Synthesis, characterization, photophysics, and anion binding properties of gold(i) acetylide complexes with amide groups

Article abstract of DOI:10.1039/c4nj01294a

A series of mononuclear gold(i) acetylide complexes with amide groups, Ph₃PAuCCC₆H₄NHC(O)C₆H₄-R-4 (R = NO₂ (3a), CF₃ (3b), H (3c), and OMe (3d)), has been synthesized and characterized. The crystal structure of Ph₃PAuCCC₆H₄NHC(O)C₆H₄-NO₂-4 (3a) was determined by X-ray diffraction. The photophysical properties of gold(i) acetylide complexes 3b-3d were studied and the complexes show luminescence both in the solid state and in degassed THF solutions at 298 K. The anion-binding abilities of complexes 3a-3d in CDCl₃ were also studied through ¹H NMR titration experiments. They show similar anion selectivity trends and 3a exhibits the highest binding affinity towards anions due to the strongest electron-withdrawing ability of the NO₂ group. In DMSO, 3a shows a dramatic color change upon addition of F^-, which provides access to naked eye detection of F^-. This journal is

Full text of DOI:10.1039/c4nj01294a

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PAPER
Synthesis, characterization, photophysics, and
anion binding properties of gold(I) acetylide
complexes with amide groups†
Cite this: New J. Chem., 2014,
38, 6168
Hua-Yun Shi, Jie Qi, Zhen-Ze Zhao, Wen-Juan Feng, Yu-Hao Li, Lu Sun,
Zhuo-Jia Lin and Hsiu-Yi Chao*
A series of mononuclear gold(I) acetylide complexes with amide groups, Ph3PAuCRCC6H4NHC(O)C6H4–
R-4 (R = NO2 (3a), CF3 (3b), H (3c), and OMe (3d)), has been synthesized and characterized. The crystal
structure of Ph3PAuCRCC6H4NHC(O)C6H4–NO2-4 (3a) was determined by X-ray diffraction. The photo-
physical properties of gold(I) acetylide complexes 3b–3d were studied and the complexes show lumines-
cence both in the solid state and in degassed THF solutions at 298 K. The anion-binding abilities of
complexes 3a–3d in CDCl3 were also studied through 1H NMR titration experiments. They show similar
anion selectivity trends and 3a exhibits the highest binding affinity towards anions due to the strongest
electron-withdrawing ability of the NO2 group. In DMSO, 3a shows a dramatic color change upon addition
of FÀ, which provides access to naked eye detection of FÀ.
Received (in Victoria, Australia)
4th August 2014,
Accepted 29th September 2014
DOI: 10.1039/c4nj01294a
www.rsc.org/njc
N–H or cationic (N–H)+ hydrogen bond donor, such as pyrrole,11
ammonium,12,13 guanidinium,14 urea,15,16 thiourea,15 and
1. Introduction
Anions are one of the most important constituents of living amide,17–19 have proven to be particularly effective anion receptors
systems because they play pivotal roles in ion transport, chemo- in organic solvents. It is interesting to note that anion binding by
sensing, and especially in the environment and in biology.1–4 proteins is mostly achieved by way of neutral amide functional
Since the first anion sensor reported by Park and Simmons in groups employing their N–H moiety as a hydrogen bond donor.20
1968,5 anion sensors have attracted much attention and become Thus, amide-based organic anion sensors with aromatic or
an important field in supramolecular chemistry. Various methods heterocyclic groups have been reported in the literature.10,21
have been applied to design effective anion sensors over the past Their structures are simple and their modification can be easily
few decades. They usually consist of two main moieties: a carried out through organic synthesis.
recognition unit and a sensing unit, which are connected either
Although most past studies on the design of anion sensors
directly or by a spacer. When the recognition unit interacts with have focused on organic receptors involving photo-induced
an anion by non-covalent interaction, the photophysical or redox electron transfer (PET) processes,22 the utilization of transition
properties of the sensing unit can be changed.6–8 Thus, anion metal complexes with amide groups as anion sensors has been
sensing can be realized by detecting optical and electrical signals relatively less explored.23–25 Compared to common organic anion
from receptors. Observations in natural anion binding systems sensors, metal complexes with various properties like redox and
have motivated researchers to develop several artificial receptors luminescence have proven to be able to provide access to anion
which employ hydrogen bonds offered by specific binding sites sensing. Some examples include ruthenium(II),26–29 rhenium(I),30–33
that are able to recognize and bind size- and shape-selective iridium(III),34 platinum(II)35,36 and gold(I)–copper(I)37 complexes
anionic guests on appropriate frameworks in various media.9,10 which utilize MLCT or metal cluster-centered excited states for
To date, a number of synthetic receptors incorporating a neutral luminescent signal transduction. Among them, gold(I) complexes
are one of the most important classes owing to their intriguing
photoluminescence behavior and their propensity to form
aurophilic AuÁ Á ÁAu interactions.38 Many studies showed that
an increase in the strength of the AuÁ Á ÁAu interaction would
lead to a shift of the emission to lower energy.39 The preference
of gold(I) for a linear coordination geometry, together with the
linearity of the acetylide unit and its p-unsaturated nature, have
made gold(I) acetylide complexes attractive building blocks for
MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry
and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275,
P. R. China. E-mail: zhaoxy@mail.sysu.edu.cn; Fax: +86-20-84112245;
Tel: +86-20-84110062
† Electronic supplementary information (ESI) available: An X-ray crystallographic
file in CIF format for complex 3a. Additional figures and tables. CCDC 1013703.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c4nj01294a
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Scheme 1 Synthetic route for gold(I) acetylide complexes 3a–3d. (i) Pd(PPh3)2Cl2, CuI, (CH3)3Si–CRCH, NEt3, reflux, N2, overnight; (ii) ClC(O)C6H4–R,
NEt3, CHCl3, reflux, N2, overnight; (iii) Ph3PAuCl, KFÁ2H2O, CH2Cl2/CH3OH, dark.
organometallic oligomeric and polymeric materials, which may
The IR spectra of the gold(I) acetylide complexes 3a–3d
possess unique properties such as optical non-linearity, electrical reveal bands at 3389–3434 and 1656–1674 cmÀ1, characteristic
conductivity and liquid crystallinity.40 The gold(I) acetylide complexes of the n(N–H) and n(CQO) vibrations of the acetylide ligands,
supported by an auxiliary phosphane ligand represent the major respectively. The 1H NMR spectra of complexes 3a–3d in CDCl3
class of luminescent gold(I) complexes.40 Che,41–44 Yam,45–50 and display singlets at d 7.68–7.84 ppm, which are attributed to the
other groups51–54 have studied the photophysical, photochemical resonances of the amide N–H of the acetylide ligands. The
and ion-sensing properties of gold(I) acetylide complexes. However, chemical shifts of these peaks are in the order 3a 4 3b B 3c 4
to the best of our knowledge, no gold(I) acetylide complex with an 3d, which is in line with the decreasing electron-withdrawing
amide group has ever been reported as an anion sensor until now. abilities of the R substituents on the acetylide ligand. In
Our group has a long-term interest in studying the relation- addition, the peaks in the region d 7.40–8.31 ppm are attributed
ship between the structures and properties of gold(I) acetylide to the resonances of the protons on the aromatic rings of the
complexes.44,53,54 We have synthesized a series of gold(I) acet- acetylide and triphenylphosphine ligands. The 31P NMR spectra
ylide complexes with urea or amide groups, and studied their of complexes 3a–3d in CDCl3 show a singlet at ca. d 43.3 ppm.
photophysical and ion-sensing properties.53,54 To extend our The NMR spectra of complexes 3a–3d are similar owing to their
studies on gold(I) acetylide complexes with different anion similar structures and the fact that the R substituents on the
binding abilities, a series of mononuclear gold(I) acetylide acetylide ligands have little effect on the chemical shifts.
complexes, Ph3PAuCRCC6H4NHC(O)C6H4–R-4 (R = NO2 (3a),
2.2. Crystal structure of 3a
CF3 (3b), H (3c) and OMe (3d); Scheme 1), has been synthesized
and characterized in this work. The crystal structure of
Ph3PAuCRCC6H4NHC(O)C6H4–NO2-4 (3a) was determined by
X-ray diffraction. We envisaged that if the photophysical prop-
erties of these gold(I) acetylide complexes could be changed
when they interact with anions, through hydrogen bonds
between the anions and the amide N–H of the complexes, then
they could be used as anion sensors. The sole binding site may
be better matched to spherical anions than non-spherical ones.
The effect of the structure, especially the nature of the R
substituent on the acetylide ligand of the complex, on the
binding abilities of the gold(I) acetylide complexes towards
anions was also studied.
The crystal structure of the mononuclear gold(I) acetylide
complex 3a was determined by X-ray diffraction crystallo-
graphy. The crystallographic data are listed in Table S1 (ESI†)
and selected bond distances and angles are listed in Table 1.
Fig. 1 shows the crystal structure of 3a. The triphenylphosphine
ligand coordinates to the gold(I) metal center and the remain-
ing gold(I) site is occupied by an acetylide ligand to give a nearly
linear geometry. The C(1)–Au(1)–P(1), Au(1)–C(1)–C(2) and C(1)–
C(2)–C(41) angles of 174.52(14)1, 174.3(5)1 and 177.0(6)1,
respectively, are deviated from the idealized angle of 1801,
probably as a result of the steric demand of the ligands and
the crystal packing forces. The Au(1)–C(1) and Au(1)–P(1) bond
distances for 3a (2.012(5) and 2.2802(18) Å, respectively) are
similar to those reported for other gold(I) arylacetylide com-
plexes with triphenylphosphine ligands.55,56 The CRC bond
distance (1.187(8) Å) is in the range of those typical for gold(I)
2. Results and discussion
2.1. Syntheses and characterization
Scheme 1 shows the synthetic route for acetylide ligands with
amide groups (2a–2d) and mononuclear gold(I) acetylide com-
plexes (3a–3d). The reaction of 4-[(trimethylsilyl)ethynyl]aniline
with the corresponding acyl chloride in refluxing chloroform in
the presence of triethylamine gave acetylide ligands 2a–2d.
Mononuclear gold(I) acetylide complexes 3a–3d were obtained by
reaction of Ph3PAuCl with the corresponding acetylide ligands
2a–2d in a molar ratio of 1 : 1 in the presence of an excess of KF in
a dichloromethane–methanol mixture at 298 K. All gold(I) acetylide
complexes 3a–3d are air-stable in the solid state at 298 K and can
be well dissolved in CHCl3, CH2Cl2, THF and DMSO. They were all
characterized by IR, 1H NMR and 31P NMR (Fig. S1–S12, ESI†) and
gave satisfactory elemental analysis results.
Table 1 Selected bond lengths (Å) and angles (1) for 3a
Au(1)–C(1)
2.012(5)
2.2802(18)
1.187(8)
1.217(7)
1.224(8)
1.215(7)
174.52(14)
174.3(5)
177.0(6)
115.7(5)
123.7(6)
120.6(5)
124.0(6)
Au(1)–P(1)
C(1)–C(2)
C(3)–O(1)
N(2)–O(2)
N(2)–O(3)
C(1)–Au(1)–P(1)
Au(1)–C(1)–C(2)
C(1)–C(2)–C(41)
N(1)–C(3)–C(51)
O(1)–C(3)–N(1)
O(1)–C(3)–C(51)
O(2)–N(2)–O(3)
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Fig. 1 A view of the crystal structure of 3a with the atomic numbering
scheme. Thermal ellipsoids are shown at the 30% probability level.
acetylide systems.44,55–67 Because the angles of N(1)–C(3)–C(51),
O(1)–C(3)–N(1) and O(1)–C(3)–C(51) are 115.7(5)1, 123.7(6)1 and
120.6(5)1, respectively, the geometry of the carbonyl group is
nearly trigonal planar. The CQO distance for 3a (1.217(7) Å)
also resembles those in analogous gold(I) acetylide complexes
with carbonyl groups.50 There are intermolecular hydrogen
bonding interactions between the hydrogen atom of the amide
group and the oxygen atom (O2) of the nitro group of the
acetylide ligand of 3a (Fig. 2). The hydrogen bond parameters of
3a are listed in Table 2.
Fig. 3 The electronic absorption spectrum of 3a (1.98 Â 10À5 mol dmÀ3
)
in THF at 298 K.
in THF at 298 K. The absorption peak maxima of 3a appear at
267, 277, 292, 305 and 330 nm. The spacings of the adjacent
absorption maxima of 3a at 267–305 nm are ca. 1300–1800 cmÀ1
.
Thus, the absorption bands of complex 3a at 267–305 nm are
attributed to the p - p* transitions of the acetylide ligand.54 The
low-energy absorption band of 3a at 330 nm could be due to the
charge-transfer transition from the amide to the NO2 group of the
acetylide ligand.54 The electronic absorption spectra of non-nitro
derivatives 3b–3d in THF at 298 K exhibit one shoulder (ca. 296 nm)
and three additional bands (ca. 268, 277 and 312 nm) (Fig. S13–S15,
ESI†). Overall there are three different values for the vibrational
spacings, ca. 1200, 1700 and 2200 cmÀ1, which are ascribed to
phenyl ring deformation, CQO stretching, and CRC stretching
frequencies of the ground state, respectively.44,54,58 These absorption
bands are assigned to the 1(pp*) transitions involving the phenylic,
carbonyl and acetylenic units of the acetylide ligand.
2.3. Electronic absorption and emission spectra of complexes
3a–3d
The photophysical data for complexes 3a–3d are summarized in
Table 3. Fig. 3 shows the electronic absorption spectrum of 3a
Upon excitation at l 4 300 nm, gold(I) acetylide complexes
3b–3d in the solid state and in THF exhibit luminescence in the
visible light region at 298 K, with emission quantum yields of
5.0 Â 10À3–1.02 Â 10À2 in THF solutions, and complex 3a in
THF exhibits luminescence under the same conditions with an
emission quantum yield of 4.2 x 10À3. Fig. S16–S18 (ESI†) show
the emission spectra of 3b–3d in the solid state at room
temperature. A broad band at ca. 471 nm is observed for each
complex and its lifetime is in the microsecond range (Table 3).
Thus, the emission is attributed to come from the 3(pp*) excited
state of the acetylide ligand in the gold(I) acetylide complexes.
In THF, the emission spectra of complexes 3a–3d exhibit three
Fig. 2 A view of two molecules of 3a showing the intermolecular hydro-
gen bonding. Thermal ellipsoids are shown at the 30% probability level.
Table 2 Hydrogen bond parameters of 3a (Å and 1)
D–HÁ Á ÁA
d(D–H)
d(HÁ Á ÁA)
2.50
d(DÁ Á ÁA)
3.267(7)
+(DHA)
N(1)–H(1A)Á Á ÁO(2)a
0.86
149.7
a
Symmetry transformations used to generate equivalent atoms: Àx + 4,
y + 4, z + 2.
Table 3 Photophysical data of complexes 3a–3d at 298 K
Complex
Medium
l
abs/nm (e/dm3 molÀ1 cmÀ1
)
lem/nm (tem/ms)
Fa
3a
THF
Solid
THF
Solid
THF
Solid
THF
Solid
267 (32 170), 277 (35 350), 292 (sh, 44 040), 305 (39 950), 330 (14 240)
268 (17 420), 276 (20 000), 296 (sh, 25 810), 315 (34 950)
267 (16 310), 276 (18 640), 296 (sh, 33 230), 314 (43 640)
268 (19 900), 277 (22 420), 296 (sh, 37 630), 312 (47 320)
408 (max), 434, 465
Non-emissive
408 (max), 432, 465
471 (2.6)
407 (max), 434, 465
471 (2.5)
0.0042
3b
3c
3d
0.0059
0.0050
0.0102
410 (max), 432, 471
484 (3.5)
a
Quinine sulfate as reference.59
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bands at ca. 408, 434 and 465 nm with vibrational spacings of could not be used to obtain accurate binding constants of
approximately 1300–1900 cmÀ1, which are assigned to the complexes 3a–3d towards anions. Thus, the interactions of
stretching of the phenyl and acetylene units of the acetylide 3a–3d with anions in CDCl3 were investigated by 1H NMR
ligand (Fig. S19–S22, ESI†). Thus, the lowest-lying emissive titration experiments. All of the anions used were in the form
state of complexes 3a–3d in THF is assigned as the 3(pp*) of tetra-n-butylammonium salts. Fig. 4(a) shows the 1H NMR
excited state of the acetylide ligand, which is promoted through spectral changes of 3a upon addition of ClÀ in CDCl3. A significant
spin–orbit coupling due to the introduction of a gold atom.54,58 downfield shift in the amide N–H (Ha) signal is observed upon
For the mononuclear gold(I) acetylide complexes studied in this gradual addition of ClÀ from 0 to 5 equiv., while only small changes
paper, except the nitro-derivative 3a, the R substituent on the in the peak position are observed upon addition of more than
acetylide ligand has little effect on the electronic absorption 5 equiv. of ClÀ. The other proton signals are found to undergo
and emission spectra.
small or relatively negligible changes, suggesting the formation of
hydrogen bonds between the amide N–H of 3a and ClÀ. The slight
downfield shifts of Hb and Hc on the phenyl ring are ascribed to the
polarization effect of the C–H bond, which is introduced by the
2.4. Anion binding properties of complexes 3a–3d
Addition of the anions studied in this paper to the solutions of
3a–3d caused UV-Vis spectral changes. However, these results
1
through-space effect.60–62 The H NMR spectral changes of 3b–3d
upon gradual addition of ClÀ in CDCl3 (Fig. S31, S32, S35, S36, S43
and S44, ESI†) are similar to that of 3a. Analogous investigations of
3a–3d with Y-shaped anion OAcÀ or other halides such as FÀ, BrÀ
and IÀ in CDCl3 were also carried out, and they showed similar
spectral changes in the 1H NMR spectra (some are shown in
Fig. S23–S42, ESI†). The amide N–H (Ha) signals exhibit significant
downfield shifts of 0.6 to 2.8 ppm, while the signals of the aromatic
protons shift relatively less. The extent of the shift of Ha upon the
addition of BrÀ, IÀ, and OAcÀ is found to be obviously smaller than
that for ClÀ, while the addition of FÀ induced disappearance of the
amide N–H signals for 3a and 3b, but larger shifts for 3c and 3d.
Fig. S45 (ESI†) shows the shifts of the amide N–H (Ha) signal of 3c
upon addition of different anions in CDCl3 at 298 K. Unfortunately,
only the binding constant of 3c with FÀ can be determined because
the amide N–H (Ha) signal of 3d is too broad to be detected after
the addition of 5 equiv. of FÀ.
To determine the binding ratios between gold(I) acetylide
complexes 3a–3d and anions, Job’s plot analyses were carried
out. Fig. 5 shows the Job’s plots of 3b with ClÀ, BrÀ, IÀ and OAcÀ
in CDCl3. A plot of the changes in N–H chemical shift versus X3b
(X3b = [3b]/([anion] + [3b])) shows a break point at a molar ratio of
ca. 0.5, indicative of a 1 : 1 complexation stoichiometry.
Using the 1 : 1 binding model, the anion-binding constants
of complexes 3a–3d were obtained by nonlinear least-square fits of
Fig. 4 (a) 1H NMR spectral changes of 3a upon addition of ClÀ. (b) The
corresponding binding plot (the shifts in the signal of the amide proton Ha as
a function of [ClÀ] and the theoretical fit for the 1 : 1 binding of 3a with ClÀ).
Fig. 5 Job’s plots of complex 3b with ClÀ (K), BrÀ (m), IÀ (E) and OAcÀ
(’) in CDCl3 ([3b] + [anion] = 5.0 Â 10À3 mol dmÀ3).
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a
Table 4 Binding constants of 3a–3d for anions in CDCl3
Complex
FÀ
ClÀ
OAcÀ
BrÀ
IÀ
b
b
3a
3b
3c
3d
126.40 Æ 6.13
61.00 Æ 5.54
15.02 Æ 1.42
15.56 Æ 1.65
77.35 Æ 7.80
47.28 Æ 2.38
7.18 Æ 1.11
8.02 Æ 1.28
86.71 Æ 3.76
41.46 Æ 1.84
6.87 Æ 0.83
8.95 Æ 1.29
40.96 Æ 2.56
30.53 Æ 3.73
24.87 Æ 3.57
4.85 Æ 0.84
b
b
a
b
Binding constants were determined by a 1 : 1 model using the nonlinear fitting method. Chemical shifts were not suitable for the accurate
measurement of binding constants.
the shifts of the amide N–H (Ha) signals versus the concentration of
the added anions. The binding constants (K) for different anions
are summarized in Table 4. In general, the binding constants of the
different complexes for the same anion are in the order R = NO2
(3a) 4 CF3 (3b) 4 H (3c) E OCH3 (3d), which is in line with the
decreasing electron-withdrawing abilities of the R substituents on
the acetylide ligand. This could be rationalized by the fact that the
interactions between complexes (3a–3d) and anions are hydrogen
bonds, as stronger electron-withdrawing groups could give rise to
Fig. 6 Colors of the solutions of: (a) 3a in CDCl3, (b) 3a + 10 eq. FÀ in
stronger hydrogen bond acceptors, which in turn could form
CDCl3, (c) 3a in DMSO-d6, (d) 3a + 10 eq. FÀ in DMSO-d6. The concen-
stronger hydrogen bonds. The K values for the same complex with
tration of 3a is 5.0 Â 10À3 mol dmÀ3
.
the various anions are in the order ClÀ 4 OAcÀ E BrÀ 4 IÀ (FÀ 4
ClÀ 4 OAcÀ E BrÀ 4 IÀ for 3c), which is almost in line with the
decreasing of the basicity of the anions (FÀ 4 OAcÀ 4 ClÀ
4
À 63,64
(Fig. S65, ESI†), suggesting the formation of HF2
.
These
BrÀ 4 IÀ). The ClÀ 4 OAcÀ order could be due to the mismatching
between the mono hydrogen bond donor N–H and the Y-shape
OAcÀ (two hydrogen bond donor) anion.
results indicate the deprotonation of the amide N–H of 3a upon
addition of FÀ in DMSO-d6.
We also examined the color change of complex 3a with different
anions in DMSO. Except for with FÀ, no significant color change
could be observed (Fig. S66 and S67, ESI†). Thus, 3a shows a
selective color change towards FÀ in DMSO. Considering this
selective colour change, the anion-sensing properties of complexes
3b–3d with different anions were also examined in various solvents.
However, no significant color changes were observed.
To confirm the reliability of our results regarding the order
of the affinities of the gold(I) acetylide complexes 3a–3d for
anions, the anion-binding constants of the acetylide ligands,
HCRCC6H4NHC(O)C6H4–R-4 (R = NO2 (4a), CF3 (4b), H (4c),
and OMe (4d)), were also determined (Fig. S46–S63 and Table S2,
ESI†). For the same anion, the binding constants of the acetylide
ligands are in the order R = NO2 (4a) 4 CF3 (4b) 4 H (4c) E OCH3
(4d). For the same ligand, the K values for the various anions are in
the order ClÀ 4 OAcÀ E BrÀ 4 IÀ. These orders are in line with
those observed for complexes 3a–3d. In general, the acetylide
ligands 4a–4d have larger anion-binding constants than their
corresponding gold(I) acetylide complexes 3a–3d in CDCl3.
3. Conclusions
In this work, amide based gold(I) acetylide complexes 3a–3d
have been synthesized and characterized. Complexes 3b–3d show
luminescence both in the solid state and in degassed THF solutions
at 298 K. In CDCl3, the binding constants of 3a–3d for the same
anion are in the order R = NO2 (3a) 4 CF3 (3b) 4 H (3c) E OCH3
(3d). For the same complex, the binding constants follow the
order ClÀ 4 OAcÀ E BrÀ 4 IÀ. In DMSO, 3a shows a selective
color change towards FÀ. This makes the naked eye detection
of FÀ possible. We envisage that this class of gold(I) complexes
could have potential applications in life science and environ-
mental science by using water-soluble auxiliary ligands.
The interaction of 3a with FÀ was investigated in different
solvents. Fig. S23 (ESI†) shows the 1H NMR spectral changes of
3a in CDCl3 upon addition of FÀ, which are quite different from
those of 3a with ClÀ in CDCl3 (Fig. 4(a)). When 0.2 equiv. of FÀ
was added to the CDCl3 solution of 3a, the signal of the N–H
proton disappeared rapidly and the aromatic proton signals Hb
and Hc showed slight downfield shifts. During the addition of
FÀ, the color of the solution of 3a in CDCl3 changed from light
yellow to bright yellow (Fig. 6). On the other hand, when 10 equiv.
of FÀ was added into the solution of 3a in DMSO-d6, the solution
showed a dramatic color change from light yellow to dark red
4. Experimental
4.1. Materials and reagents
1
(Fig. 6). Fig. S64(a) (ESI†) shows the H NMR spectrum of 3a in
DMSO-d6 upon addition of 10 equiv. of FÀ. The signal of the
N–H proton again disappeared and a distinct triplet centered at Ph3PAuCl65 and 4-[(trimethylsilyl)ethynyl]aniline66 were synthesized
16.08 ppm ( J = 1À2063H,64z) appeared, which was attributed to the according to literature procedures. 4-Nitrobenzoyl chloride was
formation of HF2
.
In addition, its 19F NMR spectrum also purchased from TCI. 4-Iodoaniline, benzoyl chloride and tetra-n-
displayed a distinct doublet centered at À143.13 ppm ( J = 117 Hz) butylammonium chloride hydrate were obtained from Alfa-Aesar.
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4-Methoxybenzoyl and 4-trifluoromethylbenzoyl chloride were 0.26 (s, 9H, CH3). IR (KBr, cmÀ1): n = 3318 (N–H), 2154 (CRC),
purchased from J&K. Tetra-n-butylammonium fluoride hydrate 1660 (CQO). Anal. calcd for C18H18N2O3Si (%): C, 63.88; H, 5.36;
and tetra-n-butylammonium acetate were obtained from Sigma- N, 8.28. Found: C, 64.03; H, 5.37; N, 8.31.
Aldrich. All reactions were carried out under anhydrous and
(CH3)3SiCRCC6H4NHC(O)C6H4–CF3-4 (2b). To a solution of
anaerobic conditions using standard Schlenk techniques under
4-[(trimethylsilyl)ethynyl]aniline (134.7 mg, 0.65 mmol) and
nitrogen. All solvents were purified and distilled using standard
4-trifluorobenzoyl chloride (121.6 mg, 0.64 mmol) in CHCl3
procedures before use. All other reagents were of analytical
was added triethylamine (0.8 mL). The mixture was heated at
grade and were used as received.
reflux for 18 h. The solvent was removed under reduced
4.2. Physical measurements and instrumentation
pressure and the residue was washed with water and n-hexane
to yield a pale incarnadine solid. Yield: 132.3 mg, 57%. 1H NMR
(300 MHz, CDCl3, 298 K): d = 7.94 (d, 2H, J = 8 Hz, aromatic ring),
7.85 (s, 1H, NH), 7.73 (d, 2H, J = 8 Hz, aromatic ring), 7.59 (d, 2H,
J = 8 Hz, aromatic ring), 7.46 (d, 2H, J = 9 Hz, aromatic ring), 0.26
(s, 9H, CH3). IR (KBr, cmÀ1): n = 3432 (N–H), 2162 (CRC), 1657
(CQO). Anal. calcd for C19H18F3NOSi (%): C, 63.14; H, 5.02; N,
3.88. Found: C, 63.40; H, 5.03; N, 3.90.
Chemical shifts (d, ppm) were reported relative to tetramethyl-
silane for 1H NMR, 85% H3PO4 for 31P NMR, and NaF (d =
À122.4) for 19F NMR on a Varian Mercury-Plus 300 spectro-
meter. Electronic absorption spectra were measured on a
PGENERAL TU1901 UV-vis spectrophotometer. Emission spectra
were obtained on a FLSP920 fluorescence spectrophotometer.
Solution samples for emission spectra were degassed by four
freeze–pump–thaw cycles.
(CH3)3SiCRCC6H4NHC(O)C6H5 (2c). To a solution of 4-[(tri-
methylsilyl)ethynyl]aniline (101.4 mg, 0.54 mmol) and benzoyl
chloride (76.6 mg, 0.54 mmol) in CHCl3 was added triethyl-
amine (0.8 mL). The mixture was heated at reflux for 18 h. The
solvent was removed under reduced pressure and the residue
was washed with water and n-hexane to yield a yellow solid.
Yield: 95.5 mg, 61%. 1H NMR (300 MHz, CDCl3, 298 K): d =
7.85–7.82 (m, 3H, NH + aromatic ring), 7.59 (d, 2H, J = 9 Hz,
aromatic ring), 7.54–7.44 (m, 5H, aromatic ring), 0.25 (s, 9H,
CH3). IR (KBr, cmÀ1): n = 3270 (N–H), 2156 (CRC), 1647
(CQO). Anal. calcd for C18H19NOSi (%): C, 73.68; H, 6.53; N,
4.77. Found: C, 73.38; H, 6.54; N, 4.78.
4.3. Crystal structure determination
Crystals of 3a were grown by diffusion of diethyl ether into a
THF solution of 3a. Selected single crystals of 3a were used for
data collection on a Bruker SMART 1000 CCD diffractometer
with graphite monochromatized Mo-Ka radiation (l = 0.710 Â
73 Å) at 110 K. An empirical absorption correction was applied
using the SADABS program. The structures were solved by
direct methods and refined by full-matrix least-squares based
on F2 using the SHELXTL program package.67 CCDC 1013703
contains the supplementary crystallographic data for 3a.
4.4. Titrations and Job’s plots
(CH3)3SiCRCC6H4NHC(O)C6H4–OMe-4 (2d). To a solution of
1
For a typical H NMR titration experiment, 1 mL aliquots of a 4-[(trimethylsilyl)ethynyl]aniline (104.9 mg, 0.55 mmol) and
tetra-n-butylammonium salt (1.00 Â 10À3 mol dmÀ3 in CDCl3) 4-methoxybenzoyl (94.4 mg, 0.55 mmol) in CHCl3 was added
were added into a 0.5 mL solution of the gold(I) acetylide triethylamine (0.8 mL). The mixture was heated at reflux for
complex in CDCl3 (5.00 Â 10À3 mol dmÀ3) via syringe, and 18 h. The solvent was removed under reduced pressure and the
the 1H NMR spectral changes were recorded by a Varian residue was washed with water and n-hexane to yield a pale
1
Mercury-Plus 300 spectrometer at 298 K. The binding constant yellow solid. Yield: 119.4 mg, 67%. H NMR (300 MHz, CDCl3,
K values were determined by nonlinear fitting using a 1 : 1 298 K): d = 7.81–7.77 (m, 3H, NH + aromatic ring), 7.57 (d, 2H,
model. Job’s plots were obtained from a series of solutions in J = 8 Hz, aromatic ring), 7.43 (d, 2H, J = 8 Hz, aromatic ring),
which the fraction of the corresponding anions varied, keeping 6.93 (d, 2H, J = 9 Hz, aromatic ring), 3.85 (s, 3H, OCH3), 0.25
the total concentration (complexes and anions) constant. The (s, 9H, CH3). IR (KBr, cmÀ1): n = 3436 (N–H), 2152 (CRC), 1649
maxima of the plots indicated the binding stoichiometry of the (CQO). Anal. calcd for C19H21NO2Si (%): C, 70.55; H, 6.54; N,
complexes with anions.
4.33. Found: C, 70.61; H, 6.55; N, 4.34.
4.5.2 Synthesis of gold(I) acetylide complexes 3a–3d
Ph3PAuCRCC6H4NHC(O)C6H4–NO2-4 (3a). To a mixture of
Ph3PAuCl (51.0 mg, 0.1031 mmol) and 2a (34.9 mg, 0.1031 mmol) in
4.5. Synthesis
4.5.1 Synthesis of acetylide ligands 2a–2d
(CH3)3SiCRCC6H4NHC(O)C6H4–NO2-4 (2a). To a solution of CH2Cl2 was added KFÁ2H2O (19.2 mg, 0.2040 mmol) in methanol
4-[(trimethylsilyl)ethynyl]aniline (100.8 mg, 0.53 mmol) and dropwise. The mixture was stirred overnight in the dark. After
4-nitromethylbenzoyl chloride (99.8 mg, 0.54 mmol) in CHCl3 evaporation to dryness, the solid residue was extracted with THF.
was added triethylamine (0.8 mL). The mixture was heated at Subsequent diffusion of diethyl ether into the concentrated THF
1
reflux for 18 h. The solvent was removed under reduced solution gave light yellow crystals. Yield: 53.8 mg, 72%. H NMR
pressure and the residue was washed with water and n-hexane (300 MHz, CDCl3, 298 K): d = 8.31 (d, 2H, J = 9 Hz, aromatic ring),
to yield a pale yellow solid. Yield: 116.3 mg, 65%. 1H NMR 8.00 (d, 2H, J = 9 Hz, aromatic ring), 7.84 (s, 1H, NH), 7.56–7.40 (m,
(300 MHz, CDCl3, 298 K): d = 8.31 (d, 2H, J = 9 Hz, aromatic ring), 19H, aromatic ring). 31P NMR (CDCl3, 298 K): d = 43.27. IR (KBr,
8.00 (d, 2H, J = 9 Hz, aromatic ring), 7.97 (s, 1H, NH), 7.59 (d, 2H, cmÀ1): n = 3389 (N–H), 1674 (CQO). Anal. calcd for C33H24AuN2O3P
J = 9 Hz, aromatic ring), 7.47 (d, 2H, J = 9 Hz, aromatic ring), (%): C, 54.71; H, 3.34; N, 3.87. Found: C, 54.55; H, 3.88; N, 3.87.
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014
New J. Chem., 2014, 38, 6168--6175 | 6173

NJC
Ph3PAuCRCC6H4NHC(O)C6H4–CF3-4 (3b). To a mixture of
Paper
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Ph3PAuCl (51.3 mg, 0.1037 mmol) and 2b (37.6 mg, 0.1040 mmol) in
CH2Cl2 was added KFÁ2H2O (19.5 mg, 0.2072 mmol) in methanol
dropwise. The mixture was stirred overnight in the dark. After
evaporation to dryness, the solid residue was extracted with
CH2Cl2. Subsequent diffusion of diethyl ether into the
concentrated CH2Cl2 solution gave pale yellow crystals. Yield:
40.1 mg, 52%. 1H NMR (300 MHz, CDCl3, 298 K): d = 7.95 (d, 2H,
J = 8 Hz, aromatic ring), 7.77 (s, 1H, NH), 7.73 (d, 2H, J = 8 Hz,
aromatic ring), 7.57–7.40 (m, 19H, aromatic ring). 31P NMR
(CDCl3, 298 K): d = 43.31. IR (KBr, cmÀ1): n = 3432 (N–H), 1666
(CQO). Anal. calcd for C34H24AuF3NOP (%): C, 54.63; H, 3.24; N,
1.87. Found: C, 54.50; H, 3.24; N, 1.86.
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Ph3PAuCRCC6H4NHC(O)C6H5 (3c). To a mixture of Ph3PAuCl
(55.6 mg, 0.1124 mmol) and 2c (34.5 mg, 0.1175 mmol) in
CH2Cl2 was added KFÁ2H2O (24.8 mg, 0.2645 mmol) in methanol
dropwise. The mixture was stirred overnight in the dark. After
evaporation to dryness, the solid residue was extracted with THF.
Subsequent diffusion of diethyl ether into the concentrated THF
solution gave yellow crystals. Yield: 51.4 mg, 67%. 1H NMR
(300 MHz, CDCl3, 298 K): d = 7.83 (d, 2H, J = 7 Hz, aromatic
ring), 7.77 (s, 1H, NH), 7.57–7.40 (m, 22H, aromatic ring). 31P
NMR (CDCl3, 298 K): d = 43.32. IR (KBr, cmÀ1): n = 3434 (N–H),
1657 (CQO). Anal. calcd for C33H25AuNOP (%): C, 58.33; H, 3.71;
N, 2.06. Found: C, 58.35; H, 3.72; N, 2.07.
Ph3PAuCRCC6H4NHC(O)C6H4–OMe-4 (3d). To a mixture of
Ph3PAuCl (51.8 mg, 0.1047 mmol) and 2d (34.5 mg, 0.1067 mmol)
in CH2Cl2 was added KFÁ2H2O (24.9 mg, 0.2645 mmol) in
methanol dropwise. The mixture was stirred overnight in the
dark. After evaporation to dryness, the solid residue was
extracted with CH2Cl2. Subsequent diffusion of diethyl ether
into the concentrated CH2Cl2 solution gave pale yellow crystals.
Yield: 44.3 mg, 60%. 1H NMR (300 MHz, CDCl3, 298 K): d = 7.80
(d, 2H, J = 9 Hz, aromatic ring), 7.68 (s, 1H, NH), 7.57–7.40
(m, 19H, aromatic ring), 6.95 (d, 2H, J = 9 Hz, aromatic ring), 3.85
(s, 3H, CH3). 31P NMR (CDCl3, 298 K): d = 43.34. IR (KBr, cmÀ1):
n = 3430 (N–H), 1662 (CQO). Anal. calcd for C34H27AuNO2P (%):
C, 57.55; H, 3.84; N, 1.97. Found: C, 57.61; H, 3.85; N, 1.96.
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Acknowledgements
We acknowledge financial support from the National Natural
Science Foundation of China (20971131, J1103305), the Natural
Science Foundation of Guangdong Province (S2012010010566), the
Undergraduate Innovative Experiment Program of Guangdong
Province (1055812184) and Sun Yat-Sen University. We thank Dr
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