Daye, L D

Mathew, Cherian

Namboori, P K Krishnan

Oommen, Varughese

English

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IndiarlJournalof ChemistryYol. 2tA. March 1988.pp.258-260StructuralStudiesof Cu(II) & Ni(II)¢omplexeswithaChiralSchiffBaseL D DAYE, CHERIAN MATI-lEW*.YARYGHESE OOMMEN & P K KRISHNAN NAMBOORIUniv~rsityDepartmentof Chemistry,BhavnagarUniversity.. Bhavnagar364002ReceivJ,d7 October1986;revised9 January 1987;re-revisedandaccepted14 May 1987Cu(I.) andNi(lI) complexesof theschiffbasederivedfroill6-ethoxf-Z-hYdroXynaPhthaldehYdeand isopropylenediamine[N,N'-b (6-ethoxy-Z-hydroxynaphthalidene)isopropylenedi-amine] ayebeenprep redandchar cterisedby elem nt lan-alysis,¢agneticand spectraldata.Circular dichroismspectraldata h~wthattheCu(lI) complexhasa non-planarstructureandtheNi(lI) complexhasaplanarstructure.Investigationson metalcomplexesof chiral scl>iffbaseshave got a boost due to the fast develop-ment~fcirculardichroismand otherspectropho-tometrktechniques.Divalentmetalion complexesof qu~ridentateschiffbaseIigandsderivedfromthe re ction of diamineswith 2,5-dihydroxYflceto-phenoe, 2,5-dihydroxypropiophenoneand2,5-di-hydro benzophenonewereassignedsquare-plan-ar stru turel.2.If thediamineinvolvedin theschiffbnsec ndensationis madeopticallyactiveJ[ ~ J[*transitins in thechromophoricpartof theligands~"c .uple and produceexcitoncomponentsofopposi~ehandednessin case of deviationfromplanari~of the coordinationspherein the com-plexes3I 5. Circular dichroismspectralstudiesonCu(II) ~omplexesof the above!igandsshow thattheyhalvegot a psuedotetrah dr lstructureo.T ispromptedus to undertakesynthesisandcharacter-izationpf Cu(II) andNi(II) complexesof thechiralschiff ~aseN,N'-bis( )-ethoxy-2-hydroxynaphthal-idine)is<jlpropylenediamine(I).Isop~pylenediaminewas resolvedby standardproced~redescribedby Dwyer et aU This wastreatedi with 6-ethoxy-2-hydroxynaphthaldehydewhenyttllowcrystallineschiffbasewasinstantane-ouslyo~tained.It is solublein almostall commonorganic'!solvents.It wasrecrystallisedfrom chloro-form(mip.93°C).!25H"I' iil '~III I II '101'1111I11 IThe metalcomplexeswerepreparedby mixinghot equimolarsolutionsof ligandin methanolandcoppernitrate/nickelnitratein water.The Ni(II)complexwas formed at pH ~6. The complexesweredigestedon a waterbathandextractedsever-al timeswith chloroform.Finally, the complexeswere recrystallisedfrom chloroform.The coppercomplexis dark-greenin colour while the nickelcomplexisreddish-yellow.Carbon,hydrogenand nitrogenwereestimatedby micro-analyticalmethods.Copper and nickelwere estimated gravimetricallyas CuO andNi(DMG)2' Analytical data: Cu(II) complex:Found: C, 64.95; H, 5.23; N, 5.29; Cu, 12.00.Calc.: C, 65.46; H, 5.30, N, 5.26; Cu, 11.94%;Ni(II) complex:Found:C, 65.81;H, 5.29;N, 5.24;Ni, 11.13.Calc.:C, 66.06;H, 5.35;N, 5.32;Ni,11.14%.Elemental analysesshow that the complexeshave1:1(M:L) ratio.Thus, theligandbehavesin aquadridentatedibasicmanner.Molecular weightsof the complexesdeterminedebullioscopicallyinchloroformrevealedtheirmonomericnature.Con-ductivitymeasurementshowedthe covalentna-ture(2.2-2.7mhoscm2mol-I) of thesecomplexes.Room temperaturemagneticmomentobtainedusingGouy methodfor Cu(II) complexwasfoundto be 2.2 B.M. The excessover thatrequiredforone unpairedelectronmay be due to spin-orbitcoupling.The Ni(II) complexwasfound to be di-amagnetic.IR spectraof both thecomplexesare similar.Aband observedat 3480 em- I in the spectrumofligand,assignedto vO - H, is not observedin thespectraof the complexessuggestingthe involve-mentof oxygenatomof thehydroxylgroupin co-ordinationafterdeprotonationof OH. The bandobservedat 1580em- I in theligandspectrumdueto vC =N is shiftedto 1630 em-I in the com-plexessuggestingthe involvementof the azome-thinegroup(>C =N) in complexationthroughthenitrogenatom.vM - Nand vM - 0 modeswereobservedat530and420em- I respectively.The absorptionspectrumof theCu(l1)complexshowedonly onebandat 562 nm whichis typicalof square-planarcomplexes.The spectrumof theNi(II) complexshowedthreeweakbandsxat 557,686 and 712nm dueto thetransitions'Eg+--IAIP'A2g+--'A]gand IB]g+--'A,p respectively.PolycrystallinestateEPR spectrumof theCu(II)complexshowedthe anisotropiccharacterof theNOTES40302-'Ev"t... 100E'E."'- -----r - ,~_.-._.~._.~---------rn.., 647<l-10.Ii,.'.i-201v•..._.~,.-30AnmFig. I-CD Spectrumof Cu(I1)complex(--) in chloroformandof theligand(------) in chloroformFig. 2-CD spectrumof Ni(ll) complexin chloroformy--.>C= N:----+>C= N:groupis attachedto thenaphthylring.The - CHzgroupin the diaminepart gavea signalat 't 6.4.The signalsdue to aromaticprotons were ob-servedas strongpeaksat 't=3.1, 2.65 and 2.80.The protonattachedto theasymmetricarbonat-omin thecoordinationspheregavesignalat 't 2.7.It is highlydeshieldedand this deshieldingcouldbeduetoitspositionin thecoordinationsphere.The circulardichroism(CD) spectrumof the li-gand is typicalof excitoncouplingin a gaucheconformationwith negativeopticalfactor for thelow energycomponent.The observedfine struc-turein theCD spectrumcouldbe dueto an over-layedn-+n*transitionasshownbelow:--------.807I,J! .~~, 567 -'---------=-.--"7oi--Anm-4010080604'T§.,.~ 201.....0[1.,.•. <l-20complex.The solutionspectrumin a mixtureofCHCI, and acetoneat room temperatureshowedfour gisa bands.The two bands at higher fieldshowedsuperhyperfinesplittingdue to nitrogen.giso and Aisa valueshave been calculatedto be2.092and89.13Grespectively.The solutionspec-trumat liquidnitrogentemperaturegavethreeva-lues for the g-tensor,gx (2.02),gy (2.07)and gz(2.185).The gay valuecalculatedwasfound to beexactlythesameasthegiso value(2.092)obtainedfrom room temperaturespectrum.The first bandin thegll regionshowedthesplittingdueto nitrog-en. All =200G, Aa=89.13 G, A~u=7.0G andA~u=9.0G werealsocalculatedfromthespectra.Sincethreeg-factorsareobserved,themoleculeisrhombicwith the unpairedelectronin the dx' - yOorbitalwiththegroundstateterm2BIg" The valuesgll/~I=109.25andAu arein therangeexpectedforsquareplanarcomplexes.NMR spectrumof theNi(ll) complexshowedasignalat 't 8.6 which could be due to the two- CH, groupsin the ethoxymoietyattachedtothe naphthylring.The - CHz groupsattachedtothe - CH3 groupbroadenthe - CH3 peakduetoJ-J coupling.The signaldue to - CHz groupwasfound at 't 3.7.This signalwasdeshieldedby thepresenceof oxygenatom.The peakat 't 8.3couldbe dueto the - CH3 groupattachedto theasym-metriccarbonatomof the diamine.This wasnotsplit,confirmingthat this - CH, groupis chemi-cally isolatedfrom other protons as is evidentfromtheproposedstructure.Two sharppeaksob-servedat 't 7.0 and7.1 areassignedto the -:;:CHgroupof thealdehydethroughwhichthediamine259INDIAN J. CHEM., VOL. 27A, MARCH 1988In the\CD spectrumof theCu(II) complexof theschiff!base,transitionregionof the chromophoreis ob~rved at the sameenergylevel as in thespectr*mof schiffbase(Fig. 1);furthermore,it ex-hibits~CD spectrumtypicalof excitoncoupling.This iqdicatesa tetrahedraldistortionof theCu(II)coordi~ationsphere.The low energyexcitoncom-ponenGof thecomplexhasa positiveopticalfactorwhere~sthatof the ligandhas a negativeopticalfactor.iiThis suggeststhat the absoluteconfigura-tion oflthe ligandpart in the complexis oppositeto that'lofthefreeligand.The CD spectrumof thecomplekshowsan envelopein the Jt --+ Jt* region,indicatipgthe coppercomplexto be non-planar.HenceIthe CD spectrumof the Cu(Il) complexsuggest$a psuedotetrahedral,i.e., a deformedsquare-Planarstructurefor thecomplex.However,theele~tronicand EPR spectraclearlypoint to asqUare-~lanarstrucutrefor Cu(II) complex.Thedistortin from square-planartowardstetrahedraltructur. suggestedby the D spectrummust,therefor~,be small.In thespectrumof Ni(II) com-plex(Fig.2), thetransitionregionsof thechromo-horeof theligandandthecomplexareat differ-ent eneties suggestingthe absenceof tetrahedraldistortio of theNi(II) coordinationsphere.Thereis no .velope in the Jt --+ Jt* region in the CDIi260spectrumsuggestinga planar structurefor Ni(II)complex.Like in the caseof Cu(II) complex,theabsoluteconfigurationof the ligand part in thecomplexis oppositeto thatof thefreeligandsincethelow energyexcitoncomponentof thecomplexhasa positiveopticalfactorwhereasthatof theli-gand has a negativeoptical factor as is evidentfrom theCD spectraof thetwo.Hence,it is con-cludedthattheNi(II) complexissquare-planar.Two of the authors(eM & VO) thanI<CSIR,New Delhi andBhavnagarUniversity,respectively,for financialassistance.References] Dave L D & MohankumarV B, Indian J Chern, 12A(1974)984.2 Dave L D & PrasadB G S, Indian J Chern,12A (1974)1002.3 LarsenE, Actachernscand,23(1969)2158.4 Jensen H P & WarsenE, Acta chernscand,25 (1971)1439.5 Bernth N, Larsen E & Larsen S, Tetrahedron,37 (1981)2477.6 JensenH P, IndianJ Chern,23A (1984)475.7 DwyerF P, GarvaniF L & Schulmann,J Arn chernSoc,81(1959)290.8 Lever A B P, Inorganicelectronicspectroscopy(Elsevier,NewYork) 1968,343.

Structural Studies of Cu(II) & Ni(II) Complexes with a Chiral Schiff Base

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Structural Studies of Cu(II) & Ni(II) Complexes with a Chiral Schiff Base

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