Fluorescence Sensing of Cyanide Ions in Aqueous Solution
COMMUNICATION
CH3), 2.04 (s, 6H; Mes-CH3), 2.70 (m, 2H; CH2CH2P), 2.77 (m, 2H;
NHCH2CH2), 2.83 (s, 6H; NACHTNURGTNEUNG(CH3)2), 6.48 (s, 4H; Mes-CH), 6.72 (br, 1H;
coordination to the boron center neutralizes the electron ac-
cepting properties of the phosphonium borane unit leading
to a revival of the fluorescence of the pendant fluorophore.
The success of this approach is illustrated by the use of [2]+
for the naked-eye detection of cyanide ions at 50 ppb con-
centrations in aqueous solutions.
NH), 7.11 (d, J=7.2 Hz, 1H; dansyl-CH), 7.39–7.60 (m, 13H; Ph/dansyl-
CH), 7.71–7.74 (m, 2H; phenylene-CH), 8.08 (d, J=7.6 Hz, 1H; phenyl-
ene/dansyl-CH), 8.31 (d, J=8.4 Hz, 1H; phenylene/dansyl-CH), 8.45 (d,
J=8.4 Hz, 1H; phenylene/dansyl-CH), 8.50 ppm (m, 1H; phenylene/
dansyl-CH); 13C NMR (100 MHz, CDCl3): d=19.40 (d, JC,P =54.7 Hz),
20.81, 23.92, 25.67, 42.10 (d,
88.9 Hz), 115.53, 118.64, 119.07 (d, JC,P =85.5 Hz), 119.30, 123.07, 128.72
(d, C,P =12.9 Hz), 128.92, 129.57, 129.92, 130.20, 130.30 (d, JC,P
JC,P =16.7 Hz), 45.51, 109.89 (d, JC,P =
J
=
12.2 Hz), 131.12, 132.85, 133.54 (d, JC,P =9.8 Hz), 134.77, 135.31, 137.89
(m), 141.86, 145.98, 149.14, 151.76, 170.82 ppm; 11B NMR (128 MHz,
CDCl3): d=À12.45 ppm; 31P NMR (161 MHz, CDCl3): d=23.90 ppm; IR
(film on KBr plate): n˜ =2166.8 cmÀ1 (CNÀ); elemental analysis calcd (%)
for C53.2H59.8BN3O3.2PS ([2(CN)]·1.2CH3OH): C 73.76, H 6.96; found: C
73.28, H 6.76 (1H NMR spectrum shows the presence of residual metha-
nol).
Experimental Section
General considerations: Dimesitylboron fluoride and potassium cyanide
were purchased from Aldrich, dansyl chloride from TCI. Solvents were
dried by passing through an alumina column (toluene, acetonitrile), heat-
ing to reflux under N2 over Na/K (Et2O and THF). UV/Vis spectra were
recorded on an Ocean Optics USB4000 spectrometer with an Ocean
Optics ISS light source. IR spectra were obtained by using an ATI Matt-
son Genesis Series FT infrared spectrophotometer. Fluorescence meas-
urements were carried out by using a PTI, QuantaMaster spectrofluor-
ometer. Elemental analyses were performed by Atlantic Microlab (Nor-
cross, GA). The pH measurements were carried out with a Radiometer
PHM290 pH meter equipped with a VWR SympHony electrode. NMR
spectra were recorded on Varian Inova 300 FT NMR (299.96 MHz for
1H, 121.43 MHz for 31P) and Varian Unity Inova 400 FT NMR
(399.59 MHz for 1H, 375.99 MHz for 19F, 128.19 MHz for 11B,
161.75 MHz for 31P, 100.45 MHz for 13C) spectrometers at ambient tem-
perature unless otherwise stated. Chemical shifts are given in ppm, and
are referenced against external BF3·Et2O (11B), and 85% H3PO4 (31P).
Additional experimental and synthetic details can be found in the Sup-
porting Information.[20]
Acknowledgements
Support by the National Science Foundation (CHE-0646916, CHE-
0952912 and CHE-0755207), the Welch Foundation (A-1423), Texas
A&M University (Davidson Professorship) and the Korea Research
Foundation (Grant to H.S.H., KRF-2008-357-C00079) is gratefully ac-
knowledged.
Keywords: boranes · cyanide · fluorescence · sensors · turn-
on
Synthesis of [2]I: A mixture of N-(3-bromopropyl)-5-(dimethylamino)-1-
naphthalenesulfonamide (0.55 g, 1.48 mmol), sodium iodide (0.54 g,
3.6 mmol), and p-Ph2P-C6H4-BMes2 (0.61 g, 1.2 mmol) in acetonitrile
(10 mL) was heated to reflux overnight. After cooling to room tempera-
ture, the solvent was removed in vacuo to afford a residue which was
treated with CH2Cl2 (20 mL). The resulting mixture was filtered to afford
a CH2Cl2 solution which was concentrated in vacuo to a final volume of
about 5 mL. This concentrate was purified by flash chromatography over
silica gel by using first, ethyl acetate (20 mL) and then methanol
(20 mL). The solvents were removed in vacuo and the residue was ex-
tracted with CH2Cl2 (20 mL) and water (10 mL). The organic layer was
separated, dried over MgSO4, filtered and concentrated in vacuo. Further
purification was achieved by washing the solid with Et2O to afford [2]I as
a yellow solid (0.45 mg, 40%). 1H NMR (300 MHz, CDCl3): d=1.90
(brs, 2H; CH2CH2CH2), 1.97 (s, 12H; Mes-CH3), 2.30 (s, 6H; Mes-CH3),
[1] M. A. Holland, L. M. Kozlowski, Clin. Pharm. 1986, 5, 737–741.
[2] K. C. M. Raja, Trends Carbohydr. Chem. 1999, 5, 25–35.
[4] a) D. Nhassico, H. Muquingue, J. Cliff, A. Cumbana, J. H. Bradbury,
(Deddington UK) 1998, 8, 2–6.
[6] a) J. V. Ros-Lis, B. Garcia, D. Jimenez, R. Martinez-Manez, F. San-
Garcia-Acosta, R. Martinez-Manez, F. Sancenon, J. Soto, Chem.
5721–5723; e) M. Tomasulo, S. Sortino, A. J. P. White, F. M. Raymo,
2.84 (s, 6H;
NACHTUNGTRENNUNG(CH3)2), 3.33 (m, 2H; NHCH2CH2), 3.83 (m, 2H;
CH2CH2P), 6.83 (s, 4H; Mes-CH), 7.15 (d, J=7.5 Hz, 1H; dansyl-CH),
7.43 (t, J=8.0 Hz, 1H; dansyl-CH), 7.59–7.83 (m, 15H; Ph/phenylene/
dansyl-CH), 8.14 (d, J=6.6 Hz, 1H; dansyl-CH), 8.40–8.48 ppm (m, 2H;
dansyl-CH), NH not detected; 13C NMR (100 MHz, CDCl3): d=20.68 (d,
J
C,P =52.4 Hz), 21.39, 23.70, 23.88, 42.12 (d, JC,P =17.5 Hz), 45.53 (N-
CH3), 115.52, 117.90 (d, JC,P =85.8 Hz), 119.68, 120.45 (d, JC,P =84.3 Hz),
123.10, 128.71, 128.77, 128.96, 129.56, 129.94, 130.24, 130.72 (d, JC,P
12.1 Hz), 132.77 (d, JC,P =9.1 Hz), 133.67 (d, JC,P =9.9 Hz), 135.18, 135.32,
136.62 (d, C,P =12.1 Hz), 140.10, 140.87, 140.99, 151.71, 153.63 ppm;
=
J
31P NMR (121 MHz, CDCl3): d=+25.20 ppm; a 11B NMR signal could
not be observed despite extended acquisition times; MS (ESI): m/z:
calcd for C51H55BN2O2PS+ [MÀIÀ]+: 801.38; found 801.3569; elemental
analysis calcd (%) for C51.45H55.9BCl0.9IN2O2PS ([2]I·0.45CH2Cl2): C 63.91,
H 5.83; found: C 63.88, H 5.80 (1H NMR spectrum shows CH2Cl2 resi-
due).
5260–5262; b) K.-S. Lee, H.-J. Kim, G.-H. Kim, I. Shin, J.-I. Hong,
[8] a) H. Liu, X.-B. Shao, M.-X. Jia, X.-K. Jiang, Z.-T. Li, G.-J. Chen,
Synthesis of [2(CN)]: [2]I (50 mg, 0.054 mmol) was dissolved in methanol
(5 mL) and treated with a solution of KCN (33 mg, 0.51 mmol) in metha-
nol (2 mL), which resulted in the formation of a solid. After 30 min, the
solid was isolated by filtration, washed with methanol, and dried in vacuo
to afford [2(CN)] as a pale yellow powder (23 mg, 51%). 1H NMR
(400 MHz, CDCl3): d=1.56 (brs, 2H; CH2CH2CH2), 1.82 (s, 12H; Mes-
[9] K. Poland, E. Topoglidis, J. R. Durrant, E. Palomares, Inorg. Chem.
Chem. Eur. J. 2011, 17, 2057 – 2062
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2061