Stereoselectivity in the complex formation of histidine with cobalt(II) and nickel(II)

The stability constants of Co(II)‐ and Ni(II) complexes of L‐histidine and racemic histidine in aqueous solution have been measured. The observed difference between the stability of MDL and ML2 complexes shows a preference for the formation of the MDL molecule. The excess Gibbs energy of ½(MD2 + ML2) relative to MDL is found as 0.31 kcal/mole fir the Co(II) complex and as 0.49 kcal/mole for the Ni(II) complex.