DNA as a catalyst and catalytic template for the racemisation of metal tris-phenanthroline complexes

[Fe(1,10-phenanthroline)₃]²⁺ is known to racemise in solution and DNA is known to shift the equilibrium point of the Δ/Λ[Fe(1,10-phenanthroline)₃]²⁺ mixture from 50:50 to a position favouring a slight excess of the Δ enantiomer. In this paper it is shown that DNA catalyses the racemisation reaction, presumably by providing vibrational energy to species that bind in a less favoured mode for that enantiomer. The racemisation of [Co(1,10-phenanthroline)₃]³⁺, however, is not enhanced by DNA unless [Co(1,10-phenanthroline)3]²⁺ is also added to the solution. In this case, the DNA acts as a template to facilitate the Co^II ⇄ Co^III electron transfer. Racemisation occurs while the [Co(1,10-phenanthroline)₃]ⁿ⁺ is in the labile Co^II form.