One-dimensional coordination polymers generated from a new triazole bridging ligand and HgX₂ (X = Cl, Br and I): characterization and luminescent properties

The new 4-amino-1,2,4-triazole asymmetric bridging ligand 4-amino-5-(pyridin-3-yl)-3-[4-(pyridin-4-yl)phen­yl]-4H-1,2,4-triazole (L) has been used to generate three novel isomorphic one-dimensional coordination polymers, viz. catena-poly[[tris­[dichloridomercury(II)]-bis­{[mu]₃-4-amino-5-(pyridin-3-yl)-3-[4-(pyridin-4-yl)phen­yl]-4H-1,2,4-triazole}] aceto­nitrile monosolvate], {[Hg₃Cl₆(C₁₈H₁₄N₆)₂]·CH₃CN}_n, (I), and the bromido, {[Hg₃Br₆(C₁₈H₁₄N₆)₂]·CH₃CN}_n, (II), and iodido, {[Hg₃I₆(C₁₈H₁₄N₆)₂]·CH₃CN}_n, (III), analogs. The asymmetric ligand acts as a tridentate ligand to coordinate the three different Hg^II centers (two of which are symmetry-related). Two ligands and two symmetry-related Hg^II centers form centrosymmetric rectangular units which are linked into one-dimensional chains via the other unique Hg atoms, which sit on mirror planes. The chains are elaborated into a three-dimensional structure via inter­chain hydrogen bonds. The acetonitrile solvent mol­ecules are located in ellipsoidal cavities. The luminescent character of these three coordination complexes was investigated in the solid state.