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, 1 H-NMR, 13 C-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.

Schiff Base Polymers Obtained by Oxidative Polycondensation and Their Co(II), Mn(II) and Ru(III) Complexes: Synthesis, Characterization and Catalytic Activity in Epoxidation of Styrene

“…The same characteristic peaks of the functional groups of monomers were observed in the FT-IR spectra of the polymers. It is known that, after polycondensation, due to the increase in molecular weight, the FT-IR spectrum of polymer becomes broadened [26]. This fact is also proven in the FT-IR spectra of P 1 and P 2 .…”

“…2). In addi- tion, M 2 has broad resonances at 10.30 and 13.50 ppm due to para and ortho -OH protons to the azomethine group, respectively [26]. It is clear that after polycondensation reaction, due to either increasing molecular weight or the molecular weight distribution of the polymers, the signals of polymers become broader than their monomers [27].…”

“…The comparison of 1 H-NMR spectra of M 2 and P 2 is a more informative tool for the determination of the P 2 structure. In addition, the decrease in integral ratio of either o-OH protons or p-OH protons to the azomethine protons after polycondensation reaction, indicates that the two hydroxyl groups, which are involved in the formation of free radicals [26], also participate (C-O-C coupling) in the polymerization reaction. However, the value of decreasing in integral ratio for o-OH is different from p-OH due to different amount of C-O-C coupling by o-OH and p-OH groups (Scheme 2).…”

Cu(II) and Pd(II) complexes of water soluble O-carboxymethyl chitosan Schiff bases: Synthesis, characterization

“…After complexation with metal ions, the stretching of the imine groups of OCMCS-5a and OCMCS-6a shifted to lower wavenumbers (1-35 cm −1 ); this indicated metal complexation through the nitrogen of the imine groups [31,32]. Additionally, asymmetric and symmetric stretching of carbonyl acetate groups coordinated with copper ions were observed at 1588-1387 cm −1 (Fig.…”

Synthesis, characterization, optical and electrical properties of thermally stable polyazomethines derived from 4,4′-oxydianiline

“…The FT-IR spectra of polymers shows that the decrease in intensity of vibration bands of O−H•N in the range of 2700-2500 cm −1 may be due to the participation of O−H groups in the polymerization through C−O−C coupling. [21] All the polymers show an additional peak corresponding to C−C stretching of phenylene units formed during poly condensation via C−C coupling [22] and it appears in the range of 870-879 cm −1 . UV-visible spectra of the monomers and polymers in DMSO solution are shown in Figure 4.…”