Supramolecular assembly of 2,7-dimethyldiazapyrenium and cucurbit[8]uril: a new fluorescent host for detection of catechol and dopamine

The formation of a highly stable inclusion complex between 2,7-dimethyldiazapyrenium (Me(2)DAP(2+)) and the cucurbit8]uril host (CB8) was demonstrated by X-ray crystallography; MALDI-TOF mass spectrometry; and (1)H NMR, electronic absorption, and emission spectroscopy. The equilibrium association constant was determined to be 8.9(+/-0.2)x10(5) L mol(-1) from UV-visible data and 8.4(+/-1.5) x 10(5) L mol(-1) from fluorescence data. The Me(2)DAP(2+).CB8 inclusion complex acted as a host to bind compounds containing aromatic pi-donor moieties (D), such as catechol and dopamine. This point was demonstrated by (1)H NMR spectroscopy, and electrochemical and emission measurements. Fluorescence detection of the Me(2)DAP(2+).D.CB8 ternary complexes was evident in aqueous solution and on the surface of silica particles, to which fluorescent diazapyrenium units had been covalently immobilized.