Supporting Information
Indole-Based Fluorescent Sensors for Selective Detection of Hg2+
Yao-Lin Sun, An-Tai Wu*
Department of Chemistry, National Changhua University of Education, Changhua
50058, Taiwan
Table of contents
Page No
Content
S3
The synthesis method of 1.
S4
The synthesis method of 2.
S4
The synthesis method of 3.
S5
The synthesis method of 4.
S7
1
H and 13C NMR Spectra of 1. (Figure S1 and S2)
S8
1
H and 13C NMR Spectra of 2. (Figure S3 and S4)
S9
1
H and 13C NMR Spectra of 3. (Figure S5 and S6)
S10
1
H and 13C NMR Spectra of 4. (Figure S7 and S8)
S11
UV-vis spectra of 3 (12.4 uM) with 3 equivalents of metal ion (37.2
uM) in DMSO/ H2O (v/v , 7 : 3) (Figure S9)
S11
UV-vis spectra of 4 (15.6 uM) with 3 equivalents of metal ion (46.8
uM) in DMSO/ H2O (v/v , 7 : 3) (Figure S10)
S12
Fluorescence spectra of 3 (12.4 uM) with 3 equivalents of metal ion
(37.2 uM) in DMSO/ H2O (v/v , 7 : 3) λex= 273 nm (Figure S11)
S12
Fluorescence spectra of 4 (15.6 uM) with 3 equivalents of metal ion
S1
(46.8 uM) in DMSO/ H2O (v/v , 7 : 3) λex= 273 nm (Figure S12)
S13
Variation of fluorescence spectra of 1 (16.3 μM) in MeOH as a
function of pH at 365 nm; λex= 297 nm (Figure S13)
S13
Variation of fluorescence spectra of 2 (11.7 μM) in MeOH as a
function of pH at 346nm; λex=273 nm (Figure S14)
S14
Stern-Volmer plot of 1 with Hg(ClO4)2 in DMSO/H2O (7:3, v/v)
(Figure S15)
S15
Stern-Volmer plot of 2 with Hg(ClO4)2 in DMSO/H2O (7:3, v/v)
(Figure S16)
S14
Job plot of 1 with Hg(ClO4)2 in DMSO/H2O (7:3, v/v). (Figure S17)
S16
ESI Mass spectrum for 1-2Hg2+ complex. (Figure S18)
S16
Job plot of 2 with Hg(ClO4)2 in DMSO/H2O (7:3, v/v). (Figure S19)
S17
ESI Mass spectrum for 2-Hg2+ complex. (Figure S20)
S18
Competitive experiments in the 1 + Hg2+ system with interfering metal
ions. [1] =1.46 × 10-5 M, [Hg2+] = 1.46 × 10-4 M, and [Mn+] = 1.46 ×
10-4 M DMSO/ H2O (v/v, 7 : 3) . λex = 297 nm. (Figure S21)
S18
Competitive experiments in the 2 + Hg2+ system with interfering metal
ions. [2] =1.12 × 10-5 M, [Hg2+] = 1.12 × 10-4 M, and [Mn+] = 1.12 ×
10-4 M DMSO/ H2O (v/v, 7 : 3) . λex = 273nm. (Figure S22)
Experimental
General Methods:
All reagents were obtained from commercial suppliers and were used without
further purification. Analytical thin-layer chromatography was performed using silica
S2
gel 60 F254 plates (Merck). The 1H and 13C NMR spectra were recorded with Bruker
AM 300 (300 MHz) spectrometers. Chemical shifts are expressed in ppm with
residual CHCl3 as reference. Low- and high-resolution mass spectra were recorded
under fast atom bombardment (FAB) conditions. UV-vis spectra were recorded by
using HP-8453 spectrophotometer with a diode array detector, and the resolution was
set at 1 nm. Fluorescence spectra were recorded on a Cary Eclipse Fluorescene
spectrophotometer.
N
Cl
N
H
O
NH2
NH2
K2CO3, CHCl3
N
O
NH
NH
O
HN
HN
N-((6-((1H-indole-2-carboxamido)methyl)pyridin-2-yl)methyl)-1H-indole-2-carb
oxamide (1)
To a stirred solution of 1H-indole-2-carbonyl chloride (0.45 g, 2.50 mmol) in dry
CHCl3 (10 mL) was added (6-(aminomethyl)pyridin-2-yl)methanamine (0.165 g, 1.20
mmol), K2CO3 (0.24 g, 1.74 mmol). The reaction mixture was stirred overnight at
room temperature. After completion of reaction, the reaction mixture was added three
drops of H2O to quench the reaction. The mixture was extracted with chloroform (5
mL × 3). The chloroform layer was dried over MgSO4 and the solvent was removed
under reduced pressure to give the solid crude product. The resulting residue was
purified by silica column chromatography (EtOAc) to give white yellow solid 2 (0.18
g, 36%). Rf = 0.6 ( EtOAc); 1H NMR (300 MHz, DMSO) δ: 9.37 (s, 2H), 7.73 (t, 2H,
J = 7.8 Hz), 7.61 (d, 2H, J = 7.8 Hz), 7.45 (d, 2H, J = 8.1 Hz), 7.22 (m, 8H) , 7.03 (t,
2H, J = 7.2 Hz) , 4.61 (s, 4H); 13C NMR (75 MHz, DMSO) δ:161.40, 158.35, 137.48,
136.59, 131.63, 127.14, 123.45, 121.61, 119.81, 119.16, 112.40, 103.22, 44.31,
S3
FABMS m/z Calcd for C25H21N5O2 [M+H]+, 423.1695, found 423.1701.
NH
H
N
N
O
H
N
O
NH
N,N'-(pyridine-2,6-diylbis(methylene))bis(2-(1H-indol-3-yl)acetamide)(2)
To a stirred solution of 2-(1H-indol-3-yl)acetic acid (1.763 g, 10.06 mmol) in dry
DMF was added (6-(aminomethyl)pyridin-2-yl)methanamine (0.631 g, 4.60 mmol),
TEA (1.94 mL, 13.80 mmol) and DEPC (1.54 mL, 10.12 mmol). The reaction mixture
was stirred overnight at room temperature. After completion of reaction, filtrate and
remove the solvent by vacuum. The resulting residue was purified by column
chromatography (SiO2; 1:18 MeOH / CH2Cl2) and get white solid 3 (0.52 g, 1.15
mmol, 25%). Rf = 0.2 (1:18 MeOH / CH2Cl2); 1H NMR (300 MHz, CD3OD) δ: 7.37
(d, 2H, J = 7.2 Hz) , 7.23 (d, 2H, J = 8.4 Hz) , 7.05 (s, 2H), 6.97 (t, 2H, J = 6.9 Hz),
6.86 (t, 4H, J = 6.9 Hz) , 4.18 (s, 4H), 3.59 (s, 4H);
13
C NMR (75 MHz, CDCl3) δ:
175.05, 158.27, 138.78, 138.15, 128.45, 125.18, 122.66, 120.69, 120.01, 119.41,
112.41, 109.19, 45.33, 34.01; FABMS m/z Calcd for C27H25N5O2 [M+H]+, 451.2008,
found 452.2089.
NH
N
NH
N
H
NH
N,N'-(pyridine-2,6-diylbis(methylene))bis(1-(1H-indol-3yl)methanamine) (3)
To a stirred solution of (6-(aminomethyl)pyridin-2-yl)methanamine (0.54 g, 3.93
mmol) in MeOH was added 1H-indole-3-carbaldehyde (1.14 g, 7.87 mmole). The
reaction mixture was reflux overnight. After completion of reaction, the solvent was
evaporated and further purified by column chromatography (SiO2; 1:2 MeOH /
EtOAc) to get the imine product. To a stirred solution of the imine product in MeOH
S4
was slowly added NaBH4 (0.74 g, 19.6 mmole). The reaction mixture was stirred 2
hours and then evaporated the solvent. The resulting residue was purified by column
chromatography (SiO2; 1: 2 MeOH / EtOAc) and get white solid 5 (0.31 g, 20%). Rf =
0.2 ( MeOH ); 1H NMR (300 MHz, CD3OD:CD3Cl 2:1) δ: 7.620 (t, 2H, J = 7.8 Hz),
7.48 (d, 2H, J = 7.8 Hz), 7.33 (d, 2H, J = 8.1 Hz), 7.15 (d, 2H, J = 7.8 Hz), 7.13 (s,
2H), 7.08 (t, 2H, J = 6.9 Hz), 3.95 (s, 4H), 3.88 (s, 4H);
13
C NMR (75 MHz,
CD3OD:CD3Cl / 2:1) δ: 156.71, 136.23, 135.45, 125.74, 122.57, 120.27, 119.97,
117.71, 116.78, 110.64, 110.13, 51.78, 42.19; FABMS m/z Calcd for C25H26N5
[M+H]+, 396.2188, found 396.2184.
NH
H
N
N
H
N
NH
N,N'-(pyridine-2,6-diylbis(methylene))bis(2-(1H-indol-3-yl)ethanamine)(4)
To a stirred solution of compound 3 (0.66 g, 1.46 mmol) in dry THF was added
Me2S.BH3 (1M, 1.8 mL, 1.8 mmol). The reaction mixture was reflux 6 hours, and
then 1M HCl was added and reflux for another 3 hours. After completion of reaction,
neutralize with NaHCO3, the mixture was extracted with CH2Cl2 (5 mL × 3), the
organic layer was dried with MgSO4. Further purified by column chromatography
(SiO2; 1：2 MeOH / EtOAc) and get white yellow solid 4 (0.073 g, 0.174 mmol, 26%)
; 1H NMR (300 MHz, CD3OD) δ: 7.41 (t, 1H, J = 7.2 Hz) , 7.29 (d, 2H, J = 7.8 Hz) ,
7.17 (d, 2H, J = 7.8 Hz), 3.53 (s, 4H), 2.77 (t, 4H, J = 6.3 Hz), 2.67 (t, 4H, J = 6.3 Hz);
C NMR (75 MHz, CDCl3) δ: 157.51, 136.47, 136.21, 126.62, 121.55, 120.35,
13
120.06, 117.54, 111.32, 110.30, 52.66, 48.05, 24.19.
S5
Figure S1 1H NMR (300 MHz) Spectrum of 1 in DMSO
Figure S2 13C NMR (300 MHz) Spectrum of 1 in DMSO
S6
Figure S3 1H NMR (300 MHz) spectrum of 2 in CD3OD
Figure S4 13C NMR (300 MHz) spectrum of 2 in CD3OD
S7
Figure S5 13C NMR (300 MHz) spectrum of 3 in CD3OD:CDCl3 2:1
Figure S6 13C NMR (300 MHz) spectrum of 3 in CD3OD:CDCl3 2:1
S8
Figure S7 1H NMR (300 MHz) spectrum of 4 in CD3OD
Figure S8 13C NMR (300 MHz) spectrum of 4 in CD3OD
S9
Host
2+
Ca
2+
Cd
2+
Co
2+
Cu
2+
Hg
+
K
+
Li
2+
Mn
+
Na
2+
Ni
2+
Pb
+
Zn
0.8
0.7
Absorbance (AU)
0.6
0.5
0.4
0.3
0.2
0.1
0.0
260
280
300
320
340
360
380
400
Wavelength (nm)
Figure S9. UV-vis spectra of 3 (12.4 μM) with 3 equivalents of metal ion (37.2 μM)
in DMSO/ H2O (v/v, 7 : 3)
Host
+
Na
2+
Ca
2+
Ni
2+
Cu
2+
Co
+
Li
2+
Hg
2+
Zn
2+
Cd
2+
Mn
2+
Pb
+
K
0.8
Absorbance (AU)
0.6
0.4
0.2
0.0
260
280
300
320
340
360
380
Wavelength (nm)
Figure S10. UV-vis spectra of 4 (15.6 μM) with 3 equivalents of metal ion (46.8 μM)
in DMSO/ H2O (v/v, 7 : 3)
S10
Host
+
Na
2+
Ca
2+
Ni
2+
Cu
2+
Co
+
Li
2+
Hg
2+
Zn
2+
Cd
2+
Mn
2+
Pb
+
K
500
Intensity (a.u.)
400
300
200
100
0
300
350
400
450
500
550
Wavelength (nm)
Figure S11. Fluorescence spectra of 3 (12.4 μM) with 3 equivalents of metal ion (37.2
μM) in DMSO/ H2O (v/v, 7 : 3); λex= 273 nm
Host
+
Li
+
Na
+
K
2+
Ca
2+
Mn
2+
Co
2+
Ni
2+
Pb
2+
Hg
2+
Cu
2+
Zn
2+
Cd
500
Absorbance
400
300
200
100
0
300
350
400
450
500
Wavelength (nm)
Figure S12. Fluorescence spectra of 4 (15.6 μM) with 3 equivalents of metal ion
(46.8 μM) in DMSO/ H2O (v/v, 7 : 3); λex= 273 nm
S11
Intensity (a.u.)
250
200
150
100
50
0
2
4
6
8
10
12
[PH]
Figure S13. Variation of fluorescence spectra of 1 (16.3 μM) in MeOH as a function
of pH at 365 nm; λex= 297 nm
300
Intensity (a.u.)
250
200
150
100
50
0
2
4
6
8
10
12
[PH]
Figure S14. Variation of fluorescence spectra of 2 (11.7 μM) in MeOH as a function
of pH at 346 nm; λex= 273 nm
S12
0
-200
I: intensity at 365 nm
2+
I0:intensity at 365 nm for [Hg ]=0 M
I-I0
-400
-600
-800
-1000
0
2
4
6
8
10
2+
[Hg ]/[1]
1.45
I: intensity at 365 nm
2+
I0:intensity at 365 nm for [Hg ]=0 M
1.40
I0/I
1.35
4.6*10
1.30
1.25
4
Y=0.81356+46015X
2
R =0.997
1.20
limit detect=140ppm
1.15
0.000008 0.000009 0.000010 0.000011 0.000012 0.000013 0.000014
2+
[Hg ] M
Figure S15. Stern-Volmer plot of 1 with Hg(ClO4)2 in DMSO/H2O (7:3, v/v)
S13
3.5
I: intensity at 350 nm
2+
I0:intensity at 350 nm for [Hg ]=0 M
3.0
2.5
5.9*10
2.0
4
1.5
Y=0.567+59774X
2
R =0.983
1.0
0.000008
0.000016
0.000024
0.000032
0.000040
Figure S16. Stern-Volmer plot of 2 with Hg(ClO4)2 in DMSO/H2O (7:3, v/v)
0
-10
X*(I0-I)(365nm)
-20
-30
-40
-50
-60
-70
-80
-90
0.0
0.2
0.4
0.6
0.8
2+
X = [1] / ([1]+[Hg ])
Figure S17. Job plot of 1 with Hg(ClO4)2 in DMSO/H2O (7:3, v/v).
S14
1.0
Figure S18 ESI Mass spectrum for 1-2Hg2+ complex
0
-50
X*(I0-I)(350nm)
-100
-150
-200
-250
0.0
0.2
0.4
0.6
0.8
1.0
2+
X=[2] / ([2]+[Hg ])
Figure S19. Job plot of 2 with Hg(ClO4)2 in DMSO/H2O (7:3, v/v)
S15
Figure S20 ESI Mass spectrum for 2-Hg2+ complex
S16
1.0
(I-I0)/(IHg-I0)
0.8
0.6
0.4
0.2
0.0
Hg Na+HgHg CaHg+NiHg+CuHg+CoHg+LiHg+ZnHg+CdHg+MnHg+PbHg+K
Figure S21. Competitive experiments in the 1 + Hg2+ system with interfering metal
ions. [1] =1.46 × 10-5 M, [Hg2+] = 1.46 × 10-4 M, and [Mn+] = 1.46 × 10-4
M DMSO/ H2O (v/v, 7 : 3) . λex = 297 nm
1.0
(I-I0)/(IHg-I0)
0.8
0.6
0.4
0.2
0.0
Hg onlyHg+NaHg+CaHg+NiHg+CuHg+CoHg+LiHg+ZnHg+CdHg+MnHg+PbHg+K
Figure S22. Competitive experiments in the 2 + Hg2+ system with interfering metal
ions. [2] =1.12 × 10-5 M, [Hg2+] = 1.12 × 10-4 M, and [Mn+] = 1.12 × 10-4
M DMSO/ H2O (v/v, 7 : 3) . λex = 273 nm.
S17