In this paper, self-assembly reactions of copper(II) ions, methoxybenzoate isomers and 2,2′-bipyridine yield two copper-oxygen polynuclear complexes: [Cu2(bpy)2(2-C8H7O3)3]·(2-C8H7O3)·14H2O 1, [Cu4(bpy)4(H2O)(OH)4]·4(3-C8H7O3)·17H2O 2, and a simple mononuclear complex [Cu(bpy)(H2O)(4-C8H7O3)2] 3. (bpy = 2,2′-bipyridine, C8H7O3 = methoxybenzoate ion). Single crystal X-ray diffraction analyses reval that compound 1 is a dinuclear copper(II) complex which bridged by three carboxylate groups, and 2 presents a discrete step-like tetra-nuclear copper Cu4O4 core. Compound 3 shows a square pyramidal mononuclear geometry. The magnetic susceptibility of complex 1 measured from 2 to 300 K, revealed an antiferromagnetic interaction between the Cu(II) ions. Furthermore, the results about IR spectra and thermal analyses were discussed.