Abu-Bakr, M S

Hassan, M K

Idriss, K A

Seleim, M M

English

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Indian Journal of ChemistryVol. 27A, March 1988,pp.231-234Mixed-LigandComplexesofFe(II)&Cu(II)withAlizarinMaroollasaPrimaryLigand& 5-SulphosalicylicAcid asaSecondaryLigandM M SELEIM, K A IDRISS*, M SABU-BAKR & M K HASSANDepartmentofChemistry,Facultyof Science,AssiutUniversity,Assiut,EgyptReceived9 March1987;revised22June1987;accepted27July 1987Reactionsof Fe(II) andCu(II) withalizarinmaroon(azm)asa primaryligandand5-sulphosalicylicacid (ssa)asa secondaryligandhavebeenstudiedspectrophotometricallyandpotentiometricallyin 20%(v/v)ethanolanddiox-aneat an ionic strength1=100mmoldm-3 NaCI04 and temperature=25±0.1°C.Basedon thespectrophotomet-ric studies,a methodfor the determinationof Fe(II) and Cu(II) is proposed.The stabilityconstantsof the monoand mixed ligand complexesof Fe(II) and Cu(II) have been evaluated.The differencein stabilityconstants,.6.logKM=logKt1\=\(ssa) -logK~ (ssa)is foundto be positiveshowingan astatisticalincreasein thevaluesof mixedligandstabilityconstants.In continuationof our work on the complexationequilibriaof mixedligandcomplexesin solution1,2,we reportherethespectrophotometricandpoten-tiometricstudyof thereactionof Fe(II) andCu(II)with alizarin maroon (3-amino-1,2-dihydroxy-anthraquinone)as a primaryligandand 5-sulpho-salicylic acid as a secondaryligand. The pH-titrationtechniqueof IrvingandRossottP,4anditsmodified form5•6were employedin the presentstudyto determinethe stabilityconstantsof theternarycomplexesFe(II)-azm-ssaand Cu(II)-azm-ssa. The measurementswere carried out at25±0.1°C and at an ionic strength of0.1moldm-3 (NaCI04) in 20% (v/v) ethanolordioxane.The absorptionspectraof the mixedli-gandcomplexeswerealsoinvestigated.The funda-mentalconditionsfor the spectrophotometricde-terminationof Fe(II) and Cu(II) complexesusignFe(II)-azm-ssaandCu(II)-azm-ssaternarysystemswereestablished.MaterialsandMethodsAll thechemicalsusedwereof AR grade.Diox-anewas purifiedby recommendedprocedure7• Astock solutionof azm (10-3 moldm-3) was pre-paredby dissolvingan accuratelyweighedamountof thereagentin ethanolor dioxane.A solutionofssa (10- 3 moldm- 3) was preparedby dissolvingthe requisiteamountof the pure reagentin deio-nisedwater.Fe(II) perchloratewaspreparedfromFe(II) carbonateandperchloricacid.Cu(II) perch-loratewasa Fluka reagent.The stocksolutionsofFe(II) and Cu(II) (5x 10-3 moldm-3) were pre-paredand standardisedas recommended8.Stand-ard solutionsof NaOH (0.1moldm-3) andHCI04(2.5x 10- 2moldm- 3) werepreparedby accuratedilutions.Buffersolutionsandsolutionsof diverseions usedfor interferencestudieswere preparedasmentionedelsewhere9•All pH-metric titrationswere carried out at25±O.l°C usingon Orion (M 501A) digitalpH-meterwith a combinedglasscalomelelectrode.The ioIiic strengthof solutionswaskeptconstantat 0.1moldm-3 (NaCI04)·All the measurementswerecarriedout in 20%(v/v)ethanolor dioxane-watermedium(20%, v/v), pH valueswere cor-rectedfor partiallyaqueousmedia as describedpreviouslyiO.The absorptionspectrapf solutionswererecordedon a Pye-UnicamSP 8000spectro-photometerin the range350-750nm using 1-cmmathedstopperedquartzcells.ResultsandDiscussionSpectrophotometricstudiesRecentwork from thislaboratoryll,12on theac-id-basepropertiesof azmin aqueoussolutionorin water-ethanol(or dioxane)mixture indicatedthatthe predominantform of this reagent·withinthepH range3.0-6.0is themonocationicspecies(H3A+) whichundergoestepwiseionisationon in-creasingthepH of thesolution.The visiblespec-trum of azm exhibits an absorptionband atA=41O-420nm in the pH range 3.5-6.0.Thisband shiftsto longerwavelengthson addingthemetal ion solutions.The spectraof Fe(II) andCu(II)-azm 1:1 complexesmeasuredwith reagentblankasreferencearecharacterisedby an absorp-tionbandwithAmaxnear620 and630nm respect-ively.The solutioncontainingequimolarconcentr-ationsof azmand ssaundergoesa changein co-lour, from yellowto pink-violetwhenmixedwith231INDIAN J. CHEM., VOL. 27A,MARCH 1988Fe(II) ~r Cu(II) solution.The spectrumof thereactioqmixturemeasuredagainsta blanksolutionconta~g the sameconcentrationof the two li-gands~ows an apparentdecreasein the absorp-tio at ~10nm andtheapp a ncof a newbandat 580bm for Fe(II) and 540nm for Cu(II) ter-nary sy~tem.This band is unambiguouslydue tothe for~ation of a mixed-lig ndcomplexof themetali~nwith maximumcolour developmentbe-ing ttajinedat pH 5.8 for Fe(II) and at 5.4 forCu(II) tfrnarysystems.Stoichi4metryofthecomplexesJ~b'slme~hodof continuou~.variation13,14wasappliedI to find out thecompositlonof theternarycomple~es..The resultsindicatethattheoverallra-tio of ,*etalion:azm:ssais 1:1:1.The stoichiomet-ric ratitof the complexeswas also confirmedbyapplyin themoleratiomethod15.The eactionof Fe(II) or Cu(II) with azm andssacan, erepresentedbyEqs,M2++H3A++:t [M(HAW +2H+[M(HAW +H2L- +:t [M(HA)L]2- +2H+whereH2L - is the mononegativechargedspeciesof thesecondaryligand.Spectrophotometricdeterminationof Fe(II) andCu(I1)An aliquot of the test sample containing5-70fJ.gof Fe(II) or 10-60fJ.gof Cu(II) wastrans-ferredto a 25ml calibratedflaskandsubsequentlyazm (5mI, 10-3moldm~3)added.The pH wasadjustedto 5.8 for Fe(II) and 5.4 for Cu(II) andssa (5mI, 10-3moldm-3) was added.The solu-tion was dilutedto the requiredvolumewith de-ionizedwaterand therequiredamountof ethanolor dioxane.After thoroughlymixingthe reactionmixture,the absorbancewasmeasuredat 580nmfor Fe(II) and 540nmfor Cu(II) againsta reagentblank similarlypreparedbut containingno metalIon.'.oriIIMetjUio~TableI-Validity ofBeer'sLawMetalion Metalion(ppm) Molarper25m1 in thefinal Absorptivity(/lg) cone.20%(v/v·)Ethanol5.0-40.0 0.20-1.60 10,00020.0-60.0 0.80-2.40 7,50020%(v/v)Dioxane15.0-70.0 0.60-2.80 12,00010.0-45.0 0.40-1.80 7,000EffectofmaskingagentsandforeignionsThe addition of EDTA as a maskingagentcausesan apparentdecreasein theabsorbanceva-luesand consequentlycould not be used.On theotherhand,additionof fluorideions as a maskingagentupto 200-fold molar excessover Fe(II) orCu(II) had no effecton the sensitivityof thepro-posedmethod.The effectof diverseions at levelsof 1-14mgper 25ml on thedeterminationof me-tal ionswasexaminedby therecommendedproce-dure.There wasno interferencefrom 14mg(200-.•...11.259.769.809.53logt1~L,5.054.564.704.5712.6011.20*3.109.10ssaazmtTable'2-NegativeLogarithmsofAcidityConstantsof theLigandsandLogarithmsof theStabilityConstantsofTheirBinaryComplexeswithFe(II)andCu(II)[Ionicstrength=0.1moldIn- 3 NaCl04; temp.=2SOC]pK~2L pK~L M(Il) logK~ logK~~20%(v/v)EthanolFe(Il) 6.20Cu(II) 5.20Fe(II) 5.10Cu(II) 4.96IH ItpKHPt=6.75ttpK~3L1=7.55*Ref.11.iIiazmttssa9.502.9011.50*11.40200k(v/v)[ijoxaneFe(II) 6.40Cu(II) 5.49Fe(Il) 5.85Cu(Il) 5.155.404.595.504.3811.8010.0811.359.63232I III~."IISELEIM et aZ.:MIXED LIGAND COMPLEXES OF Fe(II)& Cu(II)Table3-Logarithmsof theEquilibriumConstantsof theTernaryM-azm-ssaSystemsandSomeRelatedData[Ionic~trength=O.1moldm-3NaCl04; temp.=25°C]Metal logp~(azm)(ssa)logK~!:::I(ssa)logK~~::I(azm)/:J.logK logXion20%(v/v)EthanolFe(II)11.755.556 60.752.45Cu(II)0 8060442200k(v/v)DioxaneII3 16 7.283ll33899... (1)... (2)The otherapproachcommonlyusedto quantifythe stabilityof a ternarycomplexis basedon theequilibriumconstant,X; as definedby equation(5)17,18;10gXmaybe calculatedaccordingto Eq.(6).tionsat m= 3 andm= 4. The divergenceof mixedligandcurvesfrombinarycurvesindicatesthatthedeprotomitionof azmor ssain theternarysystemsoccursata lowerpH. This meansthattheternarycomplexesaremorestablethanthecorrespondingbinarysystems.The valuesof the formationcon-stantofthegeneralequilibriumM+azm+ssa +t M(azm)(ssa)fi~(azm)(ssa)... (3)aregiveninTable3.One way to quantifythe stabilityof ternarycomplexesis accordingto equation(4)16,Le., bycomparingthe differencesin stability,e.g.,for thereactionbetweenM(ssa)and(azm).X= M(azm)(ssa)F/[M(azm}z][M(ssa}z] ... (5)... (6)... (4)+logfi~(ssa),)M(ssa))-logKM(ssa),M(azm))-logKM(azm),- ( logfi~(azm),( M(azm)= 10gKM(azm)(ssa)( M(ssa)+ logK M(ssa)(azm)KM(ssa) I KM~logKM =log M(ssa)(azm)- og M(azm)'M(azm) I KM=10gKM(az )(ssa)- og M(ssa)10gX=2logfi~(ssa)(azm)fold excess)of Li+, Na+, Ba2+,CI-I, 1-, NO)and SO~- or 8mg (100 fold excess)of Mg2+,C 2+ Al3+ B - C02- S02- d HP02-a, , r, 3' 3 an 4'Among the anions investigated,CN - causesaseriousnegativeerror evenwhenpresentin only- 20-foldexcess.The validityof Beer'slaw was examined.Cali-brationgraphsobtainedwerelinearovertherange1x 10-5-1X 10-4 moldm-3 of Fe(II) or Cu(II).The moalr absorptivitiesof the ternarysystemsare givenin Table 1. Ten identicalsampleseachwith a final metal ion concentration of1x 10- 5 moldm- 3 were testedaccordingto therecommendedprocedureand their absorbanceswere measured.The relativestandarddeviationwasfoundtobelessthan0.004absorbanceunit.PotentiometricstudiesThe proton-associationconstantp K~ N andthe dissociationconstantp K~ A of azm in etha-nol-waterand dioxane-watermeQium(20%,v/v)weredeterminedusingIrving-RossottipH-titrationtechnique3,4(Table 2). The detailsregardingthepotentiometricmethodhavebeenreportedearli-erl2. The valuesof the dissociationconstants(')f5-sulphosalicylicacid (ssa)were also determinedpotentiometricallyunder the same experimentalconditions.The metal-ligandtitrationcurvesex-hibittwoinflectioJlj;at m=2 andm=4 (m=nol ofbaseaddedper mol of metalion) indicatingtheformationof [M(HA)]+and['M(HAh]binarycom-plexes.The formationconstantscorrespondingto theequilibria(1 and2) werecalculatedandthevaluesaregiveninTable2.M +2 azm+t M (azmh fi~(azm),M +2 ssa+t M(ssa)2 fi~(ssahPotentiometrictitrationcurvesfor ternarysystemscontainingM(II)-azm and ssa exhibittwo inflec-The calculatedvaluesof log X arelistedin Table3.The valuesobtainedshow an astatisticalincrease233INDIAN J. CHEM., VOL. 27A, MARCH 1988in theI stabilityof the mixed ligand complexes(IogXstJt =0.6)18,19.The'ihigherstabilityof thecomplexesformedindioxan~(20%,v/v) maybe dueto thefactthattheproton*tionand the stabilityconstantvaluesaremore Sensitivieto the dielectricconstantof themediucl.In dioxane-watermixturesof low dielec-tric cohstant,thesevalueswere expectedto besignificctntlyhigherthanthosefor theaqueous-eth-anol m~dium.This may also be ascribedto thepredomPtantbasicpropertyof dioxane20•The trngherstabilityof Fe(ll) chelatesmay bedue to ~heresonancestabilisationenergyderivedthrough!the coordinationwith ligandshavingaro"matic~g system21•Referenfes1 Idrissf A, SeleimM M, HassanM K, Abu-Bakr M S &Se airaH, Analyst,110(1985)705.2 S lehM S & HashemE Y, Po-IY~dron,5 (1986)1525.3 Irving M &RossottiH S,J chemSoc,(1953)3397.4 Irving M & RossottiH S,J chemSoc,(1954)2904.5 Chid~baram M V & BhattacharyaP K, J inorg nuclCh~rn,32(1970)3271.234illl·i', I It ,IIHk1IIIHI.;6 ChidambaramM V & BhattacharyaP K, Indian J Chem,9 (1971)1294.7 Vogel A I, A text book of practical organic chemistry(LongmansGreen,London)1956,177.8 ScottW & Furman,Standardmethodsof chemicalanaly-sis,6thEdn (VanNostrand,NewYork) 1962.9 Idriss K A, SeleimM M, Abu-Bakr M S & SalehM S,Analyst,107(1982)12.10 DouheretG, Bull SocChimFr,(1967)1412.11 Idriss K A, Awad A M, SeleimM M & Abu-Bakr M S,Bull SocChimFr,(1981)180.12 Idriss K A, SeleimM M, Abu-Bakr M S & SalehM S, In-dianJ Chern,21A(1982)395.13 Job P,Ann Chim(Rome),10(1928)113.14 Shirif F G & Awad A M, J inorg nucl Chern,24 (1962)79.15 Yoe G H & Jones A L, Ind Engng Chern,Anal Ed, 16(1944)111.16 FischerBE & SieglH, InorgChern,18(1979)425.17 Martin R B & Prados R, J inorg nucl Chem,36 (1974)1665.18 DewitR & WattersJ J, JAm chemSoc,76(1954)3810.19 Kida S,Bull chemSocJapan,29(1958)805.20 SahaiR, Agrawal& KushwahaS S S, J Indian chemSoc,59(1982)1121.21 IrvingH & WilliamsRJ P,J chemSoc,(1983)3206.-.

Mixed-Ligand Complexes of Fe(II) & Cu(II) with Alizarin Maroon as a Primary Ligand & 5-Sulphosalicylic Acid as a Secondary Ligand

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Mixed-Ligand Complexes of Fe(II) & Cu(II) with Alizarin Maroon as a Primary Ligand & 5-Sulphosalicylic Acid as a Secondary Ligand

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