Theoretical Study Of Nmr Coupling System

Study on polymetal coupling interaction system is always the most active and wide field in cooperation chemistry. Many special characters induced by interaction among paramagnetic ions, attracted much attention in the field of physics, chemistry, biology and material science. Nowadays, the research on polynuclear complexes develops rapidly, and many novel complexes have been synthesized. The metal ions in polymetal coupling interaction system depend on electron transfer interaction and harmonized interaction among them and bridged groups and terminal groups, presents chemical reactivity, physical property and biological activity different from mononuclear complexes. As a result, it is important to investigate interaction among paramagnetic ions and magneto-structural correlation in such systems by theoretical chemistry method. In this paper, magnetic coupling behavior of some systems has been performed using the broken symmetry approach with the framework of density functional theory (DFT). Many conclusive are derived as follows:1. The formula of exchange coupling constant under ligand field is given. A DFT based ligand field model for magnetic exchange coupling in homonuclear transition metal dimmer complexes is presented. It is based on a model of localized d-electrons. Firstly, the energy of all microstates (single determinants) were calculated. Secondly, perturbation theory yielded for the magnetic coupling constants. In this formula, magnetic coupling constant isexpressed by Coulomb integrals (J_aa, J_bb and J_ab), exchange integrals (K_ab)and the K-S orbital energy difference (ε(b)-ε(a)). We used singledeterminants to express these parameters. So on a procedure allowing to express its parameters in terms of exchange and Coulomb integrals from DFT calculations of a homonuclear dimmer complex., we gained the expression of the magnetic coupling costants.