Optical rotatory power of co-ordination compounds. Part VI. The effects of ion-association on the circular-dichroism spectra of tris-diamine complex metal ions

Abstract

The effects of association in aqueous solution between a variety of anions and a number of tris-diamine complex d³ and d⁶ metal ions have been studied over a range of anion concentrations. It is found that all multiply charged and the majority of singly charged anions diminish and enhance the respective areas of the circular-dichroism bands due to the E_a and the A₂ components of the low-energy octahedral T_1g transition. With a number of the anions studied these trends in band-area changes are reversed at higher anion concentrations, and an interionic charge-transfer absorption and circular-dichroism band is observed. Some singly charged anions, notably hydroxide and the halides, are found to be exceptional and induce circular-dichroism changes different from those produced by the majority of the anions investigated. The factors governing the effects of ion-association on the circular-dichroism spectra of trisdiamine complex metal ions are discussed.