Synthesis, structure, and ion-binding properties of luminescent gold(I) alkynylcalix[4]crown-5 complexes

Article abstract of DOI:10.1021/om030021c

A series of luminescent dinuclear gold(I) alkynylcalix[4]crown-5 complexes, [(R_nR′_3-nP)Au]₂L (n = 0-3) (R = Ph, R′ = o-Tol, p-Tol) H₂L = 5,17-diethynyl-25,27-dimethoxycalix[4]arene-crown-5, have been synthesized and structurally characterized. The binding properties of the complexes toward alkali metal ions (K⁺ and Na⁺) have been studied by UV - visible spectrophotometry. The dinuclear gold(I) alkynylcalix[4]crown-5 complexes were shown to exhibit preferential binding toward K⁺ over Na⁺ ions.

Full text of DOI:10.1021/om030021c

2630
Organometallics 2003, 22, 2630-2637
Syn th esis, Str u ctu r e, a n d Ion -Bin d in g P r op er ties of
Lu m in escen t Gold (I) Alk yn ylca lix[4]cr ow n -5 Com p lexes
Vivian Wing-Wah Yam,* Sung-Kong Yip, Li-Hua Yuan, Kai-Leung Cheung,
Nianyong Zhu, and Kung-Kai Cheung
Open Laboratory of Chemical Biology of the Institute of Molecular Technology for Drug
Discovery and Synthesis,† Department of Chemistry, and Centre for Carbon-Rich Molecular
and Nano-Scale Metal-Based Materials Research, The University of Hong Kong,
Pokfulam Road, Hong Kong SAR, People’s Republic of China
Received J anuary 13, 2003
A series of luminescent dinuclear gold(I) alkynylcalix[4]crown-5 complexes, [(RnR′3-nP)Au]2L
(n ) 0-3) (R ) Ph, R′ ) o-Tol, p-Tol) (H2L ) 5,17-diethynyl-25,27-dimethoxycalix[4]arene-
crown-5, have been synthesized and structurally characterized. The binding properties of
the complexes toward alkali metal ions (K+ and Na+) have been studied by UV-visible
spectrophotometry. The dinuclear gold(I) alkynylcalix[4]crown-5 complexes were shown to
exhibit preferential binding toward K+ over Na+ ions.
In tr od u ction
organic system as luminophore,7 with metal-based lu-
minophores being relatively less extensively explored.8
Recently, we reported the synthesis of a dinuclear gold-
(I) alkynyl complex of calixcrown and have demon-
strated its selective ion-binding properties toward alkali
metal ions.9 As an extension of this work, a series of
related complexes with various phosphine ligands have
been designed and synthesized. It is hoped that through
a systematic variation of the electronic and steric effects
of the aryl group on the phosphine ligands, the ion-
binding properties of the complexes can be tuned.
Herein are reported the synthesis, electronic absorption,
luminescence, and ion-binding properties of a series of
dinuclear gold(I) alkynylcalix[4]crown-5 complexes. The
X-ray crystal structures of all the complexes have been
determined by X-ray crystallography.
Ion recognition plays important roles in biology and
chemistry, as well as in biomedical and environmental
science. In biological systems, metal ions such as
sodium, potassium, calcium, and magnesium ions are
involved in nerve impulse transmission, muscle contrac-
tion, and cell activity regulation. Lithium ion has also
been used for patients under depression treatment.
With regard to environmental and ecological issues,
heavy metal ions such as lead, cadmium, and radio-
active metal ions have attracted enormous attention and
worldwide concern. Thus, the ability to detect or rec-
ognize specific metal ions can be invaluable.
During the past decade, there has been a growing
interest in the development of calixarenes as ion recep-
tors.1 Calixarenes have proved themselves as important
building blocks in supramolecular chemistry owing to
their unique molecular structures, simple one-pot prepa-
rations, possible modifications of the lower and upper
rims, and their “tunable” molecular shapes and conforma-
tions.2-4 Another related class of compounds that has
also received considerable attention as ion receptor
molecules in recent years is the calixcrown,5 in which
the lower rim of the calixarene is linked by bridging
polyethyleneoxy moieties. High affinities for complex-
ation of alkali and alkaline-earth metal ions have been
reported for calixcrowns.6 The majority of the work in
this area has mainly been focused on the use of an
Exp er im en ta l Section
Ma ter ia ls a n d Rea gen ts. Potassium fluoride and tetra-
ethylene glycol-di-p-toluenesulfonate were purchased from
Aldrich Chemical Co. (Trimethylsilyl)acetylene, copper(I) io-
dide, and triethylamine were purchased from Lancaster
Synthesis Ltd. Cesium carbonate was purchased from Strem
Chemical Inc. Dichlorobis(triphenylphosphine)palladium(II)10
and 5,17-diiodo-25,27-dimethoxycalix[4]arene11 were prepared
according to the literature procedures. All the [(RnR′3-nP)AuCl]
precursor complexes were synthesized by modification of the
literature methods.12 Tetra-n-butylammonium hexafluorophos-
* Corresponding author. Tel: (852) 2859-2153. Fax: (852) 2857-
1586. E-mail: wwyam@hku.hk.
(6) Alfieri, C.; Dradi, E.; Pochini, A.; Ungaro, R.; Andreetti, G. D. J .
Chem. Soc., Chem. Commum. 1983, 1075.
(7) (a) Shinkai, S.; Matsumoto, H. Chem. Lett. 1994, 2431. (b) Kubo,
Y.; Maeda, S.; Tokita, S.; Kubo, M. Nature 1996, 382, 522. (c) J i, H.
F.; Dabestani, R.; Brown, G. M.; Sachleben, R. A. Chem. Commun.
2000, 833.
(8) Xu, W.; Rourke, J . P.; Vittal, J . J .; Puddephatt, R. J . J . Chem.
Soc., Chem. Commun. 1993, 2, 145.
(9) Yam, V. W. W.; Cheung, K. L.; Yuan, L. H.; Wong, K. M. C.;
Cheung, K. K. Chem. Commum. 2000, 16, 1513.
(10) Chatt, J .; Mann, F. G. J . Chem. Soc. 1939, 1622.
(11) Klenke, B.; Friedrichsen, W. J . Chem. Soc., Perkin Trans. 1
1998, 20, 3377.
† Area of Excellence Scheme, University Grants Committee (Hong
Kong).
(1) Valeur, B.; Leray, I. Coord. Chem. Rev. 2000, 205, 3.
(2) (a) Gutsche, C. D. Calixarenes: Monographs in Supramolcular
Chemistry; The Royal Society of Chemistry: Cambridge, 1989. (b)
Gutsche, C. D. Calixarenes Revisited; The Royal Society of Chemistry:
Cambridge, 1998. (c) Asfari, Z. Calixarenes 2001; Kluwer Academic
Publishers: Dordrecht, 2001.
(3) Gutsche, C. D.; Iqbal, M. Org. Synth., Coll. Vol. 1993, 8, 75.
(4) (a) Shinkai, S. Tetrahedron 1993, 49, 8933. (b) Bo¨hmer, V.
Angew. Chem., Int. Ed. Engl. 1995, 34, 713.
(5) Stephane, P. R.; Frederic, C.; Laurence, N.; Marc, L. J . Chem.
Soc., Perkin Trans. 2001, 2, 1426.
(12) Bruce, M. I.; Nicholson, B. K.; Shawkataly, O. B. Inorg. Synth.
1989, 26, 324.
10.1021/om030021c CCC: $25.00 © 2003 American Chemical Society
Publication on Web 05/22/2003

Gold(I) Alkynyl-Calix[4]crown-5 Complexes
Organometallics, Vol. 22, No. 13, 2003 2631
phate was recrystallized twice from hot absolute ethanol and
then dried under vacuum for 12 h before use. Dichloromethane
(Lab Scan, AR) was purified and distilled using standard
procedures before use. 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.
Positive FAB-MS: m/z 658 [M]+, 681 [M + Na]+. Anal.
Found: C 72.86, H 6.24. Calcd for C42H42O7‚1/2CH2Cl2:
C
72.79, H 6.18.
[(P P h 3)Au ]2L (1). To a stirred solution of H2L (30 mg, 0.046
mmol) in tetrahydrofuran (15 mL) was added an excess of
sodium ethoxide (freshly prepared from sodium (10 mg, 0.43
mmol) in ethanol (15 mL)) and chloro(triphenylphosphine)-
gold(I) (47 mg, 0.095 mmol). The reaction mixture was then
stirred under an inert atmosphere of nitrogen for 4 h. The
solution was extracted with dichloromethane and washed with
water. Subsequent recrystallization by layering n-hexane into
the concentrated dichloromethane solution of the product gave
1 as pale yellow crystals. Yield: 54 mg, 75%. 1H NMR (300
MHz, CDCl3, 298 K, relative to Me4Si): δ 3.12 (d, 4H, J )
12.6 Hz, Ar-CH2-Ar), 3.65-4.00 (m, 16H, OCH2CH2O), 4.05
(s, 6H, OCH3), 4.32 (d, 4H, J ) 12.6 Hz, Ar-CH2-Ar), 6.55-
7.10 (m, 10H, Ar), 7.25-7.58 (m, 30H, PPh3). 31P NMR (202
MHz, CDCl3, 298 K, relative to 85% H3PO4): δ 43.5 (s, PPh3).
IR (KBr disk, ν/cm-1): 2918 (s), 2866 (s), ν(C-Haliphatic); 2099
(w), ν(CtC). Positive FAB-MS: m/z 1597 [M + Na]+. Anal.
Found: C 59.54, H 4.72. Calcd for C78H70O7Au2P2: C 59.47, H
4.48.
[{P P h 2(p-Tol)}Au ]2L (2). This complex was prepared
similarly to 1 except chloro(diphenyl-p-tolylphosphine)gold(I)
(46 mg, 0.088 mmol) was used instead of chloro(triphenylphos-
phine)gold(I). The product was recrystallized from dichlo-
romethane/n-hexane to give 2 as pale yellow crystals. Yield:
52 mg, 71%. 1H NMR (300 MHz, CDCl3, 298 K, relative to Me4-
Si): δ 2.34 (s, 6H, PC6H4CH3), 3.14 (d, 4H, J ) 12.2 Hz, Ar-
CH2-Ar), 3.67-4.01 (m, 16H, OCH2CH2O), 4.04 (s, 6H, OCH3),
4.33 (d, 4H, J ) 12.2 Hz, Ar-CH2-Ar), 6.42-7.06 (m, 10H,
Ar), 7.21-7.52 (m, 28H, PPh2Tol). 31P NMR (202 MHz, CDCl3,
298 K, relative to 85% H3PO4): δ 42.16 (s, PPh2Tol). IR (KBr
disk, ν/cm-1): 2855 (s), 2920 (s), ν(C-Haliphatic); 2087 (w), ν(Ct
C). Positive FAB-MS: m/z 1626 [M + Na]+, 1642 [M + K]+.
Anal. Found: C 59.18, H 4.80. Calcd for C80H74O7Au2P2‚
1/2CH2Cl2‚1/2C6H14: C 59.38, H 4.89.
[{P P h (p-Tol)2}Au ]2L (3). This complex was prepared
similarly to 1 except chloro(phenyldi-p-tolylphosphine)gold(I)
(48 mg, 0.092 mmol) was used instead of chloro(triphenylphos-
phine)gold(I). The product was recrystallized from dichlo-
romethane/n-hexane to give 3 as pale yellow crystals. Yield:
56 mg, 74%. 1H NMR (300 MHz, CDCl3, 298 K, relative to Me4-
Si): δ 2.32 (s, 12H, PC6H4CH3), 3.12 (d, 4H, J ) 12.5 Hz, Ar-
CH2-Ar), 3.66-4.00 (m, 16H, OCH2CH2O), 4.05 (s, 6H, OCH3),
4.31 (d, 4H, J ) 12.5 Hz, Ar-CH2-Ar), 6.56 - 7.06 (m, 10H,
Ar), 7.16-7.49 (m, 26H, PPhTol2). 31P NMR (202 MHz, CDCl3,
298 K, relative to 85% H3PO4): δ 41.16 (s, PPhTol2). IR (KBr
disk, ν/cm-1): 2864 (s), 2920 (s), ν(C-Haliphatic); 2103 (w), ν(Ct
C). Positive FAB-MS: m/z 1654 [M + Na]+, 1670 [M + K]+.
Anal. Found: C 59.65, H 4.80. Calcd for C82H78O7Au2P2‚
1/2CH2Cl2‚1/2C6H14: C 59.81, H 5.05.
5,17-Bis(tr im eth ylsilyleth yn yl)-25,27-d im eth oxyca lix-
[4]a r en e (Ca lix-TMS). Into a 250 mL two-necked round-
bottomed flask was added 5,17-diiodo-25,27-dimethoxycalix-
[4]arene (1.00 g, 1.42 mmol), followed by a mixture of
tetrahydrofuran (130 mL) and triethylamine (20 mL). After
stirring for 5 min, trimethylsilylacetylene (0.56 g, 5.68 mmol),
copper(I) iodide (22 mg, 0.11 mmol), and dichlorobis(tri-
phenylphosphine)palladium(II) (80 mg, 0.11 mmol) were added
to the flask under a nitrogen atmosphere. The mixture was
stirred for 24 h at 42 °C. The mixture was filtered, and the
filtrate was evaporated to dryness. The brown residue was
purified by column chromatography on silica gel using petro-
leum ether/dichloromethane (1:1 v/v) as eluent to afford the
1
product as a yellow solid. Yield: 0.486 g, 53%. H NMR (300
MHz, CDCl3, 298 K, relative to Me4Si): δ 0.15 (s, 18H, Si-
(CH3)3), 3.31 (d, 4H, J ) 13.2 Hz, Ar-CH2-Ar), 3.88 (s, 6H,
OCH3), 4.15 (d, 4H, J ) 13.2 Hz, Ar-CH2-Ar), 6.72-7.14 (m,
10H, Ar), 8.03 (s, 2H, OH). 13C NMR (125 MHz, CDCl3, 298 K,
relative to Me4Si): δ 30.8, 63.7, 91.7, 105.9, 113.3, 125.3, 128.0,
129.3, 132.0, 132.5, 153.0, 154.0. IR (KBr disk, ν/cm-1): 2905
(s), 2957 (s), ν(C-Haliphatic); 2150 (m), ν(CtC). Positive FAB-
MS: m/z 645 [M]+. Anal. Found: C 73.73, H 7.16. Calcd for
C
40H44O4Si2‚1/2H2O: C 73.47, H 6.94.
5,17-Bis(tr im eth ylsilyleth yn yl)-25,27-d im eth oxyca lix-
[4]cr ow n -5 (Ca lixCr -TMS). An excess of cesium carbonate
(0.40 g, 1.24 mmol) and tetraethylene glycol-di-p-toluene-
sulfonate (0.17 g, 0.34 mmol) were added to Calix-TMS (0.20
g, 0.31 mmol) in 80 mL of acetonitrile under nitrogen atmo-
sphere. The reaction mixture was refluxed for 24 h. The solvent
was then removed under reduced pressure, and the residue
was extracted with dichloromethane and washed with water.
Evaporation of the dichloromethane extract yielded a yellow
residue, which was triturated in diethyl ether to afford the
1
product as a white solid. Yield: 0.212 g, 87%. H NMR (300
MHz, CDCl3, 298 K, relative to Me4Si): δ 0.14 (s, 18H, Si-
(CH3)3), 3.16 (d, 4H, J ) 12.4 Hz, Ar-CH2-Ar), 3.55-3.90 (m,
16H, OCH2CH2O), 4.10 (s, 6H, OCH3), 4.37 (d, 4H, J ) 12.4
Hz, Ar-CH2-Ar), 6.79 (s, 4H, aryl protons ortho to CtC), 6.89
(t, 2H, J ) 7.3 Hz, aryl protons para to OCH3), 7.09 (d, 4H, J
) 7.3 Hz, aryl protons meta to OCH3). 13C NMR (125 MHz,
CDCl3, 298 K, relative to Me4Si): δ 31.1, 61.1, 65.8, 70.7, 70.8,
71.4, 123.0, 124.5, 128.7, 132.1, 133.5, 135.6, 156.4, 158.9. IR
(KBr disk, ν/cm-1): 2922 (s), 2903 (s), 2872 (s), ν(C-Haliphatic);
2154 (m), ν(CtC). Positive FAB-MS: m/z 803 [M]+, 826
[M + Na]+. Anal. Found: C 71.63, H 7.05. Calcd for C48H58O7-
Si2: C 71.78, H 7.28.
[{P (p-Tol)3}Au ]2L (4). This complex was prepared similarly
to 1 except chloro(tri-p-tolylphosphine)gold(I) (49 mg, 0.091
mmol) was used instead of chloro(triphenylphosphine)-
gold(I). The product was recrystallized from acetone/n-hexane
5,17-Diet h yn yl-25,27-d im et h oxyca lix[4]a r en e-cr ow n -
5 (H2L). Potassium fluoride (0.12 g, 2.05 mmol) was added to
CalixCr-TMS (0.10 g, 0.13 mmol) in dimethylformamide. The
mixture was stirred under nitrogen in an oil bath at 65 °C for
3 h. The reaction was quenched with dilute hydrochloric acid,
and the product was extracted with chloroform and washed
with water. After removing the solvent, the residue was
triturated in diethyl ether to afford a pale brown solid. Yield:
64 mg, 75%. 1H NMR (300 MHz, CDCl3, 298 K, relative to Me4-
Si): δ 2.77 (s, 2H, CtCH), 3.16 (d, 4H, J ) 12.6 Hz, Ar-CH2-
Ar), 3.56-3.93 (m, 16H, OCH2CH2O), 4.10 (s, 6H, OCH3), 4.38
(d, 4H, J ) 12.6 Hz, Ar-CH2-Ar), 6.76 (s, 4H, aryl protons
ortho to CtC), 6.88 (t, 2H, J ) 7.3 Hz, aryl protons para to
OCH3), 7.08 (d, 4H, J ) 7.3 Hz, aryl protons meta to OCH3).
13C NMR (125 MHz, CDCl3, 298 K, relative to Me4Si): δ 31.1,
61.2, 70.8, 70.9, 71.5, 73.4, 75.4, 84.3, 115.9, 123.1, 128.7, 132.1,
133.8, 156.4, 158.9. IR (KBr disk, ν/cm-1): 3292 (s), ν(C-
1
to give 4 as pale yellow crystals. Yield: 48 mg, 67%. H NMR
(300 MHz, CDCl3, 298 K, relative to Me4Si): δ 2.31 (s, 18H,
PC6H4CH3), 3.12 (d, 4H, J ) 12.9 Hz, Ar-CH2-Ar), 3.67-4.01
(m, 16H, OCH2CH2O), 4.08 (s, 6H, OCH3), 4.31 (d, 4H, J )
12.9 Hz, Ar-CH2-Ar), 6.49-7.09 (m, 10H, Ar), 7.15-7.44 (m,
24H, PTol3). 31P NMR (202 MHz, CDCl3, 298 K, relative to
85% H3PO4): δ 40.79 (s, PTol3). IR (KBr disk, ν/cm-1): 2834
(s), 2915 (s), ν(C-Haliphatic); 2021 (w), ν(CtC). Positive
FAB-MS: m/z 1660 [M + H]+, 1682 [M + Na]+. Anal. Found:
C, 59.69, H, 5.03. Calcd for C84H82O7Au2P2‚CH3COCH3‚2H2O:
C, 59.59, H, 5.29.
[{P (o-Tol)3}Au ]2L (5). This complex was prepared similarly
to 1 except chloro(tri-o-tolylphosphine)gold(I) (49 mg, 0.091
mmol) was used instead of chloro(triphenylphosphine)gold(I).
The product was recrystallized from dichloromethane/n-hexane
H
alkynyl); 2909 (s), 2868 (s), ν(C-Haliphatic); 2107 (w), ν(CtC).

2632 Organometallics, Vol. 22, No. 13, 2003
Yam et al.
1
to give 5 as pale yellow crystals. Yield: 50 mg, 70%. H NMR
(300 MHz, CDCl3, 298 K, relative to Me4Si): δ 2.66 (s, 18H,
PC6H4CH3), 3.09 (d, 4H, J ) 11.8 Hz, Ar-CH2-Ar), 3.63-3.93
(m, 16H, OCH2CH2O), 3.99 (s, 6H, OCH3), 4.29 (d, 4H, J )
11.8 Hz, Ar-CH2-Ar), 6.56 - 7.39 (m, 34H, Ar, PTol3). 31P
NMR (202 MHz, CDCl3, 298 K, relative to 85% H3PO4): δ 24.63
(s, PTol3). IR (KBr disk, ν/cm-1): 2840 (s), 2913 (s), ν(C-
where Ks can be written as
[Au2L(M)]
[Au2L][M]
KS )
were obtained by a nonlinear least-squares fit of the absor-
bance (X) versus the concentration of the metal ion added (Cm)
according to eq 2:14
H
aliphatic); 2018 (w), ν(CtC). Positive FAB-MS: m/z 1660 [M +
H]+, 1682 [M + Na]+, 1698 [M + K]+. Anal. Found: C 57.71,
H 4.94. Calcd for C84H82O7Au2P2‚CH2Cl2‚H2O: C 57.93, H 4.92.
P h ysica l Mea su r em en ts a n d In str u m en ta tion . UV/VIS
spectra were obtained on a Hewlett-Packard 8452A diode array
spectrophotometer, IR spectra as KBr disks on a Bio-Rad
FTS-7 Fourier transform infrared spectrophotometer (4000-
400 cm-1), and steady-state excitation and emission spectra
on a Spex Fluorolog 111 fluorescence spectrophotometer. Solid-
state photophysical studies were carried out with solid sample
contained in a quartz tube inside a quartz-walled Dewar flask.
Solid-state samples at 77 K were conducted with liquid
nitrogen in the optical Dewar flask. Excited-state lifetimes of
solution samples were measured using a conventional laser
system. The excitation source was the 355 nm output (third
harmonic, 8 ns) of a Spectra-Physics Quanta-Ray Q-switched
GCR-150 pulsed Nd:YAG laser (10 Hz). Luminescence quan-
tum yield was measured by the optical dilute method reported
by Demas and Crosby.13 The luminescence quantum yield of
the sample was determined according to eq 1:
Xlim - X
X ) Xo +
o[Co + Cm + 1/Ks -
2Co
[(Co + Cm + 1/Ks)2 - 4CoCm]1/2] (2)
where Co is the initial concentration of the gold(I) complexes,
and Xo, X, and Xlim are the initial absorbance of the gold(I)
complexes, the absorbance after the addition of a given amount
of salt at concentration Cm, and the limiting absorbance of the
gold(I) complexes in the fully complexed state, respectively,
at a selected wavelength.
Cr ysta l Str u ctu r e Deter m in a tion . Single crystals of 1
were obtained by layering n-hexane into a dichloromethane
solution of the complex, the crystal structure of which has been
communicated previously.9
Single crystals of 2, 3, and 5 were obtained by layering
n-hexane into a dichloromethane solution of the respective
complex. Single crystals of 4 were obtained by layering
n-hexane into an acetone solution of the complex. All the
experimental details are given in Table 1. The crystals of 2-5
of dimensions 0.3 × 0.3 × 0.1 mm, 0.60 × 0.20 × 0.05 mm, 0.4
× 0.25 × 0.2 mm, and 0.3 × 0.25 × 0.15 mm, respectively,
mounted in a glass capillary were used for data collection at
28 °C on a MAR diffractometer. The images were interpreted
and intensities integrated using the program DENZO.15 The
structures were solved by direct methods employing the
SHELXS-97 program16 on a PC. The positions of H atoms of
all complexes 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.17
For complex 2, one crystallographic asymmetric unit con-
sisted of one formula unit, inclusive of one CH2Cl2 and one
n-hexane solvent molecules. In the final stage of least-squares
refinement, most non-hydrogen atoms were refined anisotro-
pically, except the C atoms of n-hexane, which were refined
isotropically. H atoms (except those on n-hexane) were gener-
ated by the program SHELXL-97.18 One phosphine ligand was
found to be the normal PPh2Tol, but the other one had the
methyl group disordered on two phenyl rings. One hexagon-
ring of C(26) to C(31) is restrained to be a normal hexagonal
ring (C-C distance 1.39 Å and C-C-C angle 120°). The
n-hexane molecule was disordered and was set at two posi-
tions. For convergence of least-squares refinements, the C-C
bond lengths of the hexane chain were restrained to be similar.
φs ) φr(Br/Bs)(ns/nr)2(Ds/Dr)
(1)
where the subscripts s and r refer to the sample and reference
solutions, respectively, B ) 1 - 10-AL. A is the absorbance at
the excitation wavelength, L is the path length, n is the
refractive index of the solvent, and D is the integrated emission
intensity. A degassed aqueous solution of quinine sulfate in
1.0 N H2SO4 solution (φem ) 0.546, excitation wavelength at
365 nm) was used as the reference.13
All solutions for photophysical studies were degassed on a
high-vacuum line in a two-compartment cell consisting of a
10 mL Pyrex bulb and a 1 cm path length quartz cuvette and
sealed from the atmosphere by a Bibby Rotaflo HP6 Teflon
stopper. The solutions were subject to not less than four
freeze-pump-thaw cycles.
1H NMR spectra were recorded on a Bruker DPX-300 FT-
NMR spectrometer (300 MHz) in CDCl3 at 298 K, and chemical
shifts are reported relative to Me4Si. 31P and 13C NMR spectra
were recorded on a Bruker DRX-500 FT-NMR spectrometer
(202 MHz for 31P and 125 MHz for 13C) in CDCl3 at 298 K,
and chemical shifts are reported relative to 85% H3PO4 and
Me4Si, respectively. Positive FAB mass spectra were recorded
on a Finnigan MAT95 mass spectrometer. Elemental analyses
of the new complexes were performed on a Carlo Erba 1106
elemental analyzer at the Institute of Chemistry, Chinese
Academy of Sciences.
(14) Bourson, J .; Pouget, J .; Valeur, B. J . Phys. Chem. 1993, 97,
4552.
The electronic absorption spectral titration for binding
constant determination was performed with a Hewlett-Pack-
ard 8452A diode array spectrophotometer at 25 °C, which was
controlled by a Lauda RM6 compact low-temperature ther-
mostat. Supporting electrolyte (0.1 mol dm-3 nBu4NPF6) was
added to maintain a constant ionic strength of the sample
solution in order to avoid any changes arising from a change
in the ionic strength of the medium. The binding constants,
Ks, for the 1:1 complexation that control the equilibrium
between an alkali cation M, the dinuclear gold(I) alkynylcalix-
[4]crown complex Au2L, and their adduct Au2L(M),
(15) Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data
Collected in Oscillation Mode. Methods in Enzymology, Volume 276:
Macromolecular Crystallography; Carter C. W., Sweet, R. M., J r., Eds.;
Academic Press: New York, 1997; Part A, pp 307-326.
(16) Sheldrick, G. M. SHELX97, Programs for Crystal Structure
Analysis (Release 97-2); University of Goetingen: Germany, 1997.
(17) Since the structure refinements are against F2, R-indices based
on F2 are larger than (more than double) those based on F. For
comparison with older refinements based on F and an OMIT threshold,
a conventional index R1 based on observed F values larger than 4σ(Fo)
2
is also given (corresponding to intensityg 2σ(I)). wR2 ) {∑[w(Fo
-
Fc2)2]/∑[w(Fo2)2]}1/2, R1 ) ∑||Fo| - |Fc||/∑|Fo|, the goodness of fit is always
based on F2: GooF ) S ) {∑[w(Fo - Fc2)2]/(n - p)}1/2, where n is the
2
number of reflections and p is the total number of parameters refined.
KS
The weighting scheme is w ) 1/[σ2(Fo2) + (aP)2 + bP], where P is [2Fc
+
2
M + Au2L y\z Au2L(M)
Max(Fo2,0)]/3.
(18) Sheldrick, G. M. SHELX97, Programs for Crystal Structure
Analysis (Release 97-2); University of Goetingen: Germany, 1997.
(13) Demas, J . N.; Crosby, G. A. J . Phys. Chem. 1971, 75, 991.

Gold(I) Alkynyl-Calix[4]crown-5 Complexes
Organometallics, Vol. 22, No. 13, 2003 2633
Ta ble 1. Cr ysta l a n d Str u ctu r e Deter m in a tion Da ta for 1-5
1
2
3
4
5
empirical formula
fw
[C78H72Au2O8P2]
1593.30
[C87H89Au2Cl2O7P2]
1773.36
[C89H93Au2Cl2O7P2]
1801.41
[C87H88Au2O8P2]
1717.45
[C88H86Au2Cl8O7 P2]
1995.04
cryst size (mm)
cryst syst
space group
a (Å)
b (Å)
c (Å)
0.25 × 0.2 × 0.1
0.3 × 0.3 × 0.1
monoclinic
P21/c
22.277(4)
13.109(2)
27.775(5)
90
98.41(4)
90
8024(2)
4
0.6 × 0.2 × 0.05
monoclinic
P21/c
22.033(4)
13.257(3)
28.870(5)
90
98.33(2)
90
8344(3)
4
0.4 × 0.25 × 0.2
0.3 × 0.25 × 0.15
monoclinic
C2/c
42.499(9)
21.013(4)
20.487(4)
90
109.44(3)
90
17253(6)
triclinic
triclinic
P1h
P1h
13.108(2)
15.195(2)
21.461(3)
83.57(2)
14.828(3)
16.138(3)
16.669(3)
88.42(3)
R (deg)
â (deg)
76.71(2)
65.43(2)
3782(1)
2
86.27(3)
82.76(3)
3947.9(13)
2
γ (deg)
V (Å3)
Z
8
F(000)
1584
3.980
1.399
301
3556
3.812
1.468
301
3620
3.667
1.434
301
1724
3.806
1.445
301
7952
3.735
1.536
301
µ (mm-1
)
density calcd (g cm-1
temperature (K)
wavelength (Å)
)
0.71073
0.71073
0.71073
0.71073
0.71069
collection range
2θmax ) 51°
h: 0 to 15
k: -16 to 18
l: -25 to 25
55 002
2θmax ) 50.94°
h: -21 to 26
k: -15 to 14
l: -28 to 29
23 241
2θmax ) 51.02°
h: -26 to 26
k: -14 to 14
l: -32 to 33
38 787
2θmax ) 51.04°
h: -16 to 16,
k: -19 to 19
l: -20 to 20
28 728
2θmax ) 50.98°
h: -51 to 51,
k: -23 to 24
l: -24 to 24
50 528
no. of reflns collected
no. of indep reflns
12 114 [R(int) )
0.045]
10 048 [R(int) )
0.0558]
11 945 [R(int) )
0.0555]
13 190 [R(int) )
0.0290]
13 760 [R(int) )
0.0528]
refinement method
full-matrix least-
squares on F2
12 114/806
2.16
full-matrix least-
squares on F2
10 048/879
0.954
full-matrix least-
s quares on F2
11 945/821
0.962
full-matrix least-
squares on F2
13 190/892
1.031
full-matrix least-
squares on F2
13 760/990
0.920
data/params
goodness-of-fit on F2
final R indices
R1 ) 0.055,a
wR2 ) 0.081a
1.15, -1.79
R1 ) 0.0513,b
wR2 ) 0.1312b
0.925, -0.976
R1 ) 0.0524,b
wR2 ) 0.1505b
1.444, -1.182
R1 ) 0.0329,b
wR2 ) 0.0874b
0.717, -1.272
R1 ) 0.0381,b
wR2 ) 0.0983b
0.835, -0.737
largest diff. peak and
hole (e Å-3
)
a
b
[I > 3σ(I)]. [I > 2σ(I)].
For complex 3, one crystallographic asymmetric unit con-
sisted of one formula unit, one CH2Cl2 and one n-hexane
solvent molecule. In the final stage of least-squares refinement,
most non-hydrogen atoms were refined anisotropically, except
one disordered methyl C atom attached to the phenyl ring of
PR3 and the C atoms of n-hexane, which were refined isotro-
pically. H atoms (except those on n-hexane) were generated
by the program SHELXL-97.18 The phenyl rings on PR3 groups
were restrained to normal phenyl rings. One phosphine ligand
was found to be the normal PTol2Ph, but the other one has
the two methyl groups disordered on three phenyl rings. The
n-hexane molecule was located with restraints of the C-C
bond lengths to 1.55 Å.
Resu lts a n d Discu ssion
Syn th esis. The synthetic route for the gold(I) alkynyl-
calix[4]crown-5 complexes is summarized in Scheme 1.
Reaction of 5,17-diiodo-25,27-dimethoxycalix[4]arene7
with (trimethylsilyl)acetylene in the presence of copper-
(I) iodide, dichlorobis(triphenylphosphine)palladium(II),
and triethylamine for 24 h at ca. 42 °C gave Calix-TMS.
Subsequent reaction with tetraethylene glycol di-p-
toluenesulfonate in the presence of cesium carbonate
in acetonitrile introduces the polyether linkage at the
lower rim followed by deprotection of the trimethylsilyl
groups with potassium fluoride gave H2L in moderate
yield. Reaction of (RnR′3-nP)AuCl (n ) 0-3) (R ) Ph,
R′ ) o-Tol, p-Tol) with H2L in the presence of sodium
ethoxide in ethanol afforded the desired complexes,
[(RnR′3-nP)Au]2L, as pale yellow crystals after subse-
quent recrystallization using dichloromethane/n-hexane
or acetone/n-hexane. The identities of complexes 1-5
have been confirmed by satisfactory elemental analyses,
1H NMR, 31P NMR, IR, and FAB-mass spectrometry.
The structures of 1-5 have also been determined by
X-ray crystallography.
Cr ysta l Str u ctu r e Deter m in a tion . The perspective
drawings of selected complexes 3 and 4 are shown in
Figures 1 and 2, respectively. Selected bond distances
and angles of complexes 1-5 are tabulated in Table 2.
The coordination geometry of the two gold atoms are
essentially linear, with P-Au-C bond angles showing
a slight deviation from the ideal 180°, probably as a
result of the steric demand of the ligands and crystal
packing forces (1, 170.5(4)° and 177.9(4)°; 2, 176.0(4)°
and 176.6(3)°; 3, 174.7(3)° and 176.6(3)°; 4, 173.09(16)°
For complex 4, the acentric space group P1 was chosen
temporarily. Four Au atoms were located according to the
direct methods. The space group was then transformed to
centric P1h and the coordinates were also transformed, so that
the two Au atoms were located with the centric space group.
The positions of the other non-hydrogen atoms were found
after successful refinement by full-matrix least-squares using
the program SHELXL-9718 on a PC. One acetone solvent
molecule was also positioned. One crystallographic asymmetric
unit consisted of one formula unit, inclusive of one acetone
solvent molecule. In the final stage of least-squares refinement,
all non-hydrogen atoms were refined anisotropically. H atoms
were generated by the program SHELXL-97.18
For complex 5, one crystallographic asymmetric unit con-
sisted of one formula unit. In the final stage of least-squares
refinement, all non-H atoms were refined anisotropically. H
atoms were generated by the program SHELXL-97.18 Four
dichloromethane solvent molecules were also located, in which
two of them were disordered. Disordered dichloromethane
molecules were restrained to have similar C-Cl and Cl-Cl
distances, respectively.

2634 Organometallics, Vol. 22, No. 13, 2003
Sch em e 1. Syn th etic Rou te of Com p lexes 1-5a
Yam et al.
a
Reagents and conditions: (i) HCtCSiMe3, Et3N, Pd(PPh3)2Cl2, CuI; (ii) tetraethylene glycol di-p-toluenesulfonate, Cs2CO3,
CH3CN; (iii) KF, DMF, 65°C; (iv) NaOEt, (RnR′3-nP)AuCl (n ) 0-3), EtOH/THF. (R ) Ph, R′ ) o-Tol, p-Tol).
and 176.12(18)°; 5, 175.8(2)° and 177.1(3)°). The CtC
bond lengths of all the complexes are typical of terminal
gold(I) acetylides19 (1, 1.180(2) and 1.170(2) Å; 2, 1.177-
(15) and 1.190(17) Å; 3, 1.194(12) and 1.199(12) Å; 4,
1.187(7) and 1.173(7) Å; 5, 1.186(8) and 1.184(9) Å). The
Au‚‚‚Au separations of complexes 1-5 are too long for
any Au‚‚‚Au interaction to occur (1, 8.567 Å; 2, 6.696
Å; 3, 6.729 Å; 4, 8.764 Å; 5, 8.870 Å). It is interesting to
find that the Au‚‚‚Au distances found in these complexes
in the solid state do not follow a trend that is governed
by the steric demands of the phosphine ligands alone,
in which a Au‚‚‚Au separation of 1 ≈ 5 < 2 < 3 < 4 is
expected. Complex 4 with three p-tolyl groups attached
to each of the phosphorus atoms would be expected to
cause the two Au atoms to move further apart in order
to avoid the steric hindrance imposed by the neighboring
(RnR′3-nP)Au moieties, while complexes 1 and 5 with
no substituents on the phenyl ring and the o-tolyl groups
on the phosphorus, respectively, would be expected to
experience the least steric hindrance between the two
(RnR′3-nP)Au moieties since the methyl substituents on
the o-tolyl group of RnR′3-nP in 5 could fold back and
direct away from the adjacent (RnR′3-nP)Au unit. How-
ever, in the solid state, different crystal packing forces
come into play, giving rise to an unexpected trend. For
example, the presence of C-H‚‚‚π(CtC) contacts in the
crystal packing of 1, in which the aromatic protons on
(19) (a) Cross, R. J .; Davidson, M. F. J . Chem. Soc., Dalton Trans.
1986, 411. (b) Yam, V. W. W.; Choi, S. W. K.; Cheung, K. K. J . Chem.
Soc., Dalton Trans. 1996, 3411. (c) Yam, V. W. W.; Choi, S. W. K. J .
Chem. Soc., Dalton Trans. 1996, 4227.

Gold(I) Alkynyl-Calix[4]crown-5 Complexes
Organometallics, Vol. 22, No. 13, 2003 2635
Ta ble 2. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for 1-5 w ith Estim a ted Sta n d a r d
Devia tion s in P a r en th eses
[(Ph3P)Au]2L (1)
Bond Distances (Å)
Au(1)-P(1)
Au(2)-P(2)
Au(1)-C(1)
2.283(3)
2.275(3)
2.04(1)
Au(2)-C(9)
C(1)-C(2)
C(9)-C(10)
2.04(1)
1.18(2)
1.17(2)
Bond Angles (deg)
Au(1)-C(1)-C(2)
Au(2)-C(9)-C(10)
177(1)
166(1)
P(1)-Au(1)-C(1)
P(2)-Au(2)-C(9)
177.9(4)
170.5(4)
[{Ph2(p-Tol)P}Au]2L (2)
Bond Distances (Å)
Au(1)-P(1)
Au(2)-P(2)
Au(1)-C(1)
2.282(3)
2.288(3)
1.991(15)
Au(2)-C(24)
2.028(13)
1.190(17)
1.177(15)
C(1)-C(2)
F igu r e 1. Perspective drawing of complex 3 with atomic
numbering. Thermal ellipsoids are shown at the 30%
probability level.
C(23)-C(24)
Bond Angles (deg)
170.5(13) C(1)-Au(1)-P(1)
C(2)-C(1)-Au(1)
C(23)-C(24)-Au(2) 176.6(11) C(24)-Au(2)-P(2) 176.6(3)
176.0(4)
[{Ph(p-Tol)2P}Au]2L (3)
Bond Distances (Å)
Au(1)-P(1)
Au(2)-P(2)
Au(1)-C(1)
2.282(2)
2.283(3)
2.007(11)
Au(2)-C(24)
1.998(10)
1.199(12)
1.194(12)
C(1)-C(2)
C(23)-C(24)
Bond Angles (deg)
172.4(9) C(1)-Au(1)-P(1)
C(2)-C(1)-Au(1)
174.7(3)
C(23)-C(24)-Au(2) 175.7(10) C(24)-Au(2)-P(2) 176.6(3)
[{(p-Tol)3P}Au]2L (4)
Bond Distances (Å)
Au(1)-P(1)
Au(2)-P(2)
Au(1)-C(1)
2.2774(16)
2.2781(15)
2.010(6)
Au(2)-C(24)
2.030(6)
1.187(7)
1.173(7)
C(1)-C(2)
C(23)-C(24)
Bond Angles (deg)
171.6(5) C(1)-Au(1)-P(1)
C(2)-C(1)-Au(1)
173.09(16)
C(23)-C(24)-Au(2) 170.7(6) C(24)-Au(2)-P(2) 176.12(18)
[{(o-Tol)3P}Au]2L (5)
Bond Distances (Å)
Au(1)-P(1)
Au(2)-P(2)
Au(1)-C(1)
2.2879(17)
2.2911(18)
2.004(7)
Au(2)-C(24)
2.010(8)
1.186(8)
1.184(9)
F igu r e 2. Perspective drawing of complex 4 with atomic
numbering. Thermal ellipsoids are shown at the 30%
probability level.
C(1)-C(2)
C(23)-C(24)
Bond Angles (deg)
176.4(7) C(1)-Au(1)-P(1)
C(2)-C(1)-Au(1)
175.8(2)
the phosphine ligands of one molecule interact with the
ethynyl groups on the adjacent molecule, causes the
Au‚‚‚Au distance to be longer than that expected based
on steric grounds alone. Similarly, the presence of a
C-H‚‚‚π(CtC) interaction between the hydrogen atom
on the dichloromethane solvent molecule and the ethy-
nyl groups in 2 causes the Au‚‚‚Au distance to be longer
than expected. On the other hand, the presence of short
Cl‚‚‚π(CdC) contacts found between the chloro group
on dichloromethane and the aromatic rings on the
phosphine in 5 causes the Au‚‚‚Au separation to in-
crease.
Electr on ic Absor p tion Sp ectr oscop y. The elec-
tronic absorption spectra of complexes 1-5 in dichlo-
romethane solution are mainly dominated by high-
energy absorption bands at 270-300 nm and a low-
energy band at ca. 342 nm with small extinction
coefficients. With reference to previous spectroscopic
works on ethynylgold(I) complexes20 and the similarities
of the absorption bands with the corresponding free
ligands [free ligand absorptions: λ = 264 nm (PPh3, Ph2-
(p-Tol)P, Ph(p-Tol)2P, (p-Tol)3P); λ = 278 nm ((o-Tol)3P);
λ = 268-320 nm (ethynylcalixcrown)], the high-energy
C(23)-C(24)-Au(2) 177.0(8) C(24)-Au(2)-P(2) 177.1(3)
absorption bands at ca. 270-300 nm are tentatively
assigned as the intraligand (IL) transitions of the
phosphine and the ethynylcalixcrown ligand, while the
low-energy absorption band at 342 nm, which is not
found in the free ligands, may be characteristic of the
gold(I) acetylide system.
Em ission P r op er ties. All the complexes synthesized
show luminescence properties. The solid-state emission
spectra of complexes 1-5 all show an emission band at
ca. 450-480 nm. The relatively high energy of the
emission is suggestive of an origin of metal-perturbed
intraligand or σ(Au-P) f π*(RnR′3-nP) character, in
which 5 with the lowest-energy absorbing tri-o-tolylphos-
3
phine shows the lowest energy metal-perturbed IL or
σ(Au-P) f π*(RnR′3-nP) emission in the solid state. The
occurrence of the excitation bands at ca. 320 nm, which
matches well with the metal-perturbed IL bands in the
(20) (a) Muller, T. E.; Choi, S. W. K.; Mingos, D. M. P.; Murphy, D.;
Williams, D. J .; Yam, V. W. W. J . Organomet. Chem. 1994, 484, 209.
(b) Yam, V. W. W.; Choi, S. W. K.; Cheung, K. K. Organometallics 1996,
15, 1734.

2636 Organometallics, Vol. 22, No. 13, 2003
Yam et al.
Ta ble 3. P h otop h ysica l Sp ectr a l Da ta for 1-5
absorptiona
abs/nm
(ꢀmax/dm3 mol-1 cm-1
276 (44440), 286 (48930), CH2Cl2 (298) 578 (6.7)
emission
medium
(T/K)
λ
λ
em/nm
(τo/µs)
complex
)
1
306 sh (31050), 344 (945) solid (298)
solid (77)
465 (1.7)
470
2
3
4
5
276 (39850), 286 (43580), CH2Cl2 (298) 584 (3.7)
300 sh (32880), 342 (880) solid (298)
solid (77)
476 (5.9)
469
274 (46420), 286 (48910), CH2Cl2 (298) 581(6.8)
300 sh (34820), 342 (740) solid (298)
solid (77)
462 (5.8)
459
274 (43410), 286 (46300), CH2Cl2 (298) 580 (7.2)
300 sh (29320), 342 (390) solid (298)
solid (77)
452 (9.2)
452
274 (47740), 283 (54720), CH2Cl2 (298) 582 (5.6)
298 sh (37480), 341 (365) solid (298)
solid (77)
480 (27.6)
472
a
In dichloromethane at 298 K.
F igu r e 4. Electronic absorption spectral traces of 2 (2.5
× 10-5 mol dm-3) in dichloromethane/methanol (1:1 v/v;
a plot of absorbance vs [K+] monitored at λ ) 270 nm (9)
and its theoretical fit (s).
n
0.1 M Bu4NPF6) upon addition of KPF6. The inset shows
Na+ ions are 2.75 ( 0.03, 2.83 ( 0.02, 2.38 ( 0.02, 3.39
( 0.04, and 2.97 ( 0.02 for complexes 1-5, respectively,
according to eq 1. A 1:1 complexation stoichiometry was
obtained as evidenced by the close agreement of the
experimental data to the theoretical fits. In the case of
K+ ions, the UV-visible absorption spectral traces upon
addition of potassium cations to the solution of 2 are
shown in Figure 4, in which a well-defined isosbestic
point was observed. The log Ks values for K+ ion-binding
are 7.24 ( 0.04, 5.08 ( 0.03, 4.66 ( 0.03, and 4.49 (
0.04 for complexes 1-4, respectively. Similarly, a 1:1
complexation stoichiometry is evidenced by the close
agreement of the experimental data to the theoretical
fits. It is interesting to note that the log Ks for Na+ ion-
binding follows the order 4 > 5 g 2 g 1 > 3, while that
for K+ ion-binding follows the order 5 . 1 > 2 > 3 > 4.
As discussed earlier, on the basis of steric grounds alone
and neglecting solid-state effects, complex 4 with three
p-tolyl groups attached to each of the phosphorus atoms
would be expected to give rise to the largest Au‚‚‚Au
separation as a result of the steric hindrance imposed
by the neighboring (RnR′3-nP)Au moieties, and hence a
smaller calixcrown cavity size. On the other hand,
complexes 1 and 5 would be expected to experience the
least steric hindrance between the two (RnR′3-nP)Au
moieties, giving rise to the largest calixcrown cavity.
This is in agreement with the observed trends in the
ion-binding properties, in which 4 gave the largest
binding constant for Na+ ion and the least binding
constant for K+ ion. In fact 5 binds so strongly to K+
ion that no satisfactory fit for eq 2 can be obtained.
Subtle steric effects of the substituents on the phosphine
ligand appear to play an important role in governing
the ion-binding properties of the complexes.
F igu r e 3. Electronic absorption spectral traces of 4 (2.5
× 10-5 mol dm-3) in dichloromethane/methanol (1:1 v/v;
0.1 M nBu4NPF6) upon addition of NaClO4. The inset shows
a plot of absorbance vs [Na+] monitored at λ ) 270 nm (9)
and its theoretical fit (s).
electronic absorption spectra, is consistent with such an
assignment. The Stokes shifts and the observed life-
times in the microsecond range for their emissions are
suggestive of a triplet parentage.
In dichloromethane, the emission band occurs at ca.
578-585 nm, with excitation bands at ca. 350 nm. The
luminescence quantum yields of the complexes are on
the order of 10-1, with the luminescence quantum yield
of 5 being 0.15. It is likely that the emission is derived
from a triplet state of metal-perturbed intraligand or
σ(Au-P) f π*(RnR′3-nP) character, typical of the Au(I)
phosphine acetylide system.20 The emission of the
complexes is found to be sensitive to oxygen quenching,
with bimolecular quenching rate constants approaching
that of the diffusion-controlled limit.
Ca tion -Bin d in g P r op er ties. Upon addition of alkali
metal cations to a dichloromethane/methanol (1:1 v/v)
solution of 1-5, the intraligand absorption band of
alkynylcalixcrowns exhibits a blue shift in absorption
energy. Figure 3 shows the electronic absorption spec-
tral traces upon addition of sodium cations to a solution
of 4, in which a well-defined isosbestic point was
observed. The log Ks values obtained for the binding of
The K+/Na+ selectivities of the complexes 1-4 are 3
× 105, 1.8 × 102, 1.9 × 102, and 13, respectively. As a
result, it can be concluded that the dinuclear gold(I)
alkynylcalix[4]crown complexes bind K+ ions preferen-
tially over Na+ ions. Similar reports on the preferential
binding of K+ ions over Na+ for the cone conformation
of the calix[4]crown-5 can be found.21

Gold(I) Alkynyl-Calix[4]crown-5 Complexes
Organometallics, Vol. 22, No. 13, 2003 2637
Similar studies using emission methods were unsuc-
cessful since no significant changes in the luminescence
properties of the complexes were observed upon addition
of metal ions.
to be further developed as selective metalloreceptors for
other metal ions.
Ack n ow led gm en t. V.W.-W.Y. acknowledges sup-
port from The University of Hong Kong Foundation for
Educational Development and Research Limited and
the University Grants Committee Area of Excellence
Scheme. The work described in this paper was sup-
ported by the Research Grants Council of the Hong
Kong Special Administrative Region, China (Project
HKU7097/01P). S.-K.Y. and K.-L.C. acknowledge the
receipt of a postgraduate studentship, and N.Z., the
receipt of a university postdoctoral fellowship, both
administered by The University of Hong Kong.
Con clu sion
A series of dinuclear gold(I) alkynylcalix[4]crown
complexes were successfully synthesized and spectro-
scopically characterized and their structures solved by
X-ray crystallography. The electronic absorption and
emission behavior of these dinuclear gold(I) alkynylcalix-
[4]crown complexes have been studied. Binding proper-
ties of the complexes toward alkali metal ions have been
studied and fine-tuned by a change in the auxiliary
ligands. In conclusion, the dinuclear gold(I) alkynylcalix-
[4]crown complexes have been shown to exhibit inter-
esting electronic absorption and luminescence properties
and also shown to function as spectrochemical ion probe.
By appropriate design and modification, dinuclear gold-
(I) alkynylcalix[4]crown complexes have the potential
Su p p or tin g In for m a tion Ava ila ble: Perspective draw-
ings of complexes 2 and 5. Tables giving atomic coordinates,
anisotropic thermal parameters, bond lengths, and bond angles
for complexes 1-5. Electronic absorption spectral traces of
complexes 2, 3, and 5 upon addition of NaClO4. Electronic
absorption spectral traces of complexes 3 and 4 upon addition
of KPF6. The material is available free of charge via the
Internet at http://pubs.acs.org.
(21) (a) Ghidini, E.; Ugozzoli, F.; Ungaro, R.; Harkema, S.; Abu El-
Fadl, A.; Reinhoudt, D. N. J . Am. Chem. Soc. 1990, 112, 6979. (b)
Ugozzoli, F.; Ori, O.; Casnati, A.; Pochini, A.; Ungaro, R.; Reinhoudt,
D. N. Supramol. Chem. 1995, 5, 179.
OM030021C