Syntheses, Structures And Properties Of Coordination Polymers And Coordination Supermolecule With Azacyclic Ligands

Crystal engineering and magnetic properties of coordination polymers have attracted much attention in recent years. In this thesis, we report the syntheses of 19 transition metal coordination compounds with some ligands containing different azacyclic groups. The compounds have been characterized by means of elemental analyses, IR spectra and single-crystal X-ray analyses. The magnetic studies on relevant compounds have also been performed. The main points are as follows:1. Eight coordination compounds with bis(5-tetrazolyl)amine have been synthesized by reacting the ligand with metal ions directly or via the in situ [2+3] cycloaddition reaction of azide and nitrile in the presence of appropriate metal ions under the hydrothermal conditions. These compounds exhibit diverse structures, ranging from discrete mononuclear complexes, co-crystallized binuclear molecules and one-dimensional chains with different tetrazole bridging modes, to two-dimensional coordination polymers. Most intriguing are the 2D compounds built from [M₃(μ₃-X)(μ₂-N-N)₃] (M = Mn, Cd; X = F, OH) triangular clusters. They are the first [M₃(μ₃-X)] compounds with tetrazolate ligands, and the [Mn₃^â…¡(μ₃-F)] structural motif is also unprecedented, whatever the coligands are. More importantly, the 2D layer constructed from the triangular clusters and mononuclear metal centers represents a novel type of geometric frustrated magnetic lattice. Magnetic studies on the Mn-F compound indicated that it indeed exhibits spin frustration and behaves as a low-temperature antiferromagnet.2. Nine new mononuclear and 1D compounds with rigid 1-(4'-pyrimidine)-2-(3'-pyridine) and 1-(3'-pyridazine)-2-(3'-pyridine) as ligands were synthesized, and structurally characterized. The most interesting aspects are the supramolecular assembly of the mononuclear complexes, which is directed by the hydrogen bonds formed between the uncoordinated pyrimidine nitrogen atoms and the coordinated/uncoordinated water molecules. While all the pyrimidine nitrogen atoms form hydrogen bonds with the coordinated water molecules, thecomplex molecules are assembled into extended two-dimensional hydrogen-bonded layers. Otherwise, one-dimensional hydrogen-bond tapes are formed, in which half of the pyrimidine nitrogen atoms form hydrogen bonds with lattice water molecules.3. The azido ion as a bridge has been an intriguing synthetic approach to molecular-based magnetic materials, due to their remarkable diversities in structural and magnetic behaviors. Two transition metal complexes with azide have been synthesized and characterized by single-crystal X-ray diffraction. The Cu(II) complex is binuclear with double end-on (EO) azido bridges and magnetic studies on the Cu(II) complex have revealed intramolecular ferromagnetic coupling.