Paper
Organic & Biomolecular Chemistry
Syntheses of compounds
54.6, 20.9, 11.5; ESI-MS m/z = 351.2 [M + H]+; CHN analysis
calcd for (C21H22N2OS): C, 71.97; H, 6.33; N, 7.99; found: C,
Compound 1. n-Propylamine (0.77 mL, 9 mmol) was added 71.53; H, 6.30; N, 7.93.
to the solution of 2-hydroxy benzaldehyde (1 mL, 9 mmol) in
Syntheses of nano-aggregates N1 and N2
10 mL of MeOH and stirred overnight at room temperature.
The solid product (1a, Schiff base) obtained was filtered and
dried in air. The Schiff base, 1a was then dissolved in 50 mL of
MeOH–THF (1 : 1, v/v) and was reduced with NaBH4 (1.5 mg,
36 mmol). The reaction mixture was allowed to stir at room
temperature overnight and the solvent was removed under
reduced pressure. The residue obtained was dissolved in
CHCl3 and extracted with water. The extracted organic layers
were dried over Na2SO4 and concentrated to afford reduced
The nano-aggregates were synthesized by a re-precipitation
method.34 A solution of the respective compound (1 mM) in
acetonitrile was prepared. 1 mL of the working solution was
slowly injected into 100 mL of water with a micro-syringe. The
solution is then sonicated for a total of 10 minutes, making
sure the temperature of the solution containing nanoparticles
did not rise above 10 °C.
amine 1b. The compound 1b was dissolved in CHCl3 (15 mL) Recognition studies
and refluxed with 1-naphthyl isothiocyanate (0.310 g, 2 mmol)
The recognition studies were performed at 25 1 °C, and the
at 60 °C for 4 hours and then stirred overnight at room temp-
erature. The solvent was removed under reduced pressure and
solid residue was recrystallized in MeOH to obtain pure com-
pound 1 in 92% yield. FT IR (KBr) (νmax, cm−1): 3365(br), 3252
(w), 2923(m), 1589(s), 1515(s); 1H NMR (400 MHz, DMSO-d6) δ:
9.76(br, 1H,NH), 9.38 (s, 1H, OH), 7.93 (d, 1H, J = 6.8 Hz, ArH),
7.84–7.77 (m, 2H, ArH), 7.51–7.48 (m, 3H, ArH), 7.32(d, 1H, J =
7.2 Hz, ArH), 7.23 (d, 1H, J = 7.4 Hz, ArH), 7.14(t, 1H, J =
7.9 Hz, ArH), 6.90–6.86(m, 2H, ArH), 5.06 (s, 2H, CH2), 3.70
(t, 2H, J = 7.5 Hz, CH2), 1.73–171 (m, 2H, CH2), 0.89 (t, 3H, J =
7.2 Hz, CH3); 13C NMR (100 MHz, DMSO-d6) δ: 181.9, 156.3,
135.4, 134.4, 131.8, 130.4, 128.7, 128.2, 127.5, 127.3, 127.0,
126.5, 126.2, 125.6, 122.5, 119.8, 117.4, 53.7, 50.2, 20.2, 11.6;
ESI-MS m/z = 351.2 [M + H]+; CHN analysis calcd for
(C21H22N2OS): C, 71.97; H, 6.33; N, 7.99; found: C, 71.63; H,
6.28; N, 7.85.
solutions were shaken for a sufficient time before recording
the spectrum. The binding ability of nano-aggregates N1–2
(10 μM) in aqueous medium was determined by adding 50 μM
of a metal nitrate/tetrabutylammonium salt of anions to 5 mL
solution of N1–2 taken in volumetric flasks. The volumetric
flasks were allowed to stand for 30 minutes before the spectra
were recorded. For Hg2+ titrations, Hg(NO3)2 was added to
volumetric flasks containing nano-aggregate solutions of N1–2
in aqueous medium. To evaluate any possible interference due
to different cations for the estimation of Hg2+, solutions were
prepared containing N1–2 (10 μM) with and without other
interfering metal ions (50 μM). The effect of ionic strength was
explored by recording the spectra at different concentrations of
tetrabutylammonium nitrate (0–200 equivalent). pH titrations
were performed to understand the effect of pH on the recog-
nition profile of N1 and N2.
Compound 2. n-Propylamine (0.82 mL, 10 mmol) was
added to
a solution of 4-hydroxy benzaldehyde (1.2 g,
10 mmol) in 10 mL of MeOH and stirred overnight at room
temperature . The solid product (2a, Schiff base) obtained was
filtered and dried in air. The Schiff base, 2a was then dissolved
in 50 mL of MeOH–THF (1 : 1, v/v) and was reduced with
NaBH4 (1.57 mg, 40 mmol). The reaction mixture was allowed
to stir overnight at room temperature and the solvent was
removed under reduced pressure. The residue so obtained was
dissolved in CHCl3 and extracted with water. The extracted
organic layers were dried over Na2SO4 and concentrated to
afford reduced amine 2b. Compound 2b was dissolved in
CHCl3 (15 mL) and refluxed with 1-naphthyl isothiocyanate
(0.227, 1.23 mmol) at 60 °C for 4 hours and then stirred at
room temperature overnight. The solvent was removed under
reduced pressure and the solid residue was recrystallized in
MeOH to obtain pure compound 2 in 64% yield. FT IR (KBr)
(νmax, cm−1): 3112(w), 2926(w), 1583(s), 1516(s); 1H NMR
(400 MHz, CDCl3) δ: 7.79 (d, 1H, J = 8.1 Hz, ArH), 7.72 (d, 1H,
J = 7.6 Hz, ArH), 7.50–7.37 (m, 5H, ArH), 7.26–7.27 (m, 1H,
ArH), 6.86 (d, 2H, J = 6.2 Hz, ArH), 6.78 (d, 1H, J = 8.1 Hz,
ArH), 4.9(s, 2H, CH2), 3.83 (q, 2H, J = 7.7 Hz, CH2), 1.82 (m,
2H, CH2), 0.96 (t, 3H, J = 7.4 Hz, CH3); 13C NMR (100 MHz,
CDCl3) δ: 183.3, 157.1, 137.5, 135.8, 134.3, 130.6, 130.3, 128.6,
127.5, 126.7, 126.2, 125.7, 125.5, 122.4, 118.8, 115.5, 113.7,
Acknowledgements
This work was supported with a research grant (SR/FT/CS-97/
2010(G) from the Department of Science and Technology
(DST), Government of India. S. K. acknowledges DST for an
INSPIRE fellowship.
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2308 | Org. Biomol. Chem., 2014, 12, 2302–2309
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