Synthesis of New Tetradentate H2salophen Ligands and Their Copper (II) Complexes

A synthesizing metal salophen complex is extremely significant owing to their wide variety of potential applications, particularly in catalysis, optical limiting materials, and pharmaceutical purposes. The present work aims to design and synthesis a series of copper salophen complexes associated with the diazo moiety according to the adapted strategy in two straight and effective steps. Salophen-type ligands containing tetradentate Schiff's base H2L were synthesized by a regular condensation reaction of azo-based salicylaldehyde derivatives (two equivalents) with o-phenylenediamine (one equivalent) in refluxing dioxane. Consequently, the previous salophen-type ligands reacted with copper chloride dihydrate to generate the corresponding copper (II) salphen complexes. The synthesized tetradentate ligands and their copper salophen complexes were characterized with elemental analysis and spectroscopic techniques, showing that the coordination of the ligands with copper ions took place through the ONNO donor sites of two azomethine-N and two deprotonated phenolic-OH donors, suggesting the complex's general formula as CuL. The thermogravimetric analysis and molar conductivity results are in good agreement with the expected structures.