Macrocyclic cryptands

Protons are relatively simple targets for sensor molecules and do not require engineered receptors, however, achievement of selective interactions with other chemical species requires much more elaborate receptors. In the most cases cations are bound via electrostatic or coordinative interactions within the receptors alkali metal cations, which are rather poor central ions and form only very weak coordination bonds, are usually bound within crown ethers, azacrown macrocycles, cryptands, podands, and related types of receptor moieties with oxygen and nitrogen donor atoms [8], Most of the common cation sensors are based on the photoinduced electron transfer (PET) mechanism, so the receptor moiety must have its redox potential (HOMO energy) adjusted to quench luminescence of the fluorophore (Figure 16.3). 

The. s-block metals are commonly complexed with the macrocyclic cryptands, sepulchrates, and related species to form large, non-interacting cations that are used to stabilize a variety of... 

The next two articles cover the chemistry of phosphorus containing macrocycles. The phosphorus containing cahxarenes have attracted much attention in recent years due to their various functions such as metal cations binding, catalysis, molecular recogination, and bioactivity. Likewise, other phosphorus-containing macrocycles, cryptands, and dendrimers find various uses in analytical chemistry and biochemistry. 

Although imines have generally not been included in the Chapter, there, however, needs to be one exception. Majoral and his coworkers utilized the previously unknown thioxo6 (l-methyl-hydrazino)phosphoranyl azide in the preparation of macrocycles, cryptands and spherands, such as 16. All compounds are isolated in a pure form and are colorless to yellow stable solids. 

An analogous route has been explored for the assembly of the macrocyclic cryptands isolated in the form of complexes [Co(L865)] " and [Co(L866)] " from [Co(L864)]3+ (Scheme 4-5) [60]. 

The tetraphosphoms macrocycle 238 possessing two tricoordinated phosphoms atoms reacts with 237 in similar way producing very original tris-macrocyclic cryptand 239 (Scheme 12.84) [214],... 

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