Abstract
A novel ditopic receptor possessing two complexation sites such as crown ether and 2-pyridylmethyl groups bearing 1,3-alternate conformation based on thiacalix[4]arene was prepared. The binding behaviors with Li+ and Ag+ have been examined by H-1 NMR titration experiment. The exclusive formation of mononuclear complexes of 1,3-alternate-5 with Li+ and Ag+ was observed even though the formation of the heterogeneous dinuclear complexes was expected. The decomplexation of Li+ from the crown moiety of 1:1 complex 1,3-alternate-5 superset of Li+ to form the Ag+subset of 1,3-alternate-5 complex by addition of AgSO3CF3 clearly shows that pyridyl moiety works as an efficient switch-off of the recognition ability of the crown moiety. We have also developed the construction of hydrogen-bonding self-assembly heterodimeric systems based on bis(4-pyridyl) and dicarboxylic acid thiacalix[4]arene derivatives in 1,3-alternate conformation. Their supramolecular behaviors are studied by H-1 NMR titration experiments with K+ and Ag+ ions. Although the values of the dimerization constants are relatively small, the stability of the dimers is strong enough to overcome only small conformational changes upon complex formation.