The magnetic properties of the divalent metal complexes [ML2(HL)] (M = Co-II, Ni-II, and Cu-II; HL = 2,3-diamino-1,4-diazabuta-1,3-diene-1,4-diol, i.e., diaminoglyoxime) with a slipped-stack structure were examined. The magnetic susceptibilities and the electron spin resonance spectra indicate that [CoL2(HL)] exhibits a ferromagnetic interaction along the stack chain, the strength of which is estimated to be 13.5 K, while [CuL2(HL)] is paramagnetic and [NiL2(HL)] is diamagnetic. The magnetic behaviors of the [ML2(HL)] complexes can be predicted precisely by comparing the spin splittings of the partially occupied molecular orbitals of the monomer complexes ML2 and the dimer complexes 2ML(2) which are equivalent in structure to the relevant moieties in the real stack chains, based on molecular calculations using the DV-X alpha method. The modes of the differential spin densities for the dimers 2ML(2) strongly suggest that the principal mechanism of superexchange on [CoL2(HL)] may operate through strong interaction of the 3d(zx) orbitals of Co atoms with the 2p(z) orbitals of two apical N atoms which form the pi(z)-type systems of the adjacent complex molecules along the stack chain.