SYNTHESIS, CHARACTERIZATION, AND A PROTON NMR-STUDY OF TOPOLOGICALLY CHIRAL COPPER(I) [2]-CATENATES AND ACHIRAL ANALOGS

Cu(I) catenates and the corresponding metal-free catenands in which one or both constitutive rings are oriented have been synthesized and characterized. Ring orientation is achieved by an appropriate substitution on the phenanthroline core of thc macrocycle. Cu(I) catenates which contain two oriented rings are topologically chiral. Their chirality has been observed by H-1-NMR spectroscopy in an optically active medium. Indeed, a splitting of the signals of the aromatic protons, which are enantiotopic by external comparison, is observed in the case of the achiral Cu(I) catenate with only one oriented ring, the signals of the aromatic protons of the nonoriented macrocycle (enantiotopic by internal comparison) are also split. Those of the oriented macrocycle are equivalent by external comparison and thus do not show any splitting. In the field of topological chirality, this study illustrates the fact that only a careful analysis of the topicity of the protons allows the possibility of distinguishing chiral molecules from achiral ones by H-1-NMR in an optically active medium.