Syntheses, Structures And Property Studies Of Coordination Polymers Based On N-heterocyclic Ligands

In this paper, two different N-containing ligands were chosen by us to assemble with metal ions, and as a result eight coordination compounds were obtained. Based on structure analyses and property investigation, the effect of the coordination geometry of metal ions, main ligands and accessorial ligands upon the structures of the resulting metal-organic complexes was studied, and the relative self-assembly principles were also explored. The main results are concluded as the following:1. Complexes of HBtz (benzotriazole). Benzotriazole is a kind of good heterocyclic organic compounds containing N atom. Two new discrete Btz—bridged pentanuclear metal cluster complexes [NH2Me2][NaHg4(Btz)6I4] (Ⅰ1) and [Zn5(Btz)6(L)3(Ac)] (Ⅰ2) (Btz= deprotonated benzotriazole, L=ρ-aminobenzoate and Ac=aceticate) were synthesized. These two complexes use the HBtz as main ligand to self-assemble with Hg(Ⅱ) and Zn(Ⅱ). ComplexⅠ1 belongs to a tetragonal space groupⅠ4. Protonated dimethylamine is not coordinated but acts as a cation. ComplexⅠ2 withρ-aminobenzoate as accessorial ligand belongs to a triclinic space group P1.In both complexes HBtz ligand uses the three N atoms to coordinate with metal ions and acts as aμ3 bridge. In both complexes each apical metal ionb in the distored tetrahedron is bridged by N(1) and N(3), and N(2) atoms from six HBtz are ligated to the central metal ion, and finally, a pentanuclear [M5(HBtz)6] structure unit is formed. ComplexⅠ1 is a hetero-metal cluster whereas complexⅠ2 is a homo-metal cluster. The thermal properties of both complexes have been determined. Meanwhile, the pentanuclear metal cluster complexes both display strong blue fluorescent emission at room temperature.2. Complexes of ligand Hpbc (3-pyride-4-yl-benzoic acid).3-Pyride-4-yl-benzoic acid is a kind of good rigid N-heterocyclic aromatic carboxylic acids. In this paper, we use this ligand to self-assemble with Pb(NO3)2, Cu(NO3)2, Sm(NO3)3, Gd(NO3)3, MnCO3 and Zn(NO3)2, respectively. The resulting six new complexes formulate [Pb(pbc)2]n (Ⅱ1), [Cu(pbc)2]n (Ⅱ2), [Sm(pbc)3(H2O)2]n·nH2O (Ⅱ3) [Gd(pbc)3(H2O)2]n·nH2 (Ⅱ4), Mn(pbc)2(H2O)4 (Ⅱ5) and [Zn(pbc)2(DMF)]n (Ⅱ6). ComplexⅡ1 belongs to monoclinic chiral space group C2. A C2 axis divides the octahedral coordination geometry of metal Pb(Ⅱ). Two Pb(Ⅱ) centers are bridged by ligand Hpbc in aμ2-kO,O':kN coordinated mode and form a two-fold interpenetrated metal-organic 2-D framework of (4,4) topology. ComplexⅡ2 belongs to triclinic space group P1. Two Cu(Ⅱ) centers are bridged by ligand Hpbc in a cis-μ-kO:kN coordinated mode and form a two-fold interpenetrated inorganic-organic 2-D framework of (4,4) topology, being very similar to that ofⅡ1. ComplexⅡ3 andⅡ4 belong to triclinic space group P1, and they are consistency in crystalline form and exhibit similar coordination environment and structure. In these two complexes, carboxyl groups COO- adopt two coordination patterns:bridging and chelating modes. Through the bridging COO-, earth-rare metal ions are linked into a 1-D chain structure. ComplexⅡ5 belongs to a monoclinic space group C2/c. In complexⅡ5, the ligands Hpbc act as terminal ligands to coordinate with metal ions through the nitrogen of pyridine, and the deprotonated carboxyl is not coordinated with metal ions. This mononuclear complex is threaded into a 2-D supermolecule structure by the effects ofπ…πstacking interactions and complicated hydrogen bonds. Complex 116 belongs to a tetragonal chiral space group P41212. The Zn(Ⅱ) centures are bridged by ligands Hpbc and form a 2-D metal-organic framework with (4,4) topology being very similar with the structure ofⅡ1, but there is no interpenetration. The thermal properties of complexesⅡ1,Ⅱ2,Ⅱ3 andⅡ5 have been determined and analysized. Complex 114 displays strong blue fluorescent emission at room temperature. The electrochemical properties of complexesⅡI,Ⅱ4 andⅡ5 were investigated too.