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specic binding sites for Hg(II).25 This reversible complex (40.0 mg, 0.21 mmol), PPh3 (55.6 mg, 0.21 mmol), and (n-
formation may allow an application of this system as a turn-on Bu)4NBr (34.0 mg, 0.11 mmol) was dissolved in toluene (5 mL)
uorescent sensor for a secondary analyte such as cysteine and and diisopropylamine (5 mL) under nitrogen atmosphere. Aer
L-glutathione that can form a more stable complex with Hg(II).26 L- 15 minutes of stirring at ambient temperature, trimethylsilyla-
Glutathione is a value-added ingredient in a variety of health cetylene (0.62 g, 6.33 mmol) was added dropwise, and the
supplements as it helps reduce oxidative stress,27 and symptoms reaction was heated at 100 ꢀC for 24 h. The crude was extracted
of neurodegenerative diseases such as Alzheimer,28 and Parkin- with CH2Cl2 and 30% NH4Cl solution. The organic phase was
son's disease.29 The quantitative analysis of L-glutathione in washed deionized water and brine, dried over anhydrous
health supplements by a competitive binding with Hg(II) in the Na2SO4, ltered, and concentrated under reduced pressure. The
DSS–Hg(II) complex will also be demonstrated.
crude residue was puried by silica gel column chromatography
with hexane as the eluent. A light-yellow solid of 2a was ob-
tained in 0.51 g (95%). 1H-NMR (400 MHz, CDCl3) d ppm 7.93 (d,
J ¼ 7.4 Hz, 1H), 7.83 (d, J ¼ 7.8 Hz, 1H), 7.58 (d, J ¼ 7.8 Hz, 1H),
7.45 (t, J ¼ 7.3 Hz, 1H), 7.19 (t, J ¼ 7.3 Hz, 1H), 6.95 (s, 1H), 6.79
(d, J ¼ 7.4 Hz, 1H), 0.24 (s, 9H), 13C-NMR (100 MHz, CDCl3)
d ppm 149.2, 147.7, 141.9, 141.4, 132.1, 128.2, 128.1, 127.8,
124.3, 122.9, 120.28, 120.27, 105.4, 95.0, 65.7, 0.1. MS (MALDI-
TOF) calcd. for C35H32Si2 ([M]+) 508.204, found 507.473.
2.3.2 Synthesis of 2,20,7,70-tetra(trimethylsilylethynyl)-9,90-
spirobiuorene (2b). A mixture of 2,20,7,70-tetrabromo-9,90-spi-
robiuorene (1b, 0.50 g, 0.79 mmol), Pd(PPh3)2Cl2 (55.5 mg,
0.08 mmol), CuI (30.1 mg, 0.16 mmol), and PPh3 (41.5 mg, 0.16
mmol) was dissolved in toluene (5 mL) and diisopropylamine (5
mL) under nitrogen atmosphere. Aer 15 minutes of stirring at
ambient temperature, trimethylsilylacetylene (0.47 g, 4.77
mmol) was added dropwise, and the reaction was heated at
100 ꢀC for 24 h. The crude was extracted with CH2Cl2 and 30%
NH4Cl solution. The organic phase was washed deionized water
and brine, dried over anhydrous Na2SO4, ltered, and concen-
trated under reduced pressure. The crude residue was puried
by silica gel column chromatography with hexane as the eluent.
A white solid of 2b was obtained in 0.52 g (94%). 1H-NMR (400
MHz, CDCl3) d ppm 7.77 (d, J ¼ 7.9 Hz, 1H), 7.52 (d, J ¼ 7.9 Hz,
1H), 6.81 (s, 1H), 0.18 (s, 9H), 13C-NMR (100 MHz, CDCl3) d ppm
148.1, 141.4, 132.4, 127.8, 123.1, 120.4, 105.1, 95.3, 65.2, 0.0. MS
(MALDI-TOF) calc. mass for C45H48Si4 ([M]+) 700.283, found
699.728.
2. Experimental
2.1 Chemicals and materials
All reagents and solvents were purchased from Merck (Ger-
many), Sigma-Aldrich (USA), or Fluka (Switzerland). Unless
stated otherwise, these chemicals were used without further
purication. All column chromatography were operated using
silica gel 60 (70–230 mesh) purchased from Merck. Water used
in all spectroscopic experiments was deionized with a Milli-Q®
reference water purication system (Merck) to a specic resis-
tivity of 18.2 MU cm. The stock solutions of DSS and TSS were
prepared in dimethyl sulfoxide (DMSO) at 1 mM and diluted
further to obtain expected concentrations. The stock solutions
of metal ions in deionized water were prepared at 10 mM using
the following commercially available salts: LiNO3, NaNO3,
KNO3, AgNO3, Ca(NO3)2, Mg(NO3)2, Ba(NO3)2, Co(NO3)2,
Cd(NO3)2, Zn(NO3)2, Pb(NO3)2, Ni(NO3)2, Cu(NO3)2, Hg(OAc)2,
Fe(OAc)2, Fe(NO3)3, Al(NO3)3, Bi(NO3)3, Cr(NO3)3, and AuCl3.
The pH-controlled and buffer solutions in deionized water (10
mM) were NaCl/HCl buffer (pH 1–2), acetate buffer (pH 3–5),
HEPES buffer (pH 6–8), and glycine/NaOH buffer (pH 9–10).
2.2 Instruments
1H and 13C NMR spectra were collected on a 400 MHz NMR
1
spectrometer which operated at 400 MHz for H and 100 MHz
for 13C (Bruker Company). Mass spectra were recorded on
a Microex MALDI-TOF mass spectrometer (Bruker Daltonics).
High-resolution mass spectra were obtained from a triple
quadrupole GC/MS (Agilent Technologies). Elemental analysis
was obtained from a CHNS/O analyzer (Flash 2000, Thermo
Scientic). Absorption spectra were obtained from a UV-2250
UV-Vis Spectrophotometer (SHIMADZU, Japan) and emission
spectra were obtained from a Carry Eclipse Fluorescence Spec-
trophotometer (Agilent Technologies). The absolute uores-
cence quantum yields and lifetimes were determined using
FLS980 Spectrometer (Edinburgh Instruments). The pH buffers
were measured from an Ohaus pH meter. Amounts of Hg(II) ion
in water samples were veried by an inductively coupled
plasma-optical emission spectrometer (ICP-OES) (iCAP 6500,
Thermo Scientic).
2.3.3 Synthesis of 2,7-diethynyl-9,90-spirobiuorene (3a).
To a solution of 2a (0.50 g, 0.98 mmol) in CH2Cl2 (16 mL) was
added a solution of NaOH (0.39 g, 9.83 mmol) in MeOH (4 mL)
under nitrogen atmosphere. The reaction was stirred at room
temperature for 15 h. The reaction mixture was extracted with
CH2Cl2 and deionized water. The organic phase was washed
brine, dried over anhydrous Na2SO4, ltered, and concentrated
under reduced pressure. The crude mixture was puried by
silica gel column chromatography with 5% CH2Cl2 in hexane as
the eluent. A light-yellow solid of 3a was obtained in 0.36 g
1
(100%). H-NMR (400 MHz, CDCl3) d ppm 7.86 (d, J ¼ 7.6 Hz,
1H), 7.80 (d, J ¼ 7.9 Hz, 1H), 7.53 (d, J ¼ 7.9 Hz, 1H), 7.40 (t, J ¼
7.5 Hz, 1H), 7.14 (t, J ¼ 7.5 Hz, 1H), 6.89 (s, 1H), 6.73 (d, J ¼
7.6 Hz, 1H), 2.98 (s, 1H), 13C-NMR (100 MHz, CDCl3) d ppm
149.4, 147.6, 141.9, 141.6, 132.2, 128.2, 128.1, 128.0, 124.2,
121.9, 120.4, 120.3, 83.9, 77.9, 65.7. MS (MALDI-TOF) calc. mass
for C29H16 ([M]+) 364.125, found 363.221.
2.3 Synthesis and characterizations
2.3.1 Synthesis of 2,7-di(trimethylsilylethynyl)-9,90-spirobi-
uorene (2a). A mixture of 2,7-dibromo-9,90-spirobiuorene (1a, (3b). To a solution of 2b (0.46 g, 0.65 mmol) in CH2Cl2 (16 mL)
2.3.4 Synthesis of 2,20,7,70-tetraethynyl-9,90-spirobiuorene
0.50 g, 1.05 mmol), Pd(PPh3)2Cl2 (74.0 mg, 0.11 mmol), CuI was added a solution of NaOH (0.26 g, 6.50 mmol) in MeOH (4
11452 | RSC Adv., 2019, 9, 11451–11458
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