Synthsis,Structure And Magnetic Propertites Of Metal Coordination Complexes Molecular Magnet

The design of molecule-based magnetic materials has been of considerable interest in recent years. In this field, coordination complexes with metal and organic ligands have received intense attention and studies, due to the versatility of the metal coordination complexes in strucrure and the versatility of the complexes in magnetic behavior. In this thesis some metal coordination complexes were obtained by self-assembly method of supermolecular chemistry which have different structure and different magnetic behavior. The impact of bridging conformations in different organic ligands on structure and magnetism has been investigated while the magnetostructural correlation in these complexes has been discussed. Moreover, a molecular magnet with 3D magnetic order state was synthesized and the abilities of a new organic ligand to construct the spin-canting weak-ferromagnet was also discussed. The main results in this thesis are as following:1. The Cu(â…¡)-EDTA and Mn(â…¡)-EDTA coordination complexes were synthesized and their structures, thermal stabilites and magnetic properties were characterized thoroughly. They are mono and tri metal centre 3D networks built through hydrogen bonds and showing antiferromagnetic coupling interactions. The magnetic data were fitted through the correspondent theoretical model and equations and obtained the value of magnetic coupling constant. The structure and magnetostructural correlations about EDTA ligand were discussed.2. The Coâ…¡,Mnâ…¡,Cuâ…¡coordination complexes bridged by fumarate ligand were synthesized and their structures and magnetic properties were characterized thoroughly. They are 1D infinite chainlike structure or dimmer structure using fumarate ligand as bridge spacer indicating antiferromagnetic coupling interactions. The impact of bridging conformations in fumarate ligands on structure and magnetism has been investigated.3. A syn-anti triatomic carboxylate-bridged chain-like Cuâ…¡complex was synthesized and magnetic properties were investigated experimentally and theoretically which show the weak ferromagnetic intrachain interaction. The magnetic data had been analyzed and interpreted in terms of Heisenberg chain model corrected by a mean molecular field. Density functional theroy (DFT) with generalized gradient approximation (GGA) was applied to calculate the electronic structure and spin distribution of the present complex. The structural and electronic factors controlling the magnetic interactions was also determined:4.Two hydrated tetra-carboxylato-bridged dinuclear Cuâ…¡coordination complex with 1,2-benzenedicarboxylate monoester ligand has been prepared and characterized by means of X-ray analysis and magnetic measurements. Both complexes adopt dimeric paddle-wheel cage structures. The magnetic data exhibited strong intramolecular antiferromagnetic interaction between the two paramagnetic metal ions. The structural and magnetic results are compared with those for other related dimmers.5. The lanthanide metal Gdâ…¢coordination complexes with dicyamide or carboxyl ate ligand were prepared and their structures were characterized thoroughly. The magnetic measurement of Gd-dca complex exhibited antiferromagnetic coupling interactions. The magnetic interactions between 4f metal Gd centre was discussed comparing to the transition metal centres.6.A new organic ligand containing two triazole rings was prepared and the single crystal structure was first obtained and discussed thoroughly. Hydrothermal treatment of Mnâ…¡ions and btr ligands provided an infrequent 3D binary manganese coordination complex. Detailed magnetic measurement exhibited the occurence of spin canting and spontaneous magnetic order at low temperature as a weak ferromagnet.