Reactive & Functional Polymers 40 (1999) 129–133

Synthesis of an oligomer-supported calix[4]arene and selective1extraction of Li

Mustafa YilmazSelcuk University, Department of Chemistry, 42079 Konya, Turkey

Received 12 October 1997; accepted 15 February 1998

Abstract

To prepare a structure with a count of more than one p-tert-butylcalix[4]arene triketon unit, oligomer (3) was reacted with25,26-diacetonyoxy-5,11,17,23-tetra-tert-butyl-26,28-dihydroxycalix[4]arene (2) and compound (4) was treated with chloro-acetone to obtain calix[4]arene units containing triketon groups. It was found that the polymeric calix[4]arene was selective

1 1 1 1 1 21 21 21 21to extract Li from an aqueous solution which contained Li , Na , K , Ag , Co , Ni , Cu , and Cd . 1999Elsevier Science B.V. All rights reserved.

1Keywords: Polymeric calix[4]arene; Calix[4]arene triester; Selective metal extraction; Li complexation

1. Introduction acetamides with a cone conformation show1remarkably high Na selectivity.

The [l ]metacyclophanes known as calix- More recent work in this field, studies on then

arenes are among the most interesting families transport of alkali and alkaline-earth cationsof host compounds, and in the last 18 years their with p-tert-butylcalix[n]arene esters andchemistry has been significantly developed amides, was carried out by Arnaud-Neu et al.[1,2]. Host–guest chemistry of the calixarenes is [16]; Reinhoult and co-workers [17] preparedof great interest, since they have complexing 1,3-alternate calix[4]arene-crown-6 as new classabilities toward alkali, alkaline-earth and some of cesium-selective ionophore; and Ungaro andtransition metal cations by means of functional co-workers [18,19] have reported the synthesis,group modification at the phenolic groups [3– structure and complexing properties of several10]. It was found later by Arduini et al. [11], 1,3-dialkoxy-p-tert-butylcalix[4]arene-crown-5,McKervey et al. [12], Chang and Cho [13] and a new class of potassium-selective ligands.Shinkai and co-workers [14,15] that calix- Until now, complexation studies have been[n]arenes can be converted into neutral ligands conducted with monomeric calixarenes. Poly-by converting the OH groups to esters or meric calixarenes are a much more recentamides. They demonstrated that the metal selec- innovation. Only a few examples have beentivity is dependent on the calix[n]arene ring size reported: a polystyrene-immobilized calix[6]-and, in particular, calix[4]aryl acetates and arene as a uranophile [20,21], a polymer of

1381-5148/99/$ – see front matter 1999 Elsevier Science B.V. All rights reserved.PI I : S1381-5148( 98 )00025-X

130 M. Yilmaz / Reactive & Functional Polymers 40 (1999) 129 –133

1calix[4]arene methacrylate as a Na ionophore[22], a silica gel-immobilized calixarene as aliquid chromatography stationary phase [23],and a series of calixcrown telomers as a GCstationary phase [24].

In our recent work [25,26], we synthesizedpolymeric calixarenes by combining 25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene with anoligomer of epichlorohydrin and chloro-methylated polystyrene with 25,26,27-triben-

31zoyloxy-28-hydroxycalix[4]arene as a Feionophore, and in our other studies [27,28] wereported compounds from calix[4]arene tetraesters supported by a polyacryloyl chloride or

1an oligomer of epichlorohydrin as a Na iono-phore.

In the present work a compound (5) wassynthesized containing more than one p-tert-butylcalix[4]arene triketon units, and its ionbinding properties studied.

Scheme 1.

2. Results and discussion

The selectivity in transfer property of triester groups containing calix[4]arene suitable forderivative of calix[4]arene toward alkali-metal alkali metal complexation, 4 was treated with

1cations, particularly Li , has been reported in chloroacetone in acetone containing K CO and2 3

the literature: Shimizu et al. [30], reported the NaI. After 3 days this reaction furnished aselectivity in transfer property of a chromogenic yellow product which was proven to be 5calix[4]arene which has within a molecule the (Scheme 2).triester moiety as a metal-binding toward al- Solvent extraction experiments were per-

1kali–metal cations, particularly Li . In this formed to ascertain the effectiveness of 5 inwork, to prepare the structure with a count of transferring the alkali metal cations, such as

1 1 1more than one p-tert-butylcalix[4]arene triketon Na , K and Li , and transition metals, such as1 1 21 21 21 21 21units, oligomer (3) was reacted with 25,26- Ag , Hg , Hg , Co , Cu , Ni and Cd ,

diacetonyoxy-5,11,17,23-tetra-tert-butyl-26,28- from aqueous phase into organic phase (chloro-dihydroxycalix[4]arene (2) in the presence of form). The results of the picrate extractionK CO and NaI in acetone under reflux for 2 studies are summarized in Table 1. These data2 3

days and furnished 4 (Scheme 1). were obtained by using a chloroform solution ofAnalysis of the product observed showed that 5 to extract metal picrate from aqueous alkaline

compound 2 was not attached to each consecu- solution; the equilibrium concentration of pic-tive (CH –Cl) group in a regular array. Instead, rate in the aqueous phase was determined2

the attachment followed a single-step alternating spectrophotometrically. From the data given insequence. Table 1, it can be seen that compound 5 is more

1Since it was interesting to synthesize triketon effective in transferring Li than the other ions.

M. Yilmaz / Reactive & Functional Polymers 40 (1999) 129 –133 131

selectivity, indicating that the compound com-1posed of phenolic oxygenes fits the size of Li

[30]. Consequently, the cavity of the triesterderivative of the p-tert-butylcalix[4]arene-tri-

1keton-fixed oligomer (5) fits the size of Li .In order to determine whether compound 5

1forms a complex with Li , the solution ofcompound (5) was mixed with aqueous solutionof LiSCN. When this mixture was shakenthoroughly, a color change of the organic phasewas observed. The IR and NMR spectra of theisolated complexes were recorded. The IR spec-tra of the complex exhibited absorption at 2050

21cm , characteristic for SCN vibration mode.Furthermore, the C=O band of compound 5 at

21 211750 cm shifted to 1740 cm in its complex.1The H NMR spectra of compound 5 exhibited

Scheme 2. rather broad signals for all protons, with twosinglets each for the tert-butyl (d 1.08 and 1.25ppm), OCH CO (d 4.65) and aromatic (d 6.852

Oligomer 2 shows little extractability to not and 7.10) residues. The H proton of the ABA

only main group metal cations but also transi- system, characteristic of the bridging methylenetion metal cations. When the extractability of the protons in tetramers in the cone conformation,1 and 5, which have the same binding site was partly obscured by two doublets at d 3.38structure, is compared, 1 shows high extract- and 4.45 ppm. Complexation affects all of theability of metal cations, especially for 1A group proton chemical shifts in the ligand, the two

1 1 1cations (Li , Na and K ); however, 5 shows a largest being those of the axial proton H of theA1much stronger affinity toward Li than the other bridging methylene groups in aromatic rings of

cations. This conclusion is not new, however, the calixarene in the cone conformation (0.10–and has been reported in the literature [8]. 0.30 ppm upfield) and the aromatic protonsTetramethyl-p-tert-butylcalix[4]arene-tetraketon (0.20 ppm downfield). This downfield shift of

11 displays peak selectivity for the Na , on the the aromatic protons suggests that the phenoxyother hand, tetramethoxycalix[4]arene which oxygen atoms are also involved in complexation

1has a smaller cavity than 1, shows the Li [8].

Table 1aExtraction of metal picrates with compound 5

Ligand Picrate salt extracted (%)1 1 1 1 21 21 21 21 21Li Na K Ag Hg Co Ni Cu Cd

b1 54.0 69.0 59.0 49.5 11.3 26.3 11.5 ,1.0 17.3b2 19.9 8.0 2.3 6.3 15.5 7.7 6.3 ,1.0 9.4

5 59.5 24.2 16.3 18.2 21.8 ,1.0 6.6 ,1.0 ,1.0a 22 23 25 23 23Aqueous phase, [metal nitrate]51310 mol dm ; [picric acid]52310 mol dm ; organic phase, chloroform; [ligand]51310 mol

23dm ; at 258C, for 1 h.bRef. [31].

132 M. Yilmaz / Reactive & Functional Polymers 40 (1999) 129 –133

In conclusion, it has been established that 3.2. Compound 5 was prepared by thenew molecular design calixarene-based iono- treatment of 4 with chloroacetone asphore 5, containing more than one p-tert- described belowbutylcalix[4]arene-triketon unit, display ver-

1 A mixture of compound 4 (1.0 g, 0.20satile affinity for Li ions.mmol), potassium carbonate (2.32 g), sodiumiodide (4.6 g) and chloroacetone (2.5 ml) in dryacetone (100 ml) was heated under reflux for 3

3. Experimental days. The cooled mixture was filtered through abed of Celite and the filtrate and acetone

Melting points were determined on a Gallen- washing of the Celite were combined and1kamp apparatus. H NMR spectra were recorded concentrated to dryness. The residue wason a Bruker 250 MHz spectrometer in CDCl3 washed with ether, dried in vacuo. Yield: 80%;

21with TMS as internal standard. IR spectra were m.p. 86–888C, IR(KBr) 1750 cm (C=O) and21 1recorded on a Mattson 1000 FTIR spectrometer 760 cm (C–Cl). H NMR (CDCl ): d 1.08–3as KBr pellets. 1.25 (s, 180H), 1.50–1.70 (s, 63H), 3.38 (broad

The preparation of tetramethyl-p-tert- d, 20H) 3.50–3.80 (broad d, 59H), 4.20 (m,butylcalix[4]arene-tetraketone (1) [8], 25,26- 11H), 4.45 (broad d, 20H), 4.65 (s, 30H) anddiacetonyoxy-5,11,17,23-tetra-tert-butyl-26,28- 6.85–7.10 (m, 44H).dihydroxycalix[4]arene (2) [29] and oligomer Anal. Calcd for (C H O Cl ?305 397 46 5(3) [25] are described elsewhere. 5CH CH OH); C, 72.68%; H, 8.27%; Cl3 2

3.36%. Found; C, 72.35%, H, 8.60; Cl,3.10.

3.1. Compound 4 was synthesized by3.3. Synthesis of LiSCN complex of 5treatment of oligomer 3 with 25,26-

diacetonyoxy-5,11,17,23-tetra-tert-butyl-26,28-A quantity of 0.02 mmol 5 was dissolved indihydroxycalix[4]arene (2) as described below

20 ml CH Cl . To this solution was added 202 2

ml of an aqueous solution containing 0.1 mmolA mixture of oligomer (1.00 g, 0.92 mmol),(6.2 mg) of LiSCN. The mixture was shaken atpotassium carbonate (4.52 g), sodium iodideroom temperature for 1 h and the solution was(9.3 g) and 7.00 g (9.20 mmol) of 2 in drythen set aside for phase separation. The organicacetone (100 ml) was heated under reflux for 2phase was separated and dichloromethane wasdays. The cooled mixture was filtered through aremoved under reduced pressure, pale yellowbed of Celite and the filtrate and acetonepowder formed, and the product was precipi-washing of the Celite were combined andtated by the addition of hexane, and filteredconcentrated to dryness. Recrystallization of theunder reduced pressure, washed several timesresidue from acetone–ethanol furnished 4.

21 with hexane and dried under vacuum. Yield:Yield: 85%, m.p. 84–868C, IR(KBr) 3450 cm2121 21 65%, m.p. . 928C (dec.). IR(KBr) 3480 cm ,(O–H), 1750 cm and (C=O), 760 cm (C–

1 21 21Cl). H NMR (CDCl ): d 1.08–1.25 (s, 180H), (O–H), 2050 cm (SCN), 1740 cm and321 11.50–1.70 (s, 48H), 3.38 (broad d, 20H) 3.55– (C=O), 760 cm (C–Cl). H NMR (CDCl ): d3

3.80 (broad d, 59H), 4.20 (m, 11H), 4.40 (broad 1.18 (s, 180H), 1.50–1.70 (s, 48H), 3.48 (broadd, 20H), 4.68 (s, 20H) and 6.85–7.10 (m, 49H). d, 20H), 3.55–3.85 (broad d, 50H), 4.30 (m,

Anal. Calcd for (C H O Cl ? 11H), 4.15 (broad d, 20H), 4.80 (s, 30H) and290 377 41 5

5CH CH OH); C, 73.16%; H, 8.34%; Cl 7.30 (m, 44H).3 2

3.55%. Found; C, 72.76%, H, 8.64; Cl,3.15. Anal. Calcd for (C H O Cl ? 5LiSCN ?305 397 46 5

M. Yilmaz / Reactive & Functional Polymers 40 (1999) 129 –133 133

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