To investigate the photophysical properties of the synthesized (21)2Fe dimer, its luminescence decay curve was evaluated. Fig. shows the emission decay curve of the sample containing 20 and (21)2Fe. The experimentally obtained decay curve could be fitted to a biexponential decay model with short and long lifetime components of 7.8 ns and 3.5 μs, respectively. To identify these two emission species, the luminescence lifetime of the BB cluster was evaluated. The emission decay of the BB cluster could be fitted to a nearly single exponential decay, with a lifetime of 3.5 μs (Fig. ). This value is consistent with the long-lived component observed in the sample containing 20 and (21)2Fe. Therefore, the luminescence lifetime of (21)2Fe is 7.8 ns. From these results, the following conclusions can be drawn: (1) the luminescence lifetime of the BB cluster remains roughly constant and is independent of the type of acetylide ligand; (2) quenching of the Au13-derived luminescence occurs upon complex formation between 21 and Fe 2+ ; and (3) the luminescence of 20 is not quenched in the presence of the coexisting complex component, (21)2Fe dimer.