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NJC
1634 and 1464 (C–C), 1383 (stretching of O–CH3), 1236 (methylene
bridge –CH2–), 1049 (bending of O–CH3). The peak at 772 cmÀ1
for 1,2,3-trisubstituted benzene disappeared.
Synthesis of methylene crosslinked calix[4]arene (MC-[4]H) (6)
A mixture of compound 5 (1.00 g, 8.32 mmol) and sodium iodide
Fig. 1 The structure of methylene crosslinked calix[4]arene (MC-[4]H).
(24.9 g, 166 mmol, 20 eq.) was added to dry CHCl3 (200 cm3). After
adding chloromethylsilane (TMSCl, 21.2 cm3, d = 0.85 g cmÀ3
,
166 mmol, 20 eq.), the mixture was heated at 80–85 1C for 72 h.
0.1 M sodium thiosulfate solution (30 cm3) was added and the
mixture was stirred for 1 h at room temperature. The mixture was
stirred in 1 M HCl (50 cm3) for 1 h and filtered with distilled water.
The product was washed with 1 M HCl and distilled water, and
dried at 80 1C for 48 h. The resin MC-[4]H, 6, was obtained as a
black powder, in 1.04 g yield. The obtained compound was
insoluble in any organic diluents and solution state characteriza-
tion by 1H-NMR spectroscopy could not be accomplished. IR: nmax
(KBr)/cmÀ1: 3262 (O–H), 2931 (C–H), 1647 (crosslinked methylene),
1475 (C–C), 1230 (bridged methylene).
the adsorption mechanism of Pt(IV) and Pd(II) on the resins are
also discussed.
Materials and methods
The 1H and 13C-NMR spectra of the obtained compounds were
recorded using NMR spectroscopy (JEOL-JNM-AL 300 MHz and
Varian Premium Shielded 400 MHz (1H) and 100 MHz (13C)
spectrometers) in CDCl3 and (CD3)2CO with TMS as an internal
standard. IR spectra were recorded using an IR spectrophoto-
meter (JASCO FT-IR 410) in KBr pellets. Thermal analysis was
carried out by using a simultaneous DTA-TG apparatus (Shimadzu,
DTG-60H). Elemental analysis was carried out using SEM-EDX
(JSM-6010PLUS/LA, JEOL). Morphological images were taken using
scanning electron microscopy (SEM) (Hitachi SU-1500). The metal
concentrations of aqueous solutions were measured by inductively
coupled plasma atomic emission spectrophotometry (ICP-AES,
Shimadzu ICPS-8100) and the pH values of aqueous solutions
were measured by using a pH meter (TOA-DKK HM-30R). All
starting materials and solvents were commercially available
and used without further purification except otherwise noted.
Dry acetone and dry chloroform were obtained by drying over
anhydrous MgSO4.
Spectral data for starting material 1, together with
un-crosslinked 3 and 4 are given in Fig. S1–S8 and Tables S1–S8
(ESI†).
The solubility test of the resins 5 and 6 and the un-crosslinked
compounds 3 and 4
5 cm3 of acidic or alkaline solution, water or organic solvent
was added to 5 mg of resin or the un-crosslinked compounds.
The solubility test was simply carried out by a visual check.
The adsorption experiments
pH dependency. The percentage adsorption of metal ions as
a function of pH was evaluated by the conventional batch
method. The tested solutions of metal ions were prepared by
dissolving metal salts of palladium nitrate hydrate and hydro-
gen hexachloro platinate(IV) hydrate in 0.1 M HNO3 and 0.1 M
HEPES buffer and they were arbitrarily mixed to adjust to the
desired pH value. 10 cm3 of the solutions tested was added to
0.01 g of resin having a mesh size less than 150 mm. The
heterogeneous mixture was shaken at a shaking speed of
150 rpm for 72 h at 30 1C. After equilibrium, the employed resin
was separated by filtration (Advantec 5C filter having +0.5 mm
Synthesis of intermediates
5,11,17,23-Tetra-tert-butyl-25,26,27,28-tetrahydroxycalix[4]arene
(tBu[4]H) (2), 25,26,27,28-tetrahydroxylcalix[4]arene ([4]H) (3)
and 25,26,27,28-tetramethoxycalix[4]arene ([4]CH3) (4) were synthe-
sized by similar procedures to those reported by Gutsche et al.20,21
Synthesis of methylene crosslinked 25,26,27,28-tetramethoxy
calix[4]arene resin (MC-[4]CH3) (5)
Acetic acid (10.7 cm3, d = 1.05 g cmÀ3, 187 mmol) was added to retention characteristics). The metal ion concentrations before
a mixture of 4 (0.500 g, 1.04 mmol) and s-trioxane (0.47 g, and after equilibrium in the filtrate were determined by ICP-AES.
5.20 mmol, 5 eq.) and heated at 80 1C for 30 min. A mixed Using the initial and equilibrium concentrations of the metal
solution of acetic acid (10.74 cm3, d = 1.05 g cmÀ3, 187 mmol) ions, each metal percentage extracted in the solid phase extractant
and sulfuric acid (1.65 cm3, 30.9 mmol) was added dropwise to was calculated by the eqn (1)
the reaction for 30 min; the mixture was heated at 110 1C for
8 h. The mixture was poured into a small portion of 5 wt% sodium
% A = (Ci À Ce)/Ci  100,
(1)
hydrogen carbonate solution. The crude product was filtered off, and where Ci and Ce (M) are the initial and equilibrium concentra-
washed with hot distilled water, 1 M (M = mol dmÀ3) hydrochloric tions of metal ions in aqueous solution, respectively.
acid and normal distilled water, sequentially. The crude product was
Loading metal capacity on the resin. The loading adsorption
dried at 80 1C for 24 h and stirred with 0.05 M sodium hydroxide capacity on the resin was also investigated by the conventional
solution for several hours. After washing with hot distilled water, 1 M batch method. A heterogeneous mixture of 0.01 g of resin in
hydrochloric acid and distilled water, the pure product was dried at 10 cm3 of tested solution (metal concentration ranging from 0.1
110 1C for 48 h. The resin MC-[4]CH3, 5, was obtained as a brownish to 10.0 mM) was shaken for 72 h at 303 K. After equilibrium, the
powder, in 0.71 g yield. IR: nmax (KBr)/cmÀ1: 2931 (C–H sp3), employed resin was separated by filtration. The filtrate was
New J. Chem.
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