Rectangular-shaped expanded phthalocyanines with two central metal atoms

Article abstract of DOI:10.1021/ja209589x

Expanded phthalocyanine (Pc) congeners with two Mo or W central metal ions and four isoindole ring moieties have been synthesized using normal Pc formation conditions in the presence of urea. The products have been characterized by electrochemistry; mass

Full text of DOI:10.1021/ja209589x

Article
pubs.acs.org/JACS
Rectangular-Shaped Expanded Phthalocyanines with Two Central
Metal Atoms
†
‡
§,∥
†
Osamu Matsushita, Valentina M. Derkacheva, Atsuya Muranaka, Soji Shimizu,
Masanobu Uchiyama,§,⊥ Evgeny A. Luk’yanets,* and Nagao Kobayashi*
,‡
,†
†
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
Organic Intermediates and Dyes Institute, B. Sadovaya 1/4, Moscow 123995, Russia
Advanced Elements Chemistry Research Team, ASI, RIKEN, Wako 351-0198, Japan
PRESTO, Japan Science and Technology Agency (JST), Saitama 332-0012, Japan
‡
§
∥
⊥
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
*
S Supporting Information
ABSTRACT: Expanded phthalocyanine (Pc) congeners with two Mo or W central
metal ions and four isoindole ring moieties have been synthesized using normal Pc
formation conditions in the presence of urea. The products have been characterized
by electrochemistry; mass spectrometry (MS); IR, electron paramagnetic resonance
(
EPR), NMR, electronic absorption, and magnetic circular dichroism (MCD)
spectroscopies; and X-ray analysis. The X-ray structures have rectangular C2v
symmetry and provide evidence that the central Mo atoms are linked by a single
bond and coordinated by two isoindole nitrogen atoms and two nitrogen atoms from
the amine moieties. The electronic absorption bands extend into the 1200−1500 nm
region. This can be explained using Gouterman’s four-orbital theory. The
experimental NMR data and theoretical calculations provide evidence for a
heteroaromatic 22-π-electron conjugation system for the ring-expanded Pc system,
̈
which satisfies Huckel’s (4n + 2)π aromaticity.
INTRODUCTION
Ever since Linstead’s initial report in 1934, phthalocyanines
Pcs) have been used as industrial materials. In recent years,
■
(
1
new applications in storage media, organic semiconductors,
laser printers, photodynamic therapy of cancer, nonlinear
optics, and deodorants due to the stability of the compounds
and the intense absorption bands in the visible region have
2
,3
been reported. Pcs can therefore be said to play a central role
in modern society. In recent years, more than 2000 patents and
4
research papers have been reported annually.
Figure 1. Structures of phthalocyanine derivatives.
A number of different synthetic methods have been reported
for metallo-Pcs. Template reactions in the presence of a
transition metal or metal salts are the most common. Systems
containing a phthalic anhydride, phthalimide, phthalamide, or
phthalonitrile in the presence of urea, or a 1H-isoindole-
6
,7
metals. Although more than 300 X-ray structures have been
8
reported for metallo-Pcs, SubPcs, and SuperPcs, all of these
compounds contain isoindole rings connected by aza nitrogen
atoms whether they are monomeric, dimeric, or oligomeric, and
no other complex types have been reported from these Pc
1,3(2H)-diimine are often used. In the presence of most metals,
normal, planar Pcs consisting of four isoindole moieties and
having approximate D symmetry are obtained. In the presence
4
h
7,9
formation reactions. In this article, we provide the first report
of a completely new type of Pc complex containing two metal
ions that is obtained under normal Pc formation reaction
conditions in the presence of molybdenum and tungsten salts.
of lanthanoids, double- and in rare cases even triple-decker
5
sandwich-type Pc complexes are obtained. When boron or
uranium ions are reacted with a phthalonitrile, cone-shaped Pc
analogues consisting of three isoindole rings [so-called sub-
phthalocyanines (SubPcs)] or deformed Pc derivatives
consisting of five isoindole rings [super-phthalocyanines
(
SuperPcs)] are formed (Figure 1) because of the smaller or
Received: October 12, 2011
Published: February 8, 2012
larger ionic radii, respectively, relative to first-row transition
©
2012 American Chemical Society
3411
dx.doi.org/10.1021/ja209589x | J. Am. Chem. Soc. 2012, 134, 3411−3418

Journal of the American Chemical Society
Article
RESULTS AND DISCUSSION
mass data obtained for 4 were also taken into consideration, all
of the mass data could be successfully reproduced only when 12
nitrogen atoms, two oxygen atoms, and two molybdenum or
tungsten atoms were included.
■
Synthesis and MS Analysis. In a similar manner to normal
9
Pc formation reactions, a mixture of phthalic anhydride or
phthalimide and excess urea (and occasionally a trace amount
of 1-chloronaphthalene for ease of stirring; see Scheme 1) was
X-ray Crystal Analysis. Crystallization was attempted for
−4, and fortuitously, single crystals suitable for X-ray
diffraction analysis were obtained by slow diffusion of ethanol
2
Scheme 1. Syntheses of 1−4
into a solution of 2 in 1-chloronaphthalene. The crystal
10
structure of 2 (Figure 2) reveals that the macrocycle
heated in the presence of a molybdenum [MoO Cl2 or
2
(
NH ) MoO ] or tungsten salt [(NH ) WO ] at 210−250 °C
4
2
4
4 2
4
for 10−30 min, and the products were purified by
chromatography using silica gel followed by a size-exclusion
column. After removal of greenish-blue bands containing
normal Pcs, another band with a brown color was collected,
and strong electronic absorption bands beyond 900 nm were
detected. The yields were always higher for molybdenum salts
(
max. 8.3%) than for tungsten salts (less than 2.0%). The
Figure 2. X-ray crystal structure of 2: (top) top view; (bottom) side
view. The thermal ellipsoids are scaled to the 50% probability level.
For clarity, H atoms and substituents have been omitted in the side
view.
tungsten derivatives tended to decompose during column
chromatography. Although the yield was low, a similar
compound (3) was obtained even when phthalonitrile and
urea were used as the starting materials. The absorption spectra
of each of these compounds did not change upon storage for up
to a year so long as they were kept in the dark in the solid state.
This demonstrates that these compounds are reasonably stable.
However, when the complexes were dissolved in solution or
stored under direct light, they decomposed more slowly than
ZnPc but more quickly than CuPc.
All of the brown compounds with intense absorption bands
beyond 900 nm were subjected to analysis by mass
spectrometry (MS). As shown in Figure S1 in the Supporting
Information (SI), the high-resolution MS (HR-MS) spectra and
calculated isotopic distribution patterns provided a reasonable
match for the compounds with two atoms of molybdenum (1a,
comprises four isoindole rings linked by two methanetriamine
moieties and contains two Mo ions in its central cavity. Two
oxygen atoms are connected to each Mo ion from the same
11
direction as axial ligands (i.e., a cis isomer). The Mo−O
bonding distance of 1.66 Å in the crystal structure is in the
1
2,13
range of lengths for MoO double bonds.
The
interatomic distance between the two Mo ions is 2.64 Å,
which corresponds to the distance of a Mo−Mo single bond.
14
Each Mo ion is further coordinated by two pyrrole nitrogen
atoms and two amino nitrogen atoms of the macrocycle (5A in
Figure 3). The overall molecular structure of 2 adopts a dome
shape. The dihedral angles formed by the isoindole moieties are
39° on average. The Mo ions lie out of the macrocyclic plane.
No significant bond-length alternation was observed for the C−
N and C−C bonds of the core structure of 2 (Figure S2 in the
SI), as would be anticipated for a heteroamatic π system. This
pattern is generally observed in the crystal structures of Pc
2
, and 3) or tungsten (1b). To provide a further confirmation
1
5
of the number of nitrogen atoms, N-labeled 1a was
synthesized using N-labeled urea. The parent peak was
observed by HR-MS at m/z 1076.1677 [M + Na], while m/z
1
theoretical isotopic distribution pattern matched the exper-
imental one almost perfectly (Figure S1 in the SI). When the
1
5
+
1
5
076.1678 was calculated for C H Mo N O Na. The
50 48 2 12 2
1
congeners. On the basis of the MS and H NMR data described
below, the only other isomer that could be formed would
3
412
dx.doi.org/10.1021/ja209589x | J. Am. Chem. Soc. 2012, 134, 3411−3418

Journal of the American Chemical Society
Article
while an intense electron paramagnetic resonance (EPR) signal
due to the coupling of the unpaired electron with the five
nitrogen atoms is observed at g ≈ 1.97, along with weaker lines
9
5
97
17
on each side due to electron−Mo /Mo coupling. In this
V
study, during the purification of 1a, tetra-tert-butylated (Mo 
+
N)Pc was obtained (HR-MS: m/z 871.2985 found for [M +
Na]; m/z 871.2984 calcd for C H MoN Na), and the
anticipated IR band was observed at 974 cm , while an EPR
48
48
9
−
1
1
Figure 3. Possible structures 5A and 5B based on the MS and H
NMR analyses.
signal was detected at g = 1.977 in toluene at room temperature
(
Figure S6 in the SI). When the IR spectrum of 1a obtained
V
contain two nitride-type nitrogen atoms connected at the axial
positions and two oxygen atoms in turn residing at the meso
positions to coordinate each Mo ion along with two pyrrole
nitrogen atoms in a square planar fashion (5B in Figure 3). A
detailed analysis of both structures revealed that the thermal
ellipsoids were properly solved for the structure 5A in Figure 3.
from the same batch as the tert-butylated (Mo N)Pc was
recorded, the spectrum shown in Figure 5 was obtained. 1a was
1
1
H NMR Spectra. H NMR signals of 1−4 appeared in the
7
same region as those observed for conventional Pc congeners,
providing strong evidence that the compounds are diamagnetic.
Figure 5. Observed IR spectrum of 1a (top) and theoretical IR spectra
of structures 5A (middle) and 5B (bottom) with tert-butyl
substituents. Red bars indicate the vibrations involving Mo and its
axial ligand.
found to be EPR-silent under the same conditions, which is
reasonable considering the coordination geometry around the
Mo ions and the presence of a Mo−Mo single bond as
observed in the crystal structure of 2 (Figure 2). Since the IR
spectra of high-symmetry (D ) and low-symmetry Pc
1
Figure 4. H NMR spectra of 2 in toluene-d (top) and 3 in CDCl
(
8
3
bottom). * indicates residual solvent peaks.
Figure 4 contains the spectra of 2 and 3, and the details of the
H NMR data for all of the compounds are described in the
4
h
1
derivatives can be reliably reproduced by theoretical
calculations in terms of both the energies and intensities of
Experimental Section. The signals of 3 were assigned on the
basis of both correlation spectroscopy (COSY) and nuclear
Overhauser effect (NOE) experiments (Figures S3 and S4 in
the SI). Two α-benzo proton signals appear at 9.23 and 9.37
ppm as singlets with the same intensity, while tert-butyl proton
signals were found at 1.42 and 1.51 ppm, indicating that 3
possesses a symmetry lower than the regular D4h symmetry of
metallo-Pcs. On the other hand, the four doublets of the
phenoxy protons observed in the 7.3−7.6 ppm region are
similar to those at 7.1−7.3 ppm for 2,3,9,10,16,17,23,24-octa(p-
tert-butyl)phenoxy zinc phthalocyanine (t-BuPhOZnPc). The
fact that signals due to the α-benzo protons of 3 appeared
significantly downfield relative to the corresponding protons of
,5-di-tert-butylphenoxyphthalonitrile (7.82 ppm in CDCl3) is
consistent with the presence of a strong ring-current effect and
a heteroaromatic π system. Similar trends as shown for 2 and 3
Figure 4) have been proposed for the H NMR spectra of 1
and 4.
IR and EPR Spectra. When a Mo salt is used as a template
in Pc syntheses in the presence of urea, nitride complexes of
18
bands, calculated IR spectra were obtained for structures 5A
and 5B (Figure 3) and compared with the experimental data for
compound 1a (Figure 5). A structure substituted with tert-butyl
groups was optimized. Although the calculated spectra for 5A
and 5B broadly reproduced the experimental data, we focused
−1
our attention on the 1080−970 cm region since 1a displays
−1
three intense characteristic peaks at 1057, 1012, and 970 cm .
As is clearly shown in Figure 5, these three strong peaks were
V
reproduced when the Mo O structure (5A) was used, while
V
in contrast, when the Mo N structure (5B) was used only
two intense peaks were predicted. Of the three intense peaks
calculated for structure 5A, the peak at the lowest energy (1014
−1
−1
cm ) corresponds to the peak observed at 970 cm , which
15
4
V
can be assigned as a Mo O stretching vibrational mode. The
V
Mo O stretching vibrational modes of Pcs that have been
−1
reported previously have always appeared in the 970−975 cm
1
19
V
(
region, while that of Mo N has been reported to lie
−1
17
between 950−980 cm . These results therefore suggest that
V
20
the compounds formed have a Mo O structure (5A).
Absorption, MCD, and Fluorescence Spectra. The
absorption, magnetic circular dichroism (MCD), and fluo-
rescence spectra of 2 are shown in Figure 6, together with the
V
16
MoPc [(Mo N)Pc] are known to be formed. For the
V
(
Mo N)Pcs reported to date, the IR signals associated with
V
−1
the Mo N bond are observed in the 950−980 cm range,
absorption and MCD spectra of tert-butylated H Pc (t-
2
3
413
dx.doi.org/10.1021/ja209589x | J. Am. Chem. Soc. 2012, 134, 3411−3418

Journal of the American Chemical Society
Article
Figure 6. Absorption (middle) and MCD (top) spectra of 2 (red) and
tBuH Pc (blue) in CHCl and theoretical absorption spectra (bottom)
2
3
of Opt2A and Opt2B (red) and H Pc (blue). The fluorescence
2
spectrum of 2 in CHCl is also shown in the middle panel.
3
Figure 7. Absorption (bottom) and MCD (top) spectra of 1a, 1b, 3,
and 4 in CCl4.
BuH Pc); the absorption and MCD spectra of 1, 3, and 4 can
2
be compared in Figure 7. The spectra of 1−4 are broadly
similar and contain bands that can be readily assigned as the Q
and B bands in the context of Gouterman’s four-orbitals
typical of the spacing observed for vibrational bands in Pc
−1
23,26
spectra (ca. 1100 cm ).
The optical spectra therefore
2
1
provide strong evidence that compounds 1−4 arise from ring-
expanded Pc analogues, which lack fourfold-symmetry axes.
The calculated absorption spectra based on structures
terminology (strictly speaking, the Q band is probably better
22
described as the L band in Platt’s terminology, since the
angular momentum change (ΔM ) of the Q band is ±9 while
L
V
V
containing Mo O (5A) and Mo N (5B) are provided in
the bottom portion of Figure 6 (for details, see the next
section). The closest match with the experimental spectrum
for 1−4 it is ±11). The peak at longest wavelength is
substantially red-shifted into the near-IR region relative to that
of t-BuH Pc, reflecting the expansion of the aromatic π systems
2
V
was obtained using the Mo ion with an oxygen atom as the
of 1−4 relative to those of conventional Pcs. The MCD spectra
axial ligand.
in the Q-band region are clearly dominated by Faraday B
2
3−25
Compound 2 was found to have a weak emission peak at
terms,
since the intensity maxima and minima are closely
1
247 nm when excited at 404 nm (Figure 6 middle).
aligned with the centers of the main absorption bands. This
provides direct spectral evidence that the molecular symmetry
Analysis of π-Electron Structure. Theoretical calculations
27
were carried out using the Gaussian 03 software package to
provide further insight into the electronic structures. Geometry
optimization calculations were carried out using the structure of
of the compounds is lower than C and that the excited states
3
are nondegenerate, as would be anticipated on the basis of the
C2v symmetry of the crystal structure of 2. The MCD bands
observed in the 1000−1300 nm and 800−1000 nm regions can
be assigned to symmetry-split y- and x-polarized Q00 bands,
since coupled oppositely signed B terms would be anticipated
in this context. Although three peaks are generally observed in
the absorption spectra in Figures 6 and 7, the second-lowest-
energy band appears to be a vibrational component of the
lowest-energy band, since the MCD signs are the same and the
5A as a model compound. The optimized structure, Opt2A
(Figure S7 in the SI), is very similar to the crystal structure of 2.
In addition, the theoretical absorption spectrum (Figure 6) and
a molecular orbital (MO) diagram (Figure 8) were calculated
for Opt2A using time-dependent density functional theory
(TD-DFT) (B3LYP/6-31G(d) for C, H, N, and O and
28
LANL2DZ for Mo) and compared with those of substituent-
−1
splittings between these bands are 1000−1200 cm , which is
free H Pc. The symmetry-split Q bands of Opt2A were
2
3
414
dx.doi.org/10.1021/ja209589x | J. Am. Chem. Soc. 2012, 134, 3411−3418

Journal of the American Chemical Society
Article
basis. The splitting of the LUMO and LUMO+1 is smaller than
that of the HOMO and HOMO−2, as would be anticipated on
the basis of the −/+ sign sequence observed for the Q bands in
the MCD spectrum in ascending energy terms. Michl has
demonstrated that a −/+ sign sequence is consistent with the
orbital angular momentum properties that arise when the
energy difference between the MOs derived from the HOMO
of a parent hydrocarbon corresponding to the inner perimeter
of the ligand (in this case the HOMO and HOMO−2) is larger
than that between the MOs derived from the LUMO (in this
2
9,30
case the LUMO and LUMO+1).
The number of nodes on
the inner ligand perimeter of Opt2A frontier π-MOs is the
same as the number observed for the frontier π-MOs of the
2
−
C H
parent hydrocarbon perimeter. For example, five
nodes are observed for the HOMO and HOMO−2 of Opt2A
2
0
20
2−
and the HOMO and HOMO−1 of C H . On this basis, it
can be stated that the four frontier π-MOs of Opt2A are similar
to those of a 20-atom, 22-π-electron annulene, which satisfies
20
20
̈
Huckel’s (4n + 2)π aromaticity rule. The strong intensity of the
Q band in the MCD spectrum relative to that observed for the
B-band region is related to the ΔM = ±11 change in orbital
L
angular momentum properties that would be anticipated for the
21
Q bands of 1−4 if the π systems were heteroaromatic. The
TD-DFT results therefore provide strong support for the
conclusion that Opt2A and therefore 1−4 have a hetero-
aromatic 22-π-electron system.
Figure 8. MO diagrams of Opt2A and H Pc. H and L indicate the
HOMO and LUMO, respectively. Arbitrary nodal lines have been
drawn on the isosurface plots.
2
Electrochemistry. Cyclic voltammograms of 1a and t-
BuH Pc were measured under similar conditions (Figure 9),
predicted to lie at 1068 and 833 nm, while those of H Pc were
2
2
predicted to lie at 601 and 594 nm. The large splitting of the
−1
two bands (2642 cm ) and the much weaker intensity of the
lower energy band of Opt2A (f = 0.080 compared with f =
0
.45) are in close agreement with the experimental data
−1
(
splitting = 2025 cm and intensity ratio ≈ 1:5; Figure 6). The
Q bands were predicted to arise primarily from the four frontier
π-MOs (Table 1). The HOMO−1 was not included since it is
derived mainly from d orbitals of the two Mo atoms. When
V
Opt2B, which is based on the structure of 5B with an Mo N
core structure, was used instead, the Q bands were calculated to
−1
lie at 796 and 773 nm with a splitting of only 374 cm , and the
intensity ratio was the opposite of that observed experimentally.
V
This provides further evidence that an Mo N core structure
is unlikely to be present.
Figure 9. Cyclic voltammograms of 1a (red lines) and tBuH Pc (blue
2
In Figure 8, the HOMO−LUMO gap of Opt2A is much
lines). Conditions: sample, 1.0 mM; solvent, distilled o-DCB;
electrolyte, 0.1 M TBAP; reference electrode, Ag/AgCl; counter
electrode, Pt wire; scan rate, 100 mV/s.
smaller than that of H Pc. The marked red shift of the Q band
2
of 2 relative to that of t-BuH Pc is readily explained on this
2
Table 1. Transition Weights of Q Bands in Opt2A, Opt2B, and H Pc Obtained Using the TDDFT Hamiltonian
2
a
state
λ (nm)
f
transition weight (density)
H → L+1 (0.70)
Opt2A
Opt2B
Qy
Qx
Qx
Qy
Qx
Qy
1068
833
796
773
601
594
0.080
0.45
0.49
0.22
0.39
0.44
H → L (0.70), H−2 → L+1 (0.14)
H → L (0.57), H−2 → L (0.20)
H → L+1 (0.61), H−2 → L+1 (0.19)
H → L+1 (0.60), H−1 → L (0.17)
H → L (0.60)
H Pc
2
a
H = HOMO; L = LUMO.
3
415
dx.doi.org/10.1021/ja209589x | J. Am. Chem. Soc. 2012, 134, 3411−3418

Journal of the American Chemical Society
Article
and four redox couples were observed for each [−1.18, −0.86,
and MO calculations has provided strong evidence for
structures containing two MoO or WO central cores.
Electronic absorption bands in the 1200−1500 nm region were
observed and could be readily assigned on the basis of
Gouterman’s four-orbital theory. Theoretical calculations were
consistent with a heteroaromatic 22-π-electron system, which
satisfies Huckel’s (4n + 2)π rule. Expanded Pc derivatives with
̈
absorption and emission bands in the NIR region have
potential applications in fields such as solar cells and
electroluminescence.
+
0
0
.07, and 0.56 V vs Fc/Fc for 1a and −1.71, −1.36, 0.35, and
.78 V for t-BuH Pc]. The HOMO−LUMO energy difference
2
for 1a estimated on the basis of the potential difference
between the first oxidation and first reduction (0.93 V) is
smaller than that of t-BuH Pc (1.71 V), as would be anticipated
2
from the red shift of the Q band of 1a relative to t-BuH Pc. The
2
potential difference of 0.50 V between the first reduction step
of t-BuH Pc (−1.36 V) and 1a (−0.86 V) was larger than the
2
difference of 0.28 V between the first oxidation steps of these
compounds (0.35 and 0.07 V, respectively) (Figure 9). This is
consistent with the prediction that the stabilization of the
LUMO of 1a relative to the normal Pc structure is larger rather
than the destabilization of the HOMO (Figure 8). This is an
important property of Pc derivatives, since the instability
toward air of larger Pc congeners such as naphthalocyanine and
anthracocyanine is consistently related to the destabilization of
EXPERIMENTAL SECTION
■
General Procedures. NMR spectra were recorded on 600 MHz
JEOL ECA-600, 400 MHz Bruker AVANCE 400, and 400 MHz JEOL
GSX-400 spectrometers. EPR spectra were measured in deaerated
toluene at room temperature with a JEOL JES-FE2X spectrometer. IR
spectra were measured by the KBr pellet method with a JASCO FT/IR
4100 spectrometer. High-resolution electrospray ionization Fourier
transform ion cyclotron resonance (ESI-FT-ICR) mass spectra were
recorded on a Bruker DALTONICS APEX III instrument. Electronic
absorption spectra were measured using Hitachi U-3410 and JASCO
V-570 spectrophotometers. MCD spectra in the 300−700 nm region
were recorded using a JASCO J-725 spectrodichrometer with a JASCO
electromagnet producing a magnetic field of up to 1.09 T, while
spectra in the 700−1300 nm region were recorded using a JASCO J-
730 spectrodichrometer with a JASCO electromagnet producing a
magnetic field of up to 1.50 T. The magnitude of the MCD signal is
18a,26a
the HOMO.
NICS(0) Calculation. Since the core structure was
elucidated on the basis of the X-ray analysis of 2, the
aromaticity of this π system was evaluated by calculating
1
nucleus-independent chemical shift (NICS) values. H NMR
chemical shifts were calculated for the corresponding non-
substituted metal-free structures using DFT with the B3LYP
31
functional and 6-31G(d) basis sets. The NICS values for
expanded C -symmetric Pcs (i.e., the metal-free π structures of
2h
expressed in units of magnetomolar circular dichroic absorption Δε
M
1−4) were calculated to be −11.8 ppm at the center of the
−1
−1
−1
(M
cm T ). Emission spectra were collected on a JASCO FP-
structure and −11.3 ppm at the center of the two central amino
nitrogen and two pyrrole nitrogen atoms (i.e., the location of
the Mo and W atoms in 1−4), while a value of −13.5 ppm at
the center of D -symmetric nonsubstituted metal-free H Pc
6600 spectrofluorometer equipped with a Hamamatsu C9940
32
photomultiplier tube, using the surface photometric method.
Crystallographic Data Collection and Structure Refinement.
Data collection for 2 was carried out at −173 °C on a Bruker APEXII
CCD diffractometer with Mo Kα radiation (λ = 0.71073 Å). The
2h
2
was predicted (Figure 10). These values suggest that the
33
structure was solved by a direct method (SHELXS-97) and refined
expanded Pc has a ring-current effect similar to that of H Pc.
33
2
using a full-matrix least-squares technique (SHELXL-97). CCDC-
8
30031 contains the supplementary crystallographic data. These data
can be obtained free of charge from the Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Electrochemistry. Cyclic voltammetry measurements were
performed using a Hokuto Denko HZ5000 potentiostat under a
nitrogen atmosphere in o-dichlorobenzene (o-DCB) solutions with 0.1
M tetrabutylammonium perchlorate (TBAP) as a supporting electro-
lyte. Measurements were made with a glassy-carbon electrode (area =
2
0
.07 cm ), a Ag/AgCl reference electrode, and a Pt wire counter
electrode. The concentration of the solution was fixed at 1.0 mM, and
+
the scan rate was 100 mV/s. The ferrocenium/ferrocene (Fc /Fc)
couple was used as an internal standard.
Figure 10. NICS values of the expanded C -symmetric Pc analogue
Computational Methods. DFT and TD-DFT calculations were
performed using the Gaussian 03 software package using 6-31G(d)
basis sets for C, H, N, and O and the LANL2DZ basis set for Mo.
Optimized structures were obtained without symmetrization.
Phthalocyanine (H Pc) was optimized using D symmetrization.
2
h
and D -symmetric free-base Pc. NICS values for the expanded Pc at
2
h
the centers of the inner 20-membered ring and the central
heteroatoms are shown in red and blue, respectively.
2
2h
Materials. All commercial chemicals were used as received. 4-tert-
3
4
34
Butylphthalic anhydride, 4-tert-butylphthalimide, and 4,5-bis(4-tert-
CONCLUSIONS
■
15
butylphenoxy)phthalonitrile were prepared according to methods
In summary, novel expanded phthalocyanine (Pc) congeners
containing two MoO or WO central cores and four
isoindole moieties coordinated by four pyrrole nitrogen atoms
and two amino nitrogen atoms have been synthesized under
normal Pc formation conditions in the presence of urea. Their
structures have been characterized using several spectroscopic
methods, and their redox properties have been explored. X-ray
analysis revealed a rectangular structure with C2v symmetry.
Although structures containing two MoN or WN cores
described in the literature. The synthesis of 4,5-dibromophthalimide
35
was carried out in high yield according to a published method
3
6
through initial oxidation of 4,5-dibromo-o-xylene with KMnO in
4
boiling 70% aqueous pyridine to form 4,5-dibromophthalic acid,
followed by heating with ammonium acetate in acetic acid to form the
target structure (mp: 238−240 °C).
4
,5-Di(phenylthio)phthalimide. This compound was formed from
by adding triethylamine (0.47 g, 4.6 mmol) dropwise to a mixture of
4
4
,5-dibromophthalimide (0.61 g, 2.0 mmol) and thiophenol (0.51 g,
.6 mmol) in 5 mL of N,N-dimethylformamide. The stirred reaction
1
are also possible on the basis of the MS and H NMR data,
careful analysis of the X-ray, IR, and electronic absorption data
mixture was kept at room temperature for 1 h and then at 50−55 °C
for 40 min. After the mixture was cooled and poured into water, the
3
416
dx.doi.org/10.1021/ja209589x | J. Am. Chem. Soc. 2012, 134, 3411−3418

Journal of the American Chemical Society
Article
precipitate was filtered off, washed with water, and crystallized from
acetic acid. Yellow crystals were obtained (yield: 0.50 g, 78%). Anal.
permeation chromatography on a Bio-Beads S-X1 column using
toluene as an eluent. After removal of the solvent under vacuum, the
compound was obtained as a dark-red solid (yield: 0.81 mg, 0.32%).
(
(
Calcd, Found for C H NO S ): C (66.09, 65.78), H (3.60, 3.45), N
20 13 2 2
+
3.85, 3.82), S(17.64, 17.61). Mp: 258−260 °C.
a. A stirred mixture of 4-tert-butylphthalic anhydride (0.41 g, 2.0
HR-MS (m/z): [M + Na] calcd for C114H112Mo N O Na,
2
12 10
1
1
2026.6656; found, 2026.6625. H NMR (600 MHz, CDCl ): δ 9.37
3
mmol), urea (0.6 g, 10.0 mmol), and molybdenum(VI) dichloride
dioxide (0.10 g, 0.5 mmol) was slowly heated for 50−60 min from 140
to 220 °C, and the temperature was then held for a further 10 min.
(s, 4H), 9.23 (s, 4H), 7.58 (d, J = 8.8 Hz, 8H), 7.52 (d, J = 8.9 Hz,
8H), 7.33 (d, J = 8.8 Hz, 8H), 7.31 (d, J = 9.1 Hz, 8H), 1.51 (s, 36H),
1.42 (s, 36H). 13C NMR (150 MHz, CDCl ): δ 161.35, 155.36,
3
The mixture of products was then cooled, extracted with CHCl , and
154.79, 153.57, 151. 94, 149.61, 148.10, 146.74, 132.04, 131.97,
3
passed through a silica gel column. The solvent was evaporated, and
the residue was purified by column chromatography on silica gel using
benzene as an eluent. The second colored fraction was collected after
127.26, 126.93, 120.01, 117. 76, 115.66, 112.99, 34.65, 34.49, 31.7,
−1
−1
31.6. UV/vis/NIR (CCl ) λmax/nm (ε/M cm ): 1152 (11000),
4
1021 (23000), 937 (39000), 439 (23000), 402 (33000).
an initial fraction containing a trace amount of t-BuH Pc had eluted.
4. A stirred mixture of 4,5-di(phenylthio)phthalimide (0.73 g, 2.0
mmol), urea (1.21 g, 20.0 mmol), and ammonium molybdate (0.08 g,
0.4 mmol) was slowly heated for 45−50 min from 120 to 250 °C and
then kept at that temperature for a further 10 min. After the reaction
mixture was cooled and benzene was added, the crude product was
collected by extraction and recrystallized three times from benzene
solution by adding methanol. The dark-brown-colored material was
purified by gel-permeation chromatography on a Bio-Beads S-X1
2
Further purification was achieved by gel-permeation chromatography
on a Bio-Beads S-X1 column using CHCl3 as an eluent. After
evaporation of the solvent, the residue was recrystallized from benzene
and hexane to provide 1a as a brown solid with a slight green tint
(
(
yield: 0.012 g, 4.6%). Anal. (Calcd, Found for C H Mo N O ): C
57.69, 56.75), H (4.65, 4.95), N (16.15, 15.58). HR-MS (m/z): [M
50
48
2
12
2
+
+
Na] calcd for C H Mo N O Na, 1064.2033; found, 1064.2033.
50
48
2
12
2
1
H NMR (600 MHz, CDCl ): δ 10.04, 9.90, 9.77, 9.71, 9.68, 9.66 (m,
column (eluent CHCl
) and by recrystallization (twice) from CHCl
3 3
3
solution with methanol, affording a wine colored solid (yield: 28.0 mg,
8
H), 8.55 (d, J = 7.9 Hz, 4H), 1.86 (m, 36H). UV/vis/NIR (CCl )
4
−1
−1
8
.3%). Anal. (Calcd, Found for C H Mo N O S ): C (58.56,
82 48 2 12 2 8
λmax/nm (ε/M cm ): 1151 (14000), 1014 (26000), 928 (52000),
−1
5
7.67), H (2.88, 3.11), N (9.99, 9.65). Fast atom bombardment MS
411 (59000). IR (KBr) cm : 2957, 1717, 1655, 1611, 1551, 1508,
1482, 1458, 1419, 1396, 1364, 1324, 1254, 1185, 1155, 1141, 1120,
1083, 1057, 1012, 970, 936, 850, 836, 782, 758, 737, 699.
+
1
(
m/z): [M ] calcd for C H Mo N O S 1681.7; found, 1682. H
82 48 2 12 2 8,
NMR (400 MHz, CDCl ): δ 7.78−7.39 (45H, SPh), 9.45, 9.41 (s,
3
−1
−1
8
1
H). UV/vis/NIR (CCl ) λ /nm (ε/M cm ): 1180 (12000),
1b. A stirred mixture of 4-tert-butylphthalimide (1.02 g, 5.0 mmol),
4 max
057 (26000), 972 (34000), 471 (30000), 409 (33000), and 324
urea (3.0 g, 50.0 mmol), and ammonium tungstate (0.28 g, 1.0 mmol)
was slowly heated for 60−70 min from 140 to 240 °C, and then the
temperature was maintained for 10 min. The mixture was then cooled
and extracted with chloroform, and insoluble impurities were removed
by filtration. The crude product was purified on a silica gel column
−1
(41000). IR (KBr) cm : 1580, 1541, 1508, 1474, 1439, 1417, 1341,
1
6
300, 1250, 1152, 1100, 1065, 1020, 970, 856, 795, 748, 733, 704, 689,
38.
using a 2:1:0.1 hexane/CHCl /MeOH mixture as an eluent. The
second green-colored fraction was collected (the first colored fraction
ASSOCIATED CONTENT
Supporting Information
Mass data for all compounds; COSY spectra of 1a and 3 in
3
■
*
S
was a trace of t-BuH Pc). The solvent was evaporated, and further
2
purification was achieved by gel-permeation chromatography on a Bio-
Beads S-X1 column using CHCl3 as an eluent. After solvent
evaporation, a dark-green residue was recrystallized twice from toluene
with hexane to give 1b as a green solid (yield: 0.01 g, 1.6%). Anal.
14
CDCl ; NOE spectrum of 3 in CDCl ; N NMR spectrum of
3
3
compound 2; ESR spectra of 1a, 3, and tetra-tert-butyl-
V
substituted (Mo N)Pc in deaerated toluene at room
(
Calcd, Found for C H N O W ): C (49.36, 49.11), H (3.98, 4.52),
temperature; geometry-optimized structure of substituent-free
2; and complete ref 27. This material is available free of charge
via the Internet at http://pubs.acs.org.
50
48 12
2
2
+
N (13.81, 13.65). HR-MS (m/z): [M + Na] calcd for
C H N O W Na, 1239.2946; found, 1239.2934. H NMR (400
1
50
48 12
2
2
MHz, CDCl ): δ 10.04−9.73 (m, 8H), 8.60−8.56 (m, 4H), 1.88−1.86
3
−1
−1
(
m, 36H). UV/vis/NIR (CCl ) λ /nm (ε/M cm ): 1405 (5000),
4 max
AUTHOR INFORMATION
Corresponding Author
rmeluk@niopik.ru; nagaok@m.tohoku.ac.jp
■
1
073 (20000), 994 (42000), 913 (28000), 384 (48000).
. A mixture of 5,6-di-4-tert-butylphenyl-1H-isoindole-1,3(2H)-
diimine (205 mg, 0.5 mmol), (NH ) MoO (19.6 mg, 0.1 mmol),
2
4
2
4
and urea (1.5 g, 25 mmol) was heated for 1 h from 160 to 220 °C. At
Notes
2
20 °C, 1-chloronaphthalene was added to the mixture, and the
The authors declare no competing financial interest.
temperature was maintained for 30 min. After the reaction mixture was
cooled to room temperature, 2 was extracted with CHCl and purified
by column chromatography on silica gel (using first hexane and then
CHCl3 as eluents, followed by toluene). The compound was
3
ACKNOWLEDGMENTS
■
This work was partly supported by the Moscow City
Government, a Grant-in-Aid for Scientific Research on
Innovative Areas (20108007, “pi-Space”) from the Ministry of
Education, Culture, Sports, Science, and Technology (MEXT),
and a Grant-in-Aid for Scientific Research (B) (23350095)
from JSPS. O.M. thanks the Global Center of Excellence (G-
COE) program of Tohoku University. A.M. is indebted to the
JST PRESTO Program. The authors thank Prof. Takeaki
Iwamoto and Dr. Shintaro Ishida (Tohoku University) for X-
ray measurements, Prof. Seigo Yamauchi and Dr. Islam Saiful
recrystallized with MeOH to give 2 as a red powder (yield: 7.1 mg,
+
7
.6%). HR-MS (m/z): [M ] calcd for C 14H Mo N O , 1874.7176;
1
112
2
12
2
1
found, 1874.7164. H NMR (400 MHz, toluene-d ): δ 10.11(s, 4H),
8
9
.66 (s, 4H), 7.77−7.17 (br, 32H), 1.37−1.19 (s, 72H). UV/vis/NIR
−1 −1
(
CHCl ) λ /nm (ε/M cm ): 1190 (22000), 1045 (48000), 959
3 max
(
94000), 461 (51000), 404 (85000).
. A mixture of 4,5-di(4-tert-butylphenoxy)phthalonitrile (0.20 g,
.50 mmol), (NH ) MoO (0.050 g, 0.25 mmol), and urea (0.30 g, 5.0
3
0
4
2
4
mmol) was ground in an agate mortar. A small amount of 1-
chloronaphthalene was added to the mixture, which was then heated at
ca. 200 °C for 1 h under nitrogen. Urea (0.10 g, 1.8 mmol) was
subsequently added, and the reactants were heated at ca. 220 °C. Urea
(
Tohoku University) for EPR measurements, and Dr. Eunsang
Kwon (Tohoku University) and JEOL RESONANCE Inc. for
N NMR measurements.
(
0.10 g, 1.8 mmol) was added three times after 3.5, 5.5, and 7 h. After
14
the mixture was heated for ca. 10 h, the crude product was cooled to
room temperature. Compound 3 was extracted with CHCl3 and
purified by column chromatography on silica gel (using first hexane
and then toluene as eluents). Further purification was achieved by gel-
REFERENCES
(1) Linstead, R. P. J. Chem. Soc. 1934, 1016−1017.
■
3
417
dx.doi.org/10.1021/ja209589x | J. Am. Chem. Soc. 2012, 134, 3411−3418

Journal of the American Chemical Society
Article
(
2) Phthalocyanines: Properties and Applications; Leznoff, C. C., Lever,
A. B. P., Eds.; VCH: New York, 1989−1996; Vols. 1−4.
3) The Porphyrin Handbook; Kadish, K. M., Smith, K. M., Guilard,
R., Eds.; Academic Press: New York, 2003; Vols. 15−20.
4) Torre, G.; Claessens, C. G.; Torres, T. Chem. Commun. 2007,
000−2015.
5) Jiang, J.; Kasuga, K.; Arnold, D. P. In Supramolecular
Photosensitive and Electroactive Materials; Academic Press: New York,
001.
6) Claessens, C. G.; Gonzalez-Rodriguez, D.; Torres, T. Chem. Rev.
002, 102, 835−853.
7) Kobayashi, N. In The Porphyrin Handbook; Kadish, K. M., Smith,
(20) A 14N NMR spectrum was recorded for 2 (Figure S5 in the SI).
The signal was measured between −1000 and 800 ppm, but only a
single peak was observed at −66 ppm. If the structure of 2 were
consistent with that of 5B in its core structure, at least two N NMR
peaks would be anticipated. Although the 1H NMR data can be
interpreted for both structures 5A and 5B (Figure 3), this result also
supports the characterization of 2 as 5A.
(
1
4
(
2
(
(21) Gouterman, M. In The Porphyrins; Dolphin, D., Ed.; Academic
Press: New York, 1978; Vol III, Part A, Chapter 1.
2
(
2
(
(22) Platt, J. R. J. Chem. Phys. 1949, 17, 484−495.
(23) Mack, J.; Stillman, M. J. In The Porphyrin Handbook; Kadish, K.
M., Smith, K. M., Guilard, R., Eds.; Academic Press: New York, 2003;
Vol. 16, Chapter 103.
K. M., Guilard, R., Eds.; Academic Press: New York, 2003; Vol. 15,
Chapter 100.
(24) Mack, J.; Stillman, M. J.; Kobayashi, N. Cood. Chem. Rev. 2007,
251, 429−453.
(25) Kobayashi, N.; Nakai, K. Chem. Commun. 2007, 4077−4092.
(26) (a) Mack, J.; Asano, Y.; Kobayashi, N.; Stillman, M. J. J. Am.
Chem. Soc. 2005, 127, 17697−17711. (b) Kobayashi, N.; Miwa, H.;
Nemykin, V. N. J. Am. Chem. Soc. 2002, 124, 8007−8020.
(c) Kobayashi, N.; Fukuda, T. J. Am. Chem. Soc. 2002, 124, 8021−
(
8) Engel, M. K. In The Porphyrin Handbook; Kadish, K. M., Smith,
K. M., Guilard, R., Eds.; Academic Press: New York, 2003; Vol. 20,
Chapter 122.
(
9) (a) Moser, F. H.; Thomas, A. L. The Phthalocyanines, CRC Press:
Boca Raton, FL, 1983; Vols. I and II. (b) In Phthalocyanines: Properties
and Applications: Leznoff, C. C., Lever, A. B. P., Eds.; VCH: New York,
8
034. (d) Asano, Y.; Muranaka, A.; Fukasawa, A.; Hatano, T.;
Uchiyama, M.; Kobayashi, N. J. Am. Chem. Soc. 2007, 129, 4516−4517.
e) Fukuda, T.; Masuda, S.; Kobayashi, N. J. Am. Chem. Soc. 2007, 129,
472−5479. (f) Takeuchi, Y.; Matsuda, A.; Kobayashi, N. J. Am. Chem.
1989; Vol. 1, Chapter 1. (c) McKeown, N. B. In The Porphyrin
Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic
Press: New York, 2003; Vol. 15, Chapter 18. (d) Nemykin, V. N.;
Luk’yanets, E. A. In Handbook of Porphyrin Science; Kadish, K. M.,
Smith, K. M., Guilard, R., Eds.; World Scientific: Singapore, 2010; Vol.
(
5
Soc. 2007, 129, 8271−8281. (g) Mack, J.; Bunya, M.; Shimizu, Y.;
Uoyama, H.; Komobuchi, N.; Okujima, T.; Uno, H.; Ito, S.; Stillman,
M. J.; Ono, N.; Kobayashi, N. Chem.Eur. J. 2008, 14, 5001−5020.
3
, Chapter 11. (e) Luk’yanets, E. A.; Nemykin, V. N. J. Porphyrins
Phthalocyanines 2010, 14, 1−40.
10) Crystallographic data for 2: C124H119N O Mo Cl, MW =
(h) Kuzuhara, D.; Mack, J.; Yamada, H.; Okujima, T.; Ono, N.;
(
12
2
2
Kobayashi, N. Chem.Eur. J. 2009, 15, 10060−10069. (i) Kobayashi,
N.; Narita, F.; Ishii, K.; Muranaka, A. Chem.Eur. J. 2009, 15, 10173−
10181. (j) Shimizu, S.; Zhu, H.; Kobayashi, N. Chem.Eur. J. 2010,
2036.64, monoclinic, space group C2/c (No. 15), a = 52.893(12) Å, b
3
=
14.406(3) Å, c = 39.178(7) Å, β = 104.803(4)°, V = 28863(10) Å ,
3
Z = 8, ρcalcd = 0.937 g/cm , T = −173 °C, 66048 measured reflns,
5359 unique reflns (Rint = 0.0820), R = 0.0657, Rw = 0.1853 (all
data), GOF = 0.889.
11) According to geometry optimization calculations for the
1
6, 11151−11159. (k) Okujima, T.; Jin, G.; Matsumoto, N.; Mack, J.;
2
Mori, S.; Ohara, K.; Ando, C.; Ono, N.; Yamada, H.; Uno, H.;
Kobayashi, N. Angew. Chem., Int. Ed. 2011, 50, 5699−5703. (l) Mack,
J.; Kobayashi, N. Chem. Rev. 2011, 111, 281−321.
(
substituent-free 2 structure, cis-2 is predicted to be more stable than
trans-2 by 13.1 kcal/mol, although the π systems of cis-2 and trans-2
are both predicted to adopt domed structures (the energy difference
was based on the total energies corrected with the zero-point
vibrational energies). This may provide an explanation for why we
obtained only the cis-2 structure as an isolable product.
(
27) Frisch, M. J.; et al. Gaussian 03, revision E.01; Gaussian, Inc.:
Wallingford, CT, 2004.
28) Muranaka, A.; Matsushita, O.; Yoshida, K.; Mori, S.; Suzuki, M.;
Furuyama, T.; Uchiyama, M.; Osuka, A.; Kobayashi, N. Chem.Eur. J.
(
2
(
(
(
009, 15, 3744−3751.
29) Michl, J. J. Am. Chem. Soc. 1978, 100, 6801−6811.
30) Michl, J. Pure Appl. Chem. 1980, 52, 1549−1563.
31) Chen, Z. F.; Wannere, C. S.; Corminboeuf, C.; Puchta, R.;
(
5
(
12) Modec, B.; Sala, M.; Clerac, R. Eur. J. Inorg. Chem. 2010, 542−
53.
13) (a) Matz, K. G.; Mtei, R. P.; Leung, B.; Burgmayer, S. J. N.; Kirk,
Schleyer, P. v. R. Chem. Rev. 2005, 105, 3842−3888.
M. L. J. Am. Chem. Soc. 2010, 132, 7830−7831. (b) Groysman, S.;
Wang, J.-J.; Tagore, R.; Lee, S. C.; Holm, R. H. J. Am. Chem. Soc. 2008,
(32) Kamino, S.; Horio, Y.; Komeda, S.; Minoura, K.; Ichikawa, H.;
Horigome, J.; Tatsumi, A.; Kaji, S.; Yamaguchi, T.; Usami, Y.; Hirota,
S.; Enomoto, S.; Fujita, Y. Chem. Commun. 2010, 46, 9013−9015. In
particular, see Figure S10.
1
4
30, 12794−12807. (c) Wang, J.-J.; Holm, R. H. Inorg. Chem. 2007,
6, 11156−11164. (d) Basu, P.; Nemykin, V. N.; Sengar, R. S. Inorg.
Chem. 2009, 48, 6303−6313. (e) Carrano, C. J.; Chohan, B. S.;
Hammes, B. S.; Kail, B. W.; Nemykin, V. N.; Basu, P. Inorg. Chem.
(
33) Sheldrick, G. M. SHELXL-97: Program for the Solution and
Refinement of Crystal Structures; University of Gottingen: Gottingen,
Germany, 1997.
34) Mikhalenko, S. A.; Barkanova, S. V.; Lebedev, O. L.; Luk’yanets,
E. A. J. Gen. Chem. USSR (Engl. Transl.) 1971, 41, 2770−2773.
35) Solov’yova, L. I.; Luk’yanets, E. A. Coll. “Anilinokrasochnaya
Promyshlennost”, Niitekhim. (Russ.) 1976, 9, 1.
̈
̈
2
003, 42, 5999−6007. (f) Inscore, F. E.; Knottenbelt, S. Z.; Rubie, N.
D.; Joshi, H. K.; Kirk, M. L.; Enemark, J. H. Inorg. Chem. 2006, 45,
67−976. (g) Mader, M. L.; Carducci, M. D.; Enemark, J. H. Inorg.
Chem. 2000, 39, 525−531.
14) Mizutani, J.; Imoto, H.; Saito, H. Acta Crystallogr. 1997, C53,
7−50.
15) Maree, S.; Nyokong, T. J. Porphyrins Phthalocyanines 2001, 5,
82−792.
16) Gorsch, M.; Kienast, A.; Huckstadt, H.; Homborg, V. Z. Anorg.
Allg. Chem. 1997, 623, 1433−1440.
17) Frick, K.; Verma, S.; Sundermeyer, J. Eur. J. Inorg. Chem. 2000,
025−1030.
(
9
(
(
4
(
7
(36) Piechocki, C.; Simon, J. Nouv. J. Chim. 1985, 9, 159−166.
(
(
1
(
18) (a) Kobayashi, N.; Nakajima, S.; Ogata, H.; Fukuda, T. Chem.
Eur. J. 2004, 10, 6294−6312. (b) Kobayashi, N.; Fukuda, T. Chem.
Lett. 2004, 33, 32−33. (c) Fukuda, T.; Makarova, E. A.; Luk’yanets, E.
A.; Kobayashi, N. Chem.Eur. J. 2004, 10, 117−133. (d) Makarova, E.
A.; Fukuda, T.; Luk’yanets, E. A.; Kobayashi, N. Chem.Eur. J. 2005,
1
(
1, 1235−1250.
19) (a) Nyokong, T. Inorg. Chim. Acta 1989, 160, 235−239.
(
b) Nyokong, T. Polyhedron 1994, 13, 215−220.
3
418
dx.doi.org/10.1021/ja209589x | J. Am. Chem. Soc. 2012, 134, 3411−3418