Abstract
Three types of Metal(II) complexes with hydrazone derived from condensation of thiophene-2-carboxylic acid hydrazide and 2-furaldehyde namely 2-furaldehyde-2thenoylhydrazone (fth) of the general formulas [M (fth-H)2],[M(fth)2 Cl2] and [M(fth)2] (NO3)2, where M= Co(II), Ni(II), Cu(II), and Zn(II), were synthesized and characterized on the basis of elemental analysis, molar conductance, magnetic moment, infrared and electronic spectral data. The infrared and molar conductance data of the complexes reveal the monobasic tridentate ONO nature of the ligand and coordination through the enolate oxygen, furan ring oxygen and azomethine nitrogen atoms, in the complexes [M(fth-H2)] upon deprotonation of the ligand. The same ligand acts as neutral bidentate ON in the chloro-complexes coordinated through the carbonyl oxygen and azomethine nitrogen atoms and neutral tridentate ONO in the nitrate complexes coordination through carbonyl oxygen and furan ring oxygen atoms in addition to the azomethine nitrogen atom. The magnetic and electronic spectral data suggested an octahedral geometry for the complexes. ــــــــــــــــ ــــــــــــــــ ــــــــــــــــ ــــ
Highlights
Three types of Metal(II) complexes with hydrazone derived from condensation of thiophene-2-carboxylic acid hydrazide and 2-furaldehyde namely 2-furaldehyde-2thenoylhydrazone of the general formulas [M2],[M(fth)2 Cl2] and [M(fth)2] (NO3)2, where M= Co(II), Ni(II), Cu(II), and Zn(II), were synthesized and characterized on the basis of elemental analysis, molar conductance, magnetic moment, infrared and electronic spectral data
Preparation of Metal Complexes: Preparation of M(II) complexes of the type [M(fth-H)2] M=Co(II),Ni(II),Cu(II), Zn(II). 2-Furaldehyde-2-thenoylhydrazone (0.44g, 0.02 mole) in hot absolute ethanol (20 ml) was magnetically stirred and (0.112g, 0.02 mole) of KOH was added followed by an ethanolic solution (20 ml) of M(II) acetate hydrate (0.001 mole) [0.247g Co(CH3COO)2. 4H2O ; 0.247g Ni (CH3 COO)2. 4H2O; 0.198g Cu(CH3COO)2
The reaction of appropriate metal (II) acetate with the hydrazone, derived from thiophene-2-carboxylic acid hydrazide and 2-furaldehyde, in the presence of KOH in a molar ratio of 1:2:2 using absolute ethanol as solvent gave a monomeric complexes of the type [M(fth-H)2] [M=Co(II), Ni(II), Cu(II) and Zn(II)]
Summary
There has been continuing interest in coordination chemistry of the hydrazones that derived from heterocyclic acid hydrazides and aldehydes or ketones (Dianu et al, 2010 ; Nair and Thankamani, 2011). The remarkable biological activity of acid hydrazides and their corresponding aroylhydrazones and the dependence of their activity on the mode of coordination with transition metal ions present in the living system have been of significant interest by many workers. An important feature in the chemistry of aroylhydrazones and their complexes is the acid character of the hydrogen of the NH group of the hydrazide moity; this allows for either neutral or anionic ligands. The reaction of aroylhydrazones with transition metal ions can proceed according to two pathways attaining the ketonic (Fig.1) or enolic structure for the hydrazide part of the molecule (Seleem et al, 2006). The present investigation reports the synthesis and characterization of some divalent transition metal complexes of the hydrazone derived from thiophene-2-carboxylic acid hydrazide and 2-furaldehyde (fth): O
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