J. Piao et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 128 (2014) 475–480
477
Fig. 1. Normalized absorption and emission spectra of both donor and acceptor
moiety. The spectral overlap between the emission of the donor and the absorption
of the acceptor is marked with oblique line.
(dd, J = 5.5, 3.0 Hz, 1H), 6.43 (d, J = 8.8 Hz, 2H), 6.37 (d, J = 2.4 Hz,
2H), 6.27 (dd, J = 8.8, 2.5 Hz, 2H), 3.33 (q, J = 7.1 Hz, 8H), 3.19
(t, J = 6.6 Hz, 2H), 2.39 (t, J = 6.6 Hz, 2H), 1.16 (t, J = 7.0 Hz, 12H).
Compound 2
In an ice bath, a solution of dansyl chloride (100 mg, 1.0 mmol)
in anhydrous dichloromethane (10 mL) was added slowly to a mix-
ture of compound 1 and triethylamine (0.5 mL) in anhydrous
dichloromethane (20 mL), and then the resulting mixture was stir-
red for 0.5 h at room temperature. With the similar workup proce-
dures as described in synthesis of compound 1, a crude product of
compound 2 was obtained. And the crude product was purified by
column chromatography (ethyl acetate:petroleum ether = 1:1) to
give 120 mg of saffron yellow 2 in 82% yield. 1H NMR (300 MHz,
CDCl3) d 8.48 (d, J = 8.5 Hz, 1H), 8.29 (d, J = 8.7 Hz, 1H), 8.11 (d,
J = 8.5 Hz, 1H), 7.89 (d, J = 6.4 Hz, 1H), 7.45 (ddd, J = 24.1, 16.5,
8.7 Hz, 4H), 7.03 (d, J = 7.5 Hz, 1H), 6.91 (d, J = 7.8 Hz, 1H), 6.28
(d, J = 2.5 Hz, 2H), 5.95 (dd, J = 8.9, 2.5 Hz, 2H), 5.84 (d, J = 8.9 Hz,
2H), 3.29 (q, J = 7.0 Hz, 8H), 3.21–3.16 (t, 2H), 2.78 (s, 6H), 2.63
(t, J = 9.9, 4.6 Hz, 2H), 1.14 (t, J = 7.0 Hz, 12H). 13C NMR (75 MHz,
CDCl3) d 169.80, 153.37, 152.66, 151.19, 148.35, 134.28, 132.31,
129.67, 129.46, 128.53, 123.79, 121.76, 119.05, 114.73, 107.63,
103.76, 97.21, 78.06, 75.91, 76.43, 76.43, 65.18, 45.02, 43.90,
39.47, 12.19. MS: [M+] at 718.
Fig. 2. Absorption (a) and emission (b) spectra of chemosensor 2 (10
addition of various metal ion (10 equiv) in ethanol solution. kex = 420 nm.
l
M) upon
Procedures for metal ion sensing
A stock solution of compound 2 (1.0 Â 10À5 M) was prepared in
ethanol. Stock solutions of the metal perchlorate salts were pre-
pared in ethanol with a concentration of 2.0 Â 10À3 M. Each time
a stock solution of compound 2 (2.0 mL) and less than 100 lL of
a metal ion stock solution were filled in a quartz cell of 1 cm optical
path length using a micro-pipette for spectral measurements. For
all measurements of fluorescence spectra, excitation wavelength
was 420 nm unless otherwise mentioned and the temperature is
20 °C.
Compound 3
Results and discussion
In an ice bath, a solution of TsCl (39.3 mg, 1.0 mmol) in anhy-
drous dichloromethane (10 mL) was added slowly to a mixture of
compound 1 and triethylamine (0.5 mL) in anhydrous dichloro-
methane (20 mL), and then the resulting mixture was stirred for
0.5 h at room temperature. With the similar workup procedures
as described in synthesis of compound 1, a crude product of com-
pound 3 was obtained. And the crude product was purified by col-
umn chromatography (ethyl acetate:petroleum ether = 1:1) to give
saffron yellow 3 in 83% yield. 1H NMR (300 MHz, CDCl3) d 7.89 (dd,
J = 6.2, 2.5 Hz, 1H), 7.66 (d, J = 8.0 Hz, 2H), 7.45 (dd, J = 5.4, 2.9 Hz,
2H), 7.20 (d, J = 8.0 Hz, 2H), 7.08–7.00 (m, 1H), 6.35 (d, J = 1.8 Hz,
2H), 6.24 (d, J = 8.8 Hz, 2H), 6.16 (dd, J = 8.9, 1.8 Hz, 2H), 6.03 (t,
J = 4.6 Hz, 1H), 3.33 (q, J = 7.0 Hz, 8H), 3.20–3.13 (m, 2H), 2.76
(dd, J = 10.3, 5.0 Hz, 2H), 2.36 (s, 3H), 1.59 (s, 2H), 1.17 (t,
J = 7.0 Hz, 13H). 13C NMR (75 MHz, CDCl3) d 169.28, 153.22,
152.83, 148.50, 142.31, 132.41, 129.91, 129.02, 127.87, 126.74,
123.42, 122.46, 107.80, 104.08, 97.37, 76.84, 76.20, 65.15, 43.96,
43.24, 39.74, 21.05, 12.19. MS: [M+] at 638.9.
As shown in Scheme 1, compound 2 (chemosensor 2) was fac-
ilely prepared by a simple condensation reaction between com-
pound 1 and dansyl chloride at room temperature in 82% yield.
The structure of chemosensor 2 was confirmed by NMR (1H and
13C) spectra, ESI mass spectrometry and IR spectroscopy (support-
ing information). The 1H NMR spectrum of chemosensor 2 dis-
played a triplet (12H) at 1.14 ppm corresponding to the methyl
protons, a singlet (6H) at 2.78 ppm corresponding to the methyl
protons, two triplet (2H each) at 2.60–2.65 and 3.18–3.21 corre-
sponding to CH2 of ethanediamine moiety, a quarlet (8H) at
3.25–3.32 ppm corresponding to the methylene protons, three
mutiplets (2H each) at 5.83–5.93, 5.94–5.97 and 6.27–6.28 ppm
corresponding to aromatic protons, seven multiplets (1H, 1H, 5H,
1H, 1H, 1H and 1H respectively) at 6.90–6.92, 7.02–7.04, 7.38–
7.51, 7.88–7.90, 8.09–8.12, 8.28–8.31 and 8.47–8.50 ppm corre-
sponding to aromatic and NH protons (Fig. S2). Mass spectrum of
chemosensor 2 showed a parent ion peak at m/z 718 (Fig. S4). A