Catenanes mixed

Figure 78 Two preformed Pd11 cage compounds that are reorganized into the three-dimensionally interlocked catenane in high yield when they are mixed in an aqueous solution.

In a serendipitous fashion, a novel mixed valence tetranuclear copper(II)/copper(III) dithiocarbamate [2]catenane was prepared in near quantitative yield by partial chemical oxidation of a preformed dinuclear copper(II) naphthyl dtc macrocycle (Scheme 6).49 X-ray structure, magnetic susceptibility, ESMS and electrochemical studies all support the tetranuclear catenane dication formulation. The combination of the lability of copper(II) dtc coordinate bonds and favourable copper(II) dtc-copper(III) dtc charge transfer stabilisation effects are responsible for the high yielding formation of the interlocked... 

Copper complexes are known in oxidation states ranging from 0 to +4, although the +2 (cupric) and the +1 (cuprous) oxidation states are by far the most common, with the divalent state predominating. Only a relatively small number of Cu complexes have been characterized and the Cu° and oxidation states are extremely rare. A few mixed valence (see Mixed Valence Compounds) polynuclear species have also been isolated examples include a CuVCu species and a Cu /Cu catenane. The coordination numbers and geometries (see Coordination Numbers Geometries) of copper complexes vary with oxidation state. Thus, the majority of the characterized Cu complexes are square planar and diamagnetic, as is common for late transition metals with d electronic configurations. 

Catenane synthesis can be also achieved by dynamic molecular association. Figure 3.27 shows an example of catenane preparation through the dynamic formation of a palladium (Pd) complex. Mixing the Pd complex with pyridine-type ligands in water induces the formation of both a monocyclic structure and an interlocked catenane. An equilibrium exists between these two structures, and the catenane structures are more favorable at higher concentrations. In the catenane structure, the benzene rings stack next to each other due to favorable... 

Larger rings have also been employed for the formation of catenanes. The 56-membered macrocycle 5, incorporating two 2,9-bis(p-biphenylyl)-1,10-phenanthroline fragments, has been demonstrated to form a catenated mixed-ligand complex 6 of type [CuLL ]+ where L = 5 and L is the smaller ring 3. ... 

Hydrogen-bonding in neutral rotaxanes The independent discovery in 1992 by Hunter [25], and Vogtle and coworkers [26, 102] of catenanes made of interlocked amide cyclophanes led to the development of a novel family of neutral catenanes and rotaxanes. In an example of rotaxane synthesis [103] macrocycle (38) and isophthaloyl dichloride (39) were mixed in dichloromethane, and the trityl amine... 

Aromatic templates, in conjunction with coordinative bonds, have been employed by Sanders et al. [42] to self-assemble a [2]catenane incorporating a chiral metallomacro-cycle. The 1,5-dioxynaphthalene-based macrocyclic polyether 60 threads onto the r-elec-tron-deficient compound 61 in MeCN. Thus, when both compounds and Zn(OS02CF3)2 are mixed in this solvent, threading of 60 onto 61 is followed by the [2 + 2] assembly of a helical metallomacrocycle as a result of the tetrahedral coordination of two Zn centers by the bipyridine ligands appended to the r-electron-deficient recognition sites. The resulting [2]catenane 62 was characterized by a combination of H-NMR spectroscopy and electrospray mass spectrometry. 

Using the same general strategy described above. Beer reported the first anion-templated synthesis of catenanes [43,44]. Mixing macrocycle 21 with... 

Stoddart et al. also reported poly (bis [2]catenane) 41 based on a transition metal chelation effect (Scheme 17.13) [98]. In this case, bis[2]catenane monomer 40, prepared using the same template-directed strategy as described above [99], was mixed with CF3 SO3 Ag in acetonitrile at room temperature, and poly(bis[2]catenane) 41 was obtained after counterion exchange. GPC analysis with protein standards indicated the M of 41 to be 150 kDa, corresponding to a DP of 40. 

Mark and Semiyen, in a series of papers, have studied the mechanism and the effect of trapping cyclics in end-linked elatomeric networks [100-103], Sharp fractions of cyclics of polyfdimethylsiloxane) (PDMS), varying in size from 31 to 517 skeletal atoms, were mixed with linear chains for different periods of time and the linear chains were then end-linked using a tetrafunctional silane. The untrapped cyclics were extracted to determine the amount trapped. It was found that while cyclics with less than 38 skeletal atoms were not at all trapped, for n>38, the percentage of cycUcs trapped increased with size, with 94% trapped in the case of the cychc with 517 skeletal atoms. In effect, the system of trapped cycUcs in the end linked PDMS network is a polymeric catenane. It is thus possible to control the elastomeric properties of the network by incorporating the appropriate sized cyclics. This study has been extended to cyclic PDMS in poly(2,6-dimethyl-l,4-phenylene oxide) [104,105] and cyclic polyesters in PDMS [106]. 

It may also be possible to use the trapping technique to prepare networks having no cross links whatsoever. Mixed linear chains, with large amounts of cyclics, are difunctionally end linked to yield an Olympic or chain-mail network (figure 7.30). Such materials are similar in some respects to the catenanes and rotaxanes that have long been of interest to a variety of scientists and mathematicians. " Computer simulations could establish the conditions most likely to produce these novel structures. 

Figure 25 (a) Synthesis of mixed benzylic amide esto catenane 93 by template-directed synthesis and (b) magic-ring catenane 95... 

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