Bis-porphyrin, dumbbell

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.

Fig. 13 Illustration of the demetalation/remetalation reactions carried out on the Cu(I)-complexed [2]rotaxane 33 to afford free [2]rotaxane 34+ and metallo-[2]rotaxanes 35 + and 36 +. In the free [2]rotaxane 34+, the macrocycle is more deeply buried inside the cavity formed by the bis-porphyrin dumbbell compared to the complexed [2]rotaxanes...

Other systems of interest in order to study through-space electron transfer processes or through-bond electron transfer with different metals coimecting the macrocycle and the dumbbell were designed, hi these [2]rotaxanes, the Zn(II) bis-porphyrin dumbbell component remains the same as in Sect. 2.3, whereas the gold porphyrin is incorporated in the macrocycle. This affects the mutual arrangement of the chromophores and therefore their electronic communication. It also changes remarkably the dynamic of the system after removal of the metal template as will be described. 

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