ISSN 2321-807X Volume 13 Number 1 Journal of Advances in chemistry 5948 | Page www.cirworld.com Synthesis, Spectral Characterization and Antibacterial Investigation of Ni(II) Coordination Complexes of Macrocyclic Schiff base ligands Derived from 4-Aminoantipyrine Srinath Boinapalli,A. Anil Kumar , Ch. Abraham Lincoln* Department of Chemistry, Osmania University, Hyderabad, Telangana State, INDIA *E-mail address:lincoln.ab86@gmail.com ABSTRACT A series of Ni(II) complexes (NiL1-NiL5) have been synthesized from macrocyclic Schiff base ligands (L1-L5) were obtained from condensation of 4-aminoantipyrine derivative (L) with different diamines and hydrazides. All these compounds were well characterized by elemental, spectral analysis(mass, IR, 1 H-NMR, electronic), magnetic suseceptibility, molar conductance and thermal studies. Macrocyclic Schiff bases are tetradentate with N4 donor system around the metal ion.Octahedral geometry have been assigned for all complexes. All ligands and complexes were examined for antibacterial activity and found that complexes were more potent when compared to ligands. Keywords 4-Aminoantipyrine; Macrocyclic Schiff base; Ni(II) complexes; Spectral analysis; antibacterial activity. 1. INTRODUCTION Antipyrine it self as named for its temperature reducing nature in humans which firstly found by Knorr. Among various derivatives of pyrazolone, 4-aminoantipyrine is significant owing to its willingly condensing property with various types of carbonyl compounds to obtain a variety of Schiff bases,which could be used in a number of major fields like biology and pharmaceutical industries 1-2 . The Schiff bases are more probable ligands in the formation of complexes with different metals due to its azomethine bond 3-8 . Much work have been reported from many fields on 4- aminoantipyrine,which act as precursor to prepare a large number of various transition metal complexes 9-11 . Specifically Schiff bases derived from 4-aminoantipyrine and their complexes are most concerned because of their utility in the field of biology 12-17 . Though, 4-aminoantipyrine and its derivatized Schiff bases exhibit fine antimicrobial activity, the activity has improved when it coordinates with metal centers 18-21 . In this context we are motivated to synthesize new Schiff bases from 4-aminoantipyrine as precursor and their Ni(II) complexes to evaluate their antibacterial property. 2. EXPERIMENTAL 2.1. Materials Nickel(II) chloride, 4-amino antipyrine, orthopthalaldehyde(OPA), 1,4-diamino butane, carbanohydrazide, 4H- 1,2,4-traizole-3,5-diamine, 2-amino benzo hydrazide and naphthalene-1,8-diamine were purchased from Aldrich and all the organic solvents such as ethanol, methanol, dichloro methane, DMSO were analytical grade. These solvents distilled and preserved under molecular sieves 22 . The purity of the compounds was confirmed by TLC using Merck 60F254 silica gel plates. 2.2. Physical Measurements The percentages of carbon, hydrogen and nitrogen present in ligands and their complexes were determined by using PerkinElmer 2400 Series II CHNS/O analyzer. Buchi-510 melting point machine was used to find melting points. The Mettler-Toledo star system has been employed to perform thermogravimetric studies under a inert atmosphere of dry nitrogen and <10 mg of sample masses utilsed. The FTIR spectra of compounds have been recorded in the range of 4000–200 cm -1 using Perkin Elmer-283 spectrophotometer. Brucker WH 300(400 MHz) and Varian Gemini (100 MHz) spectrometers were used to record NMR spectra( 1 H& 13 C NMR). CEC-21-110B, Finningan Mat 1210 and MICROMASS- 7070 spectrometers operating at 70 eV using a direct inlet system and VG-Auto-Spec-M mass spectrometer were used for mass spectra. Electronic spectra were obtained with Shimadzu UV-160A, a UV-Visible double beam spectrophotometer with matched quartz cells of path length 1 cm. Conductance measurements were carried out on 10 -3 M solution of compounds in dichloromethane at 25 0 C on Dig sun Digital conductivity meter model DL-909. Gouy balance calibrated with Hg[Co(NCS)4] was employed for the estimation of magnetic susceptibilities of complexes at normal temperature. 2.3. Synthesis of ligands Firstly 4-aminoantipyrine derivative (L) synthesized by adding 4-aminoantipyrine (2 mmol), in ethanol (25 mL), little by little with steady stirring to an alcoholic solution (25 mL) of orthophthalaldehyde (1 mmol) (Scheme-1). This reaction mixture was refluxed and evaporated under reduced pressure and kept at room temperature for two days. The yellow coloured precipitate (L) obtained has been filtered, rinsed with diethyl ether solvent and recrystalised from ethanol. In the final step the ethanolic solution of L (2 mmol) was refluxed with diamines (2 mmol) viz., 1,4-diamino butane(L1),