Synthesis and magnetic properties of a series of bi- and tri-nuclear complexes of copper(II) with the unsymmetrical tetradentate Schiff-base ligand 3-[N-2-(pyridylethyl)formimidoyl]salicylic acid, H2fsaaep, and crystal structures of [{Cu(Hfsaaep)Cl}2] and [{Cu(fsaaep)(H2O)}2]

Abstract

Three oligonuclear complexes of copper(II), [{Cu(Hfsaaep)Cl}₂] 1, [{Cu(fsaaep)(H₂O)}₂] 2 and [Cu₃(fsaaep)₂][ClO₄]₂ 3 have been synthesized, using the unsymmetrical tetradentate Schiff-base ligand 3-[N-2-(pyridylethyl)formimidoyl]salicylic acid, H₂fsaaep. The crystal structures of complexes 1 and 2 have been solved. That of 1 consists of discrete binuclear entities with copper atoms bridged by two chloride anions. The copper atoms are related by an inversion center and exhibit a slightly distorted square pyramidal stereochemistry. The Cu· · ·Cu separation within the binuclear unit is 3.825(2) Å. The structure of 2 consists of neutral centrosymmetric binuclear entities. The copper(II) ions are bridged by phenolic oxygen atoms, assuming a square-pyramidal geometry. The distance between the copper atoms is 3.0279(4) Å. Variable-temperature magnetic susceptibility measurements indicated a very weak ferromagnetic coupling of the copper(II) ions in compound 1 (J = 0.15 cm^–1) and an antiferromagnetic coupling in compounds 2 and 3 (J = –617 and –228 cm^–1, respectively).