Crystal Field Theory Optical and Magnetic Properties

5 Crystal Field Theory Optical and Magnetic Properties 

FIGURE 8.25 An octahedral field increases the energies of all five d orbitals, but the increase is greater for the and d -/ orbitals. As a result, the orbitals are split into two sets that differ by the energy Aq. The orbital occupancy shown is for (a) the high-spin (small Ao) and (b) the low-spin (large A ) complexes of Mn(lll). 

TABLE 8.5 Electron Configurations and Crystal Field Stabilization Energies for High- and Low-Spin Octahedral Complexes 

FIGURE 8.26 Energy-level structures of the 3d orbitals in square-planar and tetrahedral crystal fields. 

FIGURE 8.27 (a) If a sample of a paramagnetic substance is dipped into a magnetic field, it is drawn down into the field and weighs more than it does in the absence of the field, (b) If a diamagnetic substance is dipped into the field in the same way, it is buoyed up and weighs less than it would in the absence of the field. 

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The analogy between the two theories is only formal. Crystal field theory is a purely electrostatic approach that does not take into consideration the formation of MOs and the nature of the bond. According to crystal field theory, optical and magnetic properties are ascribed to crystal field splitting between two AOs, whereas in ligand field theory energy splitting occurs between AOs, and... 

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