Synthesis of porphyrin dimers fused with a benzene unit

Article abstract of DOI:10.1002/chem.200601644

Bicyclo[2.2.2]octadiene-connected pyrrolo-porphyrins have been prepared by an inverse-type [3+1] porphyrin synthesis of a bicyclo[2.2.2]octadiene-fused dipyrrole with a tripyrrane dicarbaldehyde. Another [3+1] porphyrin synthesis of pyrrole-connected porp

Full text of DOI:10.1002/chem.200601644

FULL PAPER
DOI: 10.1002/chem.200601644
Synthesis of Porphyrin Dimers Fused with a Benzene Unit
Hidemitsu Uno,*[a] Ken-ichi Nakamoto,[b] Kenji Kuroki,[b] Akiko Fujimoto,[a] and
Noboru Ono[b]
Abstract: Bicyclo
ACHTREUNG
pared by an inverse-type [3+1] porphyrin synthesis of a bicyclo
AHCTREUNG
fused dipyrrole with a tripyrrane dicarbaldehyde. Another [3+1] porphyrin synthe-
Keywords: conjugation dimer-
·
sis of pyrrole-connected porphyrins with the same or other tripyrrane dicarbalde-
A
·
hydes gave bicyclo
peripheral substituents of which were different. Thermal decomposition of the
bicyclo[2.2.2]octadiene skeleton to a benzene moiety gave p-system-fused porphy-
rin dimers in a highly pure form.
A
Diels–Alder reaction
interactions
·
stacking
ACHTREUNG
Introduction
tion,[2] by porphyrin synthesis[3] using pyrrole-fused porphy-
rins,[3a,b] by dehydrogenative aromatization[4] of a cyclohexa-
AHCTREUNG
Recently, compounds with a highly conjugated p system
have attracted much attention as promising organic materi-
als for electronic devices such as organic thin-film transis-
tors.[1] From a synthetic point of view, the assembly of
stable, smaller p-system units in the final step is advanta-
geous for the construction of a large p system as compared
with sequential expansion of an already quite large p
system. This is due to the intrinsic instability towards
oxygen and the low solubility in common solvents that
result from the highly planar nature of compounds of this
type with a large p system. A porphyrin p system is suffi-
ciently large and stable to be used as such a basic unit.
Therefore, successful preparative methods for p-system-
fused porphyrin dimers have been reported by several
groups. These methods may be categorized into a number of
classes according to the way in which the fused porphyrin p
system is ultimately constructed; that is, by the construction
of connecting aromatic moieties by dehydrative condensa-
diene moiety between the porphyrin rings, or by oxidative
p-system fusion[5] of porphyrins. Difficulties are often en-
countered in the purification and/or separation of the de-
sired porphyrin dimers from chemical materials such as side
products derived from the reagents, residual reagents, and,
in some cases, solvents, due to high propensity for stacking
of the target molecules. Bulky groups or long alkyl chains
have been appended in order to increase solubility in organ-
ic solvents so as to facilitate purification by column chroma-
tography or recrystallization. However, the introduction of
such groups may have an adverse effect on the electronic
properties of the systems in the context of molecular devices
by diminishing the intermolecular p-system interaction. We
have developed a new synthesis of highly pure p-expanded
porphyrins and porphyrinoids based on the final conversion
of precursors by a retro-Diels–Alder reaction,[6] and have
applied this protocol to the preparation of porphyrin dimers
fused with a benzene[7] or anthraquinone[8] unit. In this
paper, we discuss another example of the successful use of
this method, namely, for the preparation of p-system-fused
porphyrin dimers with different central metals and/or pe-
ripheral substituents, as well as the structures of these prod-
ucts.
[a] Prof. H. Uno, A. Fujimoto
Division of Synthesis and Analysis, Department of Molecular Science
Integrated Center for Sciences (INCS)
Ehime University, Matsuyama 790-8577 (Japan)
and
CREST, Japan Science Technology Corporation (JST)
Fax: ( +81)89-927-9670
E-mail: uno@dpc.ehime-u.ac.jp
Results and Discussion
[b] K.-i. Nakamoto, K. Kuroki, Prof. N. Ono
Department of Chemistry, Faculty of Science
Ehime University, Matsuyama 790-8577 (Japan)
Preparation of bicyclo[2.2.2]octadiene-fused porphyrin
dimers: Our key precursors are dipyrroles 2 and 3 fused
A
Chem. Eur. J. 2007, 13, 5773 – 5784
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5773

with a bicyclo
ACHTREUNG
role 2a was prepared from the bicyclo
AHCTREUNG
pyrrolecarboxylate ethyl ester 1 by standard construction of
another pyrrole ring at the double bond.[9] Removal of the
ethyl ester groups from 2a was achieved by treatment with
potassium hydroxide in ethylene glycol at 1708C to give 3 in
83% yield. We first attempted to prepare the target porphy-
rin dimer by a [3+1] porphyrin synthesis involving the bis-
tripyrrane 5.[10,11] Thus, dipyrrole 3 was treated with 5-(ace-
toxymethyl)-2-pyrrolecarboxylate benzyl ester 4a under
acidic conditions (p-toluenesulfonic acid (p-TSA), acetic
acid, room temperature). However, none of the desired bis-
tripyrrane was obtained. Next, a route based on [2+2] por-
phyrin synthesis[11] was examined. Acid treatment of a mix-
ture of syn-2a and 5-(acetoxymethyl)-2-pyrrolecarboxylate
tert-butyl ester 4b gave bis-dipyrromethane 6 in moderate
yield. Bis-dipyrromethane 6 was condensed with all-ethyl-
substituted dipyrromethane dicarbaldehyde 7 and then the
mixture was oxidized with 2,3-dichloro-5,6-dicyano-1,4-ben-
zoquinone (DDQ). Although the presence of the target di-
porphyrin 8 in the reaction mixture was detected by using
UV spectroscopy and TOF-MS analyses, we were unable to
isolate it.
Scheme 2. Preparation of tripyrrane dicarbaldehydes: a) 4a, AcOH,
EtOH; 72%; or 4c, p-TSA, EtOH; 29%; b) 10a, H2, Pd/C, Et3N, THF;
TFA, CH
A
AHCTREUNG
In order to carry out an inverse-type [3+1] porphyrin syn-
thesis,[8] tripyrrane carbaldehydes[12] such as 11 were re-
quired (Scheme 2). 3,4-Diethylpyrrole (9) was reacted with
5-(acetoxymethyl)pyrrolecarboxylate esters 4a and 4c in the
presence of an acid catalyst to give tripyrrane diesters 10a
and 10b in respective yields of 72 and 29%.[13] Deprotection
of esters 10a and 10b followed by formylation with methyl
orthoformate in trifluoroacetic acid (TFA) gave the target
tripyrrane dicarbaldehydes 11a and 11b in yields of 81 and
51%, respectively.
of 3 with tripyrrane dicarbaldehyde 11a afforded the
bicyclo[2.2.2]octadiene-fused porphyrin dimer 12-H4, which
AHCTREUNG
was purified as 12–Zn2 (21%) after metalation with zinc
acetate.[7] The pure free-base diporphyrin 12-H4 was ob-
tained in 98% yield by demetalation of 12–Zn2 with TFA.
Next, we planned to prepare porphyrin dimers incorporating
different metal atoms and bearing different peripheral sub-
stituents. For this purpose, a dipyrrole with differently sub-
stituted pyrrole rings was required, for which we chose the
tert-butyl and ethyl diester of dipyrroledicarboxylate, 2b
(Scheme 3). Applying the standard protocol[9] for the con-
The synthesis of a symmetric diporphyrin was examined
using 3 (Scheme 3). Inverse-type [3+1] porphyrin synthesis
Scheme 1. Early attempts to prepare porphyrin dimers fused with bicyclo
A
tBuOK, THF, RT; 99%; CNCH2CO2Et, tBuOK, THF, À208C to RT; 73%. b) KOH, (CH2OH)2, 1708C; 83%. c) 4a, p-TSA, AcOH. d) syn-2a, 4b, p-
TSA, AcOH; 41%. e) KOH, (CH2OH)2, 1708C; 7, TFA, CH2Cl2; Et3N; DDQ, CH2Cl2; trace.
5774
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 5773 – 5784

Porphyrin Dimers Fused with a Benzene Unit
FULL PAPER
Scheme 3. Preparation of porphyrin dimers fused with a bicyclo[2.2.2]octadiene unit: a) 11a, TFA, CH2Cl2; Et3N, CH2Cl2; DDQ, CH2Cl2; Zn-
G
ACHTREUNG
A
ACHTREUNG
ACHTREUNG
struction of a pyrrole ester moiety at a double bond to
bicyclo[2.2.2]octadiene-fused pyrrole 1 using tert-butyl iso-
cyanoacetate, the target diester 2b was obtained in 78%
yield. When the inverse [3+1] porphyrin synthesis with tri-
pyrrane dicarbaldehyde 11a was directly applied to the di-
ments (108CminÀ1) were also indicative of quantitative loss
of an ethylene unit during this period. Similar results were
obtained from TG experiments on the other dimers 12–
NiZn and 16: sharp weight loss started at 1358C (12–NiZn)
and 1208C (16), the half points of the TG curves were
around 1658C (12–NiZn) and 1568C (16), and in both cases
the loss stopped at 1758C. The total weight losses were
2.38% for 12–NiZn and 2.47% for 16. These values com-
pare very well with the theoretical values (2.37% for 12–
NiZn and 2.43% for 16). The somewhat slower decomposi-
tion and the slightly greater weight loss observed in the case
of the decomposition of precursor 16 were probably due to
the inclusion of a small amount of solvent. Preparative con-
versions of the precursors 12 and 16 were performed at
2008C under reduced pressure (ca. 0.2 mmHg) for 1 h,
whereby the p-conjugated dimers 13 and 17 were obtained
in quantitative yields.
ACHTREUNG
A
pyrrole ring bearing the tert-butyl ester moiety, which was
initially removed by the acid treatment. The free-base por-
phyrin 14-H2 was obtained in 27% yield and metalations
with zinc acetate and nickel(II) acetate gave the zinc– and
nickel–porphyrins 14–Zn and 14–Ni in respective yields of
98 and 85%. When we used 14–Zn as the starting material
for another porphyrin-ring construction, partial demetala-
tion occurred during both the ester group removal and the
following porphyrin synthesis. Therefore, we employed
nickel–porphyrin 14–Ni to prepare the dimers. Removal of
the ester group from 14–Ni was carried out under basic con-
ditions to give the a-unsubstituted pyrrole-fused porphyrin
15 in 82% yield. Another inverse [3+1] porphyrin synthesis
of 15 with tripyrrane dicarbaldehyde 11a, followed by met-
alation with zinc acetate, gave the nickel and zinc bis-por-
phyrin 12–NiZn in 12% yield. When all-ethyl tripyrrane di-
carbaldehyde 11b was used instead of 11a, nonsymmetric
bis-porphyrin 16 was obtained in 35% yield.
Spectroscopic analyses of the bicyclo
ACHTREUNG
1
AHCTREUNG
(CDCl3), the signals of two meso-protons were observed at
d=10.83 (inner) and 10.01 ppm (outer), while that of the
bridgehead proton was seen at d=7.88 ppm due to a sum-
mation of the large anisotropic effects of the porphyrin ring
Retro-Diels–Alder p-system fusion: Differential scanning
calorimetric analyses of the symmetrical dimers 12–Zn2 and
12–H4 showed sharp exothermic decomposition peaks at 160
and 1708C (peak widths: 155–175 and 163–1788C at
208CminÀ1), respectively. Thermogravimetric (TG) experi-
currents. In the spectrum of the bicyclo[2.2.2]octadiene-
A
bridged dimer 12–NiZn, four meso-proton signals were ob-
served at d=10.56 (inner meso-proton of the Ni porphyrin
unit), 10.55 (inner meso-proton of the Zn porphyrin unit),
9.72 (outer meso-proton of the Zn porphyrin unit), and
Chem. Eur. J. 2007, 13, 5773 – 5784
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5775

H. Uno et al.
9.31 ppm (outer meso-proton of the Ni porphyrin unit),
along with a bridgehead proton signal at d=7.70 ppm. The
corresponding signals for the nonsymmetric bis-porphyrin
16 were seen at d=10.72, 10.49, 9.98, 9.75, and 7.69 ppm, re-
spectively.
The absorption and fluorescence spectra of the dimers are
shown in Figure 1. Soret and Q bands of the zinc- and
nickel-porphyrin monomers 14–Zn and 14–Ni were ob-
served at similar positions [l (loge)=403 (5.49), 532 (4.19),
and 570 nm (4.24) for 14–Zn (Figure 1e, orange solid line); l
(loge)=394 (5.28), 516 (4.04), and 554 nm (4.37) for 14–Ni
(Figure 1g, blue solid line)] to those of the corresponding
octaalkyl-substituted metalloporphyrins. The bicyclo-
A
bands at l (loge)=394 (5.42) and 410 nm (5.49), and three
Q bands at l (loge)=535 (4.40), 555 (4.53), and 572 nm
(4.50) (Figure 1g, turquoise line). Almost the same spectrum
was recorded for 16 (Figure 1f, green solid line). The short-
er-wavelength Soret-band absorption appeared at almost the
same position as in the case of the parent nickel–porphyrin
14–Ni, with a slightly higher intensity, while the longer-
wavelength Soret band absorbed at a lower energy com-
pared with that of the zinc–porphyrin 14–Zn, with almost
the same intensity. Even in the case of the symmetric zinc–
porphyrin dimer 12–Zn2, two
separate Soret bands were ob-
served at 399 and 414 nm with
similar intensities (loge=5.65;
Figure 1a,
navy-blue
solid
line). This is due to exciton
coupling between the porphy-
rin rings by homo-conjugation
through
the
bicyclo-
AHCTREUNG
the case of the symmetric free-
base dimer 12–H4 in CHCl3,
we observed the characteristic
four Q bands and very broad
Soret bands due to stacking
(Figure 1b, magenta solid line).
When trifluoroacetic acid was
added, the absorption bands of
12–H4 became sharp, and two
sharp Soret bands were ob-
served at 400 and 419 nm (Fig-
ure 1g, brown solid line).
These were wider than that
(ca. 15 nm) reported for a pro-
tonated dimer singly connect-
ed by a methylene bridge be-
tween the b-positions.[14] This
is suggestive of a stronger in-
teraction between the orienta-
tionally constrained porphyrin
chromophores of protonated
12–H4 through the rigid
bicyclo[2.2.2]octadiene bridge.
N
Figure 1. UV/Vis and fluorescence spectra of the porphyrin dimers fused with bicyclo[2.2.2]octadiene and ben-
N
Figure 1h shows the fluores-
cence emission spectra of the
dimers: 12–H4 in CHCl3 (ma-
genta line), 12–Zn2 in CHCl3
(navy-blue line), 13–H4 in 1%
TFA/CHCl3 (dark green line),
13–Zn2 in 1% pyridine/CHCl3
(black line), 14–Zn in CHCl3
(orange line), and 16 in CHCl3
(green line). Their excitation
spectra are shown in Fig-
zene units. a) Absorption spectrum of 12–Zn2 in CHCl3 (navy-blue solid line) and excitation spectrum of 12–
Zn2 in CHCl3 for the 579 nm peak (navy-blue dotted line); b) absorption spectrum of 12-H4 in CHCl3 (ma-
genta solid line) and excitation spectrum of 12-H4 in CHCl3 for the 624 nm peak (magenta dotted line); c) ab-
sorption spectrum of 13–Zn2 in 1% pyridine/CHCl3 (black solid line) and excitation spectrum of 13–Zn2 in
1% pyridine/CHCl3 for the 640 nm peak (black dotted line); d) absorption spectrum of 13-H4 in 1% TFA/
CHCl3 (dark green solid line) and excitation spectrum of 13-H4 in 1% TFA/CHCl3 for the 663 nm peak (dark
green dotted line); e) absorption spectrum of 14–Zn in CHCl3 (orange solid line) and excitation spectrum of
14–Zn in CHCl3 for the 575 nm peak (orange dotted line); f) absorption spectrum of 16 in CHCl3 (green solid
line) and excitation spectrum of 16 in CHCl3 for the 578 nm peak (dotted green line); g) absorption spectra of
14–Ni (blue line), 12-H4 in 1% TFA/CHCl3 (brown line), 12–NiZn in CHCl3 (turquoise line), 13–NiZn (grey
line), and 17 in pyridine (red line); h) emission spectra of 12-H4 in CHCl3 irradiated at 397 nm (magenta line),
12–Zn2 in CHCl3 irradiated at 415 nm (navy-blue line), 13-H4 in 1% TFA/CHCl3 irradiated at 658 nm (dark
green line), 13–Zn2 in 1% pyridine/CHCl3 irradiated at 636 nm (black line), 14–Zn in CHCl3 irradiated at
403 nm (orange line), and 16 in CHCl3 irradiated at 410 nm (green line).
ures 1a–f as dotted lines. The
5776
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 5773 – 5784

Porphyrin Dimers Fused with a Benzene Unit
FULL PAPER
emission spectrum of the free-base dimer 12–H4 shows a
sharp fluorescence peak at 624 nm along with a broad band
at 682 nm; the Stokes shift is 2 nm (Figure 1h, magenta
line). In the emission spectrum of the symmetric zinc dimer
12–Zn2, a strong fluorescence peak is observed at 579 nm,
along with a weak peak at 624 nm (Figure 1h, navy-blue
line). This fluorescence spectrum is very similar to that of
14–Zn (575 and 621 nm, Figure 1h, orange line). Nickel–por-
phyrins are well known to show no fluorescence.[15] In the
case of the different-metal dimer 16, we expected that it
might be possible to observe fluorescence from the zinc–por-
phyrin moiety. When we examined dimer 16 in chloroform,
a fluorescence peak was observed at 578 nm (Figure 1h,
green line). The peak maxima in the excitation spectrum for
the 578 nm peak of 16 (Figure 1f, green dotted line) were
very similar to those seen in the excitation spectrum of 12–
Zn2 (Figure 1a, navy-blue dotted line). They were, however,
different from those seen in the absorption spectrum of 16
(Figure 1f, solid green line) and in the excitation spectrum
of 14–Zn (Figure 1e, orange dotted line). Although the pho-
tomultiplier response was uncorrected in all of the emission
spectra, the intensity ratios of the peak maxima for 16 and
12–Zn2 were quite different. Therefore, we conclude that
this fluorescence from the sample of 16 originated from the
zinc–porphyrin moiety.
Spectroscopic analyses of the benzene-fused porphyrin
dimers: NMR analyses of the fully conjugated dimers 13
1
and 17 were carried out. H NMR spectra of the symmetric
Figure 2. VT-NMR spectra of dimer 13–NiZn (ca. 1.0 mg in 0.5 mL of
C5D5N) at a) 80, b) 60, c) 45, and d) 258C. Signal assignments for the
nickel– and zinc–porphyrin units are shown at the top and bottom, re-
spectively.
benzene-fused dimers 13–Zn2 and 13–H4 were successfully
recorded in deuterated pyridine and deuterio-chloroform
containing 1% trifluoroacetic acid, respectively. The signals
of the meso-protons of 13–Zn2 and 13–H2 were observed at
lower fields [d=10.99 (inner) and 10.15 ppm (outer) for 13–
Zn2; d=11.45 (inner) and 10.64 ppm (outer) for 13–H4]
compared with those of the precursor dimers 12–Zn2 and
12–H4 owing to an increase in porphyrin ring current as a
result of conjugation. The signals of the protons of the
fusing benzene unit appeared at the lowest fields (d=
11.48 ppm for 13–Zn2, 11.81 ppm for 13–H4), while a very
broad absorption due to the pyrrolic protons was observed
at d=À2.25 ppm for 13–H4. We encountered a difficulty in
obtaining NMR data for the nickel and zinc–porphyrin
dimers 13–NiZn and 17 owing to their low solubility in deu-
protons of the zinc–porphyrin, and those of the benzene
unit could be successfully assigned as indicated in Figure 2
with the aid of a COSY experiment at 608C. Indeed, very in-
teresting behavior was observed: only the signals due to the
protons of the benzene and alkyl groups on the nickel–por-
phyrin unit were found at very low fields as a result of the
large anisotropic effect of the intermolecularly stacked por-
phyrin rings, and these were shifted upfield as the tempera-
ture was increased. On the other hand, the signals of the
protons of the zinc–porphyrin unit appeared at similar posi-
tions irrespective of the measuring temperature. This phe-
nomenon clearly suggests that only the nickel–porphyrin
units of the mixed-metal dimer 13–NiZn become stacked in
deuterated pyridine. Axial coordination of the solvent to the
zinc–porphyrin unit apparently prevents stacking of this part
of the molecule. In the high-temperature spectra of 13–
NiZn and 17, broad singlet signals due to two protons ap-
peared at around d=6.8 ppm at 808C and 5.8 ppm at 608C
(marked with asterisks in Figure 2), while the corresponding
signals were observed at 3.6 ppm at room temperature. We
ascribe these signals, which appear at remarkably high fields
owing to the anisotropic effect, to one set of meso-protons
1
terated solvents. Satisfactory H NMR spectra could only be
obtained for samples in [D5]pyridine, although their inter-
pretation was rather difficult. In these spectra, only three
singlet signals were observed in the low-field region besides
the solvent pyridine signals at room temperature, although
five singlet signals were expected. No other corresponding
signal was found even over 16 ppm (up to 45 ppm). In order
1
to assign these H NMR spectra, we measured the spectrum
of 13–NiZn at various temperatures, as illustrated in
Figure 2. Although the required signals were sometimes
overlapped by a broad water signal, very large residual sol-
vent peaks, and their satellite signals due to coupling with
13C, the protons of the peripheral alkyl groups, the meso-
Chem. Eur. J. 2007, 13, 5773 – 5784
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5777

H. Uno et al.
of the nickel–porphyrin unit. The other meso-proton signals
could not be identified.
the CCI system were gradually formed. The crystal struc-
tures were first refined with all solvent molecules present.
However, the solvent molecules were not properly modeled
due to disorder, and relatively strong electron-density peaks
were found near the disordered solvent molecules. There-
fore, the core porphyrin dimer structures of 16 were refined
without the solvent molecules by means of the SHELX-97
and PLATON SQUEEZE programs.[16] The final crystallo-
graphic data are shown in Table 1.
In the two crystal structures of 16·1.5PhCl, the solvent
molecules occupy rather different positions. Stacking dia-
grams of 16 are shown in Figure 3. In all of the crystal struc-
tures of 16, the zinc–porphyrin rings are tightly stacked in
the endo direction forming dimeric structures, and the dis-
tances between the zinc–porphyrin rings of 16·1.5PhCl-
In the UV/Vis spectra, strong Soret-like bands are seen in
the long-wavelength region (l=475 nm for 13–Zn2, 484 nm
for protonated 13–H4, and 470 and 477 nm for 13–NiZn;
Figures 1c, d, and g; solid lines), and moderately strong ab-
sorption bands are also observed in the Soret-band region
for the monomeric porphyrins (380–420 nm). The most dis-
tinctive features of these spectra are the longest-wavelength
absorptions of very high intensity in the Q-band region [l
(loge)=656 nm (5.23) for protonated 13–H4, 636 nm (5.27)
for 13–Zn2, and 631 nm (5.21) for 13–NiZn]. The Q-band
absorption of 13–Zn2 appears at a shorter wavelength than
that of a monocopper complexof a directly fused porphyrin
dimer (652 nm).[3b] In the case of 13–NiZn, the longest-
wavelength absorption is also the strongest. Dizinc–porphy-
rin dimer 13–Zn2 and protonated 13–H4 show fluorescence
with slightly lower energies (by 4 and 7 nm for 13–Zn2 and
protonated 13–H4, respectively) than the longest-wavelength
absorptions (Figure 1g, black line: 13–Zn2, dark green line:
protonated 13–H4). Fluorescence was not observed for the
benzene-fused dimers 13–NiZn and 17.
A
N
AHCTREUNG
phyrin rings is observed in the exo direction (3.673(7) Š,
Figure 3c), while no such contact is observed in the other
two structures (Figure 3f and i). The central zinc atoms are
offset from the porphyrin rings in the endo direction, and
are located just above the meso-carbon atoms of the other
molecules. The zinc–porphyrin rings of 16·1.5PhCl show
domed out-of-plane distortion, while those of 16·CHCl3
show ruffled out-of-plane distortion.[17] In contrast to the
zinc–porphyrin units, the nickel–porphyrin rings stack in
X-ray analyses of the dimers: Single crystals suitable for X-
ray analysis were obtained by the diffusion method. The
porphyrin dimer was placed in a small sample tube and dis-
solved in pyridine, chloroform, or a mixture of chloroform
and chlorobenzene. The sample tube was placed in a jar
containing methanol or isopropanol. The jar was tightly
capped and then left in the dark for an appropriate time
ranging from two days to several months. Recrystallization
of the benzene-fused porphyrin
both directions: the endo distances in 16·1.5PhCl
A
16·1.5PhCl(CCI), and 16·6CHCl3 are 3.586(7), 3.471(6), and
AHCTREUNG
3.146(8) Š, and the exo distances are 3.264(8), 3.200(6), and
3.692(8) Š, respectively (Figure 3b, e, and h). All of the
dimer 13–Zn2 from a pyridine/
MeOH solvent system gave
Table 1. Crystallographic summary.[a]
single crystals containing four
molecules of pyridine, two of
which were coordinated to the
zinc atoms. Two kinds of single
crystals of 16 were obtained
16·1.5PhCl
(CCM)
16·1.5PhCl
U
16·6CHCl3
13–Zn2·4C5H5N
Mr
1324.36
1324.36
1903.79
[C70H78N8NiZn]
monoclinic
C2/c
1478.60
formula
system
space group
radiation
a [Š]
b [Š]
c [Š]
a [8]
[C70H78N8NiZn]
triclinic
[C70H78N8NiZn]
triclinic
C90H98N12Zn2
triclinic
¯
¯
¯
P1
P1
P1
CuKa
MoKa
MoKa
MoKa
from
(CCM)
PhCl·CHCl3/MeOH
and PhCl·CHCl3/
14.1187(15)
23.316(4)
11.5019(12)
94.081(14)
113.082(7)
104.185(13)
3317.1(8)
2
11.581(4)
13.824(4)
23.072(9)
73.173(15)
82.513(18)
66.100(13)
3232.2(19)
2
43.739(12)
14.053(3)
31.067(9)
90
123.758(4)
90
10.0946(2)
17.1280(4)
24.2252(11)
77.063(8)
88.189(10)
69.072(7)
3807.5(2)
2
0.686
0.71070
558
17164
0.036
14050
1021
0.0768
0.1331
1.170
À100
iPrOH (CCI). Both crystals
were found to have one-and-a-
half molecules of chloroben-
zene incorporated in the unit
cell. On the other hand, single
crystals of 16 obtained from
the CHCl3/iPrOH (CI) solvent
system were found to contain
sixmolecules of chloroform.
The crystals of 16·1.5PhCl
(CCM) and 16·6CHCl3 were
found to deteriorate when they
were left in the original recrys-
tallizing systems. In the CCM
crystallizing system, the same
single crystals as obtained from
b [8]
g [8]
V [Š3]
Z
15876(7)
8
m [mmÀ1
l [Š]
]
1.745[b]
1.54178
1208
9846
0.034 [0.03]
4238 [4233]
0.778[b]
0.71070
558
14007
0.049 [0.050]
10804 [10122]
848 [722]
0.1258 [0.0986]
0.2621 [0.2498]
1.146 [1.0984]
À190
1.198[b]
0.71070
558
18067
0.106 [0.100]
9771 [9748]
2qmax
unique reflns
Requiv
obsd reflns
parameters
R1
wR2 (all)
GOF
A
R
G
A
U
ACHTREUNG
A
ACHTREUNG
T [8C]
[a] Values in brackets have been obtained by removal of solvent molecules using the PLATON SQUEEZE
program. [b] Values have been calculated based on the molecular formula containing the solvent molecules.
5778
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 5773 – 5784

Porphyrin Dimers Fused with a Benzene Unit
FULL PAPER
Figure 3. Stacking diagrams of 16. Peripheral substituents and hydrogen atoms have been omitted for clarity. a) View of sixnearest neighbor molecules
in 16·1.5PhCl(CCM). b) View along the axis perpendicular to the nickel–porphyrin ring of 16·1.5PhCl(CCM). c) View along the axis perpendicular to
the zinc–porphyrin ring of 16·1.5PhCl(CCM). d) View of sixnearest neighbor molecules in 16·1.5PhCl(CCI). e) View along the axis perpendicular to the
nickel–porphyrin ring of 16·1.5PhCl(CCI). f) View along the axis perpendicular to the zinc–porphyrin ring of 16·1.5PhCl(CCI). g) View of sixnearest
A
ACHTREUNG
A
ACHTREUNG
A
ACHTREUNG
neighbor molecules in 16·6CHCl3. h) View along the axis perpendicular to the nickel–porphyrin ring of 16·6CHCl3. i) View along the axis perpendicular
to the zinc–porphyrin ring of 16·6CHCl3.
nickel–porphyrin rings show saddle-type out-of-plane distor-
tion. The most notable features of the crystal structures are
the dihedral angles between the nickel and zinc–porphyrin
moieties. These angles are far wider than those of the
Advantages of our method are high purity of the product
dimers and diversity in the combination of peripheral sub-
stituents and central metals. As the final conversion step re-
quires only heat, the dimers could be generated in situ, such
as at electrodes. We have also revealed the stacking nature
of the nickel–porphyrin unit of the benzene-fused porphyrin
dimer by NMR and X-ray analyses. The endo space of the
bicyclo
137.23(4)8,
16·1.5PhCl
A
dipyrroles:[9a]
for 16·1.5PhCl
(CCI), and 16·6CHCl3, respectively. This widen-
148.40(5)8,
(CCM),
ACHTREUNG
ACHTREUNG
ing is believed to be mainly due to the crystal packing, al-
though rather strong homo-conjugation of the porphyrin p
systems may also be a contributing factor.
bicyclo[2.2.2]octadiene-fused porphyrin dimer has been
found to be very wide, while the benzene-fused porphyrin
dimer has an almost flat structure.
A
In the case of 13–Zn2·4C5H5N, two crystallographically in-
dependent molecules of 13 occupy the special position of À1
symmetry (Figure 4). The dihedral angles between the por-
phyrin ring and the benzene moiety reflect an almost flat
structure (3.84(10) and 1.61(9)8), and intermolecular stack-
ing is not observed due to the coordination of pyridine to
the zinc atoms as expected.
Experimental Section
General: Melting points are uncorrected. Unless otherwise specified,
NMR spectra were obtained with a JEOL JNM AL-400 or EX-400 spec-
trometer at ambient temperature by using CDCl3 as solvent and tetra-
methylsilane as internal standard for 1H and 13C. Mass spectra (EI and
FAB) were measured with an MStation spectrometer (JEOL MS-700).
MALDI-TOF mass spectra were measured on a Voyager DE Pro spec-
trometer (Applied Biosystems) by using sinapinic acid as the matrix. Ele-
mental analyses were performed on a Yanaco MT-5 elemental analyzer.
Preparative GPC was carried out on a JAI LC-9801 chromatograph
equipped with JAI-1H (F20”600 mm) and 2.5H (F20”600 mm) col-
umns. THF was distilled from sodium benzophenone ketyl and dichloro-
methane was distilled from CaH2 prior to use. DMF was distilled under
reduced pressure and then stored over 4 Š MS. Pyridine was distilled
from CaH2 and stored over 4 Š MS.
Conclusion
We have established a synthetic method for porphyrin
dimers fused with a benzene unit based on a retro-Diels–
Alder reaction of bicyclo[2.2.2]octadiene in the final step.
A
Other dry solvents were purchased
from Kanto Chemical Co. Isocyano-
acetate esters were prepared accord-
ing to the literature procedure from
the corresponding formamides.[18] 5-
Methylpyrrole-2-carboxylates
prepared by the Knorr reaction.
were
tert-Butyl
ethyl
4,8-dihydro-4,8-
ethano-2H,6H-benzo[1,2-c:4,5-c’]di-
pyrrole-1,5-dicarboxylate and 1,7-di-
carboxylate (2b): An isomeric mix-
ture of ethyl 5- and 6-phenylsulfonyl-
4,7-dihydro-4,7-ethano-2H-isoindole-
Figure 4. View of crystallographically independent molecules of 13–Zn2·4C5H5N along the a axis. Hydrogen
atoms have been omitted for clarity.
Chem. Eur. J. 2007, 13, 5773 – 5784
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5779

H. Uno et al.
1-carboxylates was prepared according to the literature procedure.[9a]
A
the mixture was poured into iced water. The precipitate that separated
was collected by filtration, washed with water, and dissolved in chloro-
form. This solution was washed with water, dried over sodium sulfate,
and concentrated. The residual solid was triturated with a small amount
of hexane to give the title compound (8.93 g, 87%) as a white powdery
solid. M.p. 1398C; 1H NMR: d=0.91 (t, J=6.8 Hz, 3H), 1.30–1.43 (m,
4H), 2.06 (s, 3H), 2.28 (s, 3H), 2.43 (t, J=6.8 Hz, 2H), 5.00 (s, 2H), 5.30
(s, 2H), 7.30–7.44 (m, 5H), 9.01 ppm (brs, 1H); 13C NMR: d=10.4, 14.0,
20.9, 22.4, 23.5, 33.5, 57.0, 65.7, 118.9, 125.4, 126.7, 127.2, 128.1, 128.1,
128.5, 136.4, 161.1, 171.5 ppm; IR: n˜max =3305, 1735, 1668, 1276,
1238 cmÀ1; MS (EI): m/z=343 [M+], 300, 284, 135; elemental analysis
calcd (%) for C20H25NO4: C 69.95, H 7.34, N 4.08; found: C 69.82, H
7.24, N 4.07.
1.0m solution of potassium tert-butoxide in THF (3.50 mL, 3.50 mmol)
was slowly added to a mixture of the sulfone (1.00 g, 2.80 mmol) and tert-
butyl isocyanoacetate (0.33 mL, 3.1 mmol) in dry THF (40 mL) at À208C
under an argon atmosphere. After the addition, the mixture was allowed
to warm to room temperature and stirred overnight. The reaction was
then quenched by the addition of a 1.0m hydrochloric acid solution (ca.
20 mL). The resulting mixture was extracted with chloroform. The organ-
ic extract was washed with water and brine, dried over sodium sulfate,
and concentrated. The residue was purified by column chromatography
on silica gel (EtOAc/hexane, 1:1) to give a syn/anti mixture (ca. 1:1) of
the title compound (0.96 g, 97%) as colorless crystals. M.p. 92–948C; 1H
NMR: d=1.38 (t, J=6.8 Hz, 3H; both isomers), 1.60 (s, 9H; one
isomer), 1.61 (s, 9H; other isomer), 1.74–1.69 (m, 4H; both isomers),
4.26 (m, 1H; syn isomer), 4.34–4.38 (m, 2H; both isomers), 4.73 (m, 1H;
syn isomer), 4.76 (m, 2H; anti isomer), 5.26 (m, 1H; syn isomer), 6.62
(m, 2H; both isomers), 8.36 ppm (br, 2H; both isomers); 13C NMR (all
observed peaks are reported; assignments to the individual isomers could
not be made): d=14.1, 14.6, 14.8, 22.7, 28.2, 28.6, 28.80, 28.82, 29.5, 30.8,
31.10, 31.13, 31.6, 59.87, 59.91, 80.3, 80.4, 112.7, 113.2, 113.3, 113.9, 114.3,
114.9, 115.6, 116.2, 130.6, 130.9, 131.4, 131.8, 134.6, 135.5, 136.7, 161.0,
161.3, 161.6, 161.7 ppm; IR: n˜max =3320, 2977, 1681, 1415, 1319,
1146 cmÀ1; MS (EI): m/z (%)=357 (4) [M++1], 329 (85) [M++1ÀC2H4],
272 (100); elemental analysis calcd (%) for C20H24N2O4·1/4MeOH·1/
4CH2Cl2: C 63.84, H 6.66, N 7.26; found: C 63.47, H 6.60, N 6.99.
tert-Butyl 5-acetoxymethyl-4-n-butyl-3-methylpyrrole-2-carboxylate (4b):
tert-Butyl 4-n-butyl-3,5-dimethylpyrrole-2-carboxylate (9.35 g, 31%) was
prepared according to a procedure analogous to that described above,
using tert-butyl acetoacetate (47.4 mL, 210 mmol) instead of benzyl ace-
toacetate. The product was obtained as colorless needles. M.p. 94–958C;
1H NMR: d=0.91 (t, J=7.3 Hz, 3H), 1.33–1.40 (m, 4H), 1.59 (s, 9H),
2.18 (s, 3H), 2.24 (s, 3H), 2.34 (t, 2H, J=7.3 Hz), 8.41 ppm (brs, 1H);
13C NMR: d=10.6, 11.5, 14.0, 22.5, 23.7, 28.6, 33.1, 79.9, 117.9, 122.1,
126.1, 128.7, 161.4 ppm; IR: n˜max =3323, 2951, 2927, 2868, 1664, 1279,
1161, 1088 cmÀ1; MS (EI): m/z (%)=251 (28) [M+], 195 (36), 178 (9),
152 (100); elemental analysis calcd (%) for C15H25NO2: C 71.67, H 10.02,
N 5.57; found: C 71.50, H 9.81, N 5.63.
4,8-Dihydro-4,8-ethano-2H,6H-benzo[1,2-c:4,5-c’]dipyrrole (3): A mix-
ture of diethyl ester 2a[9a] (0.657 g, 2.00 mmol) and potassium hydroxide
(0.65 g) in ethylene glycol (40 mL) was heated at 1608C for 3.5 h in the
dark under an argon atmosphere. After being cooled to room tempera-
ture, the mixture was poured onto ice. The resulting mixture was extract-
ed with chloroform. The organic extract was washed with water and
brine, dried over sodium sulfate, filtered through a short column of silica
gel, and concentrated to give the title compound (0.304 g, 83%) as a
white powder. M.p.>2508C; 1H NMR ([D6]DMSO): d=1.56 (m, 4H),
4.05 (m, 2H), 6.35 (d, J=2.4 Hz, 4H), 9.67 ppm (brs, 2H); 13C NMR
([D6]DMSO): d=30.3 (two kinds of carbon atom), 107.6, 129.0 ppm; IR
(KBr): n˜max =3378, 2950, 1037, 786 cmÀ1; MS (EI): m/z (%)=184 (6) [M+
], 156 (100); elemental analysis calcd (%) for C12H12N2·1/8H2O: C 77.29,
H 6.62, N 15.02; found: C 77.17, H 6.62, N 15.02.
Acetoxylation of tert-butyl 4-n-butyl-3,5-dimethylpyrrole-2-carboxylate
(1.26 g, 5.00 mmol) by the method described above gave the title com-
pound (1.21 g, 78%) as colorless crystals. M.p. 858C; 1H NMR: d=0.91
(t, J=7.3 Hz, 3H), 1.31–1.36 (m, 4H), 1.56 (s, 9H), 2.07 (s, 3H), 2.24 (s,
3H), 2.42 (t, J=7.3 Hz, 2H), 5.00 (s, 2H), 8.41 ppm (brs, 1H); 13C NMR:
d=10.4, 13.8, 20.9, 22.3, 23.6, 28.3, 33.6, 57.1, 80.6, 120.5, 125.2, 125.3,
126.1, 161.0, 171.5 ppm; IR: n˜max =3309, 2976, 2956, 2931, 2860, 1736,
1660 cmÀ1; MS (EI): m/z (%)=309 (10) [M+], 281 (41), 225 (100), 210
(32), 182 (83); elemental analysis calcd (%) for C17H27NO4: C 65.99, H
8.80, N 4.53; found: C 65.87, H 8.66, N 4.52.
Ethyl 5-hydroxymethyl-3,4-diethylpyrrole-2-carboxylate (4c): Phosphoryl
chloride (16.8 mL, 180 mmol) was slowly added to DMF (2.33 mL,
30.0 mmol) at 08C. After being stirred for 15 min at room temperature,
the mixture was diluted with dry 1,2-dichloroethane (100 mL). A solution
of ethyl 3,4-diethylpyrrole-2-carboxylate[13] (1.95 g, 10 mmol) in dry 1,2-
dichloroethane (50 mL) was then added and the resulting mixture was re-
fluxed for 2 h. Thereafter, an aqueous solution of sodium acetate (73.8 g
in 200 mL) was slowly added to quench the reaction, and the resulting
mixture was refluxed for 15 min in order to decompose the iminium in-
termediate. After being cooled to room temperature, the mixture was di-
luted with water and then extracted with chloroform. The organic extract
was washed with water, saturated sodium hydrogencarbonate solution,
and brine, dried over sodium sulfate, and concentrated. The residue was
purified by column chromatography on silica gel to give ethyl 5-formyl-
3,4-diethylpyrrole-2-carboxylate (2.12 g, 95%) as colorless crystals. M.p.
Benzyl 5-acetoxymethyl-4-n-butyl-3-methylpyrrole-2-carboxylate (4a): A
solution of sodium nitrite (19.32 g) in water (58 mL) was added over a
period of 1 h to a solution of benzyl acetoacetate (48.5 mL, 280 mmol) in
acetic acid (56 mL) while the temperature of the mixture was kept below
108C by ice cooling. The mixture was then allowed to warm to room tem-
perature and was stirred overnight. Zinc dust (27.1 g, 0.414 g atom) and
sodium acetate (33.96 g) were added to a solution of 3-butyl-2,4-pentane-
dione (12.58 g, 140.0 mmol) in acetic acid (56 mL) at 808C, and the tem-
perature was raised to 908C. The above benzyl ester mixture was slowly
added to this vigorously stirred pentanedione suspension as the reaction
temperature was maintained between 90 and 958C (ca. 35 min). After
2 h, the reaction mixture was poured into iced water (500 mL) and the
solid that separated was collected by filtration. The precipitated solid was
thoroughly washed with water and then dissolved in chloroform, to which
silica gel was added. After removal of the volatiles in vacuo, the product-
adsorbing silica gel was placed on a short column of silica gel and the
column was eluted with EtOAc/hexane (30:70). The eluate was concen-
trated and the residue was recrystallized from ethanol to give benzyl 4-
butyl-3,5-dimethylpyrrole-2-carboxylate (33.93 g, 119.0 mmol, 85%) as
1
528C; H NMR: d=1.16 (t, J=7.3 Hz, 3H), 1.24 (t, J=7.5 Hz, 3H), 1.38
(t, J=7.3 Hz, 3H), 2.71–2.79 (m, 4H), 4.36 (q, J=7.3 Hz, 2H), 9.58 (brs,
1H), 9.78 ppm (s, 1H); 13C NMR: d=12.3, 15.6, 16.6, 17.5, 60.9, 124.1,
129.4, 133.0, 136.3, 160.6, 179.2 ppm; IR: n˜max =3268, 2964, 2929, 2869,
2811, 1693, 1666, 1481, 1255 cmÀ1; MS (EI): m/z (%)=223 (100) [M+],
194 (62), 176 (43), 162 (35); elemental analysis calcd (%) for C12H17NO3:
C 64.55, H 7.67, N 6.27; found: C 64.47, H 7.48, N 6.26.
The formylpyrrole (1.88 g, 8.42 mmol) was dissolved in dry THF/EtOH
(50 mL/12.5 mL) and CeCl3·7H2O (3.14 g, 8.42 mmol) was added.
Sodium borohydride (0.330 g, 8.42 mmol) was then added in three por-
tions to the mixture at 08C. After 1 h, water was added and the precipi-
tate was removed by filtration. The filtrate was extracted with ethyl ace-
tate. The organic extract was washed with brine, dried over sodium sul-
fate, and concentrated to give the title compound as a viscous oil, which
was used without further purification. 1H NMR: d=1.09 (t, J=6.7 Hz,
3H), 1.15 (t, J=6.7 Hz, 3H), 1.36 (t, J=6.7 Hz, 3H), 1.93 (brs, 1H), 2.43
(q, J=6.7 Hz, 2H), 2.73 (q, J=6.7 Hz, 2H), 4.31 (q, J=6.7 Hz, 2H), 4.65
(s, 2H), 9.12 ppm (brs, 1H).
1
colorless needles. M.p. 818C; H NMR: d=0.91 (t, J=6.8 Hz, 3H), 1.21–
1.49 (m, 4H), 2.18 (s, 3H), 2.28 (s, 3H), 2.34 (t, J=6.8 Hz, 2H), 5.28 (s,
2H), 7.31–7.43 (m, 5H), 8.53 ppm (brs, 1H); 13C NMR: d=10.7, 11.4,
14.0, 22.4, 23.7, 33.0, 65.3, 116.3, 122.5, 127.6, 127.9, 128.0, 128.5, 130.0,
136.7, 161.4 ppm; IR: n˜max =3303, 1662, 1436, 1268 cmÀ1; MS (EI): m/z=
285 [M+], 242, 134; elemental analysis calcd (%) for C18H23NO2: C 75.76,
H 8.12, N 4.91; found: C 75.79, H 8.09, N 4.92.
Lead tetraacetate (15.38 g, 31.50 mmol) was slowly added to a stirred so-
lution of the benzyl pyrrolecarboxylate (8.56 g, 30.0 mmol) in acetic acid
(200 mL) and acetic anhydride (3.1 mL) at room temperature. After 2 h,
5780
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 5773 – 5784

Porphyrin Dimers Fused with a Benzene Unit
FULL PAPER
Bis(dipyrromethane) 6: p-TSA·H2O (0.15 g) was added to a solution of
the syn-dipyrrole syn-2a (0.657 g, 2.00 mmol) and tert-butyl 5-(acetoxy-
methyl)pyrrole-2-carboxylate 4b (1.86 g, 6.00 mmol) in acetic acid
(60 mL) and the mixture was stirred for 2 h at room temperature. Water
was then added and the resulting mixture was extracted with ethyl ace-
tate. The organic extract was successively washed with saturated sodium
hydrogencarbonate solution, water, and brine, dried over sodium sulfate,
and concentrated. The residue was purified by column chromatography
on silica gel to give the title compound (0.68 g, 41%) as a colorless
powder. M.p. 1618C (decomp); 1H NMR: d=0.88 (t, J=6.8 Hz, 6H),
1.27 (m, 8H), 1.36 (t, J=7.3 Hz, 6H), 1.48 (s, 18H), 1.72–1.80 (m, 4H),
2.25 (s, 6H), 2.35 (t, J=7.3 Hz, 4H), 3.62 (m, 1H), 3.85 (s, 4H), 4.30 (q,
J=6.8 Hz, 2H), 5.19 (m, 1H), 8.87 (brs, 2H), 8.94 ppm (brs, 2H); 13C
NMR: d=10.7, 14.0, 14.5, 22.6, 23.1, 23.8, 27.8, 28.4, 28.7, 29.1, 31.9, 33.4,
60.0, 80.2, 113.6, 119.0, 122.5, 124.6, 126.2, 128.6, 128.6, 136.5, 161.3,
162.3 ppm; IR: n˜max =3448, 3316, 2931, 1697, 1658, 1446 cmÀ1; MS (FAB+
): m/z=827 [M++1]; elemental analysis calcd (%) for C48H66N4O8: C
69.71, H 8.47, N 6.77; found: C 69.88, H 8.39, N 6.48.
washed with ethanol to give the title compound as colorless crystals. M.p.
2028C; 1H NMR: d=0.84 (t, J=6.8 Hz, 6H), 1.15 (t, J=7.3 Hz, 6H),
1.27–1.30 (m, 8H), 2.23 (s, 6H), 2.28 (m, 4H), 2.48 (q, J=7.3 Hz, 4H),
3.54 (s, 4H), 4.34 (s, 4H), 6.97 (m, 4H), 7.20–7.23 (m, 6H), 8.77 (brs,
1H), 11.22 ppm (brs, 2H); 13C NMR: d=11.1, 13.9, 16.9, 17.8, 22.1, 22.8,
23.9, 33.5, 65.2, 117.1, 118.6, 121.6, 122.4, 126.5, 126.6, 127.1, 128.0, 133.4,
137.1, 162.7 ppm; IR: n˜max =3424, 3297, 2958, 2927, 2857, 1658, 1454,
1272 cmÀ1; MS (FAB+): m/z=689 [M+]; elemental analysis calcd (%) for
C44H55N3O4: C 76.60, H 8.04, N 6.09; found: C 76.36, H 8.10, N 5.86.
All-ethyl tripyrrane dicarboxylate 10b: 3,4-Diethylpyrrole (9)[13] (0.49 g,
4.0 mmol), ethyl 5-acetoxymethyl-3,4-diethylpyrrole-2-carboxylate (4c)
(1.80 g, 8.00 mmol), and p-TSA·H2O (0.14 g, 0.80 mmol) were dissolved
in ethanol (140 mL). The solution was refluxed overnight in the dark. It
was then cooled to room temperature and concentrated to a volume of
about 50 mL in vacuo. Water was added and the resulting mixture was
extracted with ethyl acetate. The organic extract was washed with water
and brine, dried over sodium sulfate, and concentrated. The residue was
purified by column chromatography on silica gel to give the title com-
pound 10b as yellow crystals. M.p. 173–1758C; 1H NMR: d=0.61 (m,
24H), 2.44 (m, 8H), 2.63 (q, J=7.3 Hz, 4H), 3.32 (q, J=7.3 Hz, 4H),
3.76 (s, 4H), 9.11 (brs, 1H), 11.01 ppm (brs, 2H); 13C NMR: d=13.9,
16.0, 16.5, 16.6, 17.0, 17.7, 18.6, 22.2, 59.7, 117.0, 118.5, 122.1, 122.4, 131.9,
132.4, 162.6 ppm; IR: n˜max =3384, 3288, 2962, 1651, 1281 cmÀ1; MS (EI):
m/z=537 [M+], 491, 313, 207; HRMS (EI): calcd for C32H47N3O4:
537.3567; found: 537.3536.
Dipyrromethane dicarbaldehyde 7: Ethyl 3,4-diethylpyrrole-2-carboxyl-
ate[13] (5.17 g, 26.5 mmol), dimethoxymethane (5.89 mL, 66.3 mmol), and
p-TSA·H2O (0.30 g) were dissolved in ethanol (50 mL) and the solution
was refluxed overnight under nitrogen. Thereafter, water was added to
quench the reaction, and the resulting mixture was extracted with chloro-
form. The organic extract was washed with water and brine, dried over
sodium sulfate, and concentrated. The residue was purified by column
chromatography on silica gel to give diethyl dipyrromethane dicarboxy-
Tripyrrane dicarbaldehyde 11a: Palladium on charcoal (10%, 0.50 g) was
placed in a two-necked flask, one neck of which was fitted with a three-
way stopcock connected to a hydrogen balloon and a water aspirator,
while the other neck was fitted with a rubber septum. Freshly distilled
THF (20 mL) was introduced through the septum by means of a syringe.
The suspension was vigorously stirred and the three-way stopcock was
opened to the water aspirator. As soon as bubbling occurred, hydrogen
was flushed into the flask. This manipulation was repeated three times to
activate the catalyst. Then, a solution of the dibenzyl diester 10a (2.09 g,
3.03 mmol) in freshly distilled THF (30 mL) was added to the vigorously
stirred suspension by means of a syringe at room temperature. The mix-
ture was stirred overnight under a hydrogen atmosphere. The suspension
was then filtered through a Celite pad, which was thoroughly washed
with ethyl acetate. The filtrate was concentrated in vacuo and flushed
with argon. The residue was cooled in an ice-bath and then treated with
trifluoroacetic acid (5 mL) under argon. Trimethyl orthoformate (10 mL)
was slowly added to the solution at 08C and the resulting mixture was
stirred for 1 h at the same temperature. Still at 08C, a 1 m solution of
sodium hydroxide in 50% aqueous methanol was added to neutralize the
solution. The resulting mixture was poured into iced water (200 mL). The
precipitated solid was collected by filtration, washed with water, and
rinsed with hexane. The title compound was obtained in 81% yield
(1.178 g) as a pink powder. M.p. 2088C; 1H NMR: d=0.91 (t, J=7.3 Hz,
6H), 1.09 (t, J=7.3 Hz, 6H), 1.34 (m, 8H), 2.21 (s, 6H), 2.36–2.44 (m,
8H), 3.82 (s, 4H), 8.78 (brs, 1H), 9.20 (s, 2H), 9.84 ppm (brs, 2H); 13C
NMR: d=8.9, 13.9, 16.6, 17.7, 22.6, 22.7, 23.5, 32.9, 120.6, 121.6, 123.2,
128.0, 133.0, 138.4, 175.3 ppm; IR: n˜max =3251, 2958, 1639, 1446 cmÀ1; MS
(FAB+): m/z=476 [M+À1]; elemental analysis calcd (%) for
C30H43N3O2: C 75.43, H 9.07, N 8.80; found: C 75.28, H 9.00, N 8.58.
1
late (5.03 g, 94%) as colorless crystals. M.p. 1048C; H NMR: d=1.06 (t,
J=7.3 Hz, 6H), 1.15 (t, J=7.3 Hz, 6H), 1.28 (t, J=6.8 Hz, 3H), 2.42 (q,
J=7.3 Hz, 4H), 2.71 (q, J=7.3 Hz, 4H), 3.89 (s, 2H), 4.23 (q, J=6.8 Hz,
4H), 9.30 ppm (brs, 2H); 13C NMR: d=14.3, 15.8, 16.1, 17.1, 18.4, 22.9,
59.8, 117.1, 123.3, 129.4, 133.7, 161.8 ppm; IR: n˜max =3336, 2985, 1697,
1654, 1444, 1263 cmÀ1; MS (EI): m/z (%)=402 (34) [M+], 207 (100); ele-
mental analysis calcd (%) for C23H34N2O4: C 68.63, H 8.51, N 6.96;
found: C 68.61, H 8.50, N 6.80.
The dipyrromethane dicarboxylate (2.25 g, 5.60 mmol), potassium hy-
droxide (3.16 g), and ethylene glycol (100 mL) were placed in a flask,
which was then flushed with argon and protected from light. The mixture
was stirred at 1608C for 2.5 h. It was then diluted with water and extract-
ed with ethyl acetate. The organic extract was washed with saturated
sodium hydrogencarbonate solution, water, and brine, dried over sodium
sulfate, and concentrated to give the crude dipyrromethane, which was
used in the next step without further purification.
Phosphoryl chloride (3.33 mL) was slowly added to DMF (2.62 mL) at
08C. The mixture was stirred for 15 min at room temperature and then
diluted with dry dichloromethane (15 mL). A solution of the above crude
dipyrromethane in dry dichloromethane (10 mL) was then added and the
mixture was refluxed for 45 min. An aqueous solution of sodium acetate
(14.6 g in 50 mL) was slowly added to quench the reaction and then the
resulting mixture was refluxed for 1 h in order to decompose an iminium
intermediate. Thereafter, the mixture was cooled to room temperature,
diluted with water, and extracted with chloroform. The organic extract
was washed with water, saturated sodium hydrogencarbonate solution,
and brine, dried over sodium sulfate, and concentrated. The residue was
purified by column chromatography on silica gel to give the title com-
pound as a brownish powder. M.p. 1898C; 1H NMR: d=1.08 (t, J=
7.3 Hz, 6H), 1.24 (t, J=7.3 Hz, 6H), 2.45 (q, J=7.3 Hz, 4H), 2.71 (q, J=
7.3 Hz, 4H), 3.99 (s, 2H), 9.52 (s, 2H), 11.16 ppm (brs, 2H); 13C NMR:
d=15.9, 16.9, 17.2, 17.7, 22.7, 124.1, 128.0, 135.1, 139.2, 176.8 ppm; IR:
n˜max =3224, 2962, 1644, 1616, 1440, 1240 cmÀ1; MS (EI): m/z (%)=314
(70) [M+], 285 (56), 163 (100); elemental analysis calcd (%) for
C19H26N2O2: C 72.58, H 8.33, N 8.91; found: C 72.30, H 8.23, N 8.87.
All-ethyl tripyrrane dicarbaldehyde 11b: All-ethyl tripyrrane dicarboxy-
late diethyl diester 10b (0.58 g, 1.08 mmol) and LiOH·H2O (0.27 g,
6.4 mmol) were dissolved in a mixture of freshly distilled THF (18 mL),
ethanol (7 mL), and water (7 mL) under a nitrogen atmosphere. The mix-
ture was heated at 808C for 1 h. Two further portions of LiOH·H2O
(0.27 g, 6.4 mmol) were added at intervals of 1 h. The consumption of
10b and its mono ester was verified by TLC. The mixture was then
cooled to room temperature and acidified to pH 2–3 by the addition of
1% hydrochloric acid. The acidified mixture was extracted with ethyl
acetate. The organic extract was washed with brine, dried over sodium
sulfate, and concentrated to leave the corresponding dicarboxylic acid as
a solid. The flask containing the solid was flushed with argon and cooled
in ice. Trifluoroacetic acid (1.8 mL) was added and the resulting mixture
was stirred for 10 min. Trimethyl orthoformate (3.6 mL) was then slowly
Dibenzyl tripyrrane dicarboxylate 10a:[19] 3,4-Diethylpyrrole (9)[13]
(1.30 g, 10.5 mmol) and benzyl 5-acetoxymethyl-4-n-butyl-3-methylpyr-
role-2-carboxylate (4a) (7.21 g, 21.0 mmol) were dissolved in a mixture
of acetic acid (10 mL) and ethanol (150 mL). The solution was refluxed
for 18 h in the dark and then allowed to cool to room temperature. Fur-
ther ethanol (50 mL) was added and the resulting mixture was left at 08C
for 5 h. The precipitate that formed was collected by filtration and
Chem. Eur. J. 2007, 13, 5773 – 5784
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5781

H. Uno et al.
added to the solution at 08C and the resulting mixture was stirred for 1 h
at the same temperature. Still at 08C, a 1m solution of sodium hydroxide
in 50% aqueous methanol was added to neutralize the solution. The re-
sulting mixture was poured into iced water (100 mL). The precipitated
solid was collected by filtration, washed with water, and rinsed with
hexane to give the title compound (0.055 g, 11%) as a purple powder. A
further crop (0.250 g, 51%) was obtained by chromatographic purifica-
tion of the hexane washing. M.p. 148–1518C; 1H NMR: d=1.04 (m,
18H), 2.42 (m, 8H), 2.58 (q, J=7.6 Hz, 4H), 3.82 (s, 4H), 9.08 (s, 2H),
9.49 (brs, 1H), 10.26 ppm (brs, 2H); 13C NMR: d=15.8, 16.5, 16.8, 17.1,
17.6, 17.7, 22.6, 120.7, 121.4, 123.8, 127.3, 138.3, 139.8, 175.7 ppm; IR:
n˜max =3269, 2962, 1624, 1441 cmÀ1; MS (EI): m/z=449 [M+], 285, 269,
163; HRMS (EI): calcd for C28H39N3O2: 449.3042; found: 449.3039.
3.50 (s, 3H), 3.83–3.95 (m, 8H), 4.51 (m, 2H), 5.84 (s, 1H), 6.37 (s, 1H),
6.91 (d, J=2.4 Hz, 1H), 8.40 (brs, 1H), 9.74 (s, 1H), 9.74 (s, 1H), 9.88 (s,
1H), 9.94 ppm (s, 1H); 13C NMR (some signals could not be found due
to overlap): d=11.7, 11.8, 14.3, 14.9, 18.3, 19.8, 23.03, 23.05, 26.2, 29.7,
30.5, 33.3, 33.6, 35.3, 60.1, 96.6, 97.4, 97.5, 113.7, 114.9, 132.9, 134.8, 135.0,
136.65, 136.71, 140.60, 140.63, 141.0, 141.1, 141.3, 141.4, 141.68, 141.7,
142.6, 148.4, 149.3, 161.6 ppm; UV/Vis (CHCl3): lmax (loge)=394 (5.28),
516 (4.04), 554 nm (4.37); MS (MALDI-TOF): m/z=752.73 [M++1];
HRMS (FAB+): calcd for C45H51N5O2Ni+H+: 752.3474; found: 752.3532.
Nickel–porphyrin fused with pyrrole through a bicyclo[2.2.2]octadiene
A
unit (15): A mixture of 14–Ni (75 mg, 0.10 mmol) and potassium hydrox-
ide (3.4 g) in ethylene glycol (70 mL) was heated at 1808C for 2 h in the
dark under an argon atmosphere. It was then diluted with water at room
temperature and the resulting mixture was extracted with ethyl acetate.
The organic extract was washed with saturated sodium hydrogencarbon-
ate solution, water, and brine, dried over sodium sulfate, and concentrat-
ed. The residue was purified by column chromatography on silica gel
(CHCl3) to give the title compound (56 mg, 82%) as red crystals. M.p.
2108C (decomp); 1H NMR: d=0.98 (t, 6H, J=7.3 Hz), 1.58 (m, 4H),
1.71 (t, J=7.6 Hz, 6H), 2.07 (m, 6H), 2.25 (m, 2H), 3.39 (s, 6H), 3.73–
3.82 (m, 8H), 5.74 (s, 2H), 6.65 (d, J=2.2 Hz, 2H), 7.34 (brs, 1H), 9.64
(s, 2H), 9.81 ppm (s, 2H); 13C NMR: d=11.8, 14.3, 18.4, 19.8, 23.1, 26.3,
31.0, 33.2, 35.3, 96.5, 97.5, 109.0, 130.6, 135.2, 136.6, 140.5, 141.1, 141.2,
141.6, 142.5, 149.7 ppm; UV/Vis (CHCl3): lmax (loge)=393 (5.27), 516
(4.02), 553 nm (4.37); MS (MALDI-TOF): m/z=680.76 [M++1]; HRMS
(FAB+): calcd for C42H47N5Ni+H+: 680.3263; found: 680.3221.
Free-base porphyrin fused with ethyl pyrrole-2-carboxylate through a
bicyclo[2.2.2]octadiene unit (14-H2): Trifluoroacetic acid (2 mL) was
R
added to a diastereomeric mixture of dipyrrole 2b (0.356 g, 1 mmol)
under an argon atmosphere and the mixture was stirred for 10 min at
room temperature. It was then diluted with dry dichloromethane
(64 mL), tripyrrane dicarbaldehyde 11a was added, and the resulting
mixture was stirred for 1 day. Thereafter, triethylamine (2 mL) and DDQ
(0.146 g) were added, and the mixture was further stirred overnight. It
was then washed with saturated sodium hydrogencarbonate solution,
water, and brine, dried over sodium sulfate, and concentrated. The resi-
due was purified by column chromatography on silica gel (EtOAc/CHCl3,
5:95) to give a dark-red solid. Recrystallization from CHCl3/MeOH gave
the title compound (0.188 g, 27%) as red crystals. M.p. 1928C (decomp);
1H NMR: d=À3.89 (brs, 2H), 1.11 (t, J=7.3 Hz, 6H), 1.66 (t, J=7.3 Hz,
3H), 1.75 (m, 4H), 1.92 (t, J=7.3 Hz, 6H), 2.18 (m, 2H), 2.28 (m, 4H),
2.37 (m, 2H), 3.63 (s, 3H), 3.63 (s, 3H), 4.02–4.13 (m, 8H), 4.48–4.60 (m,
2H), 6.02 (s, 1H), 6.55 (s, 1H), 6.95 (d, J=2.4 Hz, 1H), 8.41 (brs, 1H),
10.08 (s, 2H), 10.20 (s, 1H), 10.26 ppm (s, 1H); 13C NMR (some signals
could not be observed owing to broadening due to tautomerism and
some signal overlap): d=11.7, 11.8, 14.2, 14.8, 18.3, 19.8, 23.1, 26.3, 29.8,
30.5, 33.5, 33.7, 35.4, 96.25, 96.27, 97.2, 97.3, 133.2, 136.4, 136.5, 138.2,
141.0, 141.5, 142.2, 146.9, 147.3, 148.0, 161.7 ppm; UV/Vis (CHCl3): lmax
(loge)=400 (5.18), 498 (4.14), 530 (3.88), 569 (3.82), 621 nm (3.65); MS
(MALDI-TOF): m/z=696.79 [M++1]; HRMS (FAB+): calcd for
C45H54N5O2+H+: 696.4275; found: 696.4283.
Symmetric zinc–porphyrin dimer fused with a bicyclo[2.2.2]octadiene
G
unit (12–Zn2): Trifluoroacetic acid (6.08 mL) was added to a stirred solu-
tion of dipyrrole 3 (93 mg, 0.51 mmol) and tripyrrane dicarbaldehyde
11a[10d] (483 mg, 1.01 mmol) in chloroform (115 mL) in the dark under a
nitrogen atmosphere. After stirring the mixture at 508C for 18 h, triethyl-
amine (10.7 mL) was slowly added at room temperature. The resulting
mixture was washed with water and dried over sodium sulfate. Zinc ace-
tate dihydrate (264 mg) was then added and the resulting mixture was
stirred at room temperature for 22 h. It was then washed with water and
brine, dried over sodium sulfate, and concentrated. The residue was puri-
fied by column chromatography on silica gel (CHCl3/hexane, 1:1) to give
the title compound (125 mg, 21%) as red crystals. M.p.>1608C
(decomp); 1H NMR: d=1.10 (t, 12H, J=7.3 Hz), 1.73 (m, 8H), 1.84 (t,
J=7.3 Hz, 12H), 2.28 (m, 8H), 2.88 (m, 4H), 3.93 (s, 12H), 4.0–4.1 (m,
16H), 7.88 (m, 2H), 10.01 (s, 4H), 10.83 ppm (s, 4H); 13C NMR: d=12.2,
14.2, 18.5, 19.8, 23.1, 26.3, 31.8, 35.4, 36.5, 97.1, 98.6, 136.6, 141.5, 142.1,
142.3, 147.5, 148.3, 148.5, 151.5 ppm; UV/Vis (CHCl3): lmax (loge)=399
(5.65), 414 (5.65), 533 (4.65), 574 nm (4.74); MS (FAB+): m/z=1162
[M+ÀC2H4]; elemental analysis calcd (%) for C72H82N8Zn2: C 72.65, H
6.94, N 9.41; found: C 72.36, H 7.03, N 9.23.
Zinc–porphyrin fused with ethyl pyrrole-2-carboxylate through a bicyclo-
A
H2 (0.139 g, 0.20 mmol) and zinc acetate dihydrate (0.65 g, 3.0 mmol) in
chloroform (90 mL) was stirred overnight under an argon atmosphere.
The mixture was then washed with water and brine, dried over sodium
sulfate, and concentrated. The residue was purified by column chroma-
tography on silica gel (EtOAc/CHCl3, 5:95) to give the zinc–porphyrin
(0.149 g, 98%) as red crystals. M.p. 1948C (decomp); 1H NMR: d=1.06
(t, J=7.3 Hz, 6H), 1.67–1.78 (m, 7H), 1.83 (t, J=7.6 Hz, 3H), 2.22 (m,
4H), 2.23 (m, 2H), 2.44 (m, 2H), 3.65 (s, 3H), 3.66 (s, 3H), 3.96 (m, 4H),
4.54 (m, 2H), 6.07 (s, 1H), 6.57 (s, 1H), 7.03 (d, J=2.4 Hz, 1H), 8.35
(brs, 1H), 9.43 (s, 2H), 10.12 (s, 1H), 10.20 ppm (s, 1H); 13C NMR
(some signals could not be found due to overlap): d=11.8, 11.8, 14.3,
14.9, 18.5, 19.5, 19.5, 23.0, 26.0, 29.9, 30.6, 33.6, 33.9, 35.4, 35.4, 60.2, 96.5,
97.9, 113.8, 115.0, 133.49, 135.96, 136.03, 141.0, 141.1, 141.4, 141.6, 141.7,
146.7, 147.5, 149.5, 147.6, 147.8, 147.9, 148.7, 161.6 ppm; UV/Vis (CHCl3):
lmax (loge)=403 (5.49), 532 (4.19), 570 nm (4.24); MS (MALDI-TOF):
m/z=757.74 [M++1]; HRMS (FAB+): calcd for C45H51N5O2Zn+H+:
758.3413; found: 758.3427.
Symmetric free-base porphyrin dimer fused with
a
bicyclo-
AHCTREUNG
stirred solution of zinc–porphyrin dimer 12–Zn2 (43 mg, 0.036 mmol) in
chloroform (5 mL) in the dark under a nitrogen atmosphere. After 1 h,
the mixture was washed with water, dried over sodium sulfate, and con-
centrated. The residue was purified by column chromatography on silica
gel (CHCl3) to give the title compound (38 mg, 99%) as a red powder.
M.p.>1708C (decomp); 1H NMR: d=À3.79 (brs, 4H), 1.13 (t, J=
6.8 Hz, 12H), 1.78 (m, 8H), 1.93 (t, J=7.3 Hz, 12H), 2.33 (m, 8H), 2.77
(m, 4H), 3.91 (s, 12H), 4.10–4.16 (m, 16H), 7.84 (m, 2H), 10.14 (s, 4H),
10.79 ppm (s, 4H); 13C NMR: d=12.2, 13.8, 17.4, 20.1, 22.9, 26.6, 29.7,
34.3, 36.5, 98.0, 100.1, 136.0, 138.4, 140.2, 142.3, 142.7, 142.7, 143.6,
148.1 ppm; UV/Vis (CHCl3): lmax (loge)=397 (5.30), 409 (5.29), 500
(4.49), 536 (4.27), 567 (4.16), 622 nm (4.02); UV/Vis (1% TFA in
CHCl3): lmax (loge)=400 (5.64), 419 (5.74), 550 (4.60), 597 nm (4.29); MS
(MALDI-TOF): m/z=1064.1 [M++1]; elemental analysis calcd (%) for
C72H86N8·8/5CHCl3: C 70.46, H 7.04, N 8.93; found: C 70.52, H 7.12, N
9.00.
Nickel–porphyrin fused with ethyl pyrrole-2-carboxylate through
a
bicyclo[2.2.2]octadiene unit (14–Ni): A solution of the free-base porphy-
ACHTREUNG
rin 14-H2 (70 mg, 0.10 mmol) and nickel(II) acetate (370 mg, 1.5 mmol)
in chloroform (90 mL) was refluxed overnight under an argon atmos-
phere. Thereafter, it was filtered, and the filtrate was washed with satu-
rated sodium hydrogencarbonate solution and brine, dried over sodium
sulfate, and concentrated. The residue was purified by column chroma-
tography on silica gel (CHCl3) to give the nickel–porphyrin (64 mg,
85%) as red crystals. M.p. 2008C (decomp); 1H NMR: d=1.07 (t, J=
7.3 Hz, 3H), 1.08 (t, J=7.3 Hz, 3H), 1.63 (t, J=7.1 Hz, 3H), 1.68 (m,
4H), 1.81 (t, J=7.7 Hz, 6H), 2.16 (m, 6H), 2.32 (m, 2H), 3.49 (s, 3H),
Nickel and zinc–porphyrin dimer fused with a bicyclo[2.2.2]octadiene
G
unit (12–NiZn): Trifluoroacetic acid (0.5 mL) was added to a stirred solu-
tion of pyrrole-fused nickel–porphyrin 15 (54 mg, 0.079 mmol) and tripyr-
rane dicarbaldehyde 11a[10d] (38 mg, 0.079 mmol) in dichloromethane
5782
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 5773 – 5784

Porphyrin Dimers Fused with a Benzene Unit
FULL PAPER
(24 mL) in the dark under a nitrogen atmosphere. After 18 h, triethyl-
2H); a signal due to two meso protons of the nickel–porphyrin unit was
not identified; UV/Vis (pyridine): lmax (loge)=390 (4.82), 469 (5.02), 477
(5.04), 579 (4.30), 620 (4.63), 634 nm (5.10).
A
DDQ (36 mg) and zinc acetate dihydrate (300 mg), and the resulting mix-
ture was stirred at room temperature overnight. It was then washed with
saturated sodium hydrogencarbonate solution, water, and brine, dried
over sodium sulfate, and concentrated. The residue was purified by
column chromatography on silica gel (CHCl3) to give the crude product.
Recrystallization from CHCl3/MeOH gave the title compound (11 mg,
12%) as red crystals. M.p.>1608C (decomp); 1H NMR: d=0.91 (t, J=
7.4 Hz, 6H), 1.08 (t, J=7.3 Hz, 6H), 1.47 (m, 4H), 1.50 (t, J=7.6 Hz,
6H), 1.70 (m, 4H), 1.78 (t, J=7.5 Hz, 6H), 1.97 (m, 4H), 2.19 (m, 4H),
2.81 (m, 4H), 3.60–3.73 (m, 8H), 3.73 (s, 6H), 3.80 (s, 6H), 3.80–3.98 (m,
8H), 7.70 (m, 2H), 9.31 (s, 2H), 9.72 (s, 2H), 10.55 (s, 2H), 10.56 ppm (s,
2H); UV/Vis (CHCl3): lmax (loge)=394 (5.42), 410 (5.49), 535 (4.40), 555
X-ray analysis: The selected single crystal was mounted in a Lindemann
glass capillary with a tiny amount of the mother liquor. X-ray measure-
ments were carried out on either a Rigaku AFC7S with a Cu target
(room temperature) or a Rigaku Mercury-7 with an Mo target (low tem-
peratures). The diffraction data were processed with CrystalStructure,
solved with SIR-97 or DIRDIF-99, and refined with SHELX-97. In the
event of the solvent molecules not being adequately modeled, the core
porphyrin molecules were refined without the solvent molecules by a
combination of the SHELX-97 and PLATON SQUEEZE programs.
CCDC-284573–284577 [16·1.5PhCl
N
N
and 13·4C5H5N] contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from the Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif/.
(4.53), 572 nm (4.50); MS (MALDI-TOF): m/z=1154.96 [M+(60Ni)+1];
A
HRMS (FAB+): calcd for C72H82N8NiZn+H+: 1181.5385; found:
1181.5432.
Asymmetric dimer 16: Dimer 16 was prepared in 35% yield according to
the procedure described above using 11b instead of 11a. It was obtained
as red crystals; m.p.>1558C (decomp); 1H NMR: d=1.07 (t, J=7.3 Hz,
6H), 1.66–1.75 (m, 4H), 1.79 (t, J=7.6 Hz, 6H), 1.81 (t, J=7.6 Hz, 6H),
1.90 (t, J=7.6 Hz, 6H), 2.13 (t, J=7.6 Hz, 6H), 2.19 (m, 4H), 2.84 (m,
4H), 3.76 (s, 6H), 3.92 (m, 8H), 3.99 (q, J=7.6 Hz, 4H), 4.08 (q, J=
7.6 Hz, 4H), 4.35 (m, 4H), 7.69 (m, 2H), 9.75 (s, 2H), 9.98 (s, 2H), 10.49
(s, 2H), 10.72 ppm (s, 2H); UV/Vis (CHCl3): lmax (loge)=394 (5.44), 410
(5.52), 535 (4.41), 556 (4.55), 570 nm (4.53); MS (MALDI-TOF): m/z=
1126.99 [M++2ÀC2H4]; HRMS (FAB+): calcd for C70H78N8NiZn+H+:
1155.5027; found: 1155.5028.
Acknowledgements
This work was partially supported by a Grand-in-Aid for Scientific Re-
search B (17350022) from the Ministry of Education, Culture, Science,
Sports and Technology, Japan. We appreciate the Research Center for
Molecular-Scale Nanoscience, of the Institute for Molecular Science, for
permitting us to carry out X-ray measurements (AFC7R-Mercury CCD).
Retro-Diels–Alder reaction conditions: A sample tube containing the ap-
propriate bicyclo[2.2.2]octadiene-fused porphyrin dimer was placed in a
G
[1] a) M. Berliocchi, M. Manenti, A. Bolognesi, A. Di Carlo, P. Ligli, R.
Paolesse, F. Mandoy, C. Di Natale, E. Proiette, G. Petrocco, A.
DꢁAmico, Semicond. Sci. Technol. 2004, 19, S354–S356; b) C. D. Di-
mitrakopoulos, D. J. Mascaro, IBM J. Res. Dev. 2001, 45, 11–30;
c) N. R. Armstrong, J. Porphyrins and Phthalocyanines 2000, 4, 414–
417; d) P. Alivisatos, P. F. Barbara, A. W. Castleman, J. Chang, D. A.
Dixon, M. L. Klein, G. L. McLendon, J. S. Miller, M. A. Ratner, P. J.
Rossky, S. I. Stupp, M. E. Thompson, Adv. Mater. 1998, 10, 1297–
1336, and references therein.
[2] a) P. Thordarson, A. Marquis, M. J. Crossley, Org. Biomol. Chem.
2003, 1, 1216–1225; b) M. J. Crossley, P. Thordarson, Angew. Chem.
2002, 114, 1785–1788; Angew. Chem. Int. Ed. 2002, 41, 1709–1712;
M. J. Crossley, L. A. Johnston, Chem. Commun. 2002, 1122–1123;
c) R. Beavington, P. L. Burn, J. Chem. Soc. Perkin Trans. 1 2000,
1231–1240; d) R. Beavington, P. L. Burn, J. Chem. Soc. Perkin
Trans. 1 2000, 605–609; e) J. R. Reimers, T. X. Lu, M. J. Crossley,
N. S. Hush, Chem. Phys. Lett. 1996, 256, 353–359; f) M. J. Crossley,
P. L. Burn, J. Chem. Soc. Chem. Commun. 1987, 39–40.
flask, and the flask was evacuated by means of a rotary vacuum pump.
The flask was then placed in a pre-heated glass tube oven at 2008C. The
red color of the porphyrin dimer immediately turned to black. After 1 h,
the flask was cooled and then flushed with argon. The fully conjugated
oligomers were obtained in quantitative yields and were sufficiently pure
for our purposes.
Dimer 13–Zn2: Green powder; m.p.>2508C; 1H NMR (C5D5N): d=1.19
(t, J=7.3 Hz, 12H), 1.85 (m, 8H), 1.96 (t, J=7.3 Hz, 12H), 2.37 (m, 8H),
3.97 (s, 12H), 4.12–4.22 (m, 16H), 10.15 (s, 4H), 10.99 (s, 4H), 11.48 ppm
(s, 2H); 13C NMR (C5D5N): d=12.1, 14.5, 19.1, 20.4, 23.5, 26.9, 36.1, 95.7,
99.0, 114.4, 136.1, 140.5, 142.3, 142.5, 147.4, 147.5, 148.1, 150.7 ppm; UV/
Vis (1 % C5H5N/CHCl3): lmax (loge)=333 (4.72), 390 (4.98), 412 (4.91),
444 (4.90), 474 (5.40), 525 (4.20), 579 (4.41), 621 (4.78), 636 nm (5.27);
MS (MALDI-TOF): m/z=1162.93 [M++4]; elemental analysis calcd (%)
for C70H78N8Zn2: C 72.34, H 6.76, N 9.64; found: C 72.08, H 6.89, N 9.36.
Dimer 13-H2: Green powder; m.p.>2508C; 1H NMR (CDCl3/TFA): d=
À2.25 (very broad signal), 1.10 (t, J=7.3 Hz, 12H), 1.63–1.73 (m, 8H),
1.76 (t, J=7.3 Hz, 12H), 2.10–2.20 (m, 8H), 3.88 (s, 12H), 4.10–4.22 (m,
16H), 10.64 (s, 4H), 11.45 (s, 4H), 11.81 ppm (s, 2H); 13C NMR (CDCl3/
TFA): d=12.0, 13.8, 17.4, 20.0, 23.0, 26.6, 34.3, 95.1, 100.5, 119.7, 134.7,
136.9, 137.1, 140.1, 140.6, 140.9, 143.4, 144.3 ppm; UV/Vis (1% TFA/
CHCl3): lmax (loge)=384 (5.26), 484 (4.49), 541 (4.42), 570 (4.45), 598
(4.55), 656 nm (5.23); MS (MALDI-TOF): m/z=1035.97 [M++1]; ele-
mental analysis calcd (%) for C70H82N8·1/2H2O: C 80.50, H 8.01, N 10.73;
found: C 80.36, H 7.88, N 10.53.
[3] a) R. Paolesse, L. Jaquinod, F. Della Sala, D. J. Nurco, L. Prodi, M.
Montalti, C. Di Natale, A. DꢁAmico, A. Di Carlo, P. Lugli, K. M.
Smith, J. Am. Chem. Soc. 2000, 122, 11295–11302; b) L. Jaquinod,
O. Siri, R. G. Khoury, K. M. Smith, Chem. Commun. 1998, 1261–
1262; c) N. Kobayashi, M. Numao, R. Kondo, S. Nakajima, T. Osa,
Inorg. Chem. 1991, 30, 2241–2244.
[4] M. G. H. Vicente, M. T. Cancilla, C. B. Lebrilla, K. M. Smith, Chem.
Commun. 1998, 2355–2356.
[5] a) A. Tsuda, A. Osuka, Science 2001, 293, 79–82; b) A. Tsuda, H.
Furuta, A. Osuka, J. Am. Chem. Soc. 2001, 123, 10304–10321; c) N.
Aratani, A. Tsuda, A. Osuka, Synlett 2001, 1663–1674; d) A. Tsuda,
A. Nakano, H. Furuta, H. Yanomochi, A. Osuka, Angew. Chem.
2000, 112, 572–575; Angew. Chem. Int. Ed. 2000, 39, 558–561; e) K.
Sugiura, T. Matsumoto, S. Ohkouchi, Y. Naitoh, T. Kawai, Y. Takai,
K. Ushiroda, K. Sakata, Chem. Commun. 1999, 1957–1958.
[6] a) T. Okujima, N. Komobuchi, Y. Shimizu, H. Uno, N. Ono, Tetrahe-
dron Lett. 2004, 45, 5461–5464; b) N. Ono, K. Kuroki, E. Watanabe,
N. Ochi, H. Uno, Heterocycles 2004, 62, 365–373; c) H. Uno, T. Ishi-
kawa, T. Hoshi, N. Ono, Tetrahedron Lett. 2003, 44, 5163–5165, and
references therein.
Dimer 13–NiZn: Green powder; m.p.>2508C; 1H NMR (C5D5N): d=
1.17 (t, J=7.3 Hz, 6H), 1.23 (brs, 6H), 1.88 (m, 4H), 2.03 (t, J=7.3 Hz,
6H), 2.17 (brs, 4H), 2.47 (m, 4H), 2.62 (brs, 6H), 3.14 (brs, 4H), 3.50
(brs, 2H), 3.80 (s, 6H), 4.23 (q, J=7.6 Hz, 4H), 4.32 (t, J=7.6 Hz, 4H),
5.69 (brs, 6H), 8.70 (brs, 4H), 9.14 (brs, 4H), 10.60 (s, 2H), 12.07 (brs,
2H), 15.30 ppm (brs, 2H); a signal due to two meso protons of the
nickel–porphyrin unit was not identified; UV/Vis (pyridine): lmax
(loge)=389 (4.94), 470 (5.13), 477 (5.15), 579 (4.41), 619 (4.73), 635 nm
(5.21).
1
Dimer 17: Green powder; m.p.>2508C; H NMR (C5D5N): d=1.23 (brs,
6H), 2.07 (m, 18H), 2.17 (brs, 4H), 2.63 (brs, 6H), 3.13 (brs, 4H), 3.58
(brs, 2H), 4.22 (q, J=7.3 Hz, 4H), 4.30 (m, 8H), 5.60 (brs, 6H), 8.70
(brs, 4H), 9.14 (brs, 4H), 10.60 (s, 2H), 12.14 (brs, 2H), 15.40 ppm (brs,
[7] S. Ito, K. Nakamoto, H. Uno, T. Murashima, N. Ono, Chem.
Commun. 2001, 2696–2697.
Chem. Eur. J. 2007, 13, 5773 – 5784
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5783

H. Uno et al.
[8] H. Uno, A. Masumoto, N. Ono, J. Am. Chem. Soc. 2003, 125,
12082–12083.
[14] J. B. Paine III, D. Dolphin, M. Gouterman, Can. J. Chem. 1978, 56,
1712–1714.
[9] a) H. Uno, S. Ito, M. Wada, H. Watanabe, M. Nagai, A. Hayashi, T.
Murashima, N. Ono, J. Chem. Soc. Perkin Trans. 1 2000, 4347–4355;
b) Y. Abel, F.-P. Montforts, Tetrahedron Lett. 1997, 38, 1745–1748.
[10] a) A. Boudif, M. Momenteau, J. Chem. Soc. Chem. Commun. 1994,
2069–2070; b) A. Boudif, M. Momenteau, J. Chem. Soc. Perkin
Trans. 1 1996, 1235–1242; c) J. L. Sessler, J. W. Genge, A. Urbach, P.
Sanson, Synlett 1996, 187–188; d) T. D. Lash, P. Chandrasekar, A. T.
Osuma, S. T. Chaney, J. D. Spence, J. Org. Chem. 1998, 63, 8455–
8469.
[15] “Photochemistry of Porphyrins and Metalloporphyrins”: F. R. Hopf,
D. G. Whitten, in Porphyrins and Metalloporphyrins (Ed.: K. M.
Smith), Elsevier, Amsterdam, 1975, Chapter 16.
[16] a) SHELXL-97, program for refinement of crystal structures from
diffraction data, University of Gçttingen, Gçttingen (Germany); G.
Scheldrick, T. Schneider, Methods Enzymol. 1997, 277, 319–343;
b) PLATON, a multipurpose crystallographic tool, Utrecht Univesi-
ty, Utrecht (The Netherlands); A. L. Spek, J. Appl. Crystallogr.
2003, 36, 7–13.
[11] K. M. Smith, in The Porphyrin Handbook, Vol. 1 (Eds.: M. K.
Kadish, K. M. Smith, R. Guilard), Academic Press, San Diego, 1999,
p. 2–44.
[17] J. A. Shelnutt, in The Porphyrin Handbook, Vol. 7 (Eds.: K. M.
Kadish, K. M. Smith, R. Guilard), Academic Press, San Diego, 2000,
p. 167–224.
[12] a) J. L. Sessler, M. R. Johnson, V. Lynch, J. Org. Chem. 1987, 52,
4394–4397; b) S. V. Shevchuk, J. M. Davis, J. L. Sessler, Tetrahedron
Lett. 2001, 42, 2447–2450.
[18] G. D. Hatmen, L. M. Weinstock, Org. Synth. 1988, 6, 620–628.
[19] S. Ito, N. Ochi, T. Murashima, H. Uno, N. Ono, Heterocycles 2000,
52, 399–411.
[13] J. L. Sessler, A. Mozaffari, M. R. Martin, Org. Synth. 1998, 9, 242–
249.
Received: November 16, 2006
Published online: March 30, 2007
5784
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 5773 – 5784