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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 Hydrogen ion-selective poly(vinyl chloride) membrane electrode based on a p-tert-butylcalix[4]arene-oxacrown-4(ELSEVIER SCIENCE BV, 2004) Demirel, A; Dogan, A; Canel, E; Memon, S; Yilmaz, M; Kilic, EA hydrogen ion-selective poly(vinyl chloride) (PVC) membrane electrode was developed using p-tert-butylcalix[4]arene-oxacrown-4 as ionophore. Apart from the ionophore, plasticisers and lipophilic anions were blended, in various proportions, with PVC in tetrahydrofurane and n-fixtures so prepared were poured onto glass surfaces to form the membrane. 2-Nitrophenylpentylether has proved to be the best alternative as plasticiser and the lipophilic anions tried have turned out to have an adverse effect on the pH response. The electrode of the optimum characteristics had a composition of 2% p-tert-butylcalix[4]arene-oxacrown-4, 68.3% o-NPPE and 29.7% PVC. The electrode showed an apparent Nernstian response in the pH range 2-11 with a slope of 54.2 +/- 0.4 mV pH(- 1) at 20 +/- 1 degreesC. It has a rapid potential-response to changes of pH, high ion selectivity towards lithium, sodium and potassium, and other characteristics comparable to those reported for the conventional pH glass membrane electrode. It appears to be a suitable potentiometric indicator electrode specifically for hydrofluoric acid solutions. (C) 2003 Elsevier B.V. All rights reserved.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 Syntheses and binding properties of polymeric calix[4]crown-4(ELSEVIER SCIENCE BV, 2001) Memon, S; Uysal, G; Yilmaz, MThree new polymers containing pendant calix[4]crown-4 units have been synthesized via radical initiated reactions involving a vinylic monomer 7 (5,7,11,23 -tetra-tert-butyl-25- [2-(Acryloxy)ethoxy]-27-methoxycalix [4]arene-crown-4) and with styrene. A five atom spacer group was incorporated between the bulky calixarene core and the acrylate moiety in order to minimize steric interactions which proved to impede the polymerization. The complexation studies were made by using liquid-liquid and solid-liquid extraction procedures. It has been deduced from the observations that the precursor 5 (5,7,11,23-tetra-tert-butyl-25-hydroxy-27-methoxycalix [4]arene-crown-4) is selective for Hg2+, whereas the polymers are not selective but better extractants for all used metal cations. The extraction data support the conformational change of the calix[4]crown from cone to the other various conformations of calixarene moiety. (C) 2001 Elsevier Science B.V. All rights reserved.Öğe Synthesis and binding properties of calix[4]arene telomers(JOHN WILEY & SONS INC, 1999) Yilmaz, A; Memon, S; Yilmaz, MTwo calix[4]arene derivatives (5 and 8) and their telomers are synthesized to estimate selective extraction of alkali and transition metal cations from the aqueous to the organic phase (chloroform). Compound 5 shows selectivity toward Hg2+. Compound 8 and telomers 6 and 9 are not selective but are good extractants for all used transition metal ions. The observations suggest that ethylene glycol bridges are efficient for carrying transition metal cations in a two-phase solvent system. (C) 1999 John Wiley & Sons, Inc.Öğe Synthesis and characterization of a novel chiral chromogenic calix[41(azoxa)crown-7(PERGAMON-ELSEVIER SCIENCE LTD, 2004) Sirit, A; Karakucuk, A; Memon, S; Kocabas, E; Yilmaz, MTwo new chromogenic compounds, 5 and 6, and a novel chiral chromogenic calix[4](azoxa)crown-7 8 have been synthesized using a calix[4]arene platform. The starting reagents chiral diamine e and calix[4]arene diacid chloride derivative 7 were prepared conveniently according to recent approaches. The H-1 and C-13 NMR, data showed that these compounds exist in a cone conformation. Compounds 5 and 8 have shown broad absorption bands in UV-vis spectra suggesting their utility in different fields, for example, as sensors for ions as well as for chiral molecules. (C) 2004 Elsevier Ltd. All rights reserved.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 and extraction studies of a novel tetra-calix[4]arene(TAYLOR & FRANCIS INC, 2002) Yilmaz, A; Memon, S; Yilmaz, M[Abstract not Available]Öğe Synthesis and metal ion recognition properties of a novel chiral calix[4](azoxa)crown-7(TAYLOR & FRANCIS LTD, 2005) Sirit, A; Kocabas, E; Memon, S; Karakucuk, A; Yilmaz, MA novel chiral calix[4](azoxa)crown-7 (9) has been synthesized and its metal ion recognition properties investigated. The starting reagents, chiral diamine 5 and calix[4]arene diacid chloride derivative 8, were prepared according to literature methods. H-1 and C-13 NMR data show that 9 exists in a cone conformation. In liquid-liquid extraction experiments, 9 exhibits selectivity for Li+ among the other alkali metals and a good extraction ability for transition metal cations, suggesting its potential use in different fields, such as a sensor for ions as well as for chiral molecules.Öğe Synthesis and study of allosteric effects on extraction behaviour of novel calixarene-based dichromate anion receptors(PERGAMON-ELSEVIER SCIENCE LTD, 2002) Yilmaz, A; Memon, S; Yilmaz, MIn this study the selective derivatization of p-tert-butylcalix[4]arene was carried out and two new calix[4]arene-based azacrown ionophores, 5,17-di-tert-butyl-11,23-di-(methyl-3,5-dioxaoctane-1,8-diimine)-25,26,27,28-tetrahydroxycalix[4]arene (6), and 5,17-di-tertbutyl-11,23-di-(methyl-3,5-dioxaoctane-1,8-diimine)-25,27-diethoxyformyl-methoxy-26,28-dihydroxycalix[4]arene (7) have been synthesized. Treatment of 5,17-di-tert-butyl-11,23-diformylcalix[4]arene-25,26,27,28-tetrol (5) with 1,8-diamino-3,6-dioxaoctane gave the ionophore 6 which was converted to its diester derivative 7 by reaction with ethylbromoacetate in the presence of potassium carbonate. In the synthesis, the upper and lower rims of p-tert-butylcalix[4]arene were modified in order to acquire binding sites for the recognition of metal cations and dichromate anions. It was observed that receptor 7 is a better extractant for Cr2O72- anions than receptors 6. The protonated alkylinium form of 7 is an effective extractant for transferring the Cr2O72- anions from aqueous into a dichloromethane layer and failed in transferring Na+ cations due to the allosteric effect produced by the crown part of the calix moiety present at the p-position. (C) 2002 Elsevier Science Ltd. 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 oligomeric calix[4]arene-crowns as novel ionophores for alkali and transition metals(TAYLOR & FRANCIS LTD, 2002) Akkuş, Gülderen Uysal; Memon, S; Yılmaz, MustafaTwo different oligomeric calix[4]arene-crowns (2b and 3b) were synthesized (via) the condensation reaction of p-tert-butylcalix[4]arene-oxacrown-4 (2a) and p-tert-butylcalix[4]arene-thiacrown-4 (3a) (calix[4]arene-crown monomers) with 1,5-dibromopentane. In these oligomerization reactions, it has been found that only three or four calix[4]arene-crowns-4 units have been linked together through alkyl bridges. Their comparative complexing properties with selected alkali and transition metals are reported here. It has been deduced that the selectivity of monomer 2a toward alkali metals has not been reserved, but a pronounced increase in its complexing ability was observed after the oligomerization. However, the selectivity of the monomer 3a toward Cu2+, Hg2+, and Ph2+ has also been lost after oligomerization, and it has been found that oligomer 3b is an efficient extractant for the transition metal cations employed in the two-phase extraction systems.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.Öğe Using of hydrogen ion-selective poly(vinyl chloride) membrane electrode based on calix[4]arene as thiocyanate ion-selective electrode(ELSEVIER SCIENCE SA, 2006) Erden, S; Demirel, A; Memon, S; Yilmaz, M; Canel, E; Kilic, EA hydrogen ion-selective electrode (ISE) is prepared by using 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetracyanometoxy-calix[4]arene and an investigation about whether it could be used as a thiocyanate ion-selective electrode is made by using its characteristic of becoming thiocyanate sensitive in acidic regions. The electrode of the optimum characteristic has a composition of 1% ionophore. 66% 2-NPOE and 33% poly(vinyl chloride) (PVC). This electrode exhibits a linear response over the range 1.0 x 10(-1) to 3.0 x 10(5) M of thiocyanate with a slope of 52.0 +/- 0.2 mV/pSCN. The effects of the pH and the membrane composition are also investigated. The lifetime of the electrode is at least 4 months and its response time is found to be 10-15 s. The selectivity coefficients of some anions are calculated by using mixed solution interference method. Application of the electrode to the potentiometric titration of thiocyanate ion with silver nitrate is reported. There is a good agreement between the results obtained by the proposed electrode and the Mohr method at 955 confidence level. (c) 2005 Elsevier B.V. All rights reserved.
