1D zigzag coordination polymers of copper(II) and nickel(II) with mixed ligands - Syntheses and structures

The one-dimensional coordination polymers [Cu(NO₃)₂(2,2′-bipy) (4,4′-bipy)]_n·2nCH₃OH (1) and [Ni(tren)(4,4′-bipy)]_n-(ClO₄)_2n (2), have been synthesized by the self-assembly of a copper(II) complex of 2,2′-bipy and a nickel(II) complex of tren with 4,4′-bipy (2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, and tren = tris-(2-aminoethyl)amine). Their X-ray crystal structures show that the metal ions in 1 and 2 display a distorted octahedral coordination geometry to bind two 4,4′-bipy ligands at the cis positions. Each 4,4′-bipy links two [Cu(NO₃)₂(2,2′-bipy)] units in 1 and two [Ni(tren)]²⁺ units in 2 to form 1D zigzag chains. In the structure of 1, these chains are linked by offset π-π interactions through 2,2′-bipy ligands, giving rise to a 2D network. The pyridine rings in the 4,4′-bipy ligand are coplanar in 1 but twisted in 2. The coordination polymer 1 shows a weak antiferromagnetic interaction between copper(II) ions with J = - 0.53 cm^-1 (H = - J∑_i=1^n-1S_AiS_Ai-1).