Syntheses and crystal structures of copper(II) coordination polymers comprising discrete helical chains

Three Cu-II helical complexes, [Cu(H2O)(4)(dpa)](n) (1), [Cu(4,4'-bipy)(dpa)](n) (2), and [Cu(dpe)(dpa)](n) (3) (H(2)dpa = diphenic acid, 4,4'-bipy = 4,4'-bipyridine, and dpe = 1,2-di(4-pyridyl)ethylene), have been synthesized and characterized by X-ray crystal structure determination. 1 is a one-dimensional helical chain of pseudo square-planar Cu(H2O)(4) bridged by bis-monodentate dpa. The hydrogen-bonding interactions extend the helical chain forming a two-dimensional layer structure. 2 and 3 are three-dimensional coordination polymers composed of Cu-dpa helical chains bridged by 4,4'-bipy and dpe, respectively. The longer spacer between coordination sites in dpe results in a 2-fold-interpenetration of the three-dimensional framework in 3. The helical pitches in 1-3 are 7.632, 11.425, and 16.022 Angstrom, respectively.