivatives 7e, 7f and 7h.
Since the Q-band in Pc derivatives corresponds to the
band gap between HOMO and LUMO, the charge carrier
mobilities may be greatly improved by the substitution of
PhS instead of PhO. Each of them rapidly decomposed
after clearing into isotropic liquid. On the other hand,
these high temperature mesophases were fairly stable
under nitrogen atmosphere but they were unstable in
the air. Thus, the present flying-seed-like liquid crystals
based on (PhS)8PcCu are unfortunately unstable at higher
temperatures in the air. If the thermal instability will be
improved by chemical modification, fast charge carrier
mobilities will be realized for the (PhS)8PcCu-based
derivativesinthefuture.Therearestillaveryfewexamples
of flying-seed-like liquid crystals. Therefore, we believe
that this work will contribute to the development of a new
research field of the flying-seed-like liquid crystals.
CONCLUSION
In this study, we have synthesize three novel flying-
seed-like liquid crystals based on (PhS)8PcCu: [(m-C1)
PhS]8PcCu (8i), [(o-C1)PhS]8PcCu (8j) and {[m,p-(C1)2]
PhS}8PcCu (8k), to investigate their mesomorphism. As
the results, each of the derivatives exhibits a columnar
mesophase at very high temperatures: 8i Coltet.o at 314.9~
362.9°C for 8i, Colro(P2m) at 287.4~334.2°C for 8j and
Colro(P2m) at 331.8~386.8°C for 8k. Very interestingly,
the mesomorphism is apparently originated from the
novel bulky groups (i~k). The Q-bands of the present
PhS-containing Pc derivatives 8i~8k significantly red-
shift by about 35 nm in comparison with those of the
Supporting information
Figures S1–S2 are given in the supplementary material.
This material is available free of charge via the Internet at
http://www.worldscinet.com/jpp/jpp.shtml.
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