Byline: Erdal Canpolat, Hakan sahal, Mehmet Kaya and Seher Gur
Summary: The complexes of Co(II), Cu(II) and Zn(II) with the Schiff base ligand derived from 4,4- diaminodiphenylether were prepared and characterized by physical, spectral and analytical data. The metal:ligand stoichiometric ratio is 1:1 in the complexes of Co(II) and Zn(II) whereas the metal:ligand stoichiometric ratio in the Cu(II) complex is 2:1. It was determined that the bidentate behaviors of the ligand are accomplished via the phenolic oxygen and the azomethine nitrogen atoms. The presence of water is revealed by thermograms and supported by the presence of relevant bands in their IR spectra.
Suitable structures have been proposed for these complexes. The synthesized compounds were tested for antimicrobial activity against in vitro antibacterial (Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Salmonella typhimurium) and antifungal activities (Candida globrata and Candida tropicalis) by the minimum inhibitory concentration (MIC) method. All of the selected compounds showed weak antimicrobial activity against test microorganisms (128-512 ug/mL).
Key words: Schiff base, transition metal complexes, antimicrobial activity, 4,4-diaminodiphenylether.
Introduction
Several Schiff base metal complexes have been studied in the past because of their wide applicability [1-3]. A large number of reports are available on the chemistry and the biological activities of transition metal complexes containing O,N and S,N donor atoms [1-5]. It is well known that some drugs have higher activity when administered as metal complexes than as free ligands [2].
Comparatively, fewer publications [6] have been devoted to the synthesis of Schiff bases with 4,4-diaminodiphenylether. Hence, in continuation with our earlier work on aromatic Schiff bases [7-15], here we report the synthesis, spectroscopic, and biological studies of Co(II), Cu(II), and Zn(II) complexes of 2-[(E)-{[4-(4- aminophenoxy)phenyl]imino}methyl]-6- methoxyphenol.
Results and Discussion
The ligand (LH) has been synthesized by the reaction of equimolar equimolar amounts of 4,4- diaminodiphenylether with 3- methoxysalicylaldehyde in absolute ethanol (Scheme 1).
The ligand and the complexes have been characterized on the basis of IR, 1 H and 13 C-NMR spectra, UV-VIS, elemental analyses, magnetic susceptibility measurements and thermogravimetric analyses. The synthesized compounds were tested in vitro for their antimicrobial activity. In the mononuclear complexes of Zn(II) and Co(II) reactions between metal ions and ligand were carried out for 1:1 molar ratio, whereas dinuclear complex with a metal: ligand ratio 2:1 have been prepared with Cu(II) salt. The complexes are intensely colored stable solids Fig. 1.
Scheme-1: Formation of the ligand.
The elemental analysis result agree with the calculated values showing that the complexes of Co(II) and Zn(II) have 1:1 metal:ligand ratios, whereas the metal: ligand ratio in the Cu(II) complex is 2:1. According to result obtained from IR, TGA and elemental analysis confirmed the compositions of the synthesized compounds. ] Fig. 1: Conformation of the ligand.
As known, magnetic susceptibility measurements provide information regarding the structure of the complexes. The magnetic moments of the complexes were measured at room temperature and are listed in Table 1. While Zn(II) complex is diamagnetic as expected for a d 10 configuration, the Co(II) complexes is paramagnetic and its...