Multistep assembling via intermolecular interaction between (bis)styryl dye and cucurbit[7]uril: Spectral effects and host sliding motion

•Spectral properties of dye in the presence of CB[7] were studied in aqueous and buffer solution.•Stepwise threading of CB[7] macrocycles on the dye towards one-to-three complex model are reported.•Host sliding upon protonation or electrostatic repulsion induced by CB[7] is observed.

The host–guest interaction between bis(styryl)pyridinium dye (BSP) and cucurbit[7]uril (CB[7]) was studied by means of optical spectroscopy, 1H and 2D (COSY, ROESY, DOSY) NMR spectroscopy and electrospray ionization mass spectrometry in different microenvironment (aqueous or phosphate buffer solution). The CB[7] macrocycles bind to BSP dye in a stepwise manner thus forming higher stoichiometric complexes such as (H+)2–BSP–(CB[7])3 in aqueous or BSP–(CB[7])3 in buffered solution. In the case of aqueous solution, complex formation is accompanied by the host-assisting protonation of the anilino-type BSP nitrogen atoms, that causes a pronounced effect on its spectral properties. Stimuli-responsive sliding movements of the CB[7] macrocycles along the stalk of dye molecule were also observed.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide