Visualization of the Molecular Properties Using Phenolphthalein Derivatives

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During the past two years, we have investigated three types of visual recognition of guest properties using host compounds, hybrid molecules of phenolphthalein and two crownethers. (i)Sequence-Selective Visual Recognition of Nonprotected Dipeptides; A host molecule has an ability for developing brilliant purple color in the presence of dipeptides with a specific amino acid-sequence containing lysine as a C-terminal. This type of color development could be extended to the detection of oligopeptides of a specific sequence at the N-terminal such as scyliorhiin I and APP_<770>(394-410). (ii)Construction of a Variable Temperature Visual Read-Out System for Sodium and Potassium Ions; We have found the first artificial recognition system in which sodium and potassium ions show opposite behaviors. Thus, the absorbance at around 566 nm by the complex of host and NaOH increased as the temperature decreased. In contrast, color development between host and KOR decreased as the temperature decreased. These phenomena were caused by an equilibrium among the host molecule, a colored complex, and a colorless complex. (iii)Visual Enantiomeric Recognition of β-Amino Alcohols; we have developed a phenolphthalein based phenyl groups substituted crown ethers host. The host molecule has an ability to discriminate chirality of β-amino alcohols by naked-eye detectable color change. We really observed strength of color development of this host molecule and (S)-or (R)-guest was reversed at inversion temperature.