Metal-organic coordination architectures of bis(1,2,4-triazole) ligands bearing different spacers: syntheses, structures and luminescent properties

In our continuous efforts to explore the effects of metal ions, ligands and counter anions on the structures and properties of metal-organic complexes, six transitional metal complexes with two structurally related ligands, 1,4-bis(1,2,4-triazol-1-ylmethyl)naphthalene (L-1) and 4,4'-bis(1,2,4-triazol-1-ylmethyl)biphenyl (L-2), [Cd(L-1)(2)(NO3)(2)(H2O)](infinity) (1), [Hg(L-1)(0.5)(Br)(2)] (2), {[Mn(L-1)(2)Cl-2](H2O)(8)}(infinity) (3), {[Cu(L-1)(2)Cl-2](H2O)(8)}(infinity) (4), {[Cd(L-2)(2)(CH3OH)(2)(NO3)(2)](H2O)}(infinity) (5) and [Cd(L-2)(3)(CH3OH)(2)(ClO4)(2)(CHCl3)](infinity) 6), were synthesized and structurally characterized. 1 has an infinite two-dimensional (2D) network structure and the 2D network further assembled into a 3D interpenetrating structure, 2 is a dinuclear structural molecule, 3 and 4 are neutral molecules with 1D chain structures and the same packing modes, and 5 and 6 have a similar structure, consisting of a 1D neutral coordination chain, but the coordination geometry around the Cd-II ion in 6 is different from that in 5. The results indicated that the structural differences among them are attributable to the difference of metal ions, counter-anions and ligands frameworks. All the complexes are air stable at room temperature. L-1 and L-2 adopt trans-gauche as well as gauche-gauche conformation with the shortest N center dot center dot center dot N distance between the two donors in all complexes. Furthermore, the fluorescent properties of complexes 1, 5, 6 and all ligands have been investigated and discussed.