Discotic liquid crystals of transition metal complexes 50: Spiranthes-like supramolecular structure of phthalocyanine-fullerene dyads

Journal of Porphyrins and Phthalocyanines

J. Porphyrins Phthalocyanines 2014; 18: 366–379

DOI: 10.1142/S1088424614500072

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

Discotic liquid crystals of transition metal complexes 50^†:

spiranthes-like supramolecular structure of phthalocyanine-

fullerene dyads

Aya Ishikawa^a, Kenta Ono^a, Kazuchika Ohta*^a◊, MikioYasutake^b,

Musubu Ichikawa^aand Eiji Itoh^c

^aSmart Material Science and Technology, Interdisciplinary Graduate School of Science and Technology, Shinshu

University, 1-15-1 Tokida, Ueda 386-8567, Japan

^bComprehensive Analysis Center for Science, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama 338-8570,

Japan

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

Japan

Received 23 November 2013

Accepted 22 January 2014

ABSTRACT: We have synthesized novel liquid crystalline Pc-C₆₀dyads (C_nS)₆PcCu-C₆₀(n = 14, 16,

18: 1a–1c) by using our developed synthetic method in order to investigate the mesomorphism and

alignment behavior. Each of the (C_nS)₆PcCu-C₆₀dyads shows perfect homeotropic alignment in the

Col_homesophase between two glass plates for n = 14, 16, 18 and also on a glass plate for n = 14, although

none of the parent Pc compounds (C_nS)₈PcCu and the Pc precursors (C_nS)₆PcCu-OH and (C_nS)₆PcCu-

OFBA shows homeotropic alignment. It may be attributed to the strong afﬁnity between fullerene and

glass surface. Although the reason is not so clear at the present time, this is very useful guideline for the

molecular design to prepare homeotropic alignment-showing discotic liquid crystals. Very interestingly,

the spherical C₆₀parts form a helical structure around the column formed by the disk-like Pc parts.

This supramolecular structure very resembles spiranthes. The spiranthes-like supramolecular structure

is compatible with one-dimensional nano-array expecting the high conversion efﬁciency of solar cells.

KEYWORDS: discotic liquid crystal, phthalocyanine, fullerene, dyad, homeotropic alignment,

spiranthes-like supramolecular structure.

of donor and acceptor [5] illustrated in Fig. 1a. If this

INTRODUCTION

structure would be realized, we could develop organic

In recent years, organic thin ﬁlm solar cell is paid

thin ﬁlm solar cell showing much higher conversion

attention very much, because it has ﬂexibility and

efﬁciency [5]. However, no method has been developed

easiness of ﬁlm formation [1–4]. However, the conversion

to obtain such an advantageous 1D nano-array structure

efﬁciency is still low in comparison with single crystal

in an easy way.

silicon solar cell [1]. Hence, the conversion efﬁciency

On the other hand, liquid crystalline donor–acceptor

has been raised mainly by using bulk hetero junction

(D–A) complexes may display superb performance in

of donor and acceptor [1]. Recently, Yoshikawa et al.

proposed one-dimensional (1D) nano-array structure

organic thin ﬁlm solar cells [6–30]. They can greatly

reduce their costs to manufacture the solar cells. Especially,

columnar mesophases in homeotropic alignment are

so favorable to obtain higher photoelectric conversion

^◊SPP full member in good standing

efﬁciency which can be attributable to larger p–p stacking

of the p-conjugated macrocycles [24]. In 2001, we found at

the ﬁrst time that phthalocyanine (Pc)-based discotic liquid

*Correspondence to: Kazuchika Ohta, email: ko52517@

shinshu-u.ac.jp, tel/fax: +81 268-21-5492

^†Part 49: reference 13 in this paper

DISCOTIC LIQUID CRYSTALS OF TRANSITION METAL COMPLEXES

367

Fig. 1. Resemblance between (a) 1D nano-array structure proposed by Yoshikawa et al. [5] and (b) homeotropic alignment with

spiranthes-like supramolecular structure of liquid crystalline Pc-C₆₀dyad found by us [36]

crystalline compounds, [(C_nO)₂PhO]₈PcCu (n = 11~14),

spontaneously show perfect homeotropic alignment

between two glass plates for the tetragonal columnar (Col_tet)

mesophase [31–34]. Furthermore, in 2007 we reported

the ﬁrst liquid crystalline phthalocyanine-fullerene dyad,

PcCu(OMalC₆₀) (OCH₃), exhibiting perfect homeotropic

alignment in the hexagonal columnar phase (Col_h) at high

temperatures [19]. Since then, the other groups also reported

liquidcrystallinephthalocyanine-fullerenedyads[23,25,29],

and we further found that several kinds of new homeotropic

alignment-showing liquid crystalline phthalocyanine-

fullerene (Pc-C₆₀) dyads [28, 30, 35, 36] which were

derived from the perfect homeotropic alignment-showing

parent Pc compound, [(C_nO)₂PhO]₈PcCu. Figure 1b illust-

rates a molecular structure and a schematic model of the

homeotropic alignment for a representative example of

[(C₁₂O)₂PhO]₆PcCu-C₆₀[36]. It was established at the ﬁrst

time by using our developed two X-ray diffraction methods

in our previous work [36] that the disk-like Pc parts pile

up to form columns, which are aligned homeotropically

between two glass plates, and the spherical C₆₀parts pile

up helically around the Pc columns. This supramolecular

structure very resembles spiranthes [37]. The spiranthes-

like supramolecular structure of the Pc-C₆₀dyad is

compatible with the 1D nano-array of donor and acceptor

mentioned above. Therefore, these Pc-C₆₀dyads may

be the most suitable material candidates for organic

thin ﬁlm solar cell. However, each of the homeotropic

alignment-showing dyads, [(C_nO)₂PhO]₆PcCu-C₆₀[36],

was obtained only from the homeotropic alignment-

showing parent Pc compound, [(C_nO)₂PhO]₈PcCu [31], as

illustrated in Fig. 2a. The synthesis of the starting materials

of phthalonitriles was long and time consuming [31, 34]. It

remained as a big problem for the application to solar cell.

On the other hand, the starting materials of phthalonitriles

for the alkylthio-substituted Pc compounds, (C_nS)₈PcCu,

could be easily prepared in shorter synthetic route, but

the (C_nS)₈PcCu derivatives do not show homeotropic

J. Porphyrins Phthalocyanines 2014; 18: 367–379

368

A. ISHIKAWA ET AL.

OR

RO

(C_nS)₈PcCu

Non-homeo.

[(C₁₂O)₂PhO]₈PcCu

Homeo.

O

RS

SR

RO

OR

RO

N

M

N

M

N

O

SR

O

RS

N

SR

N

OR

R = C_nH_2n+1

(n = 14, 16, 18)

M = Cu

O

RS

SR

R = C₁₂H₂₅

M = Cu

OR

RO

OR

RO

RS

N

SR

O

4: (C_nS)₆PcCu-OH

[(C₁₂O)₂PhO]₆PcCu-OH

Homeo.

OR

?

RO

N

M

N

M

N

RS

O

N

OC₁₂H₂₄OH

OC₁₀H₂₀OH

N

RS

SR

O

OR

RO

OR

RO

O

RS

SR

5: (C_nS)₆PcCu-OFBA

?

[(C₁₂O)₂PhO]₆PcCu-OFBA

OR

Homeo.

RO

N

M

N

M

N

RS

O

N

O

OC₁₂H₂₄

O

OC₁₀H₂₀

N

O

H

O

RS

SR

OR

RO

OR

RO

O

RS

N

SR

[(C₁₂O)₂PhO]₆PcCu-C₆₀

1: (C_nS)₆PcCu-C₆₀

?

OR

Homeo.

RO

N

RS

O

N

M

N

N M

O

OC₁₂H₂₄

O

OC₁₀H₂₀

N

SR

O

RS

OR

RO

(a) Previous work

(b) This work

Fig. 2. Purpose of this work. Can one obtain novel Pc-C₆₀dyads showing homeotripic alignment from their non-homeotropic parent

Pc derivatives?

J. Porphyrins Phthalocyanines 2014; 18: 368–379

DISCOTIC LIQUID CRYSTALS OF TRANSITION METAL COMPLEXES

369

alignment [38]. However, it was very interesting for us

EXPERIMENTAL

to investigate whether we would be able to obtain novel

homeotropic alignment-showing Pc-C₆₀dyads from the

corresponding non-homeotropic alignment-showing parent

Pc compound. Therefore, in this work we have synthesized

the present Pc-C₆₀dyads (C_nS)₆PcCu-C₆₀(n = 14, 16, 18)

from the non-homeotropic alignment-showing parent Pc

compounds(C_nS)₈PcCuviatheprecursors(C_nS)₆PcCu-OH

and (C_nS)₆PcCu-OFBA, in order to investigate their

mesomorphism and alignment behavior, as illustrated in

Fig. 2b.

Very interestingly, each of the (C_nS)₆PcCu-C₆₀(n =

14, 16, 18) dyads synthesized in this work shows

perfect homeotropic alignment similarly to the previous

[(C_nO)₂PhO]₆PcCu-C₆₀dyads, although neither the

parent (C_nS)₈PcCu compounds nor the precursors

(C_nS)₆PcCu-OFBA and (C_nS)₆PcCu-OH show homeo-

tropic alignment. Furthermore, the C₆₀moieties form a

helical structure around the column formed by the Pc

disks. This supramolecular structure very resembles

spiranthes. The spiranthes-like supramolecular structure

is compatible with one-dimensional nano-array expecting

the high conversion efﬁciency of solar cells. We wish to

report here the synthesis and interesting mesomorphism

with spiranthes-like supramolecular structure of the

novel liquid crystalline (C_nS)₆PcCu-C₆₀dyads.

Synthesis

The ﬁnal target Pc-C₆₀dyads, (C_nS)₆PcCu-C₆₀[1a–

1c: n = 14(a), 16(b), 18(c)], were synthesized according

to Scheme 1. The phthalonitriles, 2 and 3a–3c, were

prepared by the methods of Serin et al. [39] and Wöhrle

et al. [40], respectively. The Pc precursors, (C_nS)₆PcCu-

OH (4a–4c), were synthesized from these two different

phthalonitriles 2 and 3a–3c in a molecular ratio of 3:1.

The terminal OH group in 4a–4c was esteriﬁed with

p-formyl benzoic acid by Steglich reaction [41] to afford

(C_nS)₆PcCu-OFBA (5a–5c). Finally, the target Pc-C₆₀

dyads, (C_nS)₆PcCu-C₆₀(1a–5c), were synthesized from

5a–5c with N-methylglycine and fullerene by Prato

reaction [42].

We describe here the detailed procedures only for

the representative derivatives, 2, 3b, 4b, 5b and 1b. The

rest of the derivatives, 3a, 3c, 4a, 4c, 5a, 5c and 1a, 1c,

were prepared by same procedures. The details of these

compounds are described in electronic supplementary

material (see Supporting information).

4-(10-hydoroxydecyloxy)phthalonitrile (2). A mix-

ture of 4-nitrophthalonitrile (0.500 g, 2.89 mmol), dry

DMA (30 mL) and 1,10-decanediol (3.01 g, 17.3 mmol)

SR

RS

NC

(i)

NO₂

OC₁₀H₂₀OH

N

M

N

RS

(iii)

2

3

N

OC₁₀H₂₀OH

N

NC

SR

NC

Cl

(ii)

M = Cu

RS

SR

R = C_nH_2n+1

n = 14 : (a)

16 : (b)

4: (C_nS)₆PcCu-OH

18 : (c)

RS

SR

RS

SR

N

M

N

RS

(iv)

(v)

M

N

O

OC₁₀H₂₀

O

OC₁₀H₂₀

O

N

O

N

M = Cu

H

RS

SR

RS

5: (C_nS)₆PcCu-OFBA

1: (C_nS)₆PcCu-C₆₀

Scheme 1. Synthentic route for (C_nS)₆PcCu-C₆₀(1a–1c): (i) HOC₁₀H₂₀OH, K₂CO₃, DMAc, (ii) RSH, K₂CO₃, DMSO, (iii) CuCl₂,

DBU, 1-hexanol, oil bath/N₂, (iv) p-formyl benzoic acid, DCC, DMAP, C₂H₄Cl₂, for n = 14; p-formyl benzoic acid, DCC, DMAP,

CH₂Cl₂, for n = 16, 18, and (v) N-methylglycine, C₆₀, toluene. DMAc = N,N′-dimethylacetamide, DMSO = dimethylsulfoxide,

DBU = 1,8-diazabicyclo[5,4,0]-undec-7-ene, DCC = N,N′-dicyclohexylcarbodiimide and DMAP = 4-dimethylaminopyridine

J. Porphyrins Phthalocyanines 2014; 18: 369–379

370

A. ISHIKAWA ET AL.

was heated at 105°C for 0.5h with stirring under

nitrogen atmosphere. Then, potassium carbonate (2.39 g,

17.3 mmol) was added and the mixture was heated at

105°C for 18 h with stirring under nitrogen atmosphere

further. After cooling to rt, the reaction mixture was

extracted with dichloromethane and washed with

water. The organic layer was dried over Na₂SO₄and

evaporated in vacuo. The residue was puriﬁed by column

chromatography (silica gel 100g, chloroform:ethyl

acetate = 3:2, R_f= 0.63). After removal of solvent, a

pale yellow solid was obtained (0.501 g, yield 57.7%,

mp 61.0°C). IR (KBr): n, cm^-13550.50 (–OH), 2927.30,

acid (0.0246g, 0.168mmol), dry CH₂Cl₂(20mL) was

reﬂuxed under nitrogen atmosphere for 0.5 h. Then,

N,N′-dicyclohexylcarbodiimide (0.0988 g, 0.479 mmol),

N,N-dimethyl-4-aminopyridine (0.0337 g, 0.276 mmol)

was added and the mixture was reﬂuxed under nitrogen

atmosphere for 24h. 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 and

hot acetone successively, extracted with chloroform and

washed with water. The organic layer was dried over

Na₂SO₄and evaporated in vacuo. The crude product

was puriﬁed by column chromatography (silica gel

80 g, chloroform, Rf = 0.78). After removal of solvent,

dark green solid was obtained (0.0895 g, yield 83.0%).

Elemental analysis and MALDI-TOF mass data: see

Tables 1 and 2 and Fig. S1-2. UV-vis spectral data:

see Table 3 and Fig. S2. Phase transition behavior: see

Table 4.

(C₁₆S)₆PcCu-C₆₀(1b). A mixture of (C₁₆S)₆PcCu-

OFBA (5b: 0.0548g, 0.0227mmol), C₆₀fullerene

(0.0328 g, 0.0455 mmol), dry toluene (20 mL), N-methyl-

glycine (0.0050g, 0.056mmol) was reﬂuxed under

nitrogen atmosphere for 14h. After cooling to rt., the

solvent was evaporated under reduced pressure. The

residue extracted with chloroform and washed with water.

The organic layer was dried over Na₂SO₄and evaporated

in vacuo. The crude product was puriﬁed by column

chromatography (silica gel 80g, chloroform:n-hexane =

1:1, Rf = 0.40) and further puriﬁcation was carried out

by using HPLC (Japan Analytical Industry Co. Ltd:

LC-918). After removal of solvent, dark green solid was

obtained (0.0449 g, yield 62.4%). Elemental analysis

and MALDI-TOF mass data: see Tables 1 and 2 and

Fig. S1-3. UV-vis spectral data: see Table 3 and Fig. S2.

Phase transition behavior: see Table 4.

1

2850.87 (–CH₂–), 2227.51 (–CN), 1592.95 (C=C). H

NMR (CDCl₃, TMS): d, ppm 7.70 (d, 1H, J = 8.8 Hz,

Ar-H), 7.25 (d, 1H, J = 8.8 Hz, Ar-H), 7.17 (dd, 1H, J₁=

8.8 Hz, J₂= 2.8 Hz, Ar-H), 4.05 (t, 2H, J = 7.1, –OCH₂–),

3.67 (t, 2H, J = 7.3, –CH₂–), 1.89–1.81 (m, 2H, –CH₂–),

1.65~1.56 (m, 2H, –CH₂–), 1.41–1.32 (m, 12H, –CH₂–).

4,5-bis(hexadecylthio)phthalonitrile (3b). A mixture

of 4,5-dichlorophthalonitrile (1.00g, 5.08mmol), hexa-

decane-1-thiol (3.17 g, 12.3 mmol), dry DMSO (20 mL)

and potassium carbonate (2.76 g, 20.0 mmol) was

heated at 110°C for 1.5 h with stirring under nitrogen

atmosphere. After cooling to rt, the reaction mixture was

extracted with chloroform and washed with water. The

organic layer was dried over Na₂SO₄and evaporated in

vacuo. The residue was recrystallized from n-hexane at

-20°C. The residue was puriﬁed by column chromato-

graphy (silica gel 50 g, chloroform, R_f= 0.69). After

removal of solvent, lilac solid was obtained (2.42 g, yield

74.2%, mp 71.0°C). IR (KBr): n, cm^-12919.61, 2850.14

(–CH₂–), 2227.32 (–CN), 1562.96 (C=C). ¹H NMR

(CDCl₃, TMS): d, ppm 7.40 (s, 2H, Ar-H), 3.01 (t, 4H,

J = 8.1 Hz, –S–CH₂–), 1.79–1.70 (m, 4H, –CH₂–), 1.26

(s, 48H, –CH₂–), 0.88 (t, 6H, J = 7.6, –CH₃).

(C₁₆S)₆PcCu-OH (4b). A mixture of 4-(10-hydroxy-

decyloxy)-phthalonitrile (2: 0.0800g, 0.266mmol), 4,5-bis-

(hexadecylthio)-phthalonitrile (3b: 0.513 g, 0.800 mmol),

1-hexanol (15 mL) and CuCl₂(55 mg, 0.41 mmol) was

reﬂuxed under nitrogen atmosphere for 0.5h. Then,

DBU (8 drops) was added and the mixture was reﬂuxed

under nitrogen atmosphere for 24h. 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, extracted

with chloroform and washed with water. The organic

layer was dried over Na₂SO₄and evaporated in vacuo. The

crude product was puriﬁed by column chromatography

(silica gel 150 g, chloroform, Rf = 0.15). After removal

of solvent, dark green solid was obtained (0.171 g, yield

28.1%). Elemental analysis and MALDI-TOF mass data:

see Tables 1 and 2 and Fig. S1-1. UV-vis spectral data:

see Table 3 and Fig. S2. Phase transition behavior: see

Table 4.

Measurements

The infrared absorption spectra were recorded by using

a Nicolet NEXUS670 FT-IR. The ¹H NMR measurements

were carried out by using H NMR (Bruker Ultrashield

1

400 M Hz). The elemental analyses were performed by

using a Perkin-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 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

holderadoptedaMettlerFP82HThotstage.FiguresS3and

(C₁₆S)₆PcCu-OFBA (5b). A mixture of (C₁₆S)₆PcCu-

OH (4b: 0.103g, 0.0448mmol), p-formyl benzoic

J. Porphyrins Phthalocyanines 2014; 18: 370–379

DISCOTIC LIQUID CRYSTALS OF TRANSITION METAL COMPLEXES

371

S4 illustrate the setup of the SAXS system and the setup

As can be seen from the data of MALDI-TOF mass

and elemental analysis listed in Table 1, the observed

values of the Pc precursors, (C_nS)₆PcCu-OH (4a–4c) and

(C_nS)₆PcCu-OFBA (5a–5c), were in good accordance

with the calculated values, so that we conﬁrmed that they

could be surely prepared. On the other hand, elemental

analysis of the Pc-C₆₀dyads synthesized in our previous

work was also carried out, but it was not completely

burnt out that the observed carbon content showed

lower percentage than the calculated value by several

percent [35]. This is a well-known characteristic of less

ﬂammable phthalocyanine derivatives [43]. Hence, we

did not furthermore carry out the elemental analyses

for other Pc-C₆₀dyads 1a–1c and the results of the

elemental analyses are omitted here for 1a–1c. However,

as can be seen from Table 2 and Fig. S1, the observed

and calculated values of exact mass, for example, those

of (C₁₆S)₆PcCu-C₆₀(1b) are (3163.63, 2443.56) and

3163.63, respectively. The observed values gave two

peaks for all the (C_nS)₆PcCu-C₆₀(1a–1c) dyads. One

peak corresponds to the calculated exact mass. On the

other hand, another peak corresponds to an exact mass

smaller by 720 than the calculated exact mass. The

mass of 720 is compatible with the molecular weight of

fullerene (C₆₀). The fraction peak that is smaller by 720

than the calculated value may be resulted from cleavage

of the fullerene (C₆₀) moiety from the (C_nS)₆PcCu-C₆₀

(1a–1c) dyads by the laser irradiation in the MALDI-

TOF mass measurements.

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.

RESULTS AND DISCUSSION

Synthesis

Each of the phthalonitriles 2 and 3a–3c could be

easily prepared from the commercially available starting

materials by one step. The yields of 3a–3c were relatively

good at 62.2~74.2%. However, the yields of the 3:1

Pc precursors, (C_nS)₆PcCu-OH (4a–4c), were low at

28.1~31.4% (Table 1), because the 4:0 Pc by-products

were not avoided in this reaction. On the other hand,

the precursors (C_nS)₆PcCu-OFBA (5a–5c) could be

obtained in high yields at 73.8~94.0% by the esteriﬁcation

of Steglich reaction (Table 1). The reaction solvent was

dichloromethane for the esteriﬁcation of 4b, 4c → 5b,

5c, but the reaction of 4a → 5a did not well proceed in

dichloromethane. It was attributed to the low solubility

of 4a in dichloromethane. When the reaction solvent

was changed from dichloromethane (bp = 39.8°C, e =

9.1) to 1, 2-dichloroethane (bp = 83.5°C, e = 10.45),

the reaction smoothly proceeded. The ﬁnal target Pc-C₆₀

dyads, (C_nS)₆PcCu-C₆₀(1a–1e), were obtained in yields

of 55.3~62.4% by Prato reaction [42] (Table 1).

To further conﬁrm the formation of these Pc-C₆₀

dyads, electronic absorption spectra were measured for

the chloroform solutions of the (C_nS)₆PcCu-C₆₀(1a–

1c) dyads. The electronic spectral data are summarized

in Table 3. An absorption characteristic to fullerene

appears at ca. 250 nm in the electronic spectra [44]. As

can be seem from this table, each of the (C_nS)₆PcCu-C₆₀

(1a–1c) dyads gave an additional peak at ca. 250~256

nm characteristic to fullerene moiety. The (C_nS)₆PcCu-

OFBA precursors did not give such an additional peak at

Table 1. Elemental analysis data and yields of (C_nS)₆PcCu-OH (4a–4c), (C_nS)₆PcCu-OFBA (5a–5c) and (C_nS)₆PcCu-C₆₀(1a–1c)

Compound

Mol. formula (Mol. wt)

Found (Calcd.) (%)

H

Yield (%)

C

N

4a: (C₁₄S)₆PcCu-OH

4b: (C₁₆S)₆PcCu-OH

4c: (C₁₈S)₆PcCu-OH

C₁₂₆H₂₀₄N₈O₂S₆Cu (2118.96)

C₁₃₈H₂₂₈N₈O₂S₆Cu (2287.28)

C₁₅₀H₂₅₂N₈O₂S₆Cu (2455.59)

71.25 (71.42)

71.89 (72.47)

73.25 (73.37)

9.78 (9.70)

10.05 (10.05)

10.44 (10.34)

5.28 (5.29)

4.94 (4.90)

4.66 (4.56)

31.4

28.1

29.3

5a: (C₁₄S)₆PcCu-OFBA

5b: (C₁₆S)₆PcCu-OFBA

5c: (C₁₈S)₆PcCu-OFBA

C₁₃₄H₂₀₈N₈O₄S₆Cu (2251.07)

C₁₄₆H₂₃₂N₈O₄S₆Cu (2419.41)

C₁₅₈H₂₅₆N₈O₄S₆Cu (2587.71)

71.66 (71.50)

72.05 (72.48)

73.34 (73.34)

9.50 (9.31)

9.60 (9.67)

10.09 (9.97)

4.84 (4.98)

4.54 (4.63)

4.33 (4.33)

73.9

83.0

94.0

1a: (C₁₄S)₆PcCu-C₆₀

1b: (C₁₆S)₆PcCu-C₆₀

1c: (C₁₈S)₆PcCu-C₆₀

C₁₉₆H₂₁₃N₉O₃S₆Cu (2998.76)

C₂₀₈H₂₃₇N₉O₃S₆Cu (3167.16)

C₂₃₀H₂₆₁N₉O₃S₆Cu (3335.43)

—

59.0

62.4

55.3

J. Porphyrins Phthalocyanines 2014; 18: 371–379

372

A. ISHIKAWA ET AL.

Table 2. MALDI-TOF mass spectral data of (C_nS)₆PcCu-OH (4a–4c), (C_nS)₆PcCu-OFBA

(5a–5c) and (C_nS)₆PcCu-C₆₀(1a–1c)

Compound

Exact mass (M⁺) calculated

Exact mass (M⁺) observed

4a: (C₁₄S)₆PcCu-OH

4b: (C₁₆S)₆PcCu-OH

4c: (C₁₈S)₆PcCu-OH

2116.37

2284.56

2452.75

2116.30

2284.51

2452.65

5a: (C₁₄S)₆PcCu-OFBA

5b: (C₁₆S)₆PcCu-OFBA

5c: (C₁₈S)₆PcCu-OFBA

2248.39

2416.58

2584.77

2248.29

2416.53

2584.43

1a: (C₁₄S)₆PcCu-C₆₀

1b: (C₁₆S)₆PcCu-C₆₀

1c: (C₁₈S)₆PcCu-C₆₀

2995.44 (2275.44)

3163.63 (2443.63)

3331.82 (2611.82)

2995.40 (2275.36)

3163.63 (2443.56)

3331.81 (2611.88)

Table 3. UV-vis spectral data of compounds 4, 5 and 1 in chloroform

Compound

Concentration^#

(X10^-5mol/I)

l

_max(nm) (log e)

C₆₀peak

Soret-band

Q-band

4a: (C₁₄S)₆PcCu-OH

4b: (C₁₄S)₆PcCu-OH

4c: (C₁₄S)₆PcCu-OH

1.0

1.1

1.0

—

264.1 (4.62) 325.7 (4.83) 428.3 (4.36) 635.9 (4.59) 705.0 (5.07)

265.5 (4.68) 329.5 (4.85) 427.5 (4.42) 633.4 (4.62) 705.2 (5.10)

264.7 (4.71) 331.1 (4.89) 427.7 (4.44) 631.6 (4.63) 705.3 (5.12)

5a: (C₁₄S)₆PcCu-OFBA

5b :(C₁₆S)₆PcCu-OFBA

5c: (C₁₈S)₆PcCu-OFBA

1.0

—

258.1 (4.74) 328.1 (4.82) 425.3 (4.36) 632.3 (4.58) 705.8 (5.09)

259.1 (4.83) 332.1 (4.90) 424.5 (4.45) 633.4 (4.66) 705.2 (5.15)

260.2 (4.72) 333.7 (4.77) 427.5 (4.30) 632.7 (4.52) 705.7 (5.04)

0.99

1.0

1a: (C₁₄S)₆PcCu-C₆₀

1b: (C₁₆S)₆PcCu-C₆₀

1c: (C₁₈S)₆PcCu-C₆₀

1.0

255.8 (5.11)

—

325.5 (4.98) 432.6 (4.38) ca. 643 (4.62) 705.4 (4.96)

322.4 (5.04) 431.7 (4.49) ca. 642 (4.73) 705.2 (5.03)

321.5 (5.00) 427.1 (4.45) ca. 646 (4.73) 704.7 (4.98)

1.0

255.8 (5.19) 270.1 (sh)

249.6 (5.11)

0.99

—

#: In chloroform. sh: Shoulder.

ca. 250~256 nm. From these electronic spectral data, it

was also certiﬁed that each of the (C_nS)₆PcCu-C₆₀(1a–

1c) derivatives bears a fullerene moiety.

Thus, we conﬁrmed from MALDI-TOF mass spectra

and the UV-vis spectra that all the target Pc-C₆₀dyads,

(C_nS)₆PcCu-C₆₀(1a–1c), couldbesuccessfullysynthesized.

uniformly decreased with the substituents changing as

OH (4) → OFBA (5) → C₆₀(1): 4a (-35°C) 5a (-85°C)

1a; 4b (-20°C) 5b (-98°C) 1b; 4c (-12°C) 5c (-84°C).

Especially, it should be notable that when OFBA → C₆₀,

the cp drastically decreased by 84°C~98°C. This may

be attributed to the big steric hindrance of spherical

fullerenes weakening the intermolecular force between

phthalocyanine disks in the column.

Phase transition behavior

Very interestingly, each of the (C_nS)₆PcCu-C₆₀(1a–

4c) dyads shows homeotropic alignment, although none

of the corresponding Pc precursors of (C_nS)₆PcCu-OH

(4a–4c) and (C_nS)₆PcCu-OFBA (5a–5c) does not show

homeotropic alignment. When the Pc-C₆₀dyad (1a–1c)

between two glass plates was heated up over their cp and

then the isotropic liquid was cooled down under the cp,

it showed perfect homeotropic alignment. The left part of

Fig. 3 shows a photomicrograph of the homeotropically

aligned Col_homesophase of 1a between cross polarizers at

Phase transition behavior and X-ray data of the

precursors (4a–4c, 5a–5c) and the Pc-C₆₀dyads (1a–1c)

are summarized in Tables 4 and 5, respectively. The phase

transition behaviors were established by using a polarizing

microscope, a differential scanning calorimeter, and a

temperature-dependent small angle X-ray diffractometer.

As can be seen from Table 4, each of the derivatives

showedonlyonemesophase, hexagonalorderedcolumnar

(Col_ho) phase. Very interestingly, the clearing point (cp)

J. Porphyrins Phthalocyanines 2014; 18: 372–379

DISCOTIC LIQUID CRYSTALS OF TRANSITION METAL COMPLEXES

373

Table 4. Phase transition temperatures and enthalpy changes

ꢀ

^-1)]

^T^{/ C}^[∆H(^kJmo^l→

Compound

Phase

285.0 [5.88]

50.0 [73.0]

Col_ho

K_2v

I.L.

4a: (C₁₄S)₆PcCu-OH

15.0 [44.1]

K₁

68.7 [128.1]

288.3 [6.98]

4b: (C₁₆S)₆PcCu-OH

4c: (C₁₈S)₆PcCu-OH

Col_ho

K

I.L.

57.6 ^*2

244.5 [2.48]

Col_ho

I.L.

K₂

37.7 ^*1

*1 + *2 = [101.8]

K₁

60.2 ^*2

37.2 ^*1

250.5 [2.26]

Col_ho

K_2v

K_3v

I.L.

5a: (C₁₄S)₆PcCu-OFBA

5b: (C₁₆S)₆PcCu-OFBA

5c: (C₁₈S)₆PcCu-OFBA

5.0 [33.2]

*1 + *2 = [63.6]

K₁

268.2 [6.25]

31.1 [28.4]

Col_ho

44.4 ^*3

K

I.L.

232.5 [1.53]

K₂

49.2 ^*4

Col_ho

I.L.

K₁

*3 + *4 = [132.2]

110.2 [3.03]

- 8.10 [11.6]

K₂

Col_ho

I.L.

1a: (C₁₄S)₆PcCu-C₆₀

1b: (C₁₆S)₆PcCu-C₆₀

1c: (C₁₈S)₆PcCu-C₆₀

- 15.6 [10.1]

K_1v

170.0 [1.49]

42.1 [33.8]

29.2 [5.36]

23.3 [28.2]

Col_ho

K_2v

I.L.

K₃

K₁

148.2 [5.81]

52.1 [ca. 107]

Col_ho

I.L.

K₂

31.5 [60.6]

K_1v

Phase nomenclature: K = crystal, Col_ho= hexagonal ordered columnar mesophase,

Col_hd= hexagonal disordered columnar mesophase, I.L. = isotropic liquid, and v = vir-

gin sample.

= mesophase showing homeotropic alignment for the non-virgin state.

rt. The right part of this ﬁgure shows a photomicrograph

of the scratched ﬁlm. As can be seen from the left

photomicrograph, the homeotropic alignment gave a

completely dark area. On the other hand, as can be seen

from the right photomicrograph, the scratched part only

gave bright area. Under these photomicrographs in Fig. 3,

schematic models of these alignments are illustrated. The

scratched parts gave disordered alignment of columns

as illustrated in this ﬁgure, so that the parts only turn to

bright area due to the resulted birefringence.

alignment-showing parent Pc compound, [(C_nO)₂PhO]₈-

PcCu [31]. In this work, we could synthesized the

novel homeotropic alignment-showing Pc-C₆₀dyads,

(C_nS)₆PcCu-C₆₀(1a–1c), at the ﬁrst time, from the non-

homeotropic alignment-showing parent Pc compound

(C_nS)₈PcCu [38] and the Pc precursors (C_nS)₆PcCu-OH

(4a–4c) and (C_nS)₆PcCu-OFBA (5a–5c). It may be

attributed to the strong afﬁnity between fullerene and

glass surface. Although the reason is not so clear at

the present time, this is very useful guideline for the

molecular design to prepare homeotropic alignment-

showing discotic liquid crystals. Furthermore, it is

noteworthy that the derivative (C₁₄S)₆PcCu-C₆₀(1a)

shows perfect homeotropic alignment from rt to 110°C

To date, we have synthesized several kinds of Pc-C₆₀

dyads showing perfect homeotropic alignment [19, 28,

30, 35, 36]. Each of them, e.g. [(C₁₂O)₂PhO]₆PcCu-C₆₀

[36], was obtained from a corresponding homeotropic

J. Porphyrins Phthalocyanines 2014; 18: 373–379

374

A. ISHIKAWA ET AL.

Table 5. X-ray data of 4a–4c, 5a–5c and 1a–1c

Compound (mesophase)

Lattice constants/Å

Spacing/Å

Observed

Miller indices

Calculated

31.1

17.9

15.5

—

(h k l)

(1 0 0)

(1 1 0)

(2 0 0)

#

4a: (C₁₄S)₆PcCu-OH

31.1

17.7

a = 35.9

h = 3.58

Z = 1.1 for r = 1.0

(Col_hoat 180°C)

15.6

ca. 4.8

3.58

—

(0 0 1)^h

4b: (C₁₆S)₆PcCu-OH

31.5

18.3

31.5

18.2

15.7

11.9

—

(1 0 0)

(1 1 0)

(2 0 0)

(2 1 0)

#

(Col_hoat 180°C)

a = 36.3

h = 3.51

Z = 1.1 for r = 1.0

15.8

11.9

ca. 4.8

3.51

—

(0 0 1)^h

4c: (C₁₈S)₆PcCu-OH

34.4

19.2

34.1

19.7

17.0

—

(1 0 0)

(1 1 0)

(2 0 0)

#

a = 39.4

h = 3.47

Z = 1.1 for r = 1.0

(Col_hoat 150°C)

17.0

ca. 4.7

3.47

—

(0 0 1)^h

5a: (C₁₄S)₆PcCu-OFBA

31.0

17.9

31.0

18.1

15.7

—

(1 0 0)

(1 1 0)

(2 0 0)

#

a = 36.2

h = 3.50

Z = 1.1 for r = 1.0

(Col_hoat 200°C)

15.7

ca. 4.9

3.50

—

(0 0 1)^h

5b: (C₁₆S)₆PcCu-OFBA

32.7

18.8

32.7

18.9

16.4

12.4

—

(1 0 0)

(1 1 0)

(2 0 0)

(2 1 0)

#

(Col_hoat 100°C)

a = 37.8

h = 3.46

Z = 1.1 for r = 1.0

16.3

12.2

ca. 4.6

3.46

—

(0 0 1)^h

5c: (C₁₈S)₆PcCu-OFBA

34.4

19.6

34.4

19.9

17.2

13.0

—

(1 0 0)

(1 1 0)

(2 0 0)

(2 1 0)

#

(Col_hoat 70°C)

a = 39.7

h = 3.44

Z = 1.1 for r = 1.0

17.5

13.2

ca. 4.7

3.44

—

(0 0 1)^h

1a: (C₁₄S)₆PcCu-C₆₀

75.4

31.5

—

31.5

18.2

—

H

a = 36.4

h = 3.43

Z = 0.8 for r = 1.0

(Col_hoat r.t)

(1 0 0)

(1 1 0)

#

18.2

ca. 4.6

3.43

—

(0 0 1)^h

1b: (C₁₆S)₆PcCu-C₆₀

73.9

31.7

—

31.7

18.4

—

H

a = 36.7

h = 3.44

Z = 1.3 for r = 1.0

(Col_hoat 60°C)

(1 0 0)

(1 1 0)

#

18.7

ca. 4.6

3.44

—

(0 0 1)^h

1c: (C₁₈S)₆PcCu-C₆₀

79.6

34.4

—

34.4

19.9

—

H

a = 39.7

h = 3.47

Z = 0.9 for r = 1.0

(Col_hoat 70°C)

(1 0 0)

(1 1 0)

#

19.6

ca. 4.6

3.47

—

(0 0 1)^h

# = Halo of the molten alkyl chain, h = Stacking distance between the monomers. H = Helical pitch of the

fullerenes. r: assumed density (g/cm³)

J. Porphyrins Phthalocyanines 2014; 18: 374–379

DISCOTIC LIQUID CRYSTALS OF TRANSITION METAL COMPLEXES

375

Fig. 3. Photomicrographs of (C₁₄S)₆PcCu-C₆₀(1a) at rt and schematic models of the columnar alignments

not only between two glass plates but also on a glass

plate. The homeotropic alignment-showing thin ﬁlm

could be easily obtained only by casting the chloroform

solution of 1a onto a glass plate at rt. It is very favorable

for the fabrication of organic thin ﬁlm solar cells.

Temperature-dependent SAXS study

Figure 4 shows temperature-dependent small angle

X-ray diffraction patterns of the Pc precursors 4b, 5b and

the Pc-C₆₀dyad 1b. These X-ray diffractions were measured

by using a sample packed in a small hole of glass plate as

illustrated in Fig. 5a. As can be seen from Fig. 4, each of

the Pc precursors, 4b at 180°C and 5b at 100°C, gave four

sharp peaks in the low angle region and two broad peaks

in the high angle region, respectively. These four peaks in

the low angle region were assigned to the reﬂections from

(100), (110) and (210) planes of a 2D hexagonal lattice

(Table 5). On the other hand, in the high angle region the

big broad peak corresponds to the molten alkylthio chains

and the small broad peak was assigned to the reﬂection

from (001) plane corresponding to the stacking distance

between the Pc disks in a column. Hence, this mesophase was

identiﬁed as a hexagonal ordered columnar (Col_ho) phase.

As can be seen from the X-ray diffraction pattern of

the dyad 1b at 60°C gave the reﬂections from (100),

(110) and (001) in a Col_homesophase similarly to the

Pc precursors 4b and 5b. However, it gave an additional

large reﬂection peak around 2q = 1^o, which is denoted

as Peak H hereafter. This Peak H could not be observed

for the Col_homesophases of the Pc precursors 4b and

5b, as can be seen from Fig. 4. Moreover, it could not

be assigned to any reﬂections from all the 2D lattices of

liquid crystalline phases known until now.

Fig. 4. Small angle X-ray diffraction patterns of (C₁₆S)₆PcCu-

OH, (C₁₆S)₆PcCu-OFBA and (C₁₆S)₆PcCu-C₆₀

J. Porphyrins Phthalocyanines 2014; 18: 375–379

376

A. ISHIKAWA ET AL.

Fig. 6. Small angle X-ray diffraction patterns of the Col_ho

mesophase in (C₁₆S)₆PcCu-C₆₀(1b): (a) non-homeotropically

aligned sample at 60°C, (b) homeotropically aligned sample

between two glass plates at 120°C and (c) only two soda-lime

glass plates at 120°C

1D lattice (Z-axis) direction, it should disappear in the

X-ray diffraction pattern for the homeotropically aligned

sample, as illustrated in Fig. 5b.

Figures 6a and 6b show the small angle X-ray

diffraction patterns of the Col_homesophase in the Pc-C₆₀

dyad, (C₁₆S)₆PcCu-C₆₀(1b), for the samples prepared

by using two methods illustrated in Figs 5a and 5b,

respectively. As can be seen from Fig. 6a, the non-

homeotropicallyalignedsamplegaveboth(100)reﬂection

peak and Peak H. On the other hand, as can be seen from

Fig. 6b, the homeotropically-aligned sample gave clearly

the (100) peak from the 2D lattice in XY-axes direction,

but Peak H completely disappeared. Therefore, Peak H

should be a periodicity in Z-axis direction. Since the

spacing of this Peak H is 75.4 Å, it cannot be a stacking

distance between the Pc disks in the columnar structure.

This peak appears only for the Pc-C₆₀dyad (1), but it does

not appear for the Pc precursors, 4 and 5. Hence, it can be

attributed to the stacking distance of fullerene moieties.

The stacking distance of the Pc disks in column is 3.43 Å,

so that twenty-two fullerenes may stack, as can be

calculated from an equation of 75.4 Å/3.43 Å = 22. Since

the diameter of a fullerene is 10 Å, twenty-two fullerenes

cannot linearly stack in 75.4Å, which is much shorter than

220 Å (= 10 Å × 22). Therefore, the fullerene moieties

should stack helically in Z-axis direction. If the fullerene

moieties would stack randomly in Z-axis direction, the

periodicity at 75.4 Å would not appear. Accordingly, we

can conclude that the present (C_nS)₆PcCu-C₆₀(1a–1c)

dyads also show perfect homeotropic alignment forming

spiranthes-like [37] supramolecular structure, similarly to

the previous [(C_nO)₂PhO]₆PcCu-C₆₀dyads illustrated in

Fig. 1b. This supramolecular structure is compatible with

1D nano-array [5] illustrated in Fig. 1a. Therefore, the

present spiranthes-like supramolecular structure of 1a–1c

may be more favorable for the application to organic thin

ﬁlm solar cells to raise their conversion efﬁciencies [45],

Fig. 5. Illustration of X-ray photograph of (a) non-alignment

and (b) homeotropic alignment of ordered columns between

two glass plates

Recently, we also observed this additional peak in

the same small angle region for the previously reported

Pc-C₆₀dyad, [(C₁₂O)₂PhO]₆PcCu-C₆₀. It was revealed

from the precise X-ray structure analysis that this peak is

originated from a helical structure of fullerene moieties

[36]. In order to certify that Peak H of the present Pc-C₆₀

dyads, (C_nS)₆PcCu-C₆₀(1a–1c), may be also originated

from the helical structure of fullerene moieties, we have

carried out X-ray diffraction measurements using our

previously developed methods [36].

When a sample is packed in a hole of glass plate

as illustrated in Fig. 5a, both reﬂection peaks due

to the columnar packing in the 2D lattice (XY-axes)

direction and reﬂection peaks due the stacking in the

1D lattice (Z-axis) direction can be observed, because

the domains are formed in all directions. On the other

hand, when a sample is cleared over cp and then cooled

down below cp between two cover glass plates to form

perfect homeotropic alignment as illustrated in Fig. 5b,

reﬂection peaks from the 2D lattice only appear but

reﬂection peaks from the 1D lattice disappear, because

all the columns align in one direction perpendicular

to the glass plates. As already mentioned above, the

present Pc-C₆₀dyads, (C_nS)₆PcCu-C₆₀(1a–1c), show

perfect homeotropic alignment between two glass

plates, which was revealed by polarizing microscopic

observations. Therefore, if Peak H would be along the

J. Porphyrins Phthalocyanines 2014; 18: 376–379

DISCOTIC LIQUID CRYSTALS OF TRANSITION METAL COMPLEXES

377

RS

SR

(C_nS)₈PcCu

Non-homeo.

N

M

N

SR

RS

N

R = C_nH_2n+1

M = Cu

RS

SR

RS

N

SR

4: (C_nS)₆PcCu-OH

Non-homeo.

N

M

N

RS

N

OC₁₀H₂₀OH

N

RS

SR

RS

N

5: (C_nS)₆PcCu-OFBA

Non-homeo.

N

M

N

RS

N

O

OC₁₀H₂₀

N

O

H

RS

SR

1: (C_nS)₆PcCu-C₆₀

Homeo.

h

RS

SR

H

N

RS

M

O

OC₁₀H₂₀

N

SR

RS

Fig. 7. Novel (C_nS)₆PcCu-C₆₀dyads (1a–1c) showing homeotropic alignment with spiranthes-like supramolecular structure obtained

from their non-homeotropic parent (C_nS)₈PcCu compounds and precursors (C_nS)₆PcCu-OH (4) and (C_nS)₆PcCu-OFBA (5)

J. Porphyrins Phthalocyanines 2014; 18: 377–379

378

A. ISHIKAWA ET AL.

because the present dyads 1a–1c can be more easily

synthesized than the previous [(C_nO)₂PhO]₆PcCu-C₆₀

dyads.

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_

http://www.jst.go.jp/sicp/ws2009 ge3rd/abstract/20.

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16. HanY, Chen L and ChenY. J. Poly. Sci. Poly. Chem.

2012; published online: DOI: 10.1002/pola.26394.

17. Li F, Chen W and ChenY. J. Mater. Chem. 2012; 22:

6259–6266.

We have synthesized novel liquid crystalline donor–

acceptor dyads, (C_nS)₆PcCu-C₆₀(n = 14, 16, 18: 1a–1c),

connected alkylthio-substituted PcCu and fullerene. The

mesomorphic properties and alignment behavior have

been established for the Pc-C₆₀dyads (1a–1c) together

with their Pc precursors, (C_nS)₆PcCu-OH (4a–4c) and

(C_nS)₆PcCu-OFBA (5a–5c). Each of the derivatives, 4, 5

and 1, shows only one mesophase, Col_ho. As summarized

in Fig. 7, neither the parent Pc compounds (C_nS)₈PcCu

(1a–1c) nor the Pc precursors of (C_nS)₆PcCu-OH (4a–

4c) and (C_nS)₆PcCu-OFBA (5a–5c) show homeotropic

alignment, whereas the Pc-C₆₀dyads, (C_nS)₆PcCu-C₆₀

(1a–1c), show perfect homeotropic alignment between

two glass plates for the Col_homesophase. It may be

attributed to the strong afﬁnity between fullerene and

glass surface. Although the reason is not so clear at

the present time, this is very useful guideline for the

molecular design to prepare homeotropic alignment-

showing discotic liquid crystals. Very interestingly,

in the Col_homesophase the Pc-C₆₀dyads 1a–1c form

“Spiranthes-like” supramolecular structure in which

the Pc disks stack face-to-face to form columns and the

fullerene moieties helically stack around the columns.

This supramolecular structure is compatible with the 1D

nano-array structure proposed by Yoshikawa et al., so

that the present Pc-C₆₀dyads (1a–1c) are very favorable

for the application to organic thin ﬁlm solar cells to raise

the conversion efﬁciency.

18. Bushby JR, Hamley IW, Liu Q, Lozman OR and

Lydon EJ. J. Mater. Chem. 2005; 15: 4429–4434.

19. Uchida S, Kude Y, Nishikitani Y and Ota (= Ohta)

K. Jpn. Kokai Tokkyo Koho. JP 2008214227(A)-

2008-09-18 (priority number: JP2007060604; sub-

mission date: 2007-03-09).

Acknowledgements

This work is partially supported by Grant-in-Aid

for Green Innovation Research in 2013 from Shinshu

University, Japan.

20. Zhou X, Kang SW, Kumar S, Kulkarni RR, Cheng

SZD and Li Q. Chem. Mater. 2011; 20: 3551–3553.

21. de la Escosura A, Martınez-Dıaz MV, Barbera J and

Torres T. J. Org. Chem. 2008; 73: 1475–1480.

22. Tashiro K and Aida T. J. Am. Chem. Soc. 2008; 130:

13812–13813.

Supporting information

Figures S1–S4 are given in the supplementary

material. This material is available free of charge via

the Internet at http://www.worldscinet.com/jpp/jpp.

shtml.

23. Geerts YH, Debever O, Amato C and Sergeyev S.

Beilstein J. Org. Chem. 2009; 5: 1–9.

24. Thiebaut O, Bock H and Grelet E. J. Am. Chem.

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25. Hayashi H, Nihashi W, Umeyama T, MatanoY, Seki

S, Shimizu Y and Imahori H. J. Am. Chem. Soc.

2011; 133: 10736–10739.

26. Bagui M, Dutta T, Chakraborty S, Melinger JS,

Zhong H, Keightley A and Peng Z. J. Phys. Chem.

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Article Doi

Discotic liquid crystals of transition metal complexes 50: Spiranthes-like supramolecular structure of phthalocyanine-fullerene dyads

DOI: 10.1142/S1088424614500072

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Article abstract of DOI:10.1142/S1088424614500072

Full text of DOI:10.1142/S1088424614500072

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