Mononuclear gold(I) acetylide complexes with urea group: Synthesis, characterization, photophysics, and anion sensing properties

Article abstract of DOI:10.1021/ic202608r

A series of mononuclear gold(I) acetylide complexes with urea moiety, R′₃PAuC≡CC₆H₄-4-NHC(O)NHC ₆H₄-4-R (R′ = cyclohexyl, R = NO₂ (2a), CF₃ (2b), Cl (2c), H (2d), CH₃ (2e), ^tBu (2f), OCH₃ (2g); R′ = phenyl, R = NO₂ (3a), OCH ₃ (3b); R′ = 4-methoxyphenyl, R = H (4a), OCH₃ (4b)), have been synthesized and characterized. The crystal structures of Ph₃PAuC≡CC₆H₄-4-NHC(O)NHC ₆H₄-4-NO₂ (3a) and (4-CH₃OC ₆H₄)₃PAuC≡CC₆H ₄-4-NHC(O)NHC₆H₅ (4a) have been determined by X-ray diffraction. Complexes 2a-2g, 3b, and 4a-4b show intense luminescence both in the solid state and in degassed THF solution at 298 K. Anion binding properties of complexes 2a-2g, 3a-3b, and 4a-4b have been studied by UV-vis and ¹H NMR titration experiments. In general, the log K values of 2a-2g with the same anion in THF depend on the substituent R on the acetylide ligand of 2a-2g: R = NO₂ (2a) > CF₃ (2b) ≥ Cl (2c) > H (2d) > CH₃ (2e) ≈ ^tBu (2f) ≥ OCH₃ (2g). Complex 2a with NO₂ group shows the dramatic color change toward F^- in DMSO, which provides an access of naked eye detection of F^-.

Full text of DOI:10.1021/ic202608r

Article
pubs.acs.org/IC
Mononuclear Gold(I) Acetylide Complexes with Urea Group:
Synthesis, Characterization, Photophysics, and Anion Sensing
Properties
Yu-Peng Zhou, Mei Zhang, Yu-Hao Li, Qi-Rui Guan, Fang Wang, Zhuo-Jia Lin, Chi-Keung Lam,
Xiao-Long Feng, 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: A series of mononuclear gold(I) acetylide
complexes with urea moiety, R′3PAuCCC6H4-4-NHC(O)-
NHC6H4-4-R (R′ = cyclohexyl, R = NO2 (2a), CF3 (2b), Cl
(2c), H (2d), CH3 (2e), tBu (2f), OCH3 (2g); R′ = phenyl, R
= NO2 (3a), OCH3 (3b); R′ = 4-methoxyphenyl, R = H (4a),
OCH3 (4b)), have been synthesized and characterized. The
crystal structures of Ph3PAuCCC6H4-4-NHC(O)NHC6H4-
4-NO2 (3a) and (4-CH3OC6H4)3PAuCCC6H4-4-NHC(O)-
NHC6H5 (4a) have been determined by X-ray diffraction.
Complexes 2a−2g, 3b, and 4a−4b show intense luminescence
both in the solid state and in degassed THF solution at 298 K.
Anion binding properties of complexes 2a−2g, 3a−3b, and
1
4a−4b have been studied by UV−vis and H NMR titration
experiments. In general, the log K values of 2a−2g with the same anion in THF depend on the substituent R on the acetylide
ligand of 2a−2g: R = NO2 (2a) > CF3 (2b) ≥ Cl (2c) > H (2d) > CH3 (2e) ≈ tBu (2f) ≥ OCH3 (2g). Complex 2a with NO2
group shows the dramatic color change toward F− in DMSO, which provides an access of naked eye detection of F−.
complexes, gold(I) complexes with d10 closed electronic shell
INTRODUCTION
Since the first anion sensor reported by Park and Simmons in
■
and linear geometry are quite important19 due to their potential
use in the area of biology,20 drugs,21 catalysis,22 OLEDs,23a and
OPL materials.23b In addition, utilization of the rich photo-
physical properties and various geometries of gold(I)
complexes as chemosensors has been developed recently.24
The acetylide ligands with the structure of unsaturated sp C-
atom and strong σ-donating center lead to the rich structure
diversity as well as unique optical and electronic properties to
the metal complexes,25 which could provide the potential
applications in nonlinear optics, liquid crystals, luminescence,
molecule wires, and ion sensors.18c,24,25a,26−29 Yam and co-
workers have synthesized Au(I)−Cu(I) acetylide complexes
containing urea group and studied the sensing properties
toward anions.18c Other metal acetylide complexes, such as
platinum(II)28 and ruthenium(II) acetylide29 complexes with
nonurea moieties, have also been used as the anion sensors.
We have a long-term interest in studying the relationship
between the structures and photophysical properties of metal
acetylide complexes.30 To extend our work on the structures
and photophysical properties of gold(I) acetylide complexes, in
this work, a series of mononuclear gold(I) acetylide complexes
1968,1 anion sensors have attracted much attention because of
their potential applications in the environment2 and in biology.3
For an anion sensor, it usually consists of two main moieties:
recognition unit and sensing unit. The recognition unit could
interact with anions by noncovalent interactions, such as a
hydrophobic effect,4a metal or Lewis acid coordination,4b
electrostatic interactions,4c anion−π interactions,5 halogen
bonding,6 and hydrogen bonding.7 Various recognition units,
for example, thiourea,7a urea,7 amide,8 and guandinium,9 have
been utilized to interact with anions. Among them, the urea
group is one of the most frequently used recognition units
because it has unique geometry with two N−H bonds and its
modification can be easily carried out by organic synthesis.7b
Fabbrizzi,10 Gunnlaugsson,11 Gale,12 and other groups13 have
reported the synthesis of various urea-based organic anion
sensors.
In addition to an organic anion sensing unit, metal complexes
have been used as anion sensors due to their various properties
like redox and luminescence, which could provide the various
accesses of sensing.14 The incorporation of ferrocene,15
ruthenium(II) polypyridyl,16 terbium(III) cyclen,17 gold(I)
thiolate,18a,b or gold(I)−copper(I) acetylide18c into the urea
moiety has been reported in the literature. Among these metal
Received: December 5, 2011
Published: April 9, 2012
© 2012 American Chemical Society
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Scheme 1. Synthetic Route of Gold(I) Acetylide Complexes 2a−2g, 3a−3b, and 4a−4b
C19H19F3N2OSi (%): C, 60.62; H, 5.09; N, 7.44. Found: C, 60.47; H,
5.28; N, 7.34.
with urea group, R′3PAuCCC6H4-4-NHC(O)NHC6H4-4-R
(R′ = cyclohexyl, R = NO2 (2a), CF3 (2b), Cl (2c), H (2d),
CH3 (2e), Bu (2f), OCH3 (2g); R′ = phenyl, R = NO2 (3a),
1c. Yield: 365 mg, 94%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ
= 8.90 (s, 1 H, NH), 8.86 (s, 1 H, NH), 7.46 (d, J = 7 Hz, 2 H,
aromatic ring), 7.43 (d, J = 7 Hz, 2 H, aromatic ring), 7.34 (d, J = 7
Hz, 2 H, aromatic ring), 7.31 (d, J = 7 Hz, 2 H, aromatic ring), 0.21 (s,
9 H, Si(CH3)3). ESI-MS: m/z = 341 [M − H]−. Anal. Calcd for
C18H19ClN2OSi (%): C, 63.05; H, 5.59; N, 8.17. Found: C, 62.91; H,
5.55; N, 8.13.
t
OCH3 (3b); R′ = 4-methoxyphenyl, R = H (4a), OCH3 (4b);
Scheme 1), have been synthesized and characterized. The
crystal structures of Ph3PAuCCC6H4-4-NHC(O)NHC6H4-
4-NO2 (3a) and (4-CH3OC6H4)3PAuCCC6H4-4-NHC(O)-
NHC6H5 (4a) were determined by X-ray diffraction. We
envisaged that if the photophysical properties of these gold(I)
acetylide complexes could be changed when they interact with
anions through hydrogen bonds between the urea N−H of the
complexes and anions, they could be used as anion sensors. The
effect of structure, including the substituent R on the acetylide
ligand of the complex as well as the auxiliary phosphine ligand,
on the binding ability of the gold(I) acetylide complexes with
anions has also been studied.
1d. Yield: 132 mg, 89%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ
= 8.87 (s, 1 H, NH), 8.72 (s, 1 H, NH), 7.44 (d, J = 8 Hz, 2 H,
aromatic ring), 7.41 (d, J = 8 Hz, 2 H, aromatic ring), 7.34 (d, J = 9
Hz, 2 H, aromatic ring), 7.26 (dd, J1 = 8 Hz, J2 = 8 Hz, 2 H, aromatic
ring), 6.96 (dd, J1 = 8 Hz, J2 = 8 Hz, 1 H, aromatic ring), 0.22 (s, 9 H,
Si(CH3)3). ESI-MS: m/z = 308 [M − H]−. Anal. Calcd for
C18H20N2OSi (%): C, 70.09; H, 6.54; N, 9.08. Found: C, 69.81; H,
6.39; N, 9.03.
1e. Yield: 354 mg, 95%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ
= 8.79 (s, 1 H, NH), 8.57 (s, 1 H, NH), 7.42 (d, J = 9 Hz, 2 H,
aromatic ring), 7.32 (m, 4 H, aromatic ring), 7.06 (d, J = 8 Hz, 2 H,
aromatic ring), 2.23 (s, 3 H, CH3), 0.21 (s, 9 H, Si(CH3)3). ESI-MS:
m/z = 321 [M − H]−. Anal. Calcd for C19H22N2OSi (%): C, 70.77; H,
6.88; N, 8.69. Found: C, 70.59; H, 6.84; N, 8.62.
EXPERIMENTAL SECTION
■
Materials and Reagents. 4-[(Trimethylsilyl)ethynyl]aniline31 and
R′3PAuCl (R′ = cyclohexyl, phenyl, and 4-methoxyphenyl)32 were
synthesized according to literature procedures. 4-Nitrophenyl
isocyanate, p-tolyl isocyanate, 4-methoxyphenyl isocyanate, and tetra-
n-butylammonium phosphate were purchased from Acros. Tetra-n-
butylammonium fluoride hydrate and tetra-n-butylammonium acetate
were obtained from Sigma-Aldrich. 4-Chlorophenyl isocyanate, tetra-n-
butylammonium nitrate, and tetra-n-butylammonium chloride hydrate
were purchased from Alfa-Aesar. 4-(Trifluoromethyl)phenyl isocya-
nate, 4-tert-butylphenyl isocyanate, and tetra-n-butylammonium bro-
mide were obtained from J&K. Phenyl isocyanate was purchased from
Aladdin. All reactions were carried out under anhydrous and anaerobic
conditions using standard Schlenk techniques under nitrogen.
Synthesis. General procedure for the synthesis of 1a−1g: To a
solution of 4-[(trimethylsilyl)ethynyl]aniline in CH2Cl2 was added 1
equiv of the corresponding isocynate in CH2Cl2. The mixture was
heated to reflux for 24 h. The solvent was removed under reduced
pressure, and the residue was washed with n-hexane to yield yellow
solids.
1f. Yield: 379 mg, 92%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ
= 8.81 (s, 1 H, NH), 8.61 (s, 1 H, NH), 7.43 (d, J = 9 Hz, 2 H,
aromatic ring), 7.34 (m, 4 H, aromatic ring), 7.27 (d, J = 9 Hz, 2 H,
aromatic ring), 1.26 (s, 9 H, C(CH3)3), 0.22 (s, 9 H, Si(CH3)3). ESI-
MS: m/z = 363 [M − H]−. Anal. Calcd for C22H28N2OSi (%): C,
72.48; H, 7.74; N, 7.68. Found: C, 72.48; H, 7.74; N, 7.59.
1g. Yield: 123 mg, 78%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ
= 8.80 (s, 1 H, NH), 8.54 (s, 1 H, NH), 7.42 (d, J = 9 Hz, 2 H,
aromatic ring), 7.32 (d, J = 9 Hz, 4 H, aromatic ring), 6.85 (d, J = 9
Hz, 2 H, aromatic ring), 3.71 (s, 3 H, OCH3), 0.22 (s, 9 H, Si(CH3)3).
ESI-MS: m/z = 337 [M − H]−. Anal. Calcd for C19H22N2O2Si (%): C,
67.42; H, 6.55; N, 8.28. Found: C, 67.28; H, 6.59; N, 8.30.
General procedure for the synthesis of 2a−2g, 3a−3b, and 4a−4b
follows: To a mixture of R′3PAuCl (R′ = cyclohexyl, phenyl, or 4-
methoxyphenyl) and 1 equiv of the corresponding acetylide ligand in
CH2Cl2 was added 2 equiv of KF·2H2O 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 the pale yellow
crystals or solids.
1a. Yield: 164 mg, 75%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ
= 9.44 (s, 1 H, NH), 9.08 (s, 1 H, NH), 8.15 (d, J = 9 Hz, 2 H,
aromatic ring), 7.65 (d, J = 9 Hz, 2 H, aromatic ring), 7.45 (d, J = 9
Hz, 2 H, aromatic ring), 7.35 (d, J = 9 Hz, 2 H, aromatic ring), 0.20 (s,
9 H, Si(CH3)3). ESI-MS: m/z = 352 [M − H]−. Anal. Calcd for
C18H19N3O3Si (%): C, 61.17; H, 5.42; N, 11.89. Found: C, 61.10; H,
5.50; N, 11.60.
2a. Yield: 21 mg, 23%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ =
9.51 (s, 1 H, NH), 9.01 (s, 1 H, NH), 8.16 (d, J = 9 Hz, 2 H, aromatic
ring), 7.66 (d, J = 9 Hz, 2 H, aromatic ring), 7.36 (d, J = 9 Hz, 2 H,
aromatic ring), 7.19 (d, J = 9 Hz, 2 H, aromatic ring), 2.14−1.27 (m,
33 H, cyclohexyl). 31P NMR (121 MHz, DMSO-d6, 298 K): δ = 58.23.
IR (KBr, cm−1): ν = 3298 (N−H), 2054 (CC), 1715 (CO). ESI-
MS: m/z = 756 [M − H]−. Anal. Calcd for C33H43AuN3O3P (%): C,
52.31; H, 5.72; N, 5.55. Found: C, 52.02; H, 5.72; N, 5.36.
1
1b. Yield: 56 mg, 79%. H NMR (300 MHz, DMSO-d6, 298 K): δ
= 9.12 (s, 1 H, NH), 8.97 (s, 1 H, NH), 7.59 (m, 4 H, aromatic ring),
7.42 (d, J = 9 Hz, 2 H, aromatic ring), 7.33 (d, J = 9 Hz, 2 H, aromatic
ring), 0.19 (s, 9 H, Si(CH3)3). 19F NMR (228 MHz, DMSO-d6, 298
K): δ = −60.76 (s). ESI-MS: m/z = 376 [M − H]−. Anal. Calcd for
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1
2b. Yield: 18 mg, 38%. H NMR (300 MHz, DMSO-d6, 298 K): δ
= 9.08 (s, 1 H, NH), 8.81 (s, 1 H, NH), 7.62 (m, 4 H, aromatic ring),
7.32 (d, J = 7 Hz, 2 H, aromatic ring), 7.18 (d, J = 7 Hz, 2 H, aromatic
ring), 2.10−1.27 (m, 33 H, cyclohexyl). 31P NMR (121 MHz, DMSO-
d6, 298 K): δ = 58.21. 19F NMR: (228 MHz, DMSO-d6, 298 K): δ =
−60.82. IR (KBr, cm−1): ν = 3295 (N−H), 2104 (CC), 1714 (C
O). ESI-MS: m/z = 779 [M − H]−. Anal. Calcd for C34H43AuF3N2OP
(%): C, 52.31; H, 5.55; N, 3.59. Found: C, 52.47; H, 5.60; N, 3.57.
2c. Yield: 19 mg, 20%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ =
8.83 (s, 1 H, NH), 8.74 (s, 1 H, NH), 7.45 (d, J = 9 Hz, 2 H, aromatic
ring), 7.31 (m, 4 H, aromatic ring), 7.16 (d, J = 9 Hz, 2 H, aromatic
ring), 2.13−1.20 (m, 33 H, cyclohexyl). 31P NMR (121 MHz, DMSO-
d6, 298 K): δ = 58.22. IR (KBr, cm−1): ν = 3293 (N−H), 2104 (C
C), 1708 (CO). ESI-MS: m/z = 745 [M − H]−. Anal. Calcd for
C33H43AuClN2OP (%): C, 53.05; H, 5.80; N, 3.75. Found: C, 53.00;
H, 5.81; N, 3.63.
4a. Yield: 32 mg, 34%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ =
8.69 (s, 1 H, NH), 8.65 (s, 1 H, NH), 7.45−7.11 (m, 20 H, aromatic
ring), 6.95 (dd, J1 = 8 Hz, J2 = 8 Hz, 1 H, aromatic ring), 3.81 (s, 9 H,
OCH3). 31P NMR (121 MHz, DMSO-d6, 298 K): δ = 39.07. IR (KBr,
cm−1): ν = 3294 (N−H), 2046 (CC), 1714 (CO). FAB-MS: m/z
= 785 [M + H]+. Anal. Calcd for C36H32AuN2O4P (%): C, 55.11; H,
4.11; N, 3.57. Found: C, 54.83; H, 4.02; N, 3.55.
1
4b. Yield: 42 mg, 42%. H NMR (300 MHz, DMSO-d6, 298 K): δ
= 8.63 (s, 1 H, NH), 8.47 (s, 1 H, NH), 7.45−7.11 (m, 18 H, aromatic
ring), 6.85 (d, J = 9 Hz, 2 H, aromatic ring), 3.81 (s, 9 H, OCH3), 3.70
(s, 3 H, OCH3). 31P NMR (121 MHz, DMSO-d6, 298 K): δ = 39.05.
IR (KBr, cm−1): ν = 3284 (N−H), 2048 (CC), 1707 (CO). FAB-
MS: m/z = 815 [M + H]+. Anal. Calcd for C37H34AuN2O5P (%): C,
54.55; H, 4.21; N, 3.44. Found: C, 54.26; H, 4.09; N, 3.42.
Physical Measurements and Instrumentation. Chemical shifts
(δ, ppm) were reported relative to tetramethylsilane for 1H NMR, 85%
H3PO4 for 31P NMR, and NaF (δ = −122.4) for 19F NMR on a Varian
Mercury-Plus 300 spectrometer. Infrared spectra were recorded from
KBr pellets in the range 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.
Elemental analysis was performed on Elementar 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.
Solution samples for emission spectra were degassed by four freeze−
pump−thaw cycles.
Crystal Structure Determination. Crystals of 3a and 4a were
grown by diffusion of diethyl ether into THF solution of the
corresponding complexes. Selected single crystals of 3a and 4a were
used for data collection on a Bruker SMART 1000 CCD
diffractometer with graphite monochromatized Mo Kα radiation (λ
= 0.710 73 Å) at 110 K. An empirical absorption correction was
applied using the SADABS program.33 The structures were solved by
direct methods and refined by full-matrix least-squares based on F2
using the SHELXTL program package.34 CCDC 854038 and 854039
contain the supplementary crystallographic data for 3a and 4a,
respectively. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ,
U.K.; fax:(+44) 1223 336-033; or e-mail deposit@ccdc.cam.ac.uk.
Titrations and Job’s Plots. For a typical UV−vis titration
experiment, 1.5 μL aliquots of a tetra-n-butylammonium salt (1.98 ×
10−3 mol dm−3 in THF or DMSO) were added into the 3 mL solution
of the complex in THF or DMSO (1.98 × 10−5 mol dm−3 or 9.90 ×
10−6 mol dm−3) by a syringe, and the spectral changes were recorded
by a PGENERAL TU1901 UV−vis spectrophotometer at 298 K. The
volume changes after the addition of anions were kept less than 5%
(150 μL). For a typical 1H NMR titration experiment, 1 μL aliquots of
a tetra-n-butylammonium salt (1.00 × 10−1 mol dm−3 in DMSO-d6)
were added into the 0.5 mL solution of the complex in DMSO-d6
(5.00 × 10−3 mol dm−3 or 1.00 × 10−2 mol dm−3) by a 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 1:1 model.35 Job’s plots were
obtained from a series of solutions in which the fraction of the
corresponding anions varied, keeping the total concentration (the
complexes and anions) constant. The maxima of the plots indicated
the binding stoichiometry of the complexes with anions.
2d. Yield: 36 mg, 42%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ =
8.66 (s, 1 H, NH), 8.64 (s, 1 H, NH), 7.41 (d, J = 9 Hz, 2 H, aromatic
ring), 7.32 (d, J = 9 Hz, 2 H, aromatic ring), 7.25 (dd, J1 = 9 Hz, J2 = 9
Hz, 2 H, aromatic ring), 7.16 (d, J = 9 Hz, 2 H, aromatic ring), 6.94
(dd, J1 = 9 Hz, J2 = 9 Hz, 1 H, aromatic ring), 2.14−1.27 (m, 33 H,
cyclohexyl). 31P NMR (121 MHz, DMSO-d6, 298 K): δ = 58.22. IR
(KBr, cm−1): ν = 3273 (N−H), 2106 (CC), 1707 (CO). ESI-
MS: m/z = 711 [M − H]−. Anal. Calcd for C33H44AuN2OP (%): C,
55.62; H, 6.22; N, 3.93. Found: C, 55.63; H, 6.28; N, 3.85.
2e. Yield: 67 mg, 76%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ =
8.64 (s, 1 H, NH), 8.55 (s, 1 H, NH), 7.31 (d, J = 8 Hz, 2 H, aromatic
ring), 7.30 (d, J = 8 Hz, 2 H, aromatic ring), 7.15 (d, J = 8 Hz, 2 H,
aromatic ring), 7.06 (d, J = 8 Hz, 2 H, aromatic ring), 2.23 (s, 3 H,
CH3), 2.13−1.20 (m, 33 H, cyclohexyl). 31P NMR (121 MHz, DMSO-
d6, 298 K): δ = 58.22. IR (KBr, cm−1): ν = 3275 (N−H), 2106 (C
C), 1707 (CO). ESI-MS: m/z = 771 [M + EtOH − H]−. Anal.
Calcd for C34H46AuN2OP (%): C, 56.20; H, 6.38; N, 3.85. Found: C,
56.16; H, 6.32; N, 3.75.
2f. Yield: 25 mg, 27%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ =
8.62 (s, 1 H, NH), 8.56 (s, 1 H, NH), 7.33 (d, J = 9 Hz, 2 H, aromatic
ring), 7.32 (d, J = 9 Hz, 2 H, aromatic ring), 7.26 (d, J = 9 Hz, 2 H,
aromatic ring), 7.15 (d, J = 9 Hz, 2 H, aromatic ring), 2.14−1.20 (m,
42H, cyclohexyl, and C(CH3)3). 31P NMR (121 MHz, DMSO-d6, 298
K): δ = 58.22. IR (KBr, cm−1): ν = 3294 (N−H), 2108 (CC), 1709
(CO). ESI-MS: m/z = 767 [M − H]−. Anal. Calcd for
C37H52AuN2OP (%): C, 57.81; H, 6.82; N, 3.64. Found: C, 57.51;
H, 6.87; N, 3.46.
2g. Yield: 48 mg, 53%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ =
8.58 (s, 1 H, NH), 8.45 (s, 1 H, NH), 7.32 (d, J = 9 Hz, 4 H, aromatic
ring), 7.15 (d, J = 9 Hz, 2 H, aromatic ring), 6.84 (d, J = 9 Hz, 2 H,
aromatic ring), 3.70 (s, 3 H, OCH3), 2.11−1.31 (m, 33 H, cyclohexyl).
31P NMR (121 MHz, DMSO-d6, 298 K): δ = 58.22. IR (KBr, cm−1): ν
= 3275 (N−H), 2107 (CC), 1704 (CO). ESI-MS: m/z = 741 [M
− H]−. Anal. Calcd for C34H46AuN2O2P (%): C, 54.99; H, 6.24; N,
3.77. Found: C, 54.72; H, 6.19; N, 3.65.
3a. Yield: 35 mg, 39%. 1H NMR (300 MHz, DMSO-d6, 298 K): δ =
9.44 (s, 1 H, NH), 8.98 (s, 1 H, NH), 8.73 (d, J = 9 Hz, 2 H, aromatic
ring), 7.62 (d, J = 9 Hz, 2 H, aromatic ring), 7.60−7.50 (m, 15 H,
aromatic ring), 7.38 (d, J = 9 Hz, 2 H, aromatic ring), 7.24 (d, J = 9
Hz, 2 H, aromatic ring). 31P NMR (121 MHz, DMSO-d6, 298 K): δ =
42.72. IR (KBr, cm−1): ν = 3300 (N−H), 2108 (CC), 1716 (C
=
739 [M]+ . Anal. Calcd for
O). ESI-MS: m/z
C33H25AuN3O3P·CH3OH·0.25CH2Cl2 (%): C, 51.89; H, 3.75; N,
5.30. Found: C, 51.65; H, 3.69; N, 4.97.
1
3b. Yield: 19 mg, 22%. H NMR (300 MHz, DMSO-d6, 298 K): δ
= 8.62 (s, 1 H, NH), 8.46 (s, 1 H, NH), 7.60−7.50 (m, 15 H, aromatic
ring), 7.35 (d, J = 9 Hz, 2 H, aromatic ring), 7.31 (d, J = 9 Hz, 2 H,
aromatic ring), 7.20 (d, J = 9 Hz, 2 H, aromatic ring), 6.85 (d, J = 9
Hz, 2 H, aromatic ring), 3.70 (s, 3 H, OCH3). 31P NMR (121 MHz,
DMSO-d6, 298 K): δ = 42.79. IR (KBr, cm−1): ν = 3295 (N−H), 2114
(CC), 1647 (CO). ESI-MS: m/z = 723 [M − H]−. Anal. Calcd
for C34H28AuN2O2P (%): C, 56.36; H, 3.90; N, 3.87. Found: C, 56.16;
H, 3.88; N, 3.80.
RESULTS AND DISCUSSION
■
Syntheses and Characterization of Complexes 2a−2g,
3a−3b, and 4a−4b. Scheme 1 shows the synthetic route of
mononuclear gold(I) acetylide complexes 2a−2g, 3a−3b, and
4a−4b. The reaction of 4-[(trimethylsilyl)ethynyl]aniline with
the corresponding isocyanate in dichloromethane gave acetylide
ligands 1a−1g. Mononuclear gold(I) acetylide complexes 2a−
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Figure 1. Perspective view of two independent molecules of 3a with the atomic numbering scheme. Thermal ellipsoids are shown at the 50%
probability level.
2g, 3a−3b, and 4a−4b were obtained by the reaction of
R′3PAuCl (R′ = cyclohexyl, phenyl, or 4-methoxyphenyl) with
the corresponding acetylide ligands 1a−1g in a molar ratio of
1:1 in the presence of an excess of KF in dichloromethane/
methanol mixture at 298 K. The attempts to get other pure
derivatives of gold(I) acetylide complexes with PR′3 (R′ =
phenyl or 4-methoxyphenyl) were not successful. All gold(I)
acetylide complexes 2a−2g, 3a−3b, and 4a−4b gave
satisfactory elemental analyses and were characterized by
FAB, ESI mass spectrometry and IR, 1H, and 31P NMR
spectroscopy. They are air-stable in the solid state at 298 K.
The IR spectra of the gold(I) acetylide complexes 2a−2g,
3a−3b, and 4a−4b reveal the bands at 3273−3300, 2046−
2114, and 1647−1716 cm−1, characteristic of the ν(N−H),
ν(CC), and ν(CO) stretches of acetylide ligands,
1
respectively. The H NMR spectra of complexes 2a−2g, 3a−
Figure 2. Perspective view of two independent molecules of 4a with
the atomic numbering scheme. Thermal ellipsoids are shown at the
30% probability level.
3b, and 4a−4b in DMSO-d6 display two peaks at ca. δ 8.45−
9.51 ppm, which are assigned as the resonances of the urea N−
H of the acetylide ligand. For 2a−2g, the chemical shifts of
these peaks are in the following order: 2a > 2b > 2c > 2d ≥ 2e
The Au−C (1.990(9)−2.041(9) Å) and CC (1.180(11)−
≈ 2f ≥ 2g, which is in line with the decreasing of the electron-
1.206(7) Å) distances for 3a and 4a also resemble those in
withdrawing ability of R on the acetylide ligand. In addition, the
analogous gold(I) acetylide complexes.30a,36 For 3a, there are
chemical shifts at ca. δ 6.84−8.73 ppm are attributed to the
intermolecular π···π interactions (C(7A)···C(8AA) ∼3.348 Å;
resonances of the protons on the aromatic rings of the acetylide
C(8A)···C(7AA) ∼3.348 Å; C(40A)···C(41B) ∼3.365 Å;
and arylphosphine ligands (or acetylide ligands only). The 31P
C(41A)···C(40B) ∼3.365 Å) between two aromatic rings of
NMR spectra of the gold(I) acetylide complexes 2a−2g, 3a−
acetylide ligands of two molecules (Figure S1, Supporting
3b, and 4a−4b in DMSO-d6 show a singlet at ca. δ 58.22, 42.72,
Information). In addition, intermolecular N−H···π(CC)
and 39.07 ppm, respectively.
interactions between the urea N−H and CC of two
X-ray Crystal Structure Determination of 3a and 4a.
The crystal structures of the gold(I) acetylide complexes 3a and
molecules of 3a are observed (H(1AA)···C(1AA) ∼2.926 Å;
H(1AA)···C(2AA) ∼2.646 Å; H(4BA)···C(34B) ∼3.149 Å;
4a have been determined by X-ray crystallography, and their
H(4BA)···C(35B) ∼2.895 Å; ∠N(4A)−H(4BA)−C(34B)
perspective drawings are shown in Figures 1 and 2, respectively.
∼123.58°; ∠N(1A)−H(1AA)−C(1AA) ∼144.97°; ∠N(1A)−
The crystallographic data as well as selected bond distances and
angles are listed in Tables 1 and 2, respectively. For 4a, the
H(1AA)−C(2AA) ∼136.64°; ∠N(4A)−H(4BA)−C(35B)
∼119.52°) (Figure S1, Supporting Information). The oxygen
phenyl group and the amide nitrogen atom (N2 and N2A) on
the urea moiety of the acetylide ligand are disordered over two
positions with a 50:50 occupancy. The Au(I) coordination
geometry in 3a and 4a are nearly linear with the P−Au−C
angles 174.0(2)−177.51(15)°. The Au−P bond distances for
3a and 4a (2.2707(13)−2.281(2) Å) are similar to those
reported for other gold(I) arylacetylide complexes with
triphenylphosphine or tricyclohexylphosphine ligand.30a,36
atom of the nitro group and the nitrogen atom of the urea
group show weak interactions with the gold atoms of 3a
(Au(1A)···O(5A) ∼3.396 Å; Au(1A)···N(2AA) ∼4.067 Å;
Au(2A)···O(3A) ∼3.363 Å; Au(2A)···N(5B) ∼3.881 Å). There
are intermolecular hydrogen bonding interactions between
hydrogen atom (H5BB) of urea group and oxygen atom (O2A)
of nitro group in the acetylide ligands of 3a (Figure S1,
Supporting Information). The hydrogen bonding parameters of
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288, 301, and 345 nm, which are red-shifted compared to those
of the free acetylide ligand 1a. The red-shift could come from
the orbital interaction between the acetylide ligand and Au 5d
orbitals.36f The spacings of adjacent absorption maxima of 2a at
263−301 nm are ca. 1500 and 1800 cm−1. Thus, the absorption
bands of complex 2a at 263−301 nm are assigned as the π →
π* transitions of the acetylide ligands. The low-energy
absorption band of 2a at 345 nm could be due to the charge-
transfer transition from the amide to the NO2 group of the
acetylide ligand.18b The absorption spectra of non-nitro-
derivatives 2b−2g, 3b, and 4a−4b in THF at 298 K exhibit
one shoulder (ca. 264 nm) and three bands (ca. 279, 293, and
310 nm) (Figures S4−S6, Supporting Information). The
vibrational spacings are in two kinds of wavenumbers, ca.
1700 and 2000 cm−1, which are ascribed to ν(CO) and
ν(CC), respectively. These absorption bands are assigned to
1(ππ*) transition involving carbonyl and acetylenic units of the
acetylide ligand.
Excitation of complexes 2a−2g, 3b, and 4a−4b both in the
solid state and in THF solution at λ > 290 nm produces
luminescence in the visible light regime. Figure 3 displays the
emission spectrum of 2d in the solid state at 298 K (for the
emission spectra of 2a, 2b, and 2g in the solid state at 298 K,
see Figures S7 and S8 (Supporting Information)). It shows
vibronic fine structures with the progressional spacings of four
different frequencies, ca. 1100, 1600, 1700, and 2000 cm−1,
which are attributed to the phenyl ring deformation, symmetric
phenyl ring stretch, CO stretching, and CC stretching
frequencies of the ground state, respectively. Similar spacings
were observed for other gold(I) acetylide complexes.30a Except
for 3a, the gold(I) acetylide complexes studied in this paper in
THF at 298 K exhibit blue-green emission. Two emission
maxima are observed at ca. 443 and 476 nm with the vibrational
progressional spacing of approximately 1600 cm−1 (for the
emission spectra of 2a−2g, 3b, and 4a−4b in THF at 298 K,
see Figures S9 and S10 (Supporting Information)). The
observed large Stokes shifts together with long lifetimes in the
microsecond range of the emission suggest the origin of the
emission has triplet parentage. Thus, the lowest-lying emissive
state of complexes 2b−2g, 3b, and 4a−4b is assigned as the
3(ππ*) excited state of the acetylide ligand, which is promoted
through the spin−orbit coupling due to the introduction of
gold atom.30a,b The broad emission band of 2a in the solid state
Table 1. Crystallographic Data for 3a and 4a
3a
4a
formula
M (g/mol)
cryst syst
space group
a (Å)
C66H50Au2N6O6P2
1478.99
C72H64Au2N4O8P2
1569.16
triclinic
triclinic
P1
P1
̅
̅
12.4658(13)
13.2527(14)
17.6175(18)
85.927(2)
72.613(2)
87.304(2)
2769.5(5)
2
11.878(2)
15.349(3)
20.733(4)
101.74(3)
97.22(3)
90.81(3)
3668.7(13)
2
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
V (Å3)
Z
Dc (g cm−3
)
1.774
1.422
T (K)
110(2)
110(2)
reflns collected
indep reflns
Rint
21 741
27 325
10 750
14 026
0.0236
0.0392
a
b
R, Rw [I > 2σ(I)]
0.0264, 0.0804
0.0592, 0.1598
1.051
GOF
1.114
a
b
R = ∑(|Fo| − |Fc|)/∑|Fo|. Rw = [∑w(|Fo| − |Fc|)2/∑w|Fo|2]1/2
.
3a are listed in Table S1 (Supporting Information). For 4a,
there are intermolecular N−H···π(CC) interactions between
the urea N−H and CC of two molecules (H(1A)···C(5B)
∼2.424 Å; H(1A)···C(6B) ∼2.682 Å; ∠N(1)−H(1A)−C(5B)
∼166.10°; ∠N(1)−H(1A)−C(6B) ∼162.91°; H(3A)···C(1A)
∼2.382 Å; H(3A)···C(2A) ∼2.921 Å; ∠N(3)−H(3A)−C(1A)
∼164.69°; ∠N(3)−H(3A)−C(2A) ∼146.08°; H(4A)···C(1A)
∼2.444 Å; H(4A)···C(2A) ∼2.668 Å; ∠N(4)−H(4A)−C(1A)
∼160.06°; ∠N(4)−H(4A)−C(2A) ∼149.67°) (Figure S2,
Supporting Information). The nearest gold···gold distance
(Au(1)···Au(2)) is 3.0145(9) Å, indicating the existence of
weak gold···gold interaction in 4a.
Electronic Absorption and Emission Spectroscopy of
Complexes 2a−2g, 3a−3b, and 4a−4b. The photophysical
data for complexes 2a−2g, 3a−3b, and 4a−4b are summarized
in Table 3. For comparison, the photophysical data of the
corresponding free acetylide ligands 1a−1g are listed in Table
S2 (Supporting Information). Figure S3 (Supporting Informa-
tion) shows the electronic absorption spectrum of 2a in THF at
298 K. The absorption peak maxima of 2a appear at 263, 276,
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 3a and 4a
3a
4a
Au(1)−C(1)
Au(2)−C(34)
Au(1)−P(1)
Au(2)−P(2)
C(1)−C(2)
C(34)−C(35)
C(9)−O(1)
C(42)−O(4)
P(1)−Au(1)−C(1)
P(2)−Au(2)−C(34)
Au(1)−C(1)−C(2)
Au(2)−C(34)−C(35)
C(1)−C(2)−C(3)
C(34)−C(35)−C(36)
2.003(5)
2.000(5)
2.2804(13)
2.2707(13)
1.203(7)
1.206(7)
1.212(6)
1.204(6)
176.78(14)
177.51(15)
174.4(5)
176.1(5)
176.8(5)
175.5(6)
Au(1)−C(1)
Au(2)−C(5)
Au(1)−P(1)
Au(2)−P(2)
C(1)−C(2)
C(5)−C(6)
C(3)−O(7)
C(7)−O(8)
Au(1)···Au(2)
P(1)−Au(1)−C(1)
P(2)−Au(2)−C(5)
Au(1)−C(1)−C(2)
Au(2)−C(5)−C(6)
C(1)−C(2)−C(71)
C(5)−C(6)−C(91)
2.041(9)
1.990(9)
2.281(2)
2.273(2)
1.180(11)
1.202(12)
1.10(3)
1.230(9)
3.0145(9)
174.0(2)
175.4(3)
169.3(7)
176.6(11)
175.2(9)
173.4(11)
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Table 3. Photophysical Data of Complexes 2a−2g, 3a−3b, and 4a−4b
complex
medium (298 K)
λabs/nm (ε/dm3 mol−1 cm−1
)
λem/nm (τ0/μs)
443 (max, 6.5), 474
2a
THF
solid
THF
solid
THF
solid
THF
solid
THF
solid
THF
solid
THF
solid
THF
solid
THF
solid
THF
solid
THF
solid
263 (sh, 12 500), 276 (23 300), 288 (30 800), 301 (28 600), 345 (24 000)
266 (sh, 18 700), 280 (sh, 35 300), 295 (60 400), 311 (63 200)
264 (sh, 20 000), 279 (36 600), 293 (58 900), 310 (58 700)
264 (sh, 22 300), 279 (28 500), 293 (54 400), 310 (55 200)
266 (sh, 17 400), 279 (33 400), 293 (54 900), 310 (55 400)
265 (sh, 16 300), 280 (sh, 32 400), 293 (51 800), 310 (51 400)
265 (sh, 16 800), 280 (sh, 33 600), 293 (56 400), 310 (58 300)
268 (18 800), 276 (22 400), 292 (28 000), 305 (27 900), 342 (27 100)
268 (24 000), 276 (sh, 26 600), 284 (sh, 30 100), 299 (45 900), 315 (46 500)
279 (38 600), 296 (48 400), 313 (49 700)
525 (<0.1)
2b
2c
2d
2e
2f
443 (max, 7.9), 475
443, 479 (max, 18.6), 505, 528
443 (max, 7.7), 476
440, 479 (max, 15.2), 530 (sh)
444 (max, 21.5), 474
443, 479 (max, 20.3), 505, 518, 529
443 (max, 7.8), 475
440, 481 (max, 11.9), 532 (sh)
444 (max, 7.6), 475
444, 489 (max, 7.6)
2g
3a
3b
4a
4b
443 (max, 19.9), 475
440, 480 (max, 16.1), 505, 517, 529
no emission
no emission
444 (max, 8.6), 475
440, 473, 485 (max, 36.1), 510(sh)
444 (max, 7.6), 474
448, 495 (max, 15.9)
279 (sh, 37 400), 297(52 100), 314 (54 000)
443 (max, 19.4), 476
449, 503 (max, 13.2)
Figure 4. UV−vis spectral changes of 2a (1.98 × 10−5 mol dm−3) in
THF upon addition of F−. Insert: a plot of the absorbance change at
375 nm as a function of the concentration of F− and its theoretical fit
for the 1:1 binding of complex 2a with F−.
Figure 3. Emission spectrum of 2d in the solid state at 298 K (λex
293 nm).
=
centered at 525 nm (Figure S7, Supporting Information) could
be ascribed to the charge transfer from NO2 to amide of the
acetylide ligand. For the gold(I) acetylide complexes studied in
this paper, except the nitro-derivatives 2a and 3a, the
substituent R on the acetylide ligand as well as the type of
phosphine ligand have little effect on the electronic absorption
and emission spectra.
Anion Binding Properties of Complexes 2a−2g, 3a−
3b, and 4a−4b. Anion Binding of Complexes in THF. The
anion-sensing abilities of 2a−2g, 3a−3b, and 4a−4b in THF
have been studied by UV−vis titration experiments. Because
NBu4H2PO4 and NBu4HSO4 have limited solubility in THF,
the investigations toward H2PO4− and HSO4− were not carried
out. Figure 4 shows the UV−vis spectral changes of 2a upon
addition of F− in THF at 298 K. The absorbance of the
absorption bands of 2a at 263, 276, 288, 301, and 345 nm
decreases gradually, while the new absorption bands at 292,
308, and 375 nm appear gradually upon addition of F−. Well-
defined isosbestic points are observed at 290, 296, 304, 316,
and 357 nm, indicating that only two species coexist during the
titration equilibrium and suggesting the possible formation of
anion−complex adduct.
The UV−vis spectral changes of gradual addition of F− into
2b−2g, 3b, 4a, and 4b in THF are similar: three gradually
decreasing bands (ca. 279, 295, and 310 nm) and two newly
formed absorption bands (ca. 305 and 319 nm). There are
three well-defined isosbestic points at ca. 299, 310, and 313 nm
(see Figures S11−S14 (Supporting Information) for the UV−
vis spectral changes of 2b, 2d, 2e, and 2g upon addition of F−
in THF, respectively). The UV−vis spectral changes of nitro-
derivative 3a upon addition of F− in THF are similar to those of
2a, but only one isosbestic point at 357 nm is observed (Figure
S15, Supporting Information).
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Figure 5 shows the Job’s plots of 2b, 2c, and 2g with F− in
THF (for 2a, 2d, 2e, and 2f, see Figures S16−S19 (Supporting
values toward F− show the following order: 2a ≥ 3a; 2g > 3b ≈
4b; 2d > 4a. This result indicates that the change of R′ on the
phosphine ligand has a little effect on log K value.
The binding abilities of 2a−2g, 3a−3b, and 4a−4b toward
−
other anions (OAc−, Cl−, Br−, and NO3 ) have also been
investigated in THF at 298 K (Table 4). The UV−vis spectral
−
changes of 2b toward anions (OAc−, Cl−, Br−, and NO3 ) in
THF are similar to those of 2b toward F− in THF. Figure 6
■
●
▲
Figure 5. Job’s plots of complexes 2b ( ), 2c ( ), and 2g ( ) with
F− in THF ([complex] + [F−] = 1.98 × 10−5 mol dm−3).
Information), respectively). The absorbance reaches maximum
at ca. 0.5, indicating the 1:1 binding between F− and 2a−2g in
THF. Using the 1:1 binding model, the log K values of 2a−2g,
3a−3b, and 4a−4b toward F− are determined and listed in
Table 4. For the complexes 2a−2g with Cy3P ligand, their log
K values with F− are in the following order: R = NO2 (2a) >
CF3 (2b) ≥ Cl (2c) > H (2d) > CH3 (2e) ≈ tBu (2f) ≥ OCH3
(2g), which is in line with the decreasing of the electron-
withdrawing ability of the substituent R on the acetylide ligand
of 2a−2g. This could be rationalized by the fact that the
electron-withdrawing substituent R on the acetylide ligand of
2a−2g would increase the acidity of urea N−H and strengthen
the hydrogen bond interactions between the urea N−H of the
complex and F−. The trend of the average chemical shifts of
urea N−H of 2a−2g in DMSO-d6 is R = NO2 (2a) > CF3 (2b)
Figure 6. UV−vis spectral changes of 2b in THF (9.90 × 10−6 mol
dm−3) upon addition of OAc−. Insert: a plot of the absorbance change
at 321 nm as a function of the concentration of OAc− and its
theoretical fit for the 1:1 binding of complex 2b with OAc−.
shows the UV−vis spectral changes of 2b in THF upon
addition of OAc− (for the UV−vis spectral changes of 2b
−
toward Cl−, Br−, and NO3 , see Figures S20−S22 (Supporting
Information), respectively). A well-defined isosbestic point at
299 nm is found, illustrating the coexistence of complex and
corresponding anion-complex adduct. The log K values of 2b in
THF toward anions are in the following order: F− > OAc− ≈
t
> Cl (2c) > H (2d) ≥ CH3 (2e) ≈ Bu (2f) ≥ OCH3 (2g),
Cl− > Br− > NO3 . Figure S23 (Supporting Information) shows
−
revealing the order of the acidity of urea N−H of 2a−2g.
For complexes with triphenylphosphine or tris(4-
methoxyphenyl)phosphine ligand, 3a, 3b, 4a, and 4b, their
log K values with F− are in the order 3a > 3b; 4a > 4b, showing
the same substituent (R) effect on the log K value as previously
observed in 2a−2g (Table 4). For the complexes with same
acetylide ligand but different phosphine ligands, their log K
the plots of absorbance change of 2b upon addition of various
anions (for 2c and 3a, see Figures S24 and S25 (Supporting
Information), respectively). The similar order is also found in
2c−2g and 3a toward different anions (Table 4).
The anion-binding constants of the acetylide ligands, HC
CC6H4-4-NHC(O)NHC6H4-4-R (R = NO2 (5a), CF3 (5b), Cl
a
Table 4. Binding Constants of 2a−2g, 3a−3b, and 4a−4b for Anions in THF
log K
F−
OAc−
Cl−
Br−
NO3
−
complex
2a
2b
2c
2d
2e
2f
6.44 0.13
5.76 0.10
5.57 0.11
4.97 0.02
4.75 0.03
4.74 0.03
4.70 0.02
6.20 0.08
4.57 0.03
4.74 0.02
4.54 0.01
5.92 0.06
5.18 0.06
4.99 0.02
4.81 0.02
4.78 0.01
4.52 0.05
4.55 0.04
6.24 0.06
4.50 0.03
4.69 0.01
4.60 0.01
b
b
b
5.23 0.02
4.95 0.02
4.81 0.04
4.46 0.01
4.48 0.01
4.23 0.03
5.88 0.10
b
4.86 0.03
4.83 0.03
4.73 0.02
4.25 0.06
3.98 0.05
3.78 0.02
4.93 0.04
b
4.75 0.06
4.55 0.05
4.32 0.04
4.22 0.05
4.08 0.04
4.06 0.04
5.68 0.23
4.13 0.02
4.12 0.07
3.86 0.09
2g
3a
3b
4a
4b
b
b
b
b
a
b
Binding constants were determined by 1:1 model using nonlinear fitting methods. Spectral changes were not suitable for accurate measurement of
binding constant.
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t
(5c), H (5d), CH3 (5e), Bu (5f), OCH3 (5g)), in THF have
also been determined to compare with those of gold(I)
acetylide complexes 2a−2g (Table S3, Supporting Informa-
tion). For the same acetylide ligand (5a−5g), the log K values
toward anions in THF show the selectivity in the following
order: OAc− > F− > Cl− > Br− > NO3 . For the same anion,
−
the log K values of the acetylide ligands 5a−5g in THF are in
the following order: 5a > 5b ≥ 5c > 5d ≈ 5f ≈ 5g > 5e. In
general, the acetylide ligands 5a−5g show smaller anion-
binding constants than their corresponding gold(I) acetylide
complexes 2a−2g in THF.
The hydrogen bond competition investigations have been
carried out. Figure 7 shows the UV−vis spectral changes of 2a
Figure 8. UV−vis spectral changes of 2a (1.98 × 10−5 mol dm−3) in
DMSO upon addition of F−. Insert: a plot of the absorbance at 485 nm
as a function of the concentration of F−.
and S28, Supporting Information, respectively). This could be
rationalized by the fact that the electron-withdrawing
substituent R (NO2 or CF3) on the acetylide ligands of 2a or
2b could increase the acidity of urea N−H and facilitate the
deprotonation process of corresponding urea N−H in
DMSO.10b−e
Unlike the UV−vis titration spectra of 2a with F− in DMSO,
the UV−vis spectral changes of 2a toward OAc− in DMSO are
similar to those in THF and the color of the solution becomes
light yellow upon addition of OAc− (Figure S29, Supporting
Information). For comparison, the UV−vis spectra and colors
of 2a with 50 equiv of F− or OAc− in THF as well as in DMSO
are shown in Figure 9. The UV−vis spectra of 2a with 50 equiv
of F− in THF and 2a with 50 equiv of OAc− in THF as well as
Figure 7. UV−vis spectral changes of 2a with 10 equiv of F− in THF
(1.98 × 10−5 mol dm−3) upon addition of H2O. Insert: a plot of the
absorbance at 375 nm as a function of the volume of H2O.
with 10 equiv of F− in THF upon addition of H2O. Upon
addition of H2O, the UV−vis spectrum is gradually backed to
that of 2a in THF. The addition of other protic solvent, such as
MeOH or EtOH, into 2a with 10 equiv of F− in THF produces
similar spectral changes. This could be ascribed to the
formation of hydrogen bonds between the protic solvent
(water or alcohols) and F−, preventing F− from forming
hydrogen bonds with 2a.
Anion Binding of Complexes in DMSO. In order to
investigate the effect of polarity of solvent on the binding
1
abilities of complexes toward anions, UV−vis and H NMR
titration experiments of 2a, 2b, 2d, and 2g toward anions in
DMSO and DMSO-d6 have been carried out. Figure 8 shows
the UV−vis spectral changes of 2a in DMSO upon addition of
F− at 298 K. The absorbance of the absorption bands at 275,
288, 303, and 356 nm decreases, while the absorbance of the
absorption band at 324 and 485 nm gradually increases and the
solution gradually becomes orange-yellow after 1 equiv of F− is
added. The appearance of the low-energy absorption band at
485 nm, which does not appear in the titration of 2a with F− in
THF, is ascribed to the deprotonation of the urea N−H of 2a.
Upon addition of F− into 2b in DMSO (Figure S26, Supporting
Information), the additional low-energy absorption band
(compared with the spectral changes of 2b with F− in THF)
at ca. 352 nm forms, and the color of the solution becomes light
yellow. On the contrary, there is no obvious low-energy
absorption band at λ > 345 nm upon addition of F− into the
DMSO solution of 2d or 2g, and their UV−vis spectral changes
are similar to those of 2d or 2g with F− in THF (Figures S27
Figure 9. UV−vis spectra (a) and colors (b) of 2a (1.98 × 10−5 mol
dm−3) in THF or DMSO in the presence of 50 equiv of F− or OAc−.
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DMSO are almost the same, while an additional low-energy
absorption band appears at 485 nm for 2a with 50 equiv of F−
in DMSO. Addition of H2PO4− into 2a in DMSO provides the
UV−vis spectral changes similar to those of 2a with OAc− in
DMSO (Figure S30, Supporting Information). Thus, the
dramatic color change of 2a is only observed toward F− in
DMSO. This solvent-dependent and selective color change of
2a toward F− provides an access of naked eye detection of F−.
The interactions of 2a, 2b, 2d, and 2g with anions (F− and
1
OAc−) in DMSO-d6 have also been investigated by H NMR
1
titration experiments. The H NMR spectral changes of 2a
upon addition of OAc− in DMSO-d6 are shown in Figure 10.
1
Figure 11. H NMR spectral changes of 2a (10 mmol dm−3) upon
addition of F− in DMSO-d6.
Supporting Information). The 19F NMR spectra of 2a upon
addition of 5 equiv of F− in DMSO-d6 and THF-d8 are shown
−
in Figure S33 (Supporting Information). The HF2 signal
appearing at −142.7 ppm (doublet, JHF = 120 Hz)10e,37 for the
former also supports the ascription of the deprotonation
process of the urea N−H of 2a in DMSO-d6.
1
The H NMR spectral changes of 2b with F− in DMSO-d6
are similar to those of 2a with F− in DMSO-d6 (Figure S34,
Supporting Information). On the contrary, spectral changes of
2d or 2g with F− in DMSO-d6 are similar to those of 2a with
OAc− in DMSO-d6 (Figures S35 and S36, Supporting
Information, respectively). These results indicate that the
deprotonation process of the urea N−H is present in the
interaction of 2a and 2b with F− in DMSO-d6.
1
Figure 10. H NMR spectral changes of 2a in DMSO-d6 (5 mmol
dm−3) upon addition of OAc−.
The significant downfield shift of the signals of urea N−H (Ha
and Hb) is observed upon addition of OAc− from 0 to 2 equiv,
and these chemical shifts have a little change after addition of 2
equiv of OAc−, suggesting the formation of hydrogen bonds
between the urea N−H of 2a and OAc−. The signals of
aromatic protons of 2a (Hc−Hf) show the slight shift upon
addition of OAc− from 0 to 2 equiv. The slight upfield shift of
Hc and Hf could be ascribed to the increase of shielding effect
which is introduced by the enhancement of electron density of
aromatic ring by the through-bond propagation.10b−e In
contrast, the slight downfield shift of Hd and He is ascribed
to the polarization effect of the C−H bond that is introduced
by the through-space effect.10b−e
The binding constants of 2a, 2b, 2d, and 2g with OAc− as
−
well as H2PO4 in DMSO were determined from the UV−vis
titration experiments. Their log K values are listed in Table S4
(Supporting Information). The log K values of the same
complex with various anions are in the following order: OAc−
−
≥ H2PO4 , which is in line with the decrease of the basicity of
anions. The binding constants of different complexes with the
−
same anion (OAc− or H2PO4 ) are in the following order: R =
NO2 (2a) > CF3 (2b) > H (2d) ≥ OCH3 (2g). The same order
is also observed for these complexes with the same anion in
THF and suggests the same effect of the electron-withdrawing
ability of the substituent R on the acetylide ligand of complexes
on log K values. The log K values of 2a, 2b, 2d, and 2g with
OAc− in DMSO are comparatively smaller than those in THF,
and the difference among these log K values in DMSO is small.
This suggests that in this case the less polar solvent THF
exhibits a more promotive and differentiating effect on log K
values than DMSO.
1
Figure 11 shows the H NMR spectral changes of 2a upon
addition of F− in DMSO-d6, which are quite different from
those of 2a with OAc− in DMSO-d6. Upon addition of F− into
2a in DMSO-d6, the signals of two urea protons (Ha and Hb) of
2a disappear, while the distinct triplet centered at 16.08 ppm
37
−
(JHF = 120 Hz), which is assigned as the signal of HF2 ,
appears upon addition of 5 equiv of F− (Figure S31, Supporting
Information). The signals of aromatic protons Hc−Hf show
little shift when less than 1 equiv of F− is added. Upon addition
of more than 1 equiv of F− into 2a in DMSO-d6, signals of Hc,
Hd, and Hf show dramatic upfield shift, which could be ascribed
to the drastic enhancement of shielding effect resulting from
the increased electron density of aromatic ring through the
increased through-bond negative charge delocalization that
caused by the deprotonation process of urea N−H.10b−e The
downfield shift of He could be ascribed to the domination of
CONCLUSION
■
Urea based gold(I) acetylide complexes 2a−2g, 3a−3b, and
4a−4b have been synthesized and characterized. Complexes
2b−2g, 3b, and 4a−4b both in the solid state and in degassed
THF solution produce intense luminescence, which is assigned
3
to come from the (ππ*) excited state of the acetylide ligands
of the complexes. In THF, the substituent R on the acetylide
ligand of complexes has influence on the anion-binding ability,
with the log K values of 2a−2g toward the same anion in the
following order: R = NO2 (2a) > CF3 (2b) ≥ Cl (2c) > H (2d)
> CH3 (2e) ≈ tBu (2f) ≥ OCH3 (2g). On the other hand, the
substituent R′ on phosphine ligand of complexes has little effect
the polarization effect of the C−H bond.10b−e The H NMR
1
spectral changes of 2a upon addition of F− in THF-d8 are
similar to those of 2a with OAc− in DMSO-d6 (Figure S32,
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on log K values with the same anion. The less polar solvent
THF shows a more promotive and differentiating effect on log
K values than DMSO. In DMSO, 2a shows the selective color
change toward F−, and this is ascribed to the deprotonation of
urea N−H of the acetylide ligand of 2a. The solvent-dependent
and selective color change of 2a toward F− provides access for
naked eye detection of F−.
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ASSOCIATED CONTENT
■
S
* Supporting Information
X-ray crystallographic files in CIF format for complexes 3a and
4a. Additional figures and tables. 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
(13) (a) Carroll, C. N.; Coombs, B. A.; McClintock, S. P.; Johnson Ii,
C. A.; Berryman, O. B.; Johnson, D. W.; Haley, M. M. Chem. Commun.
2011, 47, 5539−5541. (b) Ahmed, N.; Geronimo, I.; Hwang, I. C.;
Singh, N. J.; Kim, K. S. Chem.Eur. J. 2011, 17, 8542−8548. (c) Jia,
C.; Wu, B.; Li, S.; Yang, Z.; Zhao, Q.; Liang, J.; Li, Q. S.; Yang, X. J.
Chem. Commun. 2010, 46, 5376−5378. (d) Meshcheryakov, D.;
Bohmer, V.; Bolte, M.; Hubscher-Bruder, V.; Arnaud-Neu, F. Chem.
Eur. J. 2009, 15, 4811−4881. (e) Schazmann, B.; Alhashimy, N.;
Diamond, D. J. Am. Chem. Soc. 2006, 128, 8607−8614. (f) Bryantsev,
V. S.; Hay, B. P. J. Am. Chem. Soc. 2006, 128, 2035−2042. (g) Hay, B.
P.; Firman, T. K.; Moyer, B. A. J. Am. Chem. Soc. 2005, 127, 1810−
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Yoon, J.; Nam, K. C. J. Am. Chem. Soc. 2003, 125, 12376−12377.
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■
We acknowledge financial support from the National Natural
Science Foundation of China (20671097, 20971131, 20901084,
and J1103305), the Doctoral Fund of Ministry of Education of
China for New Scholar (200805581015), the Natural Science
Foundation of Guangdong Province (10151027501000048),
the Undergraduate Innovative Experiment Program of
Guangdong Province (1055811083), and Sun Yat-Sen
University. We also thank the editor and reviewers for helpful
comments and suggestions.
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