Reaction of 2,2'-bipyridine (bpy) and copper(II) nitrate in methanol results in two complexes, namely light-blue bis(2,2'-bipyridine)nitratocopper(II) nitrate methanol solvate, [Cu(NO(3))(C(10)H(8)N(2))(2)]NO(3) x CH(3)OH, (I), which is unstable in air, and the product of its decomposition, catena-poly[[[bis(2,2'-bipyridine)copper(II)]-mu-nitrato-O:O'] nitrate], [[Cu(NO(3))(C(10)H(8)N(2))(2)]NO(3)](n), (II). The crystal structures of both compounds were determined from one crystal at room temperature. Later, the structure of (I) was redetermined at low temperature. In (I) and (II), the Cu atom is coordinated by two bpy and one or two nitrate ions, respectively. The second nitrate ion in (I), along with the methanol solvent molecule, is found in the outer coordination sphere, not bonded to Cu. The nitrate in (I) is chelating, while in (II), it bridges (bpy)(2)Cu complexes, forming a one-dimensional chain structure. The Cu cation in (II) lies on a twofold axis and the uncoordinated NO(3)(-) ion is located close to a twofold axis and is therefore disordered. Compound (I) converts into (II) upon loss of solvent.