Design and synthesis of calixarene-based bis-alkynyl-bridged dinuclear AuI isonitrile complexes as luminescent ion probes by the modulation of Au...Au interactions

Article abstract of DOI:10.1002/chem.200900422

Two calixarene-based bis-alkynyl-bridged Au^I isonitrile complexes with two different crown ether pendants, [{calix[4]arene-(OCH ₂CONHC₆H₄C ≡ C)₂}Au(CNR)} ₂] (R = benzo[15]crown-5 (1); R=ben

Full text of DOI:10.1002/chem.200900422

DOI: 10.1002/chem.200900422
Design and Synthesis of Calixarene-Based Bis-alkynyl-Bridged Dinuclear AuI
Isonitrile Complexes as Luminescent Ion Probes by the Modulation of
Au···Au Interactions
Xiaoming He, Wai Han Lam, Nianyong Zhu, and Vivian Wing-Wah Yam*[a]
Abstract: Two calixarene-based bis-al-
kynyl-bridged AuI isonitrile complexes
with two different crown ether pend-
crown-5 pendant, have been designed
and synthesized, and their photophysi-
cal properties have been studied. The
X-ray structure of the ligand, calix[4]-
been determined. The cation-binding
properties of these complexes with var-
ious metal ions have been studied
1
ants,
C6H4CꢀC)2}{Au
zo[15]crown-5
[{calix[4]arene-(OCH2CONH-
using UV/Vis, emission, H NMR, and
ꢀ
A
(R=ben-
arene-(OCH2CONH-C6H4C CH)2 has
ESI-MS techniques, and DFT calcula-
tions. A new low-energy emission band
associated with Au···Au interaction
could be switched on upon formation
of the metal ion-bound adduct in a
sandwich fashion.
(1);
R=benzo[18]-
crown-6 (2)), together with their relat-
ed crown-free analogue 3 (R=C6H3-
Keywords: aurophilicity calixar-
·
enes · crown compounds · lumines-
cence · sensors
A
a
mononuclear
4
with benzo[15]-
Introduction
and organometallic transition-metal complexes as chemo-
sensors, with MLCT excited states involving PET and FRET
mechanisms being most extensively studied,[7,8] while other
excited states and mechanisms have been relatively much
less explored.
There has been an increasing interest in the search for host
molecules that can selectively recognize specific guest mole-
cules through measurable photophysical changes.[1,2] Lumi-
nescence technology has been widely used in the design of
chemosensors due to its high sensitivity and the simplicity of
its equipment requirement.[2] The main mechanisms in-
volved in the photophysics of luminescent chemosensors in-
clude photoinduced electron transfer (PET),[3] photoinduced
charge transfer (PCT),[4] excimer formation,[5] and Fçrster
resonance energy transfer (FRET).[6] In recent years, there
has also been an increasing interest in the use of inorganic
During the last two decades, the chemistry of polynuclear
gold(I) complexes has attracted increasing attention, in par-
ticular with regard to the phenomenon of aurophilicity;[9]
some of which have resulted in the unique and attractive
property of luminescence.[10–18] A number of di-, tri-, and
polynuclear gold(I) complexes have been reported by
us[10–15] and others[16–18] to show strong phosphorescence,
mainly in the yellowish-green to red region, with Au···Au in-
teractions playing an important role in governing the unique
electronic absorption and emission features in these com-
plexes. In general, an increase in the Au···Au interaction
would lead to a shift of the emission to lower energy.
Recent reports have also shown that Au···Au interactions
can direct the chiral assembly of a Au16 macrocycle[12a] and
the supramolecular assembly of a Au36 crown.[12b]
In view of the rich spectroscopic and luminescence prop-
erties associated with aurophilicity exhibited by gold(I) com-
plexes, a program was initiated to explore the utilization of
the switching on and off of Au···Au interactions in optical
signal transduction for chemosensing. Previous work by us
has demonstrated the successful use of a series of dinuclear
gold(I) complexes with bridging diphosphines and crown
ether functionalized thiolate ligands for metal-ion sensing.[13]
[a] X. He, W. H. Lam, N. Zhu, V. W.-W. Yam
Centre for Carbon-Rich Molecular and
Nano-Scale Metal-Based Materials Research
Department of Chemistry
and HKU-CAS Joint Laboratory on New Materials
The University of Hong Kong, Pokfulam Road, Hong Kong (China)
E-mail: wwyam@hku.hk
Supporting information for this article (Jobꢀs plot and positive ESI-
mass spectrum for the binding of complex 1 with K+; 1H NMR spec-
tral traces of 1 upon addition of NaClO4 in the presence of nBuNPF6;
electronic absorption and emission spectral traces of 2 upon addition
of CsOTf; Cartesian coordinates of 1 and its intramolecular K+ ion-
bound sandwiched adduct) is available on the WWW under http://
dx.doi.org/10.1002/chem.200900422.
8842
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Chem. Eur. J. 2009, 15, 8842 – 8851

FULL PAPER
With our recent success in the employment of calixarenes in
supramolecular assembly[14] and chemosensing work,[15] to-
gether with the versatility of calixarenes as molecular plat-
forms for the design and construction of elaborate supra-
molecular systems due to their unique cavity shape, simple
one-pot synthesis, and ready functionalization, we believe
that the calixarene moiety would serve as ideal building
blocks for the construction of the dinuclear gold(I) scaffold.
Various luminophores based on the calixarene framework
for chemosensing work have been well documented and re-
viewed recently.[19] In this work, it is believed that the intro-
duction of the alkynyl and isocyanobenzocrown ligands to
the AuI center would lead to robust and sterically unde-
Results and Discussion
Synthesis: The synthetic route for the ligand, calix[4]arene-
(OCH2CONH-C6H4CꢀCH)2 is summarized in Scheme 1.
Reaction of tert-butylcalix[4]arene and two equivalents of
IC6H4NHCOCH2Cl in the presence of K2CO3 in acetone
gave the iodo precursor, calix[4]arene-(OCH2CONH-
C6H4I)2 in high yield. Subsequent reaction with (trimethyl-
silyl)acetylene in the presence of CuI, [PdACHTUNGTRNEG(UN PPh3)2Cl2], and
triethylamine in THF for 24 h at 508C gave calix[4]arene-
ꢀ
(OCH2CONH-C6H4C CTMS)2. This was followed by depro-
tection of the trimethylsilyl group with potassium carbonate
to give the desired ligand in cone conformation. The struc-
manding AuI complexes with stable Au C bonds, which
ture of calix[4]arene-(OCH2CONH-C6H4C CH)2 has been
ꢁ
ꢀ
would be advantageous for ion-binding studies. Introduction
of crown ether of different sizes may lead to selective bind-
ing towards various metal cations. Herein, we report the
design, synthesis and characterization of two calixarene-
based bis-alkynyl-bridged AuI isonitrile complexes with two
crystallographically characterized. tBu-C6H4OCH2CONH-
ꢀ
C6H4C CH was synthesized in a way similar to that of cal-
ꢀ
ix[4]arene-(OCH2CONH-C6H4C CH)2. The isocyanides
were synthesized from the corresponding amine by reaction
with formic acid, followed by dehydration with triphosgene,
according to the literature method.[20]
different
(OCH2CONH-C6H4C C)2}{Au
crown-5 (1); R=benzo[18]crown-6 (2)), and their related
crown-free analogue 3 (R=C6H3A(OMe)2-3,4) and mononu-
crown
ether
ꢀ
pendants,
(CNR)}2]
[{calix[4]arene-
(R=benzo[15]-
G
Complexes 1 and 2 were synthesized by the reaction of
ꢀ
[{calix[4]arene-(OCH2CONH-C6H4C C)2}Au2]1 with two
N
equivalents of the respective isocyanobenzocrown ether in
dichloromethane; the identities of which were established
by 1H and 13C NMR, and IR spectroscopy, positive ion
FAB-MS, and satisfactory elemental analysis data. Crown-
free analogue 3 and a mononuclear gold(I) complex 4 with
benzo[15]crown-5 pendant have also been designed as con-
trol complexes and were synthesized by using similar proce-
ꢀ
clear gold(I) complex 4 with benzo[15]crown-5 pendant. The
structure of the ligand, calix[4]arene-(OCH2CONH-
C6H4CꢀCH)2, has also been crystallographically character-
ized. The binding properties of these complexes with various
metal ions have been studied using UV/Vis, emission,
1H NMR spectroscopy, and ESI-MS. In addition, density
functional theory (DFT) calculations have been performed
to investigate the structural geometry of 1 and its K+ ion-
bound sandwiched adduct.
dures. A strong band due to nACTHNUTRGNEUGN(N C) was observed at 2208–
2210 cmꢁ1 in the IR spectrum for complexes 1–4, which is
comparable to the value of 2211 cmꢁ1 in [PhC
ꢀ
CAu(CNC6H3Me2-2,6)],[16c] and at higher frequency than
that found in the corresponding isocyanide ligands at 2120–
2126 cmꢁ1.
X-ray crystal structure determination: The perspective draw-
ing of calix[4]arene-(OCH2CONH-C6H4CꢀCH)2 is depicted
in Figure 1. The structure determination data are collected
in Table 1, and the selected bond lengths and angles are
tabulated in Table 2. The ligand adopts a typical cone con-
ꢀ
formation. The C C bond lengths are found to lie in the
range of 1.169–1.173 ꢂ, typical of terminal alkynes. The
bond angles of the sp-hybridized carbons are close to the
ideal value of 1808. The close distances between the oxygen
groups on the calixarene and the amide groups suggest the
presence of an intramolecular hydrogen bonding interaction.
For instance, the distances N(2)H···O(5) and N(1)H···O(6)
are 3.032 ꢂ and 3.072 ꢂ, respectively, indicating the exis-
tence of an intramolecular hydrogen bonding interaction be-
tween the amide hydrogens and the proximal phenolic oxy-
gens. The two acetylenic aryl rings adopt a parallel-displaced
configuration with a centroid–centroid distance of 4.828 ꢂ.
Electronic absorption and emisson properties: All the com-
plexes show similar UV/Vis absorption spectra in dichloro-
methane at 298 K, with high-energy bands at about 276–
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V. W.-W. Yam et al.
ꢀ
ꢀ
Scheme 1. Synthetic route for calix[4]arene-(OCH2CONH-C6H4C CH)2. Reagents and conditions: i) K2CO3, KI, acetone; ii) HC CSiMe3, Et3N, [Pd-
ACHTUNGTRENNUNG(PPh3)2Cl2], CuI, THF; iii) K2CO3, THF/MeOH.
Table 1. Crystallographic and structural determination data for calix[4]-
ꢀ
arene-(OCH2CONH-C6H4C CH)2.
empirical formula
formula weight
temperature [K]
wavelength [ꢂ]
crystal system
space group
a [ꢂ]
C69H82N2O8
1067.37
301(2)
0.71073
triclinic
¯
P1 (no. 2)
12.965(2)
b [ꢂ]
15.229(3)
c [ꢂ]
16.581(3)
a [8]
95.74(2)
b [8]
90.38(2)
g [8]
105.98(2)
3129.5(10)
2
volume [ꢂ3]
Z
1calcd
A
]
1.133
m
G
]
0.073
F
N
1148
crystal size [mm]
theta range for data collection
index ranges
0.4 mm ꢃ 0.3 mm ꢃ 0.2 mm
1.77 to 25.688
ꢁ12ꢂhꢂ15, ꢁ18ꢂkꢂ17,
ꢁ20ꢂlꢂ20
reflections collected
18497
independent reflections
completeness to q=25.688
absorption correction
refinement method
11619 [R
97.7%
none
ACHTUNGTREN(NUNG int)=0.0157]
full-matrix least-squares on F2
11619/0/668
data/restraints/parameters
goodness-of-fit on F2
1.067
final R indices[a]
N
R1 =0.0878, wR2 =0.2607
R1 =0.1136, wR2 =0.2886
0.757 and ꢁ0.409
R indices (all data)
largest diff. peak and hole [eꢂꢁ3
]
ꢀ
Figure 1. Perspective drawing of calix[4]arene-(OCH2CONH-C6H4C
CH)2 with atomic numbering. Hydrogen atoms have been omitted for
clarity. Thermal ellipsoids are shown in the 30% probability level.
2
2
[a] Rint =SjFo ꢁFo
N
ACHTUNGTRENNUNG
2
2
{S[w
U
A
.
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Calixarene-Based Bis-alkynyl-Bridged Dinuclear AuI Isonitrile Complexes
FULL PAPER
Table 2. Selected bond lengths [ꢂ] and bond angles [8] for calix[4]arene-
about 536–606 nm that are quite substantially red-shifted
from those observed in solution, whereas emission of the
mononuclear complex 4 exhibits intense emission at about
456 nm, with negligible red shift compared to that in solu-
tion. Furthermore, the emission energy in the solid state is
found to follow the trend: 2 <1 ꢃ 3 !4. Compared to the
high-energy emission of the mononuclear complex 4, the
lower emission energies of the three dinuclear complexes in
the solid state are likely to originate from triplet excited
states associated with the presence of an intramolecular
AuI···AuI interaction, and the slightly lower emission energy
of 2 may be due to a larger hydrophilic interaction between
the two benzo[18]crown-6 moieties that favor a better pack-
ing that brings the gold atoms into closer proximity.
ꢀ
(OCH2CONH-C6H4C CH)2 with estimated standard deviations in paren-
theses.
Selected bond lengths [ꢂ]
ꢁ
ꢁ
N(2) O(5) 3.031(5)
N(1) O(6) 3.072(3)
ꢁ
ꢁ
O(6) O(4) 2.701(4)
O(4) O(5) 3.027(1)
ꢁ
ꢁ
O(5) O(2) 2.717(4)
O(2) O(6) 2.930(1)
ꢁ
ꢁ
C(8) C(9) 1.169(1)
C(17) C(18) 1.172(6)
Selected bond angles [8]
C(5)-C(8)-C(9) 179.0(5)
C(14)-C(17)-C(18) 179.4(6)
292 nm and a more intense lower-energy absorption band at
about 304–316 nm. The photophysical data for all the com-
plexes are collected in Table 3. With reference to previous
studies on the related alkynylgold(I) complexes,[11,15–17] the
Cation-binding studies: Upon addition of K+ ions to a solu-
tion of 1 in dichloromethane–acetonitrile (0.1m nBu4NPF6),
the absorption band at about 310 nm shows a drop in inten-
sity, with the concomitant growth of a new low-energy
shoulder at about 350 nm. Two isosbestic points at about
295 and 330 nm are observed, indicative of a clean conver-
sion of 1 to a new chemical species, probably the ion-bound
adduct. Figure 2 shows the electronic absorption spectral
Table 3. Photophysical data for complexes 1–4.
Complex Absorption labs[a] [nm]
(e ꢃ 10ꢁ4 [dm3 molꢁ1 cmꢁ1]) T [K]
Medium
Emission lem [nm]
(t0/ms)
AHCTUNGTRENNUNG
1
2
3
4
280 sh (5.78), 292 sh (6.54), CH2Cl2 (298) 449, 477 (9.3)
308 (8.98), 318 sh (8.46)
solid (298)
solid (77)
577 (0.2)
470, 521 (5.1)
454 (33.4)
glass[b] (77)
280 sh (6.19), 292 sh (7.02), CH2Cl2 (298) 451, 478 (56.6)
308 (9.55), 318 sh (8.98)
solid (298)
solid (77)
606 (0.1)
469, 501 (12.9)
454 (58.0)
glass[b] (77)
278 sh (5.77), 292 sh (6.70), CH2Cl2 (298) 449, 478 (20.4)
308 (9.01), 318 sh (8.38)
solid (298)
solid (77)
570 (0.2)
457, 489 (9.1)
459 (43.4)
glass[b] (77)
276 sh (2.79), 282 sh (3.03), CH2Cl2 (298) 448, 476 (16.1)
306 (4.76), 316 (4.76)
solid (298)
solid (77)
456, 482 (0.6)
456 (15.1)
454 (54.3)
glass[b] (77)
[a] In dichloromethane at 298 K. [b] EtOH–MeOH–CH2Cl2 (4:1:1, v/v).
high-energy bands are tentatively assigned to the p ! p* in-
traligand transitions of the coordinated phenylalkynyl and
the aryl isocyanide units. The lower-energy absorption
bands, which are nearly absent in the free ligand, could be
assigned to arise from the ligand-to-ligand charge transfer
(LLCT) transition.
Figure 2. Electronic absorption spectral traces of
1
(1.45ꢃ10ꢁ5 m) in
CH2Cl2–MeCN (1:1 v/v, 0.1m nBu4NPF6) upon addition of KPF6 at
298 K. Inset: Plot of absorbance at 320 nm as a function of K+ concentra-
tion and its theoretical fit for the 1:1 binding of complex 1 with K+.
Excitation of complexes 1–4 in CH2Cl2 at 298 K results in
structured emission bands centered at about 448–478 nm
with vibrational progessional spacings of about 1300 cmꢁ1,
corresponding to the C:::C vibrational modes of the aromat-
ic rings. Given the close similarity of the emission of the
complexes to that of other alkynylgold(I) complexes,[11,15–17]
changes of 1 in CH2Cl2–MeCN (0.1m nBu4NPF6) upon addi-
tion of K+ ions. A binding constant, log Ks, of 5.8ꢄ0.1 is ob-
tained for K+ by a nonlinear least-squares fit[21] of the ab-
sorbance versus the concentration of the metal ion added
for a 1:1 binding mode. The close agreement of the experi-
mental data to the theoretical fits is supportive of a 1:1 com-
plexation stoichiometry, suggesting that K+ ion is bound to
the two benzo[15]crown-5 moieties in a sandwich binding
mode (Scheme 2). This 1:1 binding mode has further been
confirmed by Jobꢀs method of continuous variation.[22] The
low-energy shoulder at about 350 nm, which could not be
found upon addition of Na+, which is well known to bind to
the cavity of benzo[15]crown-5 in a 1:1 complexation mode
(Figure 3), is suggestive of an origin resulting from the for-
mation of Au···Au interaction upon sandwich binding of K+
(PPh3)],[16b] [{Au (dppe)],[16b]
such as [AuACHTUNGTRENNUNG(C CPh)ACHTUNGTRNENUGN ACHUTNGTREGNN(UN C CPh)} CTHUNGTRNENNUG
2A
ꢀ
ꢀ
[16c]
ꢀ
and [Au
(C CPh)(CNC6H3Me2-2,6)],
an origin tentatively
assigned to states arising from a metal-pertubed intraligand
ꢀ
p ! p*
ACHTUNGTRENNUNG(C C) transition, probably with some mixing of an
alkynyl to aryl isocyanide LLCT character, is suggested. The
long-lived luminescence lifetimes in the microsecond range,
together with the relatively large Stokes shift, are suggestive
of the emission of triplet parentage. In the solid state at
298 K, the dinuclear complexes 1–3 show emission bands at
Chem. Eur. J. 2009, 15, 8842 – 8851
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8845

V. W.-W. Yam et al.
Scheme 2. Schematic diagram showing the proposed formation of
AuI···AuI interaction upon the sandwich binding of metal ion.
Figure 4. Emission spectral changes of 1 (6.6ꢃ10ꢁ5 m) upon addition of
various concentrations of KPF6 in CH2Cl2–MeCN (1:1 v/v, 0.1m
nBu4NPF6). Excitation wavelength at 375 nm.
Figure 3. Electronic absorption spectral traces of
1
(1.45ꢃ10ꢁ5 m) in
CH2Cl2–MeCN (1:1 v/v, 0.1m nBu4NPF6) upon addition of NaClO4 at
298 K. Inset: Plot of absorbance at 320 nm as a function of Na+ concen-
tration and its theoretical fit for the 1:1 binding of complex 1 with Na+.
Figure 5. Excitation spectra of 1 (1.45ꢃ10ꢁ5 m) in the absence (c) and
in the presence (a) of potassium ions (1.45ꢃ10ꢁ5 m), monitored at
475 nm and 600 nm, respectively.
ion to the bis-crown unit. The log Ks value for the binding
of Na+ is found to be 4.00ꢄ0.01. On the contrary, the
crown-free analogue 3 essentially shows no absorption spec-
tral changes upon addition of K+, indicating that the UV/
Vis changes of 1 are ascribed to the specific binding of K+
to the polyether cavity of the complex rather than resulting
from changes in the microenviroment or the electronic prop-
erties of the complexes. In addition, upon titration with K+,
the UV/Vis spectrum of the mononuclear complex 4 shows
similar changes to those of 1 upon addition of Na+, with no
formation of the new low-energy band at about 350 nm.
Such findings are supportive of the intramolecular sandwich
binding mode of K+ by the bis-crown unit in 1, since a simi-
lar intramolecular sandwich binding mode is impossible and
the intermolecular sandwich binding mode unlikely under
the conditions associated with the mononuclear complex 4.
The luminescence response of 1 towards K+ has also been
investigated. Upon addition of K+ to a CH2Cl2–MeCN solu-
tion of 1 (1:1 v/v, 0.1m nBu4NPF6), pronounced changes in
the emission spectra are observed, in which a new low-
energy band at about 600 nm is formed (Figure 4). The new
low-energy emission band at about 600 nm presumably re-
sults from the switching on of the Au···Au interaction upon
the binding of the K+ ion in a sandwich binding mode,
which gives rise to a reduced HOMO–LUMO energy gap.
Figure 5 shows the excitation spectra of 1 in the absence
and in the presence of K+ ion. The excitation spectra reveal
that the low-energy emission and the high-energy emission
bands are derived from different origins. The 600 nm emis-
sion band is derived from an excitation band at about
375 nm, which coincides with the new absorption shoulder
formed at about 350 nm in the UV/Vis spectra resulting
from the switching on of the gold(I)–gold(I) interaction
upon K+ ion-binding. This further corroborates with the
proposed binding mechanism shown in Scheme 2.
An ion cluster at m/z 1980, corresponding to the 1:1 sand-
wiched adduct formed between 1 and K+ upon addition of
K+ ion to 1, is observed in the positive-ion ESI mass spec-
trum. The close resemblance of the isotopic pattern of the
expanded ion cluster with the simulated pattern confirms
the identity of the 1:1 ion-bound adduct, further supporting
the binding of K+ to the bis-crown unit.
To investigate the effect of crown size on the specificity of
the metal ion-binding, complex 2 with benzo[18]crown-6
pendants has been designed and its cation-binding exam-
ined. Upon addition of CsOTf to 2 under the same condi-
tions, UV/Vis absorption spectral changes with a new low-
energy band at about 350 nm together with two isosbestic
points at 296 and 332 nm, similar to that found for the addi-
tion of K+ to 1, are observed. A binding constant, log Ks, of
4.71ꢄ0.01 is determined by a nonlinear least-squares fit to a
1:1 binding model. The close agreement of the experimental
data to the theoretical fits is again supportive of a 1:1 bind-
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Chem. Eur. J. 2009, 15, 8842 – 8851

Calixarene-Based Bis-alkynyl-Bridged Dinuclear AuI Isonitrile Complexes
FULL PAPER
ing stoichiometry. A new low-energy emission band at about
600 nm is also observed upon addition of Cs+ ions to a solu-
tion of 2 in CH2Cl2–MeCN under the same conditions. This
demonstrates that the Cs+ ion is intramolecularly sand-
wiched between two benzo[18]crown-6 units in complex 2,
presumably due to the fact that it is too large to fit into the
cavity of benzo[18]crown-6. Therefore, on the basis of a ju-
dicious choice of an appropriate size match between the
crown ether units on the calixarene skeleton and the metal
ions, ion receptors specific for various metal ions could be
rationally designed.
structure of the benzocrown moieties upon K+ ion-binding.
A similar upfield shift in a related sandwich structure has
been observed and reported by Choi and Hamilton.[23] As
1
control experiments, the H NMR changes upon addition of
nBu4NPF6 and NaClO4 have also been studied. In the pres-
ence of 10 equivalents of nBu4NPF6, no changes in the
1H NMR spectra are observed, whereas addition of Na+ in
the presence of nBu4NPF6 causes only a downfield shift of
the proton resonances of the crown moieties as a result of
the electron-withdrawing effect of the Na+ ion-binding, as is
commonly observed upon cation-binding into the crown
cavity.
To gain further insights and obtain more structural infor-
1
mation about the binding event, H NMR titration experi-
Geometry optimization at the SVWN level of theory was
performed on complex 1 and its K+ ion-bound sandwiched
adduct to obtain the detailed
ments for K+ have been performed. Figure 6 shows the
structure of 1 before and after
complexation with the K+ ion.
The optimized structure of 1 re-
veals a cone conformation of
the calix[4]arene framework
ꢀ
with the two {(CꢀC)Au
ACHTUNGTRENNUNG
AHCTUNGERTG(NNUN benzo[15]crown-5)]}
being remote from each other
(Figure 7). In the cone struc-
ture, a circular intramolecular
hydrogen-bond
arrangement
consisting of two three-center
NH···O(ether and phenolic oxy-
gens) and two OH···OACHTUNGTRENNUNG(ether)
hydrogen bonds was observed.
A similar type of hydrogen-
bond arrangement has been re-
ported in a calix[4]arene deriva-
tive with two OCH2CO(R-phe-
nylglycine)OMe units.[19e] In the
Figure 6. 1H NMR spectral changes of 1 (1.72 mm) upon addition of K+ in CDCl3–CD3CN (1:1 v/v).
1H NMR spectral changes upon addition of K+ ions to a so-
lution of the respective complex in CDCl3–CD3CN (1:1 v/v).
Absolute assignments of the protons of complex 1 in the ab-
sence and presence of K+ have been made based on
NOESY and COSY experiments. Large upfield shifts of the
proton resonances of Ha and Hb, up to 0.66 ppm and
0.64 ppm, respectively, as well as amide (NH) and hydroxy
(OH) proton resonances are observed upon addition of K+
ions. In general, cation-binding to crown moieties would
cause a downfield shift of the proton resonances as a result
of the electron-withdrawing effect of the cation. The upfield
shifts of the NH and OH protons are likely due to the re-
moval of the intramolecular hydrogen bonding interactions
between the amide and the OH groups imposed by the rigid
sandwich structure upon K+ ion-binding, which is supported
by the DFT calculation (see below). The NOE cross peaks
between the NH and OH are very weak in intensity in the
presence of K+ when compared to that in the absence of
K+, probably as a result of the destruction of the hydrogen
bond between them. The upfield shifts of the protons Ha
and Hb are also rather unusual and may be due to the ring
current effect resulting from p-stacking in the sandwiched
optimized structure of the K+ ion-bound sandwiched
adduct, however, a partial destruction of the intramolecular
hydrogen bonding in the cyclic array was found. For exam-
ple, one of the two amide nitrogens is nearly trans to the in-
trastrand ether oxygen, which precluded the formation of
the three-center NH···O hydrogen bond (Figure 7). The
average (N)H···O(H) and (N)H···OACTHUNTGRNEUNG(ether) distances are in-
creased from 2.627 ꢂ and 2.107 ꢂ in 1 to 4.497 and 3.053 ꢂ
in the K+ ion-bound sandwiched adduct, respectively, indi-
cating the weakening of the intramolecular hydrogen bonds
in the cone structure upon binding with a K+ ion. It is also
worth mentioning that a short Au···Au contact (3.178 ꢂ)
and a parallel-displaced configuration between the aryl rings
of the two benzocrown moieties with a centroid–centroid
distance of 3.648 ꢂ were found in the K+ ion-bound adduct,
further supporting the presence of the Au···Au and p–p in-
teractions in the sandwiched ion-bound mode.
Chem. Eur. J. 2009, 15, 8842 – 8851
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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8847

V. W.-W. Yam et al.
phosphate (Aldrich) was recrystallized
twice from hot absolute ethanol and
then dried under vacuum for 12 h
before use. All solvents were purified
and distilled using standard procedures
before use.[26] All other reagents were
of analytical grade and were used as
received.
All reactions were carried out under
an inert atmosphere of nitrogen using
standard Schlenk techniques.
Syntheses
Calix[4]arene-(OCH2CONH-C6H4I)2:
To a suspension of tert-butylcalix[4]ar-
ene (1 g, 1.54 mmol) in acetone
(20 mL) were added
IC6H4NHCOCH2Cl
a
mixture of
(0.96 g,
3.24 mmol), K2CO3 (1 g, 7.25 mmol),
and KI (0.5 g, 3 mmol), and the reac-
tion mixture was allowed to heat to
reflux with stirring for 36 h. The sol-
vent was then removed under reduced
pressure and the residue taken up with
HCl (0.1m, 20 mL) and extracted with
CH2Cl2 (20 mL). The organic layer
was separated, washed with water,
dried over anhydrous MgSO4, and
evaporated to dryness. Recrystalliza-
tion from CH2Cl2–MeOH gave the
Figure 7. The optimized geometries of 1 (left) and its K+ ion-bound sandwiched adduct (right). Hydrogen
atoms except those on the amide and phenolic groups are omitted for clarity.
product as white crystals. Yield: 1.5 g,
85%. 1H NMR (400 MHz, CDCl3, 298 K, Me4Si): d=1.07 (s, 18H; -tBu),
1.29 (s, 18H; -tBu), 3.52 (d, J=13.4 Hz, 4H; -CH2-), 4.17 (d, J=13.4 Hz,
4H; -CH2-), 4.61 (s, 4H; -OCH2C), 6.98 (s, 4H; -C6H2-), 7.14 (s, 4H;
-C6H2-), 7.20 (d, J=8.8 Hz, 4H; -C6H4-), 7.48 (4H, d, J=8.8 Hz; -C6H4-),
7.96 (s, 2H; -OH), 10.11 ppm (s, 2H; -NH); positive-ion FAB-MS: m/z
1167 [M]+, 1189 [M+Na]+; elemental analysis calcd (%) for
C60H68I2N2O6: C 61.75, H 5.87, N 2.40; found: C 62.01, H 5.93, N 2.54.
Conclusions
In summary, two calixarene-based bis-alkynyl-bridged dinu-
clear gold(I) isonitrile complexes with benzo[15]crown-5
and benzo[18]crown-6 pendants have been rationally de-
signed and synthesized. All the complexes exhibit intense
emission with vibronic structures in dichloromethane solu-
tion at 298 K, which are tentatively assigned to a metal-per-
tubed intraligand (IL) transition probably with some mixing
of LLCT character. The cation-binding properties of these
complexes with various metal ions have been studied by
using UV/Vis, emission, and 1H NMR spectroscopy, ESI
mass spectrometry, and DFT calculations. The dinuclear
gold(I) complexes with crown ether pendants of different
size based on the calixarene skeleton show different binding
affinity for various metal ions, depending on the size match
between metal ion and the crown ether units. A new low-
energy emission band associated with Au···Au interaction
has been shown to be switched on upon formation of the
ion-bound adduct of 1 with K+ ion and 2 with Cs+ ion in a
sandwich binding fashion.
ꢀ
Calix[4]arene-(OCH2CONH-C6H4C CTMS)2: Into a 100 mL two-necked
round-bottomed flask was added calix[4]arene-(OCH2CONH-C6H4I)2
(0.5 g, 0.43 mmol), copper(I) iodide (12 mg, 0.065 mmol), and dichloro-
bis(triphenylphosphine)palladium(II) (45 mg, 0.065 mmol), followed by a
mixture of tetrahydrofuran (30 mL) and triethylamine (10 mL). After the
mixture had been stirred for 5 min, trimethylsilylacetylene (0.36 g,
2.58 mmol) was added to the flask under a nitrogen atmosphere. The
mixture was stirred for 24 h at 508C. The mixture was filtered, and the
filtrate was evaporated to dryness. The brown residue was purified by
column chromatography on silica gel using petroleum ether–dichlorome-
thane (1:1 v/v) as eluent to afford the product as a white solid. Yield:
0.4 g, 82%. 1H NMR (400 MHz, CDCl3, 298 K, Me4Si): d=0.26 (s, 18H;
-SiMe3), 1.10 (s, 18H; -tBu), 1.29 (s, 18H; -tBu), 3.53 (d, J=13.4 Hz, 4H;
-CH2-), 4.18 (d, J=13.4 Hz, 4H; -CH2-), 4.61 (s, 4H; -OCH2C), 7.02 (s,
4H; -C6H2-), 7.15 (s, 4H; -C6H2-), 7.32 (m, 8H; -C6H4-), 8.20 (s, 2H;
-OH), 10.27 ppm (s, 2H; -NH); positive-ion FAB-MS: m/z 959
[Mꢁ2Me3Si]+; elemental analysis calcd (%) for C70H86N2O6Si2: C 75.91,
H 7.83, N 2.53; found: C 76.02, H 7.48, N, 2.46.
ꢀ
Calix[4]arene-(OCH2CONH-C6H4C CH)2: A mixture of calix[4]arene-
ꢀ
(OCH2CONH-C6H4C CTMS)2 (100 mg, 0.09 mmol) and potassium car-
bonate (100 mg, 0.72 mmol) in tetrahydrofuran–methanol (2:1 v/v,
40 mL) was stirred at room temperature for 4 h. The mixture was filtered
and the solvent was removed under reduced pressure to give a light
brown residue. The residue was then dissolved in dichloromethane, and
washed with dilute hydrochloric acid (0.1m) and with deionized water
twice, followed by drying over anhydrous MgSO4 and filtration. Removal
of the solvent under reduced pressure gave a brown residue. The brown
residue was purified by column chromatography on silica gel using di-
chloromethane (1:1 v/v) as eluent to afford the product as a white solid.
Yield: 74 mg, 85%. 1H NMR (400 MHz, CDCl3, 298 K, Me4Si): d=1.09
(s, 18H; -tBu), 1.29 (s, 18H; -tBu), 3.04 (s, 2H; CꢀCH), 3.53 (d, J=
Experimental Section
Materials and reagents: The benzo[15]crown-5 isocyanide,[20]
IC6H4NHCOCH2Cl,[24] and cesium triflate[25] were prepared by modifica-
tion of the literature procedure. The other two isocyanides, R-NC (R=
benzo[18]crown-6, C6H3-(OMe)2-3,4),[20] were prepared in a way similar
to that reported for benzo[15]crown-5 isocyanide. Potassium
tetrachloroaurateACHTUNGTRENNUNG(III) was purchased from Strem Chemicals Inc. 2,2’-
Thiodiethanol, sodium perchlorate and potassium perchlorate were pur-
chased from Aldrich Chemical Co. Tetra-n-butylammonium hexafluoro-
8848
www.chemeurj.org
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 8842 – 8851

Calixarene-Based Bis-alkynyl-Bridged Dinuclear AuI Isonitrile Complexes
FULL PAPER
13.4 Hz, 4H; -CH2-), 4.20 (d, J=13.4 Hz, 4H; -CH2-), 4.62 (s, 4H;
-OCH2C), 7.01 (s, 4H; -C6H2-), 7.15 (s, 4H; -C6H2-), 7.32 (dd, J=8.7 and
9.1 Hz, 8H; -C6H4-), 8.11 (s, 2H; -OH), 10.24 ppm (s, 2H; -NH); posi-
tive-ion FAB-MS: m/z 963 [M]+; elemental analysis calcd (%) for
C64H70N2O6: C 79.80, H 7.32, N 2.91; found: C 79.57, H 7.26, N 3.03.
solution of the complex gave 3 as a white solid. Yield: 105 mg, 85%.
1H NMR (400 MHz, CDCl3, 298 K, Me4Si): d=1.09 (s, 18H; -tBu), 1.28
(s, 18H; -tBu), 3.47 (d, J=13.4 Hz, 4H; -CH2-), 3.93 (s, 6H; -OCH3), 3.94
(s, 6H; -OCH3), 4.20 (d, J=13.4 Hz, 4H; -CH2-), 4.58 (s, 4H; -OCH2C-),
ꢀ
6.88 (d, J=8.8 Hz, 2H; -C6H3-, aryl H meta to N C), 7.00 (m, 6H;
ꢀ
ꢀ
-C6H3-, aryl H ortho to N C and -C6H2-), 7.12 (s, 4H; -C6H2-), 7.17 (dd,
tBu-C6H4OCH2CONH-C6H4C CH: This was synthesized in a similar
way to that of calix[4]arene-(OCH2CONH-C6H4C CH)2. 1H NMR
ꢀ
ꢀ
J=2.2 and 8.8 Hz, 2H; -C6H3-, aryl H ortho to N C), 7.32 (m, 8H;
ꢀ
(400 MHz, CDCl3, 298 K, Me4Si): d=1.31 (s, 9H; -tBu), 3.06 (s, 1H; C
-C6H4-), 8.22 (s, 2H; -OH), 10.19 ppm (s, 2H; -NH); IR (KBr disk): n˜ =
1690 (C=O), 2208 cmꢁ1 (N C); positive-ion ESI-MS: m/z 1704 [M+
CH), 4.60 (s, 2H; -OCH2), 6.92 (d, J=8.8 Hz, 2H; -C6H4-), 7.37 (d, J=
8.8 Hz, 2H; -C6H4-), 7.49 (d, J=8.7 Hz, 2H; -C6H4-), 7.58 (d, J=8.7 Hz,
2H; -C6H4-), 8.34 ppm (s, 1H; -NH); elemental analyses calcd (%) for
C20H21NO2: C 78.15, H 6.89, N 4.56; found: C 78.13, H 7.12, N 4.72.
ꢀ
Na]+; elemental analysis calcd (%) for C82H86Au2N4O10·CH2Cl2: C 56.44,
H 5.03, N 3.17; found: C 56.60, H 5.04, N 3.23.
ꢀ
[(tBu-C6H4OCH2CONH-C6H4C C)Au(CN-B15C5)] (4): This was pre-
4-CN-benzo[18]crown-6 (CN-B18C6): This was synthesized according to
a method similar to that of CN-B15C5.[20] 1H NMR (400 MHz, CDCl3,
298 K, Me4Si): d=3.65–3.80 (m, 12H; -OCH2-), 3.92 (m, 4H; -OCH2-),
4.15 (m, 4H; -OCH2-), 6.79 (d, J=8.5 Hz, 1H; -C6H3-), 6.86 (s, 1H;
-C6H3-), 6.95 ppm (d, J=8.5 Hz, 1H; -C6H3-); IR (KBr disk): n˜ =
2125 cmꢁ1 (NꢀC); positive FAB-MS: m/z 338 [M]+.
CN-C6H3-(OMe)2-3,4: This was synthesized according to a method simi-
lar to that of CN-B15C5.[20] 1H NMR (400 MHz, CDCl3, 298 K, Me4Si):
d=3.91 (s, 3H; -OCH3), 3.92 (s, 3H; -OCH3), 6.83 (d, J=8.5 Hz, 1H;
pared according to the procedure for 1 except [(tBu-C6H4OCH2CONH-
ꢀ
C6H4C C)Au]1 (74 mg, 0.15 mmol) was used instead of [{calix[4]arene-
ꢀ
(OCH2CONH-C6H4C C)2}Au2]1. Recrystallization by the diffusion of di-
ethyl ether vapor into a dichloromethane solution of the complex gave 4
as a white solid. Yield: 100 mg, 85%. H NMR (400 MHz, CDCl3, 298 K,
1
Me4Si): d=1.31 (s, 9H; -tBu), 3.76 (m, 8H; -OCH2CH2O-), 3.92 (m, 4H;
-OCH2CH2OAr-), 4.15 (m, 4H; -ArOCH2CH2O-), 4.58 (s, 2H;
ꢀ
-OCH2C-), 6.85 (d, J=8.7 Hz, 1H; -C6H3-, aryl H meta to N C), 6.91 (d,
J=8.9 Hz, 2H; -C6H4-), 6.95 (d, J=2.3 Hz, 1H; -C6H3-, aryl H ortho to
-C6H3-), 6.88 (s, 1H; -C6H3-), 7.00 ppm (d, J=8.5 Hz, 1H; -C6H3-); IR
ꢀ
ꢀ
N C), 7.12 (dd, J=2.3 and 8.7 Hz, 1H; -C6H3-, aryl H ortho to N C),
7.35 (d, J=8.9 Hz, 2H; -C6H4-), 7.49 (m, 4H; -C6H4-), 8.26 ppm (s, 1H;
+
(KBr disk): n˜ =2126 cmꢁ1 (N C); positive-ion FAB-MS: m/z 164 [M] .
ꢀ
ꢀ
-NH); IR (KBr disk): n˜ =1698 (C=O), 2210 cmꢁ1 (N C); positive-ion
[Calix[4]arene-(OCH2CONH-C6H4C CAu)2]1: This was synthesized ac-
ꢀ
cording to modification of a reported procedure.[17b] [Au
(tht)Cl] (35 mg,
ESI-MS: m/z 797 [M]+, 819 [M+Na]+; elemental analysis calcd (%) for
C35H39AuN2O7·H2O: C 51.58, H 5.07, N 3.43; found: C 51.31, H 4.86, N,
3.45.
0.11 mmol) was added to
a solution of calix[4]arene-(OCH2CONH-
C6H4CꢀCH)2 (50 mg, 0.052 mmol) and NaOAc (90 mg, 1.1 mmol) in
MeOH-THF (9:1 v/v; 30 mL) solution. The mixture was stirred for 1 h.
The yellow precipitate was filtered, washed with water and methanol,
and dried under vacuum. Caution: The alkynylgold(I) polymer is poten-
tially explosive and should be handled with great caution.
Physical measurements and instrumentation: The UV/Vis spectra were
recorded on a Hewlett–Packard 8452 A diode array spectrophotometer,
and IR spectra as a KBr disk on a Bio-Rad FTS-7 Fourier transform in-
frared spectrophotometer (4000–400 cmꢁ1). 1H NMR spectra with chemi-
cal shifts relative to tetramethylsilane (Me4Si) were recorded on a Bruker
DPX-300 FT-NMR spectrometer or a Bruker Avance 400 FT-NMR spec-
trometer. Positive-ion fast atom bombardment (FAB) mass spectra were
recorded on a Finnigan MAT95 mass spectrometer. Positive-ion electro-
spray-ionization (ESI) mass spectra were obtained on a Finngan LCQ
mass spectrometer. Elemental analysis of the new complex was per-
formed on a Carlo Erba 1106 elemental analyzer at the Institute of
Chemistry of the Chinese Academy of Sciences in Beijing.
ꢀ
[{Calix[4]arene-(OCH2CONH-C6H4C C)2}{Au(CN-B15C5)}2] (1): To a
ꢀ
solution of [{calix[4]arene-(OCH2CONH-C6H4C C)2}Au2]1 (100 mg,
0.074 mmol) in dichloromethane was added a solid sample of CN-B15C5
(44 mg, 0.15 mmol) under a nitrogen atmosphere, and the reaction mix-
ture was stirred at room temperature for 2 h. The solvent was then re-
moved under reduced pressure and the residue was recrystallized from
dichloromethane–diethyl ether to give 1 as an off-white solid. Yield:
1
80 mg, 56%. H NMR (400 MHz, CDCl3, 298 K, Me4Si): d=1.09 (s, 18H;
-tBu), 1.28 (s, 18H; -tBu), 3.50 (d, J=13.4 Hz, 4H; -CH2-), 3.76 (m, 16H;
-OCH2CH2O-), 3.92 (t, J=4.3 Hz, 8H; -OCH2CH2OAr-), 4.16 (m, 8H;
-ArOCH2CH2O-), 4.20 (d, J=13.4 Hz, 4H; -CH2-), 4.58 (s, 4H; -OCH2C-
), 6.85 (d, J=8.6 Hz, 2H; -C6H3-, aryl H meta to NꢀC), 6.97 (d, J=
2.2 Hz, 2H; -C6H3-, aryl H ortho to NꢀC), 7.00 (s, 4H; -C6H2-), 7.13 (m,
6H; -C6H3-, aryl H ortho to NꢀC and -C6H2-), 7.32 (d, J=4.9 Hz, 8H;
Steady-state excitation and emission spectra were recorded on a Spex
Fluorolog-3 Model FL3–211 fluorescence spectrofluorometer equipped
with a R2658P PMT detector. All solutions for photophysical studies
were prepared under a high vacuum in a 10 mL round-bottomed flask
equipped with a sidearm 1 cm fluorescence cuvette and sealed from the
atmosphere by a Rotaflo HP6/6 quick-release Teflon stopper. Solutions
were rigorously degassed on a high-vacuum line in a two-compartment
cell with no less than four successive freeze–pump–thaw cycles. Solid-
state photophysical measurements were carried out with the solid sample
loaded in a quartz tube inside a quartz-walled Dewar flask. Liquid nitro-
gen was placed into the Dewar flask for low-temperature (77 K) photo-
physical measurements. Excited-state lifetimes of samples in fluid solu-
tions or in the solid states were measured by using a conventional laser
system. The excitation source used was the 355 nm output (third harmon-
ic, 8 ns) of a Spectra-Physics Quanta-Ray Q-switched GCR-150 pulsed
Nd:YAG laser (10 Hz).
-C6H4-), 8.20 (s, 2H; -OH), 10.17 ppm (s, 2H; -NH); IR (KBr disk): n˜ =
+
1689 (C=O), 2208 cmꢁ1 (N C); positive-ion ESI-MS: m/z 1942 [M] ; ele-
ꢀ
mental analysis calcd (%) for C94H106N4Au2O16·2H2O : C 57.08, H 5.61, N
2.83; found: C 57.01, H 5.44, N 2.87.
ꢀ
N
was prepared according to the procedure for 1 except CN-B18C6 (51 mg,
0.15 mmol) was used instead of CN-B15C5. Recrystallization from di-
chloromethane–diethyl ether gave 2 as an off-white solid. Yield: 75 mg,
50%. 1H NMR (400 MHz, CDCl3, 298 K, Me4Si): d=1.10 (s, 18H; -tBu),
1.30 (s, 18H; -tBu), 3.52 (d, J=14.6 Hz, 4H; -CH2-), 3.80–3.65 (m, 24H;
-OCH2CH2O-), 3.96 (m, 8H; -OCH2CH2OAr-), 4.20 (m, 12H;
-OCH2CH2OAr- and -CH2-), 4.61 (s, 4H; -OCH2C-), 6.85 (d, J=8.8 Hz,
2H; -C6H3-, aryl H meta to NꢀC), 7.00 (m, 6H; -C6H3-, aryl H ortho to
NꢀC and -C6H2-), 7.14 (m, 6H; -C6H3-, aryl H ortho to NꢀC and
-C6H2-), 7.34 (m, 8H; -C6H4-), 8.21 (s, 2H; -OH), 10.20 ppm (s, 2H;
Binding constant determination: The electronic absorption spectral titra-
tion for binding constant determination was performed on a Hewlett–
Packard 8425 A diode-array spectrophotometer at 258C, which was con-
trolled by a Lauda RM6 compact low-temperature thermostat, while the
emission titration was performed on a Spex Fluorolog-3 Model FL3–211
fluorescence spectrofluorometer. Supporting electrolyte (0.1 mol dmꢁ3
nBu4NPF6) was added to maintain the ionic strength of the sample solu-
tion constant during the titration to avoid any changes in the ionic
strength of the medium. Binding constants for 1:1 complexation were ob-
tained by a nonlinear least-squares fit[21] of the absorbance (A) versus the
concentration of metal ion added (CM) according to Equation (1):
-NH); IR (KBr disk): n˜ =1690 (C=O), 2209 cmꢁ1 (N C); positive-ion
ꢀ
ESI-MS: m/z 1698 [MꢁL]+, 1721 [MꢁL+Na]+, 2233 [M+Au] +; ele-
mental analysis calcd (%) for C98H114N4Au2O18·H2O : C 57.48, H 5.71, N
2.74; found: C 57.21, H 5.71, N 2.95.
ꢀ
[{Calix[4]arene-(OCH2CONH-C6H4C C)2}{Au
E
G
(3): This was prepared according to the procedure for 1 except CNC6H3-
(OMe)2-3,4 (25 mg, 0.15 mmol) was used instead of CN-B15C5. Recrys-
tallization by the diffusion of diethyl ether vapor into a dichloromethane
Chem. Eur. J. 2009, 15, 8842 – 8851
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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8849

V. W.-W. Yam et al.
Alim ꢁ A0
2C0
[3] a) A. P. de Silva, H. Q. N. Gunaratne, T. Gunnlaugsson, A. J. M.
Huxley, C. P. McCoy, J. T. Rademacher, T. E. Rice, Chem. Rev. 1997,
97, 1515–1566; b) R. A. Bissell, A. P. de Silva, H. Q. N. Gunaratne,
P. L. M. Lynch, G. E. M. Maguire, K. R. A. S. Sandanayake, Chem.
Soc. Rev. 1992, 21, 187–195; c) I. Aoki, H. Kawabata, K. Nakashi-
ma, S. Shinkai, J. Chem. Soc. Chem. Commun. 1991, 1771–1771;
d) I. Aoki, T. Sakaki, S. Shinkai, J. Chem. Soc. Chem. Commun.
1992, 730–732; e) H. F. Ji, R. Dabestani, G. M. Brown, J. Am.
Chem. Soc. 2000, 122, 9306–9307.
[4] a) I. Leray, F. OꢀReilly, J.-L. Habib-Jiwan, J.-Ph. Soumillion, B.
Valeur, Chem. Commun. 1999, 795–796; b) I. Leray, J. P. Lefevre,
J. F. Delouis, J. Delaire, B. Valeur, Chem. Eur. J. 2001, 7, 4590–4598.
[5] a) T. Jin, K. Ichikawa, T. Koyama, J. Chem. Soc. Chem. Commun.
1992, 499–501; b) N. Van Der Veen, S. Flink, M. Deij, R. Egberink,
F. Van Veggel, D. Reinhoudt, J. Am. Chem. Soc. 2000, 122, 6112–
6113.
[6] a) M. A. Hossain, H. Mihara, A. Ueno, J. Am. Chem. Soc. 2003, 125,
11178–11179; b) H. Takakusa, K. Kikuchi, Y. Urano, T. Higuchi, T.
Nagano, Anal. Chem. 2001, 73, 939–942; c) M. Arduini, F. Felluga,
F. Mancin, P. Rossi, P. Tecilla, U. Tonellato, N. Valentinuzzi, Chem.
Commun. 2003, 1606–1607.
[7] a) V. Balzani, N. Sabbatina, F. Scandola, Chem. Rev. 1986, 86, 319–
337; b) D. B. MacQueen, K. S. Schanze, J. Am. Chem. Soc. 1991,
113, 6108–6110; c) Y. Shen, B. P. Sullivan, Inorg. Chem. 1995, 34,
6235–6236; d) P. D. Beer, Acc. Chem. Res. 1998, 31, 71–80; e) P. D.
Beer, O. Kocian, R. J. Mortimer, C. Ridgway, J. Chem. Soc. Chem.
Commun. 1991, 460–462; f) P. D. Beer, J. Chem. Soc. Chem.
Commun. 1996, 689–696; g) J. E. Redman, P. D. Beer, S. W. Dent,
M. G. B. Drew, Chem. Commun. 1998, 231–232; h) P. D. Beer, R. J.
Mortimer, C. Ridgway, J. Chem. Soc. Dalton Trans. 1993, 2629–
2638; i) P. D. Beer, S. W. Dent, T. Wear, J. Chem. Soc. Dalton Trans.
1996, 2341–2346; j) P. D. Beer, S. W. Dent, G. W. Hobbs, T. J. Wear,
Chem. Commun. 1997, 99–100.
2
1=2
A ¼ A0 þ
½C0 þ CM þ 1=Ks ꢁ ½ðC0 þ CM þ 1=KsÞ ꢁ 4C0CM
ꢅ
ꢅ
ð1Þ
where A0 and A are the absorbance of the complex at a selected wave-
length in the absence and presence of the metal cation, respectively, [C0]
is the total concentration of the complex, [CM] is the concentration of the
metal cation, Alim is the limiting value of absorbance in the presence of
excess metal ion, and Ks is the stability constant.
Crystal structure determination: Crystals of the calix[4]arene-
(OCH2CONH-C6H4C CH)2 suitable for X-ray studies were obtained by
ꢀ
slow evaporation of the dichloromethane solution of the ligand. All the
experimental details are given in Table 1. A pale-yellow crystal of dimen-
sions 0.4 mm ꢃ 0.3 mm ꢃ 0.2 mm mounted on a glass capillary was used
for data collection at 288C on a Bruker Smart CCD 1000 using graphite-
monochromatized MoKa radiation (l=0.71073 ꢂ). The structure was
solved by direct methods employing SHELXS-97 program[27] on PC.
Many non-H atoms were located according to the direct methods. The
positions of the other non-hydrogen atoms were found after successful
refinement by full-matrix least-squares using program SHELXL-97[27] on
PC. One crystallographic asymmetric unit consists of one formula unit,
including one methanol and one diethyl ether solvent molecules. In the
final stage of least-squares refinement, non-H atoms of solvent molecules
were refined isotropically, other non-H atoms were refined anisotropical-
ly. The positions of H atoms were calculated based on riding mode with
thermal parameters equal to 1.2 times that of the associated C atoms,
and participated in the calculation of final R indices.
ꢀ
CCDC-720400 (calix[4]arene-(OCH2CONH-C6H4C CH)2) contains the
supplementary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif
[8] a) M. J. Li, B. W. K. Chu, V. W. W. Yam, Chem. Eur. J. 2006, 12,
3528–3537; b) M. J. Li, C. C. Ko, G. P. Duan, N. Zhou, V. W. W.
Yam, Organometallics 2007, 26, 6091–6098; c) V. W. W. Yam,
V. W. M. Lee, Inorg. Chem. 1997, 36, 2124–2129; d) V. W. W. Yam,
R. P. L. Tang, K. M. C. Wong, X. X. Lu, K. K. Cheung, N. Zhu,
Chem. Eur. J. 2002, 8, 4066–4076; e) W. S. Tang, X. X. Lu, K. M. C.
Wong, V. W. W. Yam, J. Mater. Chem. 2005, 15, 2714–2720;
f) V. W. W. Yam, K. M. C. Wong, V. W. M. Lee, K. K. W. Lo, K. K.
Cheung, Organometallics 1995, 14, 4034–4036.
[9] a) H. Schmidbaur, Chem. Soc. Rev. 1995, 24, 391–400; b) H.
Schmidbaur, Gold Bull. 2000, 33, 3–10; c) P. Pyykkç, Angew. Chem.
2004, 116, 4512–4557; Angew. Chem. Int. Ed. 2004, 43, 4412–4456;
d) P. Pyykkç, Y. Zhao, Angew. Chem. 1991, 103, 622–623; Angew.
Chem. Int. Ed. Engl. 1991, 30, 604–605.
Computational details: Geometry optimization was performed on 1 and
its intramolecular K+ ion-bound sandwiched adduct without symmetry
constraint using the density functional theory method that includes the
Slater exchange functional and the Voskko, Wilk, and Nusair correlation
functional (SVWN)[28] with the pruned (99,590) grid. The Stuttgart effec-
tive core potentials (ECPs) and the associated basis set were applied to
describe Au[29] with an f polarization function (zf(Au)=1.050).[30] For K,
C, H, O, and N atoms, the 6–31G basis set was used with a polarization
function for the O (zd(O)=0.8), N(zd(N)=0.8), K (zd(K)=0.235) atoms,
the alkynyl and the isonitrile carbons (zd(C)=0.8) as well as the phenolic
and amide hydrogens (zp(H)=1.1).[31] All calculations were performed
with the use of the Gaussian 03 package.[32]
[10] a) V. W. W. Yam, E. C. C. Cheng, Top. Curr. Chem. 2007, 267–270,
269–309; b) V. W. W. Yam, E. C. C. Cheng, Chem. Soc. Rev. 2008,
37, 1806–1813; c) V. W. W. Yam, K. K. W. Lo, Chem. Soc. Rev. 1999,
28, 323–334; d) V. W. W. Yam, K. L. Cheung, S. K. Yip, K. K.
Cheung, J. Organomet. Chem. 2003, 681, 196–209; e) S. K. Yip,
W. H. Lam, N. Zhu, V. W. W. Yam, Inorg. Chim. Acta 2006, 359,
3639–3648; f) V. W. W. Yam, S. W. K. Choi, J. Chem. Soc. Dalton
Trans. 1996, 4227–4232; g) V. W. W. Yam, S. W. K. Choi, K. K.
Leung, Organometallics 1996, 15, 1734–1739.
[11] a) V. W. W. Yam, T. F. Lai, C. M. Che, J. Chem. Soc. Dalton Trans.
1990, 3747–3752; b) V. W. W. Yam, W. K. Lee, J. Chem. Soc. Dalton
Trans. 1993, 2097–2100; c) V. W. W. Yam, E. C. C. Cheng, K. K.
Cheung, Angew. Chem. 1999, 111, 193–195; Angew. Chem. Int. Ed.
1999, 38, 197–199; d) V. W. W. Yam, E. C. C. Cheng, Z. Y. Zhou,
Angew. Chem. 2000, 112, 1749–1751; Angew. Chem. Int. Ed. 2000,
39, 1683–1685; e) V. W. W. Yam, E. C. C. Cheng, N. Zhou, Angew.
Chem. 2001, 113, 1813–1815; Angew. Chem. Int. Ed. 2001, 40, 1763–
1765; f) S. Y. Ho, E. C. C. Cheng, E. R. T. Tiekink, V. W. W. Yam,
Inorg. Chem. 2006, 45, 8165–8174.
Acknowledgements
V.W.-W.Y. acknowledges the support from The University of Hong Kong
under the Distinguished Research Achievement Award Scheme and the
URC Strategic Research Theme on Molecular Materials. This work has
been supported by a General Research Fund (GRF) grant from the Re-
search Grants Council of Hong Kong Special Administrative Region, P.
R. China (HKU 7050/08P). X.H. acknowledges the receipt of a postgrad-
uate studentship, administered by The University of Hong Kong. We also
thank the Computer Center at The University of Hong Kong for provid-
ing the computational resources.
[1] a) J. M. Lehn, Angew. Chem. 1988, 100, 91–116; Angew. Chem. Int.
Ed. Engl. 1988, 27, 89–112; b) D. J. Cram, Angew. Chem. 1988, 100,
1041–1052; Angew. Chem. Int. Ed. Engl. 1988, 27, 1009–1020;
c) C. J. Pedersen, J. Am. Chem. Soc. 1967, 89, 7017–7036.
[2] a) A. W. Czarnik in Fluorescent Chemosensors for Ion and Molecule
Recognition, ACS, Washington, 1993; b) J. R. Lakowicz, Principles
of Fluorescence Spectroscopy, 2nd ed., Kluwer Academic/Plenum
Publisher, New York, 1999.
[12] a) S. Y. Yu, Z. X. Zhang, E. C. C. Cheung, Y. Z. Li, V. W. W. Yam,
H. P. Huang, R. Zhang, J. Am. Chem. Soc. 2005, 127, 17994–17995;
b) S. Y. Yu, Q. F. Sun, T. K. M. Lee, E. C. C. Cheung, Y. Z. Li,
8850
www.chemeurj.org
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 8842 – 8851

Calixarene-Based Bis-alkynyl-Bridged Dinuclear AuI Isonitrile Complexes
FULL PAPER
V. W. W. Yam, Angew. Chem. 2008, 120, 4627–4630; Angew. Chem.
Int. Ed. 2008, 47, 4551–4554; c) Q. F. Sun, T. K. M. Lee, P. Z. Li,
L. Y. Yao, J. J. Huang, J. Huang, S. Y. Yu, Y. Z. Li, E. C. C. Cheng,
J. Harrowfield, Calixarenes in the Nanoworld, Springer, Dordrecht,
ˇ
ˇ
´
´
´
2007; e) L. Frkanec, A. Visnjevac, B. Kojic-Prodic, M. Zinic, Chem.
Eur. J. 2000, 6, 442–453.
V. W. W. Yam, Chem. Commun. 2008, 5514–5516.
[20] J. Arias, M. Bardajꢄ, P. Espinet, Inorg. Chem. 2008, 47, 3559–3567.
[21] J. Bourson, J. Pouget, B. Valeur, J. Phys. Chem. 1993, 97, 4552–4557.
[22] a) H. H. Jaffe, M. Orchin, Theory and Application of Ultraviolet
Spectroscopy, Wiley, New York, 1962; b) H. Rohwer, N. Collier, E.
Hoston, Anal. Chim. Acta 1995, 314, 219–223; c) A. Peyman, E.
Uhlmann, K. Wagner, S. Augustin, C. Weiser, D. W. Will, G. Brei-
pohl, Angew. Chem. 1997, 109, 2919–2922; Angew. Chem. Int. Ed.
Engl. 1997, 36, 2809–2812.
[23] K. Choi, A. D. Hamilton, J. Am. Chem. Soc. 2001, 123, 2456–2457.
[24] W. Zhou, J. Xu, H. Zheng, H. Liu, Y. Li, D. Zhu, J. Org. Chem.
2008, 73, 7702–7709.
[25] L. Hildebrandt, R. Dinnerbier, M, Jansen, Z. Anorg. Allg. Chem.
2005, 631, 1660–1666.
[13] a) V. W. W. Yam, C. K. Li, C. L. Chan, Angew. Chem. 1998, 110,
3041–3044; Angew. Chem. Int. Ed. 1998, 37, 2857–2859; b) V. W. W.
Yam, C. L. Chan, C. K. Li, K. M. C. Wong, Coord. Chem. Rev. 2001,
216–217, 173–194; c) C. K. Li, X. X. Lu, K. M. C. Wong, C. L. Chan,
N. Zhu, V. W. W. Yam, Inorg. Chem. 2004, 43, 7421–7430.
[14] a) S. K. Yip, E. C. C. Cheng, L. H. Yuan, N. Zhou, V. W. W. Yam,
Angew. Chem. 2004, 116, 5062–5065; Angew. Chem. Int. Ed. 2004,
43, 4954–4957; b) H. S. Lo, S. K. Yip, N. Zhou, V. W. W. Yam,
Dalton Trans. 2007, 4386–4389.
[15] a) V. W. W. Yam, S. K. Yip, L. H. Yuan, K. L. Cheung, N. Zhou,
K. K. Cheung, Organometallics 2003, 22, 2630–2637; b) V. W. W.
Yam, K. L. Cheung, L. H. Yuan, K. M. C. Wong, K. K. Cheung,
Chem. Commun. 2000, 1513–1514; c) H. S. Lo, S. K. Yip, K. M. C.
Wong, N. Zhou, V. W. W. Yam, Organometallics 2006, 25, 3537–
3540.
[16] a) C. M. Che, H. L. Kwong, V. W. W. Yam, K. C. Cho, J. Chem. Soc.
Chem. Commun. 1989, 885–886; b) D. Li, X. Hong, C. M. Che,
W. C. Lo, S. M. Peng, J. Chem. Soc. Dalton Trans. 1993, 2929–2932;
c) H. Xiao, K. K. Cheung, C. M. Che, J. Chem. Soc. Dalton Trans.
1996, 3699–3703; d) C. M. Che, H. Y. Chao, V. M. Miskowski, Y. Li,
K. K. Cheung, J. Am. Chem. Soc. 2001, 123, 4985–4991.
[26] D. D. Perrin, W. L. F. Armarego, Purification of laboratory Chemi-
cals, 3rd ed., Pergamon: Oxford, 1988.
[27] SHELXL97, Programs for Crystal Structure Analysis, Release 97-2,
G. M. Sheldrick, University of Gçtingen, Gçttingen, 1997 .
[28] S. H. Vosko, L. Wilk, M. Nusair, Can. J. Phys. 1980, 58, 1200–1211.
[29] D. Andrae, U. Hꢅussermann, M. Dolg, H. Stoll, H. Preuss, Theor.
Chim. Acta 1990, 77, 123–141.
[30] A. W. Ehlers, M. Bçhme, S. Dapprich, A. Gobbi, A. Hçllwarth, V.
Jonas, K. F. Kçhler, R. Stegmann, A. Veldkamp, G. Frenking, Chem.
Phys. Lett. 1993, 208, 111–114.
[17] a) R. J. Puddephatt, Coord. Chem. Rev. 2001, 216–217, 313–332;
b) C. P. McArdle, S. Van, M. C. Jennings, R. J. Puddephatt, J. Am.
Chem. Soc. 2002, 124, 3959–3965.
[31] a) R. Ditchfield, W. J. Hehre, J. A. Pople, J. Chem. Phys. 1971, 54,
724–728; b) W. J. Hehre, R. Ditchfield, J. A. Pople, J. Chem. Phys.
1972, 56, 2257–2261; c) P. C. Hariharan, J. A. Pople, Theor. Chim.
Acta 1973, 28, 213–222; d) V. A. Rassolov, J. A. Pople, M. A.
Ratner, T. L. Windus, J. Chem. Phys. 1998, 109, 1223–1229.
[32] Gaussian 03, Revision E.01, M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomer-
y, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyen-
gar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N.
Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,
O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian,
J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E.
Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W.
Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J.
Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C.
Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari,
J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cio-
slowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaro-
mi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng,
A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W.
Chen, M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian, Inc., Wall-
ingford CT, 2004.
[18] a) A. Vogler, H. Kunkely, Chem. Phys. Lett. 1988, 150, 135–137;
b) T. M. McCleskey, H. B. Gray, Inorg. Chem. 1992, 31, 1733–1734;
c) Q. M. Wang, Y. A. Lee, O. Crespo, J. Deaton, C. Tang, H. J. Gys-
ling, M. C. Gimeno, C. Larraz, M. D. Villacampa, A. Laguna, R. Ei-
senberg, J. Am. Chem. Soc. 2004, 126, 9488–9489; d) Y. A. Lee, R.
Eisenberg, J. Am. Chem. Soc. 2003, 125, 7778–7779; e) Y. A. Lee,
J. E. McGarrah, R. J. Lachicotte, R. Eisenberg, J. Am. Chem. Soc.
2002, 124, 10662–10663; f) J. C. Vickery, M. M. Olmstead, E. Y.
Fung, A. L. Balch, Angew. Chem. 1997, 109, 1227–1229; Angew.
Chem. Int. Ed. Engl. 1997, 36, 1179–1182; g) W. B. Jones, J. Yuan,
R. Narayanaswamy, M. A. Young, R. C. Elder, A. E. Bruce,
M. R. M. Bruce, Inorg. Chem. 1995, 34, 1996–2001; h) C. Yang, M.
Messerschmidt, P. Coppens, M. A. Omary, Inorg. Chem. 2006, 45,
6592–6594; i) S. D. Hanna, J. I. Zink, Inorg. Chem. 1996, 35, 297–
302; j) S. D. Hanna, S. I. Khan, J. I. Zink, Inorg. Chem. 1996, 35,
5813–5819; k) W. E. van Zyl, J. M. Lopez-de-Luzuriaga, A. A. Mo-
hamed, R. J. Staples, J. P. Fackler, Jr., Inorg. Chem. 2002, 41, 4579–
4589; l) A. A. Mohamed, I. Kani, A. O. Ramirez, J. P. Fackler, Jr.,
Inorg. Chem. 2004, 43, 3833–3839; m) C. King, J. C. Wang, M. N. I.
Khan, J. P. Fackler, Jr., Inorg. Chem. 1989, 28, 2145–2149.
[19] a) J. S. Kim, D. T. Quang, Chem. Rev. 2007, 107, 3780–3799; b) C. D.
Gutsche, Calixarenes Revisited, RSC, Cambridge, 1998; c) Z. Asfari,
Calixarenes 2001, Kluwer Academic, Dordrecht, 2001; d) J. Vicens,
Received: February 16, 2009
Published online: July 23, 2009
Chem. Eur. J. 2009, 15, 8842 – 8851
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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