Inorganic Chemistry
Article
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
1834
dx.doi.org/10.1021/ic202054t|Inorg. Chem. 2011, 50, 11832−11837