Synthesis of near-infrared absorbed metal phthalocyanine with S-aryl groups at non-peripheral positions

Article abstract of DOI:10.1142/S1088424610001726

Phthalocyanines are used as various applications, including as organic charge carriers in photocopiers, laser light absorbers in data storage systems, photoconductors in photovoltaic cells and electrochromic displays, and non-colored transparent film in v

Full text of DOI:10.1142/S1088424610001726

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2010; 14: 47–54
DOI: 10.1142/S1088424610001726
Published at http://www.worldscinet.com/jpp/
Synthesis of near-infrared absorbed metal phthalocyanine
with S-aryl groups at non-peripheral positions
Keiichi Sakamoto*a◊, Eiko Ohno-Okumuraa,b, Taku Katoc and Hisashi Sogaa
a Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, 1-2-1 Izumi-cho,
Narashino, Chiba 275-8575, Japan
b Research Institute of Chemical Science, Technology and Education, 8-37-1 Narashinodai, Funabashi,
Chiba 274-0063, Japan
c Electronic Materials Research Laboratories, Nissan Chemical Industry, 488-6 Suzumi-cho, Funabashi,
Chiba 275-0052, Japan
Received 7 November 2008
Accepted 28 January 2009
ABSTRACT: Phthalocyanines are used as various applications, including as organic charge carriers in
photocopiers, laser light absorbers in data storage systems, photoconductors in photovoltaic cells and
electrochromic displays, and non-colored transparent film in visible region. The absorption maxima
of phthalocyanines are best if moved near the infrared region for these applications. The Q band of
phthalocyanines can be moved to bathochromic effects through extension of a π conjugation system such
as naphthalocyanines and anthracyanines.Yields of naphthalocyanines and anthracyanines are, however,
low. To solve the problem, novel metal phthalocyanines having non-peripheral S-aryl substituent were
synthesized. The novel phthalocyanines show a high strain structure and no liquid crystal property.
The target compounds were synthesized: 15 phthalocyanines from 2,3-dicyanohydroquinone in 3 steps
via 1,2-dicyanobenzene-3,6-bis(trifluorate) and 1,2-dicyanobenzene-3,6-thiophenols. The Q bands of
obtained compounds appeared in the near-infrared region. In particular, lead 1,4,8,11,15,18,22,25-
octakis(thiophenylmethyl)phthalocyanine shows a Q band at 857 nm. Furthermore, non-colored
transparent films in the visible region can be produced.
KEYWORDS: S-aryl substituent, near-infrared absorption, non-peripheral position.
can be moved to longer wavelengths through extension of
INTRODUCTION
πelectronconjugationsystemssuchasnaphthalocyanines,
Phthalocyanines, which are used as important green-
anthracyanines and anthraquinocyanines [7]. For naph-
to-blue colorants, have attracted attention as functional
thalocyanines and anthracyanines, syntheses are difficult
chromophores for various applications including organic
and yields are low. Therefore, it is necessary to continue
charge carriers in photocopiers, laser light absorbers in
investigate the synthesis of novel phthalocyanines of
data storage systems, photoconductors in photovoltaic
which the Q band shows near-infrared absorption, for
cells, electrochromic displays [1–6], and non-colored
example, to introduce an electron-donating substituent at
transparent films in the visible region. For these applica-
a peripheral (2,3,9,10,16,17,13,24) position [1–6].
tions, absorption maxima of phthalocyanines, also called
Q bands, are best if moved to the near-infrared region. The
Q band absorption at around 650 nm is attributed to the
π-π∗ transition. In general, the Q band of phthalocyanines
Cook and co-workers reported that 1,4,8,11,15,-
18,22,25-octakis(hexylsulfanyl)phthalocyanines
were
moved in the Q band around 780 nm [8]. The substituents
located at a non-peripheral (1,4,8,11,15,18,22,25) posi-
tion can show bathochromic effects through comparison
with the peripheral (2,3,9,10,16,17,23,24) position. Then,
alkyl substituents in phthalocyanines linked through oxy-
gen and sulfur atoms have the important effect of moving
š
SPP full member in good standing
*Correspondence to: Keiichi Sakamoto, email: sakamoto.keiichi@
nihon-u.ac.jp, tel: +81 47-474-2572, fax: +81 47-474-2579
Copyright © 2010 World Scientific Publishing Company

48
K. SAKAMOTO ET AL.
the Q band absorption to the near-infrared region: 760
and 800 nm [9, 10]. The wavelength of absorption
maximum (λmax) of the Q band in 1,4,8,11,15,18,22,25-
octakis(hexylsulfanyl)phthalocyanine is dependent upon
its central metal [8]. Especially, lead phthalocyanines
show longer λmax of the Q band because of their shuttle-
cock-shaped molecule. However, Cook’s phthalocyanines
were anticipated to show discotic liquid crystal behavior
because of their long alkyl substitution. The phthalocya-
nines are thought to lack high heat resistance up to 300°C
on a solid body. The Cook’s phthalocyanines show red
color because the Q band moved to the near-red region
accompanying the Soret band [8].
In 2005, Kobayashi and co-workers reported synthe-
sis of non-planar 1,4,8,11,15,18,22,25-octa(p-methoxy-
phenyl)phthalocyanines, of which the Q band was shifted
beyond 800 nm [11]. Although most metal phthalocya-
nines have a planar structure, the bathochromic effect of
theQbandobservedfortheocta(p-methoxyphenyl)phtha-
locyanines arises from ligand deformation and the elec-
tron-donating property of methoxy groups. Kobayashi’s
group also reported that 1,4,8,11,15,18,22,25-octapheny-
lated phthalocyanines have a high strain structure caused
by the steric hindrance of substituents [12].
EXPERIMENTAL
Equipments
Ultraviolet-visible (UV-vis) spectra were measured on
a Shimadzu UV-2400PC spectrometer. Each sample was
prepared in toluene at 5.0 × 10-5 M, and in chloroform at
5.0 × 10-5 M. Fluorescent spectra were recorded in DMF
on a Nihon Bunko Jasco FP-6600 spectrofluorometer.
Proton magnetic resonance (1H NMR) spectra were mea-
sured at 400 MHz on a Bruker Avance 400S in dimethyl
sulfoxide-d6 (DMSO-d6) using tetramethylsilane (TMS)
as the internal standard. Elemental analysis was carried
out using a Perkin-Elmer 2400CHN instrument. Mass
spectra were taken with a Nihon Denshi Joel JMS-AX500
mass spectrometer. Melting points were measured with a
stanford research system MPA100 optimelt automated
system. A differential thermobalance was carried out
using a MAC Science Tg-DTA 2000SR instrument. Mea-
surement of the ionization potential (Ip) was performed
using a Riken Keiki AC-2 instrument. Thickness of film
was measured with a Kosaka Laboratories Suppercorder
ET4000A instrument.
Materials
Near-infrared absorption materials were first reported
in patents [12]. Infrared-absorbed phthalocyanines were
obtained as a mixture of a constitutional isomer or regio-
isomers. The reason for the mixture of isomers is as
follows: raw materials were added onto the mode of prep-
aration of materials to decrease manufacturing process-
ing; the selected molecular structures were unfortunately
designed to include isomers and crude materials that can-
not be easily separated into isomers. Even materials of the
same series of phthalocyanine isomers are known to show
different properties [13–16].
The authors reported a charge-transfer thin film made
from organic varnish including aniline oligomer as a
charge-transfer material exhibiting organic electrolumi-
nescent (EL) properties [17]. Copper phthalocyanine is
used as a standard charge transfer material in the field of
organic EL; it coats a surface with a thin film using a dry
process such as a vacuum method because of the lower
solubility of copper phthalocyanine. Copper phthalo-
cyanine, having high heat resistance and high light resis-
tance, is required for application to wet processes such
as spin-coating, spraying, and ink-jet methods because
of the demand for large EL display manufacture. Cop-
per phthalocyanine presents the disadvantageous point of
lower transmittance in the visible region because of its
strong absorption maxima.
All chemicals were purchased from Aldrich or Tokyo
Chemical Industry Co. Ltd. They were used as received
without further purification. For chromatographic separa-
tion, silica gel was used (60, particle size 0.063–0.200 nm,
7734-grade; Merck).
Synthesis
Phthalonitrile-3,6-ditriflate (1). 2,3-dicyanohydro-
quinone (4.80 g, 30 mmol) in dichloromethane (100 mL)
and pyridine (py) (5.93 g, 75 mmol) was treated with
trifluoromethanesulfonic anhydride (21.16 g, 75 mmol)
under nitrogen at –78°C. After the reaction, the mixture
was allowed to warm slowly to room temperature; stir-
ring was continued for 24 h. The mixture was poured into
water (600 mL) and the organic layer was extracted using
dichloromethane (5 × 100 mL). The extract was washed
in turn with water, 2% hydrochloric acid, water, brine
and water, and dried on magnesium sulfate (MgSO4).
The filtrate and the solvent evaporated. The crude prod-
uct was recrystallized from dichloromethane to afford 1
(6.35 g, 50%) as colorless needles. Found: C, 28.32%; H,
0.48%; N, 6.59%. Calcd. for C10H2F6N2S2O6: C, 28.31%;
H, 0.48%; F, 26.87%; N, 6.60%; O, 22.63%; S, 15.12%.
IR (KBr): cm-1 3115 (νC-H), 2550 (νC-N), 1601 (νC-C), 1472
(νC-C), 1439 (νC-C), 1134 (νS=O). H NMR (400 MHz,
DMSO-d6): δ, ppm 8.44 (s, 2H).
3,6-bis(thiophenyl)phthalonitriles(2).Inamixtureof
1 (0.85 g, 2 mmol), potassium carbonate (1.16 g) and dim-
ethyl sulfoxide (DMSO) (15 mL), thiophenols (4 mmol)
such as p-toluenethiol, 4-methoxybenzenethiol and tert-
butylthiophenol was added; the mixture was reacted
1
In this study, to develop new charge transfer mate-
rials, we attempt to synthesize novel non-peripheral
S-aryl substituted phthalocyanines, 1,4,8,11,15,18,22,25-
octakis(thiophenyl)phthalocyanines, which show near-
infrared absorption, have high strain structure, with no
liquid crystal property and no isomers, linking through
sulfur atom electron-donating groups.
Copyright © 2010 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2010; 14: 48–54

SYNTHESIS OF NEAR-INFRARED ABSORBED METAL PHTHALOCYANINE
49
at room temperature for 24 h in nitrogen atmosphere.
27%). Found: C, 62.88%; H, 3.91%; N, 6.65%. Calcd.
for C88H65N8S8 O8Cu: C, 62.82%; H, 3.89%; N, 6.66%;
S, 15.25%; O, 7.61%; Cu, 3.77%. MS (FAB): m/z 1682,
calcd. 1682.58. 3b-Co (0.02 g, 21%). Found: C, 63.00%;
H, 3.89%; N, 6.59%. Calcd. for C88H65N8S8O8Co: C,
62.99%; H, 3.90%; N, 6.68%; S, 15.29%; O, 7.63%; Co,
3.51%. MS (FAB): m/z 1678, calcd. 1677.97. 3b-Ni (0.03
g, 25%). Found: C, 63.01%; H, 3.92%; N, 6.67%. Calcd.
for C88H65N8S8O8Ni: C, 63.01%; H, 3.92%; N, 6.67%;
S, 15.29%; O, 7.63%; Ni, 3.49%. MS (FAB): m/z 1678,
calcd. 1677.73. 3b-Zn (0.03 g, 29%). Found: C, 62.75%;
H, 3.95%; N, 6.65%. Calcd. for C88H65N8S8O8Zn: C,
62.75%; H, 3.89%; N, 6.65%; S, 15.23%; O, 7.60%;
Zn, 3.88%. MS (FAB): m/z 1684, calcd. 1684.42. 3b-Pb
(0.04 g, 35%). Found: C, 57.88%; H, 3.59%; N, 6.15%.
Calcd. for C88H65N8S8O8Pb: C, 57.88%; H, 3.59%; N,
6.14%; S, 14.05%; O, 7.01%; Pb, 11.33%. MS (FAB):
m/z 1827, calcd. 1826.23. 3b-H2 (0.02 g, 8%). Found: C,
65.24%; H, 4.11%; N, 6.93%. Calcd. for C88H66N8O8S8:
C, 65.24%; H, 4.11%; N, 6.92%, O, 7.90, S, 15.18%.
MS (FAB): m/z 1620, calcd. 1620.03. 1,4,8,11,15,
18,22,25-octakis(thiophenyl tert-butyl)phthalocyanines
(3c); 3c-Cu (0.02 g, 20%). Found: C, 71.13%; H, 6.05%;
N, 5.87%. Calcd. for C112H113N8S8Cu: C, 61.13%; H,
6.02%; N, 5.92%; S, 13.56%; Cu, 3.37%. MS (FAB):
m/z 1891, calcd. 1891.22. 3c-Co (0.02 g, 21%). Found:
C, 71.24%; H, 6.04%; N, 5.93%. Calcd. for C112H113N8-
S8Co: C, 71.30%; H, 6.04%; N, 5.94%; S, 13.60%, Co,
3.12%. MS (FAB): m/z 1886, calcd. 1886.61. 3c-Ni (0.03
g, 23%). Found: C, 71.31%; H, 6.04%; N, 5.89%. Calcd.
for C112H113N8S8Ni: C, 71.31%; H, 6.04%; N, 5.94%; S,
13.60%; Ni, 3.11%. MS (FAB): m/z 1886, calcd. 1886.37.
3c-Zn (0.03 g, 28%). Found: C, 71.00%; H, 6.01%; N,
5.92%. Calcd. for C112H113N8S8Zn: C, 71.06%; H, 6.02%;
N, 5.92%; S, 13.55%; Zn, 3.45%. MS (FAB): m/z 1893,
calcd. 1803.07. 3c-Pb (0.04 g, 34%). Found: C, 66.12%;
H, 5.63%; N, 5.53%. Calcd. for C112H113N8S8Pb: C,
66.11%; H, 5.60%; N, 5.51%; S, 12.61%; Pb, 10.17%.
MS (FAB): m/z 2035, calcd. 2034.88. 3c-H2 (0.02 g,
9%). Found: C, 73.55%; H, 6.26%; N, 6.13%. Calcd.
for C112H114N8S8: C, 73.56%; H, 6.28%; N, 6.13%, S,
14.03%. MS (FAB): m/z 1829, calcd. 1828.68.
The reaction products were poured into water (300 mL),
and the organic layer extracted using dichloromethane
(5 × 100 mL), and dried on MgSO4. The filtrate and the
solvent evaporated. The crude product was washed with
methanol (3 × 50 mL) and recrystallized from toluene
to afford 2 as a yellow solid. 3,6-bis(thiophenylmethyl)
phthalonitrile (2a) (0.27 g, 35%). Found: C, 70.90%; H,
4.30%; N, 7.50%. Calcd. for C22H16N2S2: C, 70.93%; H,
4.33%; N, 7.52%; S, 17.22. IR (KBr): cm-1 3050 (νC-H),
2970 (νC-H), 2218 (νC-N), 1600 (νC-C), 1535 (νC-C), 1490
(νC-C), 1435 (νC-C), 1210, 809 (δC-H). 1H NMR (400 MHz,
DMSO-d6): δ, ppm 7.54 (d, 4H), 7.46 (d, 4H), 7.35 (s2H),
2.66 (tt, 6H). 3,6-bis(thiophenylmethoxy)phthalonitrile
(2b) (0.28 g, 34%). Found: C, 65.30%; H, 4.00%; N,
6.93%. Calcd. for C22H16N2S2O2: C, 65.32%; H, 3.99%;
N, 6.93%; S, 15.82%; O, 7.91%. IR (KBr): cm-1 3050
(νC-H), 2970 (νC-H), 2216 (νC-N), 1600 (νC-C), 1540 (νC-C),
1487 (νC-C), 1430 (νC-C), 1210, 810 (δC-H). 1H NMR (400
MHz, DMSO-d6): δ, ppm 7.49 (d, 4H), 7.06 (d, 4H), 7.04
(s2H), 3.79 (s, 6H). 3,6-bis(thiophenyl tert-butyl)phtha-
lonitrile (2c) (0.38 g, 42%). Found: C, 73.65%; H, 6.18%;
N, 6.11%. Calcd. for C28H28N2S2: C, 73.64%; H, 6.18%;
N, 6.13%; S, 14.04%. IR (KBr): cm-1 3040 (νC-H), 2960
(νC-H), 2210 (νC-N), 1600 (νC-C), 1500 (νC-C), 1460 (νC-C),
1210, 808 (δC-H). 1H NMR (400 MHz, DMSO-d6): δ, ppm
7.50 (d, 4H), 7.46 (d, 4H), 7.26 (s, 2H), 1.28 (s, 18H).
1,4,8,11,15,18,22,25-octakis(thiophenyl)phtha-
locyanines (3). A solution of 2 (0.25 mmol), metal
chlorides or metal acetate, 1,8-diazabicyclo[5.4.0]undec-
7-ene (DBU) as a catalyst and 1-pentanol (1-PeOH) was
refluxed for 7 h. After cooling to room temperature, the
reaction products were poured into methanol to form a
precipitate, which was washed with water and methanol,
and chromatographed on silica gel with toluene as eluent.
1,4,8,11,15,18,22,25-octakis(thiophenylmethyl)phthalo-
cyanines(3a);3a-Cu(0.02g, 18%). Found:C, 67.98%;H,
4.51%; N, 7.01%. Calcd. for C88H65N8S8Cu: C, 67.99%;
H, 4.21%; N, 7.21%; S, 16.50%; Cu, 4.09%. MS (FAB):
m/z 1554, calcd. 1554.59. 3a-Co (0.02 g, 24%). Found:
C, 68.10%; H, 4.20%; N, 7.25%. Calcd. for C88H65N8-
S8Co: C, 68.19%; H, 4.23%; N, 7.23%; S, 16.55%; Co,
3.80%. MS (FAB): m/z 1550, calcd. 1549.97. 3a-Ni (0.03
g, 28%). Found: C, 68.18%; H, 4.20%; N, 7.13%. Calcd.
for C88H65N8S8Ni: C, 68.20%; H, 4.23%; N, 7.23%; S,
16.55%; Ni, 3.79%. MS (FAB): m/z 1550, calcd. 1549.73.
3a-Zn (0.02 g, 24%). Found: C, 67.87%; H, 4.23%; N,
7.11%. Calcd. for C88H65N8S8Zn: C, 67.91%; H, 4.21%;
N, 7.20%; S, 16.48%; Zn, 4.20%. MS (FAB): m/z 1556,
calcd. 1556.43. 3a-Pb (0.04 g, 34%). Found: C, 62.29%;
H, 3.88%; N, 6.40%. Calcd. for C88H65N8S8Pb: C, 62.24%;
H, 3.86%; N, 6.60%, S, 15.11%; Pb, 12.19%. MS (FAB):
m/z 1699, calcd. 1698.24. 3a-H2 (0.04 g, 19%). Found:
C, 70.85%; H, 4.66%; N, 7.51%. Calcd. for C88H66N8S8:
C, 70.84%; H, 4.46%; N, 7.51%, S, 17.1%. MS (FAB):
m/z 1492, calcd. 1492.04. 1,4,8,11,15,18,22,25-octakis-
(thiophenylmethoxy)phthalocyanines(3b);3b-Cu(0.03g,
Reference compounds (4–6). 1,4,8,11,15,18,22,25-
octakis(thiooctyl)phthalocyaninate copper, cobalt, nickel,
zincandlead(4)weresynthesizedfrom3,6-thiooctylphtha-
lonitrile in accordance with a description in the litera-
ture [4]. 2,3,9,10,16,17,23,24-octakis(thiophenylmethyl)
phthalocyaninate copper, cobalt, nickel, zinc and lead (5)
were synthesized from phthalonitrile having thiophenyl-
methyl at a peripheral site [18]. Tetrakis(tert-butyl)phtha-
locyaninate copper (6) was synthesized. 4-Cu. Found: C,
73.90%; H, 7.65%; N, 4.76%. Calcd. for C144H177N8S8Cu:
C, 73.91%; H, 7.62%; N, 4.79%; S, 10.96%; Cu, 2.72%.
MS (FAB): m/z 2340, calcd. 2340.07. 4-Co. Found: C,
74.06%; H, 7.64%; N, 4.77%. Calcd. for C144H177N8S8Co:
C, 74.06%; H, 7.64%; N, 4.80%; S, 10.98%, Co, 2.52%.
MS (FAB): m/z 2335, calcd. 2335.46. 4-Ni. Found: C,
Copyright © 2010 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2010; 14: 49–54

50
K. SAKAMOTO ET AL.
74.02%; H, 7.64%; N, 4.77%. Calcd. for C144H177N8S8Ni:
C, 74.06%; H, 7.64%; N, 4.80%; S, 10.99%; Ni, 2.51%.
MS (FAB): m/z 2335, calcd. 2335.22. 4-Zn. Found: C,
73.85%; H, 7.65%; N, 4.78%. Calcd. for C144H177N8S8Zn:
C, 73.85%; H, 7.62%; N, 4.78%; S, 10.95%; Zn, 2.80%.
MS (FAB): m/z 2342, calcd. 2341.92. 4-Pb. Found: C,
69.63%; H, 7.18%; N, 4.41%. Calcd. for C144H177N8S8Pb:
C, 69.63%; H, 7.18%; N, 4.51%; S, 10.32%; Pb, 8.35%.
MS (FAB): m/z 2484, calcd. 2483.73. 5-Cu. Found: C,
68.00%; H, 4.28%; N, 7.29%. Calcd. for C88H65N8S8Cu:
C, 67.99%; H, 4.21%; N, 7.21%; S, 16.50%; Cu, 4.09%.
MS (FAB): m/z 1555, calcd. 1554.59. 5-Co. Found: C,
68.19%; H, 4.23%; N, 7.24%. Calcd. for C88H65N8S8Co: C,
68.19%; H, 4.23%; N, 7.23%; S, 16.55%; Co, 3.80%. MS
(FAB): m/z 1550, calcd. 1549.97. 5-Ni. Found: C, 68.21%;
H, 4.24%; N, 7.21%. Calcd. for C88H65N8S8Ni: C, 68.20%;
H, 4.23%; N, 7.23%; S, 16.55%; Ni, 3.79%. MS (FAB):
m/z 1550, calcd. 1549.73. 5-Zn. Found: C, 67.89%; H,
4.19%; N, 7.24%. Calcd. for C88H65N8S8Zn: C, 67.91%; H,
4.21%; N, 7.20%; S, 16.48%; Zn, 4.20%. MS (FAB): m/z
1556, calcd. 1556.43. 5-Pb. Found: C, 62.24%; H, 3.84%;
N, 6.57%. Calcd. for C88H65N8S8Pb: C, 62.24%; H, 3.86%;
N, 6.60%, S, 15.11%; Pb, 12.19%. MS (FAB): m/z 1699,
calcd. 1698.24. 6-Cu. Found: C, 72.03%; H, 6.05%; N,
14.01%. Calcd. for C48H48N8Cu: C, 72.02%; H, 6.04%; N,
14.00%; Cu, 7.94%. MS (FAB): m/z 801, calcd. 800.49.
was synthesized from 2,3-dicyanohydroquinon and trif-
luoromethanesulfonic anhydride for 24 h in accordance
with a description from the literature [5]. Intermedi-
ates 2 were synthesized, respectively, from 1 and thio-
phenols such as p-toluenethiol, 4-methoxybenzenethiol
and tert-butylthiophenol at room temperature for 24 h
to obtain 3,6-bis(thiophenylmethyl)phthalonitrile (2a),
3,6-bis(thiophenylmethoxy)phthalonitrile (2b) and 3,6-
bis(thiophenyl tert-butyl)phthalonitrile (2c). Intermediates
1
1 and 2 were analyzed using IR and H NMR spectros-
copy, and elemental analysis. Their analytical data showed
good agreement with the proposed structure.
The target compounds 1,4,8,11,15,18,22,25 octakis-
(thiophenylmethyl)phthalocyanines(3a),1,4,8,11,15,18,-
22,25-octakis(thiophenylmethoxy)phthalocyanines (3b)
and 1,4,8,11,15,18,22,25-octakis(thiophenyl tert-butyl)
phthalocyanines (3c) were synthesized, respectively, from
corresponding intermediates 2a, 2b, and 2c and metal
salt in the presence of DBU as catalyst in 1-PeOH for 7 h
(Scheme 1). As metal salts, chloride or acetate of copper,
cobalt, nickel, zinc, and lead were chosen [12]. Metal-
free compounds of 3 were obtained directly by refluxing
2 in 1-PeOH. The products were isolated using column
chromatography on silica gel with toluene as eluent. The
most readily apparent feature of the 3 compounds is their
solubility in various solvents.
The target compounds 3 were analyzed using elemen-
tal analysis and MS spectroscopy. The analytical data
showed good agreement with the proposed structure.
RESULTS AND DISCUSSION
Syntheses of reference compounds
Syntheses of target compounds
For comparison of properties, reference compounds
of three types were also synthesized. One kind of
reference compound included 1,4,8,11,15,18,22,25-
octakis(thiooctyl)phthalocyaninate copper, cobalt, nickel,
Target compounds, 1,4,8,11,15,18,22,25-octakis(thio-
phenyl)phthalocyanines (3) were synthesized in three steps
via intermediates, phthalonitrile-3,6-ditriflate (1) and
3,6-bis(thiophenyl)phthalonitriles (2). Intermediate 1
X
N
X
X
N
X
X
S
S
CF3
O
O
S
O
O
S
O
S
N
M
N
X
X
X
X
OH
OH
O
F3C
O
CF3
S
S
S
S
S
S
SH
X
N
N
CN
CN
MCl or MAc
CN
CN
O
O
CN
CN
Py, CH2Cl2
-78 to rt, 24 h
K2CO3, DMSO
rt, 24 h
DBU, 1-PeOH
160 °C, 7 h
N
N
O
S
O
S
S
CF3
X
1
2
3
2a: X=CH3
3a: X=CH3
2b: X=OCH3
2c: X=t-butyl
3b: X=OCH3
3c: X=t-butyl
M=Cu, Co, Ni, Zn, Pb
Scheme 1. Synthetic pathway of 1,4,8,11,15,18,22,25-octakis(thiophenyl)phthalocyanine
Copyright © 2010 World Scientific Publishing Company
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SYNTHESIS OF NEAR-INFRARED ABSORBED METAL PHTHALOCYANINE
51
S
S
N
M
N
S
S
S
S
N
N
MCl or MAc
N
N
S
S
DBU, 1-PeOH
160 °C, 7 h
N
N
NC
CN
S
S
M=Cu, Co, Ni, Zn, Pb
4
Scheme 2. Synthetic pathway of reference compound 4
S
S
S
S
S
N
NC
NC
S
S
MCl or MAc
N
N
N
N
N
N
M
N
DBU, 1-PeOH
160 °C, 7 h
S
S
S
5
M=Cu, Co, Ni, Zn, Pb
Scheme 3. Synthetic pathway of reference compound 5
zinc and lead (4) from 3,6-thiooctylphthalonitrile, in
accordance with a process described in the literature [7]
(Scheme 2).
analytical data showed good agreement of the proposed
structure.
Other reference compounds were 2,3,9,10,16,17,
23,24-octakis(thiophenylmethyl)phthalocyaninate copper,
cobalt, nickel, zinc and lead (5) synthesized from phtha-
lonitrile having thiophenylmethyl at peripheral site
[15] (Scheme 3). The other reference compound was
tetrakis(tert-butyl)phthalocyaninate copper (6), which
included four regioisomers [19]. The tetra-tert-butyl
phthalocyaninate copper was synthesized from 4-tert-
butylphthalonitrile. The reference compounds were ana-
lyzed using elemental analysis and MS spectroscopy. The
UV-vis spectra
In substituted metal and metal-free phthalocya-
nines, strong absorption is detected in the visible region
between the 650 and 690 nm, termed the Q band, and
in UV between 320 and 370 nm, called the Soret band.
A typical value for the extinction coefficient (ε) of the
Q band is around 105 cm2 . mol-1.
The absorption spectra of synthesized compounds 3
show typical shapes for phthalocyanine analogs (Figs 1–3).
Copyright © 2010 World Scientific Publishing Company
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52
K. SAKAMOTO ET AL.
longer wavelength in comparison to unsubstituted metal
phthalocyanine and reference compounds. In the case of
3a, absorption maxima are moved to longer wavelengths
in the order of Co, Ni, Cu, Zn, and Pb. Compounds 3b
and 3c show similar phenomena. In comparison to the
same central metal, non-peripheral substituted phthalo-
cyanines, 3a, 3b, and 3c show longer wavelengths than
peripheral substituted 5. Metal-free 3a, 3b, and 3c were
also synthesized. The Q band absorption peaks of 3a, 3b,
and 3c respectively appeared at longer wavelengths of
815, 820, and 816 nm. In general, metal-fee phthalocya-
nines show shorter wavelengths than corresponding metal
phthalocyanines. Metal-free 3a, 3b, and 3c, which have
remarkably bulky substituents, increase the distortion of
the molecule because the four central cavities cannot be
fixed. Then, the Q band of metal-free 3a, 3b, and 3c were
not split. The Q band is known to split into two peaks
for high symmetry; the splitting Q band decreases with
decreasing symmetry. Metal-free 3a, 3b, and 3c display
decreased symmetry as a result of the molecular distor-
tion. We leave a detailed discussion about these phenom-
ena of Q band of metal-free 3a, 3b and 3c for another
opportunity. The Q band absorption data of phthalocya-
nines are presented in Table 1.
Fig. 1. UV-vis spectra of 3a
The Q band shifts depend upon the change in the
electron distribution in the phthalocyanine ring caused
by substituents and their position. These results sug-
gest that the steric hindrance arising from the substituted
S-aryl groups appears to be as significant as reported by
Kobayashi and co-workers [12]. However, a difference
of the Q band in 3 is low between substituents, methyl,
methoxy and tert-butyl. In this case, electron-donating
substituents only slightly affect the movement to a lon-
ger wavelength. Although the effect of the central metal
on the energy of Q band is usually small [20], absorp-
tion maxima of 3 are moved to longer wavelengths, and
apparently increase with the ionic radius of the central
metal, particularly lead. Lead complexes of 3 showed
amplified structural distortion.
Fig. 2. UV-vis spectra of 3b
Because non-peripheral S-aryl substituted phthalocya-
nines having lead as the central metal have an absorption
band near 500 nm, 3a-Pb, 3b-Pb, and 3c-Pb resembles
a red solution; the other central metals of 3a, 3b, and 3c
show a slightly reddish solution.
Heat resistance test
The respective heat resistance characteristics of 3
and 4 were estimated using a differential thermobalance
instrument (Tg-DTA 2000SR; Mac Science). Heat resis-
tance testing was the following: the sample temperature
was raised from 30 to 400 °C by 1 °C every 1 min; the
temperature was recorded at a point to 5% weight less
per 400 mg sample weight. The target compounds 3a, 3b,
and 3c exhibited high 5% weight less temperature around
300°C, whereas reference compounds 4 showed a very
low temperature. Results show that 3a, 3b and 3c possess
Fig. 3. UV-vis spectra of 3c
They also displayed strong absorption peaks in the vis-
ible region at around 800 nm. The strongest peaks in
the visible region are assigned as the Q band, which
were attributed to the allowed π−π∗ transition of the
phthalocyanine ring. The Q band absorption of syn-
thesized compounds 3 shifted by 100–150 nm to a
Copyright © 2010 World Scientific Publishing Company
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SYNTHESIS OF NEAR-INFRARED ABSORBED METAL PHTHALOCYANINE
53
Table 1. Q band absorption data of target compounds 3a, 3b and 3c and reference compounds
Solvent
Central metal
3a
max, nm
3b
max, nm
3c
max, nm
4
5
λ
log ε
λ
log ε
λ
log ε
λ
max, nm
λ
max, nm
log ε
Chloroform
metal-free
815
857
805
788
795
779
5.22
5.09
5.20
4.74
4.92
4.91
820
862
808
790
795
783
5.33
5.13
5.17
4.97
5.01
4.51
816
855
805
787
789
780
5.08
4.89
5.29
5.00
5.18
4.91
Pb
Cu
Ni
Zn
Co
818
783
782
Toluene
Pb
Cu
Ni
Zn
Co
838
791
777
792
775
5.15
5.01
5.09
4.20
4.71
846
796
782
790
778
5.18
5.06
5.10
4.34
4.89
836
790
776
782
774
5.08
5.01
4.94
4.86
4.89
754
716
706
715
708
4.89
4.96
4.99
5.11
4.70
Table 2. The 5% weight less temperature for 3a, 3b and 3c, and
reference compound 4
Table 3. Ionization potential for 3a, 3b and 3c, and reference
compound 5
Central metal
3a
3b
3c
4
Central metal
3a
3b
3c
5
Pb
Cu
Ni
Zn
Co
298
305
305
312
303
298
302
301
306
301
291
300
296
303
299
73
81
80
75
78
Pb
Cu
Ni
Zn
Co
4.80
4.65
4.69
4.66
4.70
4.90
4.78
4.82
4.80
4.84
4.75
4.64
4.68
4.66
4.70
5.11
4.98
5.03
5.01
5.05
Non-peripheral substituted phthalocyanines show higher
solubility than peripheral substituted phthalocyanine
because 3a and 5 have identical substituents at differing
positions. By improving the poor solvent, 30-nm-thick
thin films containing 5 can be made.
very high heat-resistance. All 3 compounds are able to
use an organic device and a thin film coated onto a sur-
face. The 5% weightless data are presented in Table 2.
Compounds 4 show behavior of anisotropic disc-
shaped liquid crystals around 70°C because of their
longer alkyl side chains. These phenomena have been
reported for long alkyl group substituted phthalocyanines
[1, 2, 21].
The Ip of thin films were measured (AC-2; Riken Keiki
Co. Ltd.). In the case of 3, Ip were varied for the central
metal, and increased in the order of Cu, Zn, Ni, Co, and
Pb, which were independent of the S-aryl group type:
thiophenylmethyl, thiophenylmethoxy, and thiophenyl
tert-butyl. In comparison to the same central metal of 3,
the tendency of Ip shows a similar value for 3a and 3c,
and is apparently the highest for 3b. Comparison with Ip
of thin films shows that those of 3 are lower than those
of 5 by 0.5 eV. Actually, Ip is known to be around 5.0 eV
for usually used non-substituted copper phthalocyanine
thin films. The Ip of copper phthalocyanine shows a simi-
lar value for the peripheral substituted phthalocyanine,
such as 5. Because Ip means energy of Highest Occupied
Molecular Orbital (HOMO), non-peripheral S-aryl sub-
stituted phthalocyanines have the highest HOMO energy.
This result suggests that non-peripheral S-aryl substituted
phthalocyanines 3 removed a barrier of charge transfer
using the electrode.
Preparation of thin films and their ionization potentials
Under a nitrogen atmosphere, 0.3 g of 3 was dissolved
in5.0gof1,3-dimethyl-2-imidazolidinone. Cyclohexanol
(5.0 g) was added to the 1,3-dimethyl-2-imidazolidinone-
solution to afford varnish (including 3% solid content).
The varnish was spin-coated onto an indium tin oxide
(ITO) glass basal plate, which was washed with ozone
for 40 min until immediately before spin-coating. The
spin-coated ITO glass basal plates were baked at 200°C
for 10 min to obtain 30-nm-thick thin films. The thin film
thickness was measured (Supercorder ET4000A; Kosaka
Laboratory). Prepared thin films of 3 show no apparent
color difference from the solution phase.
Varnish of compound 5 is difficult to prepare to the
same composition of the solvent to manufacture for 3.
For preparation of thin films, the solvent 1,3-dimetyl-
2-imidazolidinone is an efficacious solvent for solid
content, while cyclohexanol acts as a poor solvent. The
solubility in cyclohexanol of 5 was lower than that of 3.
Therefore, the poor solvent was changed to chloroform.
CONCLUSION
Phthalocyanines having S-aryl at non-peripheral posi-
tion can be synthesized. Their strong absorption peaks in
the visible region called the Q band show around 800 nm.
Copyright © 2010 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2010; 14: 53–54

54
K. SAKAMOTO ET AL.
The synthesized phthalocyanines have high solubility for
organic solvents, high heat resistance without discotic
liquid crystal behavior, no absorption in visible region,
and a simple compound including no regio isomers.
Thin films of synthesized phthalocyanine on ITO were
prepared. The Ip measurements show that those of 3
were lower than those of 5 and copper phthalocyanine by
0.5 eV. Synthesized phthalocyanines 3 were removed as a
barrier to charge transfer using an electrode.
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Acknowledgements
We are pleased to acknowledge the considerable assis-
tance of Mr. Tomoyuki Ozawa.
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E, Urano T, Yamaoka T, Suzuki S and Cook MJ.
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