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Öğe A calix[4]arene derived dibenzonitrile receptor modified at its "lower rim" by a polymerizable group(TAYLOR & FRANCIS INC, 2004) Tabakci, M; Memon, S; Sap, B; Roundhill, DM; Yilmaz, MThe present work describes the synthesis of a new monomeric dibenzonitrile derivative of p-tert-butylcalix[4]arene containing a polymerizable group at its lower rim. This monomer with an acryl amide group has been copolymerized with styrene yielding a linear polymer with pendant calixarene groups. Extraction studies with this monomer and its copolymer show no selectivity for metal cations. Nevertheless, dibenzonitrile groups with calixarene moiety provide a suitable binding site for transferring metal salt (NaHCr2O7) as an ion-pair.Öğe A convenient approach towards the synthesis of a "Proton switchable" chromium(VI) extractant calix[4]arene(TAYLOR & FRANCIS LTD, 2004) Ediz, O; Tabakci, M; Memon, S; Yilmaz, M; Roundhill, DMA convenient synthesis and Cr(VI) extraction properties of a new calix[4]arene-based receptor (5), which has been synthesized from 5,17-diformyl-25,27-dimethoxy-carbonylmethoxycalix[4]arene (4) by treatment with 3-aminomethylpyridine in one step, are described. The receptor 5 contains four pyridinyl groups, two on each rim. Two of them are joined by an amide linkage onto the lower rim, and other two are linked by an imine-type linkage onto the upper rim of the calix[4]arene moiety. Receptor 5 is very soluble in water at low pH (<2.5). Calixarene 5 also represents a good extractant for HCr2O7-. Thus, the partially protonated form of 5 is an effective extractant for transferring HCr2O7- ions from an aqueous into a chloroform layer. Deprotonation of 5 results in a reversal, with HCr2O7- migrating back into the aqueous layer.Öğe Oligomeric calix[4]arene-thiacrown ether for toxic heavy metals(JOHN WILEY & SONS INC, 2004) Tabakci, M; Memon, S; Yilmaz, M; Roundhill, DMA new oligomeric calix[4]arene-thiacrown-4 (5) was synthesized via a condensation reaction of 5,11,17,23-tetra-tert-butyl-25,27-bis-(4-aminobenzyloxy)-calix[4]arene-thiacrown-4 (4) with adipoyl dichloride. In this oligomerization reaction only five/six calix[4]arene-thiacrown-4 units were linked in the oligomeric chain. The complexation studies of 5 were made with liquid-liquid- extraction and solid-liquid-sorption procedures. For comparison, the extraction efficiencies of monomers 1, 3, and 4 to selected transition metals are reported. The selectivity of monomers 3 and 4 toward Cu2+, Hg2+, and Pb2+ was lost after oligomerization in the two-phase extraction systems. (C) 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 186-193, 2004.Öğe Polymer supported calix[4]arene Schiff bases: A novel chelating resin for Hg2+ and dichromate anions(TAYLOR & FRANCIS INC, 2005) Karakucuk, A; Kocabas, E; Sirit, A; Memon, S; Yilmaz, M; Roundhill, DMThis article describes the synthesis and characterization of two new calix[4] arene Schiff bases and their polymeric resins. The extraction properties of these "proton switchable extractants" with alkali, transition, post transition metal cations and for dichromate anions are reported. The two new calix[4] arene based Schiff bases (5 and 6) have been synthesized from 5,17-diformyl-25,27-dipropoxy-26,28-dihydroxycalix[4]arene (4) by treatment with 3-amino-methylpyridine and 1,8-diaminooctane in two separate reaction flasks following the same procedure. Compounds 5 and 6 have been appended to a polymeric resin by treatment with Merrifield resin through a nucleophilic substitution reaction. The receptor compounds (3 and 5-8) do not extract alkali metal cations, but show some selectivity toward transition metal cations, and a particularly high selectivity to Hg2+ and Pb2+. The protonated forms of all of the calixarene-based receptors are good extractants for transferring Cr2O72-/HCr2O7- anions from an aqueous into a dichloromethane layer.Öğe Remediation and liquid-liquid phase transfer extraction of chromium(VI). A review(INST ORGANIC CHEM AND BIOCHEM, 2004) Memon, S; Roundhill, DM; Yilmaz, MChromium(VI) is a widely used industrial chemical, and is generally considered to pose a greatest human health risk because it is more toxic, more soluble, and more mobile than chromium(III). Workers in industries that use chromium, in particular stainless steel welding, chromate production, chromium plating, and chrome pigment industries, where exposure via inhalation of aerosols is primarily to hexavalent chromium, are at increased risk of chromium effects. In this article we demonstrate various studies regarding remediation methods in particular liquid-liquid extraction of chromate and dichromate anions with various functionalized calixarenes. This review article briefly discusses various molecular designs of calixarene-type macrocycles for chromium(VI) oxoanion recognition, and gives examples on the relationship between structure and selectivity. The article does not, however, attempt to cover all of the different approaches to chromium(VI) extraction. A review with 73 references.Öğe Synthesis and evaluation of extraction ability of calix[4]-crown-6 cone conformer and its oligomeric analogue(ELSEVIER SCIENCE BV, 2004) Tabakci, M; Memon, S; Yilmaz, M; Roundhill, DMThe synthesis of the cone conformers of 5,11,17,23-tetra-tert-butyl-25,27-bis[(4-nitrobenzyloxy)-26,28-dihydroxy]calix[4]-arene (2), 5,11,17,23-tetra-tert-butyl-25,27-bis[(4-nitrobenzyloxy)]calix[4]arene-crown-6 (3) and 5,11,17,23-tetra-tert-butyl-25,27-bis[(4-aminobenzyloxy)]calix[4]arene-crown-6 (4) containing polymerizable side arms, along with their oligomeric analogue 5, is reported. Extraction studies with monomers 3 and 4 and the oligomer 5 show no difference in their extraction behavior and selectivity, whereas, ionophore 2 is a poor extractant for alkali metal cations. These observations suggest that, substitution of side arms on the lower rim of calix moiety can enhance the calix[4]crown-6 cone conformers function to extract alkali metal cations in two phase extraction systems. (C) 2003 Elsevier B.V. All rights reserved.Öğe Synthesis of alkyl nitrile and alkyl benzonitrile derivatives of calix[4]arene and their polymer supported analogues: A comparative study in two-phase extraction systems(ELSEVIER SCIENCE BV, 2005) Gungor, O; Memon, S; Yilmaz, M; Roundhill, DMThe article describes the synthesis and extraction properties of new alkylnitrile and alkylbenzonitrile substituted calix[4]arene based polymers. These compounds have been synthesized via nucleophilic substitution reactions involving 5,11,17,23-tetra-tert-butyl-25,27-bis-(cyanomethoxy)-26,28-dihydroxycalix[4]arene (2a), 5,11,17,23-tetra-tert-butyl-25-(2-cyanobenzyloxy)-26,27,28-trihydroxycalix[4]arene (3a), or 5,11,17,23-tetra-tert-butyl-25,27-bis-(2-cyanobenzyloxy)26,28-dihydroxycalix[4]arene (4a), with Merrifield's resin (0.8 mM Cl/1.0 g resin). The two-phase extraction properties of ligands 2a-4a along with their polymers 2b-4b toward the selected metal cations and dichromate (HCr2O7-/Cr2O72-), anions are reported. Extraction studies with monomer 2a show selectivity for Hg2+, where as monomers 3a and 4a are selective for Cd2+ and Hg2+ cations. Nevertheless, due to the higher oxidative stability of nitrile groups, polymers 2b-4b have been developed as good extractants for transferring the selected metal cations and dichromate (HCr2O7-/Cr2O72-) anions from an aqueous into a dichloromethane phase. (c) 2005 Elsevier B.V. All rights reserved.Öğe Synthesis of polymeric calix[4]arene dinitrile and diamino-derivatives: Exploration of their extraction properties towards dichromate anion(MARCEL DEKKER INC, 2004) Memon, S; Yilmaz, A; Roundhill, DM; Yilmaz, MThe article describes the syntheses and extraction properties of new alkylnitrile and alkylamino substituted calix[4]arene based copolymers. These compounds have been synthesized via nucleophilic substitution reactions involving 5,11,17,23-tetra-tert-butyl-25,27-bis(cyanomethoxy)-26,28-dihydroxycalix[4]arene (3), or 25,27-bis(cyanomethoxy)26,28-dihydroxycalix[4]arene (4) with 1,5-dibromopentane and bisphenol-A, followed by their reduction with sodium borohydride in the presence Of CoCl2.6H(2)O. In addition an oligomer containing pendant calix[4]arene units with nitrile functionalities on its lower rim has been synthesized via nucleophilic reaction involving 5,11,17,23-tetra-tert-butyl-25,27-bis(cyanomethoxy)-26,28-dihydroxycalix[4]arene 3 with p-dibromoxylene. The extraction properties of polymers 5-9 toward the HCr2O7- anion are also reported. Due to the higher oxidative stability of nitrile groups, polymers 5-7 have been developed as good extractants for transferring the HCr2O7- anion from an aqueous into a dichloromethane phase.Öğe A useful approach toward the synthesis and metal extractions with polymer appended thioalkyl calix[4]arenes(ELSEVIER SCI LTD, 2005) Memon, S; Tabakci, M; Roundhill, DM; Yilmaz, MThis article describes a convenient method for the synthesis of two new polymeric resins via nucleophilic substitution reactions involving 5,11,17,23-tetrakis[(propylthio)methyl]-25,26,27,28-tetrahydroxycalix[4]arene 4, and 5,11,17,23-tetrakis[(methylthio)methyl]-25,26,27,28-tetrahydroxycalix[4]arene 6, as precursors with Merrifield's resin. The extraction studies were made using both liquid-liquid extraction and solid-liquid batchwise sorption procedures. The calix[4]arene based polymeric resins have high extraction ability toward metal cations and Na2Cr2O7 as compared to their monomeric precursors. (C) 2004 Elsevier Ltd. All rights reserved.
