The compounds of general form Δ,Λ-[Ru(diimine)2(L-ser)]ClO4·nH2O where L-ser is the L-serinate anion, diimine is 1,10-phenanthroline and 2,2′-bipyridyl, and n = 1.0 and 0.5 respectively, have been isolated and the complex ions resolved using cation exchange chromatography. The Λ-isomer of the bipy complex and the Δ-isomer of the phen complex spontaneously invert in aqueous solution in the presence of light. The equilibrium constants for the reaction Δ-[Ru(diimine)2(L-ser)]+(aq) ⇌ Λ-[Ru(diimine)2(L-ser)]+(aq) are 1.28(3) and 0.71(5) at 298.2 K for the phen and bipy complex cations respectively. The apparently anomalous behaviour of the bipy complex compared with other related systems indicates that steric factors are not always the most important contributors to chiral discriminations in this class of complexes.