Dimeric Calixarene-based Coordination Cages

In the specific case of calixarenes, there are very few studies related to metal-mediated self-assembly into cage molecules. Early examples reported by Shinkai and coworkers include bis(acac)-calix[4]arene dimer (1) held together by Cu2+ cations 

Cotton et al. showed the assembly of a very stable coordination cage formed by linking two calixarene scaffolds functionalized with four carboxylic acid groups via bimetal units, (DaniF)2Rli2 [21]. This capsule permanently includes an NEt4+ cation and has a BF4 counterion external to the cage, as shown by the X-ray crystal structure determination. 

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