Ligating properties of a potentially tetradentate Schiff base [(CH3)2NCH2CH2NCHC6H3(OH)(OMe)] with zinc(ii), cadmium(ii), cobalt(ii), cobalt(iii) and manganese(iii) ions: synthesis and structural studies

Abstract

A series of Zn(II), Cd(II), Co(II), Co(III) and Mn(III) complexes with the Schiff base [(CH₃)₂NCH₂CH₂NCHC₆H₃(OH)(OMe)], LH, derived from 2-dimethylaminoethylamine and o-vanillin, has been synthesised and structures of all the products have been established by X-ray crystallography. In the cases of zinc and cadmium, dimeric complexes [Zn(LH)₂(NCS)] [Zn₂(L)(µ_1,1-CH₃COO)(NCS)₃] (1), [Cd₂(L)₂(Cl)₂] (2) and [Cd₂(L)₂(NCS)₂] (3), and for cobalt and manganese, monomeric complexes [Co(LH)₂(NCS)]₂ [Co(NCS)₄] (4), [Co(LH)₂(NCS)]ClO₄ (5), [Co(L)(N₃)(o-vanillinate)]·0.5MeOH (6) and [Mn(LH)₂(MeOH)₂](ClO₄)₃ (7), are formed with various terminal ligands. All the complexes have been characterised by elemental analysis and IR spectra. UV-Vis and NMR spectroscopy, magnetic, and electrochemical studies, were also carried out where feasible. The Schiff base functions as a bi-, tri- or tetra-dentate chelating agent and coordinates via the protonated or deprotonated phenolic oxygen, amine and imine nitrogens, and only in case of 1 with the methoxy oxygen atoms, to the metal ion leading to the formation of mono- or bi-metallic complexes.