Crystal circular dichroism and spin-forbidden optical activity of tris-(diamine)cobalt(III) complexes

Abstract

The axial crystal circular dichroism spectrum of 2{Λ(+)[Co(en)₃]Cl₃}·NaCl·6H₂O (en = ethylenediamine) at liquid-nitrogen and ambient temperature has been measured. together with the corresponding aqueous-solution spectrum and those of Λ(+)[Co{(S)(pn)}₃]³⁺ and Λ(–)[Co(pd)₃]³⁺. over the range 500–1 000 nm (pn = propylenediamine and pd = propane-1,3-diamine). The optical activity associated with the spin-forbidden transitions to the ³T₁ and ³T₂: octahedral states has distinctive features which are accounted for satisfactorily by spin–orbit coupling between these states and, principally, the corresponding ¹T₁ state.