Optical Rotatory Dispersion of Dihedral Metal Complexes

Optical rotatory dispersion of dihedral metal complexes with (3d) n ( n =1, … 9, except for n =5) is studied by means of purely ionic model. Rotational strengths of the first absorption bands are given by considering the second-order asymmetric distortion of the octahedral d -orbitals due to chelation. Taking into account the splitting of the band, dispersion curve is obtained and compared with experiments. Qualitative agreement is obtained for [Crox 3 ]. A physical model is introduced in order to discuss the relation between the geometrical structure and the sign of the optical rotation. With this model, it is shown that for [Coen 3 ], twisting of the ethylenediamine molecules seems to be responsible to the rotatory dispersion. Finally, it is emphasized that molecular orbital treatment is necessary for further quantitative discussions.