A light-responsive molecular switch based on cucurbit[7]uril and 1,1'-bis(benzyl)-4-[2-(4-pyridyl)-vinyl]-pyridinium dibromide displaying white light emission.

By using 1 H NMR, ESI-MS and UV spectra, a novel light-responsive molecular switch constructed using 1,1'-bis(benzyl)-4-[2-(4-pyridyl)-vinyl]-pyridinium (1 2+ ) and cucurbit[7]uril (Q[7]) is demonstrated. The E - to Z -isomerization of the double bond in 1 2+ results in the transition of the switching states from the 1 : 2 complex E -1 2+ @Q[7] 2 to the stable 1 : 1 complex Z -1 2+ @Q[7]. In particular, both the 1 : 2 complex and the 1 : 1 complex can emit cold white fluorescence under UV light.