Syntheses, Structures And Magnetic Properties Of Carboxylate-Azide-Bridged Coordination Polymers With Dicarboxylate Coligands

The design and preparation of polynuclear complexes (especially, clusters of high nuclearity and coordination polymers) has attracted more and more attention due to the desire of obtaining novel supermolecular architectures and their importance in understanding the mechanism of magnetic interaction and the magneto-structural correlation. The pseudohalides ion such as azide is the most extensively studied bridge owing to its abilities in bridging metal ions in various modes, effectively propagating magnetic exchange of different nature. Dicarboxylates are used as bridging ligands between divalent transition metal ions, in combination with the use of azido bridging ligands. But the rather limited number species with simultaneous azido-carboxylate mixed bridges have been described. These two kinds of bridges have different influence on the magnetic properties.In this thesis, we selected transition metal ions as spin carriers, inorganic small molecules such as azide ions as transmitting magnetic exchange bridging ligands and inner-salt-type ligands as coligands to synthesize magnetic complexes. The ligands used are 1,2-bis(3-carboxylato-l-pyridinium-)ethane(L1),1,3-bis(3-carboxylato-l-pyridinium-)propane (L2),1,4-bis(3-carboxylato-1-pyridinium-)butane(L3),1,5-bis(3-carboxylato-1-pyridinium-)pen tane(L4). A series of complexes with zero, two and three dimensional structures 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. Coordination compounds with 1,2-bis(3-carboxylato-l-pyridinium-)ethane (L1) as co-ligands. (a) Two isomorphous mononuclear Co(Ⅱ),Ni(Ⅱ) complexes have been obtained in which the six coordination sites are occupied by four oxygens atoms from four water molecules and two nitrogen atoms from two azide anions, and the co-ligands L1 is not coordinated. There are a lot of intermolecular O—H…O hydrogen bonds involving the carboxylate groups and water molecules. These hydrogen bonds lead to a complicated three-dimensional architecture. (b) A novel 3D Cu(Ⅱ) coordination polymer has been obtained, in which Cu(Ⅱ) ions are connected to give rise to a 2D metal-azido layer by azido bridges and syn-syn carboxylate bridges and the layers are further linked to be a 3D network by co-ligands.2. Coordination polymers with 1,3-bis(3-carboxylato-1-pyridinium-)propane (L2) as co-ligands. (a) The compound contains uniform Mn(Ⅱ) chains with simultaneous azide and carboxylate bridges between adjacent Mn(Ⅱ) ions. The formally negative chains are interlinked by the positively charged 1,3-bis(pyridinium)propane spacer, and the spiral conformation of the spacer imports intriguing helica features to the resulting 2D network, (b) Two isomorphous Co(Ⅱ) and Ni(Ⅱ) coordination polymers have been obtained, which consist of double end-on azido and single syn-syn carboxylato mix-brigded M-N3/COO chains that are further linked by the L2 to give rise to 2D layered structure. (c) A Cu(Ⅱ) coordination polymers have been obtained, in which Cu(Ⅱ) ions are linked by azide bridges andμ2-COO bridges give rise to 2D layered structure. The layers are further linked by the L2 to result in 3D network.3. Coordination polymers with 1,4-bis(3-carboxylato-l-pyridinium-)butane (L3) as co-ligands. (a) Two Mn(Ⅱ) coordination polymers have been obtained, in which one is mononuclear Mn(Ⅱ) complexe has been obtained in which the six coordination sites are occupied by four oxygens atoms from four water molecules and two nitrogen atoms from azide. There is a lot of hydrogen bonds due to the existence of more water molecules and 3D pillared-layer network can been built by hydrogen bonds. The other Mn(Ⅱ) coordination polymer has been obtained, which contains uniform Mn(Ⅱ) chains with simultaneous azide and carboxylate bridges between adjacent Mn(Ⅱ) ions. The formally negative chains are interlinked by the positivelycharged 1,4-bis(pyridinium)butane spacer, and the spiral conformation of the spacer imports intriguing helica features to the resulting 2D network. (b) Two Ni(Ⅱ),Co(Ⅱ) 2D coordination polymers which are isomorphous have been synthesized and characterized. In the 1D Co-N3/COO chain, adjacent metal ions are linked by double N,N-end-on azide bridge and single syn-syn carboxylato bridges and each chain is linked by L3ligands to produce a 2D network. (c) A novel 3D Cu(Ⅱ) coordination polymer has been obtained, in which Cu(Ⅱ) ions are connected byμ2-1,1-N3,μ2-1,3-N3 andμ2-COO bridges to give rise to a 2D metal-azido layer and the layers are further linked to be a 3D network。4. Coordination polymers with 1,5-bis(3-carboxylato-l-pyridinium-) pentane (L4) as co-ligands. Two isomorphous Co(Ⅱ),Ni(Ⅱ) 2D coordination polymers have been synthesized and characterized. In the 1D Co-N3/COO chain, adjacent metal ions are linked by two N,N-end-on azide bridge and one syn-syn carboxylato bridges and each chain is linked by L4 ligands to produce a 2D network.