Supramolecular macrocyclic assemblies

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. 

Fig. 37. Self-assembly of either a supramolecular ribbon (top) or a supramolecular macrocycle (bottom) from barbituric acid and 2,4,6-triaminopyrimidine units [9.122].

With the above simple examples we wish to emphasize that the synthetic use of hydrogen bonding assemblies in the effective formation of supramolecular macrocycles relies on high EM values and on the establishment of stable intermolecular arrays of hydrogen bonds capable of affording a high enthalpic gain to compensate for the entropic cost of the assembly. 

Figure 3.5 Proposed self-assembly of the self-complementary molecule 16 (R = C8Hn7) into a supramolecular macrocycle schematic (left, A = acceptor, D = donor) and structural (right) representation.

An interesting ferrocene-bridged zinc porphyrin macrocycle was synthesized by Shoji et al. [146], This group succeeded in visualizing a single molecule of a supramolecular coordination assembly on Au(lll) in UHV [147], The discrete... 

There are four main sections in this chapter. Three of them deal with molecular recognition, sensing, and supramolecular self-assembly of crown ethers. The fourth one is about emerging classes of oxygen-containing macrocycles, such as calixtubes and oxacalixarenes. Emphasis has been given to their properties and usefulness, rather than their synthesis as such. The primary sources cited herein should therefore be consulted to this end. 

Marsh, A. Silvestri, M. Lehn. J.-M. Self-complementary hydrogen bonding heterocycles designed for the enforced assembly into supramolecular macrocycles. Chem. Commun. 1996. 1527. 

BaHester P, de Mendoza J. Supramolecular macrocycle synthesis by H-bonding assembly. In Diederich F, Stang PJ, Tykwinski RR, eds. Modern Supramolecular Chemistry Strategies for Macrocycle Synthesis. Weinheim Wdey-VCH 2008 69—111. 

Fujita, M. and G. Ogura (1996). Supramolecular self-assembly of macrocycles, cate-nanes, and cages through coordination of p5nidine-based hgands to transition metals. Bull. Chem. Soc. Jpn 69, 1471-1482. 

Ionic supramolecular self-assembly will be discussed in Chapter 6, but some supramolecular systems based upon ionic interactions will be discussed earlier, e.g. the organocyclosiloxanolates, which form sandwich compounds by intercalating transition metal ions between two macrocyclic rings (held together by ionic interactions) and acting as endo receptors which concurrently have crown-ether-type complexing properties (as exo receptors) (see Section 2.1.2). 

P. Ballester and J. de Mendoza, Supramolecular macrocycle synthesis by H-bonding assembly, in F. Diederich, P. J. Stang, and R. R. Tykwiski, Modem Supramolecular Chemistry, Wiley-VCH, Weinheim, 2008. 

Pyrrole-based macrocyclic assemblements were also utilized as functionalizing units for fuller-enes. Despite the fact that the first example coming to mind is a porphyrine macrocycle, the ability of such 7t-electron-rich systems to strongly bind fullerenes in a convex-planar supramolecular association will be discussed in Section 2.22.2. 

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