A new spodium bond driven coordination polymer constructed from mercury(ii) azide and 1,2-bis(pyridin-2-ylmethylene)hydrazine

In this work we report on a new HgII coordination polymer [Hg2L(N3)4]n (1), which was readily fabricated from a mixture of Hg(CH3COO)2, NaN3 and 1,2-bis(pyridin-2-ylmethylene)hydrazine (L) in MeOH. Complex exhibits a 1D zig-zag polymeric chain, constructed exclusively through the Hg-N covalent bonds. This chain is formed due to bridging organic ligands L, both coordination pockets of which chelate metal ions, as well bridging end-on coordinated azide anions. The coordination sphere of the HgII ions is completed by terminal azide anions, yielding a pentacoordinated geometry. The structure of 1 was found to be extended to a 2D supramolecular polymeric layer due to Hg⋯N spodium bonds, formed between neighbouring 1D zig-zag polymeric chains. Due to the spodium bond, the metal cation now exhibits a hexacoordinated geometry. According to the topological analysis, the 2D supramolecular polymeric layer of 1 discloses a uninodal 3-connected hcb (Shubnikov hexagonal plane net/(6,3)) topology defined by the point symbol of (63). The 2D supramolecular polymeric layer is further stabilized by intermolecular non-covalent C-H⋯N and N-N⋯π2-Py interactions. Adjacent 2D supramolecular polymeric layers are interlinked through π⋯π stacking interactions between the pyridine rings. The diffuse reflectance spectrum of 1 revealed a broad band, accompanied with a shoulder, in the UV region, corresponding to intraligand transitions, and a broad intense band in the visible region, corresponding to metal-to-ligand charge-transfer. In this work we report on a pivotal role of the HgII-derived spodium bond on the crystal packing and its characterization using DFT calculations, the quantum theory of atoms-in-molecules and the non-covalent interaction plot computational tools.