Nanometer-sized reactor - A porphyrin-based model system for anion species

Article abstract of DOI:10.1002/chem.201100633

Although many cagelike molecules can create a catalytic environment for promoting chemical reactions, the construction of receptors that can host anionic species and sensitize their reaction is novel. Here we report the photochemically induced dimerizatio

Full text of DOI:10.1002/chem.201100633

FULL PAPER
DOI: 10.1002/chem.201100633
Nanometer-Sized Reactor—A Porphyrin-Based Model System for Anion
Species
Yong-jun Li,*[a] Ying-jie Zhao,[a] Amar H. Flood,[b] Chao Liu,[a] Hui-biao Liu,[a] and
Yu-liang Li*[a]
Abstract: Although many cagelike
molecules can create a catalytic envi-
ronment for promoting chemical reac-
tions, the construction of receptors that
can host anionic species and sensitize
their reaction is novel. Here we report
the photochemically induced dimeriza-
tion of the anion radicals of TCNQ
(7,7,8,8-tetracyano-para-quinodime-
thane) in organic solvent under aerobic
conditions when they are encapsulated
inside a cationic photoactive receptor.
There is clear evidence for a rate in-
crease of over two orders of magni-
tude, photosensitization of the host,
and demonstrated turnover of the cata-
lyst.
Keywords: anions
systems photosensitization
porphyrins · reactors
·
host–guest
·
·
Introduction
motifs into a single receptor (Figure 1). In this capacity, por-
phyrins have remarkable photochemical, electrochemical,
and catalytic properties that have helped attract attention to
their use as reaction centers.[10] 1,2,3-Triazoles are new
Developing synthetic host systems that are capable of bind-
ing to specifically targeted substrates and then mimicking
the various chemical processes in nature have long been sig-
nificant goals in chemistry.[1] Encapsulation within the inner
space[2] of a molecular container can accelerate a reaction,[3]
alter the course of reactions in limited quarters,[4] perturb
equilibria,[5] contort conformations,[6] and either stabilize re-
active reagents[7] or reaction intermediates.[8,9] Intermolecu-
lar chemical reactions of two or more substrates encapsulat-
ed in a molecular cage can be greatly accelerated and poten-
tially controlled due to the dramatically increased effective
molarity and the strictly regulated orientation of the sub-
strates inside the cavity.[3] Such systems[3] artificially mimic
the ability of enzymes to manipulate reaction energetics and
chemo-, regio-, and/or stereospecificities. Anions have a
lower charge to radius ratio, a wide range of geometries,
and they are pH sensitive, so the construction of receptors
that can encapsulate anionic species and sensitize their reac-
tion is challenging and there is no report until now.
Figure 1. Design strategy of a photoactive nanoreactor.
motifs that can participate in multiple noncovalent interac-
tions, such as anion recognition[11] within flexible[12] and
shape-persistent triazolophanes,[13] and in foldamers,[14] and
they can help facilitate self-assembly.[15] Herein, we first
present the versatile preparation of a nanometer-sized mac-
rocycle based on a photoactive porphyrin moiety and on cat-
ionic triazolium and pyridinium units by taking advantage of
the CuI-catalyzed “click chemistry”[16] between azides and
acetylenes. Secondly, the anion-binding properties of this
cationic macrocyclic host are verified and then employed to-
gether with the photochemical porphyrin to establish the
use of this macrocycle as a reactor for the dimerization of
7,7,8,8-tetracyano-para-quinodimethane (TCNQ) radical
anions.
One place to begin the design of synthetic reactors is to
combine recognized catalytic moieties with known binding
[a] Dr. Y.-j. Li, Y.-j. Zhao, C. Liu, Dr. H.-b. Liu, Prof. Y.-l. Li
CAS Key Laboratory of Organic Solids
Beijing National Laboratory for Molecular Sciences
Institute of Chemistry, Chinese Academy of Sciences
Beijing 100190 (P.R. China)
Fax : (+86)10-82616576
E-mail: liyj@iccas.ac.cn
ylli@iccas.ac.cn
[b] Prof. A. H. Flood
ÀC
The dimerization of [TCNQ] radicals was selected as a
Chemistry Department, Indiana University
800 East Kirkwood Avenue, Bloomington, IN 47405 (USA)
model reaction on account of the anionic charge of the reac-
tants and the existing knowledge of its dimerization
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201100633.
2À
(Figure 1). The formation of [TCNQ]2 dimers has been ex-
Chem. Eur. J. 2011, 17, 7499 – 7505
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
7499

perimentally reported[17] in both solids and aqueous solu-
wherein the two biphenylene linkers connecting the large
porphyrin to the smaller pyridinium were used to infuse the
cavity with extra rigidity.
tion.[17b,d] The dimers are linked by either s or p bonds
2À
(Scheme 1). The p-[TCNQ]2 dianion dimers have long,
[17c,d,f]
À
multicenter intradimer C C bonding,
whereas the s-
Results and Discussion
3+
The macrocycle 1-Me3 was synthesized under conditions
of high dilution and CuI catalysis (Scheme 2).[13] The zinc
atom was removed during the methylation process. The neu-
tral macrocycle 1 proved insoluble in all solvents other than
pyridine and dimethyl sulfoxide (DMSO). Macrocycle 1-
Me3·ACHTNUTRGNE(NUG PF6)3 showed solubility in acetone and acetonitrile.
Compounds 1 and 1-Me3·ACHTNUTRGNE(UGN PF6)3 were fully characterized by
1H and 13C NMR spectroscopy and mass spectrometry.
The crystal and molecular structures of 1 were determined
by X-ray diffraction analyses. Single crystals of 1 were ob-
tained by exposing the DMSO solution of 1 in air. Macrocy-
cle 1 crystallizes in a triclinic system with a PÀ1 space
group with two molecules in a unit cell. In the crystal struc-
ture of 1 (Figure 2), the two phenylene groups attached to
the porphyrin ring have dihedral angles of 53 and 608. The
two biphenylene linkers are in different environments. One
interacts with the porphyrin ring in an intramolecular edge-
to-face manner, whereas the other helps to form one side of
a 9.5ꢁ5.0 ꢂ cavity. The crystal structure confirmed that the
relatively rigid cavity formed by one biphenylene can incor-
porate the anion-binding sites (triazole CH), an environ-
Scheme 1. Different forms of TCNQ and its possible reaction products.
The s- and p-bonded forms of the dianionic TCNQ dimers are shown.
2À
À
[TCNQ]2 dimers are connected by a single C C bond and
its existence lowers symmetry of the s-dimer. These dimers
can be generated under conducive conditions and within an
appropriate cavity. For example, the s-dimerization of the
ÀC
[TCNQ] anion radical can occur in aqueous solutions by
increasing the concentration and decreasing the temperature
or within the hydrophobic cavity of a- and b-cyclodex-
trins.[17a,17e,17 g] We envisioned, therefore, that an appropriate-
ly sized cavity coupled with a source of reducing electrons
could facilitate this dimerization. The cationic macrocycle 1-
ment for p–p stacking (biphenylene) and the nearby catalyt-
1
ic porphyrin. The H NMR spectrum of 1-Me ·
N
3+
Me3 (Scheme 2) was designed to provide such a reactor
signed based on the 2D COSY and ROESY spectra (see
Scheme 2. Preparation of 1 and 1-Me3·ACHTNUTRGNENUG(PF6)3. DBU=1,8-diazaCAHTUNGTREN[NNGU 5.4.0]bicycloundec-7-ene.
7500
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 7499 – 7505

A Porphyrin-Based Model System for Anion Species
FULL PAPER
With the anion receptor qualities shown, we considered
3+
the ability of 1-Me3 to serve as a nanoreactor by taking
advantage of the photocatalytic porphyrin. When these two
anionic guests are dragged close to the cavity at the same
time, their effective molarity will increase. To confirm this
ÀC
idea, the dimerization of the [TCNQ] radical anion by 1-
3+
Me3 and light in organic media was shown.
The iodide salt of 1-Me3 was used on account of the
3+
known reduction of TCNQ by the iodide salt of pyridini-
um.[22] The dimerization is readily demonstrated (Figure 3a)
Figure 2. Molecular structure of 1 (ORTEP drawing, 50% probability
level).
Figures S1–S2 in the Supporting Information), which indicat-
ed that the pyridyl ring and the two triazoles next to the
porphyrin were methylated (Scheme 2).
The receptor can bind anionic species with the aid of the
pyridinium and 1,2,3-triazolium cations. When halides were
added to the acetonitrile solution of 1-Me ·
ing complexes precipitated out. The higher solubility of the
complex formed between 1-Me3·A(PF6)3 and acetate provided
3 ACHTUNGTRENN(NUG PF6)3, the result-
CTHUNGTRENNUNG
an opportunity to study the binding behavior in detail. With
the addition of acetate, a shoulder (425 nm) on the Soret
band of the porphyrin increased and reached its maximum
intensity at about one equivalent (see Figure S4 in the Sup-
porting Information). In addition, a shoulder at 365 nm ap-
peared gradually during the addition of three equivalents of
acetate. Jobꢃs plots generated at 365 nm (see Figure S5a in
the Supporting Information) showed that 1-Me3·ACHTNUTRGENNG(U PF6)3
formed complexes with three acetate anions. The resulting
complex should also influence the porphyrin unit on account
of proximal electrostatic interactions. Consistently, the
shoulder peak at 425 nm and the partially quenched emis-
sion of the porphyrin by about 40% (see Figure S6 in the
Supporting Information) is attributed to this effect.
An NMR titration also indicates that the first acetate
binds with the pyridinium–bistriazole site followed by bind-
ing of two more acetate anions with the two triazolium cat-
ions. Upon addition of acetate, the pyridinium (Ho), the tri-
3+
ACHTUNGTRENNUNG
azole (Hn), and the triazolium (Hg) protons of 1-Me3 were
significantly shifted downfield as a result of the formation of
hydrogen bonding between the components of the macrocy-
cle and the acetate anions (see Figure S7 in the Supporting
Information). Upon the addition of the first equivalent of
acetate, the proton Hn of the two triazoles connected to the
pyridinium shifted (d=0.77 ppm) to a larger extent than Hg
from the triazolium units near the porphyrin (d=0.14 ppm).
Compared to the first equivalent, the following two equiva-
lents of acetate shifted the two Hn protons of the triazole by
a smaller amount (d=0.56 ppm), whereas the two Hg pro-
tons of the triazole shifted by a relatively bigger amount
(d=0.33 ppm; see Figure S8 in the Supporting Information).
This kind of binding behavior highlighted the simultaneous
Figure 3. a) UV/Vis–NIR spectroscopic changes in an acetone solution of
[1-Me3-TCNQ]2+ (12 mm) in the presence of ten equivalents of TCNQ
and 10 equivalents of TBAI by using irradiation with 400 nm light, every
5 min (l=1 cm; temperature: 258C). The inset shows the representative
color change of the [1-Me3-TCNQ]2+ solution before and after the irradi-
ation. b) The absorption changes at 580 (red empty circles: light, red
filled circles: dark) and 764 nm (blue empty squares: light, blue filled
squares: dark) of
a
solution of 1-Me33+·3IÀwith 10 equivalents of
ÀC
[TCNQ] both with and without irradiation. c) Vis–NIR changes in dea-
erated acetone solution of 1-Me33+·3IÀ (20 mm) with two equivalents of
TCNQ upon irradiation (c), then after another two equivalents of
TCNQ+TBAI (a) and continued irradiation (the absorption of por-
phyrin in this region was subtracted). Inset: red squares: 580 nm, blue cir-
cles: 764 nm).
effect of the pyridinium cation–anion interaction and the tri-
[13]
À
azole C H···acetate hydrogen bonding.
Chem. Eur. J. 2011, 17, 7499 – 7505
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
7501

Y.-l. Li, Y.-j. Li et al.
when 10 equivalents of TCNQ and 10 equivalents of tetra-
butylammonium iodide (TBAI) were added to a suspension
of 1-Me33+·3I (12 mm) in acetone. An initially yellow/orange
suspension clarified and became yellow green. This yellow/
green solution was analyzed from its UV/Vis–NIR spectra
one shifted to 2157 cmÀ1 and a second band appearing at
2130 cmÀ1, which is a much lower value relative to those
usually found in the anion radical. One shoulder peak at
794 cmÀ1 is located close to the 807 cmÀ1 band, which has
been suggested as characteristic of the s-dimer.[21]
(dark green trace in Figure 3a) to originate from a 1:1 mix-
ture of 1-Me3 and [TCNQ] with the nine equivalents of
To clarify the mechanism for the photosensitized dimeri-
zation, some control experiments were performed. To test
for the importance of the guestꢃs binding to the macrocycle,
a solution of the noncationic species 1 with the zinc ion re-
moved (free-base porphyrin) was prepared and when the so-
lution was irradiated in the presence of TCNQ (10 equiv),
the direct appearance of the anionic DCTCÀ species was ob-
served without dimerization. Second, when a mixture of free
3+
ÀC
TCNQ remaining unreduced in solution. We believe a com-
plex [1-Me3-TCNQ]2+ is ultimately formed under these con-
ditions but the radical character precluded an NMR spectro-
scopic study. The absorptions showed the characteristic
ÀC
bands of the porphyrin (ꢀ400 nm) and the [TCNQ] anion
radical (650–900 nm). Furthermore, a shoulder appears at
425 nm, which is consistent with the electrostatic interaction
between the complexed anion and the porphyrin as ob-
ÀC
base 1 and three equivalents of the pre-reduced [TCNQ]
anion radical (see Figure S14 in the Supporting Information)
was irradiated, no dimerization occurred. These results indi-
served with acetate, that is, formation of [1-Me3-TCNQ]2+
.
3+
Upon irradiation into the Soret band with 400 nm light, the
cate that the cationic form of the receptor 1-Me3 is re-
ÀC
radical bands of [TCNQ] in the 650–900 nm region grow in
quired to generate the s-dimer. We attribute this require-
ment to the importance of binding the anion around the
cavity.
to reach a maximum after 15 min (pink trace) and the
shoulder at 425 nm gradually disappears. At the same time a
new absorption band centered at 580 nm continuously grows
in. This visible band is blueshifted from the reported s-
dimer absorption recorded in aqueous media (647 nm).[17a,d]
The purple species generated by the irradiation was suffi-
ciently stable under air to remain unchanged for more than
one day at room temperature. We note that further irradia-
tion for 90 min caused the disappearance of the 580 nm
band and the appearance of the monoanionic form of the
carbonyl species a,a-dicyano-p-toluoylcyanide (DCTCÀ,
Figure 1)[18] with a peak at 488 nm (see Figure S9 in the Sup-
porting Information). This reaction could be prevented by
deaerating the solution with argon.
To identify the roles played by the porphyrin, a control
experiment was conducted in which 10 equivalents of pre-re-
ÀC
duced [TCNQ] anion radical was added into a solution of
1-Me33+·3IÀ and TBAI (10 equivalents) under light and
dark conditions (Figure 3b and Figure S15 in the Supporting
Information). The initial green solution was rapidly convert-
ed (ꢀ35 min) into the purple solution of the dimer. Keeping
the green acetone solution in the dark at room temperature
2À
also induced the generation of the same s-[TCNQ]2 dimer,
albeit much more slowly (two days in the dark). Moreover,
after only 50% conversion, the s-dimer degrades into a col-
orless species (Figure 3b and Figure S16 in the Supporting
Information). This particular control experiment indicated
that irradiation of the porphyrin unit increases the dimeriza-
tion rate by over two orders of magnitude.
The photogenerated product was analyzed to confirm its
2À
identity as the s-[TCNQ]2 dimer. ESI-MS shows fragment
2À
ions from a [TCNQ]2 dimer appearing after the solution is
irradiated with light (see Figures S10 and S11 in the Sup-
The porphyrin cation can get reduced by iodide anions.[23]
A control experiment was also performed to elucidate the
roles played by the iodide. Thus, adding two equivalents of
neat TCNQ to a suspension of 1-Me33+·3IÀ in acetone re-
sulted in a familiar looking yellow/green solution. The inten-
sity of the characteristic NIR bands (e764 =15000mÀ1 cmÀ1)
for the 1:1 [1-Me3-TCNQ]2+ complex from this solution
(Figure 3c) is close to that observed when one equivalent of
porting Information). When the 1:1 complex [1-Me3-
1
TCNQ]2+ in [D6]acetone was irradiated, the H NMR spec-
trum showed the appearance of an A2X2 spin system in the
downfield region (d=7.04, 5.23 ppm; see Figure S12 in the
Supporting Information). These signals are assigned to the
2À
two ring protons in the s-[TCNQ]2 dimer with nonequiva-
lent para substituents rather than the equivalent substitu-
tions in the parent TCNQ or from a p dimer.[17g] The IR
spectra of the solutions at different stages through the ex-
periment showed the typical features found in other TCNQ
compounds.[19] The most significant bands for the parent
TCNQ are n˜(CN) at 2228 and n˜50(b3u) at 860 cmÀ1. These
bands shift to lower frequencies on increasing the partial or
full electronic charge on the TCNQ.[20] Consistently, the ini-
tial 1:1 complex [1-Me3-TCNQ]2+ shows a cyano band at
2181 cmÀ1. The IR spectrum of the purple solution generat-
ed after irradiation showed different features that are attrib-
utable to the formation of an s bond between the two
ÀC
the pre-reduced [TCNQ] anion radical was added. Irradia-
ÀC
tion of the reactor with one equivalent of [TCNQ] around
leads to dimerization. Addition of another two equivalents
of TCNQ to this solution does not directly show the appear-
ÀC
ance of a second [TCNQ] anion until the solution is irradi-
ated (Figure 3c, inset). This observation suggests that photo-
induced electron transfer from the porphyrin to the TCNQ
is required to generate the radical anion. Further irradiation
does not induce the appearance of dimerization. Addition of
two equivalents of iodide to this solution facilitates the di-
merization (Figure 3c, inset). This observation suggests that
iodide is required to reduce the porphyrin cation. Concomi-
tantly, a further dimer is formed under these illuminated
conditions. As expected, therefore, the absorption band of
ÀC
[TCNQ] anions (see Figure S13 in the Supporting Informa-
tion). After irradiation, the 2181 cmÀ1 band from the
ÀC
[TCNQ] radical splits into two bands at lower energy with
7502
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 7499 – 7505

A Porphyrin-Based Model System for Anion Species
FULL PAPER
the dimer, at around 580 nm, doubles in intensity (Fig-
ure 3c). The continued generation of product in this and the
prior experiment with excess unreduced TCNQ (9 equiv) in-
dicated that there is no product inhibition. Therefore, the re-
ceptor can accelerate the dimerization of both the pre-re-
Conclusion
We describe a nanometer-sized macrocyclic receptor based
on a photoactive porphyrin unit and anion-binding pyridini-
um and triazolium units that was prepared by using the
ubiquitous “click chemistry”. The potential of this structure
to act as a reactor was confirmed by the photodriven dimeri-
zation of TCNQ. There is clear evidence for a rate increase
of over two orders of magnitude, photosensitization of the
host, and demonstrated turnover of the catalyst. These re-
sults for the first time show the
ÀC
duced [TCNQ] anion radical and the one generated in situ
when 400 nm light and iodide is available.
On the basis of the results and control studies, we propose
the following steps for the catalytic mechanism (Scheme 3):
ÀC
1) The [TCNQ] anion radical pre-reduced or reduced in
construction of cationic recep-
tors that can host anionic spe-
cies and sensitize their reac-
tion. This approach is of great
significance for the develop-
ment of novel nanoscale devi-
ces capable of supramolecular
catalysis.
Experimental Section
General methods: All reagents were
obtained from commercial suppliers
and used as received unless otherwise
noted. Column chromatography was
performed on silica gel (160–200
mesh) and TLC was performed on
precoated silica gel plates and ob-
served under UV light. NMR spectra
were recorded on Bruker Avance
DPS-400 and Bruker Avance DPS-
600 spectrometers at room tempera-
ture (298 K). Chemical shifts were
referenced to the residual solvent
3+
Scheme 3. Proposed mechanism of the photochemically induced dimerization of TCNQ by 1-Me3
(the
peaks. MALDI-TOF mass spectrom-
etry was performed on Bruker
ÀC
[TCNQ] might sit in the cavity or outside the cavity, but it is constrained around the pyridinium or triazolium
centers by electrostatic interactions, here only the inside case was shown).
a
Biflex III mass spectrometer. Elec-
tronic absorption spectra were mea-
sured on a JASCO V-579 spectropho-
situ formed a 1:1 host–guest [1-Me3-TCNQ]2+ complex,
2) photochemical excitation of the porphyrin unit in the re-
actor, 3) this is followed by photoinduced electron transfer
from the excited porphyrin unit to a neutral TCNQ (either
outside or inside the receptor), giving rise to a porphyrin
tometer. Fluorescence excitation and emission spectra were recorded by
using a Hitachi F-4500. All single-crystal X-ray diffraction data were col-
lected on a Rigaku Saturn X-ray diffractometer with graphite-monochro-
mator MoKa radiation (l=0.71073 ꢂ) at 173 K. Intensities were corrected
for absorption effects by using the multiscan technique SADABS (Sie-
mens Area Detector Absorption Corrections). The structures were
solved by direct methods and refined by a full-matrix least-squares tech-
nique based on F2 by using SHELXL 97 program (Sheldrick, 1997). The
extended packing plots and data from crystal packing were obtained by
using the software Mercury 1.4.1. Compounds 3 and 5 were synthesized
in accordance with literature procedures.[24,25]
ÀC
radical cation and a second [TCNQ] radial anion, 4) the
ÀC
second [TCNQ] is dragged close to the cavity with the
help of the electrostatic stabilization provided by the triazo-
ÀC
lium cations, 5) the two [TCNQ] anion radicals constrained
around the cavity rapidly formed the s-dimer, 6) at some
Compound 2: K2CO3 (0.55 g, 4 mmol) and 3-bromopropyne (0.354 g,
3 mmol) were added to a solution of 5 and 15-bis(4-hydroxyphenyl)por-
phyrin[26] (0.556 g, 1 mmol) in DMF (20 mL) and the solution was heat to
708C for 10 h. DMF was removed under vacuum. The mixture was
washed with water and the aqueous solution was extracted with CH2Cl2
(3ꢁ50 mL). The organic layer was separated, dried over MgSO4, filtered,
concentrated under reduced pressure, and the resulting crude was puri-
fied by column chromatography (CH2Cl2 containing 0.5% pyridine as
eluent) to give 2 (0.49 g, yield: 78%). 1H NMR (400 MHz, CDCl3, 258C,
TMS): d=10.16 (s, 2H), 9.32 (d, J=4 Hz, 4H), 9.06 (d, J=4 Hz, 4H),
8.14 (d, J=8 Hz, 4H), 7.35 (d, J=8 Hz, 4H), 4.97 (s, 4H), 2.69 ppm (s,
2H); 13C NMR (100 MHz, [D6]DMSO, 258C, TMS): d=157.66, 150.32,
point (either before or after the constraining of the second
ÀC
[TCNQ] anion radical), the photogenerated porphyrin
cation gets reduced by iodide, and 6) the s-dimer is either
ÀC
ejected from the host or is displaced by the [TCNQ] anion
radical. The receptor can accelerate the dimerization of at
least 10 equivalents of TCNQ, thus indicating that this re-
ceptor can bring together two reactants to accelerate a reac-
tion, and turnover like a catalyst.
Chem. Eur. J. 2011, 17, 7499 – 7505
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
7503

Y.-l. Li, Y.-j. Li et al.
149.96, 149.66, 136.33, 136.21, 132.80, 132.46, 119.36, 113.93, 106.79, 80.33,
79.36, 56.62, 40.97, 40.76, 40.55, 40.35, 40.14, 39.93, 39.72, 0.91 ppm; MS
(MALDI-TOF): m/z: calcd for C38H24N4O2Zn: 632.12 [M]+; found:
632.5; elemental analysis calcd (%) for C38H24N4O2Zn: C 71.99, H 3.82,
N 8.84; found: C 71.86, H 3.89, N 8.79.
Basic Research 973 Program of China. A.H.F. acknowledges support
from the American Chemical Society and the National Science Founda-
tion for a travel grant.
Compound 4: A solution of 2 (316 mg, 0.5 mmol), 4,4’-bis(azidomethyl)-
biphenyl (3)[24] (528 mg, 2 mmol), and DBU (4.0 mmol, 0.7 mL) in tolu-
ene (50 mL) was degassed (argon) for 30 min and heated to 708C while
flushing with argon. At 708C, CuI (0.02 mmol, 3.8 mg) was added to the
mixture. The mixture was stirred for 4 h under argon. The mixture was
concentrated in vacuo. The product was purified by chromatography
(SiO2, CH2Cl2/methanol 20:1) to afford 4 (522 mg, 90% yield) as a red
[1] J.-M. Lehn, Science 2002, 295, 2400–2403.
[2] a) D. J. Cram, Nature 1992, 356, 29–36; b) D. M. Vriezema, M. C.
Aragones, J. A. A. W. Elemans, J. J. L. M. Cornelissen, A. E. Rowan,
R. J. M. Nolte, Chem. Rev. 2005, 105, 1445–1489; c) L. R. MacGilliv-
ray, J. L. Atwood, Angew. Chem. 1999, 111, 1080–1096; Angew.
Chem. Int. Ed. 1999, 38, 1018–1033; d) X. J. Liu, R. Warmuth, Nat.
Protoc. 2007, 2, 1288–1296.
1
solid. H NMR (400 MHz, CDCl3, 258C, TMS): d=10.14 (s, 2H), 9.30 (d,
J=4 Hz, 4H), 9.03 (d, J=4 Hz, 4H), 8.11 (d, J=8 Hz, 4H), 7.61 (s, 2H),
7.60 (d, J=8 Hz, 4H), 7.52 (d, J=8 Hz, 4H), 7.40 (d, J=4 Hz, 4H), 7.33
(d, J=8 Hz, 4H), 7.28 (d, J=8 Hz, 4H), 5.64 (s, 4H), 5.49 (s, 4H),
4.29 ppm (s, 4H); 13C NMR (100 MHz, [D6]DMSO, 258C, TMS): d=
158.32, 150.27, 149.55, 140.23, 140.06, 139.41, 136.17, 135.88, 135.72,
132.67, 132.40, 129.77, 129.38, 127.86, 127.72, 119.39, 113.78, 106.66, 62.17,
53.97, 53.36, 40.94, 40.73, 40.52, 40.31, 40.10, 39.89, 39.69, 36.50, 35.19,
31.49, 30.87, 30.62, 29.74 ppm; MS (MALDI-TOF): m/z: calcd for
C66H48N16O2Zn: 1161.34 [M]+; found: 1161.1 [M+H]+, 1135.1
[M+2HÀ2N]; compound 4 was also characterized by X-ray diffraction
analysis (see Section S5 in the Supporting Information).
[3] a) J. K. M. Sanders, Chem. Eur. J. 1998, 4, 1378–1383; b) C. J. Hast-
ings, D. Fiedler, R. G. Bergman, K. N. Raymond, J. Am. Chem. Soc.
2008, 130, 10977–10983; c) J. Kang, J. Jr Rebek, Nature 1997, 385,
50–52; d) M. Yoshizawa, M. Tamura, M. Fujita, Science 2006, 312,
251–254.
[4] a) M. Yoshizawa, Y. Takeyama, T. Okano, M. Fujita, J. Am. Chem.
Soc. 2003, 125, 3243–3247; b) D. R. Benson, R. Valentekovich, F.
Diederich, Angew. Chem. 1990, 102, 213–216; Angew. Chem. Int.
Ed. Engl. 1990, 29, 191–193; c) M. Kuil, T. Soltner, P. van Leeuwen,
J. N. H. Reek, J. Am. Chem. Soc. 2006, 128, 11344–13345; d) M. D.
Pluth, R. G. Bergman, K. N. Raymond, Science 2007, 316, 85–88.
[5] a) V. M. Dong, D. Fiedler, B. Carl, R. G. Bergman, K. N. Raymond,
J. Am. Chem. Soc. 2006, 128, 14464–14465; b) L. Trembleau, J. Jr
Rebek, Science 2003, 301, 1219–1220.
[6] D. Ajami, J. Rebek, Jr., Nat. Chem. 2009, 1, 87–90.
[7] P. Mal, B. Breiner, K. Rissanen, J. R. Nitschke, Science 2009, 324,
1697–1699.
[8] M. Yoshizawa, T. Kusukawa, M. Fujita, K. Yamaguchi, J. Am.
Chem. Soc. 2000, 122, 6311–6312.
[9] M. Yoshizawa, S. Miyagi, M. Kawano, K. Ishiguro, M. Fujita, J. Am.
Chem. Soc. 2004, 126, 9172–9173.
[10] a) J. P. Collman, R. Boulatov, C. J. Sunderland, L. Fu, Chem. Rev.
2004, 104, 561–588; b) A. B. C. Deutman, C. Monnereau,
J. A. A. W. Elemans, G. Ercolani, R. J. M. Nolte, A. E. Rowan, Sci-
ence 2008, 322, 1668–1671; c) L. Cuesta, J. L. Sessler, Chem. Soc.
Rev. 2009, 38, 2716–2729; d) D. Gust, T. A. Moore, A. Moore, Acc.
Chem. Res. 2009, 42, 1890–1898.
[11] a) A. Kumar, P. S. Pandey, Org. Lett. 2008, 10, 165–168; b) H. Y.
Zheng, W. D. Zhou, J. Lv, X. D. Yin, Y. J. Li, H. B. Liu, Y. L. Li,
Chem. Eur. J. 2009, 15, 13253–13262.
Compound 1: DBU (4.0 mmol, 0.7 mL) was added to toluene (200 mL)
and left under degassed (argon) for 30 min and then heated to 708C
while flushing with argon. At 708C, CuI (0.02 mmol, 3.8 mg) was added
to the mixture. A solution of 5[25] (12.7 mg, 0.1 mmol) and 4 (116 mg,
0.1 mmol) in THF (5 mL) and toluene (30 mL) was added to the solution
slowly over 10 h and then the mixture was stirred for another 4 h under
argon. The mixture was concentrated in vacuo. The product was purified
by chromatography (SiO2, CH2Cl2/pyridine/methanol 100:1:3) to afford 1
(84 mg, 65% yield) as a purple solid. 1H NMR (400 MHz, [D6]DMSO,
258C, TMS): d=10.25 (s, 2H), 9.37 (d, J=4.4 Hz, 4H), 8.97 (d, J=2 Hz,
2H), 8.86 (d, J=4.4 Hz, 4H),8.76 (s, 2H), 8.59 (d, J=2 Hz 1H), 8.46 (s,
2H), 8.04 (d, J=8.4 Hz, 4H), 7.72 (d, J=8.4 Hz, 4H), 7.61 (d, J=8.4 Hz,
4H), 7.47 (d, J=8.4 Hz, 4H),7.43 (d, J=8.4 Hz, 4H), 7.29 (d, J=8.4 Hz,
4H), 5.77 (s, 4H), 5.63 (s, 4H), 5.60 ppm (s, 4H); 13C NMR (150 MHz,
[D6]DMSO, 258C, TMS): d=157.43, 150.00, 149.92, 149.23, 146.03,
144.13, 144.04, 139.92, 136.62, 136.02, 135.78, 135.57, 135.35, 132.38,
132.05, 129.15, 129.07, 127.65, 127.62, 127.23, 125.37, 124.37, 123.10,
119.05, 114.16, 106.36, 61.69, 53.27, 53.05 ppm; MS (MALDI-TOF): m/z:
calcd for C75H53N17O2Zn: 1287.39 [M]+; found: 1289.6 [M+2H]+, 1352.5
[M+H+Cu]+.
[12] V. Haridas, K. Lal, Y. K. Sharma, S. Upreti, Org. Lett. 2008, 10,
1645–1647.
Compound 1-Me3·ACHTUNGTRENNUNG(PF6)3: Compound 1 (13 mg, 0.01 mmol) in DMF
[13] a) Y. J. Li, A. H. Flood, Angew. Chem. 2008, 120, 2689–2692;
Angew. Chem. Int. Ed. 2008, 47, 2649–2652; b) Y. J. Li, A. H. Flood,
J. Am. Chem. Soc. 2008, 130, 12111–12122; c) Y. R. Hua, A. H.
Flood, Chem. Soc. Rev. 2010, 39, 1262–1271.
[14] a) H. Juwarker, J. M. Lenhardt, D. M. Pham, S. L. Craig, Angew.
Chem. 2008, 120, 3800–3803; Angew. Chem. Int. Ed. 2008, 47, 3740–
3743; b) R. M. Meudtner, S. Hecht, Angew. Chem. 2008, 120, 5004–
5008; Angew. Chem. Int. Ed. 2008, 47, 4926–4930.
[15] W. S. Horne, M. K. Yadav, C. D. Stout, M. R. Ghadiri, J. Am. Chem.
Soc. 2004, 126, 15366–15367.
[16] a) V. V. Rostovtsev, L. G. Green, V. V. Fokin, K. B. Sharpless,
Angew. Chem. 2002, 114, 2708–2711; Angew. Chem. Int. Ed. 2002,
41, 2596–2599; b) C. W. Tornøe, C. Christensen, M. Meldal, J. Org.
Chem. 2002, 67, 3057–3064.
[17] a) R. H. Boyd, W. D. Phillips, J. Chem. Phys. 1965, 43, 2927–2929;
b) S. Z. Goldberg, B. Spivack, G. Stanley, R. Eisenberg, D. M.
Braitsch, J. S. Miller, M. Abkowitz, J. Am. Chem. Soc. 1977, 99,
110–117; c) J. Huang, S. Kingsbury, M. Kertesz, Phys. Chem. Chem.
Phys. 2008, 10, 2625–2635; d) J.-L. Lꢄ, S. V. Rosokha, J. K. Kochi, J.
Am. Chem. Soc. 2003, 125, 12161–12171; e) C. J. Hartzell, S. R.
Mente, N. L. Eastman, J. L. Beckett, J. Phys. Chem. 1993, 97, 4887–
4890; f) I. Garcia-Yoldi, J. S. Miller, J. J. Novoa, J. Phys. Chem. A
2009, 113, 7124–7132; g) J. L. Beckett, C. J. Hartzell, N. L. Eastman,
T. Blake, M. P. Eastman, J. Org. Chem. 1992, 57, 4173–4179.
(3 mL) and MeI (1 mL) was heated at 408C overnight. The mixture was
then poured into CH2Cl2 (50 mL) to give some precipitate, which was
washed with CH2Cl2. The solid was suspended in acetone, NH2PF6
(5 equiv) was added, and the mixture became a clear solution. The sol-
vent was removed, washed the with water, and dried under vacuo to give
1-Me3·ACHTUNGTRENNUNG
(PF6)3 (16.8 mg, 95%). 1H NMR (400 MHz, CD3CN, 258C, TMS):
d=10.41 (s, 2H), 9.49 (d, J=4 Hz, 4H), 8.99 (d, J=4 Hz, 4H), 8.79 (s,
2H), 8.77 (s, 1H), 8.40 (s, 2H), 8.14 (d, J=8 Hz, 4H), 7.85 (s, 2H), 7.56
(d, J=8 Hz, 4H), 7.52 (d, J=8 Hz, 4H), 7.40 (d, J=8 Hz, 4H), 7.02 (d,
J=8 Hz, 4H), 6.43 (d, J=8 Hz, 4H), 5.85 (s, 4H), 5.69 (s, 4H), 5.45 (s,
4H), 4.68 (s, 4H), 4.49 (s, 6H), 4.19 (s, 3H), À3.31 ppm (s, 2H);
13C NMR (100 MHz, CD3CN, 258C, TMS): d=157.80, 148.35, 146.36,
142.35, 142.00, 140.71, 137.28, 136.62, 134.81, 133.49, 132.62, 132.05,
131.06, 130.82, 129.97, 129.07, 128.17, 124.45, 119.52, 116.18, 106.73, 60.46,
58.24, 54.26, 40.07, 31.25 ppm; HRMS (ESI): m/z: cald for C78H64N17O2:
423.51265 [M]3+; found: 423.51272 [M]3+
.
Acknowledgements
This work was supported by the National Nature Science Foundation of
China (21031006, 20971127, 90922017, 20831160507) and the National
7504
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 7499 – 7505

A Porphyrin-Based Model System for Anion Species
FULL PAPER
[18] M. R. Suchanski, R. P. Van Duyne, J. Am. Chem. Soc. 1976, 98, 250–
252.
[23] A. Taurog, M. L. Dorris, D. R. Doerge, Archives of Biochemistry
and Biophysics 1996, 330, 24–32.
[19] L. Ballester, A. Gutiꢅrrez, M. F. PerpiÇꢆn, M. T. Azcondo, Coord.
Chem. Rev. 1999, 190–192, 447–470.
[24] J. R. Thomas, X. J. Liu, P. J. Hergenrother, J. Am. Chem. Soc. 2005,
127, 12434–12435.
[20] K. Naka, T. Uemura, Y. Chujo, Macromolecules 2000, 33, 4733–
4737.
[25] Y. Shin, G. E. Fryxell, C. A. Johnson, M. M. Haley, Chem. Mater.
2008, 20, 981–986.
[21] H. Zhao, R. A. Heinz, K. R. Dunbar, R. D. Rogers, J. Am. Chem.
Soc. 1996, 118, 12844–12845.
[26] Q. M. Wang, D. W. Bruce, Synlett 1995, 1267–1268.
[22] L. R. Melby, R .J. Harder, W. R. Hertler, W. Mahler, R. E. Benson,
W. E. Mochel, J. Am. Chem. Soc. 1962, 84, 3374–3387.
Received: February 26, 2011
Published online: May 9, 2011
Chem. Eur. J. 2011, 17, 7499 – 7505
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
7505