Effect of chain length on thermal conversion of alkoxy-substituted copper phthalocyanine precursors

Article abstract of DOI:10.1021/ic202054t

A series of dialkoxy-substituted copper phthalocyanine (CuPc) precursors (4a-4d) have been prepared by treating phthalonitrile with the corresponding lithium alkoxide under mild conditions. The precursors exhibited high solubilities in common organic solvents, including acetone, toluene, tetrahydrofuran (THF), CH₂Cl₂, and CHCl₃. Elongation of the alkoxy chains improved the solubilities of the precursors effectively, and accordingly, the butoxy-substituted derivative (4d) showed the highest solubility among 4a-4d. X-ray crystallography clarified that the conjugated skeletons of 4a-4d are all isostructural, and have two alkoxy groups in a syn-conformation fashion, leading to highly bent structures. Thermal conversions of the precursors examined by thermogravimetry (TG) and differential thermal analysis (DTA) demonstrate that 4a was converted into CuPc via two distinct exothermic processes in the 200-250 °C temperature range, while 4d exhibits only one exothermic signal in the DTA. In the field emission scanning electron microscopy (FESEM) images of 4a, the presence of two types of distinct crystal morphology (prismatic and plate-like crystals) can be recognized, implying that the two observed exothermic processes in the DTA can be attributed to the different crystal morphologies of the samples rather than the step-by-step elimination of the alkoxy groups. The thermal formation of CuPc from the precursors has been unambiguously confirmed by X-ray powder diffraction, UV-vis spectroscopy, and elemental analysis. The precursors were converted into CuPc at lower temperature with increasing chain length, presumably because of the increased void volume in the crystals. Thermal conversion performed in the solution phase results in a bright blue-colored solution with prominent absorption bands in the 650-700 nm region, strongly supporting the formation of CuPc.

Full text of DOI:10.1021/ic202054t

Article
pubs.acs.org/IC
Effect of Chain Length on Thermal Conversion of Alkoxy-Substituted
Copper Phthalocyanine Precursors
,
†
†,‡
‡
†
,†
Takamitsu Fukuda,* Yuu Kikukawa, Ryota Tsuruya, Akira Fuyuhiro, Naoto Ishikawa,*
,‡
and Nagao Kobayashi*
†Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka Osaka 560-0043, Japan
‡Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
*
S Supporting Information
ABSTRACT: A series of dialkoxy-substituted copper phthalocya-
nine (CuPc) precursors (4a−4d) have been prepared by treating
phthalonitrile with the corresponding lithium alkoxide under mild
conditions. The precursors exhibited high solubilities in common
organic solvents, including acetone, toluene, tetrahydrofuran
(
THF), CH Cl , and CHCl . Elongation of the alkoxy chains
2 2 3
improved the solubilities of the precursors effectively, and
accordingly, the butoxy-substituted derivative (4d) showed the
highest solubility among 4a−4d. X-ray crystallography clarified that
the conjugated skeletons of 4a−4d are all isostructural, and have
two alkoxy groups in a syn-conformation fashion, leading to highly bent structures. Thermal conversions of the precursors
examined by thermogravimetry (TG) and differential thermal analysis (DTA) demonstrate that 4a was converted into CuPc via
two distinct exothermic processes in the 200−250 °C temperature range, while 4d exhibits only one exothermic signal in the
DTA. In the field emission scanning electron microscopy (FESEM) images of 4a, the presence of two types of distinct crystal
morphology (prismatic and plate-like crystals) can be recognized, implying that the two observed exothermic processes in the
DTA can be attributed to the different crystal morphologies of the samples rather than the step-by-step elimination of the alkoxy
groups. The thermal formation of CuPc from the precursors has been unambiguously confirmed by X-ray powder diffraction,
UV−vis spectroscopy, and elemental analysis. The precursors were converted into CuPc at lower temperature with increasing
chain length, presumably because of the increased void volume in the crystals. Thermal conversion performed in the solution
phase results in a bright blue-colored solution with prominent absorption bands in the 650−700 nm region, strongly supporting
the formation of CuPc.
INTRODUCTION
roles in high-tech products such as optical disks, photodynamic
therapy, and organic semiconductors. Of these, the formation
of thin films of Pcs on a substrate is an essential process to
fabricate Pc-based organic devices.
■
5
The first description of metallo phthalocyanine (Pc) appeared
in the literature in 1907, in which Braun and Tcherniak
observed the generation of unassignable blue materials by
heating phthalimide in iron vessels. Later, a series of studies
performed by Linstead and co-workers revealed that Pcs consist
1
However, Pcs having neither peripheral nor axial substituents
are barely soluble in common solvents such as water, alcohols,
6
acetone, and hydrocarbons. Therefore, the fabrication of thin
of four angularly conjugated isoindole units connected via aza
2
films of Pcs generally requires either the introduction of
appropriate substituents or the employment of the vacuum
deposition technique to sublime the Pcs directly onto the
substrate. However, substituted Pcs often lower the perform-
ance of the fabricated organic devices, while vacuum deposition
is unsuitable for facile, large-scale production of the devices.
Recently, Ono and co-workers have proposed a new
bridges. The same group also introduced the name
phthalocyanine after the Greek terms naphtha for mineral oil
and cyanine for dark blue. Not long after these pioneering
studies, the exceptional thermal and light stabilities of Pcs
attracted considerable attention as coloring materials through
the growing petrochemical industry. Among metalloPcs, CuPc
has been established as one of the most chemically and
physically stable Pc, and as a result, a large amount of CuPc
derivatives has been industrially produced worldwide, primarily
for the purpose of colorants for paints and plastics. On the
other hand, Pcs also exhibit unique photophysical and
electrochemical properties, based mainly on their π electron
configurations. As a consequence, the applications of Pcs have
been expanded recently from simple colorants to highly
advanced functional materials, so that Pcs can play pivotal
3
4
7
approach to overcome the low-solubility problem. Their Pc
derivatives have bulky substituents such as bicyclo[2.2.2]-
octadiene (BCOD) or acetonide groups at the peripheral six-
membered rings of the Pc skeleton, which deforms the planarity
of the Pcs and consequently contributes to increase the
Received: September 21, 2011
Published: October 27, 2011
©
2011 American Chemical Society
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Article
Scheme 1. Synthesis of CuPc Precursors 4a−4d
Table 1. Crystal Data and Structure Refinement Parameters
4
a
4b
4c
4d
empirical formula
formula weight
crystal color, habit
crystal dimensions [mm]
crystal system
a [Å]
C H CuN O
C H CuN O
C H CuN O
C H CuN O
40 34 8 2
3
5
26
8
3
36 26
8
2
38 30
8
2
670.19
666.20
694.25
722.29
red, prism
red, prism
pale-red, platelet
0.35 × 0.10 × 0.03
monoclinic
red, prism
0.30 × 0.20 × 0.20
monoclinic
14.038(4)
0.18 × 0.15 × 0.10
triclinic
0.31 × 0.27 × 0.07
triclinic
7.8987(2)
13.2549(7)
11.283(5)
b [Å]
13.225(4)
13.1465(3)
15.4334(3)
108.554(8)
97.024(7)
10.9039(7)
12.047(5)
c [Å]
17.039(6)
22.8570(2)
13.308(6)
α [deg]
99.948(6)
β [deg]
112.242(3)
2928.0(16)
107.793(2)
3145.5(3)
91.7156(15)
109.491(6)
1672.2(12)
γ [deg]
V [Å3]
96.510(7)
1488.0(1)
space group
Z
P2 /c
P1
̅
P2 /a
P1
̅
2
1
1
4
2
4
ρcalcd [g cm−3]
temperature [K]
residuals R/Rw
GOF
1.520
1.487
1.466
1.435
173
200
296
173
0.0446/0.1188
1.060
0.0351/0.0973
1.107
0.0515/0.0920
0.959
0.0387/0.1277
1.083
CCDC
818577
844879
844880
844881
8
solubility. After the formation of the thin films using the
soluble Pc derivative, the films can be converted into insoluble,
unsubstituted Pcs by inducing quantitative thermal elimination
of the substituents to generate peripherally fused benzo
moieties of Pcs. Although the synthesis has been focused on
the modification of the peripheral region of the Pcs, we have
recently succeeded in developing another type of thermally
convertible CuPc precursor by reacting phthalonitrile in the
presence of lithium methoxide under moderate reaction
cially available inexpensive chemicals is of particular advantage
in our method.
By extending the chain length of the substituted alkoxy
groups, further improvement of the solubilities can be
anticipated because of the enhanced structural flexibility of
the precursors. However, the effects of these structural
differences on the solubilities and thermal conversion processes
have not yet been clarified. In the present paper, we have
prepared a series of CuPc precursors 4a−4d (Scheme 1) by the
reaction of phthalonitrile and various primary alcohols, namely,
methanol (MeOH), ethanol (EtOH), 1-propanol (PrOH), and
9
conditions. The reaction of phthalonitrile with lithium
alkoxides such as LiOC H and LiOC H at high temperature
ca. 140−160 °C) generates so-called half-Pc intermediates,
followed by the successive coupling of two half-Pc units and
elimination of the alkoxy groups, leading to the formation of
5
11
6
13
1
-butanol (BuOH), in the presence of lithium, and performed a
(
comparative study on the structural and thermal conversion
properties.
10
the aromatic Pc skeleton. In contrast, we performed identical
reactions at lower temperature by using methanol as the
solvent, so that the reactions cannot proceed to the final
elimination process. As a consequence, skeleton-modified Pc
precursors, in which two methoxy groups are substituted at the
diagonal pyrrole α-carbons in a syn-conformation fashion, 4a,
EXPERIMENTAL SECTION
■
Synthesis. CuPc(OMe)
our previous paper.
, 4a. This compound was reported in
2
9
CuPc(OEt) , 4b. Phthalonitrile (0.51 g, 4.0 mmol) was added to
2
ethanol (20 mL) in which lithium metal (0.22 g, 25 mmol) was
dissolved at room temperature under a nitrogen atmosphere. The
mixture was heated at 70 °C with stirring for 13 min, followed by the
addition of anhydrous copper(II) chloride (0.15 g, 1.1 mmol). The
color of the mixture turned to dark green during the reaction. After 30
min, the solvent was evaporated in vacuo. The residue was dissolved in
CH Cl , and filtered to remove insoluble CuPc. The filtrate was
1
1,12
3
have been obtained (Scheme 1).
The sp -hybridized
carbons at the methoxy substituted sites are responsible for
the distortion of the molecular skeleton, while the presence of
the methoxy groups contributes to increase the flexibility of the
molecule. As a result, compound 4a exhibits marked solubility
in acetone, toluene, CH Cl , and so forth. By heating 4a, the
2
2
purified by alumina column chromatography using CH Cl as the
2
2
2
2
eluent. After the first red fraction was collected, the solution was
concentrated in vacuo at below 40 °C. The resulting solution was
added to hexane, to precipitate 4b as a dark red powder in 2.0% yield
(13 mg). Spectral data: UV−vis (1,2,4-trichlorobenzene, TCB): λmax
methoxy groups were removed and CuPc was generated
quantitatively. Compared to the previous thermally convertible
precursors, the one-pot facile reaction starting from commer-
1
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Inorganic Chemistry
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nm, (log ε) 507 (2.59) 408 (3.84) 390 (3.91). MS (ESI): m/z = 666
could be neither isolated nor characterized directly because of
their unstable nature, presumably, at the imine sites. To the
+
[
M] . Anal. Found: C, 63.18; H, 4.07; N, 16.11. Calcd for
C H N O Cu: C, 64.71; H, 4.22; N, 16.77.
36
26
8
2
reaction mixture containing 2a−2d was added anhydrous
CuPc(OPr) , 4c. Phthalonitrile (1.1 g, 8.2 mmol) was added to 1-
II
2
Cu Cl to couple two half-Pcs by taking advantage of the
2
propanol (40 mL) in which lithium metal (0.12 g, 15 mmol) was
dissolved at room temperature under a nitrogen atmosphere. The
mixture was heated at 75 °C with stirring for 12 min, followed by the
addition of anhydrous copper(II) chloride (0.30 g, 2.2 mmol). The
color of the mixture turned to dark green during the reaction. After 30
min, the solvent was evaporated in vacuo. The residue was dissolved in
CH Cl , and filtered to remove insoluble CuPc. The filtrate was
2
+
template effect of Cu . About a quarter equivalent of the
copper salt with respect to the phthalonitrile gave the best
II
results, while an excess amount of Cu Cl resulted in reduced
2
formation of the target compounds. Concentration of the
reactants is crucial for achieving higher yields. It appears that
oligomeric coupling of the phthalonitrile units is promoted in
excessively concentrated reaction mixtures, while overdilution
2
2
purified by alumina column chromatography using CH Cl as the
2
2
eluent. After the first red fraction was collected, the solution was
concentrated in vacuo at below 40 °C. The resulting solution was
added to hexane, to precipitate 4c as a dark red powder in 3.1% yield
reduced the reaction probability between two phthalonitriles.
II
After the addition of Cu Cl , the reaction was continued for an
2
additional 30 min. Compounds 4a and 4b exhibit partial
exchange reactions of the substituted alkoxy groups with ethoxy
and methoxy groups when these are purified by column
(
4
45 mg). Spectral data: UV−vis (TCB): λ nm, (log ε) 508 (2.43)
max
+
08 (3.74) 390 (3.80). MS (ESI): m/z = 694 [M] . Anal. Found: C,
6
5.68; H, 4.53; N, 15.83. Calcd for C H N O Cu: C, 65.74; H, 4.36;
38
30
8
2
N, 16.14.
chromatography using CHCl containing EtOH as a stabilizing
3
CuPc(OBu) , 4d. Phthalonitrile (1.1 g, 8.4 mmol) was added to 1-
agent, or using MeOH, respectively, which were detected by
the electrospray ionization (ESI) mass (see Supporting
Information, Figure S1). In contrast, compounds 4c and 4d
showed no such exchange behaviors. The reaction yields ranged
from 33 to 1.6%, depending on the alkoxy chain-length, and
higher alcohols tend to depress the yield.
The X-ray quality single crystals of 4b−4d were grown by
slow concentration of methanol (4c and 4d) and ethanol (4b)
solutions at room temperature. The ORTEP representations of
4b and 4d are depicted in Figure 1. See ref 9 and Supporting
2
butanol (40 mL) in which lithium metal (0.14 g, 18 mmol) was
dissolved at 75 °C under a nitrogen atmosphere. The mixture was
heated at 75 °C with stirring for 14 min, followed by the addition of
anhydrous copper(II) chloride (0.32 g, 2.3 mmol). The color of the
mixture turned to red brown during the reaction. After 30 min, the
resulting solution was poured into water/methanol (2: 1 (v/v)). The
suspension was filtered, and the residue was dissolved in CH Cl . After
2
2
the solution was dried with Na SO , the solvent was removed in vacuo.
2
4
The residue was purified further by alumina column chromatography
using CH Cl as the eluent. After the first red fraction was collected,
2
2
the solution was concentrated in vacuo at below 40 °C. The resulting
solution was added to hexane, to precipitate 4d as a dark red powder
in 1.6% yield (24 mg). Spectral data: UV−vis (TCB): λ nm, (log ε)
max
+
5
08 (2.73), 409 (3.73), 390 (3.78). MS (ESI): m/z = 722 [M] . Anal.
Found: C, 66.82; H, 4.79; N, 15.53. Calcd for C H N O Cu: C,
40
34
8
2
6
6.51; H, 4.74; N, 15.51.
Measurements. Mass spectra were obtained by using an AB
SCIEX QSTAR Elite Hybrid LC/MS/MS System mass spectrometer
using acetonitrile as a solvent. Elemental analyses were carried out with
a Yanaco MT-5 analyzer. Crystal structural analyses were performed at
2
00, 296, and 173 K for 4b, 4c, and 4d, respectively, on a Rigaku R-
AXIS VII diffractometer using filtered Mo−K radiation (4b), Rigaku
α
R-AXIS RAPID (4c), and Rigaku Saturn 70-CCD (4d) diffractometers
employing graphite monochromated Mo−K radiation. The structures
α
were solved by a direct method and expanded using Fourier
techniques. Hydrogen atoms were refined isotropically using a riding
model, while those of other elements were refined anisotropically.
Disorders on the substituted butoxy groups were recognized for 4d.
The crystal data and experimental details are summarized in Table 1.
X-ray powder diffraction analyses were performed at room temper-
ature using Cu−K radiation on a Rigaku Rint 2000 diffractometer.
α
Thermogravimetry (TG) and differential thermal analysis (DTA) data
were collected using a SHIMADZU DTG-60H analyzer. A scan rate of
5
K/min was employed. Field emission scanning electron microscopy
(
FESEM, JEOL JSM-7500F) was used to obtain surface images of the
crystalline samples. Electronic absorption measurements were made
with a Perkin ELMER Lambda 19 spectrophotometer.
RESULTS AND DISCUSSION
Figure 1. ORTEP representations of (a) 4b and (b) 4d (50%
probability ellipsoids). Hydrogen atoms are omitted for clarity.
■
The general reaction protocols for 4a−4d are shown in Scheme
. To prepare the alkoxy-substituted CuPc precursors,
phthalonitrile was first treated with a lithium alkoxide generated
in situ in the corresponding primary alcohols at 70−75 °C for
0−14 min. The temperature and reaction time have been
optimized for each derivative. The alkoxides attack at one of the
cyano groups of the phthalonitrile during this process, followed
by a coupling reaction between two phthalonitrile units to give
the half-Pc intermediate (2a−2d), although these intermediates
1
Information, Figure S2 for the X-ray structures of 4a and 4c,
respectively. As confirmed from the crystal structures, the π-
structures of the precursors are almost identical to each other.
In all cases, two alkoxy groups show syn-substitution at the
diagonal pyrrole α-carbons. As a consequence, the Pc skeletons
are forced to take on highly deformed, bent conformations. No
anti-substituted isomers have been characterized at present,
1
1
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although the mechanism of this selective formation is still
unclear. All precursors exhibit high solubilities in acetone,
toluene, tetrahydrofuran (THF), CH Cl , and CHCl , while 4d
2
2
3
even shows moderate solubility in hexane, as demonstrated in
Figure 2 as a pale, red-colored solution.
Figure 2. Photographs of centrifuged saturated solutions of 4a (left)
and 4d (right) in hexane at room temperature.
The thermal conversion processes of 4a−4d were inves-
tigated using TG-DTA analyses. For each measurement,
microcrystalline samples were prepared by reprecipitation of
the precursors from CH Cl /hexane, followed by vacuum
2
2
desiccation at room temperature to remove as much of the
solvated molecules as possible. The weight loss percentages of
the precursors in the course of raising the temperature under a
stream of nitrogen gas (solid line) and the corresponding DTA
curves (dashed line) are displayed in Figure 3. In the DTA, the
positive and negative signals indicate exothermic and
endothermic processes, respectively. Monotonic weight loss
with an inflection point at about 238 °C was observed for 4a in
the temperature range of about 200−250 °C, and the
corresponding DTA curve having two clear positive peaks at
Figure 3. Weight loss (solid line) and DTA curves (dashed line) of
4
a−4d (from top to bottom) during the course of thermal elevation
−1
under nitrogen. Scan rate = 5.0 K min .
2
32 and 252 °C indicates that two exothermic processes take
place in this temperature range, consistent with the stabilization
of 4a by the aromatization reaction. As already stated in ref 9,
the total weight loss of about 10% is consistent with the
quantitative conversion of 4a into CuPc. The two positive
peaks in the DTA curve suggest that two independent
exothermic processes are involved in this region. However,
two-step eliminations of the methoxy groups, in which the first
step releases one of the two methoxy groups only to give a
CuPc(OMe) intermediate, are unlikely because the inflection
point is located outside the midpoint of the total weight loss. As
discussed below, these two thermal processes can be attributed
to the presence of two types of morphology in the
microcrystalline samples. Compound 4b exhibited two separate
thermal processes. The first step at about 123 °C is
endothermic, while the second step at temperature in the
range of 230−260 °C is exothermic. The first endothermic step
can be safely assigned to elimination of the remaining solvated
molecules judging from the temperature. The observed weight
loss for the second step (ca. 12%) is slightly lower than the
theoretical value (14%). The aromatization temperature range
is almost identical with that of 4a, although the split of the
DTA peaks is less distinct for 4b compared to 4a. Contrary to
our intuitive expectation, the precursors are aromatized at lower
temperatures for 4c and 4d (ca. 229 and 227 °C, respectively)
than 4a and 4b. These observations can be rationalized by
considering the increased void volume for 4c and 4d in the
crystals, while tight crystal packing inhibits the dissociation of
the carbon−oxygen bonds to some extent. This is evidenced by
the fact that comparisons of 4a and 4c having P2 /c and P2 /a
1
1
space groups, respectively (Supporting Information, Figure S3),
and 4b and 4d having a P1 space group (Supporting
̅
Information, Figure S4) clearly indicate that higher alkoxy
groups increase the distances between the two main bodies of
the precursors in the crystals. In other words, the conversion
temperature is sensitive to the morphology of the precursors.
For application purposes, we have already observed that the
amorphous 4a on an ITO electrode can be converted into
9
CuPc at as low as 85 °C. Results of the elemental analyses of
the thermally generated products from 4a−4d broadly support
the formation of CuPc (Table 2), although the results are
slightly outside the anticipated values for the product obtained
from 4b. We tentatively attribute these observations to the
presence of unassignable impurities and/or partial decom-
position of the precursor during the thermal process.
Nevertheless, the formation of 4b and CuPc generated
therefrom can be unambiguously confirmed by the single
crystal structures (Figure 1) and X-ray powder diffraction data
(see below).
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Table 2. Results of Elemental Analysis of Thermally
Generated Materials
precursor
C(%)
H(%)
N(%)
4
4
4
4
a
b
c
66.51
64.33
66.81
66.38
66.72
2.83
2.85
2.94
2.92
2.80
19.22
18.37
19.23
18.82
19.45
d
calcd for CuPc
X-ray powder diffraction patterns of the precursors (left) and
the CuPc thermally generated by the solid-to-solid conversions
(
right) are shown in Figure 4. Although the observed patterns
differ from each other for the precursors, those of thermally
generated samples are practically independent of the starting
precursors, strongly suggesting the formation of the so-called α-
phase CuPc irrespective of the alkoxy chain-length of the
1
3,14
precursor.
a displayed in Figure 5 clearly show the presence of two
The FESEM images of the crystalline sample of
4
distinct crystal morphologies. In Figure 5a, prismatic and plate-
like crystals can be recognized in the upper left and lower right
regions, respectively. The magnified images of these crystals (b
and c) demonstrate that the columnar structures with smooth
surfaces have approximately 8−14 μm length and 2−4 μm
width, while the lamellarly structured unstriated plate crystals
have less than 500 nm thickness. The presence of these two
phases accounts for the two-step thermal eliminations observed
for 4a. The electronic absorption spectrum of 4d in TCB
exhibits practically no absorption bands above 500 nm because
of interruption of the conjugation at the alkoxy-substituted sites
(
Figure 6, dashed line). Upon heating at 180 °C, prominent
absorption bands appear in the 550−750 nm region, also
15
indicating the formation of CuPc (Figure 6, solid line).
Figure 5. FESEM images of (a) 4a prepared by reprecipitation from
CONCLUSIONS
CH Cl /hexane followed by vacuum desiccation, and (b,c) two crystal
■
2
2
morphologies appearing in (a).
In the present study, we have prepared a series of dialkoxy-
substituted copper phthalocyanine (CuPc) precursors (4a−4d)
by reacting phthalonitrile with lithium alkoxides such as
LiOMe, LiOEt, LiOPr, and LiOBu under mild conditions.
The precursors exhibited high solubilities in acetone, toluene,
THF, CH Cl , and CHCl , while elongation of the alkoxy
conjugated skeletons of 4a−4d are all isostructural. Thermal
conversions of the precursors examined by a TG-DTA analyzer
demonstrated that 4a was converted into CuPc via two distinct
exothermic processes, while 4d exhibited only one exothermic
signal in the DTA. FESEM images of 4a clearly show the
presence of two distinct morphologies, implying that the two
observed exothermic processes in the DTA can be attributed to
2
2
3
chains improved the solubility. As a consequence, we have even
succeeded in dissolving the butoxy-substituted precursors in
hexane to some degree. X-ray crystallography clarified that the
Figure 4. X-ray powder diffraction patterns of 4a−4d (left, from top to bottom) and the corresponding thermally generated CuPc (right) by solid-
to-solid conversion.
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Figure 6. Electronic absorption spectrum of 4d in TCB (dashed line)
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lines). Cell path length = 1 cm.
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(
9) Kikukawa, Y.; Fukuda, T.; Fuyuhiro, A.; Ishikawa, N.; Kobayashi,
N. Chem. Commun. 2011, 47, 8518.
10) (a) Oliver, S. W.; Smith, T. D. J. Chem., Soc. Perkin Trans. 2
the different crystal morphologies of the samples rather than
the step-by-step elimination of the alkoxy groups. The
precursors were converted into CuPc at lower temperature
with increasing chain length, presumably because of the
increased void volume in the crystals. Thermal conversion
performed in TCB resulted in a bright blue-colored solution
with prominent absorption bands in the 650−700 nm region,
also strongly supporting the formation of CuPc.
(
1987, 1579. (b) Nolan, K. J. M.; Hu, M.; Leznoff, C. C. Synlett 1997,
593.
(11) Fukuda, T.; Ogi, Y.; Kobayashi, N. Chem. Commun. 2006, 159.
(12) Molek, C. D.; Halfen, J. A.; Loe, J. C.; McGaff, R. W. Chem.
Commun. 2001, 2644.
(
(
(
13) Assour, J. M. J. Phys. Chem. 1965, 69, 2295.
14) Sharp, J. H.; Abkowitz, M. J. Phys. Chem. 1973, 77, 477.
15) (a) Barrett, A. G. M.; Broderick, W. E.; Hoffman, B. M.;
ASSOCIATED CONTENT
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Velazquez, C. S. J. Org. Chem. 1989, 54, 3233. (b) Mikhalenko, S. A.;
Lukyanets, E. A. Russ. J. Gen. Chem. 1969, 39, 2495. (c) Kovshev, E. I.;
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*
S
Supporting Information
ESI-mass of 4b, ORTEP drawing of 4c, crystal packing
structures of 4a−4d. This material is available free of charge
via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*
Phone: +81(6)6850-5410 (T.F.). Fax: +81(6)6850-5410
T.F.). E-mail: tfukuda@chem.sci.osaka-u.ac.jp (T.F.). Phone:
81(6)6850-5408 (N.I.). Fax: +81(6)6850-5408 (N.I.). E-mail:
iskw@chem.sci.osaka-u.ac.jp (N.I.). Phone: +81(22)795-7719
N.K.). Fax: +81(22)795-7719 (N.K.). E-mail: nagaok@m.
(
+
(
tohoku.ac.jp (N.K.).
ACKNOWLEDGMENTS
■
This work was partially supported by a Grant-in-Aid for
Scientific Research (C), No. 22550052, and that for Scientific
Research on Innovative Areas (No. 20108007, “pi-Space”). T.F.
is also grateful to the Kinki Regional Invention Foundation and
Mitsubishi Chemical Corporation Fund for their financial
support. The authors acknowledge Prof. Masahiro Yamashita
and Prof. Fumitoshi Kaneko for their help with thermal
measurements and X-ray powder diffraction data collection,
respectively.
REFERENCES
■
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dx.doi.org/10.1021/ic202054t|Inorg. Chem. 2011, 50, 11832−11837