660
Y. Liu et al. / Dyes and Pigments 139 (2017) 658e663
Fig. 1. (a) UV spectral changes of sensor 1 (5 ꢂ 10ꢀ5 M) upon addition of Tetrabutylammonium fluoride (abbreviate to TBAF) (0e5.0 ꢂ 10ꢀ4 M) in CH3CN at 25ꢁ C. (b) UV spectral
changes of sensor 1 (5 ꢂ 10ꢀ5 M) in the presence of TBAF (1.0 equivalent of Fꢀ) in CH3CN and then bubbling with different volumes of CO2 at 25ꢁ C.
(m, 2H), 1.29e1.39 (m, 2H), 0.91 (t, 3H, J ¼ 7.5 Hz).
tube, adding an appropriate aliquot of each stock, and diluting the
solution to 3 mL with CH3CN (sensor 1), dioxane (sensor 2). For all
measurements, excitation and emission slit widths were 3 nm/
1.5 nm, respectively.
2.2.3. 6-[3-Ethylthiourea-1-amino]-2-butylbenzo[de]isoquinoline-
1,3-dione (Sensor 1)
4 (142 mg, 0.5 mmol), ethyl isothiocyanate (50 mg, 0.57 mmol)
in acetonitrile (20 mL) were refluxed with magnetic stirring for
12 h. After cooling to room temperature, the formed precipitate
collected by filtration under reduced pressure and washed with
CH3CN and CHCl3 and dried in vacuum oven to give 1 as a dark
yellow solid (81 mg, 43.8%). M.p.: 226.1 0.2 ꢁC. 1H NMR (300 MHz,
3. Results and discussion
3.1. Synthesis
As shown in Scheme 1, intermediates 3 and 4 were prepared by
modifying the reported procedure [23]. Compound 4 was then
reacted with ethyl isothiocyanate, at reflux for 24 h to give the
desired sensor 1 in 43.8% yield, after column chromatography. 4
was also reacted with cholesteryl chloroformate, at reflux for 12 h
DMSO-d6) d 8.85 (br. s, 0.5H, N/H/N), 8.76 (br. s, 0.5H, N/H/N),
8.57 (dd, 2H), 8.46 (d, 1H, J ¼ 8.1 Hz), 8.26 (br. s, 0.5H, N/H/N),
7.80 (t, 1H, J ¼ 8.4 Hz), 7.09 (d, 1H, J ¼ 8.4 Hz), 4.12 (t, 2H, J ¼ 7.2 Hz),
3.62e3.70 (m, 2H), 1.63e1.73 (m, 2H), 1.36e1.47 (m, 2H), 1.13 (t, 3H,
J ¼ 7.2 Hz), 0.97 (t, 3H, J ¼ 7.2 Hz). 13C NMR (125 MHz, DMSO-d6)
to give the desired sensor
chromatography.
2 in 53.1% yield, after column
d
164.3, 163.6, 150.7, 134.3, 131.5, 129.7, 129.5, 125.5, 122.5, 119.9,
The compounds 1 and 2 were fully characterized by 1H and 13
C
111.9, 105.9, 104.8, 39.1, 30.5, 20.5, 15.2, 14.4. HRMS: C19H23N4O2S
([MþH]þ) calcd 371.1497, found 371.1543. IR (cm ꢀ1): 3475, 3239,
2955, 2871, 1701, 1677, 1582, 1419, 1358, 1238, 1088, 953, 776, 517.
NMR, and high-resolution mass spectroscopy.
3.2. Optical changes of 1 and 2 with anions and CO2
2.2.4. NAP-chol-2 (Sensor 2)
As shown in Fig. 1a, the addition of Fꢀ induced a new internal
charge transfer (ICT) absorption peak at 529 nm. This ICT peak can
be attributed to the strong hydrogen bonding and deprotonation of
urea NH hydrogens with Fꢀ, which are well described in previous
reports from various groups [24e26]. As shown in Fig. 2, from pale
yellow to blue purple color change was clearly observed by direct
visualization.
Compound 4 (400 mg, 1.41 mg) was added into dioxane (15 mL)
and cholesteryl chloroformate (633 mg,1.41 mmol) was then added
portionwise. The mixture was stirred at room temperature for 2 h,
then refluxed for overnight. After cooling to room temperature, the
solvent was evaporated under reduced pressure. The residue was
purified by column chromatography (silica gel, dichloromethane/
methanol ¼ 100:1, v/v) to afford 2 as a yellow solid (520 mg) in a
yield of 53.1%. M.p.: 212.0 0.2 ꢁC. 1H NMR (300 MHz, CDCl3)
d 8.39
(d, 1H, J ¼ 8.1 Hz), 8.26 (br, 1H), 7.89 (br, 2H), 7.19 (br, 1H), 7.03 (d,
1H, J ¼ 8.1 Hz), 6.69 (s, 1H), 5.44 (s, 1H), 4.63e4.74 (m, 1H), 4.17 (t,
2H, J ¼ 7.5 Hz), 2.45 (br, 2H), 1.91e2.08 (m, 4H), 0.87e1.79 (m, 31H),
0.70 (s, 3H). 13C NMR (75 MHz, CDCl3)
d 164.0, 156.9, 148.9, 139.2,
133.0, 130.1, 125.4, 125.1, 123.3, 118.8, 113.7, 105.2, 77.2, 56.7, 56.1,
50.0, 42.3, 40.1, 39.7, 39.5, 38.3, 37.9, 36.9, 36.6, 35.8, 31.9, 31.8, 30.2,
28.2, 28.0, 24.3, 23.8, 22.8, 22.6, 21.1, 20.5, 19.3, 18.7, 13.9, 11.9. FAB-
HRMS C44H62N3O4 ([MþH]þ) calcd 696.4740, found 696.4743. IR
(cm ꢀ1): 3477, 3240, 2923, 2856, 1699, 1633, 1460, 1374, 669.
2.3. Preparation of solutions for fluorescent study
Fig. 2. Color changes of sensor 1 in CH3CN (5 ꢂ 10ꢀ5 M) upon addition of various
A stock solution of 1 (1 mM) was prepared in CH3CN, a stock
solution of 2 (1 mM) was prepared in DMSO. Test solutions were
prepared, by placing 15e30 mL of the probe stock solution into a test
anions and bubbling of excess CO2: a) Free sensor 1; b) 1 þ1 eq. AcOꢀ; c) 1 þ1 eq. CNꢀ
;
d) 1 þ 1eq. Fꢀ; e) 1 þ 1 eq. AcOꢀ þ 30 mL of CO2; f) 1 þ 1 eq. CNꢀþ 30 mL of CO2; g)
1 þ 1 eq. Fꢀ þ 30 mL of CO2.