Synthesis and Characterisation of a Novel 2,3-O-di Acetyl-5,6-O-Benzylidene - L -Ascorbic Acid and its Complexes of Cr(III), Co(II), Ni(II),Cu(II) and Zn(II)

Abstract

           A new ligand type (O₂) [2,3-O-diacetyl-5,6-O-benzylidene L- ascorbic acid] [L] and its complexes of general formula [M(L)₂(X)(Y)]Cl_n (where: M=Cr^III ,X=Y=H₂O, n=3; Co^II, X = Y = 0, n= 2; Ni^II and Cu^II, X = Cl, Y = H₂O, n= 1; Zn^II, X = Y = H₂O,n = 2) are reported. The ligand was prepared in two steps; first step involved the synthesis of [5,6-O-benzylidene-L-ascorbic acid] (A). In second step derivative-A was then reacted with acetyl chloride and anhydrous pyridine as a base to give the titled ligand. Metal complexes of the ligand with Cr^III,Co^II,Ni^II,Cu^II and Zn^II were synthesised by direct reaction of the corresponding metal chloride with the ligand[L] in a 2L:1M mole ratio. The ligand and its complexes were characterised by spectroscopic methods ¹H NMR, FTIR, (UV-Vis), atomic absorption, microanalyses, chloride content, melting point and conductance measurements . These studies revealed that the geometry about Cr^III, Ni^II,Cu^II and Zn^II is octahedral while the complex of Co^II adopts a tetrahedral geometry.