Synthesis, Characterization and Thermal Properties of Oligo-N,N′-bis (2,4-dihydroxybenzylidene) ethylenediamine and Its Cobalt (II) and Manganese (II) Complexes

Abstract

In this study, the new oligomer Schiff base oligo-N,N′-bis (2,4-dihydroxybenzylidene) ethylenediamine (O-DHBEDA), with a double azomethine group, was synthesized by oxidative polycondensation (OP) of N,N′-bis (2,4-dihydroxybenzylidene) ethylenediamine (DHBEDA) with NaOCl as an oxidant in an aqueous alkaline medium at 90°C. About 69.3% DHBEDA was converted to O-DHBEDA. The structures of the products were studied by UV-Vis, FT-IR, ¹H-NMR, ¹³C-NMR and elemental analysis. According to gel-permeation chromatography (GPC) analysis of O-DHBEDA, the number-average molecular weight (M _n), weight-average molecular weight (M _w) and PDI values were found to be 5255 g/mol, 9116 g/mol and 1.73, respectively. During the polycondensation reaction, a part of the azomethine (–CH=N–) groups oxidized to aldehyde (CHO) groups (approx. 4%). Oligomer–metal complexes of oligo-N,N′-bis (2,4-dihydroxybenzylidene) ethylenediamine (O-DHBEDA) with Co (II) and Mn (II) were synthesized and characterized by FT-IR, UV-Vis, TG-DTA and atomic absorption spectroscopy (AAS). TG/DTA analyses were shown to be stable of O-DHBEDA against thermo-oxidative decomposition. The residue values of DHBEDA, O-DHBEDA, O-DHBEDA–Co and O-DHBEDA–Mn were found to be 0%, 7.1%, 14% and 13.4%, respectively, at 1000°C.

Keywords:

• SCHIFF BASE OLIGOMER
• OXIDATIVE POLYCONDENSATION
• OLIGOMER-METAL COMPLEXES
• THERMAL PROPERTIES
• OLIGO-N,N'-BIS (2,4-DIHYDROXYBENZYLIDENE) ETHYLENEDIAMINE