Syntheses, structures, and photoluminescence properties of metal(II) halide complexes with pyridine-containing flexible tripodal ligands

Seven coordination compounds, [Zn(L-3)Cl-2]center dot MeOH center dot H2O (1), [Mn(L-3)(2)Cl-2]center dot 0.5EtOH center dot 0.5H(2)O (2), [Cu-3(L-2)(2)Cl-6]center dot 2DMF (3), [Cu-3(L-2)(2)Br-6]center dot 4MeOH (4), [Hg-2(L-4)Cl-4] (5), [Hg-2(L-4)Br-4] (6), and [Hg-3(L-4)(2)I-6], H2O (7), were synthesized by the reactions of ligands 1,3,5-tris(3-pyridylmethoxyl) benzene (L3), 1,3,5-tris(2-pyridylmethoxyl) benzene (L-2), and 1,3,5-tris(4-pyridylmethoxyl) benzene (L-4) with the corresponding metal halides. All the structures were established by single-crystal X-ray diffraction analysis. In complexes 1 and 2, L3 acts as a bidentate ligand using two of three pyridyl arms to link two metal atoms to result in two different 1D chain structures. In complexes 3 and 4, each L2 serves as tridentate ligand and connects three Cu(II) atoms to form a 2D network structure. Complexes 5 and 6 have the same framework structure, and L4 acts as a three-connecting ligand to connect Hg(II) atoms to generate a 3D 4-fold interpenetrated framework, while the structure of complex 7 is an infinite 1D chain. The results indicate that the flexible ligands can adopt different conformations and thus can form complexes with varied structures. In addition, the coordination geometry of the metal atom and the species of the halide were found to have great impact on the structure of the complexes. The photoluminescence properties of the complexes were investigated, and the Zn(II), Mn(II) and Hg(II) complexes showed blue emissions in solid state at room temperature.