Catenanes, porphyrin-incorporating

Fig. 17 Two strategies for the transition metal-templated synthesis of a [2]catenane made with Zn and Au porphyrin-incorporating interlocked macrocycles. The thick lines represent chelating fragments, the black disk symbolises copper(I), the empty diamonds are Zn(II) porphyrins, and the hatched diamonds are Au(III) porphyrins...

Scheme 9.17). The macrocycle (A) of Scheme 9.1 is the dpp-incorporating 30-membered ring 8 used earlier for making catenanes (see Protocol 5) it is sufficiently small to prevent release of the bis-porphyrin dumbbell. The preparation of 22+ takes place in seven steps.1819 One of the starting materials is 4-lithiotoluene 13, which may be obtained by direct interaction of an excess of freshly cut lithium with 4-bromotoluene 12 in ether under argon at reflux (Scheme 9.10).12 The resulting organolithium compound is titrated by the double titration method described by Gilman et alP The experimental procedure is very similar to that described in Protocol 1.

The incorporation of a porphyrin group in a catenane raises the prospect that the former might serve as a centre at which photochemical, electrochemical or chemical processes are used to control the dynamic and/or conformational behaviour of the assembly as a whole. In addition, the tuning of such processes should be possible through the choice of suitable metallation as well as through the ability to vary substituents on the periphery of the porphyrin ring. 

Corresponding symmetrical, bis-porphyrin derivatives, as well as larger entities incorporating bis-porphyrin and bis-catenane groups - see 12 - have also been investigated. ... 

Other interesting units that have been incorporated in the electron-donor macro-cyclic component of catenanes are porphyrins (Figure 26) [56]. The compounds containing a free-base porphyrins can be protonated in strongly acidic solutions, causing electrostatic repulsions which result in conformational reorientations and changes in rotation rates [57]. 

More recently, porphyrin units have been incorporated in complex molecules such as catenanes [16-18] and rotaxanes [19-22]. Whereas catenanes are composed of interlocking rings only, the simplest rotaxanes... 

A natural extension of the work described in Sect. 2.4 was to prepare a Cu(l)-complexed [2]catenane with macrocycles incorporating the Zn and Au porphyrins. [2]catenanes are topologically non-trivial molecules (non-planar molecular graph) in which two rings are interlocked but not linked [23,24]. Therefore, differentiating the rings with Zn- and Au-porphyrins enables us to study photoinduced electron transfer in mechanical bond systems and also to have information on the conformation of the system. 

Rotaxanes and Catenanes Incorporating Two or Several Noncovalently Bound Porphyrins. 31... 

Very few examples have been reported of [2]-catenanes. The compounds consist of two interlocking rings, each incorporating a porphyrin moiety either as an integral part of the ring or as a hanging subunit." ... 

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