The Nature Of Intermolecular Forces And Their Magnetic Coupling

For more than three decades the study on the magnetism of molecule-based compounds has been one of advanced disciplines in area of materials science and it has mainly centred on the correlation factors between magnetic coupling properties and its relevant structures for those magnetic compounds, in which relevant spin-carriers were bridged by sole atoms or molecule, namely, the spin-carriers were connected by chemical bonds or the magnetic exchanges are through chemical bonds. Beside chemical bond the intermolecular force, such asÏ€-Ï€stacking and hydrogen bond, also play key role in magnetic interaction, but papers deal with the magnetic coupling through intermolecular force are very limited. This dissertation aims to search for some factors that dominate magnetic coupling properties and to correlate molecular force and its magnetic coupling properties. Based on this aspiration or aim three novel Cu(II) complexes were synthesized, which include the binuclear complex [Cu₂(μ₂-Br)₂(PP)₂(OClO₃)₂] (PP =2-(1H-pyrazol-1-yl)-1,10-phenanthroline) (1),the mono-nuclear complex [Cu(PP)(ONO₂)₂)] (2) and mono-nuclear complex [Cu(PhenOH)Cl(OH)] (PhenOH = 2-hydroxyl-1,10-phenanthroline) (3). The infrared spectra characterization was made on the three complexes and their crystal structures determined by X-ray diffraction. The variable-temperature (2-300 K) magnetic susceptibility measurement for complex (2) and complex (3) were performed and the fitting on the obtained magnetic data were made and the some experimental magnetic coupling properties were obtained. In order to understand the correlation between the molecular forces and the relevant magnetic coupling properties, the theoretical calculations were performed. The calculations gave the information involving the spin density, the magnetic coupling sign and the magnetic coupling magnitude of the relevant magnetic coupling pathways. From the information the correlation between the magnetic coupling properties and the relevant structural factors was performed and the some interesting results are obtained. This dissertation also involves the study on the magnetic coupling properties of other four complexes, in which their crystal structures have been reported, but no magnetic coupling information has been known, and the four complexes include mono-nuclear Mn(II) complex [Mn(L₁)(NCS)₂] (4) (L1= 2-(3,5-dimethyl-1H-pyrazol-1-yl)-1,10-phenanthroline), mono-nuclear Cu(II) complex [Cu(L₂)Br]ClO₄ (L₂ =2,9-bis(pyridin-2-methoxyl)-1,10-phenanthroline ) (5), Mono-nuclear Cu(II) complex [Cu(L3)(OSO₃)(H₂O)]H₂O (L₃ =2,2'-(1,10-Phenanthrolin-2-ylimino)- diethanol) (6) and mono-nuclear Cu(II) complex [Cu(L₁)(L₄)Br](ClO₄)(H₂O) (L₄ =3,5-dimethyl-1H-pyrazole ) (7). The study deals with experimental and theoretical calculations and the very interesting information has been obtained. The obtained general information from the seven complexes is as follows.1. The intermolecular force can result in magnetic coupling2. There occur the spin delocalization on the Cu(II) and Mn(II) 3d orbitals to the relevant coordinated atoms in the studies systems.3. There are both spin delocalization and spin polarization in the studied systems.4. McConnell I spin polarization mechanism does not explain magnetic coupling sign for all magnetic coupling system dealing with intermolecular force magnetic coupling pathways.The obtained information in this dissertation may benefit to understand the magnetic coupling mechanism arisen from molecular force and it may also benefit to design and synthesize ideal molecule-based ferromagnet, especially for those ferromagnet based on complexes and intermolecular force.