Discotic liquid crystals of transition metal complexes 44:

Journal of Porphyrins and Phthalocyanines

J. Porphyrins Phthalocyanines 2012; 16: 1114–1123

DOI: 10.1142/S1088424612500976

Published at http://www.worldscinet.com/jpp/

Discotic liquid crystals of transition metal complexes 44^†:

synthesis of hexaphenoxy-substituted phthalocyanine

derivatives showing spontaneous perfect homeotropic

alignment

Masaaki Ariyoshi^a, Makiko Sugibayashi-Kajita^a, Ayumi Suzuki-Ichihara^a,

Takayuki Kato^a, Tenpei Kamei^a, Eiji Itoh^band Kazuchika Ohta*^a◊

^aSmart Material Science and Technology, Department of Bioscience and Textile Technology, Interdisciplinary

Graduate School of Science and Technology, Shinshu University, 1-15-1 Tokida, Ueda 386-8567, Japan

^bDepartment of Electrical and Electronic Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553,

Japan

Received 4 March 2012

Accepted 27 April 2012

ABSTRACT: We have synthesized novel hexaphenoxy-substituted phthalocyanine derivatives,

2-(12-hydroxydodecyloxy)-3-methoxy-9,10,16,17,23,24-hexakis(3,4-di-n-alkoxyphenoxy)phthalo-

cyaninato copper(II) (abbreviated as C_n(OC₁₂OH)PcCu: n = 10, 12, 14), and investigated their columnar

mesomorphism and homeotropic alignment property. These hexaphenoxy-substituted Pc derivatives could be

successfully isolated and puriﬁed from the mixture products by polarity difference. It was revealed by using

polarizing optical microscopic observations, differential scanning calorimetry and temperature-dependent

X-ray diffraction studies that each of the hexaphenoxy-substituted Pc derivatives has plural mesophases, and

that the tetragonal columnar (Col_tet) mesophase shows spontaneous perfect homeotropic alignment between

two non-surface-treated glass plates without any defects and polydomain boundaries.

KEYWORDS: discotic liquid crystal, phthalocyanine, tetragonal columnar mesophase, homeotropic

alignment.

In 2001, we successfully synthesized octaphenoxy-

INTRODUCTION

substituted Pc derivatives, 2,3,9,10,16,17,23,24-octakis

Inpast10years, homeotropicalignmenthasbeenfound

(3,4-dialkoxyphenoxy)phthalocyaninato copper(II) (abb-

inthediscoticliquidcrystalsbasedontriphenylene[1–10],

reviated as [(C_nO)₂PhO]₈PcCu: 1) complexes, and found

phthalocyanine (Pc) [11–18], hexabenzocoronene [19–

that they exhibit spontaneous perfect homeotropic

21], perylene [22–26], 1,4-diazatriphenylenocyaninato

alignment in the tetragonal columnar mesophase between

copper(II) (TzCu) [27], porphyrin [28, 29], azulene [30],

two non-surface-treated glass plates [11]. They show

and triphenylamine [31]. However, it is still unclear

neither defects nor domain boundaries for the homeotropic

what kind of molecular structure could realize perfect

homeotropic alignment.

alignment. These [(C_nO)₂PhO]₈PcCu (1) derivatives

are the ﬁrst examples exhibiting perfect homeotropic

alignment in Pc-based discotic liquid crystals. Such

spontaneous perfect homeotropic alignment enables us

^SPP full member in good standing

to easily prepare the large-area uniform ﬁlm. Hence, the

octaphenoxy-substituted Pc-based discotic liquid crystals

are very suitable as novel organic semiconductors [32–38].

Figure 1 illustrates a possible origin of the spontaneous

homeotropic alignment of the octaphenoxy-substituted

*Correspondence to: Kazuchika Ohta, tel: +81-268-21-5492,

e-mail: ko52517@shinshu-u.ac.jp

^†Part 43: Mukai H,Yokokawa M, Hatsusaka K and Ohta K. Liq.

Cryst. 2010; 37: 13–21.

DISCOTIC LIQUID CRYSTALS OF TRANSITION METAL COMPLEXES 44 1115

OR

O

RO

OR

RO

X

O

OR

RO

OR

RO

N

O

Si

O

Si

O

O Si

O

N

Cu

N

Cu

N

O

Si O

O

N

RO

OR

O

OR

RO

OR

RO

1

A: [(C_nO)₂Ph]₈PcCu (2)

B: [(C_nO)₂PhO]₈PcCu (1)

4

3

2

Fig. 1. Possible origin and mechanism of the perfect homeotropic alignment of [(C_nO)₂PhO]₈PcCu (1)

[(C_nO)₂PhO]₈PcCu (1) complexes. In this ﬁgure, the

molecular structures of [A] [(C_nO)₂Ph]₈PcCu (2) [39] and

[B] [(C_nO)₂PhO]₈PcCu (1) [11] resemble each other. The

molecular difference between them is only oxygen atoms

intervened between the peripheral phenyl groups and the

central Pc core of the derivative 1. The derivative 1 shows

perfect homeotropic alignment, whereas the derivative 2

does not. Therefore, oxygen atoms in the phenoxy groups

may originate the perfect spontaneous homeotropic

alignment. Figure 1 also depicts a possible mechanism

of this spontaneous homeotropic alignment. Step 1: the

lone pairs of oxygen atom in the phenoxy groups may

coordinate to the dangling bonds of silicon atoms on the

surface of glass plate. Step 2: the ﬁrst Pc disk adhered to

the surface may trigger the stacking of the disks one after

another to form the columns perpendicular to the surface.

Step 3: the columns aggregate into the Col_tetmesophase,

(Step 4:) showing perfect homeotropic alignment.

This hypothesis can be also supported by another

example. Figure 2 illustrates tetrakis(2,3,6,7-tetraalkoxy)-

RO

OR

RO

OR

RO

OR

N

OR

RO

N

Cu N

N

Cu N

N

OR

N

RO

OR

RO

OR

(C_nO)₁₆TzCu: 4

(C_nO)₁₆TcCu: 3

(a)

(b)

Fig. 2. Molecular structures of (a): (C_nO)₁₆TcCu (3) and (b): (C_nO)₁₆TzCu (4)

J. Porphyrins Phthalocyanines 2012; 16: 1115–1123

1116 M. ARIYOSHI ET AL.

conc.H₂SO₄

/30%H₂O₂

OR

OH

RBr

HOC

HO

K₂CO₃/DMF

CHCl₃/MeOH

7

6

NC

Cl

a: R=C₁₀H₂₁

b: R=C₁₂H₂₅

c: R=C₁₄H₂₉

OR

K₂CO₃/DMSO

OR

RO

OR

NC

O

OR

RO

8

N

DBU/ CuCl₂

O

OCH₃

OC₁₂H₂₄OH

N M N

n-hexanol

N

RO

OR

OCH₃

NC

M=Cu

O

OC₁₂H₂₄OH

RO

OR

11

5 C_n(OC₁₂OH)PcCu

BrC₁₂H₂₄OH

K₂CO₃/DMF

OCH₃

Br

OCH₃

NC

OCH₃

OH

Br₂/(C₂H₅)₂O•BF₃

CHCl₃/CH₂Cl₂

CuCN

DMF

NC

OH

10

9

Scheme 1. Synthetic route of the phthalocyanine derivatives C_n(OC₁₂OH)PcCu 5a~5c. DMF = N,N-dimethylformamide, DMSO =

dimethylsulfoxide, DBU = 1,8-diazabicyclo[5,4,0]undecene-7-ene and TEA = triethylamine

triphenylenocyaninato copper(II) (abbreviated as

(C_nO)₁₆TcCu: 3[27]) and tetrakis(2,3,6,7-tetraalkoxy)-1,4-

diazatriphenylenocyaninato copper(II) (abbreviated as

(C_nO)₁₆TzCu: 4 [27]). Each of the (C_nO)₁₆TcCu (3)

derivatives does not exhibit homeotropic alignment,

whereas each of the (C_nO)₁₆TzCu (4) complexes shows

spontaneous perfect homeotropic alignment in the Col_tet.o

mesophase.The molecular difference between them is only

the additional eight nitrogen atoms in the (C_nO)₁₆TzCu (4)

derivative. Hence, in this case the heteroatoms of nitrogen

may also originate the perfect homeotropic alignment.

From these examples described above, we believe that

perfect homeotropic alignment may be originated from

the heteroatoms in the periphery of the central cores. It

is very interesting for us whether such a spontaneous

homeotropic alignment will appear or not, when the

number of the phenoxy groups in the octaphenoxy-

substituted [(C_nO)₂PhO]₈PcCu (1) complexes, which

may play an important role to show perfect homeotropic

alignment, will be reduced from eight to six. Hence,

we have synthesized the hexaphenoxy-substituted

Pc derivatives (C_n(OC₁₂OH)PcCu: n = 10, 12, 14: 5a,

5b and 5c) shown in Scheme 1, and investigated their

mesomorphism and homeotropic alignment property in

this work. As a result, perfect homeotropic alignment

could be also achieved for the hexaphenoxy-substituted

derivatives C_n(OC₁₂OH)PcCu, in spite of reduction of the

number of the phenoxy groups from eight to six. We wish

to report here these interesting ﬁndings.

EXPERIMENTAL

Synthesis

Synthetic routes of this work are shown in Scheme 1.

The phthalonitrile derivatives 8a, 8b and 8c and 11

were prepared by the methods reported by us [11] and

Nolte et al. [40], respectively. The synthetic method and

puriﬁcation of the target phthalocyanine derivatives 5a,

5b and 5c are described in detail.

2-(12-hydroxydodecyloxy)-3-methoxy-9,10,16,17,

23,24-hexakis(3,4-didecyloxyphenoxy)phthalocyani-

nato copper(II), C₁₀(OC₁₂OH)PcCu (5a). In 5 mL of

J. Porphyrins Phthalocyanines 2012; 16: 1116–1123

DISCOTIC LIQUID CRYSTALS OF TRANSITION METAL COMPLEXES 44 1117

n-hexanol, 4,5-bis(3,4-didecyloxyphenoxy)phthalonitrile

dried over the sodium sulfate. The solvent was evaporated

to give 0.84 g of green crude product. It was washed with

hot distilled methanol for ﬁve times (150 mL × 5) and

dried by blowing dry nitrogen gently. Further puriﬁcation

was carried out by column chromatography (silica gel,

chloroform, Rf = 0.80, then, silica gel, chloroform:

n-hexane = 7:1, Rf = 0.60). To the obtained product,

40 mL of distilled ethyl acetate was added and reﬂuxed

to dissolve it completely. Into this reﬂuxing solution,

80 mL of distilled ethanol was poured to reprecipitate.

This reprecipitation was carried out twice to afford 0.11 g

of green powder. Yield: 17%.

8a (0.38 g, 0.396 mmol), 4-(12-hydroxydodecyloxy)-

5-methoxyphthalonitrile 11 (0.047 g, 0.132 mmol) and

CuCl₂(0.035 g, 0.26 mmol) were dissolved. To this

solution, 6 drops of 1,8-diazabicyclo[5,4,0]undecene-7-

ene (DBU) was added from a Pasteur pipette and reﬂuxed

for 24 h under the nitrogen atmosphere. After cooling

to room temperature, the reaction solution was slowly

dropped by using a Pasteur pipette into ca. 100 mL of

methanol in a pear shape ﬂask to precipitate the product.

The supernatant was pipetted off. The residue was

puriﬁed by solid-liquid extraction with hot methanol for

5 times (100 mL × 5) and then dried under vacuum. Further

puriﬁcation was carried out by column chromatography

(silica gel, chloroform, Rf = 0.13) for 2 times to give

114 mg of green solid. Yield 27%.

Measurements

The compounds synthesized here were identiﬁed

1

with a H NMR (BRUKER Ultrashield 400 MHz), an

2-(12-hydroxydodecyloxy)-3-methoxy-9,10,16,

17,23,24-hexakis(3,4-didodecyloxyphenoxy)phthal-

ocyaninato copper(II), C₁₂(OC₁₂OH)PcCu (5b). In

7 mL of n-hexanol, 8b (0.60 g, 0.57 mmol), 11 (0.068 g,

0.19 mmol) and CuCl₂(0.040 g, 0.30 mol) were dissolved.

To this solution, DBU (0.11 g, 0.71 mmol) was added

and reﬂuxed for 26.5 h under the nitrogen atmosphere.

After cooling to room temperature, water was added into

the reaction vessel. The aqueous mixture was extracted

with chloroform. The organic layer was washed with

water and dried over the sodium sulfate. The solvent was

evaporated to give 0.98 g of green crude product. It was

washed with hot distilled methanol for ﬁve times (150 mL

× 5) and dried by gently blowing dry nitrogen. Further

puriﬁcation was carried out by column chromatography

(silica gel, chloroform, Rf = 0.25) and reprecipitation

from distilled ethyl acetate for three times to give 0.17 g

of green powder. Yield: 25%.

FT-IR (Nicolet NEXUS 670), an electronic absorption

spectrometer (Hitachi U-4100 spectrophotometer), a

MALDI-TOF-Mass (PerSeptive Biosystems Voyager

DE-Pro spectrometer) and an elemental analyzer (Perkin-

Elmer elemental analyzer 2400). The elemental analysis

data and mass spectral data of the ﬁnal products are

summarized in Table 1. The electronic spectral data are

summarized in Table 2. The phase transition temperatures

and enthalpy changes were measured with a differential

scanningcalorimeter(ShimadzuDSC-50).Thetexturesof

their mesophases were observed with a polarizing optical

microscope (Nikon ECLIPSE E600 POL) equipped with

a Mettler FP82HT hot stage and a Mettler FP90 Central

Processor. Wide-angle X-ray diffraction measurements

were carried out with Cu-Ka radiation with a Rigaku

RAD X-ray diffractometer equipped with a handmade

heating plate [41, 42] controlled with a thermoregulator.

2-(12-hydroxydodecyloxy)-3-methoxy-9,10,

16,17,23,24-hexakis(3,4-ditetradecyloxyphenoxy)-

phthalocyaninato copper(II), C₁₄(OC₁₂OH)PcCu (5c).

In 6 mL of n-hexanol, 8c (0.57 g, 0.49 mmol), 11 (0.059 g,

0.16 mmol) and CuCl₂(0.038 g, 0.28 mol) were dissolved.

To this solution, DBU (0.10 g, 0.66 mmol) was added and

reﬂuxed for 25 h under the nitrogen atmosphere. After

cooling to room temperature, water was added into the

reaction vessel. The aqueous mixture was extracted with

chloroform. The organic layer was washed with water and

RESULTS AND DISCUSSION

Synthesis of the phthalocyanine derivatives, 5a, 5b

and 5c, having six phenoxy groups

A mixture of two kinds of phthalonitrile derivatives

8a and 11 in a ratio of 3:1 was reﬂuxed in n-hexanol

with DBU and cupric chloride. The crude products

Table 1. Elemental analysis data and MALDI-TOF mass spectral data of C_n(OC₁₂OH)PcCu (n = 10, 12 and 14)

Compound

Mol. formula

(Mol. wt)

Mass spectrum

Elemental analysis: Found(Calcd.)(%)

Yield(%)

N

C

H

5a: C₁₀(OC₁₂OH)PcCu

C₂₀₁H₃₀₆N₈O₂₁Cu

(3234.23)

3233.15

3570.07

3906.69

3.45(3.47) 74.66(74.65)

3.20(3.14) 75.41(75.68)

2.92(2.87) 76.48(76.54)

9.93(9.54)

27

25

17

5b: C₁₂(OC₁₂OH)PcCu C₂₂₅H₃₅₄N₈O₂₁Cu

10.40(9.99)

(3570.87)

5c: C₁₄(OC₁₂OH)PcCu

C₂₄₉H₄₀₂N₈O₂₁Cu

(3907.44)

11.05(10.37)

J. Porphyrins Phthalocyanines 2012; 16: 1117–1123

1118 M. ARIYOSHI ET AL.

Table 2. Electronic spectral data of C_n(OC₁₂OH)PcCu (n = 10, 12 and 14)

Compound

Concentration^a

(×10^-6mol/l)

l max nm (log e)

Soret-band Q-band

5a: C₁₀(OC₁₂OH)PcCu

5b: C₁₂(OC₁₂OH)PcCu

5c: C₁₄(OC₁₂OH)PcCu

^aIn chloroform.

6.57

6.70

6.50

290.50

(4.88)

340.5

(4.93) (4.65)

339.6 613.5

(4.91) (4.63)

339.9 613.6

(4.92) (4.64)

614.5

651.5

(sh)

683.0

(5.39)

289.9

(4.85)

654.0

(sh)

682.3

(5.37)

290.0

(4.86)

653.0

(sh)

682.1

(5.40)

gave two green spots at Rf = 1.00 and 0.13 for TLC

(silica gel, chloroform). They were easily isolated into

two Pc derivatives by column chromatography (silica

gel, chloroform). Checked by the TOF-Mass spectra,

the spots at Rf = 1.00 and 0.13 corresponded to the Pc

compound 1a in a ratio of 4:0 fused 8a and 11, and the

target Pc compound 5a in a ratio of 3:1 fused 8a and

11, respectively. Thus, the (3:1)Pc compound 5a was

easily isolated by column chromatography. The terminal

hydroxyl group effectively decreased the Rf value to

isolate the target (3:1)Pc compound.

by polarizing microscopic observations, differential

scanning calorimeter (DSC) and temperature-

dependent X-ray diffraction technique.

Each of the virgin samples of 5a, 5b and 5c gave a

crystalline phase at the lowest temperatures around room

temperature. Very interestingly, each of the present Pc

derivatives 5a, 5b and 5c shows plural different Col_h

mesophases over the crystalline phase K; four for 5a, three

for 5b, and two for 5c. The longer the alkoxy chain length

becomes, the smaller the number of Col_hmesophases

becomes. Since it was reported that the distinction between

Col_hoand Col_hdwas meaningless [43, 44], the present

plural mesophases are only denoted as Col_hin this paper.

Four Col_hmesophases could be observed at most for the

present compounds. The differences among them cannot

be attributed to the conventional differences of ordered

and disordered stackings. At present the detailed reason

is not clear. However, we think that it may be attributed

to the increasing ﬂuctuation of cores with elongating

the alkoxy chain length. There have been a very few

example exhibiting more than three Col_hmesophases in

one compound. However, Swager and his co-workers

The other homologues, 5b and 5c, having different

chain length of the alkoxy groups could be easily isolated

in the same manner.

Mesomorphism of the phthalocyanine derivatives, 5a,

5b and 5c

Phase transition behavior of 5a, 5b, and 5c.

Table 3 lists the phase transition temperatures and

enthalpy changes of the Pc derivatives 5a, 5b, and 5c.

These phase transition sequences were established

Table 3. Phase transition temperatures and enthalpy changes of the phthalocyanine derivatives, 5

o

[∆H(kJ/mol)]

T( C)

Phase^a)

173.3[0.462]

[13.1]

Compound

Relaxation

Phase

74.6

15.6[115]

[16.1]

122.4[0.319]

Col_h2

145.4

189.1

94.1[0.676]

very slow

Col_tet

Col_h4

Col_h3

Cub

(Pn3m)

Col_h1

I.L.

X

5a: C₁₀(OC₁₂OH)PcCu

K

seldom

188.7

[2.91]

I.L.

[3.10]

142.3[16.5]

very slow

ca. 30-70[101]

ca.27-32[198]

182.6

180.8

154.1

153.1

Col_h2

Col_tet

5b: C₁₂(OC₁₂OH)PcCu

5c: C₁₄(OC₁₂OH)PcCu

Cub

Col_h3

Col_h1

I.L.

(Pn3m)

182.0

[2.33]

I.L.

153.3[4.89]

[27.0]

Col_h2

174.3

171.0

136.7

136.0

very slow

141.6

I.L.

Cub

Col_tet

K

Col_h1

(Pn3m)

173.6

[2.30]

I.L.

137.3

[28.1]

a) Phase nomenclature : K=Crystal, Col_h=hexagonal columnar mesophase, Col_tet=tetragonal columnar mesophase, X=unidentified mesophases, Cub=cubic mesophase and

I.L.=isotropic liquid. All heating and cooling rates for the DSC measurements were 2.5^oC/min. { = total enthalpy changes of the non-split peaks. The mesophase in a rectangle shows

homeotropic alignment.

J. Porphyrins Phthalocyanines 2012; 16: 1118–1123

DISCOTIC LIQUID CRYSTALS OF TRANSITION METAL COMPLEXES 44 1119

also reported that the long chain-substituted b-diketonato

When the I.L. was cooled down, it transformed into

the Col_tetmesophase for 5a, and the Col_h2 mesophase via

the Cub phase instead of the Col_tetmesophase for 5b and

5c. The unusual thermal behavior on cooling observed

for the present hexaphenoxy-substituted derivatives

5b and 5c is the same as the previous octaphenoxy-

substituted derivative [(C₁₄O)₂PhO]₈PcCu (8f in Ref. 11).

The precise explanation was already described in the

previous paper [11]. On further cooling, the Pc derivative

5a transformed ﬁnally into the Col_h2 mesophase (seldom

into Col_h1), which remained at room temperature by

supercooling. The Pc derivatives 5b and 5c transformed

from Col_h2 to Col_h1.

copper(II) complexes exhibited four different Col_hd

mesophases [45]. Each of the present Pc derivatives 5a,

5b and 5c gave a Col_tetmesophase over these plural Col_h

mesophases, on further heating. Generally, a mesophase

transition occurs from a lower symmetry mesophase

(e.g. Col_tet) to a higher symmetry mesophase (e.g. Col_h),

as reported by us [46, 47]. On the contrary, the present

compounds showed a phase transition from Col_hto

Col_tet. There have been very few reports on such inverse

mesophase transitions [39]. When the Col_tetmesophase

was heated, it cleared into isotropic liquid (I.L.) and

relaxed into a cubic (Cub) mesophase; on further heating,

the Cub mesophase cleared into I.L. The differences

between two clearing points are only 0.4 °C for 5a, 0.6 °C

for 5b, and 0.7 °C for 5c. They are very narrow.

Temperature-dependentX-rayliquidcrystalstructure

analyses of 5a, 5b and 5c. Table 4 lists the X-ray data of

the (3:1) Pc derivatives 5a, 5b and 5c. Since the X-ray

Table 4. X-ray data of C_n(OC₁₂OH)PcCu(n = 10(5a), 12(5b) and 14(5c))

Compound Lattice Spacing(Å) Miller indices

(mesophase)

constants(Å)

(h k l)

Observed

32.5

Calculated

†

5a: C₁₀(OC₁₂OH)PcCu

h₁= ca. 4.9

h₂= ca. 9.7

†

}

(X at 65.0 °C)

ca. 14

ca. 9.7

ca. 4.9

ca. 4.4

—

h₂

h₁

#

(Col_h1 at 85.0 °C)

(Col_h2 at 105.0 °C)

a = 39.2

a = 38.6

34.0

19.7

12.7

ca. 9.6

ca. 4.5

34.0

19.6

12.9

9.43

—

(100)

(110)

(210)

(310)

#

33.4

19.4

16.8

12.6

9.28

8.42

7.64

ca. 4.6

33.4

19.3

16.7

12.6

9.27

8.36

7.67

—

(100)

(110)

(200)

(210)

(310)

(400)

(320)

#

(Col_h3 at 130.0 °C)

(Col_h4 at 155.0 °C)

a = 38.6

33.4

18.8

17.5

12.8

11.1

9.36

ca. 4.6

33.4

19.3

16.7

12.6

11.1

9.26

—

(100)

(110)

(200)

(210)

(300)

(310)

#

a = 37.2

32.2

18.7

16.1

12.2

ca. 9.0

ca. 4.5

32.2

18.6

16.1

12.2

8.94

—

(100)

(110)

(200)

(210)

(310)

#

J. Porphyrins Phthalocyanines 2012; 16: 1119–1123

1120 M. ARIYOSHI ET AL.

Table 4 (Continued)

Compound(mesophase)

Lattice

constants(Å)

Spacing(Å)

Miller indices

(h k l)

Observed

Calculated

30.9

(Col_tetat 175.0 °C)

a = 43.7

30.9

(110)

11.8

12.1

7.73

—

(230)

(440)

#

7.77

ca. 4.4

(Cub(Pn3m)

at 188.9 °C)

a = 99.0

Z = 181

for r = 1.0^¶

40.5

35.3

32.9

29.8

28.5

21.5

ca. 4.5

40.4

35.0

33.0

29.8

28.6

21.6

—

(211)

(220)

(221)

(311)

(222)

(421)

#

5b: C₁₂(OC₁₂OH)PcCu

a = 40.1

34.8

20.2

17.7

34.8

20.1

17.4

(100)

(110)

(200)

(Col_h1 at 120.0 °C)

13.3

13.1

(210)

9.82

9.64

8.69

7.97

—

(310)

(400)

(320)

#

8.77

8.01

ca. 4.5

(Col_h2 at 147.0 °C)

a = 39.5

34.2

19.8

17.3

13.2

11.5

9.56

8.60

34.2

19.7

17.1

12.9

11.4

9.49

8.55

(100)

(110)

(200)

(210)

(300)

(310)

(400)

7.87

ca. 4.6

7.85

—

(320)

#

(Col_h3 at 153.5 °C)

a = 38.0

32.9

19.1

32.9

19.0

(100)

(110)

16.6

12.6

16.5

12.4

11.0

9.13

—

(200)

(210)

(300)

(310)

#

11.1

9.21

ca. 4.6

(Col_tetat 170.0 °C)

a = 43.6

30.8

(110)

h = ca. 3.6

Z = 1.0 for

r = 0.90^¶

22.0

ca. 4.7

ca. 3.6

21.8

—

(200)

#

h

(Cub(Pn3m) at 165.0 °C)

nonvirgin sample

a = 114.8

40.1

40.6

(220)

h = ca. 3.6

Z = 255 for

r = 1.00^¶

36.5

36.3

33.1

30.7

22.5

—

(310)

(222)

(321)

(510)

#

32.9

31.3

22.3

ca. 4.7

ca. 3.6

—

h

J. Porphyrins Phthalocyanines 2012; 16: 1120–1123

DISCOTIC LIQUID CRYSTALS OF TRANSITION METAL COMPLEXES 44 1121

Table 4 (Continued)

Compound(mesophase)

Lattice

constants(Å)

Spacing(Å)

Miller indices

(h k l)

Observed Calculated

5c: C₁₄(OC₁₂OH)PcCu

a = 41.8

h = ca. 3.5

Z = 0.98 for

r = 1.2^¶

36.2

21.1

18.4

13.9

10.3

9.24

8.50

ca. 4.6

ca. 3.5

35.9

21.0

18.2

13.8

12.3

10.3

9.24

8.37

ca. 4.6

36.2

20.9

18.1

13.7

10.5

9.05

8.31

—

(100)

(110)

(200)

(210)

(220)

(400)

(230)

#

(Col_h1 at 120.0 °C)

—

h

(Col_h2 at 137.0 °C)

a = 41.5

35.9

20.7

18.0

13.6

12.0

10.4

8.98

8.24

—

(100)

(110)

(200)

(210)

(300)

(220)

(400)

(320)

#

(Col_tetat 155.0°C)

a = 45.7

h = ca. 3.5

Z = 1.0 for

r = 0.90^¶

32.3

23.0

ca. 4.7

ca. 3.5

32.3

22.8

—

(110)

(200)

#

—

h

(Cub(Pn

at 173.0 °C)

nonvirgin sample

3

m)

a = 105.6

Z = 214 for

r = 1.00^¶

37.4

35.3

32.0

21.4

18.6

ca. 4.5

37.4

35.2

31.9

21.6

18.7

—

(220)

(221)

(311)

(422)

(440)

#

^†These peaks could not be assinged to the Miller indices of any mesophases known to date. #: Halo of

the molten alkoxy chains. h: stacking distance. Z: The number of molecures in a lattice. ¶: Assumed

density/g.cm^-3.

data of the Pc derivatives 5a, 5b and 5c are very similar,

the detailed discussion is described only for 5a.

a 2D-hexagonal lattice. Hence, this mesophase was

established as a Col_hmesophase. In the same manner,

the other Col_h2~4 mesophases could be established. The

Col_tetmesophase appeared at higher temperatures three

peaks in the low angle region, which spacings are in a

ratio of 1/√2:1/√13:1/4√2. The ratio is consistent with a

2D-tetragonal lattice. Hence, this mesophase could be

identiﬁed as a Col_tetmesophase.

The X-ray pattern of 5a at 188.9 °C is totally

different from all the patterns of general columnar

mesophases. Hence, it was analyzed by assuming

a cubic phase. All the spacings could be very well

indexed to the reﬂections from a cubic lattice with

a Pn3m symmetry. The lattice constant (a) could be

calculated to be 99.0 Å. When the density is assumed

as 1.0 [48], the unit cell contains 181 molecules. From

the extinction rules for cubic phases [49], this Cub

mesophase has a Pn3m symmetry. It is very unlikely

It is apparent from the broad halo at 2q ≈ 20° (d ≈

4.4 ~ 4.6 Å) that the X phase of 5a is not crystalline

but liquid crystalline. Interestingly, the X mesophase

gave two different stacking distances h₁= ca. 4.9 Å and

h₂= ca. 9.7 Å. Generally, the distance of face-to-face

stacking for Pc-based discotic liquid crystals can be

observed at 3.3–3.6 Å. Therefore, the disks of 5a in this

X mesophase stack not face-to-face but tilted to show

a peak at ca. 4.9 Å. Since the value ca. 9.7 Å is nearly

twice of ca. 4.9 Å, dimer formation is suggested in the

X mesophase. However, it was impossible to identify

this mesophase from only one sharp reﬂection in the low

angle region.

The Col_h1 mesophase of 5a gave four peaks in

the low angle region, which spacings are in a ratio

of 1:1/√3:1/√7:1/√13. The ratio is characteristic to

J. Porphyrins Phthalocyanines 2012; 16: 1121–1123

1122 M. ARIYOSHI ET AL.

derivatives C_n(OC₁₂OH)PcCu: n = 10, 12, 14), although

the number of the phenoxy groups was reduced from

eight to six.

Acknowledgements

This work is partially supported by Grant-in-Aid for

scientiﬁc research (Grant No. 2236012311) from the

Ministry of Education, Culture, Sports, Science and

Technology, Japan.

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J. Porphyrins Phthalocyanines 2012; 16: 1123–1123

Article Doi

Discotic liquid crystals of transition metal complexes 44:

DOI: 10.1142/S1088424612500976

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Article abstract of DOI:10.1142/S1088424612500976

Full text of DOI:10.1142/S1088424612500976

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