Linked Linear Assemblies

Boron-linked polymers are not rare. The most obvious include borosili-cate glasses and slime. However, these common materials rely primarily on borate as the key linking element and not boronic acids. Poly(boronate)s can be found in the literature as far back as the 1960s, and then, after a long drought, most progress has been made in the last decade. As seen with coordination 

FIGURE 25. Heterodimeric capsules form upon the templated assembly of tris-diol and triboronic acid calixarenes (Reprinted with permission from Ref 57. Copyright 2007 American Chemical Society.) 

The earliest recorded poly(boronate)s were tri-coordinate systems based on phenylene-l,4-diboronic acid. Some of the first materials were not in fact esters 

FIGURE 26. Covalent poly(boronate)s were first identified as (a) the borono-hydra-zone analogs before (b-e) ester linked materials were identified, (d and e) Phosphino-integrated poly(boronate)s display reactivity and structural motifs similar to the monomeric precursors. 

FIGURE 27. Poly(boronate)s using fluorene-diboronic acids with pentaerythritol (a) and 1,2,4,5-tetrahydroxybenzene (b) have shown to act as self-repairing materials (a and b) and as a new class of wide band-gap semiconductor (b). 

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Linear Polymeric Supermolecules Supramolecular CROSS-LINKING Self-assembled Dendrimers, ARBOROLS... 

The linear assembly of glycosylated amino acids in particular usually provides well-defined products following this approach, the required carbohydrate structure is attached to an amino acid residue, typically serine and threonine for O-linked glycopeptides and asparagine for N-linked glycopeptides (Fig. I).16... 

What are the chemistries needed to adopt successfully a step-wise assembly approach For example, should a bio-inspired combination of covalent and non-covalent bonds be used where covalently linked linear chains are folded into the desired architecture by noncovalent interactions Or should covalent chemistries be employed throughout to ensure the resultant materials are as robust as conventional MIPs ... 

Linear polymeric supermolecules - Supramolecular cross-linking - Self-assembled dendrimers, arborols,... 

When tubulin heterodimers are assembled into microtubules, they form linear protofilaments with the P-tubulin subunit of one tubulin molecule linking covalently with the a-subunit of the next. Direct examination by electron microscopy of tannic acid-treated specimens has shown that micrombules in neurons and the A-microtubules of cilia and flagella have 13 protofilaments arranged side to side to form a cylinder around what appears to be an empty lumen. 

A. Dondoni, A. Marra, M. Mizuno, and P. P. Giovannini, Linear total synthetic routes to [3-d-C-( 1.6)-linked oligoglucoses and oligogalactoses up to pentaoses by iterative Wittig olefination assembly, J. Org. Chem., 67 (2002) 4186—4199. 

The formation of circular or linear forms seems to depend on balances between kinetic and thermodynamic control iron(II)-poly-2,2 -diimine systems with their substitutionally inert metal centers provide useful systems for disentangling thermodynamic and kinetic contributions. The mechanism of formation of circular helicates is believed to entail a kinetically favored triple helicate intermediate. Self-assembly of chiral dinuclear binaphthol-linked iron(III) porphyrin complexes into extended polynuclear species takes place through the intermediacy of fi-oxo dimers. Predetermined //-oxo-di-iron-dimers may be used in this type of synthesis. 

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