A tetraphenylporphyrin capped with a calixaryl amide through L-alanine pillars (compound 1) has been synthesized. Owing to C4 symmetry in both the tetraphenylporphyrin and the calixarene this molecule still retains C4 symmetry. As the calixaryl amide moiety can bind alkali metal cations, and the porphyrin moiety can bind transition metal cations, compound 1 acts as a host molecule with a hard-soft ditopic metal-binding site. It was found that the ZnII complex of 1 (complex 1-ZnII) can bind KI very strongly with log Kass = 5.23 (CHCI3:MeCN = 4:1 v/v; 25 °C) whereas KC104 is scarcely captured by 1-ZnII. Absorption and fluorescence spectroscopic studies showed that I- ion is bound to this cavity, interacting with both calixarene-bound K+ through electrostatic attraction and porphyrin-bound ZnII through coordination as an axial ligand. The results establish that complex 1-ZnII acts as a unique ditopic receptor for I- ion.
|Number of pages||6|
|Journal||Journal of the Chemical Society, Perkin Transactions 1|
|Publication status||Published - 1995|
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