Abstract
In this study homo and hetero trinuclear complexes of cobalt (II), nickel (II) and copper (II) were prepared by the reaction of their salts (chloride and nitrate) with a Schiff base ligand derived from vanillin and malonylhydrazide. Complexes of the general formulae: [M3(VMH4)2X6)], [M2M'(VMH4)2X6], [MM'M"(VMH4)2X6] and K2[M3(VM)2], K2[M2M'(VM)2], K2[MM'M''(VM)2] (where M, M', M" are the dipositive ions of cobalt, nickel and copper, respectively, VMH4, VM are the neutral and tetra basic forms of the ligand and X= Cl, NO3) were isolated from both neutral and basic media, respectively. The ligand and its complexes were characterized by using analytical, physical and spectral methods. The studies revealed the hexadentate nature of the ligand which gave hexacoordinated and tetracoordinated metal complexes with the most probable octahedral and tetrahedral or square planar structures in neutral and basic media, respectively. The stability period and the stability constants of some of these complexes in neutral solution have been studied spectrophotometrically. The compositions of the complexes were determined by the use of Job method. The results indicate the formation of only 1:1 metal: ligand complexes with similar stability constants.
Highlights
The rational design and synthesis of polynuclear coordination complexes, aiming at understanding the structure and chemical factors that govern the exchange coupling between paramagnetic centers are of continuing interest in biology, chemistry and physics [1,2,3]
Particular interest has recently been focused on the development of super molecular structures created by hydrogen bonds as a new challenge for the synthesis of non-serendipitous species in order to study their magnetic behavior [47]
The stability constants were studied only for the neutral complexes but the other type precipitated on addition of alkali and prevents the measurements
Summary
The rational design and synthesis of polynuclear coordination complexes, aiming at understanding the structure and chemical factors that govern the exchange coupling between paramagnetic centers are of continuing interest in biology, chemistry and physics [1,2,3]. A variety of ligands containing N and O donor atoms have been employed for the preparation of such systems. Among such ligands are the Schiff bases [8,9,10,11,12,13]. The Schiff base compounds constitute an important class of ligands which have been extensively studied in coordination chemistry, mainly due to their facile synthesis and tunable steric, electronic and catalytic properties. N2O2 donor Schiff bases and for their role in biological systems [18,19] have been extensively studied as oxygen carriers and as catalysts for water splitting system [ 20-23]
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