Highly Ag+ selective tripodal Gold(I) acetylide-based "off-On" luminescence chemosensors based on 3(ππ*) emission switching

Article abstract of DOI:10.1021/ic400791a

Newly prepared gold(I) acetylide-based luminescent cation sensors 1c and 1d, which bear a novel three-armed flexible conformation, together with control molecule 2c, were synthesized in four steps. 1c and 1d exhibit the π → π* absorption of the acetylide

Full text of DOI:10.1021/ic400791a

Article
pubs.acs.org/IC
Highly Ag+ Selective Tripodal Gold(I) Acetylide-based “Off−On”
3
Luminescence Chemosensors based on (ππ*) Emission Switching
Yu-Peng Zhou, En-Bao Liu, Jin Wang, and Hsiu-Yi Chao*
MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat−Sen
University, Guangzhou 510275, P. R. China
S
* Supporting Information
ABSTRACT: Newly prepared gold(I) acetylide-based lumi-
nescent cation sensors 1c and 1d, which bear a novel three−
armed flexible conformation, together with control molecule
2c, were synthesized in four steps. 1c and 1d exhibit the π →
π* absorption of the acetylide ligands in fluid solutions and
3
produce the (ππ*) emission of the acetylide ligands in the
solid state and degassed THF solution. The 3(ππ*) emission of
1c in DMSO can be turned on upon addition of Ag+. The
binding ratio between 1c and Ag+ as well as the binding constant log K were determined as 1:1 and 4.35 0.12 respectively by
UV−vis titration experiments. The formation of [1c·Ag]+ adduct, which leads to the appearance of new up-field peaks, was
1
1
confirmed by H NMR spectroscopic titrations. The control H NMR titration experiments for the acetylide-free analogue 1a
and single-armed analogue 2c indicate the acetylide groups and tripodal structures are responsible for the binding of Ag+. The
control experiment for tripodal gold(I) acetylide analogue 1d suggests the change of PPh3 with P(2-Py)Ph2 induces similar
binding affinity toward Ag+ but less selectivity toward Ag+. Free 1c also exhibits the anion binding affinity toward F−, but the Ag+
adduct [1c·Ag]+ shows less affinity toward F−.
gold(I) acetylide complexes bearing the unsaturated organic
CC motif that allows strong 3(ππ*) emission facilitated
through the “heavy atom effect” is quite important. Structure−
property relationships of (ππ*) luminescence have been
reported by Che and co-workers and show the interesting and
various photophysical properties of gold(I) acetylide com-
plexes.
INTRODUCTION
■
The design of chemosensors is important as they are in great
demand in the areas of analytical and clinical chemistry,
environmental science, and medicine.1 Among the potential
sensing targets, heavy transition-metal ions have attracted
significant attention because widespread issues such as
environmental pollution pose serious problems, especially in
developing countries.2 Ag+ is one of the most critical ions since
it can form covalent, colloidal, and coordination bonds with
various natural ligands and present significant toxicity as well as
problematic detectability requiring better probe modalities.3
Current instrumental methods for detecting metal ions such as
FAAS, GFAAS, ICP−AES, and ICP−MS have been developed.
They are sufficient, mature, and in wide use, but these methods
involve expensive and intricate instrumentation and careful
operation. Thus, reliable and efficient methods for detecting
metal ions using optically reporting chemosensors are
required.4 Over the past years, certain Ag+ sensors based on
organic molecules,5a−e metal complexes,5f QDs,6 nanopar-
ticles,7 and DNA/oligonucleotides8 have been reported.
Among these, various sensors based on novel metal complex-
ation modes have attracted much attention because they have
controllable geometries, large Stokes shifts, and long lifetimes.9
For luminescent metal complexes, gold(I) complexes are an
important class that facilitate a triplet excited state emission;
relativistic effects allow for the formation of weak Au···Au
interactions.10 The studies of photophysics,11 supramolecular
building,12 and chemosensors13 based on Au···Au interactions
and gold(I) complexes have been reported. Among these,
14
3
Compared to the traditional binding units toward Ag+, such
as cyclic or acyclic N, O, S donor ligands,4 phthalocyanine,5g
and aromatic π-electrons,15 the use of acetylide Ag+ binding
groups is less explored. Yam and co-workers have reported that
Ag+ can interact with acetylide groups to perturb its emission
property in the solid state16 and act as a photoswitch toward
the photoisomerization of the host molecule.17 The Ag+ and
acetylide π-electron interactions have also been illustrated in
the crystal structures of some metal acetylide complexes.18
These results encouraged us to use the acetylide group in Ag+
binding, a motif previously used in NLO materials, liquid
crystals, and molecular wires.19
To extend our previous work on the photophysical and ion-
sensing properties of gold(I) acetylide complexes,13a,14d,e
tripodal gold(I) acetylide sensors 1c and 1d (Scheme 1)
were prepared, derived from tris(2-aminoethyl)amine (tren), a
widely used building block in anion encapsulation,20 anion
sensing,21 and anion transportation.22 The Au σ-bonded
3
acetylide group usually involves the (ππ*) emissive excited
Received: March 31, 2013
© XXXX American Chemical Society
A
dx.doi.org/10.1021/ic400791a | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Scheme 1. (a) Chemical Structures of 1c, 1d, and 2c and (b) Proposed Binding Model between 1c and Ag+
(KBr, cm−1): ν = 3300 (N−H), 1633 (CO). ESI−MS: m/z = 835
[M − H]−. Anal. Calcd for C27H27N4O3I3 (%): C, 38.79; H, 3.25; N,
6.70. Found: C, 38.97; H, 3.19; N, 6.74.
state of similar gold(I) acetylide complexes, which provides the
possibility to perturb the luminescent properties upon binding
of Ag+. The flexible tripodal structure, compared to linear or
cyclic forms, allows for conformational changes upon ion
binding, which may cause the three arms close to each other
and increase the possibility to form intramolecular Au···Au
interactions among three Au atoms attaching on each arm. In
this work, we report the synthesis, photophysical properties,
and ion-sensing ability of tripodal-based gold(I) acetylide
complexes 1c and 1d. The silver ion-sensing mechanism of 1c
has also been studied. For comparison, the mononuclear
gold(I) acetylide complex (2c) was synthesized (Scheme 1).
Synthesis of N(CH2CH2NHC(O)C6H4-4-CC−TMS)3 (1b). To a
mixture of 1a (627 mg, 0.75 mmol), CuI (40 mg, 0.20 mmol), and
Pd(PPh3)2Cl2 (50 mg, 0.07) in THF (20 mL), trimethylsilylacetylene
(330 mg, 3.4 mmol) and NHEt2 (2 mL) were added dropwise,
respectively. The mixture was stirred at room temperature under
nitrogen overnight. The solvent was removed under reduced pressure,
and the residue was purified by column chromatography on alumina
(elute: first, CH2Cl2, followed by EA/MeOH, (9:1 v/v)). The product
1
was obtained as a brown solid. Yield: 226 mg, 40%. H NMR (300
MHz, DMSO-d6, 298 K): δ = 8.39 (t, J = 5 Hz, 3 H, N−H), 7.74 (d, J
= 8 Hz, 6 H, −C6H4−), 7.44 (d, J = 8 Hz, 6 H, −C6H4−), 3.34 (m, 6
H, −CH2−), 2.69 (t, J = 6 Hz, 6 H, −CH2−), 0.25 (s, 27 H,
Si(CH3)3). IR (KBr, cm−1): ν = 3305 (N−H), 2159 (CC), 1634
(CO). ESI−MS: m/z = 745 [M − H]−. Anal. Calcd for
C42H54N4Si3O3·0.2C4H8O·0.2H2O (%): C, 67.18; H, 7.38; N, 7.32.
Found: C, 67.45; H, 7.66; N, 7.23.
Synthesis of [N(CH2CH2NHC(O)C6H4-4-CCAu)3]∞ (polymer
1). To a mixture of 1b (22 mg, 0.03 mmol) and Au(THT)Cl (29 mg,
0.09 mmol) in CH2Cl2 (10 mL), excess KF (17 mg, 0.18 mmol) in
MeOH (2 mL) was added dropwise. The mixture was stirred at room
temperature for 30 min in the dark. The dark brown precipitate was
collected and reacted with triphenylphosphine directly in the next
reaction. Caution: the gold(I) acetylide polymer is potentially
explosive.24
EXPERIMENTAL SECTION
■
Materials and Reagents. Au(THT)Cl was synthesized according
to literature procedures.23 Tris(2-aminoethyl)amine and 4-iodoben-
zoyl chloride were purchased from Alfa-Aesar. Trimethylsilylacetylene,
n-propylamine, diphenyl-2-pyridylphosphine, and triphenylphosphine
were obtained from J & K. Silver nitrate, copper(I) bromide, lead
nitrate, zinc nitrate hexahydrate, copper(II) nitrate trihydrate,
nickel(II) nitrate hexahydrate, cobalt(II) nitrate hexahydrate, cadmium
nitrate tetrahydrate, aluminum nitrate nonahydrate, calcium nitrate
tetrahydrate, magnesium nitrate hexahydrate, potassium nitrate, and
sodium nitrate were purchased from Aladdin. Tetra-n-butylammonium
fluoride hydrate, tetra-n-butylammonium chloride hydrate, tetra-n-
butylammonium bromide, tetra-n-butylammonium iodide, tetra-n-
butylammonium acetate, and tetra-n-butylammonium phosphate
were obtained from Sigma-Aldrich.
Synthesis of N(CH2CH2NHC(O)C6H4-4-CCAuPPh3)3 (1c). To
the suspension of polymer 1 in CH2Cl2 (20 mL), triphenylphosphine
(24 mg, 0.09 mmol) was added. The mixture was stirred overnight in
the dark. After filtration, the filtrate was concentrated and n-hexane
was added to form the light yellow precipitate. The precipitate was
Synthesis of N(CH2CH2NHC(O)C6H4-4-I)3 (1a). To a suspension
of 4-iodobenzoyl chloride (1.2 g, 4.5 mmol) in anhydrous CH2Cl2 (30
mL), tris(2-aminoethyl)amine (219 mg, 1.5 mmol) and NEt3 (1 mL)
in CH2Cl2 (5 mL) were added dropwise. The mixture was stirred at
room temperature overnight under nitrogen. The solvent was removed
under reduced pressure, and the residue was washed with hydrochloric
acid and dilute sodium hydroxide solution, respectively. The white
1
collected and dried in vacuum. Yield: 48 mg, 82%. H NMR (300
MHz, DMSO-d6, 298 K): δ = 8.34 (t, J = 5 Hz, 3 H, N−H), 7.71 (d, J
= 8 Hz, 6 H, −C6H4−), 7.58−7.50 (m, 45H, phenyl), 7.30 (d, J = 8
Hz, 6 H, −C6H4−), 3.35 (m, 6 H, −CH2−), 2.69 (t, J = 6 Hz, 6 H,
−CH2−). 31P NMR (121 MHz, DMSO-d6, 298 K): δ = 42.40. IR
(KBr, cm−1): ν = 3263 (N−H), 2111 (CC), 1646 (CO). ESI−
MS: m/z = 1905 [M+H]+. Anal. Calcd for C87H72Au3N4O3P3·H2O
(%): C, 54.33; H, 3.88; N, 2.91. Found: C, 54.23; H, 3.95; N, 3.03.
1
solid was collected and washed with water. Yield: 690 mg, 55%. H
NMR (300 MHz, DMSO-d6, 298 K): δ = 8.30 (t, J = 5 Hz, 3 H, N−
H), 7.70 (d, J = 8 Hz, 6 H, −C6H4−), 7.48 (d, J = 8 Hz, 6 H,
−C6H4−), 3.33 (m, 6 H, −CH2−), 2.67 (t, J = 6 Hz, 6 H, −CH2−). IR
B
dx.doi.org/10.1021/ic400791a | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
a
Scheme 2. Synthetic Route of 1c and 1d
a
(i) 4-iodobenzoyl chloride, CH2Cl2, NEt3, RT, overnight. (ii) TMS−CCH, Pd(PPh3)2Cl2, CuI, NHEt2, THF, RT, overnight. (iii) Au(THT)Cl,
KF, MeOH/CH2Cl2, RT, 0.5 h, dark. (iv) PPh3 or P(2-Py)Ph2, CH2Cl2, RT, overnight, dark.
Synthesis of N(CH2CH2NHC(O)C6H4-4-CCAuP(2-Py)Ph2)3
(1d). To the suspension of polymer 1 in CH2Cl2 (20 mL),
diphenyl-2-pyridylphosphine (26 mg, 0.10 mmol) was added. The
mixture was stirred at room temperature overnight in the dark. After
filtration, the filtrate was concentrated and n-hexane was added to form
the pale-yellow precipitate. The precipitate was collected and dried in
cm−1): ν = 3256 (N−H), 2160 (CC), 1626 (CO). ESI−MS: m/z
= 260 [M + H]+. Anal. Calcd for C15H21NOSi (%): C, 69.45; H, 8.16;
N, 5.40. Found: C, 69.43; H, 8.27; N, 5.17.
Synthesis of [CH3CH2CH2NHC(O)C6H4-4-CCAu]∞ (polymer
2). To a mixture of 2b (26 mg, 0.10 mmol) and Au(THT)Cl (32 mg,
0.10 mmol) in CH2Cl2 (10 mL), excess KF (19 mg, 0.20 mmol) in
MeOH (1 mL) was added dropwise. The mixture was stirred at room
temperature for 30 min in the dark. The dark brown precipitate was
collected and reacted with triphenylphosphine directly in the next
reaction. Caution: the gold(I) acetylide polymer is potentially
explosive.
Synthesis of CH3CH2CH2NHC(O)C6H4-4-CCAuPPh3 (2c). To
the suspension of polymer 2 in CH2Cl2 (20 mL), triphenylphosphine
(26 mg, 0.10 mmol) was added. The mixture was stirred at room
temperature overnight in the dark. After filtration, the filtrate was
concentrated and n-hexane was added to form the gray precipitate.
The precipitate was collected and dried in vacuum. Yield: 37 mg, 57%.
1H NMR (300 MHz, DMSO-d6, 298 K): δ = 8.38 (t, J = 5 Hz, 1 H,
N−H), 7.73 (d, J = 8 Hz, 2 H, −C6H4−), 7.62−7.48 (m, 15H,
Phenyl), 7.35 (d, J = 8 Hz, 2 H, −C6H4−), 3.19 (m, 2 H, −CH2−),
1.51 (m, 2 H, −CH2−), 0.88 (t, J = 7 Hz, 3 H, −CH3). 31P NMR (121
MHz, DMSO-d6, 298 K): δ = 42.41. IR (KBr, cm−1): ν = 3263 (N−
H), 2123 (CC), 1631 (CO). FAB−MS: m/z = 646 [M + H]+.
Anal. Calcd for C30H27AuNOP·0.2H2O (%): C, 55.51; H, 4.25; N,
2.16. Found: C, 55.49; H, 4.17; N, 2.04.
Physical Measurements and Instrumentation. Chemical shifts
(δ, ppm) were reported relative to tetramethylsilane for 1H NMR, 85%
H3PO4 for 31P NMR on a Varian Mercury-Plus 300 spectrometer.
Infrared spectra were recorded from KBr pellets in the range of 400−
4000 cm−1 on a Bruker-EQUINOX 55 FT−IR spectrometer.
Electrospray ionization (ESI) mass spectra were recorded on a LCQ
DECA XP quadrupole ion trap mass spectrometer. Fast atom
bombardment (FAB) mass spectra were recorded on a Thermo
MAT95XP high resolution mass spectrometer. Electron impact (EI)
mass spectra were recorded on a Thermo DSQ mass spectrometer.
Elemental analysis was performed on Elemental Vario EL elemental
analyzer. Electronic absorption spectra were measured on a
PGENERAL TU1901 UV−vis spectrophotometer. Emission spectra
were obtained on a FLSP920 fluorescence spectrophotometer.
1
vacuum. Yield: 38 mg, 60%. H NMR (300 MHz, DMSO-d6, 298 K):
δ = 8.77 (d, J = 5 Hz, 3 H, Py), 8.38 (t, J = 5 Hz, 3 H, N−H), 7.91 (m,
3 H, Py), 7.71 (d, J = 8 Hz, 6 H, −C6H4−), 7.62−7.48 (m, 36H,
phenyl and Py), 7.34 (d, J = 8 Hz, 6 H, −C6H4−), 3.36 (m, 6 H,
−CH2−), 2.69 (m, 6 H, −CH2−). 31P NMR (121 MHz, DMSO-d6,
298 K): δ = 41.70. IR (KBr, cm−1): ν = 3336 (N−H), 2108 (CC),
1643 (CO). ESI−MS: m/z = 1908 [M + H]+. Anal. Calcd for
C84H69Au3N7O3P3·H2O (%): C, 52.37; H, 3.72; N, 5.09. Found: C,
52.56; H, 4.02; N, 4.99.
Synthesis of CH3CH2CH2NHC(O)C6H4-4-I (2a). To a suspension
of 4-iodobenzoyl chloride (1.07 g, 4.0 mmol) in CH2Cl2 (20 mL), n-
propylamine (2 mL) was added dropwise. The mixture was stirred at
room temperature for 20 min. The solvent was removed under
reduced pressure, and the residue was washed with water and dilute
NaOH solution. The white solid was collected and washed with dilute
1
hydrochloric acid and water. Yield: 823 mg, 71%. H NMR (300 z,
CDCl3, 298 K): δ = 7.76 (d, J = 8 Hz, 2 H, −C6H4−), 7.46 (d, J = 8
Hz, 2 H, −C6H4−), 6.06 (s, 1 H, N−H), 3.40 (m, 2 H, −CH2−), 1.63
(m, 2 H, −CH2−), 0.98 (t, J = 7 Hz, 3 H, −CH3). IR (KBr, cm−1): ν =
3311 (N−H), 1631 (CO). EI−MS: m/z = 289 [M]+. Anal. Calcd
for C10H12INO (%): C, 41.54; H, 4.18; N, 4.84. Found: C, 41.81; H,
4.26; N, 4.83.
Synthesis of CH3CH2CH2NHC(O)C6H4-4-CC−TMS (2b). To a
mixture of 2a (289 mg, 1.0 mmol), CuI (20 mg, 0.11 mmol), and
Pd(PPh3)2Cl2 (30 mg, 0.04 mmol) in THF (10 mL) and NEt3 (10
mL), trimethylsilylacetylene (150 mg, 1.5 mmol) was added dropwise.
The mixture was stirred overnight at room temperature under
nitrogen. The solvent was removed under reduced pressure, and the
residue was purified by column chromatography on silica gel (elute:
first CH2Cl2, followed by EA). The product was obtained as a brown
1
solid. Yield: 191 mg, 74%. H NMR (300 MHz, CDCl3, 298 K): δ =
7.67 (d, J = 8 Hz, 2 H, −C6H4−), 7.49 (d, J = 8 Hz, 2 H, −C6H4−),
6.08 (s, 1 H, N−H), 3.41 (m, 2 H, −CH2−), 1.64 (m, 2 H, −CH2−),
0.99 (t, J = 7 Hz, 3 H, −CH3), 0.26 (s, 9 H, Si(CH3)3). IR (KBr,
C
dx.doi.org/10.1021/ic400791a | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Titrations, Job Plots, and Detection Limit. For the typical UV−
vis and emission titration experiments, 1.5 μL aliquots of a nitrate salt
were added into the 3 mL solution of the complex in DMSO by a
syringe, and the spectral changes were recorded by a PGENERAL
TU1901 UV−vis spectrophotometer and FLSP920 fluorescence
spectrophotometer at 298 K. The volume changes after the addition
The electronic absorption bands of 1d and 2c are similar to
those of 1c, but the molar absorptivity of 2c is smaller than that
of 1c (Figure S1 and Table S1, Supporting Information). Thus,
the absorption bands of 1c, 1d, and 2c at 260−327 nm are
assigned to the π → π* transition of the acetylide ligands. The
electronic absorption spectra of 1c as well as 2c in THF at 298
K are very similar to those in DMSO, which may suggest the
solvents have a little effect on the electronic absorption spectra
(Table S1, Supporting Information).
1
of ions were kept less than 5% (150 μL). For a typical H NMR
titration experiment, 1.0 μL aliquots of a nitrate salt were added into
the 0.5 mL solution of the complex in DMSO-d6 by syringe, and the
1H NMR spectral changes were recorded by a Varian Mercury-Plus
300 spectrometer at 298 K. The binding constant log K values were
determined by nonlinear fitting using a 1:1 binding model.25a Job plots
were obtained from a series of solutions in which the fraction of the
corresponding anions varied, keeping the total concentration (the
complexes and cations) constant. The maxima of the plots indicated
the binding stoichiometry of the complexes with cations. Detection
limit was determined by FLSP920 fluorescence spectrophotometer at
298 K when S(signal)/N(noise) = 3.3.25b
Excitation of 1c and 1d in the solid state and degassed THF
at λex > 300 nm at 298 K produces the blue-green emission with
a μs range lifetime. For the solid state emission spectra of 1c
and 1d, the observed vibrational spacings of ca. 1100 and 2000
cm−1 in 472−554 nm (Table S1 and Figure S2, Supporting
Information) are attributed to the stretches of phenyl rings
deformation and ν(CC), respectively. The emission
spectrum of 1c and 1d in degassed THF (Table S1 and Figure
S3, Supporting Information) also reveals the bands at ca. 410−
510 nm and 450−555 nm respectively with the vibrational
spacings of ca. 1100, 1600, and 2100 cm−1, which are ascribed
to the stretches of phenyl rings deformation, ν(CO), and
ν(CC), respectively. These spectra are spaced similar to
those of previously reported gold(I) acetylide complexes,
suggesting that the lowest lying emissive state of 1c and 1d for
410−555 nm emission bands may come from the acetylide-
based 3(ππ*) excited state promoted by the enhanced
intersystem crossing through the “heavy atom effect” of Au
that increases spin-orbit coupling.13a,14 In contrast, in DMSO
solutions of 1c and 1d (degassed or not degassed), the
background emission bands of DMSO appear at ca. 350−450
RESULTS AND DISCUSSION
■
Synthesis and Characterization. The synthetic route of
1c and 1d involves four steps that all bear satisfactory yields
(Scheme 2). First, tris(2-aminoethyl)amine (tren) reacted with
4-iodobenzoyl chloride in 1:3 ratio to form an insoluble
intermediate 1a in CH2Cl2. Second, through Sonogashira
coupling reaction, the iodine groups of 1a were substituted by
acetylide groups to obtain the better solubility intermediate 1b
used to react with three equivalents of Au(THT)Cl23 in the
presence of excess KF to form the gold(I) acetylide polymer 1
(caution: the gold(I) acetylide polymer is potentially
explosive24). Finally, three equivalents of phosphine ligands
were added into the suspension of polymer 1 in CH2Cl2 to
depolymerize polymer 1 to get the final products 1c and 1d
respectively (the attempts to get other pure derivatives with
alkyl substituted phosphine ligands were not successful). The
procedure for the synthesis of mononuclear analogue 2c is
similar to those for 1c and 1d (Scheme S1, Supporting
Information). Complexes 1c, 1d, and 2c are all air-stable at 298
K and were characterized by IR, 1H, and 31P NMR spectroscopy
as well as mass spectrometry (ESI, EI, or FAB) and elemental
analysis.
3
nm; the (ππ*) emission bands expected at λ > 450 nm are
difficult to observe.
Cation Sensing studies. The cation-sensing properties of
1c have been investigated by titration experiments in DMSO
(upon addition of Ag+ into the THF solution of 1c, the
precipitate was formed. Thus, the titration experiments in THF
were not tested). Common cations were screened (nitrates
were used); some cations such as Hg2+ and Fe3+ have limited
solubility in DMSO. Upon addition of Ag+ into the DMSO
solution of 1c (5.0 × 10−5 mol dm−3, λex = 311 nm), the
emission intensity at 472 nm increases dramatically together
with the color change of the luminescence: from blue-violet
(emission from DMSO solvent) to blue-green (Figure 1).
Thus, the emission at 472 nm switches on with an
The IR spectra of complexes 1c, 1d, and 2c reveal three
bands at ca. 3263−3336, 2108−2123, and 1631−1646 cm−1,
characteristic of the stretches of ν(N−H), ν(CC), and
ν(CO), respectively. The 1H NMR spectra of complexes 1c,
1d, and 2c show a triplet peak centered at 8.34−8.38 ppm,
respectively, which comes from the resonances of the protons
of N−H. The peaks appeared at ca. 7.30−7.73 ppm can be
ascribed to the resonances of protons coming from the
aromatic phenyl rings. The upfield multiplet signals at the range
of ca. 0.88−3.36 ppm come from the alkyl protons. The 31P
NMR spectra of 1c, 1d, and 2c display singlets at 41.70−42.41
ppm, similar to those of the previously reported gold(I)
acetylide complexes with triphenylphosphine.13a Well-defined
[M + H]+ peaks of complexes 1c, 1d, and 2c were observed
through the positive charge ESI and FAB mass spectrometry.
Photophysics Studies. The electronic absorption spec-
trum of 1c in DMSO at 298 K shows the absorption maxima at
ca. 260, 292, and 305 nm with shoulders at ca. 270, 275, and
324 nm, which undergo bathochromic shifting, compared with
the free ligand 1b (Figure S1a and Table S1, Supporting
Information). The vibrational progressional spacings of ca.
1500 and 2000 cm−1 ascribed to the symmetric phenyl ring
stretching and ν(CC) stretches, respectively, are observed.
Figure 1. Emission spectral changes of 1c (5.0 × 10−5 mol dm−3, λex
=
311 nm) in DMSO upon addition of Ag+ (the emission bands at λ <
450 nm come from the emission of DMSO solvent). (Inset)
Photographs of 1c in DMSO without (left) and with Ag+ (right)
under the excitation of 365 nm irradiation.
D
dx.doi.org/10.1021/ic400791a | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
enhancement of ca. 18-fold. The binding constant (log K) of 1c
with Ag+ in DMSO, determined via luminescence titration, is
4.56 0.21 (Figure S4, Supporting Information), which is in
accord to that obtained by UV−vis titration data (vide infra).
The detection limit for Ag+ is estimated to be 1.0 × 10−6 mol
dm−3 (Figure S5, Supporting Information). For comparison, a
control luminescence titration experiment of the single-arm
analogue 2c was carried out with Ag+ (Figure S6, Supporting
Information). Upon addition of Ag+, the emission band at ca.
470 nm reveals extremely small enhancement compared with
that for 1c. This result suggests that the single acetylide arm
very weakly interacts with Ag+ and multi-armed acetylide
groups may play an essential role in Ag+ binding (Scheme 1b).
The selectivity of 1c in DMSO toward other metal ions has
been investigated. The emission spectra of 1c (5.0 × 10−5 mol
dm−3, λex = 311 nm) after the addition of two equivalents of
various metal ions were recorded (Figure S7, Supporting
Information). Except Ag+, other metal ions studies in this work
cannot turn on the emission at 472 nm (Figure 2, row a). Ag+
concentration creates the ca. 18-fold emission intensity increase
at 472 nm, suggesting the remarkable responsiveness of 1c
toward Ag+.
of Cu2+, suggesting its effective quenching effect. These results
indicate that Ag+ is highly competitive to bind 1c in the
presence of various metal ions studied in this work other than
Cu2+.
Mechanism Studies for Cation Sensing. In order to
understand the mechanism for the interaction of 1c with Ag+,
UV−vis and 1H NMR spectral titration experiments were
carried out. The UV−vis spectral changes of 1c (5 × 10−6 mol
dm−3) in DMSO upon addition of Ag+ are shown in Figure 3a.
The absorption bands at 292 and 305 nm decrease gradually
whereas the absorbances at ca. 261 and 345 nm increase
gradually upon addition of Ag+. Well-defined isosbestic points
are observed at 274 and 311 nm, verifying direct cation-
complex adduct formation. In terms of specificity, other metal
ions studied in this work did not produce such spectral changes.
To further investigate the binding ratio between Ag+ and 1c,
Job analysis was carried out. The UV−vis spectra of continuous
variation with Ag+ were recorded in DMSO ([1c] + [Ag+] = 5
× 10−5 mol dm−3). The absorptions of the newly formed band
at 355 nm reveal their maximum when [Ag+]/([Ag+] + [1c])
reaches at ca. 0.5 (Figure 3b), supporting 1:1 stoichiometric
Ag+−1c binding. Using nonlinear fitting and a 1:1 binding
model, the binding constant log K′ (UV−vis titration) was
determined to be 4.35 0.12 (Figure 3a inset), in accordance
with the log K (luminescence titration) obtained before.
1
Figure 4 contains H NMR spectra reflecting clear changes
upon addition of Ag+ into 1c (1.0 mmol dm−3) in DMSO-d6.
The bottom one shows the spectrum of 1c in the absence of
Ag+. The triplet signal centered at 8.34 ppm, doublets signals
centered at 7.71 and 7.30 ppm, and the multiplet signal at
7.50−7.58 ppm are attributed to the protons of the N−H (HA),
−C6H4− (HB, HC, respectively), and phenyl rings of
triphenylphosphine moieties, respectively. Upon addition of
Ag+ gradually, the intensities of signals centered at 8.34 ppm (J
= 5.0 Hz), 7.71 ppm (J = 8.2 Hz) and 7.30 ppm (J = 8.2 Hz)
decrease. Meanwhile, a triplet centered at ca. 7.47 ppm (J = 5.1
Hz) and doublets centered at 7.12 ppm (J = 8.1 Hz) and 6.88
ppm (J = 8.0 Hz) gradually rise evenly from the baseline. At the
same time, the multiplet signal at 7.50−7.58 ppm changes from
multiple to single gradually. Signals centered at ca. 7.30 (HC),
7.71 (HB), and 8.34 ppm (HA) disappear completely when the
amount of Ag+ is larger than one equivalent, supporting
saturative behavior with a stoichiometric amount of analyte.
The pattern and coupling constants of newly formed peaks
appear closely related to those of disappearing peaks, suggesting
they may come from the [1c·Ag+] adduct. Upon addition of
Ag+, 1c transfers to [1c·Ag+] gradually (unfortunately, the
attempt to characterize the [1c·Ag+] adduct by ESI−MS was
not successful). It is interesting to note these spectral changes
differ from many host−guest systems whose NMR spectral
signals usually shift gradually upfield or downfield. The upfield
positions of the newly formed peaks here could be explained as
the formation of “closed clamp” conformation upon Ag+
binding that makes the N−H as well as −C6H4− motifs of
three arms proximal and leads to a dramatic increase of
electronic density which introduces enhanced shielding that
causes the signals to appear upfield.
Figure 2. (Row a) Relative emission intensity at 472 nm of 1c (5.0 ×
10−5 mol dm−3, λex = 311 nm) with 2 equiv of various metal ions.
(Row b) Relative emission intensity at 472 nm of 1c (5.0 × 10−5 mol
dm−3, λex = 311 nm) + 1 equiv Ag+ in the presence of various metal
ions (2 equiv for Cu2+; 10 equiv for Na+, K+, Ca2+, and Al3+; 5 equiv
for others).
In addition, the competitive binding experiments of 1c
toward Ag+ in the presence of competitive concentrations of
other metal ions (5−10 fold) have been carried out. The
emission spectra of 1c (5.0 × 10−5 mol dm−3, λex = 311 nm)
with one equivalent of Ag+ in the presence of various metal ions
were recorded. In the presence of less than 10 equivalents of
Na+, K+, Ca2+, and Al3+, the influence on the emission intensity
at 472 nm is small; in the presence of less than 5 equivalents of
Pb2+, Zn2+, Ni2+, Co2+, Cd2+, and Mg2+, the emission intensity
at 472 nm changes a little (Figure 2, row b). The metal ion that
only affects the sensing is Cu2+, suggesting reasonable
selectivity of 1c toward Ag+. The luminescence intensity at
472 nm decreases ca. 30% in the presence of more than 2 equiv
The reversibility of the binding of 1c with Ag+ has been
tested. The 1H NMR spectra upon addition of Cl−, Br−, and I−
into the DMSO-d6 solution of 1c in the presence of one
equivalent of Ag+ were recorded. Figures S8−S10 (Supporting
Information) show spectral changes that 1c undergoes (1.0
mmol dm−3) with one equivalent of Ag+ upon addition of Cl−,
E
dx.doi.org/10.1021/ic400791a | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 3. (a) UV−vis spectral changes of 1c (5.0 × 10−6 mol dm−3) in DMSO upon addition of Ag+. (Inset) Plot of the absorbance change at 355
nm as a function of the concentration of Ag+ and a 1:1 theoretical fitting of the data. (b) Job’s plot of complex 1c with Ag+ in DMSO ([1c] + [Ag+]
= 5 × 10−5 mol dm−3).
Figure 4. 1H NMR spectral changes of 1c (1.0 mmol dm−3) in
Figure 5. 1H NMR spectral changes of 2c (4 mmol dm−3) in DMSO-
d6 upon addition of Ag+.
DMSO-d6 upon addition of Ag+.
Br−, and I− (n-Bu4N salts), respectively (DMSO-d6). The sharp
signal at 7.61 ppm, which comes from the phenyl ring protons
of PPh3, undergoes an upfield shift. The triplet centered at ca.
7.47 ppm and doublets centered at 7.12 ppm and 6.88 ppm
show minimal shifting, indicating the “closed clamp” con-
formation of [1c·Ag+] is consistent, and the binding between 1c
and Ag+ is irreversible in DMSO in the presence of halides
strongly favored by Ag+ binding.
1
binding units of 1c with Ag+, the H NMR spectroscopic
titration of 1a in DMSO-d6 with Ag+ was also performed
(Figure S11, Supporting Information). The 1H NMR spectrum
of 1a without any Ag+ has the triplet centered at 8.30 ppm and
doublets centered at 7.70 and 7.48 ppm, attributed to N−H,
−C6H4− motifs, respectively. Upon addition of two equivalents
of Ag+, the 1H NMR spectral changes are very small. This may
suggest that the binding units of 1c with Ag+ do not involve the
nitrogen atoms or π-electrons of phenyl rings. Thus, three C
C moieties of 1c are corresponded to Ag+ binding.
The influence of phosphine ligand P(2-Py)Ph2 of the tripodal
gold(I) acetylide complex 1d on Ag+ binding was investigated
by luminescence, UV−vis, and NMR titration experiments,
which are shown in Figures S12−S18 (Supporting Informa-
tion). They all have similar spectral changes compared with
those of 1c. The binding constants log K1d with Ag+ were
determined to be 4.62 0.24 (luminescence) and 4.42 0.10
(UV−vis), which are close to those of 1c. However, for the
selectivity of 1d with cations, Cu2+ leads to the slight
enhancement of emission intensity, which could be rationalized
as the binding of Cu2+ on pyridine N atom (Figure S14,
Supporting Information). Thus, the change of R group with
pyridine moiety does not affect the affinity toward Ag+ but
decreases the selectivity for Ag+.
1
As a control experiment, the H NMR spectral titration of
the single-armed analogue 2c with Ag+ was carried out. Figure 5
reveals the spectral changes of 2c (4.0 mmol dm−3) in DMSO-
d6 upon addition of Ag+. The triplet centered at 8.38 ppm,
doublets centered at 7.73 and 7.35 ppm, and the multiplet
centered at 7.48−7.62 ppm are attributed to protons of the N−
H (Ha), −C6H4− (Hb, Hc, respectively), and P-phenyl ring
protons, respectively. Upon addition of Ag+ gradually, the
changes of signals centered at 8.38 ppm (Ha) and 7.73 ppm
(Hb) can be barely observed. The signal centered at 7.35 ppm
(Hc) shows slight downfield shifting. This could be due to the
interaction between Ag+ and acetylide group of 2c that reduces
the electron density of the adjacent protons of −C6H4− motif
(Hc). The signals at 7.48−7.62 ppm also show a small change
in their patterns. Thus, the spectral changes of single-armed
analogue 2c are quite different from those of three-armed
sensor 1c, suggestive of the notion that a three-armed flexible
conformation produces better hosting of Ag+.
It is interesting to compare the cation-sensing mechanism of
gold(I) acetylide complex 1c with that of other gold(I)
acetylide complexes previously reported by Yam, in which the
In the literature, N, O, and π-electrons of aromatic rings can
be used as binding units toward Ag+.4,14 In order to confirm the
F
dx.doi.org/10.1021/ic400791a | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
emission based on intramolecular Au···Au interaction could be
produced at λem > 550 nm.13c,f,g The emission band of 1c at 472
nm in DMSO solution, which can also be found in those of free
1c in the solid state and degassed THF solution, was switched
on when 1c binds Ag+. Figure S19 (Supporting Information)
shows the emission spectra of free 1c in degassed THF solution
and 1c in the presence of two equivalents of Ag+ in DMSO
solution. The maximum peaks and shoulder peaks agree with
each other very well. The lifetime of maximum band of 1c upon
addition of Ag+ in DMSO was determined as 4.4 μs. Thus, the
3
acetylide-based (ππ*) emission could be turned on when 1c
interacts with Ag+ in DMSO solution. The very weakly
emission of 1c at 472 nm in DMSO could be due to the
solvent effect of DMSO, which may reduce the radiative decay
of the triplet excited state. Upon addition of Ag+, the
interaction between acetylide groups and the Ag+ may facilitate
spin−orbit coupling and thus enhance the radiative decay of the
triplet excited state. In addition, when 1c binds Ag+, the intra-
and/or intermolecular aurophilic interactions may produce the
rigidity, which could increase the emission intensity. As a
control experiment, the titration experiment of 1c toward Cu+
was carried out (CuBr was used because it is more stable than
[Cu(CH3CN)4]PF6 in air). Upon addition of Cu+ into the
DMSO solution of 1c (5 × 10−5 mol dm−3), the intensity of the
emission band at 525 nm increases (λex = 311 nm) (Figure S20,
Supporting Information). Meanwhile, the intensity of the
emission band at 472 nm also increases, but the enhancement is
small compared with that of 525 nm emission band and that of
472 nm emission band upon addition of Ag+ (Figures S20 and
S21, Supporting Information). The excitation spectra of 1c with
4 equivalents of Cu+ and Ag+ in DMSO are shown in Figure
S22 (Supporting Information). The excitation spectrum of 1c
with Cu+ (λem = 525 nm) shows a low energy band at ca. 400
nm, which is in accord to appearance of the new absorption
band at 400 nm in the UV−vis titration experiment (Figure
S23, Supporting Information) and is absent in the excitation
spectrum of 1c with Ag+ (λem = 472 nm). Thus, the emission
band at 525 nm is attributed to come from the excited state
associated with Au···Au interactions when 1c binds Cu+ in
Figure 6. 1H NMR spectral changes of 1c (1.0 mmol dm−3) in
DMSO-d6 upon addition of F−.
Information), showing the relatively weak interactions
compared with previously reported organic analogues.27
The sensor molecule 1c can interact selectively with both
cations but also anions. Thus, it would be of interest to know
whether it can act as a ditopic ion-pair sensor or not, which is
expected to produce “cation-induced affinity”, in which the
anion binding abilities of a ditopic sensor could be enhanced in
the presence of cations.13d,28 To test this hypothesis, the H
1
NMR titration experiment was carried out. Figure S29
(Supporting Information) shows the spectral changes of 1c
(1.0 mmol dm−3) in the presence of Ag+ in DMSO-d6 upon
addition of F−. Compared with the significant downfield shift of
N−H and −C6H4− motif signals when 1c interacts with F−, the
signal changes are quite small here, which indicates the weak
interaction between [1c·Ag+] and F−. This observation is
different from that in previous investigations that ditopic
sensors bear “cation-induced affinity”.13d,28 Other anions could
also not lead to the significant spectral changes in the presence
1
DMSO. As a control experiment, the emission and H NMR
spectra of AuPPh3-free ligand 1b upon addition of Ag+ do not
change, indicating the essential role of AuPPh3 motifs during
the sensing process (Figures S24 and S25, Supporting
Information).
of Ag+ (for Cl−, Br−, I−, H2PO4 , and OAc− see Figures S8−
−
S10 and S30−S31 (Supporting Information), respectively).
This behavior could be rationalized as the formation of a
“closed clamp” conformation leading to the smaller space in
tren cavity, which prevents [1c·Ag+] from anion-binding.
Anion Binding Studies. Derivates of tris(2-aminoethyl)-
amine (tren) have been used widely for anion recognition.20−22
Thus, the anion binding properties of 1c were also investigated
1
1
CONCLUSION
by H NMR spectroscopic titrations. Figure 6 shows the H
NMR spectral changes of 1c (1.0 mmol dm−3) in DMSO-d6
upon addition of F−. The triplet peak centered at 8.34 ppm
assigned to N−H undergoes gradual downfield shifting (after
one equivalent of F− was added, the peak of N−H became very
broad and its intensity became weak), which suggests the
existence of N−H···F− hydrogen bonding. The signal of HB
coming from the −C6H4− motif which is close to the N−H
motif shows a comparably large downfield shift understood as
the increased polarization effect of C−H bond introduced by
the through-space effect.13a,26 Another proton signal HC
originating from the −C6H4− motif greatly distal from the
N−H shows very little shifting, indicating the weak influence to
HC. The titration experiments of 1c with other anions (Cl−,
■
In summary, we reported the synthesis, photophysical proper-
ties and ion-sensing studies of novel tripodal gold(I) acetylide
chemosensors 1c and 1d. Through a four-step reaction, 1c and
1d can be easily obtained. In THF and DMSO, 1c and 1d
exhibit π → π* absorption of the acetylide ligands. In the solid
3
state and degassed THF solution, 1c and 1d show the (ππ*)
emission of acetylide ligands. Upon addition of Ag+ into the
3
DMSO solution of 1c and 1d, the (ππ*) emission at 472 nm,
which is not observed in the absence of Ag+, was turned on and
the emission color changed from blue-violet (very weak,
DMSO background emission) to blue-green (strong). 1c shows
its higher selectivity and competitiveness for Ag+ over other
metal ions studied in this report. Through luminescence and
UV−vis titration experiments, the binding constants of 1c with
Ag+ (1:1) were determined to be 4.56 0.21 (log K) and 4.35
−
H2PO4 , and OAc−) have also been carried out. The spectral
changes are quite small (see Figures S26−S28, Supporting
G
dx.doi.org/10.1021/ic400791a | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Chem. Commun. 2012, 48, 3012−3014. (c) Chatterjee, A.; Santra, M.;
Won, N.; Kim, S.; Kim, J. K.; Bin Kim, S.; Ahn, K. H. J. Am. Chem. Soc.
2009, 131, 2040. (d) Coskun, A.; Akkaya, E. U. J. Am. Chem. Soc.
2005, 127, 10464−10465. (e) Yang, R. H.; Chan, W. H.; Lee, A. W.
M.; Xia, P. F.; Zhang, H. K.; Li, K. A. J. Am. Chem. Soc. 2003, 125,
2884−2885. (f) Qin, C. J.; Wong, W. Y.; Wang, L. X. Macromolecules.
2011, 44, 483−489. (g) Bilgicli, A. T.; Gunsel, A.; Kandaz, M.; Ozkaya,
A. R. Dalton Trans. 2012, 41, 7047−7056.
(6) (a) Mandal, A.; Dandapat, A.; De, G. Analyst 2012, 137, 765−
772. (b) Gattas-Asfura, K. A.; Leblanc, R. M. Chem. Commun. 2003,
2684−2685.
(7) (a) Feng, D. Q.; Liu, G. L.; Zheng, W. J.; Liu, J.; Chen, T. F.; Li,
D. Chem. Commun. 2011, 47, 8557−8559. (b) Jagerszki, G.; Grun, A.;
Bitter, I.; Toth, K.; Gyurcsanyi, R. E. Chem. Commun. 2010, 46, 607−
609.
0.12 (log K′), respectively. The formation of the “closed
1
clamp” conformation adduct [1c·Ag+] was confirmed by H
NMR titration experiments. The receptor chelating effect of
three-armed flexible conformation and the acetylide binding
unit was determined by the control experiments toward the
acetylide free analogue 1a and single-arm analogue 2c,
respectively. The P(2-Py)Ph2 containing analogue 1d shows
similar affinity but less selectivity toward Ag+. In addition, 1c
shows the binding affinity toward F− in DMSO-d6 compared to
other anions. In the presence of Ag+, 1c shows less binding
affinity toward F−. This could be rationalized by the smaller
space in tren cavity when the “closed clamp” conformation
adduct [1c·Ag+] is formed. The study for water-soluble gold(I)
acetylide chemosensors is underway.
(8) (a) Xie, W. Y.; Huang, W. T.; Li, N. B.; Luo, H. Q. Chem.
Commun. 2012, 48, 82−84. (b) Park, K. S.; Lee, J. Y.; Park, H. G.
Chem. Commun. 2012, 48, 4549−4551. (c) Tang, C. X.; Bu, N. N.; He,
X. W.; Yin, X. B. Chem. Commun. 2011, 47, 12304−12306. (d) Zhao,
C.; Qu, K.; Song, Y.; Xu, C.; Ren, J.; Qu, X. Chem.Eur. J. 2010, 16,
8147−8154. (e) Li, T.; Shi, L. L.; Wang, E. K.; Dong, S. J. Chem.Eur.
J. 2009, 15, 3347−3350. (f) Wen, Y.; Xing, F.; He, S.; Song, S.; Wang,
L.; Long, Y.; Li, D.; Fan, C. Chem. Commun. 2010, 46, 2596−2598.
(g) Man, B. Y. W.; Chan, D. S. H.; Yang, H.; Ang, S. W.; Yang, F.; Yan,
S. C.; Ho, C. M.; Wu, P.; Che, C. M.; Leung, C. H.; Ma, D. L. Chem.
Commun. 2010, 46, 8534−8536.
(9) Zhao, Q.; Li, F.; Huang, C. Chem. Soc. Rev. 2010, 39, 3007−3030.
(10) (a) Yam, V. W. W.; Cheng, E. C. C. Chem. Soc. Rev. 2008, 37,
1806−1813. (b) Yam, V. W. W.; Cheng, E. C. C. Top. Curr. Chem.
2007, 281, 269−309. (c) Pyykko, P. Angew. Chem., Int. Ed. 2004, 43,
4412−4456.
(11) (a) Tong, G. S. M.; Kui, S. C. F.; Chao, H. Y.; Zhu, N.; Che, C.
M. Chem.Eur. J. 2009, 15, 10777−10789. (b) Che, C. M.; Lai, S. W.
Coord. Chem. Rev. 2005, 249, 1296−1309. (c) Zhang, H. X.; Che, C.
M. Chem.Eur. J. 2001, 7, 4887−4893. (d) Fu, W. F.; Chan, K. C.;
Cheung, K. K.; Che, C. M. Chem.Eur. J. 2001, 7, 4656−4664.
(e) Fu, W. F.; Chan, K. C.; Miskowski, V. M.; Che, C. M. Angew.
Chem., Int. Ed. 1999, 38, 2783−2785. (f) Yip, J. H. K.; Prabhavathy, J.
Angew. Chem., Int. Ed. 2001, 40, 2159−2162.
(12) (a) Lee, T. K. M.; Zhu, N.; Yam, V. W. W. J. Am. Chem. Soc.
2010, 132, 17646−17648. (b) Yu, S. Y.; Sun, Q. F.; Lee, T. K. M.;
Cheng, E. C. C.; Li, Y. Z.; Yam, V. W. W. Angew. Chem., Int. Ed. 2008,
47, 4551−4554. (c) Sun, Q. F.; Lee, T. K. M.; Li, P. Z.; Yao, L. Y.;
Huang, J. J.; Huang, J.; Yu, S. Y.; Li, Y. Z.; Cheng, E. C. C.; Yam, V. W.
W. Chem. Commun. 2008, 5514−5516. (d) Yu, S. Y.; Zhang, Z. X.;
Cheng, E. C. C.; Li, Y. Z.; Yam, V. W. W.; Huang, H. P.; Zhang, R. B. J.
Am. Chem. Soc. 2005, 127, 17994−17995.
(13) (a) Zhou, Y. P.; Zhang, M.; Li, Y. H.; Guan, Q. R.; Wang, F.;
Lin, Z. J.; Lam, C. K.; Feng, X. L.; Chao, H. Y. Inorg. Chem. 2012, 51,
5099−5109. (b) He, X.; Zhu, N.; Yam, V. W. W. Dalton Trans. 2011,
40, 9703−9710. (c) Hau, F. K. W.; He, X.; Lam, W. H.; Yam, V. W. W.
Chem. Commun. 2011, 47, 8778−8780. (d) He, X.; Yam, V. W. W.
Inorg. Chem. 2010, 49, 2273−2279. (e) He, X.; Herranz, F.; Cheng, E.
C. C.; Vilar, R.; Yam, V. W. W. Chem.Eur. J. 2010, 16, 9123−9131.
(f) He, X.; Lam, W. H.; Zhu, N.; Yam, V. W. W. Chem.Eur. J. 2009,
15, 8842−8851. (g) He, X.; Cheng, E. C. C.; Zhu, N.; Yam, V. W. W.
Chem. Commun. 2009, 4016−4018. (h) Li, C. K.; Lu, X. X.; Wong, K.
M. C.; Chan, C. L.; Zhu, N.; Yam, V. W. W. Inorg. Chem. 2004, 43,
7421−7430.
(14) (a) Tong, G. S. M.; Chow, P. K.; Che, C. M. Angew. Chem., Int.
Ed. 2010, 49, 9206−9209. (b) Lu, W.; Zhu, N.; Che, C. M. J.
Organomet. Chem. 2003, 670, 11−16. (c) Lu, W.; Xiang, H. F.; Zhu,
N.; Che, C. M. Organometallics. 2002, 21, 2343−2346. (d) Chao, H.
Y.; Lu, W.; Li, Y.; Chan, M. C. W.; Che, C. M.; Cheung, K. K.; Zhu, N.
J. Am. Chem. Soc. 2002, 124, 14696−14706. (e) Che, C. M.; Chao, H.
Y.; Miskowski, V. M.; Li, Y.; Cheung, K. K. J. Am. Chem. Soc. 2001,
123, 4985−4991.
ASSOCIATED CONTENT
* Supporting Information
Synthetic route of 2c; UV−vis and emission spectra of 1c and
1d; photophysical data of 1a−1d and 2a−2c; emission spectral
changes of 1d and 2c with Ag+; plots of the emission changes of
1c and 1d as a function of the concentration of Ag+ and the
theoretical 1:1 fitting curves; detection limit of 1c toward Ag+;
■
S
1
emission spectra of 1c and 1d with metal ions; H NMR
spectral changes of 1c in present of one equivalent of Ag+ with
−
F−, Cl−, Br−, I−, H2PO4 , and OAc−; 1H NMR spectral changes
of 1a, 1b, and 1d with Ag+; UV−vis spectral changes of 1d with
Ag+; a Job’s plot of 1d with Ag+; a plot of the absorbance
change of 1d as a function of the concentration of Ag+ and a
1:1 theoretical fitting curve; emission spectra of 1c in THF and
DMSO with 2 equiv of Ag+; UV−vis and emission spectral
changes of 1c with Cu+; excitation spectra of 1c with 4 equiv of
Ag+ and Cu+; emission spectral changes of 1d with Ag+; H
1
NMR spectral changes of 1c with Cl−, H2PO4 , and OAc−. This
−
material is available free of charge via the Internet at http://
pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*Phone: +86-20-84110062. Fax: +86-20-84112245. E-mail:
zhaoxy@mail.sysu.edu.cn.
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We acknowledge the financial support from the National
Natural Science Foundation of China (20971131 and
J1103305), the Natural Science Foundation of Guangdong
Province (10151027501000048 and S2012010010566), and
Sun Yat−Sen University. We thank Prof. David G. Churchill of
KAIST for his assistance in proofreading this manuscript. We
also thank the editors and reviewers for their helpful comments
and suggestions.
REFERENCES
■
(1) Valeur, B. Molecular Fluorescence: Principle and Applications;
Wiley−VCH Verlag GmbH: Weinheim, 2001.
(2) Fu, F.; Wang, Q. J. Environ. Manage. 2011, 92, 407−418.
(3) Ratte, H. T. Environ. Toxicol. Chem. 1999, 18, 89−108.
(4) Zhang, J. F.; Zhou, Y.; Yoon, J.; Kim, J. S. Chem. Soc. Rev. 2011,
40, 3416−3429.
(5) (a) Zheng, H.; Yan, M.; Fan, X. X.; Sun, D.; Yang, S. Y.; Yang, L.
J.; Li, J. D.; Jiang, Y. B. Chem. Commun. 2012, 48, 2243−2245.
(b) Kim, J. M.; Lohani, C. R.; Neupane, L. N.; Choi, Y.; Lee, K. H.
H
dx.doi.org/10.1021/ic400791a | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(15) (a) Rathore, R.; Chebny, V. J.; Abdelwahed, S. H. J. Am. Chem.
Soc. 2005, 127, 8012−8013. (b) Kang, J.; Choi, I.; Kwon, J. Y.; Lee, E.
Y.; Yoon, J. J. Org. Chem. 2002, 67, 4384−4386.
(16) Yam, V. W. W.; Cheung, K. L.; Cheng, E. C. C.; Zhu, N.;
Cheung, K. K. Dalton Trans. 2003, 1830−1835.
(17) Tang, H. S.; Zhu, N.; Yam, V. W. W. Organometallics. 2007, 26,
22−25.
(18) (a) Lam, E. S. H.; Tam, A. Y. Y.; Lam, W. H.; Wong, K. M. C.;
Zhu, N.; Yam, V. W. W. Dalton Trans. 2012, 41, 8773−8776.
(b) Koshevoy, I. O.; Lin, C. L.; Karttunen, A. J.; Janis, J.; Haukka, M.;
Tunik, S. P.; Chou, P. T.; Pakkanen, T. A. Inorg. Chem. 2011, 50,
2395−2403. (c) Wei, Q. H.; Zhang, L. Y.; Yin, G. Q.; Shi, L. X.; Chen,
Z. N. J. Am. Chem. Soc. 2004, 126, 9940−9941.
(19) Yam, V. W. W.; Wong, K. M. C. Top. Curr. Chem. 2005, 257, 1−
32.
(20) (a) Arunachalam, M.; Ghosh, P. Chem. Commun. 2011, 47,
8477−8492. (b) Mullen, K. M.; Beer, P. D. Chem. Soc. Rev. 2009, 38,
1701−1713.
(21) Ravikumar, I.; Ghosh, P. Chem. Soc. Rev. 2012, 41, 3077−3098.
(22) (a) Busschaert, N.; Wenzel, M.; Light, M. E.; Iglesias-
Hernandez, P.; Perez-Tomas, R.; Gale, P. A. J. Am. Chem. Soc. 2011,
133, 14136−14148. (b) Berezin, S. K.; Davis, J. T. J. Am. Chem. Soc.
2009, 131, 2458.
(23) Uson, R.; Laguna, A.; Laguna, M. Inorg. Synth. 1989, 26, 85−91.
(24) Churchill, D. G. J. Chem. Educ. 2006, 83, 1798−1803.
(25) (a) Bourson, J.; Pouget, J.; Valeur, B. J. Phys. Chem. 1993, 97,
4552−4557. (b) Mo, H. J.; Shen, Y.; Ye, B. H. Inorg. Chem. 2012, 51,
7174−7184.
(26) (a) Gomez, D. E.; Fabbrizzi, L.; Licchelli, M.; Monzani, E. Org.
Biomol. Chem. 2005, 3, 1495−1500. (b) Esteban-Gomez, D.; Fabbrizzi,
L.; Liechelli, M. J. Org. Chem. 2005, 70, 5717−5720. (c) Boiocchi, M.;
Del Boca, L.; Esteban-Gomez, D.; Fabbrizzi, L.; Licchelli, M.;
Monzani, E. Chem.Eur. J. 2005, 11, 3097−3104. (d) Boiocchi, M.;
Del Boca, L.; Gomez, D. E.; Fabbrizzi, L.; Licchelli, M.; Monzani, E. J.
Am. Chem. Soc. 2004, 126, 16507−16514.
(27) Ravikumar, I.; Lakshminarayanan, P. S.; Ghosh, P. Inorg. Chim.
Acta 2010, 363, 2886−2895.
(28) (a) Mahoney, J. M.; Stucker, K. A.; Jiang, H.; Carmichael, I.;
Brinkmann, N. R.; Beatty, A. M.; Noll, B. C.; Smith, B. D. J. Am. Chem.
Soc. 2005, 127, 2922−2928. (b) Mahoney, J. M.; Beatty, A. M.; Smith,
B. D. Inorg. Chem. 2004, 43, 7617−7621. (c) Mahoney, J. M.; Beatty,
A. M.; Smith, B. D. J. Am. Chem. Soc. 2001, 123, 5847−5848.
I
dx.doi.org/10.1021/ic400791a | Inorg. Chem. XXXX, XXX, XXX−XXX