Synthesis and Characterization of Transition Metal Complexes with an Indole-Based Azo-Schiff Ligand

Abstract

In this study, an indole-based azo Schiff base ligand was first synthesized via diazotization coupling and Schiff base condensation. The ligand was then coordinated with four transition metal ions, namely Cu (II), Ni (II), Co (II), and Zn (II), and stable-colored solid complexes were isolated. FT-IR results showed that the characteristic peaks of ν(C=N) and ν(N=N) of the free ligand were located at 1618 cm⁻¹ and 1452 cm⁻¹, respectively. After coordination, these peak positions shifted to lower wavenumbers by 10-25 cm⁻¹, and a new ν(M-N) vibration peak appeared in the 510-560 cm⁻¹ range, confirming that the nitrogen atoms of the azomethine and azo groups participated in coordination. The absorption signals of the Cu (II), Ni (II), and Co (II) complexes at 520-760 nm were consistent with an octahedral configuration, while the diamagnetic Zn (II) complex matched a tetrahedral coordination mode. Magnetic susceptibility tests returned magnetic moments of approximately 1.8 BM for Cu (II), 3.1 BM for Ni (II), and 4.7 BM for Co (II), which support the octahedral structure. This study clarified the coordination behavior of this indole-derived ligand, which can form stable chelates with distinct geometric configurations.