Interannular Cooperativity

With reference to Fig. 17, interannular cooperativity can be quantified by a cooperativity factor, 7, that is given by the ratio of the overall experimental constant to the hypothetical overall noncooperative constant, 7 = EM EM /EM 2. 

Of course, freezing of torsional motion is just one of the possible mechanisms of interannular cooperativity other mechanisms can involve either attractive or repulsive interhgand interactions. 

The Allosteric-Interannular-Chelate Cooperative Model, (a 1, j 1, c> 0). This model, in which aU the possible types of cooperativity are taken into account, is the most general one. To separate the product aj into its components, the factor a must be evaluated separately by studying the interaction of the receptor with a monovalent ligand. For the sake of illustration, the apphcation of Eq. [51] to test the presence of interannular cooperativity in the self-assembly of the Lehn s double-stranded copper(I) trihelicate 20 (Fig. 22) is discussed in the following. 

The self-assembly equilibrium constants for the dinuclear triple-stranded lutetium(III) helicates, [Lu2(21)3] +, [Lu2(22)3] +, and [Lu2(23)3], are ideally suited to test the emergence of interannular cooperativity since equilibrium data are available also for the formation of the intermediate double-stranded helicates. The available data show that the interannular cooperativity factor y is close to 1.0, in spite of the changes in the rigidity of the hgand strand or the choice of the solvent. 

Ercolani G, Schiaffino L. Allosteric, chelate, and interannular cooperativity a mise au point. Angew Chem Int Ed. 2011 50 1762-1768. 

IdU. See 5-Iodo-2 -deoxyuridine (IdU) Inline metathesis, DLs from, 31—34 Iminium ions, 134—135 Interannular cooperativity, 42—43, 56—59 binding of divalent ligand, 56f Interannular-chelate cooperative model, 62 Intermolecular process, 4f Internal symmetry number, 44—45 Intramolecular process, 3, 4f Intramolecular reactions, 78—81, 91 2 -Iodo-2 -deoxyuridine, 136, 138 5-Iodo-2 -deoxyuridine (IdU), 125, 125f, 136... 

AUosteric-interannular-chelate cooperative model, 65 Allosteric—chelate cooperative model, 62-65... 

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