Photoprocesses in styryl dyes and their pseudorotaxane complexes with cucurbit[7]uril

The formation of inclusion complexes between styryl dyes containing a dimethylamino group or azacrown-ether residue and cucurbit[7]uril (CB[7]) in aqueous solution was studied by 1H NMR spectroscopy and quantum chemistry. The complexes are characterized by 1:1 composition and the pseudorotaxane structure, which was confirmed by quantum chemical calculations. The free dyes and dye@CB[7] complexes exhibit both prompt fluorescence and an ability to intersystem crossing. The triplet–triplet absorption spectra and the triplet lifetime of the free dyes and dye@CB[7] were measured by ns-laser photolysis.

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► 4-Pyridine styryl dyes having a dimethylamino group or aza-18-crown-6-ether residue form stable 1:1 complexes with cucurbit[7]uril in aqueous solutions.
► Pseudorotaxane structure of host–guest complexes dye@CB[7] was confirmed by 1H NMR spectroscopy and DFT calculations.
► Fluorescence was strongly increased in the presence of CB[7] due to stabilization of planar E isomer of the dye within complex.
► The formation of complexes results in increasing of the probability of the intersystem crossing.