Copper complexes chiral surfaces

It was found that tartaric acid as a modifier forms complexes on the surface of Ni-silica and Cu-silica catalysts in which IR spectra reveal quite close coordination between the COOH groups. This is confirmed by similar values of ee in which Ni-silica catalysts are modified at pH 5 and pH 10. The similarity of the effect of pH of the modifying solution on Ni and Ni-Cu catalysts indicate that the structure of chiral clusters on the surface of both catalysts remained unchanged. Probably additional introduction of copper into Ni-Cu catalyst did not produce any ligand effect and did not change the behaviour of chiral clusters, but only changed the number of such clusters ( cluster effect ). 

All proteinogenic amino acids, with the only exception of proline, were resolved into their enantiomers as dansyl (DNS) derivatives by eluting with buffer A, with or without 4 mM DPA and 1 mM cupric acetate. The use of buffer A with the copper (II) complex of the chiral selector as eluent was necessary to maintain a concentration of the chiral complex on the surface of silanized silica gel sufficiently high to resolve some specific racemates. This suggested that the copper (II)-DPA complex was less adsorbed by silanized silica gel than copper (II)-hydroxydodecylproline complex proposed by Gunther et al. [3]. Detection was effected with UV light (360 nm) and dansyl amino acids appeared as fluorescent yellow-green spots. 

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