Spectroscopic and mycological studies of Co(II), Ni(II) and Cu(II) complexes with 4-aminoantipyrine...

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Spectrochimica Acta Part A 81 (2011) 424–430 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy jou rn al hom epa ge: www.elsevier.com/locate/saa Spectroscopic and mycological studies of Co(II), Ni(II) and Cu(II) complexes with 4-aminoantipyrine derivative Amit Kumar Sharma a,b , Sulekh Chandra b,a Department of Chemistry, Ramjas College, University of Delhi, University Enclave, Delhi 110007, India b Department of Chemistry, Zakir Husain College, University of Delhi, J.L. Nehru Marg, New Delhi 110002, India a r t i c l e i n f o Article history: Received 22 February 2011 Received in revised form 8 June 2011 Accepted 16 June 2011 Keywords: Mycological assay NO-donor Schiff’s base Six coordinated complexes Tetragonal and octahedral geometries Spectroscopy a b s t r a c t Complexes of the type [M(L)X 2 ], where M = Co(II), Ni(II) and Cu(II), have been synthesized with novel NO-donor Schiff’s base ligand, 1,4-diformylpiperazine bis(4-imino-2,3-dimethyl-1-phenyl-3- pyrazolin-5-one) which is obtained by the acid catalyzed condensation of 1,4-diformylpiperazine with 4-aminoantipyrine. The elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, UV, NMR, mass and EPR studies of the compounds led to the conclusion that the ligand acts as tetradentate chelate. The Schiff’s base ligand forms hexacoordinated complexes having octahe- dral geometry for Ni(II) and tetragonal geometry for Co(II) and Cu(II) complexes. The mycological studies of the compounds were examined against the several opportunistic pathogens, i.e., Alternaria brassi- cae, Aspergillus niger and Fusarium oxysporum. The Cu(II) complexes were found to have most fungicidal behavior. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Now days, the study of the chelating ligands and their interac- tion with the metal ions is an interesting subject for the chemists [1]. Basically, the mycological investigations and the fruitful results are facilitating the chemists to explore these compounds in the challenging pharmaceutical field. A number of fungi and bacteria have been found to cause the allergies and several diseases in mil- lions of the people around the globe [2–5]. Fusarium oxysporum causes skin and nail infections, subcutaneous disease, neutropenic child managed with ganulocyte colony-stimulating factor, dis- seminated infection in hemophagocytic lymphohistiocytosis [3–5]. Aspergillus niger is one of the opportunistic pathogens which causes the lung disease Aspergillosis and ear infection Otomycosis in human beings [6]. Alternaria brassicae is a plant pathogenic fungus which causes the disease Alternaria leaf spot in most of crucifer plants [7]. It is evident from the studies that the coordination of organic compound (drug) provokes the pharmaceutical action of the drug. Moreover, the chemistry of the antipyrine derivatives and their complexes has received considerable attention for chemists due to their diverse pharmaceutical properties such as antifungal, antibacterial, analgesic, anti-inflammatory, etc. [8–11]. A num- ber of antipyrine derivatives have been synthesized and studied Corresponding author. Tel.: +91 11 22911267; fax: +91 11 23215906. E-mail addresses: [email protected] (A.K. Sharma), schandra [email protected] (S. Chandra). structurally and pharmaceutically which constitutes the antipyrine family attractive for the chemists to accept the challenging myco- logical strategy [8]. In several decades, fruitful efforts have been made to design and synthesis Schiff’s bases and Schiff’s base complexes to study these compounds in the basic and applied chemistry. We report here the synthesis, spectroscopic and fungicidal studies of Schiff’s base and its cobalt(II), nickel(II) and copper(II) complexes (Figs. 1 and 5). The structures of the compounds are characterized by using IR, UV, 1 H NMR, 13 C NMR, mass, EPR spectroscopic techniques. 2. Experimental 2.1. Materials Metal salts, different chemicals and various solvents (Fluka, S.D. Fine, E. Merck and Thomas Backer) were commercial prod- ucts and were used as supplied. 1,4-diformylpiperazine and 4-aminoantipyrine (AR grade) were obtained from Sigma–Aldrich. 2.2. Synthesis 2.2.1. Ligand 1,4-diformylpiperazine bis(4-imino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one), (L) A warmed solution of 4-aminoantipyrine (8.13 g, 0.04 mol) in acetonitrile (25 mL), was added to a hot solution of 1,4- diformylpiperazine (2.84 g, 0.02 mol) in acetonitrile (15 mL). The reaction mixture was refluxed for 5 h at 85 C in presence of few drops of acetic acid, allowed to stay at room temperature and then 1386-1425/$ see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2011.06.032

Transcript of Spectroscopic and mycological studies of Co(II), Ni(II) and Cu(II) complexes with 4-aminoantipyrine...

Page 1: Spectroscopic and mycological studies of Co(II), Ni(II) and Cu(II) complexes with 4-aminoantipyrine derivative

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Spectrochimica Acta Part A 81 (2011) 424– 430

Contents lists available at ScienceDirect

Spectrochimica Acta Part A: Molecular andBiomolecular Spectroscopy

jou rn al hom epa ge: www.elsev ier .com/ locate /saa

pectroscopic and mycological studies of Co(II), Ni(II) and Cu(II) complexes with-aminoantipyrine derivative

mit Kumar Sharmaa,b, Sulekh Chandrab,∗

Department of Chemistry, Ramjas College, University of Delhi, University Enclave, Delhi 110007, IndiaDepartment of Chemistry, Zakir Husain College, University of Delhi, J.L. Nehru Marg, New Delhi 110002, India

r t i c l e i n f o

rticle history:eceived 22 February 2011eceived in revised form 8 June 2011ccepted 16 June 2011

a b s t r a c t

Complexes of the type [M(L)X2], where M = Co(II), Ni(II) and Cu(II), have been synthesized withnovel NO-donor Schiff’s base ligand, 1,4-diformylpiperazine bis(4-imino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one) which is obtained by the acid catalyzed condensation of 1,4-diformylpiperazine with4-aminoantipyrine. The elemental analyses, molar conductance measurements, magnetic susceptibility

eywords:ycological assayO-donor Schiff’s baseix coordinated complexesetragonal and octahedral geometries

measurements, IR, UV, NMR, mass and EPR studies of the compounds led to the conclusion that the ligandacts as tetradentate chelate. The Schiff’s base ligand forms hexacoordinated complexes having octahe-dral geometry for Ni(II) and tetragonal geometry for Co(II) and Cu(II) complexes. The mycological studiesof the compounds were examined against the several opportunistic pathogens, i.e., Alternaria brassi-cae, Aspergillus niger and Fusarium oxysporum. The Cu(II) complexes were found to have most fungicidal

pectroscopy behavior.

. Introduction

Now days, the study of the chelating ligands and their interac-ion with the metal ions is an interesting subject for the chemists1]. Basically, the mycological investigations and the fruitful resultsre facilitating the chemists to explore these compounds in thehallenging pharmaceutical field. A number of fungi and bacteriaave been found to cause the allergies and several diseases in mil-

ions of the people around the globe [2–5]. Fusarium oxysporumauses skin and nail infections, subcutaneous disease, neutropenichild managed with ganulocyte colony-stimulating factor, dis-eminated infection in hemophagocytic lymphohistiocytosis [3–5].spergillus niger is one of the opportunistic pathogens which causeshe lung disease Aspergillosis and ear infection Otomycosis inuman beings [6]. Alternaria brassicae is a plant pathogenic fungushich causes the disease Alternaria leaf spot in most of cruciferlants [7].

It is evident from the studies that the coordination of organicompound (drug) provokes the pharmaceutical action of the drug.oreover, the chemistry of the antipyrine derivatives and their

omplexes has received considerable attention for chemists due

o their diverse pharmaceutical properties such as antifungal,ntibacterial, analgesic, anti-inflammatory, etc. [8–11]. A num-er of antipyrine derivatives have been synthesized and studied

∗ Corresponding author. Tel.: +91 11 22911267; fax: +91 11 23215906.E-mail addresses: [email protected] (A.K. Sharma),

chandra [email protected] (S. Chandra).

386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.saa.2011.06.032

© 2011 Elsevier B.V. All rights reserved.

structurally and pharmaceutically which constitutes the antipyrinefamily attractive for the chemists to accept the challenging myco-logical strategy [8].

In several decades, fruitful efforts have been made to design andsynthesis Schiff’s bases and Schiff’s base complexes to study thesecompounds in the basic and applied chemistry. We report here thesynthesis, spectroscopic and fungicidal studies of Schiff’s base andits cobalt(II), nickel(II) and copper(II) complexes (Figs. 1 and 5). Thestructures of the compounds are characterized by using IR, UV, 1HNMR, 13C NMR, mass, EPR spectroscopic techniques.

2. Experimental

2.1. Materials

Metal salts, different chemicals and various solvents (Fluka,S.D. Fine, E. Merck and Thomas Backer) were commercial prod-ucts and were used as supplied. 1,4-diformylpiperazine and4-aminoantipyrine (AR grade) were obtained from Sigma–Aldrich.

2.2. Synthesis

2.2.1. Ligand 1,4-diformylpiperazinebis(4-imino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one), (L)

A warmed solution of 4-aminoantipyrine (8.13 g, 0.04 mol)

in acetonitrile (25 mL), was added to a hot solution of 1,4-diformylpiperazine (2.84 g, 0.02 mol) in acetonitrile (15 mL). Thereaction mixture was refluxed for 5 h at 85 ◦C in presence of fewdrops of acetic acid, allowed to stay at room temperature and then
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A.K. Sharma, S. Chandra / Spectrochimic

NN

CH3

CH3ON

N

CH3

CH3O

C

N

H N NC

N

H

kptPC

2

s(rofia

2

AboIndmfwlacfwi

3

sEBDtatErb

Fig. 1. Structure of ligand.

ept in refrigerator overnight. The white shiny microcrystallineroduct which precipitated out, was filtered off, washed severalimes with acetonitrile and dried under vacuum over anhydrous4O10. Yield 60%, mp 210 ◦C. Elemental analyses, found (calcd.) for28H32N8O2: C, 65.58 (65.62); H, 6.21 (6.25); N, 21.83 (21.87) %.

.2.2. ComplexesTo a hot solution of ligand (1 mmol) in acetonitrile (15 mL), a hot

olution of metal salt (nitrate and chloride) (1 mmol) in acetonitrile10 mL) was added slowly with constant stirring. The mixture wasefluxed for 8–10 h at 80–90 ◦C. On keeping the resulting mixturevernight at 0 ◦C, the colored product which separated out, wasltered off, washed with acetonitrile and dried under vacuum overnhydrous P4O10.

.3. Mycological studies

The synthesized compounds were assayed against the fungi, i.e.. brassicae, A. niger and F. oxysporum for their fungicidal behaviory employing Food Poison Technique [12,13]. The stock solutionsf the compounds were prepared in DMSO solvent. The Minimumnhibition Concentration (MIC) was estimated by the dilution tech-ique by using sterile distilled water. The diluted solution wasirectly added to the PDA (Potato Dextrose Agar) medium and theixture was poured in to the Petri plate. The Petri plates were kept

or a day to check the sterility. A disc of 5 mm of test fungal cultureas placed at the center of the Petri plate with the help of inocu-

ums’ needle. The plates were sealed with parafilm and incubatedt 29 ± 2 ◦C for a week. All determinations were performed in dupli-ate. DMSO and Captan were employed as a control and a standardungicide, respectively. The fungicidal capacity of the compoundsas determined in percentage terms from the growth of the fungus

n the test plate to the respective control plate.

. Physical measurements

ESI mass spectra were recorded on a model Q Star XL LCMS–MSystem. The stoichiometric analyses were carried out on a Carlo-rba 1106 analyzer. NMR spectra were recorded with a modelruker Advance DPX-300 spectrometer operating at 300 MHz usingMSO-d6 as a solvent and TMS as an internal standard. IR spec-

ra were recorded as KBr pellets in the region 4000–200 cm−1 on FT-IR spectrum BX-II spectrophotometer. The electronic spec-

ra were recorded on Shimadzu UV mini-1240 spectrophotometer.PR spectra were recorded for solids on an E4-EPR spectrometer atoom temperature and liquid nitrogen temperature operating at X-and region with 100 KHz modulation frequency, 5 mW microwave

a Acta Part A 81 (2011) 424– 430 425

power and 2 G modulation amplitude using DPPH as a standard. Themolar conductance of complexes was measured in DMSO at roomtemperature on an ELICO (CM 82T) conductivity bridge. The mag-netic susceptibility was measured at room temperature on a Gouybalance using CuSO4·5H2O as calibrant.

4. Results and discussion

4.1. Chemistry

The synthesized Schiff’s base ligand, 1,4-diformylpiperazinebis(4-imino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one) (Fig. 1)coordinates to Co(II), Ni(II) and Cu(II) metal ions through nitrogenand oxygen binding sites. The analytical data along with otherphysical properties of the complexes are given in Table 1. Com-plexes show the general stoichiometry MLX2, where M = Co(II),Ni(II) and Cu(II), L = ligand, and X = NO3

− and Cl−. The molarconductance of complexes corresponds to their non-electrolyticbehavior with [MLX2] composition. The molar conductance of thecomplexes was measured immediately after the preparation of thesolutions. However, on keeping the solutions for long time, DMSOreplaces the anions and the complexes give molar conductancecorresponding to 1:2 electrolytes [14]. The magnetic studiesof the complexes account for high spin type complexes withtheir magnetic moments in the range 4.96–4.98, 2.96–2.97 and1.83–1.89 B.M. for Co(II), Ni(II) and Cu(II) complexes, respectively.

4.1.1. IR spectraThe selected IR bands of the compounds are listed in Table 2.

The IR spectrum of ligand shows the bands at 1667 and 1606 cm−1

which may be assigned to the �(C O) and �(C N) stretchingvibrations, respectively [8,15–17]. On complex formation, thebathochromic shift of these bands indicates that the carbonyl andazomethine groups are coordinated to metal ion through oxygenand nitrogen atoms, respectively. This indicates that the ligand actsas tetradentate coordinating species bonded to metal ion via ONNOdonor sites. The IR spectra of complexes display the new bandscentered in the range 397–505 and 505–572 cm−1 which maybe attributed �(M O) and �(M N) stretching vibrations [18,19],respectively. These additional bands are further in support thebonding of ligands to metal ion in ONNO fashion.

In addition, the IR spectra of complexes also display the bandsdue to bonded anions. The chloro complexes show the IR bandsin the region 327–346 cm−1 due to �(M Cl). The nitrato complexesshow the IR bands in the range 1406–1458 (�5), 1315–1328 (�1) and1036–1060 cm−1 (�2) due to NO stretching vibration of the NO3

ion. The ��, i.e. �5 − �1 (90–130 cm−1) indicates the unidentatecoordination of NO3

− ion [20,21].

4.1.2. NMR spectraThe 1H NMR and 13C NMR spectra of ligand were recorded in

deuterated DMSO (Fig. 2). In the 1H NMR spectrum, the peaks at ca.ı 2.33–2.66 ppm and in 13C NMR, the peaks at ca. ı 48.15–49.85 aredue to solvent [22]. The signals appeared in the 1H NMR spectrumof the ligand are discussed below:

I. The spectrum exhibits two singlets at ca. ı 2.11 ppm and2.88 ppm which may be assigned to the protons of methylgroups H3C C and H3C N, respectively, which are attached tothe pyrazolone rings.

II. A multiplet is appeared in the range at ca. ı 3.24–3.48 ppm

which may be due to the eight protons of piperazine ring.

III. The spectrum displays another multiplet in the range at ca. ı7.16–7.35 ppm which may be due to the protons of aromaticrings.

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426 A.K. Sharma, S. Chandra / Spectrochimica Acta Part A 81 (2011) 424– 430

Table 1Analytical data and physical characterization of complexes.

S. no. Complex Color �eff (B.M.) Molar conductance(�−1 cm2 mol−1)

Mp (◦C) Analytical data (%) calcd. (found)

M C H N

1 [Co(L)(NO3)2]CoC28H32N10O8 Brown 4.98 27 260 8.48 (8.44) 48.35 (48.39) 4.61 (4.57) 20.15 (20.11)2 [Co(L)Cl2] CoC28H32N8O2Cl2 Green 4.96 23 105* 9.18 (9.15) 52.34 (52.38) 4.99 (4.96) 17.45 (17.41)3 [Ni(L)(NO3)2] NiC28H32N10O8 Light green 2.96 24 220 8.45 (8.41) 48.37 (48.33) 4.61 (4.57) 20.15 (20.11)4 [Ni(L)Cl2] NiC28H32N8O2Cl2 Light green 2.97 16 215 9.15 (9.11) 52.36 (52.40) 4.99 (4.96) 17.45 (17.41)5 [Cu(L)(NO3)2]CuC28H32N10O8 Light green 1.89 19 272 9.08 (9.05) 48.03 (47.99) 4.57 (4.53) 20.01 (19.97)6 [Cu(L)Cl2] CuC28H32N8O2Cl2 Green 1.83 11 256 9.82 (9.79) 51.97 (51.93) 4.95 (4.92) 17.32 (17.28)

* Decomposition temperature.

Table 2Comparative IR data of compounds.

Compound �(C N) �(C O) �(M O) �(M N) Anion bands

Ligand 1606 1667 – – –[Co(L)(NO3)2] 1551 1594 397 566 1440, 1315, 1059[Co(L)Cl2] 1572 1600 448 505 346[Ni(L)(NO3)2] 1601 1616 452 566 1458, 1328, 1036[Ni(L)Cl2] 1601 1630 454 506 327[Cu(L)(NO3)2] 1550 1628 505 572 1406, 1316, 1060[Cu(L)Cl2] 1491 1611 450 505 338

spect

I

b

Fig. 2. 1H NMR

V. A singlet corresponding to the two protons of two H C Ngroups is appeared at ca. ı 7.97 ppm.

The 13C NMR spectrum of ligand displays the signals as discussedelow:

I. The signals at ca. ı 10.68 and 35.58 ppm are due to carbon atomsof methyl groups attached to the pyrazolone rings (H3C C andH3C N).

II. The four C-atoms of piperazine ring give the signals at ca. ı127.13, 128.90, 129.35, 129.61 ppm and the signals at ca. ı129.66, 130.34, 130.47, 131.90, 134.59, 135.30 ppm are due tosix C-atoms of aromatic rings.

rum of ligand.

III. The two kinds of C-atoms of the pyrazolone rings (Me C andN C) give signals at ca. ı 137.62 and 138.04 ppm.

IV. The signals at ca. ı 150.08 and 196.62 ppm are due to C-atomsof C N groups and C O groups respectively [23].

4.1.3. Mass spectraThe ESI mass spectrum of ligand (Fig. 3) displays the prominent

molecular ion peak (M+) at m/z = 512 and weak isotopic peak atm/z = 513 (M+ + 1). The base peak is appeared at m/z = 187 due toC11H11N2O+ ion with pyrazolone moiety. The other fragments give

the peaks at 15, 26, 112, 138, 325, 358, 435, 482 and 497 amu withvarious intensities [24,25].

The mass spectrum of [Co(L)(NO3)2] complex shows the molec-ular ion peak at m/z = 695 due to (CoC28H32N10O8)+ and isotopic

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Fig. 3. Mass spectrum of ligand.

Fig. 4. Mass spectrum of [Cu(L)(NO3)2].

Table 3Electronic spectral data and ligand field parameters of complexes.

Complex �max (cm−1) Dq (cm−1) B (cm−1) ̌ LFSE (kJ mol−1)

[Co(L)(NO3)2] 10,319, 15,576, 18,960, 38,022 997.89 665.26 0.59 95.38[Co(L)Cl2] 9727, 18,621, 22,471, 37,174 1233.71 881.22 0.79 117.92[Ni(L)(NO3)2] 10,834, 18,621, 22,471, 41,322 1083.4 372.66 0.36 155.33[Ni(L)Cl2] 10,526, 13,812, 25,773, 36,496 1052.6 854.40 0.82 150.91[Cu(L)(NO3)2] 13,106, 18,691, 27,322, 37,174 – – – –[Cu(L)Cl2] 18,621, 26,246, 37,313 – – – –

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428 A.K. Sharma, S. Chandra / Spectrochimic

NN

CH3

CH3ON

N

CH3

CH3O

C

N

H N NC

N

H

M

X

X

FX

psaTtd

TE

ig. 5. Structure of [M(L)X2] complexes, where M = Co(II), Ni(II) and Cu(II), and = NO3

− and Cl− .

eak at m/z = 696. The base peak is observed at m/z = 201 corre-ponding to (C11H11N3O)+ ion. Other two more prominent peaks

t m/z = 86 and 77 are due to the piperazine and aromatic rings.he peak at m/z = 58 is due to Co+ metal ion. The spectrum showshe peaks at 110, 138, 311, 325, 370, 384, 432, 494, 571 and 633 amuue to different fragments.

able 4PR and orbital reduction parameters of Co(II) and Cu(II) complexes.

Complex g⊥ (RT/LNT) g‖ (RT/LNT) giso (RT/

[Co(L)(NO3)2] 1.9703 2.4081 2.12

[Co(L)Cl2] 1.9618 2.7408 2.22

[Cu(L)(NO3)2] 2.0576 2.3730 2.16

[Cu(L)Cl2] 2.0382 2.3221 2.13

Fig. 6. EPR spectrum of [Cu

a Acta Part A 81 (2011) 424– 430

The mass spectrum of [Ni(L)(NO3)2] complex shows the molec-ular ion peak at m/z = 695 due to (NiC28H32N10O8)+ and isotopicpeak is observed at m/z = 696. The spectrum display the base peakat m/z = 571 corresponding to (NiC28H32N8O2)+ ion. The peak at58 amu is due to Ni+ metal ion. The peaks at 77, 84, 111, 138, 187,221, 280, 307, 325, 369, 384, 431, 446, 508, 541, 618 and 633 amuare present in the spectrum corresponding to the structural unitsof the complex.

The ESI mass spectrum of [Cu(L)(NO3)2] complex shows themolecular ion peak at highest m/z = 700 due to (CuC28H32N10O8)+

ion (Fig. 4). Another peak at higher mass number 701 amu is the iso-topic peak due to 13C and 15N isotopes. The base peak is observedat m/z = 187 corresponding to (C11H11N2O)+ ion. The Cu+ metal iongives the peak at 63 amu. The spectrum shows the peaks at 77, 86,111, 138, 201, 325, 389, 451, 501, 516, 531, 546 and 623 amu dueto different fragments.

4.1.4. Electronic spectraThe electronic spectra of the complexes were recorded by using

DMSO as a solvent. The electronic spectral data of the complexes aregiven in Table 3. All the complexes show the high energy absorp-tion band in the region 36496–41322 cm−1. The transitions may beascribed to the charge transfer band.

LNT) G k⊥2 k‖2 k

– – – –– – – –6.71 0.91 1.04 0.978.09 0.63 0.93 0.85

(L)(NO3)2] complex.

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A.K. Sharma, S. Chandra / Spectrochimica Acta Part A 81 (2011) 424– 430 429

Table 5Fungicidal activity data of the compounds.

Compound Fungicidal activity (%) (conc. in �g mL−1)

A. brassicae A. niger F. oxysporum

200 300 500 200 300 500 200 300 500

Ligand 40 56 75 42 60 72 45 64 75[Co(L)(NO3)2] 58 68 84 55 70 81 58 70 80[Co(L)Cl2] 56 64 82 50 67 80 57 68 80[Ni(L)(NO3)2] 61 69 92 58 77 86 63 70 92[Ni(L)Cl2] 60 71 92 56 75 88 61 69 90

5

2

0

t1(ro

d2(rp

d22

sg

[Cu(L)(NO3)2] 62 76 96 6[Cu(L)Cl2] 60 74 95 6Standard (Captan) 80 100 100 9

The electronic spectra of cobalt(II) complexes display the d–dransition bands in the region 9727–10319, 15576–18621 and8960–22471 cm−1. These transitions may be assigned to the 4T1gF) → 4T2g (F) �1, 4T1g (F) → 4A2g (F) �2 and 4T1g (F) → 4T1g (P) �3,espectively. The transitions correspond to the tetragonal geometryf the complexes [26] (Fig. 5).

The absorption spectra of nickel(II) complexes display three–d transition bands in the range 10526–10834, 13812–18621 and2471–25773 cm−1. The transitions may be correspond to the 3A2gF) → 3T2g (F) �1, 3A2g (F) → 3T1g (F) �2 and 3A2g (F) → 3T1g (P) �3,espectively. These transitions reveal that the nickel complexesossess octahedral geometry [26] (Fig. 5).

Electronic spectra of copper(II) complexes exhibit the–d transition bands in the range 13106, 18621–18691 and

6246–27322 cm−1. These bands correspond to 2A1g → 2B1g �1,B2g → 2B1g �2 and 2Eg → 2B1g �3 transitions, respectively. Thepectra are typical of Cu(II) complexes with an elongated tetragonaleometry (Fig. 5) [26].

Fig. 7. Fungicidal activity against A. brassicae of: (A) Ligand, (

83 92 70 85 9680 93 69 84 95

100 100 75 100 100

The ligand field parameters like Racah inter-electronic repul-sion parameter B, ligand field splitting stabilization energy 10 Dq,covalancy factor ̌ and ligand field stabilization energy (LFSE) havebeen calculated for the Co(II) and Ni(II) complexes and the data issummarized in Table 3.

4.1.5. EPR spectraThe X-band EPR spectra of Co(II) complexes were recorded at liq-

uid nitrogen temperature in polycrystalline form. The line shapedEPR spectra of Co(II) complexes with giso = 2.12–2.22 (Table 4) cor-respond to the tetragonal symmetry around the Co(II) ion [27,28].As a consequence of the fast spin-relaxation time of high-spin Co(II)ion, the signals are observed only at low temperature.

The X-band EPR spectra of copper(II) complexes were recorded

at room temperature in polycrystalline form. The spectra showonly one broad or bell shaped signal at giso = 2.13–2.16 (Fig. 6). Thespectral studies reveal that the Cu(II) ion in the complexes is in atetragonal field. The calculated values of g‖ and g⊥ for the com-

B) [Co(L)(NO3)2], (C) [Ni(L)(NO3)2], and (D) [Cu(L)Cl2].

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430 A.K. Sharma, S. Chandra / Spectrochimic

Fp

pw

eGici

4

ihiiictrlataat

mgcrfo

5

dwCmsctgcrl

[

[[[[[

[[

[[

[

[[

[

[

[

[

[

[[[

[

[[33] S. Chandra, A.K. Sharma, J. Coord. Chem. 62 (2009) 3688–3700.

ig. 8. Graph showing effect of concentration on antipathogenic behavior of com-ounds against A. brassicae.

lexes having the order as g‖ > g⊥ > 2.0023 (Table 4), are consistentith the dx2−y2 ground state [29–31].

The geometric parameter G and orbital reduction factor k werevaluated for the copper(II) complexes. The complexes show the

values greater than 4 (Table 4), which suggest the negligiblenteraction between metal centers. The low values of k (0.85–0.97)orrespond for the partial covalent nature of metal–ligand bondingn the complexes (Table 4) [32,33].

.2. Pharmacology

The data of the fungicidal activity of compounds are summarizedn Table 5. The studies reveal that the coordination compoundsave the moderate antipathogenic activities (Fig. 7). This mod-

fied antipathogenic behavior of compounds after complexations based on the fact that the polarity of the central metal ions reduced on complexation by the partial sharing of its positiveharge with donor groups of ligand (Overtone’s Concept and Chela-ion Theory) [34–36]. The charge is delocalized over the wholeing. Consequently, the compounds as complexes become moreipophilic through the lipid layer of cell membrane of organismnd they get enter easily to the cell of microorganism. Finally,he compound prevents the metabolic functions of the cell andcts as antipathogen. The experimental findings reveal that thentipathogenic capacity of the compounds increases with concen-ration (Fig. 8).

Further, the genetic material of the cell of microorganism is theain target of any drug and interaction of drug molecules with

enetic material is the basic function for its therapeutic action. Theomplexes interact with DNA of microorganisms and prevent itseplication more effectively. The main features of these complexesor this ability are their affinity for genetic material and the bindingf redox metal ion cofactor [36].

. Conclusions

Continuing the synthetic strategies, a 4-aminoantipyrineerivative has been prepared by its acid catalyzed condensationith 1,4-diformylpypartzine. The interaction of this derivative witho(II), Ni(II) and Cu(II) metal ions forms the stable complexes. Theass, IR, UV and EPR spectroscopic studies lead to the conclu-

ion that the nickel complexes have octahedral geometry, whereasobalt and copper complexes are of tetragonal geometry withhe tetradentate ligand coordinated through azomethine nitro-

en and ketonic oxygen atoms (ONNO fashion). The low value ofovalency factor ̌ for nickel and cobalt complexes and orbitaleduction factor k for copper complexes reveals the partial cova-ent interaction between ligand donor atoms and metal ions. The

[[[

a Acta Part A 81 (2011) 424– 430

mass spectra support the proposed stoichiometry of complexes byelemental analyses. It is evident from the mycological studies ofthe compounds against the opportunistic pathogens that the com-pounds show the effective fungicidal behavior. The administrationof the compound as the metal ion derivative exhibits the moder-ate antipathogenic behavior. This accounts that the efficacy of theorganic compound is positively modified on association with metalion.

Acknowledgement

The financial assistance of DRDO, New Delhi is greatly acknowl-edged.

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