Chiral Diaminodiamide Copper(II) Complexes for the Enantioselective Recognition of Amino Acids: Synthesis of the Ligands and Formation Constants

Abstract

Abstract(S,S)‐N,N′ ‐Bis(aminoacyl)ethane‐ and (S,S)‐N,N′ ‐bis(aminoacyl)propanediamines (AA‐NN‐2 and AA‐NN‐3, respectively, AA = alanine, phenylalanine, valine) were synthesized as the dihydrochlorides, and their complexes with Cu(II) studied potentiometrically. Since these ligands in the presence of Cu(II) are able to perform chiral resolution of D,L‐dansylamino acids in HPLC (reversed phase), in a certain pH range (6.5–8.5), it is important to know the equilibria existing between ligands and copper in aqueous solution. For AA‐NN‐2, four species, CuLH3+, CuL2+, Cu2L2H, and CuLH−2, were detected, whereas for AA‐NN‐3, only CuLH3+, CuL2+, and CuLH−2 were found. The aim is to find out which complexes may be involved in the recognition process.