A chelate complex of zinc(II) and 2,2′-bipyridine-6,6′-diyl bis(tert-butyl nitroxide) (bpybNO) with a metal/ligand ratio of 1/2 was structurally characterized to be [Zn(bpybNO) 2 ][Zn(hfac) 3 ] 2 , where Hhfac stands for 1,1,1,5,5,5-hexafluoropentane-2,4-dione. The magnetic susceptibility measurement indicates the presence of considerable antiferromagnetic interaction among the four S=1/2 spins. The exchange parameter J was estimated as 2J/k B =−103(1)K, on the basis of a tetrahedral coupling model. The antiferromagnetic coupling is stronger after complexation than before. The density-functional theory calculation on related model compounds supports the present analysis and clarified the role of the zinc ion as a superexchange coupler.