Flavone modified-β-cyclodextrin as a highly selective and efficient fluorescent chemosensor for Cu2+ ions and l-histidine

7-Aminoflavone modified β-cyclodextrin with a hydrazinecarbothioamide linker is synthesised for the first time and characterised by NMR, ESI-MS and elemental analysis. NOESY as well as emission spectra indicate the inclusion of phenyl ring inside the cyclodextrin cavity. The hydrazinecarbothioamide linker acts as the metal binding unit. This flavone modified CD selectively binds with Cu(II) over other metal ions. Binding with Cu(II) makes the complex non-fluorescent. Addition of histidine, among other amino acids, results in regeneration of the fluorescence enhancement. This is due to the fact that l-histidine displaces Cu2+ from Flav-CD-Cu2+ complex to release the free flavone resulting in regeneration of its fluorescence. This turn-on sensor can be utilised effectively to sense both Cu(II) among various metal ions and l-histidine (as well as histamine) among various amino acids.