Molecular recognition of viologen by zinc porphyrinic receptors with diarylurea sidearms. Toward construction of a supramolecular electron transfer system

Article abstract of DOI:10.1016/j.tet.2005.12.046

A series of zinc porphyrinic receptors for a viologen substrate (hexyl viologen, HV²⁺) were synthesized, in which varying numbers of diarylurea moieties, from one to four, were appended at the porphyrin's meso positions. The increase in the number of the diarylurea moiety led to the increase in stability of the receptor-HV²⁺ complex, showing that the convergent dipoles set up on the porphyrin platform played an essential role in the complexation. In this system, formation of the stable electron donor-acceptor complex resulted in the effective electron transfer from the singlet excited state of the zinc porphyrin to HV²⁺.

Full text of DOI:10.1016/j.tet.2005.12.046

Tetrahedron 62 (2006) 2501–2510
Molecular recognition of viologen by zinc porphyrinic receptors
with diarylurea sidearms. Toward construction
of a supramolecular electron transfer system
a
b
Masayuki Ezoe,a Shigeyuki Yagi,a, Hiroyuki Nakazumi, Mitsunari Itou,
*
Yasuyuki Arakib and Osamu Itob
aDepartment of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University,
1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan
bInstitute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira, Sendai 980-8577, Japan
Received 21 November 2005; revised 16 December 2005; accepted 21 December 2005
Available online 18 January 2006
Abstract—A series of zinc porphyrinic receptors for a viologen substrate (hexyl viologen, HV2C) were synthesized, in which varying
numbers of diarylurea moieties, from one to four, were appended at the porphyrin’s meso positions. The increase in the number of the
diarylurea moiety led to the increase in stability of the receptor–HV2C complex, showing that the convergent dipoles set up on the porphyrin
platform played an essential role in the complexation. In this system, formation of the stable electron donor–acceptor complex resulted in the
effective electron transfer from the singlet excited state of the zinc porphyrin to HV2C
q 2005 Elsevier Ltd. All rights reserved.
.
1. Introduction
complexes, only a few examples of porphyrinic
receptors for a bare viologen backbone have been so
far reported.6a,d,e
For a few past decades, photoinduced electron transfer
systems employing organic molecules as well as metal
complexes have received much attention because they
do not only serve as models for photosynthetic electron
relay systems but also give significant insights into the
development of molecular-scale opto-electronic devices.1
Especially, the supramolecular architecture of electron
donor–acceptor complexes has been eagerly studied and
established as one of powerful methods for construction
of photochemically active ensembles,2 where porphyrins
and the related compounds have been widely used as
electron donor components because of analogy to
photosynthetic pigments. Thus, designing porphyrinic
receptors for appropriate electron acceptors such as
electron-deficient aromatics,3 quinones,4 fullerenes,5 and
viologens6 has been one of major topics in supramo-
lecular photochemistry. Many covalently-linked por-
phyrin–viologen donor–acceptor systems have so far
been studied,7 where the electron transfer effectively
occurs via formation of a face-to-face donor–acceptor
complex.7d However, despite such significance of the
rational design of supramolecular porphyrin–viologen
We recently reported the doubly diarylurea-linked
cofacial zinc porphyrin dimer (DLD), which formed a
1:1 complex with a viologen substrate (hexyl viologen
perchlorate, HV2C$2ClOK4 ).8 In this system,
high stability of the complex (KZ546,000 MK1 in
Keywords: Molecular recognition; Diarylurea; Zinc porphyrin; Viologen;
Photoinduced electron transfer; Supramolecular system.
Figure 1. (a) Structure of a viologen substrate (hexyl viologen perchlorate),
and illustrations of (b) the dipole moment on diphenylurea and (c) the
convergent arrangement of four carbonyl dipoles in the receptor 4.
*
Corresponding author. Tel.: C81 72 254 9324; fax: C81 72 254 9913;
e-mail: yagi@chem.osakafu-u.ac.jp
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.12.046

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M. Ezoe et al. / Tetrahedron 62 (2006) 2501–2510
CHCl3/DMSO, 10:1, v/v) was attributed to the dipole-
cation interactions9 between the diarylurea linkages and
the viologen backbone. This interesting result impels us
to design a more sophisticated porphyrinic receptor for
viologen that is facilely prepared. Here we report
complexation of a series of diarylurea-appended zinc
porphyrins 1–4 with HV2C: arranging the carbonyl
dipoles on the zinc porphyrin platform in a convergent
manner should promise effective binding of HV2C
(Fig. 1). We also discuss the complexation-facilitated
photoinduced electron transfer from steady-state fluor-
escence quenching studies and flash laser photolysis
measurement.
2. Results and discussion
2.1. Synthesis of the zinc porphyrinic receptors
We have already reported the synthesis of the receptor 1 in
the previous work.10 In Scheme 1 are shown the syntheses
of 2–5. Acid-promoted (BF3$OEt2) condensation of
4-methyl-3-nitrobenzaldehyde 6, p-tolualdehyde 7 and
pyrrole
8
at the ratio of 2:2:4 (mol/mol/mol)
followed by oxidation with chloranil afforded a mixture of
5,10-bis(3-nitro-4-methylphenyl)-15,20-bis(4-methylphe-
nyl)porphyrin, and 5,15-bis(3-nitro-4-methylphenyl)-10,20-
bis(4-methylphenyl)porphyrin, both of which were reduced
Scheme 1. Synthesis of porphyrinic receptors.

M. Ezoe et al. / Tetrahedron 62 (2006) 2501–2510
2503
by SnCl2 in concd HCl to yield a mixture of the
corresponding amino-substituted porphyrins 9a and 9b in
the yields of 3 and 5% based on 8, respectively. Changing
the ratio of the starting materials (6:7:8Z3:1:4, mol/mol/
mol), a similar procedure afforded 10 and 11 in 6 and 4%
yields, respectively. The receptors 2–4 were easily obtained
by the reactions of the corresponding amino-substituted
porphyrins 9–11 with an excess amount of phenylisocyanate
followed by zinc insertion in 48–60% yields. The more
soluble, quadruply functionalized zinc porphyrin 5 was also
1
prepared as an analogue of 4 for H NMR spectroscopic
studies. A Sonogashira cross-coupling reaction of 4-bromo-
benzaldehyde and 1-octyne yielded 4-(1-octyn-1-yl)benzal-
dehyde 12 in 98% yield, followed by hydrogenation on
Pd–C to yield 4-octylbenzaldehyde 13 in 83% yield.
Nitration of 13 by treatment with HNO3 in H2SO4 yielded
3-nitro-4-octylbenzaldehyde 14 in 64% yield. Acid-pro-
moted (BF3$OEt2) condensation of 14 and 8 yielded a nitro-
substituted porphyrin 15 in 28% yield, which was reduced to
16 in 87% yield. Treatment of 16 with a large excess of
phenylisocyanate followed by zinc insertion yielded the
receptor 5 in 60% yield. Each compound was identified by
1H NMR, 1H–1H COSY, electronic absorption, IR, and FAB
mass spectra as well as elemental analyses.
2.2. Complexation behavior of the zinc porphyrinic
receptors with HV2D
In Figure 2 are shown electronic absorption spectral changes
of 4 in the Soret region upon addition of varying amounts of
HV2C$2ClOK4 . The red-shifted spectral changes with an
isosbestic point at 434 nm showed saturation behavior. The
stoichiometry of the 4–HV2C complex was confirmed as 1:1
bytheJob’sanalysisusingelectronicabsorptionspectroscopy.
Thebindingconstant(Kabs)wasdeterminedas(2.86G0.30)!
106 MK1 by the computer-assisted least squares analysis
based on 1:1 complexation, which was larger than that of the
DLD–HV2C complex.8 Similar complexation behavior was
observed for 1–3 upon addition of HV2C, and Kabss of 1–4 for
HV2C are summarized in Table 1. The increase in the number
of the diarylurea moiety led to the increase in the stability of
the complex, and the zinc porphyrin without any diarylurea
moieties11 did not exhibit any spectral changes even in the
presence of an excess amount of HV2C. These results indicate
that the diarylurea moieties play an essential role in binding of
Figure 2. (a) Electronic absorption spectral changes of 4 (1.5 mM) upon
addition of increasing amounts of HV2C (a–r; 0, 0.15, 0.30, 0.45, 0.60,
0.90, 1.2, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 7.5, 10, 15, 25 and 50 mM) and
(b) absorbance changes at 430 (C) and 438 nm (B) in CHCl3–DMSO (10/
1, v/v) at 293 K.
On the other hand, the complexed 5 exhibited singlet signals
of H4 and N–Hs as well as the sharp signals of H1–H6,
although a small amount of metastable conformer was
observed probably due to the flexibility of the diarylurea
arms (Fig. 3b).13 Taking it into consideration that the
increase in the number of the diarylurea moiety gave rise to
stabilization of the complex, one can see that all the
diarylurea moieties participated in the binding of HV2C
.
HV2C
.
The contribution of the dipole-cation interaction to the
complexation of HV2C was quantitatively estimated by
The complexation of HV2C to the receptors was also
confirmed by 1H NMR titration experiments. In Figure 3 are
1
shown H NMR spectra of 5, HV2C, and a 1:1 mixture of
the both. The signals of Ha, Hb and Hc of HV2C exhibited
complexation-induced upfield shifts (1.4, 3.7, and 0.6 ppm,
respectively) upon addition of an equimolar amount of 5,
and any other remarkable shifts of the signals of the alkyl
protons in HV2C were not observed (!0.2 ppm). As the
proton was close to the center of viologen backbone, the
upfield shift became large. These results were unambi-
guously due to ring-current anisotropy from the porphyrin
p-plane, indicating that the bipyridinium backbone of
HV2C was located on the porphyrin ring. The free 5
exhibited the multiple signals of H4 and two urea N–Hs as
well as the broadened signals of H1–H6 (Fig. 3c), indicating
that the receptor exists as a mixture of the atropisomers.12
Table 1. Binding constants of receptors 1–4 for HV2C obtained by
a
electronic absorption (Kabs) and fluorescence emission spectra (Kem
)
Compound
Kabs (MK1 b
)
Kem (MK1 c
)
DGabs
(kJ molK1 d
)
1
1100
2300
K17.1
K24.0
K23.8
K29.7
K36.2
2a
2b
3
18,900
17,500
195,000
2,860,000
15,000
10,700
216,000
1,940,000
4
a In CHCl –DMSO (10/1, v/v) at 293 K.
3
b Experimental errors were within 7% except for 4 (11%).
c Experimental errors were within 10% except for 4 (26%).
d DGabss were calculated from Kabss.

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M. Ezoe et al. / Tetrahedron 62 (2006) 2501–2510
Figure 5. Schematic representation of contribution of the intermolecular
interactions (DGA and DGB) to the complexation of the receptors 1–4 with
HV2C
.
2.3. Complexation-facilitated electron transfer from
the zinc porphyrinic receptors to HV2D
Addition of HV2C to solutions of 1–4 led to the fluorescence
quenching due to photoinduced electron transfer from the zinc
porphyrin unit to HV2C (Fig. 6a).6b,c,e,8 The binding constant
Kem obtainedfromfluorescenceemissionspectroscopyvalidly
corresponded with Kabs for each receptor (Table 1), indicating
that fluorescence quenching occurred via formation of the
electron donor–acceptor complex. As shown in Figure 6b,
all titration curves finally reached plateaus but
exhibited different fluorescence quenching efficiencies:
the 3–HV2C and 4–HV2C systems showed quite efficient
fluorescencequenching(97and100%,respectively,supposing
that the receptor molecules fully complexed with
HV2C), whereas the 2a–HV2C and 2b–HV2C showed quasi-
effective (79 and 75%, respectively) and the 1–HV2C showed
less effective quenching (24%). The ZnPor–HV2C system
hardly showed fluorescence quenching (ZnPor; [5,10,15,20-
tetrakis(4-methylphenyl)-porphyrinato]zinc(II)). Therefore,
Figure 3. 1H NMR spectral study of (a) HV2C (1.8 mM), (b) HV2C
(1.8 mM)C5 (1.8 mM), and 5 (1.8 mM) in CDCl3–DMSO-d6 (10/1, v/v) at
293 K.
plotting the free energy changes of the complexation
(DGabss) against the number of the diarylurea moiety
(Fig. 4). These plots showed good linearity, and the slope
obtained (K6.28 kJ/mol) is attributed to the averaged
free energy change given by one dipole-cation interaction
between the diarylurea moiety and HV2C (Fig. 5, DGA).
In addition, the intercept of the plots (K11.1 kJ/mol) is
reasonably attributed to the free energy change of the
interaction between the porphyrin platform and the
viologen backbone (Fig. 5, DGB), that is either
electrostatic or solvophobic interaction, or the sum of
both. It is noteworthy that such a good linear relationship
also indicates that, in each receptor–HV2C system, all
diarylurea moieties contribute to binding of HV2C in an
induced-fit manner to achieve the multiple dipole-cation
interaction.
Figure 6. (a) Fluorescence emission spectral changes of 4 upon addition of
increasing amounts of HV2C (a–j; 0, 0.30, 0.60, 0.90, 1.2, 1.5, 2.0, 2.5, 3.0,
and 4.0 mM; [4]Z1.5 mM) and (b) quenching titration profiles of 1–4 in
CHCl3–DMSO (10/1, v/v) at 293 K. lexZ560 nm.
Figure 4. Plots for free energy changes on complexation of 1–4 with HV2C
against the number of the diarylurea moiety in the receptors in CHCl3–
DMSO (10/1, v/v) at 293 K. R2Z0.996.

M. Ezoe et al. / Tetrahedron 62 (2006) 2501–2510
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3
the increase in the thermodynamic stability of the receptor–
HV2C complex led to the increase of fluorescence quenching
efficiency. These results indicated that multiple dipole-cation
interactions as seen in 3–HV2C and 4–HV2C fixed HV2C
tightly on the receptor in a preferred manner to photoinduced
electron transfer.
porphyrinic receptor 4* was monitored in the presence of
varying concentrations of HV2C(Fig. 8). The triplet–triplet
absorption of 4 in the absence of HV2C decayed obeying the
first-order kinetics (190 msK1). The addition of HV2C to a
solution of 4 led to the decrease in the initial intensity of the
triplet state absorption, along with the shortening of the triplet
lifetime. This result clearly indicated that the rapid electron
3
2.4. Photophysical properties of the 4–HV2D complex
transfer disturbed the formation of 4* via the intersystem
crossing. In other words, the complexation of 4 with HV2C
allowedtheefficientelectrontransferfromthesingletstateof4
to HV2C. The charge recombination rate in the 4%C–HV%C
supramolecular redox product could not be determined
because the HV%C was formed via the two electron transfer
pathwaysfrombothofthesingletandtripletexcitedstatesof4.
However, it is noteworthy that the quick rise component at
400 nm (Fig. 7b) implies that the charge recombination rate is
relatively slow. This is because the supramolecular redox
product4%C–HV%C dissociatestotheindividualredoxspecies
4%C and HV%C due to electrostatic repulsion.
In order to clarify the efficient electron transfer in the
4–HV2C system, the detailed study on photophysics was
carried out in a mixture of benzonitrile and tetrahydrofuran
(1/1, v/v).14 In this solvent system, the spectroscopic
profiles of electronic absorption and fluorescence emission
of 4 upon complexation with HV2C were similar to those in
CHCl3–DMSO (10/1, v/v), although the binding constant of
4 to HV2C significantly decreased to 3.98!103 MK1. The
lifetime of the excited state of 4, t(4), was determined as
1.89 ns from the fluorescence emission decay at 650–
700 nm, which was typical of the singlet excited state of
zinc porphyrins.15 Upon addition of HV2C(3.0 mM) to a
solution of 4 (5.0 mM), the fast decay component tCS was
observed (310 ps),16 which was attributed to quenching by
photoinduced electron transfer from the zinc porphyrin
chromophore to HV2C. According to the Eqs. 1 and 2, the
rate of charge separation kCS and charge separation quantum
yield FCS were determined as 2.7!109 sK1 and 0.84,
respectively:
K1
kCS Z tKC1S Ktð4Þ
(1)
(2)
FCS Z 1KtCS=tð4Þ
The fast electron transfer from a porphyrin singlet state to a
viologen in the stable complex has been reported by Willner
et al.6c One can explain that the quite rapid charge
separation process is caused by the intracomplex electron
transfer in the 4–HV2C donor–acceptor ensemble.
Further information for the electron transfer process was
obtained from the transient absorption spectra of 4–HV2C
measured upon 558 nm laser irradiation. As shown in
Figure 7a, the photoinduced electron transfer from 4 to
HV2C was confirmed by two characteristic bands of the
viologen cation radical HV%C at 400 and 620 nm,17 although
the absorption of the porphyrin cation radical 4%C at
640 nm7c,18 was not clear because of the overlap with the
absorption band of HV%C. As seen in Figure 7b, the fast rise
component of the viologen cation radical at 400 nm was
indicativeoftheintracomplexelectrontransferinthe4–HV2C
complex.6c The slow rise component at 400 nm was also
observed, which was attributed to the intermolecular electron
transfer from the free 4 to the uncomplexed HV2C. The other
characteristicbandappearedat470 nm, whichwasassignedto
the zinc porphyrin triplet–triplet absorption.6c,18c The rate of
the decay agreed well with the slow rise of the absorption of
HV%C, and thus, these results indicated that intermolecular
electron transfer competitively occurred from the triplet state
of 4. However, as indicated by the fluorescence lifetime
measurement, the efficient electron transfer should occur via
the formation of the 4–HV2C complex. To clarify the
intracomplex electron transfer process, the decay of the
transient absorption of the triplet excited state of the
Figure 7. (a) Nanosecond transient absorption spectra of a mixture solution
of 4 (5.0 mM) and HV2C (3.0 mM) in Ar satd PhCN–THF (1/1, v/v) at 50 ns
(C) and 500 ns (B) after the 558 nm-laser irradiation. (b) The absorption-
time profiles monitored at 400, 470 and 620 nm.
Figure 8. Decay dynamics of the triplet–triplet absorption due to 34* at
460 nm in Ar saturated PhCN–THF (1/1, v/v) upon addition of HV2C
[4]Z5.0 mM, [HV2C]Z0, 0.1, 0.2, 0.5, 1.0, 2.0, 3.0 mM.
.

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M. Ezoe et al. / Tetrahedron 62 (2006) 2501–2510
3. Conclusions
(Spectra-Physics, Quanta-Ray GCR-130, fwhm 6 ns) as an
excitation source. For measurements in the visible region
and near-IR region (400–1000 nm), a monitoring light from
a pulsed Xe lamp was detected with a Si–PIN photodiode
(Hamamatsu Photonics, S1722-02). All the sample sol-
utions in a quartz cell (1!1 cm) were deaerated by bubbling
Ar gas through the solutions for 15 min.
The zinc porphyrinic receptors bearing diarylurea sidearms
at the meso positions were newly synthesized, and their
complexation behavior with HV2C was investigated in
detail. From the electronic absorption and 1H NMR
spectroscopic studies, the receptors bound HV2C in an
induced-fit manner, employing multiple dipole-cation
interaction between the diarylurea sidearms and the
viologen backbone. The energetic contribution of one
dipole-cation interaction to the complexation was estimated
as K6.28 kJ/mol. The interaction between the porphyrin
platform and the viologen backbone (K11.1 kJ/mol) was
also found to be essential to formation of the stable
complex. The steady-state fluorescence titration study
revealed that the increase in stability of the receptor–
HV2C complex brought about the increase in the efficiency
of photoinduced electron transfer from the porphyrinic
receptor to HV2C. From the investigation of the photo-
physics of the 4–HV2C system, the formation of the donor–
acceptor complex significantly facilitated the electron
transfer from the singlet excited state of 4 to HV2C
(kCSZ2.7!109 sK1, FCSZ0.84). In the supramolecular
electron transfer system, relatively slow charge recombi-
nation was implied, which should be due to dissociation of
the redox products caused by electrostatic repulsion. The
results obtained in the present study should offer significant
insights into construction of supramolecular photoinduced
electron transfer systems.
4.2. Preparation of materials
All water-sensitive reactions were carried out under N2
atmosphere, using dried solvent. Dichloromethane was
dried over CaH2 and distilled just prior to use. The
preparation of 4-methyl-3-nitrobenzaldehyde 6 was
previously reported in Ref. 8. 4-Methylbenzaldehyde,
4-bromobenzaldehyde and 1-octyne were commercially
available. 4-Octylbenzaldehyde was prepared by the
different method from those reported.19 Size exclusion
column chromatography was performed using BioRad Bio-
Beads SX-1 with distilled THF as eluent.
4.3. Synthesis
4.3.1. Synthesis of 5,10-bis(3-amino-4-methylphenyl)-15,20-
bis(4-methylphenyl)porphyrin (9a) and 5,15-bis(3-amino-4-
methylphenyl)-10,20-bis(4-methylphenyl)porphyrin (9b). To
a solution of chloranil (2.77 g, 11.3 mmol) in dry CH2Cl2
(500 mL) were added 4-methyl-3-nitrobenzaldehyde 6
(1.24 g, 7.51 mmol), 4-methylbenzaldehyde 7 (0.901 g,
7.50 mmol) and pyrrole 8 (1.01 g, 15.1 mmol) under N2.
After the mixture was stirred for a few minutes at ambient
temperature under darkness, BF3$OEt2 (0.95 mL,
7.56 mmol) was added, and then, the mixture was stirred
for 1 h at the same temperature. The mixture was directly
poured onto the top of an alumina column and allowed to
pass through using CH2Cl2 as eluent. The resultant solution
was concentrated to ca. 200 mL on a rotary evaporator, and
then, washed with satd NaHCO3 (100 mL!3). The solution
was dried over anhydrous Na2SO4, and the solvent was
removed on a rotary evaporator. The residual dark purple
solid was roughly purified by silica gel column chromatog-
raphy (eluent; CHCl3/hexane, 4:1, v/v) to obtain a fraction
of a mixture of 5-(4-methyl-3-nitrophenyl)-10,15,20-tris(4-
methylphenyl)porphyrin, 5,10-bis(4-methyl-3-nitrophenyl)-
15,20-bis(4-methylphenyl)porphyrin, 5,15-bis(4-methyl-3-
nitrophenyl)-10,20-bis(4-methylphenyl)-porphyrin. After
removal of the solvent on a rotary evaporator, the residual
dark purple solid was added to hot concd HCl (50 mL,
65 8C), followed by addition of SnCl2$2H2O (1.34 g,
5.94 mmol), and then, the reaction mixture was stirred at
the same temperature for 2 h. After cooling, to the mixture
was carefully added 27% aqueous NH3 (70 mL) on an ice
bath, and then, CHCl3 (100 mL) was added. The mixture
was stirred vigorously at ambient temperature for 2 h. The
mixture was allowed to pass through a paper filter with
Celitew mounted. The filtrate was washed with satd
NaHCO3 (100 mL), satd brine (100 mL), and water
(100 mL). After dried over anhydrous Na2SO4, the solvent
was removed by evaporation. Purification of the resultant
mixture by silica gel column chromatography (eluent;
CHCl3/ethyl acetate, 5:1, v/v) yielded 9a (142 mg,
0.203 mmol, 5%) and 9b (83.7 mg, 0.119 mmol, 3%),
both of which were dark purple solids. Porphyrins 9a and
4. Experimental
4.1. General methods
1
1H NMR and H–1H COSY spectra were measured on a
JEOL JNM-A500 (500 MHz) or a JEOL JNM-LA400
(400 MHz) spectrometer, using tetramethylsilane
(0.00 ppm) and residual DMSO (2.49 ppm) as internal
standards for CDCl3 and DMSO-d6, respectively. FAB mass
spectra were recorded on a Finnigan MAT TSQ-70 mass
spectrometer using 3-nitrobenzyl alcohol as a matrix. IR
spectra were measured on a Shimadzu FTIR-8400S
spectrometer using KBr pellets.
Electronic absorption spectra were measured on a Shimadzu
Multispec-1500 spectrometer, and fluorescence emission
spectra were recorded on a Shimadzu RF-5000 or a JASCO
FP-6600 spectrophotometer. Solvents used for electronic
absorption and fluorescence emission spectra were of
spectroscopic grade. Just before acquisition of the spectra,
the sample solutions were subjected to N2 bubbling through
a syringe needle for 10 min.
The time-resolved fluorescence spectra were measured by a
single-photon counting method using a second harmonic
generation (SHG, 410 nm) of a Ti:sapphire laser (Spectra-
Physics, Tunami 3950-L2S, fwhm 1.5 ps) as an excitation
source and using a streakscope (Hamamatsu Photonics,
C4334-01) equipped with a polychromator as a detector.
Nanosecond transient absorption measurements were
carried out using a SHG (532 nm) of the Nd:YAG laser

M. Ezoe et al. / Tetrahedron 62 (2006) 2501–2510
2507
9b were discriminated from the 1H NMR spectral patterns of
the pyrrole b-Hs: two singlets and two coupled doublets
were observed for the b-H signals of 9a, while just two
coupled doublets were observed for those of 9b.20
4.3.5. {5,15-Bis(4-methylphenyl)-10,20-bis[4-methyl-3-
(3-phenylureylen-1-yl)phenyl]porphyrinato}zinc(II)
(2b). To a solution of 9b (50.0 mg, 0.0713 mmol) in dry
CH2Cl2 (30 mL) was added phenylisocyanate (41.6 mg,
0.349 mmol) under N2, and the mixture was stirred for 3 h
before another portion of phenylisocyanate (41.6 mg,
0.349 mmol) was added. After the reaction mixture was
stirred at ambient temperature for 15 h, the solvent was
removed on a rotary evaporator, and the residue was
dissolved in THF and filtrated to remove insoluble
materials. After removal of the solvent on a rotary
evaporator, the residual dark purple solid was added to
CHCl3 (30 mL) followed by addition of a saturated
ethanolic solution of Zn(OAc)2 (50 mL). The mixture was
stirred at 50 8C for 1 h, and the solvent was removed by
evaporation. Purification of the resultant mixture by silica
gel chromatography (eluent; CHCl3/methanol, 50:1, v/v)
followed by size-exclusion column chromatography (THF
as eluent) and recrystallization from THF–hexane yielded
2b as a purple solid (40.5 mg, 0.0404 mmol, 57%): 1H NMR
(400 MHz, DMSO-d6) d (ppm) 2.59 (s, 6H, 5,15-Ar-CH3),
2.65 (s, 6H, 10,20-Ar-CH3), 6.88 (t, JZ7.6 Hz, 2H, Ph-H),
7.18 (t, JZ7.6 Hz, 4H, Ph-H), 7.39 (d, JZ7.6 Hz, 4H, Ph-
H), 7.56–7.60 (m, 6H, 2H of 5,15-Ar-H and 4H of 10,20-Ar-
H), 7.74 (dd, JZ1.5, 7.6 Hz, 2H, 5,15-Ar-H), 8.06 (d, JZ
7.6 Hz, 4H, 10,20-Ar-H), 8.29 (br, 2H, –NH), 8.76–8.79 (m,
6H, 4H of pyrrole b-H and 2H of 5,15-Ar-H), 8.86–8.88 (d,
JZ4.6 Hz, 4H, pyrrole b-H), 9.20 (br, 2H, –NH); IR (KBr)
1653, 3362 cmK1; FAB MS m/z 1000 (MC), 1001 ([MC
1]C), 1002 ([MC2]C), 1003 ([MC3]C). Anal. Calcd for
C62H48N8O2Zn$H2O: C, 72.97; H, 4.94; N, 10.98. Found:
C, 72.90; H, 4.65; N, 10.92.
4.3.2. 5,10-Bis(3-amino-4-methylphenyl)-15,20-bis(4-
methylphenyl)porphyrin (9a). 1H NMR (400 MHz,
CDCl3) d (ppm) K2.79 (br, 2H, inner-NH), 2.51 (s, 6H,
5,10-Ar-CH3), 2.70 (s, 6H, 15,20-Ar-CH3), 3.87 (br, 4H,
–NH2), 7.39 (d, JZ7.3 Hz, 2H, 5,10-Ar-H), 7.54–7.56 (m,
8H, 4H of 5,10-Ar-H and 4H of 15,20-Ar-H), 8.09 (d, JZ
7.6 Hz, 4H, 15,20-Ar-H), 8.83 (d, JZ4.9 Hz, 2H, pyrrole b-
H), 8.84 (s, 2H, pyrrole b-H), 8.92 (s, 2H, pyrrole b-H), 8.94
(d, JZ4.9 Hz, 2H, pyrrole b-H); TLC (silica gel, eluent;
CHCl3/ethyl acetate, 5:1, v/v) RfZ0.41; IR (KBr) 1620,
3318, 3367, 3460 cmK1; FAB MS m/z 700 (MC). Anal.
Calcd for C48H40N6: C, 82.26; H, 5.75; N, 11.99. Found: C,
82.04; H, 5.92; N, 11.68.
4.3.3. 5,15-Bis(3-amino-4-methylphenyl)-10,20-bis(4-
methylphenyl)porphyrin (9b). 1H NMR (400 MHz,
CDCl3) d (ppm) K2.80 (br, 2H, inner-NH), 2.50 (s, 6H,
5,15-Ar-CH3), 2.70 (s, 6H, 10,20-Ar-CH3), 3.85 (br, 4H,
–NH2), 7.39 (d, JZ7.8 Hz, 2H, 5,15-Ar-H), 7.53–7.56 (m,
8H, 4H of 5,15-Ar-H and 4H of 10,20-Ar-H), 8.09 (d, JZ
7.8 Hz, 4H, 10,20-Ar-H), 8.83 (d, JZ4.6 Hz, 4H, pyrrole b-
H), 8.93 (d, JZ4.6 Hz, 4H, pyrrole b-H); TLC (silica gel,
eluent; CHCl3/ethyl acetate, 5:1, v/v) RfZ0.67; IR (KBr)
1620, 3311, 3367, 3451 cmK1; FAB MS m/z 700 (MC).
Anal. Calcd for C48H40N6$H2O: C, 81.21; H, 5.82; N, 11.84.
Found: C, 81.13; H, 5.67 N, 11.78.
4.3.4. {15,20-Bis(4-methylphenyl)-5,10-bis[4-methyl-3-
(3-phenylureylen-1-yl)phenyl]porphyrinato}zinc(II)
(2a). To a solution of 9a (50.0 mg, 0.0713 mmol) in dry
CH2Cl2 (30 mL) was added phenylisocyanate (41.0 ,
0.344 mmol) under N2, and the mixture was stirred for 3 h
before another portion of phenylisocyanate (41.0 mg,
0.344 mmol) was added. After the reaction mixture was
stirred at ambient temperature for 12 h, the solvent was
removed on a rotary evaporator. The residue was dissolved
in THF and filtered to remove insoluble materials. After
removal of the solvent on a rotary evaporator, the residual
dark purple solid was dissolved in CHCl3 (20 mL), followed
by addition of a saturated ethanolic solution of Zn(OAc)2
(50 mL). The mixture was stirred at 50 8C for 1 h, and the
solvent was removed by evaporation. The residue was
dissolved in THF (20 mL) and filtered to remove insoluble
materials. Purification of the resultant mixture by size-
exclusion column chromatography (THF as eluent) and
recrystallization from THF–hexane yielded 2a as a purple
4.3.6. Synthesis of 5,10,15-tris(3-amino-4-methylphenyl)-
20-(4-methylphenyl)porphyrin (10) and 5,10,15,20-tetra-
kis(3-amino-4-methylphenyl)porphyrin (11). To a sol-
ution of chloranil (2.77 g, 11.3 mmol) in dry CH2Cl2
(500 mL) were added 4-methyl-3-nitrobenzaldehyde 6
(1.24 g, 7.51 mmol), 4-methylbenzaldehyde 7 (0.901 g,
7.50 mmol), and pyrrole 8 (1.01 g, 15.1 mmol) under N2.
After the mixture was stirred for a few minutes at ambient
temperature under darkness, BF3$OEt2 (0.95 mL,
7.56 mmol) was added, and then, the mixture was stirred
for 1 h at the same temperature. The mixture was directly
poured onto the top of an alumina column, and allowed to
pass through using CH2Cl2 as eluent. The resultant solution
was concentrated to ca. 200 mL on a rotary evaporator, and
then, washed with satd NaHCO3 (100 mL!3). The organic
phase was dried over anhydrous Na2SO4, and the solvent
was removed on a rotary evaporator. The residual dark
purple solid was roughly purified by silica gel column
chromatography (eluent; CHCl3/hexane, 4:1, v/v) to obtain
a fraction of a mixture of 10,15,20-tris(4-methyl-3-
nitrophenyl)-5-(4-methylphenyl)porphyrin and 5,10,15,20-
tetrakis(4-methyl-3-nitrophenyl)porphyrin. After removal
of the solvent on a rotary evaporator, the residual dark
purple solid was added to hot concd HCl (50 mL, 65 8C),
followed by addition of SnCl2$2H2O (1.34 g, 5.94 mmol),
and then, the reaction mixture was stirred at the same
temperature for 2 h. After cooling, to the mixture was
carefully added 27% aqueous NH3 (70 mL) on an ice bath,
and then, CHCl3 (100 mL) was added. The mixture was
stirred vigorously at ambient temperature for 2 h. The
1
solid (42.1 mg, 0.0420 mmol, 59%): H NMR (400 MHz,
DMSO-d6) d (ppm) 2.59 (s, 6H, 5,10-Ar-CH3), 2.66 (s, 6H,
15,20-Ar-CH3), 6.85–6.90 (m, 2H, Ph-H), 7.14–7.20 (m,
4H, Ph-H), 7.37–7.40 (m, 4H, Ph-H), 7.56–7.60 (m, 6H, 2H
of 5,10-Ar-H and 4H of 15,20-Ar-H), 7.73–7.77 (m, 2H,
5,10-Ar-H), 8.04–8.07 (m, 4H, 15,20-Ar-H), 8.27 (br, 2H,
–NH), 8.76–8.79 (m, 6H, 4H of pyrrole b-H and 2H of 5,10-
Ar-H), 8.86–8.88 (m, 4H, pyrrole b-H), 9.17–9.20 (br, 2H,
–NH); IR (KBr) 1663, 3366 cmK1; FAB MS m/z 1000
([M]C), 1001 ([MC1]C), 1002 ([MC2]C), 1003 ([MC
3]C). Anal. Calcd for C62H48N8O2Zn$H2O: C, 72.97; H,
4.94; N, 10.98. Found: C, 72.62; H, 4.64; N, 11.05.

2508
M. Ezoe et al. / Tetrahedron 62 (2006) 2501–2510
mixture was allowed to pass through a paper filter with
Celitew mounted. The filtrate was washed with satd
NaHCO3 (100 mL), satd brine (100 mL) and water
(100 mL). After dried over anhydrous Na2SO4, the solvent
was removed by evaporation. Purification of a resultant
mixture by silica gel column chromatography (eluent;
CHCl3/ethyl acetate, 4:1, v/v) yielded 10 (162 mg,
0.226 mmol, 6%) and 11 (112 mg, 0.150 mmol, 4%) as
dark purple solids, respectively.
of 11 (50.0 mg, 0.0684 mmol) in dry CH2Cl2 (50 mL) was
added phenylisocyanate (35.0 mg, 0.294 mmol) under N2.
After the reaction mixture was stirred at ambient temperature
for4 h,thesolventwasremovedonarotaryevaporator. CHCl3
(50 mL) was poured to the residue, followed by addition of a
saturated ethanolic solution of Zn(OAc)2 (50 mL). The
mixture was stirred at 50 8C for 1 h, and then, the solvent
was removed by evaporation. The residue was dissolved in
THF (20 mL) and filtered to remove insoluble materials. The
resultant mixture was purified by size exclusion chromato-
graphy (THF as a eluent). The reside was thoroughly purified
byreprecipitation fromTHF into hexane to afford4 as a purple
4.3.7. 5,10,15-Tris(3-amino-4-methylphenyl)-20-(4-
methylphenyl)porphyrin (10). 1H NMR (400 MHz,
CDCl3) d (ppm) K2.81 (br, 2H, inner-NH), 2.46 (s, 9H,
5,10,15-Ar-CH3), 2.69 (s, 3H, 20-Ar-CH3), 3.78 (br, 6H,
–NH2), 7.36 (d, JZ7.3 Hz, 3H, 5,10,15-Ar-H), 7.49–7.56
(m, 8H, 6H of 5,10,15-Ar-H and 2H of 20-Ar-H), 8.08 (d,
JZ7.5 Hz, 2H, 20-Ar-H), 8.82 (d, JZ4.6 Hz, 2H, pyrrole b-
H), 8.90–8.93 (m, 6H, pyrrole b-H); TLC (silica gel, eluent;
CHCl3/ethyl acetate, 5:1, v/v), RfZ0.15; IR (KBr) 1616,
3312, 3367, 3451 cmK1; FAB MS m/z 715 (MC). Anal.
Calcd for C48H41N7$H2O: C, 78.55; H, 5.91; N, 13.36.
Found: C, 78.79; H, 5.58; N, 13.36.
1
solid (45.0 mg, 0.0354 mmol, 52%): H NMR (400 MHz,
DMSO-d6) d (ppm) 2.59 (s, 12H, 5,10,15,20-Ar-CH3), 6.85–
6.90 (m, 4H, Ph-H), 7.14–7.21 (m, 8H, Ph-H), 7.35–7.41 (m,
8H, Ph-H), 7.57 (m, 4H, 5,10,15,20-Ar-H), 7.75–7.77 (m, 4H,
5,10,15,20-Ar-H), 8.28 (br, 4H, –NH), 8.78–8.80 (m, 4H,
5,10,15,20-Ar-H), 8.88 (s, 8H, pyrrole b-H,), 9.16–9.20 (m,
4H, –NH); IR (KBr) 1662, 3363 cmK1; FAB MS m/z 1268
(MC), 1269 ([MC1]C), 1270 ([MC2]C), 1271 ([MC3]C).
Anal. Calcd for C76H60N12O4Zn$2H2O: C, 69.85; H, 4.94; N,
12.86. Found: C, 69.96; H, 4.61; N, 12.62.
4.3.8. 5,10,15,20-Tetrakis(3-amino-4-methylphenyl)por-
phyrin (11). H NMR (400 MHz, CDCl3) d (ppm) K2.82
1
4.3.11. 4-(1-Octyn-1-yl)benzaldehyde (12). Toa mixture of
4-bromobenzaldehyde (27.8 g, 150 mmol), bis(triphenylpho-
sphine)palladium(II) dichloride (1.12 g, 1.60 mmol) and
1-octyne (18.8 g, 171 mmol) in Et3N (200 mL) were added
cupper(I) iodide (0.609 g, 3.20 mol). The mixture was stirred
at 50 8C for 12 h under N2. Insoluble materials were removed
by filtration, and the filtrate was washed with satd brine
(100 mL!3) and water (100 mL). Purification by flash
chromatography (silica gel, hexane as eluent) afforded 12
(31.5 g, 147 mmol, 98%), which was used in the next reaction
without further purification due to instability under air. The
(br, 2H, inner-NH), 2.51 (s, 12H, Ar-CH3), 3.86 (br, 8H,
–NH2), 7.39 (d, JZ7.6 Hz, 4H, Ar-H), 7.53–7.57 (m, 8H,
Ar-H), 8.91 (s, 8H, pyrrole b-H); TLC (silica gel, eluent;
CHCl3/ethyl acetate, 5:1, v/v), RfZ0.05; IR (KBr) 1620,
3312, 3358, 3451 cmK1; FAB MS m/z 730 (MC). Anal.
Calcd for C48H42N8$H2O: C, 76.98; H, 5.92; N, 14.96.
Found: C, 77.20; H, 5.58 N, 14.84.
4.3.9. {20-(4-Methylphenyl)-5,10,15-tris[4-methyl-3-(3-
phenylureylen-1-yl)phenyl]porphyrinato}zinc(II) (3).
To a solution of 10 (50.0 mg, 0.0698 mmol) in dry
CH2Cl2 (30 mL) was added phenylisocyanate (28.0 mg,
0.235 mmol) under N2. After the reaction mixture was
stirred at ambient temperature for 15 h, the solvent was
removed on a rotary evaporator. CHCl3 (50 mL) was poured
to the residual dark purple solid, followed by addition of a
saturated ethanolic solution of Zn(OAc)2 (50 mL). The
mixture was stirred at 50 8C for 1 h, and then, the solvent
was removed by evaporation. The residue was dissolved in
THF (20 mL) and filtered to remove insoluble materials.
The resultant mixture was purified by size exclusion
chromatography (THF as eluent). Further purification of
the obtained solid by reprecipitation from THF into hexane
yielded 3 as a purple solid (37.9 mg, 0.033 mmol, 48%): 1H
NMR (400 MHz, DMSO-d6) d (ppm) 2.59 (s, 9H, 5,10,15-
Ar-CH3), 2.66 (s, 3H, 20-Ar-CH3), 6.85–6.90 (m, 3H, Ph-
H), 7.14–7.21 (m, 6H, Ph-H), 7.37–7.41 (m, 6H, Ph-H),
7.56–7.60 (m, 5H, 3H of 5,10,15-Ar-H and 2H of 20-Ar-H),
7.73–7.77 (m, 3H, 5,10,15-Ar-H), 8.06–8.08 (m, 2H, 20-Ar-
H), 8.27 (m, 3H, –NH), 8.76–8.78 (m, 5H, 2H of pyrrole b-
H and 3H of 5,10,15-Ar-H), 8.87–8.88 (m, 6H, pyrrole b-H),
9.16–9.20 (br, 3H, –NH); IR (KBr) 1663, 3369 cmK1; FAB
MS m/z 1134 (MC), 1135 ([MC1]C), 1136 ([MC2]C),
1137 ([MC3]C). Anal. Calcd for C69H54N10O3Zn$H2O: C;
71.78, H; 4.89, N; 12.13. Found: C, 71.73; H, 4.68; N, 12.04.
spectroscopic data was identical to the reported data:21 1
H
NMR (400 MHz, CDCl3) d (ppm) 0.90 (t, JZ7.1 Hz, 3H,
–CH3), 1.28–1.64 (m, 8H, –CH2–), 2.44 (t, JZ7.1 Hz, 2H,
–C^C–CH2–), 7.53 (d, JZ8.3 Hz, 2H, Ar-H), 7.80 (d, JZ
8.3 Hz, 2H, Ar-H), 9.99 (s, 1H, –CHO); IR (KBr) 1704, 2225,
2855, 2929, 2955 cmK1; FAB MS m/z 214 (MC).
4.3.12. 4-Octylbenzaldehyde (13). H2 gas was introduced
into a vigorously stirred solution of 12 (31.5 g, 147 mmol) in
ethyl acetate (200 mL) for 5 min via a syringe needle. To the
solution was added a suspension of palladium/activated
carbon (Pd 10%) (1.50 g) in ethyl acetate (30 mL). The
mixture was stirred for 6 h under H2, and then, allowed to pass
through a filter with Celitew mounted. The Celitew was
thoroughly washed with hexane (200 mL). The filtrate was
combined with the washing, and the solvent was removed on a
rotary evaporator to yield a dark yellow oil. Purification of the
resultant oil by silica gel column chromatography (eluent;
hexane/ethyl acetate, 20:1, v/v) yielded 4-octylbenzaldehyde
13 (26.8 g, 122 mmol, 83%), which was used in the next
reaction without further purification due to instability under
air: 1H NMR (400 MHz, CDCl3) d (ppm) 0.88 (t, JZ7.1 Hz,
3H, –CH3), 1.26–1.32 (m, 10H, –CH2–), 1.61–1.67 (m, 2H,
–CH2–), 2.69(t, JZ7.1 Hz, 2H, Ar-CH2–), 7.34(d, JZ7.8 Hz,
2H, Ar-H),7.80(d, JZ7.8 Hz, 2H, Ar-H),9.97(s, 1H, –CHO);
IR (KBr) 1704, 2856, 2924, 2955 cmK1; FAB MS m/z 218
(MC).
4.3.10. {5,10,15,20-Tetrakis[4-methyl-3-(3-phenylurey-
len-1-yl)phenyl]porphyrinato}zinc(II) (4). To a solution

M. Ezoe et al. / Tetrahedron 62 (2006) 2501–2510
2509
1
4.3.13. 3-Nitro-4-octylbenzaldehyde (14). To a mixture of
fuming HNO3 (1.7 mL) and concd sulfuric acid (12.4 mL)
was added 13 (4.36 g, 20.0 mmol) dropwise on an ice bath
with vigorous stirring under N2. After completion of the
addition of the aldehyde, the ice bath was removed, and the
reaction mixture was stirred for 15 min. The mixture was
poured onto ice, and then, the product was extracted into
Et2O. The organic phase was washed with satd NaHCO3
(100 mL!3) and water (100 mL). After dried over
anhydrous Na2SO4, the solvent was removed by evapo-
ration. Purification of the residual mixture by silica gel
column chromatography (eluent; hexane/CHCl3, 10:1, v/v)
yielded 14 (3.35 g, 12.7 mol, 64%), which was used in the
next reaction without further purification due to instability
under air: 1H NMR (400 MHz, CDCl3) d (ppm) 0.88 (t, JZ
7.1 Hz, 3H, –CH3), 1.21–1.51 (m, 10H, –CH2–), 1.57–1.63
(m, 2H, –CH2–), 2.95 (t, JZ7.1 Hz, 2H, Ar-CH2–), 7.54 (d,
JZ7.8 Hz, 2H, Ar-H), 8.02 (d, JZ7.8 Hz, 2H, Ar-H), 10.03
(s, 1H, –CHO); IR (KBr) 1348, 1529, 1701, 2853, 2922,
2955 cmK1; FAB MS m/z 263 (MC), 264 ([MC1]C).
0.348 mmol, 87%): H NMR (400 MHz, CDCl3) d (ppm)
K2.81 (br, 2H, inner-NH), 0.94 (t, JZ7.3 Hz, 12H, –CH3),
1.34–1.65 (m, 40H, –CH2–), 1.88–1.96 (m, 8H, Ar-
CH2CH2–), 2.81 (t, JZ7.3 Hz, 8H, Ar-CH2–), 3.87 (br,
8H, –NH2), 7.38 (d, JZ7.3 Hz, 4H, Ar-H), 7.54 (s, 4H, Ar-
H), 7.58 (d, JZ7.3 Hz, 4H, Ar-H), 8.92 (s, 8H, pyrrole b-
H); IR (KBr) 1618, 2854, 2924, 2953, 3321, 3362,
3441 cmK1; FAB MS m/z 1123 (MC), 1124 ([MC1]C).
Anal. Calcd for C76H98N8: C, 81.24; H, 8.79; N, 9.97.
Found: C, 81.11; H, 8.94; N, 10.01.
4.3.16. {5,10,15,20-Tetrakis[4-octyl-3-(3-phenylureylen-
1-yl)phenyl]porphyrin (the precursor of 5). To a solution
of 16 (200 mg, 0.178 mmol) in dry CH2Cl2 (20 mL) was
added phenylisocyanate (170 mg, 1.43 mmol) under N2. After
the reaction mixture was stirred at ambient temperature for
15 h, the solvent was removed on a rotary evaporator. The
residue was dissolved in THF (40 mL) and filtered to remove
insoluble materials. The resultant mixture was purified by size
exclusion column chromatography (THF as eluent). Repreci-
pitationoftheobtainedmaterialfromTHFintohexaneyielded
{5,10,15,20-tetrakis[4-octyl-3-(3-phenylureylen-1-yl)phe-
nyl]porphyrin as a purple solid (182 mg, 0.114 mmol, 64%),
which was used in the next step without further purification:
1H NMR (400 MHz, DMSO-d6) d (ppm) K2.90 (br, 2H,
inner-NH), 0.86–0.90 (t, JZ7.0 Hz, 12H, –CH3), 1.30–1.58
(m, 40H, –CH2–), 1.82–1.87 (m, 8H, Ar-CH2–CH2–), 2.90–
2.95 (t, JZ7.0 Hz, 8H, Ar-CH2–), 6.85–6.89 (m, 4H, Ph-H),
7.12–7.21 (m, 8H, Ph-H), 7.39–7.42 (m, 8H, Ph-H), 7.55–7.58
(m, 4H, 5,10,15,20-Ar-H), 7.80–7.82 (m, 4H, 5,10,15,20-Ar-
H), 8.24 (br, 4H, –NH), 8.70–8.71 (m, 4H, 5,10,15,20-Ar-H),
8.90 (s, 8H, pyrrole b-H), 9.14–9.16 (m, 4H, –NH); IR (KBr)
1653, 2856, 2926, 2953, 3320 cmK1; FAB MS m/z 1599
(MC), 1600 ([MC1]C), 1601 ([MC2]C).
4.3.14. 5,10,15,20-Tetrakis(3-nitro-4-octylphenyl)por-
phyrin (15). In dry CH2Cl2 (500 mL) were dissolved 14
(2.23 g, 8.47 mmol) and pyrrole 8 (568 mg, 8.47 mmol), and
the mixture was stirred for 15 min under N2$ BF3$OEt2
(0.170 mL, 1.35 mmol) was added under darkness, and the
mixture was stirred for 1 h. p-Chloranil (1.56 g, 6.34 mmol)
was added at one portion, and the mixture was stirred for 1 h at
the same temperature. Then, the resultant mixture was put on
the top of an alumina column and allowed to pass through
using CH2Cl2 as eluent. The solvent was removed on a rotary
evaporator to yield a dark brown solid, which was purified by
silica gel column chromatography (eluent; CH2Cl2/hexane,
3:2, v/v) to yield 15 as a dark purple solid (750 mg,
1
0.603 mmol, 28%): H NMR (400 MHz, CDCl3) d (ppm)
K2.87 (br, 2H, inner-NH), 0.94 (t, JZ7.1 Hz, 12H, –CH3),
1.36–1.65 (m, 40H, –CH2–), 1.93–2.01 (m, JZ7.8 Hz, 8H,
Ar-CH2CH2–), 3.24 (t, JZ7.1 Hz, 8H, Ar-CH2–), 7.78 (d, JZ
6.4 Hz, 4H, Ar-H), 8.36 (d, JZ6.4 Hz, 4H, Ar-H), 8.72 (s, 4H,
Ar-H), 8.87 (s, 8H, pyrrole b-H); IR (KBr) 1344, 1529, 2853,
2926, 2953 cmK1;FABMSm/z1243(MC),1244([MC1]C).
Anal. Calcd for C76H90N8O8: C, 73.40, H, 7.29, N, 9.01.
Found: C, 73.49; H, 7.53; N, 8.99.
4.3.17. {5,10,15,20-Tetrakis[4-(1-octyl)-3-(3-phenylurey-
len-1-yl)phenyl]porphyrinato}zinc(II) (5). {5,10,15,20-
Tetrakis[4-(1-octyl)-3-(3-phenylureylen-1-yl)phenyl]por-
phyrin (100 mg, 0.0625 mmol) was dissolved in DMSO
(10 mL), followedbyadditionofasaturatedethanolicsolution
of Zn(OAc)2 (100 mL). The mixture was stirred at reflux for
1 h, and then, the ethanol was removed by evaporation. To the
resultant mixture was added water (100 mL) followed by
filtration to yield a purple solid. The solid was dried in vacuo,
and then, dissolved in THF (50 mL) to remove insoluble
materials by filtration. The filtrate was evaporated, and the
residue was purified by size exclusion column chromatog-
raphy (THF as eluent, two times). Further purification of the
obtained solid by reprecipitation from THF into hexane
yielded 5 as a purple solid (98.0 mg, 0.0589 mmol, 94%): 1H
NMR (400 MHz, DMSO-d6) d (ppm) 0.86 (m, 12H, –CH3),
1.30–1.59 (m, 40H, –CH2–), 1.85–1.89 (m, 8H, Ar-CH2–
CH2–), 2.91–2.95 (m, 8H, Ar-CH2–), 6.86–6.89 (m, 4H, Ph-
H), 7.14–7.21 (m, 8H, Ph-H), 7.39–7.42 (m, 8H, Ph-H), 7.55–
7.58 (m, 4H, 5,10,15,20-Ar-H), 7.79–7.82 (m, 4H, 5,10,15,20-
Ar-H), 8.24 (br, 4H, –NH), 8.69–8.71 (m, 4H, 5,10,15,20-Ar-
H), 8.90 (s, 8H, pyrrole b-H), 9.14–9.16 (m, 4H, –NH); IR
(KBr)1660, 2854, 2926, 2953, 3302 cmK1;FABMSm/z1661
(MC), 1662 ([MC1]C), 1663 ([MC2]C). Anal. Calcd for
4.3.15. 5,10,15,20-Tetrakis(3-amino-4-octyl-phenyl)por-
phyrin (16). To a stirred hot concd HCl (90 mL, 65 8C) was
added 15 (500 mg, 0.402 mmol) and CHCl3 (20 mL),
followed by addition of SnCl2$2H2O (1.90 g, 8.41 mmol).
The reaction mixture was stirred at the same temperature for
2 h before another portion of SnCl2$2H2O (2.01 g,
8.91 mmol) and CHCl3 (20 mL) was added. The same
process was repeated again (CHCl3, 20 mL; SnCl2$2H2O,
1.83 g, 8.11 mmol), and then, the reaction mixture was
stirred at the same temperature for 1 h. After cooling, to the
mixture was carefully added 27% aqueous NH3 (100 mL)
on an ice bath, and then, CHCl3 (100 mL) was added. The
mixture was stirred vigorously at ambient temperature for
2 h and allowed to pass through a paper filter with Celitew
mounted. The filtrate was washed with water (100 mL) three
times. After dried over anhydrous MgSO4, the solvent was
removed by evaporation. Purification of the resultant solid
by silica gel column chromatography (eluent; hexane/ethyl
acetate, 20:1, v/v) yielded 16 as a purple solid (391 mg,
C104H116N12O4Zn$H2O: C, 74.28; H, 7.07; N, 10.00. Found:
C, 74.08; H, 7.30; N, 9.90.

2510
M. Ezoe et al. / Tetrahedron 62 (2006) 2501–2510
7. (a) Harriman, A.; Porter, G.; Wilowska, A. J. Chem. Soc.,
Acknowledgements
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Uehara, A.; Motonaga, A.; Ogata, T.; Matsuo, T. Chem. Lett.
This work was supported by a Grant-in-Aid for Scientific
Research (B) (No. 15350116) from the Japan Society for the
Promotion of Science. We are also grateful to Dr Y.
Kashiwagi for his helpful discussion.
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