научная статья по теме SYNTHESIS, CHARACTERIZATION, ANTIMICROBIAL AND ANTHELMENTIC ACTIVITIES OF SOME METAL COMPLEXES WITH A NEW SCHIFF BASE 3-[(Z)-5-AMINO-1,3,3-TRIMETHYL CYCLOHEXYLMETHYLIMINO]-1,3-DIHYDROINDOL-2-ONE Химия

ЖУРНАЛ НЕОРГАНИЧЕСКОЙ ХИМИИ, 2008, том 53, № 6, с. 979-984

КООРДИНАЦИОННЫЕ ^^^^^^^^^^^^ СОЕДИНЕНИЯ

УДК 541.49

SYNTHESIS, CHARACTERIZATION, ANTIMICROBIAL AND ANTHELMENTIC ACTIVITIES OF SOME METAL COMPLEXES WITH A NEW SCHIFF BASE 3-[(Z)-5-AMINO-l,3,3-TRIMETHYL CYCLOHEXYLMETHYLIMINO]-l,3-DIHYDROINDOL-2-ONE

© 2008 K. Rama Krishna Reddy, K. N. Mahendra*

Department of Chemistry, Central College Campus, Bangalore University, Bangalore-560001

Поступила в редакцию 07.06.2007 г.

The complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), dioxouranium(VI) and Th(IV) with a new Schiff base, 3-[(Z)-5-amino-1,3,3-trimethyl cyclohexylmethylimino]-1,3-dihydroindol-2-one formed by the condensation of isatin (Indole-2,3-dione) with isophoronediamine(5-amino-1,3,3-trimethyl-cyclohexane methylamine) (IPDA) was synthesized and characterized by microanalysis, conductivity, UV-visible, FT-IR, 1H NMR,tGa and magnetic susceptibility measurements. AH the complexes exhibit 1 : 1 metal to ligand ratio except for dioxouranium(VI) and tho-rium(IV) complexes where metal : ligand stoichiometry is 1 : 2.The spectral data revealed that the ligand acts as monobasic bidentate, coordinating to the metal ion through the azomethine nitrogen and carbonyl oxygen of the isatin moiety. Tetrahedral geometry for Co(II), Ni(II), Zn(II), Cd(II) and Hg(II) complexes, square planar geometry for Cu(II)complexes, coordination number 6 and 8 for UO2(VI) and Th(IV) complexes respectively are proposed. Both the ligand and the metal complexes were screened for their antibacterial activity against Bacillus subtilis, Staphylo-coccus aureus (S. aureus), Escherichia Coli (E.Coli) and Pseudomonas aeruginosa and the complexes are more potent bactericides than the ligand. The anthelmentic activity of the ligand and its complexes against earthworms was also investigated.

Key words: Isatin, Schiff base, complexes and isophoronediamine.

INTRODUCTION

Isatin thiosemicarbazone derivatives exhibit interesting applications as research tools in physiological studies [1]. Many isatin-derived compounds possess a wide spectrum of medicinal properties and thus, have been studied for activity against tuberculosis [2, 3], leprosy [4], fungal [5, 6], viral [7] and bacterial infections [8, 9] etc. A survey of literature reveals that the biological activity of the Schiff base was enhanced by complexation [10]. In continuation of our work to synthesize novel isatin Schiff bases [11, 12], in this paper we report the synthesis and characterization of a novel Schiff base and the complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), dioxouranium(VI) and Th(IV).The ligand and its metal complexes were screened for antibacterial activity against Bacillus subtilis, Staphylococcus aureus (S. aureus), Escherichia Coli (E. Coli) and Pseudomonas aeruginosa. Anthelmentic activity of the compounds was tested on earthworms (Peretima posthuma).

EXPERIMENTAL

The chemicals employed for the preparation of Schiff bases were of AR or LR grade. All the solvents were pu-

* Corresponding author. Te.: + 91 80 22961341; Fax: +91 80 22961331; e-mail address: Mahendra_kadidal@yahoo.co.in (Dr. K.N. Mahendra).

rified by standard methods. Isophoronediamine (IPDA) (Aldrich Chemicals) and isatin (S.D Fine chemicals) were used.

Preparation of Schiff base

The Schiff base was prepared by the reported method [12]. Equimolar ethanolic solution (50 ml each) of isatin and isophoronediamine were mixed and refluxed for about 1 h. The reaction mixture was concentrated to a small volume and allowed to cool. The Schiff base precipitated out as faint pink solid. It was filtered, washed with ethanol and recrystallised from ethanol. The purity of the Schiff base ligand was monitored by TLC using 1 : 1 ethyl acetate and petroleum ether as eluant and separated by column chromatography, m.p: 117°C (Yield 90%).

Preparation of the complexes

The metal complexes were prepared by adding ethanol-ic solution (50 ml) of the metal salt to the ligand (100 ml) in 1 : 2 molar ratio and heating under reflux for about 3 h. The reaction mixture was concentrated to a small volume. On cooling, the metal complexes crystallises out. They were filtered, washed with ethanol and dried in vacuo.

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Table 1. Analytical and physical data of the complexes

Compound Yield % Colour (%) Found (Calcd.) Mol. cond. S cm2 mol 1 M'eff BM

C H N M

HIsIPD (L) 90 Pale pink 71.95 8.33 13.98 - - -

(72.14) (8.35) (14.03)

[CuL ■ 2H2O]Cl 85 Light green 49.34 6.57 9.52 14.70 95 1.87

(49.71) (6.67) (9.66) (14.72)

[CoLCl ■ H2O] 85 Brown 52.55 6.51 10.11 14.35 12 4.54

(52.49) (6.56) (10.20) (14.33)

[NiLCl ■ H2O] 80 Brown 52.48 6.62 1 0.45 14.20 24 3.70

(52.53) (6.56) (10.41) (14.27)

[ZnLCl ■ H2O] 74 Brown 52.01 6.21 10.10 15.62 14 -

(51.81) (6.24) (10.07) (15.68)

[CdLCl ■ H2O] 78 Reddish 46.50 5.61 8.98 24.31 07 -

(46.55) (5.60) (9.05) (24.23)

[HgLCl ■ H2O] 80 Light white 39.68 4.55 7.54 36.38 12 -

(39.13) (4.71) (7.61) (36.33)

[UO2L2] ■ H2O 90 Yellow 48.80 5.92 9.44 26.84 16 -

(48.75) (5.87) (9.48) (26.86)

[ThL2(NO3) ■ 2H2O] NO3 92 Chilly Red 43.45 5.63 11.58 23.63 96 -

(43.70) (5.50) (11.44) (23.41)

Antibacterial and anthelmentic activity measurements

The ligand and its complexes with Cu(II), Co(II), Ni(II), Zn(II), Cd(II) and Hg(II) were screened for antibacterial activity against Bacillus subtilis, Staphylococcus aureus (S. aureus), Escherichia Coli (E. coli) and Pseudomonas aeruginosa at a concentration of 1mg/0.02ml in DMF by cup plate method [13]. Anthelmentic activity of the compounds was measured on earthworms (Peretima posthuma) by the reported method [14].

Analysis and physical measurements

The micro analysis of the samples was carried using Carlo Ebra analyser. The metals were estimated by the standard methods [15].The conductivity measurements were made on Systronics Conductivity Meter 304 with a dip type conductivity cell with a cell constant of 1 unit. The magnetic susceptibility measurements were carried out at room temperature using Faraday balance.Electronic spectra were recorded in DMF in the range 900-350 nm using Shimadzu UV-3101 PC UV-VIS-NIR scanning spectrophotometer. 1H NMR spectra of the ligand and its complexes were obtained using Bruker AMX 400MHz FT NMR spectrometer. IR spectra of samples in KBr pellets were recorded in the region 4000-600 cm-1 on a Nico-let Impact 400-D FT-IR spectrometer. The far IR spectra of the complexes in the region 600-250 cm-1 were recorded using a Perkin Elmer Instruments, Spectrum one FT-IR

spectrometer. The mass Spectrum of the ligand was recorded using a ESI-MS Bruker Daltronics mass spectrometer. TGA studies of the complexes were carried out using Perkin-Elmer Thermogravimetric analyser TGA 7 with a scan rate of 10°C per minute in nitrogen atmosphere.

RESULTS AND DISCUSSION

All the metal complexes are either coloured or colourless solids and are stable towards air and have high melting points (above 300°C). Analytical data of the complexes suggest that the metal to ligand composition is 1 : 1 for Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) complexes and 1 : 2 for UO2(VI) and Th(IV) complexes. The complexes have the general formula [MLCl ■ H2O] where M = Co(II), Ni(II), Zn(II), Cd(II) and Hg(II) while the Cu(II) salt, yields complex of the type[CuL ■

■ 2H2O]Cl and with UO2 (VI) and Th(IV) salts the complexes of the type [UO2L2] ■ H2O and [ThL2(NO3) ■

■ 2H2O] NO3 respectively were obtained. The complexes are insoluble in water and common organic solvents but have partial solubility in DMF and DMSO. Hence molecular weights could not be determined.

Conductivity measurements

The conductivity for 10-3 M solutions of the complexes (Table 1) in DMF show Cu(II) and Th(IV) complexes to be 1 : 1 electrolytes and the other complexes show non electrolytic behaviour.

SYNTHESIS, CHARACTERIZATION, ANTIMICROBIAL AND ANTHELMENTIC Table 2. *H NMR Chemical Shifts (S ppm) for the Schiff base and its complexes

Ligand/Complex Isatin ring Side Chain

N-H Aromatic protons NH2 Aliphatic protons

HIsIPD (L) 10.5 (1H, s) 7.5-6.8 (4H, m) 2.4 (2H, m) 1.5-0.65 (18H, m)

(C18H24N3O)

[ZnLCl ■ H2O] - 7.85-6.9 (4H, m) 2.4 (2H, m) 1.5-0.65 (18H, m)

[CdLCl ■ H2O] - 7.6-6.8 (4H, m) 2.38 (2H, m) 1.5-0.65 (18H, m)

[HgLCl ■ H2O] - 7.85-6.9 (4H, m) 2.38 (2H, m) 1.5-0.65 (18H, m)

[UO2L2] ■ H2O - 7.85-6.9 (4H, m) 2.4 (2H, m) 1.5-0.65 (18H, m)

[ThL2(NO3) ■ 2H2O ]NO3 - 7.85-6.9 (4H, m) 2.42 (2H, m) 1.5-0.65 (18H, m)

t - triplet, m - multiplet, s - singlet, br - broad.

IR spectra

The IR spectrum of the free ligand is characterized mainly by strong bands at 3220, 1717 and 1618 cm1 which are attributed to the stretching frequencies of NH, C=O and C=N [16] respectively. On complexation with the metal ion, the bands due to C=O and NH disappears with simultaneous appearance of band at 1310-1280 cm-1 which may be assigned to C-O, suggesting deprotonation of the NH group via the carbonyl oxygen atom of the isatin moiety through its lactam-lactim tautomerisum [16]. The band at 1618 cm-1 due to C=N group stretching vibration in the spectrum of the free Schiff- base ligand shifts, with splitting to lower wave numbers in all the metal complexes (1615-1590 cm-1) indicating that the azomethine nitrogen atom is coordinated to the central metal ion [16]. The bands observed in the region 3200-3150 cm-1 attributed to and symmetric modes of the NH2 group remain at nearly the same position in the spectra of the complexes indicating the nonparticipation of this group in coordination. Further these chelate spectra exhibit new bands at 520cm-1, 420-410 cm-1 and 332 cm-1, which may be assigned to M-O, M-N and M-Cl stretching modes respectively in all the complexes [10]. The IR spectra of UO2(VI) complex showed no absorption bands either due to free or coordinated nitrate groups. On the other hand the spectra of Th(IV) complex showed an absorption band

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