Delayed fluorescence of 3,3′-diethylthiacarbocyanine in the presence of cucurbit [7]uril

Abstract

Cationic dye 3,3-diethylthiacarbocyanine (TCC) in a phosphate buffer solution (pH 6.86) in the presence of cucurbit[7]uril (CB7) occurs in the form of monomeric TCC@CB7 and dimeric (TCC@CB7)₂ complexes. The TCC@CB7 and (TCC@CB7)₂ complexes display fast (conventional) and delayed (thermally activated, of type E) fluorescence, as well as free TCC. The relative yield of fast fluorescence of TCC@CB7 is six times that of free TCC. The delayed fluorescence lifetimes τ_dfl of TCC@CB7 and (TCC@CB7)₂ are 0.5 and 1.6 ms, respectively. In the presence of p-nitroacetophenone (electron acceptor), the delayed fluorescence of (TCC@CB7)₂ is quenched dynamically with the rate constant of 7 × 10⁸ L mol^—1s^—1.