Electrochemically Driven Ring Gliding Motion in Catenanes

Electrochemically Driven Ring Gliding Motion in Catenanes 

The changeover reaction converting 23 2+ to the stable 5-coordinate species 23 2+ is quantitative. It is easily monitored by visible absorption spectroscopy, since the product of the rearrangement reaction is only slightly colored (pale olive green /.m lx = 640 nm s = 125). The geometry of the copper(n) catenate obtained through decomplexation and remetallation has been confirmed by comparison of its physi- 

Both copper(n) complexes 23(42+ and 23 ysy2 1 have electronic spectra typical of 4-coordinate and 5-coordinate species, respectively, in accordance with previously reported complexes possessing analogous ligand sets)99,1001 The same interconversion process can also be monitored by EPR,198 1011 and it was demonstrated in an unambiguous fashion that 23(42+ is a distorted tetrahedral complex and that the product of the changeover, 23 s2+, is a square pyramidal compound. 

An interesting question deals with the rate of the ring gliding motion that transforms 23(4j2+ into 23 2+ or, after reduction of the latter, 23(S)+ into 23(4)+. It was 

Reversing the process, reduction of the stable species 26 62+ affords 26 +, which rapidly rearranges to the stable monovalent complex 26(4)+. The intermediate 26(5 + has not been isolated nor spectroscopically characterized, but its formation was clearly evidenced by cyclic voltammetry, due to its analogy with 23 +. 

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Electrochemically Driven Ring Gliding Motion in Catenanes I 271... 

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