Oligo catenanes

Most of the reactions that can be used to prepare distannanes can be extended to the preparation of oligo- and polystannanes, which have attracted interest for potential use in electronic and optical devices.455 The structures of the products are not necessarily those of completely linear catenanes, (R2Sn) , and different degrees of branching confer different properties. The formation of polymers is also frequently accompanied by the formation of cyclic pentamers or hexamers, and samples prepared by different methods may show substantially different properties. 

A different approach to the synthesis of oligo[2]calenanes was chosen by Mullen et al. in 1995 [57]. The bromo-substituted in/out catenane 111 was coupled with appropriate comonomers under Suzuki conditions [58]. The degree of polymerization was between one and five for the resulting oligomers 112 (Figure 45). In 1997 the same group reported the first synthesis of poly[2]catenanes of the... 

Figure 45. Synthesis of oligo[2]catenanes by co-oligomerization according to Mullen et al.

It has been observed that the isomers 41c,d and 42c,d have the same low reactivity towards polycondensation, irrespective of the reaction conditions and that only oligo[2]catenanes were reached [30, 56], This important finding rules out the... 

It is clear from comparison of the reactivity towards polycondensation of the difunctionalized [2]catenand 50b and 53 with their corresponding difunctionalized [2]catenates 50a and 54, respectively, that the mobility of the interlocked macrocycles of catenanes plays a fundamental role for the nature of the resulting polycondensates - either cyclic oligo[2]catenanes 52,54 or linear high molecular-weight poly[2]catenanes 51b,56 (Schemes 18-20). 

Weidmann. J.L. Kern. J.M. Sauvage. J.P. Muscat. D. Mullins. S. Kohler, W. Rosenauer. C. Rader, H.J. Martin. K. Geerts, Y. Poly[2]catenanes and cyclic oligo[2]catenanes containing alternating topological and covalent bonds Synthesis and characterization. Chem. Eur. J. 1999, 5. 1841-1851. 

The first amide-based oligo[2]catenanes were successfully prepared, via route 2 in Scheme 17.3, by Geerts etol. in 1995 (see Scheme 17.4) [62]. Here, the first stage of the synthesis involved the creation of a dibromide-functionalized [2]catenane, via Hunter s two-step strategy, such that two isomers - IN-OUT 6a and OUT-OUT 6b -were obtained in 5% and 9% yields, respectively. However, due to the inter-molecular hydrogen bonding, the isomeric catenanes were conformationally frozen and could not be interconverted, even at relatively high temperature [60-63]. A... 

Scheme 17.4 Synthesis of amide-based oligo[2]catenanes 8a and 8b.

Takata et al. reported another very interesting amide-based poly[2]catenane (or oligo[2]catenane) 19 (Scheme 17.8) [57]. Here, the [2]catenane monomer 18 was synthesized in a high yield by utilizing macrocycle-1 as a template (this has proven to be a good templating precursor for the synthesis of catenanes) [56, 82]. Poly[2]catenane 19 was prepared via the Diels-Alder polymerization of 18 at 140°C, without solvent, for several hours. According to GPC analysis with... 

Stepwise synthesis of macrocyclic parts accompanied with catenation can be applied to the synthesis of oligo-catenane. Stoddart et al. prepared [7]catenane on the basis of the charge-transfer interaction between the electron-deficient cyclophane bearing 4,4 -bis(pyridinium salt) and the crown ether bearing electron-rich aromatics such as... 

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