Hydrothermal synthesis and characterization of a series of luminescent Zn(ii) and Cd(ii) coordination polymers with the new versatile multidentate ligand 1,3-di-(1,2,4-triazol-4-yl)benzene

Abstract

Used a newly designed multidentate benzene-based bis-triazole ligand 1,3-di-(1,2,4-triazol-4-yl)benzene (L), a series of luminescent Zn(II) and Cd(II) coordination polymers, namely, {[Zn(μ2-L)2(H2O)2]·(SiF6)·H2O}n (1), {[Cd(μ2-L)2(H2O)2]·(SiF6)·2H2O}n (2), {[Zn(μ2-L)Br2]·H2O}n (3), {[Cd(μ2-L)2(NCS)2]·2H2O}n (4), {[Cd(μ2-L)(μ4-L)](BF4)2}n (5), {[Cd(μ2-L)(μ4-L)](ClO4)2}n (6) and {[Cd3(μ3-L)6](NO3)6}n (7) have been isolated under hydrothermal conditions. Both 1 and 2 present 1D double chain structures, which contain two kinds of different supramolecular channels. For 3, zinc(II) ions are linked by L ligands and arranged into infinite right- or left-handed helical chains. 4 presents a 2D framework in which 1D right-handed and left-handed helical structures are interlinked via Cd(II) centers as hinges. 5 and 6 respectively contain μ2- and μ4-L ligands in triazole–metal complexes. These μ4-L ligands link neighboring Cd(II) centers forming a 2D network containing infinite {Cd-(trz)2-Cd}n chains, which is quite different from the 2D arrangement in 4. 7 presents a novel 3D porous MOF (porous metal–organic framework) containing triangular nano-porous channels with edges of 13.622 A, in which free NO3− anions are located. Anion exchange experiments based on 7 also indicate that NO3− anions are able to be exchanged with ClO4− anions in the solid state. Both the dihedral angles (between two triazole rings or between triazole and aromatic benzene rings) for L are flexible and ultimately tune the coordination geometries in constructing various different coordination polymers. For 1–7 the comparison between powder X-ray diffraction (PXRD) and a simulated analysis from crystal data confirmed the pure crystal phases. Solid-state luminescent properties and thermal stabilities of 1–7 also have been determined.