Ligand field theory description

For transition metal complexes, techniques derived from a crystal-field theory or ligand-field theory description of the molecules have been created. These tend to be more often qualitative than quantitative. 

CF (ligand field) theory was one of the first theoretical tools employed for rationalization of experimental data for lanthanide compounds. There are two different CF approaches employed for the description of lanthanide complexes (i)... 

In this description the quantity AKt or 10Z)t (oct) of CFT is identified with the tlgn e MO separation. This is the basis of the ligand field theory (LFT) concept. 

Useful theory for the description of the properties of transition metal complexes and compounds has been developed in depth in a number of monographs (some classical ones are referenced here see Ligand Field Theory Spectra) Therefore, only a brief outline of theoretical developments will be presented along with some valuable results for the interpretation of magnetic data. 

In the case of optical processes involving electronic states which participate in the chemical bonding, the nature of the bonding (covalent, ionic) and the symmetry of the site at which the emitting ion is incorporated play a very important role. This is generally described by ligand field theory, which is not treated here. However, the term symbols for the description of the electronic transitions will be used. 

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