SYNTHESES AND ION SELECTIVITIES OF TRI-AMIDE DERIVATIVES OF HEXAHOMOTRIOXACALIX[3]ARENE - REMARKABLY LARGE METAL TEMPLATE EFFECT ON THE RATIO OF CONE VS PARTIAL-CONE CONFORMERS

We have found that a homotrioxacalix[3]arene (1H(3))-based ionophore with a cone conformation, which is very difficult to obtain by the reaction of 1H(3) and ethyl bromoacetate, can be synthesized quantitatively by the reaction of 1H(3) and N,N-diethylchloroacetamide in THF in the presence of NaH. The conformer distribution of the tri-amide derivative (1Am(3)) between cone and partial-cone was sensitively affected in 0 similar to 100% range by the metal template effects. Cone-1Am(3) showed the very high affinity for alkali and alkaline earth metal cations. Particularly, it formed stable complexes with alkaline earth metal cations which were scarcely bound to the tri-ester derivative. The results show that cone-1Am(3) acts as an excellent neutral ionophore owing to the three coordinative amide groups arranged in C-3-symmetry.