Synthesis of pH-dependent Ni(II) coordination complexes with Schiff base and their structural characterization

This article describes the study of two Nickel (Ni(II)) complexes based on Schiff base at pH 7.0 and pH 9.0 respectively and characterized using various characterization techniques. The reaction of C7H9N3S2 with NiCl2·6H2O at pH 7.0 resulted in the C1 complex. However, when the same reaction was performed at pH 9.0, C2 complex was obtained. The magnetic behavior (µ) of both complexes was found to be 2.92 (C1) and 2.96B.M. (C2) respectively, which showed that both complexes were paramagnetic and in octahedral shape. In a similar fashion, the electrical conductance of (181.0 Ohm-1cm2 mole-1 for (C1) and (179 Ohm−1 cm2 mole-1 for (C1) suggested that the compound was found in the 1:2 (Metal: Ligand) electrolytically nature in their coordination mode. In the electronic spectrum study, it is clearly shown that both the Ni(II) complexes (9500–10415, 14200–14940, and 23500–24000 cm−1) were octahedral. The broad band at 3350–3600 cm−1 in the IR data of C1 indicates the νOH mode of vibration of the bounded water molecules. Whereas, the 610 cm−1 band is unchanged in the C1 but found red-shifted (600 cm−1) in C2 complex. This indicates that the sulfur of the thiophene unit is not involved in the bonding coordination to metal in C1 but has coordinated with the metal C2 complex.