Paper
NJC
addition as shown in Fig. 5b. This is in contrast to the 24.32. ꢁve ESI MS: expected: 389 Da, obtained: 388 Da. IR:
ꢁ
1
behaviour upon dilution in the absence of Zn(II) where the
ratiometric response remained constant (Fig. 4b). The LOD for
6
Vmax (cm ): 3090, 2960, 2870, 1700, 1660.
0 0
N-Isopropenyl-N ,N -bis(2-pyridylmethyl)ethane-1,2-diamine (2)
2
3
in this gel matrix was determined as 0.016 mM.
In conclusion, we have developed a ratiometric polymeric 2-Pyridine carboxaldehyde (0.95 mL, 10 mmol), N-(2-aminoethyl)
sensor for Zn(II) with good selectivity and capable of measuring acetamide (0.31 mL, 5 mmol) and sodium triacetoxyborohydride
the concentration of this ion in the 0–25 mM range in aqueous (3.03 g, 143 mmol) were stirred in 1,2-dichloroethane (20 mL) for
buffer (9 : 1 H O : MeOH). Furthermore, the ratiometric change 3 hours under N . 2 M sodium hydroxide (40 mL) was added to
2 2
between the intensity of the calibration fluorophore and that of quench the reaction. The organic layer was retained and the
the Zn(II) sensitive naphthalimide fluorophore was shown to aqueous layer was separated and extracted with dichloro-
remain constant when diluted to 50% of its original concen- methane (2 ꢂ 80 mL). The organic layers were combined,
tration. However, when incorporated within a swellable hydro- washed with brine, separated and dried with anhydrous sodium
gel matrix, the sensor displayed an increasing ratiometric sulphate. The mixture was filtered and the organic layer
0
0
response upon Zn(II) addition. To the best of our knowledge, was evaporated to dryness, giving N-isopropenyl-N ,N -bis-
1
this is the first example of a ratiometric fluorescence sensor (2-pyridylmethyl)ethane-1,2-diamine (2). H NMR: (500 MHz,
capable of operating in conditions of high dilution.
CDCl
C–NH–CQO), 7.37 (2H, Ar–H), 7.20 (2H, Ar–H), 3.91 (4H,
N–CH –Ar), 3.38 (2H, N–CH ), 2.77 (2H, N–CH ), 2.04 (3H,
O–CH3). C NMR (125 MHz, CDCl ) d (ppm): 170.02, 159.12,
3
) d (ppm): 8.59 (2H, Ar–H), 7.64 (2H, Ar–H), 7.62 (1H,
2
2
2
1
3
3
Experimental
Materials and methods
1
49.07, 136.57, 123.19, 122.15, 59.89, 52.50, 37.59, 23.19. ꢁve
ꢁ1
ESI MS: expected: 284 Da, obtained: 283 Da. IR: V
(cm ):
max
All chemicals were purchased from Sigma-Aldrich (Gillingham, 3280, 3060, 2930, 2850, 1655, 1590, 1570.
UK) except for 1-ethyl-3-(3-dimethyl-amino-propyl) carbo-
0
0
N ,N -Bis(2-pyridylmethyl)ethane-1,2-diamine (3)
diimide and triethylamine which were purchased from Fischer
Scientific (Leicestershire, England) and used without further 2 was dissolved in 5 M hydrochloric acid (100 mL) and refluxed
purification. All solvents were also purchased from Sigma- for 24 hours. The solution was cooled and the pH of this was
Aldrich (Gillingham, UK), while deuterated solvents were adjusted to 10 using NaOH. The solution was then extracted
obtained from Cambridge Isotope Laboratories Inc. (Andover, with DCM (3 ꢂ 150 mL), the organic layers combined and dried
USA). In pH studies hydrochloric acid and sodium hydroxide with sodium sulphate. This solution was filtered and evapo-
0
0
were used to lower and increase pH respectively. Dialysis rated to dryness, forming N ,N -bis(2-pyridylmethyl)ethane-1,2-
1
cassettes were purchased from Sigma-Aldrich (Gillingham, diamine (3) (0.8 g, 67% yield). H NMR: (500 MHz, CDCl
UK) and used as received. NMR spectra were obtained on (ppm): 8.46 (2H, Ar–H), 7.58 (2H, Ar–H), 7.40 (2H, Ar–H), 7.05
Varian 500 MHz instrument at 25.0 ꢀ 1 1C and processed using (2H, Ar–H), 3.80 (2ꢂ 2H, –N–CH –Ar), 3.05 (2H, NH ), 2.80 (2H,
). C NMR (125 MHz, CDCl ) d (ppm): 159.59 149.01,
MS apparatus. Absorption spectra were obtained using a Varian 136.31, 122.90, 121.92, 60.73, 57.30, 39.60. +ve ESI MS:
3
) d
2
2
1
3
Bruker software. Mass spectra were obtained on Finnigan LCQ- N–CH
2
3
ꢁ
1
Cary UV-Vis spectrophotometer and fluorescence spectra using expected: 242 Da, obtained: 243 Da. IR: Vmax (cm ): 3280,
a Varian Cary Eclipse fluorescence spectrophotometer and the 3050, 3010, 2930, 2820, 1590, 1570.
Varian Cary Fibre Optic Coupler. pH was measured by a pH
6
-[6-[2-[Bis(2-pyridylmethyl)amino]ethylamino]-1,3-dioxo-
benzo[de]isoquinolin-2-yl]hexanoic acid (4)
(0.11 g, 0.28 mmol), 3 (0.25 g, 1 mmol) and triethylamine
1 mL) were refluxed in 2-methoxyethanol (15 mL) for 30 hours
meter (Hanna Instruments).
1
(
Synthesis of compounds 1–6
under N . The solution was evaporated to dryness and the
resulting oil purified using column chromatography with silica
gel (DCM : MeOH 5 : 1 increasing to 3 : 1), giving 6-[6-[2-[bis-
2
6-(6-Bromo-1,3-dioxo-benzo[de]isoquinolin-2-yl)hexanoic
acid (1)
4
6
-Bromo-1,8-naphthalic anhydride (1.5 g, 5.4 mmol) and (2-pyridylmethyl)amino]ethylamino]-1,3-dioxo-
-aminohexanoic acid (0.72 g, 5.45 mmol) were refluxed in benzo[de]isoquinolin-2-yl]hexanoic acid (4), a yellow solid
1
3
ethanol (80 mL) for 18 hours. Upon cooling crystals formed, (80 mg, 15% yield). mp: 157–158 1C. H NMR: (500 MHz, CDCl )
which were filtered under vacuum, giving 6-(6-bromo-1,3-dioxo- d (ppm): 8.68 (1H, Ar–H), 8.49 (2H, Ar–H), 8.43 (1H, Ar–H), 8.18
benzo[de]isoquinolin-2-yl)hexanoic acid (1) as a yellow solid (1H, Ar–H), 7.82 (1H, Ar–H), 7.71 (1H, Ar–H), 7.62 (2H, Ar–H),
1
(
1.58 g, 72% yield). mp: 161 1C. H NMR: (500 MHz, CDCl ) d 7.50 (2H, Ar–H), 7.20 (2H, Ar–H), 6.65 (1H, Ar–NH–C), 4.00 (2H,
3
(
ppm): 8.68 (1H, Ar–H), 8.60 (1H, Ar–H), 8.42 (1H, Ar–H), 8.05 –N–CH ), 3.89 (4H, –NH –N–), 3.52 (2H, N–CH ), 2.81 (2H, –N–
2
2
2
(
1
1H, Ar–H), 7.87 (1H, Ar–H), 4.20 (2H, N–CH ), 2.41 (2H, –CH –), CH ), 2.20 (2H, –CH –), 1.54 (2H, –CH –), 1.30 (2H, –CH –), 1.22
2
3
2
2
2
2
2
1
13
2 2
.78 (2ꢂ 2H, –CH –), 1.05 (2H, –CH –). C NMR (125 MHz, (2H, –CH
2
–). C NMR (125 MHz, CDCl
3
) d (ppm): 176.94,
CDCl
3
): 179.29, 163.55, 133.22, 132.04, 131.22, 131.07, 130.59, 165.00, 164.44 158.68, 150.55, 149.09, 136.76, 135.00, 131.11,
130.22, 128.96, 128.05, 123.05, 122.19, 40.23, 37.77, 27.63, 26.47, 130.28, 127.78, 124.45, 123.38, 123.06, 122.40, 120.48, 109.45,
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014