Synthesis and Application of Calixarene(New Host Compound)-based Functional Molecules

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Water-soluble calixarenes beaing the sulfonate groups either on the upper rim or on the loaer rim of the calixarene cavity were synthesized. These co,pounds can form host-guest-type complexes with various organic molecules and are capable of molecular recognition on the basis of the "hole-size selectivity". When aliphatic groups were introduced into the OH groups, they acted as a new class of usrfactants with the molecular recognition ability. In particula, O-dodecyl-psulfonatocalix[6]arene formed the unimolecular micelle and should a strong solubilization power in water.Chiral calixarenes were synthesized from the water-doluble calixarenes. They showed the CD spectral change upon inclusion of guest molecules. This change was sttributed to the conformational change from "alternate" to "cone". This established that the "cone" calixarene provide the cavity more suitable to the guest-binding the "alternate" calixarene.water-soluble calix[5]arene and calix(6)arene derivatives formed the stable complexes with uranyl ion (UO_2^<2+>), the stability constans being 10^<18> - 10^<19> M^<-1>. Furthermore, the selectivity factors for UO_2^<2+> vs. other metal cations were greater than 10^<12>. The remarkably large binding constants and the selectivity factors are due to the specific architecture of these calixarenes preorganized for the complex formation with UO_2^<2+>. Finally, four pKa values of the OH groups in water-soluble calix[4]arenes were deternined. The PK_<a1> (first dissociation) values were 0-1 while the PK_<a4> (1ast dissociation) values aere 12-16. The finding supports that calixarenes have a super-acidic proton and a super-basic oxyanion withina amolecule. This is due to the storng hydrogen-bonding among the OH groups.These results show that calixarenes serve as a basic skeleton to design novel ligands, surfactants, catalusts, and host molecules.