Syntheses, Structures And Properties Of Low-dimensional Pseudohalide-carboxylate Coordinated Polymers With Innersalt Coligands

The design and preparation of magnetic coordination polymers has attracted increasing attention by reason of the desire of obtaining novel supermolecular architectures and their importance in understanding the mechanism of magnetic interactions and the magneto-structural correlation. The pseudohalides ion azide is one of the most extensively studied bridge on account of its abilities in bridging metal ions in various modes and effectively propagating magnetic exchange of different nature. Carboxylates are also used as bridging ligands between divalent transition metal ions.Both of these two bridges have obvious influence on the magnetic properties.Carboxylates in combination with the use of azido bridging ligands in constructing coordination polymer may be a good approach to get new magnetic materials.In this thesis, we selected transition metal ions as spin carriers, pseudohalides ions such as azide ions as bridging ligands transmitting magnetic exchange and inner-salt-type ligands as co-ligands to synthesize magnetic coordination polymers. A series of1D complexes have been synthesized and characterized by single crystal X-ray analysis, IR, elemental analyses, and some of them have also been characterized by variable-temperature and variable-field magnetic measurements.The main points are as follows:1. Synthesis and analysis of inner-salt-type ligands.We synthesize five inner-salt-type ligands pyridinio-N-acetate(L1),3-methylpyridinio-N-acetate(L2),4-methylpyridinio-N-acetate(L3),3-aminopyridinio-N-acetate(L4) and N-benzylisonicotinate (L5).2. Synthesis and analysis of MnⅡ,ConⅡ,NiⅡCoordination compounds with azide-carboxylate mixed bridges.We get eleven complexes (compounds1-11) with azido ions in combination with inner-salt-type ligands, analyzing all the structures and researching magnetic properties of some complexes.(a) The complexlcontains Mn(Ⅱ) chains with mixed azide and carboxylate bridges between adjacent Mn(II) ions. There are two kinds of Mn(Ⅱ) ions in the structure, both assuming octahedral coordination. One is coordinate to two azides, two carboxylates and two waters, the other is coordinate to four azides and two carboxylates.(b) Complexes2-11are isomorphous. All of these Mn(Ⅱ), Co(Ⅱ) and Ni(Ⅱ) coordination polymers are consist of double end-on azido and single syn-syn carboxylato mix-brigdedchains, and most of them have weak hydrogen bonds.(c) Magnetic studies of some complexes indicated that such mixed triple bridges transmit ferromagnetic coupling between Mn(Ⅱ) ions and antiferromagnetic coupling between Co(Ⅱ) or Ni(Ⅱ) ions. Especially, complex6is a metamagnet.3. Synthesis and analysis of mixed coordinate Coordination compounds with thiocyanate and carboxylate.Complexes12and13are thiocyanate and carboxylate mixed-coordinated compounds, both are zero dimensional structures. There are hydrogen bonds between mononuclear units, forming teo dimensional structures. Such structures demonstrate that thiocyanate is hard to form bridge between metal ions.