SelectiVe Recognition of Hg2+
a
48 h at room temperature. After filtration, the filtrate was
concentrated to dryness. A yellow solid was obtained, which was
extracted with CHCl3 and washed with water and then with brine,
and the organic layer was dried with anhydrous MgSO4. Filtrate
was concentrated to dryness and recrystallized from EtOH/CHCl3
to get L2 as white crystalline solid. Yield (3.5 g, 60%.).
C76H86N2O6 · CHCl3 (1242): Anal. (% found) C 74.90, H 7.59, N
2.36, (% requires) C 74.43, H 7.01, N 2.26. FTIR: (KBr, cm-1):
1667 νCdO), 3371 (νOH). 1H NMR: (CDCl3, δ ppm): 0.97 (s, 18H,
(C(CH3)3), 1.26 (s, 18H, (C(CH3)3), 3.26 (d, 4H, Ar-CH2-Ar, J
) 13.30 Hz), 4.37 (d, 4H, Ar-CH2-Ar, J ) 13.30 Hz), 4.60, 4.70
(s, 4H, N-CH2) 4.82 (s, 4H, -OCH2CO), 6.87 (s, 4H, Ar-H), 7.00
SCHEME 2. Synthesis of L5
a (a) bromoethylacetate/K2CO3/ acetone; (b) KOH/C2H5OH/Water, reflux;
(c) EDCI/ Et3N/ HOBT/2-aminomethyl benzimidazole. R ) tert-butyl.
1b: A mixture of p-tert-butyl phenol, 1a (2.00 g, 13.3 mmol),
potassium carbonate (2.40 g, 17.3 mmol), and ethyl bromoacetate
(1.77 mL, 15.99 mmol) was taken in dry acetone (150 mL), and
the reaction mixture was stirred and heated at reflux for 12 h under
nitrogen atmosphere. The cooled reaction mixture was concentrated
under reduced pressure. The residue was dissolved in CHCl3 and
washed with 1N HCl. The organic layer was separated and washed
with brine followed by drying using MgSO4. After filtration, solvent
was evaporated by drying under vacuum to result in a yellow oil.
Yield (3.20 g, 97%). 1H NMR (CDCl3, δ ppm): 1.29 (s, 9H,
C(CH3)3), 1.30 (t, 3H, CH2(CH3)3), 4.28 (q, 2H, CH2-CH3, J )
7.33 Hz), 4.59 (s, 2H, OCH2CO), 6.84 (d, 2H, Ar-H, J ) 8.86
Hz), 7.30 (d, 2H, Ar-H, J ) 8.85 Hz).
(s, 4H, Ar-H), 7.24 (s, 2H, -OH), 7.31 (m, 10H, benzyl-H).. 13
C
NMR: (CDCl3, δ ppm): 31.2, 31.8 (C(CH3)3), 32.0(Ar-CH2-Ar),
33.9, 34.0 (C(CH3)3), 49.4, 48.6 (-NCH2), 74.1 (OCH2CO), 125.1,
125.8, 126.8, 127.4, 127.7, 127.9, 128.7, 129.1, 133.0, 136.5, 137.0,
141.3, 147.2, 150.7, 151.16 (Ar-C), 168.8 (CdO). ES-MS: m/z
1
(intensity (%), fragment) 1146.53 (40, [M + Na]+). H and 13C
NMR spectra are given in the Supporting Information, Figure S9.
L3. This compound was synthesized by following the procedure
given for L except using 2-(aminomethyl)pyridine (1.40 g,
12.94mmol), Et3N (2.18 g, 21.57mmol), and diacid chloride (4.32
g, 5.34 mmol), in dry THF (150 mL). The crude product was
recrystallized by slow evaporation of the solvent from C2H5OH/
CHCl3. Yield (2.69 g, 52%.) FTIR: (KBr, cm-1): 1682 (νCdO), 3338
1c: A mixture of the 1b, (3.20 g, 13.55 mmol) and potassium
hydroxide (1.6 g, 28.46mmol) in 120 mL of ethanol:water (2:1 v/v)
mixture were stirred and heated under reflux for 12 h and the
reaction mixture was evaporated under reduced pressure to yield a
white residue. The residue was taken in 1 N HCl (100 mL) and
CHCl3 (250 mL). The organic layer was washed with water and
dried over MgSO4. All the organic solvent was evaporated to yield
white solid as pure product. Yield (2.00 g, 71%). 1H NMR (CDCl3,
δ ppm): 1.29 (s, 9H each, C(CH3)3), 4.66 (s, 2H, OCH2CO), 6.86
(d, 2H, Ar-H, J ) 8.86 Hz), 7.32 (d, 2H, Ar-H, J ) 8.85 Hz).
L5: To a solution of 1c (0.3 g, 1.44mmol) in CH2Cl2 (75 mL)
was added Et3N (1.00 mL, 7.21mmol), 1-ethyl-(3-dimethylamino-
propyl)-3-carbodiimide hydrochloride (EDCI.HCl) (0.41 g, 2.16mmol)
and catalytic amount of 1-hydroxybenzotriazole (HOBT) and stirred
the solution at 0 °C for 30 min under N2 atmosphere. 2-Aminom-
ethyl benzimidazole (0.48 g, 2.16mmol) was added to this reaction
mixture and stirred at room temperature for overnight. The resulting
mixture was washed with water followed by saturated NaHCO3
and brine. The product can be purified either by using silica gel
column with chloroform-methanol as eluant or alternatively by
dissolving the impurities in dichloromethane and filtering off the
product, to give white solid. Yield (0.36 g, 74%). C20H23N3-
O2.CH3OH· (369.45): Anal. (% found) C 67.82, H 7.10, N 10.94,
(% requires) C 68.27, H 7.36, N 11.37. FTIR: (KBr, cm-1): 1654
(νCdO). 1H NMR (DMSO-d6, δ ppm): 1.24 (s, 9H, C(CH3)3), 4.56
(s, 2H, OCH2), 4.58 (s, 2H, NCH2), 6.92 (d, 2H, Ar-H, J ) 8.86
Hz), 7.14 (m, 2H, Benz-H), 7.30 (d, 2H, Ar-H, J ) 8.86 H), 7.51
(br, 2H, Benz-H), 8.78 (t, 1H, CONH, J ) 5.80 Hz), 12.31 (s, 1H,
Benz-NH). 13C NMR: (DMSO-d6, δ ppm): 31.4, 33.8, 36.9, 67.0,
79.3, 114.3, 121.4, 126.1, 143.4, 152.1, 155.6, 168.4. ESI MS: m/z
(intensity (%), fragment) 338.3 (100, [M + H]+).
1
(νOH). H NMR: (CDCl3, δ ppm): 0.91 (s, 18H, (C(CH3)3), 1.20
(s, 18H, (C(CH3)3), 3.28 (d, 4H, Ar-CH2-Ar, J ) 13.48 Hz),
3.98 (d, 4H, Ar-CH2-Ar, J ) 13.48 Hz), 4.45 (s, 4H, -OCH2),
4.61 (d, 4H, -NH-CH2, J ) 5.15 Hz), 6.76 (s, 4H, Ar-H), 6.96
(s, 4H, Ar-H), 7.07 (t, 2H, Py-H, J ) 6.10 Hz), 7.14 (s, 2H,
-OH), 7.32 (d, 2H, Py-H, J ) 7.53 Hz), 7.56 (t, 2H, Py-H, J )
7.73 Hz), 8.31 (d, 2H, Py-H, J ) 4.76 Hz), 9.10 (t, 2H, NHCO,
J ) 5.15 Hz) 13C NMR: (CDCl3, δ ppm): 31.1, 31.7 (C(CH3)3),
32.1(Ar-CH2-Ar), 34.0, 34.2 (C(CH3)3), 45.4 (-NCH2), 74.9
(OCH2CO), 122.4, 122.4, 125.6, 126.2, 127.2, 132.2, 136.7, 142.9,
148.3, 149.2, 149.4, 149.7, 156.9 (Ar-C), 168.62 (CdO). ESI-
MS: m/z (intensity (%), fragment) 946.6 (30, [M + 1]+).
L4. In 50 mL of THF solution of 3 (1.0 g, 1.3 mmol),
1-hydroxybenztriazol (0.392 g, 2.9 mmol) and DCC (0.598 g, 2.9
mmol) were stirred at room tempreture. To this, L-phenylalanine
methyl ester hydrochloride (0.625 g, 2.9 mmol) and triethyl amine
(1.5 mL) in 30 mL THF were added dropwise. Stirring was
continued for 48 h. Solvent was evaporated under reduced pressure.
The solid was redissolved in CH2Cl2. The reaction mixture was
washed with 1 N HCl followed by brine and the organic layer was
collected and dried with anhydrous Na2SO4. After filtration, the
solvent was removed under reduced pressure. The pure product
was obtained as white powder (0.75 g, 56.0%). C68H82N2O10
·
(1086): Anal. (% found) C 74.75, H 7.20, N 2.75, (% requires) C
75.14, H 7.55, N 2.58. FTIR (KBr, cm-1): 3458, 3304 (νNH/OH),
1
1752 (νCdO, COOMe), 1670 (νCdO, CONH). H NMR (CDCl3, δ
ppm): 1.02, 1.30 (s, 36H, C(CH3)3), 3.02-3.15 (m, 6H,
Ar-CH2-Ar, and CꢀH2-Ph), 3.47 (d, 2H, Ar-CH2-Ar, J ) 13.76
Hz), 3.64 (s, 6H, OCH3), 4.06 (d, 2H, Ar-CH2-Ar, J ) 12.9 Hz),
4.10 (d, 2H, Ar-CH2-Ar, J ) 14.2 Hz), 4.14 (d, 2H, O-CH2-CO,
J ) 15.2 Hz), 5.03 (d, 2H, O-CH2-CO, J ) 15.0 Hz), 5.10 (q,
2H, CRH, J ) 7.8, 7.0 Hz), 6.87 (d, 4H, Ar-H), 7.03 (m, 14H,
Synthesis, Isolation, and Characterization of the Hg2+
Complex of L. Metal salt, Hg(ClO4)2 (0.094 g, 0.235 mmols) was
dissolved in CH3OH (5 mL) and was added to the ligand, L (0.20
g, 0.196 mmols) in CHCl3. The solution was stirred overnight
followed by refluxing for 12 h. The resulting solution was
concentrated, washed with minimum amount of methanol and dried
Ar-H, Ph-H), 7.73 (s, 2H, OH), 9.51 (d, 2H, NH, J ) 8.3). 13
C
NMR (CDCl3, 400 MHz,): δ 30.9, 31.7 (C(CH3)3), 32.0, 32.5
(Ar-CH2-Ar), 33.9, 34.0 (tert-C), 39.0 (CH2-Ph), 52.1 (OCH3),
52.8 (CH), 74.9 (O-CH2-CO), 124.7, 125.3, 125.8, 126.4, 126.5,
126.7, 127.6, 128.1, 128.9, 132.6, 136.1, 142.3, 147.8, 149.7, 150.0
(aromatic carbons), 168.8 (CONH), 171.8 (COOMe) ppm. ES-MS:
m/z ) 1087 ([M + H]+, 100%). 1H and 13C NMR spectra are given
in Supporting Information, Figure S9.
1
under vacuum. Yield (80%, 0.22 g). H NMR: (CDCl3, 400 MHz
δ ppm): 1.10 (s, 18H, (C(CH3)3), 1.14 (s, 18H, (C(CH3)3), 3.43 (d,
4H, Ar-CH2-Ar, J ) 12.50 Hz), 4.10 (d, 4H, Ar-CH2-Ar, J )
12.50 Hz), 4.65 (s, 4H, -CH2CONH-), 5.33 (s, 4H, -CON-
HCH2-), 7.10 (s, 4H, Ar-H), 7.13 (s, 4H, Ar-H), 7.52 (m, 4H,
benzimidazole), 7.76 (s, 2H, benzimidazole), 8.19 (s, 2H, -OH),
8.27 (m, 2H, benzimidazole), 9.75 (s, 2H, CONH), 14.56 (s, 2H,
-NH-benzimidazole). Anal. (% found) C 53.02, H 6.41, N 5.57,
Hg 12.92. C64H74N6O6. 4C2H5OH. Hg(ClO4)2 (% required) C 53.41,
L5. Reference compound L5 has been synthesized as shown in
1
Scheme 2. H and 13C NMR spectra are given in the Supporting
Information, Figure S9.
J. Org. Chem. Vol. 73, No. 15, 2008 5757