Variable dimensionality from mononuclear and trinuclear to one and two dimensions: a series of copper(II) compounds with 4,4'-dipyridine dioxide.

Reaction of 4,4'-dipyridine dioxide (dpdo) and CuCl(2).6H(2)O in aqueous solution gave an adduct [Cu(H(2)O)(6)]Cl(2).2dpdo.2H(2)O 1, which has a hydrogen-bonded three-dimensional network. While substituting CuCl(2).6H(2)O with Cu(ClO(4))(2).6H(2)O, three pseudopolymorphs, namely, [Cu(dpdo)(6)][ClO(4)](2) 2, [Cu(3)(dpdo)(8)(H(2)O)(6)][ClO(4)](6).2dpdo.6H(2)O 3, and [Cu(dpdo)(H(2)O)(4)][ClO(4)](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 A x 13.44 A. 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(H(2)O)(4)](2+), yielding a three-dimensional open framework with triangular channels. ClO(4)(-) 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)][ClO(4)](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 A x 12.6 A, in which solvate 4,4'-dpdo ligand and perchlorate anions are accommodated.