Ismail Abbas

Publications (9) View all

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  Available from: Ismail Abbas

  Article: Calix[4]pyrrole macrocycle: Extraction of fluoride anions from aqueous media

  Ismail Abbas
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  ABSTRACT: Received:01Received:03Accepted:04Online:30KEYWORDSSolid‐phase(CP)fromhas.Variousconcentrationoftheanion,extractiontime,concentrationofthecalixpyrrole,pHandtemperaturewereevaluated.Langmuir,Freundlichand,Dubinin‐Redushkevish(D‐R)isotherms.Theanion.40/g/Lsolution.TheoffluorideanionsbytheCPwasfoundtobe10.0kJ/mol,indicatingthatchemisorptionisinvolved.Thefirst.Thetemperature.Thehas.LangmuirFreundlichExtractionFluorideCalix[4]pyrroleDubbin‐Redushkevich1.IntroductionWithexcesslevelsoffluoridearebecomingamatterofgreatconcern.Environmentalcontaminationbyfluoridesandfluorideexposureviadrinkingwater,foodstuffanddentalproductshasbeenthesubjectofmanyscientificpapersandreviewarticles[1‐2].Theexcessoffluorideconcentrationingroundwaterusedforhumanconsumptioncanleadtoahighrisk[3].During,researchhasbeencarriedouttofindcost‐effectiveandpracticalsolutions[4,5].Thedefluoridationtechniquescanbebroadlyclassifiedintotwocategories,namelymembraneandadsorptiontechniques[6‐10].Theadsorptiontooneofthemostpromisingmethodsforfluorideremovalfromdrinkingwater.However,thetraditionaladsorbentsandadsorptionmethodshavemanylimitationsespeciallyfordevelopingcountrieswhereformostofthem,thereisaproblem.Thesethisapproachimpracticalforwatersystemsservingafewthousandpeople.Inordertomeettheneedsofpeopleinfluoride‐contaminatedregions,alternativetechniquesarerequiredthatcaneffectivelyreducefluorideconcentrationindrinkingwatertoenvironmentallyacceptablelevelataffordable.Calixpyrroles,aclassofhetero‐calixarenes,areatopicofconsiderablecurrentinterestinsupramolecularchemistrybecauseoftheirabilitytoactasreceptorsforanions[11‐16].Keyfeaturesofsupramolecularchemistry[17‐19]involvefirstlyrecognition,wherethemacrocycleshowsselectivitytowardonesubstraterelativetoanother.Secondly,thereisachemicaltransformationinthenatureoftheguestuponcomplexationwiththereceptor,allowingthetranslocationofthethrough.Theserequirementsarefulfilledbycalix[4]pyrroles
  European Journal of Chemistry. 06/2012; 156(162-3 (2) (2012) 156‐162).
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  Available from: Ismail Abbas

  Article: Pyridine-substituted calix[4]pyrrole: a new cation receptor

  Ismail I Abbas, Jinane K Chaaban
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  ABSTRACT: Novel pyridine-substituted calix[4]pyrrole (CP), has been synthesised and characterised by different analytical techniques (1 H NMR, microanalysis and mass spectroscopy). The cation-binding behaviour of this receptor was investigated by proton NMR spectroscopy, conductometric and UV titrations. 1 H NMR measurements reveal the sites of interaction of the ligand with metal cations in deuterated acetonitrile (CD 3 CN). The results show that introduction of one pyridine group to the pendent arm of the modified CP enables the produced hybrid to bind with metal cations [Cd(II), Pb(II), Hg(II)] in acetonitrile. No interaction was observed between this ligand and other metal cations in acetonitrile. The composition of the anion complexes was established through conductance measurements. In all cases, 1:1 complexes are formed. The thermodynamics of metal cations complexation in acetonitrile is discussed.
  Journal of Supramolecular Chemistry 03/2012;
• Article: Modified calix[4]pyrrole receptor: solution thermodynamics of anion complexation and a preliminary account on the phosphate extraction ability of its oligomer.

  Angela F Danil de Namor, Mohammad Shehab, Rasha Khalife, Ismail Abbas
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  ABSTRACT: A modified calix[4]pyrrole, namely meso-tetramethyl-tetrakis-(4-hydroxyphenyl) calix[4]pyrrole, 1, has been synthesized and characterized. (1)H NMR investigations in various deuterated solvents seems to indicate that this receptor interacts with acetone-d(6). The solution thermodynamics of 1 in various solvents is reported. Complexation studies in CD(3)CN show that the NH and OH functionalities of 1 are the active sites of its interaction with the fluoride and the dihydrogen phosphate anions. The composition of the anion complexes was established through conductance measurements. In all cases, 1:1 complexes are formed. The thermodynamics of anion complexation in acetonitrile and N,N-dimethylformamide is discussed comparatively with previous reported data for the parent calix[4]pyrrole, 2, and these anions in these solvents. The medium effect on anion complexation is discussed in terms of the solvation properties of the reactants and the product in acetonitrile and N,N-dimethylformamide. An oligomeric material containing 1 as anchor group was synthesized and characterized by mass spectrometry. Preliminary studies have been performed to assess the extracting properties of this oligomer for the removal of phosphates from aqueous solutions. The effects of pH, temperature on the extraction of this anion salt from water, as well as the kinetics of the process (fast) were investigated.
  The Journal of Physical Chemistry B 11/2007; 111(42):12177-84. · 3.70 Impact Factor
• Article: Sulfur-containing hetero-calix[4]pyrroles as mercury(II) cation-selective receptors: thermodynamic aspects.

  Angela F Danil de Namor, Ismail Abbas
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  ABSTRACT: Two sulfur-containing hybrid calix[4]pyrrole derivatives (III and IV) have been synthesized and fully characterized. Several analytical techniques (1H NMR, conductance measurements, UV-vis spectrophotometry, titration potentiometry, and titration calorimetry) have been used to assess the interaction between these hybrid calixpyrrole receptors and metal cations in acetonitrile and dimethylsulfoxide. The partition constants of calix[4]pyrrole, I, II, and IV in the acetonitrile-hexane solvent system and the solubilities of the ligands in various solvents at 298.15 K were determined. 1H NMR measurements reveal the sites of interaction of calixpyrrole ligands with metal cations in CD3CN. Conductance and UV-vis spectrophotometric measurements were performed to establish the composition of mercury(II) calixpyrrole complexes in acetonitrile at 298.15 K. Titration calorimetry was used to quantitatively assess Hg(II)-calixpyrrole interactions. Thus the thermodynamics of complexation of calixpyrrole ligands with the mercury(II) cation in acetonitrile at 298.15 K are reported. Potentiometric titrations were also used to establish the stepwise stability constants for the complexation of calix[3]thieno[1]pyrrole with the Hg(II) cation in acetonitrile at 298.15 K. The results show that replacement of one or more pyrrole units by thiophene rings in calix[4]pyrrole has tuned significantly the discrimination ability of these ligands between anions and enables the produced hybrid calixpyrroles to bind selectively with Hg(II) in acetonitrile. No interaction was observed between these ligands and other metal cations in acetonitrile.
  The Journal of Physical Chemistry B 06/2007; 111(21):5803-10. · 3.70 Impact Factor
• Article: A new calix[4]pyrrole derivative and its anion (fluoride)/cation (mercury and silver) recognition.

  Angela F Danil de Namor, Ismail Abbas, Hassan H Hammud
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  ABSTRACT: A new calix[4]pyrrole-based macrocycle, meso-tetramethyl-tetrakis{4-[2-(ethylthio)ethoxy]phenyl}calix[4]pyrrole, 7, has been synthesized and fully characterized. Unlike other calixpyrrole derivatives that show selective interaction with anions, calixpyrrole 7 described in the present work forms stable complexes with both metal cations and anions. The thermodynamics of complexation of this ditopic calixpyrrole derivative with metal cations (Hg2+ and Ag+) and the fluoride anion in nonaqueous solutions have been determined by titration calorimetry, and the host-guest composition has been investigated by using conductance measurements at 298.15 K. 1H NMR studies provide clear evidence about the sites of complexation of 7 with the ionic species, which show that the NH groups are taking part in the complexation of this ligand with the fluoride anion while the sulfur donor atoms are responsible for the interaction with metal cations. Using the present data on 7 and structurally related analogues (1-6), the complexation behavior is discussed comparatively from the thermodynamic point of view. Possessing four sulfur-containing pendent arms, 7 displays an enhanced hosting ability for Hg2+ in acetonitrile. As compared with 1, the calixpyrrole derivative, 7, shows a unique interaction with fluoride among the anions investigated in acetonitrile and dimethyl sulfoxide. As far as the fluoride complex is concerned, the medium effect is assessed in terms of the thermodynamics of the transfer of reactants and product from acetonitrile (reference solvent) to dimethyl sulfoxide.
  The Journal of Physical Chemistry B 04/2007; 111(12):3098-105. · 3.70 Impact Factor