Abstract
Three azo group-containing Schiff base ligands, namely 1-{3-[(3-hydroxy-propylimino)methyl]-4-hydroxyphenylazo}-4-nitrobenzene (2a), 1-{3-[(3-hydroxypropyl-imino)methyl]-4-hydroxyphenylazo}-2-chloro-4-nitrobenzene (2b) and 1-{3-[(3-hydroxy-propylimino)methyl]-4-hydroxyphenylazo}-4-chloro-3-nitrobenzene (2c) were prepared. The ligands were characterized by elemental analysis, FTIR spectroscopy, UV-Vis spectroscopy, 13C- and 1H-NMR spectroscopy and thermogravimetric analysis. Next the corresponding copper(II) and cobalt(II) metal complexes were synthesized and characterized by the physicochemical and spectroscopic methods of elemental analysis, FTIR spectroscopy, UV-Vis spectroscopy, magnetic moment measurements, and thermogravimetric analysis (TGA) and (DSC). The room temperature effective magnetic moments of complexes are 1.45, 1.56, 1.62, 2.16, 2.26 and 2.80 B.M. for complexes 3a, 3b, 3c, 4a 4b, and 4c, respectively, indicating that the complexes are paramagnetic with considerable electronic communication between the two metal centers.
Highlights
Azo Schiff base complexes contain both azo and azomethine groups
The azo and azomethine groups on azo Schiff base ligands are oriented in such a way that coordination of both groups to a metal ion is not possible, preferential coordination of the azomethine group while the azo group is left free and uncoordinated has been observed [21–24]
Cobalt(II) complexes derived from azo-linked salicylaldimine were prepared and their structures were confirmed by elemental analysis, FTIR spectroscopy, UV-Vis spectroscopy, thermogravimetric analysis and magnetic moment measurements
Summary
Azo Schiff base complexes contain both azo and azomethine groups. The azo group possesses excellent donor properties and is important in coordination chemistry [1–3], and some azo compounds have been shown to possess good antibacterial activity [4,5]. Salicylaldimine-based ligands have found applications in preparation of metallomesogens, optical metal ion detection and enantioselective catalysis [12–15]. The azomethine group has good donor properties and can form stable complexes with transition metal ions [18–20]. Schiff bases derived from salicylaldehydes are known polydentate ligands, coordinating to metals in both their deprotonated and neutral forms [25,26]. Based on the aforementioned properties of Schiff bases and azo compounds, we reported the synthesis and spectroscopic studies as well as thermal investigation of novel salicylaldimine-based ligands 1-{3-[(3-hydroxypropyl-imino)methyl]-4-hydroxyphenylazo}4-nitrobenzene (2a), 1-{3-[(3-hydroxypropyl-imino)methyl]-4-hydroxyphenyl-azo}-2-chloro-4-nitrobenzene (2b) and 1-{3-[(3-hydroxypropyl-imino)methyl]-4-hydroxyphenylazo}-4-chloro-3-nitrobenzene (2c). Cobalt(II) complexes derived from azo-linked salicylaldimine were prepared and their structures were confirmed by elemental analysis, FTIR spectroscopy, UV-Vis spectroscopy, thermogravimetric analysis and magnetic moment measurements
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