Testing of Ligands
Molecular receptors, whose design and synthesis have been discussed in the preceding paper, are organic structures, held by covalent bonds, which are able to bind selectively substrates by the use of intermolecular interactions. These molecular interactions are of various origins: electrostatic interactions, hydrogen bonding, Van der Waals forces, etc.. The design of the receptor determines which substrate is to be bound, the energy and the specificity of complexation being governed by geometrical factors (topology of the ligand, size and shape of the internal cavity and of the substrate,. . .) and by the nature of the intermolecular interactions (electrostatic interactions for the binding of cations, presence of suitable donor binding sites for the complexation of transition metal cations, introduction of hydrogen bonds for the binding of anionic species, etc. . . .). The strength of the ligand-substrate interaction can be characterised by different physical constants. Thermodynamic (stability constants, enthalpy and entropy of formation of complexes), and kinetic parameters, are of prime importance in the definition of the properties of the ligand-substrate complex, for the understanding of the nature of the stabilising ligand-substrate interactions and in the design of new ligands.
KeywordsEntropy Enthalpy EDTA Catalysis Carboxylate
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