Molecular covalent recognition

The recognition and complexation of neutral (uncharged) guest molecules by abiotic receptors is a relatively recent area of chemical investigation, although this type of complexation plays a fundamental role in biotic systems e.g. the base-pairing of nucleic acids, or enzyme-substrate interactions. 

The neutral molecular inclusion complexes of the naturally occurring cyclodextrins (121) and the synthetic macrocyclic polyethers have been comprehensively reviewed recently (122) and are not reported. 

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The chapter is split into two major sections, ionic recognition and molecular covalent recognition. Ionic recognition discusses synthetic receptor molecules designed to bind cations (metal, ammonium, bipyridinium ions) and anions (halide, azide, sulphate, phosphate, dicarboxylate ions etc.). The section on molecular covalent recognition describes the complexation of neutral (un-... 

Supramolecular chemistry takes into consideration the weak and reversible non-covalent interactions between molecules, which include H-bond-ing, metal coordination, hydrophobic forces, van der Waals forces, n—n interactions, and covers different research fields, for example, molecular recognition, host-guest chemistry, mechanically interlocked and nanochemistry. 

Polytopic macrocyclic receptors 1, 2 (Figure 10.1) are able to complex the zwitterionic form of the amino acids by a double non-covalent charge interaction [28,29]. The unsymmetrical benzocrown sulfonamide derivative, 2 which contains benzo-18-crown-6 and benzo-15-crown-5 moieties was used as a ditopic receptor for multiple molecular recognition of the amino acids, by combining two non-covalent interactions ammonium-crown hydrogen bonding and carboxylate- complexed Na+-benzo-15-crown-5 charge interactions [28,33]. 

Fig. 1. Preparation of configurational biomimetic imprinted networks for molecular recognition of biological substrates. A Solution mixture of template, functional monomer(s) (triangles and circles), crosslinking monomer, solvent, and initiator (I). B The prepolymerization complex is formed via covalent or noncovalent chemistry. C The formation of the network. D Wash step where original template is removed. E Rebinding of template. F In less crosslinked systems, movement of the macromolecular chains will produce areas of differing affinity and specificity (filled molecule is isomer of template).

Fig. 1. Concept of molecular imprinting - the non-covalent approach. 1. Self-assembly of template with functional monomers. 2. Polymerization in the presence of a cross-linker. 3. Extraction of the template from the imprinted polymer network. 4. Selective recognition of the template molecule...

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