Halide-directed Assembly of Mercury(II) Coordination Polymers for Electrochemical Biosensing Toward Penicillin

Three 1D/2D Hg^II coordination polymers (CPs), namely {Hg₃(L)₂Cl₆](H₂O)}_n ( 1 ), Hg(L)Br₂]_n ( 2 ), and Hg(L)I₂]_n ( 3 ) were prepared by assembly of 3,4-bis(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (L) with different inorganic Hg^II salts (i.e. HgCl₂, HgBr₂ or HgI₂). Single-crystal X-ray diffraction analysis reveals two types of bimetallic subunits (Hg)₂C₆N₄] and (Hg)₂C₁₂N₆] in CP 1 , which are further extended to a 2D coordination network. Both of CPs 2 and 3 show 1D zigzag arrays bridged by L ligands. Notably, the L ligands take the (η⁴, μ₄) coordination fashion in 1 but (η², μ₂) binding mode in 2 and 3 . The structural differences of CPs 1 – 3 indicate that the L ligand can adjust its coordination fashions to meet the requirements of Hg^II centers, relying on the presence of distinct halide anions. In addition, 1 can be applied to fabricate an electrochemical biosensor for the detection of penicillin.