A green to blue fluorescence switch of protonated 2-aminoanthracene upon inclusion in cucurbit[7]uril

The inclusion of protonated 2-aminoanthracene in the cavity of cucurbit[7]uril increases its pKa values in the ground and excited states, resulting in the disappearance of the green emission of the neutral excited state and the significant enhancement of the blue emissions from the protonated excited state guest.