Strong influences of bridging ligands L on the magnetism of two Ni-9 complexes, Ni9L2(O2CMe)(8) {(2-py)(2)CO2}(4) (L=OH- 1 and N-3(-) 2) are demonstrated by magnetic interactions. Effective exchange integrals J for 1 and 2 are determined non-empirically using UB3LYP and UBLYP. The calculated magnetic susceptibility for I is wholly consistent with the experimental values. Although the ground spin state of 2 obtained using the calculated J values agrees with the experimental S = 9 state, fitting of the J values to the experimental magnetic susceptibility Curve indicates weak anti ferromagnetic interactions via the azido ligands. (c) 2006 Elsevier B.V. All rights reserved.