Cryptands macrotricyclic

Since Pedersen s disclosures, and the subsequent extension into the third dimension through Lehn and his macrobicyclic and macrotricyclic cryptands,29 there have been a plethora of papers concerning many aspects of M"+ complexation, the majority being centred on crown ether and related species. Their literature has been extensively reviewed and attention is drawn to articles by Poonia and Bajaj30 and by Vogtle and Weber31 which are comprehensive and provide excellent bibliographies of the area. 

Section 5.1.4). However such is the affinity of transition metals for nitrogen donors that even if these compounds are derivatised to give macrotricyclic cryptands (3.76), Cu(II) and Ni(II) still only form 1 1 complexes rather than a 2 1 complex taking advantage of the mixed O/N donor array.31 In contrast the analogous all-nitrogen macrocycles (3.77) form 2 1 complexes. 

The anion-binding carcerand 11 was described by the Amouri group [31]. This complex contains a tetrafluoroborate anion coordinated to two cobalt(II) ions. Each cobalt ion adopts a square-pyramidal geometry. Four benzimidazole arms of the bridging ligands fill the equatorial positions, and solvent molecules (acetonitrile) coordinate to the outside axial positions. Inside the complex the included tetrafluoroborate anions interacts with the cobalt ions whose inside axial positions are otherwise coordinatively unsaturated. No exchange of the anion was observed even at 60 °C. A detailed study of the anion-binding properties in the crystal state of similar metalla-macrotricyclic cryptands has been performed by Adarsh et al. [32],... 

The above-described spherical macrotricyclic cryptand 13 was designed for the ammonium cation, whereas the series of cylindrical macrotricycles 15 (Fig. 15) was... 

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