Copper(ii) complexes of two new pyridylAliphatic amine ligands: Synthetic, structural, EPR, and magnetic studies

Two new polyamine ligands, L ¹ and L ², incorporating pyridyl and aliphatic amine donor sites have been prepared and their reaction with copper(ii) yields the mono- and binuclear complexes [Cu(L ¹)](ClO ₄) ² (1) and [Cl ₂Cu(L ²)CuCl(H ₂O)]ClO ₄ (2), respectively. The X-ray structure of 1 confirms that the five nitrogen donors of L ¹ are bound to the central copper ion to give a distorted square pyramidal coordination sphere. In 2, L ² acts as a bridging ligand with its N ₃-donor coordination domains separated by a m-xylylene spacer group. An unusual feature of this latter complex is that symmetrical L ² gives rise to non-equivalent coordination behaviour at the individual copper sites; while both sites display five-coordination with distorted square pyramidal arrangements, they differ in having N ₃Cl ₂- and N ₃ClO-donor atom sets, respectively. The electron paramagnetic resonance (EPR) spectra of both complexes are discussed. Variable temperature magnetic susceptibility data confirmed the absence of magnetic interactions in 1 while a weak antiferromagnetic interaction between copper(ii) centres occurs in 2.