Cyclic oligomers based on complementary Zn(ii) and Sn(iv)-porphyrins

Article abstract of DOI:10.1039/b902408p

The aggregation of a 1: 1 mixture of complementary Sn(iv)- and Zn(ii)-porphyrins into cyclic decameric and dodecameric assemblies has been demonstrated by ¹H NMR, GPC, DOSY and MALDI-TOF spectrometry.

Full text of DOI:10.1039/b902408p

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/njc | New Journal of Chemistry
Cyclic oligomers based on complementary Zn(II) and Sn(IV)-porphyrinswz
Gerald A. Metselaar, Pablo Ballester and Javier de Mendoza*
Received (in Victoria, Australia) 4th February 2009, Accepted 19th February 2009
First published as an Advance Article on the web 3rd March 2009
DOI: 10.1039/b902408p
The aggregation of a 1 : 1 mixture of complementary Sn(IV)- and Zn(II)-porphyrins into cyclic
1
decameric and dodecameric assemblies has been demonstrated by H NMR, GPC, DOSY and
MALDI-TOF spectrometry.
use a two component system, in which each partner bears one
of the coordinating carboxylate moieties (Fig. 1). Many
Introduction
The design and preparation of porphyrin arrays, especially
cyclic examples, has received a great deal of interest, 1–3 mainly
the literature.8 In general, however, these systems rely on the
mixed-metal multi-porphyrin systems have been described in
because of their resemblance to the chlorophyll chromophores
coordination of only one partner to another, and not on
of light-harvesting complexes, which makes them interesting
complementary interactions. In addition, the resulting aggregates
targets for applications in photonic, electronic or optoelectronic
devices.4 Not surprisingly, many different strategies have been
based on complementary Sn(IV)- and Zn(II)-porphyrins have
are usually linear structures. Linear di- and trimeric complexes
been described by Sanders and co-workers.9 In these examples,
employed for the preparation of such arrays, ranging from
direct covalent synthetic approaches1 to supramolecular
a Zn(II)-porphyrin bearing either one or two carboxylic acid
substituents coordinates to a Sn(IV)-porphyrin containing
bonding2 and metal coordination complexes.3 A careful choice
of angles, distances and steric factors is essential to avoid
either one or two pyridyl substituents, causing it to coordinate
competition with one-dimensional polymeric assemblies.
to the Zn(II)-porphyrin.
In 2000, Hunter and co-workers reported the formation of
Here, we present a new strategy, in which complementarity
a dodecameric self-assembled cyclic aggregate formed by
between Sn(IV)- and Zn(II)-porphyrins is used to form exclusively
Co(II)-porphyrins bearing two different pyridine substituents.5
large cyclic mixed porphyrin arrays (Fig. 1). By forming a
‘pentameric core’ of Sn(IV)-porphyrins 1, the remaining axial
cobalt, together with the angle created by using two different
positions should be occupied by the carboxylate groups of the
Axial coordination of these pyridine ligands to the central
substituents, resulted in the formation of cyclic aggregates
instead of linear ones. The resulting aggregates were, however,
fumaramide side arms of N-coordinating Zn(II)-porphyrin 2,
while the zinc atom of 2 should coordinate to the pyridine in
difficult to characterise, because of the paramagnetic nature of
Co(II), which precluded their study by NMR spectroscopy.
Like Co(II)-porphyrins, Sn(IV)-porphyrins are hexacoordinate
compounds.6 Instead of N-containing ligands, however, they
strongly complex O-containing ligands such as alcohols and
carboxylic acids. More importantly, they are diamagnetic in
nature, allowing them to be easily studied by NMR techniques.
An examination of a number of literature reports7 dealing
with the X-ray structures of dicarboxylate Sn(IV)-porphyrin
complexes revealed two important geometric observations that
are essential to designing a cyclic coordination structure based
on these compounds: (1) the Sn–O–C angle usually lies
between 125 and 1401, and (2) the two CQO carbonyl groups
of both axially-bound carboxylates on the porphyrin ring are
oriented in opposite directions. Bearing these restrictions in
mind, all attempts to design a Sn(IV)-porphyrin capable of
forming self-assembled cyclic structures without alternative
linear arrangements were unsuccessful. Instead, we decided to
Institute of Chemical Research of Catalonia, Avgda, Paısos Catalans
¨
16, 43007 Tarragona, Spain. E-mail: jmendoza@iciq.es;
Fax: +34 977-920226; Tel: +34 977-920220
w Dedicated to Professor Roeland Nolte on the occasion of his 65th
birthday.
z Electronic supplementary information (ESI) available: Table with
distances of relevant protons to metal porphyrins and NMR spectra.
See DOI: 10.1039/b902408p
Fig. 1 Sn(IV)-porphyrin 1, Zn(II)-porphyrin 2 and their proposed
cyclic decameric self-assembled aggregate [1ꢀ2]5.
ꢁc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2009
New J. Chem., 2009, 33, 777–783 | 777

View Article Online
the meso-position of 1. Thus, in our design, the two different
porphyrins complement each other’s coordination needs.
Moreover, the Zn(II)-porphyrin directs the aggregation of
the Sn(IV)-porphyrin, preventing the formation of undesired
linear aggregates.
Results and discussion
Synthesis
Porphyrins 1 and 2 were prepared via standard procedures.
Thus, free base porphyrin 3 was prepared via a reaction between
p-tolualdehyde and the corresponding dipyrromethane in
propionic acid. Tin was then inserted by treating 3 with
tin(II) chloride in pyridine under reflux. After a basic aqueous
workup, Sn(IV)-porphyrin 4, bearing axial hydroxy groups, was
obtained. Hydrolysis of its methyl ester group was achieved by
treatment with LiOH in MeOH. After an acidic workup
with acetic acid, the desired Sn(IV)-porphyrin, 1, was obtained
bearing acetate groups in the axial positions (Scheme 1).
The synthesis of Zn(II)-porphyrin 2 (Scheme 2) started with
the preparation of nitroporphyrin 5 by refluxing a statistical
mixture of pyrrole, p-tolualdehyde and m-nitrobenzaldehyde in
propionic acid. The nitro group was subsequently reduced with
tin(II) chloride in concentrated HCl to yield aminoporphyrin 6.
The reaction of 6 with fumaric acid chloride monoethyl
ester afforded free base porphyrin 7. Zinc insertion using
Zn(OAc)2 and subsequent hydrolysis of the ethyl ester gave the
desired Zn(II)-porphyrin 2, with tetrahydrofuran coordinated to
the metal.
Scheme 2 Synthetic route to Zn(II)-porphyrin 2.
by gel permeation chromatography (GPC) using toluene
as mobile phase, in which it was moderately soluble
(B0.7 mg mLꢂ1
superimposed to those of monomeric model compounds 3
and 8 clearly show the small increase in size going from
monomer 3 to 8 (elution times t = 8.8 and 8.3 min, respectively).
)
(Fig. 2). Chromatograms of [1ꢀ2]n
Structural study
Zn(II)-porphyrin 2, which is poorly soluble in pure CDCl3,
readily dissolved as a 1 : 1 mixture with Sn(IV)-porphyrin 1.
1
The H NMR spectrum initially showed only broad signals,
suggesting a mixture of oligomers in slow equilibrium. Upon
equilibration for ca. 24 h, however, a spectrum of sharp signals
was obtained, consistent with the formation of a thermo-
dynamically favored product. The THF and acetic acid,
coordinated to Zn and Sn, respectively, were released upon
formation of porphyrin aggregate [1ꢀ2]n.
The formed assembly could be conveniently purified from
remaining monomeric porphyrins by passing it through a size
exclusion column (SEC). The assembly was first investigated
Fig. 2 A: Superimposed GPC traces of 3, 8 and [1ꢀ2]n, and (B) GPC
traces of [1ꢀ2]n at different concentrations.10
Scheme 1 Synthetic route to Sn(IV)-porphyrin 1.
ꢁc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2009
778 | New J. Chem., 2009, 33, 777–783

View Article Online
The signal observed for [1ꢀ2]n at t = 6.1 min indicates the
formation of a single pure oligomeric species. The signal did not
shift upon dilution (Fig. 2B, concentration range 2–0.1 mg mLꢂ1),
in good agreement with a well-defined cyclic aggregate and
excluding the presence of linear oligomers, which would be
expected to increase in length with increasing concentration.5
At first sight, diffusion-ordered spectroscopy (DOSY)
(Fig. 3) shows only one oligomeric species to be present in
solution. However, by expanding the D axis in the DOSY
spectrum (Fig. 3), it becomes evident that the observed
signal for log D actually consists of two separate signals with
rather similar diffusion coefficients, D = 2.27 ꢃ 10ꢂ10 and
2.36 ꢃ 10ꢂ10 m2 sꢂ1, corresponding to r = 17.7 and 17.1 A,
respectively, according to the Stokes–Einstein equation.11 This
suggests that there are two, instead of one, discrete species in
solution that are stable on the NMR timescale due to slow
exchange of Sn(IV)–carboxylate coordination.12
Molecular modeling (Fig. 4)13 allowed the hydrodynamic
radius to be estimated for a decameric [1ꢀ2]5 and dodecameric
[1ꢀ2]6 assembly, as r = 19.2 and 20.0 A, respectively, using the
method developed by Cohen and co-workers.14 The moderate
discrepancies between the estimated values and those calculated
using the Stokes–Einstein equation are likely to be due to
the non-spherical character of the expected disc-shaped
aggregates.11 However, a direct comparison between both
aggregates (of similar shape) should be little influenced by the
non-spherical nature of the species. Therefore, from the
Stokes–Einstein equation, it follows directly that, at constant
temperature:
Fig. 4 Top and side views of optimised structures for A: decamer
[1ꢀ2]5 and B: dodecamer [1ꢀ2]6.13
r
/r
B D
/D
[1ꢀ2]6 [1ꢀ2]5
[1ꢀ2]5 [1ꢀ2]6
Using the values given above for D[1ꢀ2] and D[1ꢀ2] , a ratio of
5
6
D[1ꢀ2] /D[1ꢀ2] = 0.96 is obtained, which nicely matches the
6
5
theoretical value of r[1ꢀ2] /r[1ꢀ2] = 0.96.
Fig. 5 The upfield-shifted region of the 1H NMR spectrum of [1ꢀ2]n.
5
6
Although completely assigning the 1H NMR spectrum
was complicated by extensive overlapping of signals in the
aromatic region, all upfield-shifted signals could be identified
and assigned to well-defined cyclic oligomeric assemblies using
COSY, NOESY and ROESY (Fig. 5 and ESIz) techniques.
Because of their fixed, well-defined conformation within the
assembly, the protons of the benzoic acid group give rise to
1
four different signals in the H NMR spectrum.15 Moreover,
since the distances between the aromatic benzoic acid protons
and the Sn(IV)-porphyrin plane are not the same in [1ꢀ2]5 and
[1ꢀ2]6 (ESI, Table S1z), and the magnitude of the upfield shift
of the protons depends on their distance from the porphyrin
plane,12 eight different signals for these protons are observed
in the spectrum.
The protons of the fumaramide also display a significant
upfield shift (Dd = 3.3), and different signals can be identified
for the decameric and dodecameric assemblies. Finally, the
protons of the pyridine ligands in position 2, vicinal to the
N-atom coordinated to the Zn(II)-porphyrin, were also
identified at very high field at d = 2.85 for [1ꢀ2]6, and at
d = 2.75 and 2.85 for [1ꢀ2]5, respectively. It is noteworthy that
no residual signals are observed for monomeric or alternative
oligomeric assemblies.
The ratio between [1ꢀ2]5 and [1ꢀ2]6 in CDCl3 solution at
room temperature could be estimated as approximately 1 : 0.9
by comparing the integrals of isolated signals of the different
assemblies (Fig. 6). Heating this solution at 65 1C overnight
lead to an increase of [1ꢀ2]6 to a ratio of 1 : 2.1, which
subsequently equilibrated back to the original ratio upon
Fig. 3 The DOSY spectrum of [1ꢀ2]n in CDCl3. The blown-up region
shows the part of the spectrum enclosed in the black square.
ꢁc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2009
New J. Chem., 2009, 33, 777–783 | 779

View Article Online
Fig. 6 A: The informative part of the 1H NMR spectrum of [1ꢀ2]n (11.5 mg in 0.5 mL CDCl3) before heating at 65 1C overnight and spectra after
standing at RT for different times. B: The ratio between [1ꢀ2]5 and [1ꢀ2]6, as derived by 1H NMR spectroscopy, as a function of cooling time after
heating at 65 1C overnight.
Fig. 7 A: The MALDI-TOF mass spectrum of [1ꢀ2]n, indicating the main masses and their corresponding fragments. B: Aggregates [1ꢀ2]5 and
[1ꢀ2]6, and their proposed fragmentation pathways leading to the observed mass fragments seen by MALDI-TOF mass spectrometry.
standing at ambient temperature for several days. Further
evidence for the formation of two different discrete aggregates,
Conclusions
In summary,
p-benzoic acid groups in opposite meso-positions, and a
Zn(II)-porphyrin bearing 3-phenylfumaramide in one
a Sn(IV)-porphyrin bearing p-pyridyl and
[1ꢀ2]5 and [1ꢀ2]6, came from MALDI-TOF mass spectrometry
of a sample of [1ꢀ2]n, prepared from a CHCl3 solution (Fig. 7).
The only two discrete species that could be observed, i.e. those
containing an equal number of 1 and 2 units, were [1ꢀ2]5 and
[1ꢀ2]6, with M = 8178 and 9820 g molꢂ1, respectively.
a
meso-position, were synthesized and their aggregation
behaviour in a 1 : 1 ratio studied. Combining the results
of MALDI-TOF mass spectrometry and DOSY, it was
concluded that at equilibrium in solution, a mixture of cyclic
decameric and dodecameric assemblies were present. These
aggregates were quite stable and could be purified by size
exclusion chromatography. GPC at different concentrations
confirmed the same aggregates to be present at different
concentrations, thereby confirming that no linear aggregates
were present.
All of the other signals in the spectrum could be assigned to
fragments of [1ꢀ2]5 and [1ꢀ2]6, based on the loss of one or
several 1 and/or 2 moieties. As expected, the external shell of
the Zn(II)-porphyrin is more prone to being lost than the
Sn(IV)-porphyrin 1, since it is only bound by one strong
Sn(IV)–carboxylate bond and a weak Zn(II)–pyridine inter-
action. The Sn(IV)-porphyrin 1, on the other hand, is fixed in
the aggregate via two strong Sn(IV)–carboxylate bonds. It is
noteworthy that the loss of one Sn(IV)-porphyrin is always
accompanied by the loss of at least two Zn(II)-porphyrins.
These co-oligomeric cyclic aggregates built up from two
different alternating porphyrins offer unique and interesting
ꢁc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2009
780 | New J. Chem., 2009, 33, 777–783

View Article Online
possibilities for materials design by undertaking suitable
modifications at the remaining meso-positions.
collected and dried over anhydrous MgSO4. The volatiles were
evaporated to dryness to yield a black residue. The crude
material was first pre-purified by column chromatography (silica)
using CH2Cl2/MeOH (97 : 3) as the eluent. The first fraction
that was isolated and precipitated with MeOH was mainly
5,15-bis(4-tolyl)-10,20-bis[4-(methoxycarbonylphenyl)] porphyrin
(0.160 g, 8.5%). A second chromatographic purification with
CH2Cl2/EtOAc (98 : 2) as the eluent yielded 3, which was
precipitated in MeOH to give a bright purple solid (71 mg,
4.1%). mp. 4315 1C. 1H NMR (400 MHz, CDCl3): d 9.04
(d, 2H, Pyr-4, J = 4.4 Hz), 8.92 (m, 4H, b-pyrrole II + III), 8.80
(m, 4H, b-pyrrole I + IV), 8.45 (d, 2H, Ar-6, J = 8.2 Hz), 8.31
(d, 2H, Ar-5, J = 8.2 Hz), 8.17 (d, 2H, Pyr-3, J = 4.3 Hz),
8.09 (d, 4H, Ar-2, J = 7.8 Hz), 7.57 (d, 4H, Ar-1, J = 7.7 Hz),
4.12 (s, 3H, OMe), 2.71 (s, 6H, Me) and ꢂ2.79 (s, 2H, NH).
13C NMR (100 MHz, CDCl3): d 167.3, 150.5, 148.3, 146.9,
138.8, 137.6, 134.5, 129.7, 129.4, 127.9, 127.5, 120.9, 119.2,
116.5, 52.4 and 21.5. UV (CHCl3): l [e (/ꢃ103 L molꢂ1 cmꢂ1)]
420 (438), 515 (17), 550 (8), 589 (5) and 646 (4). MALDI-TOF
m/z = 701.3 [M]+.
Experimental
Materials and methods
All chemicals were purchased from commercial sources and
used without further purification. Solvents were dried using
a solvent purification system (SPS). Melting points were
measured on a Buchi B-540 apparatus. NMR spectra were
¨
obtained using Bruker Avance 400 (1H: 400 MHz, 13C:
100 MHz) and 500 (1H: 500 MHz, 13C: 125 MHz) Ultrashield
spectrometers. The deuterated solvents used are indicated in
each case. Chemical shifts (d) are expressed in ppm and are
referred to the residual peak of the solvent. Mass analysis was
performed using a Bruker MALDI-TOF spectrometer. UV
spectra were recorded on a Shimadzu UV-1700 PharmaSpec
UV-vis spectrophotometer. Thin layer chromatography
(TLC) was performed on Alugram Sil G-25/UV254-coated
aluminium sheets (Macherey-Nagel) with detection by UV at
254 nm. GPC was carried out on a Waters Styragel HR
column (7.8 ꢃ 300 mm) in toluene using UV detection.
5,15-[Bis(4-tolyl)]-10-[4-(methoxycarbonylphenyl)]-20-(4-
pyridyl) tin(IV)-bishydroxyporphyrin (4). Free base porphyrin 3
(63 mg, 90 mmol) and SnCl2ꢀ2H2O (122 mg, 0.54 mmol) in
10 mL pyridine were heated to reflux for 2 h. The reaction
mixture was then distributed between CHCl3 and water, and
the organic phase was washed with water (3 ꢃ 20 mL), dried
over Na2SO4 and evaporated to dryness. The product was
precipitated from CH2Cl2 by the addition of hexane to yield 4
as a green solid (60 mg, 80%). mp. 4315 1C. 1H NMR
(400 MHz, CDCl3): d 9.21 (m, 4H, b-pyrrole II + III), 9.10
(m, 4H, b-pyrrole I + IV and Pyr-4), 8.51 (d, 2H, Ar-6,
J = 8.1 Hz), 8.42 (d, 2H, Ar-5, J = 8.1 Hz), 8.30 (m, 2H,
Pyr-3), 8.21 (d, 4H, Ar-2, J = 7.8 Hz), 7.64 (d, 4H, Ar-1,
J = 7.8 Hz), 4.13 (s, 3H, OMe), 2.74 (s, 6H, Me) and ꢂ7.42
(s, 2H, OH). 13C NMR (100 MHz, CDCl3): d 167.1, 149.8,
149.4, 148.5, 147.1, 147.0, 146.1, 145.8, 145.5, 138.0, 135.1,
135.0, 133.5, 133.3, 132.3, 131.8, 130.2, 129.7, 128.2,
127.8, 122.1, 120.2, 117.5, 52.5 and 21.5. UV (CHCl3):
l [e (/ꢃ103 L molꢂ1 cmꢂ1)] 427 (550), 560 (20) and 600 (12).
MALDI-TOF m/z = 854.2 [M + H]+.
Synthesis
Compounds 5-(4-pyridyl)dipyrromethane and 5-(p-tolyl)-
dipyrromethane were prepared via literature procedures.16,17
The ring atoms in the porphyrin systems were labelled as
shown in Fig. 8.
Compounds
5,15-[Bis(4-tolyl)]-10-(4-methylbenzoate)-20-(4-pyridyl)-
porphyrin (3). A mixture of 5-(4-pyridyl)dipyrromethane (0.55 g,
2.46 mmol), 5-[4-(methoxycarbonylphenyl)]dipyrromethane
(0.69 g, 2.46 mmol) and p-tolualdehyde (0.58 mL, 4.92 mmol)
in 40 mL propionic acid was heated at reflux for 2.5 h under air,
after which the solvent was removed in vacuo. The
resulting residue was dissolved in CH2Cl2 (100 mL) and washed
with a 1 M K2CO3 solution (3 ꢃ 20 mL). The organic layer was
5,15-[Bis(4-tolyl)]-10-[4-(carboxyphenyl)]-20-(4-pyridyl) tin(IV)-
bishydroxyporphyrin (1). Methyl ester Sn(IV)-porphyrin 4
(40 mg, 47 mmol) was dissolved in 20 mL MeOH, and 4 mL
of a 1M aqueous LiOH solution was added. The mixture was
stirred at 50 1C overnight and the MeOH then evaporated
under reduced pressure. To the resulting aqueous suspension
was added AcOH and 10 mL of water, and the aqueous
solution was extracted with CHCl3. The organic phase was
washed with water, dried over Na2SO4 and evaporated to
dryness. The product was further purified by precipitation
from CH2Cl2 by the addition of hexane to give 1 as a
greenish powder (33 mg, 78%). mp. 4315 1C. Due to the
self-association of 1, even in the presence of excess AcOH, no
well defined NMR spectra could be obtained. UV (CHCl3):
l [e (/ꢃ103 L molꢂ1 cmꢂ1)] 426 (287), 559 (15) and 599 (8).
MALDI-TOF m/z = 864.2 [M ꢂ OAc]+.
Fig. 8 Atom labelling for porphyrins 1–8.
ꢁc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2009
New J. Chem., 2009, 33, 777–783 | 781

View Article Online
5,10,15-[Tris(4-tolyl)]-20-(3-nitrophenyl)porphyrin (5).
A
(0.105 g, 84%). mp. 223–224 1C. 1H NMR (400 MHz, CDCl3):
solution of pyrrole (2.91 mL, 41.69 mmol) in 20 mL propionic
acid was added dropwise over 30 min to a solution of
m-nitrobenzaldehyde (1.00 g, 6.62 mmol) and p-tolualdehyde
(3.92 mL, 33.09 mmol) in 200 mL propionic acid at reflux. The
reaction was stirred at reflux for an additional 3 h, then cooled
to room temperature and evaporated in vacuo. The residue was
dissolved in CHCl3, washed with saturated aqueous NaHCO3,
dried over Na2SO4 and evaporated to dryness. The tetratolyl
porphyrin was precipitated from 50 mL of CH2Cl2/hexane
(6 : 4). The crude product was then purified by column
chromatography (CH2Cl2/hexane = 6 : 4). Precipitation from
CH2Cl2 by the addition of MeOH gave 5 as a purple solid
d 8.85 (m, 8H, b-pyrrole), 8.27 (s, 1H, Ar-6), 8.23
(d, 1H, Ar-3, J = 8.3 Hz), 8.09 (m, 6H, Ar-2), 8.01 (d, 1H,
Ar-5, J = 8.0 Hz), 7.89 (s, 1H, NHamide), 7.72 (t, 1H, Ar-4, J =
7.8 Hz), 7.55 (m, 6H, Ar-1), 7.14 (d, 1H, CH-7, J = 15.2 Hz),
6.98 (d, 1H, CH-8, J = 15.2 Hz), 4.16 (q, 2H, CH2, J = 7.1
Hz), 2.70 (s, 9H, CH3), 1.13 (t, 3H, CH3, J = 7.1 Hz) and ꢂ2.77
(s, 2H, NH). 13C NMR (100 MHz, CDCl3): d 165.6, 161.9,
143.2, 139.2, 137.4, 136.6, 135.9, 134.5, 131.6, 131.4, 127.4,
126.0, 120.5, 120.3, 119.5, 118.5, 61.4, 21.5 and 13.8. UV
(CHCl3): l [e (/ꢃ103 L molꢂ1 cmꢂ1)] 420 (511), 516 (19), 552
(9), 590 (6) and 648 (6). MALDI-TOF m/z = 798.3 [M + H]+.
5,10,15-[Tris(4-tolyl)]-20-(3-phenylfumaramide) zinc(II)-porphyrin
ethyl ester (8). Free base porphyrin 7 (78 mg, 98 mmol)
and zinc acetate (0.18 g, 0.98 mmol) were stirred overnight
in 20 mL of CHCl3/MeOH (7 : 3). The solution was then
washed with water (3 ꢃ 20 mL), dried over Na2SO4 and
evaporated to dryness. The residue was taken up with the
minimum amount of CH2Cl2 and precipitated by the addition
of hexane to give 8 as a purple powder (84 mg, 100%). mp.
250–254 1C. 1H NMR (400 MHz, CDCl3 + 20 mL MeOD): d
8.86 (m, 8H, b-pyrrole), 8.33 (s, 1H, Ar-6), 8.12 (d, 1H, Ar-5,
J = 8.2 Hz), 8.05 (m, 7H, Ar-2 + NHamide), 7.98 (d, 1H, Ar-3,
J = 7.0 Hz), 7.66 (t, 1H, Ar-4, J = 7.9 Hz), 7.50 (m, 6H,
Ar-1), 7.08 (d, 1H, CH-7, J = 15.3 Hz), 6.87 (d, 1H, CH-8,
J = 15.3 Hz), 4.19 (q, 2H, CH2, J = 7.1 Hz), 2.67 (s, 9H, CH3)
and 1.25 (t, 3H, CH3, J = 7.1 Hz). 13C NMR (100 MHz,
CDCl3): d 166.1, 162.2, 150.2, 150.1, 149.7, 144.2, 140.3, 137.1,
136.8, 136.0, 134.4, 131.8, 131.6, 131.3, 131.2, 130.7, 127.1,
127.0, 126.0, 120.8, 120.7, 119.3, 118.8, 61.3, 21.4 and 14.3.
UV (CHCl3): l [e (/ꢃ103 L molꢂ1 cmꢂ1)] 425 (433), 554 (15)
and 594 (5). MALDI-TOF m/z = 861.3 [M]+.
1
(0.34 g, 7.3%). mp. 4315 1C. H NMR (400 MHz, CDCl3):
d 9.09 (s, 1H, Ar-6), 8.91 (m, 6H, b-pyrrole II + III + IV),
8.70 (m, 2H, b-pyrrole I), 8.66 (d, 1H, Ar-5, J = 8.3 Hz), 8.54
(d, 1H, Ar-3, J = 7.4 Hz), 8.10 (d, 6H, Ar-2, J = 7.4 Hz), 7.93
(t, 1H, Ar-4, J = 7.8 Hz), 7.56 (d, 6H, Ar-1, J = 7.4 Hz), 2.71
(s, 9H, Me) and ꢂ2.76 (s, 2H, NH). 13C NMR (100 MHz,
CDCl3): d 147.0, 144.1, 139.8, 139.1, 139.0, 137.5, 134.5, 128.3,
127.6, 127.5, 122.8, 121.1, 120.7, 116.0 and 21.5. UV (CHCl3):
l [e (/ꢃ103 L molꢂ1 cmꢂ1)] 421 (485), 517 (22), 552 (10), 590 (7)
and 647 (6). MALDI-TOF m/z = 701.3 [M]+.
5,10,15-[Tris(4-tolyl)]-20-(3-aminophenyl)porphyrin (6). Nitro-
porphyrin 5 (0.130 g, 0.19 mmol) was dissolved in a mixture
of dioxane (12 mL) and concentrated HCl (38 mL).
Tin(II) chloride (0.23 g, 1.01 mmol) was then added and the
mixture refluxed for 3 h. The mixture was cooled to room
temperature, basified by the addition of 30% aqueous NH3
and the aqueous solution extracted with CH2Cl2. The organic
phase was dried over Na2SO4 and evaporated to dryness. The
porphyrin was precipitated from CH2Cl2 by the addition of
MeOH to yield 6 as a purple solid (0.100 g, 81%). mp. 4315 1C.
1H NMR (400 MHz, CDCl3): d 8.96 (d, 2H, b-pyrrole I,
J = 4.8 Hz), 8.88 (m, 6H, b-pyrrole II + III + IV), 8.12
(d, 6H, Ar-2, J = 7.8 Hz), 7.64 (d, 1H, Ar-6, J = 7.4 Hz), 7.56
(d, 6H, Ar-1, J = 7.6 Hz), 7.54 (m, 1H, Ar-3), 7.50 (t, 1H,
Ar-4, J = 7.7 Hz), 7.05 (m, 1H, Ar-3), 3.85 (s, 2H, NH2), 2.72
(s, 9H, CH3) and ꢂ2.73 (s, 2H, NH). 13C NMR (100 MHz,
CDCl3): d 144.5, 143.3, 139.3, 137.3, 134.5, 127.4, 127.3,
126.0, 122.0, 120.1, 120.0, 114.3 and 21.5. UV (CHCl3):
l [e (/ꢃ103 L molꢂ1 cmꢂ1)] 421 (417), 517 (16), 551 (8), 592
(5) and 648 (6). MALDI-TOF m/z = 671.4 [M]+.
5,10,15-[Tris(4-tolyl)]-20-(3-phenylfumaramide)
zinc(II)-
porphyrin (2). Zn(II)-porphyrin ester 10 (61 mg, 71 mmol) was
dissolved in 5 mL THF, and 0.5 mL of a 1 M aqueous LiOH
solution was added. After stirring at room temperature for 4 h,
the reaction mixture was divided between CHCl3 and 10% citric
acid. The organic phase was washed with water, dried over
Na2SO4 and evaporated to dryness. Subsequently, the product
was precipitated with CH2Cl2/hexane to quantitatively give 2 as a
purple powder. mp. 284–288 1C. 1H NMR (400 MHz,
CDCl3 + 20 mL MeOD): d 8.87 (m, 8H, b-pyrrole), 8.34
(s, 1H, Ar-6), 8.12 (d, 1H, Ar-5, J = 8.9 Hz), 8.06
(m, 7H, Ar-2 + NHamide), 7.98 (d, 1H, Ar-3, J = 7.5 Hz),
7.66 (t, 1H, Ar-4, J = 7.9 Hz), 7.50 (m, 6H, Ar-1), 7.08 (d, 1H,
CH-7, J = 15.3 Hz), 6.87 (d, 1H, CH-8, J = 15.3 Hz) and 2.67
(s, 9H, CH3). 13C NMR (100 MHz, CDCl3): d 167.6, 162.6,
150.0, 149.6, 140.3, 137.3, 136.6, 136.1, 134.3, 131.6, 131.5, 131.4,
131.2, 130.8, 126.9, 126.8, 120.5, 118.8 and 21.3. UV (CHCl3): l
[e (/ꢃ103 L molꢂ1 cmꢂ1)] 424 (322), 553 (12) and 595 (4).
MALDI-TOF m/z = 833.3 [M]+.
5,10,15-[Tris(4-tolyl)]-20-(3-phenylfumaramide)porphyrin ethyl
ester (7). Fumaric acid monoethyl ester (65 mg, 0.44 mmol) was
dissolved in 5 mL of dry toluene, and thionyl chloride (0.16 mL,
2.23 mmol) was added. The mixture was stirred overnight at
reflux and the solvents then evaporated in vacuo. A solution of
aminoporphyrin 6 (0.10 g, 0.15 mmol) and diisopropyl ethyl
amine (1.11 mL, 6.70 mmol) in 5 mL CH2Cl2 was added to the
residue. After stirring at room temperature for 3 h, the
reaction mixture was extracted with 10% citric acid, saturated
aqueous NaHCO3 and water, dried over Na2SO4 and evapo-
rated to dryness. The crude product was purified by column
chromatography (CH2Cl2/MeOH = 98 : 2), and was subse-
quently precipitated from the minimum amount of CH2Cl2 by
the addition of MeOH to give 7 as a purple solid powder
Acknowledgements
This work was supported by the Spanish Ministry of Science
and Education (MEC) (projects JCL-2009-1069 (to G. A. M.)
and CTQ2005-08948-C02-01/BQU), Consolider Ingenio 2010
(Grant CSD2006-0003) and the ICIQ Foundation. We thank
ꢁc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2009
782 | New J. Chem., 2009, 33, 777–783

View Article Online
Dr N. Cabello for mass spectrometry and L. H. Herna
´
GPC measurements.
ndez for
Acta Crystallogr., Sect. C: Cryst. Struct. Commun., 1997, 53,
725–726; (c) H. J. Kim, K.-M. Park, T. K. Ahn, S. K. Kim,
K. S. Kim, D. Kim and H.-J. Kim, Chem. Commun., 2004, 22,
2594–2595; (d) H.-J. Kim, H. J. Jo, J. Kim, S.-Y. Kim, D. Kim and
K. Kim, CrystEngComm, 2005, 7, 417–420; (e) P. R. Brotherhood,
R. A.-S. Wu, P. Turner and M. J. Crossley, Chem. Commun., 2007,
225–227.
8 Some examples of mixed-metal multi-porphyrin arrays based on
tin-porphyrins: (a) L. Giribabu, T. A. Rao and B. G. Maiya, Inorg.
Chem., 1999, 38, 4971–4980; (b) B. G. Maiya, N. Bampos,
A. A. Kumar, N. Feeder and J. K. M. Sanders, New J. Chem.,
2001, 25, 797–800; (c) A. A. Kumar, L. Giribabu, D. R. Reddy and
B. G. Maiya, Inorg. Chem., 2001, 40, 6757–6766; (d) J. E. Redman,
N. Feeder, S. J. Teat and J. K. M. Sanders, Inorg. Chem., 2001, 40,
2486–2499; (e) J. C. Hawley, N. Bampos and J. K. M. Sanders,
Chem.–Eur. J., 2003, 9, 5211–5222; (f) I. Bouamaied, T. Coskun
and E. Stulz, Struct. Bonding, 2006, 121, 1–47.
References
1 (a) A. K. Burrel, D. L. Officer, P. G. Plieger and D. C. W. Reid,
Chem. Rev., 2001, 101, 2751–2796; (b) Y. Nakamura, N. Aratani
and A. Osuka, Chem. Soc. Rev., 2007, 36, 831–845.
2 (a) M. J. Gunter, Struct. Bonding, 2006, 121, 263–295;
(b) T. S. Balaban, N. Berova, C. M. Drain, R. Hauschild,
X. Huang, H. Kalt, S. Lebedkin, J.-M. Lehn, F. Nifaitis,
G. Pescitelli, V. I. Prokhorenko, G. Riedel, G. Smeureanu and
J. Zeller, Chem.–Eur. J., 2007, 13, 8411–8427.
3 (a) H. Krupitsky, Z. Stein and I. Goldberg, J. Inclusion Phenom.
Mol. Recognit. Chem., 1994, 18, 177–192; (b) K.-J. Lin, Angew.
´
Chem., Int. Ed., 1999, 38, 2730–2732; (c) J. Wojaczynski and
L. Latos-Grazynski, Coord. Chem. Rev., 2000, 204, 113–171;
´
˙
9 H.-J. Kim, N. Bampos and J. K. M. Sanders, J. Am. Chem. Soc.,
1999, 121, 8120–8121.
(d) T. Imamura and K. Fukushima, Coord. Chem. Rev., 2000,
198, 133–156; (e) E. Deiters, V. Bulach and M. W. Hosseini, Chem.
Commun., 2005, 3906–3908; (f) E. Iengo, E. Zangrando and
E. Alessio, Acc. Chem. Res., 2006, 39, 841–851; (g) C. Maeda,
T. Kamada, N. Aratani and A. Osuka, Coord. Chem. Rev., 2007,
251, 2743–2752; (h) E. Kuhn, V. Bulach and M. W. Hosseini,
¨
Chem. Commun., 2008, 5104–5106.
4 (a) D. Holten, D. F. Bocian and J. S. Lindsey, Acc. Chem. Res., 2002,
35, 57–69; (b) F. Scandola, C. Chiorboli, A. Prodi, E. Iengo and
E. Alessio, Coord. Chem. Rev., 2006, 250, 1471–1496; (c) A. Satake
and Y. Kobuke, Org. Biomol. Chem., 2007, 5, 1679–1691;
10 For the GPC experiments at variable concentrations, the Zn(II)-
porphyrin had more lipophilic p-pentylphenyl groups in meso-
positions instead of p-tolyl groups.
11 r = kbT/6pZD, where kb is the Boltzmann constant, T is the
absolute temperature and Z is the viscosity of the medium. It has to
be noted that this equation considers species in solution to be
spherical.
12 J. C. Hawley, N. Bampos, R. J. Abraham and J. M. K. Sanders,
Chem. Commun., 1998, 661–662.
13 CAChe WorkSystem, version 6.1.12.33, Fujitsu Limited.
14 P. Timmerman, J.-L. Weidmann, K. A. Joliffe, L. J. Prins,
D. N. Reinhoudt, S. Shinkai, L. Frish and Y. Cohen, J. Chem.
Soc., Perkin Trans. 2, 2000, 2077–2089.
(d) N. Wintjes, D. Bonifazi, F. Cheng, A. Kiebele, M. Stohr,
¨
T. Jung, H. Spillmann and F. Diederich, Angew. Chem., Int. Ed.,
2007, 46, 4089–4092; (e) G. Sedghi, K. Sawada, L. J. Esdaile,
M. Hoffmann, H. L. Anderson, D. Bethell, W. Haiss, S. J. Higgins
and R. J. Nichols, J. Am. Chem. Soc., 2008, 130, 8582–8583.
5 R. A. Haycock, C. A. Hunter, D. A. James, U. Michelsen and
L. R. Sutton, Org. Lett., 2000, 2, 2435–2438.
15 G. A. Metselaar, J. K. M. Sanders and J. de Mendoza, Dalton
Trans., 2008, 588–590.
16 C. Ruzie, L. Michaudet and B. Boitrel, Tetrahedron Lett., 2002, 43,
´
7423–7426.
17 K. F. Cheng, C. M. Drain and K. Grohmann, Inorg. Chem., 2003,
42, 2075–2083.
6 D. P. Arnold and J. Blok, Coord. Chem. Rev., 2004, 248, 299–319.
7 (a) I.-C. Liu, C.-C. Lin and J.-H. Chen, Polyhedron, 1996, 15,
459–463; (b) W. J. Belcher, P. J. Brothers and C. E. F. Rickard,
ꢁc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2009
New J. Chem., 2009, 33, 777–783 | 783