Visible-light-modulating cucurbit[8]uril-mediated reversibly tunable Multicolor-Light emission

Multicolor emission materials in response to visible light stimuli have good prospects for application in biomedical engineering and materials science. Herein, a dual-visible-light responsive intelligent quaternary supramolecular assembly 3 with tunable multicolor fluorescence outputs is constructed from dithienylethene (DTE) derivative 1, terpyridine imidazole derivative 2, Eu(NO3)(3) and cucurbit (Qasim et al., 2017) [8]uril (CB (Qasim et al., 2017) [8]. Our experimental results indicate that both the opened and the closed forms of 1 exhibit blue fluorescence emission at 447 nm, and then complexes with CB (Qasim et al., 2017) [8] to form binary assembly 1@CB (Qasim et al., 2017) [8] with yellow fluorescence ON/OFF switching property at 540 nm by varying the wavelength of the exposed light. Compared with 1@CB (Qasim et al., 2017) [8], the quaternary supramolecular assembly 3 shows three different photoluminescent colors from yellow, white to blue by varying the irradiation time. Moreover, the solid-state assembly exhibited effective photoinduced FRET phenomenon. To our delight, the quaternary assembly was successfully used as photocontrolled cell-imaging agent and as a photoerasable fluorescent ink.