Reaction of 4,4'-dipyridine dioxide (dpdo) and CuCl2. 6H(2)O in aqueous solution gave an adduct [Cu(H2O)(6)]Cl-2. 2dpdo . 2H(2)O 1, which has a hydrogen-bonded three-dimensional network. While substituting CuCl2. 6H(2)O with Cu(ClO4)(2). 6H(2)O, three pseudopolymorphs, namely, [Cu(dpdo)(6)][ClO4](2) 2, [Cu-3(dpdo)(8)(H2O)(6)][ClO4](6). 2dpdo . 6H(2)O 3, and [Cu(dpdo)(H2O)(4)][ClO4](2). 2dpdo 4, were isolated. 2 consists of a mononuclear copper coordinated with six terminal dpdo ligands. Adjacent mononuclear units are overlapped through pi-pi stacking of pyridine rings to give a 2D sheet with a triangular channel. 3 forms a trinuclear cluster bridged by two dpdo molecules. The solvate and terminal dpdo molecules are interwoven through hydrogen bonding and pi-pi stacking to lead to a rectangular channel with a dimensionality of 12.98 Angstrom x 13.44 Angstrom. 4 has a one-dimensional chain structure bridged by dpdo. Two solvate dpdo ligands link these chains through hydrogen bonding to generate two sets of three-dimensional networks which are interwoven through a common conjunctive point [Cu(H2O)(4)](2+), yielding a three-dimensional open framework with triangular channels. ClO4-anions are included within these channels in 2-4 through weak C-H . . .O hydrogen bonding. The introduction of the second spacer, 4,4'-bipyridine, generated a 2D architecture [Cu(dpdo)(4,4'-bipy)][ClO4](2). 2H(2)O-dpdo 5, which is constructed by 4,4'-bipy and 4,4'-dpdo simultaneously, exhibiting a large channel with approximate dimensionality 11.1 Angstrom x 12.6 Angstrom, in which solvate 4,4'-dpdo ligand and perchlorate anions are accommodated.