Capsular complexes

Section 3.13). He eventually concluded that the potassium ion had fallen into the hole at the centre of the molecule (Figure 3.6), at the time a bold and highly imaginative statement. Events were quickly to prove him to be entirely correct. This initial result led rapidly to the synthesis of a related family of species (Figure 3.2) to which Pedersen gave the name crown ethers because of the crown-like shape of the capsular complex between 3.4 and K+. 

In the complexes examined so far in complexation of cations (Chapter 3), anions and neutral species, the overall message that has come across has suggested that capsular complexes, in which the guest... 

Complementarity between different molecules has also been harnessed in the pursuit of capsular complexes. Schrader and Kraft have pioneered the design of complementary systems with three- and fourfold symmetry based on 1,3,5-tris(aminomethyl)benzene derivatives [18] and calix[4]arenes [19], respectively. This approach has also been taken by Reinhoudt whose vast output of calixarene chemistry includes work on calix[4]arene dimers held together by ionic interactions [20]. Other examples show how the presence of encapsulated guests templates the formation of self-complementary capsules [21], how two host molecules may be held together by metal coordination [22-24] or where hydrogen bonding by a second entity holds the assembly together [25,26],... 

The fonnation of capsular complexes is further corroborated by ESI mass spectra of equimolar host-guest mixtures. 

The access of small molecules (eg, and T) to pyrene encapsulated in a host-cavity, without release of the entrapped pyrene, allows quenching-rate constant measurement for singlet-excited-state pyrene inside the capsule (in the previous example, such access occurred via fast opening/closing of capsular complexes). 

Fig. 5.7 The solid-state structure of the capsular complex 21dBPDBc21 [47]...

Fig. 31.11 (a) Experimental conditions for the formation of kinetically trapped capsular complexes by the melting approach and for obtaining such complexes in solution. By the melting approach, three molecules of pyrene are encapsulated in the hexameric capsules, (b) H NMR spectra tracking the pyrene-filled (Oh)—>pyrene filled (D3)- CCl4-filled hexamer process (a) prior to heating (b) 2 h at 343 K (c) 24 h at 343 K (d) 4 h at 393 K, at this temperature equilibrium is established after 4 h [46a,b]... 

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