Studies of the Pfeiffer effect induced in tris(pyridine-2,6-dicarboxylato)terbate(III) by monosaccharide aldose sugars

Abstract

Optical activity has been induced in racemic mixtures of [Tb(pydca)₃]^3–(pydca = pyridine-2,6- dicarboxylate) upon formation of outer-sphere complexes with monosaccharide aldoses, and studied by means of circularly polarized luminescence spectroscopy. No optical activity could be observed upon addition of D-glyceraldehyde to a solution of [Tb(pydca)₃]^3–, implying that the presence of a hemiacetal-ring oxygen is necessary for occurrence of the outer-sphere association. The sign of the induced optical activity was found to vary with the identity of the sugar used, but a correlation was established between the configuration at carbon 4 of the sugars (when these were present in the pyranose ring form) and the predominant [Tb(pydca)₃]^3– enantiomer. This suggests that an association process does indeed lead to the observed Pfeiffer effects, and that the forces leading to the formation of the outer-sphere complexes are rather specific in nature.