Synthesis, crystal structure and magnetic properties of [Cu(bpym)(mal)(H2O)]·6H2O and [Cu2(bpym)(mal)2(H2O)2]·4H2O (bpym=2,2′-bipyrimidine, H2mal=malonic acid)

Two new mixed-ligand complexes of formula [Cu(bpym)(mal)(H2O)]·6H2O (1) and [Cu2(bpym)(mal)2(H2O)2]·4H2O (2) (bpym=2,2′-bipyrimidine and H2mal=malonic acid) have been synthesised and characterised by X-ray diffraction methods. The crystal structure of 1 consists of mononuclear [Cu(bpym)(mal)(H2O)] units in which the copper atom shows a slightly distorted square-pyramidal environment with two bpym-nitrogen and two malonate-oxygen atoms forming the equatorial plane and a water molecule in the axial position. The structure of 2 is built by centrosymmetric bpym-bridged dinuclear [Cu2(bpym)(mal)2(H2O)2] units, in which the geometry of each Cu(II) ion is similar to that found in 1. Malonate acts as a bidentate ligand in both compounds whereas bpym exhibits chelating and bis(chelating) coordination modes in 1 and 2, respectively. The intramolecular metal–metal separation in 2 is 5.445(1) Å. The magnetic properties of 1 and 2 have been investigated in the temperature range 10–300 K. Complex 1 follows a Curie law for a magnetically isolated spin doublet, whereas 2 exhibits a relatively strong intramolecular antiferromagnetic coupling, J=−149 cm−1 (the spin Hamiltonian being defined as Ĥ=−JŜ1·Ŝ2).