The ferromagnetic coupling behavior in oxo-bridged bis (bis(cyclopentadienyl) titanium (III)) complex (Cp2Ti)2-(Ì-O) is investigated on the basis of calculations of density functional theory combined with the brokensymmetry approach. The magnetic coupling constants calculated for the experimental and optimized geometries are 11.41 and 1.29cm-1, respectively, comparable with the experimentally measured J value (8.3 cm-1). The calculated results show that the magnetic coupling constant J slightly decreases with the increase of the Ti-(Ì-O)-Ti angle and decreases exponentially with the increase of the Ti-(Ì-O) distance. In variation of the dihedral angle‚ between the two Cp2Ti fragments the transition of the magnetic coupling property occurs near B=45°ForB>45°, the coupling is ferromagnetic, and it is antiferromagnetic forB<45°. The ferromagnetic coupling interaction between the magnetic centers is almost not affected by the protonation of the oxo-bridge ligand. Molecular orbital analysis reveals that, because of the nonbonding character and electronic location character of the single-occupied molecular orbitals (SOMO), there is no antiferromagnetic coupling pathway through superexchange via the bridging atom. However, when‚ varies from 90° to 0°, the throughspace interaction between the two magnetic centers in the SOMOs occurs, leading to a gradually increscent antiferromagnetic contribution, JAF. As soon as the antiferromagnetic contribution exceeds the ferromagnetic contribution, JF, the transition of the magnetic coupling properties for the molecule occurs. The spin population analysis is briefly discussed.

A useful parameter describing magnetic coupling interactions has been inspected in transition metal dimers, in which two transition metal ions are bridged by extended bis-bidentate ligands. This parameter is the square of overlap integral between the spatial parts of magnetic orbitals in the broken symmetry state. The oxalato-bridged Cu (II) dimers, in which the Cu (II) atom is either in tetrahedral or square pyramid coordination environment, have been calculated with the density functional theory coupling the broken symmetry approach.

The long disputed mechanism for the F2 addition to ethene is elucidated by density functional theory calculations. With hybrid functionals and a large basis set, DFT provides an excellent description for the dissociation of ground state F2, and a reasonable account for the F2

The magnetic exchange behaviour for l-hydroxo and l-acetato double-bridged chromium (III) dimer is investigated based on calculations of density functional theory combined with the broken-symmetry approach. It is demonstrated that there is a magnetic exchange cooperative effect of the two bridging ligands in a double-bridged dimer systems with approximate equal coupling intensity. Meanwhile, the calculated results reveal that the deprotonation of the l-hydroxo ligand causes a sharp increase of the magnetic exchange interaction between the chromium centers. Replacing either the l-hydroxo bridging ligand by one water bridging ligand or the l-acetato bridging ligands by two terminal water ligands produces a relatively reasonable model to examine the contribution on the magnetic exchange interaction of another individual bridging ligand.

The influence of the structural parameters of Cu2CO2 core on magnetic coupling is studied in model alkoxo-bridged Cu (II) dimers using the density functional method and the broken symmetry approach. The effect of the hinge distortion of the bridge and the out-of-plane displacement of alkoxo group is also analyzed. A small Cu