ORIGINAL RESEARCH PAPER SYNTHESIS AND CHARACTERIZATION OF SCHIFF BASE METAL COMPLEXES DERIVED FROM NAPHTHO [2,1-B] FURAN-2-CARBOHYDRAZIDE AND INDOLINE- 2,3-DIONE (ISATIN) Sadu Suryakant S Department of Chemistry, VSK University, Ballari, Karnataka (India) 583 105 INTRODUCTION Benzofuran derivatives are found everywhere in nature, they mainly occur in Plantae having sort of industrial, agricultural, pharmaceutical, and biological importance.[1]–[4]. Numerous studies have shown that on complexation with metal ions these Schiff base derivatives show enhanced pharmacological properties. [5] Several studies show that on complexation with metals, Benzofuran derivatives show enhanced biological and catalytic activity. It was also reported that halide substitution on the aromatic ring greatly increased the antibacterial activity. The antimicrobial property of the compound either kills the microbe or prevent their multiplication by blocking active sites[6], [7] Isatin (1H-indol-2,3-dione) analogs have a variety of biological activity, for example, antimicrobial, anticonvulsant, analgesic, anti- inammatory, anticancer, antitubercular, antiviral, and anti-HIV, because of the presence of the indole backbone[8]. Given the extensive use of Schiff bases derived from isatin and its metal complexes in the area of coordination chemistry, we thought it’s worthwhile to prepare the napthofuran Schiff base and its metal complexes. The current article describes the synthesis of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) complexes with Schiff base derived from the condensation of naphtho[2,1-b]furan-2-carbohydrazide and indoline- 2,3-dione (Isatin) (Figure 1). EXPERIMENTAL: All the chemicals used are of AR grade with the highest purity available. Benzofuran-2-carboxamide was synthesized according to the literature procedure[9]. The metal and the chloride content were determined according to the Vogel’s procedure[10]. PROCEDURE FOR THE SYNTHESIS OF SCHIFF BASE 3-(2- HYDROXY BENZYLID ENEAMINO)-5-BROMO BENZOFURAN-2-CARBOXAMIDE [L]. A mixture of naphtho[2,1-b]furan-2-carbohydrazide (0.1 mol) and indoline-2,3-dione (Isatin) (0.1 mol) in ethanol (30 mL) are reuxed on a water bath for about 8h in presence of few drops of glacial acetic acid with occasional shaking. The product which was separated as crystalline solids on cooling was collected and recrystallized from ethanol. C H N O [L]: Molecular Weight = 355.10, mp = 228°C, 21 13 3 3 Yield= 69%. Figure 1: Synthesis of Ligand (L) GENERAL PROCEDURE FOR PREPARATION OF METAL COMPLEXES OF Co(II), Ni(II), Cu(II), Zn(II), Cd(II), AND Hg(II) WITH THE SCHIFF BASE (L). Metal chloride (0.01 mol) was mixed with Schiff base (0.01 mol) in an ethanolic medium 30 mL and the reaction mixture was reuxed for about 3hon water bath, then an aqueous solution of sodium acetate was added to the mixture to adjust the pH between 5 to 6 and further reuxed for about an hour. The complexes separated were ltered off and washed with distilled water, then with alcohol, and nally dried in vacuum over fused calcium chloride. PHYSICAL MEASUREMENTS: The IR spectra of a Schiff base and its metal complexes were recorded in KBr pellets. Molar conductivity measurement was recorded on an -3 Elico CM-180 conductivity bridge in DMF (10 M) solution using a dip-type conductivity cell tted with a platinum electrode and the magnetic susceptibility measurement was made at room temperature on Gouy balance using Hg[Co(NCS)4] as the calibrant. RESULTS AND DISCUSSION: The physical appearance and analytical results show that complexes are of the type ML Cl where M=Co/Ni/Cu) and MLCl (Where 2 2 M=Zn/Cd/Hg). The low molar conductance values (10.08 to 17.75 2 -1 ohm-1 cm mol ) indicate the non-electrolytic nature of the complexes. All the complexes are light-colored, stable, and non-hygroscopic in nature having high melting points (>300 °C). Table 1: IR Data of Ligand and its metal complexes IR STUDIES: The Infrared spectra of the ligand [L] and its metal complexes have been depicted in and I.R. assignments are listed in the -1 above Table. The band observed in the ligand at 3234 cm is attributed to ν(-NH) stretching frequency. This band unaltered in all the complexes indicating non-involvement of the nitrogen of (-NH-) in -1 bonding with metal ion[11]. The strong band observed at 1670 cm is assigned to ν(C=O) stretch of amide group undergo negative shift by -1 15 – 30 cm in the complexes indicating the involvement of the carbonyl group in coordination[12]. The Schiff base shows a strong to -1 medium intensity band at 1622 cm due to ν(C=N) stretching vibrations, this band undergoes negative shifts in the spectra of the complexes showing the involvement of the azomethine group in the -1 coordination with the metal ions[13], [14]. The band at 1192 cm is assigned to ν(C-O-C) stretch of the furan ring in the free ligand. This band is unchanged on complexation indicating non-involvement of the furan ring oxygen in the bonding–[15]. In the far IR spectra of the -1 -1, complexes, the bands in the region 554 -550 cm , 457 - 420 cm and -1 350-390 cm assigned to M-O, M-N, and MCl stretching vibrations in all the complexes[16]. All the above value indicates that the ligand acts INTERNATIONAL JOURNAL OF SCIENTIFIC RESEARCH Chemistry International Journal of Scientific Research 1 Volume - 9 | Issue - 11 | November - 2020 | PRINT ISSN No. 2277 - 8179 | DOI : 10.36106/ijsr ABSTRACT New Schiff base metal complexes having general structural formulae ML2Cl2 where M= Co(II), Ni(II) and Cu(II), and MLCl2 where M=Zn(II), Cd(II) and Hg(II) were synthesized by the condensation of indoline-2,3-dione (Isatin) and naphtho[2,1-b]furan-2-carbohydrazide. Tentative structures for the synthesized compounds have been elucidated based on analytical, IR, 1HNMR, and Mass spectral studies. Further selected compounds were tested for their antimicrobial activity. KEYWORDS Schiff base, Ligand, Complexes, Spectroscopy. Ligand/ Complex ν(C=O) ν(C=N) ν(M-O) ν(M-N) ν(M- Cl) [L] 1670 1622 ---- ---- ---- Co(II) 1655 1686 553 457 390 Ni(II) 1658 1590 551 451 361 Co(II) 1661 1590 550 455 350 Zi(II) 1623 1590 551 420 372 Cd(II) 1656 1592 554 449 365 Hg(II) 1654 1589 551 456 355 O O HN N NH O (Z)-N'-(2-oxoindolin-3-ylidene)naphtho[2,1-b]furan-2-carbohydrazide O O NH O NH O naphtho[2,1-b]f uran-2-carbohydrazide indoline-2,3-dione NH2 +