Redox active catenane

When rotaxanes and catenanes contain redox-active units, electrochemical techniques are a very powerful means of characterization. They provide a fingerprint of these systems giving fundamental information on (i) the spatial organization of the redox sites within the molecular and the supramolecular structure, (ii) the entity of the interactions between such sites, and (iii) the kinetic and thermodynamic stabilities of the reduced/oxidized and charge-separated species. 

Many other catenane species have been synthesised. These range from further simple [2]-catenanes, other [2]- as well as [3]-catenane species incorporating redox-active tetrathiafulvalene groups, other multi-ring derivatives, through to polymeric species incorporating catenane domains as part of a larger macromole-... 

Fig. 34. Deposition of a monolayer of switchable [2]catenane 21-4DMPA is deposited onto a patterned polysilicon substrate, followed by condensation of orthogonal strips of Ti through a layer mask resulting in the formation of a network of junctions, each sandwiching a single layer of redox-active [2]catenanes...

Topics which have formed the subjects of reviews this year include excited state chemistry within zeolites, photoredox reactions in organic synthesis, selectivity control in one-electron reduction, the photochemistry of fullerenes, photochemical P-450 oxygenation of cyclohexene with water sensitized by dihydroxy-coordinated (tetraphenylporphyrinato)antimony(V) hexafluorophosphate, bio-mimetic radical polycyclisations of isoprenoid polyalkenes initiated by photo-induced electron transfer, photoinduced electron transfer involving C o/CjoJ comparisons between the photoinduced electron transfer reactions of 50 and aromatic carbonyl compounds, recent advances in the chemistry of pyrrolidino-fullerenes, ° photoinduced electron transfer in donor-linked fullerenes," supra-molecular model systems,and within dendrimer architecture,photoinduced electron transfer reactions of homoquinones, amines, and azo compounds, photoinduced reactions of five-membered monoheterocyclic compounds of the indigo group, photochemical and polymerisation reactions in solid Qo, photo- and redox-active [2]rotaxanes and [2]catenanes, ° reactions of sulfides and sulfenic acid derivatives with 02( Ag), photoprocesses of sulfoxides and related compounds, semiconductor photocatalysts,chemical fixation and photoreduction of carbon dioxide by metal phthalocyanines, and multiporphyrins as photosynthetic models. 

During the past 20 years, mechanically interlocked molecules, known as catenanes and rotaxanes, many of them redox-active, have become readily accessible using template-directed protocols that rely upon the precepts of molecular recognition and self-assembly and the tenets of supramolecular assistance to covalent synthesis. By incorporating different recognition units with dissimilar redox properties into appropriate components, these compounds can often be induced to switch hysteretically between ground and metastable co-con-... 

For both rotaxane and catenane-based molecular machines, it is desirable to have recognition sites such that they can be easily controlled externally. Hence, it is preferable to build sites that are either redox-active or photo-active [144]. Catenanes can also be self-assembled [157]. An example of catenane assembled molecular motors is the electronically controllable bistable switch [158]. An intuitive way of looking at catenanes is to think of them as molecular equivalents of ball and socket and universal joints [153,159,160]. 

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