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)](.)6H(2)O (1) and [Cu-2(bpym)(mal)(2)(H2O)(2)](.)4H(2)O (2) (bpym = 2,2'-bipyrimidine and H(2)mal = 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 [Cu-2(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) Angstrom. 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 (H) over cap = -J (S) over cap (.)(1)(S) over cap (2)). (C) 2001 Published by Elsevier Science B.V.