Helical copper(II) complexes based on a bispyridylpyrrole ligand, namely the helical polymer {[Cu2(PDPH)2(N3)2]}n (1) (where HPDPH = 2,5-bis(2′-pyridyl)pyrrolide) containing a one-dimensional double-helical chain, a discrete double-helical complex [Cu2(PDPH)2(NO3)2] (2) and triple-helical complex [Cu2(PDPH)3](OTf) (3·OTf) (where OTf− = triflato) were synthesized by displacement of Cl− in [Cu(PDPH)Cl] by the anion N3−, NO3− and OTf−, respectively. The structures of these complexes directly correlate with the coordination abilities of the ligands. The N3− anion is found to favor the formation of polymeric helical structures. The helical chain in 1 is built-up by [Cu2(PDPH)2] units linked by double μ1,3-azido bridges. In 2, the anion NO3− acting as a monodentate oxygen ligand binds to each copper center, resulting in the formation of the double helical structure, while the non-coordinating OTf− ligand leaves space for three PDPH− ligands, leading to the formation of the triple-helical dicopper complex 3·OTf. Magnetic susceptibility data of 1, measured from 1.8 to 300 K, show alternating ferro- and antiferromagnetic interactions through the bridging PDPH− and μ1,3-azido pathway, respectively.
