Opposite Enantioselectivity of Mg(II) Versus Zn(II) in the Fluorescent Recognition of Amino Acids.

The addition of Mg is found to turn on the fluorescence response of a molecular probe, 3,3'-diformyl-1,1'-bi-2-naphthol, toward chiral amino acids with high enantioselectivity. It is further found that the enantioselective fluorescence responses of the molecular probe in the presence of Mg toward certain amino acids are the opposite of those in the presence of Zn, that is, using Mg with an l-amino acid generates much greater fluorescence enhancement than with the corresponding d-amino acid, but using Zn with the d-amino acid gives much greater fluorescence than with the l-enantiomer. Thus, simply changing the metal cation additive allows the chirality sense of the fluorescence-based molecular recognition to be easily regulated.