The preparation of complexes M 2 L( NO 3) 4·2 CH 3 OH·n H 2 O ( 4a-d) (M = Mn, Co, Ni, Cu; L = C 18 H 22 N 6 O 4 ( 3); n = 0.5 or 1) from pyridine-1-oxide-2,6-dialdehyde, 1,2-diaminoethane and the metal(II) nitrate is reported. The complex [Ni 2L(H 2O) 4](NO 3) 4· 2H 2O ( 5) was also prepared and its crystal structure determined. 5 is monoclinic, space group P2 1/n, a = 11.831(8), b = 12.168(8), c = 12.329(7) A ̊ , β = 114.26(5)°, Z = 2 . In the cyclic ligand 3, the pyridine-1-oxide rings are linked by CH(OH).NH.(CH 2) 2.N:CH groups, showing that partial hydrolysis of the expected Schiff-base ligand has occurred during synthesis of the complex. In the centrosymmetric complex 5, the Ni 2+ ions are bridged in a planar Ni 2O 2 unit by the N-oxide oxygen atoms, the ligand adopting a non-planar ‘stepped’ conformation with pyramidal stereochemistry at the bridging O atoms. Six-fold coordination of each Ni 2+ ion is completed by two N atoms and two cis water molecules. The magnetic susceptibilities of 4a-d were measured between 5 and 300 K and analysed to obtain values of the parameter J in the exchange Hamiltonian −2 JS 1·S 2: J = - −1.15, −5.0, −15.5 and +3.3 cm −1, respectively. These values are discussed in terms of the contributing orbital pathways.