The theory of natural optical activity in the 4frarr;4ftransitions of trigonal dihedral (D3) lanthanide(III) complexes is developed within the framework of a crystal field model. Within this model, both the chiral and achiral components of the crystal field are represented in terms of multipolehyphen;point charge and multipolehyphen;induced dipole lanthanidendash;ligand interactions. Electric dipole intensity within the 4frarr;4ftransitions is presumed to arise from interconfigurational mixing between the 4fN, 4fNminus;1thinsp;5d, and 4fNminus;1thinsp;ngconfigurational states localized on the lanthanide ion, and between the 4fNconfigurational states of the lanthanide ion and dipolar excitations localized in the ligand environment. Expressions are derived for electronic rotatory strengths, dipole strengths, and dissymmetry factors, and special attention is given to how these quantities are related to the electronic and stereochemical properties of the ligand environment and to the electronic structure of the lanthanide ion. A computational model based on the formal theory is proposed, and qualitative predictions regarding a variety of features to be found in 4frarr;4fchiroptical spectra are presented.
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