Nanoscale metal coordination macrocycles fabricated by using "dimeric" dipyrrins

Article abstract of DOI:10.1002/chem.200700444

Covalently linked dipyrrin (dipyrromethene) dimers have afforded nanoscale [2+2]-type neutral coordination macrocycles with a diagonal of about 1.6 nm. Two moieties of the achiral dipyrrin-Zn^II complex yield the chiral coordination macrocycles

Full text of DOI:10.1002/chem.200700444

DOI: 10.1002/chem.200700444
Nanoscale Metal Coordination Macrocycles Fabricated by Using“Dimeric”
Dipyrrins
Hiromitsu Maeda*[a, b] and Takashi Hashimoto[a]
Abstract: Covalently linked dipyrrin (dipyrromethene) dimers have afforded nano-
scale [2+2]-type neutral coordination macrocycles with a diagonal of about 1.6 nm.
Two moieties of the achiral dipyrrin–ZnII complex yield the chiral coordination
macrocycles as minor species, as well as major meso stereoisomers by the covalent
linkages. Tetrahedral ZnII coordination by using acyclic ligands enables the dipyr-
rin–metal complex units to readily rotate and pass through the cavity of the nano-
Keywords: chirality · macrocycles ·
metallacycles
·
N
ligands
·
nanostructures
rings in order to reveal the transitions between the chiral and achiral isomers.
Introduction
Zn(OAc)2 and “dimeric” dipyrrin derivatives in which two
A
dipyrrin units were bridged by phenylethynyl linkers.[12] Ac-
cording to the metal complexation conditions and the angles
of the linkages, coordination oligomers would form infinite
linear or discrete structures. In this article, we report the
[2+2]-type coordination macrocycles by using the all-meta-
bridged derivatives of dimeric dipyrrins under modified con-
ditions.
Coordination cavities fabricated using the metal complexa-
tion of organic molecules are fascinating and widely investi-
gated as host species to recognize guest molecules for cata-
lyzing particular reactions.[1] Metal-organic microporous ma-
terials (MOMs) based on coordination polymers using li-
gands such as oligopyridyl derivatives have been found to
encapsulate gas molecules.[2,3] On the other hand, discrete
coordination macrocycles and cages with/without positive
charge(s) have been investigated as isolated spaces to bind
specific molecules and ions in solution.[4–6] With regard to
ligand moieties, dipyrrins (dipyrromethenes) are comprised
of two pyrroles bridged by an sp2-meso carbon, similar to a
half-porphyrin unit, and essential p-conjugated bidentate
monoanionic ligands for metal ions.[7–11] As compared to
using porphyrins as rigid macrocycles, the use of dipyrrins as
acyclic ligands can afford flexible metal coordination envi-
ronments. Recently, we reported the formation of coordina-
tion polymers and nanoscale spherical architectures using
Results and Discussion
Synthesis and characterization of dipyrrin dimers and metal
complexes: As previously reported,[10,12] dimeric dipyrrin 1a
was synthesized by performing the Sonogashira coupling re-
action of 1,3-diethynylbenzene and 3-bromobenzaldehyde,
followed by condensation with pyrrole and subsequent
DDQ oxidation (Scheme 1a). Similar procedures were per-
formed in the reaction using a-alkylpyrroles to afford dipyr-
rin dimers 1b and 1c in yields of 21 and 19%, respectively,
from a diformyl intermediate. The chemical identities of
1a–c were confirmed by 1H NMR spectroscopy and FAB-
MS spectrometry; UV/Vis absorption spectra of these deriv-
atives in CHCl3 were observed at l = 435, 446, and 450 nm,
respectively, suggesting almost no electronic interactions be-
tween the two dipyrrin moieties bridged by a spacer.
[a] Prof. Dr. H. Maeda, T. Hashimoto
Department of Bioscience and Biotechnology
Faculty of Science and Engineering, Ritsumeikan University
Kusatsu 525-8577 (Japan)
Fax : (+81)77-561-2659
E-mail: maedahir@se.ritsumei.ac.jp
Next, we investigated the coordination chemistry of di-
[b] Prof. Dr. H. Maeda
meric dipyrrins. When Zn(OAc)2 was added to the CHCl3
A
Department of Materials Molecular Science
Institute for Molecular Science (IMS)
Okazaki 444-8787 (Japan)
solution of 1a with 0.5 equiv of pyrene (with a length of ca.
9 Š) as a template molecule and the mixture was heated to
the reflux temperature for two days, the solution color
slightly darkened. Purification by silica gel column chroma-
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
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FULL PAPER
ion.[8c,13] In the [2+2]-type com-
plexes such as 1a2·Zn2, two
metal-recognition sites (dipyrrin
groups) are “strapped” by phe-
nylethynyl linkers; therefore,
the ZnII complexes are classi-
fied into three types of stereo-
isomers (two diastereomers):
achiral (meso, LD) and chiral
(LL and DD),[14] as seen in the
optimized structures of 1a2·Zn2
(Figure 1) and 1b2·Zn2 at the
AM1 level.[15]
1
The H NMR spectrum in ad-
dition to the MS analysis re-
vealed 1) the formation of
[2+2]-coordination macrocycles
and 2) the existence of diaste-
reomers derived from cycliza-
tion. The two sets of signals
Scheme 1. a) Synthesis and b) ZnII complexation of dipyrrin “dimers” 1a–c.
tography and recrystallization
from CHCl3/hexane afforded a
yellow solid in a yield of 77%
(Scheme 1b).
ESI-TOF-MS
analyses of the complexes with
AgClO4 (5 equiv) as a cation
source revealed the exact com-
position of the ZnII complexes
Figure 1. Possible three stereoisomers, a) achiral (meso), b) chiral (LL), and c) chiral (DD), of 1a2·Zn2, opti-
of discrete [2+2]-type coordina- mized at the AM1 level.
tion macrocycles at, for exam-
ple, m/z 1249.26 and 1355.16
for 1a2·Zn2·H+ (exact mass: 1249.26) and 1a2·Zn2·Ag+
(1355.16), respectively. Similar results were further support-
ed by a GPC-HPLC analysis with a single peak. Other sol-
vents such as THF and toluene with pyrene and other tem-
plate molecules like C60 are also suitable to synthesize these
[2+2] complexes. Under these conditions, discrete higher
homologues have not been obtained. In contrast, it is known
that the ZnII complexation of 1a without a template mole-
cule in THF/H2Oat room temperature yields 1D coordina-
tion polymers and submicrometer-scale spherical particles
with dents.[12] The UV/Vis absorption spectrum of 1a2·Zn2 in
CHCl3 shows the absorption maximum (lmax) at 486 nm,
with a “shoulder” at about 465 nm, derived from the mix-
ture of stereoisomers described below. Further, the fluores-
cence emission of 1a2·Zn2 at 505 nm (lex =486 nm) in the
same solvent reveals a comparable Stokes shift than those in
with different integrations at a ratio of 4.6:1 derived from
the integrals of b-CH were observed in the H NMR spec-
1
trum of 1a2·Zn2 in CDCl3 (Figure 2). A similar trend was
observed in 1b2·Zn2 with a ratio of 3.2:1. The formation of
coordination nanorings is further suggested by the split
chemical shifts (Dd) in each dipyrrin b-CH signal of 1a2·Zn2
between the relative “internal” (Hk, Hl, and Hm) and “exter-
nal” (Hh, Hi, and Hj) protons (e.g. Dd=0.028 ppm at the sig-
nals around 6.71 ppm (Hh and Hk) as the “major” set) de-
rived from the cavity. All the proton signals of the major
isomer as the meso one (see below) are assigned using
1H–1H COSY and ROESY, which show correlations be-
tween Hf–Hh and Hg–Hk (see Supporting Information). The
2D NMR spectra also revealed the resonances of dipyrrin a-
CH at d 7.58 (Hj) and 7.50 (Hm) ppm, which afford Dd=
ꢀ0.08 ppm; these values are greater than those of b-CH
(0.028 and 0.013 ppm). In the case of a-CH (Hi and Hm) and
b-CH (Hi and Hl), the external protons (Hi and Hj) are ob-
served in the downfield region as compared to the internal
ones (Hl and Hm). Further, the sets of major signals derived
from pyrrole b-CH (Hh and Hk) at around 6.71 ppm in
1a2·Zn2 are observed in the upfield region than that in the
corresponding “minor” ones (ca. 6.77 ppm). The Dd value
between the internal and external b-CH signals of the minor
the other ZnII complexes (e.g., lmax =486 nm and lem
=
501 nm of the meso-mesityl–dipyrrin–ZnII complex in
CHCl3). Similar trends were observed in other derivatives
1b,c.
II
Stereoisomers formed usingtetrahedral Zn and acyclic li-
gands: Binuclear ZnII complexes are expected to afford two
chiral centers due to the tetrahedral geometry of a ZnII
Chem. Eur. J. 2007, 13, 7900 – 7907
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H. Maeda and T. Hashimoto
species, which partially overlap with the major signals, is es-
timated to be 0.043 ppm; this value is slightly greater than
that of the major isomer.
The chiral HPLC analysis of 1a2·Zn2 (Sumichiral OA-
3100, CHCl3/hexane 1:2 containing ca. 0.2% EtOH as the
eluent) revealed that the major and minor fractions are
achiral (meso) and chiral stereoisomers, respectively.[16]
These results are also consistent with the existence of two
types of diastereomers, as shown in Figure 1. Interestingly,
the UV/Vis absorption spectrum of each isomer differs as
seen in the absorption maxima at 484 and 467 nm for the
major and minor fractions (crude in both the cases), respec-
tively. The other complexes, 1b2·Zn2 and 1c2·Zn2, revealed a
more distinct resolution with a total of three peaks among
the three stereoisomers in which chiral enantiomers are con-
sidered to be the minor species. Although tetrahedral dipyr-
rin–ZnII moieties are achiral, the covalent linkages of the
same helicities afford “chiral rings”, which would be the po-
tential receptors for the chiral species.[14a] Such chirality ob-
served in the minor isomers is a unique property derived
from the distorted geometries of dipyrrin complexes as op-
posed to those of planar porphyrins.
However, the Cotton effect observed in the CD spectrum
has not been observed in one of the enantiomers in 1b2·Zn2,
possibly due to the interconversion between the stereoiso-
mers. Actually, equilibrium between the diastereomers is ob-
served in 1a2·Zn2 and 1b2·Zn2 by the 1H NMR spectral
changes (CDCl3) for various temperatures; in these com-
plexes, the ratios of meso and chiral isomers are 4.1:1 and
2.7:1, respectively, at ꢁ608C. At higher temperatures, the
ratio of meso isomers is further increased and the chemical
shifts (Dd) between the internal and external b-CH signals
at around 6.6–6.7 ppm are smaller in each isomer: for exam-
ple, Dd=0.015 and 0.055 ppm in the meso isomer of 1a2·Zn2
at 60 and ꢁ608C, respectively. The equilibrium constants K
between the chiral and meso isomers of 1a2·Zn2 are 4.6, 4.4,
and 4.1 at 20, ꢁ20, and ꢁ608C, respectively, to afford DG0
of ꢁ3.7, ꢁ3.1, and ꢁ2.5 kJmolꢁ1. On the other hand, the K
(and DG0) values of 1b2·Zn2 are 3.2 (ꢁ2.8), 3.0 (ꢁ2.3), and
2.7 (ꢁ1.7 kJmolꢁ1) at each temperature. From these data
and the van ꢁt Hoff plots, the thermodynamic parameters
(DH0 and DS0) could be estimated as 0.75 kJmolꢁ1 and
15 JKꢁ1 molꢁ1
for
1a2·Zn2
and
1.1 kJmolꢁ1
and
13 JKꢁ1 molꢁ1 for 1b2·Zn2; this suggests that for both the
cases, the chiral isomers are slightly thermodynamically
more stable than the achiral ones, particularly for methyl-
substituted 1b2·Zn2.[17]
The rate constants (k) of the rotation of the dipyrrin moi-
eties of 1a2·Zn2 and 1b2·Zn2 from each achiral to chiral
isomer have been determined to be 0.5 and 0.3 sꢁ1, respec-
tively, by means of the spin saturation transfer method
(CDCl3, 208C), irradiating one of the b-CH signals of the
minor isomers.[18] The slightly larger k value in 1a2·Zn2
might be attributed to the less sterical hindrance than in
methyl-substituted 1b2·Zn2. Such slow transitions between
the stereoisomers are consistent with the results of the
HPLC analysis to yield the mixture again after a temporary
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Nanoscale Metal Coordination Macrocycles
FULL PAPER
resolution. The transitions between the meso and chiral iso-
mers would be achieved by the 908 rotation of one of the
two dipyrrin–metal units, wherein one of the four b-CH
passes through a nanoscale ring cavity, such as that in mo-
lecular motors or vehicles.[19]
Conclusion
The [2+2]-coordination macrocycles based on the “dimeric”
dipyrrin derivatives have been formed using a template mol-
ecule. Two moieties of achiral ZnII–dipyrrin complex yield
the chiral coordination macrocycles as the minor species, as
well as major meso stereoisomers, by the covalent linkages.
Tetrahedral ZnII coordination using acyclic ligands enables
the dipyrrin–metal complex units to readily rotate and pass
through the cavity of nanoring to reveal the transitions be-
tween the chiral and achiral isomers. Presumably, this obser-
vation—derived from the combination of dipyrrin deriva-
tives and ZnII cations—is not characteristic to planar coordi-
nation moieties. The preliminary studies of dipyrrins with
other metal ions such as CuII and NiII highlight similar
trends such as those in ZnII complexes, and the chemistry
similar to other transition-metal complexes including
1a2·Cu2 and 1a2·Ni2 is currently being investigated by our
group. In sharp contrast to ZnII complexes, any diastereo-
Solid-state structure and assembly of coordination nano-
A
1a2·Zn2 as a major stereoisomer has been revealed by X-ray
diffraction analysis using a single crystal from the mixture of
two diastereomers (Figure 3a). The coordination macrocy-
cle, showing the distorted hexagonal cavity, consists of di-
meric dipyrrins and ZnII cations. The dihedral angle between
the two dipyrrin moieties (a–b) is 89.188, that is, they are
almost perpendicular to each other. The distance between
two ZnII cations is 12.35 Š, and the averaged distances be-
tween the parallel dipyrrin moieties (a–a’ and b–b’) are 6.36
and 10.93 Š, respectively; they exhibit an almost rectangular
geometry (Figure 3b), which is distorted as compared to the
optimized structure (Figure 1a). The distances between the
dipyrrinsꢁ “inner” carbons (C1–C2’) and spacersꢁ inner car-
bons (C3–C3’) are estimated to be 7.63 and 16.23 Š, respec-
tively, and the dihedral angles between the bridged-phenyl
moieties (c–d and d–e) are 30.50 and 47.348, respectively.
Here, like Rebekꢁs molecular capsules,[20] the two THF mol-
ecules used as the solvent are encapsulated in a nanoscale
cavity assisted by the interaction of oxygen with phenyl (d)
CH for a distance of 3.49 Š, although the Osite shows no
coordination with ZnII, as also seen in the phenylethynyl-
substituted dipyrrin–ZnII complex.[12] Like the [3+3]-type
complexes[8] and the assemblies in the solid state,[9] the coor-
dination nanorings in this report are the first examples of
the [2+2]-dipyrrin assemblies with a promising guest-bind-
ing cavity, which are different from the [2+2]-type helical
supramolecular assemblies based on dipyrrin derivatives.[8]
Further, intermolecular donor/donor- and acceptor/ac-
ceptor-type CH-p interactions are observed in C4’-H of di-
pyrrin and C5’-H of the aryl ring to dipyrrin plane (a) with
distances of 3.29 and 3.38 Š, respectively (Figure 3c). There-
fore, a phenyl moiety (c,c’) of the neighboring “nanoring”
seems to be encapsulated in a cavity. Four hydrogen-bond-
ing donating sites and four accepting p planes in each coor-
dination macrocycle (e.g., ring-A (gray)) form the 2D supra-
molecular networks with four macrocycles in the neighbor-
ing layers (ring-B (orange) as hydrogen-bonding donors and
ring-C (blue) as acceptors) using a total of eight interactions
(Figure 3e,f). In the same layer, a macrocycle (A) interacts
with the four neighboring macrocycles (ring-D (purple) and
ring-E (green)) using the donor/acceptor-type CH–p interac-
tions between the ethynyl units and aryl C6–H (3.39 Š) and
dipyrrin C8–H (3.67 Š) (Figure 3d–f). The macrocycles are
stacked with those in the other layers and “connected” with
those in the same layer to yield the molecular “bricks” in
the solid states.
1
mers in 1a2·Ni2 were not observed in the H NMR (CDCl3)
spectra, possibly due to the square-planar geometry of NiII.
Further, as expected from the binding of the solvent mole-
cules in the solid state, the synthesis and investigation of de-
rivatives to encapsulate guest species in solution are also
now in progress.
Experimental Section
General procedures: Starting materials were purchased from Wako
Chemical Co., Nacalai Chemical Co., and Aldrich Chemical Co. and
used without further purification unless otherwise stated. UV-visible
spectra were recorded on a Hitachi U-3500 spectrometer. NMR spectra
used in the characterization of products were recorded on a JEOL ECA-
600HR 600 MHz spectrometer. All NMR spectra were referenced to sol-
vent. Fast atom bombardment mass spectrometric studies (FAB-MS)
were made using a JOEL GCmate instrument in the positive ion mode
with a 3-nitrobenzylalcohol matrix. Electrospray ionization time-of-flight
mass spectrometric studies (ESI-TOF-MS) were made using a Bruker mi-
croTOF focus instrument in the positive ion mode with a silver(I) per-
chlorate. Matrix assisted laser desorption/ionization time-of-flight mass
spectrometric studies (MALDI-TOF-MS) were made using a SHIMAD-
ZU MALDI-II instrument in the positive ion mode with a 7,7,8,8-tetra-
cyanoquinodimethane matrix. TLC analyses were carried out on alumi-
num sheets coated with silica gel 60 (Merck 5554). Column chromatogra-
phy was performed on Sumitomo alumina KCG-1525 and Wakogel C-
300. GPC-HPLC and Chiral-HPLC analyses were performed with a
JASCOPU-980 instrument (JAIGEL 4H-AF, 3H-AF, and 2.5H-AF) and
a SHIMADZU LC-6AD instrument (SUMICHIRAL OA-3100), respec-
tively. Synthesis of compound 1a has been reported in the literature pro-
cedures.[12]
Synthesis and spectroscopic data for dipyrrin dimers, their precursors,
and metal complexes
1,3-Bis(di-5-methylpyrrol-2-ylmethylphenylethynyl)benzene (DPM-1b):
1,4-Bis(4-formylphenylethynyl)benzene (42.8 mg, 0.13 mmol) and 2-meth-
ylpyrrole (102.6 mg, 1.26 mmol) were dissolved in CH2Cl2 (11 mL) and
degassed by bubbling with nitrogen for 20 min. Trifluoroacetic acid
(3.0 mL, 0.018 mmol) was added and the solution was stirred for 20 min.
The reaction mixture was diluted with CH2Cl2 (20 mL), washed with
0.1m NaOH aq. (20 mL) and brine (20 mL), then dried over Na2SO4, and
evaporated to remove CH2Cl2. The remaining pyrrole was removed by
vacuum distillation with gentle heating. The product was purified by
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H. Maeda and T. Hashimoto
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Nanoscale Metal Coordination Macrocycles
FULL PAPER
silica gel column chromatography (50% hexane/CH2Cl2) and recrystal-
lized from CH2Cl2/hexane to afford DPM-1b (68.1 mg, 85%) as a dark
red solid. Rf =0.67 (50% hexane/CH2Cl2); 1H NMR (600 MHz, CDCl3,
208C): d=7.68 (brs, 4H; NH), 7.45 (dd, J=7.8, 1.8 Hz, 2H; ArH), 7.43
(s, 1H; ArH), 7.42 (ddd, J=7.2, 1.2, 1.2 Hz; 2H, ArH), 7.33–7.29 (m,
3H; ArH), 7.23–7.21 (m, 2H; ArH), 5.81 (dd, J=3.0, 3.0 Hz, 4H; pyr-
role-H), 5.77 (dd, J=3.0, 3.0 Hz, 4H; pyrrole-H), 5.36 (s, 2H; mesoH),
2.22 ppm (s, 12H; CH3); FABMS: m/z (%): calcd for C44H38N4: 622.31;
found: 622.4 [M]+ (100), 623.4 [M+1]+ (47).
1250.3 [M+H+1]+ (57), 1251.3 [M+H+2]+ (90), 1252.3 [M+H+3]+ (83),
1253.3 [M+H+4]+ (100), 1254.3 [M+H+5]+ (76), 1255.3 [M+H+6]+
(56), 1256.3 [M+H+7]+ (33), 1257.3 [M+H+8]+ (25), 1258.3 [M+H+9]+
(19); calcd for C80H48N8Zn2 +Ag: 1355.16; found: 1355.2 [M+Ag]+ (34),
1356.2 [M+Ag+1]+ (31), 1357.2 [M+Ag+2]+ (80), 1358.2 [M+Ag+3]+
(66), 1359.2 [M+Ag+4]+ (100), [M+Ag+5]+ 1360.2 (78), 1361.2
[M+Ag+6]+ (81), 1362.2 [M+Ag+7]+ (57), 1363.2 [M+Ag+8]+ (40),
1364.2 [M+Ag+9]+ (25), 1365.2 [M+Ag+10]+ (15).
CuII complex of 1a (1a2·Cu2): Cu
(OAc)2 (24.3 mg, 0.13 mmol) was added
A
1,3-Bis(bis-5-hexadecylpyrrol-2-ylmethylphenylethynyl)benzene (DPM-
1c): 1,4-Bis(4-formylphenylethynyl)benzene (19.5 mg, 0.06 mmol) and 2-
hexadecylpyrrole (160.2 mg, 0.55 mmol) was dissolved in CH2Cl2
(7.0 mL) and degassed by bubbling with nitrogen for 20 min. Trifluoro-
acetic acid (2.0 mL, 0.012 mmol) was added and the solution was stirred
for 40 h. The reaction mixture was diluted with CH2Cl2 (50 mL), washed
with 0.1m NaOH aq. (50 mL) and brine (50 mL), then dried over
Na2SO4, and evaporated to remove CH2Cl2. The remaining pyrrole was
removed by vacuum distillation with gentle heating. The product was pu-
rified by silica gel column chromatography (CH2Cl2/hexane/Et3N
to a CHCl3 solution (60 mL) of dipyrrin 1a (74.8 mg, 0.13 mmol) and
pyrene (13.7 mg, 0.07 mmol), and the reaction mixture was heated at
reflux temperature for 2 h. The solution was evaporated and purified by
silica gel column chromatography (10% hexane/CHCl3) and recrystal-
lized from CHCl3/hexane to afford 1a2·Cu2 (59.1 mg, 71%) as a dark red
solid. Rf =0.84 (1% MeOH/CH2Cl2); UV/Vis (CHCl3): lmax (e”10ꢁ5)=
469 nm (1.5mꢁ1 cmꢁ1); ESI-TOF-MS: m/z (%): calcd for C80H48Cu2N8 +
H: 1247.27; found: 1247.3 [M+H]+ (89), 1248.3 [M+H+1]+ (90), 1249.3
[M+H+2]+ (100), 1250.3 [M+H+3]+ (73), 1251.3 [M+H+4]+ (35),
1252.3 [M+H+5]+ (25), 1253.3 [M+H+6]+ (14); calcd for C80H48Cu2N8 +
Ag: 1353.16; found: 1353.2 [M+Ag]+ (43), 1354.2 1353.2 [M+Ag+1]+
(38), 1355.2 [M+Ag+2]+ (100), 1356.2 [M+Ag+3]+ (78), 1357.2
[M+Ag+4]+ (75), 1358.2 [M+Ag+5]+ (51), 1359.2 [M+Ag+6]+ (31),
1360.2 [M+Ag+7]+ (14).
50:49:1) to afford DPM-1c quantitatively as
a red solid. Rf =0.85
(CH2Cl2); 1H NMR (600 MHz, CDCl3, 208C): d=7.91 (brs, 4H; NH),
7.66–7.65 (m, 4H; ArH), 7.50 (m, 1H; ArH), 7.45–7.41 (m, 6H; ArH),
7.29 (t, J=8.4 Hz, 2H; ArH), 7.20 (m, 1H; ArH), 5.81 (dd, J=2.4 Hz,
4H; pyrrole-H), 5.75 (dd, J=2.4, 2.4 Hz, 4H; pyrrole-H), 5.36 (s, 2H;
meso-H), 2.52 (t, J=7.8 Hz, 8H; CH2C14H28CH3), 1.24 (m, 112H;
CH2C14H28CH3), 0.87 ppm (m, 12H; CH2C14H28CH3); ESI-TOF-MS (ob-
served with the existence of both AgClO4 and TCNQ as matrix): m/z
(%): calcd for C104H158N4 +Ag: 1570.15; found: 1570.2 [M+Ag]+ (68),
1571.1 [M+Ag+1]+ (59), 1572.1 [M+Ag+2]+ (100), 1573.2 [M+Ag+3]+
(75), 1574.2 [M+Ag+4]+ (54).
NiII complex of 1a (1a2·Ni2): Ni
(OAc)2·4H2O(34.4 mg, 0.14 mmol) was
A
added to a CHCl3 solution (60 mL) of dipyrrin 1a (77.7 mg, 0.14 mmol)
and pyrene (14.0 mg, 0.07 mmol), and the reaction mixture was heated at
reflux temperature for 24 h. The solution was evaporated and purified by
silica gel column chromatography (3% MeOH/CHCl3) and recrystallized
from CHCl3/hexane to afford 1a2·Ni2 (74.5 mg, 87%) as a dark red solid.
Rf =0.38 (1% MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3, 208C): d=
9.29 (brs, 8H; pyrrole-H), 7.74 (s, 2H; ArH), 7.61–7.60 (m, 8H; ArH),
7.48 (d, J=8.4 Hz, 4H; ArH), 7.43–7.34 (m, 18H; ArH+pyrrole-H),
6.77 ppm (brs, 8H; pyrrole-H); UV/Vis (CHCl3): lmax (e”10ꢁ5)=476 nm
(0.89mꢁ1 cmꢁ1); ESI-TOF-MS: m/z (%): calcd for C80H48N8Ni2 +Ag:
1343.18; found: 1343.2 [M+Ag]+ (52), 1344.2 [M+Ag+1]+ (57), 1345.2
[M+Ag+2]+ (100), 1346.2 [M+Ag+3]+ (89), 1347.2 [M+Ag+4]+ (83),
1348.1 [M+Ag+5]+ (70), 1349.2 [M+Ag+6]+ (43), 1350.2 [M+Ag+7]+
(35), 1351.1 [M+Ag+8]+ (27).
1,3-Bis
N
N
thane DPM-1b (67.2 mg, 0.108 mmol) dissolved in THF (20 mL) was
stirred, and DDQ (48.9 mg, 0.215 mmol) was slowly added. The reaction
mixture was purified by alumina and silica gel column chromatography
(CH2Cl2) to afford 1b (48.2 mg, 72%) as a dark red solid. Rf =0.40 (5%
MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3, 208C): d=7.71 (m, 1H;
ArH), 7.63 (m, 2H; ArH), 7.60 (ddd, J=7.2, 1.2, 1.2 Hz, 2H; ArH),
7.43–7.42 (m, 4H; ArH), 7.40 (dd, J=7.8, 7.8 Hz, 1H; ArH), 6.45 (d, J=
4.2 Hz, 4H; pyrrole-H), 6.17 (d, J=4.2 Hz, 4H; pyrrole-H), 2.45 ppm (s,
12H; CH3); UV/Vis (CHCl3): lmax (e”10ꢁ5)=446 nm (0.39mꢁ1 cmꢁ1);
FABMS: m/z (%): calcd for C44H34N4: 618.28; found: 619.4 [M+1]+
(100), 620.4 [M+2]+ (64).
ZnII complex of 1b (1b2·Zn2): Zn
(OAc)2·2H2O(8.2 mg, 0.037 mmol) was
G
added to a CHCl3 solution (20 mL) of dipyrrin 1b (23.1 mg, 0.037 mmol)
and pyrene (3.8 mg, 0.019 mmol), and the reaction mixture was heated at
reflux temperature for 4 h. The solution was evaporated and purified by
silica gel column chromatography (5% MeOH/CHCl3) and recrystallized
from CHCl3/hexane to afford 1b2·Zn2 (12.6 mg, 49%) as a dark red solid.
Rf =0.93 (5% hexane/CH2Cl2); 1H NMR (600 MHz, CDCl3, 208C): d=
7.74–7.60 (m, 10H; ArH), 7.53–7.49 (m, 8H; ArH), 7.43–7.40 (m, 4H;
ArH), 7.38–7.35 (m, 2H; ArH), 6.64–6.55 (m, 8H; pyrrole-H), 6.23–6.19
(m, 8H; pyrrole-H), 2.16–2.05 ppm (m, 24H; CH3); UV/Vis (CHCl3):
lmax (e”10ꢁ5)=493.0 nm (2.3mꢁ1 cmꢁ1); FABMS: m/z (%): 1363.3
[M+3]+ (77), 1364.3 [M+4]+ (100), 1365.2 [M+5]+ (77); ESI-TOF-MS:
m/z (%): calcd for C88H64N8Zn2+H: 1361.39; found: 1361.4 [M+H]+
(92), 1362.4 [M+H+1]+ (85), 1363.4 [M+H+2]+ (87), 1364.4 [M+H+3]+
(100), 1365.4 [M+H+4]+ (97), 1366.4 [M+H+5]+ (77), 1367.4
[M+H+6]+ (58), 1368.4 [M+H+7]+ (34), 1369.4 [M+H+8]+ (29), 1370.4
[M+H+9]+ (18); calcd for C88H64N8Zn2+Ag: 1467.29; found: 1467.3
[M+Ag]+ (31), 1468.3 [M+Ag+1]+ (31), 1469.3 [M+Ag+2]+ (73),
1470.3 [M+Ag+3]+ (73), 1471.3 [M+Ag+4]+ (100), 1472.3 [M+Ag+5]+
(82), 1473.3 [M+Ag+6]+ (90), 1474.3 [M+Ag+7]+ (58), 1475.3
[M+Ag+8]+ (47), 1476.3 [M+Ag+9]+ (29), 1477.3 [M+Ag+10]+ (18),
1,3-Bis(5,5’-bis(hexadecyl)dipyrrilylphenylethynyl)benzene (1c): Dipyrro-
A
methane DPM-1c (44.4 mg, 0.03 mmol) was dissolved in THF (15 mL).
DDQ (13.8 mg, 0.06 mmol) was added and stirred 10 min. The reaction
mixture was purified by alumina and silica gel column chromatography
(CH2Cl2) to afford 1c (31.2 mg, 70%) as a dark red solid. Rf =0.53
(CH2Cl2); 1H NMR (600 MHz, CDCl3, 208C): d=7.70 (dd, J=1.8,
1.2 Hz, 1H; ArH), 7.64 (s, 1H; ArH), 7.59 (ddd, J=7.8, 1.2, 1.2 Hz, 2H;
ArH), 7.48 (dd, J=8.4, 1.8 Hz, 2H; ArH), 7.45–7.43 (m, 2H; ArH), 7.40
(t, J=7.8 Hz, 2H; ArH), 7.33 (t, J=8.4 Hz, 1H; ArH), 6.47 (d, J=
4.2 Hz, 4H; pyrrole-H), 6.18 (d, J=4.2 Hz, 4H; pyrrole-H), 2.74 (t, J=
7.8 Hz, 8H; CH2C14H28CH3), 1.25 (m, 112H; CH2C14H28CH3), 0.87 ppm
(t, J=7.2 Hz, 12H; CH2C14H28CH3); UV/Vis (CHCl3): lmax (e”10ꢁ5)=
450 nm (0.41mꢁ1 cmꢁ1); FABMS: m/z (%): calcd for C104H154N4: 1459.22;
found: 1460.8 [M+1]+ (100), 1461.7 [M+2]+ (79).
ZnII complex of 1a (1a2·Zn2): Zn
(OAc)2·2H2O(11.4 mg, 0.05 mmol) was
G
added to a CHCl3 solution (25 mL) of dipyrrin 1a (28.0 mg, 0.05 mmol)
and pyrene (5.2 mg, 0.03 mmol), and the reaction mixture was heated at
reflux temperature for 47 h. The solution was evaporated and purified by
silica gel column chromatography (5% MeOH/CHCl3) and recrystallized
from CHCl3/hexane to afford 1a2·Zn2 (24.1 mg, 77%) as a yellow solid.
Rf =0.62 (3% MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3, 208C): d=
7.77–7.72 (m, 6H; ArH), 7.67–7.64 (m, 4H; ArH), 7.58–7.50 (m, 16H;
ArH, pyrrole-H), 7.47–7.45 (m, 4H; ArH), 7.39–7.36 (m, 2H; ArH),
6.79–6.70 (m, 8H; pyrrole-H), 6.43–6.41 ppm (m, 8H; pyrrole-H); UV/
Vis (CHCl3): lmax (e”10ꢁ5)=486 nm (2.2mꢁ1 cmꢁ1); ESI-TOF-MS: m/z
(%): calcd for C80H48N8Zn2 +H: 1249.27; found: 1249.3 [M+H]+ (59),
ZnII complex of 1c (1c2·Zn2): Zn
(OAc)2·2H2O(4.7 mg, 0.02 mmol) was
T
added to a CHCl3 solution (25 mL) of dipyrrin 1c (31.2 mg, 0.02 mmol)
and pyrene (2.4 mg, 0.01 mmol), and the reaction mixture was heated at
reflux temperature for 10 h. The solution was evaporated and purified by
silica gel column chromatography (50% hexane/CH2Cl2) to afford
1c2·Zn2 (13.1 mg, 40%) as a dark red oil. Rf =0.89 (CH2Cl2); 1H NMR
(600 MHz, CDCl3, 208C): d=7.74–7.71 (m, 2H; ArH), 7.68–7.67 (m, 4H;
ArH), 7.62–7.59 (m, 4H; ArH), 7.50–7.46 (m, 8H; ArH), 7.41–7.38 (m,
4H; ArH), 7.36–7.34 (m, 2H; ArH), 6.62–6.55 (m, 8H; pyrrole-H), 6.23–
Chem. Eur. J. 2007, 13, 7900 – 7907
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
7905

H. Maeda and T. Hashimoto
6.19 (m, 8H; pyrrole-H), 2.41–2.36 (m, 16H; CH2C14H28CH3), 1.25–1.08
(m, 224H; CH2C14H28CH3), 0.89–0.85 ppm (m, 24H; CH2C14H28CH3);
UV/Vis (CHCl3): lmax (e”10ꢁ5)=496.0 nm (1.9mꢁ1 cmꢁ1); MALDI-TOF-
MS: m/z (%): calcd for C208H304N8Zn2: 3042.26; found: 3045.8 [M+3]+
(91), 3048.6 [M+6]+ (100).
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Optimized structure: AM1 calculations of 1a,b2·Zn2 (LD-type) and
1a,b2·Zn2 (LL-type) were carried out using Gaussian 03 program[15] and
an HP Compaq dc5100 SFF computer.
X-ray crystallography: Data was collected on a Bruker SMART CCDC
for 1a2·Zn2, refined by full-matrix least-squares procedures with aniso-
tropic thermal parameters for the non-hydrogen atoms. The hydrogen
atoms were calculated in ideal positions. Solutions of the structures were
performed by using the Crystal Structure crystallographic software pack-
age (Molecular Structure Corporation).
Crystal data for 1a2·Zn2 (from THF/chlorobenzene/hexane):
C88H64N8O2Zn2, Mw =1396.21, monoclinic, C2/c (no.15), a=36.946(13),
b=17.364(5), c=11.406(4) Š, b=106.119(13)8, V=7029(4) Š3, T=
123(2) K, Z=4, 1calcd =1.319 gcmꢁ3
,
m , reflections
(MoKa)=0.739 mmꢁ1
A
collected=54701, independent reflections=14022 (Rint =0.1120), R1 =
0.0884, wR2 =0.1816, GOF=0.987 (I > 2s(I)). CCDC-635600 contains
the supplementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
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no chirality, we define configurations L and D by the moieties in-
cluding dipyrrin and the neighboring meso-aryl moiety, which is
tilted at ca. 458 to the dipyrrin plane, as shown below.
Acknowledgements
This work was supported by the “Academic Frontier” Project for Private
Universities, namely, the matching fund subsidy from MEXT, 2003–2008,
Saneyoshi Scholarship Foundation, and the Japan Securities Scholarship
Foundation. We thank Professor Atsuhiro Osuka, Mr. Shigeki Mori and
Mr. Shohei Saito, Kyoto University, for X-ray analysis, Professor Hiroshi
Shinokubo, Mr. Satoru Hiroto, and Mr. Chihiro Maeda, Kyoto Universi-
ty, for ESI-TOF-MS and HPLC analyses, Dr. Tomohiro Miyatake, Ryu-
koku University, for FAB-MS measurements, and Professor Hitoshi Ta-
miaki, Professor Tadashi Mizoguchi, and Dr. Michio Kunieda, Ritsumei-
kan University, for helpful discussions.
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7906
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Chem. Eur. J. 2007, 13, 7900 – 7907

Nanoscale Metal Coordination Macrocycles
FULL PAPER
nayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen,
M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian, Inc., Wallingford
CT, 2004.
ternal b-CH protons of the major isomer at thermal equilibrium
state; M0Ae: the magnetization of the external b-CH protons of the
major isomer at thermal equilibrium state; T1Ai: the relaxation time
of the internal b-CH protons of the major isomer; T1Ae: the relaxa-
tion time of the external b-CH protons of the major isomer; kA: the
rate constant from the major to minor isomer; kB: the rate constant
from the minor to major isomer) and the conditions such as
[16] Under this HPLC condition, one of the minor “two” peaks derived
from the chiral stereoisomers of 1a2·Zn2 overlaps with the major
single peak of the achiral isomer, as suggested from the UV/Vis ab-
sorption spectra (which differ in two stereoisomers), during the
analysis. See Supporting Information.
dðMAiþMAe
dt
Þ
,
MBi =0, T1Ai =T1Ae =T1A (by measurements), and kB =
[17] The equilibrium constants K between the chiral and meso isomers
of C16H33-substituted 1c2·Zn2 at 60, 20, and ꢁ208C are 5.4, 4.6, and
4.4, respectively, with the corresponding DG0 of ꢁ4.1, ꢁ3.7, and
ꢁ3.6 kJmolꢁ1. By using van ꢁt Hoff plots, the thermodynamic param-
eters (DH0 and DS0) of 1c2·Zn2 are estimated to be 1.7 kJmolꢁ1 and
19 JKꢁ1 molꢁ1, which are similar to those of 1a2·Zn2 and 1b2·Zn2.
The derivative with long alkyl substituents at the dipyrrin units also
seems to enable the interconversion between the two stereoisomers,
possibly due to the flexible aliphatic chains.
K·kA (K: equilibrium constant between the major and minor iso-
mers), the rate constant kA can be estimated as shown below: kA =
ðM0Ai ꢁMAiÞþðM0Ae ꢁMAe
Þg. It affords the values of 0.5 (1a2·Zn2) and 0.3 sꢁ1
T1AÂfðMAiþMAeÞꢁKÁMBe
(1b2·Zn2), respectively.
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[18] Under the irradiation of one of the internal b-CH protons of the
minor isomer for 60 s and using the hypothetical equation
dðMAiþMAe
dt
0Ai ꢁMAi
M0Ae ꢁMAe
Þ =ꢁkA
(MAi+MAe)+kB
U
+
(MAi:
T1Ai
T1Ae
the magnetization of the internal b-CH protons of the major isomer
(A); MAe: the magnetization of the external b-CH protons of the
major isomer; MBi: the magnetization of the internal b-CH protons
of the minor isomer (B); MBe: the magnetization of the external b-
CH protons of the minor isomer; M0Ai: the magnetization of the in-
[20] J. Rebek, Jr., Angew. Chem. 2005, 117, 2104–2115; Angew. Chem.
Int. Ed. 2005, 44, 2068–2078.
Received: March 22, 2007
Published online: July 3, 2007
Chem. Eur. J. 2007, 13, 7900 – 7907
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
7907