Stereoselectivity observed upon adduct formation of tris(3-trifluoroacetyl-D-camphorato)- and tris-(3-heptafluorobutyryl-D-camphorato)-europium(III) with formamide and acetamide derivatives

Abstract

The adduct formation which takes place when the title compounds bind N-alkyl and NN-dialkyl derivatives of formamide and acetamide has been studied by means of circularly polarized luminescence (c.p.l.) spectroscopy. It was determined from examinations of emission enhancements that at least two molecules of substrate are bound by the chelates, but the luminescence titrations were too indeterminate to permit a calculation of association constants. No optical activity is observed within the emission of the free chelates, but strong c.p.l. could be detected if the 1 : 2 chelate: substrate adduct could be fully formed. This chirality was found to be most developed in neat substrate solvent, and takes place even though the substrates are not inherently chiral. It is concluded that the formation of the adduct complexes is accompanied by a stereoselective rearrangement of the camphorate-ligands, thus yielding a partial resolution of the labile Eu^III complexes.