Copper(II) and nickel(II) metallopolymers derived from polyacylhydrazones

A series of polyacylhydrazones derived from condensing diacetyl with oxalic, malonic, succinic, glutaric and adipic dihydrazides was prepared, characterized and reacted with copper(II) and nickel(II) acetate to give metallopolymers of general formula [Cu2(L)(AcO)2(OH)(H2O)2] · yH2On, [Cu(L)(AcO)(HO)(H2O)] · yH2On, [Ni2(L)(AcO)2-(HO)2] · yH2On and [Ni(L)(AcO)(HO)] · yH2On, where L refers to the neutral dihydrazone unit. Magnetic susceptibility measurements in the 4.2–300 K range indicate significant antiferromagnetic coupling between the CuII centers in the metallopolymers, which may indicate the presence of two polymer chains crosslinked by bis-μ-acetatocopper(II) bridges. Based on i.r., spectral and magnetic measurements, tentative structures of the CuII and NiII metallopolymers have been proposed. The dihydrazone units in these polymers are coordinated to the metal(II) via the azomethine nitrogen(s) whereas the amide group remains uncoordinated. Each CuII is penta-coordinated in a distorted square pyramidal environment and is neutralized by one bridged acetate and a hydroxide ion, while the fifth coordination site is occupied by a water molecule. In the nickel(II) metallopolymers the metal ions are in a tetrahedral environment and are coordinated to azomethine nitrogen, two bridged acetate oxygens and to the hydroxide ion.