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.