Ligands catenane

A review13 with 53 references of the transition-metal mediated supramolecular self-assembly is presented. Focus is on the self-assembly of macrocycles, catenanes, and cages from (en)Pd(N03)2 and pyridine-based bridging ligands. 

Pt(en)(N03)2] and [Pt(OTf)2L2] (L = mono- or 1/2 bidentate tertiary phosphine) or dinuclear complexes of the type [Pt2(OTf)2(/i-monodentate tertiary phosphine cr-aryl = 4, -biphenyl, / -terphenyL 4,4 -benzophenone, etc.) other structural motifs employing platinum(II) have also been reported.2 0 The addition of bridging, multidentate N-donor ligands of various shapes and sizes to the labile complexes in a suitable solvent system has afforded several classes of discrete, plat-inum(II)-containing polygons, polyhedra, and catenanes. 

Very large organogold rings (16), as well as the related dimeric [2]catenane, have been generated by the self-assembly of complex digold(I) diacetylide with a diphosphane ligand <00AG(E)3819>. 

Our definitions of the stereoisomeric center, line, and plane all stipulate the existence of bonds between the ligating element and its ligands. The exclusive use of these elements limits our analysis to classical stereochemistry and thus does not encompass the so-called topological isomerism (47) of interlocked rings—catenanes (48)—or of knots. As there is no bond between the rings of the catenanes we cannot expect to handle such compounds with a system based on connectedness. At the present stage of development, this limitation in scope... 

Fe(bpe)2(NCS)2 MeOH, bpe = tra x-l,2-bis(4-pyridyl)ethene, is a supramolecular coordinationpoly-catenane, consisting of two interlocked 2D networks. Bis-pyridylethane and bis-pyiidylethene also appear elsewhere as bridging ligands in binuclear complexes (e.g., pentacyanoferrates (Seetion 5.4.2.2)). 

In this chapter, for space reasons, only a few paradigmatic examples of rotaxanes and catenanes based on donor-acceptor (charge transfer (CT)) and/or hydrogen bonding interactions (systems based on metal-ligand bonding are reviewed in another... 

Figure 13.19 Structure formulas of cyclophane ligand 214+, catenane ligands 224+ and 234+, and mononuclear catenane complexes.

The rearrangement rate for the four-coordinate Cu(II) complex is smaller than for the monovalent complex. It is nevertheless several orders of magnitude larger than in related catenanes or rotaxanes with more encumbering ligands ... 

Several directed syntheses of catenanes have also been reported. One of these relies upon coordination of ligands to a metallic ion to achieve the proper geometry. An example is shown in Figure 19.1,729 2,9-Bis(/7-hydroxyphenyl)-l, 10-phenanthroline 40 is converted to the macrocycle 42 by treatment with the polyether 41, in a Williamson reaction, under... 

Catenane formation from fluorinated ligand 19 is apparently more effective than that from 12. This difference is most probably because of attractive edge-to-face or CH-jt interaction working in catenane 13, as observed in the crystal structure of platinum-incorporated catenane 14 (Figure 2). In this structure, we can observe efficient edge-to-face aromatic contacts between two phenylene units or a phenylene and a pyridine ring. 

A force field calculation predicted that this box would have an appropriate interplane separation (ca. 3.5 A) in the cavity. Therefore, two molecules of inorganic box 21 are expected to slide into a catenated dimer. In fact, when we combined 11 and ligand 22, we observed the formation of a single component, catenane 23 (Eq. 4) [29],... 

Successful self-assembly of catenanes 23 and 25 and their remarkable stability imply that rectangular box structures for the component rings are very effective for catenation. Thus, we also designed the construction of rectangular frameworks from a set of 11 and two different ligands. Surprisingly, these three-component systems worked very well and we observed highly efficient three-component-... 

From the results summarized in Table 1 we can conclude that the self-assembly of Pd(II)-linked catenanes is predictable. When the component rings have a cavity with an appropriate interplane distance (ca. 3.5 A), catenanes are obtained efficiently (e.g. from ligands 12, 22, 24, 26+27, or 29+30). If, however, the cavity is too large or too small, catenanes are not assembled (e.g. from 26, 27, 35, or 36). Thus two conditions must be satisfied if metal-incorporating catenanes are to be obtained by self-assembly. Firstly, component rings should contain reversible coordinate bonds. Second, both component rings should have interplane separation of approximately 3.5 A in the cavity. 

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