Indian Journal of ChemistryVol. 21A. September 1982. pp 934-935

Complexes of Copper(II), Nickel(II),Cobalt(II), Iron(III), Manganese(II) &Zinc(II) with Schiff Base Derived from

2-Hydrazinobenzoxazole & Salicylaldehyde

(Miss) VASUDHA ATRE, G VENKA T REDDY,(Miss) L N SHARADA & M C GANORKAR*

Department of Chemistry, Osmania University, Hyderabad 500007

Received 28 January 1982; revised and accepted 21 June 1982

Cu(I1), Ni(I1), Co(ll), Fe(III), Mn(I1) and Zn(I1) complexes of theschiff base derived from 2-hydrazinobenzoxazole and salicylal-dehyde have been synthesized and characterised on the basis ofelemental analyses. conductivity. magnetic moment. TGA, infra red,electronic and ESR spectral data. These chelates have been screenedfor fungicidal activity and found to be more active than the ligand.

In continuation of our earlier work on some transitionmetal complexes derived from active organicmolecules 1.2, we now report here the synthesis andcharacterization of a few more transition metalcomplexes of the schiff base derived from 2-hydrazinobenzoxazole and salicylaldehyde (2-HBO.Sal). The fungicidal activities of the complexes againstthree fungi, viz. Curcularia sp., Fusarium sp, andAlternaria sp. have been measured. The schiff base (2-HBO. Sal) has been reported to be fungicidal andinsecticidal", but no attempt has been made tosynthesise metal chelates of this active organicmolecule and study their nature.

All the metal chlorides used were of AR grade. 0-

Aminophenol (Wilson lab.), carbon disulphide(Wilson lab.), hydrazine hydrate (98%, Ranbaxy) andsalicylaldehyde (E. Merck) were used for thepreparation of the ligand. The ligand 2-HBO. Sal wasprepared by reported procedure.' and its puritychecked by TLC and melting point determination (lit.251°C).

Synthesis of metal chelates-« The complexes wereprepared by retluxing the methanolic solutions ofmetal chlorides (0.001 ,W) and the ligand (0.002 M) for3-4 hr. The Cu(II) complex separated out immediatelyas a green crystalline compound. The chelates of othermetal ions separated on raising the pH to ~ 8 by theaddition of ammonia solution (I: I). The separatedproducts were filtered, washed with hot methanolfollowed by pet. ether (60-80) and dried in vacuo.

Elemental analyses, magnetic susceptibilitymeasurements and thermogravimetric analyses werecarried out by the methods described earlierl.4. IRspectra were also recorded as reported earlier 1.

4.

Electronic spectra and ESR spectra were recorded in

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Table l--IR and Electronic Spectral Data

Ligand/complex" IR frequencies (ern -I) Electronic---~----~- spectral

vN--H I'C=N bands( cm " I)(freering)

CI4N,02HII 3250- 1640 22620. 303002750(b) 1610

Cu(CI4N,02HIOh 3400(m) 1625 15151,27780,1600 32260

NiC 14N,02H loCI 3300(s) 1625 20000. 277801600

CoC'4N,02H,oCl 3350(m) 1615 16390.26315.1600 32260

Fe2(C 14N,02H ,oCI2), 3350(b) 1620 12900. 27780.1600 32260

MnC'4N,04H,4CI 3400- 1620 16000.26115.2700(b) 1590 32250

ZnC'4N,02H,oCI 3400(b) 16151600

• Satisfactory elemental analyses were also obtained

~--'------

nujol mull at room temperature on UV-visiblespectrophotometer DMR-21 and EPR-E4 spectro-meter respectively.

The analytical results indicate I: I (M:L) stoi-chiometry for all the complexes except the Cu(II)complex, where 1:2 stoichiometry is found. Thecomplexes are soluble in DMF, DMSO and dioxane.The molar conductance values of I x 10 -3 M solutionof the complexes in DMF (2-20 mho em? mol -I) showthem to be non-electrolytes.

Important infra red and electronic spectral bands ofthe complexes are given in Table I. The infraredspectrum of the ligand shows a broad peak around3250-2750cm -I, which has been attributed to acombination of vO--H (phenolic), vN -H and vC~Hmodes. The appearance of vOH and vNH modes atsuch a low region may be due to strong intramolecularhydrogen bonding". In the IR spectrum of the ligandtwo sharp peaks at 1640 and 1610 em 1 are assigned tovC = N (free azomethine) and vC = N (ring) re-spectively. The sharp bands observed at 1260 and 1025em -I are attributed to I'C~O (phenolic) and ring C-O---C stretch repsectively. The absence of a broadpeak in the region 3250-2750 em 1 and appearance ofa new peak around 3400-3300 em -I, assignable tovN~H in all the complexes, indicate the cleavage ofintramolecular hydrogen bond and deprotonation ofphenolic OH and its participation in coordination. Theshift in phenolic vC~-O (+ 10-50cm -I) in all thecomplexes further confirms the involvement of oxygen

of phenolic group in coordination":". The shift in vC= N (both free and ring). towards lower wave numbersindicates the coordination of nitrogens of both theazomethine groups. Further, no change is observed inC---O----C stretching frequency in complexes suggest-ing non-involvement of the oxygen of the ring inchelate formation. Hence it is concluded that 2-HBO.Sal is behaving as a monobasic tridentate ligand withONN donor system. In the spectrum of Mn(ll)complex, a broad band around 3450-3200 em - I isobserved which may be due to the overlapping of v N-H and coordinated water bands. The presence ofcoordinated water is further confirmed by appearanceof a new peak at 795 cm "" (ref. 8) andthermogravimetric analysis. Thermogravimetric ana-lysis of the chelates shows that only Mn(II) complexcontains coordinated water. TGA reveals weight lossequivalent to two water molecules per mole of Mn(H)complex at about 150°C. The peaks in the region 600-250cm -I are assigned to vM-O, vM-N and vM-Civibrations'"!".

Cutl l), Mn(H) and Fe(llI) complexes are found tobe paramagnetic. The Perf value (5.6 B.M .) for Mn(H)complex is low when compared to reported values forother high-spin Mn(lI) complexes. The low value maybe due to the presence of M n(I II) species and spin-exchange in solids II. The low l'err. value for Fe(III)complex (4.7 B.M.) when compared to values for otherhigh-spin Fe(I1n complexes may be attributed tometal-metal interactions II - 14

The electronic spectral data of the complexes arepresented in Table I. The band at 15151 cm -I inCu(lI) complex is assigned to 2 E, --> 1 T2g transition 15_

The other two bands at 27780 and 32260 em -I are dueto charge-transfer. On the basis of the magneticmoment and electronic spectral data, octahedralgeometry is proposed for the Cu(lI) complex. Theelectronic spectra of Mn(l!) and Fe(llI) complexesshow very weak bands and hence are not of much helpin deciding the band transitions. For Mnrl l) andFe(lH) complexes, octahedral and binuclear octahed-ral structures are proposed respectively.

Ni(II) complex is found to be diamagnetic. The bandat 20000 em -I is due to I A IR --> I A 2g transition and thatat 27780 em -I is due to charge-transfer. Magneticmoment and electronic spectrum of Ni(lI) complex arevery similar to those of reported Ni(II) square-planarcomplexes". The observed magnetic moment forCot l l) complex is 2.1 B. M. which agrees well withreported values for low-spin Co(ll) complexes withone unpaired electron. The square-planar geometryfor Co(II) complex is characterized by a narrow bandnear 8500 em --I and a broad strong band around20000 ern -I. The electronic spectrum of Cotlf)

NOTES

complex shows a strong broad band at 16390 cm " 'which is assigned to 2 AIR --> 2 B IX transition 17 -19. Themagnetic moment value and the electronic spectralband suggest a square-planar disposition for Co(ll)complex/". Zn(II) complex is found to diamagnetic.

ESR spectrum of Cu(lI) complex shows gll

= 2.1800 and g 1 = 2.1112. The small g values indicatestrong interaction between the ligand and the metalion.

Fungicidal activity-The ligand 2-HBO.Sal and itsmetal chelates were screened for the antifungal activityagainst three fungi, viz., Curvularia sp., Fusarium sp.and Alternaria sp. by spore germination method " atroom temperature at three different concentrations,i.e., at 1000 ppm, 500 ppm and 200 ppm. The timetaken for the germination of these spores at roomtemperature is generally 4-5 hr. It was found that theinhibition by the metal chelates is more than that bythe ligand. In general the order of inhibition is: Cu(lI)> Zn(lI) > Fe(IlI) ~ Ni(lI) > Co(ll) > Mnrll).

Two of the authors (V.A. & LN.S) are thankful tothe CSIR, New Delhi, for the award of junior researchfellowships.

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