Synthesis And Characterization Of Coordination Complexes With C₃-Symmetric Nitrogen-Containing Heterocyclic Ligands

In recent decades, investigations about functional coordination compounds aredramatically expanding. The ligands with C₃-symmetry have aroused the greatestconcern not only because of their intriguing architectures and topologies, but also due totheir potential applications in fluorescence, nonlinear optics, magnetism, catalysis,semiconductor, molecular recognition, selective guest inclusion, ion exchange and so on.It is noted that much attention has been paid to the coordination polymers that areassembled by C₃-Symmetric nitrogen-containing heterocyclic ligands. However, fewreports deal with the influence of solvent andmetal ions on the assembly system, thoughthis is potentially an important approach for controlling the supramolecular structures.In this thesis, we deliberately chose two C₃-symmetric nitrogen-containing heterocyclicligands, titmb and tptmb (titmb=1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene; tptmb=1,3,5-tris(pyrazol-1-ylmethyl)-2,4,6-trimethylbenzene) and reacted them with Group IB and IIB metalsalt. Finally, a series of coordination polymers were obtained. Based on the structuralcharacters of the corresponding complexes, we investigated their properties and solventeffect. These results were briefly described as follows:1. In the presence of hydrochloric acid, the polyimidazole ligand titmb has beenused to react with CdSO₄·8/3H2O in different solvents (water, methanol and ethanol)and isolated three coordination compounds [Cd₅Cl₈(SO₄)₂(μ-OH₂)₂(Htitmb)₂]_n(1),[Cd₂Cl₂(SO₄)(μ-MeOH)(titmb)]_n(2) and [Cd₄Cl₄(SO₄)₂(titmb)](3). Herein, we reporttheir synthesis, crystal structures and thermal properties. The study indicated that theself-assembly procedures and the structures of the resulted complexes withC₃-symmetric nitrogen-containing heterocyclic ligands are influenced by many factorssuch as the geometric requirement of the metal ions, the ratio of ligands to metal ions, and solvent system.2. Then we undertake the further studies with another flexible C₃-symmetricnitrogen-containing heterocyclic ligand. The hydrothermal reactions and solutiondiffusion reactions between metal salts and tptmb gave rise to five coordinationpolymers:[Cu(μ-I)₂(tptmb)]_n(4)ï¼›[Cu(μ-Br)₂(tptmb)]_n(5)ï¼›[CdI₂(tptmb)]_n(6);[Hg₂(μ-I)₂I₂(tptmb)]_n(7);[Ag(tptmb)₂(ClO₄)]_n(8) Compound4and5have the samecrystal structure, which have been bridged by the [Cu(μ-I)₂] unit to form the2Dnetwork. The results attest that the flexible ligand tptmb can adopt differentconformations and act as tridentate connector to form complexes with differentstuctures. Here we report the preparation, crystal structures of1D,2D or3Dsupramolecular frameworks. Due to the different metal ion salts, coordinationconformation and rotation angles of three arms of ligands, the final strucutures of5-8varied from1D zigard chain to3D polymer. The results indicated that the metal ionsplay an important role in constructing the final structures.