To confirm this, a quenching experiment was conducted using 3•(BF4)2, which has a similar structure to that of the constituent unit of the dimer, as the quencher against the 20-2-containing BB cluster (Fig. inset, Fig. ). Although attempts were made to observe quenching using steady-state luminescence, the absorption band of 3 overlapped with the entire absorption spectrum of 20-2, resulting in a decrease in emission intensity owing to the excitation inner filter effect. Therefore, steady-state emission quenching experiments were deemed inappropriate. By contrast, time-correlated singlephoton counting measurements of the emission decay confirmed that the emission lifetime of 20-2 remained constant regardless of the concentration of 3, confirming that 3 does not act as a dynamic quencher for 20-2 (Fig. ). This finding indicates that 3 cannot function as a dynamic quencher for 20-2, and considering the redox potentials of 20-2•(BF4 -)3 and 3•(BF4 -)2, it is evident that the driving force for photoinduced electron transfer from 20-2 to 3 is very small (Fig. , Fig. ). Therefore, the reduced emission lifetime of 20-2