Design of Supramolecular Cyclodextrin Complex Sensors and Construction of Functional Interfaces

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In this study, benzo-15-crown-5 (B15C5) azoprobes possessing different alkyl chain lengths of n=1 (C1-Az), n=2 (C2-Az), and n=4 (C4-Az) have been designed for construction of novel photosignal transduction systems in water based on supramolecular azoprobe/γ-CyD complexes. For all Cn-Az probes, the UV-Vis spectra exhibited a K^+-selective blue shift with reduction of molar absorptivity in the longer wavelength, indicating a selective 2:1 complex formation of Cn-Az with K^+. While in the ICD spectra, different spectral responses were observed. Thus for C1-Az and C2-Az, the K^+-selective ICD response was clearly intensified by increasing the alkyl chain length from methyl to ethyl. However for C4-Az possessing longer butyl chains, an abnormally strong ICD response was noted for TMA^+ instead of K^+. These different spectral responses between UV-Vis and ICD were ascribed to the formation of different mode of CyD inclusion complex. In addition, C4-Az was found to have a unique response function for K^+ in the absence of γ-CyD. These results were discussed in relation to their supramolecular complex structures. For chiral recognition of sugars in water, biphenylboronic acid fluorophore (BPB)/CyD complex sensors have been developed. BPB showed fluorescence emission response upon sugar binding at high pH regions (above pH 9.3). By using this pH regions, effect of CyD upon the D/L recognition ability of BPB for fructose have been examined. The results indicated that no D/L selectivity was noted in the absence of CyD or the presence of β-CyD possessing smaller inclusion cavity. Whereas in the presence of γ-CyD having larger inclusion cavity, twice higher selectivity for D(-)-isomer was found to appear for BPB/γ-CyD complex. This is a novel recognition function of supramolecular CyD complex sensors based on multi point interaction of OH groups in CyD.