Synthesis, structure and metal binding property of internally 1,3-arylene-bridged azacalix[6]aromatics

Article abstract of DOI:10.1021/jo301528f

Three internally 1,3-arylene-bridged azacalix[6]aromatics 1-3 were synthesized by the Pd-catalyzed macrocyclic fragment coupling reaction between a stellated dibrominated pentamer and N²,N⁶- dimethylpyridine-2,6-diamine or N¹,N³-dimethylbenzene-1,3- diamine. Single-crystal X-ray analysis revealed that these bimacrocyclic compounds all adopt a triply pillared groove-shaped conformation, conceptually being derived from the fusion of two 1,3-alternate macrocycles. Four host/metal discrete complexes of the all-pyridine host 1, {Co(1)(CH₃OH) ₂}(CoCl₄)·3(CH₃OH), {Ni(1)(CH ₃OH)₂}(NiCl₄), {Ni(1)(CH₃OH) ₂}(ClO₄)₂·CH₃OH and {Cd ₂(1)(CH₃CN)₄(H₂O) ₄}(ClO₄)₄, have been structurally characterized by X-ray crystallographic analysis, exploring two different metal binding modes. The metal complexation property of the host 1 in solution was then investigated by the UV-vis and NMR titration. With variation of the radii of the tested metal ions (Mn²⁺, Fe²⁺, Co²⁺, Ni ²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Hg ²⁺), the host 1 can trap one or two metal ions via four different modes by using its two coordination cavities or two marginal pyridine rings. Such metal binding diversity of internally bridged heteracalixaromatics spotlights their potential applications in metal ion transport, ion channel, and metallo-enzyme mimics.

Full text of DOI:10.1021/jo301528f

Article
pubs.acs.org/joc
Synthesis, Structure and Metal Binding Property of Internally
1,3-Arylene-Bridged Azacalix[6]aromatics
Yi-Xin Fang,† Liang Zhao,*,‡ De-Xian Wang,† and Mei-Xiang Wang*,‡
†Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
‡Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Department of Chemistry,
Tsinghua University, Beijing 100084, China
S
* Supporting Information
ABSTRACT: Three internally 1,3-arylene-bridged azacalix[6]aromatics
1−3 were synthesized by the Pd-catalyzed macrocyclic fragment coupl-
ing reaction between a stellated dibrominated pentamer and N2,N6-
dimethylpyridine-2,6-diamine or N1,N3-dimethylbenzene-1,3-diamine.
Single-crystal X-ray analysis revealed that these bimacrocyclic com-
pounds all adopt a triply pillared groove-shaped conformation, concep-
tually being derived from the fusion of two 1,3-alternate macrocycles.
Four host/metal discrete complexes of the all-pyridine host 1, {Co(1)-
(CH3OH)2}(CoCl4)·3(CH3OH), {Ni(1)(CH3OH)2}(NiCl4), {Ni(1)-
(CH3OH)2}(ClO4)2·CH3OH and {Cd2(1)(CH3CN)4(H2O)4}-
(ClO4)4, have been structurally characterized by X-ray crystallographic
analysis, exploring two different metal binding modes. The metal
complexation property of the host 1 in solution was then inves-
tigated by the UV-vis and NMR titration. With variation of the radii of the tested metal ions (Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+,
Cd2+, and Hg2+), the host 1 can trap one or two metal ions via four different modes by using its two coordination cavities or two
marginal pyridine rings. Such metal binding diversity of internally bridged heteracalixaromatics spotlights their potential applica-
tions in metal ion transport, ion channel, and metallo-enzyme mimics.
expansion of macrocycles due to their highly flexible and
fluxional conformations.
INTRODUCTION
■
The synthesis and property studies of new macrocyclic com-
pounds have been a research focus in host−guest chemistry
because of their extensive applications from ion transport,1
chemosensing and imaging,2 and catalysis3 to nuclear waste
treatment.4 Heteracalixaromatics, a new generation of macro-
cyclic host molecules with heteroatoms in place of the bridging
methylene moieties in conventional calixarenes, have received
growing attention in recent years.5 Because of different electronic
nature of heteroatoms (such as O6 and N5e,7) from the sp3 car-
bon in conventional calixarenes, these heteroatom-bridged calix-
(hetero)aromatics exhibit exceptional structural tunability and
interesting molecule and ion recognition properties.5,8 Among
them, azacalix[n]pyridines have exhibited comprehensive molec-
ular recognition properties due to the coordination and hydrogen-
bonding receptor nature of their multinitrogen-containing skele-
tons.5c For example, tetramethylazacalix[4]pyridine has been utilized
in recognizing various metal cations9 and neutral molecules
(both aromatic and aliphatic diols and monools)10 by its
dominant 1,3-alternate conformation and its protonated form
can accommodate diverse anionic guests of different size and
geometry as well.11 However, although the larger homologues of
azacalix[4]pyridine have been successfully synthesized by us in
comparable yields,7d their practical applications in molecular
recognition become increasingly difficult along with the size
Recently, Osuka and co-workers introduced an internally
bridged 1,4-phenylene group into an expanded porphyrin system
in order to suppress the intrinsic twisting of such macrocycles
with increasing number of pyrrolic subunits.12 We thus envi-
sioned that this bridging method may be applicable in stabilizing
the conformation of the large azacalixaromatics and thus facil-
itates their potential applications in molecular recognition. This
bimacrocyclic arrangement can be described as the fusion of
two regular azacalixaromatics, possibly exhibiting specific metal
ion recognition properties and providing a bimetallic cavity for
metalloenzyme mimic13 and the development of new bifunctional
catalysts.14 We report herein the synthesis of three internally 1,3-
arylene-bridged azacalix[6]aromatics 1-3, in which the 1,3-arylene
bridging unit was found to bisect and resultingly fix the macro-
cycles of azacalix[6]aromatics based on single crystal X-ray analysis
and NMR studies. The all-pyridine host 1 was screened for its
ability to bind a series of metal ions using UV−vis titration,
wherein the 1:1 and 1:2 host-metal binding stoichiometries were
observed. Further NMR investigation and crystal structure
Received: July 30, 2012
Published: October 28, 2012
© 2012 American Chemical Society
10073
dx.doi.org/10.1021/jo301528f | J. Org. Chem. 2012, 77, 10073−10082

The Journal of Organic Chemistry
Article
pyridine pentamer 7, with a consideration that the early introduc-
tion of the bulky triarylamine moieties into the coupling frag-
ments may improve the final-step macrocyclization yield of 1.
The preparation of the NH-bridged α,ω-dibrominated linear
trimer 11 was made possible in 81% yield by the nucleophilic
substitution reaction between 2,6-diaminopyridine 8 and 2,6-
dibromopyridine 10 with KOtBu as a base. However, this kind of
nucleophilic substitution reaction is not applicable for the syn-
thesis of the key building block 7 even using sodium hydride as a
strong base. We then adopted the CuI-mediated Ullmann cou-
pling reaction of 10 and 11 to prepare 7 (Scheme 2). After optimiz-
ing reaction conditions, a yield of 33% for compound 7 was
finally achieved by operating the reaction at 100 °C in dimethyl-
formamide (DMF) in the presence of NaH as a base. When the
NH-bridged arene trimer analogue 12 was employed for the
synthesis of the pentamer 13, the loading amount of CuI can be
lowed to 10% mol and a moderate yield of 51% was acquired
by performing the reaction in dimethyl sulfoxide (DMSO) in the
presence of K2CO3 and phenanthroline as a base and an additive,
respectively.
With the stellated tetrabromide compounds 7 and 13 in
hand, we carried out their macrocyclization reaction with the
diaminated compounds 6 and 14 by different combinations in
order to produce three internally bridged calixaromatic targets
1-3. In our previous work on the synthesis of azacalix[n]pyridines,
the Pd-catalyzed Buchwald−Hartwig coupling reaction has shown
high efficiency in the final macrocyclization step.7d Under similar
conditions using Pd2(dba)3 (10 mol %), dppp (20 mol %), and
NaOtBu (3 equiv), substrates 6 and 7 were refluxed in toluene for
6htoafford the desired product 1 in a yield of 34% (Table 1, entry 1).
Further elevating the amount of 6 can not improve the yield of 1,
which instead resulted in more oligomeric products. In contrast,
the yields of the macrocyclization reactions between the arene-
contained stellated pentamer 13 and the diaminated compound 6
or 14 can be enhanced upon increasing the amount of the diaminated
reactant (Table 1, entries 4 and 7). In these two reactions, high
dilution is not required to prevent polymerization (Table 1, entry 5).
This is probably ascribed to the conformation difference of
7 and 13 derived from different conjugation scenarios between
the central pyridine ring (for 7) or arene ring (for 13) and its
adjacent bridging nitrogen atoms. We hypothesize that the yield
difference between 1 and 2−3 may originate from the influence
of the electron-rich phenylene ring in 13, which is more favored
studies of four 1·metal complexes explored four different metal
binding modes of 1.
RESULTS AND DISCUSSION
■
Synthesis of Internally 1,3-Arylene-Bridged Azacalix[6]-
aromatics 1−3. Retrosynthetically, the disconnection of the
target molecule 1, an azacalix[6]pyridine internally bridged by a
pyridine ring, mainly leads to two promising routes (Scheme 1).
The first possible route (approach I) refers to the coupling be-
tween a (NH)2(NMe)2-bridged calix[4]pyridine compound 4 and a
α,ω-dibromonated linear trimer 5. However, the Pd-catalyzed
Buchwald−Hartwig coupling reaction15 between 4 and 5 at 110 °C
in toluene in the presence of bis(diphenylphosphino)propane
(dppp) as a ligand and NaOtBu as a base only produced the desired
compound 1 in a quite low yield of 5%. MALDI-TOF mass spectra
revealed that main isolated products formed in this reaction are the
oligomers of 4 and 5. This implies that the macrocyclization step is
unfavored, which can be rationalized by the fact that it is difficult to
simultaneously introduce two triarylamine moieties into a macro-
cycle due to the steric hindrance.
We then divided compound 1 into three fragments (approach II),
two 2,6-diaminated pyridine units of 6 and a stellated N-bridged
Scheme 1. Retrosynthetic Analysis of the 1,3-Pyridyl-Bridged Azacalix[6]pyridine 1
10074
dx.doi.org/10.1021/jo301528f | J. Org. Chem. 2012, 77, 10073−10082

The Journal of Organic Chemistry
Article
Scheme 2. Synthesis of the Stellated Pentamers 7 and 13
Table 1. Synthesis of the Internally 1,3-Arylene-Bridged Azacalix[6]aromatics 1−3
a
b
entry
reactant
ratio
product
yield (%)
1
2
3
4
5
6
7
7
6
0.55:1
1:6
1
1
2
2
2
3
3
34
26
36
51
49
29
48
7
6
13
13
13
13
13
6
0.55:1
1:6
6
c
6
1:6
14
14
0.55:1
1:6
a
b
c
Reaction conditions: 10 mol % of Pd2(dba)3, 20 mol % of dppp, 3 equiv NaOtBu, refluxing in toluene. Isolated yield. Concentrations of 13 and 6
are 1.1× 10−2 M and 6.6 × 10−2 M, respectively.
for the Buchwald−Hartwig reaction than the electron-deficient
pyridine-containing compound 7.
nitrogen atom (highlighted in red in Figure 1) is approximately 124°,
larger than the rest ∠C−N−C angles for the bridging nitrogen atoms
in the range of 117−120°. In addition, conjugation scenarios between
these bridging nitrogen atoms and adjacent aromatic rings are
also different in 1−3. The bridging nitrogen atoms conjugate well
with the procumbent pyridine rings in each compound case,
while as to the vertical aromatics the conjugation between the
bridging nitrogen atoms and the electron deficient pyridine rings
is better than that of the phenyl rings. It is noteworthy that two
methanol molecules are accommodated within the groove of
compound 1 through the hydrogen bonds at O1···N3 = 2.917
(4) Å and O2···N7 = 2.902 (4) Å. In contrast, compound 2 only
weakly interacts with a dichloromethane molecule (the occupancy
ratio is 0.25) by a C−H···N hydrogen bond. Compound 3 exhibits
no solvent molecule recognition based on its crystal structure. This
observation spotlights the advantage of the all-pyridine compound
1 in molecular recognition due to its multiple bonding sites of co-
ordination and hydrogen bonding.
Structural Characterization of 1−3. The molecular
structures of 1−3 were first established by X-ray crystallography.
Single-crystal X-ray crystallographic studies revealed that com-
pounds 1−3 each featuring a bicyclic scaffold adopt a juxtaposed
1,3-alternate conformation. As shown in Figure 1, four procumbent
pyridine rings in each compound constitute a groove through the
bridging of three central vertical aromatics, which are parallel to
each other but no π−π stacking therein. Each N-Me bridging
nitrogen atom in 1−3 exhibits a sp2 electron configuration with
the summation of three ∠C−N−C bond angles close to 360°. A
pair of nitrogen atoms of the triarylamine N(Ar)3 moieties in
1−3 (such as N6 and N8 in 1) were found to display significant
sp2 feature with a ∠C−N−C bond angle summation of 360° but
involving almost isometric C−N bong lengths. Because of severe
steric hindrance between aromatic rings in such triarylamine
moieties, an outward ∠Cpyridine−N−Cpyridine angle of each triarylamine
10075
dx.doi.org/10.1021/jo301528f | J. Org. Chem. 2012, 77, 10073−10082

The Journal of Organic Chemistry
Article
Figure 1. Crystal structures (thermal ellipsoids at the 50% probability level) of (a) 1·2CH3OH, (b) 2·0.25CH2Cl2 (dichloromethane molecule is
omitted for clarity), and (c) 3. Color scheme for atoms: C black, H gray, O red, N blue.
Structural investigation of 1−3 in solution was carried out with
one- and two-dimensional NMR spectroscopy (Figures S5−S19,
Supporting Information). The 1H and 13C NMR signals of 1−3
are consistent with a C2-symmetrical conformation shown in
their crystal structures. Upon the gradual introduction of the
electron-rich 1,3-phenylene ring into the bicyclo skeleton from 1
to 3, the characteristic singlet peak of the bridging N-Me moiety
undergoes a slight upfield shift from 3.31 ppm for 1, through
3.28 ppm for 2 to 3.25 ppm for 3. Although the three central
vertical aromatic rings in 1−3 have poor conjugation with
their adjacent bridging nitrogen atoms in comparison with the
four procumbent rings reflected by their crystal structures, the
resonance peaks of the protons on such three central rings are
instead at an upfield region. This is possibly associated with a
parallel face-to-face arrangement of the vertical rings. In that way,
every vertical ring is situated on the shielding region of the other
two. This rationale is also applicable to an approximately 0.4 ppm
chemical shift difference between Hc and He as shown in Figure 2.
It is obvious that each He of one pyridine ring (I) is located at
the deshielding position of the adjacent procumbent pyridine
ring (I′). From the variable-temperature proton NMR of 1
(Figure 2), we found that the resonance of Hf and Hg both
experience an upfield shift (0.14 and 0.06 ppm, respectively)
upon decreasing the temperatures from 298 to 198 K whereas the
rest proton peaks only have a small shift. A similar NMR peak
variation is observed as well in the variable-temperature proton
NMR spectra of 2 and 3 (Figures S20 and S21, Supporting
Information). This observation imply that the conformation of
the internally bridged calix[6]aromatics 1−3 are so rigid that
only the central aromatic ring can adjust its position very slightly.
Crystal Structures of Four 1·Metal Complexes. Since
compound 1 is constituted all by pyridine rings, we expect it is
suitable for metal ion recognition by metal-pyridine coordina-
tion. The phenylene-bridged compounds 2 and 3 may diminish
such coordination effects due to the steric hindrance of the C−H
fragment on the phenyl rings. In this regard, the coordination
chemistry of dipyridylamine analogues have been extensively
investigated in the past several decades, which can be employed
as molecular strings,16 luminescent materials,17 or afford a plat-
form for organometallic chemistry studies.18 As a polydentate
bimacrocycle, compound 1 is likely capable of being a host to
entrap one or two metal ions. Our attempt to crystallize some
host/metal complexes of 1 in order to facilitate our compre-
hension of the binding modes between 1 and different metal ions
led to four 1·metal complexes.
When the host 1 was individually mixed in 1:4 ratio with metal
salts (CoCl2, NiCl2, Ni(ClO4)2 and Cd(ClO4)2) to achieve saturated
coordination, four 1·metal complexes were acquired and their
X-ray quality crystals were then deposited by a solvent diffusion
or evaporation method. As shown in Figure 3a, the 1·CoCl2 com-
plex is a binuclear complex with the formula of {Co(1)(CH3OH)2}-
(CoCl4)·3(CH3OH), in which the cationic part contains a cobalt
center situated inside a cavity of 1 and the counteranionic species
is a tetrahedral [CoCl4]2− ion. The cobalt center Co1 is coordinated
to four pyridyl nitrogen atoms of 1 (N1, N3, N5 and N7) [Co−N =
2.074(3)−2.114(3) Å] and two methanol molecules [Co−O =
2.088(3)−2.128(3) Å]. The Co−N distances are comparable to the
10076
dx.doi.org/10.1021/jo301528f | J. Org. Chem. 2012, 77, 10073−10082

The Journal of Organic Chemistry
Article
Figure 2. 1H NMR spectra (600 MHz, CD2Cl2) of compound 1 at different temperatures.
Figure 3. Crystal structures of four 1·metal complexes (50% thermal ellipsoid probability level): (a) {Co(1)(CH3OH)2}(CoCl4)·3(CH3OH). The
anionic [CoCl4]2− species and three peripheral methanol molecules are omitted for clarity. (b) {Ni(1)(CH3OH)2}(NiCl4). The anionic [NiCl4]2‑
species is omitted for clarity. (c) {Ni(1)(CH3OH)2}(ClO4)2·CH3OH. Two perchlorate anions are omitted for clarity. The acetone molecule (O10) and
a pyridine ring (N5) of 1 are disordered at two positions. Only one set of positions is shown here. (d) {Cd2(1)(CH3CN)4(H2O)4}(ClO4)4). Three
other perchlorates are omitted for clarity. The perchlorate shown in this figure is disordered at two positions. Only one set of positions is shown here.
bond lengths of a previously reported cobalt complex of N,N′-bis(α-
pyridyl)-2,6-diaminopyridine (tripyridyldiamine, tpda).19 The
coordination environment of the cobalt ion in this 1·CoCl2 com-
plex can be described as an octahedral 6-coordinated mode.
The host molecule 1 underwent a significant conformation modi-
fication from its juxtaposed 1,3-alternate state to form a saddle
form plus a 1,3-alternate conformation. In contrast to the regular
saddle form of azacalix[4]pyridine metal complexes that has
10077
dx.doi.org/10.1021/jo301528f | J. Org. Chem. 2012, 77, 10073−10082

The Journal of Organic Chemistry
Article
linear coordination vectors between pyridine ring and metal
centers,9 each coordinative pyridine ring in the 1·CoCl2 complex
form an obtuse angle with the cobalt center, wherein the angle of
131° for the central bridging pyridine ring (denoted as N7) is
much smaller than that of the other three ones in the range of
149−159°.
The structure of the 1·NiCl2 complex also has a metal ion
inside the cavity of 1 (Figure 3b). This structure is isostructural
with that of the 1·CoCl2 complex and includes a [Ni(1)(CH3-
OH)2]2+ species as the cationic part and a tetrahedral [NiCl4]2‑ ion
as the anionic part. The formula of this 1·NiCl2 complex can be
expressed as {Ni(1)(CH3OH)2}(NiCl4). The mean distance be-
tween the coordinative pyridyl nitrogen atoms and the nickel
center Ni1 is 2.07 Å, a bit shorter than the mean Co−N distance
of 2.10 Å in the 1·CoCl2 complex.
The structure of the 1·Ni(ClO4)2 complex with the formula of
{Ni(1)(CH3OH)2}(ClO4)2·CH3OH is almost identical with that of
the 1·NiCl2 complex but with a methanol molecule interacting with
the host molecule by hydrogen bonding (O3···N11 = 2.767(3) Å)
(Figure 3c).
Figure 4. UV−vis titration curves of the host 1 (9.1 × 10−6 M) in a
mixture of acetonitrile and dichloromethane (4:1, v/v) in response to
the addition of the acetonitrile/dichloromethane (4:1, v/v) solution of
Zn(ClO4)2 at 298 K. The concentrations of Zn2+ for curves a−t (from
top to bottom) are 0, 0.9 × 10−6, 1.8 × 10−6, 2.7 × 10−6, 3.6 × 10−6, 4.6 ×
10−6, 5.5 × 10−6, 6.4 × 10−6, 7.30 × 10−6, 8.2 × 10−6, 9.1 × 10−6, 10.0 ×
10−6, 10.9 × 10−6, 11.9 × 10−6, 12.8 × 10−6, and 13.7 × 10−6 M. “i.p.” is
abbreviated for an isosbestic point. Inset: Job plot showing a 1:1 1·Zn2+
complex ([1] + [Zn2+] = 1.6 × 10−5 M) in a mixture of acetonitrile and
dichloromethane (4:1, v/v). λobs = 337 nm.
Colorless platelike crystals of the 1·Cd(ClO4)2 complex (the
formula is {Cd2(1)(CH3CN)4(H2O)4}(ClO4)4) were obtained
by the evaporation method. It is remarkable that this 1·Cd(ClO4)2
complex displayed a 1:2 ratio of host to metal salt. The two cad-
mium centers (Cd1 and Cd2 in Figure 3d) each adopts a trigonal
bipyramidal geometry, wherein a pyridyl and two acetonitrile
nitrogen atoms occupy the trigonal planar positions and two
water molecules lie on the axial positions. The Cd−N distances
are in the range of 2.208(3)−2.300(5) Å, and the summation of
three N−Cd−N angles for each cadmium center is approximately
360°. Moreover, the two coordinated water molecules O2 and O3
are bridged by a perchlorate anion through hydrogen bonding
(O2···O18 = 2.771 (1) Å and O3···O20 = 2.951 (1) Å). In this
1·Cd(ClO4)2 complex, the host 1 is also in the juxtaposed 1,3-
alternate conformation as similar as its unbound state. The assump-
tion that the large ionic radius of the Cd2+ ion leads to the co-
ordination difference between this cadmium complex and the
Co2+ and Ni2+ complexes is partially supported by a reported com-
plex [(tpda)2CdCl]NO3 (tpda = tripyridyldiamine), wherein the
large cadmium ion is located about 1 Å above the coordination
plane constituted by three pyridyl nitrogen atoms of tpda.20
Metal Complexation Behaviors of Host 1 in Solution.
After getting two binding modes between 1 and metal ions in
crystalline state, we sought to evaluate what host:guest ratio can
be formed in solution between metal ions and compound 1 and
to measure their association constants by UV−vis titration. The
titration curves were recorded upon the gradual addition of metal
perchlorate salts to the solution of 1. All perchlorate salts were
used to minimize the possible effects caused by counteranions.
Titration of the host 1 by a series of tested transition metal ions
including Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Hg2+ all
resulted in the variation of their corresponding UV−vis spectra.
However, the alkali and alkaline earth metal ions such as Li+, Na+,
K+, Cs+, Mg2+, Ca2+, and Ba2+ were found to have no obvious interac-
tion with the host 1 in the UV−vis titration.
isosbestic points at 272.5, 306, 332, and 348 nm were observed in
the titration curves, indicating the formation of a single new com-
plex. The Job plot based on the absorbance at 337 nm demon-
strated the formation of a 1:1 complex between 1 and zinc ion.
The binding constant for the 1−Zn2+ complexation was cal-
culated to be 1.2 × 107 M−1 by a nonlinear least-squares fit of the
titration data using a Hyperquad2003 program.21
We next screened a series of transition metal ions including
Mn2+, Fe2+, Co2+, Ni2+, and Cu2+ in the third period and Cd2+ and
Hg2+ in the same group with Zn2+ by UV−vis spectroscopic
analysis (Figures S23−S29, Supporting Information). The Job
plot studies revealed that the host 1 formed a 1:2 host/metal
complex with Mn2+, Ni2+, and Hg2+, although their association
constants K1 and K2 varied within a large range. In general, the
ionic radius of metal ion is an important factor that influences
their binding modes with a macrocyclic polydentate ligand. In
view of the crystal structure of {Ni(1)(CH3OH)2}(NiCl4) dis-
cussed vide supra wherein the nickel center is located inside a
cavity of 1, we expect two metal ions of Mn2+ or Ni2+ are possibly
accommodated inside two cavities of the host 1. The Hg2+ has the
radius of 102 pm,22 which makes itself difficult to be entrapped
into the cavities of 1. The coordination between two marginal
vertical pyridine rings of 1 and metal ions maybe accounts for
the 1:2 binding between 1 and Hg2+ according to the crystal
structure of {Cd2(1)(CH3CN)4(H2O)4}(ClO4)4). In addition,
other binding modes between 1 and Hg2+ cannot be ruled out
because not all absorption curves pass through a common point
and two sets of titration curves (red and blue in Figure S29,
Supporting Information) can be resolved. As shown in Table 2,
among the 1:1 host/metal complexes determined by the Job plot
studies the K values for Co2+ and Zn2+ are higher than the other
metal ions (Fe2+, Cu2+, and Cd2+), suggesting a better recogni-
tion effect for Co2+ and Zn2+. The Cd2+ has a low K1 value of
1.0 × 105 M−1, which is comparable with the K1 value for Hg2+. This
implies that the binding mode of Cd2+ and Hg2+ is possibly similar.
Consequently, three possible binding modes between the host
1 and transition metal ions can be concluded on the basis of the
UV−vis titration. When the radius of the entrapped metal ions is
small (such as Mn2+ and Ni2+), a [1·2M] complex with metal ions
The binding interaction of 1 with Zn(ClO4)2 in solution
was first investigated in view of the highly selective binding of
methylazacalix[4]pyridine with Zn2+ in a previous report.9 As the
zinc perchlorate acetonitrile solution was gradually added to the
dichloromethane solution of 1, the main absorption bands of
the free host 1 at 337 nm (the UV−vis spectra of 1−3 is shown in
Figure S22 in the Supporting Information) decreased, and a new
absorption band was generated at 323 nm (Figure 4). Four clear
10078
dx.doi.org/10.1021/jo301528f | J. Org. Chem. 2012, 77, 10073−10082

The Journal of Organic Chemistry
Article
a
Table 2. Association Constants between Host 1 and Metal Ions at 298 K
metal ions
radius22 (pm)
1
azacalix[6]pyridine23
K (M−1
K1 (M−1
)
K2 (M−1
)
)
Mn2+
Fe2+
Co2+
Ni2+
Cu2+
Zn2+
Cd2+
Hg2+
67 (ls), 83 (hs)
(1.23 0.03) × 106
(2.57 0.03) × 106
(5.92 0.09) × 107
(2.68 0.03) × 106
(1.31 0.02) × 106
(1.25 0.08) × 107
(1.00 0.01) × 105
(5.02 0.05) × 105
(8.34 0.03) × 105
−
61 (ls), 78 (hs)
(5.63 0.10) × 105
65 (ls), 74.5 (hs)
−
69
73
74
95
102
(1.02 0.03) × 104
(6.32 0.06) × 105
(5.39 0.03) × 105
−
−
(1.53 0.05) × 105
(4.03 0.07) × 105
a
“ls” = low-spin state. “hs” = high-spin state. “−” = azacalix[6]pyridine has no obvious response in UV−vis spectra upon the complexation with metal
ions.
Figure 5. 1H NMR spectra of the host 1 in CD3CN/CD2Cl2 (v/v 2:1) in the absence and presence of different amounts of Cd(ClO4)2 at 298 K.
situated inside two cavities of 1 can be acquired. With the in-
creasing of metal ion radius (Fe2+, Co2+, Cu2+, and Zn2+), the
host 1 can only bond to a single metal ion by its one cavity as
shown in the crystal structures of 1·Co2+ and 1·Ni2+ complexes.
As to the large metal ions Cd2+ and Hg2+, their binding mode is
likely described as one or two metal ions floating on the groove
of 1 generated by its four procumbent and three vertical pyridine
rings. Meanwhile, in contrast to the binding constants of azacalix-
[6]pyridine against several metal ions (Table 2),23 the bimacro-
cyclic host 1 exhibited a better metal ion affinity, indicating that
the internal bridging of the large azacalixaromatic rings indeed
improve their molecular recognition ability.
To elucidate the details of the binding process between 1 and
metal ions, we next examined the 1H NMR variation of 1 upon
gradually adding metal salts of Zn2+, Cd2+, and Hg2+. Such three
metal ions are purposefully selected because they are not para-
magnetic, and their ionic radii are within a wide range from 74
to 102 pm. Addition of the CD3CN solution of Zn(ClO4)2 to the
solution of 1 (2.0 mM)) in CD2Cl2 at 298 K led to the
appearance of a new set of coupled triplet and doublet signals
corresponding to the pyridyl protons at low field, indicating
the occurrence of the metal:host complexation (Figure S30,
Supporting Information). Proton signals corresponding to the
parent bimacrocycle disappeared after an equimolar amount
of Zn(ClO4)2 was added, and the singlet peak of the bridging
N−CH3 protons in its unbound state were split into two singlet
peaks in a 1:1 ratio. Further addition of Zn(ClO4)2 did not
change the NMR spectra any more, explicitly confirming the for-
mation of the 1:1 host/metal complex in this system. In contrast,
although addition of one equivalent Cd(ClO4)2 into the solution
of 1 also made the proton signals of the unbound bimacrocycle
disappear, the signals of the bridging N−CH3 only down-shifted
a little bit and preserved its singlet form (Figure 5). This means
the host molecule in this 1·Cd(ClO4)2 complex has a high sym-
metry. We propose that the Cd2+ ion is most probably hopping
between two cavities of 1 at a high frequency, a process which is
much faster in relative to the time scale of NMR. The metal ion
hopping motion in this 1·Cd(ClO4)2 complex was also reflected
by the variable-temperature proton NMR spectra. As the probe
temperature was decreased to 218 K, one singlet signal of the N-Me
10079
dx.doi.org/10.1021/jo301528f | J. Org. Chem. 2012, 77, 10073−10082

The Journal of Organic Chemistry
Article
protons was split into two singlet peaks (Figure S31, Supporting
Information). Interestingly, addition of Hg(ClO4)2 to the solution of
1 in a ratio lower than 2:1 resulted in the appearance of four new
singlet signals corresponding to the N−CH3 protons (Figure S32,
Supporting Information). We hypothesize this is due to the
interaction of the existence of several kinds of host·metal complexes.
The ESI mass spectroscopy of the mixture of Hg2+ and 1 in a 1:1 ratio
displayed three sets of peaks for the Hg2+/1 complexation in 2:1, 1:1
and 1:2 ratio (Figure S33, Supporting Information), supporting our
assumption of the coexistence of several 1·metal species. When
2 equiv of Hg(ClO4)2 was added, the four singlets of N−CH3 merged
into only one singlet. This observation confirmed the 1:2 host/metal
stoichiometry observed in the UV−vis titration.
The UV−vis titration and Job plot studies have explored that the
bimacrocyclic host 1 can form 1:1 and 1:2 host/metal complexes
with different transition metal ions. The crystalline solid-state
structures of four acquired 1·metal complexes demonstrated that
the cavities and the marginal pyridines of 1 can be employed to
trap metal ions by coordination. As shown in Scheme 3, four types
feature two juxtaposed 1,3-alternate macrocycles. The applica-
tion of a stellated tetrabrominated pentamer in this synthesis
represents an unprecedented synthetic pathway for construct-
ing complex multicyclic heteracalixaromatic compounds. The in-
corporation of a 1,3-arylene bridge into the large azacalixar-
omatics has a profound impact on the structural and electronic
properties of the resulting macrocycles, finally leading to the
conformation fixation of flexible macrocycles. Binding modes
between the all-pyridine host 1 and transition metal ions with
different ionic radius have been established by UV−vis and NMR
titration and X-ray crystallographic analysis. Four possible co-
ordination modes between 1 and metal ions including a dynamic
hopping motion potentiate the promising applications of this
bimacrocyclic host in metal ion transport, ion channel, and
metalloenzyme mimics and hierarchical supramolecular assembly.
EXPERIMENTAL SECTION
■
Methods and Materials. 1H and 13C NMR spectra were recorded
on a 300 MHz spectrometer. NOESY spectra and variable-temperature
NMR were recorded on a 600 MHz spectrometer. Chemical shifts are
reported in ppm versus tetramethylsilane with either tetramethylsilane
or the residual solvent resonance used as an internal standard. All sol-
vents were dried or purified according to standard procedures prior to
use. 2,6-Diaminopyridine 8, benzene-1,3-diamine 9, and 2,6-dibromo-
pyridine 10 were commercially available. Compounds 6, 11, 12, and 14
were prepared according to the literatures.24
Scheme 3. Schematic Representation of Four Possible
Coordination Modes of the Host 1
7: To a solution of 11 (419 mg, 1 mmol) in dry DMF (20 mL) at
room temperature was added NaH (96 mg, 4 mmol) slowly, and the
mixture was stirred at room temperature. After 1 h, 10 (4.74 g, 20 mmol)
and CuI (380 mg, 2 mmol) were added to the mixture slowly, and the
reaction mixture was heated to 110 °C for another 12 h under argon
protection and then cooled down to room temperature. Water (1 mL)
was slowly added. Ethyl acetate (50 mL) was added to the mixture, and
the combined solution was washed with saturated brine (3 × 50 mL).
The organic phase was dried over anhydrous Na2SO4. After removal of
solvent, the residue was chromatographed on a silica gel column (100−
200) with a mixture of petroleum ether (60−90 °C) and ethyl acetate
(v/v = 4:1) as a mobile phase to give pure 7 (241.9 mg, 33%) as a white
solid (mp 166−167 °C): IR (KBr): ν 1551, 1571, 1417 cm−1. 1H NMR
(300 MHz, CDCl3): δ 7.66 (t, J = 8.0 Hz, 1H), 7.43 (t, J = 7.9 Hz, 4H),
7.16 (d, J = 7.7 Hz, 4H), 7.02 (d, J = 8.0 Hz, 4H), 6.91 (d, J = 8.0 Hz,
2H). 13C NMR (75 MHz, CDCl3): δ 156.1, 154.9, 140.1, 139.6, 138.7,
123.4, 117.1, 114.6. MS (ESI) m/z: 730.0 (11), 732.0 (72), 734.0 [M + H]+
(100), 736.0 (68), 738.0 (15). Anal. Calcd for C25H15N7Br4: C, 40.96; H,
2.06; N, 13.38; Found: C, 40.71; H, 2.31, N, 13.14.
13: A mixture of 12 (8.4 g, 20 mmol), 10 (11.85 g, 50 mmol), CuI
(380 mg, 2 mmol), 1,10-phenanthroline (792 mg, 4 mmol) and potassium
carbonate (6.9 g, 50 mmol) in dry DMSO (100 mL) was stirred at room
temperature under argon protection. After 1 h, the mixture was heated to
160 °C for another 6 h and then cooled down to room temperature. Ethyl
acetate (100 mL) was added to the mixture, and the combined solution was
washed with saturated brine (3 × 100 mL). The organic phase was dried
over anhydrous Na2SO4. After removal of solvent, the residue was
chromatographed on a silica gel column (100−200) with a mixture
of petroleum ether (60−90 °C) and ethyl acetate (v/v = 5:1) as a mobile
phase to give pure 13 (7.47 g, 51%) as a white solid (mp 187−188 °C). IR
(KBr): ν 1555, 1573, 1412 cm−1. 1H NMR (300 MHz, CDCl3): δ 7.44 (t,
J = 7.8 Hz, 5H), 7.11−7.07 (m, 11H). 13C NMR (75 MHz, CDCl3): δ
156.6, 144.5, 139.7, 139.4, 131.2, 128.1, 125.9, 122.2, 114.9. MS (ESI)
m/z: 729.0 (15), 731.0 (70), 733.0 [M + H]+ (100), 735.0 (60), 735.0
(11). Anal. Calcd for C26H16N6Br4: C, 42.66; H, 2.20; N, 11.48. Found: C,
42.34; H, 2.41; N, 11.14.
of possible coordination modes can be conceptually proposed
based on the 1:1 and 1:2 host/metal stoichiometry and the two
kinds of binding sites. Among them, modes I and IV have been
substantiated by crystal structure studies of {Co(1)(CH3OH)2}-
(CoCl4)·3(CH3OH) and {Cd2(1)(CH3CN)4(H2O)4}(ClO4)4),
respectively. In solution, the NMR studies of the binding process
between Zn2+, Cd2+ and Hg2+ and 1 provide some evidence for the
occurrence of mode III. The central bridging pyridine ring in 1 may
facilitate the translocation of the medium-sized Cd2+ from one side to
another side and thus accelerate the hopping frequency by use of its
labile coordination, consequently resulting in mode III. Our hypothe-
sis of the existence of mode II is mainly derived from the Job plot
studies of Mn2+ and Ni2+ and crystal structures of {Ni(1)(CH3OH)2}-
(NiCl4) and {Ni(1)(CH3OH)2}(ClO4)2·CH3OH, although solid-
state structures of 1:2 host/metal complexes have not been
established to date.
1: Under argon protection, a mixture of tetrabrominated nonlinear
pentamer 7 (403 mg, 0.55 mmol) and diaminated monomer 6 (137 mg,
1 mmol), Pd2(dba)3 (92 mg, 0.1 mmol), dppp (82 mg, 0.2 mmol), and
sodium tert-butoxide (288 mg, 3 mmol) in anhydrous toluene (200 mL)
was heated to reflux for 8 h. The reaction mixture was cooled to room
temperature and filtered through a Celite pad. The filtrate was concentrated
CONCLUSION
■
In summary, we have described a simple procedure for the first
synthesis of 1,3-arylene-bridged azacalix[6]aromatics 1−3 that
10080
dx.doi.org/10.1021/jo301528f | J. Org. Chem. 2012, 77, 10073−10082

The Journal of Organic Chemistry
Article
Table 3. Crystallographic Data of Compounds 1−3 and Four Metal Complexes of Host 1
{Co(1)(CH3OH)2}
(CoCl4)·3(CH3OH)
{Ni(1)(CH3OH)2}
{Ni(1)(CH3OH)2}
(ClO4)2·CH3OH
{Cd2(1)(CH3CN)4
compd
formula
1·2(CH3OH)
2·0.25(CH2Cl2)
3
(NiCl4)
(H2O)4}(ClO4)4
C41H41N13O2 C40.25H34.5N12Cl0.5 C42H36N10 C44H53Cl4Co2N13O5 C41H41Cl4Ni2N13O2 C42H43Cl2NiN13O10 C47H53Cl4Cd2N17O20
FW
747.87
monoclinic
P21/c
704.02
680.81
1103.65
triclinic
P-1
1007.09
triclinic
P-1
1037.50
triclinic
P-1
1542.66
triclinic
P-1
crystal system
space group
a/Å
triclinic
P-1
triclinic
P-1
23.581(5)
15.123(3)
10.468(2)
90
10.6023(9)
13.3109(12)
13.4391(12)
109.330(8)
101.227(7)
98.434(7)
1709.2(3)
2
10.990(2)
12.415(2)
13.379(3)
89.992(7)
81.014(5)
74.842(6)
1738.7(5)
2
10.203(2)
13.486(3)
18.280(4)
101.482(3)
91.641(4)
99.266(4)
2428.2(9)
2
10.231(2)
13.510(3)
18.245(4)
102.03(3)
90.96(3)
99.91(3)
2426.1(8)
2
12.7471(5)
13.9306(5)
15.8655(6)
96.018(3)
93.271(3)
92.071(3)
2794.7(2)
2
12.393(3)
16.465(3)
17.357(5)
72.312(13)
82.496(16)
68.093(11)
3130(1)
2
b/Å
c/Å
α/deg
β/deg
γ/deg
94.086(4)
90
V/Å3
3724(1)
4
Z
Dc/g cm−3
μ/mm−1
1.334
1.409
1.300
1.509
1.379
1.375
1.637
0.088
0.164
0.081
0.963
1.044
0.651
0.935
a
R1 (I > 2σ)
0.0966
0.0602
0.0650
0.0692
0.0567
0.1457
1.067
0.0677
0.0630
b
wR2 (all data) 0.1622
0.1458
0.1526
0.1675
0.1633
0.1567
GOF
1.188
1.007
1.068
1.096
0.988
1.071
a
b
2
2
R1 = ∑∥Fo| − |Fc∥/∑|Fo|. wR2 = {∑[w(Fo − Fc2)2]/∑[w(Fo )2]}1/2
.
under vacuum to remove toluene, and the residue was dissolved in
dichloromethane (50 mL) and washed with brine (3 × 15 mL). The
aqueous phase was re-extracted with dichloromethane (3 × 15 mL), and
the combined organic phase was dried over anhydrous Na2SO4. After
removal of solvent, the residue was chromatographed on a basic alumina
column (200−300) with a mixture of dichloromethane and ethyl acetate
(v:v = 3:1) as a mobile phase to give the product 1 (136.6 mg, 34%) as a
white solid (mp 230−231 °C). Single crystals of 1 were deposited by
diffusing n-hexane into its dichloromethane solution. IR (KBr): ν 1568,
1423, 1284 cm−1. 1H NMR (300 MHz, CD2Cl2): δ 7.47 (t, J = 8.1 Hz,
4H), 7.38 (t, J = 7.8 Hz, 2H), 7.20 (t, J = 7.8 Hz, 1H), 6.76 (d, J = 8.1 Hz,
4H), 6.72 (d, J = 7.8 Hz, 4H), 6.39 (d, J = 7.8 Hz, 2H), 6.33 (d, J = 8.1
Hz, 4H), 3.31 (s, 12H). 13C NMR (75 MHz, CD2Cl2): δ 158.7, 158.3,
157.5, 154.7, 139.1, 138.7, 138.0, 121.1, 120.1, 104.1, 100.6, 37.1. MS
(MALDI-TOF) m/z: 684.6 [M + H]+ (100), 706.7 [M + Na]+ (23).
Anal. Calcd for C39H33N13: C, 68.51; H, 4.86; N, 26.63. Found: C, 68.56;
H, 4.94; N, 26.40.
2: A similar procedure with that of compound 1 using 13 (366 mg,
0.5 mmol), 6 (411 mg, 3 mmol), Pd2(dba)3 (92 mg, 0.1 mmol), dppp
(82 mg, 0.2 mmol), and sodium tert-butoxide (288 mg, 3 mmol) in
anhydrous toluene (200 mL) produced compound 2 (173.9 mg, 51%)
as a colorless crystal (mp 235−236 °C). A mobile phase of n-hexane,
dichloromethane, and ethyl acetate (v/v/v = 5:3:1) was applied for
chromatography. Single crystals of 2 were deposited by diffusing diethyl
ether into its dichloromethane solution. IR (KBr): ν 1576, 1565, 1432,
1418 cm−1. 1H NMR (300 MHz, CD2Cl2): δ 7.43 (t, J = 8.1 Hz, 4H),
7.28 (t, J = 7.8 Hz, 2H), 6.81 (t, J = 8.1 Hz, 1H), 6.76 (d, J = 7.8 Hz, 4H),
6.67 (d, J = 7.8 Hz, 4H), 6.39 (dd, J = 8.1, 2.1 Hz, 2H), 6.26 (d, J = 8.1
Hz, 4H), 6.11 (t, J = 1.8 Hz, 1H), 3.28 (s, 12H). 13C NMR (75 MHz,
CD2Cl2): δ 159.1, 158.4, 155.6, 146.6, 138.7, 138.1, 129.3, 128.1, 125.7,
120.5, 103.8, 99.4, 36.8. MS (MALDI-TOF) m/z: 683.4 [M + H]+
(100). Anal. Calcd for C40H34N12: C, 70.36; H, 5.02; N, 24.62. Found: C,
70.16; H, 5.17; N, 24.31.
39.2. MS (MALDI-TOF) m/z: 681.0 [M + H]+ (100). Anal. Calcd for
C42H36N10·0.2CH2Cl2: C, 72.64; H, 5.26; N, 20.07. Found: C, 72.42; H,
5.20; N, 19.98.
{Co(1)(CH3OH)2}(CoCl4)·3(CH3OH). After the dichloromethane
(1.2 mL) solution of 1 (7 mg, 0.01 mmol) was mixed with the methanol
solution of CoCl2·6H2O (10 mg, 0.04 mmol), n-hexane (1 mL) was
layered above the mixture. After several days, green blocklike crystals were
obtained. Yield: 53% based on 1. IR (KBr):ν 1601, 1578, 1463, 1423 cm−1.
Anal. Calcd for C41H41Cl4Co2N13O2 (formula {Co(1)(CH3OH)2}-
(CoCl4)): C, 48.88; H,4.10; N, 18.07. Found: C, 48.64; H, 4.34; N, 18.31.
{Ni(1)(CH3OH)2}(NiCl4). Diffusion of diethyl ether into the mixed
solution of 1 (7 mg, 0.01 mmol) in dichloromethane (1.2 mL) and
NiCl2·6H2O (10 mg, 0.04 mmol) in methanol (1 mL) yielded green
columnar crystals. Yield: 42% based on 1. IR (KBr): ν 1603, 1582, 1450,
1426 cm−1. Anal. Calcd for C41H41Cl4Ni2N13O2 (formula {Ni(1)-
(CH3OH)2}(NiCl4)): C, 48.90; H, 4.10; N, 18.08. Found: C, 48.56; H,
4.15; N, 18.28.
{Ni(1)(CH3OH)2}(ClO4)2·CH3OH. Host 1 (7 mg, 0.01 mmol) was
dissolved in dichloromethane (1 mL). Ni(ClO4)2·6H2O (15 mg, 0.04
mmol) was dissolved in 0.5 mL methanol, which was then added into the
host solution. Slow diffusion of diethyl ether into the mixture generated
purplish-green prismatic crystals. Yield: 51% based on 1. IR (KBr): v
1601, 1584, 1451, 1426, 1087, 627 cm−1. Anal. Calcd for C40H37Cl2N13NiO9
(formula {Ni(1)(CH3OH) }(ClO4)2): C, 49.36; H, 3.83; N, 18,71. Found:
C,49.72; H, 3.63; N, 19.04.
{Cd2(1)(CH3CN)4(H2O)4}(ClO4)4. Evaporation of the mixed solution
of 1 (1 mg, 0.0015 mmol) in dichloromethane (1 mL) and Cd(ClO4)2·
6H2O (2.5 mg, 0.006 mmol) in acetonitrile (0.3 mL) led to colorless
plate-like crystals. Yield: 32% based on 1. IR (KBr): ν 1593, 1566,
1455, 1421, 1087, 627 cm−1. Anal. Calcd for C41H40Cd2Cl4N14O18 (formula
{Cd2(1)(CH3CN) (H2O)2}(ClO4)4): C, 35.59; H, 2.91; N, 14.17. Found:
C,35.86; H, 2.73; N, 14.39.
X-ray Crystallography. Data for three internally 1,3-arylene-bridged
azacalix[6]aromatics 1-3 and four coordination complexes were col-
lected at 173 K with Mo Kα radiation (λ = 0.71073 Å) with frames of
oscillation range 0.5°. All structures were solved by direct methods,
and non-hydrogen atoms were located from difference Fourier maps.
All non-hydrogen atoms were subjected to anisotropic refinement by
full-matrix least-squares on F2 by using the SHELXTL program. The
X-Seed program25 was used to generate the X-ray structural diagrams
pictured in this paper. The parameters for the crystal data and X-ray
structure analysis are summarized in Table 3. CCDC deposition
numbers: 1 (900985); 2 (900986); 3 (900987); 1·CoCl2 (900988),
1·NiCl2 (900989), 1·Ni(ClO4)2 (906857), and 1·Cd(ClO4)2 (900991).
3: Compound 3 was prepared from 13 and 14 by a similar procedure
to the synthesis of 2. Quantities: 13 (366 mg, 0.5 mmol), 14 (408 mg,
3 mmol), Pd2(dba)3 (92 mg, 0.1 mmol), dppp(82 mg, 0.2 mmol), sodium
tert-butoxide (288 mg, 3 mmol), and anhydrous toluene (200 mL). The
product 3 was a colorless crystal (163.2 mg, 48%). Single crystals of 3 for
X-ray analysis were obtained by the evaporation of its dichloromethane
1
solution. Mp: 227−228 °C. IR (KBr): ν 1576, 1424 cm−1. H NMR
(300 MHz, CD2Cl2): δ 7.43 (t, J = 8.0 Hz, 4H), 7.10 (t, J = 7.8 Hz, 2H),
6.87 (s, 2H), 6.78 (d, J = 7.8 Hz, 4H), 6.67−6.65 (m, 5H), 6.28−6.21
(m, 7H), 3.25 (s, 12H). 13C NMR (75 MHz, CD2Cl2): δ 158.50, 158.47,
156.2, 148.1, 146.3, 138.5, 129.0, 128.4, 127.7, 124.8, 124.7, 103.3, 98.4,
10081
dx.doi.org/10.1021/jo301528f | J. Org. Chem. 2012, 77, 10073−10082

The Journal of Organic Chemistry
Article
(11) Gong, H.-Y.; Zhang, X.-H.; Wang, D.-X.; Ma, H.-W.; Zheng, Q.-
Y.; Wang, M.-X. Chem.Eur. J. 2006, 12, 9262.
ASSOCIATED CONTENT
* Supporting Information
NMR spectra data for 1−3. UV and NMR titration curves for
host 1 and metal ions. Crystal data of 1−3 and 1·metal complexes
(CIF). This material is available free of charge via the Internet at
http://pubs.acs.org.
■
S
(12) Anand, V. G.; Saito, S.; Shimizu, S.; Osuka, A. Angew. Chem., Int.
Ed. 2005, 44, 7244.
(13) Himes, R. A.; Barnese, K.; Karlin, K. D. Angew. Chem., Int. Ed.
2010, 49, 6714.
(14) Shibasaki, M.; Kanai, M.; Matsunaga, S.; Kumagai, N. Acc. Chem.
Res. 2009, 42, 1117.
(15) (a) Paul, F.; Patt, J.; Hartwig, J. F. J. Am. Chem. Soc. 1994, 116,
5969. (b) Guram, A. S.; Buchwald, S. L. J. Am. Chem. Soc. 1994, 116,
7901.
AUTHOR INFORMATION
Corresponding Author
*zhaolchem@mail.tsinghua.edu.cn; wangmx@mail.tsinghua.edu.cn.
Notes
■
(16) (a) Berry, J. F. In Multiple Bonds Between Metal Atoms; Cotton, F.
A., Murillo, C. A., Walton, R. A., Eds.; Springer: New York, 2005; pp
669−706. (b) Berry, J. F. Struct. Bonding (Berlin) 2010, 136, 1. (c) Yeh,
C.-Y.; Wang, C.-C.; Chen, Y.-H.; Peng, S.-M. In Redox Systems Under
Nano-Space Control; Hirao, T), Ed.; Springer: Heidelberg, 2006; pp 85−
115. (d) Liu, I. P.-C.; Wang, W.-Z.; Peng, S.-M. Chem. Commun. 2009,
4323−4331. (e) Ismayilov, R. H.; Wang, W.-Z.; Lee, G.-H.; Yeh, C.-Y.;
Hua, S.-A.; Song, Y.; Rohmer, M.-M.; Benard, M.; Peng, S.-M. Angew.
Chem., Int. Ed. 2011, 50, 2045−2048.
(17) (a) Vezzu, D. A. K.; Deaton, J. C.; Jones, J. S.; Bartolotti, L.; Harris,
C. F.; Marchetti, A. P.; Kondakova, M.; Pike, R. D.; Huo, S. Inorg. Chem.
2010, 49, 5107. (b) Breivogel, A.; Foerster, C.; Heinze, K. Inorg. Chem.
2010, 49, 7052. (c) Ni, J.; Wei, K.-J.; Min, Y.; Chen, Y.; Zhan, S.; Li, D.;
Liu, Y. Dalton Trans. 2012, 41, 5280. (d) Ramya, A. R.; Sharma, D.;
Natarajan, S.; Reddy, M. L. P. Inorg. Chem. 2012, 51, 8818.
(18) (a) Wang, Z.-L.; Zhao, L.; Wang, M.-X. Org. Lett. 2011, 13, 6560.
(b) Wang, Z.-L.; Zhao, L.; Wang, M.-X. Org. Lett. 2012, 14, 1472.
(c) Wang, Z.-L.; Zhao, L.; Wang, M.-X. Chem. Commun. 2012, 48, 9418.
(d) Yao, B.; Wang, Z.-L.; Zhang, H.; Wang, D.-X.; Zhao, L.; Wang, M.-X.
J. Org. Chem. 2012, 77, 3336.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Financial support by the National Natural Science Foundation of
China (21002057, 91127006, 21132005, 20972161, 21121004)
and the National Basic Research Program of China (973 pro-
gram, 2011CB932501) is gratefully acknowledged. This work is
also supported by Tsinghua University Initiative Scientific Research
Program.
REFERENCES
■
(1) (a) Seo, J.; Park, S.; Lee, S. S.; Fainerman-Melnikova, M.; Lindoy,
L. F. Inorg. Chem. 2009, 48, 2770. (b) Cazacu, A.; Tong, C.; Lee, A. V.;
Fyles, T. M.; Barboiu, M. J. Am. Chem. Soc. 2006, 128, 9541. (c) Barboiu,
M.; Cerneaux, S.; van der Lee, A.; Vaughan, G. J. Am. Chem. Soc. 2004,
126, 3545. (d) Sidorov, V.; Kotch, F. W.; Kuebler, J. L.; Lam, Y. F.; Davis,
J. T. J. Am. Chem. Soc. 2003, 125, 2840.
(2) (a) Kim, J. S.; Quang, D. T. Chem. Rev. 2007, 107, 3780.
(b) Lindoy, L. F. Dalton Trans. 2006, 43, 5115. (c) Choi, K. H.;
Hamilton, A. D. J. Am. Chem. Soc. 2003, 125, 10241. (d) Gawley, R. E.;
Pinet, S.; Cardona, C. M.; Datta, P. K.; Ren, T.; Guida, W. C.; Nydick, J.;
Leblanc, R. M. J. Am. Chem. Soc. 2002, 124, 13448. (e) Beer, P. D.; Gale,
P. A. Angew. Chem., Int. Ed. 2001, 40, 486. (f) Yang, X. G.; Knobler, C. B.;
Zheng, Z. P.; Hawthorne, M. F. J. Am. Chem. Soc. 1994, 116, 7142.
(3) (a) Oliveri, C. G.; Ulmann, P. A.; Wiester, M. J.; Mirkin, C. A. Acc.
Chem. Res. 2008, 41, 1618. (b) Vigato, P. A.; Peruzzo, V.; Tamburini, S.
Coord. Chem. Rev. 2012, 256, 953.
(19) Shieh, S.-J.; Chou, C.-C.; Lee, G.-H.; Wang, C.-C.; Peng, S.-M.
Angew. Chem., Int. Ed. Engl. 1997, 36, 56.
(20) Wei, K.; Xie, Y.; Wang, X.; Zhang, M.; Liu, Q.; Peng, S. Appl.
Organomet. Chem. 2005, 19, 178.
(21) Gans, P.; Sabatini, A.; Vacca, A. Talanta 1996, 43, 1739.
(22) Shannon, R. D. Acta Crystallogr. 1976, A32, 751.
(23) Zhang, E.-X. Ph.D. Dissertation, Institute of Chemistry, Chinese
Academy of Sciences, Beijing, 2009 (in Chinese).
(24) Yao, B.; Wang, D.-X.; Gong, H.-Y.; Huang, Z.-T.; Wang, M.-X. J.
Org. Chem. 2009, 74, 5361.
(25) (a) Barbour, L. J. J. Supramol. Chem. 2001, 1, 189. (b) Atwood, J.
L.; Barbour, L. J. Cryst. Growth Des. 2003, 3, 3.
(4) Arnaud-Neu, F.; Schewing-Weill, M.-J.; Dozol, J.-F. Calixarene for
Nuclear Waste Treatment. In Calixarenes 2001; Asfari, Z., Bohmer, V.,
Harrowfield, J., Vicens, J., Eds.; Kluwer Academic Publishers: Dordrecht,
2001.
̈
(5) (a) Sliwa, W. Chem. Heterocycl. Compd. 2004, 40, 683. (b) Kumar,
S.; Paul, D.; Singh, H. Adv. Heterocycl. Chem. 2005, 89, 65. (c) Wang, M.-
X. Chem. Commun. 2008, 4541. (d) Tsue, H.; Ishibashi, K.; Tamura, R.
Top. Heterocycl. Chem. 2008, 17, 73. (e) Wang, M.-X. Acc. Chem. Res.
2012, 45, 182.
(6) (a) Sommer, N.; Staab, H. A. Tetrahedron Lett. 1966, 7, 2837.
(b) Maes, W.; Dehaen, W. Chem. Soc. Rev. 2008, 37, 2393. (c) Shivanyuk,
A.; Far, A. R.; Rebek, J. Org. Lett. 2002, 4, 1555. (d) Li, X.; Upton, T. G.;
Gibb, C. L. D.; Gibb, B. C. J. Am. Chem. Soc. 2003, 125, 650. (e) Katz, J.
L.; Feldman, M. B.; Conry, R. R. Org. Lett. 2005, 7, 91. (f) Hao, E.;
Fronczek, F. R.; Vicente, M. G. H. J. Org. Chem. 2006, 71, 1233. (g) Katz,
J. L.; Geller, B. J.; Foster, P. D. Chem. Commun. 2007, 1026. (h) Hu, S.-
Z.; Chen, C.-F. Chem. Commun. 2010, 4199.
(7) (a) Ito, A.; Ono, Y.; Tanaka, K. J. Org. Chem. 1999, 64, 8236.
(b) Selby, T. D.; Blackstock, S. C. Org. Lett. 1999, 1, 2053. (c) Tsue, H.;
Ishibashi, K.; Takahashi, H.; Tamura, R. Org. Lett. 2005, 7, 2165.
(d) Zhang, E.-X.; Wang, D.-X.; Zheng, Q.-Y.; Wang, M.-X. Org. Lett.
2008, 10, 2565.
(8) (a) Wang, M.-X.; Yang, H.-B. J. Am. Chem. Soc. 2004, 126, 15412.
(b) Fukushima, W.; Kanbara, T.; Yamamoto, T. Synlett. 2005, 2931.
(9) Gong, H.-Y.; Zheng, Q.-Y.; Zhang, X.-H.; Wang, D.-X.; Wang, M.-
X. Org. Lett. 2006, 8, 4895.
(10) Gong, H.-Y.; Wang, D.-X.; Xiang, J.-F.; Zheng, Q.-Y.; Wang, M.-X.
Chem.Eur. J. 2007, 13, 7791.
10082
dx.doi.org/10.1021/jo301528f | J. Org. Chem. 2012, 77, 10073−10082