A calix-bis-crown with hard and soft crown cavities: Heterobinuclear K +/Ag++ complexation in solid and solution states

Article abstract of DOI:10.1002/chem.200901580

A study was conducted to demonstrate the synthesis of unsymmetrical calix[4]-bis-crown in which oxa- and thiaoxa-crown rings were bound to the calixrene scaffold. The ligand structure for the ion was optimized through the modification of the thiaoxa-crown

Full text of DOI:10.1002/chem.200901580

COMMUNICATION
DOI: 10.1002/chem.200901580
A Calix-bis-crown with Hard and Soft Crown Cavities: Heterobinuclear
K+/Ag+ Complexation in Solid and Solution States
Jai Young Lee,[a, b] Hyun Jee Kim,[a] Chul Soon Park,[a] Wonbo Sim,*[b] and
Shim Sung Lee*[a]
Calixcrowns offer particular utility since the fusion of cal-
ixarene and crown ether units enables the divergent orienta-
tion of cavities of a size and nature sufficient to accommo-
date a variety of guests.[1] Among them, calix[4]-bis-crowns[2]
with a 1,3-alternate conformation (or saddle-type) have in-
teresting features including 1) two crown cavities able to un-
dergo dinucleation and 2) HSAB-based complexation selec-
tivity.[3] Kim et al.[4] reported the synthesis of a heterodinu-
clear complex of an unsymmetrical calix-bis-crown with two
different size crown loops: a crown-5 and a crown-6 suitable
for K+ and Cs+, respectively. We recently reported the ex-
amples of calix[4]-bis-dithiacrown based, endo-coordinated
disilver(I) complexes as well as an exo-coordinated 3D net-
work connected by CuI-based clusters.[5]
er, in this case the synthesized species with monothiaoxa-
and dithiaoxa-crown as the softer rings failed to accommo-
date Ag+ probably a result of K+–Ag+ repulsion rather
than a lack of complexation affinity for Ag+. These results
motivated us to optimize the ligand structure for this ion
through the modification of the thiaoxa-crown unit and pre-
pared the unsymmetrical calix[4]arene (4) incorporating O5/
O2S3-bis-crown ringsACTHNUGRTENUNG(Scheme 1). To the best of our knowl-
Despite the existence of systems exhibiting 1) and 2)
above, neither the preparation nor the crystal structure of
any calixcrowns, which are designed to accommodate hard
and soft metal ions in their individual cavities, has been re-
ported previously. In view of this, we have focused our at-
tention to the synthesis and characterization on a new calix-
bis-crown system designed to bind both soft and hard metal
ions within its respective cavities.
In preliminary work, we synthesized an unsymmetrical
calix[4]-bis-crown, in which oxa- and thiaoxa-crown rings
are simultaneously bound to the calixarene scaffold. Howev-
[a] Dr. J. Y. Lee, H. J. Kim, C. S. Park, Prof. Dr. S. S. Lee
Department of Chemistry, and Research Institute of Natural Science
Gyeongsang National University
Scheme 1. Synthesis of ligand.
Jinju 660-701 (Republic of Korea)
Fax : (+82)55-753-7614
E-mail: sslee@gnu.ac.kr
edge, the latter is the first macrocyclic ligand system to sta-
bilize a heterobinuclear complex incorporating hard and
soft metal ions in each cavity both in the solid and in solu-
tion.
The ligand 4 was synthesized by a two-step cyclization
procedure (Scheme 1). First, cyclization of calix[4]arene 1
with tetraethyleneglycol ditosylate afforded the calix[4]-
mono-crown-5 (2). Ditosylation of 2 with ethyleneglycol di-
[b] Dr. J. Y. Lee, Prof. Dr. W. Sim
Department of Chemistry
Konyang University
Nonsan 320-711 (Republic of Korea)
Fax : (+82)41-733-7581
E-mail: wsim@konyang.ac.kr
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200901580.
Chem. Eur. J. 2009, 15, 8989 – 8992
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8989

tosylate led to the 1,3-alternate ditosyl derivative (3).[6]
while the latter behavior may be considered to reflect a
chopsticks-type p interaction, as proposed by us previous-
ly[5a,b] (Figure S4 in the Supporting Information).
The ESI-mass spectrum of 4 mixed with one equivalent of
each of KPF6 and AgPF6 was dominated by peaks for hetero-
binuclear species such as [K(4)AgPF6]+ (m/z 1081.9) and
[K(4)Ag]2+ (m/z 467.9) (Figure 2). The mononuclear species
[Ag(4)]+ (m/z 898.0) and [K(4)]+ (m/z 828.1) were also ob-
served.
ꢀ
Once again, the cyclization of 3 with (HS CH2CH2)2S gave
the desired unsymmetrical calix[4]-bis-crown (4). Unequivo-
cal confirmation of 4 was provided by a single-crystal X-ray
analysis employing a single crystal obtained by slow evapo-
ration of a CH3OH/CH2Cl2 solution of the complex. The
crystal structure showed a saddle-shaped, 1,3-alternate con-
formation of the calix[4]arene unit; the aromatic rings in
Figure 1ACHTUNGTRENNUNG(left) are tilted up (B and D) and down (A and C),
Figure 2. ESI-MS spectrum of 4 in the presence of KPF6 (1.0 equiv) and
AgPF6 (1.0 equiv) in acetonitrile.
Figure 1. Crystal structures of 4·CH3OH (left) and its heterobinuclear
Ag+ and K+ complex 5, [Ag(4)K]·2PF6·2CH3CN (right). Hydrogen
atoms, anions and solvent molecules are omitted.
In a comparative NMR study of the complexation behav-
ior, the formation of the heterodinuclear complex was also
confirmed (Figure 3). The signals of the aromatic protons
(Haꢀd) in 4 are well identified, exhibiting the characteristics
of the 1,3-alternate conformation with the C2v symmetry
(Figure 3A-a). Therefore, the peaks of aromatic ring pro-
tons Ha and Hb (red) adjacent to the sulfur donors appear
farther upfield than those of Hc and Hd (blue) near the O5-
cavity, respectively. Addition of one equivalent of silver(I)
picrate causes larger downfield shifts of the peaks for Ha
and Hb than for those of Hc and Hd (Figure 3A-b). On addi-
tion of one more equivalent of Ag+, however, more or less
no further downfield shifts was observed (Figure 3A-c). This
behavior confirms the different affinity of the donor sets –
the Ag+ is not bonded as strongly in the O5-cavity as it is in
the O2S3-cavity. However, addition of one equivalent of K+
to the above solution of Ag+ complex led to a much lager
downfield shift, in accord with the formation of the hetero-
dinuclear species [Ag(4)K]2+ (Figure 3A-d). Since both cav-
ities were already saturated by their preferred metal species,
no further shifts occurred on addition of additional K+ (Fig-
ure 3A-e).
alternately. Notably, all of the oxygen atoms in 4 are direct-
ed inwards, while the sulfur donors are directed outwards
with respect to the ring cavities.
Reaction of KPF6 and AgPF6 in acetonitrile layered onto
a dichloromethane solution of 4 yielded the crystalline prod-
uct 5. X-ray analysis revealed that 5 is a heterodinuclear K+
and Ag+ complex of formula [K(4)Ag]·2PF6·2CH3CN in
which both metal ions are accommodated in the crown-ring
cavities (Figure 1ACHTUNGTRENNUNG
(right)). The K+ is situated symmetrically
within the O5-cavity, with K+ O lengths in the range 2.766-
2.843 ꢁ. The K+ is also stabilized by cation-p interactions
with the aromatic rings A and C (K+···C12 3.220 and K+
ꢀ
···C25 3.115 ꢁ, dashed lines in Figure 1ACTHNUTRGNEUNG(right)). On the other
hand, the Ag+ occupies the remaining ring and is in a four-
coordinated environment, with three coordination sites oc-
ꢀ
ꢀ
cupied by three S donors (Ag S1 2.540, Ag S2 2.855, and
ꢀ
Ag S3 2.496 ꢁ) and the remaining site occupied by one aro-
ꢀ
ꢀ
matic C atom, yielding a cation p bond (Ag C32 2.476 ꢁ).
No significant interaction was found between the Ag+ and
C18 atom (4.393 ꢁ).
The NMR spectra of 4 were also obtained under condi-
tions involving the reverse order of salt addition (Fig-
ure 3B). According to the peak patterns and chemical shift
changes shown in Figure 3B-b,c, the potassium ion is accom-
modated in the O5-ring cavity and then the added Ag+ oc-
cupies the O2S3-ring cavity to form the heterodinuclear spe-
cies [Ag(4)K]2+ (Figure 3B-d). Interestingly, the NMR
peaks in Figure 3B-e show the same pattern to those in Fig-
Upon complexation, two major conformational changes
are observed: 1) the orientation of three sulfur donors un-
dergoes considerable rearrangement from exo- to endoden-
tate and 2) the dihedral angles of each opposite pair of aro-
ꢀ
matic rings in the free ligand are much reduced (aA C
ꢀ
37.08!23.48 and aB D 40.88!27.68). The former change
is to some extent expected to be entropically unfavorable;
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Chem. Eur. J. 2009, 15, 8989 – 8992

Calix-bis-crown K+/Ag+ Complexation
COMMUNICATION
Figure 3. Cation-induced 1H NMR spectra of aromatic region for A: stepwise addition of silver(I) and potassium(I): a) 4, b) 4+1.0 equiv Ag+, c) 4+2.0
equiv Ag+ d) 4+2.0 equiv Ag+ +1.0 equiv K+, e) 4+2.0 equiv Ag+ +2.0 equiv K+. B: stepwise addition of potassium(I) and silver(I): a) 4, b) 4+
1.0 equiv K+, c) 4+2.0 equiv K+, d) 4+2.0 equiv K+ +1.0 equiv Ag+, e) 4+2.0 equiv K+ +2.0 equiv Ag+ (as picrate salts) in CD3CN/CDCl3 (v/v 4:1).
hexane (1:2) as eluent, and recrystallized from CH2Cl2/n-hexane (1:30, v/
ure 3A-e, suggesting that the respective structural conver-
sions finally reach the same heterodinuclear complexation
equilibrium position.
In this work, we describe the synthesis and structural
characterization of a unsymmetrical calix[4]-bis-crown and
its heterodinuclear K+ and Ag+ complex. We expect that
the unsymmetrical calix-bis-crown system can offer potential
design tool for engineering new receptors for heteronuclear
guest system. Further investigation of the physical proper-
ties and related system is in progress.
v) to give a white crystalline solid in 16% yield (0.12 g). Mp=259–
2608C; 1H NMR (CDCl3, 300 MHz, 295 K): d=7.07 (dd, 8H, Ar), 6.89
(tt, 4H, Ar), 3.89 (s, 8H, ArCH2Ar), 3.48 (s, 8H, OCH2CH2O), 3.42 (t,
4H, ArOCH2CH2S), 3.35 (t, 4H, ArOCH2CH2O), 3.03 (t, 4H, Ar-
OCH2CH2O), 2.64 (s, 8H, ArOCH2CH2SCH2), 1.98 ppm (t, 4H,
SCH2CH2S); 13C NMR (CDCl3, 75 MHz, 295 K): d=134.6, 133.9, 129.3,
129.1, 123.4, 122.5, 72.8, 71.1, 70.6, 68.6, 67.4, 38.3, 35.5, 33.8, 32.2 ppm;
IR (KBr pellet): n˜ =2904, 1461, 1215, 1148, 1094, 764 cmꢀ1; MS (FAB, m/
z): 812 [M++Na], 788 [M+]; elemental analysis (%) calcd for
C44H52O7S3: C 66.97, H 6.64, S 12.19; found: C 67.02, H 6.79, S 12.55.
Preparation of [Ag(4)K]·2PF6·2CH3CN (5): AgPF6 (3.20 mg, 1.27 mmol)
and KPF6 (2.33 mg, 1.27 mmol) in acetonitrile (3 mL) were layered onto
a dichloromethane solution (3 mL) of 4 (10.0 mg, 1.27 mmol) at room
temperature. The X-ray quality single crystals were obtained in good
yield (10.7 mg, 69%). IR (KBr pellet): n˜ =2920, 2876, 2346 (CN), 2304
(CN), 1469, 1201, 1078, 756 cmꢀ1; MS (ESI): m/z: 1081.9 [K(4)Ag
ACHTUNGTRENNUNG
Experimental Section
467.9 elemental analysis (%) calcd
[K(4)Ag]2+
;
C48H58AgF12KN2O7P2S3: C 44.07, H 4.47, N 2.14, S 7.35; found: C 44.29,
H 4.54, N 2.61, S 7.76.
General: All chemicals and solvents used in the syntheses were of re-
agent grade and were used without further purification. The 1H and
13C NMR spectra were recorded by using
a Bruker Advance-300
Crystal data for 4 and 5 were collected at 100 K using synchrotron radia-
tion (l=0.85 ꢁ), employing a 6BX Bruker Proteum 300 CCD detector
and a Pt-coated Si double-crystal monochromator located at the Pohang
Accelerator Laboratory in Korea. The HKL2000 (V. 0.98.694)[7] software
package was used for data collection, cell refinement, reduction, and ab-
sorption correction. The intensity data were processed using the Saint
Plus program. All of the calculations for the structure determination
were carried out using the SHELXTL package (version 5.1).[8] In most
cases, hydrogen positions were input and refined in a riding manner
along with the attached carbons. Relevant crystal data collection and re-
finement data for the crystal structures of 4 and 5 are summarized in
Table S1. In the refinement procedure for 4, the hydrogen atoms of the
CH3OH molecule in the lattice were not included to avoid the overlap-
ping with hydrogen atoms in the ligand.
(300 MHz) NMR spectrometer. Mass spectra were obtained by using a
JEOL JMS-700 spectrometer. The FT-IR spectra were measured by
using a Shimadzu FT-IR 8100 spectrometer. The elemental analysis was
carried out by using a LECO CHNS-932 elemental analyzer.
Synthesis and characterization of 4: To a refluxed solution of K2CO3
(0.569 g, 4.12 mmol) in THF (100 mL) was added dropwise a solution of
3 (1.00 g, 1.10 mmol) and 2-mercapto ethyl sulfide (0.239 g, 1.55 mmol) in
THF (50 mL) for 3 h under nitrogen, and the reaction mixture was re-
fluxed for an additional 24 h. After cooling to room temperature, 10%
HCl (10 mL) was added and the solvent was removed under reduced
pressure. The reaction mixture was extracted with CH2Cl2 (3ꢂ50 mL),
washed with water and then dried over anhydrous MgSO4. The crude
product was chromatographed on silica gel using ethyl acetate and n-
Chem. Eur. J. 2009, 15, 8989 – 8992
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8991

W. Sim, S. S. Lee et al.
CCDC 719416 (4) and 719415 (5) contain the supplementary crystallo-
graphic 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.
Trans. 1 1998, 2307; c) J. S. Kim, A. Ohki, R. Ueki, T. Ishizuka, T. Shi-
motashiro, S. Maeda, Talanta 1999, 48, 705; d) P. Thuꢃry, M. Nierlich,
V. Lamare, J. F. Dozol, Z. Asfari, J. Vicens, J. Inclusion Phenom.
Macrocyclic Chem. 2000, 36, 375.
[3] a) R. G. Pearson, J. Am. Chem. Soc. 1963, 85, 3533; b) Z. Asfari, R.
Abidi, F. Arnaud-Neu, J. Vicens, J. Inclusion Phenom. Mol. Recognit.
Chem. 1992, 13, 163; c) C. Hill, J.-F. Dozol, V. Lamare, H. Rouquette,
S. Eymard, B. Tournois, J. Vicens, Z. Asfari, C. Bressot, R. Ungaro,
A. Casnati, J. Inclusion Phenom. Mol. Recognit. Chem. 1994, 19, 399.
[4] J. S. Kim, W. K. Lee, I.-H. Suh, J.-G. Kim, J. Yoon, J. H. Lee, J. Org.
Chem. 2000, 65, 7215.
[5] a) J. Y. Lee, J. Kwon, C. S. Park, J.-E. Lee, W. Sim, J. S. Kim, J. Seo, I.
Yoon, J. H. Jung, S. S. Lee, Org. Lett. 2007, 9, 493; b) J. Y. Lee, S. Y.
Lee, J. Seo, C. S. Park, J. N. Go, W. Sim, S. S. Lee, Inorg. Chem. 2007,
46, 6221; c) J. Y. Lee, S. Y. Lee, W. Sim, K.-M. Park, J. Kim, S. S. Lee,
J. Am. Chem. Soc. 2008, 130, 6902; d) J. Y. Lee, H. J. Kim, J. H. Jung,
W. Sim, S. S. Lee, J. Am. Chem. Soc. 2008, 130, 13838.
Acknowledgements
This work was supported by grant No. R32-2008-000-20003-0 from the
World Class University (WCU) project of the Ministry of Education, Sci-
ence & Technology (MEST) and the Korea Science and Engineering
Foundation (KOSEF) through Gyeongsang National University. Experi-
ments at PLS were supported in part by MEST and POSTECH.
Keywords: calixarenes
·
crown
compounds
·
[6] W. Sim, J. Y. Lee, J. Kwon, M. J. Kim, J. S. Kim, Bull. Korean Chem.
Soc. 2002, 23, 879.
heterobinuclear · potassium · silver
[7] Z. Otwinowski, W. Minor in Methods in Enzymology, Part A,
Vol. 276 (Eds.: C. W. Carter, Jr., R. M. Sweet), Academic Press, New
York, 1997, pp. 307–326; SHELXTL-PC, Version 5.10, G. M. Shel-
drick, Bruker, Bruker-Analytical X-ray Services, Madison, 1998.
[8] SHELXTL, Structure Determination Programs Version 6.10, Bruker,
Bruker Analytical X-ray Instruments, Madison, 2000.
[1] a) C. D. Gutsche, Calixarenes, RSC, Cambridge, 1989; b) A. Casnati,
A. Pochini, R. Ungaro, F. Ugozzoli, F. Arnaud, S. Fanni, D. N. Rein-
houdt, J. Am. Chem. Soc. 1995, 117, 2767; c) B. Pulpoka, Z. Asfari, J.
Vicens, Tetrahedron Lett. 1996, 37, 6315; d) A. Ikeda, S. Shinkai,
Chem. Rev. 1997, 97, 1713; e) S. K. Kim, S. H. Lee, J. Y. Lee, J. Y.
Lee, R. A. Bartsch, J. S. Kim, J. Am. Chem. Soc. 2004, 126, 16499.
[2] a) S. Wenger, Z. Asfari, J. Vicens, Tetrahedron Lett. 1994, 35, 8369;
b) J. S. Kim, I. H. Suh, J. K. Kim, M. H. Cho, J. Chem. Soc. Perkin
Received: June 10, 2009
Published online: August 19, 2009
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