Non-Covalent Assemblies

Pollution Prevention via Molecular Recognition and Self Assembly Non-Covalent Derivatization. Warner, J. C., in Green Chemistry Frontiers in Benign Chemical Synthesis and Processes Anastas, P. and Williamson, T. Eds., Oxford University Press, London, pp 336 - 346. 1998. 

Edder C., C. Piguet, J.-C. G. Biinzli, G. Hopfgartner, A water-stable and strongly luminescent self-assembled non-covalent lanthanide podate. J. Chem. Soc. Dalton Trans. 1997, 4657—4664... 

In biological systems molecular assemblies connected by non-covalent interactions are as common as biopolymers. Examples arc protein and DNA helices, enzyme-substrate and multienzyme complexes, bilayer lipid membranes (BLMs), and aggregates of biopolymers forming various aqueous gels, e.g, the eye lens. About 50% of the organic substances in humans are accounted for by the membrane structures of cells, which constitute the medium for the vast majority of biochemical reactions. Evidently organic synthesis should also develop tools to mimic the Structure and propertiesof biopolymer, biomembrane, and gel structures in aqueous media. 

Woolfson and Mahmoud have classified the routes to preparation of decorated self-assembling peptide materials [53] as (1) co-assembly, where the functional part is already attached to a self-assembling component prior to assembly, and (2) postassembly, where a non-functionahsed self-assembled structure is modified by covalent or non-covalent means. This discussion adheres to this classification. A third route, beyond the scope of this review, is the use of structured peptides as templates for inorganic materials. Section 4.1 discusses functionalised self-assemblies formed from co-assembly-type approaches, while post-assembly modifications of self-assembled structures are considered in Sect. 4.2. 

The value of EM for a cooperative self-assembled structure provides a measure of the monomer concentration at which trivial polymeric structures start to compete, and therefore EM represents the upper limit of the concentration range within which the cooperative structure is stable (Scheme 2). The lower limit of this range is called the critical self-assembly concentration (csac) and is determined by the stoichiometry of the assembly and the strength of the non-covalent binding interactions weaker interactions and larger numbers of components raise the csac and narrow the stability window of the assembly (8). Theoretical treatments of the thermodynamics of the self-assembly process have been reported by Hunter (8), Sanders (9), and Mandolini (10). The value of EM is lowered by enthalpic contributions associated with... 

An alternative way for the generation of a bidentate ligand makes use of a self-assembly process of monodentate to bidentate ligands employing non-covalent interactions [87]. 

Two-dimensional planar interpenetrating networks have been formed using the spacer ligand 2,2 -bis-l,6-naphthyridine with a zinc salt.274 Helicate structures have been synthesized which rely heavily on non-covalent interactions in the metal-assisted self-assembly process in solution.275... 

G. Thoma, M. B. Streiff, A. G. Katopodis, R. O. Duthaler, N. H. Voelcker, C. Ehrhardt, and C. Masson, Non-covalent polyvalent ligands by self-assembly of small glycodendrimers A novel concept for the inhibition of polyvalent carbohydrate-protein interactions in vitro and in vivo, Chem. Eur. J., 12 (2006) 99-117. 

The future prospects for the capsule project emerge from these considerations. Further increasing the size of the capsule and building chemical functionalities into the inner cavity would allow a closer emulation the functions of enzymes, especially those that require cofactors in order to catalyze chemical transformations. Another important aspect is to design capsules that can combine stereospecificity and catalysis - that is accelerate stereoselective transformations. Capsules that reversibly dimerize in water would probably contribute a lot more to our understanding of non-covalent forces and solvent effects in this most biorelevant medium. So far, water solubility and assembly have not been achieved with hydrogen-bonded capsules. 

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