The hydrothermal reaction of Cu(NO(3))(2), isophthalate (ip) and 2,2'-bipyridine (2,2'-bpy) without or with K(2)Cr(2)O(7) affords different complexes, whose structures are controlled only by the addition of the K(2)Cr(2)O(7). The reaction of Cu(NO(3))(2), isophthalate and 2,2'-bipyridine yields a novel one-dimensional double-chain coordination polymer [Cu(3)(ip)(2)(Hipa)(2)(bpy)(2)](n) (1). However, with the addition of K(2)Cr(2)O(7) in the above reaction at the same hydrothermal conditions, a discrete hexanuclear Cu(II) complex [Cu(6)(ipO)(4)(2,2'-bpy)(2)(H(2)O)(2)].6H(2)O (2) (ipOH = 2-hydroxyisophthalate) was isolated. It is interesting to find that the in situ reaction of isophthalate (ip) oxidized to 2-hydroxyisophthalate (ipOH) occurs. K(2)Cr(2)O(7) acts as an oxidant. The magnetic properties of 1 and 2 have been investigated by variable-temperature magnetic susceptibility and magnetization measurements, and the results reveal that intramolecular ferromagnetic interactions exist with weak intermolecular antiferromagnetic interactions at very low temperature in 1 and weak antiferromagnetic interactions admixture with strong ferromagnetic interactions in 2.