Complex stability preorganization

Because of the intense interest in Mg + and Ca + ISEs, a lot of work was performed in which the structures of ionophores with different levels of preorganization were varied very methodically by use of substituents with different levels of buUdness and electronegativity." Arguably, this work contributes to the most sophisticated examples in the field of supramolecular chemistry. Unfortunately, because a lot of this work was performed before methods for the determination of complex stabilities in ISE membranes became available, the majority of this work was directed by the experimentally observed potentiometric selectivities alone. Complex stabilities have only been determined much later for a few selected examples. 

The interlocking of secondary amines with polyether macrocycles enables amines to activate H2 in the presence of B(CgF5)3. DF calculations show that the amine-macrocycle complex both preorganizes a frustrated Lewis pair minimum for H2 activation and stabilizes the product through strong hydrogen bonds. ... 

Complex stability for macrocyclic carriers is determined by a number of factors including donor atom type, macrocyclic ring size, chelate ring size, pendant group characteristics, steric considerations, and degree of preorganization. Because complex stability is so crucial to carrier effectiveness, we examine a few of these factors below. 

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