Transition metals as assembling and templating species: From catenanes and knots to organized multi-porphyrins arrays

Abstract

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 X-ray structures of two dicopper trefoil knots are also presented and discussed. The transition metal-directed threading of a molecular fragment containing a central chelate and an end-attached gold(III) porphyrin into a presynthesized coordinating ring affords a general precursor to a rotaxane-type structures. After threading, construction of the second porphyrin acting as an efficient stopper affords a copper(I) complexed [2]-rotaxane as well as a novel compartmental [3]-rotaxane. © 1995 IUPAC