Structural Diversity of Mercury(II) Halide Complexes Containing Bis-pyridyl-bis-amide with Bulky and Angular Backbones: Ligand Effect and Metal Sensing.

Hg(II) halide complexes [HgCl] 2 [ = -bis(3-pyridyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diamide), , [HgBr()], , [HgI()], , [HgX()] [X = Cl, , Br, , and I, ; = -bis(4-pyridylmethyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diamide] and {[HgX()]⋅HO} [X = Cl, , Br, and I, ; = 4,4'-oxybis(N-(pyridine-3-yl)benzamide)] are reported and structurally characterized using single-crystal X-ray diffraction analyses. The linear HgCl units of complex are interlinked by the ligands through Hg---N and Hg---O interactions, resulting in 1D supramolecular chains. Complex shows 1D zigzag chains interlinked through the Br---Br interactions to form 1D looped supramolecular chains, while the mononuclear [HgI] molecules of are interlinked through Hg---O and I---I interactions, forming 2D supramolecular layers. Complexes - are isomorphous dinuclear metallocycles, and - form isomorphous 1D zigzag chains. The roles of the ligand type and the halide anion in determining the structural diversity of - is discussed and the luminescent properties of - evaluated. Complexes - manifest stability in aqueous environments. Moreover, complexes and show good sensing towards Fe ions with low detection limits and good reusability up to five cycles, revealing that the Hg-X---Fe (X = Cl and Br) interaction may have an important role in determining the quenching effect of and .