Structures reversible anion binding

A variety of structural analogs of mandelate had earlier been tested as potential substrates or reversible inhibitors of the racemase. - Consequently, much was known about the minimal structural requirements for binding to the enzyme. It was clear that both an aromatic ring and a carboxylate group (or other similar anionic group) generally aided in this binding. Therefore, initial candidates for the affinity label all included both a phenyl and carboxylate substituent. 

ATP4-.242 Results indicated associations to be influenced by macrocyclic and size effects, electrostatic interactions and structural complementarity. Of particular interest in this series is the observed very strong binding of anionic metal ion complexes. The electrochemistry of M(CN)6 /M(CN)4 (M = Fe, Ru) indicates the complexed complex to be nonlabile and the system to undergo a reversible one-electron exchange. The ability of the macrocycle to protect the reactivity of the complex is evidenced by the hindered photoaquation observed for Co(CN)j e [32]NgH8.247 The results of competition studies suggest predominantly coulombic interactions between the metal complex and macrocycle for these 1 1 complexes of complexes . 

These centres are formed by the addition of monomer to a suitable anion. They are almost always simpler than their cationic reverse part. The counter ion is usually a metal cation able to interact with the electrons of the growing end of the macromolecule, and to bind in its ligand sphere monomer or solvent molecules or parts of the polymer chain. This changes the properties of the whole centre. Therefore, by selection of the metal, the stability of the centre, the tendency of the centres to aggregation, the position of the equilibrium between the contact and solvent-separated ion pairs and free ions, and the stereoselectivity of the centre [the ability to produce polymers with an ordered structure (tacticity, see Chap. 5, Sect. 4.1)] are predetermined. The chemical reactions of the metal cations are, however, very limited. Most solvents and potential impurities are of nucleophilic character. They readily solvate the cation, leaving the anion relatively free. The determination... 

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