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  The Malaysian Journal of Analytical Sciences, Vol 16 No 3 (2012): 318 - 324 318 SYNTHESIS, CHARACTERIZATION AND CONDUCTIVITY STUDIES OF SCHIFF BASE LIGAND DERIVED FROM ISATIN AND O -PHENYLENEDIAMINE WITH ITS COBALT(II) METAL COMPLEX AND LITHIUM-SCHIFF BASE COMPOUND  (Sintesis, Pencirian dan Kajian Kekonduksian Terhadap Ligan Bes Schiff yang Terhasil Daripada Isatin dan O -Phenylenediamina dengan Kobalt(II) Kompleks Logam Peralihan serta Litium-Bes Schiffnya) Muneera Fatin Manan 1 , Karimah Kassim 2 , Mohd Abdul Fatah Abdul Manan 1 1  Faculty of Applied Sciences, 2  Institute of Science, Universiti Teknologi MARA (UiTM), Shah Alam, 40450 Selangor, Malaysia *Corresponding author: muneeramanan@gmail.com Abstract In this study, a Schiff base ligand, (E)- 3-(2-aminophenylimino)indolin-2-one (APIISA) was synthesized via  condensation reaction of o-  phenylenediamine with isatin. Metal complex and Lithium-Schiff base of this ligand were prepared. Metal complex  bis[ (E)- 3-(2-aminophenylimino)indolin-2-one]Co(II), [Co(APIISA) 2 ] was synthesized from Schiff base ligand with Cobalt acetate tetrahydrate in 2:1 ratio. While Lithium-Schiff base was prepared by using Lithium acetate dihydrate produced Lithium[ (E)- 3-(2-aminophenylimino)indolin-2-one], [Li(APIISA)]. All the synthesized compounds were characterized by variety of physicochemical techniques such as melting point, elemental analysis, infrared spectroscopy, 1 H nuclear magnetic spectroscopy, magnetic susceptibility and X-ray diffraction. Conductivity studies of the ligand, metal complex and Lithuim-Schiff base were investigated by impedance analyzer which the samples were prepared in the form of pellets. The electrical conductivities of the prepared compounds were measured by applying alternating current (ac) voltage. The conductivity values were calculated and Lithium-Schiff base showed higher conductivity value followed by Cobalt metal complex and Schiff base ligand. Keywords : Isatin, Schiff base, Cobalt(II) metal complex, Lithium-Schiff base, Conductivity studies Abstrak Dalam kajian ini, ligan bes Schiff, (E) -3-(2-aminophenylimino)indolin-2-one (APIISA) telah disintesis melalui tindak balas kondensasi o -phenylenediamina dengan isatin. Kompleks logam dan Litium-ligan bes Schiff ini telah disediakan. Metal kompleks bis [ (E) -3-(2-aminophenylimino)indolin-2-one]Kobalt(II), [Co(APIISA) 2 ] telah disintesis daripada ligan bes Schiff dengan Kobalt tetrahidrat asetat dalam nisbah 2:1. Manakala Lithium-bes Schiff telah disediakan dengan menggunakan Litium asetat dihidrat menghasilkan Litium-[ (E) -3-(2-aminophenylimino)indolin-2-one] [Li(APIISA)]. Semua sebatian yang disintesis telah dicirikan oleh pelbagai teknik kimia-fizikal seperti menentu takat lebur, analisis unsur, spektroskopi inframerah, 1 H spektroskopi resonan magnet nuklear, kerentanan magnet dan pembelauan sinar-X. Kajian kekonduksian ligan, kompleks logam dan Lithuim-bes Schiff dianalisis dengan analisis impedans dimana sampel telah disediakan dalam bentuk pelet. Kekonduksian elektrik sebatian yang telah disediakan diukur dengan menggunakan arus ulang-alik (ac). Nilai konduktiviti dikira dan Lithium- bes Schiff menunjukkan nilai kekonduksian tertinggi diikuti oleh kompleks logam Kobalt dan ligan bes Schiff. Kata kunci : Isatin, Bes Schiff, Kobalt(II) logam peralihan, Litium-Bes Schiff, Kajian kekonduksian Introduction Schiff base ligand is a compound that contains a carbon-nitrogen double bond, with the nitrogen atom connected to an aryl or alkyl group. The general formula of Schiff base is R-CH=N- R’ where R and R’ is an alkyl or aryl group  Muneera Fatin et al: SYNTHESIS, CHARACTERIZATION AND CONDUCTIVITY STUDIES OF SCHIFF BASE LIGAND DERIVED FROM ISATIN AND O -PHENYLENEDIAMINE WITH ITS COBALT(II) METAL COMPLEX AND LITHIUM-SCHIFF BASE COMPOUND 319 that makes the Schiff base a stable amine [1]. It can be synthesized by condensation of aliphatic or aromatic  primary amine with carbonyl compound [2]. Schiff base ligands and transition metal ions are the two parents and necessary components for designing stable complexes and play an important role in the development of coordination chemistry [1,3]. In 1967, Schrauzer and Windgassen found that inorganic metal complexes might exhibit conducting properties. Until now, there are very rare reports on Schiff base complexes that have such  properties [3]. For this reason, the major aims for this report are to synthesis, characterization of Schiff base ligand derived from isatin and o -phenylenediamine with cobalt(II) metal complex. To extend the investigation, Schiff base ligand has been reacted with lithium salt to produce Lithium-Schiff base compound. These three compounds were analyzed on their conductivity value by using electrochemical impedance spectroscopy method (EIS). Materials and Methods General considerations Isatin, o -phenylenediamine, cobalt(II) acetate tetrahydrate, lithium acetate dihydrate and all other reagents were used without further purification. Physical measurement Elemental analyses were performed using CHNS Analyzer Flash EA 1112 series, IR spectra were recorded on KBr discs using FTIR Perkin Elmer 100 Spectrometer. 1 H NMR spectrum was recorded on Bruker instrument using DMSO-d 6  as solvent. Magnetic susceptibility at room temperature was performed using Sherwood Magnetic Susceptibility Balance (Auto), calibrated with mercury tetrakis(isothiocyanato) cobaltate(II). X-Ray Diffraction were using Shimadzu XRD-600 diffractometer with nickel-filtered copper- Kα radiation (λ=1.54Å) at 40 kV and 200 mA. Electrochemical impedance spectroscopy measurement was done by using WEIS510 Multichannel EIS System. Synthesis of Schiff base ligand Solution of isatin (5mmol) in absolute ethanol was added to equimolar solution of o -phenylenediamine in of the same solvent. The mixture was refluxed for 3 hours. Precipitate of Schiff base was filtered, washed with cold ethanol and dried in vacuo over silica gel. The yellow product form was (E)- 3-(2-aminophenylimino)indoline-2-one [4]. Synthesis of Schiff base metal complex and Lithium-Schiff base Cobalt(II) acetate tetrahydrate (5mmol) was dissolved in ethanol. The solution was treated with solution containing Schiff base (10mmol) in ethanol. The mixture was refluxed for 6 hours. The product was filtered, washed with cold ethanol and dried in vacuo over silica gel. Synthesis of Lithium-Schiff base The mixture of o -phenylenediamine (10mmol) and lithium acetate dihydrate (5mmol) in absolute ethanol was refluxed for 1 hour. After cooled the resulting solution at room temperature, a solution of isatin (10mmol) in absolute ethanol was added slowly. The mixture was stirred until 10cm 3  of the solution   reduced. The product was filtered and dried in vacuo over silica gel [5]. Results and Discussion Physico-Chemical Data Analysis of the Schiff Base, Its Metal Complexes and Lithium-Schiff base The physical characteristics of the Schiff base ligand, its metal complex and Lithium-Schiff base compound are shown in Table 1. Quantitative elemental analysis of carbon, hydrogen and nitrogen were carried out in order to determine the elemental content of the synthesized compounds. The results were found to be in acceptable range compared with calculated values.  The Malaysian Journal of Analytical Sciences, Vol 16 No 3 (2012): 318 - 324 320 Table   1. Analytical Data and Physical Properties of Schiff Base, Metal Complex and Lithium Schiff base 1 H Nuclear Magnetic Resonance (NMR) Spectroscopy Analysis of the Schiff Base 1 H nuclear magnetic resonance spectroscopy spectrum of the synthesized Schiff base was examined in order to elucidate each distinct type of hydrogen nuclei. The solvent used for the Schiff base was acetone-d 6 . The important chemical shifts of the 1 H spectrum of the Schiff base is shown in Figure 1. The spectrum data is tabulated in Table 2. The 1 H spectrum shows single peak at 3.66 ppm which ascribed as NH 2 . Meanwhile signals between 7.24 - 8.28  ppm may be attributed to aromatic-H and isatin ring. NH    peak of isatin appear at 10.84 ppm [6]. Table 2. 1 H NMR spectrum data for APIISA Figure 1. 1 H NMR analysis for (E) -3-(2-aminophenylimino)indoline-2-one Compound Abbs Colour Melting  point ( o C) Experimental Value (Calculated Value) % C H N (E) -3-(2-aminophenylimino)indoline-2-one APIISA Yellow 244.8 71.27 (70.87) 4.35 (4.67) 17.99 (17.71) bis [ (E) -3-(2-aminophenylimino)indoline-2-one] Cobalt(II)) Co (APIISA) 2  Brown 287.7 64.88 (63.28) 4.38 (3.79) 15.92 (15.81) Lithium- (E) -3-(2-aminophenylimino)indoline-2-one LI-APIISA Dark  brown 257.0 71.69 (69.85) 4.52 (4.61) 18.36 (17.46) 1 H NMR Assignment Chemical shift, δ (ppm)   NH 2 ; H11 3.66 (singlet, 2H)  NH; H1 10.84 (singlet, 1H) Aromatic-H and pyrrole (isatin ring)-H H2, H3, H4, H5, H7, H8, H9, H10 7.24  –   8.28 (multiplet, 8H)   NHONNH 2 1 2 3 4 5 7 8 9 10 11  Muneera Fatin et al: SYNTHESIS, CHARACTERIZATION AND CONDUCTIVITY STUDIES OF SCHIFF BASE LIGAND DERIVED FROM ISATIN AND O -PHENYLENEDIAMINE WITH ITS COBALT(II) METAL COMPLEX AND LITHIUM-SCHIFF BASE COMPOUND 321 Fourier-Transform Infrared Data for the Schiff Base and Its Metal Complexes Infrared spectroanalysis was carried out in order to determine the functional group of the synthesized compounds. The IR spectra for the Schiff base ligand and its metal complex are shown in Table 3. Three key functional groups which are the ν(C=N), ν(N - H) and ν(C=O) bands were selected to provide a comparative analysis, as these bands shift either to higher or lower wavenumbers upon complexation with the metal ions. Table 3. Infrared data of the Schiff base and metal complexes The lowering ν(C=N) on complexation may be attributed to a lowering bond order as a result of coordination of ligand to metal ion via azomethine nitrogen. Furthermore, this can be confirmed by the presence of new band 521 cm -1 which assignable to ν(M -N) band [1,6-8]. Other than that, the strong ν(N -H) band was shifted toward lower wavelength compared with ligand indicating coordination of the ligand is not only at azomethine nitrogen, but also at imino nitrogen as well. Meanwhile, the ν(C=O) band display not much difference wave numbers between ligand and com  plex clearly showing no participation of carbonyl oxygen in the coordination to the metal ion [9]. The proposed structure of metal complex is shown in Figure 2. For Lithium-Schiff base, the similarities in values of the three main functional groups prove that there is no bonding  between Lithium salt with Schiff base ligand. Figure 2. Structure of metal complex Magnetic Susceptibility Analyses of the Metal Complexes The molar magnetic susceptibility χ  m  which characterizes the extent of paramagnetism of the metal complexes were measured in order to determine the spin properties of the complexes. The complex can either appear in the high spin Compound Bands (Wavelength, cm -1 )  ν(C=O)    ν(C=N)    ν(N -H)  ν(M -N)  ν(M -O) (API)ISA 1665 1617 3391 - - [(API)ISA] 2 Co 1663 1570 3381 521 - Li-(API)ISA 1663 1615 3390 - - NHONHNHNONNHCo

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