S Chandraleka, S Basha, G Chandramohan, A Panneerselvam, D Dhanasekaran
antimicrobial activity, cu iii complex, ligand, shiff base
S Chandraleka, S Basha, G Chandramohan, A Panneerselvam, D Dhanasekaran. Synthesis and antimicrobial activity of Cu (III) schiff base complex. The Internet Journal of Microbiology. 2008 Volume 6 Number 2.
The study report the synthesis of the Cu(III), with Isonicotinic acid hydrazide and 2-acetylnaphthalene and their characterization using FTIR and Magnetic susceptibility studies. Our studies reveal the presence of different mode of linkages of the ligand with Cu(III), The comparison of the IR spectra of the ligand imply that the ligand is bidentate with the amide group and azomethine –nitrogen as the two coordination sites. The complexes exhibit an identical pattern suggesting them to be isostructural with six coordinated spin free octahedral complexes. The complexes have been screened for their antibacterial and antifungal activity. The results of this study shows that the Cu(III), complex is effective against fungal pathogen than the bacterial pathogens.
Chemists have reported on the chemical, structural and biological properties of Schiff bases. Schiff Bases are characterized by the -N=CH- (imine) group which imports in elucidating the mechanism of transamination and rasemination reaction in biological system (1,2). Schiff bases are active against a wide range of organisms for example;
Antibacterial activity has been studied more than antifungal activity. Because bacteria can achieve resistance to antibiotics through biochemical and morphological modifications (3,4).
Bacteria are several types of microscopic or utra-microscobic single-celled organisms occurring in enormous numbers everywhere in nature, not only in land, sea and air, but also on or in many parts of the tissues of plants and animals, and forming one of the main biologically interdependent groups of organisms in virtue of the chemical changes which many of them bring about, e.g. all forms of decay and the building up of nitrogen compounds in the soil . Review of literature shows that there is no report of Schiff base complexes of Cu (III), formed from Isonicotinic acid hydrazide (1NH) and 2-acetyl naphthalene. Hence an attempt was made to the synthesis of Cu(III) Schiff base complexes with Isonicotinic acid hydrazide and 2-acetyl naphthalene.
Materials and Methods
Preparation of ligand
Isonicotinic acid hydrazide (1mmol) and 2-acetylnaphthalene (1mmol) were refluxed together for 3 hours in the presence of a drop of concentyrated HCl. The volume of the mixture was reduced to half. It was then cooled in a refrigerator when light yellow crystals separated .It was filtered, washed several times with cold ethanol and dried.
The ligand(16) gave the following data IR (KBr)
vmax = 1612cm-1
Synthesis of copper (III) complex
The complex was prepared by carrying out the
The complex gave the following IR spectral data
Characterization of Cu(III) complex
IR spectra were recorded in KBr medium on a Perkin–Elmer 783 spectrophotometer. UV-Vis spectra of complex was recorded in DMSO on a Shimadzu UV-1601 spectrophotometer.The magnetic property of the metal complex was studied by Magnetometer .
Mueller Hinton agar (Beef extract 0.2 g, Peptone1.75g, Starch 0.15g, Agar 2.0g, Distilled water 100 ml, pH 7.5) prepared with lawn culture using desired test organisms. The inoculated plates were kept aside for few minutes. Using well cutter 2 wells are made in those plates at required distance. In each step of well cutting, the well cutter was thoroughly wiped with alcohol. Using sterilized micropipette, 20l of different solvents with selected chemical extract was added in to one well and in another well the same volume of corresponding controls (solvent without chemical extract) were added. After diffusion, the Mueller Hinton agar plates were incubated at 37C, 24 hours for antibacterial analysis, After incubation, the zone of inhibition was analyzed and recorded.
The sterilized Sabouraud’s dextrose agar medium (Dextrose 4.0 g, Mycological peptone1.0 g,Agar 2.0 g, pH 5.0,Distilled water 100 ml,) was poured to a Petri dish in a uniform thickness and kept aside for solidification. Using sterilized swabs, even distribution of lawn culture was prepared using desired fungi such as
Determination of minimum inhibitory concentration
One ml of extract (1mg/ml) was incorporated into one ml of nutrient broth and Sabouraud’s dextrose broth and serially diluted to obtain concentration of 1000µg/ml, 500µg/ml, 125µg/ml, 62.5µg/ml, 31.25µg/ml respectively. 20l of the bacterial , fumgal inoculum was added to each of the test tubes. The tube without the extract served as control. The tubes were incubated at room temperature and readings were recorded after a period of 24 hrs for bacteria and 3 days for fungi.MIC was recorded as the lowest concentration of the extract at which no visible growth of the bacterial and fungal occurred after a period of seven days incubation.
Results and Discussion
Reaction of Isonicotinic acid hydrazide and 2-acetyl naphthalene
Reaction of Salicylaldehyde with 2-acetyl naphthalene in ethanol showed a new spot after refluxing for four hours. After usual workup a yellow solid showed the following special features.
The ligands are expected to be bidentate, the possible coordination sites being the azomethine-nitrogen and the amide group. The NH stretching absorbtion (34) in the free ligands occurs at 3330 cm-1. The ligand band due to c=o appears at 1664 cm-1. The band due to c = N mode appears at 1612 cm-1.
Reaction of the ligand and Cu (III)
Reaction of the ligand and Cu(III) in ethanol gave yellowish green solid. The IR and magnetic susceptibility measurement of the complex showed the following spectral features.
The room temperature magnetic moment of Cu(III) chelates is found to be 2.70BM indicating paramagnetic, low spin d9 complex with ground state term 2D. The magnetic moment value can be calculated as follows (Table 1).
Where, MW = Molecular weight of the complex
SW = Weight of the substance
The IR and magnetic susceptibility studies of the complex indicates that it is an octahedral complex of the type CuL3 and the structure of the complex is assigned in Fig 1.
The Cu(III) metal complexes were effective against all the test organisms, both in Ethanol and methanol extract form. The methanol extract was more active against the test organisms than the ethanol extract. The antimicrobial activity of ethanol extract of selected complexes
The minimal inhibitory concentration of Ethanol extract of Cu(III)
Various studies (5) have shown a relationship between the metal ions and their metal complexes as antitumour (6) and antibacterial agents, which is a subject of great interest. The inorganic pharmacology started to be an important field with more than 25 inorganic compounds being used in therapy as antibacterial, antiviral and anticancer drugs (7). It was seen that the biological active compounds become more bacteriostatic and carcinostatic upon chelation with metal ions. Schiff bases have also attracted considerable attention in terms with their chelating abilities and analytical applications (8,9).
Thus the present study showed the significant antimicrobial activity to