TRANSITION-METALS AS ASSEMBLING AND TEMPLATING SPECIES - FROM CATENANES AND KNOTS TO STRINGS THREADED THROUGH MOLECULAR RINGS

New dicopper(I) knots have been synthesized as well as their face-to-face isomers. The knots range from 80 to 90-membered rings and their preparation yields depend crucially on structural parameters such as number of methylene fragments linking the two chelating units and length of the polyethyleneoxy unit used in the cyclization reaction. The best yield was obtained for an 84-membered knotted ring with a -(CH2)6- connector : this relatively long fragment allows pronounced winding of the double helix precursor and is thus favorable to the knotting reaction. The face-to-face complexes were in some instances the major products, being obtained in yields amounting to 24% in the case of the dicopper (I) bis 43-membered ring system. Based on a related three-dimensional template effect, other multicomponent molecular systems have been synthesized. They contain rings, coordinating open-chain fragments and transition metals and can be constructed at will by taking advantage of the strong preference of copper(I) for bis- chelate complexes. The compounds consist of one or two rings threaded by the acyclic subunit, the various organic components being assembled via coordination to copper(I).