Signaling Recognition Events with Fluorescent Sensors and Switches.

6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures

Complexation Thermodynamics of Cyclodextrins.

The Stability of Cyclodextrin Complexes in Solution.

NMR Studies of Cyclodextrins and Cyclodextrin Complexes

α-, β-, and γ-cyclodextrin derivatives bearing a p-(dimethylamino)benzoyl (DMAB) moiety (DMAB-αCyD, DMAB-βCyD, and DMAB-γCyD, respectively) have been synthesized as fluorescent sensors of molecular recognition. These compounds show dual fluorescence emission arising from normal planar (NP) and twisted intramolecular charge transfer (TICT) exited states, and among them strong TICT emission was observed for DMAB-βCyD. The induced circular dichroism spectra of the derivatives suggest that only DMAB-βCyD among other derivatives binds the DMAB moiety into its own cavity, forming an intramolecular inclusion complex. This conformation was confirmed by the analysis of its 1 H-NMR data and was related to its strong TICT emission

Fluorescent Sensors of Molecular Recognition. Modified Cyclodextrins Capable of Exhibiting Guest-Responsive Twisted Intramolecular Charge Transfer Fluorescence

CHEMICAL indicators that change colour in response to the presence of neutral organic molecules are valuable for qualitative chemical analysis. Although some ionophores are known to exhibit colour changes on binding metal or ammonium cations1–3, however, the detection of neutral organic species in solution by this means remains problematic. We have shown recently4–7 that some fluorophore-modified cyclodextrins exhibit variations in fluorescence intensity on binding organic guests. Here we report guest-selective binding to a cyclodextrin that has been modified in such a way as to undergo a colour change on host-guest complexation. We attach the pH indicator methyl red to the wall of a β-cyclodextrin: in acidic solution, the modified cyclodextrin remains yellow owing to binding of the methyl red group inside the cavity, protecting it from protonation. When an organic guest displaces the methyl red group from the cavity, a colour change to red is observed. It should be possible to exploit the molecular recognition capability of cyclodextrins to develop a range of such 'molecular indicators'.

A modified cyclodextrin as a guest responsive colour-change indicator

Monotosylated α- and β-cyclodextrins prepared in an alkaline aqueous solution

Inclusion Complexes and Guest-Induced Color Changes of pH-Indicator-Modified .beta.-Cyclodextrins

6-O-, 2-O-, and 3-O-Dansyl-β-cyclodextrins (1, 2, and 3) were synthesized and characterized. Compounds 1 and 2 decrease their fluorescence intensities upon intermolecular complex formation. This property enables 1 and 2 to act as fluorescent sensors, converting binding of organic compounds into fluorescence variations.

Fujio Toda

Papers

Fluorescent Sensors of Molecular Recognition. Modified Cyclodextrins Capable of Exhibiting Guest-Responsive Twisted Intramolecular Charge Transfer Fluorescence

A modified cyclodextrin as a guest responsive colour-change indicator

Monotosylated α- and β-cyclodextrins prepared in an alkaline aqueous solution

Inclusion Complexes and Guest-Induced Color Changes of pH-Indicator-Modified .beta.-Cyclodextrins

Dansyl-.BETA.-cyclodextrins as Fluorescent Sensors Responsive to Organic Compounds.