Based Macrocyclic Assemblies

Of those cycles that incorporate boronate esters as an integral linkage, many involve some coordinative event between Lewis acidic and Lewis 

Conceptually, this was first demonstrated using a metallated porphyrin that was functionalized with 2 diols (zinc dicatechol porphyrin) (Fig. 5). After addition of 3-pyridylboronic acid, absorption spectroscopy indicated that the pyridyl moiety was coordinated to the Zn-porphyrin. The observed affinity constant for this interaction, however, was more than 30 times what was expected for a simple pyridyl-Zn-porphyrin complex. It was, therefore, reasoned that the diols reacted with the boronic acids to afford the esters that would result in a cyclic structure (Fig. 5). Indeed, vapor phase osmometry (VPO) confirmed the 2 2 dimeric nature of the complex. Here the ester served as the key covalent linkage, though associated coordination was required between the metal and pyridine to create the cyclic structure. 

FIGURE 5. Bis-diol functionalized porphyrins assemble into macrocycles based on boronate ester formation coupled with metal ligation to a Lewis basic pyridine. 

Maintaining approximate C3 symmetry, this hydrogen bond helps essentially freeze the cycle and limit most conformational freedom. 

Unlike the examples given, the boronate ester can be involved in both the covalent and coordinative tethers involved in completing the macrocyclization 

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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. 

Christinat, N. ScopeUiti, R. Severin, K. Multicomponent assembly of boronic acid based macrocycles and cages. Angew. Chem. Int. Ed. 2008, 47, 1848-1852. 

Stang et al. [94JA4981, 9403776, 95JA1667, 95JA6273] described the self assembly of a series of unique cationic, tetranuclear, Pd(II)- and Pt(II)-based macrocyclic squares (e.g., 25), utilizing different bidentates as the sides of these structures. The similar self-assembly complexation of dipyridyl porphyrins by cis- and tran.v-substituted Pd(II) or Pt(II) ions possessing square planar coordination afforded multiporphyrin arrays with a square... 

Mukherjee PS, Das N, Kryschenko YK, Arif AM, Stang PJ (2004) Design, synthesis, and crystallographic studies of neutral platinum-based macrocycles formed via self-assembly. J Am Chem Soc 126 2464-2473... 

The self-assembly of a new category of tetranuclear complexes of both copper(I) and silver(I) has been reported. Interaction of these metal ions with the (bis)bipyri-dine-based macrocycle 34 (Figure 6.17), incorporating phenanthroline pendant arms, results in the assembly of 4 2 (metal ligand) complexes incorporating four helical domains. An X-ray diffraction study of the species of type showed... 

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. 

Ranganathan. D. Lakshmi. C. Karle. I.L. Hydrogen-bonded self-assembled peptide nanotubes from cystine-based macrocyclic bisureas. J. Am. Chem. Soc. 1999. 121 (26), 6103-6107. 

Gallant, A. J. MacLachlan, M. J. Ion-induced tubular assembly of conjugated Schiff-base macrocycles. Angew. Chem. Int. Ed. 2003, 42, 5307-5310. 

The Schiff-base macrocycle H2L1733 (Eq. 8.39) with increased coordination capacity has been assembled in the presence of lanthanum(III) acetate from 6,6 -bis(aminomethyl)-2,2 -bipyridyl and 2,6-diformyl-4-methylphenol and isolated as the homodinuclear complex [La2(L1733)(02CCH3)4]4CH3CN-3H20 [103]. X-Ray crystallographic study of the latter showed that all ten donor atoms of the macrocycle are involved in coordination to two identical La centres. A coordination number of 10 for each La is completed by two bidentate acetate anions. Reduc-... 

An exciting development in dithiocarbamate chemistry is the synthesis by Beer and co-workers (325,1489) of a range of supramolecular complexes containing nickel(II), zinc(II), and copper(II) bis(dithiocarbamate) centers. These include the preparation of nano-sized resorcarene-based polymetallic assemblies, copper(II) dithiocarbamate macrocycles (62,326,1469,1470), crown-ether derivatives (1471), cryptands (492), and catenanes (544). Details of this work are given in this section and also within the copper and zinc sections (Section IV.H.l and IV.I.l). 

Over the last decade, the chemistry of the carbon-carbon triple bond has experienced a vigorous resurgence [1]. Whereas construction of alkyne-con-taining systems had previously been a laborious process, the advent of new synthetic methodology based on organotransition metal complexes has revolutionized the field [2]. Specifically, palladium-catalyzed cross-coupling reactions between alkyne sp-carbon atoms and sp -carbon atoms of arenes and alkenes have allowed for rapid assembly of relatively complex structures [3]. In particular, the preparation of alkyne-rich macrocycles, the subject of this report, has benefited enormously from these recent advances. For the purpose of this review, we Emit the discussion to cychc systems which contain benzene and acetylene moieties only, henceforth referred to as phenylacetylene and phenyldiacetylene macrocycles (PAMs and PDMs, respectively). Not only have a wide... 

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. 

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