Novel copper(II) complexes of “short” salen homologues. Structure and magnetic properties of the tetranuclear complex [Cu2(L2)2]2 [H2L2 = phenyl-N,N′-bis(salicylidene)methanediamine]

Abstract

Copper(II) complexes of Schiff bases derived from the condensation of two molecules of salicylaldehyde and methanediamine (L¹) or some phenyl substituted methanediamines (L²–L⁵) have been synthesized and characterised. The crystal structure of the phenylmethanediamine (L²) derivative has been determined. The ligand acts as bis-bidentate, bridging two copper atoms which are co-ordinated to two phenolato and two imino groups of two ligands. Two binuclear moieties [Cu₂(L²)₂] are held together through Cu–O(phenolato) interactions between adjacent units forming a pseudo-linear [Cu₂L²₂]₂ cluster. Variable temperature magnetic susceptibility data for this derivative reveal the presence of weak antiferromagnetic interactions (−J ≈ 2–3 cm⁻¹) between nearest neighbour spin centres. The structural factors that may be responsible for the sign and magnitude of the exchange interactions are discussed.