Supporting Information for
Detection and differentiation of ferrous and ferric ions using fluorescent
metallopolymer and oligomer chemosensors
Megan E. A. Fegley,a Trevor Sandgren,b Jetty L. Duffy-Matzner,b Anting Chena and Wayne E.
Jones, Jr.a,*
a
Department of Chemistry, State University of New York at Binghamton, Binghamton, New
York 13902-6016
b
Department of Chemistry, Augustana College, Sioux Falls, South Dakota 57197
1. Experimental Section
Materials. All materials were purchased from Sigma Aldrich or Alfa Aesar and used as
received unless otherwise noted. The 1,4-diethynyl-2,5-didodecyloxybenzene1 and 2,5-dibromo3-bromomethylthiophene2, 3 and tmpda-PPETE oligimer were synthesized according to literature
methods. Satisfactory NMR characterization of all stable intermediates was observed in each
case.
General Methods. 1H and 13C NMR spectra were recorded on a Bruker Avance III 600.
Elemental analysis was performed by Galbraith Laboratories in Knoxville, TN. The molecular
weight and distribution were determined by gel permeation chromatography (GPC) using a
solution of 0.1% (by volume) in tetrahydrofuran as the mobile phase at 35±0.5 °C with a flow
rate of 1.0 mL/min, relative to polystyrene standards. The GPC instrument used was an Agilent
1260 Infinity with a PLgel MIXED C column. UV-vis spectra were obtained on a Perkin-Elmer
Lambda 2S spectrophotometer or Panorama Fluorat 02 in tetrahydrofuran (THF) solution using
1cm quartz cuvette cells. Fluorescence spectra were measured on a Panorama Fluorat 02 using
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excitation at 446 nm with 4 nm slits. Metal cation stock solutions were prepared by dissolving a
certain amount of metal chloride salt in water to obtain a 5 mM cation solution. Pipetting 5 mL
of metal cation stock solution into a 100 mL volumetric flask and diluting with water gave 2.5 x
10-4 M metal cation solutions for use in emission experiments. The chemosensor stock solutions
were made by dissolving a certain amount of sensor in THF to prepare a 5×10-5 M solution (with
respect to the repeat unit). Pipetting 10 mL of the 5×10-5 M sensor solution into 90 mL THF
made a 100 mL sensor solution of 5 μM.
The metal cation titration experiments were carried out by adding small aliquots of the 2.5 x
10-4 M metal cation solution to 5μM sensor solutions in THF. All metal ion solutions were
prepared by dissolving their metal chlorides in water. For the tmeda-PPETE/Cu2+ hybrid
experiments, an aliquot of the 2.5 x 10-4 M Cu2+ solution was titrated via micropipette into 3 mL
of the 5 μM chemosensor polymer solution in a 1 cm quartz cuvette cell followed by thorough
mixing to reach a 1:1 mole ratio of Cu2+:tmeda receptor. Next, a small aliquot of the 2.5 x 10-4 M
metal cation solution to be test was added with mixing to the quartz cuvette. Absorption and
emission spectra were collected of the neat polymer solution, after the Cu2+ addition and after
addition of the tested metal cation. We assume using a concentrated stock solution could
minimize the influence water has on the fluorescence of the polymer. All solutions were used
within 24 hours of preparation.
For the iron buffer experiments, 5 x 10-4 M metal cation solutions were prepared from the 5
mM metal cation stock solutions. The tris-HCl buffer was prepared by dissolving 0.6057g
Tris(hydroxymethyl)aminomethane (5 mmol) in 350 mL water, adjusting the pH to 7.4 using
HCl and then diluting to 500 mL to create a 0.01 M solution. The metal cation titration
experiments were carried out by adding small aliquots of the 5 x 10-4 M iron cation solution and
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0.01 M tris-HCl solution to 5μM tmpda-PPETE solutions in THF followed by thorough mixing.
Emission spectra were collected of the neat polymer solution and after each addition of buffer
and iron cation solutions.
The fluorescence quantum yield was determined using quinine sulfate in 0.5 M H2SO4
solutions as a standard with a quantum yield of 0.546 when excited at 365 nm. A 0.01 mg/mL
solution of tmpda-PPETE in tetrahydrofuran was prepared to measure the fluorescent lifetime
under optical excitation. The solution was optically excited with the frequency-tripled output of
an EKSPLA PL-2250 series diode-pumped picosecond Nd:YAG laser. The repetition rate and
pulse width of the laser was 50 Hz and 30 ps. A 355-nm laser beam was mildly focused onto an
NMR tube containing the 0.01 mg/mL solution using a positive convex lens with a 7.5-cm focal
length. The emission was recorded at 490 nm.
Scheme S1. Synthesis of amino receptor monomer
Synthesis. N-(2,5-dibromothiophen-3-ylmethyl)-N,N,N’-trimethylpropyl-1,3-diamine was
prepared by modification of previous literature.3 A mixture of 2.42g (7.22 mmol) of 2,5dibromo-3-bromomthylthiophene in 20 mL diethyl ether, 3.17 mL (2.52g, 21.6 mol) of N,N,N'trimethyl-1,3-propanediamine, 10 mL water, and 5.74 g Na2CO3 was stirred for 48 hours. The
reaction mixture was acidified with 6M HCl and extracted with water. The aqueous layer was
separated and washed with diethyl ether. The aqueous layer was made basic by addition of 20%
Na2CO3 and then extracted with diethyl ether (3 x 50 mL). The ether layer was dried over
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anhydrous MgSO4. Removing ether under vacuum gave a white oil (1.41g, 53%). [FTIR (NaCl
plates): wavenumber (cm-1): 3096, 2947, 2777, 1543, 1461, 1347, 1259, 1173, 1121, 1039, 1003,
915, 833, 442; 1H NMR (CDCl3, 600MHz): δ 6.93 (s,1H), 3.35 (s, 2H), 2.36-2.39 (t, 2H, J=7.3
Hz), 2.25-2.28 (t, 2H, J=7.3 Hz), 2.20 (s, 6H), 2.17 (s, 3H), 1.64 (quint, 2H, J=7.3 Hz); 13C
NMR (600MHz, CDCl3): δ=140.04, 131.65, 110.71, 109.70, 57.77, 55.52, 45.54, 42.14, 25.70.
Elemental analysis: Calcd for C11H18Br2SN2: C, 35.69%; H, 4.90%; Br, 43.17%, S; 8.66%, N,
7.57%. Found: C, 35.88%; H, 4.72%; Br, 43.22%; S, 8.32%; N, 7.56%.]
Scheme S2. Synthesis of tmpda-PPETE
tmpda-PPETE. (poly[2,5-(3-[N-methyl-N-(N’,N’-dimethyl-3propanamino)methylamino]thiophenediyl)-1,2-ethynediyl-1,4-(2,5didodecoxyphenylenediyl)-1,2-ethynediyl]) A mixture of N-(2,5-dibromothiophen-3ylmethyl)-N,N,N’-trimethylpropyl-1,3-diamine (0.196g, 0.53 mmol), 1,4-diethyl-2,5didodecyloxybenzene (0.262g, 0.53 mmol), Pd(PPh3)4 (31mg, 0.03 mmol), and CuI (11 mg,
0.05 mmol) in 10 mL anhydrous THF was stirred under a nitrogen atmosphere. After
addition of 2 mL diisopropylamine, the mixture was refluxed for 24 hours. An ammonium
iodide salt formed during refluxing. The dark orange red reaction mixture was extracted into
chloroform (20 mL) and washed with dilute NaHCO3 solution (3 x 20 mL). Removing
solvent under vacuum gave a dark orange sticky solid which was washed with hot water, hot
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methanol, and hot acetone. The final product was a dark orange sticky solid (0.439g, 96%)
[FTIR: the formation of internal ethynyl link was confirmed by the presence of the 2193 cm-1
stretch; 1H NMR (600MHz, CDCl3): 6.9-7.2 (3H), 4.0 (4H), 3.4-3.7 (2H), 2.3-2.5 (4H), 2.22.3 (9H), 1.8 (4H), 1.7 (2H), 1.5-1.8 (36H), .9 (6H); UV-vis λmax: 446nm. Emission λmax:
490nm.]
Supplementary Spectra
Figure S1. 1H NMR spectrum of N-(2,5-dibromothiophen-3-ylmethyl)-N,N,N’-trimethylpropyl1,3-diamine.
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Figure S2. 1H NMR spectrum of tmpda-PPETE.
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Figure S3. 1H NMR spectra of tmpda-PPETE in comparison to its monomers, N-(2,5dibromothiophen-3-ylmethyl)-N,N,N’-trimethylpropyl-1,3-diamine and 1,4-diethyl-2,5didodecyloxybenzene.
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Figure S4. The excitation spectra for titration of Fe2+ (left) and Fe3+ (right) aqueous solution into
5 µM tmpda-PPETE solution.
Figure S5. Fluorescence response following excitation at 446 nm from 5µM tmpda-PPETE THF
solution upon titration of Fe2+ (left) and Fe3+ (right) cation aqueous solutions.
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Figure S6. Fluorescence quenching comparison of 5 µM tmpda-PPETE upon titration of Fe2+
and Fe3+ aqueous and tris-HCl buffer (pH 7.4) solutions. Inlay shows fluorescence quenching
from 0-6 µM cation concentration.
References
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2.
3.
T. M. Swager, C. J. Gil and M. S. Wrighton, The Journal of Physical Chemistry, 1995, 99, 4886-4893.
S. Mandal, Journal of the Chemical Society, Perkin Transactions 1, 1999, 2639-2644.
L. J. Fan, Y. Zhang and W. E. Jones, Jr., Macromolecules, 2005, 38, 2844-2849.
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