Biddau, M.

Chary, M. N.

Ponticelli, G.

Sastry, B. A.

English

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IndIan Journal of ChemistryVol. 15A, October 1977, pp. 883-885Studies on ESR Spectra of Some Polyamine-Cu(II) Complexes InSolution & Frozen SolutionM. N. CHARy & B. A. SASTRYPhysics Department, Osmania Univcr-itv, Hyderabad 500007andG. l'Ol\TICELLI & lV1. BIDDAUIstituto Chimico Policat tcdra, Univcrsita di Cagliari, Via Ospcda.le 72,09100 Cagliari, ItalyReceived 10 January 1977; accepted 16 May 1977ESR spectral (solution and solid), and optical absorption studies have been made on(i) [Cu(tn)2] (NCS), [tn, = bis(1,3-diaminopropane], (ii) [Cu(tn)zNCS]BIjl4(III) [Cu(dpt)NCS]Bljl4[dpt = 3,3'-diamino-dipropylamine] and (iv) [Cu(Me6tren)NCS]N03 [Mejt ren = tris (2-dia-methylaminoethyl)-amine]. The ESR spectra of the first three complexes indicate BIg groundstate to Cu(II) ion in pyridine solutions. These studies in pyridine and acetone solutions ofMe6tren complex support Alg ground state to the Cu(lJ) ion. In all the complexes, the ESRand optical absorption data support the earlier conclusions on the coordination around Cu(II)ion arrived at on the basis of IR, molar conductivity and optical data. The strength of the 0'and :n; metal-ligand bonds are estimated using the above data in solutions. In these com-plexes 0' and in-plane It-bonding is moderately strong, disproving the earlier conclusions thataliphatic polyamines are incapable of It-bonding. Out-of-plane :n;-bonding is found to beabsent in (tri), complexes.UNLIKE the ESR studies of copper(II) ionshaving square-planar, square-pyramidal andelongated octahedron symmetries, ESRstudies of Cu(II) ions having trigonal bipyramirlaland compressed octahedron symmetries are rela-tivclv few. In the latter case the ground statewill 'be Ajg and in the former, either it will beBIg or B2g. The symmetry of trigonal bipyrarnidalcomplexes dissolved in solvents is found to change,as revealed bv ESR, to give either Bg or B2g groundstate to the Cu(II) ion". To the best of ourknowledge till now no ESR spectrum of Cu(II) ionwith trigonal bipyramidal symmetry in frozen solu-tion state is recorded. In the present investigationthe authors have compared the shape of the ESRspectra of a series polyamine-Cu(II) complexeshaving A,g with those of B,g ground state andhave also studied the metal-ligand bond strengthsin solution state using ESR and optical data.Materials and MethodsThe copper(II) complexes studied in the presel~tin vestigation are (i) [Cu(tn)2](SCN)2 [tri, = ~~s(1,3-diaminopropane)], (ii) [Cu(tn)2N CS]N03, (Ill)[Cu(dpt) (NCS)]B<p4(clpt= 3,3' -diaminodipropylami~e)and (iv) [Cu(l\fe6tren) NCSJ:\T03 [l\ie6tren = tris-(2-dimethylaminoethyl) amine]. Th~:;e complexeswere prepared by the methods dcscribe.l ear~ler2,3.The symmetry of the cation [Cu(tn)2NCS]+ 111 thecomplex [Cu(tn)2(NCS)]CI04 in solid state .is. trigonalbipyramidal-, From the IR, conduct!Vlty <l:ndoptical absorption data, it is found that 111 solutionthe solvent molecules substitute the thiocvanate-.Above studies on dpt complexes indicate' sq uare-pyramidal structure. Whereas the crystal structurestudies of [Cu(dpt)(NCS)]Cl04 gave evidence of astrongly elongated octahedron". Tren and Me6trenligands have the characteristic tripod like shapewhich gives trigonal bipyramic1al configurationaround Cu(II) ions. The anions N03 and B<p4 areineffective in bringing any change in the trigonalbipyrarnidal configuration2. The crystal structureanalysis of [Cu(tren) (NCS)]SCN (ref. 6) and[Zn (tren)(NCS)]SCN confirms the trigonal bipyra-mi dal configuration?The ESR spectra of these complexes have beentaken in O'OOSM solutions of pyridine and acetonewith the help of Varian E-4 X-band ESR spectro-meter using DPPH as ,L;-marker. A Unicam SP700spectrophotometer was' used to record the opticalabsorption peaks in solutions.Results and DiscussionThe ESR spectra of (tn)2 and dpt complexes atroom temperature in pyridine (Fig. 1) solution consistof the usual four hyperfine lines of Cu(II) with spin-dependent line-widths. But the spectra of Me6trencomplex in pyridine and acetone (Fig. 1) show onlyone line perhaps due to small separation of hyperfinelines and large line-widths. The ESR spectra of(tn)2 and dpt complexes at liquid nitrogen tempera-ture (Fig. 1) are identical with those of Cu(tn)2(CI04)2and Cu(tnen) (SCN)2 in N ,N -dimethvlformamicle(DMF)8. From the computer stimulations the abovespectra are found to fit the tetragonal symmetry.Due to one to one correspondance of shape of theESR absorption curves, in both the cases we havetaken the Cu(II) ion in the complexes to possesstetrago~al :ymmetry. The gll and A II values of theCu(II) ion m the present case are directly obtained883885®INDIAN J. CHEM., VOL. 15A, OCTOBER 1977@100GL---J305 K HPYRIDINE[Cu (1012 NCS J SCN77KPYRIDINE[Cu(tnI2NCS ]SCN100GL--.I~100G \L--177KPYRIDINE[cL' Itnl;, NCS] Blii4®©77KACETONE[Cu IMe6treni N CSI]N03H-®771<PYRIDINE[Cu (dptl NCS] B~3051<PYRIDINE[Cu (dpt) NCS )BC!>477 KPYRIDINE[Cu(;"06"""; NCS] N03H--- .••..H- DPPHFig. 1 -- ESR spectra of (A,D) [Cu(tnLSCNJSCN, (C,E) [Cuttn), INCS)]Bcp., (F,G) [Cu(dpt)l\CS]Bcp, in pyriuine and(D,H, J.]) lCu(~Ic"trcn)(NCS)]"'03 in pyridine and acetone both at room (305K) and liquid nitrogen temperaturesfrom the frozen solution spectra using the procedureof Sands" and 'others!". The value of g.l and A.l areobtained from tile average g [<g> = Cgll+2g.ll/3Jand A [<A> = 'All +2A.l)/3j values obtained fromsolutions at room temperature. The g and A valuesof these complexes are giYen in Table 1. As isevident from the g (gll>g.l>2·04) values the electricfield symmetry is tetragonal formed with eitherelongated octahedron or sq uare pyramidal ancl hencethe ground state correspond to either BIg or Beg.This indicates that the trigonal bipyramidal struc-ture of :Cu(tnhSC~J+ in solid will change to squarepyramidal structure in solution clue to solvent inter-action as prc.l icted earlier by IR conductivity andoptical data. The dpt complex also exhibits asimilar behaviour.In the case of [Cu(MeGtren)(~CS)JN03 in pyridineand acetone solutions. the spectra are found to beentirely different from that of the other threecomplexes. Here lowficld side spectrum consistsof four lines with higher intensity than the highfield side spectrum where one weak line is recorded(Fig. 1). This type of spectrum can only beobserve.l in the case of trigonal bipyramidal orcompressed octahedron symmetry. In the caseof the powders of Cu(II) doped bis(1, 1,1 ,5,5 ,5-hexa-fluoro-2,4-pentanedionato)zinc(II)1l this type ofspectrum is recorded but the highfield weak lineis well re-olvcd unlike the present case. Theoptical absorption values (12500 and 14500 cm']in the above complexes are same as those found inthe present case. To make sure that the positionComplex <s> </1 > x 10' gllcln-1TABLE 1 - ESR, OPTICAL AnSORPTIO:-;[ ,\:-;D BO:-;[D PARAMETERS OF COPPER(II) POLYAMINE COMPLEXESAIIXlO' A.lxl0· !:J.Exyxl0-3 !:J.ExyxlO-3ern"! cm! crn! crrr 'Cu(tn,) (SO\'),(a) Pyridine 2·119 628 2·212 2·072 1674 105 15·20 17·60Cu(tn,)NCS.Bcp.,(a) Pyridine 2·121 62-8 2·222 2·069 172-0 8·2 15-60 18'60Cu (:'IIc6trcn )-"CSN03(a) Pyridine 1·924 2·190 93·00 14·20 11-00(b) Acetone 1·924 2·190 88·4 14'20 11-00Cu(dpt)!\CS BC;>.1(a) Pyridine 2·1204 2·233 2·065 160A 15·80884g.l0·7125 0·87210·7283 0·997 0·87200·7465 0'7381CHARY et al.: ESR SPECTRA OF POLYA~IINE-CII(II) CO?l1PLEXESof the weak line correspond to the g value, we havecalculated the g1. value from the average g [<g >=(gll+2g1.)/3], obtainerl from the room temperaturespectrum and the g1. value obtained from the frozensolution spectrum. The value obtained above talliesvery well with the value obtained from the weakline position. The values of gll, g1.' A 1. and opticalabsorption peaks obtained from acetone andpyridine are found to be nearly same indicatingthat the solvation of the complex in both thesolvents is equal. One of the most important featuresof the ESR data of this MeGtren complex is that thegll value is the smallest of all the values in Cu(H)complexes so far investigated.The nature of the c and rr bonds are investigatedin the case of (tn), and clpt complexes wherecomplete optical data (tlExy and tlExz) and ESRdata (gll, All, A1. and g1.) are available (Table 1).tlExy and tlExz are assigned to the optical absorptionpeaks observed in solutions as given in Table 1.In the case of other (t n), complexes the peak at14600 cm! is used as the tlExy (refs. 8 and 12). Inour case the value is four.d to be slightly higher.Molecular orbital theory put forward by Maki ar.dMcGarvey13 is used to calculate ar.d metal-ligai.dbond nature. In fact this theory is strictly appli-cable to square-planar complexes. But many workersapplied this theory to complexes having other thansquare-planar structure9,14-16, considering only theatoms in the principal plane for the sake of~implicity. The expressions of gll, g1.' All and A1.In terms of molecular orbital coefficients are givenas f 011OWS8,13:gl = 2·0023 -8P["'~1 -~o:'(1-~ilq(n)Jg1.= 2·0023-2[L [o:~-~20:'(1-~2)tT(11) JAll= p[ -G+Eo)a2+(gll-2)+j(g1.-2)(3,2)1/2 ]-4P,t.'(1-~D!T(11) - 7 !J.0:'(1-~2)tT(n)A1. = p[ G -](o) 0:2 +~!(g1.-2)(11·2). r J- -- - [LO: (1-~2)!T(n)14... (1)... (2)... (3)... (4)III the above expressior.s the c or.stants have theirusual meani:,gs8. 0:2, ~i <1.1 d ~2 are measures ofin-plane o, in-plar.e " ai.d out-of-plar.e -e-bor.dsrespectively. In the case of c1pt sii ce completeoptical data are not available 0:2is calculated usingthe simplified expressi on-? (5)0:2= - ~1+(gll-2'0)+~(g1. -2·0)+0·04 ... (5)sing this value of (/.2in gll expression, the valueof ~i is calculated. The bo..d parameters (",.2, ~iand ~2) thus calculated are given ill Table 1. Fromthese b or.d parameters the COIclusi oi.s drawn are:(i) A considerable in-plar.c rr-b ondi t g is observedsimilar to the other polyamine Cu(II) complexes"disproving oi.ce again the statcme: t that thealiphatic amir.es are ii.capablc of ,,-bonding;(ii) threre is IiO out-of-plane rc-b ondi r.g in (t')2 com-plexes; and (iii) the o-b ondi rg in all the cases is sameand moderately str o: g. This is of the same order asthat observed in other polyamine Cu(II) complexcs--",\\'e could Lot estimate the bor.d i.at urc inMe6tren complex as the complete optical ar.d ESRdata are not available.AcknowledgementWe are thankful to Prof. K. V. Krishna Rao, Headof the Department, for his COJstar.t cr.couragcment.YAlealso wish to thank Dr G. S. Siddhu, Director,RRL, Hyderabad, for giviJ~g facilities to take opticalelata.References1. CHARY, 1\[.:\., SASTRY, TI.A., l'O:'<TICFll.I, G. 8: :\I~ssArESI,:'II., Indian]. 1''''·c at/'I. 1'h','s., 5 (1977), 167.2. DEVOTO, G. & ] 'O],;TICELLI, G., J. iuorg. nucl . cu.«, 37(1975), 1153.3. CRISTIXT, J\. 8: POXTICELLT, G., J. i norg, nucl . Chc11?, 35(1973), 269l.4. CAl'X,\S, :'II., CART \, G. 8: :'IIAHOXGIV, G., j. chcni. Soc.Dolton Trans., (1974), 550.5. CANXAS, :'II., CARTA, G. & ?llARO:-;GTV, G., Gaez, chim. Ital.,104 (1974), 581.6. ].~I:-;, P. C. 8: LiXGAFELTER, E. c., J. A IJI. chem. Soc.,89 (1967), 613l.7. A]';DH£E1'1' 1 , G. l i., JAIN, P. C. 8: LTXGAFEL1'ER, E. c.,J. Am. chent . Soc., 91 (1969), 4112.8. BARBUCCI, R., PAOLETTI, 1'.8: CAMPl'ELL, ]\1. ]. ;\1., l norg,clii m, Acta, 10 (1974), 69.9. SANDS, E. E., Phys. Rev., 99 (1955), 1222.10. GAHSMAN, E. R. 8: SWALEN, J. D., J. chem Phys., 36(1962), 3221.11. PRADILLA-SOHZAl'O, J. 8: FACKLER, J. P., l norg, Chem.,13 (1974), 38.12. YOKOI, R. & ISODE, T., Bull. chcm, Soc. Japan 41 (1968),2835. '1:1. J\IAKI, A. H. 8: MCGARVEY, B. R., J. chem, Phys., 29(1958), 31, 3514. LEWIS, w B., _\LEI, ~r.& :'IloRGA"', L. 0., J. chem. Phys.44 (1966), 240915. BULllGGWVE, DASCOLA, G., GlORI, D. C. 8: VJ..RA, A.,I chem . Phys., 54 (1971), 219l.16. GHEGSOX, A. K. 8:~lITRA,S.,J.chem.T'hys.,49(1968),3696.17. I<IVELSON,D.8::t\EIMAN,H.,j. chrmc Phvs., 35 (1961),149.885

Studies on ESR Spectra of Some Polyamine-Cu(II) Complexes In Solution & Frozen Solution

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Studies on ESR Spectra of Some Polyamine-Cu(II) Complexes In Solution & Frozen Solution

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