Anion-controlled structural motif in one-dimensional coordination networks via cooperative weak noncovalent interactions

The self-assembly of an exoditopic N-donor ligand (3-py-3-py) with HgX2 (X = Cl, Br, I) was investigated. X-ray structure analysis shows that all the compounds have an infinite one-dimensional structure and the Hg(II) ions are in a distorted trigonal pyramidal N2HgX2 geometry. Our results indicate that the coordinated anion can control the structural motif of the resulting one-dimensional coordination polymers through cooperative weak noncovalent interactions. In the case of [Hg-2(mu-3-py-3-py)(2)Cl-4](n) (1) and [Hg-2(mu-3-py-3-py)(2)Br-4](n) (2), the 1D zigzag chains are constructed as a consequence of cooperative noncovalent interactions, such as hydrogen bonds, halogen center dot center dot center dot pi and pi-pi interactions. However, for [Hg(mu-3-py-3-py)I-2](n) (3), the coordinated iodide ion tunes the folding of the 1D structure into a helical array by bifurcated C-H center dot center dot center dot I-Hg hydrogen bonds and pi-pi interactions in a cooperative manner.